Gulf fields to use expanded methanol recovery system

Feb. 2, 2001
Williams of Tulsa, Okla., has selected Paragon Engineering Services Inc., Houston, to help it develop a shallow-water Gulf of Mexico platform that will accept deepwater production from remote subsea wells in up to 7,200 ft of water, representing the gulf�s deepest subsea development to date.


HOUSTON, Feb. 1�Williams of Tulsa has selected Paragon Engineering Services Inc., Houston, to help it develop a shallow-water Gulf of Mexico platform that will accept deepwater production from remote subsea wells in up to 7,200 ft of water, representing the gulf�s deepest subsea development to date.

Paragon said a challenge was flow assurance to the shallow-water platform. It has developed a process for the recovery and reuse of chemical methanol as a hydrate inhibitor for the project.

The methanol will be used in the development of nine subsea wells in three deepwater fields: Aconcagua, Camden Hills, and Kings Peak. The subsea wells are 55 miles south of Williams� newly proposed shallow-water platform.

The owners of the three fields�TotalFinaElf E&P USA Inc., Marathon Oil Co., BP, Pioneer Natural Resources USA Inc. and Mariner Energy Inc.�approved a project known as Canyon Express to develop the gas-gathering system and infrastructure, which will tie back the deepwater wells to the Williams Canyon Station host platform in 299 ft of water.

Paragon said production of 500 MMcfd of gas from the subsea wells is expected by summer 2002.

Paragon is performing project management, engineering, design/drafting, procurement, and fabrication inspection for the new platform.

Alan Armstrong, vice-president of gathering and processing for Williams' midstream operations, said, "Williams� Canyon Station positions us to be one of the largest independent service providers in the deepwater Gulf of Mexico. We're also designing our infrastructure and logistics to accommodate other prospects that may be developed in the East Breaks corridor."

"The use of methanol and its recovery are essential to the project�s economic viability, with significant operating cost savings anticipated,� said Hickman Brown, Paragon's project manager.

Industry use of methanol in deep, cold waters is a critical tool for inhibiting the formation of hydrates, which can block production flow. Operators have used nominal amounts of methanol for many years to inhibit hydrates. Paragon said the Williams project is unusual because of its expanded application and reuse.

The Williams Canyon Station project includes the storage, regeneration, and distribution of some 1,900 b/d of methanol. If the methanol were not recovered, Paragon estimates it would cost $60,000/day to produce 500 MMcfd from the deepwater subsea wells.

Brown said the recovery process will allow Williams Energy to recover about 80% to 90% of the chemical for reinjection.

A 110-mile, closed loop, 12.75-in. diameter pipeline will gather production from the wells to Williams Canyon Station host platform.

�Tieback of the subsea wells to the host platform presents technical challenges, as hydrates could plug the line at any point. Equally significant is the 7,200-ft water depth, where temperatures below 40� F. can cause hydrates to form at the wellhead,� said Frederik Rijkens, project manager of Canyon Express.

Brown said a 50:50 mix of methanol and produced water injected into the well will effectively inhibit the formation of hydrates to ensure gas flow. The methanol recovery process will have a design capacity of 3,000 b/d of inlet fluids: 1,900 b/d of methanol, and 1,100 b/d of water. The process involves separating the gas and produced water while boiling off the methanol for recycling. Upon regeneration, the methanol is 95% pure.

As a further benefit, the presence of methanol helps to dehydrate the gas, lowering the water dew point, which lowers the amount of glycol dehydration necessary downstream. In fact, depending on separator pressures and temperatures, a glycol system may not be required at all.