塔中隆起中-下奥陶统岩溶水文地貌条件及控储机制

塔里木盆地塔中隆起中-下奥陶统古岩溶储层是深层碳酸盐岩油气勘探的重点目标。基于地震数据分析和地震属性提取,对塔中隆起的岩溶古地貌和古水文结构进行了精细刻画;通过钻井和成像测井对比、岩心和岩石学薄片观察,揭示了古岩溶储层空间分布的差异性;探讨了水文地貌条件对储层发育的控制作用。研究结果表明：①塔中隆起的中央主垒带位于古地形平坦的岩溶高地,发育以裂隙-扩散流为代表的流场结构;北斜坡带位于地势相对陡的岩溶斜坡,有利于形成顺层-径流的水流样式。②中央主垒带储层以裂缝-孔洞系统为主,为表层岩溶带的产物,其平面分布受控于NE和NWW向断裂;北斜坡带发育规模不一的孤立洞穴和多层溶蚀孔洞,其岩溶垂向结构相对完整。③由于水文地貌条件的差异,中央主垒带和北斜坡带分别形成了"裂隙-渗流"和"顺层-径流"表生岩溶储层发育模式,为储层预测提供了理论依据。

Hydrogeomorphological condition and its control mechanism on Mid-Lower Ordovician paleo-karst reservoirs,Tazhong uplift

Mid-Lower Ordovician paleo-karst reservoirs in the Tazhong uplift of Tarim Basin are the key targets of hydrocarbon exploration in deep-buried carbonate. Based on seismic volume analysis and seismic attribute extraction, the karst paleo-geomorphology and paleo-hydrological architecture of the Tazhong uplift were precisely delineated. Moreover, the variation in the spatial distribution of paleo-karst reservoirs was revealed by a correlation cross section of drilling and imaging logging, and core and thin-section petrological observations. Then the control effect of hydrogeomorphologic conditions on reservoir development was investigated in this study. The research results indicate that the central horst belt of the Tazhong uplift is located in karst highland with gentle paleo-terrain, where the flow field structure represented by fracture and diffuse flow is developed; the north-slope zone is located in karst slope with relatively steep terrain, which is beneficial for the formation of stratiform-runoff flow pattern. The reservoirs in the central horst zone are dominated by fissure-vug system produced in the epikarst zone, showing planar distribution controlled by NE and NWW-trending faults; the multi-layered corrosion vugs and isolated caves with different scales are developed in the north slope zone, showing a complete karst vertical structure. Because of the differences in hydrogeomorphologic conditions, the development patterns of "fissure-seepage" and "stratiform-runoff" epigenic karst reservoirs were established in the central horst zone and north slope zone respectively, providing theoretical references for reservoir prediction.