Texaco North Sea U.K. Co. aims to begin production in October from the North Sea's first high-pressure/high-temperature (HP/HT) field development, but this milestone project almost did not happen.
Erskine lies in 90 m of water on U.K. Blocks 23/26a and 23/6b and is owned 50-50 by operator Texaco and BP Exploration Operating Co. Ltd. Estimated reserves are 330 bcf of gas and 75 million bbl of light oil.
Erskine was discovered in 1981 but was undeveloped for so long because of technical concerns over HP/HT reservoirs and lack of export infrastructure.
Then Amoco U.K. Exploration Co. developed Everest and Lomond fields to the north and built the Central Area Transmission System (CATS) pipeline from Everest to Teesside (OGJ, Apr. 19, 1993, p. 23).
Jeff Brubaker, principal project engineer on Erskine, said Texaco approached Amoco with a view to exporting gas and liquids via Lomond.
Texaco wanted to install an unmanned platform in Erskine field to send multiphase output to a module on Lomond platform for processing and export.
Space problem
"At first Amoco said 'No way'," said Brubaker. "There was some space on Lomond, but this was reserved for two compressors that are to be installed for late-life production. 'You're our only hope; can't we just look into the conceptual side?' we said."
Charlie Hardy, project manager at Kvaerner H&G Offshore Ltd., London, which designed the process module, said, "3D modeling was a vital design tool to get the module to fit in. Because Lomond is so congested, the design would have been impossible on a drawing board."
The resulting process module is a tall, narrow unit. In addition to the processing equipment for Erskine, it has space on one deck to carry a compressor for Amoco to use in Lomond.
The module will be skidded onto the platform, which is fitted with two drilling rig skid beams, across the well bay area, and sideways into its final slot.
Benchmark
Hardy said Erskine is the first North Sea field development to require a 15,000 psi pressure rating and sets a benchmark for design of future HP/HT developments.
Reservoir pressure and temperature are 14,000 psi and 340? C., respectively, while wellhead pressure is 10,600 psi. Erskine's six production wells will have a true vertical depth of around 16,000 ft.
The platform will have capacity to produce 118 MMcfd of gas and 26,000 b/d of liquids. All separation and processing will take place in the module.
Brubaker said much platform equipment will be for storing and deploying chemicals-particularly methanol, scale and corrosion inhibitors, and dewaxer. It will also carry a multiple pig launcher.
Among innovations, the 30-km pipeline from Erskine to Lomond will be the largest diameter insulated pipeline in the North Sea at 16 in. In-field flowlines will be especially thick at 36 mm.
Flowlines will be made of super-duplex steel, and risers will have a lining of corrosion resistant alloy.
"We thought of using titanium," said Brubaker, "but we found that everybody was more comfortable with familiar oil field materials."
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