Development And Application Of Hydrate Reservoir Numerical Simulation Software Based On HydrateResSim

In May 2017,our country successfully carried out natural gas exploration in Shenhu Area,South China Sea,realizing the historic breakthrough of China's natural gas hydrate.The numerical simulation technology links the laboratory studies with the production tests,development of numerical simulators for hydrate reservoirs has important guiding significance for production tests.The investigation found that there are many deficiencies in the current hydrate reservoir numerical simulator.Among them,HRS(HydrateResSim)is an open-source numerical simulator designed specifically for hydrate reservoirs,but the mathematical model established in HRS was established earlier,and the newly discovered physicochemical mechanism could not be well described.Therefore,this study improves the existing mathematic model based on anatomizing the code of HRS mathematical model and understanding the physicochemical mechanism of hydrate production.It mainly includes normalizing the water and gas saturation by referring to the Japanese MH21 model and correcting the relative permeability curve.Considering the latent heat of ice on the promotion of hydrate decomposition.Considering the internal energy of the inhibitor,the accuracy of numerical simulation is improved.The modified mathematical model is more perfect considering factors and describes the physicochemical mechanism more accurately during the exploitation of natural gas hydrate reservoirs.The modified mathematical model was verified using large laboratory simulations and Nanhai Shenhu's trial production data.The simulation results of the instantaneous gas production rate are highly compatible with the laboratory and field test production,verifying the correctness of the modified mathematical model.Based on the geological parameters of the hydrate deposits in the Shenhu area of the South China Sea,a conceptual model was established to study the effects of single factor changes on the exploitation results of different development methods.In depressurization exploiting,the greater depressurizing range,the greater depressurizing speed,and the greater the rate of gas production.However,depressurization exploiting can cause sand production in the reservoir and affect subsequent development,in conditions allow the lower the pressure drop of the sooner the better.In thermal stimulation exploiting,the smaller the well spacing,the higher the gas production rate,but it is prone to water breakthrough,and the cumulative gas production is reduced;The higher the injection temperature,the higher the gas production rate and gas production rate,but the lower the energy efficiency.The higher the injection speed,the greater the amount of gas produced,but the higher the reservoir pressure,the lower the hydrate decomposition and the lower the energy efficiency.In wellbore heating exploiting,the gas production rate is high in the early stage of mining,and then it declines sharply.The volume of gas produced by the production is small and the mining costs are high.Comprehensive comparison of various development methods,development effectiveness from good to poor in order: depressurization + thermal stimulation,depressurization + wellbore heating,depressurization,thermal stimulation,wellbore heating.Among those,the combined effect of depressurization + thermal stimulation is best,and the cumulative gas production and gas production rate are the highest.The combined production effect of depressurization + wellbore heating is not ideal,which is slightly better than depressurization.