Fluid loss agent for oil well cement as well as preparation method and application of fluid loss agent

Abstract

The invention provides a fluid loss agent for oil well cement as well as a preparation method and application of the fluid loss agent. The preparation method comprises the following steps: adding 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, dimethyl diallyl ammonium chloride, N-vinyl pyrrolidone, N, N-dimethylacrylamide or N, N-diethyl-2-acrylamide, allyl polyoxyethylene ether or methyl allyl polyoxyethylene ether into water, so as to obtain a first mixed solution; adjusting the pH value of the first mixed solution to 7-8 to obtain a second mixed solution; and adding an initiator into the second mixed solution for reaction to obtain the fluid loss agent for oil well cement. According to the invention, a monomer material with strong temperature resistance is preferably selected to synthesize the fluid loss agent for oil well cement, the molecular main chain pyrolysis temperature of the copolymer fluid loss agent reaches 397 DEG C, the polymer fluid loss performance reduction caused by ultra-high temperature pyrolysis can be well slowed down, the tolerable temperature of a formed cement slurry system can reach 240 DEG C, and the fluid loss performance of the slurry can be continuously maintained.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil well cementing, in particular to a fluid loss additive for oil well cement, a preparation method of the fluid loss additive for oil well cement and application of the fluid loss additive for oil well cement in oil well cement slurry. BACKGROUND

[0002] In recent years, with the extension of oil and gas resource development time and the deepening of development focus, the difficulty of increasing production and stability is increasing, and deep oil and gas resources have become the focus of current exploration and development. Due to high temperature and high pressure of deep and ultra-deep well formation, cementing engineering faces more challenges, especially the fluid loss problem of cement slurry at high temperature is particularly prominent. The fluid loss of cement slurry is one of the important factors for measuring whether the cement slurry has excellent performance, and the insufficient fluid loss of cement slurry will directly affect the safety and quality of cementing construction. The current common method is to improve the fluid loss problem by adding inorganic materials and organic polymer fluid loss additives. Inorganic materials mainly include ultra-fine materials, clay substances and thixotropic materials, etc. This kind of material generally has very small particle size and large specific surface area, has a certain adsorption and control effect on free water, and thus has a certain fluid loss reduction capacity. However, when the dosage increases to a certain extent, the slurry will be significantly thickened, which is not conducive to on-site mixing and pumping, thus limiting its application in cement slurry system to a certain extent. At the same time, with the continuous increase of temperature, the adsorption effect of van der Waals force will also be weakened; organic polymer materials include plant glue, cellulose and synthetic polymer, which can improve the fluid loss of slurry by increasing the viscosity of slurry and the viscosity between cement particles, but with the continuous increase of temperature, the pyrolysis of organic polymer will cause the reduction of fluid loss capacity, and the temperature resistance of fluid loss additive becomes the technical bottleneck restricting the technology of ultra-high temperature cementing slurry. For example, the patent document with the title of a fluid loss additive and its preparation method and application, publication number CN201910733256, which was published on February 9, 2021, records a fluid loss additive and its preparation method and application, the preparation method includes the following steps: mixing polyether macromonomer, 2-acrylamido-2-methylpropane sulfonic acid, N,N-dimethyl acrylamide, diunsaturated carboxylic acid and water to generate a monomer aqueous solution; adjusting the pH of the monomer aqueous solution to 6-7, heating the monomer aqueous solution to 50-70℃, then adding an initiator aqueous solution and reacting for 2-5h to obtain the fluid loss additive; the mass ratio of the polyether macromonomer, 2-acrylamido-2-methylpropane sulfonic acid, N,N-dimethyl acrylamide and diunsaturated carboxylic acid is (3-15):(35-90):(5-40):(2-10). The temperature range of the fluid loss additive is 30-200℃, and the fluid loss additive has a retarding effect because it uses diunsaturated carboxylic acid as a polymerization monomer material, and the most important feature of carboxylic acid group is to have a retarding effect on silicate oil well cement.

[0003] Therefore, it is extremely necessary to develop a fluid loss additive for cementing cement using monomer materials not containing carboxylic acid groups. SUMMARY

[0004] An object of the present application is to solve at least one of the above-described problems of the prior art. For example, an object of the present application is to provide a fluid loss additive capable of withstanding high temperatures, which is synthesized without using monomer materials containing carboxylic acid groups.

[0005] To achieve the above object, one aspect of the present application provides a method of preparing a fluid loss additive for oil well cement.

[0006] The method of preparing the fluid loss additive for oil well cement includes the steps of:

[0007] 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, dimethyldiallylammonium chloride, N-vinylpyrrolidone, N,N-dimethylacrylamide or N,N-diethyl-2-acrylamide, allyl polyoxyethylene ether, or methylallyl polyoxyethylene ether are added to water to obtain a first mixed solution.

[0008] The pH value of the first mixed solution is adjusted to 7 to 8 to obtain a second mixed solution.

[0009] An initiator is added to the second mixed solution to react, thereby obtaining the fluid loss additive for oil well cement.

[0010] In one exemplary embodiment of the method of preparing the fluid loss additive for oil well cement, the preparation of the initiator can include adding potassium persulfate and sodium bisulfite to water to obtain the initiator.

[0011] In one exemplary embodiment of the method of preparing the fluid loss additive for oil well cement, the adding of the initiator to the second mixed solution to react can include:

[0012] The initiator is added to the second mixed solution, and is reacted at a first temperature for a first time to obtain a third mixed solution.

[0013] The initiator is added to the third mixed solution, and is reacted at a second temperature for a second time to obtain a fourth mixed solution.

[0014] The initiator is added to the fourth mixed solution, and is reacted at a third temperature for a third time to obtain the fluid loss additive for oil well cement.

[0015] In an exemplary embodiment of the method for preparing the fluid loss additive for oil well cement, the first temperature can be 59-61℃, and the first reaction time can be 60-90 min; the second temperature can be 64-66℃, and the second reaction time can be 90-120 min; and the third temperature can be 69-71℃, and the third reaction time can be 90-120 min.

[0016] In an exemplary embodiment of the method for preparing the fluid loss additive for oil well cement, the 2-acrylamido-2-methylpropanesulfonic acid can be 85-90 parts by mass, the sodium p-styrenesulfonate can be 55-60 parts by mass, the dimethyldiallylammonium chloride can be 44-50 parts by mass, the N-vinylpyrrolidone can be 15-20 parts by mass, the N,N-dimethylacrylamide or N,N-diethyl-2-propenamide can be 40-45 parts by mass, the allyl polyoxyethylene ether or the methylallyl polyoxyethylene ether can be 0.5-1 part by mass, and the water can be 700-730 parts by mass.

[0017] In an exemplary embodiment of the method for preparing the fluid loss additive for oil well cement, the potassium persulfate can be 3-4 parts by mass, and the sodium bisulfite can be 3-4 parts by mass.

[0018] In an exemplary embodiment of the method for preparing the fluid loss additive for oil well cement, the total weight of the 2-acrylamido-2-methylpropanesulfonic acid, the sodium p-styrenesulfonate, the dimethyldiallylammonium chloride, the N-vinylpyrrolidone, the N,N-dimethylacrylamide or N,N-diethyl-2-propenamide, the allyl polyoxyethylene ether or the methylallyl polyoxyethylene ether can account for 24-28% of the weight of the first mixed solution.

[0019] In another aspect of the present application, a fluid loss additive for oil well cement is provided, which is obtained by any one of the above-mentioned methods for preparing the fluid loss additive for oil well cement.

[0020] In an exemplary embodiment of the fluid loss additive for oil well cement, the molecular weight of the fluid loss additive for oil well cement can be 200000-400000 g / mol.

[0021] In yet another aspect of the present application, the use of the fluid loss additive for oil well cement as described in any one of the above-mentioned aspects in oil well cement slurry is provided, and the temperature of the use of the fluid loss additive for oil well cement in oil well cement slurry is less than or equal to 240℃.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] The fluid loss additive for oil well cement of the present application is synthesized by designing the molecular structure and preferably using monomer materials with strong temperature resistance, to reasonably control the molecular weight of the fluid loss additive, prevent the entanglement of molecular chains by means of large side groups, cyclic structure, branching, etc., increase the steric hindrance of the movement, and strive to improve the rigidity of the molecular chain, so that the polymer molecular structure changes less at high temperature. The thermogravimetric test shows that the degradation temperature point of the main chain of the molecule is as high as 397℃, which can better slow down the decrease of the fluid loss performance of the polymer caused by super-high temperature pyrolysis, and the tolerable temperature of the formed cement slurry system can reach 240℃, and the fluid loss performance of the slurry is continuously maintained. Therefore, the fluid loss additive can avoid the significant decrease of the fluid loss performance of the polymer caused by super-high temperature pyrolysis, continuously maintain the fluid loss performance of the slurry, and effectively avoid the problem of increased fluid loss of the cement slurry caused by the intensified thermal movement of the cement slurry at high temperature, to prevent the safety and quality problems of cementing caused by the increased fluid loss of the cement slurry. BRIEF DESCRIPTION OF DRAWINGS

[0024] The above and other objects and / or characteristics of the present application will become more apparent by describing in detail the embodiments thereof with reference to the attached drawings, wherein:

[0025] Figure 1 A flow chart showing the steps of an exemplary embodiment of the method of the fluid loss additive for oil well cement of the present application is shown. DETAILED DESCRIPTION

[0026] Hereinafter, an oil well cement fluid loss additive and a preparation method and application thereof of the present application will be described in detail in conjunction with exemplary embodiments.

[0027] It should be noted that "first", "second", "third", etc. are only for the convenience of description and differentiation, and cannot be understood as indicating or implying relative importance. "Up", "down", "front", "back", "left", "right", "inside", "outside", etc. are only for the convenience of description and constitute relative positional relationships, and are not intended to indicate or imply that the components referred to must have the specific positions. The terms "S1", "S2", "S3", etc. used in the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence.

[0028] At present, most of the polymer fluid loss additives will select monomer materials containing carboxylic acid groups to copolymerize in the preparation process. In this way, the carboxylic acid groups can be strongly adsorbed on the cement particles, thereby achieving the effect of reducing fluid loss. However, in addition to the fluid loss effect, the carboxylic acid groups also have a retarding effect, which makes the fluid loss additive often have the characteristics of a retarder in application. This negative effect often leads to technical problems such as abnormal cementing and core wrapping of the cement slurry system.

[0029] To solve the above problems, the inventors propose a fluid loss additive for oil well cement, which is synthesized by using monomer materials without carboxylic acid groups. This innovative design largely avoids the retardation effect of the fluid loss additive, thereby largely solving the compatibility problems that are prone to occur in the use of ultra-high temperature cement. This improvement not only enhances the performance of the product, but also enhances the stability and reliability of the product in high-temperature and high-alkali environments.

[0030] To achieve the above object, the present application provides, in one aspect, a preparation method of a fluid loss additive for oil well cement.

[0031] In one exemplary embodiment of the preparation method of the fluid loss additive for oil well cement of the present application, as shown in Figure 1 the preparation method of the fluid loss additive for oil well cement comprises the following steps:

[0032] S1, 2-acrylamido-2-methylpropane sulfonic acid, sodium p-styrenesulfonate, dimethyldiallylammonium chloride, N-vinylpyrrolidone, N,N-dimethylacrylamide or N,N-diethyl-2-propenamide, allyl polyoxyethylene ether or methyl allyl polyoxyethylene ether are added to water to obtain a first mixed solution.

[0033] Alternatively, the 2-acrylamido-2-methylpropane sulfonic acid can be 85-90 parts by mass fraction, for example, 85, 86, 87, 88, 89, or 90 parts.

[0034] The sodium p-styrenesulfonate can be 55-60 parts, for example, 55, 56, 57, 58, 59, or 60 parts.

[0035] The dimethyldiallylammonium chloride can be 44-50 parts, for example, 44, 45, 46, 47, 48, or 48, 50 parts.

[0036] The N-vinylpyrrolidone can be 15-20 parts, for example, 15, 16, 17, 18, 19, or 20 parts.

[0037] The N,N-dimethylacrylamide or N,N-diethyl-2-propenamide can be 40-45 parts, for example, 40, 41, 42, 43, 44, or 45 parts.

[0038] The allyl polyoxyethylene ether or methyl allyl polyoxyethylene ether can be 0.5-1 part, for example, 0.5, 0.75, or 1 part.

[0039] The water can be 700-730 parts, for example, 700, 710, 720, or 730 parts.

[0040] Optionally, the total weight of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, dimethyldiallylammonium chloride, N-vinylpyrrolidone, N,N-dimethylacrylamide or N,N-diethyl-2-propenamide, allyl polyoxyethylene ether or methallyl polyoxyethylene ether can account for 24-28% of the weight of the first mixed solution, for example, can be 24, 25, 26, 27, 28%.

[0041] S2, the pH value of the first mixed solution is adjusted to 7-8 to obtain a second mixed solution. For example, the pH value can be adjusted to 7, 7.5 and 8.

[0042] S3, the initiator is added to the second mixed solution for reaction to obtain a fluid loss additive for oil well cement.

[0043] Optionally, the second mixed solution can be added to the initiator for reaction in an oxygen-free environment to obtain the fluid loss additive for oil well cement.

[0044] Optionally, the preparation of the initiator can include:

[0045] S31, potassium persulfate and sodium bisulfite are added to water to obtain the initiator.

[0046] According to the mass fraction, the potassium persulfate can be 3-4 parts, for example, can be 3, 3.5, 4 parts; the sodium bisulfite can be 3-4 parts, for example, can be 3, 3.5, 4 parts.

[0047] Optionally, adding the second mixed solution to the initiator for reaction can include:

[0048] S32, the initiator is added to the second mixed solution, and the reaction is carried out at a first temperature for a first time to obtain a third mixed solution.

[0049] S33, the initiator is added to the third mixed solution, and the reaction is carried out at a second temperature for a second time to obtain a fourth mixed solution.

[0050] S34, the initiator is added to the fourth mixed solution, and the reaction is carried out at a third temperature for a third time to obtain the fluid loss additive for oil well cement.

[0051] Alternatively, the first temperature can be 59-61℃, for example, can be 59, 60, 61℃; the first reaction time can be 60-90min, for example, can be 60, 65, 70, 75, 80, 85, 90min; the second temperature can be 64-66℃, for example, can be 64, 65, 66℃; the second reaction time can be 90-120min, for example, can be 90, 100, 110, 120min; the third temperature can be 69-71℃, for example, can be 69, 70, 71℃; the third reaction time can be 90-120min, for example, can be 90, 100, 110, 120min.

[0052] Heating in three stages and adding initiators step by step can improve the conversion rate of monomer materials in random copolymerization, and is also conducive to the control of molecular weight, avoiding too high molecular weight.

[0053] Alternatively, the amount of initiator added in steps S32, S33 and S34 is equal.

[0054] In another aspect, the application provides a fluid loss additive for oil well cement.

[0055] In an exemplary embodiment of the fluid loss additive for oil well cement, the fluid loss additive for oil well cement is obtained by the preparation method of the fluid loss additive for oil well cement in any of the above exemplary embodiments.

[0056] The fluid loss additive for oil well cement is prepared by aqueous solution polymerization, and the synthesis principle is free radical copolymerization, that is, monomers are converted into monomer radicals, and then a large number of monomer molecules are continuously added to form polymer molecular chain growth, realizing random copolymerization and.

[0057] Alternatively, the general formula of the synthesized fluid loss additive for oil well cement can be as follows:

[0058]

[0059] Wherein, m and n represent the number of two structural units in the monomer material methyl allyl polyoxyethylene ether, which reflects the molecular weight of the methyl allyl polyoxyethylene ether itself; a, b, c, d, e and f respectively represent the possible number relationship and combination mode of each monomer material forming a chain segment after copolymerization of the six monomer materials on the polymer chain.

[0060] Alternatively, the molecular weight of the fluid loss additive for oil well cement can be 200000-400000g / mol, for example, can be 200000, 310000, 400000g / mol.

[0061] In another aspect, the application provides the use of the fluid loss additive for oil well cement as described above in oil well cement slurry.

[0062] In an exemplary embodiment of the application of the oil well cement fluid loss additive in the oil well cement slurry, the temperature of the application of the oil well cement fluid loss additive in the oil well cement slurry is less than or equal to 240℃.

[0063] In order to better understand the above exemplary embodiments of the application, the following further describes the exemplary embodiments of the application in combination with specific examples and application examples, but the examples do not limit the application. In the application examples and comparative examples, the G-grade oil well cement can be Jiuhua cement, the retarder can be an AMPS polymer provided by Chuanqing Company, the defoaming agent can be dimethyl silicone oil, and the slurry mixing water can be tap water.

[0064] Example 1

[0065] In this embodiment, the preparation method of the ultra-high temperature polymer fluid loss additive for oil well cement can be realized by the following steps:

[0066] Step 1, potassium persulfate and sodium bisulfite are dissolved in water to prepare an initiator solution for later use.

[0067] Step 2, 720 parts of deionized water are put into a reaction container, and under stirring, the following are added: N,N-dimethyl acrylamide 40 parts, sodium p-styrenesulfonate 60 parts, N-vinyl pyrrolidone 15 parts, 2-acrylamido-2-methylpropanesulfonic acid 90 parts, dimethyl diallyl ammonium chloride 44 parts, and methyl allyl polyoxyethylene ether 1 part.

[0068] Step 3, 30 parts of sodium hydroxide are added to adjust the solution pH to 8.

[0069] Step 4, under ice bath conditions, nitrogen is introduced into the reaction system for 30 min, then one-third of the initiator solution is slowly added, the reaction temperature is set to 60℃, and constant temperature stirring is carried out for 90 min. The temperature is raised to 65℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 120 min. The temperature is raised to 70℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 120 min. The constant temperature device is turned off, and the product is naturally cooled to room temperature. By controlling the three-stage synthesis temperature and gradually adding the initiator, on the one hand, the conversion rate of the synthesis reaction can be improved, and higher conversion rate can reduce the probability and degree of abnormal gelation of the product in the application of the ultra-high temperature cement slurry system; on the other hand, the control of the molecular weight and distribution can also be realized, and the adverse effects of high molecular weight products on the cement slurry system and workability can be avoided.

[0070] After the product is purified, relevant performance tests are carried out, and the molecular weight is 310917 after the measurement of 1 characteristic viscosity by a Ubbelohde viscometer. The thermogravimetric test curve shows that the main chain pyrolysis temperature point of the molecule is 397℃.

[0071] Application Example 1

[0072] In this application example, each component is weighed according to the following mass ratio: G-grade oil well cement: 285 parts; reinforcing agent: 100 parts; microsilica: 15 parts; retarder SD210: 12 parts; defoaming agent: 2 parts; the ultra-high temperature polymer fluid loss additive prepared in the above-mentioned embodiment 1: 18 parts; and slurry water: 136 parts. The cement slurry is prepared according to the oil well cement test method of GB / T19139-2012.

[0073] According to the requirements of the tenth chapter “cement slurry static filtration test” in the oil well cement test method of the People's Republic of China national standard GB / T19139-2012, the filtration performance of the cement slurry at 240℃ is determined. The amount of filtrate collected in the test is 5.5ml, and the cement slurry filtration test result at 240℃ is obtained after calculation as 22ml. The filtration test filter cake is thin and dense, with a thickness of about 7mm.

[0074] Embodiment 2

[0075] In this embodiment, the preparation method of the ultra-high temperature polymer fluid loss additive for oil well cement can be realized by the following steps:

[0076] Step 1, take 3 parts of potassium persulfate and 3 parts of sodium bisulfite, respectively, and dissolve them in 10 parts of deionized water to prepare an initiator solution for later use.

[0077] Step 2, put 680 parts of deionized water into a reaction container, and under stirring, add: N,N-dimethyl acrylamide 45 parts, sodium p-styrenesulfonate 55 parts, N-vinyl pyrrolidone 20 parts, 2-acrylamido-2-methylpropanesulfonic acid 85 parts, dimethyl diallyl ammonium chloride 50 parts, and methyl allyl polyoxyethylene ether 0.5 parts.

[0078] Step 3, add 25 parts of sodium hydroxide to adjust the solution PH to 7.

[0079] Step 4, under ice bath conditions, nitrogen is introduced into the reaction system for 30min, then one-third of the initiator solution is slowly added, the reaction temperature is set to 60℃, and constant temperature stirring reaction is carried out for 90min. The temperature is raised to 65℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 100min. The temperature is raised to 70℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 110min. The constant temperature device is turned off, and the product is naturally cooled to room temperature.

[0080] After the product is purified, the relevant performance test is carried out, the Ubbelohde viscometer measures the intrinsic viscosity, and the molecular weight is 398430. The thermogravimetric test curve shows that the main chain pyrolysis temperature point of the molecule is 371℃.

[0081] Application example 2

[0082] In the application example, each component is weighed according to the following mass ratio:

[0083] G-grade oil well cement: 285 parts; reinforcing agent: 100 parts; microsilica: 15 parts; retarder SD210: 12 parts; defoaming agent: 2 parts; the ultra-high temperature polymer fluid loss additive prepared in the above embodiment 2: 30 parts; and slurry water: 136 parts. The cement slurry is prepared according to the oil well cement test method in GB / T 19139-2012.

[0084] According to the requirements of the tenth chapter “Cement slurry static filtration test” in the oil well cement test method of the People's Republic of China national standard GB / T19139-2012, the filtration performance of the cement slurry at 240℃ is determined. The amount of filtrate collected in the test is 8.8ml, and the cement slurry filtration test result at 240℃ is calculated to be 35.2ml. The filtration test filter cake is thin and dense, with a thickness of about 13mm.

[0085] Embodiment 3

[0086] In this embodiment, the preparation method of the ultra-high temperature polymer fluid loss additive for oil well cement can be realized by the following steps:

[0087] Step 1, take 4 parts of potassium persulfate and 4 parts of sodium bisulfite, respectively, and dissolve them in 10 parts of deionized water to prepare an initiator solution for later use.

[0088] Step 2, put 710 parts of deionized water into a reaction container, and under stirring, add: N,N-dimethyl acrylamide 41 parts, sodium p-styrenesulfonate 59 parts, N-vinylpyrrolidone 20 parts, 2-acrylamido-2-methylpropanesulfonic acid 89 parts, dimethyl diallyl ammonium chloride 50 parts, and methyl allyl polyoxyethylene ether 0.8 parts.

[0089] Step 3, add 28 parts of sodium hydroxide to adjust the solution PH to 7.

[0090] Step 4, under ice bath conditions, nitrogen is introduced into the reaction system for 30 minutes, and then one-third of the initiator solution is slowly added. The reaction temperature is set to 60℃, and constant temperature stirring reaction is carried out for 70 minutes. The temperature is raised to 65℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 90 minutes. The temperature is raised to 70℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 90 minutes. Turn off the constant temperature device, and naturally cool to room temperature to obtain the product.

[0091] After the product is purified, relevant performance tests are carried out. The Ubbelohde viscometer measures the intrinsic viscosity to obtain a molecular weight of 257684. The thermogravimetric test curve shows that the main chain pyrolysis temperature point of the molecule is 380℃.

[0092] Application example 3

[0093] In the application example, each component is weighed according to the following mass ratio:

[0094] G-grade oil well cement: 285 parts; reinforcing agent: 100 parts; microsilica: 15 parts; retarder SD210: 12 parts; defoaming agent: 2 parts; the ultrahigh-temperature polymer fluid loss additive prepared in the above embodiment 3: 30 parts; and slurry water: 136 parts. The cement slurry is prepared according to the oil well cement test method in GB / T 19139-2012.

[0095] According to the requirements of Chapter 10 “Cement slurry static filtration test” in the oil well cement test method of the People's Republic of China national standard GB / T19139-2012, the cement slurry filtration performance at 240℃ is determined. The amount of filtrate collected in the test is 7.2ml, and the cement slurry filtration test result at 240℃ is obtained after calculation as 28.8ml. The filter cake in the filtration test is thin and dense, with a thickness of about 10mm.

[0096] Embodiment 4

[0097] In this embodiment, the preparation method of the ultrahigh-temperature polymer fluid loss additive for oil well cement can be realized by the following steps:

[0098] Step 1, take 3 parts of potassium persulfate and 3 parts of sodium bisulfite, respectively, and dissolve them in 10 parts of deionized water to prepare an initiator solution for later use.

[0099] Step 2, put 680 parts of deionized water into a reaction container, and under stirring, add: N,N-dimethyl acrylamide 43 parts, sodium p-styrenesulfonate 55 parts, N-vinylpyrrolidone 18 parts, 2-acrylamido-2-methylpropanesulfonic acid 87 parts, dimethyl diallyl ammonium chloride 48 parts, and methyl allyl polyoxyethylene ether 0.8 parts.

[0100] Step 3, add 27 parts of sodium hydroxide to adjust the solution PH to 7.

[0101] Step 4, under ice bath conditions, nitrogen is introduced into the reaction system for 30 minutes, and then one-third of the initiator solution is slowly added. The reaction temperature is set to 60℃, and constant temperature stirring reaction is carried out for 80 minutes. The temperature is raised to 65℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 100 minutes. The temperature is raised to 70℃, one-third of the initiator solution is added, and constant temperature reaction is carried out for 120 minutes. The constant temperature device is turned off, and the product is naturally cooled to room temperature.

[0102] After the product is purified, relevant performance tests are carried out. The molecular weight is obtained as 332640 after measuring the intrinsic viscosity by an Ubbelohde viscometer. The thermogravimetric test curve shows that the main chain pyrolysis temperature point of the molecule is 388℃.

[0103] Application example 4

[0104] In the present application example, each component is weighed according to the following mass ratio:

[0105] G-grade oil well cement: 285 parts; reinforcing agent: 100 parts; microsilica: 15 parts; retarder SD210: 12 parts; defoaming agent: 2 parts; the ultrahigh-temperature polymer fluid loss additive prepared in the above Example 4: 30 parts; and slurry water: 136 parts. The cement slurry is prepared according to the oil well cement test method of GB / T 19139-2012.

[0106] According to the requirements of the tenth chapter "Cement slurry static filtration test" in the oil well cement test method of GB / T 19139-2012 of the People's Republic of China, the filtration performance of the cement slurry at 240 DEG C is determined. The filtrate amount collected in the test is 6.8 ml, and the cement slurry filtration test result at 240 DEG C is calculated to be 27.2 ml. The filtration test filter cake is thin and dense, with a thickness of about 9 mm.

[0107] In summary, the beneficial effects include:

[0108] The application provides an oil well cement fluid loss additive, a preparation method and application thereof, and mainly applies to the field of well cementing engineering. The oil well cement fluid loss additive is an ultrahigh-temperature polymer, the rigidity of the polymer main chain is enhanced by controlling the molecular weight, introducing long side chains on the macromolecular main chain, and introducing ring structure units such as five-membered rings and benzene rings, so that the temperature resistance and shear resistance are improved. The degradation temperature of the polymer fluid loss additive high molecular main chain is as high as 397 DEG C, forming an anti-240 DEG C ultrahigh-temperature cement slurry system. And as an amphoteric ion polymer, the selected monomer material excludes carboxylic acid groups. To a great extent, the retardation effect of the fluid loss additive is avoided, and good compatibility of the ultrahigh-temperature cement slurry system is realized.

[0109] Although the application has been described above with reference to the example embodiments and the accompanying drawings, it should be clear to those skilled in the art that various modifications can be made to the above embodiments without departing from the spirit and scope of the claims.

Claims

1. A method for preparing a fluid loss reducing agent for oil well cement, characterized in that, The preparation method includes the following steps: 2-Acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, dimethyldiallylammonium chloride, N-vinylpyrrolidone, N,N-dimethylacrylamide or N,N-diethyl-2-acrylamide, allyl polyoxyethylene ether or methyl allyl polyoxyethylene ether are added to water to obtain the first mixed solution. The pH of the first mixed solution was adjusted to 7-8 to obtain the second mixed solution; and An initiator is added to the second mixed solution to react and obtain a fluid loss reducing agent for oil well cement.

2. The method for preparing the fluid loss reducing agent for oil well cement according to claim 1, characterized in that, The preparation of the initiator includes adding potassium persulfate and sodium bisulfite to water to obtain the initiator.

3. The method for preparing the fluid loss reducing agent for oil well cement according to claim 1, characterized in that, The step of adding the initiator to the second mixed solution to carry out the reaction includes: The initiator is added to the second mixed solution, and the mixture is reacted at a first temperature for a first time to obtain a third mixed solution; The initiator is added to the third mixed solution, and the reaction is carried out at a second temperature for a second time to obtain a fourth mixed solution; and The initiator is added to the fourth mixed solution, and the mixture is reacted at a third temperature for a third time to obtain the oil well cement fluid loss reducer.

4. The method for preparing the fluid loss reducing agent for oil well cement according to claim 3, characterized in that, The first temperature is 59–61°C, and the first reaction time is 60–90 min; the second temperature is 64–66°C, and the second reaction time is 90–120 min; the third temperature is 69–71°C, and the third reaction time is 90–120 min.

5. The method for preparing the fluid loss reducing agent for oil well cement according to claim 1, characterized in that, By mass percentage, the 2-acrylamido-2-methylpropanesulfonic acid comprises 85-90 parts, the sodium p-styrenesulfonate comprises 55-60 parts, the dimethyl diallyl ammonium chloride comprises 44-50 parts, the N-vinylpyrrolidone comprises 15-20 parts, the N,N-dimethylacrylamide or N,N-diethyl-2-acrylamide comprises 40-45 parts, the allyl polyoxyethylene ether or methyl allyl polyoxyethylene ether comprises 0.5-1 part, and the water comprises 700-730 parts.

6. The method for preparing the fluid loss reducing agent for oil well cement according to claim 2, characterized in that, The potassium persulfate comprises 3 to 4 parts by mass, and the sodium bisulfite comprises 3 to 4 parts by mass.

7. The method for preparing the fluid loss reducing agent for oil well cement according to claim 1, characterized in that, The total weight of 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrenesulfonate, dimethyldiallyl ammonium chloride, N-vinylpyrrolidone, N,N-dimethylacrylamide or N,N-diethyl-2-acrylamide, allyl polyoxyethylene ether or methyl allyl polyoxyethylene ether accounts for 24-28% of the weight of the first mixed solution.

8. A fluid loss reducing agent for oil well cement, characterized in that, The oil well cement fluid loss reducing agent is obtained by the preparation method of the oil well cement fluid loss reducing agent as described in any one of claims 1 to 7.

9. The fluid loss reducing agent for oil well cement according to claim 8, characterized in that, The molecular weight of the water loss reducing agent for oil well cement is 200,000 to 400,000 g / mol.

10. The application of the oil well cement fluid loss reducing agent as described in any one of claims 8 to 9 in oil well cement slurry, characterized in that, The application temperature of the oil well cement fluid loss reducing agent in oil well cement slurry is less than or equal to 240°C.

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