Improving Method Analysis of Stable Productivity in Low Permeability Gas-water Well

摘要

Gas and water will be produced simultaneously in most gas wells when the development of gas reservoir enters into the middle or later stage. However, the researches on the gas-water flow theory and productivity analysis method are not perfect. For the low permeability gas-water well, the productivity test curve sometimes proves to be irregular (reverse) and the productivity analysis cannot conducted with general methods. Thus, it is necessary to develop some new methods of evaluating productivity of low permeability gas-water wells. In this paper, the authors establish a mathematical model about gaswater two-phase flowing in formation according to mechanics of flow through porous media, and analyze the causes of productivity test curve of low permeability gas-water well reverse. The bottom-hole pseudo pressure calculation method is relatively modified based on the pressure drop superposition principle, and a new productivity binomial equation is established. From practical calculation, open flow capacity error is 1.02% compared with its actual value, which indicates that the productivity of low permeability gas-water well can be evaluated with the method improved above when test productivity curve reverses, and the result becomes more precise.