Nonaqueous fluids (NAF) are widely used in offshore Guyana drilling operations. NAF are incompatible with all slurries because they affect properties such as thickening-time and compressive strength, in an unpredictable manner. Spacers are used to clean the mud on the borehole wall by water wetting; thus, reducing the mud on the wall risk by separating the mud from the cement in the casing and annulus to help acquire good cement bonding. Solids in the spacer increases the cleaning efficiency of mud on the wall. An engineered scrubbing fiber, presented in this paper, is added in the cement spacer to enhance its cleaning property by providing a scrubbing effect. This fiber removes the mud from the casing or formation by attracting the nonaqueous compound toward itself by a hydrophobic-hydrophobic interaction. The scrubbing fiber is applicable in all cement spacer applications and can be tailored to the job conditions once within its operating limits of density, temperature, and concentration. The cement spacer, with the engineered scrubbing fibers, is designed by following a sequence of laboratory tests, gathering the well and conventional cement spacer information. Laboratory testing was performed for the implementation of the scrubbing fiber in the cement spacer to confirm its performance with drilling fluid used in the Guyana operations. From comparative laboratory results, the engineered fibers at 1.5 lbm/bbl concentration in the cement spacer did not have any significant effect on cement spacer or cement slurry when compared with a cement spacer containing no fibers. The fibers, together with mutual solvent and surfactants, have been evaluated for mud removal efficiency and showed their ability to increase the cleaning efficiency as much as 93% mud removal. The best method to add the fibers to the cement spacer was also analyzed and was successfully performed during the mixing of the cement spacer on the rig and by being delivered to the well. The major benefits to the client by using engineered scrubbing fibers in the cement spacer are to improve cement bonding once in place (Eulberg and Hudson 2017) and in the case of plug cementing and liner operation, to reduce the risk of set cement in the drillpipe (Edwards et al. 2013) during pulling out of hole operations. The improved mud removal achieved by using engineered scrubbing fiber in the spacer has proven successful through laboratory tests, including cleaning efficiency. Field application of the fibers in the spacer increases the chances for successful zonal isolation and meeting a client's objectives.

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