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C'~ 5 PART IV - CONCLUSIONS - • Different pipe weights and cement types will affect the log readings, so be mindful of these factors in wells with varying pipe weights and staged cement or squeeze jobs. Collars generally do not show up on the VDL track in well- bonded sections of casing. Longer (slower) travel time due to cycle skipping or cycle stretch usually suggests good bonding. Shorter (faster) travel times indicate a de-centered tool or a fast formation and will provide erroneous amplitude readings that make evaluation impossible through that section of the log. Fast formations do not assure that the cement contacts the formation all around the borehole. Although the bond index is important, you should not base your assessment of the cement quality on that one factor alone. You should use the VDL to support any indication of bonding. Also, you must know how each portion of the CBL (VDL, travel time, amplitude, efc.) influences another. Most 3'-5' CBL's cannot identify a 1/2" channel in cement. Therefore, you also need to consider the thickness of a cemented section needed to provide zone isolation. For adequate isolation in injection wells, the log should indicate a continuous 80$ or greater bond through the following intervals as seen in TABLE 1, below: TABLE 1 -INTERVALS FOR ADEQUATE BOND PIPE DIAMETER (in) CONTINUOUS INTERVAL WITH BOND Z 80$ (ft) 4-1/2 15 5 15 5-1/2 18 7 .. 33 . 7-5/8 36 9-5/8 45 10-3/4 54 Adequately bonded cement by itself will not prevent fluid movement. If the bond log shows adequate bond through an interval where the geology allows fluid to move (permeable and/or fractured zones), fluids may move around perfectly bonded cement by travelling through the formation. Alwava cross-check your bond log with open hole cogs to nee that you have adequate bonding through the proper interval(s).