Sept. 17 (Bloomberg) -- Woodside Petroleum Ltd., the second-largest Australian oil and gas producer, rose to its highest in almost a year in Sydney trading on optimism over its share of a discovery off West Africa.

Woodside climbed 78 Australia cents, or 1.5 percent, extending a 4.8 percent gain yesterday, to settle at A$51.60, the highest close since Oct. 1. The benchmark S&P/ASX 200 Index gained 1.4 percent.

Anadarko Petroleum Corp. said yesterday the Venus B-1 well discovery forms one of two “bookends” 700 miles (1,100 kilometers) apart across two prospective basins offshore of Sierra Leone, Liberia, Cote d’Ivoire and Ghana. The two basins may each contain 150 million to 1 billion barrels of oil, Anadarko Chief Operating Officer Al Walker said.

“Our preliminary estimate of a 250 million-barrel recoverable reserve discovery at Venus implies it could be worth up to around $525 million,” or around 93 Australian cents per Woodside share, UBS AG analysts led by Melbourne-based Gordon Ramsay said in a Sept. 16 note to clients.

Woodside, which holds a 25 percent stake in Venus, sent a statement to Australian stock exchange today in response to “enquiries from investors and media,” confirming the well “intersected about 14 meters of net pay” while drilling for oil and gas. Houston-based Anadarko owns 40 percent of the well and is the operator. London-based Tullow Oil Plc owns 10 percent, and Madrid-based Repsol YPF SA 25 percent.

More Wells

Venus was drilled to about 18,500 feet (5,640 meters) in 5,900 feet of water and found, Anadarko said. More tests and studies will be needed to confirm oil can be recovered in commercial quantities, with two to five wells expected to be drilled next year.

The Venus well suggests a “very significant reservoir” in the Sierra Leone-Liberian basin, Walker said yesterday. Results support the company’s expectation that the basins each contain 150 million to 1 billion barrels of oil, Walker said.

Anadarko yesterday rose $5.68, or 9.6 percent, to $64.85 in composite trading on the New York Stock Exchange, the biggest one-day gain since November. Tullow climbed 100 pence, or 9.2 percent, to 1,187 pence, the highest closing price since the shares began trading in 1989. Repsol YPF SA advanced 1.9 percent to 18.57 euros in Madrid.

Woodside also holds a 25 percent stake in block SL7 off the Sierra Leone coast and a 17.5 percent interest in blocks L-15, L-16 and L-17 off Liberia, the company said today.

To contact the reporter on this story: Ben Sharples in Melbourne at bsharples@bloomberg.net

Last Updated: September 17, 2009 03:38 EDT