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Title: Smart Acoustic Cement Sensors Incorporating Carbon Nanotubes

Author(s): Shreya Vemuganti

Publication: Web Session

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Appears on pages(s):

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DOI:

Date: 4/1/2021

Abstract:
Wellbore cement is subjected to changing stresses caused by operations, pressure testing, and hydraulic fracturing. Development and propagation of microcracks in wellbore cement may lead to leakage along the wellbore and raise concerns about wellbore integrity. Monitoring wellbore cement is challenging because of its inaccessibility and enclosure between a steel casing and a rock formation. Ultrasonic measurements within the wellbore have been used to map cement cracking; however, a high degree of attenuation might limit the detection of cement microcracks. In this work, we present the first attempt to develop a cement sensor exhibiting wide acoustic bandgaps and offering the unique ability of wave isolation. Computational simulations of the cement sensor were used to design the cement sensor incorporating carbon nanotubes. The cement sensor's fabrication and testing demonstrated acoustic bandgaps under 300 kHz and 600 kHz, consistent with the computationally predicted bandgaps in the range of 290 – 360 kHz, 410 – 460 kHz, and 515 – 585 kHz. X-ray tomographic reconstructions showed microscopic debonding at the cement sensor interface. Frequency response analysis of a three-dimensional computational model indicated a shift of frequency of minimum transmission due to the interface debonding, but no perturbation of bandgap response was observed. The new cement sensor with acoustic bandgaps introduces a new generation of smart cement sensors that will enable non-destructive monitoring of cement and concrete by observing changes in their acoustic response. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525.