Finding New Pays in Old Plays: New Applications for Geochemical Exploration in Mature Basins
D. Schumacher and D. C. Hitzman
Geo-Microbial Technologies, Inc., Ochelata, OK
Detailed geochemical surveys document that hydrocarbon microseepage from petroleum accumulations is common and widespread, is predominantly vertical, and is dynamic. These characteristics create a new suite of applications for surface geochemical surveys: field development, finding by-passed pay, and monitoring hydrocarbon drainage. Because hydrocarbon microseepage is nearly vertical, the extent of an anomaly at the surface can approximate the productive limits of the reservoir at depth. The detailed pattern of microseepage over a field can also reflect reservoir heterogeneity and distinguish hydrocarbon-charged compartments from drained or uncharged compartments. Additionally, since hydrocarbon microseepage is dynamic, seepage patterns change rapidly in response to productioninduced changes.
Evidence for such changes are documented with detailed microbial and soil gas surveys from Texas, Oklahoma, and Kansas. When such surveys are repeated over the life of a field or waterflood project, the changes in seepage patterns can reflect patterns of hydrocarbon drainage. Applications such as these require close sample spacing, and are most effective when results are integrated with subsurface data, especially 3-D seismic data. The need for such integration cannot be overemphasized. High-resolution microseepage surveys offer a flexible, low-risk and low-cost technology that naturally complements more traditional geologic and seismic methods. Properly integrated with seismic data, their use has led to the addition of new reserves, drilling of fewer dry or marginal wells, and optimization of the number and placement of development or secondary recovery wells.
AAPG Search and Discovery Article #90900©2001 AAPG Eastern Section Meeting, Kalamazoo, Michigan