Jeremy Beckman • London
Ormen Lange well could downgrade reserves
Norske Shell has found gas with its latest appraisal well on the giant Ormen Lange field in the Norwegian Sea, but the result raises more questions than answers.
The objective was to delineate the northern extent of the field, which has been in production since 2007. The well, drilled by the semisubmersible Leiv Eriksson in 832 m (2,730 ft) of water, encountered variable quality reservoir rocks, and early evaluation suggested that the gas/water contact was shallower than in the main part of the field.
According to the Norwegian Petroleum Directorate, the findings will be factored into a new interpretation exercise designed to clarify Ormen Lange’s remaining resources. It is unclear whether the original upside potential can be realized, and that may impact future development phases. Earlier forecasts of a 50-year lifespan suddenly are looking somewhat optimistic.
In the deeper-water Voering area of the Norwegian Sea, 300 km (186 mi) from the coast, Statoil is looking at options for a new gas production hub. This could encompass the Luva, Snefrid, and Haklang discoveries, all in the same production license, and Asterix 75 km (47 mi) west, which have combined reserves of dry gas estimated at 40-60 bcm (1.4-2.1 tcf).
Following a recently completed feasibility study which included a survey of seabed conditions, the partners have resolved to spend the next two years working on an integrated process/export solution. The aim is to come up with three or four development concepts, and to evaluate various alternatives for gas transportation and power supply. The nearest offshore installation is the Norne FPSO, 140 km (87 mi) away, and the closest gas infrastructure with spare capacity is the Nyhamna pipeline terminal, 500 km (311 mi) distant, which processes supplies from Ormen Lange.
Mariner moving closer to development
Statoil has transferred imaging techniques proven on its Grane heavy oil field in the Norwegian sector to its development studies for the complex Mariner structure in the UK North Sea. Since assuming operatorship from Chevron, Statoil has acquired high-resolution 3D seismic and ocean bottom cable (OBC) seismic over the field, in addition to a platform site survey this summer.
The 3D/OBC combination has improved imaging and definition of the areal distribution of Mariner’s Heimdal Sandstone reservoir and characterization of the Maureen Sand reservoir, according to partner Nautical Petroleum. Also, areas of Maureen Sand erosion appear to be more limited than previously mapped.
Results of other new studies indicate that platform drilling costs can be reduced, recovery rates increased, and water cut decreased through use of autonomous valves. All these results will be incorporated into a revised reservoir simulation, with no further appraisal drilling required. Nautical estimates Mariner’s best-case resources at 369 MMbl, and expects a field development plan to be submitted in 2011, leading to first oil in 2015.
At the nearby Kraken, a smaller heavy-oil field, Nautical (as operator) plans to integrate sedimentological and seismic studies with results from a controlled source electromagnetic survey performed this June, to determine the location for an appraisal well next year. It aims to submit a development plan before the end of 2010. In the same region, Fugro Well Services has agreed to drill and test a horizontal production well next spring on XCite Energy’s Bentley heavy-oil field, which also will serve as an early production system. In return for carrying a substantial cost of this program, and provided that the outcome is successful, XCite will engage Fugro for more work in future.
Hurricane taps basement play WoS
Among the latest flurry of discoveries West of Shetland, Hurricane Exploration has found light oil with a well on the Lancaster prospect in block 205/21a. The company described the find as “potentially very significant,” claiming this as the first instance of a basement reservoir being planned and drilled as an exploration target anywhere on the UK shelf.
The well, managed by Senergy and drilled by Dolphin, flowed 34-39.2º API oil to surface over the reservoir section under its own energy. The target basement reservoir zones were fractured and proven to be permeable, with hydrocarbons intersected below the originally mapped structural closure. Due to positive drilling data, the operation was extended by a further 225 m (738 ft) vertical depth, although the well had to be suspended due to a combination of bad weather and malfunctioning test equipment. Hurricane aims to return next year, however, either for a re-entry/extended test, or a new appraisal well.
In block 204/13-1, OMV has confirmed that its exploratory well on the Tornado prospect in September found gas and oil. The well and subsequent sidetrack were drilled in 1,048 m (3,438 ft) of water by the drillship Stena Carron. According to partner Dana Petroleum, the Tertiary sandstone gas/oil contact in the original well was encountered at the same depth in the sidetrack.
Northwest of Shetland in block 214/30a-2, DONG Energy has completed two successful sidetracks designed to appraise its earlier Glenlivet Palaeocene gas find.
Aging installations pose problems
Maintenance of aging production facilities gets harder as time goes by, according to a new survey by Petroleum Safety Authority Norway. A survey answered by BP, ConocoPhillips, Talisman Energy, and drilling contractors Dolphin and Songa found that with older facilities, maintenance is more time-consuming, with an increasing need for modifications and replacement programs. These structures also require more intensive updating analyses, and greater focus on continuous improvement and maintenance efficiency.
|OMV's Tornado is one of three new discoveries West of Shetland.|
As for structural issues, the challenges cited included microbial corrosion on piping systems, corrosion underneath insulation, degrading of surface treatment, scaling and deposits in process equipment, and subsidence of fixed facilities.