Author

Larsen

Date of Award

8-2005

Degree Name

Master of Science

Department

Geological and Environmental Sciences

Department

Geosciences

First Advisor

Dr. William A. Sauck

Second Advisor

Dr. William B. Harrison III

Third Advisor

Dr. Michelle Kominz

Access Setting

Masters Thesis-Open Access

Abstract

Some hydrocarbon reservoirs have a documented reducing chimney, extending upward to the surface due to diffusion of hydrocarbon volatiles. This effect reportedly reduces the iron in the soil to magnetite and precipitates fine-grained pyrite if there is sufficient sulfur in the system. This study was conducted to test the detectability of the hypothetical chimney, using electrical geophysics in an environment of relatively recent glacial cover, known depth to an underlying petroleum reservoir, and known faulting.

The Calvin 28 oil field, in Cass County Michigan, is a middle Devonian domal field where reservoir rocks are draped over the central uplift block of an Ordovician impact structure with the outer crater diameter of about 4.5 km. A diffusion chimney should be detectable using induced polarization (IP), spontaneous potential (SP), and resistivity surveys. Ring fractures and faults can serve as permeable pathways and have been proven to yield enhanced halo effects. These effects can be detected and could result in important, less expensive exploration techniques. Results show possible evidence for a reducing zone and subtle spontaneous potential anomalies, supporting the hypothesis of a chimney model at Calvin 28 oil field. The recent deposition of a thick glacial overburden could be the cause of the weak SP anomalies. Induced polarization, though surveyed over a very small portion of the study area, did not show direct evidence of anomalous chargeability areas in the profile. Resistivity and VES inversion results show variations within the glacial cover near the center of the study area.

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Additional files attached.

17 Excel files.

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