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
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摘要: 摘要:【目的】库车坳陷博孜地区在8000m以深仍发育优质储层且高产工业气流,但其巴什基奇克组致密砂岩储层物性平面上存在着明显的差异。为明确此类储层发育的特征,降低深层-超深层油气勘探的风险。【方法】基于测录井、铸体薄片、高压压汞及PVT相图等实验分析结果,探讨了致密砂岩储层特征及物性差异成因。【结果】研究结果表明:博孜地区巴什基奇克组储层岩石类型为中-细粒岩屑长石砂岩和长石岩屑砂岩,碳酸盐胶结物含量平面分布差异大;中-细粒砂岩储层原始孔隙度介于32.4~38.1%,颗粒间压实强度相似,以点-线接触为主;南部储层平均孔隙度为8.6%,平均渗透率为3.4mD;中部储层平均孔隙度为6.53%,平均渗透率为0.65mD;北部储层平均孔隙度为4.9%,平均渗透率为0.62mD;南部储集空间以原生粒间孔为主,北部和中部以残余粒间孔和溶蚀孔隙为主;南部较北部和中部储层孔喉结构更好。【结论】博孜地区砂岩储层物性受沉积、成岩和构造作用(裂缝)共同控制,其中碳酸盐胶结是后期储层物性改造的主要因素。超压、烃类流体充注及裂缝发育影响了碳酸盐胶结,进而造成储层物性差异。超压较强,油气充注时间较早及裂缝充填较低导致博孜南部储层物性好于北部与中部。
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关键词:
- 关键词:深层-超深层 /
- 致密砂岩储层 /
- 物性差异成因 /
- 博孜地区 /
- 库车坳陷
Abstract: 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.
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