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Evidence for Continuity of Geochemical Halo Pattern with Depth

Douglas Denison, Ronald J. Dehaas

The Stoney Point field provides an excellent opportunity to examine the nature of geochemical halos as they vary with depth. Stoney Point Geochemical Surveys, Inc., has acquired an extensive data base of periodic crossings of the Stoney Point field. In addition, an extensive geological data base has been generated by drilling and use of mud logs in more than 60 tests of the field. Mud logs were generated from shallow depths to total depth; furthermore, virtually all of the mud logs were generated using the same (flame ionization detector) mud-logging equipment. Because such mud logs exist for both dry and productive holes in and around the field, one can compare the quantity and quality of shows at depth and the geochemical halo pattern at the surface.

The surface halo pattern in the summer months consists of low values (less than 5 ppm) of Sum C2-C4 over production, and high (ranging from 10 ppm to over 200 ppm) values of Sum C2-C4 in the proximal (dry hole) areas.

With depth, the integrated quantity of shows from the top of the Devonian Traverse limestone to the top of the productive Ordovician Trenton-Black River Limestone follows the same halo pattern. This integrated quantity indicates low (less than 10,000 ppm) quantities directly over the reservoir, with high (ranging from 10,000 ppm to more than 70,000 ppm) quantities in the proximal areas.

Although resistivity logs are uncommon in the field, the few resistivity logs available confirm the existence of the halo pattern at depth. Resistivities in the Utica Shale directly overlying the Trenton-Black River are 3-4 ohms higher in the proximal areas than directly over the reservoir.

AAPG Search and Discovery Article #91041©1987 AAPG Eastern Section Meeting, Columbus, Ohio, October 7-10, 1987.