Study On Microscopic Seepage And Imbibition Laws In Shale Reservoirs

Shale reservoirs are rich in organic matter and are considered traditional source rocks and caprocks.The shale oil reservoirs are very rich,and with the application of large-scale hydraulic fracturing technology,the exploration and development of shale oil reservoirs gradually became popular.At present,most of the research on shale oil exploration and development is based on the reservoir scale.Understanding the microscopic reservoir structure of shale and the seepage mechanism of fluid in shale is crucial to guiding the development of shale oil reservoirs.In this paper,based on digital core technology,3D images of shale cores are obtained and their structures are analyzed.Based on the 3D cores,the lattice Boltzmann method was applied to perform a single-phase seepage simulation to explore the seepage characteristics of microscopic pores.The permeability of shale directly affects the production of oil wells.Understanding the flow mechanism of shale nanopores is important for the development of shale reservoirs.To quantitatively characterize the permeability of shale,we applied fractal theory to derive an apparent permeability model for dual wettability shale fluids.Micro-scale effects were considered in the model,slip effects in organic pores,and boundary layer effects in inorganic pores,to characterize the permeability of shale oil.The shale apparent permeability model and the characterization equation are applied to characterize the relevant parameters of real shale cores.The factors affecting the apparent shale permeability are also analyzed,and guiding suggestions are made for the development of shale reservoirs.Imbibiyiom is an important mechanism for shale reservoir development.Due to the special characteristics of shale reservoirs,the conventional expressions for imbibition are no longer applicable to shale reservoirs,for which we introduce the concepts of equivalent slip length and boundary layer to obtain the expressions for shale imbibition.Based on real shale cores,the imbibition process of shale reservoirs is investigated.We also introduced the pressure gradient to characterize the forced imbibition process in shale.Simulations of forced imbibition at the shale pore scale and core scale.The factors influencing the rate of forced infiltration extraction and recovery rate of shale reservoirs were explored..