Based on this week's parade of earnings from the largest U.S. oil producers, energy companies are swimming upstream.
With one notable exception, profit from oil and gas exploration and production—otherwise known as "upstream" earnings—proved to be a saving grace for the industry in the most recent quarter, at a time when growth prospects for multinational oil companies have largely stagnated.
ExxonMobil and ConocoPhillips both beat Wall Street estimates, helped in large measure by a surge in upstream earnings. Chevron, the second largest U.S. oil producer, didn't fare as well, with upstream profit that dropped 19 percent from 2013—though that decline appears to have resulted from a shortfall overseas, not in the U.S.
Exxon got a particularly large boost from the segment, reporting $7.8 billion in earnings helped in part by the winter natural gas price surge and a rally in crude. That has helped its stock, which has risen to a new 52-week high amid a boom in energy stocks.
The results underscore the importance of energy prices in a world where Big Oil is struggling to move the needle on output volume. The more than 40 percent winter rally in natural gas, combined with crude prices that are up 10 percent year-to-date, has been a saving grace for the oil majors.
"It's upstream earnings that really drive the bus," said Stewart Glickman, equity analyst at S&P Capital IQ, in an interview. He noted that Chevron's weak performance in exploration and production—where profit plunged to $4.3 billion from $5.9 billion a year ago—was the mirror opposite of Exxon, the world's largest energy company.
"The source of weakness for Chevron was international upstream, and that's exactly where Exxon beat," he added.
Big Oil's reliance on upstream results echo what PriceWaterhouseCoopers noted was a surge in activity in the segment. During what the consulting firm called a "historic first quarter" for U.S. energy deals, the upstream sector saw 27 merger and acquisitions worth $14.2 billion. That represented 63 percent of all energy M&A plays during the quarter, PWC said this week.
The stark reality, however, is that the oil majors are still finding it difficult to profit from a resurgence in U.S. oil and gas. The shale boom in places like North Dakota's Bakken and Texas' Eagle Ford are dominated by independent gas companies such as Anadarko and EOG Resources, who were quicker to snap up shale players and benefit from their smaller size.
Big Oil companies "are profiting, but they are doing that in the context of a very large company," said S&P's Glickman.
The shale renaissance "isn't moving the needle the way it would for Anadarko and EOP. It's a large numbers problem, and easier for a small company to grow with shale like you see happening in the U.S.," he said.
Meanwhile, trends suggest the upstream boost may run out of steam. The Energy Information Administration notes that total upstream spending was relatively flat last year, after seeing average growth of 11 percent over the last 12 years.
Over the last two years, the EIA cited "flat oil prices and rising costs [that] have contributed to declining cash flow." Should those developments continue, "it could challenge future exploration and development," the agency added.
—By CNBC's Javier David.