海上超深水采油技术

海上超深水采油技术（英）

简介：随着未来超深水在海上采油中的采油量所占比例越来越大，世界上的油气供应商不断开发新技术，以使超深水采油更加经济，风险更低。

With an increasing percentage of future subsea production expected to occur in ultra-deep water, suppliers to the world’s oil and gas operators continue to push development of te chnology to make ultra-deepwater production more economic with less risk.

In May, 2005, two members of the Atwater Valley Producers Group (Anadarko Petroleum and Dominion Oil and Gas) awarded a US $110 million contract for umbilical design and manufacture for the Independence project in the Gulf of Mexico (GoM). A year later, Hydro Gulf of Mexico LLC ? also a member of the Atwater group ? awarded a contract for the design and manufacture of its deepwater umbilicals for the same project. For the first time ever, the new technologies of stainless-steel tubes and carbon-fiber rods were combined in an umbilical design.

All 15 umbilicals tie back from gas production wells to the Independence Hub, a deep-draft semisubmersible platform installed in 8,000 ft (2,500 m) of water in Mississippi Canyon Block 920, approximately 123 miles (193 km) southeast of Biloxi, Miss. At full production, Independence Hub can deliver 1 bcf/d of natural gas, which represents approximately 12% of the total volume of gas produced from the GoM.

The Independence project consists of three main components: the hub, a massive $385 million

platform with a two-level stainless steel production deck; a 24-in. diameter, 134-mile (216 km) pipeline that transports gas processed on the hub to an interconnect with a Tennessee Gas Pipeline located in West Delta Block 68; and a subsea component that includes production wellsets, umbilicals, flow lines, connectors, and manifolds for 15 initial wells. The project is operated by Anadarko Petroleum Co. and owned by Enterprise Products Partners LP and the Atwater Valley Producers Group, a consortium of independent operators.

In 2004, project owners determined that by sharing the $2 billion cost of design, manufacture, installation, and operation of the hub and pipeline, they could make production of natural gas from reservoirs previously deemed uneconomic a winning proposition. First gas flowed to the platform on July 19, 2007.

The subsea component

Umbilicals connect subsea wells from 10 anchor gas fields ? San Jacinto, Spiderman, Q, Merganser, Mondo NW, Atlas NW, Atlas, Vortex, Jubilee, and Cheyenne ? to the hub. The Cheyenne gas field contains the world’s deepest subsea production tree, which lies in 10,233 ft (3,198 m) of water. Other production trees lie in water depths ranging from 7,900 to 8,800 ft (2,469 to 2,750 m). To reach these depths, umbilical design for this project had to resolve issues exacerbated by water temperature, pressure, and depth.

Leo Caffrey, technical manager at Aker Solutions’ umbilical manufacturing facility in Mobile, Ala., explained the design approach. “We use carbon-fiber rods in umbilicals deployed at 7,580 ft (2,453 m) or more of water to provide greater axial stiffness to keep the umbilical from experiencing excessive strain (e.g., elongation), which otherwise would cause the steel tubes to yield and damage electrical cables inside the umbilicals during installation and operation. Carbon-fiber rods add significant axial stiffness, but just a fraction of the weight that would be incurred by adding armoring.”

This approach is innovative. “Before carbon-fiber rods, if you made umbilical tubes of thicker steel to give them greater strength, the added weigh t offsets the added strength,” Caffrey said. “Eventually, you get to a point of diminishing returns.”

Arild Figenschou, senior specialist engineer based in Aker Solutions’ corporate headquarters in Oslo, Norway, envisioned and led research and development that culminated in successful commercial application of carbon-fiber rods and stainless-steel tubes for umbilicals.

“Traditional thinking for umbilical design is to have one system to take the force of the load (a steel umbilical tube) and to have inside i t cables bundled together,” Figenschou explained, “but in water depths of 6,400 to 9,600 ft (2,000 to 3,000 m), where greater axial strength is required by the umbilical, carbon-fiber rods are a superior solution because they add stiffness without adding w eight.”

Innovative thinking