Four government and opposition sources say that the front-runner for the leadership is James Marape, who quit as finance minister in April over a gas deal with France's Total SA he called too generous to the oil major.
"Agreements and resources laws will be relooked at as a matter of priority", Philip Undialu, a lawmaker aligned with Marape, told Reuters by text from the Grand Papua Hotel where his supporters are based.
Marape told Papua New Guinea's National newspaper two weeks ago, in reference to the April deal, that "something is wrong somewhere when the government is not unlocking. resources for our people".
"I have every right to tweak and turn resource laws for my country", he said.
O'Neill had already received criticism for how he managed the country's natural resources.
The project would nearly double PNG's gas exports, but local communities have raised fears that they would be excluded from the benefits.
Business leaders in Papua New Guinea offered cautious support for the new leader.
Marape received 101 votes to eight in parliament in the capital, Port Moresby, a day after Peter O'Neill resigned having lost the support of the house after nearly eight years in power. The recent political turmoil will likely delay, but not threaten, that $13 billion project, analysts said this week after Marape's predecessor, Peter O'Neill, announced his resignation.
Marape has also been critical of "corrupt contracts" with Australia to settle asylum seekers on tropical island camps and demanded an investigation.
"The South Pacific Division congratulates the Honorable James Marape on becoming the eighth Papua New Guinean Prime Minister", said Pastor Glenn Townend, president of the Seventh-day Adventist Church in the South Pacific.
However, he added: "If we find any project agreement. that has not fully complied with. provisions of law, then we are open to reviewing and scrutinizing them", he said.