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DEFORM: Construction and Evaluation of Curvature Maps, I. Principles

Michael Fahy, James D. Morse

Reservoirs requiring fractures for productivity become more viable exploration targets when technology is available to "high grade" for zones of deformation. DEFORM is designed to delineate these zones based on estimates of structural curvature.

At each point of a structural contour map there exist two principal directions of curvature: K1 (the maximum) and K2 (the minimum). These curvatures describe completely the geometry of the surface.

The traditional approach has been to map a single parameter of deformation, commonly the second derivative of the depth or z-values. There are problems with this approach. First, the correct estimate for curvature, k, along a profile direction, x*, is given by:


Maps of second derivative are incorrect in concept because they neglect the dz/dx* term. Second, these maps neglect explicitly any contributions to the deformation as a result of secondary curvature.

By properly processing the interpreter's contour map, DEFORM preserves all of the interpreter's skills and structural inferences. In addition, fractured reservoirs generally also have considerable directionality, which can be inferred from the curvature terms. DEFORM correctly makes these structural inferences explicit in a manner that allows targeting for deformation zones.

AAPG Search and Discovery Article #91038©1987 AAPG Annual Convention, Los Angeles, California, June 7-10, 1987.