Simulation study on injection of CO₂-microemulsion for methane recovery from gas hydrate reservoirs

Abstract

Gas-hydrates are crystalline substances in which a solid water lattice accommodates gas molecules, such as methane, in a cage-like structure. A simulation study was conducted, both on 1-D and 2-D reservoir models, using STOMP-HYD simulator to evaluate a set of optimum parameters for methane recovery with simultaneous CO₂ sequestration. A simple 1-D analysis supports the hypothesis of enhanced gas-hydrate recovery using a CO₂-microemulsion injection technique. A series of simulations carried out on the 2-D reservoir model, revealed that the temperature and concentration of CO₂-microemulsion as well as initial CH₄-hydrate saturation in the reservoir are the key parameters in the replacement of CH₄ with CO₂ in the hydrate phase. The results from the 2-D analysis indicated that the moderate microemulsion with a CO₂ concentration in the range of 40% to 50% show good methane recoveries for the reservoir under consideration. Preliminary energy requirement calculations were also carried out to demonstrate the advantages of using the CO₂-microemulsion injection over the thermal stimulation method. These calculations indicated that the energy requirement for CO₂-microemulsion injection is less than 1/10th of that required in case of thermal stimulation method. The results support the hypothesis of using CO₂ microemulsion injection technique for methane recovery from gas-hydrate reservoirs.