London - UK shale gas company Cuadrilla Resources plans to undertake four months of exploration drilling work this summer at a site to the south of London, it said on Wednesday.
The company intends to drill a vertical well 304m deep near the village of Balcombe in West Sussex to take samples of the underground rock, with a possible horizontal leg extending 762m from the vertical section.
Cuadrilla said neither the horizontal or vertical well will be hydraulically fractured. Fracking is a way to retrieve gas trapped in tight layered rock formations by injecting high-pressure water, sand and chemicals.
Fracking remains extremely controversial in the United Kingdom, with the government only just having lifted an almost year-long ban imposed after work triggered small earthquakes near the northern seaside resort of Blackpool.
A short flow test will be carried out at the Balcombe site if any oil or gas is discovered, Cuadrilla said.
"It is envisaged that the work will take no more than four months and the site cleared of equipment no later than the end of September this year," it said.
Cuadrilla, which won planning permission for the work in 2010, promised to hold extensive technical, environmental and public consultations if it finds oil or gas.
Developers predict trillions of cubic feet of reserves could be lying under British soil, which could help the country reduce its dependence on imports.
The government is to publish its latest estimate of domestic shale gas resources in the coming months, expected to dwarf an earlier reserve estimate of 150 billion cubic metres, enough to cover Britain's gas consumption for 18 months.
Environmental groups say they remain concerned about the impact of fracking on water supplies but the industry says these are overplayed given that fracking takes place at far greater depths than fresh water aquifers.
"Although this summer's work will be unobtrusive, we're fully aware that local people will have many questions about our plans and we'll do our best to answer all of them," said Cuadrilla Chief Executive Francis Egan.