CNOOC and the curious case of Cuddle's combustible cliff

In November 1973, the Southern Evening Echo, a local paper in the English county of Dorset, ran a headline that was certain to grab readers' attention.

'The day the earth caught fire', screamed the 28-point print above a story that detailed breathlessly how a seaside cliff near the delightfully named headland of Cuddle had spontaneously burst into flames, burning with a foul stink the unfortunate witnesses later described as being like 'a mixture of paraffin and bad eggs'.

But while the newspaper story may have astonished the genteel retirees of the Dorset coast, it came as no surprise to geologists.

For more than a hundred years, the cliff at Cuddle had been known as an outcrop of oil shale, a sedimentary rock dense in hydrocarbons including natural gas.

Indeed, previous episodes of cliff-side combustion had been recorded at the same site in 1826 and 1732, when, according to one contemporary account, the rocks emitted fumes of an 'offensive savoure and extraordinary blacknesse'. In the summer of 2000, the cliff again caught fire, burning steadily for three weeks with the sulphurous smell detectable as far as two kilometres away.

Yet despite their obvious energetic potential, for years oil shales like those at Cuddle remained little more than a geological curiosity. The reason was simple enough: although similar shale formations around the world contain trillions of cubic metres of natural gas, it is locked away in tiny pores deep in the impermeable rock strata. Extraction remained a pipe-dream and big energy companies were uninterested.