Enhancing Prediction of Natural Gas Flow and Production Dynamic Behavior in Marine Sediments of the South China Sea

Accurate prediction of natural gas exploitation behavior is critical for optimizing production strategies in low-permeability reservoirs. However, existing studies lack comprehensive prediction models for characterizing the entire seepage process in low-permeability marine sediments. In this study, different water saturation cores are remolded using South China Sea sediments in a core holder, and 96 sets of natural seepage behaviors with different gas pressures (4∼7 MPa), confining pressures (5.6∼8.6 MPa), water saturations (10 and 20%) and depressurization locations (inlet, outlet) are analyzed by depressurization. The experimental results reveal the dynamic evolution of gas seepage from unstable to stable stage, and a novel empirical equation for gas seepage (EEGS) with linear coefficients that represent the stable seepage ability of different condition cores is put forward. Further coupling the gas equation of state equilibrium (GESE), gas production openness equation (GPOE), as well as the law of gas mass balance (LGMB), a production prediction model for the whole natural seepage process is proposed with good correlation coefficients of over 0.99 compared with measured values. This study provides an important theoretical basis for the production regulation of submarine natural gas exploitation in low-permeability reservoirs.