塔里木盆地库车坳陷断层相关褶皱对裂缝发育的控制

裂缝预测一直是石油地质界研究的热点和难点,其中对裂缝发育的主控因素及机制仍未清晰认识。库车坳陷中的断层相关褶皱在多期演化过程中,派生或伴生大量的构造裂缝,空间分布十分复杂。以克深气田、大北气田、迪那气田和克拉气田为例,结合区域构造背景,从野外露头、岩心观察和成像测井分析入手,对单井裂缝进行详细的统计分析。通过构造形迹分析和岩石声发射测试,恢复古构造应力场,划分裂缝发育期次。以断层相关褶皱理论为指导,选取库车河野外剖面,以有限元数值模拟为手段,恢复各褶皱的构造演化过程,对比分析共生裂缝的发育规律及形成机制。最终,建立了库车坳陷断层相关褶皱区共生裂缝系统演化地质模式,并评价了优势裂缝发育带,如克深-大北气田为典型的顶部冲起型褶皱共生裂缝模式,迪那-克拉气田为典型的顶部地堑型共生裂缝模式,为库车坳陷山前冲断带的高效勘探部署和老油气田综合治理提供有效指导。

Control of fault-related folds on fracture development in Kuqa Depression,Tarim Basin

The fracture prediction has always been one of the hotspots and difficulties in the petroleum geology study,and the key reason lies in the ambiguous understanding on the main controlling factors and mechanisms of fracture development.In the multi-stage evolution process,a large number of structural fractures,complicated in spatial distribution,were induced from or associated with the fault-related folds in the Kuqa Depression.The study takes the Keshen,Dabei,Dina and Kela gas fields as examples,and makes a detailed statistical analysis of fractures in a single well via outcrop and core observation and imaging logging analysis combined with the regional tectonic setting.The fracture development stages are determined and the paleo-tectonic stress field is restored by structural trace analysis and rock acoustic emission test.Guided by the fault-related fold theories,we select the Kuqa river outcrop to restore the tectonic evolution process of each fold,and compare and analyze the development pattern and formation mechanisms of paragenetic fractures through finite element numerical simulation.Finally,the evolutionary geological model of the paragenetic fracture system in the relevant folded region of Kuqa Depression is established through "dynamic and static analyses",and the dominant fracture deve-lopment zone is assessed.The results show that the Keshen-Dabei gas field is in a typical pattern of paragenetic fractures with folds of top pop-up type,and the Dina-Kela gas field is in a typical paragenetic fracture pattern of top-graben type,both of which provide effective guidance for efficient exploration well emplacement of the piedmont thrust belt in Kuqa Depression and comprehensive management of old oil/gas fields.