Annular Wash Cement Assurance (AWCA) has been used for several years as a cost-effective tool for Permanent Abandonment (P&A) of oil/gas wells to remediate cement behind casings in lieu of Section milling to establish a rock-to-rock barrier. In order to verify AWCA result in the annulus, originally the cement in the casing is drilled out and the casing re-log with a bond log then a cement plug re-set in the casing. With experience gained in AWCA, Companies become more and more bolder and accept the performance of the AWCA without further annulus verification. A Qualification matrix, also called Verification Matrix (VM) is used instead to justify avoiding cement drill out – cement bond log and cement plug re-set in the casing.

One of the criteria of the VM is a ‘track record’ as per NORSOK, is a minimum of three successful AWCA jobs. The definition of "successful" means verification of the annulus cement by drilling out (cement) followed by a bond log. Ref. NORSOK D10-2021 EAC Table 61.

The following AWCA jobs with similar parameters as the track record jobs (casing/lithology/fluid etc) are verified without drill-out and bond logging, i.e non destructive verification, claiming that the track record guarantees the AWCA will be satisfactory.

Other Companies do not establish track record at all, instead they use the VM as the only verification means.

The VM matrix is non other than a table comparing the job design & operational parameters vs the actual data.

The paper discusses possible short comings with the use of VM alone to justify avoiding drilling out and logging the annular cement to verify it's integrity.

Recent events have shown cases where Sustained Casing Pressure (SCP) develop several years after the AWCA job.

Also, several cases are known where the AWCA job performance were given the thumbs up passing the VM with flying colours, however when the cement was drilled out and a cement bond log ran, it shows evidence the annulus void of cement or poor cement bond.

The reluctance to do destructive verification is understood as it seems to be such a time waste. Not only do you need to drill the plug you just set, you also will need to run a scraper and wait a minimum of 48 hrs before logging the cement in the annulus. Once all done, you will need to reset the cement plug in the casing then wait for cement to harden to verify the cement barrier by tagging and pressure testing.

An alternative verification process is proposed to verify the annulus barrier as a proper barrier.

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