The Strat-Geopressure Fairways: A New Technique Advances Risk Assessment and Prediction of Deeper Potentials, Case History from the Gulf of Mexico

Selim S. Shaker
G.A.S., E.Stroudsburg, PA

The new technique of integrating stratigraphy and geopressure compartmentalization is a comprehensive risk assessment method of identifying under-explored leads and untapped deeper exploration targets. It also generates a more defined prediction of pore pressure in deeper reservoirs and their seal integrity.

Stratigraphy impacts sand (reservoirs) and shale (seals) spatial distribution. The optimum depositional environment for hydrocarbon trapping mechanism lies in the transition zone between the middle and outer shelf paleo-environment. In this zone, sand to shale ratio is conducive to sealing juxtaposed fault surfaces.

Geopressure differential plays a principal role in the migration of hydrocarbon from deeper source rocks and carrier beds to the potential closure. The subsurface geopressure profile is usually divided into two main zones: the lower geopressured and the upper hydrostatic. The divergence between the two zones sets the entrapment style and dictates production capability. Noteworthy, the transition between the two zones yields a large share of hydrocarbon accumulation.

By incorporating the established producing horizons to these Freeways, an essential fast track tool for assessing a prospect, lead and play concept can be applied. Moreover, it delineates the under-explored blocks, drilled bypass pay zones, undecided pay, and potential reservoirs and sheds light on areas of potential deeper exploration/exploitation targets.

On the Gulf of Mexico Shelf, well logs, paleo, production, and test data can be integrated in a data base. High Island-Galveston areas were used as a pilot study to test the new model. Producing, potential pays and reservoirs trends of the lower and middle Miocene were clearly following the most favorable trends where stratigraphy and geopressure gradient accommodate the optimum reservoir characteristics and effective seals.

AAPG Search and Discovery Article #90078©2008 AAPG Annual Convention, San Antonio, Texas