A SOMEWHAT flustered and angry P C Sethi, Minister of Petroleum and Chemicals, met the press immediately on his return from a foreign trip to refute criticism of his proposed deal with the French Petroleum Company, CFP, for stepping up the rate of pro-duction of crude oil from Bombay High on production-sharing basis. But the sum and substance of his refutation was extraordinary, to say the least. It amounted in effect to issuing thrests against the Oil and Natural Gas Com-mission and its technical ''personnel.