Low Permeability Gas Reservoir Gas - Water Two Phase Flow Mathematical Model Improvements And Numerical Simulation Applied Research

The low porosity and low permeability of low permeability gas reservoirs induce their complex permeability characteristics of gas and water. A lot of experiments and field applications testify that the non-linearity of percolation and multi-variability of fluidal in the low permeability gas reservoirs. The percolation of fluid need overcome starting pressure; meanwhile kinkenberg effects restrict the permeability of gas. Thus, the traditional classic percolation mathematical model cannot to be better resolved the concrete problems of low permeability gas reservoirs.Based on the literature researches, considered the complex permeability characteristics of low permeability gas reservoirs, a three-dimension gas-water two-phase percolation mathematical model is established, which reflects the concrete influence factors, such as low velocity non-Darcy flow, starting pressure gradient and slippage effect. This model is resolved with numerical solution and computer solution, namely IMPES method and LPGRS-1.0 numerical software, friendly low permeability numerical simulation software compiled own. The productivity formulae of gas well that include the influence of starting pressure and gas slippage are educed. The influence of starting pressure gradient and gas slippage on the development of low permeability gas reservoir is researched on by new written simulator and is analyzed by actual field data.Major research achievements include,1) A low permeability gas-water two-phase percolation mathematical model is established, which considers the effect of gas slippage. This model breakthrough is beyond the limitation of researches nowadays, the slippage effect model is only limited in single phase permeability researches;2) A three-dimension gas-water two-phase percolation mathematical model, which reflects the concrete influence factors, such as low velocity non-Darcy flow, starting pressure gradient and slippage effect, is established and resolved numerically;3) The productivity formulation of gas well that considers the influence of starting pressure and slippage is educed;4) The partial parameters of BOAST black oil simulator are revised and the function of it is strengthened, which break the limitations that many numerical simulators do not consider starting pressure gradient and slippage effect. The pre- disposition face for importing data for BOAST black oil simulator is compiled.5) The exploitation guideline of single well in the center of some box shape gas reservoir is simulated numerically and contrasted by the IMEX simulator with the simulator complied by own.6) Based on the example simulation calculation, the sensitivity analysis of starting pressure gradient and slippage are done. The result indicates that the influence of starting pressure gradient and gas slippage should not be neglected.