• Energy Research

The booming development and production of shale gas largely depends on extensive application of water-based hydraulic fracturing treatments and primary pressure depletion. Issues associated with this procedure include fast production rate drop, low recovery factor, high water consumption, and formation damage. It is necessary to develop new reservoir fracturing and enhanced gas recovery (EGR) technologies to reduce water usage and resource degradation, guarantee the environmental sustainability of unconventional resource developments, and boost individual well production. Building on gas storage and transport mechanisms in shales, this study investigated the feasibility of a new CO2-based reservoir treatment technology. CO2 has a higher adsorptivity than CH4, enabling it to liberate adsorbed natural gas in place. Therefore, gas production will be boosted by injecting CO2 to replace CH4. This novel reservoir treatment process will also open a large market for the beneficial utilization of CO2. In this paper, the authors discuss the theoretical principles and feasibility of using CO2 in both the stimulation stage and the secondary gas recovery stage. Following that, the authors outline a case study performed to simulate applying the CO2-EGR process in the Barnett, Eagle Ford, and Marcellus shale plays. The marginal revenue per thousand standard cubic feet (MSCF) of increased CH4 production was calculated. The profitability was found to be largely determined by the prices of natural gas and available CO2. A cost break-down analysis indicated that the CO2 procurement expense was the main component in the total cost. The proposed CO2-EGR process was mostly like to be successful in the Barnett shale.