Through the analysis of the geological conditions of shale oil and gas reservoirs in Western Canadian Basin,it is found that the oil and gas enrichment conditions in Jiyang Depression have three comparable characteristics. First,the sedimentary environment of shale oil and gas reservoirs in Western Canadian Basin is mostly marine facies,in which the homogeneous shale distributes widely and forms a large accumulation in the whole foreland basin which tilts eastward in the Rocky Mountains(north to south direction). However,the shale reservoirs in Jiyang Depression are mostly form in continental lacustrine environment,which is the typical separated-isolated basin with complete sedimentary layers,and with high source-sink symmetry coincidence. Second,there are two types of hydrocarbon generating parent material in the marine shale of the Western Canadian Basin. TypeⅠand Type Ⅰ-Ⅱ kerogens are mostly from marine plankton and algae,TypeⅡ-Ⅲ kerogens are mostly from spore pollen deposited in surface marine environment. While Type Ⅰ-Ⅱ kerogens are the major hydrocarbon-generating parent materials of continental shale in Jiyang Depression,and they are mostly from phytoplankton,dinoflagellates,coccolites,etc. Third,organic pores from thermal evolution is commonly developed in low-density Devonian sediments of Western Canadian Basin,while they are rarely found in shale of Jiyang Depression because the shale is in the middle-late stage of diagenesis and develops compact structure. In addition,the development conditions of shale oil and gas in West Canadian Basin and Jiyang Depression are quite different. The shale strata in Western Canadian Basin contain a large proportion of rigid felsic quartz particles,and the brittleness and compressibility of rocks are better,while the shale components in Jiyang Depression is comprised of more carbonate minerals with lower hardness. The content of rigid particles in Jiyang Depression is extremely low,and therefore it is difficult to establish the necessary supporting structure for later fracturing operation. The“sweet spots”of continental shale oil and gas should distributes in rhythmic bedding fracture zone,irregular cracks caused by curvature change,micro-nanopores caused by mineral crystallization and pyrolysis of organic matter in Jiyang Depression.
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ZHANG Shoupeng. Enlightenment from the comparative analysis of shale oil and gas accumulation conditions in Western Canadian Basin and Jiyang Depression[J]. Petroleum Geology and Recovery Efficiency,2019,26(1):29~36