Earth boring – well treating – and oil field chemistry – Well treating – Contains organic component
Reexamination Certificate
2002-04-03
2004-09-07
Tucker, Philip C. (Department: 1712)
Earth boring, well treating, and oil field chemistry
Well treating
Contains organic component
C507S225000, C507S226000, C507S922000, C166S308200, C166S308300
Reexamination Certificate
active
06787506
ABSTRACT:
TECHNICAL FIELD
This invention concerns a method of using water-soluble dispersion polymers to reduce friction resulting from turbulent flow in an aqueous fracturing fluid as it is pumped at high velocity through oil well casings or tubing strings.
BACKGROUND OF THE INVENTION
In a well stimulation operation, a large amount of fracturing fluid is pumped down a well bore hole under high pressure and at high flow rates to a depth of about 500 meters to 6 kilometers or more, causing the rock formation surrounding the well bore to fracture. The pressure is then relieved allowing the oil to seep through the fractures in to the well bore where it is pumped to the surface.
The turbulence produced as the fracturing fluid is pumped through the pipe under pressure results in the production of friction, thereby increasing the amount of energy required to move the amount of fluid at the same speed.
Generally, high molecular weight linear polymers are used to alter the rheological properties of the fluid so that the turbulent flow is minimized, thereby preventing consequent energy loss in the fluid as it is pumped through the pipe. A good friction reducer will cause a large decrease in friction at small concentrations, will be inexpensive, and will have high shear, temperature and pressure stability.
Despite having suitable molecular weights, standard latex emulsion polymers, where polymer solids are dispersed in a hydrocarbon solvent and stabilized with surfactants, are of limited utility due to the environmental unfriendliness of hydrocarbons and surfactants in case of spill or discharge on land or on an off shore platform and the potential fire hazards associated with the hydrocarbon solvent. The latex polymers also must be inverted prior to use, which involves the use of additional surfactants.
Dry polymers are conventionally used in these applications due to the high polymer concentration available in this form as compared to solution polymers. However, dry polymers are difficult to dissolve, requiring special equipment as well as significant energy and water consumption to assure adequate makedown of the dry polymer into an active dilute form. In remote drilling locations equipment, energy and water are often in short supply and require significant financial input to secure.
The use of copolymers of acrylamide with various cationic and anionic monomers for reducing friction loss in well fracturing processes are disclosed in U.S. Pat. No. 3,254,719. Preferred polymer compositions are those wherein 20-40 percent of the amide groups have been hydrolyzed using alkali.
The use of copolymers of acrylamide with quaternary salts of dimethylaminoethyl methacrylamide or dimethylaminopropyl methacrylamide for reducing friction loss in well fracturing processes are disclosed in U.S. Pat. No. 4,152,274.
A method of using dispersion polymers in combination with nitrogen-containing corrosion inhibitors to prevent corrosion in a pipeline in contact with crude oil emulsions being transported under turbulent flow conditions is disclosed in U.S. Pat. No. 5,939,362.
Neither of U.S. Pat. Nos. 3,254,719 and 4,154,274 addresses the handling and safety problems associated with the use of dry polymers or polymers containing surfactants and hydrocarbon solvents, while U.S. Pat. No. 5,939,362 does not address the use of polymers in aqueous fracturing fluids. Accordingly, there is an ongoing need to develop friction reducing agents for use in fracturing fluids that solve the handling, safety and environmental issues discussed above.
SUMMARY OF THE INVENTION
This invention is directed to a method of reducing friction resulting from turbulent flow in an aqueous fracturing fluid in an oil field fracturing process comprising adding to the aqueous fracturing fluid an effective friction-reducing amount of one or more water-soluble dispersion polymers, wherein the dispersion polymer is composed of from about 5 to about 95 mole percent of one or more nonionic monomers and from about 95 to about 5 mole percent of one or more cationic or anionic monomers.
The polymers of this invention are aqueous-based dispersions that contain neither organic solvents or surfactants, resulting in an environmentally friendly treatment system that addresses the environmental concerns of petroleum producing industries.
DETAILED DESCRIPTION OF THE INVENTION
Definitions of Terms
“Anionic monomer” means a monomer as defined herein which possesses a negative charge. Representative anionic monomers include (meth)acrylic acid, and it's salts, including, but not limited to acrylic acid, sodium acrylate, ammonium acrylate, methacrylic acid, sodium methacrylate, and ammonium methacrylate; 2-acrylamido-2-methylpropanesulfonic acid (AMPS) and its sodium salt; vinyl sulfonic acid and its salts including sodium vinyl sulfonate; styrene sulfonic acid and its salts; maleic acid and it's salts, including, but not limited to the sodium salt and ammonium salt; sulfopropyl acrylate or methacrylate or other water-soluble forms of these or other polymerisable carboxylic or sulphonic acids; sulfomethylated acrylamide; allyl sulfonate; itaconic acid, acrylamidomethylbutanoic acid; fumaric acid; vinylphosphonic acid; allylphosphonic acid, phosphonomethylated acrylamide, and the like.
“Cationic Monomer” means a monomer as defined herein which possesses a positive charge. Representative cationic monomers include dialkylaminoalkyl acrylates and methacrylates and their quaternary or acid salts, including, but not limited to, dimethylaminoethyl acrylate methyl chloride quaternary salt, dimethylaminoethyl acrylate methyl sulfate quaternary salt, dimethyaminoethyl acrylate benzyl chloride quaternary salt, dimethylaminoethyl acrylate sulfuric acid salt, dimethylaminoethyl acrylate hydrochloric acid salt, diethylaminoethyl acrylate, methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl chloride quaternary salt, dimethylaminoethyl methacrylate methyl sulfate quaternary salt, dimethylaminoethyl methacrylate benzyl chloride quaternary salt, dimethylaminoethyl methacrylate sulfuric acid salt, dimethylaminoethyl methacrylate hydrochloric acid salt, dimethylaminoethyl methacryloyl hydrochloric acid salt, dialkylaminoalkylacrylamides or methacrylamides and their quaternary or acid salts such as acrylamidopropyltrimethylammonium chloride, dimethylaminopropyl acrylamide methyl sulfate quaternary salt, dimethylaminopropyl acrylamide sulfuric acid salt, dimethylaminopropyl acrylamide hydrochloric acid salt, methacrylamidopropyltrimethylammonium chloride, dimethylaminopropyl methacrylamide methyl sulfate quaternary salt, dimethylaminopropyl methacrylamide sulfuric acid salt, dimethylaminopropyl methacrylamide hydrochloric acid salt, diethylaminoethylacrylate, diethylaminoethylmethacrylate and diallyldialkylammonium halides such as diallyldiethylammonium chloride and diallyldimethyl ammonium chloride.
“Dispersion polymer” means a water-soluble polymer dispersed in an aqueous continuous phase containing one or more inorganic salts. Representative examples of dispersion polymerization of water-soluble polymers in an aqueous continuous phase can be found in U.S. Pat. Nos. 5,605,970; 5,837,776; 5,985,992; 4,929,655; 5,006,590; 5,597,859; 5,597,858; 6,171,505 and 6,265,477 and in European Patent Nos. 183,466; 657,478; and 630,909 and PCT Application Number US01/10867, incorporated herein by reference.
Dispersion polymers are prepared by combining water, one or more inorganic salts, one or more water-soluble monomers, any polymerization additives such as chelants, pH buffers or chain transfer agents, and a water-soluble stabilizer polymer. In addition, further processing, structure modifying and/or stabilizing agents may be added to the mixture. All or a portion of this mixture is charged to a reactor equipped with a mixer, thermocouple, nitrogen purging tube, and water condenser. The solution is mixed vigorously, heated to the desired temperature, and then a water-soluble initiator is added. The solution is purged with nitrogen while maintaining temperature and
Blair Cecil C.
Chang Kin-Tai
Gerken Kurt S.
Treybig Duane S.
Breininger Thomas M.
Martin Michael B.
Nalco Energy Services L.P.
Tucker Philip C.
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