What type of study is this?

This is a Experimental Study study.

October 23, 2025

Well Barrier Test Sub for Evaluating Downhole Well Barrier Integrity from Below: Integrating Pressure Testing and Cement Slurry Rheology Assurance

Key Points

Effective testing of barrier materials hinges on simulating downhole conditions for reliability and accuracy.
The Coriolis flow meter was utilized to ensure precise density measurements of cement slurry during trials.
Cementing operations involved using coiled tubing to create a secure plug under specified pressure and duration.
Findings highlight advanced techniques for maintaining zonal isolation, vital for environmental protection in P&A operations.

Abstract

Abstract Ensuring permanent zonal isolation in plug and abandonment (P&A) operations is critical to preventing fluid migration between subsurface formations and the environment. Failure in zonal isolation can result in groundwater contamination, sustained casing pressure, and formation charging, leading to operational risks. This study introduces a methodology to mitigate risks in cementing operations by developing representative downhole testing setups for barrier materials. Specifically, it investigates the integration of an inline pipe viscometer for real-time viscosity and density measurements of conventional Class G cement slurry and presents the Well Barrier Test Sub (WBTS), designed to replicate downhole conditions for barrier material evaluation. A 9 ⅝-inch WBTS cell was developed with a pressure-tight system to facilitate platform piston control, gas seepage tests, and real-time temperature monitoring using a PT100 or fiber optic sensor. The system was deployed at the Ullrigg Test Centre, interfacing with the wellhead via a 10 ¾-inch casing hanger flange. Cement slurry preparation followed offshore protocols, with viscosity and density assessed using an inline pipe viscometer and a Coriolis flow meter. Comparative analyses were conducted using conventional methods, including the FANN 35 rotational viscometer and a mud balance. The cement was subsequently pumped through coiled tubing to form a 5-meter plug, cured under 20 bar for 24 hours. A gas seepage test was then performed by lowering the WBTS piston while maintaining downhole pressure, using a precision gas tester to monitor gas flow. Results demonstrate the effectiveness of the proposed methodology for testing barrier materials under realistic conditions. The inline viscometer system provided flow curves consistent with those obtained using the FANN 35 rotational viscometer. The WBTS system functioned effectively in all test phases, from piston operation to gas seepage assessment. The seepage test established a direct correlation between injected and captured gas volumes, confirming the setup’s applicability for evaluating casing annuli, P&A plugs, and complex scenarios such as tubing left in the hole.

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