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Heppard, Philip D.1, Holly L. Harrison2, David F. Greeley3, Lewis F. Kuhmichel2, Brett W. Cocales2 
(1) BP Amoco, Houston, TX 
(2) BP America Inc, 
(3) BP America Inc, Houston, TX

ABSTRACT: Pressure Prediction and Drilling of the Deep Sub-salt Play at Pompano Field, Deep Water Gulf of Mexico

A series of wells have tested Miocene age sands beneath a steeply dipping salt dome at Pompano field, Gulf of Mexico. The sub-salt wells clearly show the presence of a deformed zone along the base of the salt of several hundred feet in thickness which has significantly higher pressure than the underlying and in-place sedimentary sequence. The deformed zone is older than the underlying rock, overturned in part, and is interpreted to be a ‘shear zone’ adjacent to the salt face separated from the surrounding rock by a reverse fault zone. Lower absolute pore pressure was measured in channel complexes immediately below the shear zone which included zones of significant mud loses. During the drilling of the most recent well, risk management to deal with the inevitable uncertainties of pore pressure at the base of salt, careful prediction using offset wells and basin models, and operational monitoring was necessary to “thread the needle” within the very narrow tolerances between high pressure flows and mud loses. Savings of approximately $2 million in mud costs was the result of ECD management of down-hole mud weight using pressure while drilling measurements and a mud system designed to plug off fractures. 
The well was designed to drill as deep as possible in the Tertiary section to the top of the Cretaceous if possible. Based on a risk analysis H2S monitoring equipment was on the rig and up to 20 ppm H2S was detected while drilling the lower Miocene at 18,003 feet MD (16,192 ft TVD). The drilling was halted and the well was completed at a shallower depth.

 

AAPG Search and Discovery Article #90026©2004 AAPG Annual Meeting, Dallas, Texas, April 18-21, 2004