The Prospective Deep Miocene in the Gulf of Mexico Shelf: Compartmentalization Knowledge of the Geopressured Depositional System Sheds Light on Immense Exploration Potential
Selim S. Shaker, Walter W. Wornardt, Jr., 2013. "The Prospective Deep Miocene in the Gulf of Mexico Shelf: Compartmentalization Knowledge of the Geopressured Depositional System Sheds Light on Immense Exploration Potential", Shelf Margin Deltas and Linked Down Slope Petroleum Systems–Global Significance and Future Exploration Potential, Harry H. Roberts, Norman C. Rosen, Richard H. Fillon, John B. Anderson
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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.