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

Stratigraphy impacts sand (reservoirs) and shale (seals) spatial distributions. Generally, sandy facies prevail in most of the inner shelf environments. On the middle shelf, there is a tendency of losing the sand content with increasing distance from shore. Prograding downdip to the deeper parts of the basin, shale content continues to increases in the outer shelf. The optimum depositional environment for hydrocarbon trapping mechanism lies in the transition zone between the middle and outer shelf paleoenvironment, where sand to shale ratio is conducive to sealing juxtaposed fault surfaces.

Geopressure differentials play a principal role in the migration of hydrocarbon from deeper source rocks and carrier beds to the potential closures. The subsurface geopressure profile is usually divided into two main zones: the lower geopressured and the upper hydrostatic. The divergence between the two zones represents the top of geopressure. The depth to the top of geopressure usually corresponds to the sand content of the shallow sediment, with the higher the sand content deepening the top of geopressure. Noteworthy, the transition between the hydrostatic and the geopressured zones accommodate the migrated hydrocarbon from deeper formations to be trapped in the adequate geological setting. Therefore, the surrounding sections above and below the top of geopressure yields a large share of hydrocarbon accumulation.

The concept of combining the optimum stratigraphic and geopressure fairways in a mapable fashion is the central part idea of this technique. Figure 1 shows the relationship between the maximum flooding surface (MFS) of the stratigraphic unit and the top of geopressure (TOG). The interception (zero value) between the two surfaces yields very important outcomes. It is the pivot level where the sedimentary section with positive values is in the hydrostatically pressured system. On the other hand, negative values represent the depth of the geopressured stratigraphic unit below the top of geopressure (Fig. 2). As a result, the geopressure gradient in a specific stratigraphic sequence can be calculated at any specific location.

The “Strat-Geopressure Fairway” represents the spatial belt surrounding the interception’s contour where stratigraphic top (MFS) and TOG are met. Incorporating the established producing horizons (from the offset wells) to these fairways provides an essential fast track tool for pre-drilling assessment of a prospect, lead and play concept.

 Figure 1. The conceptual model where the stratigraphic top (MFS or maximum flooding surface) follows the shelf paleo-topography. On the other hand, it shows the rising of the top of geopressure in the downdip direction due to increases of shale/sand ratio downdip. ST-GP = Strat-Geopressure.

Figure 2. This illustration shows the “Strat-Geopressure Fairway” as a result of the interception of the top of geopressure with the maximum flooding surface.