Shares of Aban Offshore surged as much as 9.8 per cent to Rs 940, their highest level since May 14, 2010, on hopes the country's largest offshore drilling company may enjoy higher rig rates in the coming quarters, dealers say. "ONGC has okayed an expenditure sanction of an additional $501.95 million for hiring of five more offshore jack-up rigs for a period of three years," according to oil and gas industry website Indianpetro.com. An Aban spokesman was not reachable.