考虑气体加速效应的高压气井产能方程推导及其应用

Abstract

Non-Darcy flow in a gas well cannot be expressed with traditional binomial equations or trinomial equations for ultra-deep high pressure gas reservoirs, which leads to large errors of open flow capacities for the neglect of gas acceleration effects. A new method was presented with gas acceleration effects. Under the assumption of high-pressure radial gas flow, through combination of the continuity equation, the Darcy-Forchheimer equation with acceleration and the isothermal state equation, the productivity equation was derived. The proposed equation is also able to replace traditional binomial equations, but has no analytical solution. It can be simplified by analogy, and the related coefficients can be solved by trial and error. The application of the proposed method in data process of ultra-deep high pressure gas well Xi35-1 in Sichuan Basin is effective, and the comparison with the real production data proves the precision of the calculated productivity. The proposed method avoids the disadvantages of the relative error increase with the differential pressure. The work enriches the productivity prediction methods, with accurate calculation of open flow capacities and reasonable determination of high pressure gas well productivities.