The purpose of this experimental study is to investigate the impact of physical and chemical mud contaminations on cement-formation bond strength for different types of formations. Physical contamination occurs when drilling fluids (mud) dries on the surface of the formation forming a mud cake while chemical contamination on the other hand occurs when drilling fluids which is still in the liquid form interacts chemically with the cement during a cementing job. Wellbore cement has been used to provide well integrity through zonal isolation in oil & gas wells and geothermal wells. It has also used to provide mechanical support for the casing and protect the casing from corrosive fluids. Failure of cement could be caused by several factors ranging from poor cementing, failure to completely displace the drilling fluids to failure due to casing. A failed cement job could result in creation of cracks/micro annulus through which formation fluids could migrate to the surface which could lead to sustained casing pressure, contamination of fresh water aquifer and blow out in some cases. To achieve proper cementing, the drilling fluid should be completely displaced by the cement slurry. However, this is hard to achieve in practice, some mud is usually left on the wellbore which ends up contaminating the cement. This study focuses on the impact of contamination on the shear bond strength and the changes in the mineralogy of the cement at the cement-formation interface.

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