CO2 Injection for Enhanced Gas Recovery

摘要

Literature shows that there is a significant amount of natural gas available for enhanced recovery in the depleted reservoirs;at the same time,the depleted gas reservoirs are a proven storage facility for Carbon Dioxide(CO2)storage in terms of reservoir integrity.Conceptually,injecting CO2 into a depleted gas reservoir will not only potentially rejuvenalize the gas production, but will also store the greenhouse gas in a proven subsurface formation. Study on CO2 phase behavior in subsurface conditions shows that CO2 most likely will be in super-critical state which exhibits liquid-like density and gas-like viscosity.These properties are favorable in displacing natural gas reservoirs in volumetric and pore scale sweep efficiency.Using numerical reservoir simulation on a synthetic case with multiple scenarios, this paper identifies the most amenable characteristics of a reservoir for enhancing gas production by injecting CO2 and analyzes the parameters influencing this secondary recovery process.In the paper,reservoir depth,depletion pressure ratio, aquifer activity,inclination angle,reservoir heterogeneity with various permeability arrangement,injection rate,and producer bottomhole pressure will be studied on the synthetic model.Furthermore,this paper will quantify the amount of natural gas which can be produced and CO2 that can be stored in an ideal case using economic matrix. From this study,the ideal candidates for enhanced gas recovery by CO2 injection will be proposed based on simulation results,thus one can screen the available gas reservoirs for CO2 storage purpose and can quickly quantify the additional gas production from the secondary recovery.