Research On Microscale Percolation Of Tight Gas Reservoir Based On LBM

The space of gas reservoir and migration in dense gas reservoir is mostly nanometer pore,and the pore structure of reservoir is complicated,and the throat is narrow,which greatly limits the gas migration in reservoir.At present,the research method of low permeability reservoir is often used in the research of dense reservoir,but the pore throat of dense reservoir is small,the effect of microscale is obvious,the mechanism of microscale seepage of dense reservoir is not clear,and the development of dense gas reservoir is difficult.This paper introduces the lattice Boltzmann method(LBM),analyzes the gas transport mechanism,establishes the lattice Boltzmann theoretical model of gas transport in micro-nano-scale pores,analyzes the micro-scale effect in seepage process by using C language programming,and studies its influencing factors.The porous media model is generated by four-parameter random generation method(QSGS),and the porous media is percolated through the lattice Boltzmann method Numerical simulation,analysis of its flow law,explore the dense gas reservoir micro-scale seepage mechanism.It is recognized that:(1)There is a microscale effect in gas flow in nanoscale pores,which is manifested in the nonlinear and slip effects of the pressure along the path.temperature,pressure and pore size all influence the microscale effect of gas flow within the micropores.the higher the temperature,the lower the pressure and the smaller the pore size,the more obvious the microscale effect of gas migration within the micropores.(2)Nusen number Kn as an important characterization parameter of microscale flow,the change of Nusen number Kn will affect the microscale effect of gas migration in the microchannel.In slip region and free molecular flow region,the change of Nusen number Kn has little effect on microscale effect,and in transition region,the change of Nusen number Kn has a great influence on microscale effect.(3)The existence of the throat has a great inhibitory effect on the gas flow in the pores,the gas flow velocity at the throat increases sharply and the pressure drops suddenly.Compared with the pores without the throat,the velocity profile at the outlet decreases as a whole,and the flow rate decreases.At the throat or wall bulge,there may be vortex during the gas flow.(4)It is easy to form dominant channels such as pore space formed by large pore throat connection and high matching pore throat connection space in porous media.Once dominant channels are formed,gas will pass through dominant channels first.limited by the narrow throat,there are more dead pores in the porous medium.this part of the pore space does not participate in the gas flow and contributes very little to the permeability.the pore space with poor pore size but no throat restriction can also form dominant channels and has good gas circulation ability.