Shale is as dense as hardened clay, and oil does not flow from it easily. Horizontal fracturing breaks up the rock by blasting water under high pressure into horizontally drilled wells, so the oil can be extracted.
The technique is widely used in the US to produce natural gas from shale. The first success with shale oil was in the Bakken formation in the Williston Basin, stretching across North Dakota into southern Saskatchewan. Companies there have used the technique to ramp up oil production from 80 thousand barrels a day in 2004 to 300 thousand barrels a day this year. The rock formations in the Paris Basin have a similar structure and history, so oil companies hope the technology will work in France, as well. Ten companies are competing for permits that would give them the right to explore and eventually develop the fields, in what is the toughest competition for resources France has seen in decades.
"We are seeing an incredible amount of interest. Trying to sort out all the permits is like dealing with kids in the schoolyard," says Charles Lamiraux, head of oil exploration for the French energy ministry. "I think if they are fighting this hard it's because they think there is an important future there."
Vermilion Energy, already the biggest producer of oil from conventional fields in France, was the first to tap into the shale rock. Earlier this year, it used two conventional vertical wells in a farmer's field to conduct tests on the shale layer. Vermilion's vice president of European operations, Peter Sider, says the results were "encouraging."