The borehole ballooning effect may be considered during high-density cement slurry pumping. A more detailed understanding of the phenomenon can contribute to a better analysis of flow-in / flow-out measurements while cementing.

Due to the changes in equivalent circulating density and hydrostatic pressure, wellbore ballooning is the phenomena where the formation takes drilling fluid when pumping and then the injected fluid flows back into the well when the pumps are shut down. The interpretations of wellbore ballooning are divided into three categories:

1. Elastic deformation of the borehole walls;
2. opening and closure of fractures;
3. compressibility and thermal expansion of the drilling fluid and cement. Several studies have been published in the past decades for quantifying the ballooning volume caused by one of the aforementioned process while drilling. However up to date no work has been done to study these phenomena when performing the cement job.

The main objective of proposed thesis is to define the possible causes of the borehole ballooning during cementing, study the effect of the ballooning on cement top, cement bonding and estimate the return fluid volume once the cement job has been done.