Investors in Origin Energy are buckling in for a drawn-out approvals process for the $18.7 billion takeover of the major power and gas supplier that is expected to keep the share price much lower than the offer price for several months to come.

Shares in Origin closed flat on Tuesday at $8.17, despite the news late Monday of a binding agreement for North American bidders Brookfield Asset Management and EIG Partners to buy Origin at a price equivalent to $8.912 a share that is being provisionally supported by the board.