High temperature high density cement slurry and method of making

Abstract

The application provides a high-temperature and high-density cementing slurry and a preparation method thereof, which comprises the following components in parts by weight: 100 parts of oil well cement, 35-60 parts of silicon powder, 63-162 parts of weighting agent, 1-3 parts of microsilica, 3-6 parts of organic-inorganic grafted suspension stabilizer, 4-6 parts of fluid loss additive, 3-7 parts of retarder, 3-5 parts of drag reducing agent, 0.1-0.5 parts of defoaming agent and 58-67 parts of fresh water. The cementing slurry provided by the application can maintain good stability at 100-200 DEG C (BHCT, bottom hole circulating temperature), can effectively eliminate free fluid, does not affect cementing slurry preparation and cementing, has small fluid loss, and has a smooth thickening curve without core covering at high temperature, so that the cementing construction requirement can be met, and the application prospect is good.

Description

Technical Field

[0001] This invention relates to the field of petrochemical technology, and more specifically, to a high-temperature, high-density cement slurry and its preparation method. Background Technology

[0002] As exploration and development gradually moves towards deep and ultra-deep wells, ensuring cementing quality and safety remains a severe challenge and key technical problem for oil and gas well cementing technology. Among these challenges, the settling stability of the cement slurry directly affects cementing construction safety and cementing quality. Poor cement slurry stability can lead to problems such as the settling of solid particles, uneven distribution of the cement sheath, and the formation of free fluid at the top, adversely affecting the sealing ability of the cement sheath and impacting the safety of the construction operation.

[0003] With the increasing number of high-temperature deep wells, the high temperatures at the well bottom place higher demands on the stability of high-density cement slurry. High-density cement slurry contains a large amount of inert weighting materials, which are prone to settling within the slurry. This settling problem of solid particles is even more pronounced under high-temperature conditions, severely affecting the settling stability of high-density cement slurry. Therefore, maintaining the settling stability of high-density cement slurry under high-temperature conditions is crucial to ensuring cementing quality. Summary of the Invention

[0004] In view of this, the present invention proposes a high-temperature, high-density cement slurry and its preparation method, aiming to solve the problem of poor settling stability of high-density cement slurry under high-temperature conditions.

[0005] In one aspect, the present invention provides a high-temperature, high-density cement slurry comprising the following components in parts by weight: 100 parts oil well cement, 35-60 parts silica fume, 63-162 parts weighting agent, 1-3 parts microsilica, 3-6 parts organic-inorganic grafted suspension stabilizer, 4-6 parts fluid loss reducer, 3-7 parts retarder, 3-5 parts drag reducer, 0.1-0.5 parts defoamer, and 58-67 parts fresh water.

[0006] Furthermore, in the aforementioned high-temperature, high-density cement slurry, the organic-inorganic grafted suspension stabilizer comprises the following components in parts by weight: 15-45 parts sulfonic acid monomer, 60-180 parts hydrophobic monomer, 1-15 parts cationic monomer, 1-15 parts allyl ether monomer, 1-15 parts vinyl organosilicon monomer, 0.1-1.5 parts inorganic material, and 0.05-0.25 parts initiator.

[0007] Furthermore, in the above-mentioned high-temperature, high-density cement slurry, the preparation method of the organic-inorganic grafted suspension stabilizer includes the following steps:

[0008] Step 1: Add 0.1 to 1.5 parts of inorganic material and 1 to 15 parts of vinyl organosilicon monomer to 100 parts of the first solvent and mix evenly to obtain the modified inorganic material;

[0009] Step 2: Add 15-45 parts of sulfonic acid monomer, 60-180 parts of hydrophobic monomer, 1-15 parts of cationic monomer, and 1-15 parts of allyl ether monomer to 500 parts of the second solvent, and mix to form an aqueous solution system.

[0010] Step 3: Start stirring. After the components in the aqueous solution system have dissolved, add the modified inorganic material prepared above to the aqueous solution system to form a mixed solution. Adjust the pH of the mixed solution to 5-6 under ice bath conditions. Then, under nitrogen protection, heat the mixed solution to a first preset temperature, add 0.05-0.25 parts of initiator, and carry out free radical polymerization reaction for a period of time to obtain an organic-inorganic grafted cement slurry liquid suspension stabilizer.

[0011] Furthermore, in the aforementioned high-temperature, high-density cement slurry, the silica powder has a purity of ≥98% and a particle size of 100-300 mesh.

[0012] Furthermore, in the aforementioned high-temperature, high-density cement slurry, the weighting agent includes at least one of manganese ore powder and iron ore powder.

[0013] Furthermore, in the aforementioned high-temperature, high-density cement slurry, the particle size of the microsilica is less than 1 μm.

[0014] Furthermore, in the aforementioned high-temperature, high-density cement slurry, the fluid loss reducing agent includes AMPS multi-polymer fluid loss reducing agent.

[0015] Furthermore, in the aforementioned high-temperature, high-density cement slurry, the retarder includes an organic acid salt retarder; and / or the defoamer includes at least one of an organic ester defoamer and an organosilicon defoamer.

[0016] The high-temperature, high-density cement slurry of this invention maintains good stability at 100-200℃ (BHCT, bottom hole circulation temperature), effectively eliminates free fluid, does not affect the preparation and application of cement slurry, has low water loss, and exhibits a stable thickening curve without core encapsulation at high temperatures, which can meet the requirements of cementing construction and has good application prospects.

[0017] On the other hand, the present invention also proposes a method for preparing high-temperature, high-density cement slurry, comprising:

[0018] Weigh 3-6 parts of organic-inorganic grafted suspension stabilizer, 4-6 parts of water loss reducer, 3-7 parts of retarder, 3-5 parts of drag reducer, 0.1-0.5 parts of defoamer and 58-67 parts of fresh water and place them in a stirring device. Stir at the first preset speed to ensure that each additive is fully dispersed in the fresh water.

[0019] Weigh 100 parts of oil well cement, 35-60 parts of silica powder, 63-162 parts of weighting agent and 1-3 parts of microsilica, mix them thoroughly and evenly and then quickly add them to the above-mentioned mixing device. Stir at the second preset speed for a preset time to obtain high-density cement slurry.

[0020] Furthermore, in the above preparation method, the first preset rotation speed is 2000-5000 r / min, and the second preset rotation speed is 10000-15000 r / min.

[0021] The method for preparing high-temperature, high-density cement slurry provided by this invention introduces an organic-inorganic grafted cement slurry suspension stabilizer, which enables the cement slurry to maintain excellent stability at high temperatures without affecting the function of the weighting agent and other liquid additives. The process is simple, easy to implement, and conducive to large-scale promotion. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the thermogravimetric analysis (TG-DTG) curve of the suspension stabilizer prepared in Example 1 of the present invention;

[0023] Figure 2 This is a graph showing the effect of the dosage of suspending stabilizer on the settling stability of high-density cement slurry in an embodiment of the present invention.

[0024] Figure 3 A comparison diagram of the high-density cement slurry prepared according to the embodiments of the present invention at 150°C and the BP settlement test.

[0025] Figure 4 This is a shutdown curve of the high-density cement slurry prepared in Example 1 of the present invention at 200°C and 132MPa.

[0026] Figure 5 The shutdown curve of the high-density cement slurry prepared in Comparative Example 1 of this invention at 200℃ and 132MPa is shown. Detailed Implementation

[0027] The following describes preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications are also considered to be within the scope of protection of the present invention.

[0028] This invention provides a high-temperature, high-density cement slurry, comprising the following components in parts by weight: 100 parts oil well cement, 35-60 parts silica fume, 63-162 parts weighting agent, 1-3 parts microsilica, 3-6 parts suspension stabilizer, 4-6 parts fluid loss reducer, 3-7 parts retarder, 3-5 parts drag reducer, 0.1-0.5 parts defoamer, and 58-67 parts fresh water; wherein the suspension stabilizer is an organic-inorganic grafted cement slurry suspension stabilizer.

[0029] Preferably, the high-temperature, high-density cement slurry comprises the following components in parts by weight: 100 parts oil well cement, 35-50 parts silica fume, 63-162 parts weighting agent, 2-3 parts microsilica, 4-5 parts suspension stabilizer, 5-6 parts fluid loss reducer, 3-7 parts retarder, 3-4 parts drag reducer, 0.2-0.3 parts defoamer, and 60-62.5 parts fresh water.

[0030] More preferably, the density is 2.10 g / cm³. 3 The high-temperature, high-density cement slurry comprises the following components by weight: 100 parts oil well cement, 35 parts silica fume, 63 parts weighting agent, 3 parts microsilica, 4 parts suspension stabilizer, 5 parts fluid loss reducer, 7 parts retarder, 3 parts drag reducer, 0.2 parts defoamer, and 60 parts fresh water.

[0031] The density is 2.30 g / cm³. 3 The high-temperature, high-density cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 113 parts weighting agent, 3 parts microsilica, 4.5 parts suspension stabilizer, 5 parts fluid loss reducer, 7 parts retarder, 3 parts drag reducer, 0.2 parts defoamer, and 62.5 parts fresh water.

[0032] The density is 2.50 g / cm³. 3 The high-temperature, high-density cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 162 parts weighting agent, 3 parts microsilica, 5 parts suspension stabilizer, 5 parts fluid loss reducer, 7 parts retarder, 3 parts drag reducer, 0.2 parts defoamer G603, and 60 parts fresh water. Among these:

[0033] The oil well cement is Grade G oil well cement that conforms to the People's Republic of China National Standard GB / T 10238-2015 "Oil Well Cement".

[0034] The silicon powder has a purity of ≥98% and a particle size of 100-300 mesh, preferably 300 mesh, which facilitates thorough mixing with other components and helps the suspension stabilizer to function.

[0035] The microsilica has a particle size of less than 1 μm, preferably 0.1-0.8 μm, which is beneficial for assisting the dehydration reducer and suspension stabilizer to function through the close packing effect.

[0036] The weighting agent is selected from at least one of manganese ore powder and iron ore powder. In this embodiment, when the weighting agent is a mixture of manganese ore powder and iron ore powder, the amount of manganese ore powder can be 3-22 parts, and the amount of iron ore powder can be 60-140 parts. For example, the ratio of iron ore powder to manganese ore powder can be 20:1; 110:3 or 70:11. Preferably, the density of the iron ore powder is 6.0 g / cm³. 3 The density of manganese ore powder is 4.7 g / cm³. 3 By combining it with other components in a reasonable way, on the one hand, the solid phase material can be enhanced to achieve a dense packing effect in the cement slurry, and on the other hand, it can help adjust the overall fluidity of the cement slurry.

[0037] The water loss reducing agent is an AMPS multi-polymer, such as at least one of BXF-200L(AF), BCF-230L and BCG-200L from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0038] The retarder is an organic acid salt, such as at least one of BCR-500L, BCR-300L, and BXR-200L from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0039] The drag-reducing agent is a sulfonate drag-reducing agent, such as at least one of BCD-210L and BCD-230L from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0040] The defoamer is at least one of organic esters and organosilicones, such as G603 from Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0041] In this embodiment, the preferred high-temperature condition is a temperature range of 100-200℃, and high-density cement slurry refers to slurry with a density greater than 1.90 g / cm³. 3 Cement grout.

[0042] The organic-inorganic grafted cement slurry suspension stabilizer comprises the following components in parts by weight: 15–45 parts sulfonic acid monomer, 60–180 parts hydrophobic monomer, 1–15 parts cationic monomer, 1–15 parts allyl ether monomer, 1–15 parts vinyl organosilicon monomer, 0.1–1.5 parts inorganic material, and 0.05–0.25 parts initiator. The 1–15 parts vinyl organosilicon monomer modifies the 0.1–1.5 parts inorganic material to form modified inorganic material. Modifying the inorganic material and grafting monomers with various functional groups onto its surface further enhances the temperature resistance of the suspension stabilizer, thereby promoting the high-temperature stability of the cement slurry.

[0043] The inorganic material includes at least one of magnesium aluminum hydroxysilicate, montmorillonite, bentonite, and nano silica.

[0044] The sulfonic acid monomer includes at least one selected from 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and sodium vinyl sulfonate. For example, the sulfonic acid monomer can be 2-acrylamido-2-methylpropanesulfonic acid, a mixture of 2-acrylamido-2-methylpropanesulfonic acid and sodium p-styrene sulfonate, or a mixture of three sulfonic acid monomers: 2-acrylamido-2-methylpropanesulfonic acid, sodium p-styrene sulfonate, and sodium vinyl sulfonate. The amount of the sulfonic acid monomer is preferably 15-40 parts, wherein the amount of the sulfonic acid monomer can be 15, 30, 40, 45 parts, etc.

[0045] The hydrophobic monomer includes at least two of the following: methacrylamide, N-ethylacrylamide, N-n-propylacrylamide, N-benzylacrylamide, N-tert-butylacrylamide, N,N-dimethylacrylamide, N-tetradecylacrylamide, and N,N-diethyl-2-acrylamide. For example, the hydrophobic monomer can be a mixture of methacrylamide and N-ethylacrylamide, a mixture of N-n-propylacrylamide, N,N-dimethylacrylamide, and methacrylamide, a mixture of methacrylamide, N,N-dimethylacrylamide, and N-tetradecylacrylamide, or a mixture of five hydrophobic monomers: methacrylamide, N-ethylacrylamide, N-n-propylacrylamide, N-benzylacrylamide, and N,N-dimethylacrylamide. The amount of hydrophobic monomer used can be 60, 80, 100, 120, 150, or 180 parts, etc.

[0046] The cationic monomer includes at least one of dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethyl ammonium chloride, and octadecyl dimethyl allyl ammonium chloride. For example, the cationic monomer can be a mixture of dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethyl ammonium chloride, and octadecyl dimethyl allyl ammonium chloride, or a mixture of three cationic monomers: dimethyl diallyl ammonium chloride, methacryloyloxyethyltrimethyl ammonium chloride, and octadecyl dimethyl allyl ammonium chloride; wherein the amount of cationic monomer used can be 5, 10, 15 parts, etc.

[0047] The allyl-containing ether monomer includes at least one of polyethylene glycol monoallyl ether, allyl ether, and allyl hydroxyethyl ether. For example, the allyl-containing ether monomer can be polyethylene glycol monoallyl ether, a mixture of polyethylene glycol monoallyl ether and allyl ether, or a mixture of polyethylene glycol monoallyl ether, allyl ether, and allyl hydroxyethyl ether; wherein the amount of the allyl-containing ether monomer can be 5, 10, or 15 parts, etc.

[0048] The vinyl organosilicon monomer includes at least one selected from γ-(methacryloyloxy)propyltrimethoxysilane (KH570), vinyltriethoxysilane (A151), and vinyltrimethoxysilane (A171). For example, the vinyl organosilicon monomer can be KH570, a mixture of KH570 and A151, or a mixture of A151 and A171; wherein the amount of vinyl organosilicon monomer used can be 1, 5, 10, 15 parts, etc., preferably 5 parts.

[0049] The initiator includes at least one selected from ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and azobisisobutyramidine hydrochloride. For example, the initiator can be ammonium persulfate, a mixture of potassium persulfate and azobisisobutyronitrile, a mixture of azobisisobutyronitrile and azobisisobutyramidine hydrochloride, or a mixture of four initiators: ammonium persulfate, potassium persulfate, azobisisobutyronitrile, and azobisisobutyramidine hydrochloride. The amount of initiator used can be 0.1, 0.2, 0.3, or 0.4 parts, preferably 0.2 parts.

[0050] As can be seen, the suspension stabilizer in this embodiment is prepared using an organic-inorganic grafting process. First, the inorganic material is modified with a vinyl organosilicon monomer to obtain a modified inorganic material. Then, a long-chain polymer is grafted onto the surface of the modified inorganic material. Sulfonic acid monomers are introduced to improve the temperature and salt resistance of the polymer. Hydrophobic groups with carbon chains of different lengths are introduced. These hydrophobic groups with different carbon chains interweave with each other through intermolecular forces, forming a network structure that inhibits the high-temperature dilution of cement slurry. The introduction of cationic monomers and allyl ether monomers is beneficial for the wetting of cement particles, which can reduce surface tension and shorten the cement slurry settling time.

[0051] In this embodiment, the preparation method of the organic-inorganic grafted suspension stabilizer includes the following steps:

[0052] Step 1: Add 0.1 to 1.5 parts of inorganic material and 1 to 15 parts of vinyl organosilicon monomer to the first solvent and mix evenly to obtain the modified inorganic material.

[0053] Specifically, the first solvent can be anhydrous ethanol. The preferred inorganic material is magnesium aluminum hydroxysilicate.

[0054] In this embodiment, the hydroxyl groups on the surface of the inorganic material magnesium aluminum hydroxysilicate and the silane groups in the organosilicon monomer undergo a chemical reaction to dehydrate and graft, forming a modified inorganic material.

[0055] In specific implementation, 0.1–1.5 parts of magnesium aluminum hydroxysilicate and 1–15 parts of vinyl organosilicon monomer are added to anhydrous ethanol, stirred at room temperature for 10–14 hours, filtered, and dried to obtain the modified inorganic material. The preferred stirring time is 12 hours.

[0056] Step 2: Add 15-45 parts of sulfonic acid monomer, 60-180 parts of hydrophobic monomer, 1-15 parts of cationic monomer, and 1-15 parts of allyl ether monomer to the second solvent and mix to form an aqueous solution system.

[0057] Specifically, the second solvent can be deionized water. The amount of deionized water used can be determined according to the actual situation, as long as it is sufficient to fully dissolve all the above components. For example, 500 parts of deionized water can be used.

[0058] In this embodiment, sulfonic acid monomers, hydrophobic monomers, cationic monomers, and allyl ether monomers are mixed in water to obtain an aqueous solution system of organic monomers containing carbon-carbon double bonds.

[0059] Step 3: Start stirring. After all components in the aqueous solution system have dissolved, add the modified inorganic material obtained above to the aqueous solution system to form a mixed solution. Adjust the pH of the mixed solution to 5-6 under ice bath conditions. Then, under nitrogen protection, heat the mixed solution to a first preset temperature and add 0.05-0.25 parts of initiator at once to carry out a free radical polymerization reaction to obtain an organic-inorganic grafted cement slurry liquid suspension stabilizer. Because excessively high temperatures may cause self-polymerization of the reactants, affecting the subsequent polymerization reaction, this step requires adjusting the pH to 5-6 under ice bath conditions.

[0060] Among them, NaOH can be used to adjust the pH of the mixed solution. The amount of NaOH used should be determined according to the actual situation, and it is sufficient to ensure that the pH reaches 5-6.

[0061] The first preset temperature is 50–70℃, preferably 55–60℃. The free radical polymerization reaction time is 2–8 hours, preferably 2–4 hours.

[0062] This invention also provides a method for preparing high-temperature, high-density cement slurry, comprising the following steps:

[0063] Step 1: Weigh 3-6 parts of organic-inorganic grafted suspension stabilizer, 4-6 parts of water loss reducer, 3-7 parts of retarder, 3-5 parts of drag reducer, 0.1-0.5 parts of defoamer, and 58-67 parts of fresh water and place them in a stirring device. Stir at a first preset speed to ensure that each additive is fully dispersed in the fresh water. The first preset speed is 2000-5000 r / min, preferably 4000 r / min.

[0064] Step 2: Weigh 100 parts oil well cement, 35-60 parts silica powder, 63-162 parts weighting agent, and 1-3 parts microsilica. Mix them thoroughly and quickly add them to the above-mentioned mixing device. Mix at the second preset speed for the preset time to obtain a high-density cementing slurry. The second preset speed is 10000-15000 r / min, preferably 12000 r / min. The time for adding solid materials to the mixing device should be controlled within 30 seconds, and the mixing time at the second preset speed should be controlled within 20-40 seconds, preferably 35 seconds.

[0065] The cement slurry provided by this invention maintains good stability at 100-200℃ (BHCT, bottom hole circulation temperature), effectively eliminates free fluid, does not affect the preparation and application of the cement slurry, has low water loss, and exhibits a stable thickening curve without core encapsulation at high temperatures (e.g., Figure 4 As shown in the figure, it can meet the needs of cementing construction and has good application prospects.

[0066] The present invention will be further illustrated below with reference to specific embodiments, the purpose of which is to better understand the content of the present invention and to demonstrate the essential features of the present invention. Therefore, the embodiments described should not be regarded as a limitation on the scope of protection of the present invention.

[0067] The materials used in the embodiments and comparative examples of this invention are as follows:

[0068] Grade G oil well cement is a product manufactured by Jiahua Special Cement Co., Ltd.; silica fume is a product manufactured by Tianjin Yuyang Ultrafine Mineral Powder Processing Co., Ltd.; microsilica fume is a product manufactured by Gansu Sanyuan Microsilica Powder Co., Ltd.; iron ore powder has a density of 6.0 g / cm³. 3 The product is manufactured by Emeishan City Tuoyang Oilfield Engineering Technology Co., Ltd.; manganese ore powder with a density of 4.7 g / cm³. 3 The manganese ore powder; the water loss reducing agent BXF-200L(AF), the retarder BXR-200L, BCR-500L, the drag reducing agent BCD-210L and the defoamer G603 are all products manufactured by Tianjin Zhongyou Boxing Engineering Technology Co., Ltd.

[0069] The cement slurry in Examples 1-3 and Comparative Examples 1-3 was prepared in accordance with the People's Republic of China National Standard GB / T19139-2012 "Test Methods for Cement in Oil Wells".

[0070] The method for calculating the density of cement in Examples 1-3 and Comparative Examples 1-3 of this invention is as follows: After cleaning and drying the container that can hold each component in the formula, weigh it. Add each substance in the formula to the container to a preset volume, weigh the container plus each component substance again, and subtract the weight of the container to get the weight of the cement slurry prepared by each formula. Divide the weight by the volume to get the density of the cement slurry in each example and comparative example.

[0071] Example 1

[0072] This embodiment provides a density of 2.10 g / cm³. 3 The cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts 100-mesh silica fume, 60 parts iron ore powder, 3 parts manganese ore powder, 3 parts 0.2μm micro silica, 4.0 parts suspension stabilizer A, 5 parts water loss reducer BXF-200L(AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 60 parts fresh water.

[0073] The preparation method of suspension stabilizer A is as follows: 0.5 parts magnesium aluminum hydroxysilicate and 5 parts vinyltriethoxysilane (A151) are added to 100 parts of anhydrous ethanol, stirred at room temperature for 12 h, filtered and dried to obtain modified inorganic material; 30 parts of 2-acrylamido-2-methylpropanesulfonic acid, 5 parts of sodium vinyl sulfonate, 100 parts of N,N-dimethylacrylamide, 10 parts of N-ethylacrylamide, 5 parts of N-tert-butylacrylamide, 10 parts of dimethyl diallyl ammonium chloride, and 5 parts of polyethylene glycol monoallyl ether are added to 500 parts of deionized water to form an aqueous solution system. Start stirring and, after all components in the aqueous solution system have dissolved, add modified inorganic materials. Under ice bath conditions, use NaOH to adjust the pH of the mixed solution obtained after dissolving all components to 5-6. Start heating and raise the temperature to the initiation temperature of 60°C under nitrogen protection. Add 0.2 parts of ammonium persulfate at once and carry out free radical polymerization reaction for 3 hours to obtain organic-inorganic grafted cement slurry liquid suspension stabilizer A.

[0074] Example 2

[0075] This embodiment provides a density of 2.30 g / cm³. 3 The cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts 200-mesh silica fume, 110 parts iron ore powder, 3 parts manganese ore powder, 3 parts 0.4μm micro silica, 4.5 parts suspension stabilizer B, 5 parts water loss reducer BXF-200L(AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 62.5 parts fresh water.

[0076] The preparation method of suspension stabilizer B is as follows: 0.5 parts magnesium aluminum hydroxysilicate and 5 parts vinyltriethoxysilane (A151) are added to 100 parts of anhydrous ethanol, stirred at room temperature for 12 h, filtered and dried to obtain modified inorganic material; 20 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of sodium p-styrene sulfonate, 80 parts of N,N-dimethylacrylamide, 10 parts of N-benzylacrylamide, 10 parts of N,N-diethyl-2-acrylamide, 5 parts of dimethyl diallyl ammonium chloride, and 5 parts of polyethylene glycol monoallyl ether are added to 500 parts of deionized water and mixed to form an aqueous solution system. Start stirring and, after all components in the aqueous solution system have dissolved, add modified inorganic materials. Under ice bath conditions, use NaOH to adjust the pH of the mixed solution obtained after dissolving all components to 5-6. Start heating and raise the temperature to the initiation temperature of 60°C under nitrogen protection. Add 0.2 parts of ammonium persulfate at once and carry out free radical polymerization reaction for 3 hours to obtain organic-inorganic grafted cement slurry liquid suspension stabilizer B.

[0077] Example 3

[0078] This embodiment provides a density of 2.50 g / cm³. 3 The cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts 300-mesh silica fume, 140 parts iron ore powder, 22 parts manganese ore powder, 3 parts 0.8μm micro silica, 5 parts suspension stabilizer C, 5 parts water loss reducer BXF-200L(AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 60 parts fresh water.

[0079] The preparation method of suspension stabilizer C is as follows: 0.5 parts magnesium aluminum hydroxysilicate and 5 parts vinyltriethoxysilane (A151) are added to 100 parts of anhydrous ethanol, stirred at room temperature for 12 h, filtered and dried to obtain modified inorganic material; 15 parts of 2-acrylamido-2-methylpropanesulfonic acid, 10 parts of sodium p-styrene sulfonate, 5 parts of sodium vinyl sulfonate, 100 parts of N,N-dimethylacrylamide, 5 parts of N-benzylacrylamide, 5 parts of N,N-diethyl-2-acrylamide, 5 parts of N-tetradecylacrylamide, 5 parts of N-tert-butylacrylamide, 5 parts of dimethyl diallyl ammonium chloride, 5 parts of methacryloyloxyethyltrimethylammonium chloride, and 10 parts of polyethylene glycol monoallyl ether are added to 500 parts of deionized water to form an aqueous solution system. Start stirring and, after all components in the aqueous solution system have dissolved, add modified inorganic materials. Under ice bath conditions, use NaOH to adjust the pH of the mixed solution obtained after dissolving all components to 5-6. Start heating and raise the temperature to the initiation temperature of 60°C under nitrogen protection. Add 0.2 parts of ammonium persulfate at once and carry out free radical polymerization reaction for 3 hours to obtain organic-inorganic grafted cement slurry liquid suspension stabilizer C.

[0080] Comparative Example 1

[0081] This comparative example provides a density of 2.10 g / cm³. 3 High-density cement slurry.

[0082] The cement slurry of this comparative example comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 60 parts iron ore powder, 3 parts manganese ore powder, 3 parts microsilica, 5 parts water loss reducer BXF-200L(AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 63 parts fresh water.

[0083] Comparative Example 2

[0084] This comparative example provides a density of 2.30 g / cm³. 3 The high-density cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 110 parts iron ore powder, 3 parts manganese ore powder, 3 parts microsilica, 5 parts water loss reducer BXF-200L(AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 67 parts fresh water.

[0085] Comparative Example 3

[0086] This comparative example provides a density of 2.50 g / cm³. 3 The high-density cement slurry comprises the following components in parts by weight: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 140 parts iron ore powder, 22 parts manganese ore powder, 3 parts microsilica, 5 parts water loss reducer BXF-200L(AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 65 parts fresh water.

[0087] Test case

[0088] (1) The thermal stability of the suspension stabilizer prepared in Example 1 was tested using a Swiss-Mettler-TGA / DSC3+ simultaneous thermal analyzer, and the results are as follows: Figure 1 As shown, from Figure 1 It can be seen from this:

[0089] The thermal decomposition of suspension stabilizer molecules mainly consists of two stages:

[0090] The first stage is thermal degradation within the temperature range of 251–333℃, with a mass loss of 23.1%. The DTG curve for this stage shows a trough at 298℃. The main reason for the weight loss in this stage is the extensive decomposition and breakage of side chain groups such as amide and sulfonic acid groups in the suspension stabilizer molecules. The second stage is thermal degradation within the temperature range of 333–507℃, with a mass loss of 39.1%. The DTG curve for this stage also shows a trough at 398℃. The main reason for the weight loss in this stage is the initial breakage of the main chain in the suspension stabilizer molecules. Above 507℃, the thermogravimetric curve tends to stabilize, leaving only a small amount of carbonaceous residue. In summary, the suspension stabilizer has high temperature resistance and can meet the cementing requirements of most deep wells.

[0091] (2) The comprehensive performance of the cement slurries prepared in Examples 1-3 and Comparative Examples 1-3 was investigated. The comprehensive performance test results of the cement slurries at 200℃ (BHCT) are shown in Table 1. The test method for the settlement stability of the cement slurries is as follows:

[0092] Cement slurry was cured according to the test method specified in Section 3, Chapter 15 of the National Standard of the People's Republic of China GB / T 19139-2012. The cured cement slurry was stirred at 4000 rpm for 15 seconds, and then 400 mL was poured directly into a clean, dry 500 mL graduated cylinder within 1 minute. The cylinder opening was sealed with plastic film, and the cylinder was immediately placed in a water bath preheated to 90°C for 2 hours. The density of the cement slurry in the upper and lower 200 mL portions was measured and recorded using a digital liquid density meter according to the test method specified in Chapter 6 of GB / T 19139-2012. The density difference between the upper and lower 200 mL portions of cement slurry was used to determine the settling stability of the cement slurry.

[0093] Table 1. Comprehensive performance test of high-density cement paste at 200℃ (BHCT)

[0094]

[0095] According to the experimental data in Table 1, the cement slurry without suspending stabilizer (Comparative Examples 1-3) showed severe settling at high temperatures. After adding the suspending stabilizer, the stability of the cement slurry in this embodiment (smaller density difference between the top and bottom layers) was significantly better than that of the comparative examples. The density difference between the top and bottom layers of the cement slurry prepared in this embodiment was less than 0.030 g / cm³. 3 The fluidity and water loss of the cement slurry meet the performance requirements under high-temperature environments and construction requirements.

[0096] (3) The suspension stabilizer A sample prepared in Example 1 of this invention was selected, and the effect of different dosages of the suspension stabilizer on the stability of cement paste at 100-200℃ (BHCT) was tested. The test results are shown in […]. Figure 2 .

[0097] The cement grout has a liquid-to-solid ratio of 0.293 and is prepared to have a density of 2.40 g / cm³. 3 Cement grout.

[0098] The cement slurry formulations with different amounts of suspending stabilizer, based on parts by weight, are as follows:

[0099] When the dosage of suspension stabilizer is 3.0% (based on the mass of G-grade cement as 100%), the cement slurry raw materials include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts microsilica, 3.5 parts suspension stabilizer, 5 parts water loss reducer BXF-200L(AF), 3-7 parts retarder (BCR-500L:BXR-200L=4:1), 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 60-63 parts fresh water.

[0100] When the dosage of suspension stabilizer is 3.5% (based on the mass of G-grade cement as 100%), the raw materials of cement slurry include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts microsilica, 3.5 parts suspension stabilizer, 5 parts water loss reducer BXF-200L (AF), 3-7 parts retarder (BCR-500L:BXR-200L = 4:1), 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 60-63 parts fresh water.

[0101] When the dosage of suspension stabilizer is 4% (based on the mass of G-grade cement as 100%), the cement slurry raw materials include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts microsilica, 4 parts suspension stabilizer, 5 parts water loss reducer BXF-200L(AF), 3-7 parts retarder (BCR-500L:BXR-200L = 4:1), 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 60-63 parts fresh water.

[0102] When the dosage of suspension stabilizer is 4.5% (based on the mass of G-grade cement as 100%), the cement slurry raw materials include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts microsilica, 4.5 parts suspension stabilizer, 5 parts water loss reducer BXF-200L(AF), 3-7 parts retarder (BCR-500L:BXR-200L = 4:1), 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 59-63 parts fresh water.

[0103] When the dosage of suspension stabilizer is 5% (based on the mass of G-grade cement as 100%), the raw materials of cement slurry include the following components: 100 parts of Jiahua G-grade oil well cement, 35 parts of silica fume, 120 parts of iron ore powder, 13 parts of manganese ore powder, 3 parts of microsilica, 5 parts of suspension stabilizer, 5 parts of water loss reducing agent BXF-200L(AF), 3 to 7 parts of retarder (BCR-500L:BXR-200L = 4:1), 3 parts of drag reducing agent BCD-210L, 0.2 parts of defoamer G603, and 59 to 62 parts of fresh water.

[0104] in, Figure 2 Table 2 shows the corresponding retarder dosage at different temperatures when the dosage of the suspension stabilizer is fixed. Taking the mass of Grade G cement as 100%, calculate the retarder dosage (e.g.,...). Figure 2 A 3% concentration of medium-strength suspension stabilizer corresponds to 3 parts by mass, a 4% concentration corresponds to 4 parts, and so on, with a 5% concentration corresponding to 5 parts. The amount of fresh water added is determined by the liquid-to-solid ratio. The amount of fresh water added = (mass of G-grade oil well cement + mass of silica fume + mass of iron ore powder + mass of manganese ore powder + mass of microsilica) × liquid-to-solid ratio - mass of other liquid admixtures.

[0105] Table 2 Figure 2 Retarder dosage at different temperatures

[0106] temperature 100℃ 120℃ 140℃ 150℃ 160℃ 180℃ 200℃ Increase the amount of retarder 3 copies 3.5 copies 4 copies 5 copies 5 copies 6 copies 7 copies

[0107] The experimental results show that as the dosage of the suspending stabilizer increases, the density difference of the cement slurry gradually decreases, and the settling stability of the cement slurry is significantly improved. For example, at 100℃, the cement slurry achieves good stability with a dosage of only 3%. As the temperature rises, increasing the dosage of the suspending stabilizer has a significant promoting effect on settling stability. In other words, the high-density cement slurry provided in this embodiment of the invention, when supplemented with a dosage of 3.0% to 5.0% suspending stabilizer, can maintain good settling stability at temperatures of 100 to 200℃ (BHCT) (density difference between the upper and lower layers of the cement slurry is less than 0.05 g / cm³). 3 ).

[0108] (4) Cement slurries with different stabilizer dosages were prepared according to the following mass ratios for high-temperature settling tests and BP settling tests. The static stability of the cement slurries was determined by the BP settling test, and compared with the settling stability results to verify the settling stability of the cement slurries prepared by each formulation. The liquid-to-solid ratio of the cement slurry was 0.293, and the density was prepared to be 2.40 g / cm³. 3 Cement grout.

[0109] The cement slurry formulations with different amounts of suspending stabilizer, based on parts by weight, are as follows:

[0110] When the dosage of suspension stabilizer is 5% (based on the mass of G-grade cement as 100%), the cement slurry raw materials include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts 0.1μm micro silica, 5 parts suspension stabilizer A, 5 parts water loss reducing agent BXF-200L (AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducing agent BCD-210L, 0.2 parts defoamer G603, and 59 parts fresh water.

[0111] When the dosage of suspension stabilizer is 5.5% (based on the mass of G-grade cement as 100%), the cement slurry raw materials include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts microsilica, 5.5 parts suspension stabilizer A, 5 parts water loss reducer BXF-200L (AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 58.5 parts fresh water.

[0112] When the dosage of suspension stabilizer is 6% (based on the mass of G-grade cement as 100%), the cement slurry raw materials include the following components: 100 parts Jiahua G-grade oil well cement, 35 parts silica fume, 120 parts iron ore powder, 13 parts manganese ore powder, 3 parts microsilica, 6 parts suspension stabilizer A, 5 parts water loss reducer BXF-200L (AF), 5.6 parts retarder BCR-500L, 1.4 parts retarder BXR-200L, 3 parts drag reducer BCD-210L, 0.2 parts defoamer G603, and 58 parts fresh water.

[0113] The test method for the BP settlement test is as follows: Cement slurry is cured according to the test method specified in Section 3, Chapter 15 of the People's Republic of China National Standard GB / T19139-2012. The cured cement slurry is stirred at 4000 r / min for 15 seconds and then poured into the settling tube approximately 20 mm from the top. The inner diameter of the settling tube should be 25 mm ± 5 mm, and the minimum length should be 100 mm. A thin layer of grease should be applied to the inner surface of the settling tube and all joints to ensure no leakage of cement slurry and to prevent damage to the cement specimen during disassembly. During the test, the settling tube should not react with the well cement and should not deform. The cement slurry in the settling tube should be stirred to remove air bubbles, and then the settling tube should be filled with cement slurry. The top of the settling tube should be covered to prevent cement slurry from overflowing. The top cover should have a pressure-transmitting hole. The settling tube filled with cement slurry should be placed vertically in a heating / cooling container filled with water. The container should be preheated or precooled to the test temperature. If the test temperature is higher than 90°C, the curing container should be preheated or precooled to 90°C. Cure the cement slurry for 24 hours or until it solidifies. Remove the settling tube from the curing container and place it in a water bath at 27°C ± 6°C. After the settling tube has cooled, remove the cement specimen and immerse the specimen in water to prevent it from drying out. Measure the length of the cement specimen and make two marks approximately 20 mm from the bottom and top of the specimen. Divide the specimen into approximately equal parts (at least two parts) between these two marks and mark them. Cut the specimen at these marks and arrange the cut specimens in order.

[0114] Before weighing each section of the test block, keep them submerged in water. The balance accuracy should be 0.01g, preferably 0.001g. The preferred method for determining the density of each cement test block is as follows: Place a beaker containing water on the balance, remove the tare weight to zero the balance. Remove one section of the test block from the water bath and gently dry it with a paper towel. Place the test block next to the beaker on the balance and record its mass (m). i Then remove the test piece from the balance. Tare the sample again to zero the balance. Tie a thin string around the test piece, suspend it with the string, and place it in a beaker of water, ensuring the entire sample is completely submerged without touching the bottom or sides of the beaker, and that no air bubbles adhere to it. Record the mass of the sample in water (m). i,w Then, remove the test block from the water and weigh it off the balance. Repeat the above steps to determine the density of each cement test block. Applying Archimedes' principle, according to formula d... rel =m i / m i,w Calculate the relative density d of each cement test block. rel Finally, the density difference between the top and bottom stones is calculated to determine the density distribution and settlement stability of the cement sample.

[0115] The results of the cement slurry settling test and the BP settling test of the high-density cement slurry of Example 1 (containing suspending stabilizer A) at 150°C were compared. The test results are as follows: Figure 3 .

[0116] The suspension performance of the suspension stabilizer at high temperature was examined by two test methods. The comparison of the test results showed that the density difference between the upper and lower parts of the cement slurry was almost the same in the two test methods. This indicates that the addition of the suspension stabilizer in the embodiment of the present invention enables the high-density cement slurry to maintain good settling stability at high temperature.

[0117] (5) The high-density cement slurries containing suspending stabilizers prepared in Example 1 and Comparative Example 1 were subjected to a shutdown test at 200°C, and the results are as follows: Figure 4 and Figure 5 .

[0118] The experimental results show that the cement slurry prepared in Comparative Example 1, without the addition of a suspending stabilizer, exhibited fluctuations in its consistency curve. The consistency of the system decreased significantly with increasing temperature, and the change in consistency value before and after shutdown exceeded 15 Bc, indicating poor stability. In contrast, the cement slurry containing the suspending stabilizer obtained in Example 1 had a smaller impact on initial consistency, a more stable consistency curve, no core-forming phenomenon, a smaller decrease in consistency with increasing temperature, and a smaller change in consistency value before and after shutdown, with an increase not exceeding 10 Bc. This demonstrates that the high-density cement slurry can maintain stability at high temperatures.

[0119] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A high-temperature, high-density cement slurry for well cementing, characterized in that, It includes the following components in parts by weight: 100 parts oil well cement, 35-60 parts silica fume, 63-162 parts weighting agent, 1-3 parts microsilica, 3-6 parts organic-inorganic grafted suspension stabilizer, 4-6 parts water loss reducer, 3-7 parts retarder, 3-5 parts drag reducer, 0.1-0.5 parts defoamer, and 58-67 parts fresh water.

2. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The organic-inorganic grafted suspension stabilizer comprises the following components in parts by weight: 15-45 parts sulfonic acid monomer, 60-180 parts hydrophobic monomer, 1-15 parts cationic monomer, 1-15 parts allyl ether monomer, 1-15 parts vinyl organosilicon monomer, 0.1-1.5 parts inorganic material, and 0.05-0.25 parts initiator.

3. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The preparation method of the organic-inorganic grafted suspension stabilizer includes the following steps: Step 1: Add 0.1 to 1.5 parts of inorganic material and 1 to 15 parts of vinyl organosilicon monomer to 100 parts of the first solvent and mix evenly to obtain the modified inorganic material; Step 2: Add 15-45 parts of sulfonic acid monomer, 60-180 parts of hydrophobic monomer, 1-15 parts of cationic monomer, and 1-15 parts of allyl ether monomer to 500 parts of the second solvent, and mix to form an aqueous solution system. Step 3: Start stirring. After the components in the aqueous solution system have dissolved, add the modified inorganic material prepared above to the aqueous solution system to form a mixed solution. Adjust the pH of the mixed solution to 5-6 under ice bath conditions. Then, under nitrogen protection, heat the mixed solution to a first preset temperature and add 0.05-0.25 parts of initiator to carry out free radical polymerization reaction to obtain an organic-inorganic grafted cement slurry liquid suspension stabilizer.

4. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The silicon powder has a purity of ≥98% and a particle size of 100-300 mesh.

5. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The weighting agent includes at least one of manganese ore powder and iron ore powder.

6. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The particle size of the microsilicon is less than 1 μm.

7. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The water loss reducing agent includes AMPS multi-polymer water loss reducing agent.

8. The high-temperature, high-density cement slurry according to claim 1, characterized in that, The retarder includes organic acid salt retarder; and / or the defoamer includes at least one of organic ester defoamer and organosilicon defoamer.

9. A method for preparing high-temperature, high-density cement slurry as described in any one of claims 1-8, characterized in that, include: Weigh 3-6 parts of organic-inorganic grafted suspension stabilizer, 4-6 parts of water loss reducer, 3-7 parts of retarder, 3-5 parts of drag reducer, 0.1-0.5 parts of defoamer and 58-67 parts of fresh water and place them in a stirring device. Stir at the first preset speed to ensure that each additive is fully dispersed in the fresh water. Weigh 100 parts of oil well cement, 35-60 parts of silica powder, 63-162 parts of weighting agent and 1-3 parts of microsilica, mix them thoroughly and evenly and then quickly add them to the above-mentioned mixing device. Stir at the second preset speed for a preset time to obtain high-density cement slurry.

10. The method for preparing high-temperature, high-density cement slurry according to claim 9, characterized in that, The first preset speed is 2000-5000 r / min, and the second preset speed is 10000-15000 r / min.

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