Woodside Petroleum Ltd, Australia's biggest independent oil and gas producer, has approached smaller rival Oil Search Ltd with an $8 billion all-share takeover plan, which Oil Search said on Tuesday it was considering. A takeover of Oil Search would help fill a gap in Woodside's growth prospects, giving it a 29 percent stake in Oil Search's Papua New Guinea Liquefied Natural Gas project, which started producing last year and is considered one of the lowest cost, expandable LNG projects in the world.