ABSTRACT

In the Gulf of Mexico, several salt related basins have attracted exploration. Keathley Canyon Block 255 Well #1 (TD 21550) has tested one of these basins. Extensive geological and Repeated Formation Tester data were collected from this well. Integration of the geopressure profile and the structural setting demonstrates two distinctive main compartments.

A hydrodynamically active compartment exists between the sea floor and the Hyalinea balthica upper Pleistocene shale section. This phenomenon may be responsible for the drilling problems and shallow water flow in this and similar relatively young basins. Therefore, entrapment of commercial volumes of hydrocarbon in this upper section is unlikely.

A hydrostatically geopressured main compartment extends between the upper effective seal of Hyalinea balthica to the Pliocene section at the bottom of the basin. This geopressured thick section shows a progressive pressure profile with depth and can be divided into five mini-compartments (C1, C2, C3, C4, & C5). Four of these mini-compartments show effective seals (S1, S2, S4 & S5). On the other hand, on both sides of the incompetent seal (S3), the pore-pressure gradient remains in the same hydrostatic envelope. This also exhibits communication between C2 and C3 and indicates exploration targets in the C3 are high risk.

Seals and reservoir lithology have a direct impact on the geopressure profile progression with depth. On the other hand, the structural setting is responsible for pore pressure differential between the seal and reservoir (centroid concept). Drilling on the crest of high relief closure can be a challenging task in deep water exploration.