Some have opted to invest in natural gas — either unconventional gas from North American gas shales or liquefied natural gas from countries such as Qatar.
Now the shale boom is beginning to spread to Europe, which also boasts large reserves of unconventional gas.
Such unconventional gas production accounts for nearly a quarter of total production in the United States, according to the latest figures from the Energy Information Administration.
Indeed, the rush for shale assets in Europe has been led by many of the big firms that at first overlooked unconventional gas in America.
Mr. Howarth included methane losses associated with flow-back and drill-out processes in hydraulic fracturing and other unconventional gas drilling techniques.
