Nigerian energy company Oando Plc has prepaid $238 million out of the $900 million it borrowed to part finance the acquisition of ConocoPhillips' Nigerian oil and gas business, the company said on Tuesday. Oando bought ConocoPhillips's upstream oil and gas business in Nigeria last July for $1.5 billion, helping it transition from a marketer of refined petroleum products into one of the top players in the West African country's oil industry.