Effect of casing eccentricity on cement sheath integrity
Elaheh Arjomand A C and Terry Bennett BA Room 419, EM building, School of Civil, Environmental and Mining Engineering, Engineering North N136, North Terrace Campus, The University of Adelaide, SA 5005, Australia.
B Room 240, Engineering North building, School of Civil, Environmental and Mining Engineering, Engineering North N136, North Terrace Campus, The University of Adelaide, SA 5005, Australia.
C Corresponding author. Email: elaheh.arjomand@adelaide.edu.au
The APPEA Journal 58(2) 669-673 https://doi.org/10.1071/AJ17187
Accepted: 29 March 2018 Published: 28 May 2018
Abstract
Cement sheaths play an important role in providing zonal isolation and preventing the migration of formation fluids to aquifers and the surrounding environment. The condition of a cement sheath may change because of the imposed pressure and temperature alterations during a wellbore lifetime. Cement sheath mechanical failure may happen because of poor cement placement, development of cracks within the cement sheath and debonding at the cement sheath, casing and rock interfaces. A three-dimensional finite element framework, employing an appropriate constitutive model (Concrete Damage Plasticity, CDP) for cement sheath and a surface-based cohesive behaviour for the interfaces, is developed for integrity investigations. The incorporation of the CDP is very advantageous to model quasi-brittle materials due to its capabilities to simulate both compression and tensile damage. The effect of casing eccentricity on stress distribution within the cement sheath and the integrity of the cement sheath is investigated while enhancing the wellbore pressure. Three different degrees of casing eccentricity (30%, 50% and 70%) were considered. The huge stress concertation within the narrower part of the cement sheath makes this section susceptible to compression and tensile damage. The high magnitude of compression and tensile damage in the scenario with 70% casing eccentricity highlights the importance cement sheath centralisation.
Keywords: casing eccentricity, constitutive model, finite element, well integrity.
Elaheh Arjomand got her bachelor’s degree in civil and structural engineering in Iran in 2009 and moved to Australia thereafter. Elaheh got her master’s degree in civil and environmental engineering from the University of Adelaide in 2012. After working in a construction and mining company, she returned to the University of Adelaide in 2014 and is currently a PhD student working on well integrity investigations and cement sheath performance subjected to different loading scenarios during the lifetime of wellbores. |
Terry Bennett studied the modelling of soil-structure interaction for his PhD, with emphasis on how to avoid spurious reflections encountered on the boundary of numerical models, which can render analysis results meaningless. Following his studies, Terry joined TNO Bouw in the Netherlands where he worked on the development and maintenance of the general-purpose finite element code DIANA. He then worked a Postdoctoral Researcher at Delft University of Technology in the faculty of Civil Engineering and Geosciences. Terry had a brief stint in industry working for a multi-national consultancy firm as a Numerical Modelling Specialist. With a diverse workload ranging from the dynamic response of foundation systems using ABAQUS to the analysis and design of an irrigation system using EPANET linked to ArcGIS, Terry returned to academia as a Postdoctoral Researcher at Cardiff University in the School of Engineering. Terry worked on advanced constitutive models for cementitious composite materials, with consideration for aggregate interlocking in shear and experimental tests for validating of numerical models. This was followed by the development of a meshless numerical technique for modelling the damage of solids and structures. Terry returned to the University of Sheffield in 2006 and was appointed as a RCUK Research Fellow in 2007 and as a Lecturer in 2012. During this time, Terry worked on higher-order continua, high strain rate response of materials and deformation of porous media. Terry was a Postgraduate Tutor for the Department of Civil and Structural Engineering and in 2012 was appointed as Deputy Faculty Director of Research and Innovation, with a portfolio for overseeing the development and progress of the faculty’s (~700) Postgraduate Research Students and (~400) Postdoctoral Researchers. In September 2013, Terry moved to Adelaide to take up the appointment of Senior Lecturer in the School of Civil, Environmental and Mining Engineering at the University of Adelaide. |
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