Meandering Channel-Fill Facies Architecture using Ground Penetrating Radar in the Ferron Sandstone (Upper Cretaceous), Emery County, Utah
Abatan, Oluwasegun; Kerr, Dennis R.; Ramachandran, Kumar
Detailed investigations of meandering channel belts in the Ferron Sandstone was made using ground penetrating radar (GPR) with the aim of characterizing riffle facies elements. Riffles facies architecture elements are developed along channel thalweg reaches between two successive pools and flanked by lateral accretion bar facies architecture elements. Riffle elements have received little attention, despite their potential importance to pore-fluid flow within meandering channel reservoirs. This study describes the geometry and facies architecture of meandering channel fill using 2-D and 3-D GPR imaging data. GPR data acquisition was guided by outcrop exposures of a meandering channel belt segment. A 2-D GPR data acquired on 65,000 sq meters, with an embedded 36,000 sq meters of 3-D GPR surveys, were acquired along a channel thalweg between successive pools.
GPR data were processed and corrected for direct wave influences, topography and background noise. The GPR reflection times and trace amplitudes were used to interpret the geometry and facies architecture of the meandering channel-fill deposits. The reflectors are interpreted as bounding surfaces and the reflection amplitudes are used to describe GPR facies architecture.
Using an average velocity of 0.15m/ns, estimated depth to the base of the channel-fill deposit is a maximum of 4m below the surface which corresponds to a basal laterally continuous strong reflector. Geometry of outcrop exposures of lateral accretion bars projected into the subsurface can be observed in the GPR data as less continuous reflectors down-lapping against the basal reflector. The geometry and GPR radar characters of sedimentary structures interpreted from 2-D and 3-D GPR data correlate with outcrop characterization. A pseudo 3-D GPR data volume constructed from 2-D GPR data is used to identify the riffle location and describe the boundaries and evolution of the channel belt element. Preliminary interpretation of 3-D GPR data acquired over the presumed riffle tracts identify the riffle element as having low variable density (VD) contrast amplitude values, which might be due to a high level of textural sorting in riffle sandstones.
AAPG Search and Discovery Article #90163©2013AAPG 2013 Annual Convention and Exhibition, Pittsburgh, Pennsylvania, May 19-22, 2013