Smaller oil and gas producers face an uphill task to deliver returns to shareholders amid battered commodity prices but buying opportunities are to be had among larger stocks that have fallen out of favour as investors flee the sector, according to contrarian investor Allan Gray. The fund manager's energy analyst, Suhas Nayak, said the shorter reserve life of the assets held by the smaller companies meant the "treadmill" of investment faced by all oil and gas companies to maintain and grow production and deliver returns "just has to run that much faster".