Dispersion-resistant fluid loss agent for oil well cement and preparation method of dispersion-resistant fluid loss agent

Abstract

The invention relates to the technical field of oil well cement admixtures, and provides an anti-dispersion fluid loss agent for oil well cement and a preparation method of the anti-dispersion fluid loss agent. The invention relates to an anti-dispersion fluid loss agent for oil well cement, which is prepared from the following raw materials in parts by weight: 30 to 40 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 to 15 parts of polyacrylamide, 5 to 8 parts of polyvinyl alcohol, 2 to 6 parts of itaconic anhydride, 0.2 to 0.3 part of inorganic material, 0.3 to 0.5 part of initiator, 0.1 to 0.3 part of chain transfer agent and 220 to 300 parts of water, the hydrolysis degrees of the first polyacrylamide and the second polyacrylamide are different. According to the technical scheme, the problem of poor dispersion resistance of the fluid loss agent for oil well cement in the prior art is solved.

Description

Technical Field

[0001] The invention relates to the technical field of oil well cement admixtures, and in particular to an anti-dispersion fluid loss reducer for oil well cement and a preparation method thereof. Background Art

[0002] In the oil and gas extraction operation, cementing is a key step to ensure the long-term stable operation of the oil well. As an indispensable additive for oil well cement, fluid loss reducer plays a vital role in it. Fluid loss reducer is mainly used to control the water loss of oil well cement slurry during the cementing process. Most fluid loss reducer designs focus on controlling water loss, and do not take into account the anti-dispersion performance of cement slurry under special conditions.

[0003] In the process of oil extraction, it is very common for oil wells to cross aquifers. When cementing such oil wells, the cement slurry needs to face strong interference from the water in the aquifer, which puts strict requirements on the performance of the cement slurry. In the aquifer environment, ordinary cement slurry is very easy to disperse once it comes into contact with water. The cement particles will spread rapidly under the action of the water flow, causing the original structure of the cement slurry to be destroyed and unable to maintain its uniformity and stability. This will not only seriously affect the subsequent coagulation and hardening process of the cement slurry, but also greatly reduce the quality of the cement stone. Therefore, it is very necessary to develop a fluid loss reducer for oil well cement with anti-dispersion properties. Summary of the invention

[0004] The invention provides an anti-dispersion fluid loss reducer for oil well cement and a preparation method thereof, which solves the problem of poor anti-dispersion performance of the fluid loss reducer for oil well cement in the related art.

[0005] The technical scheme of the present invention is as follows: The present invention provides an anti-dispersion fluid loss agent for oil well cement, comprising the following component raw materials in parts by weight: 30-40 parts of 2-acrylamido-2-methylpropane sulfonic acid, 10-15 parts of polyacrylamide, 5-8 parts of polyvinyl alcohol, 2-6 parts of itaconic anhydride, 0.2-0.3 parts of inorganic materials, 0.3-0.5 parts of initiators, 0.1-0.3 parts of chain transfer agents, and 220-300 parts of water, wherein the polyacrylamide consists of a first polyacrylamide and a second polyacrylamide, and the first polyacrylamide and the second polyacrylamide have different degrees of hydrolysis.

[0006] As a further technical solution, the hydrolysis degree of the first polyacrylamide is 30%-35%, the hydrolysis degree of the second polyacrylamide is 40%-45%, and the mass ratio of the first polyacrylamide to the second polyacrylamide is 2:2-3.

[0007] As a further technical solution, the initiator includes one or both of ammonium persulfate and potassium persulfate.

[0008] In the present invention, a proper amount of initiator is added to initiate the polymerization reaction. The proper amount of initiator can ensure that the formed polymer has a suitable molecular weight distribution, so that it has good water solubility and molecular chain length, and improves the dispersibility and stability of the fluid loss reducer in cement slurry.

[0009] As a further technical solution, the chain transfer agent includes one or more of n-butyl mercaptan, hypophosphorous acid, and n-dodecyl mercaptan.

[0010] In the present invention, the chain transfer agent can undergo a chain transfer reaction with the growing active chain during the polymerization reaction, transfer the active center to itself, thereby terminating the growing active chain and re-initiating a new active chain, which can effectively prevent the polymer molecular weight from being too high, obtain a polymer product with a more uniform molecular weight, and ensure that the fluid loss reducer can stably exert its anti-dispersion and water loss reduction functions.

[0011] As a further technical solution, the inorganic material consists of calcium carbonate and diatomaceous earth, and the mass ratio of the calcium carbonate to the diatomaceous earth is 1:3-4.

[0012] In the present invention, calcium carbonate and diatomaceous earth are added to form an inorganic material. Calcium carbonate is a common inorganic compound with high hardness and strength. Calcium carbonate is used as a filler and is filled between cement particles to improve the compactness and strength of cement slurry. When the cement slurry solidifies, the calcium carbonate particles can be filled in the gaps in the cement gel structure, making the cement stone structure more compact, thereby improving its compressive strength and impact resistance, helping to improve the stability of oil well cement underground, and preventing damage to the oil well caused by external pressure or formation movement. The porous structure of diatomaceous earth can improve the microstructure of cement slurry, and the high specific surface area and unique surface properties of diatomaceous earth make it have good adsorption capacity, further assisting the fluid loss reducer to play the function of reducing water loss.

[0013] As a further technical solution, the diatomaceous earth is a composite diatomaceous earth of alkylsulfonylbenzene derivatives.

[0014] As a further technical solution, the alkylsulfonylbenzene derivatives include one or two of 4-hexadecylsulfonanilide and ((4-methylphenyl)sulfonyl)octadecylamine.

[0015] In the present invention, alkyl sulfonyl benzene derivatives are added to composite diatomite. The alkyl sulfonyl benzene derivatives have longer alkyl chains. When they are composited in diatomite, they give the diatomite stronger hydrophobicity, which can limit the free diffusion path of water, making it difficult for water to quickly seep out of cement slurry, thereby improving the water loss reducing performance of the fluid loss reducer.

[0016] As a further technical solution, the raw materials of the alkylsulfonylbenzene derivative composite diatomaceous earth include alkylsulfonylbenzene derivative and diatomaceous earth in a mass ratio of 1 to 2:20.

[0017] As a further technical solution, the preparation method of the alkylsulfonylbenzene derivative composite diatomaceous earth comprises the following steps: mixing diatomaceous earth and alkylsulfonylbenzene derivatives, wet ball milling, drying, breaking up and screening to obtain the alkylsulfonylbenzene derivative composite diatomaceous earth.

[0018] As a further technical solution, the solvent used in the wet ball milling is anhydrous ethanol, and the mass ratio of the anhydrous ethanol to diatomaceous earth is 3:1.

[0019] As a further technical solution, the rotation speed of the ball mill is 200 r / min, and the ball milling time is 4 h.

[0020] As a further technical solution, the sieve used for screening has an aperture of 400 meshes.

[0021] The present invention also provides a method for preparing an anti-dispersion fluid loss additive for oil well cement, comprising the following steps: S1. Weighing an inorganic material and dispersing it in a portion of water to obtain a dispersion; S2, mixing 2-acrylamido-2-methylpropanesulfonic acid, polyacrylamide, polyvinyl alcohol, itaconic anhydride and the remaining water, adjusting the pH to 5-6, heating to 55-60° C., adding a chain transfer agent and an initiator, and reacting to obtain a polymer solution; S3, adding the polymer solution into the dispersion, cooling to room temperature after the reaction, and obtaining a fluid loss additive.

[0022] As a further technical solution, the amount of water used in S1 is 40% of the total mass of water.

[0023] As a further technical solution, the reaction temperature in S2 is 75-85°C, and the reaction time is 2-3h.

[0024] As a further technical solution, the mixing time in S2 is 30 to 45 minutes.

[0025] As a further technical solution, the reaction temperature in S3 is 75-85°C, and the reaction time is 40-50 min.

[0026] The working principle and beneficial effects of the present invention are: In the present invention, 2-acrylamide-2-methylpropanesulfonic acid, polyacrylamide, polyvinyl alcohol and itaconic anhydride are used as main raw materials to prepare a fluid loss reducer. 2-acrylamide-2-methylpropanesulfonic acid and itaconic anhydride can effectively improve the rheological properties of cement slurry, improve the stability of cement slurry in complex underground environment, and ensure smooth construction. The addition of polyvinyl alcohol enhances the film-forming property of the fluid loss reducer, forms a dense protective film between the cement slurry and the formation, and effectively prevents the water in the cement slurry from being lost to the formation. The initiator and the chain transfer agent accurately control the polymerization reaction to ensure that each component fully reacts. The polyacrylamide is hydrolyzed to form a film-forming film between the cement slurry and the formation. The first polyacrylamide and the second polyacrylamide with different hydrolysis degrees are composed. After addition, the second polyacrylamide with high hydrolysis degree can be quickly dissolved in water and begin to hydrolyze. The carboxyl groups on its molecular chain are ionized, and the large amount of negative charges generated make it quickly adsorbed to the surface of cement particles, providing the cement slurry with initial anti-dispersion ability. The first polyacrylamide has a low degree of hydrolysis and a relatively more stretched molecular chain. It can further extend into the gaps between cement particles on the basis of the adsorption layer formed by the second polyacrylamide, making the relative position between cement particles more stable, exerting the synergistic effect of the two, and improving the anti-dispersion performance of the fluid loss reducer. DETAILED DESCRIPTION

[0027] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0028] In the following examples and comparative examples: The first polyacrylamide: the degree of hydrolysis is 30%~35%, and the manufacturer is Beijing Sanhe Runjing Technology Co., Ltd.; Second polyacrylamide: hydrolysis degree is 40%~45%, the manufacturer is Henan Jinghua New Materials Technology Co., Ltd.; Polyvinyl alcohol: model 2488; Calcium carbonate: average particle size is 400 mesh; Diatomaceous earth: The average particle size is 325 mesh.

[0029] Example 1 A method for preparing an anti-dispersion fluid loss additive for oil well cement comprises the following steps: S1, weighing 0.2 parts of inorganic material and dispersing it in 88 parts of water to obtain a dispersion, wherein the inorganic material is composed of calcium carbonate and diatomaceous earth in a mass ratio of 1:3; S2, 30 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of polyacrylamide, 5 parts of polyvinyl alcohol, 2 parts of itaconic anhydride and 132 parts of water were mixed for 30 minutes, the pH was adjusted to 5, the temperature was raised to 55°C, 0.1 parts of n-butyl mercaptan and 0.3 parts of ammonium persulfate were added, the temperature was raised to 75°C and reacted for 3 hours to obtain a polymer solution, wherein the polyacrylamide consisted of a first polyacrylamide and a second polyacrylamide in a mass ratio of 1:1; S3. Add the polymer solution into the dispersion, react at 75°C for 50 minutes, and then cool to room temperature to obtain a fluid loss additive.

[0030] Example 2 A method for preparing an anti-dispersion fluid loss additive for oil well cement comprises the following steps: S1, weighing 0.25 parts of inorganic material and dispersing it in 104 parts of water to obtain a dispersion, wherein the inorganic material is composed of calcium carbonate and diatomaceous earth in a mass ratio of 1:4; S2, 35 parts of 2-acrylamido-2-methylpropanesulfonic acid, 12 parts of polyacrylamide, 6 parts of polyvinyl alcohol, 4 parts of itaconic anhydride and 156 parts of water were mixed for 30 minutes, the pH was adjusted to 5.5, the temperature was raised to 58°C, 0.2 parts of hypophosphorous acid and 0.4 parts of ammonium persulfate were added, the temperature was raised to 80°C and reacted for 2.5 hours to obtain a polymer solution, wherein the polyacrylamide was composed of a first polyacrylamide and a second polyacrylamide in a mass ratio of 1:1; S3. Add the polymer solution into the dispersion, react at 80°C for 45 minutes and then cool to room temperature to obtain a fluid loss additive.

[0031] Example 3 A method for preparing an anti-dispersion fluid loss additive for oil well cement comprises the following steps: S1, weighing 0.3 parts of inorganic material and dispersing it in 120 parts of water to obtain a dispersion, wherein the inorganic material is composed of calcium carbonate and diatomaceous earth in a mass ratio of 1:4; S2, 40 parts of 2-acrylamido-2-methylpropanesulfonic acid, 15 parts of polyacrylamide, 8 parts of polyvinyl alcohol, 6 parts of itaconic anhydride and 180 parts of water were mixed for 30 minutes, the pH was adjusted to 6, the temperature was raised to 60°C, 0.3 parts of n-dodecyl mercaptan and 0.5 parts of potassium persulfate were added, the temperature was raised to 85°C and reacted for 2 hours to obtain a polymer solution, wherein the polyacrylamide was composed of a first polyacrylamide and a second polyacrylamide in a mass ratio of 1:1; S3. Add the polymer solution into the dispersion, react at 85°C for 40 minutes and then cool to room temperature to obtain a fluid loss additive.

[0032] Example 4 Compared with Example 1, the difference of Example 4 is that the polyacrylamide consists of a first polyacrylamide and a second polyacrylamide in a mass ratio of 2:3.

[0033] Example 5 Compared with Example 4, the difference of Example 5 is that S1 is different. S1 includes the following steps: mixing 20 parts of diatomaceous earth and 1 part of 4-hexadecylsulfonanilide, adding 60 parts of anhydrous ethanol, ball milling at 200r / min for 4h and then drying, breaking up and passing through a 400-mesh sieve to obtain an alkylsulfonylbenzene derivative composite diatomaceous earth, dispersing a total of 0.2 parts of the alkylsulfonylbenzene derivative composite diatomaceous earth and calcium carbonate in 88 parts of water to obtain a dispersion, wherein the mass ratio of calcium carbonate to the alkylsulfonylbenzene derivative composite diatomaceous earth is 1:3.

[0034] Example 6 Compared with Example 5, the difference of Example 6 is that the added amount of 4-hexadecylsulfonanilide is 2 parts.

[0035] Example 7 Compared with Example 6, Example 7 is different in that 4-hexadecylsulfonanilide is replaced by an equal amount of ((4-methylphenyl)sulfonyl)octadecylamine.

[0036] Comparative Example 1 Compared with Example 1, the difference of Comparative Example 1 is that the polyacrylamide is the first polyacrylamide.

[0037] Comparative Example 2 Compared with Example 1, the difference in Comparative Example 2 is that the polyacrylamide is the second polyacrylamide.

[0038] The fluid loss reducer prepared in Examples 1 to 4 and Comparative Examples 1 to 2 was added to the cement slurry formula. The cement slurry formula was as follows: 700 g Shengwei G-grade cement + 2 g drag reducer BCD-200S + 4.5 g fluid loss reducer + 0.2 g defoamer G603 + water, with a water-cement ratio of 0.45. 680 g of cement slurry was poured into a beaker filled with 800 mL of water, and the pH of the upper 600 mL slurry was measured to evaluate the anti-dispersion performance of the fluid loss reducer.

[0039] The test results are shown in Table 1: Table 1 Performance test results of the fluid loss additives prepared in Examples 1 to 4 and Comparative Examples 1 to 2

[0040] Compared with Comparative Examples 1 and 2, the pH of Example 1 is smaller, indicating that the first polyacrylamide and the second polyacrylamide play a synergistic role and can improve the anti-dispersion performance of the fluid loss additive.

[0041] The fluid loss reducers prepared in Examples 4 to 7 were tested according to the test method specified in SY / T 5504.2-2013 "Evaluation Methods for Oil Well Cement Admixtures Part 2: Fluid Loss Reducers", with 5% of the mass of cement added to the fluid loss reducers, and the water loss of the samples was tested at a test temperature of 120°C.

[0042] The test results are shown in Table 2: Table 2 Performance test results of the fluid loss additives prepared in Examples 4 to 7

[0043] Compared with Example 4, the water loss of Examples 5 to 7 is less than that of Example 4, indicating that the addition of the alkylsulfonylbenzene derivative composite diatomaceous earth can reduce the water loss of the fluid loss reducer.

[0044] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. An anti-dispersion fluid loss agent for oil well cement, characterized in that: The invention comprises the following raw materials in parts by weight: 30-40 parts of 2-acrylamido-2-methylpropane sulfonic acid, 10-15 parts of polyacrylamide, 5-8 parts of polyvinyl alcohol, 2-6 parts of itaconic anhydride, 0.2-0.3 parts of inorganic material, 0.3-0.5 parts of initiator, 0.1-0.3 parts of chain transfer agent and 220-300 parts of water, wherein the polyacrylamide consists of a first polyacrylamide and a second polyacrylamide, and the first polyacrylamide and the second polyacrylamide have different degrees of hydrolysis.

2. The anti-dispersion fluid loss additive for oil well cement according to claim 1, characterized in that: The hydrolysis degree of the first polyacrylamide is 30%-35%, the hydrolysis degree of the second polyacrylamide is 40%-45%, and the mass ratio of the first polyacrylamide to the second polyacrylamide is 2:2-3.

3. The anti-dispersion fluid loss additive for oil well cement according to claim 1, characterized in that: The initiator includes one or both of ammonium persulfate and potassium persulfate.

4. The anti-dispersion fluid loss additive for oil well cement according to claim 1, characterized in that: The chain transfer agent includes one or more of n-butyl mercaptan, hypophosphorous acid, and n-dodecyl mercaptan.

5. The anti-dispersion fluid loss additive for oil well cement according to claim 1, characterized in that: The inorganic material consists of calcium carbonate and diatomaceous earth, and the mass ratio of the calcium carbonate to the diatomaceous earth is 1:3-4.

6. The anti-dispersion fluid loss additive for oil well cement according to claim 5, characterized in that: The diatomaceous earth is a composite diatomaceous earth of alkylsulfonylbenzene derivatives.

7. The anti-dispersion fluid loss additive for oil well cement according to claim 6, characterized in that: The alkylsulfonylbenzene derivatives include one or two of 4-hexadecylsulfonylanilide and ((4-methylphenyl)sulfonyl)octadecylamine.

8. The anti-dispersion fluid loss additive for oil well cement according to claim 6, characterized in that: The raw materials of the alkylsulfonylbenzene derivative composite diatomaceous earth include alkylsulfonylbenzene derivative and diatomaceous earth in a mass ratio of 1 to 2:

20.

9. The method for preparing an anti-dispersion fluid loss additive for oil well cement according to any one of claims 1 to 8, characterized in that: The following steps are involved: S1. Weighing an inorganic material and dispersing it in a portion of water to obtain a dispersion; S2, mixing 2-acrylamido-2-methylpropanesulfonic acid, polyacrylamide, polyvinyl alcohol, itaconic anhydride and the remaining water, adjusting the pH to 5-6, heating to 55-60° C., adding a chain transfer agent and an initiator, and reacting to obtain a polymer solution; S3, adding the polymer solution into the dispersion, cooling to room temperature after the reaction, and obtaining a fluid loss additive.

10. The method for preparing an anti-dispersion fluid loss additive for oil well cement according to claim 9, characterized in that: The reaction temperature in S2 is 75-85° C., and the reaction time is 2-3 h.

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