Numerical Simulation Of Fluid-solid Coupling For Gas Hydrate Development

Natural gas hydrate reservoirs are generally cemented loose sandstone,and the rock is prone to occur fluid-solid coupling due to changes of in-situ stress during development.The current hydrate development simulation can only simulate the porosity change of the formation during elastic deformation.This article aims to add the model describing process of formation rock dilation and compaction to the simulator.Then we study the fluid-solid coupling numerical simulation of natural gas hydrate development.First,we established a mathematical model of hydrate development,including the establishment of mass and energy conservation equations,determining discrete methods and numerical solution methods.Then,the Tough simulator was compiled,and the calculation examples of the more complex initial phase states were selected,and the numerical simulation of fluid-solid coupling in the elastic range was carried out.Referring to the Dilation / Recompaction model of the CMG-STARS simulator and the Hysteresis model of the Eclipse simulator,we putted forward a nonlinear elastic pseudo Dilation/Recompaction model and a hysteresis model which can describe the phenomenon of formation dilation and compaction.On this basis,the nonlinear elastic pseudo Dilation/Recompaction model and the hysteresis model were added to the Tough simulator,and the fluid-solid coupling numerical simulation of the hydrate development process was studied.And we compared simulation results of three models: the original model,the nonlinear elastic pseudo Dilation/Recompaction model and the hysteresis model.The results of fluid-solid coupling numerical simulation of hydrate development show that the results of the three models are significantly different,and the dilation or compaction generated with the changes of fluid pressure have a great influence on the hydrate development process and result.During the hydrate development process,the phenomenon of fluid-solid coupling cannot be ignored.In actual engineering applications,if the plastic deformation of the formation is too large,reasonable measures should be taken to prevent the occurrence of disasters such as formation collapse,submarine landslide,and collapse of casing.