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    June, 2005

Vol 2 Chapter 3: Natural CO₂ Fields as Analogs for Geologic CO₂ Storage

Scott H. Stevens

Abstract: Our study evaluated three underground gas fields in the USA that have been effective CO₂ traps for millions of years: the Jackson, McElmo, and St. Johns Domes. Together, these fields stored 2.4 billion t of CO₂, equivalent to more than 1 year of USA power plant emissions. Because CO₂ in these fields has been commercially extracted for industrial uses, the fields offer data on natural CO₂ reservoirs, cap rocks, and production operations. M0cElmo Dome, the largest and most important field, originally stored 1.6 billion t of supercritical CO₂ within a carboniferous carbonate reservoir at a depth of 2300 m. Carbon isotope data indicate the CO₂ originated from a nearby igneous intrusion dated to 70 Ma. Its cap rock is a 400-m thick sequence of salt (halite), which is finely layered and unperturbed by faults which cut the underlying reservoir; there is no evidence of CO₂ leaking into the overlying strata. McElmo Dome has two decades of safe operational history. It currently produces 15 million t/year (800 MMcfd) of 99%-pure CO₂, which is transported 900 km via pipeline to depleted oil fields for re-injection and enhanced recovery. However, the three fields in our study represent a small sampling of geologic situations, insufficient for defining universal criteria for cap rock integrity. Building scientific and public acceptance for geologic CO₂ storage may be facilitated if proposed projects each had a local or regional natural analog.

Carbon Dioxide Capture for Storage in Deep Geologic Formations – Results from the CO₂ Capture Project Geologic Storage of Carbon Dioxide with Monitoring and Verification - Volume 2
Edited by: Sally M. Benson, Lawrence Berkeley Laboratory, Berkeley, CA, USA

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