IDENTIFYING SUBTLE FRACTURE TRENDS IN THE MISSISSIPPIAN SALINE AQUIFER UNIT USING NEW 3-D SEISMIC ATTRIBUTES
New 3-D seismic attributes, including a suite of volumetric reflector curvature attributes developed at the University of Houston, have the potential to reveal subtle lineaments that can be related to fractures in the aquifer. Volumetric curvature attributes are calculated directly from a seismic data volume, with no prior interpretation required, and have been shown to be useful in delineating faults, fractures, flexures, and folds.
Volumetric curvature attributes applied to 3-D seismic surveys over the Mississippian aquifer in Kansas reveal two main lineament directions within the Mississippian, with orientations of approximately N45E and N45W. The N45E-trending lineaments parallel a down-to-the-north normal fault at the northwestern corner of one of the seismic surveys, and appear, on average, to have greater length and continuity than the N45W-trending lineaments. Fluid and pressure data tied to flow simulation suggest that the N45E-trending lineaments may be related to shale-filled fractures, while the N45W-trending lineaments may be related to open fractures that are conduits for water. Both sets of lineaments are related to karst-enhanced fracturing in the Mississippian.
Imaging of natural fractures within an aquifer system to be used for CO2 sequestration is required to maximize injection and storage of CO2 and minimize early breakthrough between wells. Also, detection of fractures is critical to evaluating the integrity of overlying seal. New 3-D seismic attributes help to locate these fractures and could become an important tool in the evaluation of potential geological sequestration sites.