CALGARY, Alberta, May 20 (Reuters) - Talisman Energy Inc (TLM.TO: Quote, Profile, Research, Stock Buzz) now estimates its North American lands have as much as 132 trillion cubic feet of unconventional natural gas in place, more than 30 tcf of which may be recoverable, its chief executive said on Wednesday.

Talisman, which has spent the past 20 months reshaping its asset portfolio to focus on longer-term opportunities, also aims to make producing gas from shale plays in British Columbia, Alberta, Pennsylvania and Quebec profitable at a $4 per thousand cubic feet gas prices, CEO John Manzoni said.

"We've learned more about that land base and we now estimate 132 tcf of gas in place. We believe this to be a more tightly defined estimate than last year," Manzoni said at a company-sponsored investor conference in New York.

As much as 30 tcf could be developable over time at such plays as Montney, Outer Foothills and Marcellus, he said. That excludes any contribution from its Quebec lands, which are still in the early evaluation stage.

"Our unconventional base is improving all the time. We've not stopped adding to our lands and our pilot activity continues into this year. In some areas we're moving to development," Manzoni said.

Unconventional natural gas has changed the North American gas market over the past few years, as companies have developed technology to uncover trillions of cubic feet of new reserves across the continent.

Shale plays require rapid-fire drilling and rock-fracturing techniques to maintain and increase gas production.

"We're working to bring down the break-even price of these plays all the time, but we believe we can certainly make them work at $4 gas prices," Manzoni said.

The focus on unconventional gas is part of Manzoni's strategy of concentrating on areas around the world that offer the best long-term returns. The others include its operations in Southeast Asia and the North Sea, where it announced a discovery in the Norwegian sector on Tuesday called Grevling.