Second exponential equation with start-up pressure for low permeability gas reservoirs and its application

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 determination 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 examples. 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.