John D. Grace1
(1) Earth Science Associates, Long Beach, CA
ABSTRACT: Extension Exploration with 3-D and 4-D GIS
Regional exploration has dominated traditional GIS applications in petroleum geology. Heretofore, the technology's limitation to 2-D impeded its application to field extension problems. Recent advances in GIS technology have radically lowered the barrier to exploiting GIS in the data-rich, but inherently 3-D environment of a producing field.
A comprehensive 3-D GIS covering all of the fields of the Gulf of Mexico was developed based on data released by the US Minerals Management Service. This includes all wells, completions, paleo picks and 3-D polygons ("volygons") for over 7,500 producing reservoirs. The drainage area of each reservoir's completions and the thickness of each perforation were used to estimate reservoir volygons. All elements of the 3-D model are tied back to their engineering and geologic attributes, supporting very flexible mapping and access to production and test data within the 3-D environment.
The fourth dimension, time, is introduced by sorting monthly observations on production (or well tests) by completion within a reservoir. These data are gridded within each reservoir for each month (or year) and the maps then draped on the top surface of the reservoir volygon. By draping each month's (or year's) map sequentially, changes in the variable can be "animated" by stepping forward or backward in time through the maps.
This 4-D perspective, combined with GIS functionality, aids in identification of by-passed pay, reservoir heterogeneities, water coning and pressure maintenance problems. Analysis of reservoir performance in 4-D also suggests locations for step-out and in-fill drilling locations within and around producing units.
AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado