Jacky Oil Field, United Kingdom

The Jacky field is located in block 12/21c in the UK Continental Shelf, in water depths of 30m-40m, about 19km east of the Moray Firth Caithness cliffs. It was discovered in April 2007 and development approval was granted by the UK authorities in November 2008.

Jacky is owned by Ithaca Energy (67.275% and operator), Dyas (22.725%) and North Sea Energy (10%).

The Jacky reservoir occurs in the Beatrice A sands, a mid-Jurassic sandstone formation just over 2,000m below the surface. Reservoir pressure is low and the temperature of the reservoir's fluid is about 85°C. The oil is sweet, waxy and, at 38.9° API, relatively light. It also has a low gas-oil ratio, so there is no significant production, and no export, of gas.

Gross proven and probable reserves are put at 5.1 million barrels, giving the field a predicted economic life of up to 5.5 years.

The capital cost of the project was originally estimated at £59.7m but shifts in exchange rates have meant the final figure is likely to rise by 20-24%.

Jacky field development

The field is being developed in phases. The first phase consisted of installing a single production well, using the Ensco 92 jack-up drilling rig, tied in through a normally unmanned and removable wellhead platform. The platform, which was installed using the Hermod lift barge, has been fixed to the seabed using removable suction piles.

Also in phase one, a 6in insulated oil pipeline, an 8in water injection pipeline and a power cable and control umbilical, all 10.5km long, were laid from the Jacky platform to the existing Alpha processing facility in the nearby Beatrice field, which is owned by Ithaca (74.75%) and Dyas (25.25%).

In addition a small manifold has been installed to enable connections for two short pipelines to the Beatrice Bravo satellite platform for potential future use. Ithaca has also restarted production from Beatrice Bravo, which was delivering about 800bpd when it was shut in by the previous owners of the field in July 2007.

Jacky started producing in early April 2009 and by that May was flowing without artificial lift at gross rates of about 8,800bpd. Ithaca says that this compares favourably with predevelopment expectations that artificial lift would be required to achieve 7,800bpd gross.

Processing

All processing takes place on Beatrice Alpha. Two parallel oil production trains are sized to process 50,000bpd of wellhead fluids while a test train, which allows individual testing of wells, can process up to an extra 25,000bpd.

Produced gas is flashed off in the separators and handled by flare systems, while the process system is designed to remove free water below 30ppm oil in water.

Processing oil, along with 50% water, is exported through a 16in pipeline to the Nigg oil terminal, which is also held 74.75%:25.25% by Ithaca and Dyas, in the Cromarty Firth.

Gas rates from Jacky will tail off rapidly during the first year of production.

Future plans

As of early May 2009, the intention was to allow reservoir pressure to fall during the subsequent few weeks to allow the start of artificial lift, which is expected to increase production rates further.

Phase two of the development is expected to take place around mid-2010, depending on Jacky's performance, and will entail drilling and completing a second production well and a water injection well. Both will be drilled via slots on the Jacky platform.