METHOD FOR TEMPORARY PRODUCTIVE RESERVOIR INTERVAL PLUGGING Russian patent published in 2007 - IPC E21B43/32 

FIELD: oil and gas industry, particularly temporary plugging of productive reservoir intervals, killing of wells having abnormally low reservoir pressure during well repair and to separate gas and oil intervals during plugging of multizone reservoir under combined development thereof and lost-circulation zone isolation during well drilling.

SUBSTANCE: method involves creating porous packer by injection of two compositions, namely polymeric solution and plugging liquid in well, wherein polymeric composition includes water-soluble polymer, cross-linking agent, foaming agent and water. The water-soluble polymer is polyacrylamide and/or carboxymethylcellulose and/or styromaleate. Above components are taken in the following amounts (% by weight): water-soluble polymer - 0.1-10, cross-linking agent, namely Cr₂(SO₄)₃, Cr(C₂H₃O₂)₃, CrCl₃, - 0.05-10, foaming agent, namely sodium alkyl benzene sulfonate, Neonol, sulfanole, Neftenol, - 0.1-5.0, remainder is water. The composition may additionally have gaseous agent, namely nitrogen, carbon dioxide, natural gas so that expansion ratio of the composition is 1.28-3.0. The plugging liquid is invert emulsion based on hydrocarbon phase, namely oil and/or hydrocarbon solvent, aqueous phase, namely water and/or salt solution of CaCl₂ or NaCl₂ or MgCl₂ or BaCl₂ in emulsifier presence. Above components are taken in the following amounts (% by weight) - hydrocarbon phase 15-18, aqueous phase - 72-82, emulsifier is 3-10. The composition is serially injected in well and followed by well killing liquid injection. Extreme dynamic shearing stress of polymeric solution is 25-110 Pa. Static shearing stress of porous packer is 50-410 Pa. Composition is formed on surface with cementing agent usage. The compositions are injected in laminar flow regime. Packer porosity is 10-50%. Plugging liquid volume is 2-4 m₃, density thereof exceeds that of well killing liquid. The injection is carried out in two stages and time interval between the stages is not less than 30 min. Injection pressure is not higher than proof-test pressure. In winter unfreezing liquid is added to polymeric composition. Packer density is changed by heaving agent, namely metal salt CaCl₂, KCl, MgCl₂, BaCl₂ solution addition. Packer is also used to create elastico-viscous screen to protect against mechanical impurities entering from exploitable reservoir or to isolate reservoirs during simultaneous or serial reservoir exploitation. Packer is retained for predetermined time interval.

EFFECT: possibility to maintain collecting properties of reservoir during current well repair and well workover.

20 cl, 5 ex, 3 tbl