36 JUNE 2021 WorldWide Drilling Resource® Always On ~ Geothermal in the United Kingdom Compiled by Carol C. Schimpf, Editorial Assistant, WorldWide Drilling Resource® As first reported in by WWDRin November 2018, and again in December 2019, two deep directional geothermal wells were completed, forming Cornwall’s United Downs geothermal plant. Now, renewable energy supplier Ecotricity has reached a “pioneering” agreement to purchase electricity derived from the hot granite rocks in Cornwall, marking the first time geothermal power will be produced and sold in the United Kingdom (UK). The ten-year power purchase agreement with Geothermal Engineering Ltd. will allow Ecotricity to receive a minimum of three megawatts of baseload electricity from the United Downs deep geothermal site. Baseload refers to the minimum amount of electric power needed to be supplied to the electrical grid at any given time. One megawatt equals one millions watts, and three megawatts is enough to power 10,000 homes per year. Electricity from the facility will be sent to Ecotricity customers via the national grid. The first geothermal plant in the UK will be fully operational by 2022. On an industrial site near Redruth, Cornwall, two deep directional wells were drilled into the earth: the production well to a depth of 16,700 feet, the deepest well ever drilled on shore in the UK, and the injection well to 7851 feet deep, accessing the Porthtowan Fault Zone. With a temperature of up to 390ºF (200ºC), these wells will provide constant clean electricity and heat, available regardless of weather conditions at the surface. Herrenknecht’s Innovarig, a new generation semiautomatic hydraulic rig, was used to drill the wells. It is the quietest rig of its size in Europe, specifically designed for use in urban and noise sensitive areas. It used 38 drill bits, tri-cone with tungsten carbide inserts, to complete the wells. Four sizes were used for the production well and three for the injection well. A smaller rig was used to complete the wellhead and enable test equipment to be used to take core samples, temperature, and flow test. The wells are steel cased for most of their length with just the deepest section open to allow water to circulate. A binary power plant, with no plumes of vapor and very little to see on the surface, was constructed for production. Ecotricity Chief Executive Dale Vince said, “We’re pleased to be part of this project and to add the power to our customers’ energy mix.” Geothermal Engineering believes untapped geothermal resources can deliver clean power and heat across Cornwall. During the next two years, they are hoping to secure funding for future geothermal sites, each producing a minimum of 5 MW of renewable baseload electricity and up to 20 MW of renewable heat. Experts predict geothermal power eventually will provide up to 10% of the country’s energy need and be an “always on” renewable source. GEO
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