Acoustic measurements of pore-scale displacements

[1] We describe how experimentally measurable acoustic and hydroacoustic events occur when one fluid displaces another within a porous medium. We show that the events are directly related to discrete fluid bursts (Haines jumps'') that occur at the pore scale. We find that the events show power law statistics with respect to magnitude for drainage ( air invading) but not for imbibition ( water invading). These observations agree with simple conceptual arguments on how the displacements take place. The results show that acoustic and hydroacoustic measurements can be an excellent technique for observing Haines jumps in-situ.