Experimental study on effects of lattice expansive agent on cement-casing interfacial bonding quality

Cement-sheath shrinkage after the injection of cement slurry in an annulus has a detrimental effect on cement-casing interface.A lattice expansive agent can make up for the cement-sheath shrinkage,further studies,however,are needed on whether or not the lattice expansive agent can improve the consolidation strength of cement-casing interface.In this paper,we used a self-designed testing device to qualitatively measure the shear-cementing strength between expansive cement and casing,studied consolidation properties with variations in temperature and pressure,and compared the expansive cement with conventional one.In addition,a relationship between microstructures of cement-casing interface and macroscopic mechanical behaviors of interface consolidation was investigated.The results showed that the addition of lattice expansive agent could significantly reduce the consolidation strength of cement-casing interface and increased the elastic modulus of cement sheath,which could weaken the resistance of the cement-casing interface consolidation strength to variations in temperature and pressure.In order to meet the requirement of temperature and pressure conditions encountered in exploitation,it is significant to develop a new expansive agent that can be expansible and of help to improving the interfacial consolidation strength and mechanical properties of cement sheath.