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A Fundamental Approach to Dipmeter Analysis

Milton B. Enderlin, Diana K. T. Hansen

Historically, in dipmeter analysis, depositional patterns are delineated for environmental, structural, and stratigraphic interpretations. The proposed method is a fundamental approach using raw data measurements from the dipmeter sonde to help the geologist describe subsurface structures on a stratigraphic scale. Raw data are available at the well site, require no post-processing, and can be combined with computed results, if available. They also are cost effective and easy to use, and they require only a basic knowledge of sedimentary features and facies. Case studies illustrate the successful reconstruction of sedimentary features from raw data logs recorded by four-and six-arm dipmeters.

The dipmeter is a wireline tool with a series of evenly spaced, focused electrodes applied to the circumference of the borehole wall. The raw data are presented as curves representing the electrode response and tool orientation. Using these data on an expanded scale, the geologist can reconstruct a plausible three-dimensional picture of individual sedimentary features. In outcrop, the geologist usually can see an entire sedimentary feature in a large frame of reference, that is, with the surrounding landscape. Thus, a large range of features can be recognized. However, in the borehole environment, the frame of reference is reduced to the borehole diameter, which because of its size, reduces the range of recognizable features. In our study, we developed a table that identifies the feat res distinguished by the proposed method, as a function of borehole diameter.

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