Current methods for determining the depth to the top of cement (TOC), blockages, or wellbore features are limited to intrusive applications that require a significant amount of associated time, equipment, risk, and cost. This is a long-standing challenge to operators, particularly when critical decisions need to be made to promptly verify downhole status or remediate flow restrictions to restore production. This paper details a systematic, comprehensive, and proven solution to these challenges using pressure wave analysis.

The method is based on analyzing the return reflections generated by a pressure wave transiting the well to and from the blockage location. By capturing high-resolution pressure measurement on an ultrahigh-speed logger, the generated pressure wave can be recorded for analysis. Applying acoustic velocity gradient modeling in conjunction with effects of the well and fluid medium, the distance from the recording location to the blockage can be accurately determined without the use of intrusive or localized external tools.

This work shows that the method theory is substantiated by results observed when used during a controlled full-scale field trial in addition to subsequent activities to locate blockages and features within actual wells. A case study is presented demonstrating that the method can be used to identify where a blockage or feature is located. The theoretical method for calculation of acoustic velocity for known system and fluid parameters is shown to be accurate within tolerances compared to the acoustic velocity obtained in the field by recording the time of flight between two known points. It is demonstrated that blockages can be detected to a level of accuracy up to 0.3% of system length, verified by comparison with known measured well construction details.

The method presented significantly differentiates itself from traditional depth determination systems and applications. It can provide information with a repeatable and verified level of accuracy without the need for costly and time-consuming intrusive intervention, which allows operators the opportunity to target remediation work in the most efficient and cost-effective manner.

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