Study on the development of regional fractures and characteristics of tectonic faults in high stress difference stratum

Abstract

The development of fissures and the study of tectonic faults in the stratigraphic area are important geological parameters for the study of oil and gas reservoirs, which is of great significance to the exploration, development and exploitation of oil and gas fields. However, due to the variable conditions of the underground stress field, especially the high stress difference stratum, the characteristics of regional fractures and faults are not yet clear. In this paper, the Wunan oil field in Qaidam Basin, Qinghai, which has a significant feature of high stress difference, has been selected as the research object. Combined with the Kaiser effect experiment and the analysis of the dip-log, the magnitude and direction of the main target segment in the region are determined the stress distribution characteristics of the region, and discusses the development and the relationship between faults distribution and stress distribution of the cracks. The results show that: 1) The distribution of the ground stress in this area is dominated by the maximum horizontal stress > vertical stress > minimum horizontal stress and the maximum horizontal principal stress is about 300°-310°, which belongs to typical high stress difference stratum. 2) The development direction of fractures in this area mainly converge between 314 ° and 325 °, which shows that it is more developed along the direction of the maximum principal stress, and the natural fractures are extremely developed, the fracture types are vertical seams. 3) The faults in this block have a general trend of NWW, which tends to be SSW, and basically the same as the horizontal maximum principal stress direction. The larger the difference of the horizontal in-situ stress is, the more obvious the formed faults will be, and the distance between the faults is significantly larger.