Application of an Innovative Spacer System Designed for Optimal Performance in HTHP Wells

Abstract

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.

Evaluation of a water-based spacer fluid with additives for mud removal in well cementing operations

“…The following properties are essential for each spacer. Compatibility with drilling fluid and cement slurry Controlled viscosity for creating a plug flow to move drilling fluids out of the well Pumpability with cementing equipment Ability to carry cuttings ([ 12 ]; foroushan et al, 2020) Capability to wash the mud cake from the formation (Richardson et al, 2013) Conversion of the formation surface from oil-wet to water-wet (in the case of using Oil Based Mud (OBM)) ([ 13 ]; Hunt et al, 1982) Cost-effectiveness …”

Identifying applicability viscoelastic systems in the context of improving well casing processe

“…These problems are made worse by the difficulty of cleaning the wellbore and the need to ensure that the drilling fluid is completely displaced by the cement mixture. Due to the unsatisfactory rheological properties of the spacer systems used, which provide an unsuitable flow profile and flow regime in the annulus, their effectiveness is often limited [2].…”

Weighted Spacer Design for Elevated Temperature Conditions to Mitigate Barite Settling by Identifying Suitable Viscosifier

“…Spacer is comprised of water (as base fluid), heavy weight additive and spacer blend package (contains rheological modifiers). A gelling agent to modify the viscosity, a weighting agent to vary the density, a surfactant package to clean the drilling fluid and water-wet contact surface, and an antifoaming agent to minimize air entrainment are known as the composition of an aqueous spacer system [4]. The density gel strength and viscosity of spacer must be less than cement slurry and greater that drilling fluid.…”