Excess natural gas is being flared, or burnt off, at a flare stack at the refinery in Tula. Mexico’s oil refining industry, saddled for years with bloated costs, chronic under-investment and generous government fuel subsidies, ought to be on the verge of a bright new dawn. A shake-up last month dismantled the state-run Pemex oil and gas monopoly, potentially opening the door to foreign oil companies.