Mitsui's $602 million all-cash takeover offer for AWE has been deemed "fair and reasonable" by an independent expert, adding to momentum behind the proposed deal.

The 95¢-a-share takeover bid from the Japanese trading house sits just above the mid-point of a valuation range by Grant Thornton of 78¢ to $1.06 for the oil and gas producer's stock and supports the recommendation from the target's board that shareholders should accept.