Comparing PP and PS seismic characterization of fractures in the Mississippian Meramec and Osage intervals of the STACK play, Oklahoma

Abstract

Fractures often provide a mode of secondary porosity and significantly improve rock permeability and reservoir quality. This study characterized fractures within the Mississippian Meramec and Osage intervals of the STACK play in central Oklahoma using the converted mode PS seismic data (waves propagate down as P-wave and reflect as S-wave). The study also evaluated the efficacy of the PS data for fracture characterization by comparing the results of this study with a previous seismic PP (waves propagate down as P-wave and reflect as P-wave) study of the same geological intervals and the shear wave dipole-dipole sonic log. The study adopts a seismic-based fracture characterization workflow that integrates multiple seismic attributes and builds a Discrete Fracture Network (DFN) to better describe fractures density and orientation. The PS data showed the highest concentration of fractures in the westernmost area of the PS survey with a strike direction ranging from ~90-150 degrees, which correlates well with the fractures in the shear wave dipole-dipole sonic log. Comparing the DFN from the PP and PS seismic data indicates a good correlation between the results of the two seismic data sets. However, the PP data showed slightly more fractures, likely due to the higher frequency of the PP data, with a slightly different orientation from the fractures from the PS data. The shear wave dipole-dipole sonic log showed fractures with orientations that correlate with both the PP and PS fractures. Based on the results of this study, PP and PS data showed similar large-scale fractures; however, PS data have resolved fractures that were not characterized by the PP data. The study confirms the need to include joint PP-PS fracture characterization for a more robust fracture characterization of a reservoir. Joint interpretation of the PP and PS seismic data is highly recommended for better fracture characterization of a given reservoir instead of relying only on the analysis of PP seismic data.