Compositions and methods for sealing off flow channels in contact with set cement

A method of treating a subterranean formation, the method comprising:

• providing to the subterranean formation a composition comprising:
• a maleic anhydride copolymer comprising:
• first repeat units I and II:
• wherein each R1 is independently selected from the group consisting of —H, —O(C1-C5) alkyl, and —(C1-C5) alkyl, and each R2 is independently selected from the group consisting of —H, —O(C1-C5) alkyl, and —(C1-C5) alkyl;
• and
• and at least one second repeat unit selected from the group consisting of repeat units III and IV:
• wherein each R3 is independently selected from the group consisting of —OH and —O−M1, each M1 is independently selected from the group consisting of an alkali metal, an alkaline earth metal, an ammonium ion, and a quaternary ammonium ion, and each R4 is independently selected from the group consisting of —NH2 and —OM1;
• an amine crosslinker;
• and
• a gelling agent comprising at least one of:
• a calcium chelating agent;
• a calcium precipitating agent;
• a pH buffer;
• an agent reactive with hydroxide;
• an acid generating agent;
• and
• crosslinking the maleic anhydride copolymer of the composition with the amine crosslinker of the composition to form a sealant, wherein the gelling agent promotes formation of the sealant in contact with set cement.

A method of treating a subterranean formation, the method comprising:

• providing, to the subterranean formation comprising a cemented zone comprising set cement, an aqueous solution comprising a gelling agent to yield a pretreated subterranean formation, wherein gelling agent comprises at least one of:
• a calcium chelating agent;
• a calcium precipitating agent;
• a pH buffer;
• an agent reactive with hydroxide;
• and
• an acid generating agent;
• providing to the pretreated subterranean formation a composition comprising:
• a maleic anhydride copolymer comprising:
• first repeat units I and II:
• wherein each R1 is independently selected from the group consisting of —H, —O(C1-C5) alkyl, and —(C1-C5) alkyl, and each R2 is independently selected from the group consisting of —H, —O(C1-C5) alkyl, and —(C1-C5) alkyl;
• and
• at least one second repeat unit selected from the group consisting of repeat units III and IV:
• wherein each R3 is independently selected from the group consisting of —OH and —O−M1, each M1 is independently selected from the group consisting of an alkali metal, an alkaline earth metal, an ammonium ion, and a quaternary ammonium ion, and each R4 is independently selected from the group consisting of —NH2 and —OM1;
• and
• an amine crosslinker;
• and
• crosslinking the maleic anhydride copolymer of the composition with the amine crosslinker of the composition to form a sealant, wherein the gelling agent promotes formation of the sealant in contact with set cement.