Drilling/Production Significant E&D projects fan out across gulf

Gulf of Mexico operators last week disclosed a flurry of news on significant exploration and development projects.

Here's what's happening, moving from west to east across the gulf:

Shell Offshore Inc. and three partners plan late this month to spud a wildcat in a world record water depth: 7,625 ft. Site will be about 200 miles southeast of Corpus Christi, Tex., in the Alaminos Canyon federal planning area.
Phillips Petroleum Co. and Anadarko Petroleum Corp., 50-50, disclosed gauges on another discovery in the subsalt play. Their 1 Agate wildcat on Ship Shoal Block 361 flowed a combined 4,126 b/d of oil and 24 MMcfd of gas from two zones in a single sand formation.
Fifty-fifty partners Texaco Exploration & Production Inc. and Marathon Oil Co. announced that a three well appraisal program of their Viosca Knoll Block 786 discovery in the deepwater Gulf of Mexico confirmed reserves estimated at 80-100 million bbl of oil equivalent. The companies have formed an interdisciplinary, intercompany project team to facilitate development.

Shell et al.

The water depth record wildcat planned by Shell and partners will test the BAHA prospect, reportedly underlying a six block spread of leases. Water depths across the BAHA prospect range from 6,500 to 9,000 ft.

Sources earlier said a four company group was preparing to test the U.S. portion of the Perdido fold belt, which covers more than 1,150 sq miles in 6,000-9,000 ft of water (OGJ, Feb. 26, p. 73).

In addition, a paper published last fall by the Gulf Coast Association of Geological Societies reported individual Perdido structures as large as 150 sq miles with more than 6,500 ft of closure.

Joining operator Shell with a 25% interest each in the BAHA ultradeepwater test are Amoco Production Co., Mobil Exploration & Producing U.S. Inc., and Texaco Exploration & Production Inc.

The partners, who hold adjoining leases, agreed to cross-assign their interests on a 25% equity basis. The group named the joint prospect BAHA by using the first letter from the inhouse name of each company's prospect: Shell's Brachiosaurus, Amoco's Anaconda, Mobil's HI-C, and Texaco's Alpha Centauri.

Partners refused to disclose details on which tracts form the BAHA spread. Sources earlier reported the group planned to drill the "Baja" prospect in 7,800 ft of water on Alaminos Canyon Block 809 (OGJ, Mar. 4, Newsletter).

BAHA partners have taken under contract Sonat Offshore Drilling Inc.'s Discoverer 534 drillship for their wildcat. The dynamically positioned rig is dry docked at Mobile, Ala., for upgrades that will enable it to work in BAHA's water depth. Drilling is expected to take about 4 months.

Shell in 1987-88 set the existing water depth drilling record in the gulf with a wildcat in 7,520 ft of water on Mississippi Canyon Block 657 (OGJ, Nov. 13, 1989, p. 21).

Minerals Management Service in 1988 assigned Order 4 status to the Mississippi Canyon 657 wildcat, meaing the well found more than 15 ft of pay (OGJ, Aug. 15, 1988, Newsletter). Shell abandoned the well after reaching total depth in January 1988 but still holds the lease on inactive status.

Phillips-Anadarko

The first zone in Phillips-Ana- darko's Agate discovery flowed 2,788 b/d of oil and 14.44 MMcfd of gas through a 17/64-in. choke with 6,773 psi flowing tubing pressure.

The second zone flowed 1,388 b/d and 9.67 MMcfd through an 18/64-in. choke with 7,038 psi flowing tubing pressure.

Agate is the third discovery for Phillips and its partners in the Gulf of Mexico's subsalt trend. Phillips, Anadarko, and Amoco Production Co. in 1993 Mahogany field, scheduled to start up in late 1996. Phillips and Anadarko also drilled a discovery on their Teak prospect in 1994.

The 1 Agate lies in 400 ft of water 72 miles south of Terrebonne Parish, La., and 6 miles southwest of Mahogany field. Drilled to 16,163 ft, the Agate cut a gross hydrocarbon section of 105 ft. The well has been suspended for future production.

Phillips and Anadarko will continue to evaluate test results and are considering appraisal drilling. Agate field could possibly be produced through the Mahogany platform, significantly lowering development costs.

Phillips operates Agate.

Texaco-Marathon

The Texaco-Marathon team expects during the next few weeks to award contracts for preliminary design of a development concept for the Viosca Knoll discovery. Selection of the final concept is expected this summer, with production to begin in late 1998 or early 1999.

The 1 Viosca Knoll Block 786 strike lies on a 5,760 acre block in 1,750 ft of water, 130 miles southeast of New Orleans (see map, OGJ, Sept. 25, 1995, p. 40). A test of a prospect Texaco named Petronius flowed 7,700 b/d of oil and 4.4 MMcfd of gas last August.

Since that time, Texaco-Marathon has drilled three delineation wells:

2 Viosca Knoll Block 786 was directionally drilled to 11,554 ft measured depth with a bottom hole location 0.6 miles northeast of the No. 1 discovery well.
A down dip sidetrack of the No. 2 well was drilled to 14,050 ft measured depth with a bottom hole location 1.1 miles southwest of the discovery well.
The No. 3 well was directionally drilled to 16,695 ft measured depth with a bottom hole location 2.0 miles southwest of the discovery.

Three of the four wells on the prospect have been suspended and will be reentered and completed early in the development phase of the project. This will allow early production while the rest of the development program is under way.

Petronius prospect was one of three Texaco operated, 3D seismic generated discoveries in the gulf chalked up by the first wildcats in a multiyear deepwater drilling program.

Also under evaluation last September were:

Fuji prospect in 4,243 ft of water on Green Canyon Block 506, where Texaco holds a 75% interest and Shell 25%.
Gemini prospect in 3,393 ft of water on Mississippi Canyon Block 292, where Texaco holds a 60% interest and Chevron U.S.A. Inc. 40%.

Meantime, Marathon is pursuing opportunities in the deepwater Gulf of Mexico, where it operates the Ewing Bank Block 873 platform and recently announced development plans for the Green Canyon Block 244 Unit.

Marathon, which holds interests in 42 deepwater gulf leases, has identified 18 leads and prospects. It plans to drill six gulf deepwater wildcats in 1996.