Electromagnetism could ease the flow in oil pipelines.

Oil drillers often heat crude oil or dilute it with gasoline to make it runny enough to flow through pipelines to refineries. Now, physicists find that a few seconds to minutes of exposure to a modest magnetic or electric field, instead of the standard treatments, sharply reduces crude oil's viscosity for hours at a time.

The new oil-thinning technique could reduce the difficulty and cost of pumping crude oil, particularly from offshore rigs that feed pipelines passing through deep, cold waters, the scientists say.

Rongjia Tao and Xiajun Xu, both of Temple University in Philadelphia, observed that either a magnetic or electric field reduced the viscosity of crude oil that's rich in paraffin wax. Another kind of crude oil rich in asphalt thinned from exposure only to electric fields, the researchers report in the September-October Energy & Fuels.

The team theorizes that the fields induce nanometer-scale paraffin particles to bunch in larger specks. Because the larger but fewer specks are less likely to collide with each other, the fluid's viscosity drops.

Asphalt particles responded too weakly to magnetic fields to bunch up, the researchers found.--P.W.