Royal Dutch Shell, like other companies, has decided to continue investing in deep water despite low oil prices. Pictured, Shell’s Olympus tension leg platform in Ingleside, Texas, in 2013.

(Wall Street Journal) The standoff between major global energy producers that has created an oil glut is set to continue next year in full force, as much because of the U.S. as of OPEC.

American shale drillers have only trimmed their pumping a little, and rising oil flows from the Gulf of Mexico are propping up U.S. production. The overall output of U.S. crude fell just 0.2% in September, the most recent monthly federal data available, and is down less than 3%, to 9.3 million barrels a day, from the peak in April.

Some analysts see the potential for U.S. oil output to rise next year, even after Saudi Arabia and the Organization of the Petroleum Exporting Countries on Friday again declined to reduce their near-record production of crude . With no end in sight for the glut, U.S. oil closed on Friday below $40 a barrel for the second time this month.

The situation has surprised even seasoned oil traders. “It was anticipated that U.S. shale producers, the source of the explosive growth in supply in recent years, would be the first to fold,” Andrew Hall, chief executive of the commodities hedge fund Astenbeck Capital Management LLC, wrote in a Dec. 1 letter to investors reviewed by The Wall Street Journal. “But this hasn’t happened, at least not at the rate initially expected.” He declined to comment further.

For the past year, U.S. oil companies have been kept afloat by hedges—financial contracts that locked in higher prices for their crude—as well as an infusion of capital from Wall Street in the first half of the year that helped them keep pumping even as oil prices continued to fall. The companies also slashed costs and developed better techniques to produce more crude and natural gas per well.