SPE Reservoir Evaluation & Engineering
Volume 12, Number 3, June 2009, pp. 399-407

Summary

Sequestration of carbon dioxide (CO₂) in geologic formations will be part of any substantive campaign to mitigate greenhouse gas emissions. The risk of leakage from the target formation must be weighed against economic feasibilities for this technology to gain stakeholder acceptance. The standard approach to large-scale geologic sequestration into saline aquifers assumes that CO₂ will be injected as a bulk phase. In this case, the primary driver for leakage is the buoyancy of CO₂ under typical deep-reservoir conditions (depths > 2,600 ft or 800 m). Investigating alternative approaches that use inherently safe trapping mechanisms can help to characterize the price of reducing the risk of leakage.

In this paper, we examine a process in which CO₂ is dissolved in brine before injection into deep subsurface formations. The CO₂-laden brine is slightly denser than brine containing no CO₂, so the complete dissolution of all CO₂ into brine at the surface before injection will eliminate the risk of buoyancy-driven leakage. The process considered here involves dissolving CO₂ at surface facilities. We determine the capital costs for the additional facilities and compare them the capital costs for injecting bulk-phase CO₂. We also estimate the power requirements to determine the additional operating costs. The additional capital and operating costs can be regarded as the price of this form of risk reduction.

Comparing this alternative to the standard, we find that an additional power consumption of 3 to 9% of the power plant capacity will be required, and the capital costs will increase by approximately 60%. Brine is required at rates of millions of barrels per day and would be lifted from the target aquifer. The bulk volume of the aquifer is on the order of a hundred million acre-ft for reasonable power plant sizes (250 to 1,000 MW) and for reasonable injection periods (30 to 50 years). Although this alternative results in higher costs, surface dissolution may be attractive when the costs of monitoring or ensuring against buoyancy-driven CO₂ leakage exceed these additional costs.

© 2009. Society of Petroleum Engineers

View full textPDF ( 1,532 KB )

History

• Original manuscript received: 2 August 2007
• Meeting paper published: 11 November 2007
• Revised manuscript received: 2 August 2008
• Manuscript approved: 22 August 2008
• Published online: 1 June 2009
• Version of record: 1 June 2009