Annular-A characterization for inner tubular eccentricity and wave propagation speed estimation

A method for processing ultrasonic-based signals for data preparation for eccentricity estimation, comprising:

• extracting, by a pulse-echo tool conveyed in a cased wellbore, at least one pulse-echo signal, at least at one acquisition azimuth, and at least at one depth in the cased wellbore, wherein the pulse-echo tool comprises a tool face and at least one ultrasonic transducer rotating relative to the tool face;
• determining an inner tubular echo signal envelope peak amplitude and a time providing a same feature of the echo signal, at least including a closest zero-crossing to a peak for each signal extracted;
• aligning each of the extracted pulse-echo signals referring to the time of the same feature to achieve a pre-processed data set, wherein the pulse-echo signals are transmitted and received by the ultrasonic transducer;
• normalizing each of the extracted pulse-echo signals using the envelope peak amplitude;
• enhancing third interface echo signals by reducing the inner tubular specular echo and inner tubular ringing;
• preparing at least one model-based delay profile of eccentricities in the pre-processed data set;
• back-propagating the pre-processed data set according to each of the model-based delay profiles to compensate for an eccentricity-dependent delay of an outer casing echo and generate one or more back-delayed signals;
• estimating pipe eccentricity data based on the enhanced third interface echo signals and the normalized pulse-echo signals, wherein the pipe eccentricity data includes at least one of an inner tubular eccentricity, an azimuthal direction and a wave propagation speed of annular material;
• and
• outputting the estimated pipe eccentricity data for use in evaluating a borehole.

An article of manufacture having a non-volatile memory, the non-volatile memory configured to store a list of instructions, the list of instructions comprising, at least in part, a method for processing signals that may be read and performed by a computing device, the method comprising:

• obtaining, by a pulse-echo tool conveyed in a borehole of a well, data for evaluation, wherein the pulse-echo tool comprises a tool face and at least one ultrasonic transducer rotating relative to the tool face, and wherein the data includes pulse-echo signals acquired at a plurality of circumferential positions of the borehole or at a plurality of acquisition azimuths of the borehole;
• conducting a pre-processing evaluation of the data obtained to achieve a pre-processed data set by aligning the pulse-echo signals based on an inner tubular echo arrival time, wherein the pulse-echo signals are transmitted and received by the ultrasonic transducer;
• determining a third interface echo arrival time for the pre-processed data set;
• preparing at least one model-based delay profile of eccentricities in the pre-processed data set;
• back-propagating the pre-processed data set according to each of the model-based delay profiles to compensate for an eccentricity-dependent delay of an outer casing echo and generate one or more back-delayed signals;
• computing a coherence of back-delayed signals derived from the pre-processed data set for the at least one model-based delay profile;
• selecting a delay profile providing a maximum coherence of data;
• determining an absolute value of echo arrival time, at least at one evaluation azimuth of the selected delay profile;
• determining a wave propagation velocity from the determined absolute value of echo arrival time and the at least at one evaluation azimuth of the selected delay profile;
• determining an eccentricity based upon the determined wave propagation velocity;
• and
• outputting at least one of the eccentricity or the wave propagation velocity for use in evaluating the borehole.