Viscoelastic surfactant formulations and use in subterranean formations
A viscoelastic surfactant formulation may include a zwitterionic surfactant with a general formula (I): where A is a C or SO, E 1 is a linear or branched, saturated or unsaturated hydrocarbon chain having 1 to 4 carbon atoms, R 1 and R 2 are selected from alkyl groups of from 1 to about 4 carbon atoms, and R 3 is a linear or branched, saturated or unsaturated alkyl chain having less than 22 carbon atoms or is —(CH 2 ) n NHC(O)—R 4 , where R 4 is a linear or branched, saturated or unsaturated alkyl chain having less than 22 carbon atoms and n ranges from 1 to 6; a synergistic co-surfactant containing a primary, secondary, or tertiary amine; amido group; amine oxide; or combinations thereof; and at least one miscible solvent.
1 . A viscoelastic surfactant formulation, comprising:
a zwitterionic surfactant with a general formula (I):
where A is a C or SO, E 1 is a linear or branched, saturated or unsaturated hydrocarbon chain having 1 to 4 carbon atoms, R 1 and R 2 are selected from alkyl groups of from 1 to about 4 carbon atoms, and R 3 is a linear or branched, saturated or unsaturated alkyl chain having less than 22 carbon atoms or is —(CH 2 ) n NHC(O)—R 4 , where R 4 is a linear or branched, saturated or unsaturated alkyl chain having less than 22 carbon atoms and n ranges from 1 to 6;
a synergistic co-surfactant containing a primary, secondary, or tertiary amine; amido group; amine oxide; or combinations thereof, wherein the co-surfactant is present in an amount higher than 9.5 wt % and less than 22 wt % based on a total weight of the surfactants; and
at least one miscible solvent,
wherein a viscosity of the viscoelastic surfactant formulation is maintained within a range having a lower limit of more than 85 cP at temperatures ranging from 175° F. to 250° F., wherein the viscosity is measured using a Grace M5600 Viscometer at a shear rate of 100 s −1 .
2 . The viscoelastic surfactant formulation of claim 1 , wherein R 4 has 16-20 carbon atoms.
3 . The viscoelastic surfactant formulation of claim 2 , wherein R 4 has 18 carbon atoms.
4 . The viscoelastic surfactant formulation of claim 1 , wherein the synergistic co-surfactant has the formula:
where R 1 is a branched or linear, saturated or unsaturated alkyl chain with 9 to 18 carbon atoms or an alkyl aryl bearing a linear or branched alkyl chain ranging from 4 to 16 carbon atoms; or is R 0 —C(O)— where R 0 is a branched or linear, saturated or unsaturated alkyl chains with 9 to 18 carbon atoms or an alkyl aryl bearing a linear or branched alkyl chain ranging from 4 to 16 carbon atoms; and A 1 and A 2 are independently selected from H, —CH 2 CH 2 OH or —(CH 2 CH 2 —O—) n H or —(CH 2 ) x —NH 2 , where n ranges from 1 to 4, and x ranges from 1 to 4.
5 . The viscoelastic surfactant formulation of claim 1 , wherein the co-surfactant is diethanol oleyl amide, oleylamine, tallow alkyl amine ethoxylate, or tallow di-amine ethoxylate.
6 . The viscoelastic surfactant formulation of claim 1 , wherein the co-surfactant is present in an amount of between 9.9 wt % to 10.1 wt % based on the total weight of the surfactants.
7 . The viscoelastic surfactant formulation of claim 1 , wherein the zwitterionic surfactant is present in amount ranging from 5 wt % to 60 wt % by weight of the viscoelastic surfactant formulation.
8 . The viscoelastic surfactant formulation of claim 1 , wherein the at least one miscible solvent is water, secondary alcohols, glycols, glycol ethers, acetone, glycerol, or combinations thereof.
9 . The viscoelastic surfactant formulation of claim 1 , wherein the zwitterionic surfactant is present in amount ranging from 0.5 wt % to 5 wt % by weight of the viscoelastic surfactant formulation.
10 . The viscoelastic surfactant formulation of claim 1 , wherein the viscosity of the viscoelastic surfactant formulation is maintained within a range having an upper limit up to 170 cP at temperatures ranging from 175° F. to 250° F.
11 . A well treatment fluid comprising:
an aqueous fluid;
an acid;
a zwitterionic surfactant with a general formula (I):
where A is a C or SO, E 1 is a linear or branched, saturated or unsaturated hydrocarbon chain having 1 to 4 carbon atoms, R 1 and R 2 are selected from alkyl groups of from 1 to about 4 carbon atoms, and R 3 is a linear or branched, saturated or unsaturated alkyl chain having less than 22 carbon atoms or is —(CH 2 ) n NHC(O)—R 4 , where R 4 is a linear or branched, saturated or unsaturated alkyl chain having less than 22 carbon atoms and n ranges from 1 to 6; and
a synergistic co-surfactant containing a primary, secondary, or tertiary amine; amido group; amine oxide; or combinations thereof, wherein the co-surfactant is present in an amount higher than 9.5 wt % and less than 22 wt % based on a total weight of the surfactants,
wherein the zwitterionic surfactant and synergistic co-surfactant are added to the well treatment fluid as a viscoelastic surfactant formulation further comprising at least one miscible solvent, wherein a viscosity of the viscoelastic surfactant formulation is maintained within a range having a lower limit of more than 85 cP at temperatures ranging from 175° F. to 250° F. wherein the viscosity is measured using a Grace M5600 Viscometer at a shear rate of 100 s −1 .
12 . The well treatment fluid of claim 11 , wherein the viscoelastic surfactant formulation has a viscosity greater than 85 cP at a temperature of at least 225° F.
13 . The well treatment fluid of claim 11 , wherein the zwitterionic surfactant and synergistic co-surfactant are present in a combined amount ranging from 0.5 to 5 wt % of the treatment fluid.
14 . The well treatment fluid of claim 11 , wherein the synergistic co-surfactant has the formula:
where R 1 is a branched or linear, saturated or unsaturated alkyl chain with 9 to 18 carbon atoms or an alkyl aryl bearing a linear or branched alkyl chain ranging from 4 to 16 carbon atoms; or is R 0 —C(O)— where R 0 is a branched or linear, saturated or unsaturated alkyl chains with 9 to 18 carbon atoms or an alkyl aryl bearing a linear or branched alkyl chain ranging from 4 to 16 carbon atoms; and A 1 and A 2 are independently selected from H, —CH 2 CH 2 OH or —(CH 2 CH 2 —O—) n H or —(CH 2 ) x —NH 2 , where n ranges from 1 to 4, and x ranges from 1 to 4.
15 . The well treatment fluid of claim 11 , wherein the co-surfactant is diethanol oleyl amide, oleylamine, tallow alkyl amine ethoxylate, or tallow di-amine ethoxylate.
16 . The well treatment fluid of claim 11 , wherein the co-surfactant is present in an amount of between 9.9 wt % to 10.1 wt % based on the total weight of the surfactants.
17 . A method of treating a formation, comprising:
injecting the well treatment fluid of claim 11 into a formation.
18 . The method of claim 17 , wherein the well treatment fluid is injected during an acidizing operation.