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Encapsulated chemicals for use in controlled time release applications and methods

  • US 6,527,051 B1
  • Filed: 07/12/2002
  • Issued: 03/04/2003
  • Est. Priority Date: 05/05/2000
  • Status: Expired due to Term
First Claim
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1. 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.

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