Fault‐caprock Dual Control Hydrocarbon Accumulation Regularity in Volcanic Rocks in Xujiaweizi Fault Depression

depression under the fault-cap rock dual control, this paper is base on the material of Xujiaweizi which includes threedimensional seismic processing results interpretation of logging curves outcrop core observation and analytical test in laboratory, Analysis of the lithology, distribution and brittle ductile characteristics of ductile brittle of Xujiaweizi depression, evaluating sealing property of cap rock, studying deformation mechanism of the fracture in patch of cap rock, analyzing the top sealing ability and vertical adjustment of gas. Study on the internal structure of the fracture zone, analyzing sealing mechanism of different types of fault, establishing quantitative sealing evaluation method on corresponding fault, and quantitatively evaluating fault sealing in gas reservoir controlled by fault, research on the correlativity between fault sealing and gas distribution, systematically summarize the forming models of gas controlled by different fault-cap rock passage system. There are three main types of deep gas cap rock in Xujiaweizi fault depression, and they are mud stone, volcanic rock and clayey breccia. Mudstone is mainly distributed in the 1st and 2nd Member of Quantou Formation, the 4th,3rd and 2nd Member of Denglouku Formation, it is primarily regional cap rock of deep gas in Xujiaweizi fault depression. Volcanic rock is mainly distributed in the 1st and 3rd Member of Yingcheng Formation and clayey breccia is mainly distributed in the 4th Member of Yingcheng, both of them constitute Yingcheng group’s gas top locality cap rock in Xujiaweizi fault depression. Volcani crock and clayey breccia are intercalary strata at the 1st and 3rd Member of Yingcheng. Taking into account the formation and evolution of the sealing capacity of cap rock. During Quantou group’s late deposition and Qingshankouzu group’s early deposition, the 1st Member of Yingcheng top local cap rock , and the 2nd Member of Denglouku Formation and the 1st and 2nd Member of Quantou Formation cap rock had entered the late diagenesis A subage period, and keeped in plastic state with strong sealing ability. The cap rock did not produce a large number of cracks and lost the sealing ability with fracture activity. During the Mingshui group last phase, the deep cap rack had common entered the late diagenesis B subage period, the cap rock was dehydration and brittle, If there was a large scale fault activity, will produce a large number of cracks and cap rock sealing ability will be lost. While Qingshankou group’s cap rock was in strong closed stage at the late diagenesis A subage period, the deep gas at inversion structure belt was adjusted into Fuyang reservoirs to accumulate. According to the role of the vertical adjustment of natural gas, the intensely activity fault in late Quantou deposition early Qingshankou deposition prompted a large-scale natural gas vertical migration. Fault often dislocate mixed rock cap on the top of volcanic rock, gas source fault, as well as the unconformity between the 4th Member of Yingcheng Formation conglomerate and the lower volcanic rocks constitutes the deep gas conduit system. The migration pattern of natural gas is a short distance along the unconformity lateral migration following the vertical migration. lateral migration areas are mainly distributed in the ancient central uplift belt and Xujiaweizi rift convergence of the site. Natural gas in controlled by the 2nd Member of Denglouku Formation, appearing multi-layer aggregation. Although the mixed rock cap on top of volcanic rock was cutted by the faults in Key Time, resulting in poor vertical sealing capability in the fault zone, industrial air is still found in Yingcheng Formation, indicating that this volcanic cap plays a role of seal to prevent a large number of hydrocarbon diffusion HE Jia, FU Xiaofei, LIU Bo, MENG Lingdong, WANG Haixue and HE Bo, 2015. Fault-caprock dual control hydrocarbon accumulation regularity in Volcanic Rocks in Xujiaweizi Fault Depression. Acta Geologica Sinica (English Edition), 89(supp.): 245-246.