The SPDR S&P Oil & Gas Exploration & Production ETF (XOP) is the best performer among energy sector-related funds. The ETF, which counts companies like Whiting Petroleum, Anadarko Petroleum and RSP Permian among its largest holdings, likely does well because many traders have said (even before the Saudis) that $50 a barrel is the point when exploration would become profitable again. Below that, there is not much incentive to find more crude.
It's worth noting that consumer stocks are still able to post gains at these levels, which are likely still not high enough to lead to surging gasoline prices at the pump.
Disclosure: NBCUniversal, parent of CNBC, is a minority investor in Kensho.