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BP, Chevron Bring Two More Offshore Projects on Stream

BP's 120,000-BO/D Clair Ridge bridge-linked platforms (left) and Chevron's 75,000-BO/D Big Foot tension-leg platform (right). Sources: BP and Chevron.

BP and Chevron have overcome development challenges to recently launch production from two offshore projects that were years in the making.

The British major said 23 November that oil is flowing from its giant Clair Ridge project in the West of Shetland region offshore UK. Two days earlier, San Ramon, California-based Chevron said that it started production from the deepwater Big Foot field in the US Gulf of Mexico.

Clair Ridge, the larger of the two projects, is the second phase of development of the Clair field, targeting 640 million bbl of oil reserves with output expect to ramp up to a peak of 120,000 BO/D. BP’s £4.5-billion investment involved the construction of two new bridge-linked platforms along with oil and gas pipelines. The facilities, 75 km West of Shetland, are designed to operate for 40 years.

Oil is exported from the facilities via a 5.5-km, 22-in. pipeline linked to the Clair Phase 1 line, eventually reaching the Sullom Voe Terminal on Shetland. Gas is sent through a 14.6-km, 6-in. export line into the West of Shetland Pipeline Systems also connected to Sullom Voe.

With Big Foot, Chevron—also a Clair Ridge partner—is attempting to tap into some 200 million BOE in recoverable resources and will be able to produce as much as 75,000 BO/D and 25 MMcf/D of gas. The project sits in 1,584 m of water 360 km south of New Orleans, Louisiana, consisting of a 15-slot drilling and production tension-leg platform, which Chevron says is the deepest of its kind in the world. Discovered in 2006, the field has an expected production life of 35 years.

Technology Ends Delays

Like many other offshore projects in recent years, particularly during the downturn, Clair Ridge and Big Foot encountered delays. Clair Ridge, sanctioned in 2011, was initially slated to begin production in 2016. Big Foot, sanctioned in 2010, was first intended to start up in 2014.

For Chevron, the major setback came in 2015 when it was attempting to install the platform on location. Nine of the platform’s 16 tendons used to attach it to the seafloor failed, forcing the company to tow it back near shore.

BP, meanwhile, had to figure out how to further develop the Clair field’s complex, naturally fractured reservoir while keeping costs in check.

“The start-up of Clair Ridge is a culmination of decades of persistence,” said Bernard Looney, BP upstream chief executive, in a news release. “Clair was the first discovery we made in the West of Shetland area in 1977. But trying to access and produce its 7 billion bbl proved very difficult. We had to leverage our technology and ingenuity to successfully bring on the first phase of this development in 2005.”

BP now hopes to boost performance through use of its LoSal enhanced oil recovery technology, which involves the injection of low-salinity water into reservoirs to avoid issues that can arise when fresh water causes clays to swell and clog oil-bearing pores. The company believes LoSal can result in up to 40 million bbl being cost-effectively recovered over the lifetime of the development.

Contractor Worley Parsons deployed a digital twin during the project’s design, fabrication, and commissioning phases, and it will continue to be used during the production phase. The asset information hub serves as a web portal, acting as a single point of information for the 3D model, tag data, and project documents. 

Use of the digital twin assisted in what BP says is the largest commissioning in the North Sea in more than 20 years. During 2015–2016, some 53,000 tonnes of modules were installed, including a drilling rig and supporting equipment.

The rig will undertake a roughly 10-year, ongoing development program from the remaining 34 of 36 well slots, with the other slots being used for the tieback of predrilled wells. The drilling facility includes Cyberbase-controlled drill floor equipment and cement unit control systems, and can perform standalone well interventions.

Clair field is operated by BP with a 28.6% interest. Shell has 28%; ConocoPhillips, 24%; and Chevron, 19.4%. BP in July said it agreed to buy another 16.5% stake from ConocoPhillips, which would shift project interests to 45.1% for BP and 7.5% for ConocoPhillips. The partners are evaluating a possible third phase of development of the field.

Big Foot is operated by Chevron with a 60% interest. Partners Equinor and Marubeni Oil & Gas have 27.5% and 12.5%, respectively.

BP, Chevron Bring Two More Offshore Projects on Stream

Matt Zborowski, Technology Writer

26 November 2018


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