In recent weeks, as oil traded around $40 a barrel, the conventional wisdom among specialists was that the price decline that began last summer was largely over. Amid production cuts by the OPEC cartel, oil had apparently found a floor that would last until the global economy rebounded.

But a growing chorus of analysts and economists is questioning that notion. While theirs is a minority view, they see troubling conditions in the oil market that could still push prices down sharply  and a global economy that is getting worse, not better. Some are predicting that oil could fall to $20 a barrel and stay low for years.

Petroleum executives generally do not regard this prospect as likely. But in a year when dire predictions about the economy keep coming true, they fear it is a possibility. Another big drop could lead to a sustained period of low investments, and many executives say that would set the stage for prices to soar once the global economy finally starts to recover.

“The industry needs reasonable prices,” Zhou Jiping, the vice president of the China National Petroleum Corporation, said at a conference last month in Houston held by Cambridge Energy Research Associates. “If prices stay below $40 a barrel, a large number of wells have to be shut down.”