咸化湖盆页岩油微观运移富集过程对流动性的影响OA

Mixed shales occur in continental saline lacustrine basins in China,exhibiting complex lithologies and various types of pores.The occurrence and distribution characteristics of multicomponent hydrocarbons within shale pores affect shale oil mobility and estimated ultimate recovery(EUR)per well.Focusing on the 2nd member of the Kongdian Formation(also referred to as the Kong 2 Member)in the Cangdong Sag,Bohai Bay Basin,we analyze the geochemical characteristics,biomarker variations,and reservoir fluorescence characteristics of shale oil produced at different recovery stages.Accordingly,the occurrence characteristics of shale oil within micro-and nano-scale pores and their impacts on shale oil mobility are systematically analyzed.The results indicate that the hydrocarbon components of shale oil exhibit cyclic variations during the development process.A higher frequency of these variations is associated with more rapid replenishment of light hydrocarbons,as well as a more stable miscible flow regime and a higher flow rate of multicomponent hydrocarbons.During the recovery of shale oil at great burial depths,hydrocarbons produced in the early stage show higher maturity,while those recovered in the late stage exhibit lower maturity.This pattern indicates that shale oil generated in different periods occurs in independent micro-and nano-scale pores without mixing.In contrast,for shale oil at shallow burial depths,no significant differentiation in hydrocarbon maturity is observed throughout the oil recovery.Hydrocarbons with higher maturity occur primarily within the micron-scale macropores in felsic laminae,whereas those with lower maturity are primarily confined to nano-scale micropores.Saline lacustrine basins are characterized by early and multi-stage hydrocarbon generation,coupled with multi-stage hydrocarbon accumulation and enrichment.Consequently,shale oil with different hydrocarbon compositions occurs in subsurface micro-and nano-scale pores.This facilitates hydrocarbon component flow,thereby enhancing the expulsion of heavy components from micro-and nano-scale pores and ultimately increasing the flow rate of shale oil.