Gas Reservoir Nonlinear Flow Numerical Simulation Study

There exit complicated non-linear characteristics between gas flow velocity and pressure gradient in lots of discovered natural gas reservoirs. Many gas reservoir simulation programs are based on the linear Darcy's Law; it is difficult to accurately describe the above-mentioned non-linear percolation rule. It is even useless in many practical applications. The research of numerical simulation of non-linear flow in gas reservoir is helpful to clearly understand non-linear flow characteristics, and provide scientific theory foundation for the establishment of development strategies. This thesis is based on deep and systematical research of non-linear flow mechanism, and the basic theory of flow mechanics. Integrated gas reservoir non-linear flow simulation' theory, techniques and methods are developed synthetically using flow mechanics, gas reservoir engineering, modern mathematics, computer and other techniques The main contents are following:(1) Based on the relevant.literatures investigated, through the study of development characteristics and concrete mechanism of non-linear percolation in gas reservoir, lots of non-linear percolation rule were mathematically described.(2) Based on the mathematical description, a mathematical model was developed for the first time, which can describe linear Darcy's Law, and non-linear percolation rule (start-up pressure gradient effect, high velocity gas flow, Klinkenberg effect, deformable medium gas flow).(3) A fully implicit 3-dimension gas-water numerical model was derived using finite difference method. Based on the design idea of software engineering, a 3-D gas-water non-linear flow simulator (NL-GW3D) was developed, which can be used in research of non-linear flow mechanism, and simulation of real natural gas reservoir. The simulator was proved to be reliable through the comparison with a commercial simulator.(4) The non-linear flow mechanism was studied thoroughly, taking an ideal gas reservoir as one example, using the 3-D gas-water non-linear flow simulator (NL-GW3D) developed in this thesis. The effect of non-linear flow on gas reservoir production performance was analyzed, and the correctness and reliability of the simulator were verified thoroughly.(5) The simulator was used successfully in the history match and performance prediction of Li 1-1 gas reservoir' M75-1 Well Region, located in Moxi gas field. Meaningful results were obtained. Some proposition was provided for the making of development strategies .Through the research of this thesis, the mathematical model of non-linear percolation in gas reservoir was proposed; a corresponding numerical simulator was developed. It is very significant for further study of gas reservoir non-linear percolation theory and efficient development and production of gas reservoirs.