NEW YORK (TheStreet) -- Marathon Oil (MRO - Get Report) stock is gaining 2.61% to $15.14 in afternoon trading on Thursday after lower stockpiles at a U.S. delivery hub boosted oil prices.

WTI crude is up 1.85% to $50.04 per barrel on the New York Mercantile Exchange, while Brent crude is rising 1.90% to $50.83 per barrel on the Intercontinental Exchange this afternoon.

Genscape data showed that inventories at the Cushing, OK delivery hub fell by almost 1 million barrels for the week ended June 21, Reuters reports.

Oil prices are also increasing because of higher expectations that the U.K. will choose to stay in the European Union. The referendum is being held today.

If Britain chooses to remain in the EU, "the global market reactions are likely to be muted," but if the country decides to leave, the markets are likely to be a risk because it would be unexpected, Energy Management Institute senior partner Dominick Chirichella told Reuters.

Houston-based Marathon Oil is an oil and gas exploration and production company operating in North America, Europe and Africa.

Separately, Marathon Oil has a "sell" rating and a letter grade of D at TheStreet Ratings because of the company's poor profit margins, weak operating cash flow, generally disappointing stock performance, disappointing return on equity and feeble earnings per share growth.

You can view the full analysis from the report here: MRO

TheStreet Ratings objectively rated this stock according to its "risk-adjusted" total return prospect over a 12-month investment horizon. Not based on the news in any given day, the rating may differ from Jim Cramer's view or that of this article's author.