SPH Simulation Of The Flow Of Single-phase Oil Displacement System At The Pore Scale

After many years of water injection development,most oil fields have entered the stage of high water cut or ultra high water cut development,and the micro-pore structure of the reservoir has changed greatly compared with the initial stage of development.The test results based on the original core rock samples are no longer accurate To describe the seepage law of the reservoir,it is urgent to fully understand the fluid flow law in the reservoir at the pore scale to provide a basis for oilfield development.Therefore,in this paper,based on the smooth particle hydrodynamics(SPH)method,the migration laws of three different oil displacement systems at the pore scale,Newtonian fluid,power law fluid and viscoelastic fluid,are studied.First,the SPH calculation program was compiled,and the classic Poiseuille flow was used to verify the accuracy and reliability of the program calculation.Then,the trapezoidal pore theory is used to simplify the complex pore structure and a simplified capillary model is established.Finally,based on the capillary model,the flow state of the three different oil displacement systems of water,HPAM and Oldroyd-B in the capillary at the pore scale was simulated.The velocity distribution in the capillary tube and the corresponding velocity change cloud maps obtained the relationship between the pressure difference and the flow rate under different hole-to-hull ratios.The calculation results show that the flow rate and pressure difference of Newtonian fluid at the pore scale are always linear,and the pressure difference and flow rate of power law fluid and viscoelastic fluid have an exponential relationship.For Newtonian fluids,when the hole-to-roar ratio is greater than 2.5,and as the hole-to-roar ratio increases,the non-linear relationship between the flow rate and the pressure difference gradually becomes apparent.For non-Newtonian power-law fluids and viscoelastic fluids,when the hole-to-well ratio is greater than 5,the flow rate and pressure difference in the capillary begin to show a non-exponential relationship,and the greater the hole-to-roar ratio,the worse the non-exponential nature of the flow rate and pressure difference.By comparing the capillary models of different cross-sectional shapes,it is found that when the pore shape is circular,the flow resistance is the smallest.When the oil displacement system is Newtonian fluid,the flow rate of the fluid in the capillary tube with the circular cross section is the largest,the flow rate in the capillary tube with the rectangular cross section is the second,and the flow rate in the capillary tube with the triangular cross section is the smallest;the oil displacement system is a power law fluid and a viscoelastic fluid At the time,the flow rate of the circular cross-section capillary tube is the largest,the equal cross-section capillary tube,the triangular cross-section fluid flow rate is the second,and the rectangular cross-section fluid flow rate is the smallest;while the variable crosssection capillary tube is the opposite.