Weak US shale liquids production contributed to a $2.2bn (£1.4bn) charge, Shell revealed in August, and was a key factor in its decision to abandon its goal to deliver four million barrels a day of production by 2017.
“We didn’t get the results which we were expecting to get in the shorter term and we will therefore have to develop this a little bit more before we can take benefits from it,” Voser told reporters at the World Energy Congress in South Korea. “It was clearly not as successful as thought.”
Vast reserves of shale oil and gas are likely to make the US the largest oil and gas producer in the world, but the rush to cash in on the shale bonanza has cost some latecomers to the market dearly.
Shell said last year that it planned to spend at least $1bn exploiting China’s potentially vast resources of shale gas.
Voser is due to retire from Shell at the end of March 2014 after 29 years with the company, and will be replaced by downstream director Ben van Beurden.