The Role of Supercritical Carbon Dioxide for Recovery of Shale Gas and Sequestration in Gas Shale Reservoirs

The rise of hydraulic fracturing and horizontal drilling has unlocked vast reserves of shale gas, yet the standard water-based methods come with environmental consequences, such as the potential for contaminating groundwater, surface water, and soil. As a potential remedy, supercritical carbon dioxide (SC-CO2), due to its unique physical properties, offers a promising alternative to water for enhancing shale gas extraction. This review delves into the evolution of shale gas extraction techniques, the emergent role of SC-CO2 as an alternative stimulation fluid, and its potential for geological carbon sequestration within shale reservoirs.

SC-CO2 presents several advantages over traditional fracturing fluids. Notably, its ability to break through rock is superior to that of water, making it particularly effective in shale formations. Furthermore, fractures induced by SC-CO2 tend to be rougher and more intricate than those from hydraulic fracturing, leading to increased permeability. An added bonus of using CO2 in shale gas recovery is the simultaneous opportunity for its sequestration in the reservoirs, offsetting carbon emissions and possibly tapping into carbon tax incentives. However, interactions between shale and CO2, especially in the presence of brine or water, can have repercussions on the reservoir's attributes. Preliminary data indicates that the shale–CO2 imbibition process can last for several years, contrasting sharply with the few days anticipated in many lab settings. A deeper insight into the impact of SC-CO2 injection on shale gas recovery's efficacy, its economic feasibility, and environmental considerations is essential. Comprehensive laboratory and field tests, particularly those emphasizing geochemical, petrophysical, geomechanical, and hydraulic characteristics, will be instrumental in advancing safe sequestration techniques and efficient recovery methods.