Methods and systems for preparing surfactant polyelectrolyte complexes for use in subterranean formations

1. A method comprising:

providing a first solution comprising at least one surfactant and a second solution comprising at least one polyelectrolyte, wherein the surfactant and the polyelectrolyte carry opposite charges;

using a stop-flow mixing apparatus at a well site to mix the first and second solutions to form one or more surfactant-polyelectrolyte complexes;

using a low-dose pumping apparatus at the well site to transfer the one or more surfactant-polyelectrolyte complexes from the stop-flow mixing apparatus to a blending apparatus at the well site, wherein the low-dose pumping apparatus is capable of transferring a fluid to the blending apparatus at a rate of less than 1 gallon per thousand gallons of fluid mixed in the blending apparatus;

using the blending apparatus to mix the one or more surfactant-polyelectrolyte complexes with an aqueous base fluid to form a treatment fluid; and

introducing the treatment fluid into a well bore penetrating at least a portion of a subterranean formation at the well site.

2. The method of claim 1 wherein the treatment fluid is a fracturing fluid, and the fracturing fluid is introduced into the well bore at a pressure sufficient to create or enhance one or more fractures within the subterranean formation.

3. The method of claim 1 wherein:

the stop-flow mixing apparatus comprises an observation cell into which the first and second solutions flow after mixing, and a measurement device configured to monitor the contents of the observation cell, and

the method further comprises using the measurement device to confirm the presence of one or more surfactant-polyelectrolyte complexes in the observation cell.

4. The method of claim 3 wherein the measurement device comprises a UV-visible spectrometer.

5. The method of claim 1 further comprising using the blending apparatus to mix a plurality of proppant particulates with the one or more surfactant-polyelectrolyte complexes and the aqueous base fluid to form the treatment fluid.

6. The method of claim 1 wherein the blending apparatus comprises a pump and blending system, and the treatment fluid is introduced into the well bore using the pump and blending system.

7. The method of claim 1 wherein the surfactant comprises at least one surfactant selected from the group consisting of sodium, potassium, and ammonium salts of long chain alkyl sulfonates and alkyl aryl sulfonates; dialkyl sodium sulfosuccinates; alkyl sulfates; alkyl sulfonates; alkoxylated sulfates; ethoxylated alcohols; polyglucosides; ethoxylated long-chain alcohols; alkyl ammonium bromides; hydroxysultaines; and any combination thereof.

8. The method of claim 1 wherein the polyelectrolyte comprises at least one polyelectrolyte selected from the group consisting of polyacrylate, poly(styrenesulfonate), poly(styrenesulfonic acid), poly(2-acrylamido-2-methyl-1-propane sulfonic acid), sulfonated poly(ether ether ketone), sulfonated lignin, poly(ethylenesulfonic acid), poly(methacryloxyethylsulfonic acid), poly(acrylic acid), poly(methacrylic acid), HV-sodium alginate, sodium alginate, sodium hyaluronate, heparin sulfate, cellulose sulfate, kappa carrageenan, pentasodium tripolyphosphate, low-esterified pectin(polygalacturonic acid), polyglutamic acid, carboxymethylcellulose, chondroitin sulfate-6, chondroitin sulfate-4, collagen, polyalkylene imines, polyethylene polyamine, polypropylene polyamine, polyvinylamine, polyallyamine, poly(vinylalchhol/vinylamine), chitosan, polylysine, polymyxin, spermine hydrochloride, protamine sulfate, poly(methylene-co-guanidine)hydrochloride, polythethylenimine-ethoxylated, polyethylenimine-ex-ichlorhydrin modified, and any combination thereof.

9. The method of claim 1 wherein the polyelectrolyte comprises poly(styrenesulfonic acid).

10. The method of claim 1 wherein the polyelectrolytes have a molecular weight of from about 100 Daltons to about 300,000 Daltons.

11. The method of claim 1 wherein the surfactant comprises one or more alkyl aryl sulfonates.

12. The method of claim 1 wherein the treatment fluid further comprises one or more salts.

13. The method of claim 1 wherein the treatment fluid further comprises one or more additional surfactants.

14. A system for preparing surfactant-polyelectrolyte complexes at a well site comprising:

a pump and blender system disposed at a surface of a well bore penetrating at least a portion of a subterranean formation;

a stop-flow mixing apparatus having at least a first inlet for receiving a solution comprising a surfactant, a second inlet for receiving a solution comprising an electrolyte, and an outlet through which a solution comprising one or more surfactant-polyelectrolyte complexes flows out of the stop-flow mixing apparatus;

a low-dose pumping apparatus coupled between the outlet of the stop-flow mixing apparatus and an inlet of the pump and blender system, wherein the low-dose pumping apparatus is capable of transferring a fluid to the blending apparatus at a rate of less than 1 gallon per thousand gallons of fluid mixed in the blending apparatus; and

a base fluid source coupled to an inlet of the pump and blender system.

15. The system of claim 14 further comprising a proppant source coupled to an inlet of the pump and blender system.

16. The system of claim 14 wherein the stop-flow mixing apparatus further comprises an observation cell disposed between the outlet and the first and second inlets through which a solution mixed by the stop-flow mixing apparatus flows, and a measurement device configured to monitor the contents of the observation cell.

17. The system of claim 16 wherein the measurement device comprises a UV-visible spectrometer.

18. A method comprising:

providing a first solution comprising at least one surfactant and a second solution comprising at least one polyelectrolyte, wherein the surfactant and the polyelectrolyte carry opposite charges;

using a stop-flow mixing apparatus at a well site to mix the first and second solutions to form one or more surfactant-polyelectrolyte complexes, the stop-flow mixing apparatus having an observation cell into which the first and second solutions flow after mixing, and a measurement device configured to monitor the contents of the observation cell;

using the measurement device at the well site to confirm the presence of one or more surfactant-polyelectrolyte complexes in the observation cell;

using a low-dose pumping apparatus at the well site to transfer the one or more surfactant-polyelectrolyte complexes from the stop-flow mixing apparatus to a blending apparatus at the well site, wherein the low-dose pumping apparatus is capable of transferring a fluid to the blending apparatus at a rate of less than 1 gallon per thousand gallons of fluid mixed in the blending apparatus;

using the blending apparatus to mix the one or more surfactant-polyelectrolyte complexes with an aqueous base fluid to form a fracturing fluid; and

introducing the fracturing fluid into a well bore penetrating at least a portion of a subterranean formation at the well site at a pressure sufficient to create or enhance one or more fractures within the subterranean formation.

19. The method of claim 18 further comprising using the blending apparatus to mix a plurality of proppant particulates with the one or more surfactant-polyelectrolyte complexes and the aqueous base fluid to form the fracturing fluid.

20. The method of claim 18 wherein the measurement device comprises a UV-visible spectrometer.