Patent ID: 7111684

Claim:
A method of using a fluid in a subterranean formation comprising the step of introducing a fluid comprising a hydraulic cement and an invert emulsion of an oleaginous fluid, a nonoleaginous fluid, and an emulsifying surfactant into the formation, wherein the emulsifying surfactant: comprises an ether carboxylic acid; has an LC 50 or EC 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.