裂缝发育对超深层致密砂岩储层的改造作用——以塔里木盆地库车坳陷克深气田为例

doi:10.11743/ogg20180108

摘要/Abstract

摘要： 塔里木盆地库车坳陷是“西气东输”的主力气源地之一，克深气田区白垩系巴什基奇克组是库车山前的主力产气层段，埋深超过6 000 m，储层基质渗透率低，普遍小于0.1×10^-3 μm²。裂缝发育可以显著改善储层渗透率，分析、量化裂缝发育特征，预测裂缝渗透率空间分布规律是该区天然气开发的关键问题。利用钻井取心、FMI成像、碳氧同位素年代学分析与露头区全息激光扫描裂缝建模，结合CT扫描定量分析、扫描电镜、阴极发光、激光共聚焦显微镜、高压压汞以及电子探针显微镜等实验分析方法，从静态定性到动态定量分析了裂缝发育对该区储层储集性的改造作用。克深气田构造裂缝以半充填剪切缝为主，有效开启度为0.2～1.5 mm。主要发育3期构造裂缝，不同期次裂缝受控于构造应力，以不同的排列方式分布在不同构造位置。裂缝孔隙度整体小于0.1%，但可提升储层渗透率1～3个数量级，纵向上不整合面下方150 m以内发育裂缝改造的高渗流储层。早期和中期裂缝成为致密储层成岩胶结的通道，不利于连通孔喉的保存；晚期裂缝发育伴随油气充注期，对储层基质孔喉有溶蚀扩大的改造作用；微裂缝对储层孔喉沟通具有一定的选择性及局限性，仅沟通其开度10~100倍范围内的孔喉。总之，晚期形成的裂缝网络为储层的高渗流区，是气田高产的关键。

关键词: 超深层, 裂缝, 储层, 致密砂岩, 库车坳陷, 塔里木盆地

Abstract: Kuqa Depression in Tarim Basin is one of the major gas sources for the west-east national gas transmission project.The Lower CretaceousBashijiqike Formation in the Keshen gas field is the major pay zone with a burial depth exceeding 6 000 m and low matrix porosity and permeability (<0.1×10^-3 μm²).Fractures can tremendously improve the permeability of reservoirs.Therefore, a thorough analysis and quantitative description of fracture growth and accurate prediction of the spatial distribution pattern of fracture permeability of the Formation are critical to natural gas development in the study area.Methods including drilling and coring, FMI imaging, carbon oxygen isotopic chronological analyses, fracture modeling through holograhic laser scanning of outcropwere combined with experimental analysis procedures such as CT scanning, SEM, cathode luminescence, laser scanning confocal microscope, high pressure mercury injection and electron microprobe to study both qualitativelyand quantitativelythe enhancement ofreservoir propertiesof the Formation by fractures.The fractures in the gas field aredominated by half-filled shear fractures with an effective opening ranging between 0.1 and 1.5 nm.There arethree stages of structural fractures developed in the Formation, and the fractures of each stage line up in different patterns at different structural locationsunder the control of structural stress.The fractures have a general porosity of less than 0.1%, but they caneffectively improve the permeability of the reservoirs by 1 to 3 orders of magnitude and result inthe formation of high-permeability reservoirs 150 m below the unconformity face.Fractures formed during early and middle stages served as pathways of fluids for tight reservoir diagenesis and cementation, unfavorable for the preservation of connective pores and throats.Those formed during later stage were accompanied by oil and gas charging processes and enlarged pore throats in reservoir matrix through dissolution.Micro-fractures had limited effect upon the connectivity of pores and throats in the reservoirs (only effectively connecting pore-throats with aperture between 10 to 100 times).In summary, fracture network formed during the late stage is the key to high productivity of the gas field.

Key words: ultra-deep layer, fracture, reservoir, tight sandstone, Kuqa Depression, Tarim Basin

中图分类号:

TE121.2

王俊鹏,张惠良,张荣虎,等. 裂缝发育对超深层致密砂岩储层的改造作用——以塔里木盆地库车坳陷克深气田为例[J]. 石油与天然气地质, 2018, 39(1): 77-88. doi: 10.11743/ogg20180108 Wang Junpeng,Zhang Huiliang,Zhang Ronghu,et al. Enhancement of ultra-deep tight sandstone reservoir quality by fractures: a case study of Keshen gas field in Kuqa Depression, Tarim Basin[J]. Oil & Gas Geology, 2018, 39(1): 77-88. doi: 10.11743/ogg20180108

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