* Britain needs new onshore drilling infrastructure
* Thousands of wells might be needed and have short life
* Cuadrilla estimates 330 tcf of gas trapped in licence area
By Nina Chestney
LONDON, March 5 (Reuters) - Britain may be a prime locationfor shale gas exploration in Europe, but a lack of onshoredrilling infrastructure and local opposition will impededevelopment, experts and geologists said at a shale conferencein London.
Britain is in the early stages of exploring forunconventional gas to counter growing dependence on imports andto emulate the success the United States has had in lowering itsenergy prices due to a shale boom.
The current crisis in Ukraine has renewed calls forcountries in Europe, including Britain, to diversify away fromRussian natural gas.
In eastern Europe, Polish gas monopoly PGNiG saidlast month it had found a new gas deposit in south-easternPoland, and Ukraine has signed agreements with Royal Dutch Shell and U.S. energy major Chevron for shale gasexploration.
Several companies have announced plans to explore for shalegas in Britain using hydraulic fracturing, known as fracking, atechnique of injecting water, sand and chemicals deep into rockformations to release hydrocarbons.
"Probably the UK (is Europe's prime location) from atechnical point of view as we have some very thick shale, butthere are still a number of question marks," Ron Oxburgh, a former Shell chairman and member of the House of Lords SelectCommittee on Science and Technology, said on the sidelines ofthe two-day Shale UK shale conference.
"We may get more out of a single hole than in other parts ofthe world, but we need new onshore drilling infrastructure whichwe don't have now. The issue of noise is also a limiting factorin the near term (...) These are brutes, they are big pumpingmachines," he added.
WELLS
The British Geological Survey has estimated that rockformations in so-called Bowland Basin in central Britain holdaround 1,300 trillion cubic feet (tcf) of gas, far more than the3 tcf of gas a year currently consumed, but the amount that canactually be extracted is uncertain.
The Upper Bowland area, a part of the basin that has alreadyattracted exploration, could have 260 tcf of gas present, saidAndy Aplin, professor of unconventional petroleum at DurhamUniversity and former adviser to BP.
"We would need 33,000 wells to drain all that," he told thetwo-day Shale UK conference in London. That compares with anannual average of 19 onshore wells drilled in Britain over theperiod 1902-2013.
Analysts at energy consultancy Poyry estimate that by 2024around 100 new wells will need to be approved each year to pavethe way for significant shale gas production.
But shale gas wells have a short life. Based on the U.S.experience, their flow rate is reduced by 85 percent over threeyears, compared with a conventional gas well which would stillhave high flow rates after 30 years, Oxburgh said.
Cuadrilla is the only company so far to have used frackingin its test wells in the Bowland area and has applied forpermission to drill and frack at up to four new explorationwells in the area.
The company has been repeatedly targeted by protesters andenvironmentalists concerned about groundwater contamination,earthquakes and the expansion of fossil fuel use.
Cuadrilla estimated in 2011 there was around 200 tcf of gastrapped in the shale rock of its licence area in Lancashire butnow thinks there might be closer to 330 tcf, according to HuwClarke, geologist at Cuadrilla.
Other parts of the country have potential as well.
Al Fraser, professor at Imperial College and formergeologist at BP, highlighted the so-called Gainsborough Trougharea of northern England. French oil major Total bought a 40 percent interest in two licenses in that area inJanuary.
"I would have picked that. If it doesn't work there, itwon't work anywhere," he said.