Schlumberger

Technical Paper: Leading Edge Developments in Ultrasonic Logging Improves Cement Evaluation Quality in Extreme Conditions

Society: SPE
Paper Number: 182533
Presentation Date: 2016
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Abstract

Improvements in ultrasonic cement evaluation technology are increasing operational efficiency and reliability and extending the operating envelope into extreme environments with heavy muds and larger and thicker casings. Tool hardware, software, and firmware have been substantially redesigned and optimized to increase acquisition efficiency and data quality output. One key aspect is the complete redesign of various ultrasonic transducers to enable acquisition in the heaviest, highly attenuative muds. A specially designed transducer for thick casings and large rotating logging heads are pushing the thickness and diameter envelope to cover almost all possible scenarios.

Yard tests were conducted to emulate extreme downhole conditions in a controlled way: A casing filled with heavy mud (2-g/cm3 synthetic oil-based mud [SOBM]) and cemented in an eccentered position inside a simulated formation was tested with two complementary ultrasonic techniques, pulse-echo and flexural wave imaging. These tests demonstrated the proper performance of both measurements despite the highly attenuative logging mud and made it possible to determine annulus material impedance, casing centralization, and location of the position of a "simulated measurement cable" (such as fiber-optics bundles) cemented inside the annulus. Through two field tests we further confirmed the efficiency improvements concerning logging speed (i.e. software/firmware). Logs have been obtained in extremely heavy mud environments and 26.7-mm (1.05-in.) thickness casing.

These new developments in ultrasonic cased hole technology enable cement evaluation and pipe inspection in environments of the heaviest muds and casings of extremely large size and greater thickness, thus augmenting the industry's ability to diagnose well integrity while helping to reduce uncertainty and risk in well construction or before abandonment operations.

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