The effect of cellulose nanocrystal (CNC) on the water permeability of early aged oil well cement

Abstract

Well cementing is one of the most crucial steps in any well completion. Oil well cement paste is employed to fill the annulus between the casing string and the well bore. However, since the cementing process takes place at the end of the drilling process, a satisfying and acceptable job may not be performed. When pumped inside the annular space between the casing and the ground formation, oil well cement has to isolate and protect the casing from any kind of damage. Therefore, the durability of the cement paste utilized in oil well cementing is extremely important. In the absence of aggregates, concerns arise both in the short term performance including fluid loss (filtration) and flowability, and in the long term as in shrinkage cracking and permeability of the cementitious slurry. Nowadays, various commercial additives are produced and employed in oil well cements to address the durability issues. In this study, cellulose nanocrystal (CNC) is utilized as a replenishable and non-toxic additive to oil well cement paste, in order to reduce the permeability of the system. Early aged hollow cylindrical specimens dosed with CNC were tested by using a pressurized permeability cell. Furthermore, the water permeability of the specimens were evaluated using Darcy’s law for laminar flow. The results were then compared to the water permeability of neat oil well cement paste with no additive.