Osareni Ogiesoba
The University of Texas at Austin, USA
Title: Seismic attribute analysis for TOC, brittle zones, and faults within the Austin Chalk and Eagle Ford Shale, South Texas Gulf Coast
Biography
Biography: Osareni Ogiesoba
Abstract
Results from hydraulic fracturing have shown that high hydrocarbon-producing zones within shale resource plays are located in fractured, high-total organic carbon (TOC) rich zones. Thus, it is necessary to determine TOC distribution and fractures in shale resource plays, with the aim of matching high-TOC-bearing zones with fracture clusters. We integrated seismic attributes and acoustic impedance (AI) with wireline logs to determine TOC distribution within the Eagle Ford Shale and Austin Chalk in South Texas. We computed TOC from wireline logs using the ï„Log R method and then used seismic attributes to predict TOC and deep-resistivity log distribution, and identify brittle zones within the seismic survey. Our investigations show that although the lower Austin Chalk and upper and lower Eagle Ford Shale intervals constitute hydrocarbon-sweet-spot zones, resistivity values and TOC concentrations are not evenly distributed; thus, the rock intervals are not productive everywhere. Most productive zones within the lower Austin Chalk are associated with Eagle Ford Shale vertical-subvertical en echelon faults, suggesting hydrocarbon migration from the Eagle Ford Shale. High resistivity occurs in high-quality-factor (Q) attribute zones. Furthermore, resistivity and TOC increase as Q increases, suggesting that the Eagle Ford Shale is a unique shale in which TOC increases with increasing bed resistance—increasing carbonate. Because a strong positive linear relationship exists between AI and Q, Q can be used to identify brittle zones. The method described in this paper can be applied in other areas with similar geologic setting.