新疆火山岩双重介质气藏供排气机理数值模拟研究

Numerical simulation study of mechanism for gas supplying and draining in volcanic gas reservoir in Xinjiang based on dual media model

根据火山岩气藏特点建立了反映气藏渗流特征的双重介质数学模型,应用数值模拟的方法研究基质孔隙-裂缝-井筒之间的供排气机制,定量分析了不同产量的气井定产条件下,窜流系数λ对火山岩气藏稳产的影响程度。数值模拟结果表明,双重介质气藏气体窜流过程包括过渡段和稳定段,过渡段基质窜流量小于井底产出量,井底压降快,稳定段窜流量与井底产量相当,井底压降变缓,气体窜流进入稳定段所需时间决定于窜流系数。当窜流系数大于10-7时,窜流对气井生产影响较小;但当窜流系数小于10-8时,气井稳产受窜流影响严重,此时根据气井窜流系数的大小合理配产显得十分重要。结合新疆某口井的实例进行计算,验证了数值模拟结果的可靠性,证明供排气机理数值模拟对气藏高效稳产开采有一定的指导意义。

A double media mathematical model is established according to the feature of the Xinjiang carboniferous volcanic rock gas reservoir; the cross flow among the matrix pore-fracture-borehole is studied by means of the numerical simulation; and how the interporosity flow coefficient 2 influenced on the rate maintenance capability is analyzed quantitatively. Results indicate that there are two periods in the process of cross flow： transition period and stabilization period. In the transition period, the cross flow amount is smaller than the bottom hole inflow, and the bottom hole pressure drops quickly; in the stabilization period, the cross flow amount is equivalent to the bottom hole inflow, and the bottom hole pressure flattens out. The time needed from transition period to stabilization period is depended on the interporosity flow coefficient 2; the greater the λ, the shorter the time is need. If λ 〉10^-7, interporosity flow has little influence on gas well production. If λ 〈10^-8, stable yields is greatly influenced by the interporosity flow, and it is important to fix production according to the interporosity flow coefficient 2. Finally, an example is given to verify the correctness of these results.