Combining Ground Penetrating Radar and Outcrop Analysis to Reveal 3-D Sedimentary Architectures and Flow Properties in Deepwater Deposits of the Jackfork Formation, Arkansas

Abstract

High net-to-gross deepwater channel systems are desirable targets as reservoirs but difficult to map at high resolution in conventional seismic due to the lack of differentiation of their sandy lithologies from their silt-rich muds. Here, the 3D interplay of stratigraphic elements of deepwater slope channels are explored at the meter (m) scale in the high net-to-gross deposits of the Jackfork Formation in Pulaski County, Arkansas, a middle Pennsylvanian deepwater slope depositional system along the passive margin of an oblique foreland basin opposite the encroaching Ouachita accretionary prism. The study area consists of outcrops and near-outcrop subcrops of the Jackfork Formation interpreted by others to contain channel architectural elements including crevasse splays, sheets, and debris material. Previously acquired and processed ground penetrating radar (GPR) data of the top 3-5 m of subcrops are the primary data set for this study. GPR lines were shot in both two-dimensional (2D) lines and as tight grids interpolated into 3D. GPR data from multiple locations are interpreted to determine the of 2D and 3D geometries and dimensions of deepwater slope channel stories and map the 3D distribution and geometric relationships between various architectural elements. Where GPR data were collected directly above an outcrop, detailed outcrop analysis is carried out to check the quality of the GPR data in representing the stratigraphy and to correlate basic rock properties with the GPR data. Findings are extrapolated to locations lacking outcrop control in order to assess and model basic flow properties within and between stratigraphic architectural elements, identifying the 3D relationship between flow units and baffling facies within the channel. Further work will attempt to generate synthetic seismic using the outcrop-informed GPR data and upscale it to conventional seismic frequencies to determine if these high-resolution features create any detectable subtleties in conventional seismic data. Combined, this work provides insight into the nature of high net-to-gross deepwater channel deposits and can assist in identifying potential baffles and barriers to flow prior to full-scale, deepwater subsurface developments around the world.

AAPG Datapages/Search and Discovery Article #90259 ©2016 AAPG Annual Convention and Exhibition, Calgary, Alberta, Canada, June 19-22, 2016