A New Method for the Evaluation of Productivity of Water-Producing Gas Wells in Specific Tight Sandstone Reservoirs

The tight sandstone reservoirs in the Sulige Gas Field have complex pore structures and gas-water distribution, and the water production law in the complex gas-water distribution areas has not been clarified. The water production of gas wells in different regions varies greatly, and the water production of gas wells seriously affects the efficient development of natural gas. In order to improve the benefit of gas field development, this study takes stress-sensitive effects, gas-water immiscibility, and constant production conditions of gas wells under a certain gas-water ratio Rgw as constraints, and considers the fluid seepage as an isothermal seepage process, an evaluation model of the productivity of a theoretical water-producing gas well and a relative permeability model of the gas phase are constructed. Moreover, the influence of water production on the degree of pressure drop, gas well productivity, and gas well recovery was systematically analyzed. This study shows that when the water-gas ratio of gas wells is less than 1, 1-2, 2-3, 3-4, 4-5, and greater than 5, its influence on productivity is less than 40%, 52%, 50%, 58%, 61%, 65% and greater than 65%, respectively. The average water-gas ratio of the water-producing gas wells in the Sulige Gas Field is 1.27 m³/10 ⁴ m³. The effect of water production on recovery is compared with the case of no water production: for water-producing gas wells, the recovery rate of Type I wells is reduced by 8.45%, that of Type II wells is reduced by 9.58%, and that of Type III wells is reduced by 11.54%.