Semester

Summer

Date of Graduation

2006

Document Type

Thesis

Degree Type

MS

College

Eberly College of Arts and Sciences

Department

Geology and Geography

Committee Chair

Thomas Wilson

Abstract

This study presents a detailed analysis of open fracture systems observed in FMI logs through the oil producing Tensleep Formation at Teapot Dome. Open fracture systems in the Tensleep were compared to surface fracture distributions reported by Cooper (2000). Systematic fracture sets observed in the Tensleep consisted primarily of W and WNW striking sets oriented obliquely to the northwest trending hinge of the Dome and dipping on average between 78° and 58°. Hinge-parallel and hinge-perpendicular sets, common at the surface, were rarely encountered in the wellbore. Observations were made in vertical wells along the hinge of the anticline where bedding is nearly horizontal, and the probability of intersecting vertical fractures, small. The present day maximum compressive stress inferred from drilling induced fractures is oriented, on average, N80W. CO2 flooding and hydraulic fracturing will generally enhance production along the W and WNW open fracture trends.;2D fracture networks were created of the Tensleep Formation using the NETL program FRACGEN. Fracture orientation, dip and aperture measurements were calculated directly from FMI logs. Fracture dip, bedding plane dip, and the frequency of fractures per foot of borehole were used to determine fracture spacing. Fracture spacing appeared to increase in a broad linear fashion as the thickness of the Sandstone A and Sandstone B increased. The Dolomite B layer revealed a broad linear decrease per bed thickness. A histogram of fracture apertures indicated an exponential decay distribution. There are many small apertures (less than 0.0012in) and few large apertures (greater than 0.0028in). A power law relationship between aperture and length was used to estimate fracture length in the Tensleep. Fracture lengths estimates range from 0.47 meters to 27.42 meters. Fracture lengths were shorter for the Sandstone A and Dolomite B layers, and larger for the thicker Sandstone B layer.

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