Beatrice Field, U.K. North Sea: Multi-Source Giant Field, with Two Generations of Offshore Windfarms

The Beatrice Field in the Inner Moray Firth in the U.K. North Sea has unique attributes that make it a useful case study for both the development of offshore oil and wind. It also has fascinating geology, with two source rocks (Devonian and Jurassic) and fault traps detectable with seismic.

Discovered in 1976, Beatrice is also significant in that wind energy and oil production were essentially collocated, and there was a dual use of infrastructure and the workforce. The offshore wind was so successful that after decommissioning, a new, larger windfarm was built and deployed in 2019.

Oil Discovery. Long considered prospective for oil production the Lower and Middle Jurassic were investigated offshore through a seismic acquisition program completed in 1971, and which revealed the structure of the Inner Moray Firth Basin, which included numerous faults, and a tilted faulted anticline.

The main reservoir consists of massive Callovian shallow marine to shoreface sands, along with secondary reservoirs in other Jurassic fluvial deltaic sands. The Lower and Middle Jurassic produce over 1,100 feet of sandstone, siltstone, and claystone sediments.

The oil is unique in that it is from two separate source rocks, and after kerogen pyrolysis the fluids migrated under pressure through faults and fracture networks. The principle source of the Beatrice oil is a Devonian lacustrine sediment and it contains non-marine organic matter, with oil-prone type I and II kerogen.?The other source is of Middle Jurassic age, and it was derived from degraded marine plankton, with types II and III kerogen. The result is a crude oil with a high wax content.

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While developing the Beatrice Field, it was found that the reservoir had very little energy, and so it was necessary to improve the reservoir drive by means of a combination of water injection and downhole submersible pumps. The produced oil flowed through a 42-mile pipeline to an oil terminal on the Cromarty Firth. The field was estimated to have had a total of 480 million barrels in place.

While Beatrice was producing oil in the North Sea, in another, wind energy was successfully designed and deployed. The first offshore windfarm was designed at Vindeby, off the southeast coast of Denmark.?Vindeby consisted of 11 turbines in 3 – 5 meters of water. It generated 5 MW each year, which was enough to provide electricity to 2,200 Danish households. After this successful deployment, other windfarms were designed and deployed, so that between 1991 and 2001, at least 15 windfarms were established in the North Sea, all of which used Vindeby’s design and operational innovations. Firsts at the Vindeby windfarm included incorporating an airtight nacelle to avoid corrosion from the salty sea air, installing dehumidifiers within the turbines, and building in heat exchangers to cool the equipment.

After Vindeby, came wind energy at Beatrice in 2007. The 10 MW capacity Beatrice Demonstration Windfarm was unique in that it was collocated in the Inner Moray Firth with the Beatrice production platforms. where it was possible to have dual-purpose infrastructure, trained workers, and dual-purpose transportation.?While there were similarities between the operations, there were significant differences which required modifications for workforce procedures, safety protocols, and environmental protection.?Operated by Talisman (the purchased by Repsol), it had at one time the largest offshore turbine in the world.

Because of the success of the Beatrice Demonstration Windfarm, a vastly expanded windfarm was designed and deployed for a total of 2.6 billion pounds ($3.0 billion) in 2019. The Beatrice Offshore Windfarm Ltd. (BOWL) project consists of 84 turbines (Siemens Gamesa), which rise to a height of 188 from sea level to blade tip for a capacity of 7 MW each. Located 13 km from the Scottish coast, the new Beatrice windfarm generates enough electricity to power 450,000 Scottish households per year. Transmission and distribution are done through Siemens Transmission.

New generation windfarms (such as the new Beatrice windfarm) and the latest generation production platforms are planned as NUF (Normally Unattended Facilities) installations.?As such, operations require new functions, which include digital monitoring, predictive maintenance, simplified mechanical design, sensor and corrosion management, leak detection, and automation.

However, one can keep in mind that there could be additional oil and gas reserves in place in other fault traps.?If that were the case, once depleted, the reservoir could be utilized for carbon and energy storage. In addition, the electricity generated from the windfarm could be harnessed to produce hydrogen.

Personal Note:

Kerr-McGee was a 25% owner of Beatrice. I worked for Kerr-McGee during that time, and there was enormous pride for the innovative approaches being implemented, which included an unmanned Platform C which was used for water injection to create an effective water drive in the reservoir. My first trip to the U.K. was in relation to the Beatrice Field, and I learned a great deal about operations in the North Sea as well as Kerr-McGee's diversified operations (coal, uranium, titianium dioxide, chemicals, refining, drilling, retail, forest products, and more).

REFERENCES

Beatrice Offshore Windfarm, Ltd. (BOWL). https://www.beatricewind.com/

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Daily Oklahoma. (1981). Kerr-McGee Announces Landmark. https://www.oklahoman.com/story/news/1985/06/11/kerr-mcgee-announces-landmark/62761186007/

Lempriere, Molly (Nov. 21, 2017) Full circle: decommissioning the first ever offshore windfarm. Power Technology.?https://www.power-technology.com/features/full-circle-decommissioning-first-ever-offshore-windfarm/

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Linsley, Phillip N., Potter, Henry C., McNab, Greg, and David Racher. (1979). The Beatrice Field, Inner Moray Firth, U. K. North Sea. Giant Oil and Gas Fields of the Decade 1968-1978. AAPG. P. 117 – 129.

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Peters, K. E., Moldowan, J. M., Driscole, A. R., and Demaison, G. J. (1989) Origin of Beatrice Oil by Co-Sourcing from Devonian and Middle Jurassic Source Rocks, Inner Moray Firth, United Kingdom. AAPG Bulletin. Vol 73, No 4 (April 1990), P. 454-471.

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Rassenfoss, Stephen (Sept 22, 2021). Offshore Oil and Wind are Similar but Different. JPT / Journal of Petroleum Technology.

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Stevens, V. (1991). The Beatrice Field, block 11/30a, UK North Sea. Geological Society, London, Memoirs. Vol 14. P 245-252.

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Vindeby Offshore Wind Farm: For Demonstrating the Viability of Offshore Wind as a Clean Energy Powerhouse (Most Influential Projects: #32) (2019). PM Network, 33, 66–67.

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