Repurposing Idle Oil and Gas Wells for Large-Scale Subsurface Energy Storage in Saline Aquifers

Abstract

Abstract The continued adoption of intermittent renewable power generation sources, such as wind or solar requires large-scale, long-duration energy storage to buffer the intermittency of renewable power sources so as to supply 100% dispatchable power whenever it is demanded. When required for durations greater than 24 hours and at large (500+ MW) scale, current energy storage solutions offer only 4-10 hours storage, becoming prohibitively expensive, as in the case of batteries, or very site-constrained and environmentally challenged Pumped Hydro systems (PHS). A Hyper-Scale Energy Storage (HSES) solution using repurposed idle oil & gas wells to store energy in subsurface saline aquifers is presented here. The screening criteria for the selection of suitable subsurface saline aquifers that can be accessed via idle oil and gas wells is discussed. Repurposing idle wells or subsurface energy storage could provide an alternative to costs associated with traditional well abandonment and remediation. Repurposing idle wells could also provide a means for reducing current methane emission profiles. The proposed zero-carbon storage solution offers energy storage durations much longer than available alternatives, making possible a national grid with 100% variable renewable generation from solar and wind, and the retirement of many fossil generating plants. Conventional Compressed Air Energy Storage (CAES) plants operate with low efficiency and use salt caverns. Scaling up for a longer duration becomes expensive and site-constrained as it is contingent on the availability of large volume salt caverns. They use natural gas fuel to heat expanding air through gas turbines for power generation and thus are not a zero-carbon operation. While the current focus is on the approximately 38000 idle wells in California oil and gas fields, the proposed process and associated storage system could well apply broadly to the many US and global petroleum operations with large inventories of aging and idle oil and gas wells.