February 25th, 2010, Lunch at 12:00, Talk 12:30.
Room number: 02.110, Stevinweg 1, Faculty CEG, Delft University of Technology
David Smeulders
Seismoelectric reflection: finding the Oil-Water Contact?
When grain surfaces of rocks and soils are in contact with a fluid electrolyte, they typically acquire a surface charge that is balanced by mobile counter ions in a thin fluid layer sourrounding the grains. A compressional seismic wave will create pressure gradients on the scale of the wavelength. The resulting hydraulic flow will transport the counter ions relative to the immobile bound charge. In this way, counter ions accumulate in pressure troughs, and bound charge becomes exposed in pressure peaks, creating an electric co-seismic field. We note that there is no net electric current. The electric field generated by the relative motion of the counter ions with respect to the bound charge, drives a conduction current that exactly balances the hydraulic current flow. For interfaces, however, this is no longer the case. Here, an electric current imbalance is produced resulting in electromagnetic waves that can propagate freely outside the support of the pressure waves. Detection of these waves can give information that is complementary to seismic surveys, especially on OWC. The generation of these waves defines new reflection and transmission coefficients of electrokinetic nature. We developed an experimental setup to measure the electrokinetic reflection coefficient at an interface between water and a water-satured porous material. A comparison with theoretical results is presented in the 200-800 kHz range.
Biography
David Smeulders,
Associate professor, Delft University of Technology
David Smeulders holds a MSc in Aronautics and a PhD in Physics (1992). Since 1992 he is working as a petrophysicist at Delft University of Technology, currently as associate proffessor. The topics his group is working on are (borehole) acoustics, seismic Q, and electrokinetic coupling phenomena. He is currently VP Technology of the DPS and head of the Geotechnology Laboratory.