Marathon Oil ( MRO) said second-quarter earnings will be handicapped by a trio of issues not currently reflected in existing analyst estimates. The Houston oil giant must mark down a supply contract, will produce slightly less natural gas than previously thought, and faces higher administrative expenses in the quarter, it said in a release. The issues will be partially offset by an exploration expense that is at the low end of previous guidance. Analysts were expecting the company to earn $1.13 a share in the second quarter. The stock was down $1.33, or 3.4%, to $36.53. The gas-supply contract markdown comes to $95 million, reflecting a strengthening in the price of 18-month futures in the U.K. Meanwhile, administrative expenses in the second quarter will be about $23 million higher than previously estimated because of both outsourcing costs and a higher equity-based compensation expense. Regarding output, Marathon put second-quarter worldwide production at 341,000 barrels of oil equivalent per day, compared with previous guidance of 348,000 barrels. It cited delays in a natural gas expansion in Equatorial Guinea.