(Adds comparison to estimates, unit info)
By Ernest Scheyder
HOUSTON, July 27 (Reuters) - U.S. oil and natural gas producer Chevron Corp posted a lower-than-expected quarterly profit on Friday and executives launched a long-awaited $3 billion share buyback program.
Shares of the San Ramon, Calif.-based company fell 2.4 percent to $121 in premarket trading.
The company posted second-quarter net income of $3.41 billion, or $1.78 per share, compared to $1.45 billion, or 77 cents per share, in the year-ago quarter.
Analysts expected earnings of $2.09 per share, according to Thomson Reuters I/B/E/S.
Chevron's expenses rose about 15 percent during the quarter to $37.33 billion.
Production rose about 2 percent to 2.83 million barrels of oil equivalent per day.
"Results in 2018 benefited from higher crude oil prices, strong operations and higher production," Chief Executive Mike Wirth said in a press release.
Executives plan to discuss quarterly results on a conference call with investors on Friday morning. (Reporting by Ernest Scheyder Editing by Nick Zieminski)