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Canyon (Pennsylvanian) Sand Prospecting in Nolan County, Texas, Using Electrotelluric Survey Methods

Robert B. Lanter, Michael R. Birkos

The Upper Pennsylvanian section of the Eastern shelf is comprised of several channel sands encased in shales. Typically, exploration for these sands involves using existing well control. Locations are picked by extrapolating the sand continuity from both well control and the depositional trends of sands in surrounding fields.

Electrotelluric surveying, a method which uses a passive surface detector of electrotelluric radiation, was employed in Lake Tramell field of Nolan County to define the limits of a locally productive Canyon sand. Using existing well control to calibrate the instrument, the electrotelluric response for the prospective sand was ascertained. Several electrotelluric survey points were taken across the field. Sand extent was determined by correlating the electrotelluric response patterns from calibration points to the various survey points. Two well locations were staked on survey points that exhibited a potentially commercial thickness of sand.

When the two locations were drilled, the accuracy of the electrotelluric survey, with respect to sand presence and thickness, was confirmed. The electrotelluric survey provided an effective method of evaluating potentially productive sands from the surface prior to drilling.

AAPG Search and Discovery Article #91037©1987 AAPG Southwest Section, Dallas, Texas, March 22-24, 1987.