This paper presents experimental and simulation studies to evaluate the feasibility of sequestering supercritical CO2 in depleted gas reservoirs. Experimental results were simulated to obtain gas-liquid relative permeability curves used in the field simulation study.

A 3D simulation model of one eighth of a 5-spot pattern was constructed to evaluate injection of supercritical CO2 under typical field conditions. Simulation results indicate the following. First, a large amount of CO2 in sequestered: about 1.2 million tons in 29 years (40-acre pattern), and 4.8 million tons in 56 years (80-acre pattern). Second, a significant amount of natural gas is also produced: about 1.3 BSCF or 74% OGIP (40-acre pattern), and 4.9 BSCF or 68% OGIP (80-acre pattern). Third, at $2.00/MSCF, produced gas revenue amounts to about $2.6 million to $9.8 million, which could help defray the cost of CO2 sequestration. In short, CO2 sequestration in depleted gas reservoirs appears to be a win-win technology.

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