New Fiber Technology to Improve Mud Removal

Abstract

As drilling muds evolve to satisfy well requirements, cementing preflush technologies need to change to ensure proper mud removal during cementing jobs. A new component—engineering-designed fiber—was added to a preflush fluid and tested in the laboratory, with promising results. The system was then implemented in Latin America. Obtaining proper mud removal is very important for achieving zonal isolation at cementing jobs. The new technology consists of the addition of an engineering-designed fiber to cementing preflush fluids to significantly improve the removal of nonaqueous fluids from the well during cementing operations. The fibers are compatible with both cement slurries and mud. They work by removing the mud from the casing or formation through two mechanisms: by mechanical cleaning and by attracting the nonaqueous compound of the mud toward itself by hydrophobic-hydrophobic interaction. Two different methodologies were used to evaluate the fiber's ability to enhance the chemical wash and spacer capabilities to clean and demulsificate the nonaqueous mud fluids. The laboratory tests were performed with cementing preflush fluids with and without the fibers. Results indicated that the preflushes with the fibers were able to clean and demulsificate the drilling mud much more efficiently than preflush without the fibers. Indeed, it was possible to optimize the amount of the preflush surfactants and still obtain excellent results. Some successful cases of field implementation of this technology corroborated the laboratory findings. In both cementing jobs, results indicated very efficient mud removal, and, consequently, zonal isolation and well integrity were achieved. The fibers were successfully pumped in a field in Latin America. This innovative technology is able to enhance cement bonding in both casing and formation and reduces potential remedial job costs in a wide range of challenging environments.

Novel Evaluation Method for Flushing Efficiency Based on the Principle of Wall Shear Rate Equality under High Temperature and High Pressure

“…The more organic salt, the more ζ potential drop, resulting in a higher repulsion, 40 leading to a poor flushing effect on mud cake, while the flushing effect of fiber flushing fluid on mud cake is obvious in the early stage of flushing. This may be due to the fibers removing the mud cake from the formation by two mechanisms: mechanical cleaning and attracting nonaqueous compounds from mud cakes, 41 so in the early stage of flushing, flushing efficiency rises quickly. And the emulsified fluid’s flushing efficiency is increased more obviously as the flushing time increases, which is consistent with the rule observed above.…”

Fundamentals of Plug Placement

“…To achieve the objectives, drilling fluid and pre-flushes must be fully removed from the openhole interval and be exchanged fully with cement or any plugging material. The fluid removal process is a function of borehole quality, circulation and displacement efficiency, fluid conditioning and properties of drilling fluids, spacers and washes [1][2][3][4][5][6]. Fluid removal process can be carried out in two main different ways: hydraulically or mechanically.…”