2005 Salt Lake City Annual Meeting (October 16–19, 2005)

Paper No. 4
Presentation Time: 2:20 PM


FORSTER, Craig B.1, PASALA, Sangeetha2, DEO, Milind2 and PARRY, William T.3, (1)College of Architecture+Planning, University of Utah, 375 S. 1530 E, Room 235, Salt Lake City, UT 84112, (2)Department of Chemical Engineering, University of Utah, 50 S Central Campus Dr, Room 3290 MEB, Salt Lake City, UT 84112, (3)Geology and Geophysics, University of Utah, 135 South 1460 East, Room 719, Salt Lake City, UT 84112, forster@arch.utah.edu

Outcrop-to-simulation studies of faulted Navajo Sandstone of southeastern Utah provide a foundation for exploring how faults might affect CO2 sequestration in high-porosity quartz sandstones. In places, naturally occurring CO2 reservoirs are breached and CO2-charged water discharges to the surface along permeable faults. Two fault types are considered; low-permeability faults dominated by deformation-band networks and high-permeability faults dominated by fracture networks. Simple averaging calculations indicate that equivalent permeability (k) values range from <10-14 m2 for deformation band dominated faults to >10-12 m2 for fracture dominated faults. Water-CO2 fluid flow simulations model CO2 injection into high-k sandstone (5x10-13 m2) with either low-k (5x10-17 m2) or high-k (5x10-12 m2) fault zones that correspond to deformation band or fracture dominated faults, respectively. After 500 days, the free CO2 rises to produce an inverted cone of free and dissolved CO2 that spreads laterally away from the injection well. Free CO2 fills less than than 41% of the pore space behind the advancing CO2 front where dissolved CO2 is also at or near geochemical saturation. The low-k fault zone exerts the greatest impact the advancing CO2 front and restricts the bulk of the CO2 to the region upstream of the fault barrier. In this high-k aquifer, the high-k fault zone exerts only a small influence on the shape of the advancing CO2 front. In lower-k aquifers, high-k fault zones will become more important as CO2 pathways. Although high-k fault conduits might lead to reduced sequestration efficiency, aquifer compartmentalization by low-k fault barriers may lead to improved efficiency because lateral CO2 migration is restricted and the volume of CO2 emplaced is maximized. Combining insights gained from the numerical simulations with geochemical modeling results suggests that CO2 injection into a non-reactive sandstone aquifer such as the Navajo Sandstone will lead to geochemical saturation with dissolved CO2 concentrations that approach the maximum value throughout the region of sequestered CO2. Meanwhile, the low reactivity of the Navajo Sandstone and a lack of geochemically altered fault rocks suggests that little CO2 induced change in porosity and permeability should be anticipated in the Navajo Sandstone.