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Allochthonous Salt Base—Structure and Stratigraphy from Pompano Field, VK 989/990, Gulf of Mexico


Harrison, Holly, Lew Kuhmichel, Phil Heppard, Alexei Milkov, Joshua Turner, Dave Greeley, BP America, Inc, Houston, TX


The Pompano salt canopy has been penetrated by six wells to test and develop various subsalt and extra-salt plays. The wells are aligned in a dip direction along the length of the salt canopy from the upturned section (which onlaps the flank of the salt), to 5,600 feet back from the leading edge of the salt. In addition, almost the entire Miocene section was tested below the salt. Pressure, dipmeter, and paleontological data indicate a zone about 400 feet thick below the base of salt, roughly conformable with the base of salt, and which terminates rapidly towards the leading edge of the salt canopy. The transition between the section adjacent to the salt and the country rock is abrupt and has all the attributes of a major fault or shear.

The Pompano salt canopy is anomalous among salt sheets because permeable sands occur immediately beneath, and juxtaposed against, the base of salt. This provides a rare opportunity to measure the high pore pressure and to generate pressure profiles below the salt.

Within the section near the base of salt, anomalous structural dips were encountered which were generally parallel to the base of salt. Biostratigraphic data collected immediate­ly beneath salt can indicate that the sequence is upright or overturned, and consistently older than the rock found below. The shear zone section can be up to 1,000 feet structural­ly higher than the estimated cut-off on the footwall. Data from these wells provide insight into subsalt geologic models that may be applicable to other subsalt prospects.