Total started production from the Edradour and Glenlivet fields West of Shetland ahead of targets mainly thanks to lessons learned on the adjoining Laggan-Tormore fields in recent years.
The Edradour and Glenlivet gas and condensate fields are in about 300 to 435 m (984 to 1,427 ft) of water in the West of Shetland area near the Laggan-Tormore fields, which came onstream in February 2016.
“The project was sanctioned in 2014 based on starting up Edradour at the end of October 2017 and Glenlivet at the end of October 2018,” said Kevin Boyne, Total E&P UK’s asset director for West of Shetland. “We learned during the Laggan-Tormore project that it was very difficult to carry out drilling and project construction operations at the same field in the same season.
“With the new fields, we deliberately decided that we would try to avoid carrying out drilling and project operations in the same year at the same location. The wells had already been drilled in 2015. But to complete the wells in 2018 we wanted to avoid the project vessels competing for access to the wells, well area and manifold area at the same time.”
However, the company decided after conducting a review in 2016 to conduct Glenlivet drilling operations and Edradour completion operations concurrently. Boyne admitted there was some resistance to the challenge.
“We did have a fall-back situation where we’d have to stop the drilling at a certain point and come back in 2018 if things had gone slower or more poorly on the drilling. But we had very little what we call non-productive time during the drilling operation, so it went a month faster than we expected,” Boyne said. “We had finished the drilling operations by June so we took that risk and continued with the next well. As it happened we managed to complete both wells and we managed to put both wells onstream. The whole project is now more or less complete; we’re just doing the final works.”
The company learned the importance of focusing on the summer seasons with detailed execution planned, while using the winter season to work with drilling and project installation contractors on scheduling for the following season, he said.
“A certain amount of flexibility is required in the planning, but a certain amount of conservatism in terms of not trying to carry out operations that could then lead to massive rework and major problems by trying to carry out operations in poor weather conditions,” Boyne said.
The Edradour and Glenlivet development will bring additional production capacity of up to 56,000 barrels of oil equivalent a day. “The startup of the fields demonstrates our ability to deliver projects, taking advantage of favorable market conditions and simplifying designs to optimize execution,” Boyne added. “We have completed this project ahead of schedule and 30% under the initial budget. This development will contribute to our production growth in the North Sea.”
The Edradour and Glenlivet development consists of a 35-km (22-mile) tieback of three subsea wells to the existing Laggan-Tormore production system, which includes the 143-km (89-mile) pipeline and the onshore Shetland Gas Plant. Following treatment at the gas plant, gas is exported to the U.K. mainland via the Shetland Island Regional Gas Export System and FUKA pipeline and will serve the U.K. domestic market. The condensates are exported via the Sullom Voe Terminal.
“One of the ways that we kept cost down was by adopting some standardization from our experience on Laggan-Tormore,” Boyne said. “We used the same Christmas trees from Laggan-Tormore. In fact we had a couple left over and also used some other common subsea components. We tried to use stock equipment that had been already designed, not undertake re-engineering and pay for re-engineering in our new subsea system.
“Because the design for Laggan-Tormore was done probably 10 years ago at least, things have slightly moved on since then so we had to deviate from any new specifications that have come in since then to allow us to use a design dating back to that time,” Boyne continued. “This fitted very well with our existing deployment systems, which were adapted to those types of trees. It also saved the big expense at the start of Laggan-Tormore to kit out rigs to deploy them.”
Boyne pointed to the depth of the wells as one of the main challenges they faced. Even the shallowest of the three, Edradour, is in more than 300 m of water, which is much deeper than the usual North Sea range of 50 to 100 m (164 to 328 ft).
“At those depths in this region the temperature is an issue,” he continued. “You have to inject hydrate inhibitor continuously so we have a system for sending kind of anti-freeze out to the wells to avoid any kind of hydrate formation.”
As for future developments in the area, Boyne said there are still some smaller discoveries in that region which the company will explore. “We have quite a large exploration portfolio around Laggan-Tormore, Edradour and Glenlivet but also farther to the north on what they call the Corona Ridge as well. It’s quite a disbursed set of prospectivity. There are also other plots coming up as well so there’s an opportunity potentially to acquire more acreage.”