Patent ID: 9157312
Filing Date: 2015-10-13
Classification: E21B,G01V

Abstract:
1. A method of characterizing a casing installed in a borehole in an earth formation, the method comprising: activating a transducer at at least one azimuthal orientation in the borehole and generating an acoustic pulse; receiving a signal comprising a plurality of events resulting from the generation of the acoustic pulse; bandpassing the received signal using two modulated filters in a time domain, the two modulated filters being orthogonal to one another, and providing a bandpassed signal; estimating an envelope of the bandpassed signal; and estimating from the envelope of the bandpassed signal an arrival time of each of the plurality of events, the arrival times being characteristic of a property of at least one of: (i) the casing, and (ii) a cement in an annulus between the casing and the formation.