Sequence Stratigraphy and Environments of Deposition for the Springer Shale at Carter-Knox Field, Anadarko Basin, Oklahoma

Abstract

Proprietary whole cores penetrating the reservoir and non-reservoir facies of the Springer Shale reveal stark contrasts in lithology which help explain the mechanisms responsible for this tight oil play. In Carter-Knox Field and immediately adjacent areas, successful horizontal Springer Shale wells land near the base of a limited, ~40 ft. to 250 ft. thick horizon (the “Upper Springer Target”) within a more than 2000 ft. thick gross, “non-reservoir” section. Compared to the non-reservoir, the Upper Springer has elevated total organic carbon (3.4 % vs 1.6 %), quartz (50 wt. % vs 28 wt. %), and total carbonate (14 wt. % vs. <0.5 wt. %) concentrations, and lower clay mineral concentrations (28 wt. % vs 68 wt. %). Additionally, closely-spaced handheld XRF data indicate higher concentrations of redox- and productivity-sensitive trace elements (U, Mo, V, Cu, Ni) and lower concentrations of detrital-associated trace elements (Al, Ti, Zr) in the Upper Springer Target than in the encasing non-reservoir rock. Based on stacking pattern analysis of the detrital trace element and spectral gamma ray curves, we interpret that the Upper Springer Target represents highstand systems tract deposits from a second-order depositional sequence. During the highstand, the relatively proximal position of the shoreline trapped clay-rich detrital material near the coast, concentrating authigenic silica and calcite in basinal deposits. The highstand may also have brought about water column stratification and increases in primary productivity, concentrating and preserving organic matter in the Upper Springer Target. Non-reservoir portions of the Springer Shale are lowstand and transgressive systems tract deposits, and a maximum flooding surface occurs near the base of the Upper Springer Target. At least four regionally-correlative, increasing-upward cycles in detrital trace element concentrations and thorium gamma ray occur within the Upper Springer Target; we interpret these features as third-order paraseqeuences. The Upper Springer Target is a successful tight oil reservoir both because of its self-sourcing potential (elevated TOC) and because it contains sufficient concentrations of brittle minerals (quartz, calcite) to be susceptible to hydraulic fracturing. High gas-to-oil ratios (~50,000 scf/bbl) for Springer Shale wells on Carter-Knox despite thermal maturities in the early to peak oil window suggest a significant component of migrated hydrocarbons.

AAPG Datapages/Search and Discovery Article #90323 ©2018 AAPG Annual Convention and Exhibition, Salt Lake City, Utah, May 20-23, 2018