Since drilling started in the 1920s along the Nemaha Ridge of north central Oklahoma and south central Kansas, the Cleveland Formation has traditionally been viewed as a shallow (2,500'-3,000'), thin, tight-oil tertiary objective on the way down to other more economic objectives. By integrating high-resolution 3D seismic and detailed sequence stratigraphic analysis, thicker, productive Cleveland reservoir fairways can be identified and drilled economically on the Nemaha Ridge.
Cleveland depositional systems in the Nemaha Ridge area include river-dominated deltas and incised valleys, each with distinctive log and seismic characteristics. Deltaic reservoir successions occur in the upper two thirds of the Cleveland interval and are usually the best reservoirs. The deltaic reservoir units are composed of very fine to finegrained sanding-upward successions exhibiting dip-elongate behavior and rapid changes along strike.
Optimal drilling locations are best identified by fine-scale correlations and seismic mapping, linked to subtle syn-sedimentary tectonics. High-resolution 3D seismic and multi-attribute analysis has proven a key tool in differentiating and predicting optimal reservoir trends in this new play and sets up an opportunity for focused horizontal exploitation that can be broadly applied to a number of other similar plays in old development areas.
The study area is located along the Nemaha Ridge in Kay County, Oklahoma and Sumner County, Kansas (Figure 1). Production along the Nemaha Ridge has historically been generated from Paleozoic sediments ranging from Cambrian to Permian in age trapped within "pop-up" and other structural features that formed as a consequence of wrench style tectonics initiated during the early Pennsylvanian that formed the Nemaha Ridge. Conservatively, ~2.8 billion barrels of oil have been produced from primarily structural traps in and around the Nemaha Ridge but stratigraphically-trapped accumulations of oil have been pursued with much less vigor. This case study will demonstrate how new technology (i.e. cost effective, high-effort 3D seismic and multi-attribute analysis) used in concert with highly detailed sequence stratigraphic correlations and horizontal drilling and completion techniques can be applied in a mature area to exploit more complexly-distributed reservoirs in a repeatable fashion.