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Methods of Interpreting Wireline Logs in an Igneous Reservoir

Bert A. Weimer, Mark S. Manwaring

New interpretation methods were derived for log evaluation in a reservoir composed of igneous rock. The hydrocarbon reservoir studied was the fractured igneous basement rocks that produce in the Panhandle field in Texas. The need to locate concentrations of natural fractures, recognize petrographic differences, and possibly determine fracture mineralogy created the need for improved interpretation of existing standard logs.

Logs used in this project were Dual Laterolog/Micro Spherically Focused Log, compensated neutron/lithodensity, density, natural gamma spectroscopy, continuous dipmeter, lithology analysis, oriented micro-resistivity, bond, and associated caliper logs. Many of the logs give similar information on reservoir parameters, but each provides uniquely useful data. Fracture occurrence can be determined from most of the logs, but a comparison of all logs yielded methods for qualitatively evaluating such features.

With such a cross section of referenced data, we can better evaluate reservoir quality from fewer key logs, which reduces logging costs with no loss of understanding in evaluating a well. Completion procedures and costs can be better controlled in wells when the reservoir is more fully understood. Although the study focused on only one area, the basic observations should be applicable in similar areas.

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