BP NSI | Ravenspurn North

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Ravenspurn North

The Ravenspurn North Gas Field was discovered in October 1984 and later developed in April 1988 by the operator Hamilton Bros. Ravenspurn North is located in Blocks 43/26a and 42/30 in the southern sector of the North Sea and lies approximately 80 kilometres off the East Yorkshire coast.

In January 1998, BP took over operatorship of Ravenspurn North as part of its Southern North Sea assets.

First gas was produced in July 1990 and gas reserves are estimated to be:

1.0 trillion cubic feet.

Peak gas sales rate of 376 million cubic feet per day.`

Field life is estimated at 22 years.

Facilities:

The field was developed at a cost of #600 million using: a concrete gravity based structure supporting the central processing platform, a bridge-linked steel wellhead tower - located 60 metres away and two steel satellite platforms, ST-2, ST-3 (NUI's). (5 and 13 kilometres from the central processing platform)

Produced gas from ST-2 and ST-3, are fed through 14-inch diameter pipelines. These two platforms are normally unattended and remotely controlled from the central platform.

Each of the three platforms has 18 well slots. A total of 42 wells has been drilled by the end of 2004 - 17 from the central processing platform's wellhead tower, 11 from ST-2 and 14 from ST-3.

Construction/installation

The concrete gravity structure serves as the base for the central processing platform and was constructed from:

23,500 tonnes of concrete - the first use of concrete in a southern North Sea structure.

It weighs 28,000 tonnes and stands 65.5 metres high.

Built in 15 months by Laing ETE at the Graythorpe yard on Teesside at a cost of #15 million.

Installed in August 1989, in preparation for the single 6,000 tonne topside lift the following Spring.

Combined accommodation/processing facilities, built at Redpath Offshore on Teesside are supported on two of the concrete base's three shafts.

The overall height of the platform from its highest point to the seabed is 125 metres.

The satellite platforms, (ST-2)- built at Highland Fabricators, Nigg and (ST-3) built at THC Fabricators, Hartlepool, weigh 3,500 tonnes each (topsides and jacket) and are a total of 81 metres high.

During 1993 gas compression facilities were installed on the third concrete leg of the central processing platform. The 3,600 tonne deck was constructed at THC Fabricators in Hartlepool and became operational in December 1993. The provision to add 68.5 MW of compression facilities a few years into the life of Ravenspurn North was included in the field's development plans, with a view to handling gas production from a reservoir with declining pressure.

After the gas has been separated, cooled and dehydrated on the central processing platform, it is exported through a 24-inch, 24 kilometre pipeline to BP's Cleeton platform. Here it is mixed with processed gas from the fields receiving processing services from Cleeton for onward transmission to Dimlington terminal on the East Yorkshire coast. The gas is then processed to standards, which enable it to be accepted into the National Grid NTS. The output from Ravenspurn North is all sold under contract to British Gas Trading.

There are 51 beds available on Ravenspurn North, with the base crew level being 30. Although the two satellite platforms are normally unattended, they both have emergency accommodation for eight people. Three Watercraft 60 man totally enclosed survival crafts are located on the central processing platform and there are ten-man life rafts on ST-2 and ST-3. There is a comprehensive sick bay with first aid facilities on the central processing platform.

Currently Johnston, a subsea development operated by E.On-Ruhrgas UK is tied back to Ravenspurn North. Johnston has been in production since 1994 with peak production of 90 MMscfd. Gas is transported to Ravenspurn North where it is processed, compressed and exported to the Dimlington Terminal via the Cleeton Platform. This is performed under a tri-partite agreement between the Johnston Owners, The Ravenspurn North Owners and the Dimlington Terminal Owner. During 2005 the Johnston Owners tied in an extension to the field bringing on the J4 well. In 2007 the J5 well was tied in and commenced production.

Potential future developments can send their gas through Ravenspurn North or alternatively depending on the situation they may be able to tie back to Johnston. In certain circumstances subject to the availability of blend gas it may be possible to offer a transportation and processing service for gas outside the normal entry specification.