Schlumberger Technology Corporation

Clara Carelli

Sylvaine Le Roy-Delage

Simon James

Michel Michaux

Bruno Drochon

Loic Regnault De La Mothe

This invention relates to methods for servicing subterranean wells, in particular, fluid compositions and methods for remedial operations during which the fluid compositions are pumped into a wellbore and make contact with well cements placed during primary cementing or previous remedial cementing operations.

Silica composition for servicing subterranean wells

A remedial method for repairing a damaged cement sheath, especially for use in wells in which fluids with a pH lower than 6 are injected, stored or extracted, comprises placing an acid swellable composition adjacent to the cement sheath. In the event of cement-matrix failure, or bonding failure between the cement/casing interface or the cement/borehole-wall interface, the composition may be injected into or adjacent to the cement sheath so that the material swells when contacted by acid gases, including carbon dioxide and hydrogen sulfide. The swelling seals voids in the cement matrix, or along the bonding interfaces, thereby restoring zonal isolation.

Compositions and methods for well completions

Compositions and methods for servicing subterranean wells

A composition for repairing voids or cracks in a cement sheath or plug comprises an aqueous epoxy resin, a hardener, an alkali-swellable material and an aqueous carrier fluid. The particle size of the alkali-swellable material is preferably smaller than 200 nanometers, thereby allowing the composition to penetrate cracks as small as 60 micrometers. A method for repairing voids or cracks in a cement sheath, thereby restoring zonal isolation, comprises preparing the composition, injecting the composition into voids or cracks in a cement sheath or plug and allowing the composition to viscosify and harden.

Aqueous resin compositions and methods for cement repair

Fluid compositions containing a silica-particle suspension with no intrinsic cementitious properties may be pumped into a wellbore. Upon making downhole contact with previously placed well cements from primary-cementing or previous remedial-cementing operations, the silica suspension reacts to form a gel that seals voids, cracks or fissures in the cement sheath. Portland cement is the preferred cement with which the silica-particle suspensions interact downhole.

Compositions containing an alkali swelling polymer and a pH buffer with a pH between 3 and 7 may be used to treat a wellbore. The pH buffer prevents the swelling of the alkali swellable polymer. The compositions may be placed in the wellbore, whereupon they contact another material with pH increasing properties. The pH of the compositions increases, causing the compositions to swell and form a seal. The alkali swelling polymer may be an alkali swelling latex.

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Cambridge, United Kingdom

Clara Carelli