Acidification drag reducer applicable to carbonate reservoir as well as preparation method and application of acidification drag reducer

Abstract

The invention relates to the technical field of oil and gas field development chemistry, and provides an acidification drag reducer applicable to carbonate reservoirs and a preparation method and application thereof, the acidification drag reducer comprises the following components: 0.15-0.40 wt% of hyperbranched polysulfonamide copolymer, 0.10-0.20 wt% of cocamidopropyl hydroxy sulfobetaine, 0.05-0.15 wt% of C12-C14 fatty alcohol-polyoxyethylene ether, 0.3-0.7 wt% of soluble calcium salt, 2.0-6.0 wt% of C1-C3 lower alcohol and 0.02-0.10 wt% of phenol free radical scavenger, and the balance of water. The mass percent of the six raw materials is based on the total mass of 20 + / -2wt% hydrochloric acid acidizing fluid. According to the invention, 0.15 to 0.40 wt% of HB-PSA-co-VP is used as a core; cAPHS is used as an ampholytic surfactant and can be compounded with alcohol ether to form wormlike micelles, so that the drag reduction efficiency is enhanced; therefore, according to the scheme, the drag reduction rate can be improved through double-effect synergy of the hyperbranched polymer and the wormlike micelles.

Description

Technical Field

[0001] This invention relates to the field of chemical technology for oil and gas field development, specifically to an acidizing drag-reducing agent suitable for carbonate reservoirs, its preparation method, and its application. Background Technology

[0002] In oil and gas field development, carbonate reservoirs, due to their low porosity and poor permeability, require acidizing operations to dissolve blockages in the rock matrix or fractures, thereby improving reservoir conductivity. To enhance dissolution efficiency, acidizing operations often employ high-concentration hydrochloric acid systems of 15–28 wt%. However, when high-concentration hydrochloric acid is pumped at high flow rates (2–4 m³ / min), it generates significant flow friction in the wellbore and fractures, leading to excessively high surface pump pressure (even exceeding the equipment's pressure limit), limiting the acid penetration distance, and reducing the acidizing effect.

[0003] Drag-reducing agents are the core chemical agents for reducing friction in acid solutions. Existing technologies mainly suffer from the following three major drawbacks:

[0004] First, the problem of strong acid degradation: Traditional drag-reducing agents (such as polyacrylamide PAM and polyethylene oxide PEO) contain amide or ether bonds in their main chain, which are easily hydrolyzed and broken in 20 wt% hydrochloric acid (pH≈-0.3), resulting in a rapid decrease in molecular weight and loss of drag-reducing performance (see patents CN103436321B and US10752845B2).

[0005] Second, the problem of high temperature instability: The temperature of deep carbonate reservoirs is generally 100–120℃. At high temperatures, traditional polymer chains are prone to thermal oxidation and breakage. Existing products generally have a stability time of <24 hours at this temperature, which cannot meet the requirements of long-term construction.

[0006] Third, the drag reduction efficiency is insufficient: existing drag reduction agents (including some surfactant micelle synergistic systems, such as CN108728076B) are still based on linear polymers, and their drag reduction rate in 20 wt% hydrochloric acid is generally <60%, and it further decreases with increasing temperature, which cannot meet the engineering requirement of "drag reduction rate ≥70% + stable for 48 h".

[0007] In addition, existing products also have problems such as significant reservoir damage (high polymer adsorption capacity and difficulty in backflow) and high patent barriers (depending on PAM / PEO structure).

[0008] Therefore, developing a novel drag-reducing agent with a molecular structure resistant to strong acids, an efficient topological configuration, synergistic stability of the system, and low reservoir damage has become a key technical requirement for acidizing operations in deep carbonate reservoirs. Summary of the Invention

[0009] The first objective of this invention is to solve the technical problem that traditional drag-reducing agents cannot stably improve carbonate rock salt reservoirs under strong acid and high temperature conditions, and to provide an acidizing drag-reducing agent suitable for carbonate rock reservoirs, which is applicable to acid fracturing and acid washing work in deep carbonate rock salt reservoirs.

[0010] To achieve the above objectives, the present invention provides an acidizing drag-reducing agent suitable for carbonate reservoirs, the drag-reducing agent comprising the following components: 0.15~0.40 wt% hyperbranched polysulfonamide copolymer, 0.10~0.20 wt% cocamidopropyl hydroxysulfonate betaine, and 0.05~0.15 wt% C 12- C 14 The formula comprises fatty alcohol polyoxyethylene ether, 0.3–0.7 wt% soluble calcium salt, 2.0–6.0 wt% C1–C3 lower alcohols, 0.02–0.10 wt% phenolic free radical scavenger, and 31 wt% industrial hydrochloric acid. This formula uses 0.15–0.40 wt% HB-PSA-co-VP as the core component; CAPHS, as an amphoteric surfactant, can be compounded with the alcohol ether to form worm-like micelles, enhancing drag reduction efficiency. Therefore, this formula can improve drag reduction rate through the synergistic effect of "hyperbranched polymer-worm-like micelles".

[0011] Preferably, the C 12- C 14 The ethylene oxide addition number of fatty alcohol polyoxyethylene ether is 6–8. The C2000 selected in this scheme... 12- C 14 Fatty alcohol polyoxyethylene ether is a nonionic co-surfactant that can adjust the morphology of micelles and improve their stability at 120°C.

[0012] Preferably, the soluble calcium salt is calcium chloride or calcium acetate, and the soluble calcium salt is used to provide Ca. 2+ Adjusting the ionic strength of the solution. Ca2+ is provided by soluble calcium salts. 2+ It adjusts the ionic strength of transparent homogeneous solutions containing lower alcohols, soluble calcium salts, and surfactants, promotes the orderly assembly of micelles, and inhibits high-temperature dissociation of the solution.

[0013] Preferably, the C1-C3 lower alcohol includes at least one of methanol, ethanol, or propanol. As a co-solvent for the reaction, the C1-C3 lower alcohol can improve the solubility between the polymer and CAPHS, preventing phase separation at high temperatures.

[0014] Preferably, the HB-PSA-co-VP is prepared by a reversible addition-fragmentation chain transfer polymerization method, specifically including the following steps:

[0015] S11. Preparation: Weigh styrene, N-vinylpyridine, and p-styrenesulfonyl chloride in a molar ratio of 40:55:5 to prepare monomers. Use RAFT chain transfer agent at 0.8% of the total molar amount of monomers and initiator at 0.2% of the total molar amount of monomers. Mix 1,4-dioxane with water in a volume ratio of 4:1 to form the first solvent.

[0016] S12. Polymerization reaction: Dissolve the monomer and RAFT chain transfer agent in 400 mL of the first solvent to form the second solvent; purge nitrogen gas into the second solvent to remove oxygen from the mixed solvent for 30 minutes; heat to 70±2℃, add the initiator, and react at a constant temperature for 6–10 hours to form the third solvent.

[0017] S13, Hydrolysis and Precipitation: Cool the third solvent to room temperature, add 25 wt% ammonia water dropwise to adjust the pH until the pH is 8-9, so that -SO2Cl in styrene sulfonyl chloride is hydrolyzed to -SO2NH2; add 2 volumes of anhydrous ethanol to the third solvent, after precipitation and filtration, vacuum dry at 60-70℃ for 8-12 hours to obtain a white powder intermediate;

[0018] S14. Quaternization reaction: Dissolve the white powder intermediate in deionized water at a solid-liquid ratio of 1:10 (g / mL) to form a fourth solvent; add iodomethane at a molar ratio of 1.2:1 to the N-vinylpyridine derivative unit; stir the reaction at 60±2℃ for 2-3 hours; after the reaction is complete, rotary evaporate to concentrate to 1 / 3 of the original volume of the white powder intermediate, add ethanol for secondary precipitation, and vacuum dry to obtain the target copolymer.

[0019] This method yields HB-PSA-co-VP, which serves as the core drag-reducing component of the acid-reducing drag reducer. HB-PSA-co-VP employs a full CC backbone, enabling it to withstand strong acid hydrolysis. It contains side chains with sulfonamide and quaternized pyridine groups. The hyperbranched structure formed in HB-PSA-co-VP can increase the hydrodynamic volume and is stabilized by quaternized pyridine groups in synergistic micelle formation.

[0020] Preferably, the RAFT chain transfer agent is cyanoisopropylphenyl dithioester, and the initiator is azobisisobutyronitrile.

[0021] A method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs includes the following steps:

[0022] S21. Solvent pretreatment: Add water to the mixing tank and stir. Add 5.0wt% C1-C3 lower alcohol to the mixing tank and stir until completely dissolved.

[0023] S22, Calcium salt dissolution: Keep the stirring rate in the mixing tank, add 0.50 wt% soluble calcium salt, and continue stirring for 10-15 minutes until the solution is clear and free of solid particles;

[0024] S23, Surfactant compounding: Add 0.15 wt% CAPHS and 0.10 wt% C sequentially. 12- C 14 Fatty alcohol polyoxyethylene ether: After each component is added, stir for 8-12 minutes to form a transparent homogeneous solution in the mixing tank.

[0025] S24. Polymer dissolution: Slowly add 0.30 wt% HB-PSA-co-VP solid to the mixing tank. The addition rate of HB-PSA-co-VP should be ≤0.5 kg / min to avoid agglomeration. After the addition is complete, continue stirring for 30-30 minutes until the polymer is completely dissolved.

[0026] S25. Preparation of hydrochloric acid: Under stirring conditions, slowly add 31wt% industrial hydrochloric acid to the mixing tank at a rate of 10~15 L / min, stir for 20~30 minutes, and finally obtain the drag-reducing agent composition.

[0027] Preferably, the drag-reducing agent composition is a 20±0.5 wt% hydrochloric acid acidification solution, wherein the pH of the 20±0.5 wt% hydrochloric acid acidification solution is approximately -0.2, and the density of the 20±0.5 wt% hydrochloric acid acidification solution is 1.12 g / cm³.

[0028] Preferably, the method further includes the addition of functional additives, which are added between steps S24 and S25, comprising adding 8.0 kg of 0.80 wt% composite corrosion inhibitor and 5.0 kg of 0.50 wt% iron ion stabilizer, and stirring for 15-20 minutes; the iron ion stabilizer includes at least one of citric acid or disodium EDTA. By adding the composite corrosion inhibitor, the wellbore metal in oil and gas field development can be protected, preventing hydrochloric acid corrosion; the iron ion stabilizer can complex Fe... 2+ / Fe 3+ To avoid the formation of Fe(OH)3 precipitate, which could clog carbonate reservoirs.

[0029] The application of an acidizing drag-reducing agent suitable for carbonate reservoirs as described in any one of claims 1 to 9 in acidized carbonate reservoirs.

[0030] The beneficial effects of this invention are as follows: using 0.15~0.40 wt% HB-PSA-co-VP as the core; CAPHS, as an amphoteric surfactant, can be compounded with alcohol ethers to form worm-like micelles, thereby enhancing drag reduction efficiency; therefore, this solution can improve drag reduction rate through the dual synergistic effect of "hyperbranched polymer-worm-like micelles".

[0031] After aging in a sealed environment at 20℃ for 48 hours, the solution remained clear, with a molecular weight retention rate of HB-PSA-co-VP > 93%, and the stability time was more than twice that of existing products.

[0032] The hyperbranched structure has low adsorption capacity and micelles are easy to backflow. Combined with the anti-precipitation effect of iron ion stabilizers, the conductivity recovery rate of carbonate cores is ≥92.7%. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the present invention. Detailed Implementation

[0034] To make the objectives, technical solutions, and advantages of the embodiments clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. When the following description refers to the drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The embodiments described in the following exemplary embodiments do not represent all embodiments consistent with this disclosure. Rather, they are merely examples of apparatuses and methods consistent with some aspects of this disclosure as detailed in the appended claims.

[0035] In this disclosure, unless otherwise stated, directional terms such as "inner" and "outer" are defined based on the contours of the corresponding components. Terms such as "first" and "second" used in this disclosure are for distinguishing one element from another and do not imply sequence or importance.

[0036] This invention provides an acidizing drag-reducing agent suitable for carbonate reservoirs, comprising the following components: 0.15~0.40 wt% hyperbranched polysulfonamide copolymer (HB-PSA-co-VP), 0.10~0.20 wt% cocamidopropyl hydroxysulfonate betaine (CAPHS), and 0.05~0.15 wt% C 12- C 14 Fatty alcohol polyoxyethylene ether, 0.3~0.7wt% soluble calcium salt, 2.0~6.0 wt% C1-C3 lower alcohols, 0.02~0.10 wt% phenolic free radical scavenger and 31wt% industrial hydrochloric acid.

[0037] This solution uses 0.15~0.40 wt% HB-PSA-co-VP as the core and CAPHS as an amphoteric surfactant, which can be compounded with alcohol ethers to form worm-like micelles, thereby enhancing drag reduction efficiency. Therefore, this solution can improve drag reduction rate through the dual synergistic effect of "hyperbranched polymer-worm-like micelles".

[0038] The above-mentioned alcohol-ether combination refers to CAPHS and C12- C 14 Compounding of fatty alcohol polyoxyethylene ethers.

[0039] The C 12- C 14 The ethylene oxide addition number of fatty alcohol polyoxyethylene ether is 6–8. The C2000 selected in this scheme... 12- C 14 Fatty alcohol polyoxyethylene ether is a nonionic co-surfactant that can adjust the morphology of micelles and improve their stability at 120°C.

[0040] The soluble calcium salt is calcium chloride or calcium acetate, and the soluble calcium salt is used to provide Ca. 2+ Adjusting the ionic strength of the solution. Ca2+ is provided by soluble calcium salts. 2+ It adjusts the ionic strength of the solution, promotes the orderly assembly of micelles, and inhibits high-temperature dissociation.

[0041] The C1-C3 lower alcohols include at least one of methanol, ethanol, or propanol. As a co-solvent for the reaction, the C1-C3 lower alcohols can improve the solubility of the polymer and surfactant, and prevent phase separation at high temperatures.

[0042] The phenolic free radical scavenger includes at least one of hydroquinone, 2,6-di-tert-butyl-p-cresol, or propyl gallate. The phenolic free radical scavenger can remove high-temperature free radicals, inhibit the thermal oxidative breakage of polymer chains, and prolong the polymer chain stabilization time.

[0043] A method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs includes the following steps:

[0044] S1. Solvent pretreatment: Add 355 L of clean water to the mixing tank and stir. Add 50 L of 5.0 wt% methanol to the mixing tank and stir for 5-10 minutes until completely dissolved.

[0045] S2, Calcium salt dissolution: Keep the stirring rate in the mixing tank, add 5.0 kg of 0.50 wt% calcium chloride, and continue stirring for 10-15 minutes until the solution is clear and free of solid particles;

[0046] S3, Surfactant Compound: Add 1.5 kg of 0.15 wt% CAPHS and 1.0 kg of 0.10 wt% C sequentially. 12- C 14 Fatty alcohol polyoxyethylene ether: After each component is added, stir for 8-12 minutes to form a transparent homogeneous solution in the mixing tank.

[0047] S4. Polymer dissolution: Slowly add 3.0 kg of 0.30 wt% HB-PSA-co-VP solid to the mixing tank. The addition rate of HB-PSA-co-VP should be ≤0.5 kg / min to avoid agglomeration. After the addition is complete, continue stirring for 30-30 minutes until the polymer is completely dissolved.

[0048] S5. Preparation of hydrochloric acid: Under stirring conditions, slowly add 645 L of 31wt% industrial hydrochloric acid to the mixing tank at a rate of 10~15 L / min, stir for 20~30 minutes, and finally obtain the drag-reducing agent composition.

[0049] Specifically, the drag-reducing agent composition is a 20±0.5 wt% hydrochloric acid acidification solution with a pH of approximately -0.2 and a density of 1.12 g / cm³.

[0050] The HB-PSA-co-VP is prepared by a reversible addition-fragmentation chain transfer polymerization method, specifically including the following steps:

[0051] S41. Preparation: Weigh styrene, N-vinylpyridine, and p-styrenesulfonyl chloride in a molar ratio of 40:55:5 to prepare monomers. Use RAFT chain transfer agent at 0.8% of the total molar amount of monomers and initiator at 0.2% of the total molar amount of monomers. Mix 1,4-dioxane with water in a volume ratio of 4:1 to form the first solvent.

[0052] S42. Polymerization reaction: Dissolve the monomer and RAFT chain transfer agent in 400 mL of the first solvent to form the second solvent; purge nitrogen gas into the second solvent to remove oxygen from the mixed solvent for 30 minutes; heat to 70±2℃, add the initiator, and react at a constant temperature for 6–10 hours to form the third solvent.

[0053] S43, Hydrolysis and Precipitation: Cool the third solvent to room temperature, add 25 wt% ammonia water dropwise to adjust the pH until the pH is 8-9, so that -SO2Cl in styrene sulfonyl chloride is hydrolyzed to -SO2NH2; add 2 times the volume of anhydrous ethanol to the third solvent, after precipitation and filtration, vacuum dry at 60-70℃ for 8-12 hours to obtain a white powder intermediate;

[0054] S44. Quaternization reaction: Dissolve the white powder intermediate in deionized water at a solid-liquid ratio of 1:10 (g / mL) to form a fourth solvent; add iodomethane at a molar ratio of 1.2:1 to the N-vinylpyridine derivative unit; stir the reaction at 60±2℃ for 2-3 hours; after the reaction is complete, concentrate the mixture by rotary evaporation to 1 / 3 of the original volume of the white powder intermediate, add ethanol for secondary precipitation, and vacuum dry to obtain the target copolymer.

[0055] This method yields HB-PSA-co-VP, which serves as the core drag-reducing component of the acid-reducing drag reducer. HB-PSA-co-VP employs a full CC backbone, enabling it to withstand strong acid hydrolysis. It contains side chains with sulfonamide and quaternized pyridine groups. The hyperbranched structure formed in HB-PSA-co-VP can increase the hydrodynamic volume and is stabilized by quaternized pyridine groups in synergistic micelle formation.

[0056] The HB-PSA-co-VP has a molecular structure that meets the requirements of "strong acid resistance + high drag reduction", and its specific structure is as follows:

[0057] Main chain structure: It adopts a full CC main chain, which is copolymerized from 40 mol% styrene-derived units, 55 mol% N-vinylpyridine-derived units, and 5 mol% sulfonamide-functionalized styrene-derived units, and has no easily hydrolyzed amide / ether bonds;

[0058] Side chain functional groups: sulfonamide group (-SO2NH-) and quaternized pyridinium group (-C5H4N) are used. + -CH3), containing sulfonamide groups (-SO2NH-) to enhance compatibility with acidic solutions, quaternized pyridinyl groups (-C5H4N) + -CH3) synergistically activates surfactants through electrostatic interactions;

[0059] Molecular weight and topology: Weight-average molecular weight (Mw) 8.0 × 10⁻⁶ 6 –1.2×10 7 The molecular weight distribution index (PDI) is 1.25-1.35, and the three-dimensional hyperbranched topology (hydrodynamic radius, Rh is significantly larger than that of the linear standard) is significantly larger.

[0060] Therefore, after the HB-PSA-co-VP was fabricated, its structure was verified by GPC-MALS testing: weight-average molecular weight Mw = 9.8 × 10⁻⁶. 6 PDI=1.32, Rh=85 nm (linear PAM standard Rh=42 nm, confirming hyperbranched structure);

[0061] Also through infrared spectroscopy (IR): 1340 cm⁻¹ -1(–SO2NH– stretching vibration), 1630 cm -1 (Characteristic peak of quaternized pyridine α-yl group), 2920 cm⁻¹ -1 (C–C main chain stretching vibration) confirms the successful introduction of the target functional group.

[0062] The RAFT chain transfer agent is cyanoisopropylphenyl dithioester, and the initiator is azobisisobutyronitrile.

[0063] The mixing tanks in S21-S25 are equipped with low-shear stirring, and the stirring speed is 300~500 rpm.

[0064] It also includes the addition of functional additives, which are added between S24 and S25, consisting of 8.0 kg of 0.80 wt% composite corrosion inhibitor and 5.0 kg of 0.50 wt% iron ion stabilizer, and stirred for 15-20 minutes; the iron ion stabilizer includes at least one of citric acid or disodium EDTA. By adding the composite corrosion inhibitor, the wellbore metal in oil and gas field development can be protected, preventing hydrochloric acid corrosion; the iron ion stabilizer can complex Fe... 2+ / Fe 3+ To avoid the formation of Fe(OH)3 precipitate, which could clog carbonate reservoirs.

[0065] An acidizing drag-reducing agent suitable for carbonate rock reservoirs is applied to carbonate rock salt reservoirs with a formation temperature of 100~120℃ and a well depth >4000m. During operation, the drag-reducing agent composition is injected into the wellbore through a high-pressure pump at a discharge rate of 2~4m³ / min. During the injection process, the surface pump pressure drops by ≥30%, and the core conductivity recovery rate of the carbonate rock reservoir after acidizing is ≥90%.

[0066] The following detailed explanation illustrates the specific implementation methods:

[0067] Example 1:

[0068] The following experimental materials were selected for the preparation of HB-PSA-co-VP:

[0069] Styrene (St, 99% purity);

[0070] N-vinylpyridine (VP, 98% purity);

[0071] p-Styrenesulfonyl chloride (SSC, 98% purity);

[0072] RAFT chain transfer agent CPDB (97% purity);

[0073] Initiator AIBN (98% purity);

[0074] 1,4-Dioxane (analytical grade);

[0075] Ammonia solution (25 wt%, analytical grade);

[0076] Iodomethane (99% purity);

[0077] Anhydrous ethanol (analytical grade).

[0078] Preparation steps: Add styrene (40 mmol, 4.24 g), N-vinylpyridine (55 mmol, 5.83 g), p-styrenesulfonyl chloride (5 mmol, 1.11 g), and CPDB (0.8 mmol, 0.20 g) to a 500 mL four-necked flask, add 400 mL of 1,4-dioxane / water mixed solvent (volume ratio 4:1), and stir magnetically until completely dissolved;

[0079] High-purity nitrogen (99.999%) was introduced for 30 minutes to remove oxygen. The flask was sealed, and the oil bath was heated to 70°C. AIBN (0.2 mmol, 0.033 g) was added, and the reaction was carried out at a constant temperature for 8 hours.

[0080] After the reaction was complete, the flask was cooled to room temperature, and 25 wt% ammonia was added dropwise to adjust the pH to 8.5. The mixture was stirred for 1 hour to allow the SO2Cl to be completely hydrolyzed.

[0081] The reaction solution was slowly poured into 400 mL of anhydrous ethanol and allowed to stand for 2 hours, resulting in the precipitation of a white precipitate. The precipitate was filtered through a Buchner funnel and dried in a vacuum drying oven at 65 °C for 10 hours to obtain an intermediate powder (approximately 10.5 g).

[0082] Dissolve 10g of intermediate powder in 100mL of deionized water, transfer to a 250mL three-necked flask, add iodomethane (6.2g, 1.2eq relative to the VP unit), and stir in an oil bath at 60℃ for 2.5 hours.

[0083] After the reaction was completed, the mixture was concentrated to 30 mL by rotary evaporation (50 °C, -0.09 MPa), poured into 20 mL of anhydrous ethanol for secondary precipitation, filtered, and vacuum dried for 8 hours to obtain the target copolymer HB-PSA-co-VP (approximately 9.8 g).

[0084] Test characterization results: GPC-MALS: weight-average molecular weight Mw = 9.8 × 10⁻⁶ 6 The number-average molecular weight Mn = 7.4 × 10⁻⁶ 6 PDI = 1.32;

[0085] Dynamic light scattering (DLS): Rh = 85 nm (25 °C, 0.1 wt% aqueous solution);

[0086] Infrared spectrum (FT-IR): 3350 cm⁻¹ -1(-NH- stretching), 1340cm -1 (-SO2- telescopic), 1630cm -1 (Pyridyl C=N stretching), 2920cm -1 (CC main chain stretching) confirms the functional group structure.

[0087] Example 2: Formulation and performance testing of a 1000L drag-reducing agent composition

[0088] Raw material usage (based on a total mass of 1000 kg of 20 wt% hydrochloric acid acidification solution)

[0089] Preparation steps of drag-reducing agent composition: Add 355L of deionized water to a 1000L mixing tank, turn on the stirrer (400rpm), add 50L of methanol, and stir for 8 minutes until dissolved;

[0090] Add 5.0 kg of calcium chloride and stir for 12 minutes until completely dissolved (the solution is clear).

[0091] Add 5.0 L of CAPHS aqueous solution and 1.0 kg of C in sequence. 12- C 14 Fatty alcohol polyoxyethylene ether, stir for 10 minutes in each step;

[0092] Slowly add 3.0 kg of HB-PSA-co-VP solid (in 3 portions, 1 kg each time, with 5-minute intervals), and stir for 35 minutes until no flocculation occurs;

[0093] Add 8.0 kg of composite corrosion inhibitor and 5.0 kg of citric acid, and stir for 18 minutes;

[0094] Turn on the hydrochloric acid feed pump and add 645L of 31wt% industrial hydrochloric acid at a rate of 12L / min. Stir for 25 minutes, and take a sample to test the hydrochloric acid concentration. The concentration is 20.1wt%, which is the finished product.

[0095] Performance tests and results of the drag-reducing composition of the present invention:

[0096] (1) Drag reduction rate test (according to SY / T5107-2016 standard)

[0097] Test setup: Φ50 mm high-voltage loop;

[0098] Test conditions: Displacement 3 m 3 / min, temperature 25℃;

[0099] Pressure drop of blank hydrochloric acid (ΔP) D ): 1.85 MPa;

[0100] Pressure drop (ΔP) of hydrochloric acid with added agent: 0.40 MPa;

[0101] Drag reduction rate calculation: [(1.85–0.40) / 1.85]×100% = 78.4%.

[0102] (2) Thermal stability test

[0103] Test conditions: 120℃ sealed reactor, aging for 48 hours;

[0104] Appearance observation: The solution remains clear and transparent, without layering, precipitation, or discoloration;

[0105] GPC test: Mw = 9.1 × 10⁻⁶ for HB-PSA-co-VP 6 Molecular weight retention rate = 9.1 × 10 6 / 9.8×10 6 ×100%=92.9%;

[0106] Residual drag reduction rate: drag reduction rate after aging = 76.2%.

[0107] (3) Core damage test (carbonate core from Iraq A oilfield)

[0108] Core parameters: diameter 25mm, length 50mm, basic permeability 15mD;

[0109] Test procedure: core saturated with formation water → measure basic permeability K1 → inject drag-reducing agent composition (discharge rate 2 m³ / min, continuous for 12 hours) → measure restored permeability K2;

[0110] Test results: K2=13.9mD, flow rate recovery rate=13.9 / 15×100%=92.7%.

[0111] (4) Compatibility test

[0112] Test conditions: Mix with common acidification aids (corrosion inhibitors, iron stabilizers, demulsifiers) at a mass ratio of 10:1, and age at 120℃ for 48 hours;

[0113] Results: No precipitation, stratification, or discoloration was observed, indicating good compatibility.

[0114] Three common drag-reducing agents widely used in current oilfield acidizing operations were selected as comparative objects for the drag-reducing agent composition of this invention, specifically the following three common drag-reducing agents:

[0115] The first method uses a conventional micellar drag reducer, whose main component is dodecyl betaine, which is a single amphoteric surfactant without polymer synergistic components.

[0116] The second method uses a common polymer drag reducer, whose main component is partially hydrolyzed polyacrylamide (HPAM) without micellar system assistance.

[0117] The third option is to use a conventional compound drag reducer, whose main components are cocamidopropyl betaine (CAPB) + polyethylene glycol (PEG), which is a traditional surfactant-polymer compound system.

[0118] The following table compares the full performance of the three common drag-reducing agents mentioned above with the acidified drag-reducing agent of this invention:

[0119]

[0120] Comparative Example 1: Preparation steps of drag-reducing agent composition: Add 355L of deionized water to a 1000L mixing tank, turn on the stirrer (400rpm), add 50L of methanol, and stir for 8 minutes until dissolved;

[0121] Add 5.0 kg of calcium chloride and stir for 12 minutes until the solution is clear, at which point the calcium chloride will be completely dissolved.

[0122] Add 5.0 L of CAPHS aqueous solution and 1.0 kg of C solution sequentially. 12- C 14 Fatty alcohol polyoxyethylene ether, stir for 10 minutes in each step;

[0123] Add 8.0 kg of composite corrosion inhibitor and 5.0 kg of citric acid, and stir for 18 minutes;

[0124] Turn on the hydrochloric acid feed pump and add 645L of 31wt% industrial hydrochloric acid at a rate of 12L / min. Stir for 25 minutes to obtain the finished product of Comparative Example 1.

[0125] The following table compares the test parameters of the drag-reducing agent without HB-PSA-co-VP with those of the drag-reducing agent composition of the present invention:

[0126] Comparative Example 2: Preparation steps of drag-reducing agent composition: Add 355L of deionized water to a 1000L mixing tank, turn on the stirrer (400rpm), add 50L of methanol, and stir for 8 minutes until dissolved;

[0127] Add 5.0 kg of calcium chloride and stir for 12 minutes until completely dissolved;

[0128] Slowly add 3.0 kg of HB-PSA-co-VP solid (in 3 portions, 1 kg each time, with 5-minute intervals), and stir for 35 minutes until no flocculation occurs;

[0129] Add 8.0 kg of composite corrosion inhibitor and 5.0 kg of citric acid, and stir for 18 minutes;

[0130] Turn on the hydrochloric acid feed pump and add 645L of 31wt% industrial hydrochloric acid at a rate of 12L / min. Stir for 25 minutes to obtain the finished product of Comparative Example 2.

[0131] Comparative Example 3: Preparation steps of drag-reducing agent composition: Add 355L of deionized water to a 1000L mixing tank, turn on the stirrer (400rpm), add 50L of methanol, and stir for 8 minutes until dissolved;

[0132] Add 5.0 kg of calcium chloride and stir for 12 minutes until completely dissolved (the solution is clear).

[0133] Add 5.0L of CAPHS aqueous solution and stir;

[0134] Slowly add 3.0 kg of HB-PSA-co-VP solid (in 3 portions, 1 kg each time, with 5-minute intervals), and stir for 35 minutes until no flocculation occurs;

[0135] Add 8.0 kg of composite corrosion inhibitor and 5.0 kg of citric acid, and stir for 18 minutes;

[0136] Turn on the hydrochloric acid feed pump and add 645L of 31wt% industrial hydrochloric acid at a rate of 12L / min. Stir for 25 minutes, and take a sample to test the hydrochloric acid concentration. The concentration is 20.1wt%, which is the finished product of Comparative Example 3.

[0137] Comparative Example 4: Preparation steps of drag-reducing agent composition: Add 355L of deionized water to a 1000L mixing tank, turn on the stirrer (400rpm), add 50L of methanol, and stir for 8 minutes until dissolved;

[0138] Add 5.0 L of CAPHS aqueous solution and 1.0 kg of C in sequence. 12- C 14 Fatty alcohol polyoxyethylene ether, stir for 10 minutes in each step;

[0139] Slowly add 3.0 kg of HB-PSA-co-VP solid (in 3 portions, 1 kg each time, with 5-minute intervals), and stir for 35 minutes until no flocculation occurs;

[0140] Add 8.0 kg of composite corrosion inhibitor and 5.0 kg of citric acid, and stir for 18 minutes;

[0141] Turn on the hydrochloric acid feed pump and add 645L of 31wt% industrial hydrochloric acid at a rate of 12L / min. Stir for 25 minutes to obtain the finished product of Comparative Example 4.

[0142] Comparative Example 5:

[0143] Preparation steps of drag-reducing agent composition: Add 355L of deionized water and 5.0kg of calcium chloride to a 1000L mixing tank, and stir until completely dissolved;

[0144] Add 5.0 L of CAPHS aqueous solution and 1.0 kg of C in sequence. 12- C 14 Fatty alcohol polyoxyethylene ether, stir for 10 minutes in each step;

[0145] Slowly add 3.0 kg of HB-PSA-co-VP solid (in 3 portions, 1 kg each time, with 5-minute intervals), and stir for 35 minutes until no flocculation occurs;

[0146] Add 8.0 kg of composite corrosion inhibitor and 5.0 kg of citric acid, and stir for 18 minutes;

[0147] Turn on the hydrochloric acid feed pump and add 645 L of 31wt% industrial hydrochloric acid at a rate of 12L / min. Stir for 25 minutes to obtain the finished product of Comparative Example 5.

[0148] Comparative Examples 2-5 represent the test parameters for drag-reducing agents lacking one or more key components. The drag-reducing agent compositions of the present invention are compared with those of Comparative Examples 2-5, as shown in the table below:

[0149]

[0150] Comparative Example 2 (without CAPHS): CAPHS is a key amphoteric surfactant for the formation of worm-like micelles. Without it, micelles are difficult to form effectively, and the drag reduction rate decreases by 27.1%. At high temperatures, the remaining components are difficult to stabilize the system, resulting in slight stratification and a 9.2% decrease in the recovery rate of core conductivity.

[0151] Comparative Example 3 (Missing C) 12- C 14 Fatty alcohol polyoxyethylene ether: This component can adjust the micelle morphology and improve high-temperature stability. Its absence reduces micelle stability and drag reduction rate by 22.7%. After aging, the drag reduction rate decreases by 24.1%.

[0152] Comparative Example 4 (without soluble calcium salt): Soluble calcium salt provides Ca²⁺ to regulate ionic strength and promotes ordered assembly of micelles. After its absence, the micelle assembly effect deteriorates, the drag reduction rate decreases by 18.2%, and the core conductivity recovery rate decreases by 5.1%.

[0153] Comparative Example 5 (C1-C3 lower alcohols missing): Lower alcohols act as co-solvents to improve the solubility of polymers and surfactants. After their absence, compatibility decreased slightly, drag reduction rate decreased by 15.9%, and the solution became slightly turbid.

[0154] The above descriptions are merely embodiments of the present invention, and common knowledge regarding specific structures and characteristics is not elaborated upon here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the structure of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An acidizing drag-reducing agent suitable for carbonate reservoirs, characterized in that: The drag-reducing agent comprises the following components: 0.15~0.40 wt% hyperbranched polysulfonamide copolymer, 0.10~0.20 wt% cocamidopropyl hydroxysulfonate betaine, and 0.05~0.15 wt% C. 12- C 14 Fatty alcohol polyoxyethylene ether, 0.3~0.7 wt% soluble calcium salt, 2.0~6.0 wt% C1-C3 lower alcohols, 0.02~0.10 wt% phenolic free radical scavenger and 31 wt% industrial hydrochloric acid.

2. The acidizing drag-reducing agent applicable to carbonate reservoirs according to claim 1, characterized in that: The C 12- C 14 The number of ethylene oxide additions for fatty alcohol polyoxyethylene ethers is 6 to 8.

3. The acidizing drag-reducing agent applicable to carbonate reservoirs according to claim 1, characterized in that: The soluble calcium salt is calcium chloride or calcium acetate, and the soluble calcium salt is used to provide Ca. 2+ Adjust the ionic strength of the solution.

4. The acidizing drag-reducing agent applicable to carbonate reservoirs according to claim 1, characterized in that: The C1-C3 lower alcohols include at least one of methanol, ethanol, or propanol.

5. A method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs, used to prepare the acidizing drag-reducing agent suitable for carbonate reservoirs as described in any one of claims 1-4, characterized in that: Includes the following steps: S1. Solvent pretreatment: Add 5.0 wt% C1-C3 lower alcohol to the container and stir until completely dissolved; S2, Calcium salt dissolution: Add 0.50 wt% soluble calcium salt to the container and continue stirring until the solution is clear and free of solid particles; S3, Surfactant Compounding: Add 0.15 wt% cocamidopropyl hydroxysulfonate and 0.10 wt% C to the container sequentially. 12- C 14 Fatty alcohol polyoxyethylene ether: after each component is added, the mixture is stirred, and a transparent homogeneous solution is formed in the container. S4. Polymer Dissolution: Add 0.30 wt% of hyperbranched polysulfonamide copolymer solid to the container. The addition rate of the hyperbranched polysulfonamide copolymer should be ≤0.5 kg / min to avoid agglomeration of the hyperbranched polysulfonamide copolymer. After the addition is completed, continue stirring until the polymer is completely dissolved. S5. Preparation of hydrochloric acid: Under stirring conditions, 31wt% industrial hydrochloric acid is slowly added to the container, and the mixture is stirred to obtain the drag-reducing agent composition.

6. A method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs according to claim 5, characterized in that: The drag-reducing agent composition is a 20±0.5 wt% hydrochloric acid acidified solution with a pH of approximately -0.2 and a density of 1.12 g / cm³.

7. The method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs according to claim 5, characterized in that: The hyperbranched polysulfonamide copolymer added in S4 is prepared by a reversible addition-fragmentation chain transfer polymerization method, specifically including the following steps: S41. Preparation: Weigh the monomers prepared from styrene, N-vinylpyridine, and p-styrenesulfonyl chloride in a molar ratio of 40:55:

5. Use RAFT chain transfer agent at 0.8% of the total molar amount of the monomers and initiator at 0.2% of the total molar amount of the monomers. Mix 1,4-dioxane with water in a volume ratio of 4:1 to form the first solvent. S42. Polymerization reaction: Dissolve the monomer and RAFT chain transfer agent in 400 mL of the first solvent to form the second solvent; purge nitrogen into the second solvent to remove oxygen from the mixed solvent for 30 minutes; heat to 70±2℃, add the initiator, and react at a constant temperature for 6–10 hours to form the third solvent. S43, Hydrolysis and Precipitation: Cool the third solvent to room temperature, add 25 wt% ammonia water dropwise to adjust the pH until the pH is 8-9, so that -SO2Cl in styrene sulfonyl chloride is hydrolyzed to -SO2NH2; add 2 times the volume of anhydrous ethanol to the third solvent, after precipitation and filtration, vacuum dry at 60-70℃ for 8-12 hours to obtain a white powder intermediate; S44. Quaternization reaction: Dissolve the white powder intermediate in deionized water at a solid-liquid ratio of 1:10 (g / mL) to form a fourth solvent; add iodomethane at a molar ratio of 1.2:1 to the N-vinylpyridine derivative unit; stir the reaction at 60±2℃ for 2-3 hours; after the reaction is complete, concentrate the mixture by rotary evaporation to 1 / 3 of the original volume of the white powder intermediate, add ethanol for secondary precipitation, and vacuum dry to obtain the target copolymer.

8. The method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs according to claim 7, characterized in that: The RAFT chain transfer agent is cyanoisopropylphenyl dithioester, and the initiator is azobisisobutyronitrile.

9. A method for preparing an acidizing drag-reducing agent suitable for carbonate reservoirs according to claim 5, characterized in that: The steps also include adding functional additives, which are added between steps S4 and S5. This involves adding 8.0 kg of a 0.80 wt% composite corrosion inhibitor and 5.0 kg of a 0.50 wt% iron ion stabilizer, followed by stirring for 15-20 minutes. The iron ion stabilizer includes at least one of citric acid or disodium EDTA. By adding the appropriate corrosion inhibitor, the wellbore metal in oil and gas field development can be protected against hydrochloric acid corrosion; the iron ion stabilizer can complex Fe... 2+ / Fe 3+ To avoid the formation of Fe(OH)3 precipitate, which could clog carbonate reservoirs.

10. The application of an acidizing drag-reducing agent suitable for carbonate reservoirs as described in any one of claims 1 to 9 in acidized carbonate reservoirs.

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