Quote:
Originally Posted by SeeGeeWhy
I'm sure you've reviewed CBLs. How many have you seen that you can be confident there is isolation top to bottom? It might be less than 10% from what I've reviewed, and in my opinion - that blows.
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Well the discussion was initially about frac fluids entering groundwater zones, and I guess I was getting at the argument that's not likely happening in the majority of cases. But yeah, I am there with you on the other side of it - isolation among shallower zones is far more dubious. Operators aren't interested in spending the money to get good cement up to surface.
But another aspect of the argument is that a CBL is only the best of a bad lot of tools for evaluating a cement job. In my experiences, it can be a mixed bag in terms of using it to demonstrate hydraulic isolation.
Quote:
Originally Posted by fotze
Probably less than .01% if you are needing isolation for all zones with porosity greater than 1-3% (as per unenforced regs).
Also would be very hard to prove isolation without extreme cost.
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Yup, this is basically what I'm saying. A CBL is one thing, but many times it's an indicator of sweet-F-all, depending on cement density, tool centralization, presense of microannuli (which may or may not actually be a problem).
Add to that fact, every service company seems to have its own special way of displaying the data and you have mass confusion as to what a good CBL even looks like these days. Overseas was even more fun when Service Company Blue (for anonymity) would do the CBL of our jobs when they were trying to get our cementing work! Nope, no conflict of interest there.
Anyway, what I'm saying is that no CBL would convince me there is or isn't isolation top to bottom. It may correlate somewhat. Empirical observation is really the best tool there is, and in your words, "that blows". The only time you know you have a problem is, well, when you have a problem.