Methods of and apparatuses for improving log data

Abstract

Disclosed herein is method of computing formation attributes from acoustic measurements in a borehole. The acoustic measurements can be made by operating an acoustic source at multiple frequencies to excite the formation and operating receivers at multiple, longitudinally spaced receiver stations to receive acoustic energy from the formation. The method can include: deriving phase data from the spectrum of received acoustic signals; unwrapping phase information of the phase spectrum data; determining two or more values of difference of phase between acoustic signals at each of a range of frequencies each based on a single generated signal received at two or more pairs of adjacent said receiver stations; generating a value of slope of phase difference values; and in any case of slope ambiguity, unwrapping phase difference information and deriving a dominant slope, at each frequency, from which slowness of the acoustic signal in the formation can be derived.