Evaluation of Cement Systems for Oil and Gas-Well Zonal Isolation in a Full-Scale Annular Geometry

TLDR

Loss of zonal isolation in wells arises from cement mechanical failure or microannulus formation, with sealant behavior governed by rock properties and boundary conditions. The study performed large‑scale laboratory tests of cement sheaths in annular geometries under simulated downhole stresses to assess failure modes as functions of cement properties, loading, and boundary conditions. The experimental data validated an analytical model that predicts cement‑sheath failure.

Abstract

Summary Loss of zonal isolation in a wellbore can be caused by mechanical failure of the cement or by development of a microannulus. However, behavior of the sealant is driven by specific boundary conditions such as rock properties. Large-scale laboratory testing of the cement sheath in an annular geometry and a confined situation was performed to simulate various downhole stress conditions and evaluate the behavior of several sealants. Failure modes of the cement sheath were determined as a function of cement mechanical properties, loading parameters, and boundary conditions. Results were used to validate an analytical model that predicts cement-sheath failure.