Intermediate Casing Of all the casing run this one normally takes the worst beating. Prolonged drilling can and often will damage it. Corrosion is common as such a string will often cover salt zones. The justification for this string is to cover many of the problem zone that are encountered  in the top sections of the hole such as lost circulation and water flows. Such zone need to be isolated as the drilling fluid weight may have to be raise in the deeper section of the hole. It will also be use too support the completion and any other string that may be ran later. The casing point " where the shoe is to be set" must be in a firm and solid formation as the secondary well control equipment will be installed on top. A leak off or integrity test will be carried out to test the shoe.  Should there be any leak the shoe must be re-cemented by squeezing it off as the casing must withstand any drilling fluid raise in weight or kick from the formation. Often run to depths of 5 or 6000 ft. and would normally cemented back to surface. A shoe, float collar and sometimes a cement diverter will be used. This string will often be the largest cement job and could be done in two stages. "The cement diverter " is a ported  tool the same size of the casing that is opened and closed with plugs and darts. The first section will be cemented. The cement is pumped down the casing and out of the shoe into the annulus. As this is often a two stage job a water spacer will be pumped ahead of the cement and should end up just around the outside of the cement diverter once the tail cement is put  in place with the wiper plug. An opening dart will then be dropped and landed on the sleeve of the cement diverter. Pressure will be applied to push the sleeve into the open position. The well will then be circulated from the ports and the hole conditioned ready for the next stage. The second stage will then be pumped and a closing plug will be pumped and bumped.