The effective use of electromagnetic methods to delineate a fluvial paleochannel system controlling oil migration near Glenrock, Wyoming
- Roy F. Weston, Inc., Albuquerque, NM (United States)
- Univ. of Southern Maine, Gorham, ME (United States)
- EPA, Cincinnati, OH (United States)
A combination of three different electromagnetic methods was effectively used to map the shallow lithologic variation interpreted to control the subsurface migration pattern of hydrocarbons near Glenrock, Wyoming. Petroleum hydrocarbons were seeping from the south bank of the North Platte River approximately one half mile west of the Township of Glenrock, Wyoming. Product was moving along the top of the water table through coarse grained sediments and discharging into the river. Initial investigations, resulting in the excavation of three trenches, were unable to determine the source-an&migration pathways that the hydrocarbons were following. A geophysical survey was performed that provided a map of the subsurface geology that controlled free and dissolved product migration. The geophysical methods used included terrain conductivity, using two instruments that allowed two different coil separations (the Geonics EM-31 and EM-34), and transient electromagnetics (TEM). The portability and data collection efficiency of the EM-31 guided its use as a reconnaissance tool. Data from the EM-31 provided a map of near-surface conductivity patterns indicative of shallow lithologic variation between coarse-grained paleochannel deposits and fine-grained fluvial overbank sediments. Correlation of the EM-31 response with, known geology observed in test pit excavations resulted in some concern as to whether the mapped lithologic variation was too shallow to have controlled groundwater migration. To address this, the EM-31 was operated at ground, and at 3 and 7 feet (ft) heights above ground over a hi h conductivity zone (interpreted to be fine grained material). Data obtained indicated that the high conductivity material was not a thin surficial veneer, but instead represented fine- grained deposits at depths of 0 to greater than 10 ft.
- OSTI ID:
- 381522
- Report Number(s):
- CONF-960477--
- Country of Publication:
- United States
- Language:
- English
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