SAN RAMON, Calif. ( TheStreet) -- Lower commodity prices, weak demand and forex issues engulfed yet another oil and gas operation in the second quarter. On Friday, Chevron ( CVX), the nation's second-largest oil company, reported a 71% profit slump. Slightly better results in the company's refining operations -- a bright spot as refiners get hit by thinning refining margins -- wasn't enough to offset the 51% sales slump. According to a press release, Chevron fell to $1.75 billion in profit, or 87 cents per share. The steep fall came from the year-earlier earnings post of $5.98 billion, or $2.90 a share. The results also included a $453 million foreign currency impact. Though able to beat top-line estimates, the company posted a fall of total revenues to the tune of $40.2 billion in the second quarter. In the year-ago period, the integrated oil and gas operation reported revenues of near $83 billion. On average, a group of analysts polled by Thomson Reuters expected Chevron to post EPS of 95 cents and revenues of $33.41 billion. The sales slip came as a result of Chevron's exploring and production segment, which saw earnings drop 79% from the year-earlier period. According to the company's statement, average sales prices for oil and natural gas liquids plunged by more than half since last summer's astronomical highs. Average natural gas prices fell by two-thirds domestically and nearly one-third overseas. Still, Chevron's global production volumes ticked up 5% to 2.67 million barrels per day. Capital exploratory expenditures also grew to $11.4 billion in the first half of 2009, compared with $10.3 billion in the year-ago period. The company was also able to narrow its loss in U.S. refining, while swinging to a profit in international downstream and total downstream operations overall. Even so, CEO Dave O'Reilly tempered the unit's results, citing still narrow refining margins.