The new concept of integrating sequence stratigraphy and geopressure compartmentalization is a comprehensive risk assessment tool, and this concept is essential for the risk assessment of the deep gas (reserves) on the shelf area of the Gulf of Mexico. This is especially true in the mature West-East Cameron areas where untested large, deep Miocene structural closures exist. In the early 80's, the crests of some of these deep structural closures (>15,000 feet) were tested. Exploration of these deep Miocene closures was discouraging by the failure to find commercial hydrocarbon-bearing formations. Building sedimentary models using well logs, paleoenvironment data, sand maps, and sequence stratigraphy helps project the pattern of the sediment influx from the outer shelf to the slopes and bathyal environments. Ponded sand sheets and basin floor fans are the reservoir facies in the slopes and the bathyal environment. The deep-water environment in the slopes and bathyal promote the forming of the maximum flooding seals. The paleoenvironment spatial distributions in relation to the structural setting of the sequence stratigraphic units, such as progradational and retrogradational deposition of sequences are responsible for the architectural development of lateral pressure compartments. Maximum flooding surfaces form effective seals and have great impact on the vertical partitions. These deep compartments are generally geopressured (abnormally pressured). The hydrocarbon entrapment capability in this deeply buried section is a function of the ratio between the pore pressure and the fracture pressures. Pressure transgression and regression are mainly impacted by the communication between these laterally and vertically partitioned stratigraphic systems. Reservoir quality and the shale cap sealing capacity of the structural closure are determined by the interrelationship of the sediment paleoenvironment and the subsurface pore pressure development. Several case histories in the deep Miocene promote some new exploration approaches and enhance old play concepts.

Abstract The complex interaction between salt and surrounding sediments makes risk assessment of a prospect or play concept a challenge. Geopressure compartmentalization in the Gulf of Mexico Tertiary-Quaternary salt basins is created mainly by the principle stresses resulting from interaction between the sediment load and tectonic movement of salt. The unique petrophysical properties of salt contribute to changes in the structural setting and affect the sealing capacity and hydrocarbon retention capability of traps. The low density of salt may retard the sealing capacity in subsalt sediments, while enhancing the seal capacity in supra-salt sediments. Because salt is relatively impermeable, its contact with surrounding sediments forms a barrier to hydrocarbon movement. The integrity of the sealing interface is usually impacted by the salt tectonic history. The ductile nature of salt creates different forms of salt tectonics, such as diapirs, ridges, salt withdrawal basins, overhangs, canopies, etc. , that have a direct impact on stress orientation. Establishing the predicted pore pressure in the impermeable beds (shale) compared to the measured pressure in the reservoir facies (sands), plays an important role in assessing the entrapment and sealing capacity of traps. In this study, wells are analyzed from several different salt tectonic settings in the Garden Banks, Mississippi Canyon, and Green Canyon protraction areas ( Fig. 1 ). While a great deal is known about salt body delineation from geological and geophysical data, this paper addresses salt-related hydrocarbon traps from a geopressure standpoint. Figure 1. Location map shows the areas discussed in this paper.