Shell drops plans to purchase a stake in KazMunayGas National Co. after a due diligence process, according to sources. : (Bloomberg) -- Royal Dutch Shell Plc dropped plans to purchase a stake in KazMunayGas National Co. after a due diligence process that included discussions about the risk of corruption at the Kazakh state oil company, people with knowledge of the matter said. An investigation conducted on Shell’s behalf discussed the informal control one of Kazakh President Nursultan Nazarbayev’s sons-in-law exercises over the oil and gas producer, three people said, asking not to be identified as the issue is not public.