When brokers representing oil-and-gas producer Occidental Petroleum came to his rural district east of Houston last year, Dennis Dugat thought they were pulling his leg.

Occidental was offering a lot of money to lease not the property or minerals, but the porous rock deep under Dugat's 750-acre farm and that of his neighbors. The company proposed to store carbon dioxide there, a procedure the 69-year-old rancher and constable says he had never heard of.

Then energy giant Chevron came by and offered even more money to lease the land, making Dugat a believer and kicking off a bidding war between the companies as they wooed local landowners, he says. Dugat ended up leasing to Chevron; some of his neighbors went with Occidental. ConocoPhillips and Exxon Mobil are also on the prowl nearby, Dugat says he has heard.

"I don't quite understand all of what they're doing," he says. "Apparently it's something that a lot of the oil and gas people are interested in."

That something is carbon sequestration, the process of taking carbon dioxide -- the greenhouse gas associated with the bulk of the world's warming emissions -- and removing it from circulation by compressing it and injecting it deep underground. If the world is to ward off a dangerous increase in temperature by the end of the century, it needs to shut away more than 5 billion metric tons of carbon dioxide a year by 2050, the International Energy Agency estimates.

A few companies have been in so much of a hurry to secure space underground that they have leased properties without thoroughly checking whether the geology is right, some industry executives say.

"Now the strategy is: Lock it down; we'll figure out the details later," says Kirk Barrell, an oil-and-gas geologist whose company, Barrell Energy, is gathering groups of landowners for carbon-sequestration projects in four areas of Texas and Louisiana.

wsj.com - New land grab by oil giants is deep underground