U.S. oil production surged in 2013 to the highest level in 25 years as a boom in shale drilling boosted output, the Energy Information Administration (EIA) said on Thursday. Oil production for the year rose by nearly 1 million barrels per day (bpd), its largest-ever annual increase, to hit an annual output level of 7.46 million bpd, the highest since 1989, the EIA said in its monthly petroleum supply report. The data also marked a number of other milestones reflecting the transformation of the U.S. oil industry. Exports of refined petroleum products rose to a record high of 3.3 million bpd. Meanwhile, net imports of crude and fuels fell to 5.1 million bpd in December, the lowest level of net imports since 1987, the data showed. U.S. propane exports remained near a record high at 402,000 bpd in December. (Reporting by Jonathan Leff, Elizabeth Dilts and Edward McAllister; editing by David Gregorio and G Crosse)