Sedimentary and reservoir characteristics of Late Pliocene deep-water depositional units in Rakhine Basin in the Bay of Bengal
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摘要:
近年来, 孟加拉湾北部若开盆地新生界沉积地层内不断取得深水油气勘探发现。本研究基于高分辨率3D地震反射资料, 在若开盆地上上新统沉积地层内识别出水道、天然堤、朵体(决口扇、含分支水道朵体)、半深海泥、块体搬运沉积体等多种深水沉积单元。结合钻井的测井、岩屑样品结果, 进一步确认了水道、天然堤、朵体沉积单元, 并针对过井沉积体开展沉积储层特征及勘探潜力的分析和对比研究, 获取了储层级别及其平面分布范围。由于若开盆地上新世以来沉积地层整体埋藏较浅, 压实作用较弱且成岩作用程度低, 水道、天然堤和朵体均可能为若开盆地中新统-上新统生物气的主力勘探烃藏提供储集空间。其中, 蜿蜒型紧密叠置浊积水道是尤其具有厚沉积、强连通、广展布、高砂地比和高孔隙系数的优质深水油气储集类型。研究成果可为深水油气勘探提供重要指导和启示。
Abstract:Significance In recent years, notable discoveries in deep-water oil and gas exploration have emerged in the Rakhine Basin, located in the northern Bay of Bengal.
Methods In this study, high-resolution 3D seismic data from the Rakhine Basin were used to identify deep-water sedimentary architectural elements, including channels, levees, lobate fans (such as crevasse-splay lobes and distributary channel-lobe complexes), hemipelagic mud, and mass-transport deposits. Alongside drilling logs and sampling results, the reservoir characteristics and exploration potential of channels, levees, and lobes in the wells were further analyzed, and the reservoir hierarchy and spatial distribution were determined.
Results Notably, the Rakhine Basin is characterized by relatively shallow burial depths, weak compaction, and minimal diagnostic alteration since the Pliocene, positioning channels, levees, and lobate fansas potential exploration targets for shallow biogenic gas. In particular, meandering stacked channels emerge as a high-quality reservoir type due to their thick sediment accumulation, strong connectivity, widespread distribution, and elevated high sand content and porosity.
Conclusion The research findings can provide important guidance and insights for deep-water oil and gas exploration.
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Key words:
- Bengal Fan /
- Rakhine Basin /
- deep-water sedimentary architectural element /
- channel /
- levee /
- lobate fan /
- reservoir characteristic
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图 2 若开盆地年代地层格架及NA、EK井震标定结果
(钻孔位置见图 1b, 下同)
Figure 2. Age-stratigraphic framework of the Rakhine Basin and the seismic calibration results for wells NA and EK
图 3 过NA井(a)和EK井(b)地震剖面深水沉积单元解释及测井GR、岩性特征
①NA井上上新统深度2 820~2 830 m处朵体沉积镜下薄片照片; ②NA井上上新统深度2 940~2 950 m处朵体沉积镜下薄片照片; ③EK井上上新统深度2 960~2 970 m处水道沉积镜下薄片照片; ④EK井上上新统深度3 020~3 030 m处天然堤沉积镜下薄片照片。Q.石英; Pl.长石; Mus.白云母; Clay.黏土矿物
Figure 3. Deep-water sedimentary architectural elements identified on seismic profiles, along withith log GR, lithological characteristics across the NA well (a)and EK well (b)
图 4 沉积结构单元RGB分频属性图(a, b)及其沉积相解释与平面位置分布图(c, d)
Figure 4. RGB spectral decomposition attribute maps(a, b) of sedimentary architectural elements with deposition faces detailed, and planar position distribution(c, d)
图 5 水道的地震剖面与RGB属性特征
a.水道垂向位置, 图中编号ⓑ~ⓔ分别对应b~e图水道垂向位置; b.曲流型孤立水道; c.顺直型孤立水道；d.蜿蜒型孤立水道; e.蜿蜒型紧密叠置水道(带点坝); f.曲流型松散叠置水道；白色线为右侧剖面测线；下同
Figure 5. Seismic profiles and RGB attribute maps of channels
图 6 小型(a)和大型(b)天然堤的地震剖面与RGB属性特征
Figure 6. Seismic profiles and RGB attribute maps of small-scale (a) and large-scale (b) levees
图 7 主水道边缘(a)和决口水道末端(b)决口扇的地震剖面与RGB属性特征
Figure 7. Seismic profiles and RGB attribute maps of crevasse-splay lobes adjacent to the main channel margin(a) and the end of the crevasse channel(b)
图 8 含分支水道朵体的地震剖面与RGB属性特征
(a.工区西部；b.工区中部)
Figure 8. Seismic profiles and RGB attribute maps of distributary channel lobes
图 9 块体搬运沉积体的地震剖面与RGB属性特征
Figure 9. Seismic profiles and RGB attribute maps of mass transport deposits
图 10 NA井、EK井及两井平均砂地比、孔隙度柱状图
Figure 10. Column charts displaying the sand thickness-to-stratum thickness ratio and porosity for the NA well, EK well, and the average of both wells
图 12 上上新统下段(早期)(a)和上段(晚期)(b)不同储层级别分布范围
Figure 12. Distributions of various reservoir grades in the lower (a) and upper (b) sections of the Upper Pliocene strata
表 1 若开盆地上上新世水道几何形态参数统计
Table 1. Geometric morphology parameters of channels from the Late Pliocene strata in Rakhine Basin
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表 2 3种深水沉积单元砂地比与孔隙度统计
Table 2. Summary of the sand/all ratios and porosities of the three deep-water sedimentary architectural elements
沉积单元 编号 亚类 埋深/m 砂地比/% 孔隙度/% 水道 NAC① 曲流型松散叠置水道 3 013~3 090 37.12 22.10 NAC② 曲流型松散叠置水道 2 869~2 890 96.26 31.36 NAC③ 曲流型孤立水道 2 575~2 806 40.07 24.90 EKC① 蜿蜒型紧密叠置水道 3 123~3 180 91.05 27.20 EKC② 曲流型松散叠置水道 2 914~2 963 36.89 12.64 天然堤 NALe 小型天然堤 2 530~2 575 50.38 25.69 EKLe 小型天然堤 2 963~3 034 31.89 11.26 朵体 NALo① 含分支水道朵体 2 943~3 013 22.61 20.79 NALo② 含分支水道朵体 2 806~2 869 29.53 21.95 EKLo 主水道边缘决口扇 3 034~3 076 37.94 14.65
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[1] CURRAY J R, EMMEL F J, MOORE D G. The Bengal Fan: Morphology, geometry, stratigraphy, history and processes[J]. Marine and Petroleum Geology, 2002, 19(10): 1191-1223. doi: 10.1016/S0264-8172(03)00035-7 [2] REILLY B T, BERGMANN F, WEBER M E, et al. Middle to Late Pleistocene evolution of the Bengal Fan: Integrating core and seismic observations for chronostratigraphic modeling of the IODP expedition 354 8° north transect[J]. Geochemistry, Geophysics, Geosystems, 2020, 21(4): e2019GC008878. doi: 10.1029/2019GC008878 [3] ALI S, HATHORNE E C, FRANK M. Persistent provenance of South Asian monsoon-induced silicate weathering over the past 27 million years[J]. Paleoceanography and Paleoclimatology, 2021, 36(3): e2020PA003909. doi: 10.1029/2020PA003909 [4] POLISSAR P J, UNO K T, PHELPS S R, et al. Hydrologic changes drove the Late Miocene expansion of C4 grasslands on the northern Indian subcontinent[J]. Paleoceanography and Paleoclimatology, 2021, 36(4): e2020PA004108. doi: 10.1029/2020PA004108 [5] KHAN A A. Geological evolution and the hydrocarbon potentiality of the Bay of Bengal[J]. BMJ, 2021, 5(1): 127-140. [6] CURRAY J R. The Bengal depositional system: From rift to orogeny[J]. Marine Geology, 2014, 352: 59-69. doi: 10.1016/j.margeo.2014.02.001 [7] WEBER M E, REILLY B T. Hemipelagic and turbiditic deposits constrain lower Bengal Fan depositional history through Pleistocene climate, monsoon, and sea level transitions[J]. Quaternary Science Reviews, 2018, 199: 159-173. doi: 10.1016/j.quascirev.2018.09.027 [8] BERGMANN F, SCHWENK T, SPIESS V, et al. Middle to Late Pleistocene architecture and stratigraphy of the lower Bengal Fan: Integrating multichannel seismic data and IODP expedition 354 results[J]. Geochemistry, Geophysics, Geosystems, 2020, 21(1): e2019GC008702. doi: 10.1029/2019GC008702 [9] HUBSCHER C, SPIESS V, BREITZKE M, et al. The youngest channel-levee system of the Bengal Fan: Results from digital sediment echosounder data[J]. Marine Geology, 1997, 141(1/4): 125-145. [10] KOLLA V, BANDYOPADHYAY A, GUPTA P, et al. Morphology and internal structure of a recent upper Bengal Fan-valley complex[C]//PRATHER B E, DEPTUCK M E, MOHRIG D, et al. Application of the principles of seismic geomorphology to continental-slope and base-of-slope systems: Case studies from seafloor and near-seafloor analogues. [S. l. ]: SEPM (Society for Sedimentary Geology), 2012: 347-369. [11] FAUQUEMBERGUE K, FOURNIER L, ZARAGOSI S, et al. Factors controlling frequency of turbidites in the Bengal Fan during the last 248 kyr cal BP: Clues from a presently inactive channel[J]. Marine Geology, 2019, 415: 105965. doi: 10.1016/j.margeo.2019.105965 [12] BLUM M, ROGERS K, GLEASON J, et al. Allogenic and autogenic signals in the stratigraphic record of the deep-sea Bengal Fan[J]. Scientific Reports, 2018, 8(1): 7973. doi: 10.1038/s41598-018-25819-5 [13] QI K, GONG C L, STEEL R J, et al. The formation and development of avulsions and splays of submarine channel systems: Insights from 3D seismic data from the northeastern Bengal Fan[J]. Sedimentary Geology, 2022, 440: 106239. doi: 10.1016/j.sedgeo.2022.106239 [14] RANGIN C, SIBUET J C. Structure of the northern Bay of Bengal offshore Bangladesh: Evidences from new multi-channel seismic data[J]. Marine and Petroleum Geology, 2017, 84: 64-75. doi: 10.1016/j.marpetgeo.2017.03.020 [15] YANG S Y, KIM J W. Pliocene basin-floor fan sedimentation in the Bay of Bengal (offshore northwest Myanmar)[J]. Marine and Petroleum Geology, 2014, 49: 45-58. doi: 10.1016/j.marpetgeo.2013.09.007 [16] WANG M, CHEONG D. Reconstruction of burial history and analysis of the hydrocarbon potential using sedimentary modeling the middle Bengal Fan, Myanmar[J]. Geosciences Journal, 2016, 20(6): 813-825. doi: 10.1007/s12303-016-0015-z [17] MA H X, FAN G Z, SHAO D L, et al. Deep-water depositional architecture and sedimentary evolution in the Rakhine Basin, Northeast Bay of Bengal[J]. Petroleum Science, 2020, 17(3): 598-614. doi: 10.1007/s12182-020-00442-0 [18] 马贵明, 马宏霞, 邵大力, 等. 孟加拉湾若开盆地深水沉积体系结构单元类型及演化模式[J]. 海相油气地质, 2016, 21(1): 41-51.MA G M, MA H X, SHAO D L, et al. Structural units and evolution model of deepwater depositional system in Rakhine Basin, Bay of Bengal[J]. Marine Origin Petroleum Geology, 2016, 21(1): 41-51. (in Chinese with English abstract) [19] 丁梁波, 王海强, 张颖, 等. 孟加拉湾东北部缅甸若开海域深水生物气成藏条件及油气勘探方向[J]. 地质论评, 2020, 66(增刊1): 71-72.DING L B, WANG H Q, ZHANG Y, et al. Geologic conditions of biogenic gas accumulation and exploration direction in Rakhine offshore, NE Bengal Bay[J]. Geological Review, 2020, 66(S1): 71-72. (in Chinese with English abstract) [20] COLIN C, TURPIN L, BERTAUX J, et al. Erosional history of the Himalayan and Burman ranges during the last two glacial-interglacial cycles[J]. Earth and Planetary Science Letters, 1999, 171(4): 647-660. doi: 10.1016/S0012-821X(99)00184-3 [21] KHIN K, SAKAI T, ZAW K. Neogene syn-tectonic sedimentation in the eastern margin of Arakan-Bengal basins, and its implications on for the Indian-Asian collision in western Myanmar[J]. Gondwana Research, 2014, 26(1): 89-111. doi: 10.1016/j.gr.2013.04.012 [22] CHEN C J, NORTON G J, PRICE A H. Genome-wide association mapping for salt tolerance of rice seedlings grown in hydroponic and soil systems using the Bengal and Assam aus panel[J]. Frontiers in Plant Science, 2020, 11: 576479. doi: 10.3389/fpls.2020.576479 [23] NAJMAN Y, BICKLE M, BOUDAGHER-FADEL M, et al. The Paleogene record of Himalayan erosion: Bengal Basin, Bangladesh[J]. Earth and Planetary Science Letters, 2008, 273(1/2): 1-14. [24] CURRAY J R. Sediment volume and mass beneath the Bay of Bengal[J]. Earth and Planetary Science Letters, 1994, 125(1/4): 371-383. [25] WEBER M E, WIEDICKE-HOMBACH M, KUDRASS H R, et al. Bengal Fan sediment transport activity and response to climate forcing inferred from sediment physical properties[J]. Sedimentary Geology, 2003, 155(3/4): 361-381. [26] 党亚云. 莺歌海盆地东方区黄流组一段海底扇地震沉积学研究[J]. 地质科技通报, 2023, 42(6): 118-128. doi: 10.19509/j.cnki.dzkq.tb20220208DANG Y Y. Seismic sedimentology of submarine fan system in the 1st Member of the Huangliu Formation, Dongfang area, Yinggehai Basin, China[J]. Bulletin of Geological Science and Technology, 2023, 42(6): 118-128. (in Chinese with English abstract) doi: 10.19509/j.cnki.dzkq.tb20220208 [27] 苏海霞, 刘姗, 张莉, 等. 南海南部北康盆地晚中新世以来深水沉积单元时空分布特征及其控制因素[J]. 地质科技通报, 2023, 42(6): 129-139. doi: 10.19509/j.cnki.dzkq.tb20220126SU H X, LIU S, ZHANG L, et al. Spatiotemporal distribution characteristics and controlling factors of deep-water sediments in the Beikang Basin since the Late Miocene, southern South China Sea[J]. Bulletin of Geological Science and Technology, 2023, 42(6): 129-139. (in Chinese with English abstract) doi: 10.19509/j.cnki.dzkq.tb20220126 [28] PICKERING K T, HISCOTT R N, Deep marine systems: Processes, deposits, environments, tectonics and sedimentation[J]. Agu Earth Science, 2015. [29] ZHOU L H, SUN Z H, TANG G, et al. Pliocene hyperpycnal flow and its sedimentary pattern in D block of Rakhine Basin in Bay of Bengal[J]. Petroleum Exploration and Development, 2020, 47(2): 318-330. doi: 10.1016/S1876-3804(20)60049-0 [30] LU Y T, SHI B Q, LUAN X W, et al. Fine-grained deep-water turbidite gas reservoirs in upper Bengal Fan[J]. Marine and Petroleum Geology, 2023, 158: 106547. doi: 10.1016/j.marpetgeo.2023.106547 -
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