Common well cements and the mechanism of cement-formation bonding

This article reviews the common well cements and describes the basic nature of the cement-formation bond in zonal isolation and its effects on the mechanical and hydraulic performance. The cements are Classes G and H Portland well cements. The cement-formation interface bonding mechanism is a combination of the mechanical indentation of the cement hydrates that interlock to the formation surface and the chemical reactions that occur between the cement slurry and constituents of the rock grains. Mechanical indentation occurs as the hydration products epitaxially grow at the formation surface. The degree to which each of these processes accounts for the formation of the bond is unknown. Here we provide a review of well cement and cement-formation bonds and a discussion of the possible factors that are proposed to influence the microstructural, chemical, and mineralogical properties at the cement-formation interface. In addition, we present some findings about how these factors affect the mechanical and hydraulic performance of the cement-formation bond in zonal isolation.