Patent ID: 6527051
Filing Date: 2003-03-04
Classification: B01J,C04B,C09K,Y10S,Y10T

Abstract:
An improved method of removing drilling fluid filter cake in a well bore penetrating a subterranean producing formation comprising the steps of:(a) preparing a cleaning composition comprising water and a controlled time release encapsulated particulate solid acid or an acid forming chemical, said particulate solid acid or acid forming chemical having a first coating of a hydrophobic film forming material or a sparingly soluble material which provides a dry shield on said acid or chemical and provides a delay in the release of said acid or chemical for a time period of less than about 2 hours, and a second coating of a porous cross-linked hydrophilic polymer which prevents the substantial dissolution of the resulting encapsulated acid or chemical for a selected period of time; (b) placing said cleaning composition in said well bore adjacent to said subterranean formation to be cleaned; and (c) allowing said cleaning composition to react with and remove said filter cake and the like.