Viscous Fluid Mud Displacement Technique
Authors: Ritter J.E. , McDaniel G.W. 
Published: December 2007

American Institute of Mining, Metallurgical and Petroleum Engineers, Inc.
This paper was prepared for the SPE Rocky Mountain Regional Meeting to be held in Casper, Wyo., May 22–23, 1967. Permission to copy is restricted to an abstract of not more than 300 words. Illustrations may not be copies. The abstract should contain conspicuous acknowledgement of where and by whom the paper is presented. Publication elsewhere after publication in the JOURNAL OF PETROLEUM TECHNOLOGY or the SOCIETY OF PETROLEUM ENGINEERS JOURNAL is usually granted upon request to the Editor of the appropriate journal provided agreement to give proper credit is made.
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Abstract
This discussion presents a novel cementing preflush that aids in obtaining more successful primary and remedial cement jobs. The preflush utilizes the viscous fluid displacement principle to remove drilling mud. Viscous fluid mud removal technique promotes better cement jobs over the complete range of flow, rates and downhole configurations. This newly developed fluid system has the unique properties of low fluid loss and flow friction pressure; in addition, it can be weighted, it contains additives to remove oil film from the casing, and it is compatible with all types of muds presently being used.
Laboratory tests and more than two hundred field operations indicate that this system removes mud more effectively than conventional preflush materials. The success ratio for cement plugback, whip-stock plugs, cementing liners, multiple string completions, and squeeze cementing operations has been substantially increased by using this new approach to drilling mud removal.

Introduction
A successful primary cement job requires removal of substantially all of the drilling mud from the borehole where cement is to be placed. Drilling mud retention can result in channeling, cement contamination, poor bonding to casing and/or formation, and generally an unsatisfactory cement job.
Placement concept using turbulent flow and contact time has been developed to a high degree, and up to this time has proved to be one of the most successful deterrents to cement contamination. Turbulent flow, however, is not always practical or desirable for all phases of cementing operations. The requirements of contact time, friction pressure, pump rates and expensive ingredients can often place substantial restrictions on the effective use of turbulent flow to achieve desired results.
In an effort to improve materials and techniques available for cementing, research studies by Byron Jackson Inc. laboratories have produced a method that removes mud effectively over a wide range of flow rates and down-hole conditions. This method uses a material known as MUD SWEEP preflush.

DEVELOPMENT AND CHARACTERISTICS OF MUD SWEEP PREFLUSH METHOD
Many materials have been developed to improve mud removal efficiency during primary cementing operations. Water, acids and chemical mixtures have been used as preflushes to thin, react with and disperse mud solids. Slurries of inert solids have been utilized for the physical actions of abrasion and viscosity reduction in mud removal.