Many small fields to be developed in North Sea

Across the North Sea there are many small accumulations of oil and gas, some discovered 10 or 15 years ago, others more recently. They have lain fallow for a number of reasons, perhaps thought of as uneconomic to develop, or far from available infrastructure. Now a range of factors - modern seismic and drilling technology, host platforms and pipelines with spare capacity, the flavour for floating production technology and higher oil prices - have brought them off the shelf and into the development arena.
Some of the names are already known to the industry, others are just beginning to emerge.
Conoco for example, has let it be known that it is pushing ahead with the development of the Maclure (formerly known as Gremlin) oilfield, discovered in 1991, where reserves are put at 22 mm barrels. This lies in block 9/19, 10 km north-west of the Buckland oil and gasfield for which Conoco is working on development via a FPO. Reserves in Buckland are put at 40 mm barrels of oil.Conoco is also studying the development of the Sorby gas and condensate discovery in the same block, 10 km north-east of Maclure. This was discovered with well 9/9-2 in 1976. No reserve figures have been announced.
Decisions on development will be made this year. Steve Lawless, manager of Conoco's Central North Sea Operating Unit, says that floating production systems or tie-backs to FPSO vessels are likely to feature in all three scenarios.Some clues to other potential candidates can be found in the latest edition of the UK's "Current Future UKCS Oil and Gas Prospects", which the UK's Oil, Gas and Petrochemicals Supplies Office, known as the OSO, publishes. According to the OSO, there are 29 oil and gas projects under development on the UKCS, with 30 future projects likely to be developed within the next few years.
Amerada Hess is listed as having four future prospects, whereas in the October 1996 edition of the report, it had none. The most advanced is Abbot, in block 29/1b, which was discovered in July 1996 and which stretches into the 29/1a block where Shell is operator and calls the field Razorbill. "Both companies have aspirations to operate the field (thought to have reserves of 100 mm barrels). A process of joint appraisal of development concepts is underway," says the OSO. Both companies want a fast-track project with the possibility of a field development plan to the Department of Trade and Industry (DTI) in the second or third quarter of this year. While refraining from giving a first production date for Abbott, the OSO puts June 1999 for Razorbill. The contending solutions include a free-standing FPSO, favoured by Amerada, or a subsea tie-back to local infrastructure, for example a platform bridge- linked to Shell's Gannet. Amerada is progressing matters with contractors who responded to its Official Journal notice seeking lease and purchase options on the provision of an FPSO. Gas exports could be either via the Central Area Transmission System (CATS) or the Fulmar line.
The Perth oilfield in block 15/21 is forecast to come onstream in April 1998. Foster Wheeler is carrying out a feasibility study on facilities. Export options are, to a large extent, dependent on the nature of the crude which has a high hydrogen sulphide content. Wellstream fluids could be processed at either Tartan or Scott. Further appraisal will be required, and an extended well test (EWT) is planned for this year. Development, says the OSO, would probably be phased with a single well tie-back initially followed by a further phase to increase production to around 20,000 bpd.
The OSO does not say much about the Hannay oil and gas prospect. It does note however that the "base case is currently a subsea tie-back to Buchan Alpha. However, there are several interesting prospects nearby and the operator will investigate a possible stand-alone facility." The prospect was discovered by well 20/5c-6 drilled last year with the semi- submersible John Shaw. This was a joint venture between the licensees of block 14/30b and block 20/5c, both operated by Amerada. The well tested at a rate of 8,647 bpd of light hydrocarbons through a 2 in choke. It was suspended for possible future use. Amerada said at the time the discovery was made that "plans for further appraisal are being formulated". So far, eight months later, no further wells have been drilled. The prospect is located 25 km south-west of the Ivanhoe/Rob Roy fields, operated by Amerada, and 12 km North west of Buchan. Amerada is keeping tight-lipped about the fourth prospect, known as Melville.
Another newcomer to the catalogue is Marathon's Braemar gas/condensate field, where the OSO says first production would be in December 2000. It also says that Marathon may undertake testing by delineation well or EWT in 1997 to gather information prior to a development decision. Marathon says it expects to recommend a development plan by the end of this year, with the aim of first production by the 1999 first quarter. A delineation well would be drilled in 1998, with one, or possibly two wells drilled the following year. While a minimum facilities platform tied back to Brae B, 20 km to the south-west is a possibility, it is more probable that there will be a subsea tie-back. The field was discovered in 1985, 10 km North of the East Brae platform. A re-entry in 1995 tested at a combined rate of 49 mmcf of gas per day, and 2,400 bpd of condensate.While the OSO puts gas reserves at around 48 bncf, Marathon estimates them as in excess of 400 bncf.