Probing sandstone's pore network.

Oil-bearing sandstone is a highly porous, intricately interconnected material that is often difficult to characterize precisely. Researchers have now demonstrated that a novel variant of nuclear magnetic resonance (NMR) imaging can capture crucial details of a porous rock's structure and elucidate its effect on fluid flow through the material. Ronald L. Walsworth of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., and his collaborators report their results in the Oct. 18 PHYSICAL REVIEW LETTERS.

In the new technique, researchers inject xenon gas into the porous material, held in a powerful magnetic field. As the gas atoms diffuse rapidly through the rock, they signal their positions by sending out radio waves. The scientists then use the radio data to calculate the ratio of surface area to volume of pores and determine how the material's convoluted structure restricts gas or liquid flow. The technique may also prove useful for characterizing foams and lung and sinus passageways.