Title

Microstructure and micromechanics of wellbore cements under compression and thermal loading

Document Type

Conference Proceeding

Publication Date

1-1-2015

Abstract

The primary objective of wellbore cement is to provide zonal isolation as a hydraulic barrier and ensure controlled fluid flow from the reservoir to the production facilities. During the lifetime of a well, cement has to cope with variations in stress, temperature and pressure. Frequent and dramatic oscillations of stress, temperature and pressure can cause damage within cement and its interfaces as well, which may leads to damage of cement sheath integrity, resulting in loss of zonal isolation and sustained casing pressure. This study investigated the effect of the mechanical compression and cyclic temperature variations on the mechanical properties of the cement, such as hardness and Young's modulus; furthermore, this study included evaluation of cement slurries typically used in the deep drilling in the Gulf of Mexico US for cement compression. Micro indentation tests were conducted on cement samples to evaluate the changes in mechanical properties with various cement designs. Analysis of indentation results on the cement samples showed: (a) a decrease in hardness and Young's modulus right after compression while an overall increase one month after compression; (b) cyclic temperature variations significantly decreased neat cement hardness and Young's modulus, but this effect varied when cement had other chemical additives; (c) hardness and Young's modulus decreased after increasing water to cement ratio. Based on these results we are further investigating how to optimize cement slurries for field application that are characterized by thermal oscillation and under confined compression of cement sheath.

Publication Source (Journal or Book title)

49th US Rock Mechanics / Geomechanics Symposium 2015

First Page

552

Last Page

561

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