Cementing of the casing is critical in well completion and is highly dependent on wellbore cleaning of the drilling mud prior to cement placement. Typically, a water-based intermediate cleaning fluid called spacer is pumped downhole ahead of the cement to carefully displace the drilling mud and clean the well. However, effective well cleaning is challenging and continues to be a problem. Currently, there is no universal spacer formulation that can clean all types of mud. Moreover, maintaining a constant viscosity of the aqueous-based cleaning fluid is extremely difficult to achieve, as it is exposed to a wide temperature disparity from surface to bottom hole circulating temperature (BHCT), creating a challenging scenario to design an effective spacer even with today's displacement softwares.

This paper presents a highly unique and cost-effective wellbore cleaning fluid, which provides superior wellbore cleaning and efficient mud displacement. Unlike many spacer fluids, this new cleaning fluid utilizes a novel material that is not very susceptible to temperature and thus provides a relatively constant viscosity from surface to BHCT, indicating homogeneous and stable suspension of particulates in the fluid at different temperatures. It preserves and extends pumpability, which is useful during prolonged job delays on location or extended residence time inside the wellbore. The innovative material has exceptional physical properties for tightly holding the carrier water while simultaneously upholding the viscosity of the fluid at elevated temperature, translating in a more efficient and realistic fluid removal simulation.

The key novelty and invaluable contribution of this research to the field is the application of a unique material with an exceptional physical property of sustaining flat viscosity of the wellbore cleaning fluid from surface to BHCT, which is highly desirable. To the best of our knowledge, this new material has not been exploited for non-settable spacer fluid applications.

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