Analysis of factors affecting fractures of Chang-8 subsection based on Dingbian-Wuqi area of Shaanxi province
MA Haiyong1, ZHOU Lifa2,ZHANG Xuefeng3 , HAN Tianyou3
(1 College of Geology & Environment, Xi′an University of Science and Technology, Xi′an 710054, Shaanxi, China;2 Department of Geology, Northwest University, Xi′an 710069, Shaanxi, China;3 Exploration and Development Research Institution, PetroChina Changqing Oilfield Company， Xi′an 710018， Shaanxi, China）
Abstract:
Based on the characteristics of tectonics evolution, the well drilling,log information and microscopic, high resolution boreholemicro resistivity image logs (FMI), the flat distribution regulation and genesis of the fractures of Chang-8 subsection of Yanchang Formation in Dingbian-Wuqi area of Shaanxi province were analyzed.The research showed that the horizontal compression stress formed the fractures.The E—W and NW—SE regional fractures were formed by the horizontal compression stress of NWW—SEE orientation during the Yanshanian movement, the NE—SW and N—S fractures were formed by the horizontal compression stress of NNW—SEE orientation during the Himalayan movement.Affected by the influences of the strong terrane anisotropism made by sedimentary and diagenesis, the development of two sets of conjugate shear fractures at the same time was different in the dissimilar sedimentary system, NW—SE and E—W shear fractures would develop well,NW—SE and N—S fractures was restrained. It is found that E—W fractures developed well where closed to Yishan slope, and NW—SE fractures developed well neared Tianhuan depression or faults.The directions of the present tectonic stress fields in the basin were NEE—SWW which controlled the fracture connectivity and permeability. It is very important to exploration and the oilfield network arrangement of low-permeability oil.
KeyWords:
Dingbian-Wuqi area; Yanchang Formation; FMI; fracture; sedimentary
