Pragmatic consideration of geologic carbon storage design based upon historic pressure response to oil and gas production in the southern San Joaquin basin

Abstract:

Annual CO₂ emissions from large fixed sources in the southern San Joaquin Valley and vicinity in California are about 20 million metric tons per year (MMT/Y). Cumulative net fluid production due to oil and gas extracted from below the minimum depth for geologic carbon storage (taken as 1,500 m) was 1.4 billion m³ at reservoir conditions as of 2010. At an average CO₂ storage density of 0.5 metric tons per m³, this implies 35 years of storage capacity at current emission rates just to refill the vacated volume, neglecting possible reservoir consolidation.

However, the production occurred from over 300 pools. The production rate relative to average pressure decline in the more productive pools analyzed suggests they could receive about 2 MMT/Y raising the field average pressure to nearly the fracturing pressure. This would require well fields as extensive as those used for production, instead of the single to few wells per project typically envisioned. Even then, the actual allowable injection rate to the larger pools would be less than 2 MMT/Y in order to keep pressures at the injection well below the fracture pressure. This implies storing 20 MMT/Y would require developing storage operations in tens of pools with hundreds, if not over a thousand, wells.

This utilization of one of the basins with the most storage capacity in the state would result in reducing the state’s fixed source emissions by only one eighth relative to current emissions. The number of fields and wells involved in achieving this suggests a different strategy might provide more capacity at similar cost. Specifically, staging wells that initially produce water in the vicinity of fewer injection wells could result in both more storage. This water could be directed to a shallower zone, or supplied to the surface at a similar cost. The commencement of ocean water desalination in the state indicates the economics of water supply might support treating this water for beneficial use, particularly if it has a lower salinity than sea water.