Computational Fluid Dynamics Simulation On Microscale Water-Gas Flow Behavior

The development of carbonate gas reservoirs is often accompanied by water intrusion,which seriously affects development benefits.Macroscopic water invasion is an integrated manifestation of microscopic gas-water flow.The study of gas-water two-phase flow law and its sensitivity as well as multi-channel flow interference at the micro scale is helpful to deepen the understanding of water invasion mechanism and improve the pertinence of water invasion management.The research results of this paper can provide a theoretical basis for the development of carbonate gas reservoirs.At present,the microscopic flow of gas-water two-phase is mainly studied through physical simulation.Due to the high complexity of the microscopic flow of gas and water,the traditional Darcy’s law cannot be described.Existing physical simulations can only perform qualitative observations at the mesoscopic scale(hundreds of microns),and cannot achieve quantitative research at the micron scale.In view of this,this paper carries out numerical simulation by means of computational fluid dynamics(CFD).Firstly,the paper establishes a simulation model based on the analysis of the microscopic pore structure characteristics of the target gas reservoir,selects the actual fluid property parameters,adopts a sufficiently fine mesh and small enough iteration time step,so as to ensure the representativeness of the CFD model and the simulation accuracy.physicality and reliability.Secondly,the microscopic gas-water two-phase flow law was studied for seven pore structure models.The analysis shows that the flow stability is destroyed when the channel shape is changed,and the final formation of the residual in the channel mainly depends on the pore structure.Next,five pore structure models were selected to carry out the microscopic gas-water two-phase flow sensitivity analysis.The study shows that changing the sensitivity factor will have an impact on the flow;when only one sensitivity factor is changed,the final impact on different models varies.Finally,the microscopic gas-water two-phase multi-channel flow disturbance simulation is carried out for the four pore-fracture models.The study believes that for multi-channel flow,there is flow interference between different branches and different fluids,which makes the flow rate of each phase,mixed flow and pore-fracture flow ratio inside different branches change continuously with the flow,and this flow interference is important to the flow.There is a significant effect on the final residual fluid distribution and volume.