Geological Aspects of Carbon Dioxide Sequestration in Northeast British Columbia, Canada*
Search and Discovery Article #80010 (2008)
Posted August 1, 2008
from oral presentation at AAPG Annual Convention,
1Resource Development and Geoscience Branch, British Columbia Ministry of Energy, Mines and Petroleum Resources, Victoria, BC, Canada. ([email protected]a)
Geosequestration of carbon dioxide (CO2) is feasible for reducing greenhouse gas emissions in Northeast British Columbia, Canada. Currently there are 12 acid gas disposal sites permanently storing ~130,000 tonnes of CO2 per year in saline aquifers or depleted natural gas reservoirs. Gas pools are the most secure storage options, having demonstrated the ability to trap natural gas over geological time. Nearly 67% of existing pools appropriate for geosequestration will not be depleted until post-2020.
The near-term need for large-scale storage sites will necessitate using saline aquifers to bridge the timing gap. Triassic and Devonian aquifers are likely candidates offering a good combination of storage security, capacity, and areal distribution. Both systems are isolated by thick aquitards that restrict interformational hydrodynamic flow. Lateral facies changes and updip erosional events create stratigraphic barriers, further impeding fluid movement.
The Triassic Doig-Halfway-Charlie Lake succession represents a thick transgressive-regressive cycle of shoreline to shelf sandstones and shales culminating with a mixed clastic-carbonate deposit. The overlying marine carbonates of the Triassic Baldonnel and Pardonet formations represent the final flooding stage. Erosion to the northeast limits Triassic storage opportunities to the southern area.
To the north, the Middle Devonian Keg River-Sulphur Point-Slave Point succession of reefal to platform carbonates were deposited as a series of shallowing-upward cycles and offer ample CO2 storage capacity. Dolomitization associated with regional faulting and hydrothermal fluid migration has created excellent reservoir characteristics primarily at shelf margins. The regional geological/tectonic setting and reservoir characteristics of these Triassic and Middle Devonian strata make them excellent candidates for CO2 storage.
Approximately 1.5 Gt of CO2 storage capacity will become available as major gas pools are depleted in Northeast British Columbia. Poor timing of availability and geographic distribution of depleting pools require use of saline formations. Triassic reservoirs are the best storage candidates in the southern portion, while Devonian rocks are likely the only option in the north. Acid gas (H2S and CO2) re-injection projects demonstrate the technological feasibility of geosequestration of CO2.
Bachu, Stefan, 2008, CO2 Sequestration Program web site map: http://www.ags.gov.ab.ca/co2_h2s/program_components.html.
Edwards, D.E., J.E. Barclay, D.W. Gibson, G.E. Kvill, and E. Halton, E. 1994. Triassic strata of the Western Canada Sedimentary Basin, in Geological Atlas of the Western Canada Sedimentary Basin, G.D. Mossop and I. Shetson (compilers): Canadian Society of Petroleum Geologists, p. 257-275.
ERCB/AGS web site poster, 2006, Acid Gas and CO2 Storage: http://www.ags.gov.ab.ca/co2_h2s/co2_acidgas.html.
Petrel Robertson, 2003, Exploration Assessment of Deep Devonian Gas Plays, Northeast British Columbia.