Study on adhering sand on casing to improve cementing strength

To improve cementing strength, the interface strength between sand adhering casing and cement sheath was tested, and a calculating model of sand adhering casing cement strength was established. It also analyzed the influence on the cementing strength by the ratio of joint compound thickness to sand particle radius, sand adhering density, jointing compound shear strength and cement sheath compressive strength. The study results showed that when the ratio of jointing compound thickness and sand particle radius is 1, the cementing strength is maximum, and the cementing strength varied with the ratio of jointing compound thickness and sand particle radius. Within the critical sand adhering density, the cementing strength increase linearly with the increase of sand adhering density and jointing compound shear strength. When the ratio of jointing compound thickness and sand particle radius is 1, the sand adhering density is 80 percent, the amount of additive tetraethylenepentamine in jointing compound is 13 percent and the cement compressive strength is greater than 1.5 times of jointing compound shear strength, the maximal cementing strength of sand adhering casing can be achieved.