Manipulating hydrophilicity of conventional dye molecules for water tracer applications

A method of making a functionalized fluorescent dye, comprising:

• dissolving a water-soluble isothiocyanate-containing fluorescent dye in an aqueous solvent to yield an aqueous dye solution, wherein the water-soluble isothiocyanate-containing fluorescent dye is selected from the group consisting of fluorescein isothiocyanate, Rhodamine B isothiocyanate, or tetramethylrhodamine isothiocyanate, or any isoform thereof;
• dissolving a functional group in water to yield an aqueous functional group solution, wherein the functional group comprises a primary amine and is selected from Group I or Group II, wherein:
• Group I consists of aminomethanesulfonic acid, 2-aminoethanesulfonic acid, 3-amino-1-propanesulfonic acid, 2-aminoethyl(trimethyl)azanium, and 3-aminopropyl(trimethyl)azanium;
• and
• Group II consists of 4-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 2-aminobenzenesulfonic acid, 3-amino-4-hydroxybenzenesulfonic acid, 4-amino-3-hydroxybenzenesulfonic acid, (4-aminophenyl)-trimethylazanium, 6-amino-4-hydroxy-2-naphthalenesulfonic acid, 4-amino-3-hydroxy-1-naphthalenesulfonic acid, 7-aminonaphthalene-1,3-disulfonic acid, 4-aminonaphthalene-1,7-disulfonic acid, 8-amino-1,3,6-naphthalenetrisulfonic acid, and 8-aminopyrene-1,3,6-trisulfonic acid;
• and mixing the aqueous dye solution and the aqueous functional group solution to form the functionalized fluorescent dye, wherein the functionalized fluorescent dye is a reaction product of the water-soluble isothiocyanate-containing dye and the functional group.

A method of tracing fluid flow in a subterranean formation, comprising:

• mixing a functionalized fluorescent tracer and a fluid to yield a tracer fluid, wherein the functionalized fluorescent tracer comprises an isothiocyanate-containing dye functionalized with a functional group comprising a primary amine, wherein:
• the isothiocyanate-containing dye is selected from the group consisting of fluorescein isothiocyanate, Rhodamine B isothiocyanate, or tetramethylrhodamine isothiocyanate, or any isoform thereof;
• and
• the functional group is selected from Group I or Group II, wherein:
• Group I consists of aminomethanesulfonic acid, 2-aminoethanesulfonic acid, 3-amino-1-propanesulfonic acid, 2-aminoethyl(trimethyl)azanium, and 3-aminopropyl(trimethyl)azanium;
• and
• Group II consists of 4-aminobenzenesulfonic acid, 3-aminobenzenesulfonic acid, 2-aminobenzenesulfonic acid, 3-amino-4-hydroxybenzenesulfonic acid, 4-amino-3-hydroxybenzenesulfonic acid, (4-aminophenyl)-trimethylazanium, 6-amino-4-hydroxy-2-naphthalenesulfonic acid, 4-amino-3-hydroxy-1-naphthalenesulfonic acid, 7-aminonaphthalene-1,3-disulfonic acid, 4-aminonaphthalene-1,7-disulfonic acid, 8-amino-1,3,6-naphthalenetrisulfonic acid, and 8-aminopyrene-1,3,6-trisulfonic acid;
• flowing the tracer fluid into a first subterranean formation;
• recovering a sample from the first subterranean formation or a second subterranean formation connected to the first subterranean formation;
• and analyzing the sample for a fluorescent signal.