Nigeria, Dec. 22 -- Nigeria's oil sector rumbled last week, when the Chairman of the Dangote Group of Companies, Alhaji Aliko Dangote alleged that the Chief Executive Officer of the Nigerian Midstream and Downstream Petroleum Regulatory Authority (NMDPRA), Farouk Ahmed, was spending millions of dollars on his children's education in Switzerland, an amount far beyond his means as a public servant. Prior to that, he had accused the same Ahmed of economic sabotage for undermining domestic fuel refining efforts in Nigeria. Dangote insisted that the leadership of the NMDPRA under Ahmed was colluding with international traders and oil importers to frustrate local refining through the continued issuance of import licenses for petroleum products....