A magnetically enhanced temporary plugging agent, its preparation method and application

Abstract

This invention discloses a magnetically enhanced temporary plugging agent, its preparation method, and its application. The magnetically enhanced temporary plugging agent comprises a plugging agent matrix and modified magnetic particles dispersed within the plugging agent matrix. By incorporating the magnetic particles into the plugging agent, the attractive force between the plugging particles is increased. Furthermore, to effectively seal the gaps between the plugging particles and improve the sealing effect, this invention also applies an elastic material coating to the outside of the plugging particles. This coating, with a low glass transition temperature, imparts elasticity and can effectively seal the gaps between the particles during particle stacking, achieving highly efficient sealing.

Description

Technical Field

[0001] This invention belongs to the field of temporary plugging agents for fracturing, and particularly relates to a magnetically enhanced temporary plugging agent, its preparation method, and its application. Background Technology

[0002] The increasing scarcity of energy has made crude oil play a vital role in modern industry, and a stable supply of crude oil is crucial for economic and social development. Formation fracturing is a key means of improving oil and gas recovery.

[0003] Fracturing is the process of injecting high-pressure fluid underground to create fractures in the formation, thereby enhancing the production channels for oil or natural gas, or the injection channels for oil displacement agents, and thus improving the extraction capacity of oil and gas.

[0004] During fracturing, the formation initiation pressure varies at different locations within the same section. Initiating fractures prematurely consumes a large amount of fluid, reducing the effectiveness of fracture creation at later initiation points and ultimately impacting the overall fracturing outcome. Temporary plugging materials are polymeric fracturing materials developed to improve fracture creation.

[0005] During fracturing operations, the addition of temporary plugging materials can seal the fractures that are preferentially opened, causing the fluid flow to redirect to unopened areas and improving the fracture creation effect. After the operation is completed, the temporary plugging material can slowly degrade and become ineffective under the influence of formation temperature and water. After degradation, it does not seal the formation or fractures and does not affect subsequent production.

[0006] Biodegradable polymers such as polyglycolic acid and polylactide are used as temporary plugging materials due to their good mechanical properties and degradation characteristics. Temporary plugging agents that seal cracks mainly consist of a mixture of biodegradable materials with different particle sizes. As the liquid flows into the crack, it bridges and traps the liquid, thus sealing the crack.

[0007] However, due to the relatively weak intermolecular forces between biodegradable polymer resin particles, a large number of these particles will flow into the depths of the fracture with the fracturing fluid before bridging and sealing can occur. This results in a low actual bridging and sealing efficiency. A large number of particles are ineffectively dispersed within the fracture, failing to aggregate and bridge for effective sealing. Summary of the Invention

[0008] This invention primarily addresses the problem of weak interaction forces in ordinary biodegradable particulate plugging agents, leading to low efficiency due to the inability of some particles to effectively aggregate and bridge after entering the formation. To solve this problem, this invention provides a magnetically enhanced plugging agent, its preparation method, and its application. By incorporating magnetic particles into the plugging agent matrix, the attractive force between the plugging agents is increased. The magnetic particles are introduced into the plugging agent matrix, and the permanent magnetism of the particles is enhanced by a magnetizing machine, thus creating a plugging agent with magnetic attraction. Simultaneously, controlling the content of magnetic particles allows for the regulation of the attractive force between particles. Under the high shear conditions of fracturing operations, the plugging agent can disperse in solution, but when it enters the formation fractures, the flow rate decreases, and the plugging agents aggregate due to magnetic interaction, effectively enhancing the aggregation and bridging of the plugging agent in the fractures and improving the plugging efficiency. Furthermore, to effectively seal the gaps between the plugging particle accumulations and improve the sealing effect, this invention also attaches an elastic material coating to the outside of the plugging particles. This coating has a low glass transition temperature, giving it elasticity, and can effectively seal the gaps between the particles during accumulation, achieving highly efficient sealing. Meanwhile, in the high-temperature water environment of the oil reservoir, the coating can dissolve slowly without affecting the degradation of the temporary plugging material.

[0009] The present invention provides a magnetically enhanced temporary plugging agent, which includes a temporary plugging agent matrix and modified magnetic particles dispersed in the temporary plugging agent matrix.

[0010] In this invention, the temporary plugging agent matrix is ​​selected from biodegradable polymers, preferably from one or more of the following: polyglycolic acid, polylactide, polybutylene succinate, polycaprolactone, polybutylene terephthalate, polybutylene terephthalate, polybutylene succinate, polymethyl ethylene carbonate, polyhydroxyalkanoates, or a mixture thereof or a copolymer of their structural units.

[0011] In this invention, the modified magnetic particles are compatibilizer-modified magnetic particles. Preferably, the compatibilizer is selected from at least one of epoxy compounds, silane compatibilizers, copolymers containing maleic acid or its anhydride or its amide, titanate compatibilizers, aluminate compatibilizers, zirconate esters, borate esters, and aluminum-titanium composite compatibilizers. More preferably, based on 100 parts by weight of magnetic particles, the compatibilizer is 0.1%-1% by weight, preferably 0.2%-0.6% by weight.

[0012] In this invention, the magnetic particles are selected from at least one of ferrite, neodymium iron boron, samarium cobalt, alnico, manganese aluminum carbon, and iron chromium cobalt; and / or, the particle size of the magnetic particles is 100-800 nm, preferably 100-500 nm; and / or, in the magnetically reinforced temporary plugging agent, based on 100 parts by weight of the temporary plugging matrix, the modified magnetic particles are 5-30 parts by weight.

[0013] In this invention, the magnetically enhanced temporary plugging agent further comprises an elastic material coating on the surface of the temporary plugging agent matrix; preferably, the elastic material is selected from polymers with ester bonds in the side chains, preferably polyvinyl acetate; more preferably, based on 100wt% of the temporary plugging agent matrix and the modified magnetic particles, the elastic material coating is 1-10wt%, preferably 3-5wt%.

[0014] In this invention, the magnetically enhanced temporary plugging agent optionally includes an additive; preferably, the additive is selected from at least one of antioxidants, stabilizers, and anti-hydrolysis agents; more preferably, based on 100 parts by weight of the temporary plugging agent matrix, the antioxidant is 0.1%-1% by weight, the stabilizer is 0.001%-0.1% by weight, and the anti-hydrolysis agent is 0.1%-1% by weight.

[0015] A second aspect of the present invention provides a method for preparing a magnetically enhanced temporary plugging agent, comprising: melt-blending and extruding the temporary plugging agent matrix, the modified magnetic particles and optionally the additives into granules, then magnetizing and optionally pulverizing them to obtain the magnetically enhanced temporary plugging agent.

[0016] In this invention, obtaining the modified magnetic particles includes: mixing the compatibilizer with the magnetic particles, raising the temperature to 40-100°C, holding the temperature, and drying to obtain the modified magnetic particles.

[0017] In this invention, the magnetization process is performed as follows: magnetization for more than 3 seconds in a magnetizer with a magnetization voltage of 0-2000, preferably excluding 0V.

[0018] In this invention, after magnetization and optional pulverization (the temporary plugging agent) is immersed in a solution containing the elastic material, filtered out, and dried to obtain the magnetically reinforced temporary plugging agent.

[0019] A third aspect of the present invention provides the application of the magnetically reinforced temporary plugging agent in fracturing.

[0020] The endpoints and any values ​​of the ranges disclosed in this invention 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. In the following, various technical solutions can, in principle, be combined with each other to obtain new technical solutions, which should also be considered as specifically disclosed herein.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] (1) The magnetically enhanced temporary plugging agent obtained by the technical solution of the present invention has permanent magnetism. Therefore, as the fracturing fluid enters the formation fracture, when the flow rate decreases, they aggregate with each other, which strengthens the blocking and bridging of the particles in the fracture and improves the temporary plugging efficiency.

[0023] (2) The magnetically enhanced temporary plugging agent obtained by the technical solution of the present invention has magnetic properties that enable the interaction force between particles to be broken apart under high shear, without affecting the solution preparation and pipeline transportation in fracturing construction;

[0024] (3) The magnetically enhanced temporary plugging agent obtained by the technical solution of the present invention will degrade and fail under the action of water and heat in the formation for a long time. In the end, the polymer matrix degrades into small molecules, while the magnetic particles are small-diameter rigid particles that can be discharged with the backflow or formation produced fluid without affecting subsequent construction and production.

[0025] (4) Compared with ordinary unmodified biodegradable particles, the magnetically reinforced temporary plugging agent obtained by the technical solution of the present invention has a higher retention rate in the artificial crack sealing experiment, which significantly improves the efficiency of the temporary plugging material and slightly increases the sealing strength.

[0026] (5) In order to effectively seal the gaps between the temporary plugging particles and improve the sealing effect, the present invention also applies an elastic material coating to the outside of the temporary plugging particles. This coating has a low glass transition temperature, which gives it elasticity. When the particles are piled up, it can effectively seal the gaps between the particles and achieve efficient sealing. At the same time, in the high-temperature water environment of the reservoir, the coating can slowly dissolve without affecting the degradation of the temporary plugging material;

[0027] (6) The present invention modifies the surface of the temporary plugging particles with an elastic material, so that the magnetically reinforced temporary plugging agent can maintain a high retention rate and temporary plugging strength even in a low dispersion system (e.g., a dispersion system of less than 10%, or a dispersion system of less than 9% or a dispersion of less than 8%). Detailed Implementation

[0028] The features and advantages of the present invention will become clearer and more apparent from the following detailed description.

[0029] One of the objectives of this invention is to provide a magnetically enhanced temporary plugging agent, which includes an elastic coating of a temporary plugging agent matrix and modified magnetic particles dispersed within the temporary plugging agent matrix.

[0030] In a preferred embodiment, the temporary plugging agent matrix is ​​selected from biodegradable polymers.

[0031] In a further preferred embodiment, the degradable polymer is selected from one or more of the following: polyglycolic acid, polylactide, polybutylene succinate, polycaprolactone, polybutylene terephthalate, polybutylene terephthalate, polybutylene succinate, polymethyl ethylene carbonate, polyhydroxyalkanoates, or a mixture thereof or a copolymer of their structural units.

[0032] In a further preferred embodiment, the melt index of the degradable polymer is above 1 g / 10 min.

[0033] In a preferred embodiment, the modified magnetic particles are compatibilizer-modified magnetic particles.

[0034] In a further preferred embodiment, the compatibilizer is selected from at least one of epoxy compounds, silane compatibilizers, copolymers containing maleic acid or its anhydride or its amide, titanate compatibilizers, aluminate compatibilizers, zirconate esters, borate esters, and aluminum-titanium composite compatibilizers.

[0035] In a further preferred embodiment, the compatibilizer is selected from at least one of 3-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-β-(aminoethyl)-γ-aminopropylmethyldimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, and N-(β-aminoethyl)-γ-aminopropyltriethoxysilane.

[0036] In a preferred embodiment, based on 100 parts by weight of magnetic particles, the compatibilizer is 0.1%-1% by weight, preferably 0.2%-0.6% by weight, for example 0.1%, 0.2%, 0.3%, 0.4%, 0.5%, 0.6%, 0.7%, 0.8%, 0.9%, or 1% by weight.

[0037] Adding a compatibilizer can increase the bonding strength between magnetic particles and the matrix material, improve the dispersion effect of magnetic particles, increase the strength of the composite material, and reduce the impact of interfacial defects between magnetic particles and the matrix material on the mechanical properties of the material.

[0038] In a preferred embodiment, the magnetic particles are selected from at least one of ferrite, neodymium iron boron, samarium cobalt, alnico, manganese aluminum carbon, and iron chromium cobalt.

[0039] In a further preferred embodiment, the particle size of the magnetic particles is 100-800 nm, preferably 100-500 nm (more preferably excluding 100 nm), for example 150 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm or 800 nm.

[0040] Among them, since it is used as a temporary plugging agent, the particle size of the magnetic particles cannot be too large. The reasons are: (1) if the particle size is too large, the magnetic particles will settle severely in the water after the matrix material degrades, which will not be conducive to their return to the ground with the flowback fluid; (2) if the particle size is too large, it may cause blockage in the formation near the well, affecting subsequent construction.

[0041] In a preferred embodiment, the modified magnetic particles in the magnetically enhanced temporary plugging agent comprise 5 to 30 parts by weight, based on 100 parts by weight of the temporary plugging matrix, for example, 5, 8, 10, 12, 15, 18, 20, 22, 25, 28, or 30 parts by weight. Since the temporary plugging agent is used in fracturing, it first enters the wellbore with the fracturing fluid at high shear rates, and then enters the opened fractures (where the flow rate is very slow). Therefore, to adapt to this specific application scenario, the inventors, after extensive experimentation, discovered that controlling the content of the modified magnetic particles to 5 to 30 parts by weight yields superior results.

[0042] Specifically, controlling the modified magnetic particles within the aforementioned range addresses the issue of how to effectively disperse them in the liquid during fracturing operations after imparting permanent magnetism to the temporary plugging agent. Specifically, by controlling the content of magnetic particles in the composite material, the interaction forces between the temporary plugging agents are adjusted so that the interaction forces between particles can meet the following conditions: 1) During the preparation, stirring, and pipeline transportation of high-shear solutions, the particles can be dispersed by the high-shear liquid flow and enter the underground with the liquid flow; 2) When the liquid flow enters the formation fracture, the shear rate decreases, and the magnetic attraction between particles can effectively endow the particles with the ability to aggregate, helping to increase the probability of bridging and plugging, and improving the sealing effect; 3) When the degradable polymer degrades and fails under the action of water and heat, the modified magnetic particles, as small-diameter rigid particles, can be discharged with the flowback or formation produced fluid without affecting subsequent construction and production.

[0043] In a preferred embodiment, the magnetically reinforced temporary plugging agent further includes an elastic material coating covering the surface of the temporary plugging agent matrix.

[0044] In a further preferred embodiment, the glass transition temperature of the elastic material is lower than the glass transition temperature of the temporary plugging agent matrix.

[0045] In a further preferred embodiment, the elastic material is selected from materials with a glass transition temperature of 40-60°C, preferably 45-55°C, for example 40°C, 45°C, 50°C, 55°C or 60°C.

[0046] The elastic material is water-soluble at the target formation temperature (when it is polyvinyl acetate, its side groups are water-soluble after degradation at the target formation temperature).

[0047] In a preferred embodiment, the elastic material is selected from polymers with ester bonds in their side chains, such as polyvinyl acetate.

[0048] In a further preferred embodiment, the molecular weight of the elastic material is 10,000 to 100,000, preferably 15,000 to 50,000.

[0049] Most preferably, the elastic material is a polymer with side chains containing ester bonds and a molecular weight of 15,000 to 50,000 (e.g., polyvinyl acetate), and its degree of alcoholysis is 30% to 60%.

[0050] In a preferred embodiment, the elastic material coating is 1 to 10 wt%, preferably 3 to 5 wt%, based on 100 wt% of the temporary plugging agent matrix and the modified magnetic particles.

[0051] In a preferred embodiment, the magnetically enhanced temporary plugging agent further includes an additive.

[0052] In a further preferred embodiment, the adjuvant is selected from at least one of antioxidants, stabilizers, and anti-hydrolysis agents.

[0053] In a further preferred embodiment, the antioxidant is selected from at least one of phosphate esters and hindered phenolic compounds; and / or, the stabilizer is selected from at least one of dibutyltin maleate, dibutyltin dilaurate, dibutyltin maleate laurate, di-n-octyltin maleate, di-n-octyltin dilaurate, and bis(isooctyl thioglycolate) di-n-octyltin; and / or, the anti-hydrolysis agent is selected from bis(2,6-diisopropylphenyl)carbodiimide.

[0054] Stabilizers primarily improve thermal stability at high temperatures and enhance stability during processing. Anti-hydrolysis agents mainly delay degradation. While biodegradable polymers are ultimately meant to degrade, faster degradation isn't always better; anti-hydrolysis agents are added to regulate the degradation rate.

[0055] In a preferred embodiment, based on 100 parts by weight of the temporary plugging agent matrix, the antioxidant is 0.1%-1% by weight, preferably 0.2%-0.6% by weight; the stabilizer is 0.001%-0.1% by weight, preferably 0.01%-0.05% by weight; and the anti-hydrolysis agent is 0.1%-1% by weight, preferably 0.2%-0.6% by weight.

[0056] For example, based on 100 parts by weight of the temporary plugging agent matrix, the antioxidant is 0.1%, 0.2%, 0.4%, 0.6%, or 1% by weight; the stabilizer is 0.001%, 0.005%, 0.01%, 0.02%, 0.04%, 0.06%, 0.08%, or 0.1% by weight; and the anti-hydrolysis agent is 0.1%, 0.2%, 0.4%, 0.6%, 0.8%, or 1% by weight.

[0057] In a preferred embodiment, the magnetically reinforced temporary plugging agent can be any range of values, mainly estimated based on the size range of the underground cracks, for example, a particle size of 20 to 240 mesh.

[0058] In a preferred embodiment, the magnetically enhanced temporary plugging agent is magnetic, preferably permanent magnetic.

[0059] The magnetically enhanced temporary plugging agent is a temporary plugging agent particle that has undergone magnetization treatment.

[0060] In a further preferred embodiment, magnetization is performed for more than 3 seconds in a magnetizer with a magnetization voltage of 0-2000, preferably without 0V.

[0061] Among them, permanent magnetism is formed after full magnetization.

[0062] A second objective of this invention is to provide a method for preparing the magnetically enhanced temporary plugging agent described in one objective of this invention, comprising: melt-blending and extruding the temporary plugging agent matrix, the modified magnetic particles and optionally the additives into granules, followed by magnetization and pulverization to obtain the magnetically enhanced temporary plugging agent.

[0063] In a preferred embodiment, obtaining the modified magnetic particles includes: mixing the compatibilizer with the magnetic particles, raising the temperature to 40–100°C (e.g., 40°C, 50°C, 60°C, 70°C, 80°C, 90°C, or 100°C), holding the temperature, and drying to obtain the modified magnetic particles.

[0064] In a further preferred embodiment, the mixing is carried out as follows: the compatibilizer is dispersed in an aqueous solution of alcohol, the magnetic particles are added, and the mixture is stirred.

[0065] Preferably, the alcohol is selected from C1 to C6 alkyl alcohols, such as ethanol.

[0066] In a further preferred embodiment, the heat preservation treatment is carried out for 10 to 40 hours, preferably 15 to 35 hours, for example 10 hours, 15 hours, 20 hours, 25 hours, 30 hours, 35 hours or 40 hours.

[0067] In a preferred embodiment, the extrusion is performed at 150°C to 250°C, preferably 175°C to 240°C, for example 150°C, 160°C, 180°C, 200°C, 220°C, 240°C or 250°C.

[0068] For example, when the biodegradable matrix is ​​polyglycolic acid, the extrusion temperature is 220°C to 240°C, and when the biodegradable matrix is ​​polylactide, the extrusion temperature is 175°C to 200°C.

[0069] In a preferred embodiment, the extrusion is performed inside an extruder with a rotational speed of 50 rpm to 1000 rpm, preferably 100 rpm to 500 rpm, more preferably 150 rpm to 200 rpm, for example 50 rpm, 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm.

[0070] In a preferred embodiment, the magnetization process is performed as follows: magnetization for more than 3 seconds in a magnetizer with a magnetization voltage of 0-2000V.

[0071] In a preferred embodiment, the material is pulverized into 20-240 mesh particles.

[0072] In a preferred embodiment, after magnetization and optional pulverization, magnetic pretreated particles are obtained, which are then immersed in a solution containing the elastic material, filtered out, and dried to obtain the magnetically reinforced temporary plugging agent.

[0073] In a further preferred embodiment, the concentration of the elastic material solution is 5-50 wt%, preferably 10-30 wt%, for example 5 wt%, 10 wt%, 15 wt%, 20 wt%, 25 wt%, 30 wt%, 35 wt%, 40 wt%, 45 wt%, or 50 wt%.

[0074] In a further preferred embodiment, the solvent in the solution of the elastic material is an organic solvent, such as at least one of methanol, acetone, chloroform, ethyl acetate, and benzene.

[0075] The third objective of this invention is to provide the application of the magnetically enhanced temporary plugging agent described in the first objective of this invention or the magnetically enhanced temporary plugging agent described in the second objective of this invention in fracturing, specifically in the fracturing and stimulation of oil and gas reservoirs.

[0076] The magnetically enhanced temporary plugging agent of this invention possesses magnetic properties that enable the interparticle interaction forces to be dispersed and separated under high shear, without affecting solution preparation and pipeline transportation during fracturing operations. The magnetically enhanced temporary plugging agent of this invention has permanent magnetism; therefore, as the fracturing fluid enters the formation fracture, it aggregates with each other when the flow rate decreases, strengthening the plugging and bridging of particles in the fracture and improving the temporary plugging efficiency. The magnetically enhanced temporary plugging agent of this invention will degrade and fail under long-term service under the influence of formation water and heat. Ultimately, the polymer matrix degrades into small molecules, while the magnetic particles become small-diameter rigid particles that can be discharged with flowback or formation produced fluid without affecting subsequent construction and production.

[0077] Compared to ordinary unmodified biodegradable particles, the magnetically reinforced temporary plugging agent described in this invention exhibits a higher retention rate in artificial crack sealing experiments, significantly improving the efficiency of the temporary plugging agent. Furthermore, the sealing strength of the magnetically reinforced temporary plugging agent described in this invention does not decrease even when the injection amount of the temporary plugging agent is reduced.

[0078] Example

[0079] The present invention will now be described in detail with reference to specific 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. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0080] It should also be noted that the various specific technical features described in the following embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the various possible combinations will not be described separately in this invention.

[0081] Furthermore, various embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention. The resulting technical solutions are part of the original disclosure of this specification and also fall within the protection scope of the present invention.

[0082] Unless otherwise specified, the raw materials used in the examples and comparative examples are all disclosed in the prior art, such as those that can be directly purchased or prepared according to the preparation methods disclosed in the prior art.

[0083]

Example 1

[0084] Preparation of modified magnetic particles:

[0085] 0.4 parts of compatibilizer KH550 were dissolved in 20g of 95% ethanol aqueous solution to prepare a homogeneous solution. 100 parts of 100nm iron oxide magnetic particles were added and stirred evenly. The mixture was then sealed and kept at 70℃ for 24 hours and dried at 120℃ for 4 hours to prepare 100nm modified magnetic particles (the compatibilizer is only for surface treatment and will not significantly change the particle size).

[0086] Preparation of magnetically enhanced temporary plugging agent:

[0087] 100 parts by weight of polyethylene glycol, 0.3 parts by weight of pentylenetetrol di(2,4-di-tert-butylphenyl) phosphite, 0.01 parts by weight of dibutyltin maleate, 0.4 parts by weight of bis(2,6-diisopropylphenyl)carbodiimide, and 20 parts by weight of the above modified magnetic particles were melt-blended and extruded into granules. The extrusion temperature was 220℃~240℃, and the extruder speed was 350rpm. After extrusion granulation, the particles were magnetized for 4 seconds in a magnetizer with a magnetization voltage of 2000V, and then pulverized into particles between 20-240 mesh. The particles were immersed in a 20% polyvinyl acetate methanol solution for 1 minute, filtered, and dispersed on a tray. After drying with hot air at 50℃ for 30 minutes, the dried particles were collected. The adhering particles were broken up by extrusion and shredding, and the particles between 20-240 mesh were sieved as the product.

[0088]

Example 2

[0089] Preparation of modified magnetic particles:

[0090] 0.4 parts of compatibilizer KH550 were dissolved in 20g of 95% ethanol aqueous solution to prepare a homogeneous solution. 100 parts of 500nm AlNiCo alloy magnetic particles were added and stirred evenly. The mixture was then sealed and kept at 70℃ for 24 hours and dried at 120℃ for 4 hours to prepare 500nm modified magnetic particles.

[0091] Preparation of magnetically enhanced temporary plugging agent:

[0092] 100 parts by weight of polyethylene glycol, 0.5 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite, 0.03 parts by weight of dibutyltin maleate, 0.3 parts by weight of bis(2,6-diisopropylphenyl)carbodiimide, and 30 parts by weight of the above modified magnetic particles were melt-blended and extruded into granules. The extrusion temperature was 220℃~240℃, and the extruder speed was 400rpm. After extrusion granulation, the particles were magnetized for 3 seconds in a magnetizer with a magnetization voltage of 2000V, and then pulverized into particles between 20-240 mesh. The particles were immersed in a 20% polyvinyl acetate methanol solution for 1 minute, filtered, and dispersed on a tray. After drying with hot air at 50℃ for 30 minutes, the dried particles were collected. The adhering particles were broken up by extrusion and shredding, and the particles between 20-240 mesh were sieved as the product.

[0093]

Example 3

[0094] Preparation of modified magnetic particles:

[0095] 0.4 parts of compatibilizer KH550 were dissolved in 20g of 95% ethanol aqueous solution to prepare a homogeneous solution. 100 parts of 100nm NdFeB alloy magnetic particles were added and stirred evenly. The mixture was then sealed and kept at 70℃ for 24 hours and dried at 120℃ for 4 hours to prepare 100nm modified magnetic particles.

[0096] Preparation of magnetically enhanced temporary plugging agent:

[0097] 100 parts by weight of polylactide, 0.4 parts by weight of pentylenetetrol di(2,4-di-tert-butylphenyl) phosphite, 0.02 parts by weight of dibutyltin maleate, 0.2 parts by weight of bis(2,6-diisopropylphenyl)carbodiimide, and 20 parts by weight of the above modified magnetic particles were melt-blended and extruded into granules. The extrusion temperature was 175℃~200℃, and the extruder speed was 350rpm. After extrusion granulation, the particles were magnetized for more than 3.5 seconds in a magnetizer with a magnetization voltage of 2000V, and then pulverized into particles between 20-240 mesh. The particles were immersed in a 20% polyvinyl acetate methanol solution for 1 minute, filtered, and then dispersed and spread evenly on a tray. After drying with hot air at 50℃ for 30 minutes, the dried particles were collected. The adhering particles were broken up by extrusion and shredding, and the particles between 20-240 mesh were sieved as the product.

[0098]

Example 4

[0099] Preparation of modified magnetic particles:

[0100] 0.4 parts of compatibilizer KH550 were dissolved in 20g of 95% ethanol aqueous solution to prepare a homogeneous solution. 100 parts of 500nm iron-chromium-cobalt alloy magnetic particles were added and stirred evenly. The mixture was then sealed and kept at 70℃ for 24 hours and dried at 120℃ for 4 hours to prepare 500nm modified magnetic particles.

[0101] Preparation of magnetically enhanced temporary plugging agent:

[0102] 100 parts by weight of polylactide, 0.2 parts by weight of tris(2,4-di-tert-butylphenyl) phosphite, 0.05 parts by weight of dibutyltin maleate, 0.5 parts by weight of bis(2,6-diisopropylphenyl)carbodiimide, and 30 parts by weight of the above modified magnetic particles were melt-blended and extruded into granules. The extrusion temperature was 175℃~200℃, and the extruder speed was 400rpm. After extrusion granulation, the particles were magnetized for 3 seconds in a magnetizer with a magnetization voltage of 2000V, and then pulverized into particles between 20-240 mesh. The particles were immersed in a 20wt% polyvinyl acetate methanol solution for 1 minute, filtered, and dispersed on a tray. After drying with hot air at 50℃ for 30 minutes, the dried particles were collected. The adhering particles were broken up by extrusion and shredding, and the particles between 20-240 mesh were sieved as the product.

[0103] Comparative Example 1

[0104] The process of Example 1 was repeated, except that the modified magnetic particles were not added during melt extrusion, while other conditions remained unchanged.

[0105] Comparative Example 2

[0106] The process of Example 4 was repeated, except that: (1) the modified magnetic particles were not added during melt extrusion; (2) the amount of antioxidant was 0.2 parts by weight; (3) the amount of stabilizer was 0.05 parts by weight; and (4) the amount of anti-hydrolysis agent was 0.5 parts by weight.

[0107] Comparative Example 3

[0108] The process of Example 4 was repeated, except that the amount of modified magnetic particles was changed to 40 parts by weight when preparing the magnetically enhanced temporary plugging agent, while other conditions remained unchanged.

[0109] Comparative Example 4

[0110] The process of Example 4 is repeated, except that the final polyvinyl acetate coating process is not performed when preparing the magnetically reinforced temporary plugging agent.

[0111]

Experiment Example 1

[0112] The temporary plugging agents prepared in the examples and comparative examples were used to conduct temporary plugging experiments in artificially fractured rock cores. The specific steps are as follows:

[0113] Partially hydrolyzed polyacrylamide with a molecular weight of 15-17 million (degree of hydrolysis 20%) was prepared into a 1000 ppm aqueous solution. The temporary plugging agent was dispersed in this aqueous solution and stirred to prepare a dispersion system with a temporary plugging agent content of 10%. This dispersion system was placed in a piston container equipped with a mechanical stirrer and injected into an artificially fractured core at a constant speed of 1000 rpm using a constant speed pump. The injection rate was 5 ml / min. The artificially fractured core was 10 cm long and 2.5 cm in diameter, and the fracture width was controlled to 1 mm using a copper plate. Injection continued until the maximum pressure point was reached, and the pressure was recorded as the plugging strength. When the pressure exceeded the maximum plugging pressure, the temporary plugging particles failed, and the pressure began to drop, the valve was immediately closed, and injection was stopped. The produced fluid was collected and filtered to separate the temporary plugging agent, and the amount of outflowing temporary plugging agent was recorded. The uninjected dispersion system was removed and filtered to calculate the remaining temporary plugging agent. The difference between the initial amount and the remaining amount was the injected temporary plugging agent. The retention rate of the temporary plugging agent is calculated as the ratio of the difference between the injected and outflowing temporary plugging agent to the injected temporary plugging agent. The results are shown in Table 1.

[0114] The samples prepared in the examples and comparative examples were each configured into a 10% aqueous dispersion system and incubated at 90°C in a sealed environment for 48 hours. The particles lost their mechanical properties and crumbled into fine powder. The degradation products had no sealing ability for cracks and did not affect subsequent construction and production. However, if the magnetic particles used have a particle size greater than 800 nm, after the temporary plugging agent degrades, the magnetic particles larger than 800 nm will settle significantly, affecting subsequent construction and production.

[0115] Table 1. Retention rate and temporary plugging strength of the temporary plugging agents prepared in the examples and comparative examples in a 10% dispersion system.

[0116] Retention rate % sealing strength MPa Example 1 86.2 41.4 Example 2 90.1 42.6 Example 3 85.4 32 Example 4 91.6 32.3 Comparative Example 1 62.1 40.7 Comparative Example 2 59.2 31.5 Comparative Example 3 ----- ---- Comparative Example 4 90.7 31

[0117] As can be seen from Table 1, the magnetically enhanced temporary plugging agent increases the attraction between particles. Therefore, in the temporary plugging experiment, the retention rate of the temporary plugging agent in the crack is significantly improved. The lowest retention rate of the sample in the example is 23% higher than that of the control sample 1, which proves that the system obtained by the present invention effectively improves the efficiency of the temporary plugging agent.

[0118] Comparative Example 3 has a higher magnetic particle content than Example 4. At a mechanical stirring speed greater than 1000 rpm, the magnetic particles agglomerate and cannot be effectively dispersed in the solution. Therefore, they cannot be effectively injected, cannot temporarily plug the cracks, and cannot obtain effective data.

[0119] Comparative Example 4 did not introduce a polyvinyl acetate coating in the technical solution of the present invention. Therefore, the gaps between the temporarily plugging particles could not be effectively sealed and filled, and the sealing strength was affected to a certain extent.

[0120] The above data confirms the effectiveness and superiority of the technical solution of this invention, which can enhance the efficiency of temporary plugging particles in fracturing operations and provide a more efficient solution for formation stimulation and oil and gas field production enhancement.

[0121]

Experiment Example 2

[0122] The temporary plugging experiment described in [Experimental Example 1] was repeated, except that a dispersion system with a temporary plugging agent content of 8% was prepared. The results are shown in Table 2 below.

[0123] Table 2. Retention rate and temporary plugging strength of the temporary plugging agents prepared in the examples and comparative examples in an 8% dispersion system.

[0124] Retention rate % sealing strength MPa Example 1 85.8 41.2 Example 2 89.8 41.7 Example 3 85.3 31.8 Example 4 91.2 31.9 Comparative Example 1 11.4 0.0 Comparative Example 2 13.2 0.0 Comparative Example 3 ----- ---- Comparative Example 4 89.7 27.4

[0125] As shown in Table 2, when the content of the temporary plugging agent is reduced to 8%, the sample of the example still has a high retention rate and plugging strength, while Comparative Examples 1 and 2 cannot effectively establish a pressure difference, with a plugging strength of 0 and a retention rate of only 11.4% and 13.25%, respectively, which cannot effectively plug the crack. Comparative Example 4 has a higher retention rate due to the reinforcement of magnetic particles, but due to the absence of a coating, the plugging effect is reduced to some extent, and the reduction is more significant compared to the data with a temporary plugging particle content of 10%.

[0126] The present invention has been described in detail above with reference to specific embodiments and exemplary examples; however, these descriptions should not be construed as limiting the present invention. Those skilled in the art will understand that various equivalent substitutions, modifications, or improvements can be made to the technical solutions and embodiments of the present invention without departing from the spirit and scope of the invention, and all such modifications and improvements fall within the scope of the present invention. The scope of protection of the present invention is defined by the appended claims.

Claims

1. A magnetically enhanced temporary plugging agent, comprising a plugging agent matrix and modified magnetic particles dispersed within the plugging agent matrix, wherein the modified magnetic particles are magnetic particles modified with a compatibilizer, and the compatibilizer is selected from silane compatibilizers; based on 100 parts by weight of magnetic particles, the compatibilizer is 0.1%-1% by weight; the magnetic particles are selected from at least one of ferrite, neodymium iron boron, samarium cobalt, alnicotinic cobalt, manganese aluminum carbon, and iron chromium cobalt, and the particle size of the magnetic particles is 100-800 nm; in the magnetically enhanced temporary plugging agent, based on 100 parts by weight of the plugging agent matrix, the modified magnetic particles are 5-30 parts by weight.

2. The magnetically reinforced temporary plugging agent according to claim 1, characterized in that, The temporary plugging agent matrix is ​​selected from biodegradable polymers.

3. The magnetically reinforced temporary plugging agent according to claim 1, characterized in that, The temporary plugging agent matrix is ​​selected from one or more of the following: polyglycolic acid, polylactide, polybutylene succinate, polycaprolactone, polybutylene terephthalate, polybutylene terephthalate, polybutylene succinate, polymethyl ethylene carbonate, polyhydroxy fatty acid ester, or a mixture thereof, or a copolymer of their structural units.

4. The magnetically enhanced temporary plugging agent according to claim 1, characterized in that, Based on 100 parts by weight of magnetic particles, the compatibilizer is 0.2%-0.6% by weight.

5. The magnetically reinforced temporary plugging agent according to claim 1, characterized in that, The magnetic particles have a particle size of 100~500nm.

6. The magnetically enhanced temporary plugging agent according to any one of claims 1 to 5, characterized in that, The magnetically reinforced temporary plugging agent further includes an elastic material coating on the surface of the temporary plugging agent matrix. The elastic material is selected from polyvinyl acetate, and the elastic material coating is 1~10 wt% based on the temporary plugging agent matrix and the modified magnetic particles being 100 wt%.

7. The magnetically reinforced temporary plugging agent according to claim 6, characterized in that, Based on the fact that the temporary plugging agent matrix and the modified magnetic particles are 100 wt%, the elastic material coating is 3~5 wt%.

8. The magnetically reinforced temporary plugging agent according to claim 6, characterized in that, The magnetically enhanced temporary plugging agent further includes additives.

9. The magnetically enhanced temporary plugging agent according to claim 8, characterized in that, The adjuvant is selected from at least one of antioxidants, stabilizers, and anti-hydrolysis agents.

10. The magnetically reinforced temporary plugging agent according to claim 9, characterized in that, Based on 100 parts by weight of the temporary plugging agent matrix, the antioxidant is 0.1%-1% by weight, the stabilizer is 0.001%-0.1% by weight, and the anti-hydrolysis agent is 0.1%-1% by weight.

11. A method for preparing the magnetically enhanced temporary plugging agent according to any one of claims 1 to 10, comprising: The temporary plugging agent matrix and the modified magnetic particles are melt-blended, extruded, and granulated, and then magnetized to obtain the magnetically enhanced temporary plugging agent.

12. The preparation method according to claim 11, characterized in that, include: The temporary plugging agent matrix, the modified magnetic particles, and the additives are melt-blended, extruded, and granulated, then magnetized and pulverized to obtain the magnetically enhanced temporary plugging agent.

13. The preparation method according to claim 11, characterized in that, The modified magnetic particles are obtained by: mixing the compatibilizer with the magnetic particles, heating to 40~100℃, keeping at that temperature, and drying to obtain the modified magnetic particles.

14. The preparation method according to claim 11, characterized in that, The magnetization process is performed as follows: magnetization for more than 3 seconds in a magnetizer with a magnetization voltage of 0-2000V.

15. The preparation method according to any one of claims 12 to 14, characterized in that, After magnetization and pulverization, the mixture is immersed in a solution containing an elastic material, filtered, and dried to obtain the magnetically enhanced temporary plugging agent.

16. The application of a magnetically reinforced temporary plugging agent according to any one of claims 1 to 10, or the application of a magnetically reinforced temporary plugging agent according to any one of claims 11 to 15, in fracturing.