The problem with an oil company ETF is there will be a lot of marginal producers along with good companies that can weather the slump in oil prices and acquire weaker rivals to come out better on the other side.
You have a few options:
1- Really any of the majors should do ok. I would buy a basket of quality oil companies and oil service providers and wait. It could take a really long time (even 5-10 years) for oil prices to return to $100/barrel. You do not want to be holding companies with production costs in the 70's and 80's. They will go under and/or be bought out at a discount.
Quality Oil Co's (or service providers): XOM, NBL, NOV, DVN, and KMI
2- Your other option is to buy companies that are beaten up by low oil, but have other business lines to weather the low prices and decreased production. Rail, Shipping, Engineering Co's, Natural Gas Co's beaten up for some of their oil holdings, etc.
3- Buy companies that benefit from weak oil. Travel and Leisure, trucking/logistics, maybe fast food and discount retail (more disposable income).
You could just stick to buying low cost index funds and leave this to the pros/speculators. There is really no telling how long oil prices will stay low. If they spring back this year you could make a killing in some of the leveraged shale oil producers. If they stay low for 2-3 years those same producers will be gone. It's hard to analyze the majors because they have so many moving parts. XOM and BP have very economic reserves, but BP has its legal issues and has a meaningful exposure to Russia. Proceed at your own risk!