271-11 Characterization of Fractures in the Shakopee Dolomite of Indiana for Subsurface Energy Activities

Session: Geologic Energy Resources and Storage for Now and the Future (Posters)

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Characterization of subsurface fracture networks is an important step in site selection for subsurface energy projects. The National Energy Technology Laboratory (NETL) possesses a suite of computed tomography scanning equipment that can be used to characterize cores and obtain mm to cm-scale lithologic data for collaborative research initiatives. The Mitchell CarbonSAFE project is one such feasibility study which assesses the potential to store carbon dioxide in Cambro-Ordovician strata, such as the Shakopee Dolomite, in Mitchell, Indiana. A 4,200 ft stratigraphic test well was drilled to understand the lithostratigraphic characteristics of potential targets and seals. NETL’s medical, industrial, and micro-CT scanners were used to scan 300 ft of core from the well.   

The Mitchell core was non-destructively characterized through the use of data produced by the CT scanners, a multi-sensor core logger, and other measurements including resistivity, porosity, and permeability. The resulting scans were analyzed to isolate and characterize fracture geometries, secondary porosity, and mineralogy. In particular, a new methodology was developed using a suite of ImageJ plugins, including Labkit, BoneJ, and OrientationJ, to segment images from a representative selection of depths using a random forest machine learning algorithm and to perform image analysis for quantifying fracture and vug morphologies.   

Major features were identified in sections dense with void spaces and were compared to less porous sections to understand the variability within the Shakopee. Secondary porosity was calculated to be as high as 5.1% in especially vuggy sections or as low as 0.2% for sections with a single identifiable fracture. The differences may correlate with the depositional environment, as higher numbers of fractures are expected to be associated with subtidal settings. Other parameters such as length, thickness, and sphericity were recorded, as well as orientation, revealing a high percentage of vertically angled features. This data will provide key insights for the Mitchell CarbonSAFE project, particularly in understanding the secondary porosity within the Shakopee, likelihood of injection-stimulated fractures, their orientation, and potential for vertical fluid migration. These pore-scale dynamics offer novel considerations for modeling buoyant fluid injection scenarios and predicting fracture connectivity in formations targeted for resource extraction. 

Geological Society of America Abstracts with Program. Vol. 57, No. 6, 2025

doi: 10.1130/abs/2025AM-9131

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