Study On The Law Of Sand Production In Gas Hydrate Production By Depressurization

With the decomposition of gas hydrate in the process of gas hydrate depressurization,the physical properties of the reservoir and the mechanical properties of the rock will change.In the process of mining,the reservoir is often accompanied by the sand production.The reservoir sand production will cause the decline of gas production and the wear and tear of the oil and casing,which will increase the development cost,and will also plug the pore of the formation seriously,causing the oil and gas wells to stop production.It can accurately describe the law of gas hydrate decomposition in reservoir and its influence on the physical properties of reservoir and rock mechanics,reveal the mechanism of reservoir sand production,establish the prediction side of reservoir sand production,and get the law of reservoir sand production to prevent and control the sand production from the hydrate reservoir.Therefore,to carry out gas hydrate mining process of reservoir sand law research.Considering the effect of hydrate decomposition on porosity and permeability of reservoir in natural hydrate reservoir,combined with the equilibrium equation of hydrate phase state and multiphase seepage equation,a dynamic decomposition model describing natural gas hydrate in the process of depressurization is established,and the reliability of the model is verified with the data of literature experiment,and the numerical simulation is used to analyze the depressurization process.The decomposition law of hydrate reservoir.Considering the influence of hydrate decomposition on the rock mechanics characteristics,such as cohesive force and internal friction angle,the dynamic evaluation model of hydrate reservoir stability is established by combining the elastic mechanics of porous media,rock mechanics and seepage mechanics.Considering the law of hydrate decomposition and the stability of reservoir,a prediction model of dynamic sand production in the process of gas hydrate reservoir is established.Through numerical simulation,the law of reservoir sand production in the process of gas hydrate recovery is revealed.By comparing with the experimental results of gas hydrate extraction in the literature,it is found that the model model of the dynamic hydrate decomposition model has predicted that the maximum gas production rate error is less than 9%,the cumulative gas production error is less than 1.7%,and the model is suitable for predicting the hydrate decomposition law in the process of gas hydrate production.The biogas production rate(the same cumulative gas production)is bigger,but with the increase of production time,the increase of gas pressure is not obvious.In the process of hydrate decomposition,the additional stress in the near well zone is large,the decrease of cohesive force is obvious and the stability of the reservoir is the worst.The simulation results of sand production prediction model show that the more critical sand production radius is,the more serious the critical sand production radius is,the more serious the sand production is in the hydrate reservoir.