After suffering its longest rout in history, crude rebounded Tuesday, entering a bull market after soaring 24 percent from a six-year low reached in January. Behind the gain was speculation that curbs in investment will cut production.

For all the optimism among traders, firms from Barclays Plc to Societe Generale SA and UBS Group AG say the rally is just temporary because less spending won’t eliminate a glut overnight. Instead of heading back to $100 a barrel, oil could fall as low as $30 because supply surpluses won’t disappear overnight, said Miswin Mahesh, a commodities analyst at Barclays.

“We don’t think we’ve seen the bottom yet,” Giovanni Staunovo, a commodities analyst at UBS in Zurich, said by e-mail on Tuesday. “We expect U.S. commercial crude oil stocks to hit a new 84-year high on Wednesday, while U.S. oil production is likely to stay strong in the near term.”

Brent crude, the international benchmark, rose $3.16 to $57.91 a barrel in London on Tuesday, capping the biggest four-day advance since 2009 as drilling activity plunged in the U.S. and oil companies deepened spending cuts to more than $40 billion since Nov. 1. The rally halted Wednesday amid estimates that U.S. crude stockpiles increased last week from the highest level in three decades.

Crude’s Slide

Crude slumped 48 percent last year, the most since 2008, as the Organization of Petroleum Exporting Countries maintained production to defend market share against U.S. output that represented 80 percent of global supply growth in 2014. While oil drillers outside OPEC responded by idling rigs and reducing investments, they will still pump more crude this year, according to the International Energy Agency. U.S. oil stockpiles rose to the highest since at least 1982 last week, Energy Information Administration data showed.

U.S. companies pulled 94 oil rigs out of fields in a single week, the most in Baker Hughes Inc. data starting in 1987, the company said on Jan. 30. The Permian Basin of Texas and New Mexico, the country’s biggest oil field, was hit hardest, losing 25 rigs.

“The huge drop in U.S. rigs triggered a first wave of speculative long buying,” Hans van Cleef, senior energy economist at ABN Amro Bank NV in Amsterdam, said by e-mail. “The support of recent days is providing some hopes that the recovery could continue.”

WTI Rebound

West Texas Intermediate, the U.S. benchmark, gained $3.48 to $53.05 Tuesday, leaving it shy of a bull designation, with a gain of 19 percent from its Jan. 28 low. The rally in Brent halted a slide that began on June 20 and became the longest plunge ever, covering 207 days. Bull and bear markets are commonly defined by 20 percent shifts in closing prices.

Brent may average $61 a barrel this year, while WTI recovers to $57, according to a Bloomberg Intelligence survey of 86 investment professionals. That exceeds the 20-year average of about $55 for Brent and $54 for WTI, according to data from ICE Futures Europe and the New York Mercantile Exchange.

The biggest-ever collapse in Brent crude, from $146.08 a barrel to $36.61 between July and December 2008, was interrupted by a brief rally of almost 20 percent. The price jumped from $89.22 on Sept. 16 to $106.04 six days later amid efforts by the U.S. government to stem a banking crisis, only to resume its slide for another 3 months as data showed oil demand was slumping as the economy shrank.

Spending Cuts

Chevron Corp. reduced its drilling budget by the most in 12 years on Jan. 30 and said it may delay some shale projects. Royal Dutch Shell Plc said it will trim $15 billion of investment over three years. Occidental Petroleum Corp., ConocoPhillips and BP Plc also announced lower spending.

Total investment in oil projects may fall by $100 billion, or 15 percent, this year, IEA Chief Economist Fatih Birol said at the World Economic Forum in Davos Jan. 21. The Paris-based adviser to 29 nations cut its forecast for supply growth outside OPEC in 2015 by 350,000 barrels a day to 950,000 on Jan. 16.

While spending cuts may affect production in 2016 or 2017, they don’t resolve the near-term supply glut, said Barclays’s Mahesh. U.S. crude inventories expanded by 8.9 million barrels to 406.7 million in the week ended Jan. 23, according to the Energy Department’s statistical arm. The country’s oil production rose to 9.21 million barrels a day, a record in EIA data collected since 1983.

Oil Stockpiles

Oil halted its four-day rally Wednesday amid estimates that U.S. crude stockpiles rose again last last week. Brent for March settlement fell $1.78 to $56.13 a barrel in London at 2:45 p.m. WTI dropped $2.43 to $50.62 in New York.

Inventories probably increased 3.25 million barrels to 410 million last week, according to a Bloomberg survey of nine analysts. Stockpiles rose 6.1 million barrels last week, the American Petroleum Association was said to report, according to accounts on Twitter.

“I am not convinced prices have hit bottom — it is too soon to say that,” Mike Wittner, Societe Generale’s New York-based global head of oil research, said by e-mail Tuesday. “Rig counts are important because they are a leading indicator of production. But there is a lag of several months before we see an impact on production.”