Multiscale filtering of acoustic data to extract subsurface formation properties

Characterization of a complex medium consisting of a layered earth formation with multiphase fluid is a challenging problem. In applications to oilfield exploration, a wellbore-typically 15 to 30 cm in diameter-is drilled to a depth of a few kilometers. Metal pipes (referred to as “casing”) are installed in the wellbore for well stability. Earth formation and fluid properties (e.g., lithology, porosity, resistivity, fluid composition, saturation) are determined by a host of sensors employing multiple physics for their operation. One of the important measurements is based on acoustic wave propagation in which sonic sources transmit monopole or higher-order waves that interact with the wellbore and the formation. Waveforms recorded by a set of sensors located along the wellbore axis are then processed to invert to determine the desired formation properties.