Local and Global Impacts of Carbon Capture and Storage Combined with Enhanced Oil Recovery in Four Depleted Oil Fields, Kern County, California

Abstract:

Depleted oil reservoirs are attractive targets for geologic carbon storage (GCS) because they possess proven trapping mechanisms and large amounts of data pertaining to production and reservoir geometry. In addition, CO₂ enhanced oil recovery (EOR) can improve recovery of the remaining oil at recovery factors of 6 to 20% of original oil in place in appropriate reservoirs. CO₂ EOR increases the attractiveness of depleted oil and gas reservoirs as a starting point for CCS because the CO₂ becomes a commodity that can be purchased by field operators for EOR purposes thereby offsetting the costs of CO₂ capture at the power plant.

In California, Kern County contains the largest oil reservoirs and produces 76% of California’s oil. Most of the production at depths suitable for CCS combined with CO₂ EOR comes from three reservoirs: the Vedder and Temblor formations and the Stevens Sandstone of the Monterey Formation. These formations were evaluated for GCS and CO₂ EOR potential at the North and South Coles Levee (Stevens Sandstone), Greeley (Vedder) and McKittrick (Temblor) fields.

CO₂ EOR could be expected to produce an additional 150 million bbls of oil. The total storage space created by pre- and post-EOR fluid production for all three reservoirs is approximately 104 million metric tons (MMT). Large fixed sources in California produce 156 MMT/yr of CO₂, and sources in Kern County produce 26 MMT/yr (WESTCARB, 2012). Therefore, the fields could store about four years of local large fixed source emissions and about two thirds of statewide emissions. However, from a global perspective, burning the additional oil produced by CO₂ EOR would generate an additional 65 MMT of CO₂ if not captured. This would result in a net reduction of greenhouse gas of only 39 MMT rather than the full 104 MMT. If the water produced along with the oil recovered during CO₂ EOR operations is not reinjected into the reservoir, the storage space could be much higher.