Classifications

• • C—CHEMISTRY; METALLURGY
  • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
  • C09K—MATERIALS FOR MISCELLANEOUS APPLICATIONS, NOT PROVIDED FOR ELSEWHERE
  • C09K8/00—Compositions for drilling of boreholes or wells; Compositions for treating boreholes or wells, e.g. for completion or for remedial operations
  • C09K8/42—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells
  • C09K8/46—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement
  • C09K8/467—Compositions for cementing, e.g. for cementing casings into boreholes; Compositions for plugging, e.g. for killing wells containing inorganic binders, e.g. Portland cement containing additives for specific purposes
  • C09K8/487—Fluid loss control additives; Additives for reducing or preventing circulation loss
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B24/00—Use of organic materials as active ingredients for mortars, concrete or artificial stone, e.g. plasticisers
  • C04B24/24—Macromolecular compounds
  • C04B24/26—Macromolecular compounds obtained by reactions only involving carbon-to-carbon unsaturated bonds
  • C04B24/2623—Polyvinylalcohols; Polyvinylacetates
• • C—CHEMISTRY; METALLURGY
  • C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
  • C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
  • C04B28/00—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements
  • C04B28/02—Compositions of mortars, concrete or artificial stone, containing inorganic binders or the reaction product of an inorganic and an organic binder, e.g. polycarboxylate cements containing hydraulic cements other than calcium sulfates
  • C04B28/04—Portland cements
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F18/00—Homopolymers and copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an acyloxy radical of a saturated carboxylic acid, of carbonic acid or of a haloformic acid
  • C08F18/02—Esters of monocarboxylic acids
  • C08F18/04—Vinyl esters
  • C08F18/08—Vinyl acetate
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F2/00—Processes of polymerisation
  • C08F2/04—Polymerisation in solution
  • C08F2/06—Organic solvent
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F216/00—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical
  • C08F216/02—Copolymers of compounds having one or more unsaturated aliphatic radicals, each having only one carbon-to-carbon double bond, and at least one being terminated by an alcohol, ether, aldehydo, ketonic, acetal or ketal radical by an alcohol radical
  • C08F216/04—Acyclic compounds
  • C08F216/06—Polyvinyl alcohol ; Vinyl alcohol
• • C—CHEMISTRY; METALLURGY
  • C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
  • C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
  • C08F8/00—Chemical modification by after-treatment
  • C08F8/12—Hydrolysis

Definitions

• the present invention relates to polyvinyl alcohol-based polymers, and their uses and manufacturing methods.
• Polymers having a polyvinyl alcohol (PVA) skeleton (hereinafter collectively referred to as "polyvinyl alcohol polymers”, “vinyl alcohol polymers”, or simply “PVA”) have hydrophilic properties. It is known as a synthetic resin with many properties, and a variety of applications that take advantage of its properties are being developed.
• Oil well cement in the form of a slurry mixed with water and other additives, is filled into the gap between the steel pipe (casing) and the wellbore to secure and protect it. Therefore, it is preferable that the cement slurry has high fluidity so that it can be easily filled.
• the phenomenon in which water content is lost from the cement slurry due to the high pressure and underground heat during injection is generally referred to as "fluid loss.” Fluid loss reduces the fluidity of the cement slurry, resulting in poor cementing and poor hardening of the cement after hardening. Therefore, fluid loss reducing agents are usually added to oil well cement slurries.
• Patent Documents 1 and 2 describe PVA used as a fluid loss reducing agent.
• Patent Document 3 discloses a saponified product of a copolymer of a vinyl ester monomer and a polyfunctional monomer, which has a degree of saponification of 70 to 95 mol%, and a viscosity average degree of polymerization.
• An additive for oil well cement is disclosed that contains a vinyl alcohol-based polymer having a polyvinyl alcohol of 1,000 to 10,000.
• Patent Document 4 describes homopolymers made of vinyl ester monomers, copolymers of vinyl ester monomers and monofunctional monomers other than vinyl esters, and copolymers of vinyl ester monomers and polyfunctional monomers.
• a polyvinyl alcohol-based polymer obtained by saponification of a copolymer with a vinyl ester monomer, a monofunctional monomer other than vinyl ester, and a polyfunctional monomer, , a 0.4% by mass aqueous solution of a polyvinyl alcohol polymer is characterized in that the particle diameter at a cumulative frequency of 50% in the particle size distribution measured by dynamic light scattering at a temperature of 25°C is 50 nm or more. There is.
• the present invention can provide the following.
• a polyvinyl alcohol polymer obtained by saponification of a copolymer of a vinyl ester monomer and a polyfunctional monomer containing two or more polymerizable unsaturated bonds in the molecule has an average degree of polymerization of 3000 to 6000 as measured by the method described in JIS K 6726:1994, A polyvinyl alcohol polymer characterized by a reaction rate of polymerizable unsaturated bonds of a polyfunctional monomer of 55 to 75%.
• the number of polymerizable unsaturated sites in the polyfunctional monomer may be 2 to 5. In one embodiment, the amount of polymerizable unsaturated sites relative to the total of vinyl alcohol units and vinyl acetate units in the polyvinyl alcohol-based polymer may be 0.05 to 0.30 mol%. In one embodiment, the amount of polyfunctional monomer units relative to the total of vinyl alcohol units and vinyl acetate units in the polyvinyl alcohol-based polymer may be 0.05 to 0.30 mol%.
• the viscosity of the 4% aqueous solution of the polyvinyl alcohol polymer may be 40 to 200 mPa.s, and the degree of saponification may be 75 to 99 mol%.
• the passage rate of a 1.0 mass% aqueous solution of the polyvinyl alcohol polymer through a filter with an opening of 45 ⁇ m is 95 mass% or more in terms of solid content, and the 1.0 mass% aqueous solution of the polyvinyl alcohol polymer
• the passage rate through a membrane filter with a pore size of 0.45 ⁇ m may be 5% by mass or less in terms of solid content.
• the particle size of the polyvinyl alcohol polymer may be 20% by mass or less of 75 ⁇ m or less, and 10% by mass or less of 500 ⁇ m or more.
• an additive for oil well cement containing the above polyvinyl alcohol polymer can also be provided.
• a method for producing the above-mentioned polyvinyl alcohol polymer can also be provided. A plurality of these embodiments may be arbitrarily combined as long as they do not contradict each other.
• the polyvinyl alcohol polymer according to the present invention can suppress the formation of solvent-insoluble deposits during the manufacturing process, and exhibits an excellent fluid loss reduction effect even under severe high temperature or high pressure environments.
• polymer refers to the definition of polymer by the International Union of Pure and Applied Chemistry (IUPAC) Polymer Nomenclature Committee, that is, "a polymer molecule is a molecule with a large relative molecular mass; A substance having a structure composed of many repetitions of units derived substantially or conceptually from a small molecule.'''
• the polyvinyl alcohol-based polymer according to the present invention includes a homopolymer consisting of a vinyl ester monomer, a copolymer of a vinyl ester monomer and a monofunctional monomer other than vinyl ester, and a copolymer consisting of a vinyl ester monomer and a monofunctional monomer other than vinyl ester.
• the polyvinyl alcohol-based polymer according to the present invention has a higher-order polymer structure different from that of conventional PVA, so that it can maintain a swollen state at high temperatures. Having such a polymer structure means that the average degree of polymerization measured by the method described in JIS K 6726:1994 is 3000 to 6000, and that the reaction of the polymerizable unsaturated bonds of the polyfunctional monomer is sufficient. This can be confirmed from the fact that the rate is between 55 and 75%.
• the vinyl ester monomers mentioned above may be, for example, vinyl acetate, vinyl propionate, vinyl butyrate, vinyl valerate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, vinyl pivalate, etc. Mixtures of these may also be used. From the viewpoint of ease of polymerization, vinyl acetate is preferred.
• Examples of monofunctional monomers copolymerizable with vinyl ester monomers include the following compounds.
• ⁇ -olefin monomers such as ethylene and propylene.
• (meth)acrylic acid alkyl ester monomers such as methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, and 2-ethylhexyl (meth)acrylate.
• Unsaturated amide monomers such as (meth)acrylamide and N-methylolacrylamide.
• Unsaturated carboxylic acid monomers such as (meth)acrylic acid, crotonic acid, maleic acid, itaconic acid, and fumaric acid.
• Alkyl (methyl, ethyl, propyl, etc.) ester monomers of unsaturated carboxylic acids Anhydrides of unsaturated carboxylic acids such as maleic anhydride. Salts of unsaturated carboxylic acids, such as sodium, potassium, and ammonium. Sulfonic acid group-containing monomers such as 2-acrylamido-2-methylpropanesulfonic acid or salts thereof. Alkyl vinyl ether monomer.
• the polyfunctional monomer copolymerizable with the vinyl ester monomer a compound having two or more polymerizable unsaturated bonds in the molecule can be used.
• the number of polymerizable unsaturated sites in the polyfunctional monomer is preferably 2 to 5.
• Examples of such compounds include the following. Divinyl ethers such as ethanediol divinyl ether, propanediol divinyl ether, butanediol divinyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, polyethylene glycol divinyl ether, propylene glycol divinyl ether, polypropylene glycol divinyl ether, etc.
• Sulfonic acid compounds Diene compounds such as pentadiene, hexadiene, heptadiene, octadiene, nonadiene, and decadiene.
• Diallyl ether compounds such as glycerin diallyl ether, diethylene glycol diallyl ether, ethylene glycol diallyl ether, triethylene glycol diallyl ether, polyethylene glycol diallyl ether, trimethylolpropane diallyl ether, and pentaerythritol diallyl ether.
• Triallyl ether compounds such as glycerin triallyl ether, trimethylolpropane triallyl ether, and pentaerythritol triallyl ether.
• Tetraallyl ether compounds such as pentaerythritol tetraallyl ether.
• Polyfunctional monomers containing allyl ester groups such as diallyl phthalate, diallyl maleate, diallyl itaconate, diallyl terephthalate, and diallyl adipate.
• Diallylamine compounds such as diallylamine and diallylmethylamine, and polyfunctional monomers containing allylamino groups such as triallylamine.
• Polyfunctional monomers containing allyl ammonium groups such as diallyl ammonium salts such as diallyl dimethyl ammonium chloride.
• Polyfunctional monomers containing two or more allyl groups such as triallyl isocyanurate, 1,3-diallylurea, triallyl phosphate, and diallyl disulfide.
• a polyfunctional monomer containing (meth)acrylic acid such
• a polyfunctional monomer containing (meth)acrylamide such as N,N'-methylenebis(meth)acrylamide and N,N'-ethylenebis(meth)acrylamide.
• Polyfunctional aromatic monomers such as divinylbenzene and trivinylbenzene.
• Glycidyl group-containing polyfunctional monomers such as allyl glycidyl ether and glycidyl (meth)acrylate.
• PVA is obtained by saponifying a copolymer of a vinyl ester monomer and a polyfunctional monomer, so that a crosslinked structure is formed from the polyfunctional groups, so that it is resistant to dissolution at high temperatures. It has the effect of gaining sex.
• a polyfunctional monomer a compound having a ring structure is preferable, a compound having a heterocyclic structure is more preferable, and triallyl isocyanurate (TAIC) is particularly preferable.
• the polyvinyl alcohol polymer has an average degree of polymerization of 3000 to 6000, preferably 3000 to 5500, more preferably 3000 to 5000, as measured by the method described in JIS K 6726:1994 "3.7 Average degree of polymerization". It's fine.
• the reaction rate (consumption rate) of the polymerizable unsaturated bonds of the polyfunctional monomer in the present polyvinyl alcohol polymer is in the range of 55 to 75%, preferably in the range of 55 to 73%. good.
• the reaction rate can be calculated using 1 H-NMR or 13 C-NMR in heavy water or heavy dimethyl sulfoxide solvent. For example, when using NMR, the amount of comonomer modification and the amount of residual unsaturation can be calculated by the following procedure, and the reaction rate can be derived therefrom.
• the amount of copolymerization is the amount of monomers other than vinyl esters per 100 mol% of structural units derived from vinyl alcohol units in the vinyl alcohol polymer.
• the content of structural units derived from the body is preferably 0.001 to 1.0 mol%, more preferably 0.005 to 0.5 mol%, and even more preferably 0.01 to 0.2 mol%.
• the amount of polymerizable unsaturated sites relative to the total of vinyl alcohol units and vinyl acetate units in the present polyvinyl alcohol-based polymer is preferably 0.05 to 0.30 mol%, more preferably 0.10 to 0.30 mol%. preferable.
• the amount of polyfunctional monomer units relative to the total of vinyl alcohol units and vinyl acetate units in the present polyvinyl alcohol polymer is preferably 0.05 to 0.30 mol%, more preferably 0.10 to 0.30 mol%. More preferred.
• the amount of copolymerization of polyfunctional monomers in PVA can be calculated using 1 H-NMR or 13 C-NMR in heavy water or heavy dimethyl sulfoxide solvent, or using a trace total nitrogen analyzer. .
• trace total nitrogen analyzer "TN-2100H” (manufactured by Nitto Seiko Analytech)
• the following procedure can be used for calculation.
• a sample of the vinyl alcohol polymer was collected on a quartz board, set on the autoboat controller "ABC-210" (manufactured by Nitto Seiko Analytech), and automatically inserted into the electric furnace and placed in an argon/oxygen stream. Burn it with.
• the NO gas generated at this time is measured with a chemiluminescence detector.
• the amount of unsaturation (mol%) in a polyvinyl alcohol polymer is determined by the amount of methylene groups in the main chain derived from vinyl alcohol units of the polyvinyl alcohol polymer and the methylene groups in the main chain derived from vinyl acetate units (1.8 to 2.5 ppm). It can be calculated from the integral value of the peak derived from unsaturation using the integral value of the peak as a reference. Specifically, in the 1 H-NMR spectrum, b is the integral value of the main chain methylene group derived from the vinyl alcohol unit and the main chain methylene group derived from the vinyl acetate unit.
• the reaction rate of the polymerizable unsaturated bond of the polyfunctional monomer can be calculated from the amount of modification of the comonomer of the vinyl alcohol polymer and the amount of residual unsaturation.
• n in the formula is the number of polymerizable unsaturated bonds in the polyfunctional monomer.
• the saponification degree of PVA can be measured by the method described in Japanese Industrial Standard JIS K6726:1994 "3.5 Saponification degree".
• the degree of saponification of the polyvinyl alcohol polymer is preferably 75 to 99 mol%, more preferably 77 to 97 mol%, even more preferably 79 to 95 mol%.
• the particle size distribution of the present PVA particles can be determined by performing dynamic light scattering measurement on a 0.4% by mass aqueous solution (dilute aqueous solution) of PVA at a temperature of 25°C.
• the particle diameter at a cumulative frequency of 50% in the particle size distribution of PVA particles is preferably 50 nm or more, more preferably in the range of 70 to 1000 nm. Note that the cumulative frequency is determined from the scattering intensity distribution frequency obtained by dynamic light scattering measurement.
• the average particle diameter of PVA in the dilute aqueous solution can be set depending on the application, and is preferably, for example, 60 to 2000 nm, more preferably 70 to 1500 nm. Note that the average particle diameter of PVA in a dilute aqueous solution in this specification is determined by performing cumulant analysis of the particle diameter distribution obtained by performing dynamic light scattering measurement on a 0.4% by mass aqueous solution of PVA at a temperature of 25 ° C. It will be done.
• the average particle size of PVA in the dilute aqueous solution is 60 nm or more, as this makes it difficult for PVA in the cement slurry to flow out and improves fluid loss reduction performance. It is preferable from the viewpoint of productivity that the average particle diameter of PVA in the dilute aqueous solution is 2000 nm or less.
• the PVA particles do not contain excessive gel particles from the viewpoint of the strength of the cement after hardening and the production of PVA. More specifically, the passage rate of a 1.0 mass% aqueous solution of PVA through a 300 mesh (opening 0.045 mm) filter is preferably 95 mass% or more in terms of solid content, and should be in the range of 97 to 100 mass%. is more preferable.
• the filter passage rate of 300mesh can be calculated using the following procedure.
• the dried PVA is dissolved in water at 25°C to obtain an aqueous solution with a concentration of 1.0% by mass.
• 100 mL of the resulting PVA aqueous solution is filtered through a 300 mesh (mesh opening: 0.045 mm) filter, and the mass of PVA remaining on the filter is measured.
• the percentage of PVA that has passed through the filter is calculated from the measured mass of PVA residue.
• the PVA particles have a particle size distribution that makes it difficult to pass through a membrane filter with a pore size of 0.45 ⁇ m. More specifically, the passage rate of a 1.0 mass % aqueous solution of PVA through a membrane filter with a pore size of 0.45 ⁇ m is preferably 10 mass % or less in terms of solid content, and more preferably in the range of 0 to 5 mass %. .
• the passage rate of the 0.45 ⁇ m membrane filter can be calculated using the following procedure.
• a PVA aqueous solution adjusted to a concentration of 1.0% by mass is filtered under reduced pressure (10 mmHg) for 10 minutes using a 0.45 ⁇ m filter (manufactured by ADVANTEC, Material: Mixed Cellulose ester, pore size: 0.45 ⁇ m, diameter 47 mm).
• the passage rate is calculated from the solid content in the filtrate.
• the particle size of the present polyvinyl alcohol polymer is preferably 20% by mass or less, and more preferably 18% by mass or less, of 75 ⁇ m or less (under the 75 ⁇ m sieve).
• the particle diameter of 500 ⁇ m or more (on a 500 ⁇ m sieve) is 10% by mass or less, more preferably 5% by mass or less.
• the particle size may be 20% by weight or less of 75 ⁇ m or less and 10% by weight or less of 500 ⁇ m or more.
• the viscosity of the polyvinyl alcohol polymer can be measured by the method described in JIS K 6726:1994 "4.2 Measurement of viscosity.”
• the viscosity is preferably in the range of 40 to 200 mPa.s, more preferably in the range of 50 to 160 mPa.s, from the viewpoint of improving productivity.
• the vinyl ester monomer or copolymer thereof may be polymerized using a two-step polymerization method as described below.
• a two-step polymerization method as described below.
• an initiator is added to a mixture of a vinyl ester monomer and a polyfunctional monomer having two or more unsaturated bonds in the molecule, and the mixture is heated in an organic solvent until the first polymerization rate is reached.
• the first polymerization rate may be, for example, in the range of 5 to 60%, preferably in the range of 10 to 55%.
• an organic solvent is added separately from the previous one (the same organic solvent or a different organic solvent may be used), and the second polymerization reaction is continued until the second polymerization rate is reached. I do.
• the second polymerization rate is higher than the first polymerization rate, and may be, for example, in the range of 10 to 65%, preferably in the range of 15 to 60%.
• Alcohol can preferably be used as the organic solvent.
• the alcohol for example, methanol, ethanol, butanol, etc. can be used, and methanol is preferably used.
• the concentration of the polymer in the organic solvent solution can be set arbitrarily, and may be, for example, 10% by mass or more and 80% by mass or less.
• the unreacted vinyl ester monomer is discharged from the polymerization system, and the resulting polymer (polyvinyl ester, etc.) solution is saponified by any method to remove PVA.
• An example of a saponification method is a method in which an alkali catalyst is added to an alcoholic solution of a polymer. An example of the saponification procedure will be described below.
• the alcohol serving as a solvent for the polymer for example, methanol, ethanol, butanol, etc. can be used, and methanol can be preferably used.
• the concentration of the polymer in the alcohol solution can be set arbitrarily, and may be, for example, 10% by mass or more and 80% by mass or less.
• an alkali catalyst is added to the above solution to perform a saponification reaction.
• the alkali catalyst include alkali metal hydroxides and alcoholates such as sodium hydroxide, potassium hydroxide, sodium methylate, sodium ethylate, and potassium methylate. Among these, it is preferable to use sodium hydroxide.
• the amount of the alkali catalyst added is not particularly limited, but it is preferably 1.0 to 100.0 mmol equivalent, more preferably 5.0 to 30.0 mmol equivalent, based on the polymer.
• the reaction temperature during saponification is not particularly limited, but is preferably 10 to 70°C, more preferably 30 to 55°C.
• the reaction time is also not particularly limited, and may be, for example, 20 minutes or more to 2 hours.
• the degree of saponification can be adjusted appropriately depending on the use of PVA, and may be, for example, 72 to 99 mol%, preferably 75 to 99 mol%. Note that after the saponification reaction, a washing step for removing impurities such as sodium acetate and a drying step may be performed as necessary.
• an additive for oil well cement containing PVA as described above can be provided and can be suitably used in cementing oil wells, gas wells, steam wells for geothermal power generation, and the like.
• Cementing which is performed during well drilling, is the process of injecting cement into the gap between the drilled well and the steel pipe inserted into it.
• a widely used method for cementing is to mix cement and various additives such as fluid loss additives in a dry state, then slurry the mixture with high-pressure water and inject it with a pump.
• PVA as a fluid loss reducing agent can reduce the loss of water contained in the cement slurry during cementing (i.e. reduce fluid loss) and maintain the fluidity of the cement slurry. becomes.
• the fluid loss is large, the fluidity of the cement slurry is lost, making it difficult to perform sufficient cementing.
• Fluid loss evaluation is one of the evaluation items for oil well cement defined by the American Petroleum Institute (API). The fluid loss test method is described in Recommended Practice for Testing Well Cements, API Recommended Practice 10B-2, April 2013.
• an oil well cement composition for oil wells
• an oil well cement composition can be provided that includes an oil well cement and the oil well cement additive described above.
• the above-mentioned oil well cement may be any cement used in cementing oil wells, gas wells, steam wells for geothermal power generation, etc., and is not particularly limited.
• the content of the oil well cement additive in the above composition is preferably 0.01 to 10% bwoc, more preferably 0.05 to 5% bwoc. With such a range, fluid loss can be effectively reduced.
• bwoc by weight of cement means cement weight basis, and refers to the weight of dry additives added to a cement composition based only on the solid content of cement.
• an oil well cement slurry can also be provided that includes oil well cement, the oil well cement additive described above, and water.
• the cement slurry preferably has a water content of 20 to 40% by mass.
• the method of incorporating the oil well cement additive into the cement slurry is not particularly limited. Examples include a method of preparing a composition containing oil well cement and additives and then mixing the composition with water, and a method of mixing oil well cement, additives, and water without preparing the composition. It will be done.
• Example 1 In a polymerization vessel equipped with a reflux condenser, a dropping funnel, and a stirrer, 100 parts by mass of vinyl acetate, 70.2 parts by mass of methanol (described as "initial methanol” in the table), and triallyl isocyanurate (TAIC) as a polyfunctional monomer were placed. ) and 5.0 ⁇ 10 ⁇ 6 parts by mass of Perloyl NPP (manufactured by NOF Corporation) as an initiator were charged, and polymerization was carried out at the boiling point while stirring in a nitrogen atmosphere.
• TAIC triallyl isocyanurate
• a methanol solution of sodium hydroxide was added to the obtained methanol solution of the vinyl acetate-TAIC copolymer (0.008 mol% of sodium hydroxide based on the copolymer). Thereafter, a saponification reaction was carried out at 45°C for 45 minutes to obtain PVA with a saponification degree of 91.3 mol%.
• Examples 2 to 6, Comparative Examples 1 to 4 PVAs of Examples 2 to 6 and Comparative Examples 1 to 4 were obtained in the same manner as in Example 1, except that the charging amount was changed as shown in Table 1 below. Note that Comparative Examples 2 and 3 are reproductions of Examples 3 and 5 of Patent Document 3, respectively. Further, Comparative Example 4 is a reproduction of Example 5 of Patent Document 4. That is, in the comparative example, methanol was not added in portions.
• Class G oil well cement is blended with the amount of PVA listed in the table and 0.4% bwoc of a hardening retarder (CR-270, manufactured by Flotek Industries), according to American Petroleum Institute (API) Standard 10B-2 (2013 April 2013). These and water were mixed according to the procedure described in 1997) to obtain a cement slurry with a water content of 30% by mass. The obtained cement slurry was put into a fluid loss evaluation tester "Model 7120" (manufactured by Chandler Engineering), and according to the procedure described in American Petroleum Institute (API) Standard 10B-2 (April 2013), The test was conducted at the temperature described in 1,000 psi under pressure, and the amount of fluid loss was calculated.
• a hardening retarder CR-270, manufactured by Flotek Industries
• API American Petroleum Institute
• the additive for oil well cement of the present invention has good fluid loss reduction performance, and can be produced without generating deposits that are insoluble in solvents and without excessively increasing the viscosity in the system. was confirmed. On the other hand, in the comparative example, it was also confirmed that some performance was lacking.
• a polyvinyl alcohol polymer obtained by saponification of a copolymer of a vinyl ester monomer and a polyfunctional monomer containing two or more polymerizable unsaturated bonds in the molecule has an average degree of polymerization of 3000 to 6000 as measured by the method described in JIS K 6726:1994, A polyvinyl alcohol polymer characterized by a reaction rate of polymerizable unsaturated bonds of a polyfunctional monomer of 55 to 75%.
• a membrane filter in which the passage rate of a 1.0 mass% aqueous solution of the polyvinyl alcohol polymer through a filter with an opening of 45 ⁇ m is 95 mass% or more in terms of solid content, and the pore size of the 1.0 mass% aqueous solution of the polyvinyl alcohol polymer is 0.45 ⁇ m.
• the polyvinyl alcohol polymer according to any one of Supplementary Notes 1 to 6, which has a passage rate of 5% by mass or less in terms of solid content.
• Appendix 8 The polyvinyl alcohol polymer according to any one of appendices 1 to 7, wherein the polyvinyl alcohol polymer has a particle size of 20% by mass or less of 75 ⁇ m or less and 10% by mass or less of 500 ⁇ m or more.
• a method for producing a polyvinyl alcohol polymer comprising: An initiator is added to a mixture of a vinyl ester monomer and a polyfunctional monomer containing two or more polymerizable unsaturated bonds in the molecule, and the mixture is heated in an organic solvent until a first polymerization rate is reached. a step of performing a polymerization reaction; After the first polymerization reaction, adding an organic solvent and performing a second polymerization reaction until a second polymerization rate higher than the first polymerization rate is reached; A solution of an alkali catalyst in an organic solvent is added to the solution of the copolymer of the vinyl ester monomer and the polyfunctional monomer obtained after the second polymerization reaction to perform a saponification reaction.
• the average degree of polymerization measured by the method described in JIS K 6726:1994 is 3000 to 6000, and the reaction rate of the polymerizable unsaturated bond of the polyfunctional monomer is 55 to 75%.

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