Study On Transient Seepage Of Fractured Wells Based On Complex Percolation Mechanism In Shale Gas Reservoirs

Oil and gas resources are an important part of the energy industry and are of strategic importance to a country.With the development of conventional oil and gas resources,more and more oilfields have entered declining production period,and even no longer deserve to industrial exploitation and are facing discard.As a succession of conventional oil and gas resources,unconventional energy have drawn increasing attention from all sectors of society.China is rich in shale gas resources and developing shale gas is of great significance for alleviating the pressure on China's energy resources and ensuring economic development.Unlike conventional reservoirs,shale gas reservoirs are characterized by low porosity and low permeability and hydrocarbon organic matter self-generating and self-storing.Its reservoir spatial structure is very complex,which has multi-scale features.Due to the complicated spatial structure of shale reservoirs and the diversity of shale gas occurrences,the percolation mechanism is more complicated and can't apply the theory of conventional gas reservoirs directly.In order to further deepen the multi-scale and complex seepage mechanism of shale gas,the shale gas unsteady seepage mechanism of fractured vertical wells and multi-stage fractured horizontal wells are studied respectively.It is helpful for our country to achieve economic,efficient and reasonable development of shale gas.The main research contents and conclusions are as follows:1)Reasonable abstraction of the shale pore structure and establishment of gas accumulation and migration mechanism model.Three kinds of shale gas microscopic infiltration mechanism models have been constructed,which lays the foundation for the study of unstable seepage law for fractured wells in shale;2)Study on unsteady seepage of fractured vertical wells in shale gas reservoirs.Firstly,an unstable seepage model for fractured vertical wells is established in shale gas reservoirs and then the seepage model is solved.Finally,influence factors analysis is carried out and results show that the more seepage mechanism being considered in the model,the less energy is consumed effectively during daily production.3)Study on the unsteady seepage mechanism of multistage fractured horizontal wells in shale gas reservoirs.Firstly,an unsteady seepage model for multi-stage fractured horizontal wells in shale gas reservoir is established and solved.After that influence factor analysis is carried out and results show that the Knudsen diffusion and slippage effects mainly affect the apparent permeability of the matrix pores and change the appearance time of the turbulent flow.The more severe the Knudsen diffusion and slippage effect,the earlier the turbulent flow occurs and the higher the gas production.