低渗透气藏气水两相渗流模型及其产能分析

开发实践与室内实验表明，低渗透气藏的气、水渗流规律不遵循达西定律。为此，建立了符合低渗透气藏气水耦合渗流特征的广义达西渗流模型，推导得到了低渗透砂岩气藏气水两相稳态径向渗流问题的半解析解。利用该模型对广安低渗透气田气水同产气井建立了单井气、水两相流入动态关系理论曲线，模拟计算了气井的合理井距及生产压差。算例表明，含水饱和度是影响气井产能的主控因素，当含水饱和度达到40%时，气井无阻流量的损失幅度约为70%；低渗气井的合理生产压差应该控制在5～10 MPa，井距以600 m内为宜。实验和计算结果可以为低渗气藏气水同产气井产能预测及井距评价提供科学、适用的依据。

A gas-water two-phase flow model for low permeability gas reservoirs and deliverability analysis thereof

Field studies and laboratory experiments indicated that gas water two phase flow for low permeability gas reservoir fails to follow Darcy's law. In such a case, a generalized Darcy flow model, in accordance with the gas water coupling character of low permeability gas reservoirs, was established, furthermore, semi analytical solution for the water gas two phase steady state radial flow of low permeability sandstone gas reservoirs was derived therefrom. Based on this model, theoretical curves of a single well's gas water two phase inflow performance relationships were drawn for water gas production wells in the low permeability Guang'an gas field, and then rational well spacing and producing pressure differential were worked out through simulation. The sample shows that the water saturation is the main controlling factor affecting the deliverability of a gas well, the absolute open flow potential (AOF) of unsaturated reservoir at Sw=40% decreases by 70% compared with that of a dry gas well.; the rational producing pressure differential of a gas well with low permeability should be 5  10 MPa, and the optimized well spacing should be less than 600 m. The laboratory experimental results and numerical analytical solution presented in this paper are capable to provide scientific and reasonable references for the deliverability estimation of the water gas wells for low permeability gas reservoir and well spacing evaluation.