Giants still stand tall in the Gulf of Mexico.
This spring, ChevronTexaco confirmed its 2002 deepwater Tahiti discovery in the GOM with two appraisal wells - one of which encountered more than 1,000 feet of net pay in high-quality sandstones.
Results from the appraisal wells confirmed one of the most significant net pay accumulations in the history of the deepwater Gulf.
The two-well appraisal program also confirmed that the reservoirs in Tahiti are well developed and correlate over a three-mile stretch. Results validated the hydrocarbon reservoirs found in the Tahiti discovery well.
The appraisal wells, located in Green Canyon blocks 596 and 640 about 190 miles southwest of New Orleans, were drilled in slightly more than 4,000 feet of water. They were drilled simultaneously using two rigs - the Glomar Explorer and the Transocean Discoverer Deep Seas - each drilling a vertical well with a sidetrack.
Company officials noted that drilling two appraisal wells simultaneously is unusual - particularly in the deepwater - but the benefit is that key reservoir information is obtained in half the time, allowing ChevronTexaco to begin development planning for the field sooner and ultimately shortening the time to first production.
The Tahiti appraisal program verified ChevronTexaco's initial field estimates of 400 to 500 million barrels of ultimate recoverable oil reserves, announced in June 2002, soon after the discovery.
"These two appraisal wells greatly increased our confidence in the reserves estimate, and ChevronTexaco will get additional reservoir data from a production test of the discovery well that is set for the second quarter of next year," according to a ChevronTexaco spokesman.
The company will revisit the appraisal program after the current appraisal wells are complete, but officials do not anticipate additional appraisal work.
New Possibilities
Tahiti opens a whole new area of exploration for ChevronTexaco.
The company owns additional leases surrounding the new field, and a follow-up prospect called Tonga will be drilled after the drillship Discoverer Deep Seas completes the Tahiti south appraisal well.
"After the success of the discovery well, we have aggressively pursued appraisal and project team activities, including the drilling of two appraisal wells simultaneously and early staffing of a project development team," said Peter Robertson, the company's vice chairman.
"Considerable work is still ahead to evaluate the results of these wells and to screen development alternatives to optimize value," he added. "However, our aggressive approach is designed to reduce cycle time without compromising investment-decision quality."
The Tahiti discovery well was drilled on block 640 in about 4,017 feet of water, to a total depth of 28,411 feet using the Transocean Discoverer Deep Seas drilling vessel.
Results from the exploratory well indicated the presence of high quality reservoir sand with total net pay of over 400 feet.
The Tahiti prospect was generated using advanced sub-salt 3-D seismic imaging technology, along with interpretation of geologic data to identify the presence of reservoir sand development, hydrocarbon charge and migration into a geologic trap, according to company officials.
This region of the deepwater province is very difficult for 3-D seismic interpretation due to a thick salt layer above reservoir sands - but ChevronTexaco used proprietary 3-D seismic technology that enabled scientists to see below the thick salt canopy.