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Allochthonous Salt Base—Structure and Stratigraphy from Pompano Field, VK 989/990,
Harrison, Holly, Lew Kuhmichel, Phil Heppard, Alexei Milkov, Joshua
Turner, Dave Greeley, BP America, Inc,
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.