Major gas confirmed in Slyne Trough

Enterprise Oil confirmed a second successful appraisal on its Corrib gasfield discovery, situated 70 km from Achill Island, off western Ireland. Well 18/25-1, drilled in 350 meters water depth in the Slyne Trough by the Sedco 711 semisubmersible, was 2 km from the first appraisal well, 18/20-2z.

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Location of the Enterprise Oil gas discoveries off western Ireland.
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Enterprise Oil confirmed a second successful appraisal on its Corrib gasfield discovery, situated 70 km from Achill Island, off western Ireland. Well 18/25-1, drilled in 350 meters water depth in the Slyne Trough by the Sedco 711 semisubmersible, was 2 km from the first appraisal well, 18/20-2z. The latest well was drilled to 3,740 meters true vertical depth (TVD) in Triassic Sherwood sandstone, and tested up to 64 MMcf/d of gas through a 1 1/4-in. choke, with wellhead flow pressure of 1,650 psi.

Enterprise's Ireland General Manager, John McGoldrick, claimed that the southern end of Corrib was now well delineated. The next step will be to drill the Shannon prospect, 8 km to the south. In-place gas is thought to be sufficient to meet half of Ireland's current gas requirements. Wood Mackenzie had estimated Corrib reserves at 1.2 tcf, prior to the latest assessment.

Enterprise has also been awarded 100% of licence 99/2, 60 km to the northwest of Ireland in the Donegal Basin. This area has barely been explored - indications are of another gas-dominated play. New 2D seismic was recently acquired over the acreage by Fugro-Geoteam. Geco-Prakla has also been busy this summer shooting seismic for Elf in the Rockall Trough and South Porcupine Basin. The other driller at present is Marathon Oil, which re-entered a well in the Celtic Sea using the Glomar Arctic III.

UK oil output still climbing

Rising oil prices are easing the pressure on UKCS oil producers, according to the Royal Bank of Scotland's Business Economics division. Their latest survey shows daily oil revenues from the sector up 31% on the previous month's, at just over £31 million. Production of both oil and gas also broke the previous record for the month of July, averaging 2.602 million b/d and 6,816 MMcf/d.

Wood Mackenzie is forecasting an average for 1999 as a whole of 2.67 million b/d. That would also represent a new UK record, ahead of last year's 2.62 million b/d, but the analysts had been estimating 2.99 million b/d at the year's outset. Factors behind the shortfall include:

  • Severe weather early on, restricting offshore tanker loading
  • Failure of a pipeline on BHP's Douglas platform in Liverpool Bay
  • Separator problems on Texaco's Captain Field
  • Postponement of the subsea tieback of Ranger's Kyle Field to the Banff FPSO
  • Damage to a cargo tank on Amerada Hess' Uisge Gorm FPSO, by over-pressurization.

Despite the hitches, the analysts still foresee a new high of shipments to shore via tankers - 746,000 b/d - provided that the new Bittern/ Guillemot FPSO starts up on time.

Dutch drillers reaping rewards

During the North Sea's recent cooling-off period, The Netherlands emerged as the comfort-zone exploration play. Elf Petroland reports a new discovery in its K5A block stronghold, following an earlier success in April on neighboring block L4A. The well tested 895,000 cm/d from the Rotliegendes at a depth of 4,036 meters. Also in K4, Coflexip Stena Offshore has been booked to lay an 8,000 meter flexible gas flowline and an 8,000 meter flexible glycol line.

Clyde Petroleum announced a combined flow of 54 MMcf/d from two separate Triassic zones during recent tests on its Q4-9 discovery well. The location is just 6 km northwest of another Triassic find, Q4-8, drilled by Clyde last year. Production licences for both finds are currently under negotiation.

Germany's Veba - an emerging force in the North Sea - has farmed into two E quadrant licences awarded to NAM in the Northwest Dutch shelf. Newly acquired 3D seismic is currently being processed. This is higher risk exploration acreage, although just to the north is a shallow gas Tertiary reservoir.

Spar disposal costs triple that planned

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Hanze is Veba's first operated field development in the Dutch North Sea.
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Disposal costs for the Brent Spar were effectively triple the original estimate of £21.5 million, according to a post-mortem briefing by Shell Expro. This includes the costs of numerous hearings as well as added safety and environmental management measures following the aborted deep-sea disposal project.

Decommissioning Manager Eric Faulds pointed out that numerous unforeseen challenges have to be expected when dealing with such an old structure. The sheer scale of the tank cleaning exercise was one. Exceptionally high levels of hydrogen sulfide had dissolved in the tanks' water. The cleaning process itself also released much higher levels of benzene vapor and methane gas than anticipated.

The aim of generating a positive energy balance from re-use of the Spar rings sections, in addition to recycling the topsides and transition column, was not achieved. Monitoring of the project revealed an overall net increase in energy consumption. In total, decommissioning took 330,000 man-hours to complete.

Norway development planning resumes

Development planning is cranking up again in Norway following the one-year hiatus imposed by the government, aimed at curbing over-spending.

  • Kvaerner Oil & Gas has started work on a NKr 70 million pre-engineering contract for the Grane Field. Operator Norsk Hydro aims to submit a PDO this December for what could be one of Norway's largest integrated platforms.
  • Esso has confirmed its intention to develop the Balder Field satellites Forseti and Ringhorn, following an appraisal effort that pitched combined reserves at around 100 million bbl. A wellhead platform would be installed, exporting the oil through a new pipeline to the Balder FPSO's process facilities. Project costs could reach NKr 4 billion.
  • Sygna, a 125 million bbl oilfield spanning blocks 33/9b and 34/7a, could be tapped as a subsea satellite to the Statfjord C platform. If so, two producer wells - one horizontal and one water injector will likely be drilled, the latter from the Statfjord North injection template 5.5 km away. The producers would be drilled from a new four-slot template, to be supplied by Kongsberg. This in turn would be connected to the Statfjord C platform via a 20 km, 7-in. flowline, installed by Colfexip Stena Offshore/Rockwater. The field life forecast is 11 years.

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