Oil futures settled with a loss on Thursday for a fourth straight session, as turmoil in China continued to raise the risk for a slowdown in energy demand from one of the world’s top consumers. With prices already at their lowest levels in more than 11 years, analysts have been weighing the likelihood that U.S. prices could plunge to $20 a barrel this year.

Meanwhile, natural-gas prices surged more than 5% on the back of a much-bigger-than-expected drop in weekly U.S. supplies. February Brent crude LCOG6, -1.52% the global oil benchmark, fell 48 cents, or 1.4%, to $33.75 on London’s ICE Futures exchange. Prices settled Thursday at their lowest level since June 2004, according to FactSet data.

On the New York Mercantile Exchange, February West Texas Intermediate crude CLG6, -2.18% shed 70 cents, or 2.1% to settle at $33.27 a barrel on the New York Mercantile Exchange. It traded as low as $32.10 but also tapped a high of $34.26. Thursday’s settlement was the weakest since February 2004, FactSet data, based on the most-active contracts showed. FULL REPORT