Just east of Argentina's Andean foothills, an oil field called the Vaca Muerta - "dead cow" in English - has finally come to life.

In May, the Argentine oil company YPF announced that it had found 150 million barrels of oil in the Patagonian field, and President Cristina Fernández de Kirchner rushed onto national television to praise the discovery as something that could give new impetus to the country's long-stagnant economy.

"The importance of this discovery goes well beyond the volume," said Sebastián Eskenazi, YPF's chief executive, as he announced the find. "The important thing is it is something new: new energy, a new future, new expectations."

Although there are significant hurdles, geologists say that the Vaca Muerta is a harbinger of a possible major expansion of global petroleum supplies over the next two decades as the industry uses advanced techniques to extract oil from shale and other tightly packed rocks.

Exploration of similar shale fields has already begun in Australia, Canada, Poland and France. Indian and Chinese oil companies are investing in pilot projects that, if successful, could make their countries significant oil producers, possibly reshaping energy geopolitics and stemming future price rises. Ukraine and Russia are also thought to have sizable shale fields of oil and gas, as do many North African and Middle Eastern countries.

"The potential is huge, on the order of hundreds of billions of barrels of recoverable reserves," said Michael C. Lynch, president of Strategic Energy and Economic Research, a consulting firm, who is preparing a report on global shale oil.

Similar fields in North Dakota and Texas are already beginning to gush oil. The techniques used to extract it include hydraulic fracturing, in which high-pressure fluids are used to break up shale rock to release the oil, and horizontal drilling, which allows drillers to tap thin layers of oil-filled shale that are sandwiched between layers of other rock.

Oil experts caution that geologists have only just begun to study shale fields in much of the world, and thus can only guess at their potential. Little seismic work has been completed, and core samples need to be retrieved from thousands of feet below the surface to judge how much oil or gas can be retrieved.

David Fuller's view Fullermoney maintains that the shale gas and oil story is most definitely a 'game changer'. The supplies are huge and situated in many countries. However it will take time for the expertise to spread so that these fields can be developed commercially. This is already occurring in the USA, Canada and on a small scale in a few other countries. Consequently, we may not see the full global benefits for another twelve to fifteen years.