June 19 (Bloomberg) -- Queensland Gas Co., BG Group Plc's partner in a proposed Australian liquefied natural gas plant, said reserves of coal seam gas will jump by 80 percent, taking it closer to the volume needed to proceed with the project.

Proven and probable, or 2P, reserves will rise to more than 2,370 petajoules, about 2.2 trillion cubic feet, of which Queensland Gas's share will be more than 1,895 petajoules, the Brisbane- based company said in a statement, citing a report by Netherland Sewell & Associates. Queensland Gas gained the most in a week in Sydney trading.

The venture between Queensland Gas and BG is one of five seeking to build an LNG plant in northeastern Australia using coal seam gas as a fuel. The Australian company has increased drilling as it targets the 7,000 petajoules of 2P reserves required for the partners to go ahead with the project. The plant will export 3-4 million metric tons a year of LNG to Asia.

``This is a key step in arriving at a final investment decision in 2010 for the LNG project with our alliance partner BG Group,'' Queensland Gas Managing Director Richard Cottee said in the statement, sent to the Australian stock exchange.

Queensland Gas gained 14 cents, or 2.8 percent, to A$5.15 on the exchange, after earlier reaching as high as A$5.48.

Proven coal seam gas reserves in Queensland Gas's licenses will rise to more than 560 petajoules, from 477 petajoules, Queensland Gas said, citing the modeling from Netherland Sewell, which is expected to be confirmed by the independent certifier by June 30. Proven, probable and possible reserves, a wider category, will more than double to over 7,100 petajoules, the company said.