Water Production Prediction in Tight and Low Pressure Gas Wells Considering the Dynamic Change of Gas-Water Permeability Relationship

Abstract

The production of water in tight low-pressure gas wells is the main problem that restricts the efficient development of tight gas. How to accurately predict the water production of gas wells is the key to develop water control and stimulation measures. Through the experimental study of gas-water two-phase flow in the core of water-bearing gas reservoir in the west of Sulige, it is found that the gas-water phase flow curve in the tight core has obvious dynamic characteristics under different displacement pressure differences. The existing gas-water two-phase seepage model generally uses the relative permeability curve which does not change with the displacement pressure difference, which brings great error to the gas-water dynamic prediction. Therefore, a gas-water two-phase seepage model of fractured wells was established, which considers the dynamic change of gas-water permeability relationship with pressure gradient. By using finite element method and finite volume method, the gas-water production performance of tight and low pressure gas well under different production systems is obtained. The influence of gas-water phase permeability and production pressure difference on water gas production was analyzed. The effect of output setting on water flooding in gas well was studied. The results show that the greater the production pressure difference, the greater the water-gas ratio, the greater the risk of gas well water flooding, but the smaller the production pressure difference, the lower the production of gas well, it will also lead to water flooding due to insufficient gas carrying capacity of the wellbore. Therefore, rational proration plays a key role in prolonging the stable production period of gas wells. Through the interpretation and analysis of gas and water production data in the west of Sulige, it is confirmed that the new model is reliable and practical, which provides scientific basis for rational proration.KeywordsTight gasWater-bearing gas reservoirRational prorationWater floodingRelative permeability curveFinite element methodFinite volume method