[CCoE Notice] Cullen College Dissertation Defense Announcement - Ahmed Aldughather

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[Dissertation Defense Announcement at the Cullen College of Engineering]

The Petroleum Engineering Department Presents



Reactance Based Self Sensing Well Cement



Ahmed Nabil Aldughather

December 6, 2022; 1:00 PM - 4:00 PM (CST)
Location: Tech Bridge Building 9 – Room 124


Committee Chair and Co-Chair:

George K. Wong, Ph.D. and Cumaraswamy Vipulanandan, Ph.D.

Committee Members:
| Mohamed Y. Soliman, Ph.D. | Guan Qin, Ph.D. | Arthur Hale, Ph.D. |

Abstract

Well zonal isolation failure may severely impact health, safety, and the environment. Thus, long-term monitoring of well cement integrity is an active industry research area. This challenge could be addressed by converting the well cement into a permanent downhole intrinsic sensor. Currently, self-sensing cement research focuses on improving the electrical resistance response to applied stress (piezoresistivity) by adding conductive fillers. However, despite the extensive research and progress made in the self-sensing cement technology for civil engineering applications, the lack of laboratory standardization and disparities with well cement operational requirements have hindered the applications of this technology for petroleum engineering. Hence, this study presents a method to design a self-sensing cement that closely follows the recommended practices of the American Petroleum Institute.

The proposed method uses multiscale carbon fibers and the alternating current (AC) two-probe approach to evaluate the impedance response to the deviatoric stress under uniaxial compression. Test results showed improvement in cement compressive strength and that the reactance response is more sensitive than the resistance at the measured frequency of 300 kHz. At the optimum carbon fiber dosage, in the pre-percolation region, the fractional change of bulk reactance was -50%, while the fractional change of bulk resistance was -40% at failure. The dielectric components were extracted using an equivalent AC circuit for the bulk cement that contains a resistor and a capacitor in parallel. Dielectric loss was the most sensitive component to stress for all tested samples. The findings from this work help postulate that the self-sensing mechanism is related to changes in the electric permittivity with stress through dielectric breakdown; consequently, reactance is a crucial component.

The potential utilization of quantitative real-time monitoring of well cement deformation using electric impedance spectroscopy shows promise and warrants further studies.

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