Positive economic sentiment from OPEC, coupled with global currency movements, pulled crude oil price indices back Thursday from near six-year lows.

The bear market for crude oil, down substantially from June 2014 highs above the $100 per barrel mark, has sparked early 2015 fears of stagnation in the global economy. Russia, which relies heavily on oil export revenue, is expected to experience negative growth, while inflation levels in the British and European economies are trending toward the negative.

The Organization of Petroleum Exporting Countries, in its January market report, said it was keeping its global growth forecast static at 3.6 percent for the year, up from 3.2 percent last year, despite the knock-down impacts of low crude oil prices. That comes after several key banks in the United States expressed some pessimism in the low price environment.

With some futures contracts expiring late Thursday, crude oil indices pulled back from near six-year lows early in the session to post one of the strongest rallies for the year. The price for Brent, the global benchmark, gained 1.8 percent from the previous close to inch closer to the $50 threshold, trading near $49.50 for the February contract.

The price for West Texas Intermediate, the U.S. benchmark, moved above Brent early in Thursday's sessions, gaining more than 3.8 percent to trade above the $50 mark for the first time in more than a week.

The crude oil rally was supported by a surprise decision from the Swiss National Bank to end its three-year currency peg on the euro Thursday, triggering a decline in the value of the U.S. dollar.

Oil is priced in U.S. dollars, meaning a decline in the value of the U.S. currency usually translates to a gain in crude oil and other commodities.

The rally may be short-lived, however, as OPEC said uncertainty about U.S. monetary policy moving forward meant "the volatility in currency markets is expected to continue."

In terms of demand, OPEC said it revised its growth for 2014 up by 20,000 barrels per day, driven largely by economic performances from North America and China in the fourth quarter. For 2015, the 12-member group said it expected demand to be around 1.15 million bpd, an upward revision of about 30,000 bpd from the December report.

Concerns remain elsewhere in the global market. OPEC said the bearish sentiment on Europe "seems to be endless."