The race for the country's natural gas riches grew more crowded Monday with the announcement that France's Total SA would spend $2.25 billion to gain new access to deep fields in Texas.

Total's deal with Chesapeake Energy Corp. comes just three weeks after Exxon Mobil Corp. said it will buy XTO Energy Inc., another prolific natural gas company, in a $31 billion all-stock deal.

Estimates of total U.S. gas reserves have risen so sharply in just two years, thanks to improvements in technology developed in the U.S., they have caught the eye of major integrated oil companies that until recently had left unconventional natural gas plays in the U.S. to smaller producers.

And Total, like Exxon, promised to take what it learns in the U.S. to natural gas fields across the globe.

"It reaffirms, if there could be any doubt, ... that the world is looking to the U.S. to learn about gas shales," Chesapeake CEO Aubrey McClendon said in an interview.

U.S. companies in the past decade have learned to drill down thousands of feet and then splay lines out for more than a mile, blasting tight shale formations with sand, water and chemicals to free natural gas.

Total, the world's fifth largest oil and gas company, will acquire a 25 percent interest in Chesapeake's Barnett shale assets in north Texas for $800 million in cash. It will pay an additional $1.45 billion to help fund 60 percent of Chesapeake's share of drilling and completion expenses.

Chesapeake, based in Oklahoma City, is the second largest producer in the Barnett, the source of half of all production in the U.S., according to Chesapeake.

Production in the Barnett has leveled off to around 5 billion cubic feet per day over the past year because so much gas has already flooded the market and prices have crashed, said Gene Powell of the Powell Barnett Shale Newsletter.

Enormous supplies combined with looming climate legislation have already prompted some utilities to switch from coal-fired plants to natural gas turbines because they emit fewer greenhouse gases.

That has allowed Chesapeake to hold out long-term contracts as an option power providers as a way of ensuring stable prices, something that producers have not been able to do in the past.

No such deals have been struck but the enormous amount of natural gas may have shifted the energy balance from coal and major oil companies are getting on board.

Total CEO Christophe de Margerie said in a statement that the deal will allow his company to expand its unconventional drilling worldwide.