Master's Theses

Document Type

Thesis - campus only access

Date of Award

Fall 1989

Degree Name

Master of Science (MS)

Department

Geosciences

Advisor

Ken Neuhauser

Abstract

The Welch-Bornholdt field in Rice and McPherson counties, Kansas is located in a region characterized by ancient structural trends that have undergone intermittent movements since the Precambrian. These movements affected lithofacies patterns and the generation, migration, and trapping of hydrocarbons during and after the deposition of the Simpson Group (Middle Ordovician). The study area covers approximately 500 square miles and includes several oil and gas producing fields along with the Welch -Bornholdt field. The Simpson Group was subdivided into depositional facies using electric logs and sample analysis. The analysis of selected well samples and available geologic reports indicates that the upper part of the Simpson Group is increasingly calcareous in nature and characterized by rapid lithofacies changes. In addition, hydrocarbon shows are primarily found in the upper part of the Simpson Group. Electric logs of the upper part of the Simpson Group exhibit a consistent profile that is traceable across the study area, indicating lateral continuity. Horizons of interest were picked from and correlated by electric logs and were entered into a data base. Computer-generated structure contour and isopach maps were constructed in order to compare the structural conditions of the Welch-Bornholdt field to those found in other fields that produce from the Simpson Group. Relatively few electric logs penetrate the entire Simpson Group, thus shallow marker beds were used to infer deeper structural attitudes. Production form the Simpson Group is presently limited to fairly well-defined structural trends east of the axis of the Conway Syncline. Faulting has enhanced the trapping conditions in some fields. The Welch-Bornholdt field, located west of the axis of the Conway syncline, occupies a favorable position with respect to hydrocarbon generation and migration. Source rock studies and oil shows indicate the potential of hydrocarbon reservoirs in rocks of the Simpson Group. Similar lithologies and identical electric log profiles and responses are found in the Welch-Bornholdt filed and other fields producing from the Simpson Group. In addition, previously proposed fault trends would enhance potential traps. Areas of structural closure on the shallower horizons, thin isopach intervals, and the previously proposed fault trend should be explored for production from the Simpson Group as a secondary hydrocarbon target below the Mississippian.

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Rights

© 1989 Michael P. Fletcher

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