川中—川南过渡带非背斜油气藏主要地质特征

THE MAIN GEOLOGICAL CHARACTERISTICS OF NON-ANTICLINAL OIL AND GAS POOL OF THE TRANSITIONAL ZONE IN CENTRAL-SOUTH SICHUAN

本文对区内主要储层(震旦系灯影组—下侏罗统大安寨组)和非背斜油气藏主要类型(古风化缝洞型、裂缝型、晶孔-裂缝型、生物礁或生物滩型、溶孔-裂缝型、粒孔-裂缝型等)作了阐述,对油气形成特点作了探讨。根据地震资料的特殊处理剖面,结合已有钻井资料等,认为本区为四川盆地油气重要远景区之一。油气分布虽较分散,但具点多、层多的特点。区内油气分布可分为北、中、南三个含油气区。

The transitional zone is one part of Chuanzhong (middle Sichuan basin) uplifted belt (antekles), being an important prospecting area of oil-gas pool in Sichuan basin. The main reservoirs are Dengying formation, Sinian system; middleupper Cambrian; lower-middle Ordovician; middle Carboniferous; Qixia formation and Maokou formation, lower Permian; Changxing formation, upper permian; Jialingjiang formation, lower Triassic; Leikoupo formation; middle Triassic; Xiangxi group, upper Triassic as well as Daanzhai formation and Lianggaoshan upper formation, lower Jurassic etc; in which Maokou, Changxing and Jialingjiang formation are very important formations reservoir. The main type of oil-gas pools are: (1) ancient weathering fracture type; (2) fracture trap type; (3) intercrystalline poresfracture type; (4) reef or bio-shoal type; (5) solution cavities fracture type; (6) intergranular pores-fracture type. The evolution of oil-gas among P-Z is highly too over matured, their vitrinite reflectance (R_o) is 1.75-2.1%, odd-even predominance(OEP) is 0.15-1.12 and composition of natural gas is characterized by 90%-99% methane, and very low heavy phdrocarbon; those in T is highly matured composition of natural gas is characterized by 88%-95% CH_4. Those in Daanzhai formation with lianggaoshan upper formation is matured, and composition of natural gas is charactericed by 85%-90% methane with a high perentage of heavy bydrocarbon. It is a favourables stage for oil accumulation. In this region, oil/gas-bearing area may be divided into three parts that is; (1) north oil/gas-bearing area; (2) south oil/gas-bearing area; (3) middle oil/gas-bearing area.