The Development Characteristics And Distribution Of Fracture Of Da’anzhai Member In Fuling Area,Eastern Sichuan Basin

The reservoir of Da’anzhai member in Fuling area is of ultra-low porosity and ultra-low permeability. Its lithology is mainly crystalline shell limestone and black shale, with three sub-members:1st sub-member of Daanzhai member,2nd sub-member of Daanzhai member and3rd sub-member of Daanzhai member. The lithology of the1st sub-member and3rd sub-member of Daanzhai member are shell limestone with a stable thickness distribution, the lithology of the2nd sub-member of Daanzhai member is mainly black shale with the thin limestone bands. Overall, Daanzhai member is of poor reservoir properties and strong heterogeneity, and fracture is its major reservoir space and migration pathways.In this paper,we collected the drilling, well logging, seismic, core analysis and other basic geological data in the area of research, utilized the principle and methods of sedimentology, organic geochemistry and logging geology to study the characteristic、 development periods、 and distribution of fracture of Daanzhai member. The main research results of papers obtained as follows:1.By observation of fracture through the fracture in outcrops and cores, occurrence, development density, opening width, length, effectiveness and so on of fracture are detailly analyzed.2.According to the observed characteristics of fracture,the imaging logging fracture identification is carried out,and the response characteristics of the fracture in the conventional well logs is analysised,and various lithology fracture comprehensive identification standard that base on conventional logging are established3.It is concluded that, lithology, thickness, faults, the regional tectonic stress and so on are also controlling the development of the natrual fracture. Combined with the results of regional tectonic evolution, isotope analysis and rock acoustic emission test,Daanzhai member has gone three major tectonic movement, namely,, Yanshan movement and the early and late Himalayan movement.4.Using stress simulation software, the ancient stress field of the Himalayan and Yanshan period is simulated. According to the coefficient of the rock fracture, plane is divided to fracture developed area, fracture relatively developed area and no fracture developed area. Further more, the development index of the fracture near the fault is predicted. Combined with this two analytical methods, plane distribution of the fracture is summarized by superposition.