How Dangerous is The Micro or Macro Channels:
 
If a channel has a width of 0.0018 “ behind 7”, 26 #/ft, L-80 liner (for example), then there will be no problem with this
well ONLY IF the GOR is around 800 or less and if the well produces oil. This is because the capillary of the water in cement prevents any oil movement in the future.
If a channel is more than 0.0018” behind the same liner, then we need to be careful about this well, because oil will move
over the length of that channel. After years of production, the channels extend toward up. This is why both 0 and 1000 psi
pass is important to run for tools that have pads touching casing.
 
In gas well, be aware that any micro channel will be dangerous.
 
When Do You Need to Run Cement Logs:
 
Once you do cement job, it is very important to have the following:
   
How much Retarder was put in the cement, and what type. Why ? because each Retarder will keep the cement under
liquid or jelly condition for certain time. Over this time we can apply pressure on the casing and make the passes. Do
not worry on pressure pass that might break cement, because Drilling always do LOT once they drill the shoe. Drilling
Engineers can explain this point.
Temperature of the hole. Why ? because cement hydrates and its initial setting is affected by the temperature.
How long you waited on cement to initially set. Why ? so that we know whether cement is under liquid, jelly condition,
or initially set
   

Cement in some local spot might initially set in as low as 20 hours, while in other spots it might need over 100 hours or
longer to initially set. Final cement set might take 10 to 30 days.
It Is Better To Apply Pressure on Casing When The Cement Is Initially Set. Why ? Cement can re-construct itself as it has thixotropy behavior

72 hours is NOT ideal time for all wells, setting depends on the additives mixed with cement.
An average of 40 – 90 hours is the range for Class G cement with different % of Retarders under 190 – 230 F. Cement
Engineer is the right person to explain and tell this.

 
What is the Minimum Channel Cement log tool should See ?
 
At least 25% of the size of the tool pad that touches the casing