Productivity Evaluation And Numerical Simulation Of Shale Gas Well

The flow of shale gas in dual porosity medium is a complex multi-scale flow process, the migration and production mechanism are special, and the mathematical representation of the process of seepage is more complicated. The seepage models for shale gas seepage process characterization set up by others at home and abroad are not perfect and accurate, and most of the two phase flow model didn’t consider the effect of slippage effect and adsorption of shale gas to liquid seepage rule, it largely reduces the model to describe the accuracy of the liquid seepage process. A large number of experimental and theoretical studies have confirmed that the slippage effect and adsorption of shale gas have important influence on the migration process of reservoir fluid. Therefore, establishing shale gas single well numerical model that considering desorption, diffusion, seepage and slippage effect into the whole process is important to guide the single well production capacity factor analysis and reservoir numerical simulation research.In this paper, through a large number of literature research, the shale gas reservoir characteristics, occurrence way and migration and production mechanism of shale gas are analyzed. The dual medium three dimensional shale gas reservoir gas-water two phase seepage mathematical model is established, and the shale gas reservoir horizontal well exploitation numerical model is established by numerical simulation method. Use commercial numerical simulation software Eclipse2011to simulate and analyze the shale gas well production performance. On the basis of the model, the influences of slippage effect and adsorbed gas on shale gas reservoir horizontal well production are studied. And the sensitivity analysis of parameters that have influence on shale gas well production is completed.According to the above research, main research results obtained in this paper are as follows:(1) According to the understanding of the shale gas reservoir characteristics, occurrence way and migration and production mechanism of shale gas, and basing on the numerical simulation and multiphase fluid seepage theory, the dual medium three dimensional shale gas reservoir gas-water two phase seepage mathematical model considering desorption, diffusion, seepage and slippage effect is established. And the shale gas reservoir horizontal well exploitation numerical model is established by numerical simulation method, and it was solved by iteration programming;(2) On the basis of programming to solve the numerical model, the effect of slippage effect on permeability is studied. The strong and weak of slippage effect depends largely on the size of the pore pressure of reservoir in the process of the gas seepage. The smaller the reservoir pore pressure, the more obvious the slippage effect. The fracture pore of shale reservoir has obvious slippage effect. And the sensitivity analysis of the parameters is completed, such as natural fracture permeability, Langmuir pressure constant, Langmuir volume constant and horizontal well horizontal section length.(3) The staged fracturing shale gas horizontal well model that considering slippage effect and gas adsorption-desorption has been established by commercial numerical simulation software Eclipse2011, and the production performance of gas well is simulated and analyzed. The slippage effect was beneficial to the improvement of the shale gas well production in the late development. Shale gas well production is determined by the migration of free gas and desorption of adsorbed gas together. The influence of the slippage effect and adsorbed gas in the process of shale gas development and production can’t be ignored;(4) On the basis of the shale gas well model which is established by commercial numerical simulation software Eclipse2011, the sensitivity analysis of parameters which have influence on the shale gas well production have been made; The shale reservoir rock compressibility change on the sensitivity of the gas well gas production is very weak; The diffusion of the gas inside the matrix system, the isothermal adsorption law and the adsorption gas content have great influence on the mid-late production of gas well. The change of natural fracture permeability, fracturing cracks spacing, fracturing cracks conductivity and fracturing cracks half length have great influence on horizontal well production, the sensitivity is very strong.