Earth boring – well treating – and oil field chemistry – Earth boring – Contains organic component
Reexamination Certificate
2001-01-26
2004-11-16
Tucker, Philip C. (Department: 1712)
Earth boring, well treating, and oil field chemistry
Earth boring
Contains organic component
C507S138000, C507S110000, C507S111000, C507S112000, C507S113000, C507S114000, C507S115000, C507S119000, C507S124000, C507S209000, C507S211000, C507S212000, C507S213000, C507S214000, C507S215000, C507S216000, C507S217000, C507S224000, C507S230000, C507S261000, C507S265000, C507S925000, C516S104000, C516S105000, C516S106000, C516S107000, C524S275000, C524S276000
Reexamination Certificate
active
06818597
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to stable non-aqueous suspensions of water-soluble polymers and, more particularly, but not by way of limitation to suspensions characterized by a medium of low molecular weight polyethylene glycol and a stabilizer of hydrogenated castor wax or oil.
2. Description of the Related Art
Hydrophilic polymers or gums are widely used in industry. They are used to thicken, suspend or stabilize aqueous systems. These gums can produce gels or act as emulsion stabilizers, flocculants, binders, film formers, lubricants and friction reducers. In many of these applications, the polymers are used to adjust and control the Theological properties of the aqueous system to which they are being added.
For commercial and industrial applications, rapid addition of these gums to water is highly desirable. Doing so, however, often results in the formation of lumps (“fisheyes”) of unhydrated polymer. These lumps are gel-like agglomerates of many individual polymer particles. They are frequently wet on the outside but dry on the inside, and form as a result of the polymer beginning to hydrate before the individual polymer particles are dispersed. Once the outer layer of polymer is hydrated, the lump or fisheye often cannot be dispersed even with vigorous mixing. Removal of these lumps results in significant losses of time, material, and polymer efficiency.
Many treatments and procedures are carried out in industry utilizing high viscosity fluids to accomplish a number of purposes. For example, in the oil industry, high viscosity aqueous well treating fluids are utilized in treatments to increase the recovery of hydrocarbons from subterranean formations such as by creating fractures in the formations, acidizing the formations, etc. High viscosity aqueous fluids are also commonly utilized in well completion procedures. For example, during the completion of a well, a high viscosity aqueous completion fluid having a high density is introduced into the well to maintain hydrostatic pressure on the formation which is higher than the pressure exerted by fluids contained in the formation thereby preventing the formation fluids from flowing into the wellbore.
Heretofore, in preparing high viscosity treating fluids it has been necessary to utilize a number of dry additives that are mixed with water or other aqueous fluid at the job site. A number of disadvantages are inherent in such mixing procedures, particularly when large volumes of treating fluids are prepared. For example, special mixing equipment for mixing the dry additives with water is required and problems such as chemical dusting, uneven mixing, lumping of gels while mixing and extended preparation and mixing time are involved. In addition, the mixing and physical handling of large quantities of dry chemicals require a great deal of manpower, and where continuous mixing is required, the accurate and efficient handling of chemicals such as salts, viscosifying agents, crosslinkers, gel breakers, fluid loss control additives, and surfactants is extremely difficult.
These lumps are particularly problematic in the oil and gas industry where water soluble polymers are used downhole during drilling, workover, completion, stimulation and reservoir flooding operations. These unhydrated lumps, substantially inert to enzymes, chemical breakers and acids, cause a variety of problems including plugging of the well and permeability impairment of the oil-bearing strata. In addition, when polymers are used they are typically added to water in a dilute solution. During this operation fugitive dust is often generated. This dust has a number of potential detrimental effects. Workers preparing the solution can inhale the dust. Some of the polymers that can be suspended in a non-toxic solvent produce dust when handled in a powdered form that may produce a respiratory allergenic response and/or irritation to some individuals. Dust can also drift to areas where it is not intended.
To avoid lump or dust formation and its associated problems, the polymers can be added to the aqueous systems as liquid slurries or suspensions. A number of methods for accomplishing this, and the compositions prepared thereby, are described in the prior art. Unlike the present invention, they often use oil carriers (e.g., mineral, isoparaffin or diesel) to suspend and deliver the polymers to the aqueous systems. Recent regulations by the Environmental Protection Agency limit the amount of oil or grease that can be used in offshore oilfield applications for well treatment fluids. The National Pollutant Discharge Elimination System (NPDES) General Permit issued on Apr. 19, 1999 (Federal Register Vol. 64 No. 74) limits the oil and grease to a daily maximum concentration of 42 mg/l and a monthly average of 29 mg/l when the slurry is diluted to the intended use level with fresh or salt water. Unlike the liquid slurries that contain diesel fuel or other hydrocarbon solvents the suspensions of the present invention contain minimal detectable oil or grease when diluted to the concentration appropriate for use as a well treatment fluid.
U.S. Pat. No. 5,091,448 discloses a suspending medium for a water-soluble polymer. This patent utilizes isopariffin oils as the solvent for a suspension where a styrene/isoprene copolymer is used as the suspension agent. Upon dilution to the intended use concentration in fresh or salt water for a well treatment fluid, the dilution will contain a much higher concentration of oil and grease than is permitted by the above regulations. Furthermore the styrene/isoprene copolymer that is used to stabilize the suspension is insoluble in water miscible solvents such as the polyalkylene glycols of the present invention.
In addition to the oil carrier fluid, many hydrocarbon solvent-based slurries usually contain clay or clay like particulates that act to viscosify and stabilize the non-aqueous slurry. The disadvantages of these carrier systems are that attempts to eliminate the oil, often an undesirable component, result in the substitution of oil by toxic glycol ether. The clay component itself is also often times an undesirable component. This is particularly true in oil and gas field applications where incorporation of the clay into the slurries, which is necessary to keep the polymer in solution, impairs the permeability of the oil or gas bearing strata. This is not unlike the very problem caused by the formation of fisheyes that the oil slurry is supposed to eliminate.
U.S. Pat. No. 4,176,107 discloses liquid polymer compositions and to methods of preparing these compositions which comprise a high molecular weight water-soluble vinyl addition polymer, water, one or more surfactants, and a water-soluble polyalkylene glycol, or water-soluble ethoxylated alcohol, alkylphenol or fatty acid. U.S. Pat. No. 4,453,979 describes the use of water with a high molecular weight blend of water and polyethylene glycol to disperse hydrophilic gums. European Publication 58 017 describes the use of a water and clay based drilling fluid that contains high molecular weight polyethylene glycol. Polyethylene glycols ranging in molecular weight from 1000 to 10,000,000, which are solid at room temperature, are mentioned. U.S. Pat. No. 4,799,962 discloses a particulate water-soluble polymer dispersed in a liquid medium comprised of low molecular weight polyethylene glycol, water, and high molecular weight polyethylene glycol in amounts sufficient to impart stability to the dispersion. U.S. Pat. No. 5,362,312 discloses a carrier for water-soluble polymers that includes polyethylene glycol; one or more viscosified polyol fluid components; and one or more viscosifying polysaccharides. U.S. Pat. No. 5,932,193 discloses a carrier for water-soluble polymers that include polyethylene glycol and a hydrated thickening silica to aid in the stability of fluidized polymer slurry.
U.K. Patent No. 1,363,182 discloses a transparent or translucent gel toothpaste composition comprising polyethylene glycol having molecular weight below
Benchmark Research & Technology, Inc.
Makay Christopher L.
Tucker Philip C.
LandOfFree
Suspensions of water soluble polymers in surfactant free... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Suspensions of water soluble polymers in surfactant free..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Suspensions of water soluble polymers in surfactant free... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3339252