Cement setting problem across shale section

11 February 2011 Folks,
Has anyone observed problems with cement not setting up correctly across shale sections resulting in poor bonding/micro annuli even though the cement above and below the shale section has set up correctly? This phenomenon has been observed in several wells with batch mixed 7” liner jobs were a portion of the liner is across a shale section. The 8 1/2” section is drilled with WBM - no problems encountered while drilling, hole in good condition and no problems getting the liner to bottom. No problems mixing/pumping the job - adequate liner RPM while pumping and plugs bumping as per schedule. However the results of both a CBL and USIT log show poor cement across the shale section every time with good bonds above and below (sandstone) the shale sections.
The spacer is fresh water based, barite weighted with KCL (2% BWOW) the cement is G neat (batch mixed) with gas block and various other proprietary additives - no KCL.

Has anyone encountered this problem before - come up with any solutions? The poor cement across the shale is having a big impact on future perforating / Fracing operations.

Thanks
Sean

3 Answer(s)

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