Methods and apparatus for cement bond evaluation through production tubing

A method evaluating cement bond quality in a well with a particular casing/tubing configuration using waveforms of acoustic energy returning from the tubing and the casing with the tubing present, comprising:

• determining a frequency spectrum from the recorded waveforms;
• determining amplitudes of the returning acoustic energy at one or more preselected frequency(s) of interest of a range of frequencies at which the amplitudes are noticeably affected by cement bond quality for the particular casing/tubing configuration;
• and
• comparing the determined amplitudes with one or more baseline amplitudes to look for indications of cement bond quality.

A method evaluating cement bond quality in a well, comprising:

• in a well with a particular casing/tubing configuration, recording waveforms of acoustic energy returning from the tubing and the casing with the tubing present;
• determining the lengths of wave cycles of the recorded waveforms for at least one preselected time window for the particular casing/tubing configuration;
• and
• determining if the lengths of the wave cycles increase or decrease relative to a baseline wave cycle length and at what depths to look for indications of cement bond quality.

An apparatus for evaluating cement bond quality, comprising:

• storage device for storing recorded waveforms of acoustic energy, in a well with a particular casing/tubing configuration, returning from the tubing and the casing with the tubing present;
• and
• a processor programmed to determine the lengths of wave cycles of the recorded waveforms for at least one preselected time window for the particular casing/tubing configuration;
• and
• determine if the lengths of the wave cycles increase or decrease relative to a baseline wave cycle length and at what depths to provide indications of cement bond quality.

A computer readable medium having computer-executable instructions for performing a method comprising:

• in a well with a particular casing/tubing configuration, recording waveforms of acoustic energy returning from the tubing and the casing with the tubing present;
• determining a frequency spectrum from the recorded waveforms;
• determining amplitudes of the returning acoustic energy at one or more preselected frequency(s) of interest of a range of frequencies at which the amplitudes are noticeably affected by cement bond quality for the particular casing/tubing configuration;
• and
• comparing the determined amplitudes with one or more baseline amplitudes to look for indications of cement bond quality.