Microhardness Measurements on Chemically and Mechanically Altered Well Bore Cements

Abstract:

The focus of this research was to investigate the effect of water to cement ratio (w/c), water salinity and additives on its microstructure and mechanical properties. Microhardness test was utilized to evaluate the change in cement mechanical properties. Nanovea^® Nano/Micro-Indenter is based on the standards for instrumented indentation, ASTM E2546 and ISO 14577. The indenter tip with a known geometry (Vickers Diamond) is driven into the cement sample to be tested, by applying an increasing normal load. Analysis of indentation test results on the cement samples showed: (a) a decrease of both Young’s modulus and hardness after increasing w/c and/or water salinity, and (b) additives have a significant impact on both hardness and Yong’s modulus.

The most likely mechanism behind all changes in cement structure and its properties is that the difference of cement components resulted in a change of the cement matrix porosity and grain size. Scanning Electron Microscopy (SEM) imaging also indicated changes in cement, as can be observed from micrographs of control and altered cement taken at the same magnification. This unique research provides an important insight to the understanding of mechanical properties of cement