A stratigraphic well drilled in December 2011 is providing WESTCARB with rock core and fluid samples to characterize the CO2 storage potential of regionally extensive geologic formations in the southwestern part of the Sacramento Basin of California.
The Citizen Green well, drilled directionally to a vertical depth of 6,900 feet in a California Energy Commission project, reused the pad and surface casing of an existing depleted natural gas well on King Island, which is located in an agricultural area near Stockton. The King Island gas field is part of northern California’s natural gas producing region and is in close proximity to major industrial and power plant CO2 sources.
Rock samples and logging data collected from the well are providing WESTCARB with the opportunity to assess the capacity of major regional sandstone formations to store CO2 and the integrity of the overlying shale units to provide seals against leakage. Whole core recovered during drilling included 19 feet of the transition between the Nortonville Shale and Domengine Sandstone and 57.5 feet of the upper Mokelumne River Sandstone. In addition, 43 sidewall cores were recovered from the Domengine, Mokelumne, and upper Starkey* (or lower H&T) sandstones, and the Nortonville, Capay, and H&T shales. A suite of wireline logs was run over a vertical depth range of 3,250 to 6,880 feet to provide data on the porosity, permeability, mineralogy, and geomechanical properties of the formations.
The core samples are being analyzed and used in experiments by WESTCARB researchers at Lawrence Berkeley National Laboratory.
WESTCARB’s findings from the Citizen Green well samples and logging data will provide information to help CO2 emitters assess geologic storage options for meeting their greenhouse gas reduction targets, as well as helping natural gas producers determine how CO2 storage may extend the useful life of depleted natural gas fields.
*A preliminary assessment of the Mokelumne River and Starkey formations is contained in a WESTCARB study by the California Geological Survey.