TotalFinaElf SA unit Total Oil Marine PLC was recently supplied with two variable-speed drive packages to control multiphase pumps on its Dunbar platform in the UK North Sea; the pumps started up in late 1999 (OGJ, Nov. 15, 1999, p. 34).
The multiphase pumping module, with a combined weight of nearly 700 tonnes, is shown here being loaded from the Heerema yard in Hartlepool, UK, before being shipped to the platform's location, about 120 km northeast of the Shetland Islands.
The drive packages were supplied by a consortium of Sulzer Pumps France and ABB Automation Ltd. Through the development of an offshore pumping installation, Total was able to achieve a 30% reduction in capital expenditure and structural weight, says ABB Automation.
The drive systems' equipment consists of two ABB 6,300-kv, Megastar 6300D3300 24-pulse frequency converters; two 6-mv multiwinding, oil-filled, water-cooled feed, purge-pressurized, stainless-steel transformers; and two ABB vertical flange-mounted, water-cooled, purge-pressurized motors, rated at 4,500 kw each.
The pumps are designed to increase production by enabling simultaneous liquids pumping and gas compression of the comingled wellhead fluids. The process negates the need to install a separation plan with compressors for the separated gas and additional pumps for the separated oil, says ABB Automation, and enables oil firms to pump more oil from older, low-pressure fields. ABB Automation says that this is the first time this type of pump installation has been used in an offshore application.
"Compared with an equivalent conventional 'separator' solution, the multiphase installation at Dunbar saved 300 tonnes in overall weight," said Jean-François Renault, Total Oil Marine project manager for the Dunbar multiphase-pump project. "The toughest part of the project was to marry the existing structure and facilities to the equipment that we needed for the job. We had to reassess the power distribution in the oil field and overcome strict structural limitations," he said.
