Subterranean fluids are provided that have improved environmental
characteristics, and more particularly, subterranean fluids are provided
that include a hydraulic cement in an invert emulsion. Methods of using
such fluids in subterranean operations also are provided. An example of a
method is a method of using a fluid in a subterranean formation. An
example of a composition is a fluid comprising a hydraulic cement and an
invert emulsion of an oleaginous fluid, a nonoleaginous fluid, and an
emulsifying surfactant, wherein the emulsifying surfactant: has an
LC.sub.50 or EC.sub.50 that is greater than about 10 milligrams/liter
with respect to Skeletonema costatum, Acartia tonsa, Scopthalmus maximus
(juvenile), or Corophium volutator; and demonstrates a biodegradability
of: greater than about 70% biodegradation in 28 days when tested
according to method OECD 301A or 301E; or greater than about 60%
biodegradation in 28 days when tested according to method OECD 301B,
301C, 301F, or 306.