Date of Graduation

8-2012

Document Type

Thesis

Degree Name

Master of Science in Geology (MS)

Degree Level

Graduate

Department

Geosciences

Advisor/Mentor

Xie, Xiangyang

Committee Member

Manger, Walter L.

Second Committee Member

Zachry, Doy L.

Keywords

Earth sciences; Carbonate; Oklahoma; Petroleum; Reservoir

Abstract

The Reeds Spring Formation (Osagean) is a member of the Lower Mississippian carbonate series developed on the Cherokee Platform Province of northeastern Oklahoma. On the western flank of the Ozark Dome, these rocks dip in a west-southwest direction into the subsurface where they are oil and gas reservoirs. A series of road cuts and surface exposures are cropped out in the tri-state area of northwest Arkansas, northeastern Oklahoma, and southwestern Missouri. Outcrop characteristics, including an abundant amount of nodular, anastomosing chert, generally finer-grained carbonate texture, and stratigraphic relationships provide an analog for its subsurface counterpart. Based on core description and well log correlation, the Reeds Spring Formation developed in the Cherokee Platform in western Osage and eastern Kay County, Oklahoma reflect transportation of crinozoan detritus, spicules, and carbonate mud off the Burlington shelf, passing downslope from the north, northwest, and

northeast, into deeper waters of the deep shelf margin setting. As the result, its subsurface lithologies are characterized by shaly fine-grained spiculitic crinoid wackestone. Subdivision of the formation, which exceeds 200 feet in the subsurface, offers more control on determining reservoir quality across a large study area (approx. 840 square miles). Criteria used to examine reservoir quality include clean carbonate content, true porosity, and high resistivity signatures. Additionally, Formation Micro-Image (FMI) log evaluation shows that the chert content does not develop in the Reeds Spring Formation where low gamma ray (<40 >API) and high resistivity (+90 ohm-m) signatures are absent. An anomalous amount of silt and clay content, identified by thin section and petrophysical analysis, reveals that the Reeds Spring Formation lacks vertically and laterally continuous reservoir grade rocks across a large area. Across western Osage and eastern Kay County, Oklahoma the lower member of the Reeds

Spring offers the poorest reservoir quality, the middle member the best, and the upper member moderate quality.

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