Numerical Modeling Aspects of Fluid-driven Interface Debonding after Wellbore Plugging and Abandonment

Document Type

Conference Proceeding

Publication Date

1-1-2019

Abstract

Deepwater wells are plugged and abandoned at the onset of uneconomic production. Moreover, strict government policies are constantly imposed on offshore operators in an effort to prevent abandoned wellbore leaks. After a well is plugged, integrity loss via fluid-driven interfacial debonding has been identified as the primary mechanism for wellbore leakages. In this paper, modeling aspects employed to investigate fluid-driven interface debonding along the cross section of a plugged and abandoned system are introduced. 2-D Semi-circular bend (SCB) test models were developed for bi-material specimens consisting of rock-cement, cement-casing and casing-plug interfaces. Consequently, cohesive zone traction separation laws (TSL) are developed considering appropriate constitutive material and interfacial properties. An approach to utilize fully coupled, 3-D global and sub finite element models is introduced to associate field and near wellbore scale events. Hydrocarbon production is modeled as a fatigue mechanism, while fluid leakage is driven by long-term reservoir re-pressurization at the casing shoe, after abandonment. Simulation results quantify debonded fracture geometry in the near wellbore region and in the plug/cement sheath. The proposed approach is set up for experimental validation and applicable for wellbore leakage detection, and long term performance assessment of industry acceptable plugging materials.

Publication Source (Journal or Book title)

53rd U.S. Rock Mechanics/Geomechanics Symposium

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