SUMMARY OF WYTCH FARM OIL FIELD

INTRODUCTION• The Wytch Farm oil field, located 17 miles from Poole and six miles from Wareham in the Purbeck district, Dorset, England, is the biggest onshore oil field in Europe.

•  It is a mature oil field that has been extracting oil and associated gas from sandstone and limestone oil reservoirs in the Wessex Basin since 1979.

• French oil and gas company Perenco holds 50.10% interest and operates the Wytch Farm. The other stake holders of the onshore field include Premier (30.09%), Maersk (7.43%), Summit (7.43%) and Talisman (4.95%).

RESERVOIR DETAILSThe Wytch Farm oil field was discovered and initially operated by the nationalised British Gas Corporation. The first phase of the field development, completed in 1980, involved four well sites targeting the Bridport reservoir.The Wytch Farm oil field comprises three separate oil reservoirs, including the Bridport and Sherwood Jurassic sandstone oil reservoirs and the Frome clay/limestone oil reservoir which is a minor reservoir.The ultimate recoverable oil reserves (including cumulative production and remaining reserves) of the Wytch Farm oil field as of 2003 were estimated at 480 million barrels with the Sherwood reservoir accounting for around 90% of the total reserves. The remaining oil reserves of the field as of September 2013 were 43 million barrels. The Frome reservoir at a depth of 750 m was discovered later.

Sherwood Reservoir situated at a depth of 1,600m was discovered in 1978.

Bridport Reservoir lying 900m beneath surface, was discovered in 1973.

HISTORY AND DEVELPMENT• The Wytch Farm oil field was discovered and initially operated by the nationalised British Gas Corporation. The first phase of the field development, completed in 1980, involved four well sites targeting the Bridport reservoir.

• The field started producing from both Bridport and Sherwood reservoirs with the completion of the second phase.

• The third phase of development initiated in 1993 involved extended reach drilling from the mainland under Poole Bay and the construction of a new well site on the Goathorn Peninsula.

• The oil production from Wytch Farm peaked at 110,000 barrels per day in 1997 compared to 6,000 barrels per day in 1984.

• The oil production, however, gradually declined since then to 50,000 barrels per day in 2002 and to 16,000 barrels per day in 2011.

• BP, in 2011, sold its 67.8% interest in the Wytch Farm to Perenco which further sold 17.7% to Premier. The new operator started infill drilling at the site in the first quarter of 2012.

INFRASTRUCTURE• More than 100 wells (including producers and water injectors) were being operated from 13 well sites at the Wytch Farm oilfield as of June 2012. The oil field also uses a sea water-pumping station.

• Oil from the gathering station is sent via a 91km long and 16-inch diameter pipeline via the Fawley refinery to the Hamble oil terminal. Natural Gas (methane) produced at Wytch Farm is piped to Sopley located north of Christchurch. The LPG produced from the gathering station is exported by road tankers.

OIL AND GAS PRODUCTION

The average daily oil production of the oil field during the year ending in November 2013 was more than 17,000 barrels. The associated gas production from the field averaged at three million cubic feet during the period. Wytch Farm was the UK's fifth biggest oil producing field and the highest producing onshore oil field in 2013.

FUTURE DEVELOPMENT• Perenco was granted permission by the Dorset County Council in September 2013 to extend the field life of Wytch Farm from 2016 to 2037.

• The approval, however, necessitates the operator to restore the surrounding environment and prohibits against fracking wells for shale gas at the field which is located in one of the most environmentally sensitive areas of the UK.

• The future development at the oilfield will include drilling new wells and maintaining the existing ones. Perenco drilled three new wells as part of the infill drilling programme at the site as of 2013.

REFERENCES: http://www.hydrocarbons-technology.com, http://www.southampton.ac.uk