CO2-Enhanced Oil Recovery Mechanism in Canadian Bakken Shale

The recovery factor in unconventional reservoirs is typically 5-10%, with extensive hydraulic fracturing and infill drilling to maintain the production rate. Concurrently, the rush towards decarbonization is opening up new possibilities for CO2 utilization, enhanced oil recovery (EOR) being one example. CO2-EOR in unconventional reservoirs presents an opportunity for both financial gain through improved recovery factors, as well as reducing the carbon footprint of the produced oil. In this work, we examine the CO2-EOR potential in 4 organic-rich shale samples from the Canadian Bakken Formation. A number of characterization tests alongside CO2 extraction experiments were performed to gain insight into the controlling factors of CO2-EOR in these ultra-tight formations. The results show CO2 can penetrate the tight rock matrix and recover a substantial amount of hydrocarbon. Concentration gradient driven diffusion is the dominant form of recovery.

Automated summary

The recovery factor in unconventional reservoirs is typically low, and methods such as hydraulic fracturing and infill drilling are needed to increase production. CO2-EOR is a method for enhancing oil recovery using carbon dioxide, which can improve the recovery factor and reduce carbon emissions. This study examined the potential of CO2-EOR in organic-rich shale samples from the Canadian Bakken Formation, and found that concentration gradient driven diffusion is the dominant form of recovery.