MELBOURNE, Oct 30 (Reuters) - Oil Search Ltd OSH.AX , which rebuffed an A$11.7 billion ($8.3 billion) takeover offer from Woodside Petroleum Ltd WPL.AX last month, just grew more expensive for its suitor, after MSCI said it would add Oil Search to its Australian indices.
MSCI said late on Thursday it would expand its Australia equity universe to include companies incorporated in Papua New Guinea and listed on the Australian Securities Exchange, such as Oil Search and Steamships Trading Co SST.AX .
The changes are set to be announced in its semi-annual index review on November 12, MSCI said in a statement.
"That would trigger buying of the stock by passive funds. They'll need to own Oil Search," said UBS analyst Nik Burns.
Oil Search shares jumped as much as 9 percent on Friday, valuing the company at more than A$12 billion and outperforming the broader market, as index fund managers topped up their portfolios with Oil Search shares. Woodside rose 1.2 percent.
After the MSCI inclusion announcement, Oil Search stock was trading 8 percent above the implied value of Woodside's offer. It had consistently traded around 5 percent below the value of Woodside's 1-for-4 share offer proposal ever since it rejected the offer on Sept 14 this year.
Oil Search spokeswoman Ann Diamant said she was unaware of any other factors driving the shares up on Friday.
Woodside declined to comment.
($1 = 1.4059 Australian dollars)