Cement Bond Logging is not an approved
mechanical integrity test under the US EPA underground injection control (UIC) regulations. In Direct Implementation (DI) programs including Kentucky, EPA may require cement bond logging under the regulations during the construction of Class I (hazardous waste) injection wells; and under some circumstances, during the construction of new Class II wells (see 40 CFR §146.22(f), although this requirement does not apply to existing Class II injection wells). But these uses of the cement bond log pursuant to the UIC regulations are specifically not as an MIT.|
Home | Tech & Tips |
Cement Bond Logging |
UIC MIT Menu |
The original EPA 1976 UIC regulatory proposal contained no specific MITs, although there was a general prohibition against "leaks in the system". The 1979 reproposal contained six MITs for the demonstration of external or Part II (absence of fluid movement) mechanical integrity: (a)
cement records, (b)
cement bond log, (c) sonic log, (d)
temperature log, (e) density log, or (f) dual neutron log. EPA's 1980 final regulations retained only cementing records, temperature logs, or
noise logs as external MITs. (It should be noted that cement records were no longer considered an acceptable MIT for Class I wells, but were retained for Class II wells subject to mid-course evaluation (MCE). FOIA requests, and depositions of EPA Region IV personnel, reveal that EPA violated its own MCE regulation at 40 CFR §146.25(c), now repealed, by not collecting certain well logging data intended to shed light on the efficacy of the cementing records external MIT.)
The UIC regulations provide for the adoption of "alternative" MITs, but the procedure is arduous, even including Federal Register notices (see 40 CFR §146.8(d) and headquarters UIC Guidance 61). Since 1980, the radioactive tracer survey (RTS or as we prefer RATS) and the oxygen activation log have been approved as external MITs, with use of the RATS as an external MIT approved under certain conditions. The EPA MIT Workgroup, now disbanded and replaced with the National Technical Workgroup, was considering pushing for approval of cement bond logging as an alternative external MIT, but nothing ever came of the discussions. In 1993, as a part of Reg-Fix (and presumably as a result of an MCE Workgroup recommendation), a new subsection (f) was added to 40 CFR §146.8 allowing the Director to require additional MITs, but this new section does not allow the Director to require an unapproved MIT. Any required MIT must have been included in the final UIC regulations or later approved as an alternative MIT pursuant to said regulations.
But EPA does not seem to realize they never got around to approving cement bond logging as an external or Part II MIT. A revealing document is the
Final Work Product #6 of the National UIC Technical Workgroup. This document discusses the distinction between 40 CFR §146.22 and MIT requirements, but goes on to show how cement bond logs are actually being required for Class II existing wells as MITs in some jurisdictions. Said document contains the statement, "A CBL is not necessarily required by each DI program in an operators primary submission. However, if an operator is unable to provide the cementing record documentation the DI program requires, the CBL is requested as a substitution…." The second sentence in the preceding quote is interesting and is discussed in detail below, but the first sentence is just plain wrong. A cement bond log cannot be required as an external MIT under any circumstances, not even under Reg-Fix's 40 CFR §146.8(f); cement bond logging is not a legal external or Part II MIT. Interestingly, at least EPA Region V seems to recognize that cement bond logs can only be used as substitute records of cementation. In an amendment to their Region V MIT guidance document, they have removed the cement bond log from its listing as an external MIT; it is now listed under Cementing Records (Attachment #9) (though they continue to improperly require a VDL curve).
What a cement bond log can do is save a Class II well from extinction (plugging) where there are no cementing records (of course some operators solve this little problem with phony records). The cement bond log is very good at showing the top of cement; it is ordinarily easy to pick the top from the amplitude curve generated from any single receiver tool. So an operator can run a "cement top log" and submit the results as a variation of the cement records MIT contemplated at 40 CFR §146.8(c)(2). The distinction here is not trivial. The cement bond log is not an approved MIT; it is merely being used to generate substitute records of cementation. EPA cannot require a dual receiver tool, a VDL curve, or any of the more exotic or expensive so called cement evaluation logs, only a good old single receiver cement bond tool used for a cement top log. Anything beyond using a cement bond log to show the top of cement would amount to an improper use of said log as an unapproved MIT; it can only be used as a type of cementing record, and no cement record reveals quality of bonding (the ability of cement bond logs and cement evaluation logs to reliably indicate bond quality remains controversial, anyway). (Some state oil and gas programs have independent requirements concerning cement bond logging beyond the scope of this discussion.)
Curiously, EPA has spent a small fortune researching cement bond logging, including the funding of reports and some interesting research conducted at the Robert S. Kerr Environmental Research Laboratory (RSKERL or Kerr Lab) in Ada, Oklahoma (said research was headed up by our friend Jerry T. Thornhill). The final report, "Injection Well Integrity", EPA/625/9-89/007 is worth reading if you have any illusions about the efficacy of cement evaluation tools, at least those available at the time of the report. Unfortunately, the original research material has been lost (probably simply thrown out), a horrible loss and waste of countless taxpayer dollars.
We believe the cement bond log external MIT was removed from the UIC regulations for good reason. It probably should not be approved as an alternative MIT at this late date. When used as a variant of the cementing records MIT, it is excellent; it shines as a top of cement indicator. However, EPA should not treat cement bond logging as though it is an approved external MIT, nor should they require anything but the simplest single receiver cement bond tool when the log is used as a replacement cementing record.
Cement Bond Logging Overview for basic information on cement bond logging technology. Contact us if you need more detailed information; we have thousands of pages on the subject!