| Popis: |
The radial bond tool consists of multiple receivers normally 2 to 3 ft from the source in addition to the standard 3 to 5 ft of receiver spacing. The standard interpretation from these tools consists of 6 to 8 amplitude measurements presented as either curves or as an image, indicating circumferential cement to casing bond. Evaluating bond quality of the annular space between casing and formation has been extremely difficult using existing logging tools and interpretation techniques. The discussed technique processes segmented waveforms in an innovative way, providing additional circumferential cement bond information at varying depths of investigation in annular space. A new method of interpretation has been applied to the cement bond log (CBL) waveform that examines the peaks and troughs of the waveform to help determine the cement bond between the casing and formation. The interpretation provides up to four different amplitude curves at different depths of investigation in the annular space. Applying the same methodology to the segmented waveforms, but with additional steps, allows the circumferential bond to be determined between the casing and formation. Depending on the length of the segmented waveforms, these annular shells can extend from the casing to the formation, and can be corrected for the relative bearing of the tool. The example is a standard cement evaluation immediately above and below the surface casing shoe, with a washout immediately below the casing shoe. Both the raw and advanced cement evaluation revealed poor bond in the washout region. With the new processing of the radial waveforms, a channel in the annular space was shown to extend almost all the way to the surface, which is not visible using standard interpretation techniques. Using older standard evaluation techniques, the channel would have been missed or incorrectly evaluated. The use of the radial shell technique provided accurate interpretation of the annular space between the casing and formation. Standard interpretation of radial bond data does not include use of segmented waveforms. With this new processing technique, not only are the segmented waveforms used, but the annular space is broken into regions or circumferential shells, which can be further evaluated. These shells allow evaluation between the casing and formation, and allow a more accurate and complete evaluation of the cement sheath. This can help provide a more precise assessment of wellbore integrity and help prevent loss of the wellbore attributed to cement and or casing failure. |
