Geochemical controls on CO₂ interactions with deep subsurface shales: implications for geologic carbon sequestration

Area of Science:

• Geochemistry
• Environmental Science
• Petroleum Engineering

Background:

• Rising CO2 emissions drive global warming, necessitating carbon reduction strategies.
• Geologic CO2 sequestration (GCS) in shale formations is a viable solution.
• Shale reservoirs, developed for hydrocarbons, offer potential for GCS.

Purpose of the Study:

• To review geochemical interactions between CO2 and shale for GCS.
• To assess factors influencing CO2 storage permanence in shales.
• To explore CO2 utilization in enhanced shale gas and oil recovery.

Main Methods:

• Literature review of CO2-shale interface geochemistry.
• Analysis of parameters affecting CO2-shale interactions (pressure, temperature, moisture).
• Examination of CO2 as a fracturing fluid and its role in enhanced recovery.

Main Results:

• Shale properties significantly impact CO2 sequestration efficiency and permanence.
• Geochemical reactions at CO2-fluid-shale interfaces are complex and varied.
• CO2 can be used for enhanced hydrocarbon recovery and as a fracturing fluid.

Conclusions:

• Further research is needed on CO2 solubility, reaction kinetics, and heterogeneity effects in shales.
• Understanding different CO2 states (gaseous, brine, supercritical) is vital for GCS.
• Optimizing CO2 use in fracturing and enhanced recovery requires detailed geochemical insights.