An advanced experimental setup has been developed to study the sealing process of realistic cracks in the cement sheath by flowing CO2 through radial cracks and investigate the effect of flow rate and exposure time for different cement systems. The setup consists of a modular based downscaled section of a wellbore with rock, cement, and casing, and allows for a confining pressure up to 100 bar around the rock. Pressure cycling experiments are performed on the cement sheath by increasing the pressure from inside the casing, causing realistic radial cracks in the cement sheath. When these cracks are connected axially through the sample, they provide a leak path for fluids through the cement. This novel setup allows for a direct exposure of the bottom of a microannuli or radial crack with CO2, and thus measure the flow through the cracks and study the possible healing effects by CO2. The novelty of the setup lies in a movable support of the cement sheath. The first position allows a firm support for the cement upon curing, and the second, at a lower level opens the ports for CO2 exposure and exposes the full bottom surface of the cement sheath. The cracks in the cement sheath were visualized using μ-CT both prior to and after CO2 experiments.
The paper describes in detail the novel laboratory setup and the applicability of the setup.