The U.S. energy revolution is holding strong, according to the American Petroleum Institutes survey on drilling costs.

The survey found U.S. companies invested $153.7 billion in drilling approximately 46,736 oil and natural gas wells in 2012, a 23.1 percent increase over 2011 levels.

Totals

The total number of new wells increased 5.8 percent from 2011. Expenditures on oil represented 61.1 percent of all drilling costs in 2012, up from 49.3 percent in 2011.

Expenditures on gas drilling fell from 44.2 percent in 2011 to 30.7 percent in 2012.

The report also shows that expenditures on shale drilling represented 34.6 percent of costs, down from 52.5 percent in 2011. Most of the decline occurred in natural gas drilling, while the number of new shale oil wells increased from 3,414 in 2011 to 3,619 in 2012.

Overall investment in offshore production also increased from 6.5 percent of all domestic oil and gas production expenditures in 2011 to 7.1 percent in 2012.