High-temperature suspension stabilizer for high-density well cementation cement slurry and preparation method of high-temperature suspension stabilizer

Abstract

The invention discloses a high-temperature suspension stabilizer for high-density well cementation cement slurry and a preparation method of the high-temperature suspension stabilizer, and relates to the technical field of oil and gas well cementation. The high-temperature suspension stabilizer comprises the following components in parts by mass: 30-50 parts of a thermal tackifying polymer; 30-40 parts of dolomite powder; 15 to 20 parts of water-soluble polyvinyl alcohol; and 5-10 parts of hectorite powder. The high-temperature suspension stabilizer disclosed by the invention can effectively prevent a weighting agent in high-density well cementation cement slurry from sinking under the action of high temperature, ensures the high-temperature sedimentation stability of the cement slurry, has small influence on the normal-temperature rheological property of the high-density well cementation cement slurry, and realizes the collaborative development of the normal-temperature rheological property and the high-temperature stability. The method is simple, the high-temperature suspension stabilizer can be rapidly prepared, and the well cementation construction safety of the high-density well cementation cement slurry is guaranteed.

Description

Technical Field

[0001] The invention relates to the technical field of oil and gas well cementing, and in particular to a high-temperature suspension stabilizer for high-density cementing slurry and a preparation method thereof. Background Art

[0002] The geology of high-pressure oil and gas and ultra-deep oil and gas reservoirs is complex and faces an abnormally high-pressure environment. In order to ensure the quality of cementing, a cementing agent with a density of 2.00 to 2.60 g / cm 3 In order to ensure the uniformity and stability of high-density cement slurry weighting materials and gelling materials under high temperature conditions, high-temperature suspension stabilizers need to be added.

[0003] The high-temperature suspension stabilizers used in the prior art are mainly composed of one or more combinations of high molecular polymers, clay minerals, and inorganic thickeners. Among them, the high molecular polymers are mainly AMPS / AM type viscosity-enhancing polymers, the clay minerals are mainly silicate (aluminum) minerals such as bentonite, attapulgite, and sepiolite, and the inorganic thickeners are mainly magnesium aluminum silicate, nano-silicon dioxide, fumed silica and other substances. The above-mentioned high-temperature suspension stabilizers can effectively ensure that the density is 2.30g / cm 3 The following is the high-temperature sedimentation stability of high-density cementing slurry. When the density and use temperature of cement slurry are further increased, the water-solid ratio of cement slurry decreases, and the dosage of weighting agent and high-temperature suspension stabilizer increases. In addition, under high temperature conditions, due to the poor working performance or failure of existing high molecular polymers, existing suspension stabilizers such as clay minerals and inorganic thickeners do not work, resulting in high-density cement slurry with serious room temperature thickening, large flow friction, and poor high-temperature sedimentation stability. For example: when preparing 2.30g / cm 3 When the cement slurry is subjected to the above high density, the existing high temperature suspension stabilizer has the problems of poor stabilization effect, room temperature thickening, high temperature failure, etc., which makes the pumping performance and high temperature stability of the cement slurry worse. The density difference of cement slurry or cement stone is much greater than 0.05g / cm 3 Due to the unstable density of the slurry, the displacement efficiency of the cement slurry is reduced, and the oil, gas and water layers cannot be effectively stabilized, resulting in well leakage or air leakage in the annulus, which leads to poor cementing quality. In addition, the strength of the cement sheath in the cement sealing section after curing is different, and it cannot meet the requirements of isolating the formation and protecting the casing, making it difficult to ensure the cementing quality. Summary of the invention

[0004] In order to overcome the defects and shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a high-temperature suspension stabilizer for high-density cementing slurry and a preparation method thereof, so as to solve the problems of severe room temperature thickening, poor high-temperature stability, poor construction performance, and poor sedimentation stability existing in the above-mentioned prior art high-temperature suspension stabilizer for high-density cementing slurry.

[0005] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a high-temperature suspension stabilizer for high-density cementing slurry, comprising the following components in parts by mass:

[0007] 30-50 parts of thermal viscosity-increasing polymer;

[0008] 30-40 parts of dolomite powder;

[0009] 15-20 parts of water-soluble polyvinyl alcohol;

[0010] 5 to 10 parts of lithium soapstone powder.

[0011] In some embodiments of the present invention, the thermal viscosity-increasing polymer is a random copolymer with a molecular weight between 20,000 and 40,000, and the thermal viscosity-increasing polymer is prepared by free radical micellar polymerization of 40 to 60 parts by mass of acrylamide, 25 to 35 parts of sodium methyl propylene sulfonate, 10 to 15 parts of 2-hydroxyethyl acrylate, and 0.5 to 1.5 parts of 2-dodecyl acrylate monomer under the action of a surfactant and an initiator, wherein the surfactant is 0.5 to 1.5 parts of sodium dodecyl sulfate, and the initiator is 1 to 2 parts of ammonium persulfate.

[0012] In some embodiments of the present invention, the method for preparing the thermally tackifying polymer comprises the following operations:

[0013] S1. At room temperature, add 40 to 60 parts of acrylamide and 25 to 35 parts of sodium methyl propylene sulfonate, by mass, to 100 parts of water, and fully dissolve and mix to obtain a first mixed solution;

[0014] S2. At room temperature, add 10 to 15 parts by mass of 2-hydroxyethyl acrylate to 50 parts of hot water at 50° C., and stir to obtain a second mixed solution;

[0015] S3. At room temperature, add 0.5 to 1.5 parts by mass of sodium dodecyl sulfate to 50 parts of hot water and fully disperse to obtain a third mixed solution; add 0.5 to 1.5 parts of 2-dodecyl acrylate monomer to the third mixed solution and stir continuously to obtain a fourth mixed solution;

[0016] S4, stirring and mixing the first mixed solution, the second mixed solution and the third mixed solution to obtain a fifth mixed solution;

[0017] S5. At room temperature, adjusting the pH of the fifth mixed solution to 7-8 using a sodium hydroxide solution with a mass concentration of 20 wt %, to obtain a sixth mixed solution;

[0018] S6. At room temperature, add 1 to 2 parts by mass of ammonium persulfate to 23 to 24 parts of water, and fully dissolve and mix to obtain a seventh mixed solution;

[0019] S7, transferring the sixth mixed liquid to a reactor with a stirring device, introducing nitrogen to remove oxygen in the reactor to maintain a nitrogen atmosphere, stirring and heating the sixth mixed liquid to 60° C., and then adding the seventh mixed liquid dropwise to the sixth mixed liquid using a constant pressure funnel device to obtain an eighth mixed liquid; preferably, the stirring speed is 200 r / min, and the dropping speed is 10 drops / min;

[0020] S8, keeping the eighth mixed solution at 60° C. for 3 h, then naturally cooling it to 45° C. and keeping it at 45° C. for 1-2 h, and then taking it out to obtain a ninth mixed solution;

[0021] S9. Add 100 parts of anhydrous ethanol to the ninth mixed solution, wash and purify it several times and filter out the anhydrous ethanol to obtain a white viscous substance, and then freeze-dry the white viscous substance in vacuum to obtain the thermal viscosity-increasing polymer; preferably, the vacuum freeze-drying temperature is -5°C and the time is 8 hours.

[0022] Thermal viscosity-increasing polymers are insoluble at room temperature (or have low solubility), soluble at high temperature, and thermally viscous. As the temperature rises, the properties of thermal viscosity-increasing polymers change significantly, the thermal viscosity-increasing polymers begin to dissolve, and the viscosity increases significantly, which can effectively prevent the sinking of weighting agents in high-density cementing slurries. In addition, due to its characteristics of being insoluble at room temperature and soluble at high temperature, it has basically no significant effect on the room-temperature rheological properties of cement slurries, thereby synergistically enhancing the room-temperature rheological properties and high-temperature sedimentation stability of high-density cementing slurries.

[0023] In some embodiments of the present invention, the physical properties of the dolomite powder meet the following requirements: purity ≥ 98%, specific surface area ≥ 500 kg / m 3 .

[0024] Dolomite powder has fine particles and a high specific surface area and surface activity, which enables it to form a large number of physical adsorption points in the dispersion medium. Like countless small "anchor points", it can stably adsorb the weighting agent particles in the high-density cementing slurry to prevent them from aggregating and sinking due to gravity. In addition, there are a large number of polar hydroxyl groups on the surface of dolomite powder, which will form a three-dimensional network structure in the high-density cementing slurry through interactions such as van der Waals forces and hydrogen bonds, effectively hindering direct contact between particles and preventing the formation of sedimentation. At the same time, it can also increase the viscosity of the system, further enhancing the anti-sedimentation effect. Under the action of external forces (such as stirring), the three-dimensional structure formed by dolomite powder in the high-density cementing slurry will be destroyed. Therefore, it has little effect on the rheological properties of the cement slurry at room temperature. However, when the external force is removed, it can quickly restore its stable network structure, thereby maintaining the sedimentation stability of the cement slurry.

[0025] In some embodiments of the present invention, the water-soluble polyvinyl alcohol is a mixture of polyvinyl alcohol 1788 and polyvinyl alcohol 1792 in a mass ratio of 1:1.

[0026] In some embodiments of the present invention, the physical properties of polyvinyl alcohol 1788 and polyvinyl alcohol 1792 meet the following requirements: purity ≥ 98%, specific surface area ≥ 200 kg / m 3 .

[0027] Water-soluble polyvinyl alcohol has the characteristics of slow dissolution at room temperature and fast dissolution at high temperature. It can also synergistically enhance the room temperature rheological properties and high temperature sedimentation stability of high-density cementing slurry. Polyvinyl alcohol has a large number of polar hydroxyl groups on its molecular chain, which can form a polymer film with certain mechanical strength and elasticity, and form a network structure in high-density cementing slurry to prevent the sinking of the weighting agent. In addition, the long-chain molecules of polyvinyl alcohol will wrap around the surface of the particles, forming a protective film with the particles through physical adsorption or chemical bonding, preventing the particles from direct contact and aggregation, thereby greatly reducing the sedimentation of the weighting agent in the high-density cementing slurry.

[0028] In some embodiments of the present invention, the hectorite powder is industrial-grade aqueous hectorite powder, and the chemical composition of the hectorite powder satisfies: SiO2 ≥ 59%, MgO ≥ 27%, Li2O ≥ 1%, Na2O ≤ 2.5%, and loss on ignition ≤ 8%. The physical properties of the hectorite powder meet the following requirements: purity ≥ 99%, specific surface area ≥ 350 kg / m 3 .

[0029] Lithopsite powder is composed of tiny layered structures, which can absorb water and swell in water to form a three-dimensional network structure. It has strong gelling properties in water systems, excellent thixotropy, dispersibility, high-temperature suspension and thickening properties, thereby further improving the high-temperature sedimentation stability of high-density cement slurry.

[0030] The present invention also provides a method for preparing a high-temperature suspension stabilizer for high-density cementing slurry, comprising the following operations:

[0031] According to mass parts, 30 to 50 parts of thermal viscosity-increasing polymer, 30 to 40 parts of dolomite powder, 15 to 20 parts of water-soluble polyvinyl alcohol, and 5 to 10 parts of laponite powder are weighed and mixed thoroughly to obtain the high-temperature suspension stabilizer for high-density cementing slurry.

[0032] The preparation method of the present invention is simple, and a high-temperature suspension stabilizer can be quickly prepared to ensure the safety of cementing construction of high-density cement slurry, thereby improving the efficiency and exploitation safety of deep high-pressure oil and gas resources and meeting the country's demand for deep and ultra-deep oil and gas resources.

[0033] Compared with the prior art, the present invention has the following beneficial effects:

[0034] 1. Compared with ordinary high-temperature suspension agents, the high-temperature suspension stabilizer for high-density cementing slurry of the present invention has better suspension stability, which can effectively prevent the sinking of the weighting agent in the high-density cementing slurry under high temperature, and ensure the high-temperature sedimentation stability of the cement slurry. In addition, compared with the existing high-temperature suspension agents, the high-temperature suspension stabilizer has less effect on the room-temperature rheological properties of the high-density cementing slurry, achieving the coordinated development of room-temperature rheological properties and high-temperature stability.

[0035] 2. The high-temperature suspension stabilizer of the present invention has good adaptability in high-density cementing slurry. Compared with the high-temperature suspension stabilizer in the prior art, the high-temperature suspension stabilizer of the present invention has better compatibility with existing admixtures such as high-temperature retarders and high-temperature fluid loss reducers. When used in combination, a high-density cementing slurry with good room temperature rheological properties, no free liquid, small water loss (<60mL, 120°C), excellent high-temperature thickening performance, no abnormal gelling of cement slurry, good high-temperature sedimentation stability, and no decline in high-temperature strength can be prepared, which meets the cementing quality of high-pressure oil and gas wells and ultra-deep oil and gas wells, and ensures the efficient and safe exploitation of deep oil and gas resources.

[0036] 3. The high-temperature suspension stabilizer provided by the present invention has a certain high-temperature water loss control effect, which can reduce the amount of high-temperature water loss reduction and reduce the cost of cementing materials. In addition, the preparation method of the high-temperature suspension stabilizer provided is simple, the raw material source is wide, and the price is low, and it can be widely used in high-density cement slurry. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 It is a high temperature thickening curve diagram of the high density cementing slurry mixed with the high temperature suspension stabilizer of the present invention.

[0038] Figure 2The high temperature thickening curve of the high density cementing slurry mixed with the high temperature suspension stabilizer of the prior art.

[0039] Figure 3 This is the high-temperature thickening curve of high-density cementing slurry without any high-temperature suspension stabilizer. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical scheme and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0041] In an embodiment of the present invention, the thermal viscosity-increasing polymer is a random copolymer with a molecular weight between 20,000 and 40,000. The thermal viscosity-increasing polymer is prepared by free radical micellar polymerization of 40 to 60 parts by mass of acrylamide, 25 to 35 parts of sodium methyl propylene sulfonate, 10 to 15 parts of 2-hydroxyethyl acrylate, and 0.5 to 1.5 parts of 2-dodecyl acrylate monomer under the action of a surfactant and an initiator. The surfactant is 0.5 to 1.5 parts of sodium dodecyl sulfate, and the initiator is 1 to 2 parts of ammonium persulfate.

[0042] In an embodiment of the present invention, the method for preparing the thermally tackifying polymer comprises the following operations:

[0043] S1. At room temperature, add 40 to 60 parts of acrylamide and 25 to 35 parts of sodium methyl propylene sulfonate, by mass, to 100 parts of water, and fully dissolve and mix to obtain a first mixed solution;

[0044] S2. At room temperature, add 10 to 15 parts by mass of 2-hydroxyethyl acrylate to 50 parts of hot water at 50° C., and stir to obtain a second mixed solution;

[0045] S3. At room temperature, add 0.5 to 1.5 parts by mass of sodium dodecyl sulfate to 50 parts of hot water and fully disperse to obtain a third mixed solution; add 0.5 to 1.5 parts of 2-dodecyl acrylate monomer to the third mixed solution and stir continuously to obtain a fourth mixed solution;

[0046] S4, stirring and mixing the first mixed solution, the second mixed solution and the third mixed solution to obtain a fifth mixed solution;

[0047] S5. At room temperature, adjusting the pH of the fifth mixed solution to 7-8 using a sodium hydroxide solution with a mass concentration of 20 wt %, to obtain a sixth mixed solution;

[0048] S6. At room temperature, add 1 to 2 parts by mass of ammonium persulfate to 23 to 24 parts of water, and fully dissolve and mix to obtain a seventh mixed solution;

[0049] S6, transferring the sixth mixed liquid to a reactor with a stirring device, introducing nitrogen gas to remove oxygen in the reactor to maintain a nitrogen atmosphere, stirring and heating the sixth mixed liquid to 60° C. at 200 r / min, and then adding the seventh mixed liquid to the sixth mixed liquid dropwise at 10 drops / min using a constant pressure funnel device to obtain an eighth mixed liquid;

[0050] S7, keeping the eighth mixed solution at 60° C. for 3 h, then naturally cooling it to 45° C. and keeping it at 45° C. for 1-2 h, and then taking it out to obtain a ninth mixed solution;

[0051] S8. Add 100 parts of anhydrous ethanol to the ninth mixed solution, wash and purify it several times and filter out the anhydrous ethanol to obtain a white viscous substance, and then freeze-dry the white viscous substance at -5°C for 8 hours to obtain the thermal thickening polymer.

[0052] In the embodiment of the present invention, the physical properties of dolomite powder meet the following requirements: purity ≥ 98%, specific surface area ≥ 500 kg / m 3 .

[0053] In the embodiment of the present invention, the water-soluble polyvinyl alcohol is a mixture of polyvinyl alcohol 1788 and polyvinyl alcohol 1792 in a mass ratio of 1:1.

[0054] In the embodiment of the present invention, the physical properties of polyvinyl alcohol 1788 and polyvinyl alcohol 1792 both meet the following requirements: purity ≥ 98%, specific surface area ≥ 200 kg / m 3 .

[0055] In the embodiment of the present invention, the hectorite powder is an industrial-grade aqueous hectorite powder, and the chemical composition of the hectorite powder satisfies: SiO2≥59%, MgO≥27%, Li2O≥1%, Na2O≤2.5%, and loss on ignition≤8%. The physical properties of the hectorite powder meet the following requirements: purity≥99%, and specific surface area≥350kg / m 3 .

[0056] Example 1

[0057] As a preferred embodiment of the present invention, the high-temperature suspension stabilizer for high-density cementing slurry disclosed in this embodiment has a specific composition as shown in Table 1.

[0058] Table 1 Composition of high temperature suspension stabilizer in Example 1

[0059] Component name Mass parts / parts Thermal Adhesion Polymer 30 Dolomite powder 40 Water-soluble polyvinyl alcohol 20 Hectorite powder 10

[0060] According to the mass parts in Table 1, 30 parts of thermal viscosity-increasing polymer, 40 parts of dolomite powder, 20 parts of water-soluble polyvinyl alcohol, and 10 parts of hectorite powder were weighed and mixed thoroughly to obtain high-temperature suspension stabilizer 1# for high-density cementing slurry.

[0061] Example 2

[0062] As a preferred embodiment of the present invention, the high-temperature suspension stabilizer for high-density cementing slurry disclosed in this embodiment has a specific composition as shown in Table 2.

[0063] Table 2 Composition of high temperature suspension stabilizer in Example 2

[0064] Component name Mass parts / parts Thermal Adhesion Polymer 40 Dolomite powder 35 Water-soluble polyvinyl alcohol 17 Hectorite powder 8

[0065] According to the mass parts in Table 2, 40 parts of thermal viscosity-increasing polymer, 35 parts of dolomite powder, 17 parts of water-soluble polyvinyl alcohol, and 8 parts of hectorite powder are weighed and mixed thoroughly to obtain the high-temperature suspension stabilizer 2# for high-density cementing slurry.

[0066] Example 3

[0067] As a preferred embodiment of the present invention, the high-temperature suspension stabilizer for high-density cementing slurry disclosed in this embodiment has a specific composition as shown in Table 3.

[0068] Table 3 Composition of high temperature suspension stabilizer in Example 3

[0069] Component name Mass parts / parts Thermal Adhesion-Increasing Polymers 45 Dolomite powder 32 Water-soluble polyvinyl alcohol 16 Hectorite powder 7

[0070] According to the mass parts in Table 3, 45 parts of thermal viscosity-increasing polymer, 32 parts of dolomite powder, 16 parts of water-soluble polyvinyl alcohol, and 8 parts of hectorite powder are weighed and mixed thoroughly to obtain the high-temperature suspension stabilizer 3# for high-density cementing slurry.

[0071] Example 4

[0072] As a preferred embodiment of the present invention, the high-temperature suspension stabilizer for high-density cementing slurry disclosed in this embodiment has a specific composition as shown in Table 4.

[0073] Table 4 Composition of high temperature suspension stabilizer in Example 4

[0074] Component name Mass parts / parts Thermal Adhesion-Increasing Polymers 50 Dolomite powder 30 Water-soluble polyvinyl alcohol 15 Hectorite powder 5

[0075] According to the mass parts in Table 4, 50 parts of thermal viscosity-increasing polymer, 30 parts of dolomite powder, 15 parts of water-soluble polyvinyl alcohol, and 5 parts of hectorite powder are weighed and mixed thoroughly to obtain the high-temperature suspension stabilizer 4# for high-density cementing slurry.

[0076] Comparative Example 1

[0077] This comparative example uses a commercially available high-density high-temperature suspension stabilizer for cementing cement, which is mainly composed of a common viscosity-increasing macromolecular polymer and clay minerals.

[0078] Comparative Example 2

[0079] This comparative example is a blank group without any high temperature suspension stabilization.

[0080] Test Case

[0081] The high-density cement slurry obtained in Examples 1 to 4 was added to the cement slurry with a high-temperature suspension stabilizer, and the density was 2.50 g / cm according to the following formula, calculated by weight. 3 High density cementing slurry:

[0082] G-grade oil well cement (G-grade oil well cement 100%) + 0.3% polycarboxylic acid drag reducer + 150% iron powder weighting agent + 30% quartz sand-metakaolin high temperature strength stabilizer + 0.4-0.8% high temperature suspension stabilizer + 0.8% AMPS-AA (2-acrylamide-2-methylpropanesulfonic acid / acrylic acid copolymer) high temperature retarder + 3% AMPS-AM (2-acrylamide-2-methylpropanesulfonic acid-acrylamide copolymer) high temperature loss reduction cement + 0.3% dimethyl silicone oil defoamer + 75% water (the cementing slurry formula is not limited to the above-mentioned cementing cement admixtures).

[0083] Comparative Example 1 and Comparative Example 2 (blank group) were set up at the same time. Comparative Example 1 used a commercially available common high-temperature suspension stabilizer to replace the high-temperature suspension stabilizer for high-density cementing slurry of the present invention, while Comparative Example 2 (blank group) did not add any high-temperature suspension stabilizer. The other proportions and conditions were the same as the above preparation, and the preparation density was 2.50 g / cm 3 High density cementing slurry.

[0084] According to GB / T19139-2012 Oil Well Cement Test Method, high-density cementing slurry was prepared, and the high-temperature sedimentation stability and other properties of the high-density cementing slurry in the embodiment and the comparative example were tested according to SY / T6544-2017 Oil Well Cement Slurry Performance Requirements. The test method for high-temperature sedimentation stability is as follows: according to the thickening test steps, the high-density cementing slurry is heated to 170°C, maintained for 60 minutes, stirring is stopped, and after cooling to 60°C, the thickening slurry cup is taken out, and the thickened oil on the upper layer of the slurry cup is removed, and the cement slurry density in the upper and lower parts of the slurry cup is tested respectively, and the density difference between the upper and lower parts is calculated. The experimental results are shown in Table 5.

[0085] Table 5 Experimental results of examples and comparative examples

[0086]

[0087]

[0088] From the results in Table 5, it can be seen that when no high temperature suspension stabilizer is added (Comparative Example 2), 2.50 g / cm 3 The high-density cementing slurry has poor high-temperature stability, the weighting agent has serious high-temperature sedimentation, and the density difference between the upper and lower parts of the cement slurry is as high as 1.32g / cm 3 In addition, from Figure 3 It can also be seen that the high-temperature thickening performance of the cement slurry is seriously poor, and abnormal gelation occurs, which is specifically manifested as "bulging" and "stepping" on the high-temperature thickening curve. The above results show that when the high-temperature suspension stabilizer is not added, the construction performance of the high-density cementing cement cannot meet the requirements at all, and the cementing quality of high-pressure and deep oil and gas formations cannot be guaranteed, and even cementing failure may occur. After adding the high-temperature suspension stabilizer of the prior art (Comparative Example 1), 2.50g / cm 3 The high-temperature sedimentation stability of high-density cementing cement has been improved to a certain extent, but the density difference between the upper and lower cement slurries is still greater than 0.05g / cm 3 , the high temperature sedimentation stability still needs to be further improved. In addition, from Table 5 and Figure 2 It can also be seen that after adding the high-temperature suspension stabilizer of the prior art, the rheological properties of the high-density cementing slurry are significantly reduced, which is specifically manifested in the decrease in the fluidity of the cement slurry and the initial consistency in the high-temperature thickening experiment is greater than 30Bc, resulting in poor construction performance of the cement slurry, which needs to be further improved. In addition, it can also be seen that the high-temperature suspension stabilizer of the prior art significantly reduces the high-temperature thickening time of the cement slurry. Further, it can be seen from Table 5 that after adding the high-temperature suspension stabilizer provided by the present invention, 2.50g / cm 3 The high-temperature sedimentation stability of the high-density cementing slurry is significantly improved. The upper and lower density differences of the cement slurries in Examples 1 to 3 are all less than 0.05 g / cm 3 , the lowest is even less than 0.02g / cm 3 This shows that the high temperature suspension stabilizer of the present invention has excellent high temperature suspension stability and can effectively prevent the weighting agent from sinking. Figure 1 It can also be seen that the rheological properties of the cement slurry are good, specifically, the fluidity of the cement slurry is greater than 195mm, and the initial consistency of the cement slurry in the high-temperature thickening experiment is only 22Bc. In addition, it can also be seen that the high-temperature thickening performance of the cement slurry is excellent, and no abnormal gelling occurs, specifically, the high-temperature thickening curve of the cement slurry is stable. In addition, the high-temperature water loss of the high-density cementing cement slurry is low. In summary, the high-density cementing cement slurry mixed with the high-temperature suspension stabilizer of the present invention has excellent comprehensive working performance, can effectively guarantee the cementing quality of high-pressure oil and gas wells, deep wells and ultra-deep wells, and ensure the safe and efficient exploitation of high-pressure and deep oil and gas resources.

[0089] Finally, it should be noted that the above embodiments are only preferred embodiments of the present invention to illustrate the technical solutions of the present invention, rather than limiting them, and certainly not limiting the patent scope of the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention. In other words, any changes or modifications made to the main design concept and spirit of the present invention that have no substantive significance, and the technical problems they solve are still consistent with the present invention, should be included in the protection scope of the present invention. In addition, the direct or indirect application of the technical solutions of the present invention in other related technical fields is also included in the patent protection scope of the present invention.

Claims

1. A high-temperature suspension stabilizer for high-density cementing slurry, characterized in that: It includes the following components by mass: 30-50 parts of thermal viscosity-increasing polymer; 30-40 parts of dolomite powder; 15-20 parts of water-soluble polyvinyl alcohol; 5 to 10 parts of lithium soapstone powder.

2. A high-temperature suspension stabilizer for high-density cementing slurry according to claim 1, characterized in that: The thermal viscosity-increasing polymer is a random copolymer with a molecular weight between 20,000 and 40,000. The thermal viscosity-increasing polymer is prepared by free radical micellar polymerization of 40 to 60 parts by mass of acrylamide, 25 to 35 parts of sodium methyl propylene sulfonate, 10 to 15 parts of 2-hydroxyethyl acrylate, and 0.5 to 1.5 parts of 2-dodecyl acrylate monomer under the action of a surfactant and an initiator. The surfactant is 0.5 to 1.5 parts of sodium dodecyl sulfate, and the initiator is 1 to 2 parts of ammonium persulfate.

3. A high-temperature suspension stabilizer for high-density cementing slurry according to claim 2, characterized in that: The preparation method of the thermally tackifying polymer comprises the following operations: S1. At room temperature, add 40 to 60 parts of acrylamide and 25 to 35 parts of sodium methyl propylene sulfonate, by mass, to 100 parts of water, and fully dissolve and mix to obtain a first mixed solution; S2. At room temperature, add 10 to 15 parts by mass of 2-hydroxyethyl acrylate to 50 parts of hot water at 50° C., and stir to obtain a second mixed solution; S3. At room temperature, add 0.5 to 1.5 parts by mass of sodium dodecyl sulfate to 50 parts of hot water and fully disperse to obtain a third mixed solution; add 0.5 to 1.5 parts of 2-dodecyl acrylate monomer to the third mixed solution and stir continuously to obtain a fourth mixed solution; S4, stirring and mixing the first mixed solution, the second mixed solution and the third mixed solution to obtain a fifth mixed solution; S5. At room temperature, adjusting the pH of the fifth mixed solution to 7-8 using a sodium hydroxide solution with a mass concentration of 20 wt %, to obtain a sixth mixed solution; S6. At room temperature, add 1 to 2 parts by mass of ammonium persulfate to 23 to 24 parts of water, and fully dissolve and mix to obtain a seventh mixed solution; S7, transferring the sixth mixed liquid to a reactor with a stirring device, introducing nitrogen to remove oxygen in the reactor to maintain a nitrogen atmosphere, stirring and heating the sixth mixed liquid to 60° C., and then adding the seventh mixed liquid dropwise to the sixth mixed liquid using a constant pressure funnel device to obtain an eighth mixed liquid; preferably, the stirring speed is 200 r / min, and the dropping speed is 10 drops / min; S8, keeping the eighth mixed solution at 60° C. for 3 h, then naturally cooling it to 45° C. and keeping it at 45° C. for 1-2 h, and then taking it out to obtain a ninth mixed solution; S9. Add 100 parts of anhydrous ethanol to the ninth mixed solution, wash and purify it several times and filter out the anhydrous ethanol to obtain a white viscous substance, and then freeze-dry the white viscous substance in vacuum to obtain the thermal viscosity-increasing polymer; preferably, the vacuum freeze-drying temperature is -5°C and the time is 8 hours.

4. The high-temperature suspension stabilizer for high-density cementing slurry according to claim 1, characterized in that: The physical properties of the dolomite powder meet the following requirements: purity ≥ 98%, specific surface area ≥ 500 kg / m 3 .

5. The high-temperature suspension stabilizer for high-density cementing slurry according to claim 1, characterized in that: The water-soluble polyvinyl alcohol is a mixture of polyvinyl alcohol 1788 and polyvinyl alcohol 1792 in a mass ratio of 1:

1.

6. A high-temperature suspension stabilizer for high-density cementing slurry according to claim 5, characterized in that: The physical properties of polyvinyl alcohol 1788 and polyvinyl alcohol 1792 meet the following requirements: purity ≥ 98%, specific surface area ≥ 200 kg / m 3 .

7. The high-temperature suspension stabilizer for high-density cementing slurry according to claim 1, characterized in that: The hectorite powder is industrial-grade water-based hectorite powder. The chemical composition of the hectorite powder meets the following requirements: SiO2≥59%, MgO≥27%, Li2O≥1%, Na2O≤2.5%, and loss on ignition≤8%. The physical properties of the hectorite powder meet the following requirements: purity≥99%, and specific surface area≥350kg / m 3 .

8. The method for preparing a high-temperature suspension stabilizer for high-density cementing slurry according to any one of claims 1 to 7, characterized in that: The following operations are included: According to mass parts, 30 to 50 parts of thermal viscosity-increasing polymer, 30 to 40 parts of dolomite powder, 15 to 20 parts of water-soluble polyvinyl alcohol, and 5 to 10 parts of laponite powder are weighed and mixed thoroughly to obtain the high-temperature suspension stabilizer for high-density cementing slurry.

Images