Gas-water interface migration characteristics of shallow gas reservoirs in Hangzhou Bay during advanced exhaust

It is of great significance to study the water-gas interface migration in gas reservoirs caused by gas release for advanced exhaust wells. Based on the theory of elastic water drive gas reservoirs, a theoretical model describing the variation of gas-water interface in reservoirs is derived. The controlling gas exhaust of the reservoirs in Hangzhou Bay is simulated, and the evolution laws of water-coning formation, shape and height in the reservoirs under different wellhead velocities are emphatically discussed. The results show that different degrees of water coning occur in the process of the exhaust, and the water coning directly affects the efficiency of the exhaust wells. The wellhead velocity is the most significant factor affecting the shape and height of the water-coning, and it is negatively correlated with the water coning sweep area and positively correlated with the water-coning height. The larger the wellhead velocity, the sharper the shape of water coning. The smaller the wellhead velocity, the gentler the water coning shape. During the same exhaust time, the larger the water-coning sweep area, the better the exhaust effects. The higher the water-coning height, the faster the exhaust well flooded. In practice, a low wellhead flow-rate should be controlled to avoid premature well flooding so as to achieve the purpose of effective exhaust.