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Ultrasonic Log Response Evaluates Barrier Cells for Cementing Applications

Borehole-cement-evaluation logs are used to verify the quality of the cement bond to the casing and formation and identify any defects that could compromise the quality of the annular seal. This study used ultrasonic logging to evaluate reference barrier cells constructed with known defects. The cell concept was developed with an emphasis on low cost and ease of use. Comparison of ultrasonic tool response against reference barrier cells validates the measurements, which are crucial in the decision-making process during well construction and abandonment.

Background: Barrier Verification

In 2013 and 2014, full-scale experiments were performed to investigate the sealing ability of annulus cement for a plug-and-abandonment design in which the tubing is left in hole (TLIH). The experimental configurations used 9⅝-in. casing with a 7-in. tubing, both with and without control lines clamped to the tubing surface. Experiments were run first using standard Class G cement. In a second phase, Class G cement with an expansion additive was used to compare the quality of the seal achieved. The barrier quality of the cement was evaluated by pressure-testing the casing cement sheath and the tubing plug. The test assemblies subsequently were cut into sections, enabling the cement displacement to be controlled visually. The results showed that good cement placement could be achieved with the tubing left in the well both with and without control lines. The pressure testing showed that the control lines did not have a detrimental effect on the barrier-seal quality compared with the test without control lines.

The choice of leaving the tubing in hole when abandoning a well is dependent on an assessment of the quality of the casing cement sheath. The barrier-verification project was initiated to build on the TLIH experiments by investigating the performance of annular-barrier evaluation technologies.

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 199578, “Validating Ultrasonic Log Response Against Reference Barrier Cells Simulating Downhole Well Conditions Encountered During Well Construction and Abandonment Operations,” by Amit Govil, SPE, Schlumberger; Dave Gardner, SPE, Norwegian Research Centre; and Guillermo Obando, Schlumberger, et al., prepared for the 2020 IADC/SPE International Drilling Conference, Galveston, Texas, 3–5 March. The paper has not been peer reviewed.
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Ultrasonic Log Response Evaluates Barrier Cells for Cementing Applications

01 May 2020

Volume: 72 | Issue: 5

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