Electrical logging has been widely used in the exploration and development of the Illinois basin oil fields of Illinois, Indiana, and Kentucky. Standard logging techniques have evolved during the decade of activity in the basin.

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The relations of electrical values to formation fluids, lithology, porosity and permeability, drilling fluids, and hole diameter are discussed.

Electrical logs have furnished valuable records of the wells drilled. They have formed the basis for much of the stratigraphic and structural work in the territory. Recognition of commercial saturation in wells and prediction of reservoir behavior have been successful in some cases by integration of electrical log data with core and production information. The electrical log has been a valuable tool in guiding completions.

The available electrical-log information on the wells of the Illinois basin promises additional future value in further exploration and secondary-recovery operations.

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