低渗透气藏含启动压力指数方程及应用

Exponential equation with threshold pressure for low permeability gas reservoir and its application

低渗透气藏考虑启动压力梯度的拟稳态或稳态三项式产能方程虽较二项式产能方程有较大改进,但待定参数的确定随意性较大,且建立的三项式产能方程的表达形式不唯一,计算的无阻流量也不唯一。为克服上述缺陷,从径向流两区渗流物理模型出发,建立了含启动压力的n次幂指数产能方程,并结合实例,验证对比了此方法与原方法的优劣。结果表明,此方法简便可靠,待定参数和方程形式唯一;此外,使用未达稳定状态流量值计算时,三项式产能方程计算无阻流量偏于乐观,矿场生产中建议采用此方法计算的无阻流量值。

Trinomial deliverability equation, considered threshold pressure gradient, of pseudo-steady state or steady state has a greater improvement than that of binomial in low permeability gas reservoir. However, the arbitrary of the determination of undetermined parameter is large and the established trinomial deliverability equation is not unique. And the calculated open flowcapacity is not unique too. To overcome the shortcomings, based on the physical model of the two areas of radial flow, the deliverability equation of n-th power exponent with threshold pressure is set up and this method is compared with original method. The results show that this method is simple and reliable and that the undetermined parameter and equation are determined with uniqueness. In addition, using the flow value of unstab｜e state, the open flow capacity calculated by trinomial deliverabihty equation is optimistic, the relatively conservative open flow capacity calculated by the method is proposed to use in mining production.