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

TLDR

Zonal isolation loss in wells can result from cement mechanical failure or microannulus formation, with sealant behavior governed by boundary conditions such as rock properties. Large‑scale laboratory tests of cement sheaths in annular geometry under confined conditions simulated various well scenarios to evaluate sealant behavior under downhole stress. The study identified cement sheath failure modes as functions of cement mechanical properties, loading parameters, and boundary conditions, and used these results to validate an analytical model that predicts cement sheath failure.

Abstract

Abstract In a wellbore, loss of zonal isolation can be caused by the mechanical failure of the cement or by the generation of a microannulus. However, the behavior of the sealant is driven by the specific boundary conditions like the rock properties. Large-scale laboratory testing of the cement sheath in an annular geometry and in a confined situation was performed to simulate various well conditions and to evaluate the behavior of several sealants under simulated downhole stress conditions. The failure modes of the cement sheath were determined as a function of the cement mechanical properties, loading parameters, and boundary conditions. The results were used to validate an analytical model that predicts cement sheath failure.