New Model of Oil Migration in Shale Nanopores Considering Microscopic Deformation Induced by Stress and Pore Pressure

Abstract

During the exploitation of shale oil, the stress and pore pressure of the reservoir generally change, resulting in the deformation of the shale pore structure, which affects the oil migration in shale nanopores. Establishing an oil migration model and a permeability model that take into account the effects of reservoir stress and pore pressure is important for the numerical simulation shale oil development. In this paper, a new oil migration model in inorganic (IM) and organic (OM) nanopores of shale and a new shale apparent liquid permeability (ALP) model that consider the effects of reservoir stress and pore pressure are established. The molecular dynamics simulation data and experimental data are used to verify the validity of the proposed model. The results show that the model can reasonably describe the transport process of oil in IM and OM nanopores and calculate the ALP. The flow enhancement factor in inorganic and organic nanopores and the shale ALP are negatively correlated with the mean compressive stress and positively correlated with the pore pressure. When the shale bulk modulus is small, the flow enhancement factor and ALP are more sensitive to the stress and pore pressure. Moreover, the effects of stress or pore pressure on shale microscopic flow capacity which was evaluated by the flow enhancement factor and macroscopic flow capacity which was evaluated by ALP are consistent.