An intelligent dissolvable bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism and a preparation method thereof

Abstract

The application relates to the technical field of oil and gas downhole tools, in particular to an intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual-triggering mechanism and a preparation method thereof. The intelligent soluble bridge plug comprises a base body, a pH-sensitive coating and an electromagnetic response material layer, wherein the inside of the base body is provided with a through channel; the pH-sensitive coating is coated on the outer surface of the base body, and the electromagnetic response material layer is deposited on the surface of the through channel. Through the composite design of the pH-sensitive coating (such as polyacrylic acid) and the electromagnetic response material (such as Fe3O4 doped magnesium alloy), the dual-triggering degradation of the downhole environment is realized.

Description

Technical Field

[0001] This invention relates to the field of downhole tools technology for oil and gas wells, and in particular to an intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism, and its preparation method. Background Technology

[0002] Dissolvable bridge plugs are widely used in multi-stage fracturing operations. Their main function is to temporarily isolate the wellbore during fracturing, and they decompose naturally through chemical or physical degradation after the operation is complete, eliminating the need for drilling and thus reducing operating costs and downhole residual risks. With the growth of global energy demand and the deepening of unconventional oil and gas development, soluble bridge plug technology is of great significance in improving development efficiency and reducing environmental impact.

[0003] Currently, the core technologies for soluble bridge plugs focus on the research and development of soluble materials, optimization of degradation mechanisms, and adaptability to downhole environments. The degradation time of existing chemically degradable and polymer-based soluble bridge plugs is significantly affected by fluctuations in the downhole environment (such as pH and temperature), making it difficult to achieve precise and controllable degradation under complex well conditions such as high temperature and pressure, and acidic well fluids, leading to delays or premature failure in fracturing operations. Existing trigger-type bridge plugs rely on a single chemical triggering mechanism (such as acidic well fluids), which is prone to false triggering or failure under unstable well fluid pH or complex geological conditions, failing to meet the degradation requirements of varying well conditions. Existing bridge plugs lack remote control capabilities, requiring additional chemical injection or downhole operations, increasing operating costs and safety risks, and the degradation products may pollute the downhole environment.

[0004] The magnesium alloy bridge plug described in US Patent 20170191341A1 exhibits significant variations in degradation time (3-30 days) under different well conditions, potentially leading to delays or premature failure in fracturing operations. Polymer-based bridge plugs are highly susceptible to degradation rates influenced by downhole temperature and pH. Under high temperature and pressure (>150°C, >70 MPa) or complex geological conditions, they may fail or degrade too slowly, impacting operational efficiency and resulting in low degradation control precision. The trigger-type bridge plugs described in US Patent 20220178222A1 often rely on a single chemical trigger (such as in acidic environments). Due to the limitations of their single trigger mechanism, they are easily disrupted in complex downhole environments. For example, fluctuations in well fluid pH may cause false triggering or failure of the coating, making them unsuitable for varying well conditions.

[0005] Therefore, there is an urgent need to develop a precise and controllable degradation time that can adapt to complex environments such as high temperature and high pressure and acidic well fluids, as well as low-cost and environmentally friendly degradation products and remote or intelligent operation to reduce bridge plugs in downhole operations, so as to meet the precise control requirements under complex well conditions. Summary of the Invention

[0006] To address the above problems, this invention provides an intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism, and its preparation method.

[0007] This invention provides the following technical solution:

[0008] This invention provides an intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism. The intelligent soluble bridge plug includes a substrate, a pH-sensitive coating, and an electromagnetic response material layer, wherein the substrate has a through channel inside.

[0009] A pH-sensitive coating is applied to the outer surface of the substrate, and an electromagnetically responsive material layer is deposited on the surface of the through-channel.

[0010] Furthermore, the matrix is ​​a magnesium alloy, the composition of which includes magnesium, zinc, aluminum and calcium, wherein the mass fraction of each component is 95.5%-97% magnesium, 1.5%-2.0% zinc, 1.0%-1.5% aluminum and 0.2%-0.5% calcium.

[0011] Furthermore, the diameter of the substrate is 80-120 mm, and the length is 300-400 mm; and / or,

[0012] The diameter of the through-channel within the matrix is ​​10-20 mm; and / or,

[0013] The outer wall thickness of the substrate is 10-15 mm.

[0014] Furthermore, the pH-sensitive coating comprises a polymer and a crosslinking agent, wherein,

[0015] The polymers include one or more of polyacrylic acid, polymethacrylic acid, or polyacrylic acid-acrylamide copolymers;

[0016] The crosslinking agent includes one or more of N,N'-methylenebisacrylamide, divinylbenzene, or ethylene glycol dimethacrylate.

[0017] Furthermore, the thickness of the pH-sensitive coating is 80-200 μm.

[0018] Furthermore, the electromagnetic response material layer comprises Fe3O4 nanoparticles and magnesium alloy, wherein, by mass parts,

[0019] The Fe3O4 nanoparticles account for 6%-15% of the total mass, with the remainder being magnesium alloy.

[0020] Furthermore, the Fe3O4 nanoparticles have a particle size of 20-30 nm.

[0021] Furthermore, the thickness of the electromagnetic response material layer is 0.5-2 mm.

[0022] Furthermore, the intelligent soluble bridge plug also includes a sealing element, a first anchoring mechanism, and a second anchoring mechanism, wherein,

[0023] The first anchoring mechanism, the sealing element, and the second anchoring mechanism are sequentially arranged on the outer surface of the substrate.

[0024] Furthermore, the first and second anchoring mechanisms are made of the same magnesium alloy as the base material; and / or,

[0025] The first anchoring mechanism and the second anchoring mechanism are connected to the base.

[0026] The outer diameter of the first anchoring mechanism and the second anchoring mechanism is 2-5 mm larger than the outer diameter of the base.

[0027] Furthermore, the first and second anchoring mechanisms are magnesium alloy clips; the surface of the magnesium alloy clips is coated with an anti-corrosion coating.

[0028] Furthermore, the anti-corrosion coating is composed of polyurea or epoxy resin, and / or...

[0029] The thickness of the anti-corrosion coating is 5-15μm.

[0030] Furthermore, the sealing element is adhered to the outer surface of the substrate, contacting the wellbore or casing to form a seal; and / or,

[0031] The sealing element is an annular elastomer with a thickness of 5-10 mm.

[0032] Furthermore, the components of the cyclic elastomer include polyether polyol, isocyanate and silane coupling agent, wherein the mass fraction of each component is 60%-70% polyether polyol, 20%-30% isocyanate and 0.5%-1.0% silane coupling agent.

[0033] The method for preparing the smart soluble bridge plug based on the dual triggering mechanism of pH-sensitive coating and electromagnetic as described above is also provided.

[0034] Weigh magnesium ingots, zinc granules, aluminum granules, and calcium granules, place them in a furnace, introduce inert gas, heat to 700℃-740℃ for melting, stir for 30-60 minutes, let stand, filter, pour into a steel mold for casting, and machine on a lathe to obtain the matrix;

[0035] A pH-sensitive coating is sprayed onto the outer surface of the substrate, and an electromagnetically responsive material layer is deposited on the surface of the through-channel inside the substrate.

[0036] Furthermore, a first anchoring mechanism, a sealing element, and a second anchoring mechanism are sequentially connected to the outer surface of the substrate after the pH-sensitive coating is sprayed.

[0037] The technical effects and advantages of this invention are as follows:

[0038] This invention proposes an intelligent soluble bridge plug based on a dual triggering mechanism of pH and electromagnetics. Through the composite design of pH-sensitive coating (such as polyacrylic acid) and electromagnetically responsive material (such as Fe3O4-doped magnesium alloy), dual-triggered degradation in the downhole environment is achieved.

[0039] (1) Dual triggering improves control accuracy: pH-sensitive coating responds to acidic well fluid, and electromagnetic response material accelerates degradation through external signals, overcoming the limitations of a single triggering mechanism.

[0040] (2) Adapting to complex well conditions: The bridge plug maintains its mechanical strength in high temperature, high pressure and acidic environment, and the degradation time can be adjusted according to well conditions and signals.

[0041] (3) Intelligent and remote operation: Electromagnetic triggering allows for remote control, reducing the number of downhole operations.

[0042] (4) Environmental protection and cost-effectiveness: The degradation products are non-toxic, the preparation process is compatible with existing technologies, and it is suitable for large-scale production.

[0043] This invention achieves the following objectives through a composite design of a pH-sensitive coating and an electromagnetically responsive material: Under complex well conditions such as high temperature, high pressure, and acidic well fluids, the pH-sensitive coating responds to the acidic environment of the well fluid, while the electromagnetically responsive material responds to external electromagnetic signals, enabling precise control of degradation time. The synergistic effect of this dual triggering mechanism improves the reliability and anti-interference capability of the degradation process, adapting to the variability of the downhole environment. Remote electromagnetic triggering is achieved, reducing the number of downhole operations and lowering operating costs, while ensuring that the degradation products are non-toxic and reducing environmental pollution.

[0044] Other features and advantages of the invention will be set forth in the following description, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description and the drawings. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of an intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism provided in an embodiment of this application;

[0046] Figure 2 This is a schematic diagram of the intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism provided in the embodiments of this application;

[0047] Figure 3a This is a partial schematic diagram of the connection between the magnesium alloy latch and the substrate provided in the embodiments of this application;

[0048] Figure 3b This is a cross-sectional schematic diagram of the connection between the magnesium alloy latch and the substrate provided in the embodiments of this application;

[0049] Figure 3c This is a front view of the magnesium alloy chuck provided in the embodiments of this application;

[0050] Figure 4a This is a front view of the sealing element provided in an embodiment of this application;

[0051] Figure 4b This is a cross-sectional schematic diagram of the connection between the sealing element and the substrate provided in the embodiments of this application.

[0052] In the figure: 1. Substrate; 2. Electromagnetic response material layer; 3. First anchoring mechanism; 3-1. Outer surface of the first anchoring mechanism; 4. Second anchoring mechanism; 5. Sealing element; 6. pH sensitive coating; 7. Connection; 8. Anti-corrosion coating. Detailed Implementation

[0053] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0054] To address the shortcomings of existing technologies, this invention discloses a smart soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual-trigger mechanism, such as... Figure 1 and 2 As shown, the intelligent soluble bridge plug includes a substrate 1, a pH-sensitive coating 6, and an electromagnetically responsive material layer 2, wherein the substrate 1 has a through channel inside;

[0055] A pH-sensitive coating 6 is applied to the outer surface of the substrate 1, and an electromagnetically responsive material layer 2 is deposited on the surface of the through-channel.

[0056] In one specific embodiment of the present invention, the matrix 1 is a magnesium alloy, the components of which include magnesium, zinc, aluminum and calcium, wherein the mass fraction of each component is 95.5%-97% magnesium, 1.5%-2.0% zinc, 1.0%-1.5% aluminum and 0.2%-0.5% calcium.

[0057] like Figure 1 and 2 As shown, the substrate 1 is cylindrical with a diameter of 80-120 mm and a length of 300-400 mm. The diameter of the internal through-channel is 10-20 mm, preferably 15 mm.

[0058] The substrate surface roughness Ra < 0.5 μm, grain size 20-40 μm, outer wall thickness 10-15 mm, and an electromagnetic response material layer 2 deposited on the inner surface of the channel.

[0059] The matrix provides mechanical support, with a compressive strength >300 MPa, and withstands high downhole temperatures and pressures (>150°C, >70 MPa). Trace element doping regulates the degradation rate (6-24 hours), synergizing with pH and electromagnetic triggering. Calcium doping refines the grain size and reduces Mg(OH)₂ precipitation (<0.5 g / L). Channels (10-20 mm, preferably 15 mm) form fracturing fluid transport paths (flow rate 100-500 mL / s), supporting electromagnetic material deposition.

[0060] Compared to commercially available magnesium alloys (such as AZ31, Al 3%-9%, degradation takes several weeks, precipitation 1-2 g / L), the matrix of this invention, through low Al (1.0%-1.5%) and Ca (0.2%-0.5%) doping, has a degradation time deviation of <±10%, which is superior to traditional bridge plugs (such as US Patent US20170191341A1, deviation ±50%). The channel diameter range of this application is adaptable to various well conditions, which is superior to fixed designs (such as Chinese Patent CN113863889A, 12 mm). In this application, zinc and aluminum solid solution strengthening, and calcium grain refinement slow down corrosion (Mg → Mg). 2+ + 2e - ).

[0061] In one specific embodiment of the present invention, a pH-sensitive coating 6 is coated on the outer surface of the substrate 1. The components of the pH-sensitive coating 6 include a polymer and a crosslinking agent, wherein the polymer includes one or more of polyacrylic acid, polymethacrylic acid, or polyacrylic acid-acrylamide copolymer.

[0062] The crosslinking agent includes one or more of N,N'-methylenebisacrylamide, divinylbenzene, and ethylene glycol dimethacrylate.

[0063] For example, polyacrylic acid (PAA, molecular weight 50,000-80,000, mass fraction ≥98%) is used, with the addition of crosslinking agent N,N'-methylenebisacrylamide. Other crosslinking agents such as divinylbenzene or ethylene glycol dimethacrylate (0.5%-1.0%, preferably 0.5%) can also be selected. The carboxylation of PAA leads to polymer dissolution, and the crosslinking agent forms a network to improve durability.

[0064] The pH-sensitive coating 6, applied to the outer surface of the substrate, is a dense film with a roughness Ra < 0.5 μm. The dense film has a thickness of 80-200 μm, preferably 100-150 μm. The roughness can be measured using an atomic force microscope (AFM) or a surface roughness meter, and the coating thickness can be measured using a scanning electron microscope or a thickness gauge. The pH-sensitive coating is in external contact with the well fluid.

[0065] For example, in acidic well fluids (pH < 6), the pH-sensitive coating 6 dissolves within 2 hours, exposing the magnesium alloy substrate and triggering the first stage of the dual-trigger mechanism. In neutral or alkaline well fluids (pH ≥ 6), the coating remains stable for over 48 hours, preventing premature degradation of the substrate. A crosslinking agent enhances the adhesion between the coating and the substrate (> 5 MPa), ensuring durability under downhole conditions. Compared to conventional chemical coatings (such as US Patent US20220178222A1, with a response deviation of ±30%), the pH-sensitive coating of this invention has a response deviation of < ± 5%, improving trigger reliability by approximately 25%.

[0066] In one specific embodiment of the present invention, the electromagnetic response material layer 2 comprises Fe3O4 nanoparticles and a magnesium alloy, wherein, by mass percentage, the Fe3O4 nanoparticles account for 6%-15%, and the remainder is magnesium alloy. Exemplarily, the Fe3O4 nanoparticles have a particle size of 20-30 nm, and the magnesium alloy is doped with 6%-15% (preferably 8%-12%), the same composition as the matrix. The thickness of the electromagnetic response material layer is 0.5-2 mm, preferably 1-1.5 mm. The Fe3O4 is uniformly dispersed and metallurgically bonded to the inner surface of the matrix channels. The hysteresis loss of Fe3O4 generates heat, accelerating the corrosion of the magnesium alloy.

[0067] Fe3O4 is deposited on the inner wall of the through-channel of the substrate, and is located on the inner and outer sides of the substrate, respectively, separated by the substrate wall thickness (10-15 mm).

[0068] Under an alternating electromagnetic field (frequency 10-100 kHz, preferably 20-50 kHz; intensity 0.1-0.5 T, preferably 0.2 T), Fe3O4 generates heat through the magnetocaloric effect, causing the local temperature of the inner wall and surrounding area of ​​the matrix channel to rise by 30-50°C from the downhole ambient temperature (100-150°C) to 130-200°C (preferably 160-200°C). This temperature rise significantly accelerates the degradation of the magnesium alloy matrix (6-24 hours, deviation <±10%), constituting a second trigger and supporting remote control (response time <1 hour).

[0069] Electromagnetic triggering is achieved through an alternating electromagnetic field generator. An electromagnetic field with a frequency of 20-50 kHz and an intensity of 0.1-0.3 T is applied to the electromagnetically responsive material layer (Fe3O4 mass fraction 6%-15%), generating a magnetocaloric effect and raising the temperature by 30-50°C, accelerating the degradation of the substrate, sealing elements, and slips. The generator is delivered to the vicinity of the bridge plug (0.5-1 m) via cable or drill pipe, and the field is applied continuously for 5-30 minutes. Remote control is supported, and the false triggering rate is <5%. Compared to traditional electromagnetic applications (such as Chinese patent CN116291360A, which only transmits signals), this invention directly triggers degradation through the Fe3O4 magnetocaloric effect, improving efficiency by 80%.

[0070] In one specific embodiment of the present invention, the intelligent soluble bridge plug further includes a sealing element 5, a first anchoring mechanism 3, and a second anchoring mechanism 4, wherein the first anchoring mechanism 3, the sealing element 5, and the second anchoring mechanism 4 are sequentially disposed on the outer surface of the substrate 1. Specifically, the first anchoring mechanism 3 and the second anchoring mechanism 4 are connected to both ends of the outer surface of the substrate 1; the sealing element 5 is adhered to the outer surface of the middle portion of the substrate 1, and the first anchoring mechanism 3 and the second anchoring mechanism 4 are located on both sides of the sealing element 5. Exemplarily, the connection method between the first anchoring mechanism 3 and the second anchoring mechanism at both ends of the outer surface of the substrate 1 can be a fixed connection or a detachable connection, and the connection method is not limited to threaded connection, insertion, etc.

[0071] For example, such as Figures 3a-3c As shown, the first anchoring mechanism 3 and the second anchoring mechanism 4 of the present invention are identical, and the outer side is coated with an anti-corrosion coating similar to epoxy resin. For example, both the first anchoring mechanism 3 and the second anchoring mechanism 4 are serrated magnesium-aluminum alloy clips. The outer side of the first anchoring mechanism 3 and the second anchoring mechanism 4 is coated with an anti-corrosion coating similar to epoxy resin, and then connected to the substrate at both ends via threads. A pH-sensitive coating 6 is sprayed on the outer surface of the substrate 1, but does not include the connection point 7 between the substrate and the first anchoring mechanism or the second anchoring mechanism, so as not to affect the connection accuracy between the first anchoring mechanism 3 or the second anchoring mechanism 4 (serrated magnesium-aluminum alloy clips) and the substrate 1.

[0072] In one specific embodiment of the present invention, the components of the first anchoring mechanism 3 and the second anchoring mechanism 4 are the same as those of the base; and / or, the outer diameter of the first anchoring mechanism 3 and the second anchoring mechanism 4 is 2-5 mm larger than the outer diameter of the base.

[0073] For example, the first anchoring mechanism 3 and the second anchoring mechanism 4 are magnesium alloy clips; the magnesium alloy clips have the same composition as the substrate, namely Mg 95.5%-97%, Zn 1.5%-2.0%, Al 1.0%-1.5%, and Ca 0.2%-0.5%. The outer diameter of the magnesium alloy clips is 2-5 mm larger than that of the substrate, preferably 3 mm. An anti-corrosion coating is sprayed onto the surface of the magnesium alloy clips. The anti-corrosion coating consists of polyurea or epoxy resin, with a thickness of 5-15 μm, preferably 10 μm.

[0074] The surface of the magnesium alloy clip is coated with an anti-corrosion coating 8, preferably an epoxy anti-corrosion coating.

[0075] like Figure 3c As shown, the first anchoring mechanism 3 and the second anchoring mechanism 4 have the same structure. The outer surface 3-1 of the first anchoring mechanism has a serrated structure, the magnesium alloy clasp has a serrated structure, the inner surface has threads (pitch 1-2 mm), the compressive strength is >300 MPa, and the anchoring force is >100 kN.

[0076] The magnesium alloy slips are fixed to both ends of the base by threaded connection, and the serrated outer surface engages with the well wall to achieve anchoring.

[0077] Magnesium alloy slips anchor the bridge plug to the wellbore (anchoring force >100 kN), and an anti-corrosion coating protects the magnesium alloy for short-term use (6-24 hours) in acidic well fluids (pH <6). Degradability is synchronized with the substrate (6-24 hours), avoiding residue and superior to traditional ceramic slips (non-degradable, requiring drilling and grinding removal). Compared to ceramic slips, the magnesium alloy slips of this invention have a compressive strength >300 MPa, meeting downhole pressure (70 MPa), and degrade synchronously, reducing operating costs.

[0078] like Figure 4a and 4b The sealing element 5 is bonded to the outer surface of the substrate and forms a seal in contact with the well wall or casing; the sealing element 5 is an annular elastomer with a thickness of 5-10 mm, preferably 8 mm.

[0079] The components of the cyclic elastomer include polyether polyol, isocyanate and silane coupling agent. For example, the mass fraction of each component is 60%-70% polyether polyol, preferably 65%; 20%-30% isocyanate, preferably 25%; and 0.5%-1.0% silane coupling agent, preferably 0.8%.

[0080] For example, the outer diameter of the sealing element 5 is 0.95-0.97 times the inner diameter of the sleeve, the inner diameter matches the outer diameter of the base material (80-120 mm), the elongation is >200%, and the surface roughness Ra is <1 μm.

[0081] The ring-shaped elastomer is bonded to the outer periphery of the substrate using an adhesive (possibly with a pH-sensitive coating) and forms a seal with the wellbore or casing. A silane coupling agent (such as KH-550, 0.8%), or alternatively KH-560, can be used. Adhesives, including silane coupling agents, epoxy resins, and other adhesives, bond the ring-shaped elastomer to the outer surface of the substrate.

[0082] For example, the bonding method is as follows: Spray a silane coupling agent (ethanol solution, 1%) onto the substrate (magnesium alloy, outer diameter 100 mm, possibly with a 120 μm pH-sensitive coating), dry (90°C, 30 minutes), place it in a hot press, heat to 120°C, apply 2 MPa pressure, and hold for 45 minutes to bond the polyurethane to the outer wall of the substrate.

[0083] The process involves chemical reactions, in which the -Si-OH of silane forms Si-O-Mg (or Si-OC and PAA) bonds with the matrix, and forms hydrogen bonds or amide bonds with the -OH of polyurethane. The effect achieved is that the polyurethane is firmly bonded and, after expansion, fits the sleeve (inner diameter 120 mm).

[0084] In this embodiment, sealing element 5 ensures segmented sealing in the well (pressure resistance >70 MPa), while the silane coupling agent enhances adhesion (>2 MPa) and acid resistance (pH <6, corrosion resistance improved by 30%). Under acidic well fluids (pH <6) and high temperatures (100-150°C), it degrades synchronously with the matrix via ester bond hydrolysis (6-24 hours), avoiding wellbore residue. Compared to traditional soluble rubber, the polyurethane of this invention, optimized with a silane coupling agent, improves acid resistance and adhesion by 30%, with degradation time precisely matched to the matrix (6-24 hours).

[0085] This invention also provides a method for preparing a smart soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism. This method focuses on realizing the dual triggering mechanism of pH and electromagnetics, integrating the processes of the magnesium alloy substrate 1, the pH-sensitive coating 6, and the electromagnetically responsive material layer 2 to ensure synergistic performance.

[0086] The method includes:

[0087] Weigh magnesium ingots, zinc granules, aluminum granules, and calcium granules, place them in a furnace, introduce inert gas, heat to 700℃-740℃ for melting, stir for 30-60 minutes, let stand, filter, pour into a steel mold for casting, and machine on a lathe to obtain the matrix;

[0088] A pH-sensitive coating 6 is sprayed onto the outer surface of the substrate 1, and an electromagnetically responsive material layer is deposited on the surface of the through-channel inside the substrate 1.

[0089] A first anchoring mechanism, a sealing element, and a second anchoring mechanism are sequentially connected to the outer surface of the substrate after the pH-sensitive coating is sprayed.

[0090] In a specific embodiment of the present invention, (1) preparation of magnesium alloy matrix

[0091] Materials: Magnesium (95.5%-97%), Zinc (1.5%-2.0%), Aluminum (1.0%-1.5%), Calcium (0.2%-0.5%).

[0092] Process steps:

[0093] High-purity magnesium ingots (purity ≥99.9%) are melted in a vacuum induction furnace with zinc, aluminum, and calcium granules at 650-700°C (preferably 680°C) under argon protection (0.01-0.05 MPa) and stirred for 15-30 minutes (preferably 20 minutes). A billet is formed by pressure casting (0.5-1 MPa, preferably 0.8 MPa) and cooled at 10-20°C / s (preferably 15°C / s). The billet is then heat-treated at 400-450°C (preferably 420°C) for 1-2 hours (preferably 1.5 hours) and cooled at 5-10°C / min (preferably 8°C / min). The substrate (diameter 80-120 mm, length 300-400 mm) is CNC machined, channels (10-20 mm, preferably 15 mm) are drilled, and polished to Ra < 0.5 μm. The outer surfaces at both ends are threaded and matched with the annular slips of the anchoring mechanism described later for threaded suspension connection.

[0094] The magnesium alloy prepared by this invention ensures that the degradation rate matches the triggering mechanism, and the channel interior supports Fe3O4 deposition. Precise doping and heat treatment outperform commercially available alloys (such as AZ31, with a degradation deviation of ±50%), and the degradation time deviation is <±10%. Doping and heat treatment optimize the crystal structure and regulate the corrosion rate.

[0095] (2) Preparation of electromagnetic response material layer

[0096] Material:

[0097] Fe3O4 (6%-15%, preferably 8%-12%), magnesium alloy (same as matrix).

[0098] Process steps:

[0099] Fe3O4 was synthesized by chemical coprecipitation: FeCl3·6H2O and FeCl2·4H2O (molar ratio 2:1) were dissolved in deionized water, and the pH was adjusted to 9-11 (preferably 10) with NaOH. The mixture was stirred at 70-90°C (preferably 80°C) for 0.5-2 hours (preferably 1 hour), followed by magnetic separation and drying. Fe3O4 was then mixed with magnesium alloy powder (particle size 50-100 μm) by ball milling at 200-300 rpm (preferably 250 rpm) for 3-6 hours (preferably 4 hours). The mixture was then laser cladding deposited onto the inner surface of the channel at a power of 1-2 kW (preferably 1.5 kW) and a speed of 5-10 mm / s (preferably 8 mm / s) to achieve a layer thickness of 0.5-2 mm (preferably 1-1.5 mm).

[0100] The magnetocaloric effect of Fe3O4 accelerates corrosion, and cladding forms a metallurgical bond. Fe3O4 supports electromagnetic triggering, and laser cladding ensures bonding with the substrate (adhesion >10 MPa). Laser cladding achieves integrated trigger layer, which is superior to traditional processes.

[0101] (3) Preparation of pH-sensitive coating

[0102] Materials: PAA (≥98%), crosslinking agent (0.5%-1.0%).

[0103] Process steps:

[0104] PAA and crosslinking agent are dissolved in ethanol (concentration 5%-10%, preferably 8%) and stirred for 20-40 minutes (preferably 30 minutes). The solution is sprayed onto the outer wall of the soluble bridge plug using high-pressure spraying (0.1-0.3 MPa, preferably 0.2 MPa) to a thickness of 80-200 μm (preferably 100-150 μm). The solution is then dried at 80-120°C (preferably 100°C) for 0.5-2 hours (preferably 1 hour). This forms a pH-triggered coating with adhesion >5 MPa and a response time <2 hours. The pH-sensitive coating response deviation is <±5%. Spraying ensures uniformity, and the crosslinking agent enhances durability.

[0105] (3) Sealing elements

[0106] Composition and materials: biodegradable polyurethane (60%-70% polyether polyol, 20%-30% isocyanate, 0.5%-1.0% silane coupling agent), thickness 5-10 mm, preferably 8 mm.

[0107] Sealing element manufacturing process:

[0108] Polyether polyol, isocyanate, and silane coupling agent are mixed in a ratio of 65:25:0.8 and stirred at 80-100°C (preferably 90°C) for 30-60 minutes (preferably 45 minutes) to form a homogeneous prepolymer. The prepolymer is injected into a ring mold (inner diameter 80-120 mm, thickness 5-10 mm, preferably 8 mm) and hot-pressed using a hot press (heating plate temperature 150-200°C, preferably 170°C; hydraulic pressure 5-10 MPa, preferably 8 MPa) for 10-20 minutes (preferably 15 minutes). The mixture is cooled to room temperature at 10-15°C / s (preferably 12°C / s), demolded, and the edges are trimmed to ensure a surface roughness Ra < 1 μm.

[0109] Equipment: Hot press (with heating plate and hydraulic system), ring mold, stirring reactor, cooling system.

[0110] Application: To prepare annular polyurethane sealing elements with excellent elasticity (elongation >200%), adaptable to the outer periphery of the substrate, providing high-pressure sealing and supporting degradation. Place the sealing element on the outer periphery of the substrate (possibly covered with a pH-sensitive coating) and hot-press it for 45 minutes using a hot press (120°C, 2 MPa). Cool to room temperature and check adhesion (>2 MPa). Ensure the sealing element is firmly bonded (pressure resistance >70 MPa) and degrades simultaneously.

[0111] (4) Anchoring mechanism

[0112] Composition and Materials

[0113] Magnesium alloy clasps (with the same matrix composition, Mg 95.5%-97%, Zn 1.5%-2.0%, Al 1.0%-1.5%, Ca 0.2%-0.5%), with an outer diameter 2-5 mm larger than the matrix, preferably 3 mm, and the surface is sprayed with an anti-corrosion coating (thickness 5-15 μm, preferably 10 μm).

[0114] Anchoring mechanism manufacturing process:

[0115] Magnesium alloy blanks are placed on CNC lathes or milling machines and machined into serrated outer surfaces (outer diameter 2-5 mm larger than the substrate, preferably 3 mm; inner surface threaded, pitch 1-2 mm), with a surface roughness Ra < 0.8 μm. An anti-corrosion coating (5-15 μm thick, preferably 10 μm) is sprayed onto the surface of the slab using a high-pressure spraying device (spraying pressure 0.1-0.3 MPa, preferably 0.2 MPa), and dried at 80-100°C (preferably 90°C) for 1-2 hours (preferably 1.5 hours). The slabs are then screwed tightly to both ends of the substrate using threaded connections, with a thread adhesion force > 100 kN.

[0116] Equipment: CNC lathes or milling machines, high-pressure spraying equipment, drying ovens, and thread processing equipment.

[0117] Function: To prepare serrated magnesium alloy clips with a compressive strength >300 MPa, an anti-corrosion coating to enhance acid resistance (pH<6), and threaded fixing to ensure anchoring stability.

[0118] (5) Application process

[0119] The invention of the intelligent soluble bridge plug is used in downhole high temperature and high pressure environments (100-150°C, >70 MPa) and is lowered into the target well section (casing inner diameter 100-150 mm) by a delivery tool.

[0120] During deployment, the serrated outer surface of the anchoring mechanism (magnesium alloy slips) engages with the wellbore (anchoring force >100 kN), and the sealing element (biodegradable polyurethane) deforms to fit the wellbore (pressure resistance >70 MPa), achieving segmented isolation. In conventional well fluids (pH ≥ 6), the pH-sensitive coating (PAA) is stable (>48 hours), supporting the transport of fracturing fluid through the matrix channel (100-500 mL / s).

[0121] Degradation is achieved through a dual triggering process: pH triggering involves injecting acidic well fluid (pH < 6), dissolving the pH-sensitive coating (< 2 hours), exposing the substrate, hydrolyzing the ester bonds of the sealing element, and corroding the substrate and slips; electromagnetic triggering involves applying an alternating electromagnetic field (20-50 kHz, 0.2 T), heating the Fe3O4 layer by 30-50°C (reaching 160-200°C), accelerating degradation. The substrate, sealing element, and slips degrade simultaneously (6-24 hours, deviation < ± 10%), leaving no residue and ensuring unobstructed wellbore flow.

[0122] The purpose of this invention is to provide an intelligent soluble bridge plug that achieves rapid, precise, and controllable degradation (6-24 hours, deviation <±10%) through a dual triggering mechanism of pH and electromagnetic induction, eliminating the need for drilling and grinding removal, thus reducing the operating costs of oil and gas wells. It is also suitable for downhole high-temperature and high-pressure environments (>150°C, >70 MPa) and acidic well fluids (pH<6). This invention employs a magnesium alloy substrate (Mg 95.5%-97%, compressive strength >300 MPa), a pH-sensitive coating (PAA, thickness 100-150 μm), an electromagnetically responsive material layer (Fe3O4, heating 30-50°C), a biodegradable polyurethane sealing element (thickness 8 mm, pressure resistance >70 MPa), and a magnesium alloy anchoring mechanism (slips, anchoring force >100 kN) to synergistically achieve the above objectives. Compared to the prior art, this invention has the following advantages, features, and positive effects, supported by the following data:

[0123] a) Rapid and precise degradation time:

[0124] Under the triggering of acidic well fluid (pH<6) and electromagnetic field (20-50 kHz, 0.2 T), the bridge plug degrades in 6-24 hours with a deviation of <±10%, ensuring rapid wellbore unblocking after fracturing. Rapid degradation (6-24 hours) shortens the operation cycle and reduces downtime, saving approximately 50-100 hours of operation time per well.

[0125] b) High-precision dual triggering mechanism:

[0126] The synergistic effect of pH triggering (pH-sensitive coating dissolves at pH < 6, response time < 2 hours, deviation < ± 5%) and electromagnetic triggering (Fe3O4 heating at 30-50°C, response time < 1 hour) reduces the false triggering rate to < 5%. This dual triggering reduces the risk of false triggering (< 5% vs. > 30%), improves the success rate of fracturing operations, and reduces rework costs per well by approximately 20%-30%.

[0127] c) Fully biodegradable, no drilling or grinding required:

[0128] The magnesium alloy matrix, slips (compressive strength >300 MPa), and polyurethane sealing elements (elongation >200%) completely degrade within 6-24 hours, leaving no residue. Mg(OH)2 precipitation is <0.5 g / L, ensuring unobstructed wellbore flow. No drilling or grinding is required, saving approximately 50% of operating costs per well (approximately 100,000-200,000 RMB / well) and reducing environmental pollution (residue reduced by 90%).

[0129] d) Excellent adaptability to downhole environments:

[0130] The bridge plug is resistant to high temperature and pressure (>150°C, >70 MPa), the sealing element withstands pressure >70 MPa, the slip anchoring force is >100 kN, and it is suitable for acidic well fluids (pH<6). Anti-corrosion coating (slips, 10 μm) and silane coupling agent (sealing element) ensure stable function for 6-24 hours. It adapts to complex downhole environments (pH 2-6, >150°C), improving the success rate of operations by 15%-20%, and is suitable for deep wells and acidic reservoirs.

[0131] e) Highly efficient remote control capabilities:

[0132] Electromagnetic triggering activates the Fe3O4 layer through an external electromagnetic field (20-50 kHz, 0.2 T), raising the temperature by 30-50°C within seconds (reaching 160-200°C), with a response time of less than 1 hour, and supports remote operation. Remote control reduces the number of downhole operations, saving approximately 30%-40% in operating costs per well (approximately 50,000-100,000 RMB / well).

[0133] The technical solution of the present invention will be further described below with reference to specific embodiments.

[0134] Example 1:

[0135] (1) Magnesium alloy matrix: Materials: Magnesium (Mg, 96.0 wt%), Zinc (Zn, 1.8 wt%), Aluminum (Al, 1.2 wt%), Calcium (Ca, 0.3 wt%).

[0136] Shape: Cylindrical, 100 mm in diameter, 350 mm in length, with an internal through-channel diameter of 15 mm and an outer wall thickness of 12 mm. Both ends are threaded (1.5 mm pitch).

[0137] Equipment: Vacuum induction furnace (Model: ZG-0.01, Shanghai Electric Furnace Factory).

[0138] Process: Weigh 960 g magnesium ingots, 18 g zinc granules, 12 g aluminum granules, and 3 g calcium granules. Place them in a furnace, introduce argon gas (pressure 0.1 MPa), and heat to 720°C for melting. Stir for 45 minutes (300 rpm, magnetic stirrer). Let stand for 10 minutes and remove slag using a ceramic filter. Pour into a steel mold (preheated to 300°C) and cast using a pressure casting machine (model: Yizumi DC400) at 620°C and 15 MPa. Cool using a water-cooled mold (circulating water temperature 20°C) at 15°C / s. Machin the outer surface using a CNC lathe (model: CK6150, Shenyang Machine Tool) (speed 1000 rpm, feed rate 0.1 mm / r), and machine threads at both ends (pitch 1.5 mm, depth 1 mm).

[0139] (2) pH-sensitive coating:

[0140] Materials: Polyacrylic acid (PAA, molecular weight 60,000, mass fraction 98.5 wt%), crosslinking agent N,N'-methylenebisacrylamide (0.8 wt%).

[0141] Thickness: 120 μm film, covering the outer surface of the substrate.

[0142] Equipment: High-pressure sprayer (model: Graco GMAX II 3900, Graco Corporation, USA), electric drying oven (model: DHG-9140A, Shanghai Yiheng).

[0143] Process: Weigh PAA (98.5 g) and crosslinking agent (0.8 g), dissolve in ethanol (900.7 g, 8 wt%), and stir for 30 minutes (500 rpm, 25°C) using a magnetic stirrer (model: HJ-6, Shanghai Keheng). Apply evenly to the outer surface of the substrate using a sprayer (nozzle diameter 0.5 mm, pressure 0.2 MPa, spraying distance 15 cm), with each layer approximately 40 μm, spraying 3 times to reach 120 μm. Place in a drying oven (100°C, air atmosphere, 1 hour), and allow to cool naturally to room temperature. See attached... Figure 2 .

[0144] (3) Electromagnetic response material layer:

[0145] Materials: Fe3O4 nanoparticles (particle size 25 nm, mass fraction 10 wt%) doped with magnesium alloy (Mg 96.0 wt%, Zn 1.8 wt%, Al 1.2 wt%, Ca 0.3 wt%).

[0146] Layer thickness: 1.2 mm, deposited on the inner wall of the channel.

[0147] Equipment: Chemical reactor (model: GSH-5L, Shandong Weihai Chemical), planetary ball mill (model: QM-3SP4, Nanjing University Instruments), laser cladding machine (model: Trumpf TruLaser Cell 7040, Germany Trumpf).

[0148] Process: Weigh 16.2 g of FeCl3·6H2O and 5.97 g of FeCl2·4H2O (molar ratio 2:1), dissolve in 200 mL of deionized water, and add NaOH (1 mol / L) dropwise to pH 10 in a reactor. Stir at 80°C for 1 hour (500 rpm). Separate using a magnetic separator and dry at 110°C for 6 hours (vacuum drying oven, model: DZF-6050, Shanghai Jinghong) to obtain Fe3O4 particles (particle size 25 nm). Weigh 10 g of Fe3O4 and 90 g of magnesium alloy powder (particle size 75 μm), and ball mill in a ball mill (250 rpm, 4 hours, ball-to-material ratio 10:1, argon protection). Deposit the 1.2 mm layer onto the inner wall of the substrate channel using a laser cladding machine (power 1.5 kW, scanning speed 8 mm / s, argon flow 10 L / min), and cool to room temperature.

[0149] (4) Sealing elements:

[0150] Materials: Biodegradable polyurethane, polyether polyol (65 wt%), isocyanate (25 wt%), silane coupling agent (0.8 wt%, γ-aminopropyltriethoxysilane).

[0151] Shape: Ring-shaped elastomer, inner diameter 100 mm, thickness 8 mm, bonded to the outer periphery of the substrate.

[0152] Equipment: Reactor (Model: FCH-50L, Shandong Longxing Chemical), Hot press (Model: YLJ-100T, Hefei Kejing), Ring mold (customized, inner diameter 100 mm).

[0153] Process: Weigh 650 g of polyether polyol (molecular weight 2000), 250 g of isocyanate (MDI), and 8 g of silane coupling agent (γ-aminopropyltriethoxysilane), and place them in a reactor (90°C, stirring for 45 minutes, 300 rpm, nitrogen protection) to obtain a prepolymer. Inject into a ring mold (preheated to 120°C) and shape using a hot press (170°C, 8 MPa, 15 minutes). Cool to room temperature with water (12°C / s, circulating water temperature 20°C), demold, and smooth the edges with sandpaper (1000 grit) (roughness Ra < 1 μm). Apply silane coupling agent (0.8 wt%, approximately 10 μm thick) to the inner surface using a brush coater (model: BYK-Gardner, BYK Germany), and let it dry for 15 minutes (25°C).

[0154] (5) Anchoring mechanism:

[0155] Materials: Magnesium alloy clasps (Mg 96.0 wt%, Zn 1.8 wt%, Al 1.2 wt%, Ca 0.3 wt%), anti-corrosion coating (polyurea, 100% by mass, 10 μm thick).

[0156] Shape: Serrated, inner and outer diameter 103 mm / 100 mm, pitch 1.5 mm, threaded.

[0157] Equipment: CNC lathe (model: CK6150, Shenyang Machine Tool), high-pressure sprayer (Graco GMAX II 3900), drying oven (DHG-9140A).

[0158] Process: Weigh 500 g of magnesium alloy billet (same proportion as the base material). Machin a serrated jaw using a CNC lathe (inner / outer diameter 103 mm / 100 mm, tooth height 2 mm, pitch 1.5 mm, speed 1200 rpm, feed rate 0.08 mm / r). Apply a polyurea coating (10 μm, 3 μm per layer, 3 coats) using a spray gun (0.2 MPa, nozzle diameter 0.3 mm, distance 10 cm). Place in a drying oven (90°C, 1.5 hours) and cool to room temperature. Tighten the jaws to the threads at both ends of the base material using a hand wrench.

[0159] (6) Sealing element bonding:

[0160] Equipment: Hot press bonding machine (model: HP-100T, Shanghai Xinnuo Instruments).

[0161] Process: Place the sealing element on the outer periphery of the substrate (covered with a pH-sensitive coating) and use a hot press adhesive (120°C, 2MPa, 45 minutes). Allow to cool naturally to room temperature (25°C).

[0162] Function Description:

[0163] The pH-sensitive coating responds to acidic environments, the Fe3O4 layer provides electromagnetic heating, the sealing element forms a barrier, and the slips anchor the wellbore, together achieving dual-trigger degradation.

[0164] Example 2:

[0165] (1) Magnesium alloy matrix:

[0166] Materials: Magnesium (95.5 wt%), Zinc (2.0 wt%), Aluminum (1.5 wt%), Calcium (0.5 wt%).

[0167] Shape: Cylindrical, 90 mm in diameter, 320 mm in length, 12 mm in channel diameter, and 10 mm in outer wall thickness. Channel diameter 12 mm, thread pitch 1.2 mm.

[0168] Equipment: Vacuum induction furnace (ZG-0.01), pressure casting machine (Yizumi DC400), CNC lathe (CK6150).

[0169] Process: Weigh magnesium ingots (955 g), zinc granules (20 g), aluminum granules (15 g), and calcium granules (5 g), and melt them at 740°C (argon, 350 rpm, 40 minutes). Let stand for 8 minutes to remove slag, then cast at 650°C and 20 MPa (steel mold preheated to 350°C), and cool at 18°C / s (water cooling). Machin the outer surface on a lathe (1200 rpm, feed rate 0.12 mm / r), and cut threads (pitch 1.2 mm, depth 0.8 mm).

[0170] (2) pH-sensitive coating:

[0171] Materials: PAA (molecular weight 80,000, mass fraction 98.0 wt%), crosslinking agent (1.0 wt%).

[0172] Thickness: 100 μm.

[0173] Equipment: High-pressure sprayer (Graco GMAX II 3900), drying oven (DHG-9140A).

[0174] Process: Weigh PAA (98 g) and crosslinking agent (1 g), dissolve in ethanol (801 g, 10 wt%), and stir for 40 minutes (600 rpm, 25°C). Spray (0.3 MPa, nozzle 0.4 mm, distance 12 cm), each layer approximately 33 μm, spray 3 times to reach 100 μm. Dry at 80°C for 2 hours, then cool to room temperature.

[0175] (3) Electromagnetic response material layer:

[0176] Material: Fe3O4 (15 wt% by mass, 20 nm particle size) doped magnesium alloy (Mg 95.5 wt%, Zn 2.0 wt%, Al 1.5 wt%, Ca 0.5 wt%).

[0177] Layer thickness: 1.5 mm.

[0178] Equipment: Chemical reactor (GSH-5L), ball mill (QM-3SP4), laser cladding machine (Trumpf TruLaserCell 7040).

[0179] Process: Fe3O4 synthesis was the same as in Example 1. Fe3O4 (15 g) and magnesium alloy powder (85 g, particle size 50 μm) were weighed and ball-milled (300 rpm, 3 hours, ball-to-material ratio 8:1). Laser cladding was performed (2 kW, 10 mm / s, argon flow 12 L / min) to a layer thickness of 1.5 mm, and then cooled to room temperature.

[0180] (4) Sealing elements:

[0181] Materials: biodegradable polyurethane, polyether polyol (70 wt%), isocyanate (20 wt%), silane coupling agent (1.0 wt%, γ-aminopropyltriethoxysilane).

[0182] Shape: Ring, inner diameter 90 mm, thickness 6 mm.

[0183] Equipment: Reactor (FCH-50L), hot press (YLJ-100T), ring mold (inner diameter 90 mm).

[0184] Process: Weigh out 700 g of polyether polyol, 200 g of isocyanate, and 10 g of silane coupling agent, and stir at 90°C for 40 minutes (350 rpm). Pour into a mold (preheated to 110°C), and hot press (180°C, 10 MPa, 12 minutes). Cool at 15°C / s, demold, and trim (using 800-grit sandpaper). Brush on silane coupling agent (1.0 wt%, 10 μm thickness) and let dry for 10 minutes.

[0185] (5) Anchoring mechanism:

[0186] Materials: Magnesium alloy clips (same proportion as substrate), anti-corrosion coating (epoxy resin, 100% by mass, 8 μm thickness).

[0187] Shape: Serrated, inner and outer diameters 93 mm / 90 mm, serration density increased by 10%, pitch 1.2 mm.

[0188] Equipment: CNC milling machine (model: VMC850, Shenyang Machine Tool), spraying machine (Graco GMAX II 3900), drying oven (DHG-9140A).

[0189] Process: CNC milling machine is used to machine the chuck (tooth height 1.8 mm, speed 1500 rpm, feed rate 0.1 mm / r). Epoxy resin is sprayed (0.3 MPa, nozzle 0.3 mm, 8 μm, 2 coats). The chuck is dried at 100°C for 1 hour, and the threads are tightened.

[0190] (6) Sealing element bonding:

[0191] Equipment: Hot press bonding machine (HP-100T).

[0192] Process: Hot pressing (120°C, 2.5 MPa, 40 minutes), then cooling to room temperature.

[0193] Example 3:

[0194] (1) Magnesium alloy matrix:

[0195] Materials: Magnesium (Mg, 96.0 wt%), Zinc (Zn, 1.8 wt%), Aluminum (Al, 1.2 wt%), Calcium (Ca, 0.3 wt%).

[0196] Shape: Cylindrical, 100 mm in diameter, 350 mm in length, with an internal through-channel diameter of 15 mm, threads at both ends (pitch 2 mm), and an outer wall thickness of 12 mm.

[0197] Equipment: Vacuum induction furnace (Model: ZG-0.01, Shanghai Electric Furnace Factory).

[0198] Process: Weigh 960 g of magnesium ingots, 18 g of zinc granules, 12 g of aluminum granules, and 3 g of calcium granules. Place them in a furnace, introduce argon gas (pressure 0.1 MPa), and heat to 700°C for melting. Stir for 50 minutes (250 rpm, magnetic stirrer). Let stand for 12 minutes and remove slag using a ceramic filter. Pour into a steel mold (preheated to 280°C) and cast using a pressure casting machine (model: Yizumi DC400) at 600°C and 12 MPa. Cool using a water-cooled mold (circulating water temperature 20°C) at 12°C / s. Machin the outer surface using a CNC lathe (model: CK6150, Shenyang Machine Tool) (speed 800 rpm, feed rate 0.15 mm / r), and machine threads at both ends (pitch 2 mm, depth 1.2 mm).

[0199] (2) pH-sensitive coating:

[0200] Materials: Polyacrylic acid (PAA, molecular weight 50,000, mass fraction 98.5 wt%), crosslinking agent N,N'-methylenebisacrylamide (0.8 wt%).

[0201] Thickness: 150 μm film, covering the outer surface of the substrate.

[0202] Equipment: High-pressure sprayer (model: Graco GMAX II 3900, Graco Corporation, USA), electric drying oven (model: DHG-9140A, Shanghai Yiheng).

[0203] Process: Weigh PAA (98.5 g) and crosslinking agent (0.8 g), dissolve in ethanol (1496.7 g, 6 wt%), and stir for 20 minutes (400 rpm, 25°C) using a magnetic stirrer (model: HJ-6, Shanghai Keheng). Apply evenly to the outer surface of the substrate using a sprayer (nozzle diameter 0.6 mm, pressure 0.1 MPa, spraying distance 18 cm), with each layer approximately 50 μm, spraying 3 times to reach a total thickness of 150 μm. Place in a drying oven (120°C, air atmosphere, 0.5 hours) and allow to cool naturally to room temperature.

[0204] (3) Electromagnetic response material layer:

[0205] Materials: Fe3O4 nanoparticles (30 nm in diameter, 6 wt% in mass) doped with magnesium alloy (Mg 96.0 wt%, Zn 1.8 wt%, Al 1.2 wt%, Ca 0.3 wt%).

[0206] Layer thickness: 0.8 mm, deposited on the inner wall of the channel.

[0207] Equipment: Chemical reactor (model: GSH-5L, Shandong Weihai Chemical), planetary ball mill (model: QM-3SP4, Nanjing University Instruments), laser cladding machine (model: Trumpf TruLaser Cell 7040, Germany Trumpf).

[0208] Process: Weigh 16.2 g of FeCl3·6H2O and 5.97 g of FeCl2·4H2O (molar ratio 2:1), dissolve in 200 mL of deionized water, and add NaOH (1 mol / L) dropwise to pH 10 in a reactor. Stir at 80°C for 1 hour (500 rpm). Separate using a magnetic separator and dry at 110°C for 6 hours (vacuum drying oven, model: DZF-6050, Shanghai Jinghong) to obtain Fe3O4 particles (particle size 30 nm). Weigh 6 g of Fe3O4 and 94 g of magnesium alloy powder (particle size 75 μm), and ball mill in a ball mill (200 rpm, 5 hours, ball-to-material ratio 12:1, argon protection). Deposit the 0.8 mm layer onto the inner wall of the substrate channel using a laser cladding machine (power 1 kW, scanning speed 5 mm / s, argon flow 8 L / min), and cool to room temperature.

[0209] (4) Sealing elements:

[0210] Materials: Biodegradable polyurethane, polyether polyol (60 wt%), isocyanate (30 wt%), silane coupling agent (0.5 wt%, γ-aminopropyltriethoxysilane).

[0211] Shape: Ring-shaped elastomer, inner diameter 100 mm, thickness 10 mm, bonded to the outer periphery of the substrate.

[0212] Equipment: Reactor (Model: FCH-50L, Shandong Longxing Chemical), Hot press (Model: YLJ-100T, Hefei Kejing), Ring mold (customized, inner diameter 100 mm).

[0213] Process: Weigh 600 g of polyether polyol (molecular weight 2000), 300 g of isocyanate (MDI), and 5 g of silane coupling agent (γ-aminopropyltriethoxysilane), and place them in a reactor (90°C, stirring for 50 minutes, 250 rpm, nitrogen protection) to obtain a prepolymer. Inject into a ring mold (preheated to 100°C) and shape using a hot press (150°C, 6 MPa, 20 minutes). Cool to room temperature with water (10°C / s, circulating water temperature 20°C), demold, and smooth the edges with sandpaper (1200 grit) (roughness Ra < 1 μm). Apply silane coupling agent (0.5 wt%, approximately 10 μm thick) to the inner surface using a brush coater (model: BYK-Gardner, BYK Germany), and let it dry for 20 minutes (25°C).

[0214] (5) Anchoring mechanism:

[0215] Materials: Magnesium alloy clasps (Mg 96.0 wt%, Zn 1.8 wt%, Al 1.2 wt%, Ca 0.3 wt%), anti-corrosion coating (polyurea, 100% by mass, 12 μm thick).

[0216] Shape: Serrated, inner and outer diameter 103 mm / 100 mm, pitch 2 mm, threaded.

[0217] Equipment: CNC lathe (model: CK6150, Shenyang Machine Tool), high-pressure sprayer (Graco GMAX II 3900), drying oven (DHG-9140A).

[0218] Process: Weigh 500 g of magnesium alloy billet (same proportion as the base material). Machin a serrated jaw using a CNC lathe (inner / outer diameter 103 mm / 100 mm, tooth height 2.2 mm, pitch 2 mm, speed 1000 rpm, feed rate 0.1 mm / r). Apply a polyurea coating (12 μm, 3 μm per layer, 4 coats) using a sprayer (0.2 MPa, nozzle diameter 0.3 mm, distance 10 cm). Place in a drying oven (80°C, 2 hours) and cool to room temperature. Tighten the jaws to the threads at both ends of the base material using a hand wrench.

[0219] (6) Sealing element bonding:

[0220] Equipment: Hot press bonding machine (model: HP-100T, Shanghai Xinnuo Instruments).

[0221] Process: Place the sealing element on the outer periphery of the substrate (covered with a pH-sensitive coating) and apply using a hot press (120°C, 1.8 MPa, 60 minutes). Allow to cool naturally to room temperature (25°C).

[0222] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A smart soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism, characterized in that, The intelligent soluble bridge plug includes a matrix, a pH-sensitive coating, and an electromagnetically responsive material layer, wherein the matrix has a through channel inside; A pH-sensitive coating is applied to the outer surface of the substrate, and an electromagnetically responsive material layer is deposited on the surface of the penetrating channel. The pH-sensitive coating comprises a polymer and a crosslinking agent. The polymers include one or more of polyacrylic acid, polymethacrylic acid, or polyacrylic acid-acrylamide copolymers; The crosslinking agent includes one or more of N,N'-methylenebisacrylamide, divinylbenzene, or ethylene glycol dimethacrylate; The electromagnetic response material layer consists of Fe3O4 nanoparticles and magnesium alloy. By mass percentage, the Fe3O4 nanoparticles account for 6%-15%, and the remainder is magnesium alloy.

2. The intelligent soluble bridge plug according to claim 1, characterized in that, The matrix is ​​a magnesium alloy, and the magnesium alloy comprises magnesium, zinc, aluminum and calcium, wherein the mass fraction of each component is 95.5%-97% magnesium, 1.5%-2.0% zinc, 1.0%-1.5% aluminum and 0.2%-0.5% calcium.

3. The intelligent soluble bridge plug according to claim 1, characterized in that, The substrate has a diameter of 80-120 mm and a length of 300-400 mm; and / or, The diameter of the through-channel within the matrix is ​​10-20 mm; and / or, The outer wall thickness of the substrate is 10-15 mm.

4. The intelligent soluble bridge plug according to claim 1, characterized in that, The thickness of the pH-sensitive coating is 80-200μm.

5. The intelligent soluble bridge plug according to claim 1, characterized in that, The Fe3O4 nanoparticles have a particle size of 20-30 nm.

6. The intelligent soluble bridge plug according to claim 1, characterized in that, The thickness of the electromagnetic response material layer is 0.5-2 mm.

7. The intelligent soluble bridge plug according to any one of claims 1-6, characterized in that, The intelligent soluble bridge plug also includes a sealing element, a first anchoring mechanism, and a second anchoring mechanism, wherein... The first anchoring mechanism, the sealing element, and the second anchoring mechanism are sequentially arranged on the outer surface of the substrate.

8. The intelligent soluble bridge plug according to claim 7, characterized in that, The first and second anchoring mechanisms are made of the same magnesium alloy as the base material; and / or, The first anchoring mechanism and the second anchoring mechanism are connected to the base. The outer diameter of the first anchoring mechanism and the second anchoring mechanism is 2-5 mm larger than the outer diameter of the base.

9. The intelligent soluble bridge plug according to claim 8, characterized in that, The first and second anchoring mechanisms are made of magnesium alloy slips; The surface of the magnesium alloy clip is coated with an anti-corrosion coating.

10. The intelligent soluble bridge plug according to claim 9, characterized in that, The anti-corrosion coating is composed of polyurea or epoxy resin, and / or... The thickness of the anti-corrosion coating is 5-15μm.

11. The intelligent soluble bridge plug according to claim 8, characterized in that, The sealing element is bonded to the outer surface of the substrate and contacts the wellbore or casing to form a seal; and / or, The sealing element is an annular elastomer with a thickness of 5-10 mm.

12. The intelligent soluble bridge plug according to claim 11, characterized in that, The components of the ring elastomer include polyether polyol, isocyanate and silane coupling agent, wherein the mass fraction of each component is 60%-70% polyether polyol, 20%-30% isocyanate and 0.5%-1.0% silane coupling agent.

13. The method for preparing the intelligent soluble bridge plug based on a pH-sensitive coating and an electromagnetic dual triggering mechanism as described in any one of claims 1-12, characterized in that, Weigh magnesium ingots, zinc granules, aluminum granules, and calcium granules, place them in a furnace, introduce inert gas, heat to 700℃-740℃ for melting, stir for 30-60 minutes, let stand, filter, pour into a steel mold for casting, and machine on a lathe to obtain the matrix; A pH-sensitive coating is sprayed onto the outer surface of the substrate, and an electromagnetically responsive material layer is deposited on the surface of the through-channel inside the substrate.

14. The preparation method according to claim 13, characterized in that, The method also includes, A first anchoring mechanism, a sealing element, and a second anchoring mechanism are sequentially connected to the outer surface of the substrate after the pH-sensitive coating is sprayed.

Images