Summary
The annular cement sheath is one of the most-important well-barrier elements, both during production and after well abandonment. It is, however, well-known that repeated pressure and temperature variations in the wellbore during production and injection can have a detrimental effect on the integrity of the cement sheath.
A unique laboratory setup with downscaled samples of rock, cement, and pipe has been designed to study cement-sheath-failure mechanisms during thermal cycling, such as debonding and crack formation. With this setup, it is possible to set the cement under pressure and subsequently expose the cement to temperature cycling under pressure as well. Cement integrity before and after thermal cycling is visualized in three-dimensional by X-ray computed tomography (CT), which enables quantification of and differentiation between debonding toward the casing, debonding toward the formation, and cracks formed inside the cement sheath itself.
This paper describes in detail the development and functionality of this laboratory setup along with the experimental procedure. Several examples to demonstrate the applicability of the setup, such as tests with different types of casing surfaces and different rocks, are also shown.
