SUBSEA PRODUCTION TECHNOLOGY: Canyon Express novel approach to deepwater marginal development

The field layout of Canyon Express.

Canyon Express has been called the most advanced subsea tieback yet. The $600 million project combines production from multiple wells on three deepwater subsea fields. Each of the fields is controlled by a different operator.

In addition to the operating partners, there are a number of other partners involved, including Mariner Energy, Pioneer Natural Resources Co, and Baker Hughes. With so many players involved, Canyon Express has proved to be a political as well as technological challenge.

Flow assurance carrying this production up the slope toward the continental shelf and around the King's Peak salt dome was a major hurdle, as was the multiphase metering of production from each field. Other deepwater technological challenges included the installation of deepwater remote-controlled valves, deepwater connectors (electrical, hydraulic fluid, and production line connectors), variable rate methanol injector valves (mounted on the subsea trees), remote controlled sliding sleeves in the deepwater wells to isolate reservoir zones, and in-line flowline sleds to pick up production from individual wells.

The deepest of the three fields, Camden Hills, lies in water depths over 7,250 ft in Mississippi Canyon Blocks 173/217. That makes it the deepest subsea tieback on record, assuming something deeper doesn't come along before the project goes on line in 2002.

Marginal development

Canyon Express represents a novel approach to marginal field development. Three fields operated by three companies are involved:

• Aconcagua: operated by TotalFinaElf's affiliate Elf Exploration, Inc. in Mississippi Can-yon Block 305 features two wells with plans for a third
• King's Peak: operated by BP in Desoto Canyon 177 and 133, has four existing wells
• Camden Hills: operated by Marathon in Mississippi Canyon 348, has two wells.

None of these fields was seen as economically viable on its own, so the decision was made to combine them in one subsea tieback to the shelf.

Originally, the plan was to tie production from the three fields back 48 miles to the Virgo platform, located in Vioska Knoll. Virgo seemed a perfect fit; it is owned by Elf Exploration, Inc., one of the Canyon Express partners, and operated by Duke Energy.

In September of this year, the project had reached the point where materials were being ordered and contracts were being awarded.

At this late date, the partners realized a deal with Duke was not in the cards. All of a sudden, the Virgo platform was scrapped as a destination. The operators scrambled for a new host, as the project continued to move forward. Pulling out their maps, they quickly identified a handful of potential platforms that could handle the production, in terms of weight and space, and were located within about 15 miles of Virgo. A new call for a tender was sent to the most promising prospects.

Williams to the rescue

One of the facilities under consideration had a commercial connection with Williams. Once Williams received the bid materials, the company realized two things: it was interested in processing the Canyon Express production, and the existing structure being considered could not handle the topsides requirements of this project. Kevin Rehm, Asset Manager for Williams, said his company was committed to this deal after receiving approval from the board of directors. "Just like any investment opportunity, we looked at it and said 'Hey, we can do this.'"

While the host facilities were still out for bids, several contracts had already been let. Saipem would install the twin 12-in. flowlines and umbilicals. The umbilicals themselves would be supplied by Kvaerner out of Norway. Kvaerner-FSSL, based on Houston, would supply the subsea control systems.

The subsea trees, subsea valves, and subsea pipe connectors would be provided by Cameron. Oceaneering was slated to supply the intervention and workover control system for the project. Intec Engineering and Paragon Engineering had both been working on the project since the beginning of the year.

As the Canyon Express operators considered their options, Williams volunteered to install a jacket in Main Pass 261 specifically to handle the Canyon Express production. This platform was only about seven miles from the Vioska Knoll location and would require very little alteration to the original design. Basically, the addition of the seven-mile pipeline to reach the new jacket was the only change required.

The partners decided to take up the offer from Williams and selected Williams' bid. Now the company needs to install a jacket quickly and outfit it with topsides and processing equipment. The service provider will also need to organize tie-ins with the existing infrastructure to get this production to shore.

Williams said the jacket will be in about 280 ft of water and will be named "Canyon Station". According to reports, this change will not alter the schedule for the Canyon Express installation and first oil. Rehm said the jacket and topsides should be in place ready to go by second quarter 2002.

The four-pile jacket will accept gas production from twin-12-in. flow lines and export the gas through three pipelines that will tie into the existing infrastructure onshore. Aside from typical gas handling, treatment, and dehydration, Canyon Station will also recycle the methanol from the fields.

The methanol will be separated out and then reinjected into the system, returning the 56 miles to the subsea wells.