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Tobago discovery further validates Perdido Foldbelt play; Unocal says could be part of Alaminos Canyon hub
Ray Tyson Petroleum News Houston correspondent
Unocal says its oil discovery at the Tobago prospect in the Gulf of Mexico, though small by ultra-deepwater standards, would be large enough to include in a proposed hub development that would be supported by other larger discoveries in Alaminos Canyon.
Drilled in about 10,000 feet of water to a total depth of 18,510 feet, the Tobago discovery well at Alaminos Canyon block 859 found about 50 feet of net oil pay in high quality reservoir sandstones, Unocal said May 5. The discovery was further delineated by a sidetrack of the main well drilled to 18,425 feet, the company said. Tobago was considered important because of its relatively close proximity to Unocal’s Trident discovery and Shell’s Great White discovery, which together could hold reserves exceeding 600 million barrels of oil equivalent.
Trident contains an estimated 150-200 million barrels of oil equivalent. And though Shell has never disclosed Great White reserves, analysts believe the field holds at least 400 million barrels of equivalent. Tobago was drilled to further test the giant Perdido Foldbelt play, Unocal said.
“The discovery confirms its previous expectations that Tobago could be part of any Alaminos Canyon area development that may be built in the future,” the company said. No pipelines or other infrastructure in area Because the discoveries are located in such a remote area of Alaminos Canyon, where pipelines and other infrastructure do not exist, the owners are considering a so-called floating production, storage and offloading facility, to transport oil ashore via marine tankers. FPSOs are typically used for isolated fields around the globe but have yet to make their debut in the Gulf.
Unocal is the operator at Tobago and holds a 40.01 percent working interest. Unocal’s partners are Shell with a 30 percent interest; ChevronTexaco with a 16.66 percent interest, and Nexen with a 13.33 percent interest.
The Tobago well was temporarily plugged and abandoned, and the Discoverer Spirit drillship was moved to Walker Ridge block 678 to conduct appraisal drilling on the St. Malo discovery.
Industry analysts are keeping a close watch on St. Malo, which is said to have encountered more than 450 feet of net oil pay over a gross hydrocarbon column of 1,400 feet, indicating a major accumulation by Gulf standards.
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