AN OPTIMUM CO2 PRESSURE AND TEMPERATURE INJECTION INTO DEPLETED GAS RESERVOIR TO MITIGATE HYDRATE FORMATION AND THERMAL STRESS EFFECT

摘要

A depleted Gas Reservoir is a promising target for carbon dioxide sequestration. The objective is to determine the optimum CO2 injection pressure and temperature into a depleted gas reservoir. During CO2 injection into a depleted gas reservoir, the pressure near the injection well declines rapidly as gas expands. If the Joule-Thomson expansion was large, the injectivity and formation permeability could be altered by formation of hydrates, freezing of residual water, and fracturing due to thermal stress which reduces the critical pressure required for initiation of fractures. The initiation of fractures poses a potentially serious risk for CO2 leakage to upper formation or even to the surface. CMG-GEM, PROSPER, and HYSYS are the numerical simulators used to develop an understanding of the CO2 behavior while injecting into a depleted gas reservoir. A one eight five-spot hypothetical reservoir model was developed by CMG-GEM and produced until it reached a depleted reservoir pressure. Then, an injection well was drilled to inject pure CO2 into the depleted gas reservoir. The rate of CO2 injection, bottom hole temperature and pressure, estimated from Prosper will be evaluated to determine whether the Joule-Thomson effect results in thermal stress and hydrate formation. As a result of this study, the objective of reducing emission of CO2 into the atmosphere, is achieved by injected and permanently storage of CO2 in the reservoir. Carbon dioxide injection above critical point will initiate hydrate formation and thermal stress effects. Carbon dioxide injection below critical point (73.8 bars and 31.1°C ) until reach final pressure then injecting carbon dioxide above critical point would be feasible way to prevent hydrates risk and thermal effect stress.