Sunday, March 23, 2014

CO2 sequestration potential in Arizona's Cedar Mesa Sandstone

AZGS has published another report in our series of assessments of the potential for geologic sequestration of carbon dioxide. This latest report examines the Permian-aged Cedar Mesa Sandstone in the northeast part of the state.     There are large coal-fired power plants in the area that may need to find ways to dispose of CO2 generated by burning the coal for electricity.  [Right, geologic map showing study area.  Black squares indicate power plants.  Credit, AZGS]

The report is posted online in the AZGS Document Repository for free viewing and downloading.  
The publication summary notes:
Northeastern Arizona encompasses the southwestern part of the Colorado Plateau, an area of gently dipping to slightly tilted Paleozoic and Mesozoic strata that include porous and permeable sandstone units. The Lower Permian Cedar Mesa Sandstone was identified for study as a potential target for CO2 sequestration in order to reduce anthropogenic CO2 emissions to the atmosphere. The Cedar Mesa Sandstone is overlain by the impermeable Organ Rock Formation, which is necessary to prevent escape of sequestered CO2. The salinity of groundwater in the Cedar Mesa Sandstone is unknown, but must be determined before CO2 can be sequestered because CO2 sequestration is not permitted in potable groundwater under current regulatory conditions. Well logs for 755 drill holes were used to evaluate the extent, depth, and thickness of subsurface formations. ESRI® ArcMap™ software was then used to calculate the volume of the Cedar Mesa Sandstone where the top of the unit is below 3000 feet (915 meters) depth, which is the minimum depth necessary for CO2 sequestration where the CO2 is under sufficient pressure to remain in a dense, nearliquid state. Well logs were used to evaluate porosity, which was then used to calculate the amount of pore space that is theoretically available for CO2 storage (the effective porosity). We calculate that there are between 30 km3 and 80 km3 of pore space in the Cedar Mesa Sandstone. The fraction of pore-space volume that is accessible to CO2 injection is estimated to be approximately 0.5% to 5%. Applying this storage efficiency to the Cedar Mesa Sandstone indicates that 0.15 km3 to 4.3 km3 of pore space is accessible to injected CO2, and that 0.114 to 3.24 billion tonnes of CO2 could be sequestered in this pore space at a density of approximately 750 kg/m3. 
Ref:  Rauzi, S. L. and Spencer J.E., 2014, An evaluation of carbon dioxide sequestration potential of the Permian Cedar Mesa Sandstone, northeastern Arizona. Arizona Geological Survey Open File Report, OFR-14-03, 22 p.

No comments:

Post a Comment