Supercritical Carbon Dioxide Utilization for Hydraulic Fracturing of Shale Reservoir, and Geo-Storage: A Review

Abstract

Hydraulic fracturing has completely revolutionized how shale resources are exploited to extracthydrocarbons. However, sustainability and environmental issues have fueled the desire for alternate fracturing technologies. Supercritical carbon dioxide (Sc-CO2) fracturing is a new method that uses high-pressure, high-temperature CO2 in its supercritical state (7.38 MPa and 31.1 °C) to generate fractures in shale formations, thereby increasing reservoir permeability. This Review thoroughly analyzes the effects of Sc-CO2 on shale reservoirs during the fracturing process, including the factors that affect fracture breakdown pressure and the complexity and roughness of fracture induced by Sc-CO2. Sc-CO2 can fracture rock at a fracturing pressure lower than that of slick water. CO2, in its supercritical state, shows strong permeability, low viscosity, and extremely low surface tension, like gas, because of which it can infiltrate any space larger than its kinetic diameter (0.330 nm). Many research investigations illustrate how Sc-CO2 affects shales with diverse pore structures, mineral compositions, and mechanical properties when exposed to Sc-CO2 for several hours to days. It is challenging to effectively store CO2 in shale gas reservoirs due to their low permeability and limited storage capacity. To improve the effectiveness of CO2 storage, shale can be fractured to increase the pore space and surface area in reservoirs. Thereby, a certain amount of the CO2 pumped for shale gas production can be securely stored in shale formations, reducing carbon emissions and allowing for a zero-carbon footprint. This paper discusses the pathway and different chemical reactions involved in the storage of CO2 after fracturing over a period. However, fully understanding the interactions between Sc-CO2 and shale rock and the possibility of long-term storage of CO2 in shale formations is quite challenging. It is because of a lack of research and limited knowledge in the above field. Hence, more investigation and development are required in the research area of Sc-CO2 fracturing and the interaction of CO2 with shale rock.

Research on Evolutionary Laws of Mechanical Properties and Pore Structure during CO2 Pre-Injection Fracturing in Shale Reservoirs

“…CO 2 fracturing can avoid water sensitivity and water block effects, as it replaces waterbased fracturing fluids with CO 2 [25][26][27]. Therefore, it has been widely applied in shale reservoir development in recent years [28,29].…”

The Influence of SC-CO2 on the Nanopore Structures of Different Types of Shales Based on Small-Angle Neutron Scattering and Multifractal Methods

“…The utilization of SC-CO 2 as an alternative to water for enhanced shale oil and gas extraction has become the frontier of research in recent years . Some scholars have shown that the utilization of SC-CO 2 for reservoir fracturing modification can aid in shale oil and gas extraction. , Injecting CO 2 into oil reservoirs can enhance oil recovery and effectively sequester CO 2 . This technique has been proven to be the most economically valuable carbon capture, utilization, and storage (CCUS) technology. , This approach achieves the goals of sequestering carbon dioxide and enhancing the recovery rate of shale oil and gas reservoir rocks.…”