Plugging agent, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of oilfield chemistry for ultra-deep-well well-drilling fluids in the petroleum industry, and specifically relates to a plugging agent, and a preparation method therefor and the use thereof. The plugging agent has a core-shell structure, and comprises an inorganic core and a shell layer coating the inorganic core, wherein the inorganic core comprises apatite modified with an alkenyl-terminated coupling agent, and the shell layer comprises a fluorosilicone-modified acrylic resin. The particle size D50 of the plugging agent is 145-200 nm. The fluorosilicone-modified acrylic resin comprises a fluorine-containing structural unit represented by formula (I) and a silicon-containing structural unit represented by formula (II), wherein in formula (I), R11 is selected from H or C1-C6 alkyl, and R12 is selected from C1-C9 fluoroalkyl; and in formula (II), R21, R22 and R23 are each independently selected from C1-C8 alkyl or C1-C8 alkoxy, and at least one of R21, R22 and R23 is selected from C1-C8 alkoxy.

Description

Blocking agents, their preparation methods and applications

[0001] Cross-reference to related applications

[0002] This application claims the benefit of Chinese Patent Application No. 202411841737.6, filed on December 13, 2024, the contents of which are incorporated herein by reference. Technical Field

[0003] This invention relates to the field of oilfield chemistry technology for ultra-deep well drilling fluids in the petroleum industry, specifically to a plugging agent, its preparation method, and its application. Background Technology

[0004] As my country intensifies its exploration and development of deep and ultra-deep oil and gas resources, drilling operations face increasing challenges. High temperatures (>180℃), high pressure, high salinity, and fracture development are particularly severe downhole conditions, placing extremely high demands on the high-temperature and high-pressure resistance of drilling fluids. Drilling fluids need to possess the characteristics of "three highs and one long," namely, high temperature resistance, high density, high salinity resistance, and long-term performance stability. Under high-temperature and high-pressure environments, drilling fluid treatment agents are prone to failure, and the rheological properties and settling stability of the drilling fluid are poor, making performance control difficult. This can lead to problems such as wellbore stability and leakage prevention / plugging, increasing the risks of drilling operations.

[0005] For ultra-deep fractured formations, in addition to the aforementioned problems associated with deep and ultra-deep wells, the high abrasiveness and poor drillability of the formations make the wellbore highly susceptible to instability, potentially leading to problems such as blockage and stuck pipe, severely restricting drilling operations in deep and ultra-deep fractured formations. This necessitates drilling fluids with excellent wellbore stability properties to prevent wellbore collapse and blockage. Effectively reducing drilling fluid pressure transmission and improving the hydrophilicity of the rock surface are crucial for ensuring the stability of fractured formations. Currently, a series of plugging agents and anti-collapse agents are typically added to the drilling fluid to ensure wellbore stability in fractured formations. However, existing plugging agents and anti-collapse agents often have limited functionality and temperature resistance. Therefore, there is an urgent need to develop high-temperature resistant, multifunctional drilling fluid treatment agents to provide necessary technical support for drilling in deep and ultra-deep fractured formations.

[0006] CN115260404A prepared a high-temperature resistant hydrophobic nano-plugging agent, which was prepared from silicon-based hydrophobic polyamines, cationic monomers, N-isopropylacrylamide, and high-temperature resistant monomers. The nanoparticles ranged in size from 48.2 to 199.4 nm and were relatively concentrated, effectively improving the hydrophilicity of rock surfaces. However, the plugging performance of this agent on nano- and micro-sized pores was not investigated. CN114350328A prepared a modified nano-alumina plugging agent, which was prepared from nano-alumina, silane coupling agents containing olefin bonds, dienol compounds, carboxylic acid compounds containing olefin bonds, and benzene ring-containing alkenyl ether compounds. This agent could prevent drilling fluid from invading the formation, prevent well collapse accidents, and enhance wellbore stability, with a size ranging from 57 to 332 nm. However, this plugging agent had a single function, and its plugging performance on micro- and nano-pores under ultra-high temperature conditions was not evaluated. Summary of the Invention

[0007] The purpose of this invention is to overcome the problem of formation hydration and collapse caused by drilling fluid intrusion in existing technologies, and to provide a plugging agent, its preparation method and application. This plugging agent can effectively seal the micro- and nano-pores of the formation, prevent the pressure transmission of drilling fluid into the formation, and reduce the intrusion of drilling fluid into the formation under pressure difference. In addition, the plugging agent also has excellent high temperature resistance, and its shell coating inorganic core has good stability at high temperature (220°C).

[0008] To achieve the above objectives, the first aspect of the present invention provides a plugging agent having a core-shell structure, comprising an inorganic core and a shell layer covering the inorganic core; wherein the inorganic core comprises apatite modified with an end-alkene coupling agent, and the shell layer comprises fluorosilicone modified acrylic resin; the D50 particle size of the plugging agent is 145-200 nm.

[0009] Based on the total mass of apatite modified with terminal alkenyl coupling agent, the mass content of terminal alkenyl coupling agent is 35-45 wt%.

[0010] The fluorosilicone modified acrylic resin comprises a fluorine-containing structural unit as shown in formula (I) and a silicon-containing structural unit as shown in formula (II):

[0011] In equation (I), R 11 Selected from H or C1-C6 alkyl groups, R 12 Selected from C1-C9 fluoroalkyl groups;

[0012] In equation (II), R 21 R 22 R 23 Each is independently selected from C1-C8 alkyl or C1-C8 alkoxy groups, and R 21 R 22 R23 At least one of the alkoxy groups selected from C1-C8.

[0013] The second aspect of the present invention provides a method for preparing a plugging agent, the method comprising: in the presence of an initiator, an aqueous phase containing an emulsifier, an acrylic monomer and a hydrolysis inhibitor and an oil phase containing an alkenyl coupling agent-modified apatite, a fluorinated monomer and a silicon monomer undergoing emulsion polymerization, wherein the mass content of the alkenyl coupling agent is 35-45 wt%, based on the total mass of the alkenyl coupling agent-modified apatite;

[0014] The structure of the fluorinated monomer is shown in formula (IA):

[0015] In formula (IA), R 11 Selected from H or C1-C6 alkyl groups, R 12 Selected from C1-C9 fluoroalkyl groups;

[0016] The structure of the silicon-containing monomer is shown in formula (IIA):

[0017] In formula (IIA), R 21 R 22 R 23 Each is independently selected from C1-C8 alkyl or C1-C8 alkoxy groups, and R 21 R 22 R 23 At least one of the alkoxy groups selected from C1-C8.

[0018] A third aspect of the present invention provides a plugging agent, wherein the plugging agent is a plugging agent prepared by the method described in the second aspect of the present invention.

[0019] The fourth aspect of the present invention provides the application of a plugging agent in drilling fluid, wherein the plugging agent is the plugging agent described in the first aspect of the present invention or the plugging agent described in the third aspect of the present invention.

[0020] Through the above technical solution, the present invention has at least the following beneficial effects:

[0021] 1. The plugging agent in this invention has a particle size at the nano-micron scale, contains an internal inorganic micro-core and an external flexible polymer coating layer, which can effectively plug the formation, prevent the drilling fluid from transmitting pressure into the formation, and reduce the intrusion of drilling fluid into the formation under the action of pressure difference;

[0022] 2. The sealing agent in this invention has excellent temperature resistance; for example, after aging at 220°C for 16 hours, the D50 particle size retention rate can reach 92.2%.

[0023] 3. The plugging agent in this invention can effectively adsorb onto the rock surface. The nanoparticles and the fluorine-containing low surface energy chemical structure will hydrophobically modify the rock surface, causing the wetting reversal phenomenon on the rock surface, thus avoiding the risk of wellbore instability caused by hydration of the wellbore rock. Detailed Implementation

[0024] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and 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.

[0025] The first aspect of the present invention provides a plugging agent having a core-shell structure, comprising an inorganic core and a shell layer covering the inorganic core; wherein the inorganic core comprises apatite modified with an end-alkene coupling agent, and the shell layer comprises fluorosilicone modified acrylic resin; the D50 particle size of the plugging agent is 145-200 nm;

[0026] Based on the total mass of apatite modified with terminal alkenyl coupling agent, the mass content of terminal alkenyl coupling agent is 35-45 wt%.

[0027] The fluorosilicone modified acrylic resin comprises a fluorine-containing structural unit as shown in formula (I) and a silicon-containing structural unit as shown in formula (II):

[0028] In equation (I), R 11 Selected from H or C1-C6 alkyl groups, R 12 Selected from C1-C9 fluoroalkyl groups;

[0029] In equation (II), R 21 R 22 R 23 Each is independently selected from C1-C8 alkyl or C1-C8 alkoxy groups, and R 21 R 22 R 23 At least one of the alkoxy groups selected from C1-C8.

[0030] The plugging agent in this invention has a particle size at the nano-micro scale and contains an internal inorganic micro-core and an external flexible polymer coating layer, which can effectively plug the formation. In addition, the plugging agent also has excellent high temperature resistance. For example, after aging at 220°C for 16 hours, the D50 particle size retention rate of the plugging agent can reach 92.2%.

[0031] In this invention, the C1-C6 alkyl group can be either a straight-chain alkyl group or a branched-chain alkyl group, and there are no special limitations on this. For example, it can be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, sec-pentyl, tert-pentyl, n-hexyl, etc. In formula (I) of this invention, R 11 The use of methyl groups as an example illustrates the advantages of this invention, but does not imply any limitation on the invention.

[0032] In this invention, a C1-C9 fluoroalkyl group refers to a C1-C9 alkyl group in which at least one hydrogen atom is replaced by a fluorine atom. This replacement can be complete or partial; preferably, more than three-fifths of the hydrogen atoms in the C1-C9 alkyl group are replaced by fluorine atoms. In preferred formula (I), R... 12 Selected from C5-C7 fluoroalkyl groups. In formula (I) of the present invention, R 12 The advantages of the present invention are illustrated by using dodecyl fluoroheptyl as an example, but this does not imply any limitation on the invention.

[0033] In this invention, the C1-C8 alkyl groups that can be listed include C1 alkyl (referring to methyl), C2 alkyl (referring to ethyl), C3 alkyl (referring to n-propyl, isopropyl), C4 alkyl (referring to n-butyl, isobutyl, or tert-butyl, etc.), C5 alkyl (referring to n-pentyl, isopentyl, etc.), C6 alkyl (referring to n-hexyl, isohexyl, neohexyl, etc.), C7 alkyl (referring to n-heptyl, isohexyl, neoheptyl, etc.), and C8 alkyl (referring to n-octyl, isooctyl, sec-octyl, etc.); the C1-C8 alkoxy groups that can be listed include C1 alkoxy (methoxy), C2 alkoxy (ethoxy), C3 alkoxy (propoxy), C4 alkoxy (butoxy), C5 alkoxy (pentoxy), C6 alkoxy (hexoxy), C7 alkoxy (heptoxy), and C8 alkoxy (octoxy). In a preferred embodiment, in formula (IIA), R 21 R 22 R 23 Each is independently selected from methyl, ethyl, methoxy, or ethoxy; in a preferred embodiment, R 21 R 22 R 23 At least one group is selected from C1-C8 alkoxy groups. In formula (IIA) of the present invention, R... 21 Methyl, R 22 For methoxy, R 23 The use of methoxy groups is provided as an example to illustrate the advantages of the invention, but does not imply any limitation thereof.

[0034] The plugging agent of this invention possesses the aforementioned fluorinated structural units, which constitute a fluorinated low surface energy chemical structure, thereby improving the hydrophobicity of the plugging agent to rock surfaces. The content of the fluorinated structural units can be selected within a wide range, provided that the objectives of this invention are achieved. According to one embodiment of this invention, based on the mass of the fluorosilicone-modified acrylic resin, the content of the fluorinated structural units is 8-20 wt%, for example, 8 wt%, 9 wt%, 12 wt%, 15 wt%, 18 wt%, or 20 wt%. The plugging agent of this invention possesses the aforementioned silicon-containing structural units, which can improve the adsorption of the plugging agent to rock surfaces.

[0035] According to the present invention, the content of silicon-containing structural units can be selected within a wide range as long as the purpose of the present invention can be achieved. In one embodiment, based on the mass of the fluorosilicone modified acrylic resin, the content of the silicon-containing structural units is 15-40 wt%, for example, 15 wt%, 18 wt%, 20 wt%, 22 wt%, 24 wt%, 28 wt%, 30 wt%, 32 wt%, 36 wt%, 38 wt%, or 40 wt%.

[0036] According to a preferred embodiment of the present invention, the fluorosilicone-modified acrylic resin has acrylic structural units, and the content of the acrylic structural units is 30-60 wt%, based on the mass of the fluorosilicone-modified acrylic resin. By employing the aforementioned embodiment, the plugging performance of the plugging agent can be improved.

[0037] According to a preferred embodiment of the present invention, the fluorosilicone-modified acrylic resin has cationic structural units as shown in formula (IIIa) and / or formula (IIIb):

[0038] In equation (IIIa), R 31 and R 32 Each is independently selected from C1-C5 alkylene groups, R 33 and R 34 Each is independently selected from C1-C5 alkyl groups, R 35 and R 36 Each is independently selected from H or C1-C3 alkyl groups, where N is a nitrogen atom; in formula (IIIb), R 41 Selected from C1-C5 alkylene groups; R 42 R 43 and R 44 Each is independently selected from C1-C3 alkyl groups, R 45 The components are selected from H or C1-C3 alkyl groups, where X is O or NH, and N is a nitrogen atom. Plugging agents containing the aforementioned structural units can improve adsorption to rock surfaces and exhibit better plugging performance.

[0039] In this invention, the C1-C5 alkylene groups are divalent groups formed by the loss of one H from the C1-C5 alkyl groups listed in this invention. According to a preferred embodiment of this invention, in formula (IIIa), R... 31 and R 32 Each is independently selected from C1-C3 alkylene groups, R 33 and R 34 Each is independently selected from methyl or ethyl, R 35 and R 36 Each is independently selected from H or methyl; according to a preferred embodiment of the present invention, in formula (IIIb), R 41 Selected from C1-C3 alkylene groups, R 42 R 43 and R 44 Each is independently selected from methyl or ethyl; R 45 Selected from H or methyl. The cationic structural unit in this invention has the structure shown in formula (IIIa) (R) 31 R 32 For methylene, R 33 and R 34 For methyl, R 35 and R 36 The purpose of H) is to illustrate the advantages of the present invention, but does not imply any limitation on the present invention.

[0040] According to one embodiment of the present invention, the content of the cationic structural unit is 10-30 wt%, based on the mass of the fluorosilicone modified acrylic resin, for example, 10 wt%, 12 wt%, 15 wt%, 19 wt%, 21 wt%, 23 wt%, 26 wt%, or 30 wt%.

[0041] According to a preferred embodiment of the present invention, the terminal alkenyl coupling agent in the terminal alkenyl coupling agent modified apatite is selected from terminal alkenyl silane coupling agents. According to a preferred embodiment of the present invention, in the terminal alkenyl coupling agent modified apatite, the terminal alkenyl groups in the terminal alkenyl coupling agent are chemically bonded to fluorosilicone-modified acrylic resin. Using the aforementioned method, this plugging agent can effectively plug formations and also has high-temperature resistance.

[0042] According to one embodiment of the present invention, in the terminal alkenyl coupling agent modified apatite, the silicon atoms in the terminal alkenyl coupling agent are connected to the oxygen atoms in the apatite by forming silicon-oxygen bonds; specifically, the silanoxy groups in the terminal alkenyl coupling agent undergo hydrolysis in water to form silanols, and then the silanol groups undergo dehydration condensation with the hydroxyl groups on the apatite to form silicon-oxygen bonds. Using the aforementioned method, this plugging agent can effectively plug formations and also has high-temperature resistance.

[0043] According to the present invention, the terminated alkenyl silane coupling agent refers to a silane coupling agent containing a terminated alkenyl group. The specific selection is not particularly limited as long as the purpose of the present invention is achieved. In one embodiment, the terminated alkenyl silane coupling agent includes at least one of γ-methacryloyloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane, and vinyltriethoxysilane. According to one embodiment of the present invention, the D50 particle size of the blocking agent is 149-166 nm. The blocking agent in the present invention has a particle size at the nano-micron scale, enabling it to exhibit good blocking performance on polytetrafluoroethylene microporous filter membranes with different pore sizes (100 nm-500 nm); it still maintains blocking performance on microporous filter membranes with different pore sizes after aging at 220°C for 16 h.

[0044] The plugging agent in this invention has a core-shell structure, containing an internal inorganic microcore and an external flexible polymer coating layer. According to one embodiment of the invention, the inorganic core has a thickness and particle size of 17-70 nm. In this invention, the particle size of the plugging agent is the sum of the thickness and particle size of the inorganic core and the thickness of the outer coating layer.

[0045] In this invention, the thickness and particle size of the inorganic core are determined by a nanoparticle size potentiometer method.

[0046] In this invention, "particle size" refers to particle size D50.

[0047] The second aspect of the present invention provides a method for preparing a plugging agent, the method comprising: in the presence of an initiator, an aqueous phase containing an emulsifier, an acrylic monomer and a hydrolysis inhibitor and an oil phase containing an alkenyl coupling agent-modified apatite, a fluorinated monomer and a silicon monomer undergoing emulsion polymerization, wherein the mass content of the alkenyl coupling agent is 35-45 wt%, based on the total mass of the alkenyl coupling agent-modified apatite;

[0048] The structure of the fluorinated monomer is shown in formula (IA):

[0049] In formula (IA), R 11 Selected from H or C1-C6 alkyl groups, R 12 Selected from C1-C9 fluoroalkyl groups;

[0050] The structure of the silicon-containing monomer is shown in formula (IIA):

[0051] In formula (IIA), R 21 R 22 R 23 Each is independently selected from C1-C8 alkyl or C1-C8 alkoxy groups, and R 21 R 22 R 23 At least one of the alkoxy groups selected from C1-C8.

[0052] In this invention, "mass content of terminal alkenyl coupling agent" refers to the ratio of the amount of terminal alkenyl coupling agent added to the amount of terminal alkenyl coupling agent modified apatite obtained during the preparation of terminal alkenyl coupling agent modified apatite.

[0053] The plugging agent prepared in this invention can effectively seal the micro- and nano-pores in the formation, prevent the drilling fluid from transmitting pressure into the formation, and reduce the intrusion of the drilling fluid into the formation under the action of pressure difference. It can be effectively adsorbed on the surface of the wellbore rock. The nanoparticles and the fluorine-containing low surface energy chemical structure will modify the rock surface hydrophobically, avoiding the risk of wellbore instability caused by hydration of the wellbore rock.

[0054] In this invention, the C1-C6 alkyl group can be either a straight-chain alkyl group or a branched-chain alkyl group, and there are no special limitations on this. For example, it can be methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl, sec-pentyl, tert-pentyl, n-hexyl, etc. In formula (IA) of this invention, R 11 The use of methyl groups as an example illustrates the advantages of the invention, but does not imply any limitation thereof.

[0055] In this invention, C1-C9 fluoroalkyl refers to a C1-C9 alkyl group in which at least one hydrogen atom is substituted by a fluorine atom. This substitution can be complete or partial; preferably, more than three-fifths of the hydrogen atoms in the C1-C9 alkyl group are substituted by fluorine atoms. In the preferred formula (IA), R... 12 Selected from C5-C7 fluoroalkyl groups. In formula (IA) of this invention, R 12 The advantages of the present invention are illustrated by using dodecyl fluoroheptyl as an example, but this does not imply any limitation on the invention.

[0056] In this invention, the C1-C8 alkyl groups that can be listed include C1 alkyl groups (referring to methyl), C2 alkyl groups (referring to ethyl), C3 alkyl groups (referring to n-propyl, isopropyl), C4 alkyl groups (referring to n-butyl, isobutyl, or tert-butyl, etc.), C5 alkyl groups (referring to n-pentyl, isopentyl, etc.), C6 alkyl groups (referring to n-hexyl, isohexyl, neohexyl, etc.), C7 alkyl groups (referring to n-heptyl, isohexyl, neoheptyl, etc.), and C8 alkyl groups (referring to n-octyl, isooctyl, sec-octyl, etc.); the C1-C8 alkoxy groups that can be listed include C1 alkoxy (methoxy), C2 alkoxy (ethoxy), C3 alkoxy (propoxy), C4 alkoxy (butoxy), C5 alkoxy (pentoxy), C6 alkoxy (hexoxy), C7 alkoxy (heptoxy), and C8 alkoxy (octoxy). In a preferred embodiment, in formula (II), R 21 R 22 R 23Each is independently selected from methyl, ethyl, methoxy, or ethoxy; in a preferred embodiment, R 21 R 22 R 23 At least one group is selected from C1-C8 alkoxy groups. In formula (IIA) of the present invention, R... 21 Methyl, R 22 For methoxy, R 23 The use of methoxy groups is provided as an example to illustrate the advantages of the invention, but does not imply any limitation thereof.

[0057] Using the aforementioned method, the silicon-containing groups in the silicon-containing monomers will hydrolyze and then undergo a dehydration condensation reaction with the silicon-hydroxyl groups on the rock surface, effectively adsorbing onto the rock surface of the well wall. This causes a wetting reversal phenomenon on the rock surface, avoiding the risk of well wall instability caused by hydration of the rock.

[0058] According to one embodiment of the present invention, the preparation method of the terminal alkenyl coupling agent modified apatite includes:

[0059] S1, under alkaline conditions, undergoes a precipitation reaction with an aqueous solution containing calcium salts and phosphate compounds to obtain a precipitate.

[0060] The S2 precipitate is contacted with the terminal alkenyl coupling agent, and then washed and dried.

[0061] In this invention, the apatite is a hydroxyl-containing apatite. There are no special restrictions on the type of apatite as long as the purpose of this invention can be achieved; it can be obtained commercially or through conventional preparation methods in the art. This invention prepares apatite via a precipitation method. A specific preparation method for the apatite includes: adding an alkaline aqueous solution dropwise to an aqueous solution containing calcium salts to adjust the pH of the system to 9-12, then adding an aqueous solution containing phosphate compounds to carry out a precipitation reaction to obtain apatite.

[0062] This invention does not impose any particular limitation on the type of calcium salt; it can be either anhydrous calcium salt or calcium salt existing in hydrate form, as long as the calcium salt can dissolve in water to form a corresponding aqueous solution containing the calcium salt. According to one embodiment of the invention, in step S1: the calcium salt is selected from at least one of calcium nitrate, calcium chloride, and calcium sulfate.

[0063] This invention does not impose any particular restrictions on the types of phosphoric acid compounds, as long as they can dissolve in water to form an aqueous solution containing the corresponding phosphoric acid compound. According to one embodiment of the invention, in step S1: the phosphoric acid compound is selected from at least one of diammonium hydrogen phosphate, ammonium phosphate, and phosphoric acid.

[0064] Both the terminal alkenyl group and the silaneoxy group in the terminal alkenyl coupling agent are reactive; the terminal alkenyl group is reactive to organic substances while the silaneoxy group is reactive to inorganic substances. Therefore, the three can form an organic substance-terminated alkenyl coupling agent-inorganic substance structure. According to one embodiment of the present invention, the terminal alkenyl coupling agent includes at least one of γ-methacryloyloxypropyltrimethoxysilane (KH570), vinyltrimethoxysilane, and vinyltriethoxysilane. In a preferred embodiment, the terminal alkenyl coupling agent is selected from γ-methacryloyloxypropyltrimethoxysilane (KH570).

[0065] According to one embodiment of the present invention, the molar ratio of the calcium salt and the phosphate compound is 0.8-1.2:1.

[0066] According to one embodiment of the present invention, the mass ratio of the calcium salt to the terminal alkenyl coupling agent is 0.8-1.5:1.

[0067] According to one embodiment of the present invention, the total mass content of calcium salt and phosphate compound in the aqueous solution is 5-10 wt%.

[0068] The precipitation method for preparing apatite requires the system to be under alkaline conditions. According to one embodiment of the present invention, in step S1, the alkaline conditions include: a pH of 9-12, achieved using conventional methods in the art, such as adding an aqueous solution of sodium hydroxide with a mass fraction of 10-30 wt%.

[0069] According to one embodiment of the present invention, in step S1, the conditions for the precipitation reaction include: a temperature of 40-55°C, and the precipitation reaction time can be adjusted accordingly based on the temperature, preferably 4-7 hours.

[0070] According to one embodiment of the present invention, in step S2, the contact conditions include: a temperature of 30-50°C, and the contact time can be adjusted accordingly based on the temperature, preferably 2-5 hours.

[0071] According to one embodiment of the present invention, the aqueous phase further contains cationic monomers represented by formula (IIIA) and / or formula (IIIB).

[0072] In formula (IIIA), R 31 and R 32 Each is independently selected from C1-C5 alkylene groups, R 33 and R 34 Each is independently selected from C1-C5 alkyl groups, R 35 and R 36 Each is independently selected from H or C1-C3 alkyl groups, N is a nitrogen atom, and Y1 is a halogen; in formula (IIIB), R 41Selected from C1-C5 alkylene groups, R 42 R 43 and R 44 Each is independently selected from C1-C3 alkyl groups, R 45 The alkyl group is selected from H or C1-C3, X is O or NH, N is a nitrogen atom, and Y2 is a halogen. Using the aforementioned embodiments, the plugging agent of the present invention exhibits better plugging performance.

[0073] In this invention, the C1-C5 alkylene groups are divalent groups formed by the loss of one H from the C1-C5 alkyl groups listed in this invention. According to a preferred embodiment of this invention, in formula (IIIA), R... 31 and R 32 Each is independently selected from C1-C3 alkylene groups, R 33 and R 34 Each is independently selected from methyl or ethyl, R 35 and R 36 Each is independently selected from H or methyl; according to a preferred embodiment of the present invention, in formula (IIIB), R 41 Selected from C1-C3 alkylene groups, R 42 R 43 and R 44 Each is independently selected from methyl or ethyl; R 45 Selected from H or methyl. The cationic monomer in this invention has the structure shown in formula (IIIA) (R) 31 and R 32 For methylene, R 33 and R 34 For methyl, R 35 and R 36 (H is H, Y1 is a chlorine atom) This illustrates the advantages of the present invention, but does not represent a limitation of the present invention.

[0074] According to one embodiment of the present invention, the mass ratio of the cationic monomer to the acrylic monomer is 0.3-0.8:1. For example, it is 0.3:1, 0.4:1, 0.5:1, 0.6:1, 0.7:1, or 0.8:1. The present invention uses a mass ratio of cationic monomer to acrylic monomer of 0.5:1 as an example to illustrate the advantages of the present invention, but this does not constitute a limitation thereof.

[0075] In the reaction system for preparing the plugging agent, the silicon-oxygen bonds in the silicon-containing monomer can be hydrolyzed into silanols. To inhibit the hydrolysis of these silicon-oxygen bonds, a hydrolysis inhibitor needs to be added. There are no particular limitations on the type of hydrolysis inhibitor, as long as the objective of this invention is achieved. According to one embodiment of the invention, the hydrolysis inhibitor is selected from at least one of ethylene glycol, isopropanol, and n-propanol, preferably ethylene glycol.

[0076] In this invention, the type of emulsifier is not particularly limited as long as the purpose of the invention can be achieved. According to one embodiment of the invention, the emulsifier is selected from at least one of Span80, Tween80, hexadecyltrimethylammonium chloride and sodium dodecyl sulfate, preferably Span80 and Tween80. Using a composite emulsifier can obtain a suitable HLB value. As long as the purpose of the invention can be achieved, the specific amount of Span80 and Tween80 is not particularly limited. In this invention, a mass ratio of Span80 to Tween80 of 4:1 is used as an example to illustrate the advantages of the invention, but it does not represent a limitation of the invention.

[0077] In this invention, the initiator can be any initiator in the art capable of initiating monomer polymerization. According to one embodiment of the invention, the initiator is selected from oxidizing initiators and reducing initiators. Using a redox initiation system can lower the activation energy of the free radical generation reaction and increase the polymerization rate.

[0078] According to a preferred embodiment of the present invention, the oxidizing initiator is selected from at least one of ammonium persulfate, potassium persulfate, and benzoyl peroxide.

[0079] According to a preferred embodiment of the present invention, the reducing initiator is selected from at least one of sodium bisulfite, sodium sulfite, and sodium thiochloride.

[0080] According to one embodiment of the present invention, the mass ratio of the oxidizing initiator to the reducing initiator is (1-3):1.

[0081] In this invention, ammonium persulfate and sodium bisulfite in a mass ratio of 2:1 are used as an example to illustrate the advantages of the invention, but this does not constitute a limitation thereof. In this invention, the initiator is added to the reaction system dropwise, and the dropwise addition time is not included in the reaction time.

[0082] According to one embodiment of the present invention, the mass ratio of the fluorinated monomer to the acrylic monomer is 0.1-0.4:1. For example, it is 0.1:1, 0.15:1, 0.2:1, 0.25:1, 0.3:1, 0.39:1, or 0.4:1. The present invention uses a mass ratio of fluorinated monomer to acrylic monomer of 0.39:1 as an example to illustrate the advantages of the present invention, but this does not represent a limitation thereof.

[0083] According to one embodiment of the present invention, the mass ratio of the silicon-containing monomer to the acrylic monomer is 0.45-0.8:1. For example, it is 0.45:1, 0.5:1, 0.6:1, 0.63:1, 0.7:1, 0.75:1, or 0.8:1. The present invention uses a mass ratio of silicon-containing monomer to acrylic monomer of 0.62:1 as an example to illustrate the advantages of the present invention, but this does not constitute a limitation thereof.

[0084] According to one embodiment of the present invention, the mass ratio of the terminal alkenyl coupling agent modified apatite to the acrylic monomer is 0.2-0.5:1. For example, it is 0.2:1, 0.25:1, 0.3:1, 0.32:1, 0.4:1, 0.45:1, or 0.5:1. The present invention uses a mass ratio of 0.32:1 of the terminal alkenyl coupling agent modified apatite to the acrylic monomer as an example to illustrate the advantages of the present invention, but this does not constitute a limitation thereof.

[0085] According to one embodiment of the present invention, the mass ratio of the initiator to the acrylic monomer is 0.005-0.01:1. For example, it is 0.005:1, 0.006:1, 0.007:1, 0.008:1, 0.009:1, or 0.01:1. The present invention uses a mass ratio of 0.006:1 for the initiator to the acrylic monomer as an example to illustrate the advantages of the invention, but this does not constitute a limitation thereof.

[0086] According to one embodiment of the present invention, the content of the acrylic monomer is 5-10 wt%, based on the total mass of the aqueous phase.

[0087] According to one embodiment of the present invention, the content of the emulsifier is 1-3 wt%, based on the total mass of the aqueous phase.

[0088] According to one embodiment of the present invention, the content of the hydrolysis inhibitor is 0.1-2 wt%, based on the total mass of the aqueous phase. For example, it is 0.1 wt%, 0.22 wt%, 0.3 wt%, 0.5 wt%, 0.7 wt%, 1 wt%, 1.2 wt%, 1.5 wt%, 1.7 wt%, or 2 wt%.

[0089] According to a preferred embodiment of the present invention, the pH of the aqueous phase is 4-7. By employing the aforementioned embodiment, the hydrolysis of silicon-containing monomers can be suppressed, and the particle size of the sealing agent can be controlled.

[0090] In this invention, any pH adjuster in the art can be used to adjust the pH of the aqueous phase to 4-7, and there are no special limitations on this.

[0091] According to one embodiment of the present invention, the conditions for the emulsion polymerization reaction include: a temperature of 50-70°C, and the time of the emulsion polymerization reaction is adjusted by the corresponding temperature, preferably 4.5-8 hours.

[0092] According to a specific embodiment of the present invention, water, emulsifier, acrylic acid, hydrolysis inhibitor and optionally cationic monomer are mixed at room temperature to obtain an aqueous phase. The pH of the aqueous phase is adjusted to 4-7, and then the aqueous phase is controlled to the solution polymerization temperature. Fluorine-containing monomer, silicon-containing monomer and terminal alkenyl coupling agent modified apatite are mixed evenly to obtain an oil phase. The oil phase is controlled to the solution polymerization temperature, and the oil phase is added to the aqueous phase for mixing. After mixing, an initiator is added dropwise to the reaction system and the system is kept under a protective atmosphere for a period of time to obtain an emulsion containing a blocking agent.

[0093] The choice of the protective atmosphere is not particularly limited as long as the purpose of the present invention can be achieved; for example, it can be nitrogen.

[0094] A third aspect of the present invention provides a plugging agent, wherein the plugging agent is a plugging agent prepared by the method described in the second aspect of the present invention.

[0095] The fourth aspect of the present invention provides the application of a plugging agent in drilling fluid, wherein the plugging agent is the plugging agent described in the first aspect of the present invention or the plugging agent described in the third aspect of the present invention.

[0096] The plugging agent in this invention can not only effectively plug the formation, but also modify the rock surface hydrophobically, avoiding the risk of wellbore instability caused by hydration of the wellbore rock. In specific applications, the emulsion containing the plugging agent after emulsion polymerization can be directly applied to the drilling fluid.

[0097] D50 particle size was determined by a nanoparticle size potentiometer method;

[0098] The thickness and particle size of the inorganic core were determined using a nanoparticle size potentiometry method.

[0099] Example 1

[0100] Prepare 55.3g of calcium nitrate aqueous solution by taking 5.3g of calcium nitrate tetrahydrate and adjusting the pH of the system to 10; then add 52.95g of diammonium hydrogen phosphate (2.95g) aqueous solution to the above system, stir at 50℃ for 6h, add KH570 (4.8g) and continue stirring for 3h; finally, place the above system in a vacuum drying oven and heat at 40℃ for 12h, wash the product with ethanol aqueous solution and centrifuge 3 times, and finally dry to constant weight to obtain about 11g of terminal alkenyl coupling agent modified apatite.

[0101] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.3 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0102] Take 3.925g of dodecafluoroheptyl methacrylate, 6.24g of dimethoxymethylvinylsilane, and 3.2g of alkenyl-terminated coupling agent modified apatite. Mix the three ingredients evenly and heat them to 60℃ in a water bath to obtain the oil phase.

[0103] The aqueous phase was transferred to a three-necked flask, the pH of the system was adjusted to 5, and the system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 min. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 min, and the reaction was allowed to proceed for 6 h to obtain the blocking agent (inorganic core thickness and particle size of 22.5-68.9 nm).

[0104] Based on the amount of raw materials added, it is estimated that, in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 15.6 wt%, the content of the silicon-containing structural unit is approximately 24.8 wt%, and the content of the acrylic structural unit is approximately 39.7 wt%.

[0105] Example 2

[0106] Prepare 55.3g of calcium nitrate aqueous solution by taking 5.3g of calcium nitrate tetrahydrate and adjusting the pH of the system to 10; then add 52.95g of diammonium hydrogen phosphate (2.95g) aqueous solution to the above system, stir at 50℃ for 6h, add KH570 (4.8g) and continue stirring for 3h; finally, place the above system in a vacuum drying oven and heat at 40℃ for 12h, wash the product with ethanol aqueous solution and centrifuge 3 times, and finally dry to constant weight to obtain about 11g of terminal alkenyl coupling agent modified apatite.

[0107] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.15 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0108] Take 3.925g of dodecafluoroheptyl methacrylate, 6.24g of dimethoxymethylvinylsilane, and 3.2g of alkenyl-terminated coupling agent modified apatite. Mix the three ingredients evenly and heat them to 60℃ in a water bath to obtain the oil phase.

[0109] The aqueous phase was transferred to a three-necked flask, the pH of the system was adjusted to 5, and the system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 min. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 min, and the reaction was allowed to proceed for 6 h to obtain the blocking agent (inorganic core thickness and particle size of 22.5-68.9 nm).

[0110] Based on the amount of raw materials added, it is estimated that, in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 15.6 wt%, the content of the silicon-containing structural unit is approximately 24.8 wt%, and the content of the acrylic structural unit is approximately 39.7 wt%.

[0111] Example 3

[0112] Prepare 55.3g of calcium nitrate aqueous solution by taking 5.3g of calcium nitrate tetrahydrate and adjusting the pH of the system to 10; then add 52.95g of diammonium hydrogen phosphate (2.95g) aqueous solution to the above system, stir at 50℃ for 6h, add KH570 (4.8g) and continue stirring for 3h; finally, place the above system in a vacuum drying oven and heat at 40℃ for 12h, wash the product with ethanol aqueous solution and centrifuge 3 times, and finally dry to constant weight to obtain about 11g of terminal alkenyl coupling agent modified apatite.

[0113] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.3 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0114] Take 2.355g of dodecafluoroheptyl methacrylate, 6.24g of dimethoxymethylvinylsilane, and 3.2g of alkenyl-terminated coupling agent modified apatite, mix them evenly, and heat them to 60℃ in a water bath to obtain the oil phase.

[0115] The aqueous phase was transferred to a three-necked flask, the pH of the system was adjusted to 5, and the system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 min. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 min, and the reaction was allowed to proceed for 6 h to obtain the blocking agent (inorganic core thickness and particle size of 22.5-68.9 nm).

[0116] Based on the amount of raw materials added, it is estimated that in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 10.0 wt%, the content of the silicon-containing structural unit is approximately 26.5 wt%, and the content of the acrylic structural unit is approximately 42.4 wt%.

[0117] Example 4

[0118] Prepare 55.3g of calcium nitrate aqueous solution by taking 5.3g of calcium nitrate tetrahydrate and adjusting the pH of the system to 10; then add 52.95g of diammonium hydrogen phosphate (2.95g) aqueous solution to the above system, stir at 50℃ for 6h, add KH570 (4.8g) and continue stirring for 3h; finally, place the above system in a vacuum drying oven and heat at 40℃ for 12h, wash the product with ethanol aqueous solution and centrifuge 3 times, and finally dry to constant weight to obtain about 11g of terminal alkenyl coupling agent modified apatite.

[0119] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.3 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0120] Take 3.925g of dodecafluoroheptyl methacrylate, 3.84g of dimethoxymethylvinylsilane, and 3.2g of alkenyl-terminated coupling agent modified apatite, mix them evenly, and heat them to 60℃ in a water bath to obtain the oil phase.

[0121] The aqueous phase was transferred to a three-necked flask, the pH of the system was adjusted to 5, and the system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 min. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 min, and the reaction was allowed to proceed for 6 h to obtain the blocking agent (inorganic core thickness and particle size of 22.5-68.9 nm).

[0122] Based on the amount of raw materials added, it is estimated that in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 17.2 wt%, the content of the silicon-containing structural unit is approximately 16.9 wt%, and the content of the acrylic structural unit is approximately 43.9 wt%.

[0123] Example 5

[0124] Prepare 55.3g of calcium nitrate aqueous solution by taking 5.3g of calcium nitrate tetrahydrate and adjusting the pH of the system to 10; then add 52.95g of diammonium hydrogen phosphate (2.95g) aqueous solution to the above system, stir at 50℃ for 6h, add KH570 (4.8g) and continue stirring for 3h; finally, place the above system in a vacuum drying oven and heat at 40℃ for 12h, wash the product with ethanol aqueous solution and centrifuge 3 times, and finally dry to constant weight to obtain about 11g of terminal alkenyl coupling agent modified apatite.

[0125] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.3 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0126] Take 3.925g of dodecafluoroheptyl methacrylate, 6.24g of dimethoxymethylvinylsilane, and 2g of alkenyl-terminated coupling agent modified apatite. Mix the three ingredients evenly and heat them to 60℃ in a water bath to obtain the oil phase.

[0127] The aqueous phase was transferred to a three-necked flask, the pH of the system was adjusted to 5, and the system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 min. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (containing 0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 min, and the reaction was allowed to proceed for 6 h to obtain the blocking agent (inorganic core thickness and particle size of 18.5-57.6 nm).

[0128] Based on the amount of raw materials added, it is estimated that, in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 15.6 wt%, the content of the silicon-containing structural unit is approximately 24.8 wt%, and the content of the acrylic structural unit is approximately 39.7 wt%.

[0129] Example 6

[0130] Prepare 55.3g of calcium nitrate aqueous solution by taking 5.3g of calcium nitrate tetrahydrate and adjusting the pH of the system to 10; then add 52.95g of diammonium hydrogen phosphate (2.95g) aqueous solution to the above system, stir at 50℃ for 6h, add KH570 (4.8g) and continue stirring for 3h; finally, place the above system in a vacuum drying oven and heat at 40℃ for 12h, wash the product with ethanol aqueous solution and centrifuge 3 times, and finally dry to constant weight to obtain about 11g of terminal alkenyl coupling agent modified apatite.

[0131] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.3 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0132] Take 3.925g of dodecafluoroheptyl methacrylate, 6.24g of dimethoxymethylvinylsilane, and 3.2g of alkenyl-terminated coupling agent modified apatite. Mix the three ingredients evenly and heat them to 60℃ in a water bath to obtain the oil phase.

[0133] The aqueous phase was transferred to a three-necked flask, and the pH of the system was adjusted to 7. The system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 minutes. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (containing 0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 minutes, and the reaction was allowed to proceed for 6 hours to obtain the blocking agent (with an inorganic core thickness and particle size of 22.5-68.9 nm).

[0134] Based on the amount of raw materials added, it is estimated that, in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 15.6 wt%, the content of the silicon-containing structural unit is approximately 24.8 wt%, and the content of the acrylic structural unit is approximately 39.7 wt%.

[0135] Example 7

[0136] Same as in Example 1, except that dodecafluoroheptyl methacrylate was replaced with an equal mass of 4-trifluoromethylstyrene to obtain a blocking agent (the thickness and particle size of the inorganic core is 22.5-68.9 nm).

[0137] Based on the amount of raw materials added, it is estimated that, in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 15.6 wt%, the content of the silicon-containing structural unit is approximately 24.8 wt%, and the content of the acrylic structural unit is approximately 39.7 wt%.

[0138] Example 8

[0139] Same as in Example 1, except that dimethoxymethylvinylsilane is replaced by dimethyldivinylsilane in equal mass to obtain a blocking agent (the thickness and particle size of the inorganic core is 22.5-68.9 nm).

[0140] Based on the amount of raw materials added, it is estimated that, in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 15.6 wt%, the content of the silicon-containing structural unit is approximately 24.8 wt%, and the content of the acrylic structural unit is approximately 39.7 wt%.

[0141] Example 9

[0142] Same as Example 1, except that the cationic monomer diallyldimethylammonium chloride was not added to the aqueous phase to obtain the blocking agent (the thickness and particle size of the inorganic core is 22.5-68.9 nm).

[0143] Based on the amount of raw materials added, it is estimated that in this embodiment, using the mass of fluorosilicone modified acrylic resin in the sealing agent shell as a benchmark, the content of the fluorine-containing structural unit is approximately 19.5 wt%, the content of the silicon-containing structural unit is approximately 30.9 wt%, and the content of the acrylic structural unit is approximately 49.6 wt%.

[0144] Comparative Example 1

[0145] Similar to Example 1, except that the amount of KH570 added was reduced to 1.44g when preparing the terminal alkenyl coupling agent modified apatite, resulting in approximately 8g of terminal alkenyl coupling agent modified apatite, and thus a blocking agent (with an inorganic core thickness and particle size of 17.5-64.1nm).

[0146] Comparative Example 2

[0147] Similar to Example 1, except that ethylene glycol was not added to the aqueous phase during the preparation of the blocking agent, resulting in a blocking agent (with an inorganic core thickness and particle size of 22.5-68.9 nm).

[0148] Comparative Example 3

[0149] Similar to Example 1, except that dodecafluoroheptyl methacrylate was not added to the oil phase during the preparation of the plugging agent, resulting in a plugging agent (with an inorganic core thickness and particle size of 22.5-68.9 nm).

[0150] Comparative Example 4

[0151] Similar to Example 1, except that dimethoxymethylvinylsilane was not added to the oil phase during the preparation of the plugging agent, resulting in a plugging agent (with an inorganic core thickness and particle size of 22.5-68.9 nm).

[0152] Comparative Example 5

[0153] Same as in Example 1, except that no terminal alkenyl coupling agent is added to modify apatite in the oil phase during the preparation of the plugging agent.

[0154] Comparative Example 6

[0155] 50g of dry quartz powder was heated to 50℃, 1g of ammonia water was added, and the mixture was stirred at a stirring rate of 500r / min for 1h. The resulting product was dried at 120℃ for 5h to obtain dried quartz powder. 10g of the dried quartz powder was heated to 70℃, and 0.2g of KH570 was added. The mixture was stirred at 50℃ for 3h. The product was then placed in a vacuum drying oven and heated at 40℃ for 12h. The product was washed with an ethanol aqueous solution and centrifuged 3 times. Finally, it was dried to constant weight to obtain approximately 9g of quartz powder modified with terminal alkenyl coupling agent.

[0156] A composite emulsifier was prepared by mixing Span80 and Tween80 at a mass ratio of 4:1. 120 mL of deionized water was placed in a beaker, and 10 g of acrylic acid, 5 g of diallyl dimethyl ammonium chloride, and 1.5 g of the composite emulsifier were added to the beaker. Then, 0.3 g of ethylene glycol was added, and the mixture was stirred at room temperature for 20 min to obtain the aqueous phase.

[0157] Take 3.925g of dodecafluoroheptyl methacrylate, 6.24g of dimethoxymethyl vinylsilane, and 3.2g of quartz powder modified with terminal alkenyl coupling agent. Mix the three ingredients evenly and add them to a water bath at 60°C to obtain the oil phase.

[0158] The aqueous phase was transferred to a three-necked flask, the pH of the system was adjusted to 5, and the system temperature was heated to 60°C using a water bath. The heated oil phase was then added to the aqueous phase, and the mixture was stirred for 20 min. Using a syringe pump, 2.52 g of sodium bisulfite aqueous solution and 2.54 g of ammonium persulfate aqueous solution (0.02 g sodium bisulfite and 0.04 g ammonium persulfate) were added dropwise to the three-necked flask. Finally, the system was purged with nitrogen for 30 min, and the reaction was allowed to proceed for 6 h to obtain the blocking agent (inorganic core thickness and particle size of 23.2-85.6 nm).

[0159] Test case

[0160] (1) Impact on drilling fluid properties

[0161] To prepare a drilling fluid-based slurry with a mass fraction of 4%, measure 400 mL of tap water and add it to a high-speed stirring cup. Then, add 0.56 g of Na2CO3 and 16 g of drilling fluid-grade bentonite in sequence, stir at high speed for 40 min, and let it age at room temperature for 24 h.

[0162] The example and comparative samples, each with a mass fraction of 2%, were added to the drilling fluid base slurry and stirred at room temperature for 40 min to obtain the drilling fluid after sample addition. The rheological properties (50℃) and filtration loss (FL) of the drilling fluid after sample addition were determined using a six-speed rotational viscometer and a medium-pressure filtration loss meter, according to the method specified in GB / T 16783.1-2014. API Subsequently, the base slurry and each sample of drilling fluid were placed in an aging tank and aged at 220°C for 16 hours in a roller furnace. After cooling to room temperature, the rheological and filtration properties of the drill fluid were measured. The experimental results are shown in Table 1.

[0163] Table 1. Effects of plugging agents on the basic properties of drilling fluids Note: "Base slurry" refers to drilling fluid base slurry.

[0164] (2) Particle size distribution

[0165] 400 mL of 2 wt% aqueous solutions of the examples and comparative examples were prepared and sonicated at room temperature for 40 min. The particle size distribution of the high-temperature hydrophobic nanoparticle blocker before aging was determined using a nanoparticle size potentiometer. The sample solutions were then placed in an aging tank and aged at 220 °C for 16 h in a roller furnace. After aging, the solutions were cooled to room temperature, and the particle size distribution of the high-temperature hydrophobic nanoparticle blocker in the aged sample solutions was determined using a nanoparticle size potentiometer. The experimental results are shown in Table 2: D50 retention rate (%) = D50 after aging / D50 before aging × 100%.

[0166] Table 2 Particle size distribution of the plugging agent

[0167] (3) Microporous membrane clogging

[0168] Add 2% (w / w) of the example or comparative sample to 400 mL of clean water. Following the medium-pressure filtration loss test procedure, replace ordinary drilling fluid filter paper with polytetrafluoroethylene (PTFE) microporous membranes. The pore sizes of the microporous membranes are 100 nm, 300 nm, and 500 nm, named PTFE-100, PTFE-300, and PTFE-500, respectively. The sealing performance of the sample aqueous solution on the PTFE microporous membrane is measured. Simultaneously, the sample solution is aged at 220℃ for 16 h, cooled to room temperature, and the sealing performance of the sample solution on the PTFE microporous membrane is further measured. The experimental results are shown in Table 3. Pure water will rapidly and completely filter out.

[0169] Table 3. Blocking performance of PTFE microporous membranes by sample slurry in various examples and comparative samples.

[0170] (4) Effect on rock surface wettability

[0171] Black mudstone and shale from the Songlin area of ​​Sichuan Province were selected and cut into circular slices with a thickness of 0.5 mm and a diameter of 25 mm. 350 mL of each of the example and comparative samples (2% by mass) were prepared. The solutions were poured into aging tanks, and one mudstone and shale slice was added to each. The aging tanks were sealed and placed in a roller furnace at 220°C for 16 hours. After aging, the aging tanks were removed and cooled to room temperature. The black mudstone and shale slices were then dried to constant weight in a vacuum drying oven. The water contact angle of the rock surface was measured using a contact angle meter, and the average value was taken from three measurements. The rock slices treated with water served as the control group. The experimental results are shown in Table 4.

[0172] Table 4. Water contact angle of rock surface for each embodiment and comparative sample.

[0173] 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 technical features in any other suitable manner. 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.

Claims

1. A sealing agent, characterized in that, The plugging agent has a core-shell structure, comprising an inorganic core and a shell layer covering the inorganic core; wherein the inorganic core comprises apatite modified with an end-alkene coupling agent, and the shell layer comprises fluorosilicone modified acrylic resin; the D50 particle size of the plugging agent is 145-200 nm. Based on the total mass of apatite modified with terminal alkenyl coupling agent, the mass content of terminal alkenyl coupling agent is 35-45 wt%. The fluorosilicone modified acrylic resin comprises a fluorine-containing structural unit as shown in formula (I) and a silicon-containing structural unit as shown in formula (II): In equation (I), R 11 Selected from H or C1-C6 alkyl groups, R 12 Selected from C1-C9 fluoroalkyl groups; In equation (II), R 21 R 22 R 23 Each is independently selected from C1-C8 alkyl or C1-C8 alkoxy groups, and R 21 R 22 R 23 At least one of the alkoxy groups selected from C1-C8.

2. The sealing agent according to claim 1, characterized in that, In equation (I), R 12 Selected from C5-C7 fluoroalkyl groups; and / or In equation (II), R 21 R 22 R 23 Each is independently selected from methyl, ethyl, methoxy, or ethoxy.

3. The sealing agent according to claim 1, characterized in that, Based on the mass of the fluorosilicone-modified acrylic resin, the content of the fluorinated structural unit is 8-20 wt%; and / or Based on the mass of the fluorosilicone-modified acrylic resin, the content of the silicon-containing structural unit is 15-40 wt%; and / or The fluorosilicone-modified acrylic resin has acrylic structural units, and the content of the acrylic structural units is 30-60 wt%, based on the mass of the fluorosilicone-modified acrylic resin.

4. The sealing agent according to claim 1, characterized in that, The fluorosilicone-modified acrylic resin also has cationic structural units as shown in formula (IIIa) and / or formula (IIIb): In equation (IIIa), R 31 and R 32 Each is independently selected from C1-C5 alkylene groups, R 33 and R 34 Each is independently selected from C1-C5 alkyl groups, R 35 and R 36 Each is independently selected from H or C1-C3 alkyl groups, and N is a nitrogen atom; In equation (IIIb), R 41 Selected from C1-C5 alkylene groups; R 42 R 43 and R 44 Each is independently selected from C1-C3 alkyl groups, R 45 Selected from H or C1-C3 alkyl groups, where X is O or NH and N is a nitrogen atom.

5. The sealing agent according to claim 4, characterized in that, In equation (IIIa), R 31 and R 32 Each is independently selected from C1-C3 alkylene groups, R 33 and R 34 Each is independently selected from methyl or ethyl, R 35 and R 36 Each is independently selected from H or methyl; and / or In equation (IIIb), R 41 Selected from C1-C3 alkylene groups, R 42 R 43 and R 44 Each is independently selected from methyl or ethyl, R 45 Selected from H or methyl; and / or Based on the mass of the fluorosilicone-modified acrylic resin, the content of the cationic structural unit is 10-30 wt%.

6. The sealing agent according to claim 1, characterized in that, The terminal alkenyl coupling agent in the modified apatite is selected from terminal alkenyl silane coupling agents; and / or In the terminal alkenyl coupling agent modified apatite, the terminal alkenyl groups in the terminal alkenyl coupling agent are chemically bonded to the fluorosilicone modified acrylic resin.

7. The sealing agent according to claim 6, characterized in that, In the terminal alkenyl coupling agent modified apatite, the silicon atoms in the terminal alkenyl coupling agent form silicon-oxygen bonds with the oxygen atoms in the apatite; and / or The terminal alkenyl silane coupling agent includes at least one of γ-methacryloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane.

8. The sealing agent according to any one of claims 1-7, characterized in that, The D50 particle size of the plugging agent is 149-166 nm; and / or The inorganic core has a thickness and particle size of 17-70 nm.

9. A method for preparing a plugging agent, characterized in that, The method includes: In the presence of an initiator, an aqueous phase containing an emulsifier, acrylic monomer, and hydrolysis inhibitor undergoes emulsion polymerization with an oil phase containing terminal alkenyl coupling agent-modified apatite, fluorinated monomer, and silicon-containing monomer. Among them, based on the total mass of apatite modified with terminal alkenyl coupling agent, the mass content of terminal alkenyl coupling agent is 35-45 wt%. The structure of the fluorinated monomer is shown in formula (IA): In formula (IA), R 11 Selected from H or C1-C6 alkyl groups, R 12 Selected from C1-C9 fluoroalkyl groups; The structure of the silicon-containing monomer is shown in formula (IIA): In formula (IIA), R 21 R 22 R 23 Each is independently selected from C1-C8 alkyl or C1-C8 alkoxy groups, and R 21 R 22 R 23 At least one of the alkoxy groups selected from C1-C8.

10. The method according to claim 9, characterized in that, The preparation method of the terminal alkenyl coupling agent modified apatite includes: S1, under alkaline conditions, undergoes a precipitation reaction with an aqueous solution containing calcium salts and phosphate compounds to obtain a precipitate. The S2 precipitate is contacted with the terminal alkenyl coupling agent, and then washed and dried.

11. The method according to claim 10, characterized in that, The calcium salt is selected from at least one of calcium nitrate, calcium chloride, and calcium sulfate; and / or The phosphoric acid compound is selected from at least one of diammonium hydrogen phosphate, ammonium phosphate, and phosphoric acid; and / or The terminal alkenyl coupling agent comprises at least one of γ-methacryloyloxypropyltrimethoxysilane, vinyltrimethoxysilane, and vinyltriethoxysilane; and / or The molar ratio of the calcium salt and the phosphate compound is 0.8-1.2:1; and / or The mass ratio of the calcium salt to the terminal alkenyl coupling agent is 0.8-1.5:1; and / or The total mass content of calcium salts and phosphate compounds in the aqueous solution is 5-10 wt%.

12. The method according to claim 10, characterized in that, In step S1, the alkaline conditions include: a pH of 9-12; and / or In step S1, the conditions for the precipitation reaction include: a temperature of 40-55℃; and / or a time of 4-7 hours; and / or In step S2, the contact conditions include: a temperature of 30-50°C; and / or a time of 2-5 hours.

13. The method according to claim 9, characterized in that, The aqueous phase also contains cationic monomers represented by formula (IIIA) and / or formula (IIIB). In formula (IIIA), R 31 and R 32 Each is independently selected from C1-C5 alkylene groups, R 33 and R 34 Each is independently selected from C1-C5 alkyl groups, R 35 and R 36 Each is independently selected from H or C1-C3 alkyl groups, where N is a nitrogen atom and Y1 is a halogen; In equation (IIIB), R 41 Selected from C1-C5 alkylene groups, R 42 R 43 and R 44 Each is independently selected from C1-C3 alkyl groups, R 45 Selected from H or C1-C3 alkyl groups, X is O or NH, N is a nitrogen atom, and Y2 is a halogen.

14. The method according to claim 13, characterized in that, The mass ratio of the cationic monomer to the acrylic acid monomer is 0.3-0.8:

1.

15. The method according to claim 9, characterized in that, The hydrolysis inhibitor is selected from at least one of ethylene glycol, isopropanol, and n-propanol; and / or The emulsifier is selected from at least one of Span80, Tween80, cetyltrimethylammonium chloride, and sodium dodecyl sulfate; and / or The initiator is selected from oxidizing initiators and reducing initiators.

16. The method according to claim 15, characterized in that, The hydrolysis inhibitor is selected from ethylene glycol; and / or The emulsifier is selected from Span 80 and Tween 80; and / or The oxidizing initiator is selected from at least one of ammonium persulfate, potassium persulfate, and benzoyl peroxide; and / or The reducing initiator is selected from at least one of sodium bisulfite, sodium sulfite, and sodium thiochlorate; and / or The mass ratio of the oxidizing initiator to the reducing initiator is (1-3):

1.

17. The method according to claim 9, characterized in that, The mass ratio of the fluorinated monomer to the acrylic monomer is 0.1-0.4:1; and / or The mass ratio of the silicon-containing monomer to the acrylic monomer is 0.45-0.8:1; and / or; The mass ratio of the terminal alkenyl coupling agent-modified apatite to acrylic monomer is 0.2-0.5:1; and / or The mass ratio of the initiator to the acrylic monomer is 0.005-0.01:

1.

18. The method according to claim 9, characterized in that, Based on the total mass of the aqueous phase: The content of the acrylic monomer is 5-10 wt%; and / or The emulsifier content is 1-3 wt%; and / or The content of the hydrolysis inhibitor is 0.1-2 wt%.

19. The method according to claim 9, characterized in that, The pH of the aqueous phase is 4-7; and / or The conditions for the emulsion polymerization reaction include: a temperature of 50-70°C; and / or a time of 4.5-8 hours.

20. A sealing agent, characterized in that, The plugging agent is the plugging agent prepared by the method described in any one of claims 9-19.

21. The application of a plugging agent in drilling fluid, characterized in that, The plugging agent is the plugging agent according to any one of claims 1-8 or the plugging agent according to claim 20.

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