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Collars generally do not. show up on the ~DL track in well- <br />bonded sections of casing. <br />Longer (slower) travel time due to cycle skipping or cycle <br />stretch usually suggests. good bonding. <br />Shorter (faster) travel times indicate a de-centered tool or <br />a fast formation and will provide erroneous amplitude <br />readings that make evaluation impossible through that <br />section of the log. Fast formations do not assure that the <br />cement contacts the formation all around the borehole. <br />Although the bond index is important, you should not base <br />your assessment of the cement quality on that one factor <br />alone. You should use the VDL to support any indication of <br />bonding. Also, you must. know how each portion of the CBL <br />(VDL, travel time, amplitude, etc.) influences another. <br />Most 3'-5' CBL's cannot identify a 1/2" channel in cement. <br />Therefore, you also need to consider the thickness of a <br />cemented section needed to provide zone isolation. For <br />adequate isolation in injection wells, the log should <br />indicate a continuous 80$ or greater bond through the <br />following intervals as seen in TABLE 1, below: <br />TABLE 1 - INTERVALS FOR ADEQUATE BOND <br />PIPE DIAMETER (in) CONTIN[JOUS INTERVAL WITH BOND s 80$ (ft) <br />4-1/2 15 <br />5 15 <br />5-1/2 18 <br />7 33 <br />7-5/8 36 <br />9-5/8 45 <br />10-3/4 54 <br />Adequately bonded cement by itself will not prevent fluid <br />movement. If the bond l.og shows adequate bond through an <br />interval where the geology allows fluid to move (permeable <br />and/or fractured zones), fluids may move around perfectly <br />bonded cement by travel].iag through the formation. Alwavs <br />cross-check your bond log with open hole logs to see that <br />you have adequate Bondi=ig through the proper interval(s). <br />`6f3' Printed on Recycled Paper <br />