Keywords and Phrases
Cement failure; Cement hardening; Finite element modeling; Leakage; Pore pressure; Wellbore integrity
“The integrity of the cement sheath is the key part to maintain zonal isolation and prevent the inter-zonal communication. Loads arising from multiple stages of wellbore life span may induce various modes of cement failure within the cement (disking and radial cracks) and at the cement-casing and the cement-formation interfaces (debonding fractures). This research utilizes the integrated laboratory and numerical approach to investigate the cement hardening process, to predict the cement failure under various loading conditions. An innovative experimental setup is established to measure the cement pore pressure variation during the hardening process under downhole conditions, and a staged 3D finite element analysis approach including loads from various operations is used to establish an in-situ downhole condition and predict the failure occurrence. The results show that (1) the degree of poro-elastic bulk shrinkage has significant implications for both shear and tensile failure initiation -- the less the cement shrinks, the less likely the failure initiation is; (2) cement integrity increases with increasing depth; (3) cement pore pressure evolution has significant implications for tensile failure - if cement pore pressure decreases more, higher temperature differences can be sustained before an MA occurs; (4) cement temperature fluctuations during hardening promote the initiation of debonding failure; and (5) a high cement Young’s modulus promotes the occurrence of radial cracks. In summary, the results presented indicate that establishing downhole conditions to quantitatively analyze cement failure is necessary. The knowledge from this study can raise the awareness of predicting and evaluating cement failure under downhole conditions and can be used to supplement and improve future laboratory experiments”--Abstract, page iii.
Hilgedick, Steven Austin
Geosciences and Geological and Petroleum Engineering
Ph. D. in Petroleum Engineering
Missouri University of Science and Technology
xvii, 147 pages
© 2020 Weicheng Zhang, All rights reserved.
Dissertation - Open Access
Electronic OCLC #
Zhang, Weicheng, "Integrated approach to investigate the wellbore integrity under downhole conditions" (2020). Doctoral Dissertations. 2927.