关键词: 苏里格气田, 国际合作区, 开发效果, 关键技术, 重要启示

Abstract: In order to identify the differential development mechanism and distribution law of reservoirs in the Middle Permian Maokou Formation in Zigong area in Sichuan Basin, reservoir types and main controlling factors are comprehensively analyzed by using abundant wireline logging, mud logging, core samples and well testing data. The study results show that there are two main reservoir types in the study area, i.e., limestone and dolomite. The dolomite reservoirs were mainly developed in the second member (Mao 2) and the fourth member (Mao 4) of Maokou Formation, with a single layer thickness of over ten to tens of centimeters, and generally developed at the top of upward shallowing sedimentary sequence. Laterally, the dolomite reservoir in Mao 2 member is mainly distributed in Weiyuan-Zigong-Fushun area and that in Mao 4 member mainly in Guanyinchang-Qinggangping area. The limestone reservoirs show a large variation in thickness and strong heterogeneity, which are distributed in Mao 2-Mao 4 members vertically, and the paleo highland or slope zone of the depositional or weathering crust karst geomorphology laterally. The further analysis shows that the formation of dolomite reservoirs was related to evaporation concentration-reflux infiltration dolomitization and short-term karst exposure driven by high-frequency sea level drop, and the limited evaporative seawater environment was intensified in the study area by the relative slope break during the depositional period and overlapping migration of beach bodies; The genesis of limestone reservoirs was classified into types, i.e., beach controlled early diagenetic karst, weathering crust karst and fault dissolution reconstruction, which were controlled by slope break, highland or slope of karst landform and fault, respectively. It is concluded that the highly heterogeneous and multi-genetic reservoirs in Maokou Formation were jointly controlled by “four-paleo” factors, namely, paleo geomorphology during the depositional period, paleo environment, paleo weathering crust karst geomorphology, and paleo faults. The favorable reservoirs are distributed along the “circum-slope highland”. The exploration orientation in the near future includes the stereoscopic exploration of multi-layer and multi-type reservoirs in Zigong-Fushun area in the northeast and the large-scale dolomite reservoirs in Guanyinchang-Qinggangping area in the southwest.