Earnings rose 18% in Chevron's ( CVX) second quarter, missing estimates. Chevron earned $4.4 billion, or $1.97 a share, in the quarter, compared with $3.7 billion, or $1.76 a share, a year ago. Excluding a charge, earnings were $2.10 a share in the latest quarter. Analysts surveyed by Thomson First Call were forecasting earnings of $2.21 a share in the quarter. Sales were $52 billion in the quarter, up from $47 billion a year ago. Sales rose due to higher prices for crude oil and refined products and the inclusion of revenue related to the former Unocal operations that Chevron acquired in August 2005. An accounting change governing certain purchase and sales contracts partially offset those gains. The company generated $3.27 billion of upstream exploration and production revenue in the quarter, up from $2.77 billion a year ago. It had $998 million of refining and marketing revenue in the latest quarter, up from $976 million. Chevron had worldwide production of 2,669,000 barrels a day in the second quarter, up 10% from a year ago. The company got $60 a barrel, on average, for oil and equivalents in the period, up $16. Average natural gas prices fell 7% to $5.90 per thousand cubic feet. Chevron closed at $67.73 on Thursday. In premarket trading Friday, the stock lost $1.93, or 2.9%, to $65.80.