Abstract
Primary well cementing is performed to isolate annular space behind casing, protect casing from corrosive downhole fluids, holding casing in place and maintain well integrity. To fulfill these requirements, the desired barrier material should long last in the wellbore during the life cycle of well. Some limitations have been observed and reported by operating companies and scientist have been stated and documented during many years. Hence, efforts are made to find alternative materials to Ordinary Portland Cement (OPC) or enhancing the performance of oil well cement.
In this study, the rheological behavior and short-term mechanical properties of a commercial expansive oil well cement has been studied and compared with neat class G cement as the base case. The experiments were performed at equal conditions for the both cements. These tests include characterization of rheology profiles, static fluid-loss, and impact of pressure on pumping time of the cement slurries. In addition, mechanical properties of the cement systems after hardening were studied by testing uniaxial compressive strength, non-destructive sonic strength development, indirect tensile strength (Brazilian test) and flexibility of samples up to 14 days.
Our results in laboratory scale showed that using industrial chemicals as additive improved the rheological properties of cement by controlling the fluid-loss and retarding thickening time of the slurry. In case of the mechanical properties of the expansive cement, tensile strength of the specimens did not change and lower ductility was noticed comparing to the neat class G cement, even though uniaxial compressive strength of the barrier material was increased.
