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Mapping and characterization of potential geologic reservoirs are key components in planning carbon dioxide (CO2) injection projects. The geometry of target and confining layers is vital to ensure that the injected CO2 remains in a supercritical state and is confined to the target layer. Also, maps of injection volume (porosity) are necessary to estimate sequestration capacity at undrilled locations. Our study uses publicly filed geophysical logs and geostatistical modeling methods to investigate the reliability of spatial prediction for oil and gas plays in the Medina Group (sandstone and shale facies) in northwestern Pennsylvania. Specifically, the modeling focused on two targets: the Grimsby Formation and Whirlpool Sandstone. For each layer, thousands of data points were available to model structure and thickness but only hundreds were available to support volumetric modeling because of the rarity of density-porosity logs in the public records. Geostatistical analysis based on this data resulted in accurate structure models, less accurate isopach models, and inconsistent models of pore volume. Of the two layers studied, only the Whirlpool Sandstone data provided for a useful spatial model of pore volume. Where reliable models for spatial prediction are absent, the best predictor available for unsampled locations is the mean value of the data, and potential sequestration sites should be planned as close as possible to existing wells with volumetric data.
Erik Venteris, a senior geologist for the Ohio Department of Natural Resources, Division of Geological Survey, has worked on various carbon sequestration projects involving soil-based and geology-based approaches and has been collaborating with the MRCSP since 2004. His interests include applying statistics and geostatistics to earth science problems. Erik holds a Ph.D. in soil science and an M.S. degree in geology from the Ohio State University, and a B.S. degree in geology from Western Illinois University.
Kristin Carter joined the Pennsylvania Geological Survey in 2001 and currently serves as the chief of the Carbon Sequestration Section. Kristin researches oil, gas, and subsurface geology in Pennsylvania and surrounding states, particularly as they relate to geologic carbon sequestration opportunities. Kristin received an M.S. degree in geological sciences from Lehigh University and a B.S. degree in geology and environmental science from Allegheny College.