Completion and workover fluids

Workover fluids are used during the time that a well is taken off-line and some mechanical operation is being performed on the well. The role of the fluid is to control the downhole pressure while the mechanical operation is being performed. Workover fluids contain brines that are similar to those described above and also may or may not contain organic polymers. 

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Siace 1980 over 1000 patents have been issued for drilling fluid systems and materials ia the United States alone. A 1994 listing of products from 117 supphers offers ca 3000 trade names (6). This array of trade name products actually represents less than 100 separate chemical types that may be purchased iadividuaHy or as a blend. Moreover, some of these materials are for completion and workover fluids. These differ from drilling fluids ia that completion fluids are used after the well has been drilled and prior to the initia tion of production whereas workover fluids are used duting remedial work on older wells. 

Testing of Drilling Fluids 652. Composition and Applications 664. Oil-Based Mud Systems 675. Environmental Aspects 682. Typical Calculations in Mud Engineering 687. Solids Control 691. Mud-Related Hole Problems 695. Completion and Workover Fluids 701. 

Solids content Ideal requirements no solids in completion and workover fluids. Practical recommendation Solids smaller than two microns can be tolerated as well as the bridging solids. The bridging solids should be (1) greater than one-half of the average fracture diameter (2) readily flushed from the hole acid or solvent soluble. 

The polymers used for completion and workover fluids may be either natural or synthetic polymers. Guar gum is a natural polymer that swells on contact with water and thus provides viscosity and filtration control it is used in concentrations of 1 to 3 Ib/bbl. Guar gum forms a filter cake that may create... 

Oil-Base Systems. Oil-base completion and workover fluids contain oil as the continuous phase. Their application is limited by their density to formations with... 

Foam Systems. The preparation, composition, and maintenance of foam completion and workover fluids is similar to that of foam drilling fluids. The advantage of foam is the combination of low density and high lifting capacity at moderate flow rates. The use of foam as a completion fluid can be justified by. 

Anonymous. World oil s 1991 guide to drilling, completion and workover fluids. World Oil, 212(6) 75-112, June 1991. 

G. T. Forrest. Drilling, completion, and workover fluid comprising ground peanut hulls. Patent EP 873379,1998. 

Hydroxypropyl Guar 1 36 3 C N,S. N,S, R Drilling fluids, spacers, completion and workover fluids, friction reducer in fracturing, fracturing and lost circulation (crosslinked HPG gels), fluid loss additive in drilling spacer and fracturing fluids... 

Uses Emulsifier, thickener, binder, stabilizer in foods fluid loss control agent in drilling muds, completion and workover fluids... 

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