Filtercake removal composition and system
AssigneeSchlumberger Technology Corporation
InventorsLaurent Pirolli, Mehmet Parlar
Life of this patent
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Abstract
A treatment fluid and system are disclosed for cleaning borehole filtercake using the treatment fluid, wherein the filtercake contains reservoir drilling fluid (RDF) solids. 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.
Claims20
A composition, comprising an aqueous mixture comprising:
- a fluoride source at a fluoride concentration from 1.2 to 5 molar;
- a combination of acids effective to provide a pH in the mixture at 25° C. between 1.8 and 5, wherein the acids comprise at least one mineral acid;
- and
- a corrosion inhibitor.
A composition, comprising an aqueous mixture comprising:
- a fluoride source at a fluoride concentration from 1.2 to 5 molar, wherein the fluoride source is selected from the group consisting of ammonium fluoride, ammonium bifluoride, polyvinylammonium fluoride, polyvinylpyridinium fluoride, pyridinium fluoride, imidazolium fluoride, sodium tetrafluoroborate, ammonium tetrafluoroborate, salts of hexafluoroantimony, and mixtures thereof;
- and
- a combination of mineral acid and organic acid effective to provide a pH in the mixture at 25° C. between 1.8 and 5, wherein the mineral acid is selected from HCl, H2SO4 and the combination thereof, wherein the organic acid is selected from formic acid, oxalic acid and the combination thereof.
A well treatment system for cleaning filtercake, comprising
- an aqueous mixture in contact with a filtercake;
- wherein the filtercake comprises drilling fluid solids and calcite;
- wherein the aqueous mixture comprises:
- a fluoride source at a fluoride concentration from 1.2 to 5 molar;
- and
- acid in an amount effective to provide a pH in the mixture at 25° C. between 1.8 and 5.
Dependencies are inferred from the claim text.