OPTIMIZATION OF THE METHOD FOR DETAILED FAULT DESCRIPTION IN HYDROCARBON MIGRATION:TAKING SOUTHWEST HUIZHOU OF ZHUJIANGKOU BASIN, NORTH CHINA SOUTH SEA AS AN EXAMPLE

Migration is one of the key elements to hydrocarbon accumulation. It includes two stages: primary and secondary migrations. The secondary migration is the process which determines the main migration directions of oil and gas, the spatial assemblage of source-reservoir-accumulation and the hydrocarbon migration through reservoir and other types of passages. Secondary migration is caused by the change of conditions prevailed in oil and gas accumulation, including the migration to a new reservoir along the pathways of faults and unconformities. Doubtlessly, faults play a very important role in hydrocarbon migration and accumulation. However, previous researches about faults and their effects on hydrocarbon migration and transportation are mainly qualitative which are too far from enough. Macroscopic, three dimensional and practical studies are obviously lacking. Therefore, in this paper, geophysical approaches are adopted firstly to obtain high quality fault profiles to describe in detail the faults strikes and microfractures distribution patterns, then to analyze the difference between hydrocarbon sealing and transportation caused by faults, and finally to provide necessary support for the analysis of oil and gas migration pathways. The adopted methods includes the followings: at first, conduct variance cube attribute analysis for seismic data and extract time slices to acquire the spatial distribution of faults; then, based on the variance attributes, using ant-tracking technique to characterize the microfracture overview, and analyze the difference between hydrocarbon sealing and transportation for different faults and/or the different parts of a fault; then use 3D visualization with high imaging precision to further analyze the effect of faults on hydrocarbon sealing and transportation spatially to supply new ideas and methods for the in-depth study of hydrocarbon migration pathways. Such a research idea and method brings seismic and geology closely, and can much enhance the precision and reliability of direction identification of hydrocarbon secondary migration. It has proved efficient to trap evaluation and optimization in hydrocarbon exploration.