AAPG ANNUAL CONFERENCE AND EXHIBITION
Making the Next Giant Leap in Geosciences
April 10-13, 2011, Houston, Texas, USA
Reducing Reservoir Uncertainty in a Phased Development – Tahiti Field, Deepwater Gulf of Mexico, USA
(1) Chevron, Houston, TX.
(2) Chevron, Covington, LA.
Tahiti-2 is the next phase of development for the Tahiti Field and provides the opportunity to continue development of the high potential asset. The field was discovered in April 2002, and after drilling exploration, appraisal, and the first phase of development wells, oil production began in May 2009. Tahiti is a subsalt, three-way structural closure trapped against a salt keel/root. The primary Miocene-aged M-21 reservoir interval ranges in depth from 23,000 to 28,000 feet subsea. In addition, structural dips range from approximately 20° near the oil-water contact to 70° or more near the salt face.
Due to significant uncertainties remaining after appraisal, which include reservoir connectivity, well productivity, and aquifer strength, a phased development strategy was developed to address whether a water injection project was necessary for reservoir pressure support, as well as the quantity, location, and timing of water injection and/or additional production wells.
The 9 to 12 month surveillance period after first oil collected critical reservoir data for the next phase of development in the field including: well ramp-up bottom-hole pressures for understanding connectivity, production performance to better understand oil in-place and aquifer strength, and geochemical analysis to recognize zonal flow contributions. In addition, a wide-azimuth 3D seismic survey was reprocessed to improve subsalt structure, faulting, and salt-sediment imaging and integrated with the surveillance data. Key findings from the surveillance period include better than expected pressure connectivity between wells and field-wide pressure decline is trending toward lower aquifer strength.
The asset team’s recommendations are as follows: a water injection project is required and additional production wells are necessary, both of which improve estimated ultimate recovery compared to primary recovery only. Reservoir surveillance data indicates that incremental resource will be obtained from implementation of a pressure maintenance project in the M-21 Sand.
Approaching Tahiti through a phased development strategy allows the project team to reduce subsurface uncertainty, apply reservoir management best practices, and maximize return on investment.
The Tahiti Asset is a Chevron operated joint venture with its partners Total and Statoil.