四川盆地下二叠统断层与缝洞发育关系研究

四川盆地下二叠统碳酸盐岩为典型的缝洞型储层,断层带钻探获得了较好的效果。较多的研究认为断裂带是有利的裂缝发育带并沿裂缝形成溶洞,研究发现地表剖面溶洞充填物被断层切割错动,溶洞次生方解石充填物中可见沥青质包裹体和沥青团块,沥青物质为原油裂解成天然气后残留,而石油裂解成气的时间远早于构造断层菜成期,钻井质资料统计表明,放空的井次在断点附近并没有明显优势,放空井段通常造近侵蚀面顶部,而断层带以裂缝发育为主,因此,下二叠统储层中溶并非断层裂缝形成后的产物,溶洞发育时间在构造褶皱,断层形成之前,而构造褶皱,断层发育后并发未发生较大规模的岩溶作用。

STUDY ON THE RELATIONSHIP OF FAULT AND FRACTURE-CAVITY RESERVOIR IN THE LOWER PERMIAN IN SICHUAN BASIN

The typical fracture cavity reservoir has developed in the Lower Permian carbonate in Sichuan Basin. Many gas wells have been got with drilling along the faulting zone. The faulting zone has been believed as the favorable zone where fracture develops and cavity develops along the fracture in the previous studies. The study detects that the mineralized cavities are cut by the fault in the crops, and bitumen inclusive bodies and bitumen masses can been found in the secondary calcite crystal filled in cavities. The bitumen is the residual matter when oil cracks into gas in high temperatures, which took place earlier than the formation of the fault in Sichuan Basin. Based on the drilling geological data, fracture develops near the fault point, but the number of well with the bit drop during drilling far from the fault point is far more than that near the fault point, and the interval of the bit drop is often near the top erosion surface of the Lower Permian. Thus, this paper puts forward that the cavity formed mainly in the subaerial meteoric environment earlier than the development of the structure fault.