Patent Number: 7,712,536

Title: Filtercake removal

Abstract: A treatment fluid and a method are disclosed for cleaning borehole filtercake using the treatment fluid, wherein the filtercake contains reservoir drilling fluid (RDF) solids. The method includes pumping the treatment fluid downhole in contact with the filtercake to be removed to establish a differential pressure between the treatment fluid and the formation adjacent the filtercake, and evenly propagating treatment of the filtercake during the differential pressure period to delay breakthrough by the treatment fluid for a period from 1 to 12 hours. The treatment fluid comprises a fluoride source providing a 1.2 to 5 molar fluoride concentration, and another acid or combination of acids to provide a pH between 1.8 and 5. The treatment fluid is balanced for a dissolving power high enough to have significant dissolution of the filtercake, but low enough for even propagation to avoid premature leak-off.

Inventors: Pirolli; Laurent (Houston, TX), Parlar; Mehmet (Sugar Land, TX)

Assignee: Schlumberger Technology Corporation

International Classification: E21B 21/00 (20060101)

Expiration Date: 5/11/12018