Fracking for natural gas

In this Jan. 17, 2013, photo, Universal Well Services fracturing engineering team leader Mike Michaelson points to the 50 liter, 16 cylinder, Cummins diesel engine with four turbo-chargers that has been converted to run on a blend of diesel and natural gas at the Cummins Bridgeway facility in Gibsonia, Pa. Oil- and gas-field companies from Pennsylvania to Texas are experimenting with converting the huge diesel engines that operate pumps that propel millions of gallons of water, sand and chemicals down a well bore in the fracturing process to break apart rock or tight sands that trap natural gas.

In this Jan. 17, 2013, photo, the truck and trailer rig with a huge converted engine that runs a pump used in extracting gas from wells, sets outside the Cummins Bridgeway facility in Gibsonia, Pa. The unit on the front of the trailer cools the 50 liter, 16 cylinder Cummins diesel engine that occupies the center of the trailer. The pump for the fracking fluid is at the rear.

In this Jan. 17, 2013, photo, Universal Well Services fracturing engineering team leader Mike Michaelson opens the cover of a display panel before he starts the 16 cylinder diesel engine for the first time since it was converted to run on a blend of diesel and natural gas at the Cummins Bridgeway facility in Gibsonia, Pa. Since there was no natural gas available at this facility, the engine would run on diesel fuel alone this day.

In this Jan. 17, 2013, photo, technician Sean Cline works on securing a wiring harness as he finishes up the conversion of a 50 liter, 16 cylinder, Cummins diesel engine with four turbo-chargers that has been converted to run on a blend of diesel and natural gas at the Cummins Bridgeway facility in Gibsonia, Pa.

In this Jan. 17, 2013, photo, exhaust comes from the emissions converter as the 50 liter,16 cylinder Cummins diesel engine, with four turbo-chargers, fires up for the first time after it was converted to run on a blend of diesel and natural gas at the Cummins Bridgeway facility in Gibsonia, Pa.

In this Jan. 17, 2013, photo, Universal Well Service fracturing engineering team leader Mike Michaelson, right, talks with technician Sean Cline before they start the 16 cylinder diesel engine that has been converted to run on a blend of diesel and natural gas at the Cummins Bridgeway facility in Gibsonia, Pa.

In this Jan. 17, 2013, photo, technician Sean Cline finishes up the conversion of a 50 litre, 16 cylinder, Cummins diesel engine with four turbo-chargers that has been converted to run on a blend of diesel and natural gas at the Cummins Bridgeway facility in Gibsonia, Pa.