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, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230484
International Research Progress and Development Suggestions of Hot Dry Rock EGS System Flow Test
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230644
Hot dry rock is a widely distributed and abundant geothermal resource. Its development and utilization are of great significance for reducing fossil energy consumption, alleviating environmental pollution and ensuring energy security. The enhanced geothermal system is the main way to develop dry hot rock at present, which is generally implemented through several links such as project site selection, geothermal drilling, thermal storage construction, flow test and commissioning power generation. Among them, the cycle test is an important link to undertake the construction of thermal storage and power generation engineering, which is used to form injection-production well groups, evaluate the cycle circuit, expand the heat exchange capacity, and lay the foundation for the final safe and stable realization of power generation objectives. The implementation process of the flow test is characterized by long-term and complexity, which is easy to cause problems such as insufficient connectivity, strong microseism, liquid leakage, scaling of the circulating fluid, and insufficient equipment reliability. Therefore, the flow test construction of dry-hot rock development sites in the world is often interspersed with drilling and reservoir reconstruction, and accompanied by scheme adjustment, to gradually achieve the goal of power generation. This paper briefly summarizes the flow test experience of developing EGS system for typical dry hot rock at home and abroad, expounds the influence of various factors on flow test, and puts forward development suggestions based on the actual situation of the site in Qinghai Republic, providing reference for technical personnel engaged in relevant fields.
Fine-grained Identification of Internal Characteristic Zones within the Strike-slip Fault Using the XGBoost Algorithm
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230583
Constrained by the strong heterogeneity within the internal structure of the strike-slip fault, the variability of reservoir spaces, and the complex distribution of fluids, the logging responses among the three characteristic zones within the strike-slip fault—namely, the fracture zone, fractured zone, and dissolution zone—are highly complex and variable. This complexity poses challenges for the effective utilization of imaging and conventional logging data to identify these three internal characteristic zones within the strike-slip fault.An analysis of the logging response characteristics of the "three zones" within the internal structure of the strike-slip fault was conducted. Sensitive logging curves were selected to construct a feature vector space based on mean and variance. The Extreme Gradient Boosting (XGBoost) algorithm was employed to establish XGBoost regression prediction models for the dissolution zone, fractured zone, and fracture zone within the strike-slip fault. Key parameters of the XGBoost model were optimized using multi-class evaluation metrics, resulting in an improved accuracy of identifying the "three zones" within the internal structure of the strike-slip fault.Utilizing the constructed XGBoost model, the identification of the "three zones" within the strike-slip fault in the study area achieved an accuracy rate of 88.89%. This indicates that the XGBoost-based identification model for the internal characteristic zones within the strike-slip fault can effectively distinguish the fracture zone, fractured zone, and dissolution zone. It holds valuable implications for a fine-grained characterization of the internal structure of the strike-slip fault.
Automatic Detection of Effective Microseismic Events Based on U-Net Neural Network
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230689
Abstract: [Objective]Automatic pickup of effective events is an important part of microseismic monitoring, and the accuracy of pickup directly affects the accuracy and reliability of subsequent seismic source localization and seismic source mechanism inversion. [Methods] In this paper, a 10-layer U-Net neural network model framework is constructed, the original microseismic data from 3D finite-difference simulation and the raw microseismic data from the measured gas storage reservoirs are made into labeled images, which are cut into 128*128 sized slices and input into the U-Net neural network for learning, and then the output of predicted slices is outputted and merged, and then the predicted images are binarized, and the microseismic effective events are extracted in the end of the P-wave first arrivals. This makes the edge segmentation of background noise and effective signal image more fine, and improves the efficiency and accuracy of automatic picking up of effective microseismic events.[Results]Quantitatively analyze and compare the pickup rate, wrong pickup rate and pickup error of U-Net method and STA/LTA method, the test results show that the pickup effect of U-Net is better than that of STA/LTA method, and U-Net also has a strong anti-jamming ability and generalization ability; Evaluate the effect of different label widths on the first-to-pickup results, the results show that the label pickup effect based on the event's primary cycle is The results show that the label pickup effect based on the main cycle of the event is the best.[Conclusion] The U-Net neural network first-to-automatic pickup algorithm established in this paper is an important part of the highly efficient and high-precision reservoir integrity microseismic intelligent monitoring system, which is of great significance to improve the level of microseismic monitoring technology in China.
The most dangerous sliding surface of the three-dimensional slope of the open-pit mine was generated based on multiple profiles
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230690
At present, the two-dimensional profile is widely used for slope stability analysis, which can efficiently and accurately evaluate the stability of the slope. However, the two-dimensional section cannot describe the three-dimensional spatial shape and three-dimensional sliding body of the most dangerous sliding surface of the slope. In order to solve this problem, based on the stability analysis of the two-dimensional section slope, the three-dimensional most dangerous sliding surface of the slope is fitted by using the spline function by associating multiple sections with the three-dimensional slope model. Firstly, the relationship between the two-dimensional profile and the three-dimensional slope space is established by setting the profile name, horizontal coordinate positioning and elevation positioning of the graphic elements in the profile line and the two-dimensional profile. Secondly, the most dangerous sliding surface lines of each section are automatically generated, and the most dangerous sliding surface lines of each two-dimensional section are converted to three-dimensional slope space by using the coordinate transformation formula. Finally, the spline function interpolation is used to fit the most dangerous slip surface lines in the three-dimensional space to construct the three-dimensional most dangerous slip surface. Taking the southwest slope of an open-pit mine in Xilinhot, Inner Mongolia as an example, a three-dimensional engineering geological model of the slope is established, and five two-dimensional profiles for slope stability analysis are generated. Through this method, the three-dimensional most dangerous sliding surface and three-dimensional sliding body of the slope are successfully generated.
Discussion on fine 3D modeling method of complex vein ore body
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20240050
Abstract: 【objective】 The surface structure and internal physical properties of geological bodies are simulated by using 3D geological modeling technology, which provides a reliable basis for revealing the spatial distribution of geological resources, resource estimation and resource development, and is the core technology of the construction of "glass earth". It is also an important carrier of geological time and space big data. Since the 1990s, 3D geological modeling technology has been developed rapidly. Researchers proposed many different modeling methods, but there were still many problems in fine modeling of complex orebodies. Compared with the implicit modeling method, the explicit modeling method was more accurate in depicting small-scale geological structure features. However, for the large-scale fine 3D modeling of geological bodies such as complex vein orebodies, there were still some problems, such as low modeling accuracy and poor morphological expression of the model, so it is difficult to meet the needs of mine production and resource estimation at present. 【Methods】 In this paper, aiming at a series of complex geological phenomena of local vein orebody, such as bifurcation compound, non-ore skylight, rock entrapment, fault cutting and so on, the techniques of orebody split line, segmented modeling and orebody suture are comprehensively used to construct orebody split line, segmented modeling, orebody suture and so on. Four kinds of explicit 3D modeling methods of complex vein orebody, such as bifurcation composite orebody, non-ore skylight orebody, stone-bearing orebody and fault cutting orebody are studied systematically. Among them, the constraint point is generally located in the ore center and the outline of the orebody, and the complex part of the model needs to add constraint points to complete the constraint of the shape of the orebody. The splitting line is the connecting line between the cusp-out point at both ends of the boundary line of the orebody and the central point of the ore-seeing project. it is mainly used to split the complex vein orebody, and the split line is used to model the branch-bifurcated composite orebody according to the regional geological law. Segmented modeling is to model the complex parts of complex orebodies separately. The stitching of orebody is to assemble the segmented model along the strike to form a complete model. 【Results and conclusion】 Through the above technology and the explicit modeling method based on measured data, the high-precision and fast 3D modeling of complex vein orebody is realized, and the difficult problem of narrow, thin and complex vein orebody modeling is solved effectively. The 3D modeling process of different complex vein orebodies is improved, and the orebody model is displayed in 3D space in multi-angle, and the most real geological shape of the orebody is reconstructed with the outline of the orebody. High-precision model will not only obtain detailed 3D information of orebody, but also will grasp the distribution law of orebody quickly and accurately. This modeling method is of great significance to the fine 3D modeling of rare and precious metal and other complex vein orebodies, the estimation of mineral resources and the formulation of mineral resources development and utilization plan, and will better guide the exploration and prospecting work.
Tracing of the sources of dissolved organic matter in coastal groundwater based on fluorescent indices and end-element mixing analysis
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230711
Dissolved organic matter (DOM) in coastal groundwater is derived from multiple sources including marine water, river and leachate from sediments. Quantitative estimation of the contribution of difference sources to coastal groundwater is importing for understanding the carbon reactive transport in the coastal area. Isotopic tracer, fluorescent indices, and end-element mixing analysis (EMMA) were used to identify the sources of DOM in coastal groundwater and quantify their contributions. The results showed that DOM in coastal groundwater was mainly originated from DOM in river water, seawater and sediments, with contributions of 44.0% ± 22.2%、33.0% ± 10.8% and 22.9% ± 13.1%, respectively. Groundwater collected from the north part of study is affected by both seawater intrusion and fresh water recharge, showing a high proportion of seawater DOM and autogenous characteristics. In the south part, groundwater has higher total dissolved solids (TDS), saline water releases DOM in sediments, showing higher proportion of DOM in sediments and humification characteristics. This study demonstrates the DOM in coastal groundwater is affected by hydrodynamic and hydrogeological conditions. End-element mixing analysis based on fluorescent indices can efficiently quantify the sources of DOM in coastal groundwater, which provides a new perspective and assessment method for the study of terrestrial-oceanic carbon cycle.
Study on the influence of aggregation angle of aggregated landslide debris flows based on discrete element model
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230564
Abstract: [Objective]Landslide debris flow is a common geological disaster, which has the characteristics of large scale, long sliding distance and fast speed, and the terrain of hillside ravines and valleys will affect the trajectory of landslide debris flow and then block, turn, pile up and a series of impacts, so the landslide debris flow is not only a simple straight line path, but also by the influence of the terrain factors, the path of its movement is complex and varied.[Methods]This paper is mainly based on the aggregation behavior in different motion trajectories of landslide debris flows, and uses EDEM software to analyze the motion impact and accumulation characteristics of symmetric aggregated landslide debris flows in different aggregation angles.[Results]The results of the study show that: (1) the effect of the polymerization angle on the movement velocity: the larger the polymerization angle, the smaller the Vy, the higher the degree of separation of the landslide debris flow, and the longer the landslide sliding time; (2) the effect of the polymerization angle on the accumulation morphology: the larger the polymerization angle, the landslide is stabilized at the foot of the slope, and the morphology of the accumulation zone, the length of which is increased on the slide side, and the height of which is decreased at the blocking structure; (3) the effect of the polymerization angle (3) Effect on impact performance: the larger the polymerization angle, the lower and later the peak impact force on the barrier structure; the residual impact force after stopping the movement to form a static accumulation area is also lower, and the value of the residual impact force is also closer to the peak impact force.[Conclusion]The research results provide a fundamental role for the in-depth study of the complex path movement of landslide debris flows and a theoretical reference for the optimization of landslide debris flow control structures.
Quantitative characterization of clastic particle size of tight sandstone and its indicative significance for productivity
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230582
[Objective]Particle size analysis is important for the evaluation of clastic oil and gas reservoirs because it can identify the stratigraphic depositional environment and evaluate the permeability of reservoirs. [Methods]Taking the dense sandstone reservoir of Shaximiao Formation in Tianfu Gas Field in Sichuan Basin as the research object, firstly, we analyzed the influence of the particle size and shape of the clastic rock on the permeability of the reservoir, and then, based on this, we combined the median value of the particle size, the C value of the particle size, and the sorting coefficient, and put forward a comprehensive characterization of the indicator parameter of the particle size PI, and then we carried out a principal component analysis on the natural gamma, the photoelectric absorption cross section index, and the neutron, which are more sensitive to the particle size. The exponential relationship model between the particle size indicator parameter PI and the principal component parameter is established. Finally, the correlation between the particle size indicator parameter PI and reservoir production capacity is analyzed by combining the test and logging data. [Results]The statistics of 8 test gas sections of 7 wells in Shaximiao Formation of Tianfu Gas Field were collected, and the values of particle size indicator parameter PI of 7 wells were calculated by the above method, and the response relationship between the unimpeded flow rate of the test sections and the particle size indicator parameter PI was analyzed, and the results show that: the cumulative values of unimpeded flow rate of the test sections in Shaximiao Formation of Tianfu Gas Field and the particle size indicator parameter PI, X, showed an exponential relationship, and their correlation coefficients reach to 0.85. [Conclusion]The study shows that for reservoirs with lithology mainly dominated by medium-fine-grained sandstone, with large variation of grain size, and with storage space dominated by residual intergranular pores, the grain size indication parameter PI can to some extent indicate the production capacity of this type of reservoir.
Structural features of south Hubei Province along the northern margin of the Mufushan pluton and structural ore-controlling of polymetallic deposits
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230525
[Objective] An intensive Early Cretaceous magmatic-hydrothermal metallogenic system occurred in the Mufushan area, central Jingnan Orogen. The Jingnan Orogen in the South China Block resulted from the accretion and subsequent collision of the Yangtze and Cathaysia blocks during the Early Neoproterozoic, consisting of Li-Be-Cs-Nb-Ta rare metal deposits and Pb-Zn-Cu-Au-Sb nonferrous metal deposits. The northeast Hunan Province and the south Hubei Province are located to the
Geochemistry, zircon U-Pb age and Lu-Hf isotope characteristics of in Daliuhang Mesozoic granites in Jiaodong area and their tectonic significance
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230693
[Objective] To determine the Mesozoic granite type, age and tectonic setting and discuss the relationship between the granite and gold mineralization in Daliuhang, Jiaodong Peninsula. [Methods] In this study, the Mesozoic Yanshanian Linglong-type granites (Qijiagou monzonitic granite) and Gujialing-type granites (Gusidian monzonitic granite), which were located in the north of Qixia-Penglai gold metallogenic belt in eastern Jiaodong Peninsula. These samples are selected to analyze whole-rock geochemistry, U-Pb dating and Lu-Hf isotope study of zircon. [Results] The results show that the U-Pb age of the zircon from Qijiagou monzonite is 172.8±1.5 Ma, and the εHf(t) value of the zircon is -27.7 ~ -20.3. The zircon U-Pb age of Gusidian monzonitic granite is 127.3±0.8 Ma, the εHf(t) value of zircon is -15.7 ~ -13.4. The 87Sr/86Sr ratio of Gusidian monzonitic granite is 0.710937 ~ 0.712735, and the εNd (t) range is -16.8 ~ -11.3. [Conclusion] The source of Qijiagou monzonitic granite is ancient lower crust, which is mainly from the North China Craton lower crust. The magma source of Qijiagou monzonitic granite may be mixed with the Yangtze craton crust. Gusidian monzonitic granite is formed by partial melting of mafic rocks of lower crust, which added mantle components in the process. The diagenetic tectonic background of Gusidian magma formation is extensional, which may be caused by the subduction and retreatment of the Pacific plate. The Gusidian monzonitic granites have high coordination with the characteristics of early Cretaceous gold mineralization in Jiaodong Peninsula, suggesting that Gusidian monzonitic granite may be related to gold mineralization in this area.
Kinetic Characteristics of Methane Hydrate in Functionalized Multi-walled Carbon Nanotubes and L-leucine Compounding System
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230215
Accelerated natural gas hydrate formation is important for the promotion of natural gas storage, gas separation and CO2 capture technologies based on hydrate method. The kinetic characteristics of methane hydrate of 0.05 wt% functionalized (hydroxylated, carboxylated and aminated) multi-walled carbon nanotubes and 1.0 wt% L-leucine complexed system were investigated by constant temperature and constant volume method. It is shown that the compounding of multi-walled carbon nanotubes, carboxylated and hydroxylated multi-walled carbon nanotubes with L-leucine can significantly reduce the nucleation time of natural gas hydrate induction to about 25, 22 and 13 min, the promotion effect is comparable to that of typical promoter sodium dodecyl sulfate, and the promotion effect is better than that of the single additive system. The methane storage density of the compounded system has good performance up to 136-142 mg/g. The analysis of the average and instantaneous methane uptake rate shows that the multi-walled carbon nanotubes have little effect on the growth kinetics of methane hydrate in the growth phase. The growth of methane hydrate in the compounded and L-leucine systems had similarities, both showed a rapid increase of uptake rate to the maximum value, follwed by a rapid decrease and completion of growth. The comprehensive analysis indicates that the compounding system of multi-walled carbon nanotubes and L-leucine has a synergistic enhancement effect on the nucleation rate of methane hydrate, while the process and rate of the growth phase are mainly influenced by L-leucine. This study provides a new idea to explore the differentiation mechanism of different types of additives in enhancing the kinetics of methane hydrate generation.
Source-sink characteristics of Weihe Graben and its controlling effect on deposition and reservoir characteristics
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230531
Property of provenance plays an important role in controlling Paleogene deposition and reservoir development in China's offshore basins. However, due to the cost of coring and the interpretation ambiguity of seismic data, the relevant understanding lacks visual evidence support. Weihe Graben is a Cenozoic rifting basin. Regional geological studies reveal that there are significant differences in provenance system between north and south of Weihe Graben, and its tectonic setting and provenance system show strong analogy with the offshore basins. Based on outcrops and systematic sampling in Weihe Graben, zircon U-Pb dating, cast thin section, backscattering and X-ray diffraction analysis are carried out to analyze the source system, deposition and reservoir characteristics of the northern and southern sandbodies in Weihe graben. The detrital zircons in the northern Huacheng section have two typical peaks of ~2500 Ma and ~1800 Ma reflecting the influence of North China Craton, and two younger peaks correspond to Caledonian and Hercynian movement. The conglomerate gravel types at the bottom of the sequence are mainly carbonate rocks, calcarenous clastic rocks and metamorphic rocks, which have distinct characteristics of Paleozoic carbonate rocks and clastic rock of Weibei Uplift in the north. The late Caledonian and Late Indosinian peaks dominate the detrital zircons in the southern profiles, and the gravel types are dominated by granites and metamorphic rocks, with distinct provenance characteristics of the southern Qinling Mountains. Typical profile observations show that the difference in provenance leads to significant differences between sedimentary system and reservoir characteristics. The carbonate provenance area of Weibei Uplift corresponds to a small and mud-rich sedimentary body, and the bottom conglomerate directly changes to silty sand and mudstone, with high calcium content in the reservoir. The southern Qinling orogenic belt is characterized by large distribution of sedimentary bodies, multi-cycle sand-rich deposits, and low calcium content. Different types of provenance systems provide material basis and prerequisite for reservoir and subsequent diagenesis. The outcrop system analysis of Weihe graben can provide references for offshore basin research in China.
Geological characteristics, controlling factors and prospecting directions of associated cobalt deposits in the Weiningbeishan area , Ningxia
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230691
The Weiningbeishan is located in the eastern section of the North Qilian orogenic belt, which is one of the areas with the best cobalt mineralization conditions in Ningxia.【Objective】In order to understand the formation conditions and mineralization patterns of cobalt deposits in this area,【Methods】this paper summarizes the geological characteristics, controlling factors, and spatiotemporal distribution patterns of typical associated cobalt deposits in the Weiningbeishan based on detailed field investigations and previous exploration results, and proposes exploration directions.【Results】Research has shown that the Datonggou copper cobalt deposit, Chaliangzi iron cobalt deposit, and Tuyao iron cobalt deposit are currently three representative associated cobalt deposits discovered in the Weiningbeishan. Among them, three copper cobalt ore bodies were discovered in Datonggou, with the highest Co grade of 0.06%. Cobalt-bearing minerals mainly include pyroxenite, cobalt-bearing pyrite and cobalt-bearing limonite. There are 4 ore belts and 8 iron cobalt ore bodies distributed in Chaliangzi, with the highest Co grade of 0.03%. The cobalt-bearing minerals are mainly cobalt-bearing limonite. Only one iron cobalt ore body was found in Tuyao, with the highest Co grade of 0.20%. The cobalt-bearing minerals are similar to the Chaliangzi. Cobalt mineralization is clearly controlled by faults, with the western cobalt deposit mainly controlled by east-west faults and their combined control with northeast faults, while the eastern cobalt deposits are mainly controlled by north-south faults. Cobalt ore mainly existed in the Tupo Formation of the Upper Carboniferous, which was the main source layer. The lithological control mainly manifested in the "silicon calcium surface" and lithological combination interfaces with different workability, which controlled mineral precipitation. The formation time of cobalt mineralization is mainly in the Indosinian. Co was mainly closely related to Cu, Au, Fe and Mn. Cobalt deposits related to Cu and Au were mainly distributed in the west, while cobalt deposits related to Fe and Mn were mainly distributed in the east. The main reason for the diversity of mineral species in this area may be the multi-stage superimposition of structures and reformation of hydrothermal fluids. 【Conclusion】The most favorable locations to look for cobalt deposits are the east-west faults and their intersections with the northeast faults in the western part, the north-south Carboniferous and Devonian interface faults in the eastern part, the "silicon calcium surface" within the Tupo Formation, and the lithological combination interface with different connectivity. The peacock petrification and limonitization alteration are the most important prospecting indicators for copper cobalt deposits and iron cobalt deposits.
Experimental study of dissolution damage to carbonate rocks by acidic leachate
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230633
Strongly acidic wastewater is highly corrosive to carbonate rocks, which can lead to significant changes in the physical and mechanical properties of carbonate rocks. In this paper, through carrying out different flow conditions, different time length of phosphogypsum acidic leaching solution on the dissolution of limestone test research, analyze before and after the test of limestone specimens of the apparent characteristics, quality, porosity, uniaxial compressive strength, and acoustic emission counts and other indicators of the law of change, to discuss the dissolution damage of acidic leaching solution to carbonate rock and mechanical damage, revealing the impact of the acidic leaching solution on the physical and mechanical properties of the carbonate rock. The test results show that the dissolution rate and porosity increment of the rock samples are positively correlated with the dissolution time and the flow rate of filtration solution, and the mechanical strength is negatively correlated with the dissolution time and the flow rate of filtration solution. With the dissolution, the surface of the rock samples will be attached with thicker and thicker fluorite minerals, which makes the dissolution rate of the rock samples slower. The damage form of the uniaxial specimen gradually changed from shear damage to tensile damage. Under the acidic environment of phosphogypsum leachate dissolution, the internal mineral composition of limestone is dissolved, which causes changes in macro-mechanical parameters, and the results of the study can provide theoretical and experimental data for the stability analysis of karst media under the influence of acidic wastewater, acidic wastewater treatment, and tailing project safety design.
Orbital cycle recognition and sequence stratigraphic division of the Lower Carboniferous Dawuba Formation shales in Southwest Guizhou
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230546
【Objective】The Lower Carboniferous Dawuba Formation in southwest Guizhou has developed a set of shale with great exploration potential. However, the scheme of sequence stratigraphic division is not unitive and the understanding of sequence development mechanism is unclear, which restricts the promotion of unconventional oil and gas exploration. Therefore, this paper carries out cyclostratigraphic analysis and sequence stratigraphy research on this set of shale stratum, aiming to realize the "quantitative" stratigraphic division of shale from the perspective of orbital cycles.【Methods】The Well QSD-1 (1457-2466 m) was selected as the research object, and the gamma ray logging curve was used as the proxy index, the cyclostratigraphic analysis and sequence stratigraphy were carried out by using time series analysis, INPEFA analysis and wavelet analysis.【Results】Obvious orbital cycles have been recognized of the Lower Carboniferous Dawuba Formation shales in Southwest Guizhou. The optimal sedimentation rate of the stratum was estimated by COCO is 16.4 cm/ka, and the matching sedimentation thickness of 66.42 m represents the long eccentricity cycle of 405 ka. Spectral analysis was conducted again for GR series (1457-1932 m and 1932-2466 m) of Well QSD-1, and the optimal sedimentation rate was estimated to be 16.5 cm/ka in the upper section and 11.2 cm/ka in the lower section. The filtering results show that 19 long eccentricity cycles are recorded in Dawuba Formation. The "floating" astronomical time scale of Dawuba Formation is established, and the duration of Dawuba Formation is estimated to be about 7.86Ma. The relative sea level change curve of Dawuba Formation is restored by establishing the sedimentary noise model (DYNOT and ρ1) of the research interval. Based on the age framework established by the cyclostratigraphic research, according to the extreme value of the relative sea level change curve, combined with the results of INPEFA analysis and wavelet analysis, the third-level sequence boundary and the maximum flooding surface of Well QSD-1 were recognized. Six third-order sequence boundaries and five third-order sequences were recognized in Well QSD-1 Dawuba Formation, and the development of third-order sequences were correlated by obliquity amplitude modulation (AM) cycle (~1.2 Ma). 【Conclusion】The research method of cyclostratigraphy is applied to the stratigraphic division of Lower Carboniferous Dawuba Formation shale in southwest Guizhou, and the relationship between astronomical orbit parameters and relative sea level changes at different time scales is discussed, and the third and fourth order stratigraphy are divided. Cyclostratigraphic provides the possibility for the correlation of marine shales on the ten thousand years time scale, provides a fine age framework for the prediction of high-quality source rock development intervals in shale oil and gas exploration, and provides theoretical guidance for oil and gas exploration in shale.
Research on information extraction method of dangerous rock mass on high and steep slopes based on multi-source remote sensing data fusion
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230695
Abstract:[Objective]There are a large number of high and steep slopes in mountainous areas in my country. Due to their hidden and dangerous characteristics, it is currently difficult to accurately obtain the distribution location and characteristic information of rock masses on high and steep slopes through manual surveys and single non-contact measurements. [Methods]This paper fuses point cloud data obtained from airborne LiDAR, ground LiDAR and UAV oblique photogrammetry with multi-source data to complement each other's advantages. The fused point cloud is then used to analyze high and steep slope hazards. Extract information from the scale boundary, trailing edge characteristics, occurrence information and structural plane characteristic parameters of the rock. [Results]The results show that the multi-source data fusion method used in this article effectively complements the advantages of various data. The fused point cloud is used to extract scale boundary, trailing edge information and structural plane characteristic parameter information of dangerous rocks on high and steep slopes. The extraction accuracy meets [Conclusion]The relevant specification requirements provide a technical method for the refined extraction of geometric parameter information of rock mass on high and steep slopes in mountainous areas.
Numerical study on the disturbance law between rock fractures in the coupling process of high voltage electric pulse- hydraulic fracturing
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230364
The purpose of this study is to investigate the disturbance law between rock fractures during the coupling process of high-voltage electric pulse-hydraulic fracturing. Based on elasticity, fracture mechanics, damage mechanics, the discharge process of high-voltage pulse discharge under water pressure (3 MPa) was numerically simulated by using extended finite element method, and the cracks in rock mass were analyzed. The results show that under a discharge voltage of 5 kV, the maximum crack width of high-voltage electric pulse-hydraulic fracturing is increased by 35% compared to traditional hydraulic fracturing. With the increase of discharge voltage, the maximum crack width and crack initiation pressure of cracks increase, which improves the interference ability between cracks. In addition, the interference between cracks in rock mass is also related to the principal stress difference, injection rate and the number of cracks. Specifically, under the same voltage, the faster the injection rate, the longer the crack length, the more obvious the stress shadow effect, and the stronger the disturbance between cracks; Under the same injection rate, the larger the principal stress difference, the more obvious the directionality of the crack extending towards the maximum principal stress. The initiation pressure and maximum crack width both decrease with the increase of the principal stress difference. Multiple crack branches can expand and cross each other at the same time, and the stress shadow area of three cracks is wider than that of two cracks. The research results aim to provide a theoretical basis and research method for the research of underwater high-voltage electric pulse fracturing and coal seam permeability enhancement technology, and lay a certain foundation for artificial control of cracks in practical projects.
Characteristics and causes of difference of physical properties of deep and ultra deep tight sandstone reservoirs: a case study of the Bashijiqike Formation in Bozi area of Kuqa Depression
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230567
Abstract: [Objective]Despite depths exceeding 8000 meters, it still retains high-quality reservoir and exhibits prolific production of industrial gas flow in Bozi area of Kuqa Depression. However, there are obvious differences in the physical properties plane of the tight sandstone reservoirs of the Bashijiqike Formation. In order to clarify the development characteristics of such reservoirs and reduce the risks associated with deep-ultra-deep oil and gas exploration. [Methods]Based on the experimental analyses of well logging, thin section petrography, high pressure mercury injection and PVT phase diagrams, the characteristics of tight sandstone reservoirs and the causes of physical property differences were discussed. [Results] The rock types of Bashijiqike Formation reservoir in Bozi area which the study highlights are medium-fine grained lithic feldspar sandstone and feldspar lithic sandstone. Notable differences exist in the spatial distribution of carbonate cement content. Original porosity in the medium-fine sandstone reservoirs that ranges from 32.4% to 38.1%, exhibiting comparable intergranular compaction strength primarily reliant on point-line contacts. Southern reservoirs maintain an average porosity of 8.6% and an average permeability of 3.4 mD. Central reservoirs present an average porosity of 6.53% and an average permeability of 0.65mD. The average porosity and permeability of the northern reservoir are 4.9% and 0.62mD respectively. Primary intergranular pores dominate the southern reservoir space, whereas residual intergranular pores and dissolution porosity prevail in the northern and central zones. Furthermore, superior pore-throat structures characterize the southern region compared to the northern and central sectors. [Conclusion] The physical properties of sandstone reservoirs in Bozi area are controlled by sedimentation, diagenesis and tectonic processes (fissures), among which carbonate cementation emerging as the principal factor of the late reservoir physical properties alterations. Overpressure, hydrocarbon fluid charging, and fracture development significantly affect carbonate cementation, subsequently causing variations in reservoir physical properties. Stronger overpressure, earlier oil and gas charging time and limited fracture filling result in better reservoir properties in southern Bozi than those in northern and central areas.
Sedimentary Characteristics and Evolution Law of Shallow-Water Fan Delta: A case study of Baikouquan Formation in Madong slope area, Junggar Basin
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230518
[Objective]Conglomerate is unique oil and gas reservoir, and understanding its sedimentary origin and evolution is important for accurately predicting the distribution of high-quality reservoir. [Methods]Based on core logging, petrology identification, heavy mineral and grain size analysis, combined with well logging data, the sedimentary characteristics, spatial distribution and sedimentary provenance of the Lower Triassic Baikouquan Formation conglomerate in the Madong slope area are defined, the sedimentary mechanism of the formation is clarified and the sedimentary model is established. [Results]The results show that the Baikouquan Formation was deposited in the shallow-water fan delta, and the fan body developed three subfacies, namely fan delta plain, fan delta front and pro-fan delta, including 9 microfacies, containing debris flow, braided channel, flood deposit, subaqueous debris flow, subaqueous main channel, subaqueous branch channel, sandy clastic flow, far sand bar and pro-fan delta mudstone deposits. It contains 10 types of lithofacies. [Conclusion]Combined with the paleoclimate background of the early Triassic which changed from drought to moisture, the conglomerate is the sedimentary product of flood induced gravity flow, which has the characteristics of complex lithofacies associations, significant signs of eventful deposition, sedimentary model dominated by paleoclimate, and obvious transformation of lake wave. In terms of spatial extent, the grain size of the Baikouquan Formation conglomerate in the Madong slope region gradually becomes finer from bottom to top, which reflects the sedimentary sequence of the lake transgression and presents the signature of a multi-period superposition of debris flows, underwater debris flows, and subaqueous channel deposits.
Detrital Zircon U—Pb Age Characteristics and Provenance Analysis of Submarine Fan of Middle Miocene in the Qiongdongnan Basin
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230534
[Objective]The middle Miocene submarine fan in the Qiongdongnan Basin is an important target for natural gas exploration in the northern South China Sea. However, for a long time, there has been no consensus on the source of the submarine fan sediments, The provenance analysis will be of great significance to the optimization of natural gas exploration in this area. [Methods]In this paper, the detrital zircon U—Pb age spectrum characteristics of drilling cores of the middle Miocene submarine fan in the Qiongdongnan Basin was analyzed and compared with the U—Pb age of the zircon in the potential provenance area to trace the source of submarine fan in the study area. [Results]The results show that : ①The U—Pb ages of detrital zircons from N-1, N-2, N-3 and N-4 wells in the northern part of the basin are characterized by the age peaks of Yanshanian (160 Ma, 157 Ma, 133 Ma, 107 Ma, 102 Ma, 99 Ma), Indosinian ( 249 Ma, 241 Ma, 239 Ma ) and Caledonian ( 466 Ma, 455 Ma ), and have high similarity with the U—Pb age characteristics of detrital zircons from the Hainan Island sediments, but with low similarity with the U—Pb age characteristics of detrital zircons from Red River and central Vietnam sediments. ②The detrital zircon U—Pb age characteristics of three wells ( S-1, S-2, S-3 ) in the southern part of the basin show the peak age characteristics of Indosinian ( 242 Ma, 238 Ma, 237 Ma ), Caledonian (431 Ma, 431 Ma, 425 Ma,), Hercynian (392 Ma, 392 Ma) and Yanshan ( 143 Ma ). The S-2 well has a younger unimodel Himalayan ( 21 Ma ) age peak. [Conclusion] It is confirmed that the sediment source of the middle Miocene in the northern part of the basin is mainly from Hainan Island. The influence of the provenance in the Red River and Central Vietnam are very limited. The provenance of the middle Miocene in the southern Qiongdongnan Basin has a double-source supply from the Red River and Hainan Island, and is dominated by the former one, with an apparent difference from west to east.
Reservoir characteristics and development control factors of Benxi Formation bauxite in Linxing area of Ordos Basin
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230657
In recent years, the bauxite gas exploration of Taiyuan Formation in Longdong area of Ordos Basin has made a major breakthrough, which has attracted wide attention at home and abroad. In the same period, the bauxite rock gas of Benxi Formation in Linxing area has also made some progress, but the characteristics and controlling factors of bauxite reservoir in this area are unclear, which restrict the exploration process. [Objective]In order to identify the reservoir characteristics and control factors of Benxi Formation bauxite in Linxing area, [Methods]The paper carried out XRD, casting sheet image, SEM-EDS, mercury intrusion porosimetry, nitrogen adsorption, carbon dioxide adsorption, routine porosity detection and other analysis methods. The mineral composition, pore structure and physical properties of the bauxite reservoir are characterized, and the controlling factors of the development of the bauxite reservoir are discussed based on seismic logging data. [Conclusion]The results show that the aluminum-bearing minerals in the bauxite of Benxi Formation in Linxing area are mainly diaspore, and the pore types are mainly intra granular pores, intergranular pores, matrix pores, intergranular pores and micro-cracks, and occasionally organic pores. In addition, the pore volume of bauxite rocks is mainly provided by mesoporous and macroporous pores, and the distribution range of pore peaks is mainly 30-70 nm, 80-130 nm and 4-13 μm. Thirdly, the physical property conditions of the bauxite reservoir are general, with an average porosity of 3.28% and an average permeability of 1.398×10-3 μm2, but the upper section with higher content of diaspore at the bottom still has better physical property conditions. Finally, the development of bauxite reservoir in Linxing area is controlled by palaeo-geomorphology, palaeo-sedimentary environment and diagenesis. Among them, The accumulation and distribution of bauxite are controlled by the paleogeomorphology of depressions and troughs and the enclosed and semi-enclosed intermittent swamps and lagoons sedimentary environment, while diagenesis controls the reservoir space type and physical property conditions of bauxite reservoirs based on the sedimentary environment.
Geochemical factors affecting oxidation dissolution and permeability enhancement of Yichang gas producing shale, Hubei province
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230204
[Objective]It has become a mature method to exploit shale gas by chemical oxidation and infiltration technology,The purpose of this study is to explore the influence of geochemical factors in the exploitation process. [Methods] In this study, the Doushantuo Formation shale in Yichang, Hubei Province, which has a good shale gas exploitation prospect and rich organic matter content of pyrite, was selected as the research object. Two commonly used oxidants, 15wt% H2O2 and 0.5mol/L Na2S2O8, were selected to carry out the oxidation corrosion experiment at normal temperature and pressure. The results were measured by the determination of cation concentration, pH, Eh, mass loss and XRD analysis after the reaction. According to the relevant ground water data, Na+ and SO42- are selected because they are the main ions in the Doushantuo Formation Marine sedimentary water, and Ca2+ and Mg2+, which are easy to precipitate by SO42- in the overlying Dengying formation water, are selected. The four ions and their concentrations, as well as the influence of pH and temperature, which have strong influence on the oxidation and dissolution effect in related mining technologies, are also selected. [Results]The results show that Na2S2O8 is superior to H2O2, and the advanced oxidation process driven by pyrite and the erosion effect of carbonate under acid production make the acidic environment more suitable for the dissolution of carbonate-rich shale, and the stronger the acidity, the better the oxidation dissolution effect. For carbonate-rich shale, it is necessary to appropriately increase the acidity of the reaction system to increase the permeability of shale. Temperature rise can promote the thermal decomposition of Na2S2O8 and H2O2.The thermal decomposition of H2O2 produces O2, and Na2S2O8 produces H2SO4, O2 and SO4?- with strong oxidation, so that the promotion effect of temperature on Na2S2O8 is better than H2O2. Sodium ion (chloride) can promote the release of Ca2+ and Mg2+ in the oxidation process of Na2S2O8 and H2O2, so the groundwater environment with high concentration of NaCl plays a positive role in the oxidation and dissolution of shale. Magnesium silicate precipitation will be produced in the reaction system of weakly basic magnesium ion, which is more obvious to inhibit the oxidative corrosion of H2O2. Both calcium ions and sulfate ions can produce gypsum precipitation by influencing the interaction between the reactions, thus affecting the oxidative dissolution of shale. Low concentration of exogenous calcium ions inhibits the buffer effect of carbonate and produces a promotion effect, while high concentration of exogenous calcium ions will produce secondary mineral precipitation, block shale pores and hinder the oxidation and dissolution of shale. However, the effect of sulfate ions on the oxidative corrosion of shale is opposite to that of calcium ions. The low concentration of exogenous sulfate ions inhibits the oxidative corrosion of shale by generating secondary ore and inhibiting the oxidation reaction of pyrite. [Conclusion]Therefore, in the future, in the process of shale gas oxidative fracturing, it is necessary to investigate the water chemical parameters of the exploitation formation in advance, and select the oxidation liquid and mining mode according to temperature, pH and cation ions. In chemical oxidation infiltration technology, there are still some problems, such as O2 doping in natural gas caused by H2O2 decomposition, which needs further research.
Calculation method of reasonable well spacing in sandstone geothermal reservoir based on production-reinjection equilibrium simulation
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230268
(Objective) In order to achieve the goal of sustainable development and utilization of geothermal energy, it is necessary to clarify the production-reinjection well spacing under different reinjection quantities and reinjection temperatures. (Methods) Therefore, taking the thermal reservoir of Guantao Formation in northern Shandong as the research object, the conceptual model and mathematical model of layered thermal reservoir development are established. COMSOL Multiphysics multi-field coupling simulation software was used to establish a geothermal production-reinjection well spacing calculator. The accuracy of the model is verified by parameter fitting and simulation results. (Results) Then, based on the software APP compilation function, guided by the use of ordinary users, the relevant parameter input is simplified, and the APP for geothermal production-reinjection well spacing calculator is established. Different from the previous studies, which only gave the production-reinjection well spacing, in order to meet the actual production needs, the corresponding reasonable production-reinjection well spacing was calculated under different conditions. The calculation results show that when the exploitation quantities are 40m3/h, 60m3/h,80m3/h and 100m3/h,the reasonable production-reinjection well spacing without thermal breakthrough is 290m, 330m, 360m and 390m respectively.(Conclusion) It is concluded that: In the layered conductive sandstone thermal reservoir area of northern Shandong, after the conceptual model is simplified, the numerical simulation results are reliable, and the geothermal production-reinjection well spacing calculator can be established in this area. Hydrothermal numerical simulation is a powerful means to calculate the reasonable production-reinjection well spacing. It can determine the key parameters of geothermal development and utilization projects, such as exploitation quantity, recharge quantity, injection temperature and production-reinjection well spacing, which is conducive to the sustainable development and utilization of geothermal resources.
Landslide Disaster Vulnerability Mapping Study in Henan Province: Comparison of Different Machine Learning Models
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230338
Henan Province has a complex geomorphological type and faces the challenge of frequent landslide disasters. Therefore, efficient and accurate landslide susceptibility mapping (LSM) has great significance to local governments and residents. [Objective] However, in the study of LSM, how to choose the suitable machine learning model for Henan landslide disaster data set to improve the evaluation accuracy still needs further investigation. [Methods] The research focuses on Henan Province, where landslide data is collected and compiled into a landslide disaster database. Using the recursive feature elimination method, 11 factors with the highest relative impact on landslides (slope, elevation, plan curvature, profile curvature, land cover, lithology, soil type, precipitation, road density, river density, fault density) are selected and integrated into a spatial dataset. Then, the models of multilayer perceptron (MLP) neural network , random forest, extreme gradient boosting, and support vector machine were trained, and the performances of the models were evaluated using the receiver operating characteristic curve and the area under the curve (AUC). In the end, we create high precision landslide susceptibility zoning map. [Results] The research results indicate that the MLP model has the strongest adaptability to the landslide disaster dataset in Henan Province, achieving the highest AUC of 0.95. In comparison to SVM, XGBoost, and RF models, the MLP model predicts the smallest proportion of landslide disasters in highly susceptible areas, thus more accurately defining high-risk regions for potential landslide disasters. The predicted extremely high and high susceptibility areas are mainly distributed in the western mountainous and hilly areas of Henan Province, where terrain factors play a dominant role in the development of landslide disasters. [Conclusion] The results can provide a reference for the evaluation of landslide susceptibility with high accuracy in large-scale regions.
Genetic mechanism of low resistance in shale analyzed by triaxial compression test
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230533
【Objective】The gas shale of Wufeng-Longmaxi Formation in the southern Sichuan Basin shows the low-resistance anomaly in multiple areas. Statistical analysis reveals that the low-resistivity zone (<10 Ω·m) in the Wufeng-Longmaxi shale is spatially associated with tectonic faults. To reveal the coupling mechanism between shale resistivity and tectonic fault, 【Methods】this paper determined the petrological and geochemical characteristics of the outcrop samples obtained from the Wufenglongmaxi shale of Southern Sichuan Basin through analyses of thin-section identification, X-ray diffraction, laser Raman spectroscopy, whole-rock asphalt reflectance, and conventional physical property. Subsequently, the characteristics of shale resistivity change during the deformation were revealed using the triaxial compression tests. The impact of the fracture system generation and the conductive fluid intrusion on low-resistance shale was also clarified.【Results】The results show that the resistivity of shale samples, primarily composed of uniform clay minerals, pyrite, and organic matter with high thermal maturity, significantly decreased after being saturated with various salinity brines. There is a positive correlation between the reduction of resistivity (95.07%-98.70%) and the brine salinity. After reaching the limit of compressive strength, the resistivity of brine-saturated samples generally experienced a further resistivity decrease of 5.7 Ω·m to 25.7 Ω·m (with an average value of 13.3 Ω·m). This decrease maintained a linearly positive correlation with the resistivity observed after cracking.【Conclusion】The intrusion of conductive fluid and the generation of the fracture system in shale were the primary controlling factors for shale resistivity reduction, and the resistivity after cracking was governed by both the intruded brine salinity and the fracture density. This research elucidates and supplements the influence mechanism of tectonic fault zones on shale resistivity, enriching the theoretical framework for understanding the genesis of low-resistivity shale, and holds significant implications for exploration and development of low-resistivity shale formations.
Experimental study of the freeze-thaw resistance of MICP-treated soil
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230462
[Objective] Microbially induced carbonate precipitation (MICP) method is a potentially effective and environmentally friendly technique to improve the unfavorable soil conditions. MICP treatment can improve soil strength. However, the durability of MICP-treated soil under freeze-thaw cycles has not been investigated. [Methods] This study investigates the effects of freeze-thaw cycles on unconfined compressive strength, erosion resistance, and water retention capacity of soil which treated with MICP under different conditions. The surface of the specimens was treated using the spray method, and then some specimens were subjected to erosion tests. Unconfined compressive strength (UCS) and water evaporation rate of the specimens under different freeze-thaw cycles were tested. Combining the mechanism of soil resistance to erosion damage and the test results of specimens under freeze-thaw cycles, the reasons for the deterioration of reinforced soil properties due to freeze-thaw cycles are investigated. [Results] The results show that the UCS of the sample has increased from 43.83kPa to 69.92kPa after MICP-treated. After 20 freeze-thaw cycles, the UCS of the MICP-treated sample is 1.48 times that of the uncured sample, and the erosion amount of the MICP-treated sample is much less than half of that of the uncured sample. The results indicate that the microbially induced calcium carbonate deposits can effectively fill the internal pores of the soil and bind the loose soil particles, thus significantly improving the soil strength and effectively weakening the damaging effect of freeze-thaw on the soil. [Conclusion] Although the consolidation effect of the soil gradually deteriorated due to the increase of the freeze-thaw cycle, the MICP-treated soil still had high strength under the short-term freeze-thaw environment and could effectively resist the erosion effect of rainwater.
Study on the spatial characteristics and genetic mechanism of geothermal resources in Zhangye Basin by multi-source fusion modeling and heat-flow coupling simulation
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230590
Abstract: The traditional temperature and pressure field analysis approach, which is based on the interpolation of existing borehole data, cannot accurately represent the seepage-heat transfer coupling process of geothermal resources, resulting in insufficient understanding of the genetic mechanism of geothermal resources. First, a high-precision three-dimensional geological model of Zhangye Basin is built by combining multi-source data including borehole information, geophysical information and elevation data. Compared with the traditional interpolation model, multi-source data fusion modeling can improve the accuracy of inter-hole strata by 50-300 m. The numerical simulation of basin seepage-heat transfer field coupling process is carried out. The results show that the multi-field coupling analysis more reasonable represents the temperature and pressure characteristics of the reservoir than the key point spatial interpolation approach. The geothermal water in the study area flows from southeast to northwest and supplies the reservoir via faults. The geothermal field totally heats it during the seepage process. The temperature field is high in the basin center and low around it, with the central temperature reaching 78℃. The water head is greater towards the southeast of the basin's center and progressively drops to the northeast. Finally, a 3D geothermal conceptual model is developed to explain the genetic mechanism of geothermal resources in terms of structural, hydrogeological, and geothermal geological perspectives. This 3D conceptual mode coupling with heat-flow transfer modeling more specifically explain the spatial distribution and reveal more clearly the underlying mechanism of forming the geothermal resources compared with conventional 2D model.
Optimized negative sampling strategies of gradient boosting decision tree and random forest for evaluating Wenchuan coseismic landslides susceptibility mapping
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230037
Strong earthquake-induced landslides have the characteristics of a large number, wide distribution, and large scale, which seriously threaten the safety of people's lives and property. Landslide susceptibility mapping (LSM) can quickly predict the spatial prone-area distribution, which is of great significance for reducing risky disasters post-earthquakes. However, in the study of co-seismic landslide LSM, how to select the landslide negative samples and integrated machine learning model to improve the evaluation accuracy still needs further investigation. In this research, the landslides induced by the Wenchuan Earthquake were selected as a case study in mountainous areas. Firstly, 10 landslide influencing factors such as topography, geological environment, and seismic parameters were selected to analyze the landslide spatial distribution; secondly, collinearity analysis was used to test data redundancy. Non-negative sample points of sampling strategies were randomly selected at the extremely low susceptible regions by frequency ratio method (FR). Finally, Gradient Boosting Decision Tree (GBDT), Random Forest (RF), and their optimal models were used to map the co-seismic landslides susceptibility, conduct a comparative study of the models and carry out the accuracy assessment. The results show that: ①The landslide spatial distribution is controlled by multi-level factors; ②the accuracy of the models is FR-RF (AUC=0. 943) > FR-GBDT (AUC=0. 926) > RF (AUC=0. 901) > GBDT (AUC=0. 856). Selecting the landslide-negative samples at low-prone areas could significantly improve the LSM accuracy, and the research results can provide a reference for selecting landslide-negative samples and constructing the evaluation models, as well as for providing theoretical support for disaster prevention and mitigation of post-earthquake.
Formation and Evolution Mechanism of Jiangdingya Ancient Landslide and Stability Evaluation of Accumulation Body
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230076
Abstract: The resurrection of ancient landslide accumulations is one of the main types of geological disasters in the Qinghai-Tibet Plateau in China, and it is also one of the main security threats faced by major traffic and water conservancy projects under construction in western China. Therefore, it is extremely important to study the formation and evolution mechanism of ancient landslide and evaluate the stability of their accumulations, which can provide theoretical support for the early identification and prevention design of the revival of ancient landslide accumulations. In the past ten years, the accumulation of ancient landslide in Jiangdingya, Zhouqu County, Gansu Province, has been partially revived several times, forming landslides to block the Bailongjiang River, posing a serious threat to the safety of local people's lives and property. In this paper, the morphological and structural characteristics of the ancient landslide accumulation of Jiangdingya were identified through on-site investigation and UAV oblique photography, and the evolutionary mechanism and dynamic process of the landslide were analyzed on this basis, and the stability of the accumulation was qualitatively evaluated by combining the inSAR deformation data. According to the results, the ancient landslide of Jiangdingya is a typical large-scale seismic landslide, and the sliding mass slides down in three directions, forming a multi-step accumulation body form today. Under seismic loading, the dynamic process of landslides can be divided into the middle and upper shock-pulling stages, leading edge locking section shearing-landslide starting, trailing edge pulling-sliding body acceleration, leading edge obstruction-sliding body deceleration, and stability stage. Due to the overall decline of the ancient landslide under the seismic load, a large number of rock masses with complete structure exist in the upper accumulation body, so it is relatively stable. Most of the middle and lower accumulations are weak structures composed of fault fracture zones and broken rock masses, which have poor stability and are very likely to be revived in the future.
Micro-continuum approach in reactive transport modeling
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230081
Fluid-solid interactions in reactive transport processes, controlled by physical and chemical heterogeneities, govern the evolution of geomaterials in the subsurface, resulting in nonlinear behaviors and multiscale features. It has become increasingly evident that the investigation of the feedback between microscopic features and macroscopic behaviors in geomaterials is critical in many academic and industrial applications. While providing important insights, the continuum scale modeling or pore-scale modeling suffers from a gap between theoretical understanding and
Tectonic evolution and prototype basins Reconstruction in the Jimsar and Jinan depressions, Eastern Junggar Basin
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230095
Since 2020, with the in-depth research of the Shuangji structure belt in the Jimsar depression of the Junggar Basin, and the high-yield oil flow obtained from the Triassic Jingjingzigou Formation in the Sa Tan 1 well, it has been demonstrated that the Jimsar depression and Jinan depression have good potential for conventional oil and gas exploration. In order to further study the geological characteristics and exploration potential of the Jimsar and Jinan depressions, this paper comprehensively analyzes data from core samples, logging, well logging, and seismic surveys, identifies regional unconformities, divides different tectonic stages, and establishes the relationship between tectonic and stratigraphic evolution. Based on this, the development process of each stratum is restored, the coupling relationship between tectonic and the evolution of the uplift and depression within the research area is established, and the prototype basin is restored. The study shows that there are five large unconformities in the Jimsar and Jinan depressions, which have undergone four tectonic activities. The stratigraphic evolution characteristics of the study area have developed from "north high and south low" in the early Permian to "south high and north low" in the Paleogene and Neogene. The original basin also changed from the "multi-convex and multi-concave" pattern in the early Permian to the "few convex and large concave" structural pattern in the Paleogene and Neogene. The establishment of the coupling relationship between tectonic and the evolution of the uplift and depression at different times and the restoration of the prototype basin at each period lays an important foundation for clarifying the basin characteristics of the Jimsar and Jinan depressions at different periods and helps to deepen oil and gas exploration in these areas.
Formation time and fluid source of calcite veins of Triassic Qinglong Formation in Huangqiao area, Subei Basin
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230099
Calcite veins in the reservoir record crucial information about fluid activity, which has important indicator for hydrocarbon accumulation process. A multi approaches consisting of thin section observation, cathodoluminescence, U-Pb isotope dating, REE, C, O and Sr isotopes of calcite veins from the Triassic Qinglong carbonate reservoirs in Huangqiao area of Subei Basin is used to analyze the source of calcite vein forming fluid. Four stages of calcite veins were successively formed at 115.30±0.42 Ma, 97.03±0.43 Ma, 85.29±0.25 Ma and 45.5±19.0 Ma, respectively. The first and second stage of calcite veins were derived from deep hydrothermal fluids and the mixed fluids of atmospheric fresh water and seawater respectively. The vein-forming fluid of the third stage of calcite veins was the mixed fluid of the same stratum water and deep shell source hydrothermal fluid. The fourth stage of calcite veins was derived from the same layer water mixed with the deep mantle-derived hydrothermal fluid. The formation time of the four stages of the Triassic Qinglong Formation carbonate reservoir in the Huangqiao area of Subei Basin corresponds to the sub-tectonic activities at different periods, which implies that fluid evolution was controlled by multi stages of tectonic movements. Importantly, three stages of deep hydrothermal fluid in the reservoir is the result of deep fault opening caused by tectonic activities, indicating multi-stages of oil and gas charges in the Qinglong Formation of the Triassic in the Huangqiao area.
Prediction model of joint roughness coefficient based on Gaussian process regression
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230113
The joint roughness coefficient (JRC) estimation may produce a sufficiently unreliable result, due to limitation of single statistical parameter method for characterizing morphology. A model based on Gaussian process regression (GPR) combined with principal component analysis (PCA) was proposed for the quantitative evaluation of JRC. Notably, eight parameters were selected as indicators for the comprehensive expression of the rock joint roughness. In order to analyze the model’s performance, 112 published rock joint profiles were used as the database, of which 95 were chosen as training database and 17 as validation database. The reliability of the model was verified by comparing the predicted results with the measured data. Results show that the derived GPR model demonstrates promising performance (R^2=0.972, MSE=0.517) for estimating JRC, reflecting the high applicability for multi-parameter JRC prediction even when the number of training dataset is small. In general, the GPR model may provide a new way of thinking about estimating JRC values with artificially intelligent.
Control of tectonic evolution on karstification and karst collapse in Lianzhou Basin, northwestern Guangdong Province
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230120
There is still a lack of systematic understanding of the evolution process of Lianzhou Basin since the Mesozoic and its response to karstic development law (Objective). Based on the comprehensive analysis of the latest field geological investigation, hydrogeological drilling, dissolution experiment, and three-dimensional geological modeling, the tectonic evolution stages of the basin can be divided and karstification of each stage is discussed by considering the existing geological data (Methods). Before the Cretaceous, carbonate rocks with strong dissolution were successively deposited under the rise or fall movement of the crust, which laid a material foundation for karstic development. The Indosinian movement caused vertical multilayered strata to form an EW-trending structure, and Yanshanian movement made the straddle-oblique superimposed NE-SW-trending structure. They controlled the geological structures, spatial distribution characteristics, and dissolution behaviors of carbonate rocks, the distribution of mountains and water systems was established. However, karst was generally not developed. Intracontinental and intermountain faulted confluence lake basin was formed from the Cretaceous to Paleogene, the slow crustal uplift strengthened the karstification around the basin, and it retains the early karst platform now. Later, they were buried-filled-consolidated by alluvial deposits, therefore, karst basically stopped developing, generating a thick-covered red strata basin. Since the Neogene, the rapid uplift of crust leads to the continuous elevation of mountains around the basin, deepening of rivers, and strong development of karst, shaping multilevel karst platforms. When part of Cretaceous red strata in the basin are denuded or cut through, the karstification is reactivated. After many changes and penetrations of water systems, the Quaternary shallow covered karst fault basin is formed (Results). Tectonic evolution controls karstic development, karstification influences internal structure of the basin, soil structure breeds karst ground collapse (Conclusion). This study can provide a scientific basis and guidance for comprehension of karst collapse conditions in covered karst areas.
Study on Fractal Characteristics of Displacement and Cracks of Baishuihe Landslide in the Three Gorges Reservoir Area
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230166
The surface displacement and fracture development are the most intuitive manifestation of landslide deformation and evolution. Therefore, it is of great practical significance to reveal the characteristics and evolution stages of landslide deformation and fail-ure through displacement monitoring data and surface fracture development. In this paper, Baishuihe landslide in the Three Gorges Reservoir area is selected as the research object, and the monitoring data of 2003-2016 are systematically collected and analyzed. The monitoring data of ZG93 and ZG118 are selected. Firstly, the fractal parameter Hurst index R/S analysis is carried out for the displacement data. Secondly, the multi fractal dimension calculation and research are carried out for the displacement of the two monitoring points at the time interval of each year. Finally, the theory of stage matching of landslide cracks is intro-duced, and the fracture fractal dimension of Baishuihe landslide is calculated. The results show that there is a certain positive correlation between the landslide displacement sequence, and the fractal dimension H index of the two monitoring points is greater than 0.5. The evolution process of Baishuihe landslide can be divided into steady deformation state (June 2003 June 2007 June 2007), accelerated deformation state (June 2007 December 2009), and steady deformation state (December 2009 December 2015). According to the matching law of fracture stages, the development of the landslide is still in I stage, i.e. initial deformation stage.
Study on energy dissipation of red bed soft rock collapse in Shengzhou-Xinchang area, Zhejiang Province
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230174
Taking red-bed soft rock in Shengzhou-Xinchang area of Zhejiang Province as the research object, The surface energy characteristics of red bed soft rock collapse in this area were investigated, based on the principle of energy dissipation, by analyzing the energy conversion, transfer and dissipation of three groups of different compositions of red-bed soft rock in the process of disintegration under the action of wet and dry cycling, the law of energy conversion from absorbed energy to surface energy during the process of disintegration of red-bed soft rock was obtained. The results show that with the increasing number of wet and dry cycles, the cumulative increase of surface energy of red bed soft rocks in this area has three different processes, with a gentle increase at the beginning. In the middle stage, the surface energy increases sharply and the growth rate becomes faster and faster. The cumulative increase of surface energy gradually maintained a stable state in the late disintegration period. The experiment also shows that the higher the clay mineral content is, the more surface energy is generated and the worse the disintegration resistance is. The energy dissipation model proposed in this paper provides reference value for treating various red bed soft rock problems in Shengzhou-Xinchang area of Zhejiang Province.
A comparative study of kriging and deep learning methods for groundwater level estimation - A case study of Shenshan special cooperation zone
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230192
The knowledge of regional groundwater level distribution is an important foundation for groundwater resource evaluation and environmental protection. Due to the limited groundwater level data observed at regional scale, kriging interpolation and deep learning methods are gradually used for regional groundwater level prediction, but their applicability and robustness lack comparative analysis. In this paper, spatial interpolation of groundwater levels in Shenshan special cooperation zone was carried out using ordinary kriging, cokriging and deep learning methods to explore the potential of the three methods in the practical application of regional groundwater level predictions. In order to investigate the effect of the training set sample size on the prediction effect of the three methods, 239 monitoring wells were divided into two groups of 76 and 163 wells for the training of the three models, respectively. The results showed that the cokriging, which considered surface elevations, was significantly better than the ordinary kriging and deep learning in regional groundwater levels predictions, when the training sample size was 76. When the training sample size was increased to 163, the prediction accuracies of ordinary kriging, cokriging, and deep learning were significantly improved. The RMSEs of the three methods on the validation dataset differed very little, but the spatial distribution characteristics of the predicted regional groundwater levels still differed significantly among the methods. In summary, when the observed data are sparse, the prediction accuracy of cokriging incorporating surface elevation is significantly higher than that of ordinary kriging and deep learning. However, the prediction accuracies of the three methods are close to each other, when the observed data are dense.
Seasonal variations of groundwater discharge and associated nutrient fluxes in Changhu Lake
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230205
To reveal the contribution and seasonal variation of groundwater discharge to lake water and nutrients budgets, this study investigated Changhu Lake in the middle reaches of the Yangtze River. Field sampling was conducted during both wet and dry seasons using multiple tracing techniques, including electrical conductivity (EC), stable isotopes (2H and 18O), hydrochemical elements (Ca2+ and Mg2+), and 222Rn isotopes. The 222Rn mass balance model was employed to quantify LGD and associated nutrient fluxes in different seasons. Our results show that LGD rate during the wet and dry seasons was 64.52 mm/d and 14.95 mm/d respectively, with a significant difference between these seasons. Furthermore, during the wet and dry seasons, groundwater carried TN inputs of approximately 25.68×106 g/d and 5.58×106 g/d, respectively. While TP inputs were approximately 8.14×106 g/d and 0.17×106 g/d in wet and dry seasons, respectively. Differences in LGD rate between the wet and dry seasons elucidated the variation in TN and TP input flux carried by groundwater, and the input of TP during the wet season was also influenced by agricultural activities during this season. The greater precipitation and evaporation experienced during the wet season drove higher LGD intensity and increased TN and TP fluxes. Overall, our study provides important theoretical insights that can inform water resources management and aquatic ecosystem preservation efforts in the Changhu area.
Effect of sedimentary environment on salt migration ability of ancient brine in coastal plain of Laizhou Bay
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230307
The coastal sedimentary environment serves as the fundamental basis for comprehending the evolution and movement of groundwater. To gain a comprehensive understanding of the distribution and mobility of brackish groundwater in the southern coast of Laizhou Bay, two archetypal Quaternary boreholes (LZ01 and LZ02) were sampled, and porewater was extracted through mechanical squeezing, and the grain size composition of sediments and the Cl- content of porewater were determined. Both boreholes are dominated by fine-grained sediments with an average particle size of 5.5φ.By examining the characteristics of sediment lithology and grain size parameters, it was discovered that LZ01 and LZ02 boreholes contained 10 and 9 alternating sedimentary facies, respectively, indicating three sets of marine stratigraphic units since the late Pleistocene period. The porewater was found to be predominantly composed of brine (saline) water, with the Cl- profile displaying three peaks corresponding to the three sets of marine stratigraphic units. These results demonstrate the presence of residual marine ancient brine water in the sediment and its permeation into neighboring sediments. In the study, it was observed that the hydraulic index of sedimentary water exhibited a clear zonal pattern, with the vertical change rate of Cl- serving as a crucial indicator. Notably, under moderate hydraulic conditions, Cl- displayed a robust diffusion and migration capability in pore water, as confirmed by sensitive particle size analysis. The dominant particle size range for pore water migration was found to be between 45.61-111.47μm. Additionally, the distribution of brine was controlled by ancient marine invasion events, while low permeability and lithology played a crucial role in sealing the ancient brine. Overall, these research findings provide a strong theoretical foundation for comprehending the genesis, salinization, and transportation of brine in the Laizhou Bay coastal plain.
Research on intelligent identification method of shale lithology based on deep coupling of logging curves
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230361
【Objective】The Wufeng-Longmaxi formations in the Yuxi Block of the Sichuan Basin are typical shale gas reservoirs in China. The strong interbedded heterogeneity of these formations leads to a significant amount of redundancy in the collected logging curve information and complex coupling relationships between curves, resulting in the difficulty and low accuracy of lithofacies identification using traditional methods, which urgently needs technical innovation. 【Methods】In this study, based on lithofacies classification and analysis, an intelligent lithofacies identification method combining Principal Component Analysis (PCA) and Random Forest algorithm was developed. 【Results】The research findings are as follows: Firstly, by optimizing the logging curves using PCA, the deep coupling of logging curves can be achieved, thereby reducing the impact of factors such as redundancy of logging information and complex coupling relationships between curves on lithofacies identification, resulting in more scientifically effective data information. Secondly, by adding minor variations to the original data without altering its lithofacies, data augmentation can be achieved, addressing to some extent the problem of poor generalization ability and stability of the model caused by small or imbalanced datasets when using the Random Forest algorithm. Finally, the intelligent lithofacies identification method constructed by combining PCA and Random Forest algorithm achieved an identification accuracy of over 83%, demonstrating its high precision and strong applicability. 【Conclusion】This method not only overcomes the difficulties in lithofacies identification in the study area to a certain extent but also greatly improves the efficiency of lithofacies identification, which is of great significance for promoting the economic and efficient development of shale gas in the study area.
Ore-bearing discrimination of granite rock mass in Nanling area based on data-driven
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230363
As an important participant in mineralization, the study of granite is helpful to understand the geochemical process of tungsten-tin mineralization and distinguish the ore-bearing property of rock mass. In this paper, the data of major elements and rare earth elements of tungsten-bearing granite, tungsten-tin-bearing granite and non-ore-bearing granite in Nanling area are collected, a total of 466 sets of data of 42 rock masses. The geochemical characteristics of the three types of rock masses are summarized and compared.The relationship between ore-bearing properties and geochemical characteristics of rock mass is explored from the perspective of data-driven and machine learning. The restricted Boltzmann machine is used to train the auto-encoder neural network to eliminate the dimensional difference between major elements and rare earth elements, and the intermediate features are extracted. Then the intermediate features are input into random forest and multi-layer BP neural network to establish AE-RF and AE-BP rock mass ore-bearing classification models. The importance of classification characteristics is output by random forest. The results show that the evolution degree of tungsten-bearing granite is slightly higher, followed by tungsten-tin-bearing granite, and the ore-free granite is the lowest.Both models have high accuracy ( > 90 % ) on the test set, and the practical application effect of the AE-BP model on the blind test set is better. Six groups of rock masses were randomly selected as the blind test set. Among the 21 rock masses, the correct rate of 13 rock masses was greater than 80 %, the correct rate of two rock masses was greater than 70 % less than 80 %, and the correct rate of two rock masses was greater than 50 % less than 70 %. There are four rock mass accuracy is less than 50 %. Major elements such as iron, manganese, phosphorus, calcium and magnesium and light and heavy rare earth elements are important features to distinguish the three types of rock masses. The similarity of geochemical characteristics and the difference of tungsten-tin deposit types will lead to the wrong classification of the model, and it is pointed out that the Beitou rock mass has certain metallogenic potential. The main elements such as iron, manganese, phosphorus, calcium and magnesium determine whether the rock mass can contain ore, while light rare earth is an important index to distinguish tungsten-bearing rock mass and tungsten-tin-bearing rock mass. It is believed that the degree of differentiation and evolution of magma determines whether the rock mass can contain ore, and the addition of mantle-derived materials is to distinguish whether the rock mass contains tungsten or tungsten-tin.
An improved method in oil and gas resource assessment—acquiring the coefficient of resource scale variation (k) and its application case
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230371
Reservoir size sequential analysis is based on Pareto principle. The key and the difficulty is acquiring the value of coefficient as ‘k’ which describes the gradient in variation of resource scale, which restricts the effectiveness of corresponding method. Through calculating ratio of the scales of the discovered resources and applying the possible sequential number, a specific optimized methodology is proposed. It mainly includes establishing the cross plot with the axes of sequential number and k according to the calculated ratio, searching and locating the combination of data points from different ratio which can form an approximately straight and vertical line against the k axis, and acquiring the value in the k axis for the intersection as a solution of k. The principles in optimizing and determining the result after acquiring the solution set to satisfy the need in resource assessment are furtherly suggested. From the re-analysis about the classic data set from open published academic literature, it presents that applying related method can effectively acquire the value of such coefficient (k). An actual application about tight gas contained in reservoir as 6th group of Jurrasic Shaximiao formation in Yanting block of Jinqiu gas-producing area located in the center part of Sichuan Basin is also provided as further support. The linear relevant fitting result is favorable between forecast outcome and actual data. The calculated result of resource scale of this case is consistent with current recognition from tight gas exploration in Sichuan Basin. This methodology is with serval advancements, which includes low dependency on geological experience, no demand in setting analytic step size or complicated determinant and matrix manipulation. The subjectivity and calculative complexity in deciding the key parameters are effectively reduced. Corresponding algorithm is achieved to be coded as computer program. The efficiency is accordingly promoted. It can be helpful in further application of reservoir size sequential method.
A Study on the Threshold Model of Landslide Rainfall in Chongqing Based on Different Geological Environment Zones
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230375
Considering the rainfall characteristics and geological environment of historical landslides in the region, it is important to construct a reasonable rainfall threshold model for the prediction and prediction of regional landslide disasters. In this paper, 1368 rain-induced landslides in Chongqing from 2013 to 2021 were selected as the research objects. Based on detailed landslide cataloging data and regional geological environment data, rainfall events were divided and landslide sample database was constructed. Based on Random forest (RF) algorithm, a rainfall threshold model of the day's triggered rainfall - previous effective rainfall (Rd-Rp) was established, and different warning levels were divided based on probability classification. Based on the medium early warning probability, 19 threshold criterions of critical rainfall were constructed according to four geological environments, namely disaster pregnant environment, engineering rock group, land use and soil type. The results show that the Rd Rp threshold model can well reflect the impact of the daily excitation rainfall and the early effective rainfall on the landslide development, and the early effective rainfall plays a leading role in the landslide induction. Different geological environment types have different sensitivity to rainfall factors, and tectonics, engineering properties of rock and soil mass, vegetation coverage and soil properties have important effects on landslide development. The threshold of rock formations mainly composed of hard rocks is higher than that of rock formations mainly composed of soft rocks, and the threshold of forest land is higher than that of cultivated land. The threshold of areas severely damaged by human engineering activities will decrease. The study can provide new ideas and reference for the meteorological early warning management of rainfall landslides in Chongqing.
Exploring the feasibility and influencing factors of phosphorus recovery as struvite from phosphorus-rich groundwater
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230379
ABSTRACT: Phosphorus (P) supply shortage and aquatic P contamination are both emerging as serious crises around the world. Struvite precipitation is the most cost-effective method of P recovery and has been applied to a wide range of sewage resources. However, P recovery as struvite from P-rich groundwater has not been explored properly yet. This study explored the feasibility and influencing factors of P recovery as struvite from groundwater rich in P, Ca, Fe, and fulvic acid (FA). Synthetic and natural groundwater were analyzed by X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The results showed that a high concentration of Ca can significantly inhibit the formation of struvite. Effects of Fe and FA on struvite formation were relatively weak than Ca. The coupling of factors further exacerbated the inhibition of struvite formation. Notably, struvite precipitation obtained after the coupling of three factors was the most similar to the precipitation obtained from actual groundwater. This indicated that the coupling of three factors determines if struvite would be effectively precipitated in groundwater. This study identified the factors and mechanisms that hinder the recovery of P from groundwater through struvite precipitation. The findings of this study would be helpful in developing the strategies of P recovery from P-rich groundwater. KEYWORDS: Struvite; Phosphorus Recovery; Groundwater; Calcium; Iron
Rock fracture detection and identification in outcrop area based on improved YOLOv7
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230425
[Objective]The detection of rock fractures in the outcrop area is of great significance for the geological exploration of fractured oil and gas reservoirs, but the traditional image processing algorithm is not effective for the detection of rock fractures, the classical depth learning model is characterized by high complexity, slow convergence and detection speed, and low detection accuracy for rock fractures with complex geological background, therefore, this paper presents an improved outcrop rock fracture detection algorithm YOLOv7-PCN. [Methods]Firstly, PConv (Partial Convolution) Convolution module is used to replace the standard Convolution in the backbone network, resulting in reduced computational complexity and improved detection speed. Moreover, the integration of the Coordinate Attention (CA) mechanism further improves the feature extraction capability, especially for capturing key information from critical fracture locations. Finally, the bounding box regression loss function is measured by NWD (Normalized Wasserstein Distance), which optimizes the training convergence rate of the network, the location and detection accuracy of small target fracture with lower resolution in complex environment is improved. At the same time, in data processing, A dataset of rock fractures in outcrop areas is created using data augmentation techniques to enhance the generalization capability of the network model. [Results]Experimental findings reveal an impressive average accuracy of 82.5%, surpassing the original YOLOv7 algorithm by 7.7%. Furthermore, the model's parameters are significantly reduced by 29.6%, resulting in a 31.2% reduction in computational workload. Additionally, the model's detection speed is impressively improved by 39.2%, which proves the effectiveness of the improved algorithm model. [Conclusion]The proposed enhanced YOLOv7 algorithm for rock fracture detection in this paper integrates the strengths of traditional convolutional neural network models with advanced deep learning-based target detection models, with fewer parameters and reduced computation. As a result, it achieves a higher level of accuracy in detecting rock fractures even in challenging and complex environments. The algorithm successfully meets the requirements for both accuracy and real-time performance in rock fracture detection tasks.
Transfer learning and its application in solid Earth geoscience
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230429
As geoscience enters the era of big data, machine learning has become an emerging tool that can discover and describe complex structures and patterns of data, and is rapidly applied in the field of solid Earth geoscience. As an important subfield of machine learning, deep learning gradually learns massive amounts of data by constructing multi-level hidden layers, which can improve classification or prediction performance. However, most of machine learning models require massive amounts of data as support, which limits their widespread applications in the field of solid Earth geosciences. Transfer learning is a type of machine learning methods in the absence of adequate data, which aims to improve the performance of new tasks by using pre-trained knowledge of similar tasks in advance. By using the knowledge learned from the source domain and transferring it to the target domain, it can to some extent overcome insufficient data availability. This paper provides a brief overview of the basic concepts and categories of transfer learning, discusses the challenges faced by existing transfer learning approaches applied to geoscience by analyzing the typical cases of transfer learning in solid Earth geosciences. At present, deep transfer learning approaches have initially shown great potential in automatic identification and classification of rocks and minerals, identification of geochemical anomalies, etc. With the advantage of improving model generalization performance and avoiding overfitting, deep transfer learning approaches have broad application prospects in the field of solid Earth geosciences.
Research on characterization model for equivalent hydraulic aperture of nonmatching fracture based on MIC
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230443
Equivalent hydraulic aperture can quantitatively characterize the hydraulic conductivity of rough fractures under Darcy flow conditions, accurately predicting the equivalent hydraulic aperture is of great importance for many practical engineering applications. [Objective]The equivalent hydraulic aperture of rough fractures is influenced by complex geometric features such as wall surface topography and aperture distribution. This study comprehensively consider the geometric information of fractures, use the maximal information coefficient (MIC) method to determine the key controlling factors of the equivalent hydraulic aperture, and establish a characterization model for the equivalent hydraulic aperture of rough fractures based on these key factors. [Methods]First, based on the Barton's 10 standard curves, 900 sets of nonmatching rough fractures were constructed, the geometric information of the wall was used to obtain 13 geometric parameters and the equivalent hydraulic apertures of all fractures were obtained through direct numerical simulations. Then, the maximal information coefficient method was employed to analyze the correlation between the equivalent hydraulic aperture and 13 geometric parameters, [Results]as a result, 4 major controlling factors were identified, based on these factors, a characterization model for the equivalent hydraulic aperture of rough fractures was established. [Conclusion]Based on the data of 900 rough fractures, two existing models for representing the equivalent hydraulic aperture were selected for comparative analysis, the analysis results showed that the hydraulic aperture model proposed in this study exhibited better characterization performance compared to the existing models. Finally, the study investigated the influence of size effects on establishing an equivalent hydraulic aperture representation model, and discussed the methods of extending the research of this paper to three-dimensional fractures.
Mechanism of CO2/N2 stripping shale oil based on molecular dynamics simulation
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230456
Abstract:[Objective]The aim of this research is to investigate the storage state of tight oil and the mechanism of its replacement by CO2 using molecular dynamics simulations.[Methods]The Monte Carlo method and molecular dynamics simulation algorithms were employed to model the storage state of alkanes of varying molecular weights on rock surfaces. These models helped to examine the storage characteristics of alkane molecules on different types of rock surfaces and to analyze the micro-mechanisms of tight oil replacement by CO2 and N2. The simulated temperature and pressure conditions were selected to tight reservoir in the Sichuan basin (343.13K, 20MPa).[Results]The measured diffusion coefficients of C7 in CO2 were 1.88×10-5 and 1.83×10-5 on quartz and calcite surfaces, respectively. In contrast, the coefficients were lower in N2, at 6.4×10-6 and 9.01×10-6, respectively.[Conclusion]The findings indicate that CO2 is significantly more effective than N2 in replacing tight oil. The difficulty of displacing alkane molecules from rock surfaces increases with the relative molecular weight. As the relative molecular weight increases, it becomes more challenging to displace alkane molecules from the rock surface, and the adsorption of alkane molecules on the calcite surface is stronger than on the quartz surface. Based on the experimental results presented in this paper, the CO2 replacement mechanism can be broadly categorized into four stages: molecular diffusion, competitive adsorption, emulsification and dissolution, and a mixed-phase stage (involving low molecular weight alkanes).
Risk assessment of landslide geological hazards under different rainfall conditions based on P-III curve
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230472
[Objective] Rainfall is one of the important factors that induce geological disasters such as landslides and collapses, posing a great threat to the safety of people's lives and property. Therefore, it is necessary to take effective prevention and control measures as well as to avoid and relocate. [Methods] This article takes Yezhi Town as the study area, the grid unit is used as the evaluation unit. 9 evaluation factors including elevation, land use type, slope, aspect, elevation, landform type, engineering geological rock group, land use type, distance from river, distance from fault, curvature were selected. Using Pearson correlation analysis, the correlation between the 9 factors is weak, can participate in subsequent calculations. The Random Forest algorithm was used to analyze the feature importance of 9 factors, based on the feature importance, obtain a weighted information model that combines subjective and objective factors, using this model as a susceptibility evaluation for collapses and landslides. Then select rainfall as the risk assessment factor. Predicting the rainfall of the study area once in 10 years, once in 20 years, once in 50 years, once in 100 years through calculation and P-III curve, and import the data into ArcGIS, utilizing the raster calculator function, four different rainfall conditions were obtained. Then superimposing the rainfall conditions and the susceptibility assessment model to obtain the risk assessment. [Results] According to the statistics, he susceptibility assessment results are divided into four levels using the natural discontinuity method: low, medium, high, and extremely high susceptibility areas, which occupied 32.8%, 34.02%, 21.96% and 11.22% of the study area respectively. ROC curve was used to verify the accuracy, and the AUC value was 89.2%, falling into a better range. The risk assessment results of the four rainfall conditions were divided into four grades according to a certain range: low, medium, high and extremely high risk zones. The results of geological hazard risk assessment under different rainfall conditions is determined. [Conclusion] By comparing with the actual investigation, the landslide and collapse risk assessment results under different rainfall conditions are highly consistent with the actual situation. This article can provide a basis for reasonable disaster prevention and mitigation, as well as risk avoidance and relocation. Subsequently, a comparative analysis will be conducted on the selection of evaluation units to select the most suitable evaluation unit for the study area. I will also apply InSAR to identify hidden danger points of geological disasters in high altitude areas that are difficult for people to reach in the study area, and apply hidden danger point data to the susceptibility evaluation and risk assessment system.
Reservoir characteristics and exploration potential of Paleogene shale oil in the Ganchaigou area, Western Qaidam Basin
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230493
The Well C902 achieved a major breakthrough in the exploration of Paleogene shale oil by obtaining high production oil flow in the Ganchaigou area, Western Qaidam Basin. However, problems such as unclear evaluation criteria and resource potential of Paleogene shale oil restrict the efficient development of shale oil in the Ganchaigou area. Based on exploration results of Well C902 and other wells, the exploration potential of Paleogene shale oil in the Ganchaigou area is evaluated comprehensively by using the lithology, physical property, pore structure and hydrocarbon generation potential of shale oil. The results show that lithofacies types of shale oil reservoirs include lamellar limestone, lamellar limestone, lamellar limestone, lamellar clay shale and lamellar mudstone. Carbonate rock has obvious mixed characteristics, and the proportion of brittle minerals ranges of 60 ~ 90%, showing good compressibility. The average porosity and permeability are 5.1% and 0.24mD, respectively, indicating the low-porosity and ultra-low permeability reservoirs. The reservoir space is dominated by intergranular pores, solution pores, laminar fractures and microfractures, and the proportion of intergranular pores and laminar fractures is up to 85%. The average value of TOC is more than 0.9%. The chloroform asphalt "A" and S1+S2 jointly indicate that the hydrocarbon generation potential is high. The organic matter type is mainly Ⅰ-Ⅱ1 type. Combined with Ro values, Paleogene shale oil is in the peak period of oil generation. The Ⅳ ~ Ⅵ layers of upper member of Xiaganchaigou Formation are widely developed and have the characteristics of good source rock quality, porosity and fracture development and integration of source and reservoir, which is conducive to the nearby preservation of shale oil after formation. Second, the overlying salt rock is also widely developed and has good sealing, contributing to generating overpressure and improving oil and gas recovery after fracturing. Therefore, the Paleogene shale oil in the Ganchaigou area has great exploration potential.
The newly identified iron oxide-apatite deposit in the Beishan area and its implication for regional metallogeny: a case study of Biyushan deposit, Inner Mongolia
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230559
Numerous iron deposits hosted in Carboniferous marine volcanic rocks have developed in the Beishan Orogenic Belt, eastern Tianshan. Biyushan iron deposit is a typical iron deposit hosted in Carboniferous marine volcanic rocks. This deposit is located at the northwestern margin of Inner Mongolia. Our preliminary work has revealed that iron ores in the Biyushan deposit commonly have the mineral assemblage of magnetite-apatite, with apatite having abundant monazite inclusions due to the dissolution-reprecipitation processes. In addition, magnetite grains commonly have high Ti content with ilmenite exsolution. Thus, the mineral assemblage of iron ores and mineralogical features of apatite and magnetite are similar to the typical Kiruna-type deposits. Based on our preliminary analysis of the geological characteristics, we suggest the Biyushan iron deposit in Inner Mongolia is likely a Kiruna-type iron deposit hosted in submarine volcanic rocks which have not yet been documented before. Therefore, this finding can provide guidance for future exploration of iron oxide-apatite deposits in this region.
Landslide Susceptibility Assessment in the Alpine and Canyon Areas based on Ascending and Descending InSAR data
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230560
[Objective]In recent years, Interferometric Synthetic Aperture Radar (InSAR) data reflecting surface deformation factors have gradually been introduced into landslide susceptibility assessment as factors reflecting surface deformation. However, these studies did not consider differences in SAR images. Especially in the alpine and canyon area, the imaging effect of InSAR ascending and descending varies greatly, and there is a large error in the response to surface deformation. [Methods]In this paper, the reservoir area of Xiangbiling Hydropower Station was selected as the research area. After the correlation analysis of index factors, 11 inducing factors and InSAR deformation data related to landslide in alpine and canyon areas were selected for landslide susceptibility evaluation. [Results]Comparing whether to use deformation data and using different deformation data, it is found that supplementing the sparse ascending data of sampling points in the susceptibility evaluation will reduce the accuracy of susceptibility evaluation, and the descending SAR data with more sampling points can improve the susceptibility accuracy by 2.7% to a certain extent (AUC=0.9248).[Conclusion]Therefore, the introduction of InSAR deformation data as a factor in landslide susceptibility assessment will affect the evaluation results, and it is necessary to select appropriate InSAR deformation data to improve the accuracy of susceptibility evaluation.
Study on spatial distribution of earthquake-induced landslide in densely populated area of the Luding 9.5 earthquake
, Available online  , doi: 10.19509/j.cnki.dzkq.tb20230619
On September 5, 2022, an earthquake with Ms6.8 occurred in Luding County, Ganzi, Sichuan Province, causing heavy casualties and economic and property losses. Because the earthquake-stricken areas are mostly mountainous and canyon landforms and dense vegetation, it is difficult to investigate geological disasters on the artificial ground, and it is difficult to accurately identify the landslide boundary under high vegetation coverage by satellite images. Therefore, in order to deeply understand the spatial distribution characteristics of this earthquake-induced landslide, this paper provides a visual interpretation of the coseismic landslide based on the 0.2m resolution optical image (DOM) obtained after the earthquake, and then the boundary of the coseismic landslide under the vegetation layer is corrected by using the digital elevation model (DEM) with a resolution of 0.5m, at the same time, the potential earthquake landslide under the vegetation layer is interpreted, combined with the field investigation, 9248 landslides induced by this earthquake are finally obtained, with a total area of about 45.57km2. On this basis, the relationship between the geological background such as topography, geological structure and seismic factors and the distribution of coseismic landslides is analyzed, aiming at providing an important basis for the investigation of hidden dangers of geological disasters in disaster areas, disaster assessment and site selection for post-disaster resettlement, as well as providing an important foundation and guarantee for post-disaster reconstruction and geological disaster prevention.