A composition and method for improving the fluid efficiency of many
oilfield treatments is given. The composition is a solid additive, in a
viscosified fluid, in a size range small enough that it enters formation
pores; it optionally bridges there to form an internal filter cake, and
then decomposes to provide a breaker for the viscosifying system for the
fluid. Examples of suitable additives include waxes, polyesters,
polycarbonates, polyacetals, polymelamines, polyvinyl chlorides, and
polyvinyl acetates. Degradation of the additive may be accelerated or
delayed.