断裂对塔北地区哈拉哈塘油田奥陶系非暴露岩溶缝洞型储集层的控制作用

Fault controlling on non-exposed karst fracture-vug reservoirs of the Ordovician in Halahatang Oilfield,northern Tarim Basin

塔里木盆地海相碳酸盐岩缝洞型储集层形成机理复杂,非均质性极强。当前以塔河油田为代表的潜山风化壳缝洞型储集层是碳酸盐岩地层暴露地表受到大气淡水淋滤所形成的,而在塔北地区哈拉哈塘油田奥陶系发育的非暴露区仍存在大量非暴露岩溶缝洞型储集层。在充分认识该油田区域构造背景的基础上,选取油田非暴露区典型区块,应用岩石学、地球化学等资料,对非暴露岩溶缝洞型储集层进行研究。研究认为：（1）大气淡水是非暴露区岩溶作用最关键的岩溶流体,岩溶储集层的形成并不受热液影响;（2）非暴露区存在＂三期三级＂构造缝和＂两期三级＂走滑断裂,断裂及伴生构造裂缝是非暴露区岩溶缝洞型储集层发育的必要条件;（3）从断裂对岩溶的控制出发将缝洞型储集层细分为早期断裂和明河双控洞穴、晚期断控洞穴、早期裂缝孔洞和晚期微裂缝孔洞4类;（4）非暴露区非暴露缝洞型储集层先后经历了加里东中期断裂发育、良里塔格组水系下切溶蚀、晚加里东—早海西期断裂发育3个主要过程。此研究深化了非暴露缝洞型储集层的形成机理,并在一定程度上拓宽了非暴露区岩溶储集层勘探开发的思路。

The carbonate fracture-vug reservoirs of marine facies in Tarim Basin have complicated evolutionary mechanism and extremely high heterogeneity. Fracture-vug reservoirs in weathering crust of buried hills in the typical region of Tahe Oilfield is originated from carbonatic rocks which underwent meteoricwater when they were lifted up to the ground. But a large number of non-exposed karst fracture-cug reservoirs exist in non-exposed district where the Ordovician is complete in Halahatang Oilfield,northern Tarim Basin. Based on ananlysis of reginal geological background,selecting the typical oilfield wellblock,utilizing the petrological and geochemical data,the analysis of non-exposed karst fracture-vug reservoirs was carried out,and we concluded that：（ 1） Meteoric water is the key karst fluid in non-exposed district,and the hydrothermal fluid have no influence on the formation of the karst reservoirs.（ 2） There exists structural fractures of two periods and three levels,and strike-slip faults of three periods and two levels in non-exposed district,and the faults and associated structure fracture is the necessary conditions for the development of karst fracture-vug reservoirs.（ 3） The fracture-vug reservoirs can be divided into four types,including caves controlled by faults and rivers in early phase,caves controlled by faults in late phase,fracture-vug in early stage and micro fracture-vug in late stage.（ 4） The development of non-exposed karst fracture-vug reservoirs includes three stages in sequence,including faults forming in the mid-Caledonian,river system incision and dissolution during the depositional period of Lianglitage Formation,faults forming in late Caledonian-early Hercynian. The study made a deeper understanding of fracture-vug reservoir＇s formation mechanism and broadened the thought in exploration and production in fracture-vug reservoir.