Abstract: The invention provides solids-free, viscous fluids (pills) for use in various well workover and completion operations including as displacement spacer pills, standard fluid loss control pills, post gravel pack in-screen pills, perforation sealing, and the like. The pills comprise a viscous solution of a polyethylene glycol having a molecular weight of 1,000 to 8,000,000 in an aqueous liquid comprising a solution of one or more soluble bromide salts having a density sufficient to provide the desired hydrostatic pressure at the location of use of the fluid in a well. The minimum concentration of the polyethylene glycol in the pill varies with the average molecular weight as follows: MW=1,000 to 10,000=100 ppb; MW=10,001 to 100,000=75 ppb; MW=100,001 to 250,000=50 ppb; MW=250,001 to 500,000=10 ppb; MW=500,001 to 8,000,000=5 ppb.

Abstract: Emulsifiable oil, suitable for use as oil phase in oil-based drilling fluids, having one or more ketones with a flashpoint of at least 55.degree. C., in particular oligoketones obtainable by co-oligomerization of carbon monoxide and olefins.