FILLON, RICHARD H., RONALD L. PHAIR, and ROSEANNE J. JOWITT, Texaco, Inc., New Orleans, LA

Abstract: Well Data Projection into Undrilled Exploration Areas Using Gravimetric and/or Seismic Isochore Steering Functions

Regional deposystem maps offer insights into reservoir distribution in space and time. They can be valuable tools for exploration; however, their full potential for predicting reservoir quality ahead of the drill bit is limited by the location, quality and congruity of stratigraphic well control. Maximizing the impact of control data that may be abundant but spatially restricted, and improving the prediction of reservoir facies in undrilled areas are the principal objectives of this study. To this end, ordinary stratigraphic rationale was encoded and applied to: 1) check the reliability of stratigraphic event data from many sources; 2) determine an optimum stratigraphic record for each well by intelligently dealing with out-of-order events; 3) assign standardized ages to the optimized well records; and, 4) compute deposystem parameters suitable for gridding, e.g., uncorrected interval accumulation rates (UIARs). UIARs and other similarly derived parameters are based on selected chronostratigraphic intervals (e.g., 23.0 MY - 24.0 MY) rather than on restricted, and not always exactly equivalent events of variable nomenclature populating typical decades-old databases, e.g., Liebusella top; Discorbis "G" top; Cyclicargolithus abisectus top; "LH" flooding surface. The less restrictive canonical intervals maximize available well control for all standard bio/litho-stratigraphic units, permit the selection of arbitrary units, and provide an optimal base upon which to apply gridded steering operators to guide deposystem map extension into areas of limited well control. These steering operations may be performed in most of the popular gridding and mapping software packages. Second vertical derivative (SVD) gravity, ie. density-driven steering of deposystem data into rank exploration areas is currently favored in the salt canopied northern Gulf of Mexico where we have generated geologically reasonable deposystem and sand maps. Seismic isochron steering is favored for exploration in unconfined basinal deposystems.

AAPG Search and Discovery Article #90924©1999 GCAGS Annual Meeting Lafayette, Louisiana