Plugging agent, preparation method thereof and application of plugging agent in plugging slurry for oil exploitation

Abstract

The invention relates to the field of petroleum drilling engineering, and discloses a plugging agent comprising an inorganic material with hydroxyl on the surface and a copolymer grafted on the surface of the inorganic material, a preparation method of the plugging agent and application of the plugging agent in plugging slurry for petroleum exploitation. The plugging agent is simple in preparation method and relatively low in cost, can be used for deep well and ultra-deep well operation, remarkably reduces the pressure transmission effect of well drilling, maintains relatively good well wall stability, effectively solves the problems of well wall instability, reservoir pollution and the like in well drilling work, improves economic benefits, reduces the occurrence rate of underground complex accidents, and has good application prospects. Guarantee is provided for the safety of drilling operation, and the application prospect is very wide.

Description

Technical Field

[0001] This invention relates to the technical field of oil drilling engineering, specifically to plugging agents, their preparation methods, and their application in oil development using plugging slurries. Background Technology

[0002] Currently, domestic and international plugging agents are mainly classified into organic nano plugging agents, inorganic nano plugging agents, and organic / inorganic nano plugging agents. However, existing plugging agents are difficult to achieve both high-temperature resistance and a wider pore size distribution range for broad-spectrum plugging, and cannot effectively plug cracks of different sizes, leading to frequent wellbore instability and severe drill string sticking.

[0003] During drilling operations, when encountering mudstone interlayers with numerous micro- and nano-pore fractures, these interlayers are prone to collapse. The resulting filtrate entering the formation alters pore pressure and mechanical strength, inducing wellbore instability and causing frequent drill string sticking. Furthermore, the high temperatures in deep wells cause degradation and other destructive effects on drilling fluid treatment agents, resulting in poor plugging performance. This places even more stringent requirements on plugging agents. Existing inorganic plugging agents possess good high-temperature resistance, but their particle size cannot meet the requirements for plugging various fractures with a wide size distribution. Organic plugging agents, on the other hand, lack sufficient high-temperature resistance and are prone to degradation under high-temperature conditions, leading to plugging failure. To address these issues, developing a novel temperature-adaptive micro / nano plugging agent for drilling fluids that combines the advantages of both inorganic and organic plugging agents, thereby reducing drilling fluid filtrate loss and slowing pressure transmission, is key to solving the problem of wellbore instability. Summary of the Invention

[0004] The purpose of this invention is to overcome the problem of existing technologies that struggle to simultaneously achieve high-temperature resistance and broad-spectrum plugging performance, by providing a plugging agent, its preparation method, and its application in plugging slurries for oil extraction. The plugging agent, when applied to plugging slurries, offers advantages such as low concentration, excellent plugging effect, wide plugging range, good high-temperature resistance, and particle size that can change bidirectionally with temperature. It can effectively plug pores from nano-micron to micron levels, meeting the plugging requirements of high-temperature deep wells, enhancing wellbore stability, reducing instability risks, and improving drilling efficiency and safety.

[0005] According to a first aspect of the present invention, the present invention provides a plugging agent comprising: an inorganic material having hydroxyl groups on its surface and a copolymer grafted onto the surface of the inorganic material; said copolymer comprising: structural unit A of formula (I), structural unit B of formula (II), structural unit C of formula (III), structural unit D of formula (IV), and structural unit E of formula (V).

[0006] In equation (I), R 13 R 14Each of the alkylene groups selected from C0-C3 is connected to the inorganic material via position 1 of structural unit A, when R 13 When it is a C0 alkylene group, structural unit A is connected to the inorganic material through O-Si bonds, and when R... 13 When it is a C1-C3 alkylene group, structural unit A is connected to the inorganic material through C-Si bonds; in formula (II), R 2 Alkyl groups selected from C1-C6 and -CO-NH-R 15 - one or more of the following, where R 15 Selected from one or more alkylene groups of C0-C6, R 3 Selected from one or more alkyl groups selected from H and C1-C6; in formula (III), R 4 Selected from one or more alkyl groups of H and C1-C3, R 5 R 6 Each is selected from one or more alkyl groups selected from H and C1-C6; in formula (IV), R 7 Selected from one or more alkylene groups of C0-C6, R 8 R 9 Each is selected from one or more alkyl groups selected from H and C1-C6; in formula (V), R 10 Selected from one or more of H and -CH3, R 11 -R 16 -R 17 , where R 16 Selected from one or more alkylene groups of C1-C6, R 17 Selected from one or more of -SO3H and -CO3H.

[0007]

[0008]

[0009] According to a second aspect of the present invention, the present invention provides a method for preparing the blocking agent of the present invention, the method comprising: copolymerizing a substance a having the structure shown in formula (i), a monomer b having the structure shown in formula (ii), a monomer c having the structure shown in formula (iii), a monomer d having the structure shown in formula (iv), and a monomer e having the structure shown in formula (v) in the presence of an initiator. In formula (i), R... 1 For the inorganic material, R 12 -R 13 -OOC-R 14 -CH = CH2, when R 13 When it is a C0 alkylene group, R 12 Through O-Si bonds and R 1 Connection, when R 13When R is a C1-C3 alkylene group, 12 Through C-Si bonds and R 1 Connection. In equation (ii), X - It is a monovalent anion. In equations (i) to (v), R 1 -R 11 and R 13 -R 17 As described above, it will not be repeated here.

[0010]

[0011]

[0012] According to a third aspect of the present invention, the present invention provides a plugging agent prepared by the preparation method of the present invention, wherein the number average molecular weight of the plugging agent is 200,000 to 1,000,000.

[0013] According to a fourth aspect of the invention, the invention provides the application of the plugging agent of the invention in a plugging slurry used in oil extraction.

[0014] The plugging agent provided by this invention is applied to plugging slurry. It has a low concentration, good plugging effect, wide plugging range, good high temperature resistance, and the particle size can change bidirectionally with temperature. It can effectively plug pores from nano-micron to micron level, can be used in high temperature deep well environments, stabilize the well wall, reduce the risk of instability, improve drilling efficiency, and protect operational safety. Attached Figure Description

[0015] Figure 1 This is the sealing grout sample from Example 1. Detailed Implementation

[0016] The following provides a detailed description of specific embodiments of the present invention. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the invention. The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values; these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0017] This invention provides a plugging agent comprising: an inorganic material with hydroxyl groups on its surface and a copolymer grafted onto the surface of the inorganic material; the copolymer comprises: structural unit A of formula (I), structural unit B of formula (II), structural unit C of formula (III), structural unit D of formula (IV), and structural unit E of formula (V). The plugging agent provided by this invention has a low concentration, good plugging effect, wide plugging range, good high-temperature resistance, and particle size that can change bidirectionally with temperature. It can effectively plug pores from nanometer to micrometer scale, can be used in high-temperature deep well environments, stabilizes the wellbore, reduces the risk of instability, improves drilling efficiency, and protects operational safety.

[0018] In equation (I), R 13 R 14 Each of the alkylene groups selected from C0-C3 is connected to the inorganic material via position 1 of structural unit A, when R 13 When it is a C0 alkylene group, structural unit A is connected to the inorganic material through O-Si bonds, and when R... 13 When it is a C1-C3 alkylene group, structural unit A is connected to the inorganic material through C-Si bonds; in formula (II), R 2 Alkyl groups selected from C1-C6 and -CO-NH-R 15 - one or more of the following, where R 15 Selected from one or more alkylene groups of C0-C6, R 3 Selected from one or more alkyl groups selected from H and C1-C6; in formula (III), R 4 Selected from one or more alkyl groups of H and C1-C3, R 5 R 6 Each is selected from one or more alkyl groups selected from H and C1-C6; in formula (IV), R 7 Selected from one or more alkylene groups of C0-C6, R 8 R 9 Each is selected from one or more alkyl groups selected from H and C1-C6; in formula (V), R 10 Selected from one or more of H and -CH3, R 11 -R 16 -R 17 , where R 16 Selected from one or more alkylene groups of C1-C6, R 17 Selected from one or more of -SO3H and -CO3H.

[0019]

[0020]

[0021] In this invention, the alkylene group of C0 is not present, and the groups at both ends of the group are directly connected.

[0022] In this invention, a wide range of inorganic materials can be selected, and commonly used types in the art can all achieve the objectives of this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of the invention, the inorganic material is selected from one or more of SiO2 nanocrystals, Fe3O4 nanocrystals, TiO2 nanocrystals, and Al2O3 nanocrystals.

[0023] In this invention, the particle size of the inorganic material can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the size of the inorganic material is 10-150 nm.

[0024] The aforementioned preferred inorganic materials have the advantages of high thermal stability, high compressive strength, and rigid bridging capability.

[0025] In this invention, R 2 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 2 Alkyl groups selected from C1-C3 and -CO-NH-R 15 One or more of the above-mentioned preferred R. 2 It has the advantages of low toxicity, no pollution, improved salt resistance, hydrophilicity, and stable rheological properties.

[0026] In this invention, R 15 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 15 One or more alkylene groups selected from C0-C3. The aforementioned preferred R... 15 It has the advantages of improving coalescence stability, hydrophobicity, temperature resistance, and enhancing the stability of drilling fluid properties.

[0027] In this invention, R 3 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 3 One or more alkyl groups selected from H and C1-C3. The aforementioned preferred R... 3 It has the advantages of adjusting molecular weight, hydrophobicity, improving polymer stability and temperature resistance.

[0028] In this invention, R 4 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R...4 Selected from one or more of H and methyl. The aforementioned preferred R... 4 It has the advantages of improving stability, hydrophobicity, temperature resistance and rheological stability.

[0029] In this invention, R 5 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 5 One or more alkyl groups selected from H and C1-C3. The aforementioned preferred R... 5 It has the advantages of adjusting molecular weight, hydrophobicity, improving polymer stability and temperature resistance.

[0030] In this invention, R 6 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 6 One or more alkyl groups selected from H and C1-C3. The aforementioned preferred R... 6 It has the advantages of adjusting molecular weight, hydrophobicity, improving polymer stability and temperature resistance.

[0031] In this invention, R 7 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 7 One or more alkylene groups selected from H and C0-C2. The aforementioned preferred R... 7 It has the advantages of improving stability, hydrophobicity, temperature resistance and rheological stability.

[0032] In this invention, R 8 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 8 One or more alkyl groups selected from H and C1-C3. The aforementioned preferred R... 8 It has the advantages of adjusting molecular weight, hydrophobicity, improving polymer stability and temperature resistance.

[0033] In this invention, R 9 The range of possible types is quite wide; the following examples are illustrative but do not limit the scope of the invention. According to a preferred embodiment of the invention, R... 9 One or more alkyl groups selected from H and C2-C3. The aforementioned preferred R... 9 It has the advantages of improving stability, hydrophobicity, temperature resistance and rheological stability.

[0034] In this invention, the molar ratio of structural units A, B, C, D, and E in the sealing agent can be selected within a wide range. The following is an illustrative example, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the molar ratio of structural units A, B, C, D, and E is 0.1-1:0.1-2:0.01-0.2:0.1-2:1, preferably 0.15-0.5:1-2:0.1-0.5:0.2-1:1. Using the aforementioned preferred ratio has advantages such as improved overall temperature resistance, salt resistance, reduced cost, adjustable molecular weight, and controllable hydrophilicity / hydrophobicity.

[0035] In this invention, the molecular weight of the blocking agent can be selected from a wide range, as illustrated below, but this does not limit the scope of the invention. According to a preferred embodiment of the invention, the number-average molecular weight of the blocking agent is 200,000 to 1,000,000.

[0036] All plugging agents possessing the aforementioned characteristics can achieve the objectives of this invention. There are no special requirements for their preparation methods. The following is an illustrative description, but it does not limit the scope of this invention. According to one embodiment of this invention, the preparation method of the plugging agent includes: copolymerizing a substance a having the structure shown in formula (i), monomer b having the structure shown in formula (ii), monomer c having the structure shown in formula (iii), monomer d having the structure shown in formula (iv), and monomer e having the structure shown in formula (v) in the presence of an initiator. In formula (i), R... 1 For the inorganic material, R 12 -R 13 -OOC-R 14 -CH = CH2, when R 13 When it is a C0 alkylene group, R 12 Through O-Si bonds and R 1 Connection, when R 13 When R is a C1-C3 alkylene group, 12 Through C-Si bonds and R 1 Connection. In equation (ii), X - It is a monovalent anion. In equations (i) to (v), R 1 -R 11 and R 13 -R 17 As described above, it will not be repeated here.

[0037]

[0038]

[0039] In this invention, the amounts of substance a, monomer b, monomer c, monomer d, and monomer e used in the preparation method can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the molar ratio of substance a, monomer b, monomer c, monomer d, and monomer e is 0.1-1:0.1-2:0.01-0.2:0.1-2:1, preferably 0.15-0.5:1-2:0.1-0.5:0.2-1:1. Using the aforementioned preferred ratio has advantages such as improved overall temperature resistance, salt resistance, reduced cost, adjustable molecular weight, and controllable hydrophilicity / hydrophobicity.

[0040] In this invention, in the preparation method, X - The range of available types is relatively wide, and can be selected by those skilled in the art according to their needs. According to a preferred embodiment of the present invention, X - It is a halide ion. The aforementioned preferred X is used. - It has the advantages of improving antibacterial properties, drilling fluid stability, and corrosion resistance.

[0041] In this invention, during the preparation method, to ensure thorough mixing of substance a, monomer b, monomer c, monomer d, and monomer e, mixing can be carried out under dynamic conditions, as needed. According to a preferred embodiment of the invention, the rotation speed is 400-700 rpm. Other steps can also be carried out under stirring conditions, as needed.

[0042] In this invention, the copolymerization temperature can be selected over a wide range in the preparation method. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the copolymerization temperature is 50-80°C.

[0043] In this invention, the copolymerization time in the preparation method can be selected and adjusted according to the temperature; for example, the copolymerization time is generally 4-48 hours.

[0044] In this invention, the pH range for the preparation method is relatively wide. The following is an illustrative description, but it does not limit the scope of the invention. According to a preferred embodiment of the invention, the pH is 7-8.

[0045] In this invention, there are no special requirements for the pH adjuster; any commonly used substance can be used, such as sodium hydroxide or acetic acid.

[0046] According to a preferred embodiment of the present invention, in the preparation method of the present invention, copolymerization is carried out in an inert gas.

[0047] In this invention, the range of inert gases that can be selected in the preparation method is relatively wide, and commonly used types can achieve the purpose of this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of the invention, the inert gas is selected from one or more of nitrogen, helium, neon, and argon.

[0048] In this invention, the duration of inert gas introduction in the preparation method can be selected within a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of the invention, the duration of inert gas introduction is 5-300 min.

[0049] In this invention, the preparation method allows for sufficient copolymerization, which can be carried out under dynamic conditions as needed. According to a preferred embodiment of the invention, the rotation speed is 400-700 rpm.

[0050] In this invention, the copolymerization is preferably carried out under solution conditions in the preparation method, generally by adding water, with no special requirements on the amount of water. According to a preferred embodiment of the invention, the mass of water is 120%-150% of the total mass of substance a, monomer b, monomer c, monomer d, and monomer e. Other solvents, such as ethanol, may also be added as needed.

[0051] In this invention, the range of initiators that can be selected in the preparation method is relatively wide. Commonly used initiators can all be used in this invention. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of this invention, the initiator is selected from one or more of the following: haloalkanes, azobisisobutyronitrile (AIBN), α-ketoglutaric acid, potassium persulfate, ammonium persulfate, sodium bisulfite, cerium ammonium nitrate, and azobisisobutyramidine hydrochloride (V50).

[0052] In this invention, the amount of initiator used in the preparation method can be selected from a wide range. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of the invention, the mass of the initiator is 0.02-3% of the total mass of substance a, monomer b, monomer c, monomer d, and monomer e.

[0053] In this invention, during the preparation method, to ensure thorough mixing of the initiator and copolymer raw materials, the initiator can be added under dynamic conditions as needed. According to a preferred embodiment of the invention, the rotation speed is 100-200 rpm.

[0054] In this invention, any substance a having the structure shown in formula (i) can achieve the purpose of this invention in the preparation method, and there are no special requirements for its preparation method. The following is an illustrative description, but it does not limit the scope of this invention. According to a preferred embodiment of the present invention, the preparation method of substance a is to use a substance capable of providing R 12The monomer of the structural unit modifies inorganic materials with hydroxyl groups on their surface. The modification method is as follows: the inorganic material is mixed with toluene solvent and then sonicated at low power for 0.5-3 hours to prepare an inorganic material suspension. The monomer is dissolved in water, the pH is adjusted to 3-4, and pre-hydrolyzed for 100-200 minutes to obtain a pre-hydrolyzed solution. The inorganic material suspension is sheared at 600-1000 rpm for 0.1-3 hours, then heated to 60-90℃, the pre-hydrolyzed solution is added and mixed. The mixture is then refluxed at 60-90℃ for 7-8 hours. The resulting solid is separated from the liquid, and the solid obtained is substance a.

[0055] The present invention provides a blocking agent prepared by the preparation method described herein, wherein the number average molecular weight of the blocking agent is 200,000 to 1,000,000.

[0056] The plugging agent of the present invention is particularly suitable for use in oil extraction using plugging slurries.

[0057] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various specific technical features in any suitable manner. To avoid unnecessary repetition, the present invention will not describe the various possible combinations separately. However, these simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

[0058] The present invention will be described in detail below through embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Those skilled in the art can make some non-essential improvements and adjustments to the present invention based on the above description.

[0059] For any experimental steps or conditions not specified in the examples and comparative examples, the procedures or conditions described in the literature in this field can be followed. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0060] A. Raw materials of the example

[0061] Nano-sized silica monomer (purity 99wt%, size 20nm, specific surface area 140.21m²) 2 / g), from Shanghai Titan Technology Co., Ltd.

[0062] Nano-sized titanium dioxide monomer (purity 99.8 wt%, size 25 nm, specific surface area 80.21 m²) 2 / g), from Shanghai Titan Technology Co., Ltd.

[0063] (3-Acrylamidopropyl)trimethylammonium chloride, CAS No.: 5034-06-0, from Shanghai Titan Technology Co., Ltd., is used as monomer b in the examples and comparative examples.

[0064] 1,3-Divinyltetramethyldisiloxane, CAS No.: 2627-95-4, from Shanghai Titan Technology Co., Ltd., is used as monomer c in the examples and comparative examples.

[0065] N-vinylpyrrolidone, CAS No.: 88-12-0, from Shanghai Titan Technology Co., Ltd., is used as monomer d in the examples and comparative examples.

[0066] 2-Acrylamido-2-methylpropanesulfonic acid, CAS No.: 15214-89-8, from Shanghai Titan Technology Co., Ltd., is used as monomer e in the examples and comparative examples.

[0067] Potassium persulfate (99wt%) and ammonium persulfate (99wt%) were both sourced from Shanghai Titan Technology Co., Ltd.

[0068] Toluene (99.9% purity) was obtained from Shanghai Titan Technology Co., Ltd.

[0069] Silane coupling agent KH570, CAS No.: 2530-85-0, is from Shanghai Titan Technology Co., Ltd.

[0070] B. Experimental Equipment

[0071] The electronic balance (ME104 / 02), constant temperature magnetic stirrer (T09-1S), digital display constant temperature water bath (XMTD203), electric stirrer (HD2004W), variable frequency high-speed stirrer (GJSS-B12K), 1103 type six-speed rotational viscometer (MK-03), variable frequency high-temperature roller heating furnace (GW300), high temperature and high pressure water loss meter (GGS71-A), and high temperature and high pressure water loss meter (GGS42-2) are all from Qingdao Tongchun Petroleum Instrument Co., Ltd.

[0072] The nanoparticle size and zeta potential analyzer (SZ-100V2) and the laser particle size analyzer (LA-960V2) are both from HORIBA, Japan.

[0073] C. Preparation method of substance a:

[0074] Inorganic materials were modified using the silane coupling agent KH570: Inorganic materials and toluene were added to a beaker and sonicated at high power for 0.5 h, followed by sonication at low power for 1 h to obtain an inorganic material suspension. Water was added to the KH570 liquid, and the pH was adjusted to 3.5 with acetic acid. Pre-hydrolyzing was performed for 143 min to obtain a KH570 pre-hydrolyzed solution. The inorganic material suspension was poured into a three-necked flask and stirred at 800 rpm for 0.5 h. The temperature was then raised to 75 °C, and the KH570 pre-hydrolyzed solution was added to the three-necked flask and stirred thoroughly. The mixture was then refluxed at 75 °C for 7 h. The resulting product was centrifuged, and the resulting solid was washed, dried, and finally ground in a mortar to obtain substance a.

[0075] D. Testing Methods

[0076] 1) Particle size analysis of the plugging agent:

[0077] a. Preparation and testing of unaged samples: Take 1000 mL of deionized water, add 0.1 g of sealing agent sample (weighed to 0.01 g), and prepare 10... -4 The sample was stirred at a high speed of 11,000 r / min for a total of 20 min, with at least two stops during which the sample adhering to the cup wall was scraped off. The sample was taken, and the aqueous solution was filtered through a 0.45 μm filter membrane and placed in a cuvette. The particle size of the sealing agent in the unaged state was determined using a nanoparticle size analyzer.

[0078] b. Preparation and testing of aging samples: Take 1000 mL of deionized water, add 0.1 g and 10 g of sealing agent samples (weighed to 0.01 g), and prepare 10 samples respectively. -4 10 -2 For samples of the order of magnitude, high-speed stirring was carried out at 11000 rpm for a total of 20 minutes, with at least two stops to scrape off the sample adhering to the cup wall. The sample was then collected, and the aqueous solution was filtered through a 0.45 μm filter membrane and transferred to a high-temperature aging tank. Nitrogen gas was purged at 0.7 MPa for 30 seconds. The aging tank was then placed in a roller furnace and hot-rolled at 150°C for 16 hours. After removing the aging tank and cooling to room temperature, the sample in the aging tank was transferred to a stirring cup and stirred at high speed for 5 minutes. The sample was then collected in a cuvette, and the particle size of the sealing agent after aging at 150°C for 16 hours was determined using a nanoparticle size analyzer.

[0079] c. Calculation: Calculate the expansion rate of the sealing agent in samples a and b before and after aging at 150℃ for 16 hours. Calculation formula:

[0080]

[0081] 2) Blockage reduction rate test:

[0082] a. Preparation of base slurry: Add 400 mL of distilled water and 0.64 g (weighed to 0.01 g) of anhydrous sodium carbonate to a high-speed stirring cup. After dissolving, slowly add 16.0 g (weighed to 0.01 g) of bentonite for drilling fluid test slurry preparation under high-speed stirring to prevent it from forming lumps. Stir at high speed for a total of 20 min, stopping at least twice during this period to scrape off the bentonite adhering to the cup wall. Cure in a sealed environment at 25℃±1℃ for 24 h.

[0083] b. Plugging Rate Determination: Take 300 mL of the prepared base slurry and slowly add 2 wt% of the plugging agent material (effective content, weighed to 0.01 g). Stir at 11000 r / min for a total of 20 min, stopping at least twice to scrape off the sample adhering to the cup wall. Use a consolidation sand disc (5 μm) to simulate the filtration formation. Add the stirred plugging slurry to the mud cup. After raising the temperature to the set test temperature, open the upper and lower valves sequentially. Adjust the pressure by controlling the opening and closing of the upper valve. After the lower valve is opened, measure the instantaneous filtration volume V0. Then start timing. Increase the pressure difference between the upper and lower valves to 1 MPa from 1 to 7.5 min, increase it to 2 MPa from 7.5 to 15 min, and increase it to 3.5 MPa from 15 to 30 min. Measure the cumulative filtration volume V1 during the pressure increase process to complete the routine permeability filtration evaluation. Then close the upper and lower valves, and after cooling down, reduce the pressure in the mud cup to 1 MPa.

[0084] c. Calculate the reduction rate of high-temperature and high-pressure plugging. Calculation formula:

[0085] Blocking reduction rate = slurry leakage - slurry leakage with added copolymer / slurry leakage.

[0086] Example 1

[0087] 20g of nano-silica monomer and 6000g of toluene solvent were added to a beaker, and the mixture was sonicated at high power for 0.5h, followed by sonication at low power for 1h to prepare an inorganic material suspension. 6g of water was added to 8g of KH570 liquid, and the pH was adjusted to 3.5 with acetic acid. Pre-hydrolyzing was performed for 143min to obtain a KH570 pre-hydrolyzed solution. The inorganic material suspension was poured into a three-necked flask, stirred at 800rpm for 0.5h, and then heated to 75℃. The KH570 pre-hydrolyzed solution was then poured into the three-necked flask and stirred until homogeneous. The mixture was then refluxed at 75℃ for 7h. The resulting product was centrifuged, and the resulting solid was washed, dried, and finally ground in a mortar to obtain substance a.

[0088] In a beaker, water (133% of the total mass of substances a, monomers b, c, d, and e) was added, followed by substances a, b, c, d, and 207.2 g of monomer e (molar ratio 0.2:1:0.15:0.4:1). The pH was adjusted to 7.5 using sodium hydroxide, and the mixture was stirred at 500 rpm until homogeneous. The resulting solution was transferred to a 250 mL three-necked flask fixed in a constant-temperature water bath. Potassium persulfate (0.02% of the total mass of substances a, b, c, d, and e) was added at a uniform rate while stirring at 150 rpm. Nitrogen gas was bubbled into the three-necked flask for 20 min to purge oxygen. The copolymerization reaction was carried out at 70 °C and 500 rpm for 12 h to obtain the blocking agent, named W1, with a number-average molecular weight of 356,000.

[0089] Example 2

[0090] The method was followed in Example 1, except that the molar ratio of substance a, monomer b, monomer c, monomer d, and monomer e was 0.1:0.5:0.05:0.15:1. The resulting blocking agent was named W2, with a number average molecular weight of 231,000.

[0091] Example 3

[0092] The method was followed in Example 1, except that the molar ratio of substance a, monomer b, monomer c, monomer d, and monomer e was 0.6:0.7:0.08:1.5:1. The resulting blocking agent was named W3, with a number average molecular weight of 587,000.

[0093] Example 4

[0094] The method was followed in Example 1, except that the pH of the reaction solution was adjusted to 9 and the copolymerization temperature was 85°C. The resulting blocking agent was named W4, with a number-average molecular weight of 407,000.

[0095] Example 5

[0096] The method was followed in Example 1, except that the initiator was ammonium persulfate, and the initiator was added at a mass of 1% of the total mass of substances a, b, c, d, and e. The resulting blocking agent was named W5, with a number average molecular weight of 624,000.

[0097] Example 6

[0098] The method of Example 1 was followed, except that the nano-silica monomer was replaced with nano-titanium dioxide monomer. The resulting blocking agent was named W6, with a number-average molecular weight of 464,000.

[0099] Comparative Example 1

[0100] The method was followed in Example 1, except that the raw materials did not contain substance a. The resulting plugging agent was named WD1.

[0101] Comparative Example 2

[0102] The method was followed in Example 1, except that monomer b was not present in the raw materials. The resulting plugging agent was named WD2.

[0103] Comparative Example 3

[0104] The method was followed in Example 1, except that the raw materials did not contain monomer c. The resulting plugging agent was named WD3.

[0105] Comparative Example 4

[0106] The method was followed in Example 1, except that the raw materials did not contain monomer d. The resulting plugging agent was named WD4.

[0107] Comparative Example 5

[0108] The method was followed in Example 1, except that the raw materials did not contain monomer e. The resulting plugging agent was named WD5.

[0109] Prepare 10g of the sealing agent according to the above method. -4 Order of magnitude and 10 -2 Samples of varying sizes were tested. Particle size expansion properties were measured under both unaged and 150°C hot-rolled conditions for 16 hours. 10 samples were included. -4 The test results for the samples of the order of magnitude are shown in Table 1.

[0110] Table 1 shows the 10 solutions prepared with the sealing agent. -4 Particle size expansion properties of samples of varying sizes under different conditions

[0111]

[0112]

[0113] The data in Table 1 show that the sealing agent provided by the present invention has an expansion effect after being hot rolled at 150°C for 16 hours. It can effectively expand at high temperature, with an expansion ratio between 5 and 10 times, and the water absorption and expansion performance is controllable.

[0114] The particle size of the plugging agent was monitored in real time as a function of temperature. The experimental results are shown in Table 2 below.

[0115] Table 2 shows the 10 solutions prepared with the sealing agent. -4 Order-of-magnitude sample particle size variation with temperature response

[0116]

[0117]

[0118]

[0119]

[0120] As can be seen from the data in Table 2, the particle size of the plugging agent changes with temperature, as analyzed by a nanoparticle size analyzer. The plugging agent provided by this invention has excellent water absorption and expansion properties, and has the temperature adaptive characteristics of effectively expanding with increasing temperature and effectively shrinking with decreasing temperature.

[0121] The effect of the concentration of the plugging agent on the particle size was then tested. 10 -2 The particle size expansion performance test results of the samples are shown in Table 3.

[0122] Table 3 shows the 10 solutions prepared with the sealing agent. -2 Particle size expansion properties of samples of varying sizes under different conditions

[0123]

[0124]

[0125]

[0126] The data in Table 3 show that the sealing agent provided by the present invention has an expansion effect after being hot rolled at 150°C for 16 hours. It can effectively expand at high temperature and the expansion ratio is moderate, which can overcome the shortcomings of other polymer materials with excessive or insufficient expansion ratio.

[0127] Comparing the data in Tables 1 and 3, it can be found that the particle size of the plugging agent exhibits a polydisperse characteristic, especially at lower concentrations (e.g., 10). -4 At concentrations on the order of magnitude (e.g., 10⁻⁶), the size is nanometers; at higher concentrations (e.g., 10⁻⁶), the size is nanometers. -2 At concentrations on the order of magnitude (in micrometers), due to entanglement between polymer chains, the originally nano-sized plugging agent particles may aggregate, reaching sizes up to the micrometer level. Different plugging agent concentrations result in different sizes, which helps to achieve multi-level sealing of nanometer- and micrometer-sized pores and microcracks.

[0128] The plugging agents were formulated into plugging slurries and named L0 (no plugging agent added), L1 (plugging agent W1), L2 (plugging agent W2), L3 (plugging agent W3), L4 (plugging agent W4), L5 (plugging agent W5), L6 (plugging agent W6), LD1 (plugging agent WD1), LD2 (plugging agent WD2), LD3 (plugging agent WD3), LD4 (plugging agent WD4), and LD5 (plugging agent WD5). The plugging reduction rate was tested at room temperature (25±2℃) and 150℃. The smaller the plugging reduction rate, the better the plugging effect. The test results are shown in Table 4.

[0129] Table 4. Evaluation of Blocking Performance

[0130]

[0131]

[0132] As can be seen from the data in Table 4, the plugging agent provided by this invention, when formulated into a plugging slurry, exhibits excellent plugging performance and good high-temperature resistance. At room temperature, it can significantly reduce the cumulative filtration volume to 5 mL; under high-temperature conditions of 150℃, it can significantly reduce the cumulative filtration volume to 12 mL, achieving a plugging reduction rate of 85.71% compared to the base slurry.

[0133] Based on the data results in Tables 1-4, it can be concluded that the plugging agent provided by this invention can change with temperature response, has excellent expansion performance, can be applied to well bottoms at different temperatures, and achieves significant broad-spectrum plugging effect on nano- and micro-sized pores.

[0134] The plugging agent provided by this invention has a simple preparation method and low cost. It can be used in deep well and ultra-deep well operations, significantly reducing the pressure transmission effect of drilling, maintaining good wellbore stability, effectively solving problems such as wellbore instability and reservoir contamination in drilling operations, improving economic efficiency, and reducing the incidence of complex downhole accidents, thus providing a guarantee for the safety of drilling operations. Therefore, this invention has a very broad application prospect.

Claims

1. A sealing agent, characterized in that, The plugging agent comprises: an inorganic material with hydroxyl groups on its surface and a copolymer grafted onto the surface of the inorganic material; The copolymer comprises: structural unit A of formula (I), structural unit B of formula (II), structural unit C of formula (III), structural unit D of formula (IV), and structural unit E of formula (V); In equation (I), R 13 R 14 Each of the alkylene groups selected from C0-C3 is connected to the inorganic material via position 1 of structural unit A, when R 13 When it is a C0 alkylene group, structural unit A is connected to the inorganic material through O-Si bonds, and when R... 13 When it is a C1-C3 alkylene group, structural unit A is connected to the inorganic material through C-Si bonds; In equation (II), R 2 Alkyl groups selected from C1-C6 and -CO-NH-R 15 - one or more of the following, where R 15 Selected from one or more alkylene groups of C0-C6, R 3 One or more selected from H and C1-C6 alkyl groups; In equation (III), R 4 Selected from one or more alkyl groups of H and C1-C3, R 5 R 6 Each is selected from one or more alkyl groups selected from H and C1-C6; In equation (IV), R 7 Selected from one or more alkylene groups of C0-C6, R 8 R 9 Each is selected from one or more alkyl groups selected from H and C1-C6; In equation (V), R 10 Selected from one or more of H and -CH3, R 11 -R 16 -R 17 , where R 16 Selected from one or more alkylene groups of C1-C6, R 17 Selected from one or more of -SO3H and -CO3H.

2. The sealing agent according to claim 1, characterized in that, The inorganic material is selected from one or more of SiO2 nanocrystals, Fe3O4 nanocrystals, TiO2 nanocrystals and Al2O3 nanocrystals.

3. The sealing agent according to claim 1, characterized in that, The inorganic material has a size of 10-150 nm.

4. The sealing agent according to claim 1, characterized in that, The R 2 Alkyl groups selected from C1-C3 and -CO-NH-R 15 One or more of - the R 15 One or more alkylene groups selected from C0-C3.

5. The sealing agent according to claim 1, characterized in that, The R 3 One or more alkyl groups selected from H and C1-C3.

6. The sealing agent according to claim 1, characterized in that, The R 4 Selected from one or more of H and methyl.

7. The sealing agent according to claim 1, characterized in that, The R 5 One or more alkyl groups selected from H and C1-C3.

8. The sealing agent according to claim 1, characterized in that, The R 6 One or more alkyl groups selected from H and C1-C3.

9. The sealing agent according to claim 1, characterized in that, The R 7 One or more alkylene groups selected from C0-C2.

10. The sealing agent according to claim 1, characterized in that, The R 8 One or more alkyl groups selected from H and C1-C3.

11. The sealing agent according to claim 1, characterized in that, The R 9 One or more alkyl groups selected from H and C2-C3.

12. The sealing agent according to any one of claims 1-11, characterized in that, The molar ratio of structural unit A, structural unit B, structural unit C, structural unit D and structural unit E is 0.1-1:0.1-2:0.01-0.2:0.1-2:

1.

13. The plugging agent according to any one of claims 1-11, characterized in that, The number-average molecular weight of the plugging agent is 200,000 to 1,000,000.

14. A method for preparing the plugging agent according to any one of claims 1-13, characterized in that, The method includes: In the presence of an initiator, a substance a having the structure shown in formula (i), a monomer b having the structure shown in formula (ii), a monomer c having the structure shown in formula (iii), a monomer d having the structure shown in formula (iv), and a monomer e having the structure shown in formula (v) are copolymerized. In equation (i), R 1 For the inorganic material, R 12 -R 13 -OOC-R 14 -CH = CH2, when R 13 When it is a C0 alkylene group, R 12 Through O-Si bonds and R 1 Connection, when R 13 When R is a C1-C3 alkylene group, 12 Through C-Si bonds and R 1 connect; In equation (ii), X - It is a monovalent anion; 15. The method according to claim 14, characterized in that, In step (1), the molar ratio of substance a, monomer b, monomer c, monomer d and monomer e is 0.1-1:0.1-2:0.01-0.2:0.1-2:

1.

16. The method according to claim 14 or 15, characterized in that, The X - It is a halide ion.

17. The method according to claim 14 or 15, characterized in that, The conditions for copolymerization include: The copolymerization temperature is 50-80℃; and / or The copolymerization time is 4-48 hours; and / or pH 7-8; and / or The process is carried out in an inert gas; and / or It is performed dynamically, with a speed of 400-700 rpm.

18. The method according to claim 14 or 15, characterized in that, The copolymerization is carried out in water, and the mass of the water is 120%-150% of the total mass of substance a, monomer b, monomer c, monomer d, and monomer e.

19. The method according to claim 14 or 15, characterized in that, The initiator is selected from one or more of the following: haloalkanes, azobisisobutyronitrile, α-ketoglutaric acid, potassium persulfate, ammonium persulfate, sodium bisulfite, cerium ammonium nitrate, and azobisisobutyramidine hydrochloride.

20. The method according to claim 14 or 15, characterized in that, The mass of the initiator is 0.02-3% of the total mass of substance a, monomer b, monomer c, monomer d, and monomer e.

21. The plugging agent prepared by the method according to any one of claims 14-20, wherein the number average molecular weight of the plugging agent is 200,000 to 1,000,000.

22. The application of the plugging agent according to any one of claims 1-13 and 21 in the use of plugging slurry in oil extraction.

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