Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Polymers from only ethylenic monomers or processes of...
Reexamination Certificate
2000-12-08
2002-10-15
Henderson, Christopher (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Polymers from only ethylenic monomers or processes of...
C526S274000, C526S287000
Reexamination Certificate
active
06465587
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to the composition and use of water-soluble or water-dispersible copolymers for oil field applications. Specifically, the present invention relates to polymers containing allyloxy linkage and its functional derivatives for use in oil field applications as fluid additives for drilling and cementing processes.
BACKGROUND OF THE INVENTION
Polymers are used extensively in oil field application as fluid additives for drilling, cementing, gas and oil well fracturing and enhanced—oil-recovery processes. Synthetic, organic, and inorganic polymers, as well as cellulose ethers and guar gum and guar derivatives, are widely used in oil field applications. These materials are also applied in a variety of formation-damage control applications and as dispersing agents.
In the initial drilling operation of an oil or gas well, a drilling fluid, commonly referred as “drilling mud,” is pumped under pressure down to a string of drill pipes through the center of the drilling bit, back through the space or annulus between the outside of the drilling stem and the borehole wall, and finally back to the surface. After a well has been drilled and oil discovered, one or more subterranean, hydrocarborn-producing formations are most often encountered. The well is then completed to obtain the maximum hydrocarbon production from the subterranean producing formations.
Completion of a well refers to the operations performed during the period from drilling-in the pay zone until the time the well is put into production. These operations may include additional drilling-in, placement of downhole hardware, perforation, sand control operations, such as gravel packing, and cleaning out downhole debris. A completion fluid is often defined as a wellbore fluid used to facilitate such operations. The completion fluid's primay function is to control the pressure of the formation fluid by virtue of its specific gravity. The type of operation performed, the bottom hole conditions, and the nature of the formation will dictate other properties, such as viscosity. Use of completion fluids also clean out the drilled borehole. Oil well cement compositions are used in the completion operation to make a permanent, leak proof well for continuous use.
In cementing operations of gas or oil wells, a hydraulic cement is normally mixed with sufficient water to form a pumpable slurry and the slurry is injected into a subterranean zone to be cemented. After placement in the zone, the cement slurry sets into a hard mass. In primary cementing , where a cement slurry is placed in the annulus between a casing or liner and the adjacent earth formations, loss of fluid is a major concern. The formations can result in premature gelation of the cement slurry and bridging of the annulus before proper placement of the slurry. In remedial cementing operations, the control of fluid loss is necessary to achieve the more precise cement slurry placement associated with such operations.
Among all other slurry properties, fluid loss control is one of the critical concerns for cement slurry formulation, especially at high temperature, high pressure (squeeze cement) and salt environments. The main purpose of fluid loss additives is to prevent the dehydration of the cement slurry that can reduce its pumpability as well as affecting its other designed properties. Loss of a significant amount of water from the cement slurry can cause changes in several important job parameters, such as reduced pumping time and increased frictional pressure. Fluid loss additives are used to help prevent water loss from cement slurries to the rock formation as the slurry is pumped into the annulus between the casing and the well bore. This allows displacing the maximum amount of mud, compressive strength development, and bonding between the formation and the casing. In fact, under harsh conditions and due to permeable zones, the slurry can dehydrate quickly and become unpumpable, preventing the extension of slurry into voids and channels, particularly where the annular space between the liner and the open hole is too narrow. Any bridging problem due to high fluid loss would considerably disturb the cement job and affect the integrity of the cement column.
Deep oil wells are generally subjected to high temperature gradients that may range from 40° F. at the surface to 400° F. at the bottom hole. The geology of the well traversed may also contain environments, such as massive salt formations, that can adversely affect the cementing operation.
In general, two types of fluid loss additives are used in the cementing industry. They are classified as low temperature (<230° F.) or high temperature (>230° F.) fluid loss additives (“FLACs”). Synthetic polymers and derivatives of polysaccharides are used in oil field operations from the drilling fluids to the completion fluids as well as in oil well cements.
Partially hydrolyzed polyacrylamide and copolymers of acrylamide, and sodium acrylate, acrylic acid are commonly used in the oil field. Replacing the acrylamide amide hydrogen atoms by other groups reduces the hydrolysis rate and increases viscosity in brines of the polymers. Homopolymers and acrylamide copolymers of 2-acrylamide-2-methylpropanesulfonic acid and salts, N-methylacrylamide, N-isopropylacrylamide , N-butylacrylamide, N,N-dimethylacrylamide, N-hydroxymethylacrylamide, N-hydroxymethylacrylamide and other N-alkylacrylamides have been disclosed for use in polymer flooding. Terpolymers of acrylamide, acrylic acid and 2-hydroxypropylacrylate prevent fluid-loss in drilling mud. Other monomers such as N-vinylpyrrolidinone, vinylchlroide, vinylsulfonate, styrene and styrene sulfonate, maleic anhydride and various vinyl acrylates are also used in copolymerizing acrylamide or acrylic acid for drilling fluid applications. However, these conventional acrylamide copolymers are not hydrolytically and thermally stable at severe operating conditions such as under extreme high temperature and high salt content and a caustic environment.
Examples of polysaccharides derivatives are cellulose ether compounds such as methylcellulose(MC), ethylcellulose(EC), carboxymethylcellulose(CMC), hydroxyethylcellulose(HEC), hydroxypropylcellulose(HPC), carboxymethylhydroxyethylcellulose(CMHEC), ethylhydroxyethylcellulose (EHEC) and hydrophobically modified hydroxyethylcellulose(HMHEC). Examples of guar derivatives are hydroxyethyl guar and hydroxypropyl guar. These cellulose and guar compounds are used in drilling fluids and cementing spacers to suspend solid particles, and in fracturing fluids to suspend sand and other proppants and to prevent fluid loss in these applications. However, due to its polysaccharide structure and acetal linkage, these naturally derived materials are subject to hydrolysis at temperature above 350° F. and high levels of salt in deep well conditions.
DESCRIPTION OF RELATED ART
U.S. Pat. Nos. 4,895,663, 4,895,664 and 4,944,885 (Chen) disclose using copolymers of acrylic acid and sodium 3-allyloxy 2-hydroxypropanesulfonate (AHPS) as a scale inhibitor and deposti control agent for cooling water treatment.
Water soluble copolymers containing 2-acrylamido-2-methylpropanesulfonic acid (AMPSR) are described in U.S. Pat. Nos. 3,898,037; 4,641,793 and 4,717,542. The copolymers are used for water treatment in general.
U.S. Pat. No. 5,032,995 (Matz et al.) discloses an amphoteric copolymers containing nonionic, anionic and cationic monomers for use as deflocculants in drilling mud.
U.S. Pat. No. 5,169,537 (Chen) discloses using terpolymers of acrylic acid, 3-alloxy-2-hydroxypropanesulfonate and sodium 3-allyloxy 2-hydroxypropanesulfonate as a scale inhibitor.
U.S. Pat. No. 5,403,821 (Shioji) describes water soluble anionic copolymers containing carboxylic acid and allyl ether sulfonate moieties, having an average molecular weight of 1,000 to 50,000 as drilling additives for stabilizing muddy water.
None of the aforementioned prior art describes the specific copolymers of the present invention for oil field applications, espe
Bair Keith A.
Chen Fu
Loo De-Kai
Melbouci Mohand
Young Teng-Shau
Edwards David
Henderson Christopher
Hercules Incorporated
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