Technology portfolios optimization to deliver cost-effective shale gas development: Using CO2 versus water

Hydraulic fracturing is widely used in shale gas development, while it could cause decline in production in water -sensitive formations. Using CO2 for reservoir fracturing, injection to enhance gas recovery, and sequestration in depleted shale reservoirs can solve this problem, increase shale gas production, and store CO2 underground. Given the high expense of these CO2 techniques, the trade-off between the rising cost of deploying CO2 tech-niques and the benefit of increased shale gas production influences the technology portfolios for shale gas development. Financial incentives for carbon credits can provide compensation for the cost of CO2 techniques, further influencing the technology portfolios. Currently, questions remain regarding the optimal technology portfolios for achieving cost-effective shale gas development under different reservoir conditions and the impacts of the carbon price incentive. Here, we propose a novel optimization model that simultaneously integrates the hydraulic fracturing, CO2 fracturing, CO2 injection, and CO2 sequestration techniques to investigate the optimal technology mix for cost-effective shale gas development. We select the non-water sensitive formations and water sensitive formations as two representative scenarios. The results show that to cost-effectively develop shale gas, hydraulic fracturing is preferred in the non-water sensitive scenario whereas CO2 fracturing and CO2 injection are preferred in the water sensitive scenario. The synergistic deployment of CO2 fracturing and CO2 injection techniques can not only improve economic performance but also sequestrate more CO2. Our findings provide policy makers with critical insights into achieving cost-effective shale gas development while curbing carbon emissions.