Fluid flow in boreholes can give scientists important information about hydrogeological processes deep beneath the surface. Most studies measure flow using heat pulse, electromagnetic, and impeller flowmeters, but these methods are time-consuming and can actually obstruct the fluid being measured.
Read et al. show that a flowmeter can instead be made using armored fiber-optic cables. The technique sends pulses from a laser at known frequencies through the cable. This technology already has applications for everything from fire detection to soil moisture studies and flowing rivers.
The team tested their method at a field site in Brittany, France, where four boreholes were already in place and a large number of studies had been done in the past for comparison. The authors demonstrated that their technique allows for measurements of spatial dynamics in situations where traditional borehole measurements will not work.
However, the scientists say there is still work to be done before the method can be fully implemented. The fiber-optic cables were sensitive to touching the edges of the boreholes and cumbersome for use in remote locations. Still, once the method is optimized, the research points the way to future sensors that might be used in the field. (Water Resources Research, doi:10.1002/2014WR015273, 2014)
—Eric O. Betz, Writer
Citation: Betz, E. O. (2014), Fiber optics can improve borehole measurements, Eos Trans. AGU, 95(49), 472, doi:10.1002/2014EO490015.