The importance of free water control upon slurry design and performance in deviated and horizontal wellbores has been recognized and documented. The literature contains suggested procedural modifications to API Spec 10, Free Water Test, to better approximate bottom-hole cementing conditions. Suggestions include (1) pre-conditioning the slurry in a pressurized consistometer at bottom-hole conditions, (2) conducting the Free Water Test at various angles from a vertical position, (3) utilization of a new settling tube for evaluating the degree of segregation of the cement particles (density segregation). Little has been written on the interaction of temperature, pressure and increased slurry surface area due to deviated conditions on free water and cement slurry stability.
This paper presents laboratory results of a comparison between the current API Free Water procedure, modified API Free Water procedure and modified British Petroleum Settling Tube Test. The comparison includes differences in both free water and slurry stability at elevated temperatures and pressure at various angles. From this research, results highlight possible unsupported optimism concerning cement slurry performance in deviated and horizontal applications when based on current API Free Water Test procedure.