# US 2019/0376380 A1 · Methods and apparatus for cement bond evaluation through production tubing > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0376380 A1 - Document ID: US20190376380A1 - Status: Published application - Kind: A1 - Application number: 16/006,064 - Filed: 2018-06-12 - Published: 2019-12-12 - Earliest claimed: 2018-06-12 - Assignees: Probe Technology Services, Inc. - Applicants: Probe Technology Services, Inc. - Inventors: Jun Zhang; Yibing Zheng - Web page: https://patentgrep.com/patent/US20190376380A1 ## CPC - E21B 47/005: Monitoring or checking of cementation quality or level - G01V 1/40: specially adapted for well-logging - G01V 1/48: Processing data - G01V 1/50: Analysing data - E21B 33/14: for cementing casings into boreholes - G01V 2210/1299: Subsurface, e.g. in borehole or below weathering layer or mud line - G01V 2210/1429: Subsurface, e.g. in borehole or below weathering layer or mud line - E21B: EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS - G01V: GEOPHYSICS; GRAVITATIONAL MEASUREMENTS; DETECTING MASSES OR OBJECTS; TAGS (means for indicating the location of accidentally buried, e.g. snow-buried, persons A63B29/02) ## Abstract Various downhole logging tools and methods of using and making the same are disclosed. In one aspect a method evaluating cement bond quality in a well is provided. In a well with a particular casing/tubing configuration, waveforms of acoustic energy returning from the tubing and the casing with the tubing present are recorded. A frequency spectrum from the recorded waveforms is determined. 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 are determined. The determined amplitudes are compared with one or more baseline amplitudes to look for indications of cement bond quality. Other aspects involve time domain analysis. ## Claims ### Claim 1 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 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. ### Claim 2 (depends on 1) The method of claim 1, comprising adjusting the one or more baselines for variations in casing weight. ### Claim 3 (depends on 1) The method of claim 1, comprising determining the frequency spectrum for a whole waveform. ### Claim 4 (depends on 1) The method of claim 1, comprising determining the frequency spectrum for a wave segment of a whole waveform. ### Claim 5 (depends on 1) The method of claim of claim 1, wherein the one or more preselected frequency(s) of interest are preselected by comparing a first frequency spectrum of acoustic waveforms for a region of known good cement bond for the particular casing/tubing configuration and a second frequency spectrum of acoustic waveforms for a region of known bad cement bond for the particular casing/tubing configuration and identifying the one or more frequencies of the range of frequencies where the amplitudes of acoustic waveforms for the known bad bond region are noticeably affected by bond quality. ### Claim 6 (depends on 1) The method of claim of claim 1, wherein the one or more preselected frequency(s) of interest are preselected by comparing a first modeled frequency spectrum of modeled acoustic waveforms for a region of known good cement bond for the particular casing/tubing configuration and a second modeled frequency spectrum of modeled acoustic waveforms a region of known bad cement bond for the particular casing/tubing configuration and identifying the one or more frequencies of the range of frequencies where the amplitudes of modeled acoustic waveforms for the known bad bond region are noticeably affected by bond quality. ### Claim 7 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. ### Claim 8 (depends on 7) The method of claim 7, comprising adjusting the one or more baselines for variations in casing weight. ### Claim 9 (depends on 7) The method of claim 7, comprising determining the frequency spectrum for a whole waveform. ### Claim 10 (depends on 7) The method of claim 7, comprising determining the frequency spectrum for a wave segment of a whole waveform. ### Claim 11 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. ### Claim 12 (depends on 11) The method of claim 11, wherein the wave cycles comprise the time between every other zero crossing of the recorded waveforms. ### Claim 13 (depends on 11) The method of claim 11, wherein the wave cycles comprise the time between adjacent amplitude peaks or adjacent amplitude troughs of the recorded waveforms. ### Claim 14 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 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. ### Claim 15 (depends on 14) The method of claim 14, wherein the wave cycles comprise the time between every other zero crossing of the recorded waveforms. ### Claim 16 (depends on 14) The method of claim 14, wherein the wave cycles comprise the time between adjacent amplitude peaks or adjacent amplitude troughs of the recorded waveforms. ### Claim 17 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 a frequency spectrum from the recorded waveforms, to determine 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 to generate a comparison of the determined amplitudes with one or more baseline amplitudes to provide indications of cement bond quality. ### Claim 18 (depends on 17) The apparatus of claim 17, comprising a downhole logging tool, the storage device and processor contained in the downhole logging tool. ### Claim 19 (depends on 17) The apparatus of claim 17, comprising a downhole logging tool, the storage device and processor not contained in the downhole logging tool. ### Claim 20 (depends on 17) The apparatus of claim 17, wherein the processor is programmed to adjusting the one or more baselines for variations in casing weight. ### Claim 21 (depends on 17) The apparatus of claim 17, wherein the processor is programmed to determine the frequency spectrum for a whole waveform. ### Claim 22 (depends on 17) The apparatus of claim 17, wherein the processor is programmed to determine the frequency spectrum for a wave segment of a whole waveform. ### Claim 23 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. ### Claim 24 (depends on 23) The apparatus of claim 23, comprising a downhole logging tool, the storage device and processor contained in the downhole logging tool. ### Claim 25 (depends on 23) The apparatus of claim 23, comprising a downhole logging tool, the storage device and processor not contained in the downhole logging tool. ### Claim 26 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. ### Claim 27 (depends on 26) The computer readable medium of claim 26, wherein the method comprises adjusting the one or more baselines for variations in casing weight. ### Claim 28 (depends on 26) The computer readable medium of claim 26, wherein the method comprises determining the frequency spectrum for a whole waveform. ### Claim 29 (depends on 26) The computer readable medium of claim 26, wherein the method comprises determining the frequency spectrum for a wave segment of a whole waveform. ### Claim 30 A computer readable medium having computer-executable instructions for performing a method of 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 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.