A conventional drilling rig with a giant-sized drill bit rotating at variable speeds, depending on the density of the rock, drills into the earth, with water or mud circulating through the well shaft to bring rock cuttings to the surface and keep the drill bit (and the well bore) cool.

The technique changes only in the presence of high-temperature steam reservoirs. Then, the final step of drilling is accomplished with air, under pressure, to prevent drilling mud from clogging the bore and preventing the steam from emerging. The method is very nearly as old as the discovery of oil as a fuel source, and is expensive, time-consuming, dangerous and environmentally hazardous – at least in terms of fossil fuel extraction.

A better method, called “spallation,” which refers to chipping or flaking of stone, involves using jet engines to produce superheated, pressurized air which breaks rock.

BP has challenged widespread scientific claims that vast plumes of oil are spreading underwater from its blown-out rig in the Gulf of Mexico. The denial comes as the oil giant prepares for a new operation to put an end to the worst oil spill in US history – which could see the leak get worse before it gets better.

The company’s challenge to several scientific studies is likely to put it further at odds with an increasingly angry Obama administration, which has accused it of playing down the size of the leak in an effort to limit possible fines.