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

Abstract

ABSTRACT Regional deposystem maps offer insight into reservoir distribution in space and time. They can be valuable tools for exploration, yet 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 value of reservoir property prediction in undrilled areas are the principal objectives of this study. To this end, ordinary stratigraphic rationale was encoded to: 1) check the reliability of stratigraphic event data from many sources (in-house paleo; MMS tops; sequence stratigraphic studies; etc.); 2) determine an optimum stratigraphic record for each well by intelligently dealing with out-of-order events (remove; infer an unconformity; infer sub-salt; etc. ); 3) assign standardized ages to the optimized well records; and, 4) compute deposystem parameters suitable for gridding, e.g., uncorrected interval accumulation rate. Parameters such as accumulation rate are based on selected chronostratigraphic intervals (e.g., 23.0 MY - 24.0 MY) rather than on restricted, and not always equivalent events of variable nomenclature populating typical decades-old databases, e.g., Liebusella top, Cyclicargolithus abisectus top, etc. The less restrictive canonical intervals maximize available well control for all standard bio- /litho-stratigraphic units, permit the selection of arbitrary synoptic units, and provide an optimal base upon which to apply gridded steering operators to guide deposystem map extension into areas of limited well control. Steering operations may be performed in most of the popular gridding and mapping software packages. Second vertical derivative (SVD) gravity, i.e. density-driven steering of deposystem data into rank exploration areas is currently favored in the salt canopied northern Gulf of Mexico where geologically reasonable deposystem and sand maps have been generated. Seismic isochron steering is favored for exploration applications in unconfined basinal deposystems.