LONDON (AP) — Shares in Britain's BG Group PLC jumped yesterday after Brazil's state-run oil company said prospective production from its Iara oilfield would be higher than first expected, apparently confirming the massive hydrocarbon potential of the subsalt layer off Brazil's coast.

Petrobras SA said that the offshore field — in which BG Group has a 25-percent stake — is expected to yield the equivalent of three billion to four billion barrels of recoverable light crude and natural gas, adding to recent promising reserves the country has discovered.

Petrobras said the estimate is higher than expected when the Santos Basin Iara well, which lies about 140 miles offshore from Rio de Janeiro in pre-salt reservoirs about 1.4 miles below sea level, was discovered in August.