Goldman Sachs Group Inc. says crude prices need to remain lower for a longer time to allow the oil market to find equilibrium amid a supply glut.

Storage may be filled by the fall with global crude oversupply running at 2 million barrels a day and low-cost producers continuing to boost output, Goldman analysts including Jeffrey Currie said in a report dated Thursday. Low prices are needed to offset productivity gains and keep investment to a minimum, the report said.

Oil last month slumped the most since 2008 on signs the global surplus is persisting. Royal Dutch Shell Plc said in July it is braced for a prolonged downturn as the U.S. is producing near the fastest rate in three decades and OPEC’s largest members pump record volumes.

“The rebalancing of supply and demand will likely prove to be far more difficult than what was previously priced into the market,” Goldman said. “The risks remain substantially skewed to the downside.”

Even after the balance between supply and demand is restored by 2016, prices may not rebound as Iran emerges from sanctions and other members of the Organization of Petroleum Exporting Countries seek to earn revenue by increasing output, Goldman said.

Goldman maintained a near-term target for West Texas Intermediate of $45 a barrel.

WTI for September delivery fell 27 cents to $44.88 a barrel in electronic trading on the New York Mercantile Exchange at 11:13 a.m. in London.

The oil industry is struggling after making investments when crude was $100 a barrel, Goldman said.

“Energy companies at present cannot earn their cost of capital over the long term,” according to the report. “They are wealth-destroying propositions from the get go.”