Leaking stoppage polymer as well as preparation method and application thereof

Abstract

The invention relates to a leaking stoppage polymer as well as a preparation method and application thereof. The leaking stoppage polymer is of a carrageenan derived structure containing imine bonds. The plugging polymer provided by the invention takes natural polysaccharide carrageenan as a matrix, is more environment-friendly, has good compatibility with water-based drilling fluid and can form gel, and the gel state of the plugging polymer can meet the plugging requirements of various crack sizes; by utilizing reversible condensation and hydrolysis reaction of dynamic covalent bonds and imine bonds, particles of the material are self-healed under pressure stimulation to generate a consolidation effect, so that the retention capacity of the material in formation fractures is improved, effective plugging is realized, and re-leakage is prevented.

Description

Technical Field

[0001] This invention relates to the field of petroleum additives technology, and in particular to a plugging polymer, its preparation method, and its application. Background Technology

[0002] Shale is a sedimentary rock formed by the cementation of clay minerals under certain temperature and pressure. It is relatively brittle and hard, and is prone to hydration and expansion when immersed in water. During oil and gas extraction, water enters the nano- and micro-sized pores. The hydration and expansion of clay minerals in shale can easily cause wellbore instability phenomena such as wellbore collapse, diameter reduction, and wellbore enlargement. At the same time, water entering shale fractures and nano- and micro-sized pores can easily cause well leakage.

[0003] To address well leakage issues, current methods involve using plugging agents to seal the leaking layers. Conventional bridging plugging, the most widely used method in the field, has a complex formulation, making it difficult to match particle size with the formation. It also suffers from a low success rate on the first attempt, poor temperature resistance (<120℃), short effective period, and a high risk of re-leakage. Expandable resins, after expansion, exhibit some elasticity and plasticity, improving their ability to seal fractures to some extent; however, their expansion rate and strength after water absorption are difficult to control. High-water-loss plugging formulations are unsuitable for mudstone well sections where the wellbore is prone to instability. Furthermore, in large fracture leakage channels, the poor retention capacity of the plugging material prevents water loss and the formation of a plugging sluice. Cement plugging, due to its high density and poor retention capacity, carries high construction risks and is prone to being used as a filler or flagpole. Its high strength after solidification makes it highly susceptible to creating new holes in loose sandstone formations.

[0004] With the continuous improvement of drilling technology, leakage plugging technology has also made significant progress, and the variety of leakage plugging materials has been increasing. Gel materials, due to their excellent deformability, can be shaped to suit the size of leakage channels. They absorb water and swell, swelling but not dissolving, thus filling and blocking the leakage. They play a crucial role in leakage plugging materials. For example, CN118165712A discloses a three-dimensional network gel plugging agent, belonging to the field of drilling fluid leakage prevention and plugging technology. It comprises the following raw materials by mass percentage: 5%-10% monomer composition, 1%-3% POSS-based crosslinking component, 1%-5% bentonite component, 0.02%-0.2% initiator, 0.2%-0.5% surfactant, and the balance being deionized water. The monomer composition undergoes polymerization under the action of the initiator and POSS-based crosslinking component to form a viscoelastic organic gel. At high temperatures, the isocyanate groups in the POSS-based crosslinking component unblock and release active isocyanate groups, which react with amino and hydroxyl groups in the organic gel to form a three-dimensional network. The bentonite hybrid component is then stably filled within this network, ultimately forming an organic-inorganic composite hybrid gel. However, gel plugging materials are expensive and difficult to penetrate the leaking layer under conditions where well shut-in pressure is not maintained. Furthermore, their strength alone is insufficient to meet the requirements for plugging severe leakage.

[0005] Therefore, how to provide a sealing material with excellent retention capacity and good sealing effect in formation fractures has become an urgent problem to be solved. Summary of the Invention

[0006] To address the problems of poor size matching between existing gel-based bridging and plugging materials and formation fractures, as well as poor inter-particle bonding leading to easy dispersion by formation fluids, this invention provides a plugging polymer, its preparation method, and its application. The plugging polymer is a pressure-responsive smart polymer material that can dissolve in water-based drilling fluids, allowing it to smoothly enter leakage channels. Under pressure stimulation, the material particles undergo self-healing and consolidation, thereby improving the material's retention capacity in formation fractures and achieving excellent plugging results.

[0007] To achieve this objective, the present invention adopts the following technical solution:

[0008] In a first aspect, the present invention provides a plugging polymer having a structure as shown in Formula I:

[0009]

[0010] Among them, R1, R2, R 1 and R 2 Each is independently selected from H, C1-C6 (e.g., C2, C3, C4, C5) straight-chain or branched alkyl groups;

[0011] The A in each structural unit is independently selected from Na. + K + Ca 2+ or NH4 + ;

[0012] z represents a group The quantity is selected from natural numbers between 0 and 3, for example, it can be 0, 1, 2 or 3;

[0013] a and b are each independently selected from natural numbers from 1 to 6, for example, they can be 1, 2, 3, 4, 5 or 6;

[0014] x, y, s, and t are each independent natural numbers, and x and y are not both 0, and s and t are not both 0.

[0015] The plugging polymer provided by this invention contains imine bonds in its molecular chain, which are dynamic covalent bonds. In aqueous environments, imines undergo reversible condensation and hydrolysis reactions. When gel particles containing this polymer accumulate in formation fractures, they come into contact with each other under pressure, and the imine bonds in the gel particle molecules are recreated, causing adjacent gel particles to heal. This macroscopically manifests as consolidation, thereby preventing the gel particles from being dispersed by formation fluids and improving the retention capacity of the plugging gel in formation fractures, thus contributing to a higher plugging success rate. Furthermore, this invention uses natural polysaccharide carrageenan as the matrix structure, which can be extracted from red algae such as *Euphorbia tirucalli*, *Gynostemma pentaphyllum*, and *Gnaphalium affine*. It is widely available and inexpensive, and the resulting plugging polymer and gel meet the modern technological requirements of green development.

[0016] In this invention, the A values ​​in each structural unit may be the same or different; when A is Ca 2+ Then, the two sulfonic acid groups in Formula I share a total of one Ca. 2+ .

[0017] In this invention, C1-C6, etc., all refer to the number of carbon atoms contained in the group.

[0018] In this invention, the term "alkyl" refers to a group formed by losing any one hydrogen atom from an alkane molecule.

[0019] Preferably, R1, R2, and R in Formula I 1 and R 2 Each is independently selected from H, CH3, CH2CH3 or CH2CH2CH3, with H or CH3 being more preferred.

[0020] Preferably, a and b in Formula I are each independently selected from natural numbers from 1 to 3, for example, they can be 1, 2 or 3.

[0021] Preferably, the sum of x and y is 450-1400, for example, it can be 500, 600, 700, 800, 1000 or 1200, etc.

[0022] Preferably, the sum of s and t is 450-1400, for example, it can be 500, 600, 700, 800, 1000 or 1200, etc.

[0023] In a second aspect, the present invention provides a method for preparing the plugging polymer as described in the first aspect, the method comprising the following steps:

[0024] The leak-stopping polymer is obtained by freeze-thawing amino carrageenan derivatives and aldehyde carrageenan derivatives and then injecting them into saturated brine.

[0025] Preferably, the amino carrageenan derivative includes an aminolated derivative of κ-carrageenan.

[0026] Preferably, the structure of the aminocarrageenan derivative is shown in Formula II-1:

[0027]

[0028] Among them, R1, R2, R 1 R 2 The ranges of A, a, b, x, and y are consistent with those in Equation I.

[0029] Preferably, the aminocarrageenan derivative is prepared by the following method:

[0030] κ-carrageenan is subjected to a substitution reaction with epichlorohydrin to obtain an etherified intermediate; the etherified intermediate is then subjected to an amino compound under alkaline conditions to obtain the aminocarrageenan derivative.

[0031] Preferably, the number average molecular weight of the κ-carrageenan is ≥200,000 g / mol, for example, it can be 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 500,000 g / mol, 600,000 g / mol, 700,000 g / mol, 800,000 g / mol or 1,000,000 g / mol, etc., and more preferably 200,000-600,000 g / mol.

[0032] Preferably, the substitution reaction is carried out in the presence of water.

[0033] Preferably, the mass percentage concentration of κ-carrageenan in water is 2.0%-20.0%, for example, it can be 2.5%, 3%, 3.5%, 4%, 5%, 8%, 10%, 12%, 15% or 18%, more preferably 2.0%-10.0%, and even more preferably 2.0%-4.0%.

[0034] Preferably, the mass ratio of epichlorohydrin to κ-carrageenan is 1:(2-20), wherein the specific value of (2-20) can be, for example, 3, 5, 7, 9, 10, 11, 13, 15 or 18, and more preferably 1:(5-15), and even more preferably 1:(8-12).

[0035] Preferably, the pH value of the substitution reaction is 1.0-5.0, for example, it can be 1.5, 2, 2.5, 3, 3.5, 4 or 4.5, and more preferably 2.0-4.0.

[0036] Preferably, the substitution reaction is carried out by adjusting the pH value with concentrated hydrochloric acid.

[0037] Preferably, the mass percentage concentration of the concentrated hydrochloric acid is 20.0%-37.0%, for example, it can be 22%, 25%, 28%, 30%, 32%, 34% or 36%, and more preferably 30.0%-37.0%.

[0038] Preferably, the temperature of the substitution reaction is 40-90°C, for example, 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, and more preferably 50-80°C.

[0039] Preferably, the substitution reaction takes 4-16 hours, for example, 5 hours, 7 hours, 9 hours, 11 hours, 13 hours or 15 hours, and more preferably 8-12 hours.

[0040] Preferably, the amination reaction step includes dissolving the etherification intermediate in an alkaline solution and adding an amino compound to carry out the amination reaction.

[0041] Preferably, the alkaline solution comprises a sodium hydroxide solution.

[0042] Preferably, the mass percentage concentration of alkali in the alkaline solution is 1.0%-10.0%, for example, it can be 2%, 3%, 4%, 5%, 6%, 7%, 8% or 9%, more preferably 2.0%-8.0%, and even more preferably 3.0%-6.0%.

[0043] Preferably, the mass percentage concentration of the etherification intermediate in the alkaline solution is 2.0%-20.0%, for example, it can be 2.5%, 3%, 3.5%, 4%, 5%, 8%, 10%, 12%, 15% or 18%, more preferably 2.0%-10.0%, and even more preferably 2.0%-5.0%.

[0044] Preferably, the mass ratio of the amino compound to κ-carrageenan is 1:(1-5), wherein the specific value of (1-5) can be, for example, 1.5, 2, 2.5, 3, 3.5, 4 or 4.5, and more preferably 1:(1-3).

[0045] Preferably, the structural formula of the amine compound is shown in III-1:

[0046]

[0047] Among them, R1, R2, R 1 R 2 The ranges of a, b, and z are consistent with those in Equation I.

[0048] Preferably, the temperature of the amination reaction is 40-90°C, for example, it can be 45°C, 50°C, 55°C, 60°C, 65°C, 70°C, 75°C, 80°C or 85°C, and more preferably 50-70°C.

[0049] Preferably, the amination reaction takes 2-10 hours, for example, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours or 9 hours, and more preferably 4-8 hours.

[0050] Preferably, after the amination reaction is completed, the pH is adjusted to neutral using concentrated hydrochloric acid, and the product is then filtered, washed, and dried to obtain the aminocarrageenan derivative.

[0051] Preferably, the solvent used for washing includes water and / or ethanol.

[0052] Preferably, the drying temperature is 30-40℃, for example, it can be 31℃, 33℃, 35℃, 37℃ or 39℃, etc.

[0053] Preferably, the aldehyde-based carrageenan derivative includes aldehyde-modified derivatives of κ-carrageenan.

[0054] Preferably, the structure of the aldehyde-based carrageenan derivative is shown in Formula II-2:

[0055]

[0056] The ranges of A, s, and t are consistent with those in Equation I.

[0057] Preferably, the aldehyde-based carrageenan derivative is prepared by the following method:

[0058] The κ-carrageenan was reacted with an oxidizing agent to obtain the aldehyde-based carrageenan derivative.

[0059] Preferably, the number average molecular weight of the κ-carrageenan is ≥200,000 g / mol, for example, it can be 250,000 g / mol, 300,000 g / mol, 350,000 g / mol, 400,000 g / mol, 500,000 g / mol, 600,000 g / mol, 700,000 g / mol, 800,000 g / mol or 1,000,000 g / mol, etc., and more preferably 200,000-600,000 g / mol.

[0060] Preferably, the reaction is carried out in the presence of water.

[0061] Preferably, the mass percentage concentration of κ-carrageenan in water is 2.0%-20.0%, for example, it can be 2.5%, 3%, 3.5%, 4%, 5%, 8%, 10%, 12%, 15% or 18%, more preferably 2.0%-10.0%, and even more preferably 2.0%-4.0%.

[0062] Preferably, the oxidant includes sodium periodate.

[0063] Preferably, the mass ratio of the oxidant to κ-carrageenan is (0.1-0.5):1, wherein the specific value of (0.1-0.5) can be, for example, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4 or 0.45, and more preferably (0.2-0.4):1.

[0064] Preferably, the reaction is carried out in a protective atmosphere.

[0065] Preferably, the protective atmosphere comprises any one or a combination of at least two of nitrogen, helium, or argon.

[0066] Preferably, the reaction is carried out under light-protected conditions.

[0067] Preferably, the reaction temperature is 30-90°C, for example, it can be 40°C, 50°C, 55°C, 60°C, 65°C, 70°C or 80°C, and more preferably 50-70°C.

[0068] Preferably, the reaction time is 2-12 hours, for example, 3 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours, 6 hours, 7 hours, 8 hours or 10 hours, and more preferably 4-6 hours.

[0069] Preferably, after the reaction is completed, the mixture is allowed to stand, precipitated in acetone, and then filtered, washed, and dried to obtain the aldehyde-based carrageenan derivative.

[0070] Preferably, the settling time is 10-60 minutes, for example, 15 minutes, 20 minutes, 30 minutes, 40 minutes or 50 minutes.

[0071] Preferably, the precipitation time is 1-6 hours, for example, it can be 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours or 5 hours, and more preferably 2-4 hours.

[0072] Preferably, the solvent used for washing includes water and / or ethanol.

[0073] Preferably, the drying temperature is 30-40℃, for example, it can be 31℃, 33℃, 35℃, 37℃ or 39℃, etc.

[0074] Preferably, the mass ratio of the amino carrageenan derivative to the aldehyde carrageenan derivative is (2-16):1, wherein the specific value of (2-16) can be, for example, 3, 4, 5, 6, 8, 10, 12 or 14, and more preferably (3-6):1.

[0075] Preferably, the amino carrageenan derivative, aldehyde carrageenan derivative and water are mixed to form a mixed solution and then subjected to freeze-thaw reaction.

[0076] Preferably, the total mass percentage concentration of the amino carrageenan derivative and the aldehyde carrageenan derivative in the mixed solution is 2.0%-20.0%, for example, it can be 3%, 4%, 5%, 6%, 7%, 8%, 10%, 12%, 15% or 18%, and more preferably 4.0%-8.0%.

[0077] Preferably, the mixing temperature is 40-100℃, for example, it can be 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, 80℃ or 90℃, and more preferably 50-80℃.

[0078] Preferably, the mixing time is 4-12h, 5h, 6h, 7h, 8h, 9h, 10h or 11h, and more preferably 6-10h.

[0079] Preferably, the freeze-thaw process includes freezing the mixed solution at a low temperature and then restoring it to the temperature before freezing to thaw it.

[0080] Preferably, the freezing temperature is -35°C to -15°C, for example, it can be -30°C, -28°C, -25°C, -22°C, -20°C or -18°C, and more preferably -30°C to -20°C.

[0081] Preferably, the freezing time is 2-6 hours, for example, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours or 5.5 hours.

[0082] Preferably, the number of freeze-thaw cycles is ≥3, for example, 3, 4, 5, 6, 8 or 10 times, and more preferably 3-6 times.

[0083] Preferably, the saturated saline solution is injected using a micro-injection pump.

[0084] Preferably, the injection pump rate is 0.2-2.0 mL / min, for example, it can be 0.5 mL / min, 0.7 mL / min, 0.9 mL / min, 1.1 mL / min, 1.5 mL / min or 1.8 mL / min, and more preferably 0.5-1.0 mL / min.

[0085] Preferably, after being injected into saturated saline solution, post-processing is performed to obtain the plugging polymer.

[0086] Preferably, the post-processing includes settling, filtration, washing, dialysis, and drying.

[0087] Preferably, the settling time is 16-32 hours, for example, 18 hours, 20 hours, 22 hours, 24 hours, 26 hours, 28 hours or 30 hours.

[0088] Preferably, the solvent used for washing includes water.

[0089] Preferably, the dialysis time is 2-5 days, for example, 2.5 days, 3 days, 3.5 days, 4 days or 4.5 days.

[0090] Preferably, the molecular weight cutoff of the dialysis is ≤8000Da, for example, it can be 7000Da, 6000Da, 5500Da, 5000Da, 4500Da, 4000Da, 3000Da, 2000Da or 1000Da, and more preferably 4000-6000Da.

[0091] Preferably, the drying method includes spray drying.

[0092] Thirdly, the present invention provides a sealing gel comprising a dispersion medium and a sealing polymer as described in the first aspect.

[0093] Preferably, the dispersion medium comprises water.

[0094] Fourthly, the present invention provides the application of the plugging polymer as described in the first aspect and the plugging gel as described in the third aspect in petroleum additives.

[0095] On the other hand, the present invention provides a sealing slurry comprising bentonite slurry and a sealing polymer as described in the first aspect.

[0096] Preferably, the mass percentage of the plugging polymer in the plugging slurry is 1%-10%, for example, it can be 2%, 4%, 6% or 8%, etc.

[0097] Compared with the prior art, the present invention has at least the following beneficial effects:

[0098] The plugging polymer provided by this invention links amino carrageenan derivatives and aldehyde carrageenan derivatives through imine bonds. The resulting polymer can dissolve in water-based drilling fluids to form a gel, which can smoothly enter the leakage channels and meet the plugging requirements of fractures of various sizes. Furthermore, since it is based on natural polysaccharide carrageenan, it reduces the production cost of plugging agents, making it green and efficient. When the gel particles accumulate in the formation fractures, the material particles undergo self-healing and consolidation due to pressure, which improves the retention capacity of the plugging gel in the formation fractures and enables successful plugging. Attached Figure Description

[0099] Figure 1 The FT-IR spectrum of the amino carrageenan derivative (C1) prepared in Example 1;

[0100] Figure 2 The image shows the FT-IR spectrum of the aldehyde-based carrageenan derivative (K1) prepared in Example 1. Detailed Implementation

[0101] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, the following examples are merely simplified examples of the present invention and do not represent or limit the scope of protection of the present invention. The scope of protection of the present invention is determined by the claims.

[0102] All materials used in the following examples are commercially available products. κ-carrageenan was purchased from Jiangsu Duoyang Bioengineering Technology Co., Ltd., bentonite was purchased from Xinjiang Zhongfei Xiazijie Bentonite Co., Ltd., chitosan (degree of deacetylation ≥80%) was purchased from Shanghai Chuangsai Technology Co., Ltd., and dialdehyde starch (degree of aldehydeization ≥80%) was purchased from Hubei Xinmingtai Chemical Co., Ltd.

[0103] This invention uses the Kjeldahl method to determine the nitrogen content of aminocarrageenan derivative molecules, which includes two steps: Kjeldahl digestion and Kjeldahl nitrogen determination. The specific determination method is as follows:

[0104] (i) Kjeldahl digestion

[0105] Weigh a quantitative amount of the ground sample of the amino-modified derivative of κ-carrageenan, and record its mass as m (generally 0.2-2.0 g). Place it in a washed and dried digestion tube, add 12.0 mL of concentrated sulfuric acid and 2 Kjeldahl digestion tablets (each tablet contains 3.5 g K2SO4 + 0.4 g CuSO4·5H2O). Place the digestion tube in a digestion furnace and digest at 420 °C for 60 min to obtain a clear solution. After cooling, add distilled water to 80 mL for later use.

[0106] (ii) Kjeldahl nitrogen determination

[0107] Turn on the ZDDN-II Kjeldahl nitrogen analyzer, set the alkali addition to 50 mL, heating time to 5 min, and 20-30 mL of boric acid solution as the receiving solution. Place the sample consumed in step (i) into the Kjeldahl nitrogen analyzer and press the analysis button to start the determination. After completion, remove the receiving solution and add methyl orange as an indicator. At this time, the receiving solution is blue-green. Titrate with hydrochloric acid with a molar concentration of c, and record the volume of hydrochloric acid consumed when the blue-green color disappears (titation endpoint), denoted as V1. Calculate the nitrogen content according to the Kjeldahl nitrogen determination formula (test method from: Fang Zhen. Preparation and Application Research of Modified Sodium Lignosulfonate Heavy Metal Adsorbent [D]. Master's Thesis, Guangxi University, 2013).

[0108] Example 1

[0109] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0110] (1) Synthesis of aminocarrageenan derivatives:

[0111] Add 6.0 g of κ-carrageenan (Mn = 400000 g / mol, Na) to the reactor. + 83.74%, K + 11.32%, Ca 2 + 2.11%, NH4 + 2.83% (epichlorohydrin) and 194 mL of water were heated in a water bath to 65 °C to dissolve completely. 0.6 g of epichlorohydrin was added, and the pH of the solution was adjusted to 3.0 with concentrated hydrochloric acid with a mass percentage of 33.0%. The reaction was carried out for 10 h under stirring, followed by vacuum distillation and drying to constant weight to obtain the etherified intermediate.

[0112] Dissolve 4.0 g of the etherification intermediate in 100 mL of 4.5% NaOH solution, and add 4.0 g of ethylenediamine (R1, R2, R...). 1 and R 2 All are H (z = 0, a = b = 1), heated in a water bath to 60°C, and reacted for 6 hours. The mixture was then adjusted to neutral with 33.0% hydrochloric acid, filtered, washed three times with deionized water and ethanol, and dried under vacuum at 35°C to constant weight to obtain the aminocarrageenan derivative, denoted as C1, containing 1.69% N. The chemical reaction formula is shown below:

[0113]

[0114] Fourier transform infrared (FT-IR) spectroscopy was performed on C1, and the spectrum is shown below. Figure 1 As shown, the spectral analysis is shown in Table 1.

[0115] Table 1

[0116] <![CDATA[Peak / cm -1 > Corresponding chemical bonds and vibration types 2928.71 C-H asymmetric stretching vibration peak in methylene 2854.90 C-H symmetric stretching vibration peak in methylene 1466.09 C-H bending vibration peak in methylene 2891.35 C-H stretching vibration peak in methine 1125.74 C—O asymmetric stretching vibration peak in ether bond 3348.54 N-H asymmetric stretching vibration peaks in amine groups (primary and secondary amines) 3266.92 N-H symmetric stretching vibration peaks in amine groups (primary and secondary amines) 1623.14 N-H bending vibration peaks in amine groups (primary and secondary amines) 798.31 N-H in-plane rocking vibration peaks in amine groups (primary and secondary amines) 1351.00 C-N stretching vibration peaks in amine groups (primary and secondary amines) 3607.55 O-H stretching vibration peak in hydroxyl group 1002.82 C—O stretching vibration peak in hydroxyl group 1399.72 S-O stretching vibration peak in sulfate ester group 1191.06 S=O stretching vibration peak in sulfate ester group 885.26 C—O—S stretching vibration peak in sulfate ester group

[0117] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0118] Add 6.0 g of κ-carrageenan (Mn = 400000 g / mol, Na) to the reactor. + 83.74%, K + 11.32%, Ca 2 + 2.11%, NH4 + Dissolve 2.83% NaIO4 in 194 mL of water in a water bath at 60°C until fully dissolved. After stirring, add 1.8 g of NaIO4 and react under nitrogen protection in the dark for 5 h. Let stand for 0.5 h, precipitate in acetone for 3 h, filter, wash with ethanol, dehydrate, and dry under vacuum at 35°C to constant weight to obtain the aldehyde-based carrageenan derivative, denoted as K1. The chemical reaction formula is shown below:

[0119]

[0120] Fourier transform infrared (FT-IR) spectroscopy was performed on K1, and the spectrum is shown below. Figure 2 As shown, the spectral analysis is shown in Table 2.

[0121] Table 2

[0122]

[0123] (3) Synthesis of plugging polymers:

[0124] 4.0 g C1 and 1.0 g K1 were added to 80 mL of deionized water and stirred at 65 °C for 8 h. The mixture was then transferred to a beaker and frozen at -25 °C for 4 h, followed by thawing at 65 °C. This freeze-thaw cycle was repeated four times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was uniformly injected into a saturated NaCl solution at a pumping rate of 0.8 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 3 days using a dialysis bag (molecular weight cutoff: 5000 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S1, was obtained.

[0125] Example 2

[0126] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0127] (1) Synthesis of aminocarrageenan derivatives:

[0128] Add 4.0 g of κ-carrageenan (Mn = 600000 g / mol, Na) to the reactor. + 82.66%, K + 12.19%, Ca 2 + 3.05%, NH4 + Add 2.10% (2.10%) and 196 mL of water, heat in a water bath to 80 °C to dissolve completely, add 0.5 g of epichlorohydrin, adjust the pH of the solution to 2.0 with concentrated hydrochloric acid with a mass percentage of 37.0%, react for 12 h under stirring, distill under reduced pressure, and dry to constant weight to obtain the etherified intermediate product.

[0129] Dissolve 2.1 g of the etherification intermediate in 100 mL of 6.0% NaOH solution, and add 2.1 g of tetraethylenepentamine (R1, R2, R...). 1 and R 2 All are H, z=3, a=b=1), heated in a water bath to 70℃, and reacted for 8 hours. The mixture was adjusted to neutral with concentrated hydrochloric acid with a mass percentage concentration of 37.0%, filtered, washed three times with deionized water and ethanol respectively, and dried under vacuum at 35℃ to constant weight to obtain the aminocarrageenan derivative, denoted as C2, with a nitrogen content of 2.15%.

[0130] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0131] Add 4.0 g of κ-carrageenan (Mn = 600000 g / mol, Na) to the reactor. + 82.66%, K + 12.19%, Ca 2 + 3.05%, NH4 + 196 mL of water (2.10%) was heated to 70 °C in a water bath to dissolve completely. After stirring evenly, 1.6 g of NaIO4 was added. The mixture was reacted under helium protection and in the dark for 6 h. After standing for 0.5 h, the mixture was placed in acetone to precipitate for 2 h. After filtration, the mixture was washed with ethanol and dehydrated. The mixture was then vacuum dried at 35 °C to constant weight to obtain the aldehyde carrageenan derivative, denoted as K2.

[0132] (3) Synthesis of plugging polymers:

[0133] 6.0 g C2 and 1.0 g K2 were added to 168 mL of deionized water and stirred at 80 °C for 10 h. The mixture was then transferred to a beaker and frozen at -20 °C for 5 h, followed by thawing at 80 °C. This freeze-thaw cycle was repeated 6 times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was injected into a saturated NaCl solution at a uniform injection rate of 1.0 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 5 days using a dialysis bag (molecular weight cutoff: 6000 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S2, was obtained.

[0134] Example 3

[0135] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0136] (1) Synthesis of aminocarrageenan derivatives:

[0137] Add 8.0 g of κ-carrageenan (Mn = 200000 g / mol, Na) to the reactor. + 85.17%, K + 11.53%, Ca 2 + 1.95%, NH4 + 1.35% (epichlorohydrin) and 192 mL of water were heated in a water bath to 50 °C to dissolve completely. 0.66 g of epichlorohydrin was added, and the pH of the solution was adjusted to 4.0 with concentrated hydrochloric acid with a mass percentage of 37.0%. The reaction was carried out under stirring for 8 h, followed by vacuum distillation and drying to constant weight to obtain the etherified intermediate.

[0138] Dissolve 5.0 g of the etherification intermediate in 95 mL of 3.0% NaOH solution, and add 2.5 g of 2,3-dimethyl-2,3-butanediamine (R1, R2, R...). 1 and R 2 All are CH3 (z=0, a=b=1), heated in a water bath to 50°C, and reacted for 4 hours. The mixture was then adjusted to neutral with 30.0% concentrated hydrochloric acid, filtered, washed three times with deionized water and ethanol, and dried under vacuum at 35°C to constant weight to obtain the aminocarrageenan derivative, denoted as C3, containing 1.84% N.

[0139] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0140] Add 4.0 g of κ-carrageenan (Mn = 200000 g / mol, Na) to the reactor. + 85.17%, K + 11.53%, Ca2 + 1.95%, NH4 + 96 mL of water (1.35%) was heated to 50 °C in a water bath to dissolve completely. After stirring evenly, 0.8 g of NaIO4 was added. The mixture was reacted under argon protection and in the dark for 4 h. After standing for 0.5 h, the mixture was placed in acetone to precipitate for 4 h. After filtration, the mixture was washed with ethanol and dehydrated. The mixture was then vacuum dried at 35 °C to constant weight to obtain the aldehyde carrageenan derivative, denoted as K3.

[0141] (3) Synthesis of plugging polymers:

[0142] 3.0 g C3 and 1.0 g K3 were added to 46 mL of deionized water and stirred at 50 °C for 6 h. The mixture was then transferred to a beaker and frozen at -30 °C for 3 h, followed by thawing at 50 °C. This freeze-thaw cycle was repeated three times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was uniformly injected into a saturated NaCl solution at a pumping rate of 0.5 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 2 days using a dialysis bag (molecular weight cutoff: 4000 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S3, was obtained.

[0143] Example 4

[0144] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0145] (1) Synthesis of aminocarrageenan derivatives:

[0146] Add 5.0 g of κ-carrageenan (Mn = 350000 g / mol, Na) to the reactor. + 24.86%, K + 72.79%, Ca 2 + 2.00%, NH4 + Add 0.61% (0.61%) and 180 mL of water, heat in a water bath to 60 °C to fully dissolve, add 0.6 g of epichlorohydrin, adjust the pH of the solution to 2.5 with concentrated hydrochloric acid with a mass percentage of 32.0%, react under stirring for 8.5 h, distill under reduced pressure, and dry to constant weight to obtain the etherified intermediate product.

[0147] Dissolve 4.0 g of the etherification intermediate in 96 mL of 4.0% NaOH solution, and add 2.25 g of 1,6-hexanediamine (R1, R2, R...). 1 and R 2All are H, z=0, a=b=3), heated in a water bath to 55℃, and reacted for 7.5h. The mixture was adjusted to neutral with concentrated hydrochloric acid with a mass percentage concentration of 32.0%, filtered, washed three times with deionized water and ethanol respectively, and dried under vacuum at 35℃ to constant weight to obtain the amino carrageenan derivative, denoted as C4, with a nitrogen content of 1.75%.

[0148] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0149] 4.0 g of κ-carrageenan (Mn = 350000 g / mol, Na) was added to the reactor. + 24.86%, K + 72.79%, Ca 2 + 2.00%, NH4 + 0.61% NaIO4 was added to 120 mL of water and heated to 55 °C in a water bath to dissolve it completely. After stirring evenly, 0.96 g of NaIO4 was added. The mixture was reacted under nitrogen protection and in the dark for 4.5 h. After standing for 0.5 h, it was placed in acetone to precipitate for 2.5 h. After filtration, it was washed with ethanol and dehydrated. It was then vacuum dried at 35 °C to constant weight to obtain the aldehyde carrageenan derivative, denoted as K4.

[0150] (3) Synthesis of plugging polymers:

[0151] 5.0 g C4 and 1.0 g K4 were added to 75 mL of deionized water and stirred at 55 °C for 7.5 h. The mixture was then transferred to a beaker and frozen at -24 °C for 4 h, followed by thawing at 55 °C. This freeze-thaw cycle was repeated 5 times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was uniformly injected into a saturated NaCl solution at a pumping rate of 0.75 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 4 days using a dialysis bag (molecular weight cutoff: 4500 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S4, was obtained.

[0152] Example 5

[0153] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0154] (1) Synthesis of aminocarrageenan derivatives:

[0155] Add 5.0 g of κ-carrageenan (Mn = 480000 g / mol, Na) to the reactor. + 21.82%, K + 71.65%, Ca 2 + 1.77%, NH4+ 4.74% (epichlorohydrin) and 150 mL of water were heated in a water bath to 65 °C to dissolve completely. 0.525 g of epichlorohydrin was added, and the pH of the solution was adjusted to 3.5 with concentrated hydrochloric acid with a mass percentage of 35.0%. The reaction was carried out under stirring for 8.0 h. The solution was then distilled under reduced pressure and dried to constant weight to obtain the etherified intermediate.

[0156] Dissolve 4.0 g of the etherification intermediate in 80 mL of 5.0% NaOH solution, and add 2.5 g of 1,2-diamino-2-methylpropane (R1 and R2). 1 All are H, R2 and R 2 All are CH3 (z=0, a=b=1), heated in a water bath to 65°C, and reacted for 5 hours. The mixture was then adjusted to neutral with concentrated hydrochloric acid (35.0% by mass), filtered, washed three times with deionized water and ethanol, and dried under vacuum at 35°C to constant weight to obtain the aminocarrageenan derivative, denoted as C5, containing 1.82% N.

[0157] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0158] Add 4.0 g of κ-carrageenan (Mn = 480000 g / mol, Na) to the reactor. + 21.82%, K + 71.65%, Ca 2 + 1.77%, NH4 + 110 mL of water (4.74%) was heated to 65 °C in a water bath to dissolve completely. After stirring evenly, 1.0 g of NaIO4 was added. The mixture was reacted under nitrogen protection and in the dark for 5 h. After standing for 0.5 h, the mixture was placed in acetone to precipitate for 2.5 h. After filtration, the mixture was washed with ethanol and dehydrated. The mixture was then vacuum dried at 35 °C to constant weight to obtain the aldehyde carrageenan derivative, denoted as K5.

[0159] (3) Synthesis of plugging polymers:

[0160] 5.0 g C5 and 1.0 g K5 were added to 68 mL of deionized water and stirred at 60 °C for 6.5 h. The mixture was then transferred to a beaker and frozen at -20 °C for 3.5 h, followed by thawing at 60 °C. This freeze-thaw cycle was repeated four times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was uniformly injected into a saturated NaCl solution at a pumping rate of 0.6 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 5 days using a dialysis bag (molecular weight cutoff: 5000 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S5, was obtained.

[0161] Example 6

[0162] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0163] (1) Synthesis of aminocarrageenan derivatives:

[0164] Add 5.0 g of κ-carrageenan (Mn = 500000 g / mol, Na) to the reactor. + 60.04%, K + 37.25%, Ca 2 + 1.52%, NH4 + 1.19% (1.19%) and 132 mL of water were heated in a water bath to 75 °C to dissolve completely. 0.5 g of epichlorohydrin was added, and the pH of the solution was adjusted to 3.0 with concentrated hydrochloric acid with a mass percentage of 35.0%. The reaction was carried out for 9.5 h under stirring, followed by vacuum distillation and drying to constant weight to obtain the etherified intermediate.

[0165] Dissolve 4.0 g of the etherification intermediate in 80 mL of 3.5% NaOH solution, and add 3.2 g of 1,3-diaminopropane (R1, R2, R...). 1 and R 2 All are H, z=0, a=1, b=2), heated in a water bath to 60℃, and reacted for 8.5h. The mixture was adjusted to neutral with concentrated hydrochloric acid with a mass percentage concentration of 35.0%, filtered, washed three times with deionized water and ethanol respectively, and dried under vacuum at 35℃ to constant weight to obtain the amino carrageenan derivative, denoted as C6, with a nitrogen content of 1.80%.

[0166] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0167] 4.0 g of κ-carrageenan (Mn = 360000 g / mol, Na) was added to the reactor. + 60.11%, K + 34.92%, Ca 2 + 2.54%, NH4 + 100 mL of water (2.43%) was heated to 65 °C in a water bath to dissolve completely. After stirring evenly, 1.12 g of NaIO4 was added. The mixture was reacted under nitrogen protection and in the dark for 5 h. After standing for 0.5 h, the mixture was placed in acetone to precipitate for 2 h. After filtration, the mixture was washed with ethanol and dehydrated. The mixture was then vacuum dried at 35 °C to constant weight to obtain the aldehyde carrageenan derivative, denoted as K6.

[0168] (3) Synthesis of plugging polymers:

[0169] 4.5 g C6 and 1.0 g K6 were added to 75 mL of deionized water and stirred at 70 °C for 6 h. The mixture was then transferred to a beaker and frozen at -20 °C for 3 h, followed by thawing at 70 °C. This freeze-thaw cycle was repeated four times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was injected into a saturated NaCl solution at a uniform injection rate of 0.8 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 4 days using a dialysis bag (molecular weight cutoff: 5000 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S6, was obtained.

[0170] Example 7

[0171] A leak-sealing polymer, said leak-sealing polymer being prepared by the following method:

[0172] (1) Synthesis of aminocarrageenan derivatives:

[0173] Add 5.0 g of κ-carrageenan (Mn = 420000 g / mol, Na) to the reactor. + 80.57%, K + 17.24%, Ca 2 + 0.16%, NH4 + Add 2.03% (2.03%) and 185 mL of water, heat in a water bath to 80 °C to dissolve completely, add 0.6 g of epichlorohydrin, adjust the pH of the solution to 3.0 with 30.0% concentrated hydrochloric acid, react for 10 h under stirring, distill under reduced pressure, and dry to constant weight to obtain the etherified intermediate.

[0174] Dissolve 4.0 g of the etherification intermediate in 96 mL of 3.8% NaOH solution, and add 2.8 g of triethylenetetramine (R1, R2, R... 1 and R 2 All are H, z=2, a=b=1), heated in a water bath to 62℃, and reacted for 6.5h. The mixture was adjusted to neutral with concentrated hydrochloric acid with a mass percentage concentration of 30.0%, filtered, washed three times with deionized water and ethanol respectively, and dried under vacuum at 35℃ to constant weight to obtain the amino carrageenan derivative, denoted as C7, with a nitrogen content of 1.87%.

[0175] (2) Synthesis of aldehyde-based carrageenan derivatives:

[0176] 4.0 g of κ-carrageenan (Mn = 320000 g / mol, Na) was added to the reactor. + 79.25%, K + 17.07%, Ca 2+ 2.39%, NH4 + 1.29% NaIO4 was added to 116 mL of water and heated to 62 °C in a water bath to dissolve the aldehyde. After stirring, 1.0 g of NaIO4 was added. The mixture was then reacted under nitrogen protection and in the dark for 5 h. After standing for 0.5 h, the aldehyde was placed in acetone to precipitate for 4 h. The precipitate was then filtered, washed with ethanol, dehydrated, and dried under vacuum at 35 °C to constant weight to obtain the aldehyde carrageenan derivative, denoted as K7.

[0177] (3) Synthesis of plugging polymers:

[0178] 3.5 g of C7 and 1.0 g of K7 were added to 80 mL of deionized water and stirred at 62 °C for 8 h. The mixture was then transferred to a beaker and frozen at -28 °C for 4 h, followed by thawing at 62 °C. This freeze-thaw cycle was repeated three times to obtain the plugging polymer precursor. Using a micro-injection pump, the plugging polymer precursor was injected into a saturated NaCl solution at a uniform injection rate of 0.8 mL / min. After standing for 24 h, the solution was filtered, and the polymer was collected. It was washed with deionized water and dialyzed for 4 days using a dialysis bag (molecular weight cutoff: 4000 Da) to remove residual salts. The polymer was then freeze-dried to constant weight, pulverized, and the plugging polymer, denoted as S7, was obtained.

[0179] Example 8

[0180] A plugging polymer, the only difference between the plugging polymer and Example 1 is that the κ-carrageenan (Mn = 400000 g / mol) used to prepare the amino carrageenan derivative and the aldehyde carrageenan derivative is replaced with an equal mass of κ-carrageenan (Mn = 160000 g / mol), while the other materials, amounts and preparation methods are the same as in Example 1. The resulting plugging polymer is denoted as S8.

[0181] Example 9

[0182] A leak-stopping polymer, the only difference between the leak-stopping polymer and Example 1 is that the water bath heating temperature during the preparation of the amino carrageenan derivative is replaced with 85°C instead of 65°C. All other materials, amounts and preparation methods are the same as in Example 1. The resulting leak-stopping polymer is denoted as S9.

[0183] Example 10

[0184] A leak-stopping polymer, the only difference between the leak-stopping polymer and Example 1 is that the freezing time during the synthesis of the leak-stopping polymer is replaced by 1 hour instead of 4 hours. All other materials, amounts and preparation methods are the same as in Example 1. The resulting leak-stopping polymer is denoted as S10.

[0185] Comparative Example 1

[0186] A leak-stopping polymer, the only difference between the leak-stopping polymer and Example 1 is that the amino carrageenan derivative C1 in the preparation step of the leak-stopping polymer is replaced with chitosan (degree of deacetylation ≥80%), and the other materials, amounts and preparation methods are the same as in Example 1. The resulting leak-stopping polymer is denoted as D1.

[0187] Comparative Example 2

[0188] A leak-sealing polymer, differing from Example 1 only in that the aldehyde-based carrageenan derivative K1 in the preparation step is replaced with dialdehyde starch (aldehyde degree ≥80%), while all other materials, amounts, and preparation methods are the same as in Example 1. The resulting leak-sealing polymer is designated D2. The above-mentioned leak-sealing polymer was subjected to the following tests:

[0189] (1) Leakage sealing performance

[0190] The prepared plugging polymers S1-S10, D1, and D2 were added to 4.0% bentonite slurry to prepare a 6.0% plugging slurry. This slurry was poured into a DLM-01 high-temperature, high-pressure plugging evaluation device. Wedge-shaped crack molds with widths of 1.0mm, 2.0mm, and 3.0mm were selected, and the test temperature was set to 100℃. Pressure was applied uniformly at a frequency of 0.2MPa / min. When positive displacement with the plugging slurry was used, the pressure at which liquid dripped from the rear end of the artificial core crack was the positive breakthrough pressure (P). 正 The test results are shown in Table 3. When deionized water is used for reverse displacement, the pressure at the front end of the wedge-shaped crack mold when liquid drips is the reverse breakthrough pressure (P). 反 The test results (MPa) are shown in Table 4.

[0191] Table 3

[0192]

[0193] Table 4

[0194]

[0195]

[0196] As can be seen from Tables 3 and 4, under the action of pressure difference, the sealing slurry obtained in Examples 1-7 can form a gel plug in the crack, thereby effectively sealing the crack. In contrast, when the carrageenan used in Examples 8-10 and Comparative Examples 1-2 has a smaller molecular weight, a higher synthesis temperature of the amino carrageenan derivative, a shorter freezing time of the sealing polymer, or does not use carrageenan as a raw material, the sealing effect is poor.

[0197] (2) Consolidation properties under pressure stimulation

[0198] The prepared plugging polymers S1-S10, D1, and D2 were added to 4.0% bentonite slurry to prepare a 5.0% plugging slurry. This slurry was poured into a DLM-01 high-temperature, high-pressure plugging evaluation device. A wedge-shaped crack mold with a crack width of 2.0 mm was selected. The test temperature was set to 100℃, and pressure was applied uniformly at a frequency of 0.2 MPa / min until it reached 8.0 MPa. After standing for 1 hour, pressure was applied uniformly again at a frequency of 0.2 MPa / min, and the pressure (P) was measured. 正 .

[0199] Repeat the above steps, except that the settling time is set to 2h, 3h, and 4h respectively, and P is measured after different settling times. 正 The measurement results are shown in Table 5.

[0200] Table 5

[0201]

[0202]

[0203] As can be seen from Table 5, with the extension of the standing time, the crack P formed by the plugging polymer prepared by the present invention in the formation of gel decreases. 正 The gradual increase indicates that the gel trapped in the crack underwent self-healing after being squeezed together, i.e., a consolidation process occurred. This increased the pressure at which the gel septum in the crack migrated, which played a positive role in improving the success rate of plugging and preventing re-leakage.

[0204] When the carrageenan used in Examples 8-10 has a small molecular weight, the synthesis temperature of the amino carrageenan derivative is high, and the freezing time of the plugging polymer is short, the positive breakthrough pressure of the resulting plugging slurry is small, and the consolidation effect deteriorates.

[0205] When the amino carrageenan derivative was replaced with chitosan or the aldehyde carrageenan derivative was replaced with dialdehyde starch in Comparative Examples 1 and 2, no obvious solidification phenomenon was observed.

[0206] In summary, the carrageenan-based plugging polymer provided by this invention can adapt to various fracture sizes. Through reversible imine condensation and hydrolysis, the material particles undergo self-healing and consolidation, thereby improving the material's retention capacity in formation fractures. The fracture breakthrough pressure is significantly increased, achieving a good plugging effect. At the same time, it can prevent re-leakage and solve the problems of poor matching between existing gel-based bridging plugging materials and formation fracture sizes, poor bonding ability between material particles, and easy dispersion by formation fluids.

[0207] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A leak-sealing polymer, characterized in that, The plugging polymer has the structure shown in Formula I: Among them, R1, R2, R 1 and R 2 Each is independently selected from H, C1-C6 straight-chain or branched alkyl groups; The A in each structural unit is independently selected from Na. + K + Ca 2+ or NH4 + ; z represents a group The quantity is selected from natural numbers between 0 and 3; a and b are each independently selected from natural numbers 1-6; x, y, s, and t are each independent natural numbers, and x and y are not both 0, and s and t are not both 0.

2. The plugging polymer according to claim 1, characterized in that, In Formula I, R1, R2, R 1 and R 2 Each is independently selected from H, CH3, CH2CH3 or CH2CH2CH3, preferably H or CH3; Preferably, in Formula I, a and b are each independently selected from natural numbers from 1 to 3; Preferably, the sum of x and y is 450-1400; Preferably, the sum of s and t is 450-1400.

3. A method for preparing the plugging polymer as described in claim 1 or 2, characterized in that, The preparation method includes the following steps: The leak-stopping polymer is obtained by freeze-thawing amino carrageenan derivatives and aldehyde carrageenan derivatives and then injecting them into saturated brine.

4. The preparation method according to claim 3, characterized in that, The amino carrageenan derivatives include aminolated derivatives of κ-carrageenan; Preferably, the structure of the aminocarrageenan derivative is shown in Formula II-1: Among them, R1, R2, R 1 R 2 The ranges of A, a, b, x, and y are consistent with those in Equation I.

5. The preparation method according to claim 4, characterized in that, The amino carrageenan derivative was prepared by the following method: κ-carrageenan was subjected to a substitution reaction with epichlorohydrin to obtain an etherified intermediate; the etherified intermediate was then subjected to an amino compound under alkaline conditions to obtain the aminocarrageenan derivative. Preferably, the number average molecular weight of the κ-carrageenan is ≥200,000 g / mol, more preferably 200,000-600,000 g / mol; Preferably, the substitution reaction is carried out in the presence of water; Preferably, the mass percentage concentration of κ-carrageenan in water is 2.0%-20.0%, more preferably 2.0%-10.0%, and even more preferably 2.0%-4.0%. Preferably, the mass ratio of epichlorohydrin to κ-carrageenan is 1:(2-20), more preferably 1:(5-15), and even more preferably 1:(8-12); Preferably, the pH value of the substitution reaction is 1.0-5.0, more preferably 2.0-4.0; Preferably, the substitution reaction is carried out by adjusting the pH value with concentrated hydrochloric acid; Preferably, the concentrated hydrochloric acid has a mass percentage concentration of 20.0%-37.0%, more preferably 30.0%-37.0%; Preferably, the temperature of the substitution reaction is 40-90°C, more preferably 50-80°C; Preferably, the substitution reaction takes 4-16 hours, more preferably 8-12 hours; Preferably, the amination reaction step includes dissolving the etherification intermediate in an alkaline solution and adding an amino compound to carry out the amination reaction; Preferably, the alkaline solution comprises a sodium hydroxide solution; Preferably, the mass percentage concentration of alkali in the alkaline solution is 1.0%-10.0%, more preferably 2.0%-8.0%, and even more preferably 3.0%-6.0%. Preferably, the mass percentage concentration of the etherification intermediate in the alkaline solution is 2.0%-20.0%, more preferably 2.0%-10.0%, and even more preferably 2.0%-5.0%. Preferably, the mass ratio of the amine compound to κ-carrageenan is 1:(1-5), more preferably 1:(1-3); Preferably, the structural formula of the amine compound is shown in III-1: Among them, R1, R2, R 1 R 2 The ranges of a, b, and z are consistent with those in Equation I; Preferably, the temperature of the amination reaction is 40-90°C, more preferably 50-70°C; Preferably, the amination reaction takes 2-10 hours, more preferably 4-8 hours; Preferably, after the amination reaction is completed, the pH is adjusted to neutral with concentrated hydrochloric acid, and the product is then filtered, washed, and dried to obtain the aminocarrageenan derivative. Preferably, the solvent for washing includes water and / or ethanol; Preferably, the drying temperature is 30-40°C.

6. The preparation method according to any one of claims 3-5, characterized in that, The aldehyde-based carrageenan derivatives include aldehyde-modified derivatives of κ-carrageenan; Preferably, the structure of the aldehyde-based carrageenan derivative is shown in Formula II-2: The ranges of A, s, and t are consistent with those in Equation I.

7. The preparation method according to claim 6, characterized in that, The aldehyde-based carrageenan derivative was prepared by the following method: The κ-carrageenan was reacted with an oxidizing agent to obtain the aldehyde-based carrageenan derivative; Preferably, the number average molecular weight of the κ-carrageenan is ≥200,000 g / mol, more preferably 200,000-600,000 g / mol; Preferably, the reaction is carried out in the presence of water; Preferably, the mass percentage concentration of κ-carrageenan in water is 2.0%-20.0%, more preferably 2.0%-10.0%, and even more preferably 2.0%-4.0%. Preferably, the oxidant includes sodium periodate; Preferably, the mass ratio of the oxidant to κ-carrageenan is (0.1-0.5):1, more preferably (0.2-0.4):1; Preferably, the reaction is carried out in a protective atmosphere; Preferably, the protective atmosphere comprises any one or a combination of at least two of nitrogen, helium, or argon; Preferably, the reaction is carried out under light-protected conditions; Preferably, the reaction temperature is 30-90°C, more preferably 50-70°C; Preferably, the reaction time is 2-12 hours, more preferably 4-6 hours; Preferably, after the reaction is completed, the mixture is allowed to stand, precipitated in acetone, and then filtered, washed, and dried to obtain the aldehyde-based carrageenan derivative. Preferably, the settling time is 10-60 minutes; Preferably, the precipitation time is 1-6 hours, more preferably 2-4 hours; Preferably, the solvent for washing includes water and / or ethanol; Preferably, the drying temperature is 30-40°C.

8. The preparation method according to any one of claims 3-7, characterized in that, The mass ratio of the amino carrageenan derivative to the aldehyde carrageenan derivative is (2-16):1, preferably (3-6):1; Preferably, the amino carrageenan derivative, aldehyde carrageenan derivative and water are mixed to form a mixed solution and then subjected to freeze-thaw reaction; Preferably, the total mass percentage concentration of the amino carrageenan derivative and the aldehyde carrageenan derivative in the mixed solution is 2.0%-20.0%, more preferably 4.0%-8.0%; Preferably, the mixing temperature is 40-100℃, more preferably 50-80℃; Preferably, the mixing time is 4-12 hours, more preferably 6-10 hours; Preferably, the freeze-thaw process includes freezing the mixed solution at a low temperature and then thawing it at the temperature before freezing. Preferably, the freezing temperature is -35°C to -15°C, more preferably -30°C to -20°C; Preferably, the freezing time is 2-6 hours; Preferably, the number of freeze-thaw cycles is ≥3, more preferably 3-6 times; Preferably, the saturated saline solution is injected using a micro-injection pump; Preferably, the injection pump rate is 0.2-2.0 mL / min, more preferably 0.5-1.0 mL / min; Preferably, after being injected into saturated saline solution, post-treatment is performed to obtain the plugging polymer; Preferably, the post-treatment includes settling, filtration, washing, dialysis, and drying; Preferably, the settling time is 16-32 hours; Preferably, the solvent used for washing includes water; Preferably, the dialysis time is 2-5 days; Preferably, the molecular weight cutoff of the dialysis is ≤8000 Da, more preferably 4000-6000 Da; Preferably, the drying method includes spray drying.

9. A sealing gel, characterized in that, The plugging gel comprises a dispersion medium and a plugging polymer as described in claim 1 or 2; Preferably, the dispersion medium comprises water.

10. The use of a plugging polymer as described in claim 1 or 2, or a plugging gel as described in claim 9, in petroleum additives.

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