Study on gas-water-sand-hydrate foam flow and discharge in the wellbore during hydrate depressurisation production

To address sand and water production in hydrate reservoirs that affect the production efficiency, this study innovatively considers the application of foam drainage to hydrate production scenarios.Using a multi-physics field coupling approach, a numerical model of continuous foam drainage in wellbores based on the liquid-and solid-carrying models and other models is developed, and its evaluation accuracy was verified to be up to 95% by comparing with the indoor experimental data.Correlation factor analysis showed that increasing nitrogen injection rate, gas production rate and gas-liquid ratio enhanced liquid and solid transport efficiency.However, both excessive foam viscosity and overly low viscosity adversely affect system performance.Under South China Sea hydrate trial conditions, the study employed model predictions and multi-factor analysis to determine optimal foam injection rates for varying water/sand production levels.The findings provide theoretical guidance for optimising continuous foam drainage technology in hydrate wells, aiding in productivity enhancement.[