Extreme well conditions, especially higher temperatures, are becoming more commonplace. This in turn requires improvements to our wellbore fluids. This study focuses on the development of a new spacer system designed especially for those wells exhibiting extremely high temperatures.
A critical characteristic of this spacer is that the surface rheology must not be overly excessive as to maintain a pumpable fluid; however, the downhole rheology must not diminish due to thermal thinning or degradation of the gelling agent so the spacer remains stable. To ensure the spacer suitably meets these requirements, both ambient and elevated temperature rheologies are analyzed and reported. The stability of the spacer related to settling of solid particulates is examined by conducting dynamic settling tests at 300°F and above.
In this study, spacer compositions and densities were adjusted to examine effects on rheology and stability of the solids within the system at elevated temperatures. Results show that conventional spacer systems are not adequate at elevated temperatures especially above 300°F. The newly developed spacer system shows much improved results from dynamic settling tests even up to 400°F. Also, the surface rheology of the new spacer system is not significantly different from that of the conventional system.
The innovative spacer system within this paper was shown to add significant value to extreme cementing operations. In addition, by comparing the results between these two testing methods, the dynamic settling test should be considered as an alternate procedure for testing the stability of spacers under high temperature conditions.