ENDERLIN, MILTON, Phillips Petroleum Company, Bartlesville, OK

ABSTRACT: Using Strike to Find Dip: Neural-Optic Approach for Processing Non-Digital Dipmeter Data

When digital processing of dipmeter data is unattainable, untimely, unsuccessful, or questionable (such as in the presence of oil-based mud and/or very steep "in-hole dips", fast rotating and/or excessive tool motion, distorted and/or fractured rocks), neural-optic processing provides an approach for quickly ascertaining geologically sensible dip information. The neural-optic processing of non-digital dipmeter data is a simple method requiring the following items: (1) dipmeter pad response log at 1:20 to 1:240 scale; (2) tool orientation data such as azimuth of pad 1 and relative bearing; (3) borehole data such as diameter (preferably via calipers), deviation, and direction; (4) magnifying bar; (5) measuring scale; (6) stereonet; (7) hand calculator with trigonometric function. The ke element in neural-optic processing is identifying which pad response pairs have virtually no depth offset upon correlation with the aid of a magnifying bar. Such zero depth offset pad pairs are by definition positioned along strike. By knowing the dipmeter tool's geometry and orientation, the strike direction is then defined. Depth offsets of other pad pairs are measured with the magnifying bar and a scale. Taking the inverse tangent of the largest quotient of depth offsets and the distances between the pads, the "in-hole" dip magnitude is determined. The "in-hole" dip direction is in the general heading of the lowest (deepest) pad but EXACTLY at a right angle to the strike. A simple rotation of the stereonet subtracts the borehole direction and deviation from the "in-hole" dip orientat on to produce the "true" dip magnitude and direction.

AAPG Search and Discovery Article #90987©1993 AAPG Annual Convention, New Orleans, Louisiana, April 25-28, 1993.