Polymer delivery in well treatment applications

Abstract

This invention relates to compositions and methods for treating subterranean formations, in particular, oilfield stimulation compositions and methods using water-in-water polymer emulsions to uniformly dissolve a rheologically active polymer, such as a thickener or friction reducer, in the treatment fluid. The emulsions have a low viscosity and are easily pumped for mixing into a treatment fluid, where upon dilution with an aqueous medium, the polymer is easily hydrated without forming fish-eyes. The partitioning agent in the water-in-water emulsion does not generally affect the rheology of the treatment fluid. The invention also relates to further processing of the emulsion by wet grinding, high shear mixing and/or heating to enhance the hydration rate in the preparation of the well treatment fluid.

1 . A method of preparing a polymer concentrate for use in a fluid for treating a subterranean formation penetrated by a well bore, comprising the steps of:
 a. admixing a rheological polymer, a partitioning agent and a first aqueous medium to form a heterogeneous mixture comprising a dispersed polymer-rich phase and a partitioning agent-rich phase; and   b. mechanically, thermally, or mechanically and thermally processing the heterogeneous mixture to increase a rate of hydration of the polymer upon dilution.   
     
     
         2 . The method of  claim 1  wherein the processing step comprises heating the heterogeneous mixture to a temperature above 60° C. 
     
     
         3 . The method of  claim 1  wherein the processing step comprises wet grinding the heterogeneous mixture. 
     
     
         4 . The method of  claim 1  wherein the processing step comprises high shear mixing of the heterogeneous mixture. 
     
     
         5 . The method of  claim 1  wherein the processing step comprises ultrasonification of the heterogeneous mixture. 
     
     
         6 . A polymer concentrate prepared by the method of  claim 1 . 
     
     
         7 . The polymer concentrate prepared by the method of  claim 1  wherein the heterogeneous mixture comprises from 5 to 20 percent of the rheological polymer, by weight of the water in the mixture, and a weight ratio of the partitioning agent to the thickening polymer is from 1:4 to 4:1. 
     
     
         8 . A method of preparing a well treatment fluid comprising mixing the polymer concentrate of  claim 6  with a second aqueous medium to disperse the polymer in the resulting mixture. 
     
     
         9 . The method of  claim 8  wherein the resulting mixture is completely dispersed within 90 seconds. 
     
     
         10 . A method of preparing a fluid for treating a subterranean formation penetrated by a well bore comprising:
 a. providing an apparatus comprising:   i. a solids feeder for supplying rheological polymer solids to a first mixing zone receiving a metered stream of a partitioning agent and a first aqueous stream to form a water-in-water emulsion stream;   ii. a dilution zone for mixing the water-in-water emulsion stream with a second aqueous stream to mutually dissolve the rheological polymer- and the partitioning agent and form a rheologically modified aqueous stream;   iii. a line for supplying the rheologically modified aqueous stream to a stirred header tank; and,   iv. additive pumps for supplying one or more well treatment fluid additives to the header tank;   b. forming a treatment fluid using the apparatus.   
     
     
         11 . The method of  claim 10 , wherein the apparatus further comprises a prehydration processing unit for the water-in-water emulsion stream in advance of the dilution zone. 
     
     
         12 . The method of  claim 10 , wherein the apparatus further comprises a wet grinder for the water-in-water emulsion stream in advance of the dilution zone. 
     
     
         13 . The method of  claim 10 , wherein the apparatus further comprises a high shear mixer for the water-in-water emulsion stream in advance of the dilution zone. 
     
     
         14 . The method of  claim 10 , wherein the apparatus further comprises a heater for heating the water-in-water emulsion stream in advance of the dilution zone. 
     
     
         15 . The method of  claim 10 , wherein the apparatus further comprises an ultrasonic generator for ultrasonification of the water-in-water emulsion stream in advance of the dilution zone. 
     
     
         16 . The method of  claim 14 , wherein the water-in-water emulsion stream is heated to a temperature above 60° C. 
     
     
         17 . The method of  claim 10 , wherein the water-in-water emulsion stream is exposed to high shear mixing. 
     
     
         18 . The method of  claim 10 , wherein the water-in-water emulsion stream comprises a heterogeneous mixture comprising from 5 to 20 percent of the rheological polymer, by weight of the water in the mixture, and a weight ratio of the partitioning agent to the thickening polymer is from 1:4 to 4:1. 
     
     
         19 . The method of  claim 10  wherein the treatment fluid is provided within 90 seconds. 
     
     
         20 . A method for supplying a hydrated polymer solution, comprising:
 a. supplying rheological polymer solids, a partitioning agent and a first aqueous stream to a mixing zone to form a water-in-water emulsion stream;   b. optionally mechanically, thermally or mechanically and thermally processing the water-in-water emulsion stream to improve hydratability of the rheological polymer;   c. supplying the water-in-water emulsion stream with a second aqueous stream to a dilution zone to form a rheologically modified aqueous stream.