Regulatory Intelligence
What should an engineer explain when using CBL/RBL evidence to support a disposal application?
Category:
Well Integrity
Research Basis
Archive Period
1994-2016
Records Reviewed
6
Primary Topics
CBL; RBL; VDL; pipe bond; formation bond; channels; microannulus; lightweight cement
Current Reference
AER Directive 051; AER Directive 009
Common Question
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What should an engineer explain when using CBL/RBL evidence to support a disposal application?
Archive Findings
The Cement Bond Log quick reference in the folder is not a generic handout; it maps the interpretation problems that affect D051 evidence. Good pipe and formation bond is associated with low 3-foot amplitude, lack of pipe arrivals in the VDL, low radial amplitudes, formation arrivals, and travel time tracking lithology. Free pipe shows high, consistent amplitude and pipe arrivals. Channels may not be obvious on the average CBL but can appear on radial bond mapping and may provide a conduit between zones or to surface. Microannulus can improve under pressure and should not be mistaken for no cement. The 1994 guide similarly expected cement integrity logs to be interpreted against their objective and warned that tool selection, cement type, centralization, pressure history, and pressure during logging matter.
Engineering Insight
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Treat the log package as an engineering interpretation, not a PDF attachment. State what the CBL/RBL/VDL is being used to prove: cement top, pipe bond, formation bond, absence of channels, or pressure-responsive microannulus. Tie intervals of poor bond to geological risk: nearby porous zones, groundwater, hydrocarbon-bearing zones, and the proposed injection interval. If lightweight cement or fast formation could distort amplitude or travel-time conclusions, say so and explain the alternate indicators.
Current Guidance
Current Directive 051 requires cement top location logs when cement is not returned to surface and requires hydraulic isolation logging for each well class as applicable. Appendix 3 identifies cement integrity logging design considerations, including well history, cement type, tool centralization, pressure history, and logging under appropriate pressure where possible.
Related Regulatory Insights
Historical newsletter insights that reference the same directive, manual, rule or regulatory requirement.