• Integrated Application of Petrophysical and Geophysical Inversion Techniques for Reservoir Quality Prediction in the Cretaceous Nanushuk Formation, North Slope, Alaska

      Foreman, Jennafer L. (University of Alaska Anchorage, 2021-05-01)
      Recent Brookian discoveries on Alaska’s North Slope has re-focused petroleum exploration, redirecting industry interest towards pursuing younger, shallower, often stratigraphically trapped reservoirs of the Nanushuk and Torok formations. In order to effectively and continuously characterize the reservoir properties of these prospective reservoir formations, an advanced, integrated petrophysical and seismic interpretation workflow is needed. By infusing the post-stack model-based inversion workflow with the results of a detailed petrophysical, the resultant inverted acoustic impedance cube reveals quantifiable reservoir property information based on optimized log-measured data inputs at every trace location across the entire 3D seismic volume. This integrated workflow was applied to the Nanuq South 3D seismic volume to detect quantifiable variations in Brookian reservoir quality across the study area. The low frequency background model used to guide the inversion process was generated based on log-measured data from the Itkillik River Unit 1 well. Drilled in 1978, this well contains data of a quality consistent with the logging technology available at the time and is representative of the type of data available across much of Alaska’s exploratory basins. The integrated inversion workflow generated an inverted impedance volume that successfully detected the Narwhal Sand, a Nanushuk equivalent reservoir penetrated by the Putu 2 and Putu 2A wells, despite failing the majority of the blind well tests. By selecting a well with legacy or vintage data to train the background model, this project demonstrated that seismic inversion can yield meaningful results regardless of the vintage of well data chosen to train the background model.