低渗透气藏含启动压力的二次幂指数方程及应用

Second exponential equation with start-up pressure for low permeability gas reservoirs 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二次幂指数产能方程,并结合实例对比了该方法与原方法的优劣。结果表明,该方法简便可靠,待定参数和方程形式唯一确定;此外,三项式产能方程所计算无阻流量偏于乐观,矿场生产中建议采用含启动压力的二次幂指数产能方程计算无阻流量值。

The pseudo-state or steady state trinomial cube deliverability equation considering the start-up pressure gradient has been improved largely compared with the binomial cube equation in low permeability gas reservoirs, but the flexible of parameters de- termination is great. In addition, the expression of trinomial cube deliverability equation is not unique and so does the resulted open flow capacity. A deliverability equation with the start-up pressure based on the radial flow physical model in two areas has been established to overcome these shortcomings. And then the new method has been verified and compared with the original one through specific ex- amples. The results show that this method is simple and reliable, the unknown parameters and the form of equations are capable of being ascertained. In addition, the open flow capacity calculated using the trinomial cube deliverability equation is optimistic, so that the open flow calculated with this method is proposed in mining production.