Study on erosion mechanism and critical erosion prediction of gas-liquid-solid three phase in P110 injection-production string in UGSs

In underground gas storage(UGS) facilities, prolonged cyclic injection-production operations and extreme peak-shaving conditions induce fatigue degradation of reservoir formations, intensifying sand production and resulting in gas-liquid-solid three-phase flow within the wellbore. This multiphase interaction complicates erosion mechanisms within the injection-production string. To address these challenges, under conditions of gas flow velocity of 17-50 m/s, sand content of 0.0001%-0.02%, and liquid holdup of 0.001%-0.01%, erosion experiments were conducted utilizing a gas-liquid-solid three-phase visual pipe flow erosion apparatus, with P110 carbon steel injection-production string specimens subjected to annular flow conditions incorporating circumferential erosion distribution analysis. The erosion rate was measured using weight-loss method and analyzed combining with microscopic morphology observation. These findings indicate that the relationship between gas flow velocity and erosion rate exhibits exponential trend, and that between sand content and erosion rate follows logarithmic trend, and that between liquid holdup and erosion rate can be described by binomial pattern. The chart of critical erosion coefficient under complicated operation conditions was plotted and a gas-liquid-solid three-phase critical erosion prediction model for P110 injection-production string was established by characterizing key factors such as sand content and liquid holdup. A comparison of the experimental actual values with the predicted values revealed a prediction error of 6.52%, which is significantly lower than the existing API RP 14E model under gas-liquid-solid three-phase operating conditions.In conclusion, the gas-liquid-solid three-phase erosion prediction model developed in this study can provide theoretical support for determining the peak gas volume of individual wells and safe operation of injection-production string in UGS facilities.