Seismic reservoir characterization of the Bone Spring and Wolfcamp Formations in the Delaware Basin: Challenges and uncertainty in characterization using rock physics — A case study: Part 2

Abstract

The Bone Spring, Wolfcamp, Barnett and the Mississippian formations are the various prospective zones in the Delaware Basin, with the former two the most productive and thus are the most-drilled zones. Attempts at seismic reservoir characterization of these formations have been discussed in part 1, in which, after providing the geologic background of the area of study, the preconditioning of prestack seismic data, well-log correlation, accounting for the temporal and lateral variation in the seismic wavelets and building of robust low-frequency model for prestack simultaneous impedance inversion were explained. In part 2, we elaborate on the challenges and the uncertainty in the characterization of the Bone Spring, Wolfcamp, the Barnett and Mississippian sections, and how we overcame those. In the light of these uncertainties, we conclude that any deterministic approach for characterization of the target formations of interest may not be appropriate and build a case for adopting a robust statistical approach. Making use of neutron porosity and density porosity well-log data in the formations of interest, we demonstrate how the type of shale, volume of shale, effective porosity and lithoclassification can be carried out. Using the available log data, multimineral analysis was also carried out using a nonlinear optimization approach, which lent support to our facies classification. This exercise was then extended to derived seismic attributes for determination of the lithofacies volumes and their probabilities, together with their correlations with the facies information derived from mud log data.