Assessment of oil and gas fields in California as potential CO2 storage sites

Abstract

California's total annual greenhouse gas (GHG) emissions (425.3 MtCO2e) in 2018 were about 6.4% of the US total (6,677 MtCO2e) and around 1% of global emissions. About 39% of 2018 GHG emissions in California were from the industrial and electrical sectors. Many of these emissions were from large stationary point sources and were suitable for carbon capture retrofit with subsequent storage of the captured carbon dioxide (CO2) in geological formations. Previous studies of California found suitable geology and CO2 storage resource. This study refines and furthers prior work using a three-stage screening process of oil fields, gas fields, and underground natural gas storage (UGS) sites by combining criteria from previous studies while excluding sites that pose technical risk or are located in regions with surface restrictions including sensitive habitats and dense populations. In the first stage, 129 CO2 storage sites in California were identified using qualification criteria based upon formation properties including geological conditions and pore pressure. The second stage identified sensitive sites by applying conservative screens including seismic activity, faulting, population density, restricted lands, and sensitive habitats. During the third stage, 61 CO2 potential storage sites were identified by subtraction of stage 2 areas from stage 1. The potential storage volume in the third stage ranged from 1.0 to 2.0 GtCO2. Finally, we applied a scoring system with seven parameters to rank the 61 potential sites based on subsurface technical criteria. The scored sites are classified as high priority, medium priority, and sites for future study. Prospective CO2 storage sites with high and moderate priority were selected and linked to CO2 sources. There are 14 prospective sites (above 20 MtCO2 storage resource per site) with a total storage resource of 1024 MtCO2 distributed in Northern and Southern California. Of these sites, there are 9 potential CO2-EOR sites and 1 depleted oil field with a total estimated CO2 storage volume of ∼800 MtCO2 in the Southern San Joaquin and Ventura Basin. These 10 prospective sites with a storage resource greater than 20 MtCO2 could potentially deliver more than 20 years of storage with an average injection rate of 40 MtCO2/year. The remaining 4 highly prospective sites are in Northern California. Study results also suggest that saline formations should be re-evaluated in concert with storage in oil, gas, and natural gas storage reservoirs.