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Chevron takes stock of signature project

The Jack and St Malo fields opened up a host of possibilities and technical challenges for Chevron and its partners in the deepwater Gulf of Mexico project.

Jack & St Malo, which began production in 2014 on time and under budget, required several technologies that were new to the operator and included several industry firsts, said Travis Flowers, the project's asset manager for Chevron.

At a meeting of the Marine Technology Society in Houston, Flowers described the development in detail, including the initial 2004 Jack field discovery in 7000-foot (2133-metre) water depths.

“We didn’t have the needed technology to develop it at the time,” said Flowers, who joined the project in 2014. “Someone had to go out on a limb and believe we could develop the technology to bring this oil to the market.”

The Jack & St Malo semi-submersible host facility has only been online for about two and a half years, he said, so the project is “in the toddler years of what is at least a 30-year asset”.

Chevron aims to recover more than 500 million barrels of oil equivalent through what it considers a “signature” Gulf of Mexico development, the operator’s first in the deepwater Wilcox trend.

“It’s producing from a four-way salt-cored anticline structure in the Lower Tertiary Wilcox trend consisting of weakly confined to unconfined turbidite channel and fan complexes deposited in a deep submarine setting,” he said. “If anybody has a development like this, it’s going to work, because it worked this time.”

One of the subsurface uncertainties was whether the reservoirs were fragmented or compartmentalised, or whether they were connected, Flowers said.

“We went in expecting surprises” with the reservoir, he recalled. “But we’ve mostly gotten good surprises.”

Ocean bottom node seismic technology provides images of the subsurface nearly 30,000 feet below the mudline. The information gathered will influence later drilling plans, Flowers said.


Enhanced technology

The Jack & St Malo project included the first deepwater execution of Halliburton’s Enhanced Single-Trip Multizone (ESTMZ) completion system, which saved an average of 25 days per completion per well, resulting in roughly $29 million per well based on rig rates at the time, according to Chevron.

“The ESTMZ completions are yielding better-than-forecast well productivity,” Flowers said.

A total of 10 wells are online at present, producing more than 100,000 barrels of oil equivalent per day.

The operator is running production tracers to ensure production is flowing from all zones in each of the wells.

“There are lots of zones. We want reserves recovery from every zone,” he said.

The project also installed the largest and deepest subsea boosting system at the time.

New technology for Chevron included the first use of subsea multiphase meters and subsea sampling skid.

Metering was particularly important because of the complex ownership of the project. Chevron operates the project in a joint venture with Statoil, Petrobras, Maersk Oil, ExxonMobil and Eni.

Additionally, the project required Chevron’s heaviest casing string run.

“With a string that big it’s a one-way trip. If you don’t get it right, you don’t get it out,” Flowers said.

He said the overall project has produced a number of lessons learned to help decrease the development cost per barrel on new developments.


More wells

Jack & St Malo’s second stage involves four additional wells — two in each field each in the pair of fields — the first of which went online in the third quarter of 2016.

Chevron intends to continue development drilling in 2017. Stage three, which will include two more wells at St Malo and one at Jack, has been sanctioned, Flowers said.

The Jack & St Malo production semisub is located in Walker Ridge Block 718. Its nameplate capacity is 170,000 barrels per day of oil, 42 million cubic feet per day of gas and 130,000 bpd of water. The platform has 20 well slots. ExxonMobil’s Julia field has produced via a subsea tieback to the host platform for about a year.

The deep-draft floating production unit has 18 steel catenary risers inside the pontoons and 25 umbilicals suspended from the centre well area of the deck box. It has a displacement of 160,000 tonnes, making it the industry’s largest steel hull semisub by displacement, and is held in place by 16 chain-polyester-chain mooring lines.

Flowers, referencing the 1989 film Field of Dreams, said the floating production unit’s additional capacity will serve the project well as it matures.

“Build it and they will come,” he said. “We built it for future tieback opportunities.”

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