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