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ABSTRACT: Modeling Salt in a Three-Dimensional Structural Context


The three-dimensional nature of salt bodies has historically been a problem in visualization and interpretation. Traditional approaches, based on two-dimensional grids, cannot handle the multi-valued surfaces of salt overhangs, lenses, or other features. Some three-dimensional modeling approaches allow multi-valued surfaces, but cannot combine the image of a salt body with surrounding structural layers. These limitations can be avoided by combining appropriate salt modeling techniques with a geospatial structural model.

The geospatial modeling process treats faults and horizons as separate entities; this approach is ideally suited for modeling faulted structures. Horizons are truncated against fault surfaces (and/or other horizons), providing an internal consistency in the resulting structural model. Previously, the geospatial model required a three-dimensional object, such as a salt body, to be represented by a three-dimensional grid. This data structure, while useful, was too cumbersome to handle some of the fine detail of a salt body, and required a significant amount of data preparation.

A new methodology of surface generation, which bypasses the gridding step, has been developed and incorporated into the geospatial modeling process. This new methodology allows more complicated shapes to be built and changed easily, while still providing all of the benefits of the structural model's fault block-oriented display. This approach has been used successfully to develop structural models for accurate and precise well planning, increasing the confidence in the interpretation and decreasing the uncertainty and risk often associated with drilling near salt.

AAPG Search and Discovery Article #90941©1997 GCAGS 47th Annual Meeting, New Orleans, Louisiana