A deep well and ultra-deep well cementing spacer fluid and a preparation method thereof

Abstract

The present application relates to a kind of deep well ultra-deep well spacer fluid and its preparation method, the spacer fluid contains suspending agent by adding crosslinking agent to make polymer form micro-crosslinking polymer with space net structure, and simultaneously contains intercalation modified inorganic mineral, so that its surface is rich in carboxyl, which improves its dispersing property on one hand, and further improves the suspension stability of spacer fluid under high temperature salt condition on the other hand.The spacer fluid contains flushing agent, which can improve the effect of flushing fluid by the synergistic effect of wetting, dispersing, solubilizing, stabilizing, chelating and decontamination, etc., so that the flushing efficiency of oil-based drilling fluid can reach more than 95% under the condition of less than 10% addition.The spacer fluid is particularly suitable for cementing operation in deep well ultra-deep well, and has good salt resistance, good rheological property at low temperature, good suspension stability at high temperature, strong wetting reverse ability, excellent oil washing effect and other characteristics, and good comprehensive performance, which can effectively guarantee the safety of cementing construction and improve the cementing quality.

Description

Technical Field

[0001] This invention relates to the field of cement slurry and drilling fluid isolation technology in the cementing process of oil exploration, and in particular to a cementing isolation fluid for deep and ultra-deep wells and its preparation method. Background Technology

[0002] Currently, domestic oil and gas exploration and development is advancing towards ultra-deep formations reaching depths of 10,000 meters. Deep and ultra-deep oil and gas formations are becoming important replacement areas for increasing my country's oil and gas reserves and production. Cementing faces challenges such as ultra-high temperatures (>200℃), ultra-high pressures (>150MPa), and high densities (up to 2.60g / cm³). 3 Extreme formation conditions such as high salt content (>10%) pose a significant challenge to wellbore working fluids.

[0003] Separating fluid is a working fluid used in cementing processes to separate cement slurry and drilling fluid. On the one hand, it serves to flush out mud cake and improve interfacial bonding; on the other hand, it separates cement slurry and drilling fluid to prevent them from coming into contact and contaminating each other.

[0004] Suspension stability is one of the most important properties of a release fluid. The suspension stability of release fluids differs from that of cement slurry. In cement slurry systems, most components of cement and admixtures effectively participate in hydration, forming an effective cementitious structure and ensuring stability at high temperatures. However, release fluids, apart from some functional additives, mainly consist of inert weighting materials such as barite and iron ore powder. Therefore, ensuring the suspension stability of release fluids, especially under ultra-high temperature and saline conditions, is more difficult. Poor suspension stability of the release fluid can lead to solid-phase deposition, causing minor issues like annular blockage and pump stalling, or more serious problems like "sausage filling" and "flagpole insertion." Currently, research on suspension stabilizers for release fluids is limited, with xanthan gum as the main component, having a temperature resistance not exceeding 150℃ and offering little salt resistance. Research on suspension agents for cement slurry is more active, shifting from natural polymers to synthetic polymers, with temperature resistance reaching up to 200℃. However, the main materials in the release fluid are mostly inert weighting materials such as barite and iron ore powder, which, unlike cement particles, cannot participate in hydration and adsorb onto polymers to achieve suspension stability. Therefore, some suspending agents that have high temperature resistance and good suspension properties in cement slurry may become ineffective in the release fluid.

[0005] Oil flushing efficiency is another important performance characteristic of the separator fluid. Oil-based drilling fluids are difficult to completely displace, resulting in poor interfacial bonding and affecting cementing quality. Currently, domestic flushing agents have unstable cleaning performance for some types of oil-based (especially white oil-based) drilling fluids, and the dosage is generally greater than 10%, even reaching more than 30%. Moreover, flushing agents can easily affect the stability of the separator fluid system, making it difficult to achieve both flushing efficiency and stability.

[0006] Therefore, it is necessary to develop high-efficiency isolation fluids with good salt resistance, good rheological properties at low temperatures, good suspension stability at high temperatures, strong wetting reversal ability, and excellent oil washing effect to ensure cementing quality in deep and ultra-deep wells. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a deep well and ultra-deep well isolation fluid, comprising the following components by weight: water, 100 parts; suspending agent, 4-10 parts; flushing agent, 6-12 parts; fluid loss reducing agent, 3-5 parts; retarder, 5-8 parts; drag reducing agent, 5-10 parts; weighting agent, 90-400 parts; industrial salt, 0-15 parts; and defoamer, 0.1 parts.

[0008] The suspending agent comprises the following components in parts by weight: synthetic polymer, 5-10 parts; modified inorganic minerals, 80-100 parts;

[0009] The synthetic polymer comprises the following components in parts by weight: 100 parts of 2-acrylamide-2-methylpropanesulfonic acid; 5-10 parts of N,N-diethylacrylamide; 8-10 parts of cyclic monomers; 0.3-0.5 parts of crosslinking agent; 0.5-1.0 parts of carboxylic acid monomers; and 300-400 parts of water. The modified inorganic minerals include intercalated modified attapulgite fibers and basalt fibers.

[0010] The rinsing agent comprises the following components in parts by weight: water, 100 parts; emulsifying viscosity reducer, 12-24 parts; wetting reversal agent, 10-20 parts; cosolvent, 5-10 parts; and chelating agent, 4-8 parts.

[0011] Furthermore, the weighting agent is barite and / or micro-manganese.

[0012] Furthermore, the defoamer is tributyl phosphate.

[0013] Furthermore, the industrial salt is sodium chloride.

[0014] Specifically, intercalation-modified inorganic minerals include intercalated attapulgite fibers or basalt fibers. After intercalation modification, their surfaces are enriched with carboxyl groups to improve their dispersion and adsorption properties. A rich carboxyl group surface means the fibers themselves carry a strong negative charge; the repulsion between charges facilitates fiber dispersion. Simultaneously, the good hydrophilicity of carboxyl groups further promotes rapid and uniform dispersion of the modified fibers in water. Furthermore, the charged carboxyl groups can effectively adsorb onto positively charged barite and iron ore powders to improve the suspension stability of the weighting material, thereby enhancing the stability of the suspending agent.

[0015] Specifically, the attapulgite and basalt fibers need to undergo intercalation modification to enrich their surface with carboxyl groups, thereby improving their dispersion and adsorption properties. A surface rich in carboxyl groups means the fibers themselves carry a strong negative charge; the repulsion between charges facilitates the dispersion of fibers. Simultaneously, the good hydrophilicity of carboxyl groups further promotes the rapid and uniform dispersion of the modified fibers in water. Furthermore, the charged carboxyl groups can effectively adsorb onto positively charged barite and iron ore powder, improving the suspension stability of the weighting material and thus enhancing the stability of the suspending agent.

[0016] Furthermore, the crosslinking agent is N,N-methylenebisacrylamide.

[0017] Preferably, the crosslinking agent can be present in weight parts of 0.3, 0.4, 0.5, etc., and the carboxylic acid monomer can be present in weight parts of 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, etc.

[0018] It should be noted that when the weight percentage of the crosslinking agent exceeds 0.5%, the isolation liquid prepared by the suspending agent provided in the embodiments of the present invention has high viscosity and poor rheological properties. Furthermore, the thickened linear structure is prone to problems such as "bulging" and "core-encasing." Conversely, when the weight percentage of the crosslinking agent is less than 0.3%, the amount of suspending agent needs to be increased, and the suspension stability of the system is relatively poor. Therefore, the weight percentage of the crosslinking agent should not exceed 0.5%.

[0019] Preferably, the crosslinking agent is present in a weight ratio of 0.3 to 0.5.

[0020] Specifically, the polymer is made to form a micro-crosslinked structure, with the molecular weight controlled between 1 million and 1.5 million and the molecular weight distribution being 1.5 to 2.0; this can ensure both the ash settling time and low-temperature rheological properties of the isolation liquid, as well as the suspension stability at high temperatures.

[0021] Specifically, the synthesized polymer has a suitable molecular weight and molecular weight distribution, which facilitates rapid dissolution in water and uniform dispersion. Simultaneously, the introduction of a cross-linking agent forms a certain three-dimensional network structure, which can support the inert weighting material and provide suspension stability. Therefore, when this suspension stabilizer is added to the isolation liquid, it produces the characteristics of not thickening at low temperatures and maintaining suspension stability at high temperatures. The introduction of cyclic monomers improves the rigidity of the polymer molecular chain, thereby enhancing the polymer's temperature resistance. The introduction of carboxylic acid monomers further enhances the adsorption performance of the suspending agent, enabling it to adsorb onto the surface of cement particles, supporting the cement particles and further ensuring their suspension stability.

[0022] In summary, the suspending agent has the characteristics of rapid ash release, good rheological properties at low temperatures, and excellent stability at high temperatures. It has good overall performance and can effectively ensure the safety of cementing operations and improve cementing quality when applied to cementing fluids.

[0023] Furthermore, the cyclic monomer is at least one of N-vinylpyrrolidone and 4-vinylpyridine.

[0024] Furthermore, the carboxylic acid monomer is at least one of itaconic acid and acrylic acid.

[0025] Preferably, the carboxylic acid monomer is present in a weight fraction of 0.5 to 1.0.

[0026] It should be noted that when the weight percentage of carboxylic acid monomers exceeds 1.5%, the thickening time of the cement slurry prepared by the suspending agent provided in the embodiments of the present invention will be prolonged, and the strength development at low temperatures will be slow. Therefore, in the embodiments of the present invention, the weight percentage of carboxylic acid monomers does not exceed 1.0%. Preferably, the weight percentage of carboxylic acid monomers is 0.5 to 1.0.

[0027] Specifically, the flushing agent can improve the flushing effect through multiple mechanisms such as wetting, dispersing, solubilizing, stabilizing, chelating and decontaminating. Under the condition of adding less than 10%, the flushing efficiency of oil-based drilling fluid can reach more than 95%.

[0028] Furthermore, the emulsifying viscosity reducer comprises tetradecyl alcohol polyoxyethylene ether, sodium methylamine alkyl sulfonate, and N-amide amino acid salt;

[0029] Further, the wetting reversal agent comprises: 100 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 to 10 parts by weight of acrylamide, and 3 to 5 parts by weight of sodium 2-acrylamidotetradecanesulfonate.

[0030] Furthermore, the co-solvent includes allyl polyether and propoxylated alcohol;

[0031] Furthermore, the chelating agent includes trisodium citrate dihydrate and sodium hexametaphosphate.

[0032] Furthermore, the water loss reducing agent is a 2-acrylamide-2-methylpropanesulfonic acid / N,N-dimethylacrylamide polymer;

[0033] Furthermore, the retarder is a 2-acrylamide-2-methylpropanesulfonic acid / itaconic acid polymer;

[0034] Furthermore, the drag-reducing agent is a 2-acrylamide-2-methylpropanesulfonic acid / APEG-2400 polymer.

[0035] The components of the flushing agent work synergistically. The emulsifying viscosity reducer, through its hydrophilic and hydrophobic groups in its molecular structure, significantly enhances the solubility of insoluble solid particles and organic matter in oil-based drilling fluids, promoting their uniform dispersion. The wetting reversal agent, by reducing interfacial tension, refines the oil droplets of oil-based drilling fluid and disperses them uniformly in the flushing fluid, reversing the wettability of the well wall and casing from oleophilic to hydrophilic, which is beneficial for thoroughly flushing away the oil-based drilling fluid. The co-solvent enhances the stability and uniformity of the flushing fluid, helps regulate the rheology of the solution, prevents component stratification or precipitation, and makes the flushing fluid more stable during use. The chelating agent can strongly chelate with metal ions in oil-based drilling fluids, sealing them and eliminating their adverse effects on the flushing agent. It can also reduce the surface tension of the flushing fluid, playing a synergistic and enhancing role for the emulsifying viscosity reducer and the wetting reversal agent. This flushing agent enhances the flushing fluid's effectiveness through synergistic effects of wetting, dispersing, solubilizing, stabilizing, chelating, and decontaminating mechanisms. With an addition of less than 10%, it achieves a flushing efficiency of over 95% for oil-based drilling fluids. The interfacial tension between this flushing agent and white oil is less than 1 mN / m, and it exhibits excellent wetting reversal properties, allowing the wettability on the wellbore and casing to reverse from oleophilic to hydrophilic, which is beneficial for cement stone interfacial bonding. This flushing agent possesses good temperature and salt resistance, withstanding temperatures up to 240℃ and salt concentrations up to 15%, making it particularly suitable for cementing operations in deep and ultra-deep wells. Its freezing point is below -5℃, without affecting the stability of the isolation fluid system. It exhibits good compatibility with on-site drilling fluids and cement slurries, meeting on-site safety requirements. The production process of this flushing agent is simple, safe, and environmentally friendly.

[0036] The present invention provides a deep well and ultra-deep well isolation fluid with the following advantages: the suspending agent contained in the isolation fluid is made into a micro-crosslinked polymer with a spatial network structure by adding a crosslinking agent, which can not only ensure the ash settling time and rheological properties at low temperature, but also improve the suspension performance of the isolation fluid at high temperature; by intercalating and modifying the inorganic minerals to make them rich in carboxyl groups, on the one hand, their dispersion performance is improved, and on the other hand, the suspension stability of the isolation fluid under high temperature and saline conditions is further improved. Combining the two further leverages their respective advantages. The suspending agent in the separator fluid of this invention exhibits characteristics such as rapid ash release, good rheological properties at low temperatures, and excellent stability at high temperatures, resulting in excellent overall performance. This effectively ensures the safety of cementing operations and improves cementing quality. The flushing agent in the separator fluid of this invention can work synergistically through multiple mechanisms such as wetting, dispersion, solubilization, stabilization, chelation, and decontamination, thereby enhancing the flushing fluid's effectiveness. Under conditions where the dosage is less than 10%, the flushing efficiency for oil-based drilling fluids can reach over 95%. This separator fluid is particularly suitable for cementing operations in deep and ultra-deep wells. It possesses characteristics such as good salt resistance, good rheological properties at low temperatures, excellent suspension stability at high temperatures, strong wetting reversal ability, and excellent oil washing effect, resulting in excellent overall performance. This effectively ensures the safety of cementing operations and improves cementing quality.

[0037] Another aspect of the present invention provides a method for preparing a deep well and ultra-deep well isolation fluid, comprising:

[0038] To prepare a suspending agent, the polymer and inorganic minerals are prepared separately, and then the two are stirred evenly according to a preset ratio to obtain the suspending agent.

[0039] To prepare the rinsing agent, add a predetermined amount of emulsifying viscosity reducer, wetting reversal agent, solubilizer and chelating agent to a predetermined amount of hot water, stir and mix well, and cool to room temperature to obtain the rinsing agent.

[0040] To prepare the isolation fluid, water and a suspending agent are mixed and stirred. Then, rinsing agent, water loss reducer, retarder, drag reducer, industrial salt, and defoamer are added in sequence according to the proportion. The mixture is stirred thoroughly and then a weighting agent is added and stirred until homogeneous. The isolation fluid is thus obtained.

[0041] Furthermore, the method for preparing the suspending agent includes:

[0042] Polymer preparation involves sequentially adding water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomers, crosslinking agents, and carboxylic acid monomers into a reactor to obtain a reaction solution. The solution is stirred and the pH value is adjusted. After adding an initiator and reacting, the solution is dried and pulverized to obtain polymer powder.

[0043] The modified inorganic mineral preparation involves soaking the inorganic mineral in acid to remove impurities and washing it until neutral, then ultrasonically pulverizing and dispersing it, adjusting the pH value to a preset value, adding an initiator to initiate polymerization, and grinding the inorganic mineral components.

[0044] The suspending agent is prepared by mixing the prepared polymer and the inorganic mineral modified powder in a preset ratio to obtain the suspending agent.

[0045] Furthermore, the method for preparing the polymer includes:

[0046] According to the weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomer, crosslinking agent and carboxylic acid monomer were added to the reactor in sequence to obtain the reaction solution;

[0047] Stir at 200 rpm until all components are dissolved, adjust the pH of the reaction solution to 6-7, and raise the temperature of the reaction solution to 50-60°C.

[0048] An initiator was added to the reaction solution, and the reaction was carried out for 2-3 hours. The mixture was then cooled to room temperature to obtain colorless and pale yellow viscous liquids. After microwave drying and pulverization, polymer powder materials were obtained.

[0049] Furthermore, the method for preparing the modified inorganic mineral includes:

[0050] Soak attapulgite fibers or basalt fibers in a 10% dilute hydrochloric acid solution to remove impurities such as carbonates, and then rinse them repeatedly with deionized water until neutral to obtain pure attapulgite fibers or basalt fibers.

[0051] Pure raptor fiber or basalt fiber is added to deionized water and dispersed evenly using an ultrasonic cell disruptor.

[0052] Liquid acrylic acid was adjusted to pH 6 with a 28% sodium hydroxide solution and then added to a fiber dispersion. The mixture was heated to 60°C, and an initiator was added to initiate polymerization. The polymer particles were washed with hot ethanol solution, dried at room temperature, and then ground into powder.

[0053] Preferably, the initiator is at least one selected from ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine hydrochloride.

[0054] Furthermore, the method for preparing the rinsing agent includes:

[0055] Component preparation: Prepare the pre-set amounts of emulsifying viscosity reducer, wetting reversal agent, solubilizer, and chelating agent;

[0056] To prepare the rinsing agent, heat 100 parts of water, then add 12-24 parts of emulsifying viscosity reducer, 10-20 parts of wetting reversal agent, 5-10 parts of cosolvent, and 4-8 parts of chelating agent. Stir and mix well, then cool to room temperature to obtain the rinsing agent.

[0057] Furthermore, the method for preparing the wetting reversal agent includes:

[0058] To prepare the reaction solution, add a predetermined amount of water, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and sodium 2-acrylamidotetradecanesulfonate monomers sequentially to the reactor to obtain the reaction solution. After stirring and dissolving evenly, adjust the temperature and pH of the reaction solution for later use.

[0059] To prepare a wetting reversal agent, an initiator is added to the prepared reaction solution to carry out the reaction, and then the solution is cooled to room temperature to obtain the wetting reversal agent.

[0060] Furthermore, the initiator comprises an azobisisobutyrazoline hydrochloride solution.

[0061] The present invention provides a method for preparing a cementing and isolation fluid for deep and ultra-deep wells, which has the following advantages: the preparation method is simple, and the isolation fluid prepared by this method has good salt resistance, good rheological properties at low temperatures, good suspension stability at high temperatures, strong wetting reversal ability, and excellent oil washing effect. It has good comprehensive performance and can effectively ensure the safety of cementing operations and improve the quality of cementing. Attached Figure Description

[0062] The above and other objects, features, and advantages of the present invention will become clearer from the following description of embodiments of the invention with reference to the accompanying drawings. The drawings are for illustrative purposes only and are not intended to limit the scope of the invention.

[0063] Figure 1 This is a thickening and curing curve of Example 1 at 240℃;

[0064] Figure 2 The isolation fluid at 240℃ has a concentration of 2.4 g / cm³. 3 The flushing efficiency of oil-based drilling fluids. Detailed Implementation

[0065] The present invention will be further described in detail below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it should be understood that the present disclosure may be implemented in various forms and should not be limited to the embodiments set forth herein. Rather, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the disclosure to those skilled in the art. It should be noted that, unless otherwise specified, the embodiments and features described in the present invention can be combined with each other.

[0066] This invention discloses a cementing and isolation fluid for deep and ultra-deep wells, comprising the following components by weight: water, 100 parts; suspending agent, 4-10 parts; flushing agent, 6-12 parts; fluid loss reducing agent, 3-5 parts; retarder, 5-8 parts; drag reducing agent, 5-10 parts; weighting agent, 90-400 parts; industrial salt, 0-15 parts; and defoamer, 0.1 parts.

[0067] In this embodiment, the suspending agent comprises the following components in parts by weight: polymer, 5-10 parts; modified inorganic mineral, 80-100 parts;

[0068] The polymer comprises the following components in parts by weight: 100 parts of 2-acrylamide-2-methylpropanesulfonic acid; 5-10 parts of N,N-diethylacrylamide; 8-10 parts of cyclic monomers; 0.3-0.5 parts of crosslinking agent; 0.5-1.0 parts of carboxylic acid monomers; and 300-400 parts of water. The modified inorganic minerals include intercalated attapulgite fibers and basalt fibers.

[0069] The rinsing agent comprises the following components in parts by weight: water, 100 parts; emulsifying viscosity reducer, 12-24 parts; wetting reversal agent, 10-20 parts; cosolvent, 5-10 parts; and chelating agent, 4-8 parts.

[0070] In this embodiment, specifically, the suspending agent is suitable for salt-resistant isolation fluid systems.

[0071] In this embodiment, the crosslinking agent is N,N-methylenebisacrylamide.

[0072] In this embodiment, the cyclic monomer is at least one of N-vinylpyrrolidone and 4-vinylpyridine.

[0073] In this embodiment, the carboxylic acid monomer is selected from at least one of itaconic acid and acrylic acid.

[0074] Specifically, N,N-methylenebisacrylamide can form micro-crosslinked polymers with a spatial network structure, which can support inert weighting materials and improve suspension stability under high temperature and high salt conditions. N-vinylpyrrolidone and 4-vinylpyridine contain rigid groups, which can increase the rigidity of polymer molecular chains and improve their structural stability at high temperatures. Itaconic acid and acrylic acid have strong adsorption properties and can be adsorbed around cement particles to support them and further ensure their stability. However, excessive addition will prolong the thickening time of cement slurry and delay the strength development of cement slurry at low temperatures.

[0075] In this embodiment, the rinsing agent comprises the following components in parts by weight: water, 100 parts; emulsifying viscosity reducer, 12-24 parts; wetting reversal agent, 10-20 parts; cosolvent, 5-10 parts; and chelating agent, 4-8 parts.

[0076] Specifically, the components of the flushing agent work synergistically. The emulsifying viscosity reducer, through its hydrophilic and hydrophobic groups in its molecular structure, significantly enhances the solubility of insoluble solid particles and organic matter in oil-based drilling fluids, promoting their uniform dispersion. The wetting reversal agent, by reducing interfacial tension, refines the oil droplets of oil-based drilling fluid and disperses them uniformly in the flushing fluid, reversing the wetting properties of the wellbore and casing from oleophilic to hydrophilic, which is beneficial for thoroughly flushing away the oil-based drilling fluid. The co-solvent enhances the stability and uniformity of the flushing fluid, helps regulate the rheology of the solution, prevents component stratification or precipitation, and makes the flushing fluid more stable during use. The chelating agent can strongly chelate with metal ions in oil-based drilling fluids, sealing them and eliminating their adverse effects on the flushing agent. It can also reduce the surface tension of the flushing fluid, playing a synergistic and enhancing role for the emulsifying viscosity reducer and the wetting reversal agent. The composition of each raw material does not affect the stability of the isolation fluid system, has good compatibility with the drilling fluid and cement slurry on site, and meets the requirements for safe on-site construction.

[0077] In this embodiment, the emulsifying viscosity reducer includes tetradecyl alcohol polyoxyethylene ether, sodium methylamine alkyl sulfonate, and N-amide amino acid salt.

[0078] The molecular formula of the emulsifying viscosity reducer tetradecyl alcohol polyoxyethylene ether is C 14 H 29O(CH2CH2O)nH, where n = 9–15, the hydrophobic part is composed of long-chain fatty alcohol groups C 14 H 29 The first part is compatible with oil-based drilling fluids, forming a mixed phase that facilitates the detachment of the fluid from the wellbore and casing. The hydrophobic portion has a long alkyl chain, exhibiting high hydrophobicity. This long-chain structure remains relatively stable at high temperatures, resisting breakage or degradation. The hydrophilic portion consists of polyoxyethylene groups, i.e., repeating oxyethylene units (-CH2CH2O-), linked by ether bonds (-O-). These ether bonds possess good chemical stability at high temperatures, resisting hydrolysis or oxidation. Some polyoxyethylene groups can form hydrogen bonds with water, making the molecule water-soluble. This helps disperse the detached oil-based drilling fluid from the wellbore and casing in water, preventing redeposition.

[0079] The molecular formula of the emulsifying viscosity reducer sodium methylamine alkyl sulfonate is C 15 H 31 CONCH3CH2SO3Na has a hydrophobic portion consisting of a long-chain alkyl group and a hydrophilic portion consisting of sulfonate groups. Its hydrophobic portion interacts with oil-based drilling fluids, while its hydrophilic portion interacts with water. It effectively removes oil-based drilling fluids through emulsification and dispersion.

[0080] The emulsifying viscosity reducer N-amide amino acid salt has the molecular formula R-CONH-CH(R')-COO. The hydrophobic part is a long-chain fatty acid alkyl group R, and the hydrophilic part is a carboxylate ion and an amino acid residue R'. Its hydrophobic part interacts with oil-based drilling fluid, and its hydrophilic part interacts with water. It effectively removes oil-based drilling fluid through emulsification and dispersion.

[0081] In this embodiment, the wetting reversal agent comprises: 100 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5-10 parts by weight of acrylamide, and 3-5 parts by weight of sodium 2-acrylamidotetradecanesulfonate. By reducing interfacial tension, the wetting reversal agent refines the oil droplets of the oil-based drilling fluid and disperses them evenly in the flushing fluid, reversing the wettability of the wellbore and casing from oleophilic to hydrophilic, which facilitates the thorough flushing away of the oil-based drilling fluid.

[0082] In this embodiment, the co-solvent includes allyl polyether and propoxylated alcohol. The allyl polyether has the molecular formula CH2=CHCH2O(CH2CH2O)nH, and the propoxylated alcohol has the molecular formula RO(CH2CH(CH3)O)nH. Both can interact with emulsifying viscosity reducers and wetting reversal agents to form stable micelle structures, thereby improving the solubility and stability of the flushing fluid in water and preventing component stratification or precipitation. This allows the flushing fluid to be more effectively adsorbed onto the surface of oil-based drilling fluid, promoting the emulsification and dispersion of the oil-based drilling fluid.

[0083] In this embodiment, the chelating agent includes trisodium citrate dihydrate and sodium hexametaphosphate.

[0084] The chelating agent, trisodium citrate dihydrate, has the molecular formula C6H5Na3O7·2H2O, and sodium hexametaphosphate has the molecular formula (NaPO3)6. They can form coordinate bonds with metal ions to form chelates. This chelating effect helps to remove metal ions from drilling fluid, reduce the adhesion of drill cuttings, and also reduces the surface tension of flushing fluid. It also has a synergistic effect on emulsifying viscosity reducers and wetting reversal agents, thereby improving cleaning efficiency.

[0085] In this embodiment, the water loss reducing agent is a 2-acrylamide-2-methylpropanesulfonic acid / N,N-dimethylacrylamide polymer;

[0086] In this embodiment, the retarder is a 2-acrylamide-2-methylpropanesulfonic acid / itaconic acid polymer;

[0087] In this embodiment, the drag-reducing agent is a 2-acrylamide-2-methylpropanesulfonic acid / APEG-2400 polymer.

[0088] In this embodiment, the weighting agent is barite and / or micro-manganese.

[0089] In this embodiment, the defoamer is tributyl phosphate.

[0090] In this embodiment, the industrial salt is sodium chloride.

[0091] This invention also discloses a method for preparing cementing and isolation fluid for deep and ultra-deep wells.

[0092] First, the preparation of the suspending agent, the preparation method includes:

[0093] Step 1: According to the weight proportions of each component, add water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomer, crosslinking agent and carboxylic acid monomer to the reactor in sequence to obtain the reaction solution.

[0094] The components are added in the following weight proportions: 300-400 parts water, 100 parts 2-acrylamide-2-methylpropanesulfonic acid, 5-10 parts N,N-diethylacrylamide, 8-10 parts cyclic monomers, 0.3-0.5 parts crosslinking agent, and 0.5-1.0 parts carboxylic acid monomers. The corresponding weight proportions of each component are added to the reactor in sequence.

[0095] The reactor can be a four-necked flask equipped with a thermometer, stirrer, and reflux condenser.

[0096] Step 2: Stir at 200 rpm to adjust the pH of the reaction solution to 6-7 and raise the temperature of the reaction solution to 50-60℃.

[0097] In this step, the pH of the reaction solution can be adjusted using NaOH solution. The concentration of the NaOH solution can be set and changed as needed, and is not specifically limited in this embodiment of the invention. For example, the concentration of the NaOH solution can be 0.05 mol / L, 0.1 mol / L, or 0.2 mol / L.

[0098] Step 3: After all components have dissolved, add the initiator to the reaction solution, react for 2-3 hours, cool to room temperature, and obtain the suspension.

[0099] In this step, the initiator is used to initiate the polymerization reaction of the components of the suspending agent to obtain the suspending agent. In this embodiment of the invention, the initiator is at least one selected from ammonium persulfate, potassium persulfate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine imidazoline hydrochloride. In this embodiment of the invention, no specific limitation is made.

[0100] Step 4: The prepared polymer is dried and pulverized by microwave to obtain a powder material.

[0101] Step 5: Soak the palygorskite fiber or basalt fiber in a 10% dilute hydrochloric acid solution to remove impurities such as carbonates, and then rinse repeatedly with deionized water until neutral to obtain pure palygorskite fiber or basalt fiber.

[0102] Step 6: Add the pure raptosite fiber or basalt fiber to deionized water and disperse it evenly using an ultrasonic cell disruptor.

[0103] Step 7: Adjust the pH of the liquid acrylic acid to 6 using a 28% sodium hydroxide solution, then add it to the fiber dispersion. Heat the mixture to 60°C and add potassium persulfate solution to initiate polymerization. Wash the polymer particles with hot ethanol solution, air dry at room temperature, and grind them into powder.

[0104] Step 8: Mix 5-10 parts by weight of the polymer powder material prepared above with 80-100 parts by weight of the mineral fiber intercalation modified powder material in a certain proportion to obtain the suspending agent.

[0105] The above-mentioned suspending agent is simple to prepare and has the characteristics of fast ash release, good salt resistance, good low-temperature rheology and good high-temperature stability. It is especially suitable for high-temperature salt-containing isolation liquid systems.

[0106] Secondly, the preparation methods of the rinsing agent include:

[0107] Step 1: Preparation of wetting agent reversal agent. According to the weight proportions of each component, water, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and sodium 2-acrylamidotetradecanesulfonate monomers are added sequentially to the reactor to obtain a reaction solution. The mixture is stirred at 200 rpm until all components are dissolved. The pH of the reaction solution is adjusted to 6-7, and the temperature is raised to 50-60°C. An initiator is added to the reaction solution, and the reaction is carried out for 2-3 hours. The mixture is then cooled to room temperature to obtain the wetting agent reversal agent. In this embodiment, azobisisobutyrazoline hydrochloride solution is used as the initiator.

[0108] Step 2: Preparation of rinsing agent. Heat 100 parts of water, add 12-24 parts of emulsifying viscosity reducer, 10-20 parts of wetting reversal agent, 5-10 parts of cosolvent, and 4-8 parts of chelating agent. Stir and mix at 200 rpm, cool to room temperature, and the rinsing agent is obtained.

[0109] Finally, the method for preparing the isolation fluid includes:

[0110] Place water and suspending agent in a stirrer and stir at 1000 rpm for 10 minutes. Then add rinsing agent, water loss reducer, retarder, drag reducer, industrial salt and defoamer in sequence according to the preset ratio. Stir at 4000 rpm for 15 seconds to make the liquid fully mixed. Then quickly add weighting agent at 4000 rpm and stir evenly to obtain the isolation liquid.

[0111] The following specific embodiments illustrate the cementing and separation fluid for deep and ultra-deep wells described in this application.

[0112] Example 1

[0113] A cementing and separation fluid for deep and ultra-deep wells, with the following components and weights:

[0114]

[0115] (1) Preparation method of suspension

[0116] According to the weight proportions of each component, 300 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 5 parts by weight of N,N-diethylacrylamide, 0.3 parts by weight of N,N-methylenebisacrylamide, 8 parts by weight of N-vinylpyrrolidone, and 0.5 parts by weight of itaconic acid were added to the reactor in sequence to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 6, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate initiator was added to the reaction solution, the reaction was carried out for 2 hours, cooled to room temperature, and then microwave-dried and pulverized to obtain polymer powder.

[0117] To remove impurities such as carbonates, patazoite or basalt fibers are soaked in a 10% dilute hydrochloric acid solution. They are then repeatedly rinsed with deionized water until neutral to obtain pure patazoite or basalt fibers. The pure patazoite or basalt fibers are added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid is adjusted to pH 6 with a 28% sodium hydroxide solution and added to the fiber dispersion. The mixture is heated to 60°C, and potassium persulfate solution is added to initiate polymerization. The polymer particles are washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0118] A suspending agent was obtained by mixing 5 parts of polymer powder with 100 parts of intercalated modified mineral fiber.

[0119] (2) Preparation method of rinsing agent

[0120] Add 300 parts by weight of fresh water to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser, at a ratio of 1 g per part by weight. Then, add 100 parts by weight of AMPS, 5 parts by weight of acrylamide, and 3 parts by weight of sodium 2-acrylamidotetradecanesulfonate sequentially. Adjust the pH of the reaction system to 7 by adding NaOH solution while stirring at 200 rpm. Then, raise the temperature to 60°C. After the reactants are completely dissolved, add 0.5 parts by weight of azobisisobutyrazoline hydrochloride solution dropwise to the reaction system. The concentration of the azobisisobutyrazoline hydrochloride solution is: 0.6 g of azobisisobutyrazoline hydrochloride dissolved in 10 ml of water. The azobisisobutyrazoline hydrochloride solution is added dropwise over 3 minutes, and the reaction is maintained at a constant temperature for 2 hours. Finally, allow it to cool naturally to room temperature to obtain a colorless liquid with a certain viscosity, which is the wetting and reversing agent for well cementing flushing.

[0121] Add 100 parts of tap water to the reactor, start stirring at 200 rpm, heat to 50°C, add 20 parts of emulsified viscosity reducer (composed of 10 parts of tetradecyl alcohol polyoxyethylene ether, 8 parts of sodium methylamine alkyl sulfonate and 2 parts of N-amide amino acid salt), and fully dissolve the emulsified viscosity reducer; add 10 parts of wetting reversal agent, add 5 parts of cosolvent (composed of 2 parts of allyl polyether and 3 parts of propoxylated alcohol), and stir for 30-50 minutes; add 4 parts of chelating agent (composed of 2 parts of trisodium citrate dihydrate and 2 parts of sodium hexametaphosphate), stir for 15-30 minutes, and cool to room temperature to obtain the deep well and ultra-deep well cementing and oil displacement flushing agent.

[0122] Example 2

[0123] A cementing and separation fluid for deep and ultra-deep wells, with the following components and weights:

[0124]

[0125] (1) Preparation method of suspension

[0126] According to the weight proportions of each component, 350 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 8 parts by weight of N,N-diethylacrylamide, 0.4 parts by weight of N,N-methylenebisacrylamide, 9 parts by weight of 4-vinylpyridine, and 1 part by weight of acrylic acid were added sequentially to the reactor to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate, the initiator, was added to the reaction solution, and the reaction was carried out for 2 hours. After cooling to room temperature, the polymer powder was obtained by microwave drying and pulverization.

[0127] To remove impurities such as carbonates, patazoite or basalt fibers are soaked in a 10% dilute hydrochloric acid solution. They are then repeatedly rinsed with deionized water until neutral to obtain pure patazoite or basalt fibers. The pure patazoite or basalt fibers are added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid is adjusted to pH 6 with a 28% sodium hydroxide solution and added to the fiber dispersion. The mixture is heated to 60°C, and potassium persulfate solution is added to initiate polymerization. The polymer particles are washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0128] Eight parts of polymer powder were mixed with 90 parts of intercalated modified mineral fiber to obtain a suspending agent.

[0129] (2) Preparation method of rinsing agent

[0130] Add 300 parts by weight of fresh water to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser, at a ratio of 1 g per part by weight. Then, add 100 parts by weight of AMPS, 8 parts by weight of acrylamide, and 4 parts by weight of sodium 2-acrylamidotetradecanesulfonate sequentially. Adjust the pH of the reaction system to 7 by adding NaOH solution while stirring at 200 rpm. Then, raise the temperature to 60°C. After the reactants are completely dissolved, add 0.5 parts by weight of azobisisobutyrazoline hydrochloride solution dropwise to the reaction system. The concentration of the azobisisobutyrazoline hydrochloride solution is: 0.6 g of azobisisobutyrazoline hydrochloride dissolved in 10 ml of water. The azobisisobutyrazoline hydrochloride solution is added dropwise over 3 minutes, and the reaction is maintained at a constant temperature for 2 hours. Finally, allow it to cool naturally to room temperature to obtain a colorless liquid with a certain viscosity, which is the reversing agent for cementing flushing.

[0131] Add 100 parts of tap water to the reactor, start stirring at 200 rpm, heat to 50°C, add 15 parts of emulsified viscosity reducer (composed of 8 parts tetradecyl alcohol polyoxyethylene ether, 6 parts sodium methylamine alkyl sulfonate and 1 part N-amide amino acid salt) to fully dissolve the emulsified viscosity reducer; add 10 parts of wetting reversal agent, add 5 parts of cosolvent (composed of 2 parts allyl polyether and 3 parts propoxylated alcohol), stir for 30-50 min; add 4 parts of chelating agent (composed of 2 parts trisodium citrate dihydrate and 2 parts sodium hexametaphosphate), stir for 15-30 min, cool to room temperature to obtain the deep well and ultra-deep well cementing and oil displacement flushing agent.

[0132] Example 3

[0133] A cementing and separation fluid for deep and ultra-deep wells, with the following components and weights:

[0134]

[0135] (1) Preparation method of suspension

[0136] According to the weight proportions of each component, 400 parts by weight of water, 100 parts by weight of 2-acrylamide-2-methylpropanesulfonic acid, 10 parts by weight of N,N-diethylacrylamide, 0.5 parts by weight of N,N-methylenebisacrylamide, 5 parts by weight of vinylpyrrolidone, 5 parts by weight of 4-vinylpyridine, 0.5 parts by weight of acrylic acid, and 0.5 parts by weight of itaconic acid were added to the reactor in sequence to obtain a reaction solution. The reaction solution was stirred at a speed of 200 rpm, the pH of the reaction solution was adjusted to 7, and the temperature of the reaction solution was raised to 60°C. After all components were dissolved, ammonium persulfate initiator was added to the reaction solution, the reaction was carried out for 2 hours, cooled to room temperature, and then microwave-dried and pulverized to obtain polymer powder.

[0137] To remove impurities such as carbonates, patazoite or basalt fibers are soaked in a 10% dilute hydrochloric acid solution. They are then repeatedly rinsed with deionized water until neutral to obtain pure patazoite or basalt fibers. The pure patazoite or basalt fibers are added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid is adjusted to pH 6 with a 28% sodium hydroxide solution and added to the fiber dispersion. The mixture is heated to 60°C, and potassium persulfate solution is added to initiate polymerization. The polymer particles are washed with hot ethanol solution, dried at room temperature, and ground into powder.

[0138] A suspending agent was obtained by mixing 10 parts of polymer powder with 80 parts of intercalated modified mineral fiber.

[0139] (2) Preparation method of rinsing agent

[0140] Add 300 parts by weight of fresh water to a four-necked flask equipped with a thermometer, stirrer, and reflux condenser, at a ratio of 1 g per part by weight. Then, add 100 parts by weight of AMPS, 10 parts by weight of acrylamide, and 5 parts by weight of sodium 2-acrylamidotetradecanesulfonate sequentially. Adjust the pH of the reaction system to 7 by adding NaOH solution while stirring at 200 rpm. Then, raise the temperature to 60°C. After the reactants are completely dissolved, add 0.5 parts by weight of azobisisobutyrazoline hydrochloride solution dropwise to the reaction system. The concentration of the azobisisobutyrazoline hydrochloride solution is: 0.6 g of azobisisobutyrazoline hydrochloride dissolved in 10 ml of water. The azobisisobutyrazoline hydrochloride solution is added dropwise over 3 minutes, and the reaction is maintained at a constant temperature for 2 hours. Finally, allow it to cool naturally to room temperature to obtain a colorless liquid with a certain viscosity, which is the reversing agent for cementing flushing.

[0141] Add 100 parts of tap water to the reactor, start stirring at 200 rpm, heat to 50°C, add 24 parts of emulsified viscosity reducer (composed of 12 parts of tetradecyl alcohol polyoxyethylene ether, 10 parts of sodium methylamine alkyl sulfonate and 2 parts of N-amide amino acid salt), and fully dissolve the emulsified viscosity reducer; add 8 parts of wetting reversal agent, add 5 parts of cosolvent (composed of 2 parts of allyl polyether and 3 parts of propoxylated alcohol), and stir for 30-50 minutes; add 3 parts of chelating agent (composed of 1 part of trisodium citrate dihydrate and 2 parts of sodium hexametaphosphate), and stir for 15-30 minutes, cool to room temperature, and obtain the deep well and ultra-deep well cementing and oil displacement flushing agent.

[0142] Comparative Example 1

[0143] The components and their weights are as follows:

[0144]

[0145] The performance of the isolation fluid containing the above three examples and one comparative example suspension is shown in Table 1.

[0146] Table 1 contains the performance of the isolation fluid in the three examples and two comparative examples mentioned above.

[0147]

[0148]

[0149] Table 1 shows that the performance of the three examples and one comparative example differs significantly. When no suspending agent or rinsing agent is added to the isolation fluid, such as in Comparative Example 1, its sedimentation stability at 240°C is poor, with a density difference greater than 1.2 g / cm³. 3The above results show that with free fluid concentrations exceeding 3.0% and flushing efficiency of only 32.01%, neither of which meets the requirements for cementing operations. Compared to Comparative Example 1, the three isolation fluids prepared in Examples 1, 2, and 3 have faster ash-dispensing times, which can be controlled within 40 seconds; they also exhibit good rheological properties, with K values ​​controlled at 0.15 Pa·s. n Within a certain range; good settling stability at high temperatures, with the density difference between the upper and lower parts controllable within 0.04, and zero free liquid; rinsing efficiency reaches over 98%, with excellent overall performance.

[0150] In summary, the deep and ultra-deep well isolation fluid and its preparation method disclosed in this invention have the following advantages: The suspending agent in this isolation fluid, through the addition of a crosslinking agent, forms a micro-crosslinked polymer with a spatial network structure, which not only ensures the cementing time and rheological properties at low temperatures but also improves the suspension performance of the isolation fluid at high temperatures. By intercalating and modifying the inorganic minerals to make them rich in carboxyl groups, its dispersibility is improved, and the suspension stability of the isolation fluid under high-temperature and saline conditions is further enhanced. Combining these two aspects further leverages their advantages. This suspending agent exhibits excellent comprehensive performance, including rapid cementing, good rheological properties at low temperatures, and excellent stability at high temperatures, effectively ensuring cementing construction safety and improving cementing quality. The flushing agent in this isolation fluid can synergistically improve the flushing effect through multiple mechanisms such as wetting, dispersion, solubilization, stabilization, chelation, and decontamination. With an addition of less than 10%, the flushing efficiency for oil-based drilling fluids can reach over 95%. In summary, this separator fluid is particularly suitable for cementing operations in deep and ultra-deep wells. It has good salt resistance, good rheological properties at low temperatures, excellent suspension stability at high temperatures, strong wetting reversal ability, and excellent oil washing effect. Its comprehensive performance is good, which can effectively ensure the safety of cementing operations and improve the quality of cementing.

[0151] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0152] Finally, it should be noted that the above embodiments are merely examples for clearly illustrating the present invention and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A deep well / ultra-deep well isolation fluid, characterized in that, It comprises the following components by weight: water, 100 parts; suspending agent, 4-10 parts; rinsing agent, 6-12 parts; water loss reducing agent, 3-5 parts; retarder, 5-8 parts; drag reducing agent, 5-10 parts; weighting agent, 90-400 parts; industrial salt, 0-15 parts; defoamer, 0.1 parts. The suspending agent comprises the following components in parts by weight: synthetic polymer, 5-10 parts; modified inorganic minerals, 80-100 parts; The synthetic polymer comprises the following components in parts by weight: 100 parts of 2-acrylamide-2-methylpropanesulfonic acid; 5-10 parts of N,N-diethylacrylamide; 8-10 parts of cyclic monomers; 0.3-0.5 parts of crosslinking agent; 0.5-1.0 parts of carboxylic acid monomers; and 300-400 parts of water. The modified inorganic minerals include intercalated attapulgite fibers and basalt fibers. The rinsing agent comprises the following components in parts by weight: water, 100 parts; emulsifying viscosity reducer, 12-24 parts; wetting reversal agent, 10-20 parts; cosolvent, 5-10 parts; and chelating agent, 4-8 parts.

2. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that, The weighting agent is barite and / or micro-manganese; the defoamer is tributyl phosphate; and the industrial salt is sodium chloride.

3. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that: The crosslinking agent is N,N-methylenebisacrylamide.

4. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that: The cyclic monomer is at least one of N-vinylpyrrolidone and 4-vinylpyridine.

5. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that: The carboxylic acid monomer is at least one of itaconic acid and acrylic acid.

6. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that, The emulsifying viscosity reducer includes tetradecyl alcohol polyoxyethylene ether, sodium methylamine alkyl sulfonate, and N-amide amino acid salt.

7. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that, The wetting reversal agent comprises: 100 parts by weight of 2-acrylamido-2-methylpropanesulfonic acid, 5 to 10 parts by weight of acrylamide, and 3 to 5 parts by weight of sodium 2-acrylamidotetradecanesulfonate.

8. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that, The co-solvents include allyl polyethers and propoxylated alcohols.

9. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that, The chelating agents include trisodium citrate dihydrate and sodium hexametaphosphate.

10. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that: The water loss reducing agent is a 2-acrylamide-2-methylpropanesulfonic acid / N,N-dimethylacrylamide polymer.

11. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that: The retarder is a polymer of 2-acrylamide-2-methylpropanesulfonic acid / itaconic acid.

12. The deep well and ultra-deep well isolation fluid according to claim 1, characterized in that: The drag-reducing agent is a 2-acrylamide-2-methylpropanesulfonic acid / APEG-2400 polymer.

13. A method for preparing a deep well / ultra-deep well isolation fluid, characterized in that, include: To prepare a suspending agent, the polymer and inorganic minerals are prepared separately, and then the two are stirred evenly according to a preset ratio to obtain the suspending agent. To prepare the rinsing agent, add a predetermined amount of emulsifying viscosity reducer, wetting reversal agent, solubilizer and chelating agent to a predetermined amount of hot water, stir and mix well, and cool to room temperature to obtain the rinsing agent. To prepare the isolation fluid, water and a suspending agent are mixed and stirred. Then, rinsing agent, water loss reducer, retarder, drag reducer, industrial salt, and defoamer are added in sequence according to the proportion. The mixture is stirred thoroughly and then a weighting agent is added and stirred until homogeneous. The isolation fluid is thus obtained.

14. The method for preparing the deep and ultra-deep well isolation fluid according to claim 13, characterized in that, The method for preparing the suspending agent includes: Polymer preparation involves sequentially adding water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomers, crosslinking agents, and carboxylic acid monomers into a reactor to obtain a reaction solution. The solution is stirred and the pH value is adjusted. After adding an initiator and reacting, the solution is dried and pulverized to obtain polymer powder. The modified inorganic mineral preparation involves soaking the inorganic mineral in acid to remove impurities and washing it until neutral, then ultrasonically pulverizing and dispersing it, adjusting the pH value to a preset value, adding an initiator to initiate polymerization, and grinding the inorganic mineral components. The suspending agent is prepared by mixing the prepared polymer and the inorganic mineral modified powder in a preset ratio to obtain the suspending agent.

15. The method for preparing the isolation fluid for deep and ultra-deep wells according to claim 14, characterized in that, The method for preparing the polymer includes: According to the weight proportions of each component, water, 2-acrylamide-2-methylpropanesulfonic acid, N,N-diethylacrylamide, cyclic monomer, crosslinking agent and carboxylic acid monomer were added to the reactor in sequence to obtain the reaction solution; Stir at 200 rpm until all components are dissolved, adjust the pH of the reaction solution to 6-7, and raise the temperature of the reaction solution to 50-60°C. An initiator was added to the reaction solution, and the reaction was carried out for 2-3 hours. The mixture was then cooled to room temperature to obtain colorless and pale yellow viscous liquids. After microwave drying and pulverization, polymer powder materials were obtained.

16. The method for preparing the deep and ultra-deep well isolation fluid according to claim 14, characterized in that, The method for preparing the modified inorganic mineral includes: Soak attapulgite fibers or basalt fibers in a 10% dilute hydrochloric acid solution to remove impurities such as carbonates, and then rinse them repeatedly with deionized water until neutral to obtain pure attapulgite fibers or basalt fibers. Pure raptor fiber or basalt fiber is added to deionized water and dispersed evenly using an ultrasonic cell disruptor. Liquid acrylic acid was adjusted to pH 6 with a 28% sodium hydroxide solution and then added to a fiber dispersion. The mixture was heated to 60°C, and an initiator was added to initiate polymerization. The polymer particles were washed with hot ethanol solution, dried at room temperature, and then ground into powder.

17. The method for preparing the isolation fluid for deep and ultra-deep wells according to claim 13, characterized in that, The method for preparing the rinsing agent includes: Component preparation: Prepare the pre-set amounts of emulsifying viscosity reducer, wetting reversal agent, solubilizer, and chelating agent; To prepare the rinsing agent, heat 100 parts of water, then add 12-24 parts of emulsifying viscosity reducer, 10-20 parts of wetting reversal agent, 5-10 parts of cosolvent, and 4-8 parts of chelating agent. Stir and mix well, then cool to room temperature to obtain the rinsing agent.

18. The method for preparing the isolation fluid for deep and ultra-deep wells according to claim 17, characterized in that, The method for preparing the wetting reversal agent includes: To prepare the reaction solution, add a predetermined amount of water, 2-acrylamido-2-methylpropanesulfonic acid, acrylamide, and sodium 2-acrylamidotetradecanesulfonate monomers sequentially to the reactor to obtain the reaction solution. After stirring and dissolving evenly, adjust the temperature and pH of the reaction solution for later use. To prepare a wetting reversal agent, an initiator is added to the prepared reaction solution to carry out the reaction, and then the solution is cooled to room temperature to obtain the wetting reversal agent.

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