July 1999 Vol. 220 No. 7  Offshore

Robert E. Snyder,  Editor

New fields, new technology

Texaco and Chevron announced in early June that they have begun producing natural gas and condensate from Gemini, a state-of-the-art subsea system of wells, manifold and flowlines located in the Gulf of Mexico in 3,400-ft water. Initial flow rates were 77 MMcfd gas and 1,500 bcpd from one well. These initial rates are expected to peak at 150 to 200 MMcfd and 2,000 to 3,000 bcpd by year-end with two additional wells.

The field is located in Mississippi Canyon Blocks 292 and 247, 90 mi SE of New Orleans. Texaco Exploration and Production is the operator, with a 60% working interest; Chevron U.S.A. holds the other 40%. Projected recoverable reserves are estimated at 250 to 300 Bcf gas and 3 to 4 million barrels condensate.

Several Gulf Coast contractors provided services for this unique project, including drilling, design / fabrication / installation of processing facilities on an existing host platform, a subsea manifold and dual gas export flowlines.

Discovered in 1995, Gemini is also one of the first deepwater subsalt projects in the Gulf. Reaching the objective required drilling through more than 3,000 ft of shallow salt. Design, construction and deployment of the subsea system was accomplished in less than 18 months following project approval.

Other new field developments. In another Gulf of Mexico success, Chevron U.S.A. Production Co. has announced positive results on a second appraisal, prompting it and Broken Hill Proprietary Co. to tentatively plan first oil from the Typhoon deepwater project on Green Canyon 237, by mid-2001. The area is located 100 miles off the Louisiana coast in 2,000-ft water.

Appraisals GC 237-1 and 2 were drilled following Chevron’s first Typhoon exploration well, GC 236-1, which penetrated 130 net feet of oil on a separate fault block in 1998. A third appraisal is in progress and should be completed in July. A joint Chevron / BHP project team is working toward a first oil target date of July 1, 2001. Appraisal continues and the team is evaluating development options.

Typhoon will be Chevron’s third deepwater development in the Gulf. Genesis, which Chevron operates with 57% interest, began production in January. It currently produces 25,000 bopd and 25 MMcfd gas from two development wells. Gemini is the third development. The three projects will net the company about 70,000 bopd equivalent by 2002.

And in the North Sea, on April 20, Talisman Energy announced first oil production from Ross field, in the Moray Firth, 48 mi NE of the St Fergus oil / gas terminal in the North of Scotland. The field’s 60 MMbo and 20 to 30 Bcf gas reserves will be produced using the Bleo Holm FPSO, owned and operated by Bluewater (Floating Production).

Production will build this summer with the commencement of water injection and commissioning of the gas export system, at 40,000 bpd oil equivalent. A fourth development well is being drilled. The FPSO, which arrived in February, can store 700,000 bbl oil and will offload to a shuttle tanker.

The gas is exported directly from the FPSO via a 6-in. pipeline connected to the main Frigg UK pipeline 25 km away. In addition to the gas export line, the complex has three drill center manifolds, flowlines, risers and a subsea control system capable of supporting up to 16 wells.

Partners in Ross are Talisman Energy (UK), 51.99%; Lasmo (UKL), 16.33%; Kerr McGee Petroleum (U.K.), 14.49%; Intrepid Energy North Sea, 13%; and Nippon Oil Exploration and Production (MF), 4.19%.

Subsea exploration-drilling innovation. The Centre for Marine and Petroleum Technology (CMPT) in Aberdeen, is seeking industry participation in the feasibility study of a revolutionary drilling concept that would eliminate need for an expensive mobile offshore rig to drill an exploratory hole. The project is called Drilling Independent of Depth, or DIODe.

The system is perceived as a mobile unit capable of being easily moved from one seabed location to another with minimal surface facilities. It will be capable of drilling both vertical and deviated exploration wells, supported only by a relatively simple surface support vessel, at substantially less cost than a drillship or semisubmersible.

Using remote control technology that is already well understood by the manufacturers of remotely operated vehicles, the system will be controlled via an umbilical to a surface support vessel. The same umbilical will be used to supply the seafloor system with power, drilling fluids and other consumables. It would also utilize closed-loop drilling fluid systems developed for underbalanced drilling.

While the concept has not been completely described, it would involve moving the mechanics of the drilling operation to the seabed, using several modules deployed by a surface vessel. These modules would include well control and power. Instead of running pipe from the surface unit, reeled pipe contained in a downhole module would be used, supposedly in a version of coiled tubing drilling (with downhole motors). Casing could conceivably be some type of reeled composite.

All this would apparently be made possible by drilling small-diameter exploration holes. And the project looks like it could be tied into slimhole coiled tubing studies also underway with CMPT and XL Technology Ltd.

Although many of the technologies required to develop a full DIODe system are already available, CMPT says it is recognized that many other engineering and operational challenges remain, although the prize of cheaper exploration operations gives the project considerable potential.

DIODe is a three-phase, fast-track project which aims to deliver, within three years: Phase 1 (9 months) — Feasibility analysis, preliminary design; Phase 2 (9 months) — Final design, prototype planning; and Phase 3 (18 months) — Build / test prototype, commercialization.

Phase 1 participation, based on 10 subscribers, would cost 17,500 £ — or less, if some work is done "in kind." Interested companies can contact: Dick Winchester, CMPT, Aberdeen, Tel: 44 870 608 3400; Fax: 44 870 608 3480; E-mail: d.winchester@cmpt.com.

Copyright © 1999 World Oil
Copyright © 1999 Gulf Publishing Company