Mechanisms for Permanent CO2 Trapping in Sedimentary Rocks

Steven L. Bryant, Gary A. Pope

Funding source: Advanced Technology Program (State of Texas)

Funding amount: $150,000 for the period of January 2004 - December 2006

Geological sequestration is one way greenhouse gases can be mitigated in sufficient volumes. This project focuses on obtaining quantitative assessments of the potential for permanent geological sequestration of carbon dioxide in aquifers.

 Mechanisms for Permanent CO2 Trapping in Sedimentary RocksCurrent schemes for sequestering CO2 depend on storage in the gas phase and assume the gas will flow upward in the aquifer until a geological seal is reached. These schemes require seal integrity over long periods of time and do not assure integrity. CO2 can escape through abandoned wellbores, faults and fractures. Three ways the CO2 can be sequestered that avoids these concerns include: 1) CO2 can dissolve in brine, 2) CO2 can chemically react to form an immobile solid phase, and 3) CO2 can form a CO2-rich gas phase that is not mobile due to trapping by capillary forces for saturations below the residual gas saturation. How can these three highly desirable forms of sequestration be maximized so that very large volumes of CO2 are permanently stored in aquifers without a mobile gas phase? Flow and transport models are available to quantitatively answer this question under realistic aquifer conditions. We will simulate CO2 injection into large aquifers for time scales of several years, simulating the gravity driven flow of the CO2-rich gas and CO2-saturated brine for 1000 years or more.