Abstract: To address the poor applicability of existing methods for predicting water invasion and evaluating aquifer activity in carbonate gas reservoirs with bottom water before water breakthrough,the reservoir characteristics and water invasion behaviors of such reservoirs were systematically analyzed.A mathematical model for bottom-water coning in carbonate gas reservoirs with bottom water was developed,incorporating derived formulas for calculating breakthrough time and water cone height.The morphological evolution of water cones at different production stages was characterized,enabling prediction of water invasion volume and water drive index before gas well breakthrough.The research results are applied to the Well PT102 in the Deng-2 gas reservoir of the Penglai Gasfield in central Sichuan, indicating that this method combines theoretical derivation with practical application,achieving dynamic description and quantitative prediction of water invasion before gas well water breakthrough,and solves the problem of early water invasion prediction in gas wells,addressing the insufficient accuracy and applicability of traditional methods.The predicted water breakthrough time is 169 days,with an absolute error of only 8 days (relative error 4.5%) compared to the measured value of 177 days.The water invasion volume before water breakthrough reaches 2.52×10⁴ m³,and the water drive index stabilizes at 0.30,verifying the model′s reliability.Reasonably reducing gas well production can effectively delay the water breakthrough time and significantly suppress the degree of water invasion.When the gas well production is reduced by 25%,the water breakthrough time can be delayed by about 24%,the cumulative water invasion volume is reduced by 18.4%,and the water drive index decreases from 0.30 to 0.27,indicating a significant suppression of water body activity.The research results fill the gap in early water invasion prediction methods for carbonate gas reservoirs with bottom water before water breakthrough and provide a reference for optimizing production allocation in similar gas reservoirs.

Key words: gas reservoirs with bottom water, coning, carbonate, water invasion prediction, water body activity, early water invasion, Penglai Gasfield