He started his career in the oil industry by working for Stampede Energy and for the R.L. Burns Corporation. He purchased his first oil well for $13,000 in 1982 and launched Lewis Energy the next year. In 1995, he borrowed $5 million from Enron Capital & Trade and repaid the loan in eight months. Alongside drilling in South Texas, he has drilled in Mexico for Pemex, and in Colombia for Hupecol Caracara and Solana Resources. In 2003, he sold much of his Texas pipelines to Dan Duncan, the CEO of Enterprise Products Partners. He is the first American wildcatter to drill in Mexico since former President Lázaro Cárdenas made it illegal for anyone but the Mexican government to do so. Forbes magazine called Lewis "the only gringo allowed to drill in Mexico." He can collect as much as $350 million annually from Pemex for drilling on 80,000 acres near the border. He does not own the oil or natural gas but is compensated for drilling the land. Lewis owns at least 350,000 acres of the Eagle Ford Shale property. In 2010, British Petroleum began drilling on 80,000 acres of Eagle Ford Shale property that Lewis owns.