Self-adaptive plug removal pre-packed sand control screen pipe based on hydrophobic-negative double functional coating and preparation method thereof

Abstract

The present application relates to the well completion technology in the field of oil and gas field, natural gas hydrate and other underground resource exploitation, and specifically provides a self-adaptive plug removal pre-packed sand control screen pipe based on hydrophobic-negative double functional coating and a preparation method thereof, the filled multifunctional pre-packed particles are of core-shell structure, the inner core comprises pre-packed particles, the shell comprises hydrophobic-negative double functional coating, the hydrophobic-negative double functional coating has hydrophobicity and negative electricity and can synergize, the water contact angle is greater than or equal to 110 degrees, and the Zeta potential is less than or equal to -30 mV, through reducing the water phase wettability and generating electrostatic repulsion, the double repulsion to the water phase and the negatively charged clay particles is realized, and the anti-mud jam and self-adaptive plug removal without external energy can be realized.

Description

Technical Field

[0001] This invention relates to the field of underground resource extraction technology, specifically to an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating and its preparation method. Background Technology

[0002] In the development of oil and gas fields, especially unconventional oil and gas (such as shale gas and tight oil) and natural gas hydrates, sand control is a crucial link in ensuring safe, efficient, and long-term production. Pre-filled sand control screens are widely used due to their advantages such as high sand control accuracy and simple construction. However, in typical silty mudstone-type natural gas hydrate reservoirs such as the Shenhu area of ​​the South China Sea, the reservoirs generally have the characteristics of "non-diagenetic, weak cementation, high mud content, and low permeability," which poses a severe challenge to existing sand control technologies. The core problem lies in the dual contradiction between "sand production" and "blockage."

[0003] Traditional slotted screens, wire-wound screens, and conventional gravel packing techniques are highly susceptible to internal blockage in silty sand reservoirs with extremely fine particle sizes (<74μm) and high clay content (up to 30-40%). Driven by production pressure differentials, these fine clay particles migrate into the pores of the sand control layer, forming a dense "mud film" that causes a sharp drop in permeability, severely limiting production capacity. Studies have shown that when the clay content exceeds a certain threshold (e.g., 35%), conventional sand control layers may completely fail.

[0004] International mainstream technologies (such as Halliburton's PrePak) TM Baker Hughes' FlexPac TM Optimized graded quartz sand or ceramsite is often used as prefill material, focusing on structural design (such as high flow area design) and construction technology (such as pump-filling). However, the prefill material itself has an inert hydrophilic surface, which easily undergoes physical adsorption and capillary action with aqueous phase and clay minerals. Although expandable screen tube technology explored in recent years can reduce annular blockage, it still has not solved the fundamental problem of adsorption of clay particles on the surface of the prefill layer or screen and internal siltation.

[0005] Domestic research is keeping pace with international advancements. Recently, CNOOC Energy Development Co., Ltd. proposed a self-heating pre-filled sand control screen. By integrating heating and power generation devices, it uses the kinetic energy of the fluid in the well to generate electricity and heat the screen, thus preventing secondary hydrate blockage. This is a cutting-edge exploration in the field of active intelligent sand control in China. However, its technical approach relies on external energy input and a complex control system. It mainly addresses the blockage of hydrate phases caused by temperature and pressure changes. It does not address the long-term physical blockage caused by the migration of native mud particles in the reservoir. Furthermore, its solution (heating) is not targeted and is costly.

[0006] Currently, existing technologies suffer from several common shortcomings, including: 1. Lack of material functionality: The surface chemical properties of pre-filled particles are not functionally designed for high-muddy environments, lacking the ability to actively repel aqueous phases and clay particles. 2. Passive anti-clogging mechanism: Primarily relying on mechanical filtration and structural optimization, this is a form of "passive interception," easily leading to "bridging" and "deep clogging" of fine sands, and subsequent unclogging is difficult. 3. Dependence on external intervention for unclogging: Unclogging often involves post-processing operations such as chemical cleaning and high-pressure flushing, which are costly, risky, and may damage the reservoir. 4. Limitations of the "adaptive" concept: Existing "intelligent" screens largely rely on external sensors, energy sources, and actuators to achieve "active unclogging," resulting in complex systems whose reliability faces challenges in harsh downhole environments with high temperatures and pressures.

[0007] Therefore, existing technologies, whether foreign structural optimization schemes or emerging domestic external energy-driven schemes, have failed to effectively solve the fundamental problem of physical clogging of pre-filled layers caused by the migration of fine silt in high-muddy reservoirs. Their technical approaches mainly focus on "passive interception" and "external intervention," lacking an "active repulsion" strategy based on the intrinsic properties of the materials. An ideal solution should endow the sand-control material with continuous anti-clogging and self-cleaning capabilities, achieving "passive adaptive" protection without external energy input. Currently, there is a lack of pre-filled screen pipe technology that can actively and continuously repel silt particles without relying on external energy input by endowing the pre-filled material with hydrophobicity and negative charge, thus achieving long-term sand control. This invention addresses this technological gap by proposing a novel material-structure synergistic technical approach. Summary of the Invention

[0008] In view of the problems existing in the prior art, the present invention provides an adaptive unclogging pre-filled sand screen pipe based on a hydrophobic-negatively charged dual-functional coating. The filling multifunctional pre-filled particles have a core-shell structure, with the core including the pre-filled particles and the outer shell including the hydrophobic-negatively charged dual-functional coating. The hydrophobic-negatively charged dual-functional coating has both hydrophobicity and negative charge and can work synergistically. The water contact angle is ≥110° and the Zeta potential is ≤-30mV. By reducing the wettability of the aqueous phase and generating electrostatic repulsion, it achieves dual repulsion of the aqueous phase and negatively charged clay particles, which can realize anti-mud siltation and adaptive unclogging without external energy.

[0009] To achieve this objective, the present invention adopts the following technical solution: One objective of this invention is to provide an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating. The adaptive unblocking pre-filled sand-control screen pipe includes a central base pipe, an inner sheath, an outer sheath, a first annular end cap, a second annular end cap, and multifunctional pre-filled particles. The inner sheath and outer sheath are sequentially fitted onto the outer side of the central base pipe, and the first annular end cap and the second annular end cap are respectively attached to the ends of the inner and outer sheaths. A pre-filled chamber is formed between the inner sheath, the outer sheath, the first annular end cap, and the second annular end cap and filled with the multifunctional pre-filled particles. The multifunctional pre-filled particles have a core-shell structure, with the core consisting of pre-filled particles and the outer shell consisting of a hydrophobic-negative dual-functional coating; the hydrophobic-negative dual-functional coating is prepared from a coating solution containing a hydrophobic polymer and a negatively charged group modifier.

[0010] This invention provides an adaptive unclogging pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating. The filling multifunctional pre-filled particles have a core-shell structure, with the core consisting of pre-filled particles and the outer shell consisting of a hydrophobic-negatively charged dual-functional coating. The hydrophobic-negatively charged dual-functional coating has both hydrophobicity and negative charge and can work synergistically. The water contact angle is ≥110° and the Zeta potential is ≤-30mV. By reducing the wettability of the aqueous phase and generating electrostatic repulsion, it achieves dual repulsion of the aqueous phase and negatively charged clay particles, thus achieving anti-mud siltation and adaptive unclogging without external energy.

[0011] As a preferred technical solution of the present invention, both the inner sheath and the outer sheath are alternating distributed composite sheaths. The alternating distributed composite sheaths are arranged in an alternating configuration of a wound wire structure and a bridge structure along the axial direction to form a filtration gradient in the axial direction.

[0012] Preferably, in the alternating distribution composite sheath, the bridge structure area accounts for 60%-80% of the total sheath area, such as 60%, 63%, 65%, 68%, 70%, 72%, 75%, 78%, or 80%, etc., and the wire winding structure area accounts for 20%-40% of the total sheath area, such as 20%, 22%, 25%, 26%, 28%, 30%, 32%, 35%, 38%, or 40%, etc., but is not limited to the listed values, and other unlisted values ​​within the above range are also applicable.

[0013] It should be noted that in the alternating distribution composite sheath described in this invention, the bridge structure area accounts for 60%-80% of the total sheath area, and the wire winding structure area accounts for 20%-40% of the total sheath area, with the sum of the two being 100%. The alternating distribution composite sheath is configured with alternating wire winding and bridge structures along the axial direction, forming an axial filtration gradient. The bridge structure provides a main flow channel to ensure high flow rate, while the wire winding structure achieves fine filtration and uniform liquid distribution. The combination of the two forms an axial gradient pore structure, which can optimize fluid flow and support the pre-filled layer. In the actual preparation process, laser cutting technology is used to process bridge-shaped gaps on the steel plate after the metal pipe or coil is flattened. The gap width is 0.3~0.5mm, the gap length is 50~100mm, the bridge width is 0.3mm, and the opening rate is 65%~80%. The opening rate refers to the percentage of the total area of ​​all bridge-shaped gap openings on the bridge-shaped screen plate to the surface area of ​​the screen plate. The prepared bridge-shaped screen plate is rolled and welded into the bridge structure in the alternating distribution composite sheath. Then, the skeleton required for winding wire is welded to the end face of the obtained bridge structure. The winding wire (wire diameter 0.3~0.5mm, gap width 0.15~0.3mm, error ≤±0.05mm) is wound on the outer surface of the skeleton using a full winding welding process. Each intersection is connected by fusion welding to form an alternating distribution composite sheath. Generally, along the axial direction, the length of the bridge structure area in each alternating repeating unit in the alternating distribution composite sheath is 0.5-1m.

[0014] It should be noted that the materials of the central base tube, the inner sheath, the outer sheath, the first annular end cap, and the second annular end cap of the present invention are all stainless steel or nickel-based alloy.

[0015] A second objective of this invention is to provide a method for preparing an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating, as described in one objective. The preparation method includes the following steps: (1) Prepare a coating solution containing a hydrophobic polymer and a negatively charged group modifier, immerse the pre-filled particles in the coating solution for surface coating, remove them and dry and cure them to obtain multifunctional pre-filled particles; (2) Prepare the inner sheath, outer sheath, first annular end cap, and second annular end cap and assemble them. The multifunctional prefilled particles described in step (1) are filled into the prefilled cavity and sintered and fixed as a whole to form a prefilled assembly. (3) The central base pipe is fixedly connected to the pre-filling component described in step (2) to obtain an adaptive unblocking pre-filling sand screen pipe based on a hydrophobic-negative dual-function coating.

[0016] As a preferred technical solution of the present invention, the pre-filled particles in step (1) include any one or a combination of at least two of the following: quartz sand, ceramsite, or alumina particles.

[0017] Preferably, the particle size D50 of the pre-filled particles is 0.45-0.90 mm, such as 0.45 mm, 0.50 mm, 0.55 mm, 0.60 mm, 0.65 mm, 0.70 mm, 0.75 mm, 0.80 mm, 0.85 mm or 0.90 mm, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0018] As a preferred technical solution of the present invention, in the coating solution containing hydrophobic polymer and negatively charged group modifier in step (1), the hydrophobic polymer includes any one or a combination of at least two of polydimethylsiloxane (PDMS), polytetrafluoroethylene (PTFE) or fluorinated acrylate copolymer.

[0019] As a preferred technical solution of the present invention, in the coating solution containing hydrophobic polymer and negatively charged group modifier in step (1), the negatively charged group modifier includes a surface modifier containing negatively charged functional groups, the negatively charged functional groups include any one or a combination of at least two of sulfonic acid group (-SO3H), carboxyl group (-COOH) or phosphate group (-PO4H2), and the surface modifier includes a silane coupling agent.

[0020] As a preferred technical solution of the present invention, the preparation method of the coating solution containing hydrophobic polymer and negatively charged group modifier in step (1) includes: dissolving the hydrophobic polymer in an organic solvent, adding the negatively charged group modifier, and stirring evenly.

[0021] Preferably, the uniform stirring includes: magnetic stirring at a speed of 100-500 rpm for 0.5-6 hours at a temperature of 40-80℃; more preferably, magnetic stirring at 60℃ for 2 hours.

[0022] It should be noted that the stirring temperature described in this invention is 40-80℃, such as 40℃, 45℃, 50℃, 55℃, 60℃, 65℃, 70℃, 75℃, or 80℃, etc. The stirring speed described in this invention is 100-500 rpm, such as 100 rpm, 150 rpm, 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm, or 500 rpm, etc. The stirring time described in this invention is 0.5-6 hours, such as 0.5 hours, 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, or 6 hours, etc., but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0023] It should be noted that the stirring temperature of 40-80℃ described in this invention is limited based on the solubility characteristics of polymers such as PDMS in organic solvents. If the temperature is too low (<40℃), the dissolution is slow and the production efficiency is low. If the temperature is too high (>80℃), the solvent evaporates quickly, which is not conducive to controlling the concentration of the coating solution.

[0024] Preferably, the organic solvent includes any one or a combination of at least two of toluene, acetone, or ethanol.

[0025] As a preferred embodiment of the present invention, the ratio of the hydrophobic polymer to the organic solvent is (0.05-0.20):1 g / mL, for example, 0.05 g / mL, 0.08 g / mL, 0.10 g / mL, 0.13 g / mL, 0.15 g / mL, 0.18 g / mL or 0.20 g / mL, etc., preferably 0.10 g / mL. The ratio of the negatively charged group modifier to the organic solvent is (0.01-0.10):1 g / mL, for example, 0.01 g / mL, 0.03 g / mL, 0.05 g / mL, 0.06 g / mL, 0.08 g / mL or 0.10 g / mL, etc., preferably 0.05 g / mL, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0026] As a preferred technical solution of the present invention, the immersion time in step (1) is 5-60 minutes, such as 5 minutes, 10 minutes, 15 minutes, 20 minutes, 25 minutes, 30 minutes, 35 minutes, 40 minutes, 45 minutes, 50 minutes, 55 minutes or 60 minutes, preferably 30 minutes. The immersion process in step (1) is accompanied by stirring, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0027] As a preferred technical solution of the present invention, the drying and curing temperature in step (1) is 60-120℃, such as 60℃, 70℃, 80℃, 90℃, 100℃, 110℃ or 120℃, and the time is 2-6 hours, such as 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, 5.5 hours or 6 hours, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. Preferably, drying and curing is carried out at 80-100℃ for 4 hours.

[0028] As a preferred embodiment of the present invention, in step (2), the filling density is 1.5-2.0 g / cm³. 3 For example, 1.5g / cm 3 1.6g / cm 3 1.7g / cm3 1.8g / cm 3 1.9g / cm 3 Or 2.0g / cm 3 The values ​​may vary, but are not limited to those listed. Other unlisted values ​​within the above range also apply, with 1.8 g / cm³ being the preferred value. 3 .

[0029] Preferably, in step (2), the overall sintering fixation includes: heating to 200-400℃ at a rate of 2-10℃ / min, such as 200℃, 220℃, 250℃, 280℃, 300℃, 330℃, 350℃, 370℃, 380℃, or 400℃, for 0.5-3 hours, such as 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours, and then cooling to room temperature with the furnace, but not limited to the listed values, other unlisted values ​​within the above range are also applicable; preferably, heating to 280℃ at a rate of 5℃ / min, holding for sintering for 1.5 hours, and then cooling to room temperature with the furnace.

[0030] Compared with existing technical solutions, the present invention has at least the following beneficial effects: (1) Dual Active Repulsion, Source-Based Anti-Clogging: The core innovation of this invention lies in the material-level functionalization of the pre-filled particles. A hydrophobic-negatively charged dual-functional coating is applied to the outside of the pre-filled particles, realizing a dual active repulsion mechanism. The hydrophobicity greatly reduces the surface energy of the particles, forming a "water-repellent" effect, weakening capillary forces, and preventing water film from carrying fine particles into the strata. The negative charge generates a strong electrostatic repulsion with the generally negatively charged clay minerals (such as montmorillonite) in the strata, preventing their adsorption and aggregation. These two mechanisms synergistically inhibit the occurrence of mud siltation from physical and electrochemical perspectives, endowing the sand-proof layer with inherently high anti-clogging performance.

[0031] (2) Passive adaptive unblocking, safe and long-lasting: The "adaptive" characteristic of this invention originates from the material itself and does not require activation. Once the production fluid flows through, the coating function automatically and continuously takes effect, dynamically repelling contact blockages and maintaining unobstructed pores. This is a "passive adaptive unblocking" mechanism with zero external energy consumption, no moving parts, and intrinsic safety, completely eliminating the dependence on expensive and unreliable external intervention systems and achieving low-maintenance long-lasting protection.

[0032] (3) Structure-Material Synergistic Optimization: Both the inner and outer sheaths of this invention are composite sheaths composed of a wire-wound structure and a bridge structure. The innovative wire-wound-bridge composite sheath is not a simple superposition, but a functional integration. The bridge structure ensures a high flow area (>8%) and mechanical strength, while the wire-wound structure ensures filtration accuracy and uniform flow field. This optimized structure provides ideal physical support and a hydrodynamic environment for the multifunctional particle layer, maximizing the anti-clogging performance of the functional coating and achieving a synergistic effect of 1+1>2.

[0033] (4) Performance verification is sufficient and the advantages are significant: Simulation experiments have shown that under the same harsh conditions, the clogging pressure difference growth rate of the pre-filled sand-proof screen pipe of the present invention is much lower than that of conventional screen pipes, and the dual-function coating shows a significantly better synergistic anti-clogging effect than the single-function coating.

[0034] (5) Broad application prospects: This invention is particularly suitable for high muddy silt-type natural gas hydrate reservoirs such as the Shenhu area of ​​the South China Sea. It can also be widely applied to complex reservoirs with high mud content and easy sand production, such as onshore shale oil and gas and heavy oil. It provides a new and efficient technical solution for solving the sand control bottleneck of such reservoirs and has significant engineering application value and market prospects. Attached Figure Description

[0035] Figure 1 This is a schematic diagram of the structure of the multifunctional pre-filled particles described in a specific embodiment of the present invention.

[0036] Figure 2 This is a schematic diagram of the alternating distribution composite sheath described in a specific embodiment of the present invention. Detailed Implementation

[0037] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0038] This invention provides an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating. The adaptive unblocking pre-filled sand-control screen pipe includes a central base pipe, an inner sheath, an outer sheath, a first annular end cap, a second annular end cap, and multifunctional pre-filled particles. The inner sheath and outer sheath are sequentially fitted onto the outer side of the central base pipe, and the first annular end cap and the second annular end cap are respectively attached to the ends of the inner and outer sheaths. A pre-filled chamber is formed between the inner sheath, the outer sheath, the first annular end cap, and the second annular end cap and filled with the multifunctional pre-filled particles. Wherein, as... Figure 1 As shown, the multifunctional pre-filled particles have a core-shell structure, with the core consisting of pre-filled particles and the outer shell consisting of a hydrophobic-negative dual-functional coating; the hydrophobic-negative dual-functional coating is prepared from a coating solution containing a hydrophobic polymer and a negatively charged group modifier.

[0039] Furthermore, both the inner sheath and the outer sheath are alternating composite sheaths, such as... Figure 2 As shown, the alternating distribution composite sheath is arranged with alternating wire-wound structure and bridge structure along the axial direction; in the alternating distribution composite sheath, the bridge structure area accounts for 60%-80% of the total area of ​​the sheath, and the wire-wound structure area accounts for 20%-40% of the total area of ​​the sheath.

[0040] To better illustrate the present invention and facilitate understanding of its technical solutions, typical but non-limiting embodiments of the present invention are as follows: Example 1 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating. The preparation method includes the following steps: (1) Take 100g of spherical ceramic particles with a particle size D50 of 0.60mm, ultrasonically clean them with deionized water for 30 minutes, and dry them at 80℃ for 2 hours; dissolve 10g of polydimethylsiloxane (PDMS) in 100mL of toluene, add 5g of silane coupling agent (KH-580) containing sulfonic acid group, and magnetically stir at 300rpm for 2 hours at 60℃ to obtain a uniform and transparent coating solution; The dried ceramsite is completely immersed in the above coating solution for surface coating for 30 minutes, during which it is slowly stirred to ensure uniform coating. After coating, the ceramsite is removed, excess solution is drained, and it is placed in a forced-air drying oven and dried and cured at 80°C for 4 hours to obtain multifunctional pre-filled granules with a hydrophobic-negative dual-function coating on the surface. Among them, the performance of the prepared multifunctional pre-filled particles was characterized; (i) hydrophobicity test: using a contact angle meter, the water contact angle of the multifunctional pre-filled particle tablet surface was measured to be 118°±3°, showing strong hydrophobicity; (ii) surface electrical property test: using a Zeta potential analyzer, the Zeta potential of the particle suspension was measured to be -38mV±2mV, confirming that strong negative charge was successfully introduced into the surface; (2) Prepare and assemble the inner sheath, outer sheath, first annular end cap, and second annular end cap. Fill the formed pre-filled cavity with the multifunctional pre-filled particles described in step (1), with a filling density of 1.8 g / cm³. 3 Then, the whole assembly is sintered and fixed. The temperature is raised to 280°C at a rate of 5°C / min, and held for sintering for 1.5 hours. The assembly is then cooled to room temperature in the furnace to form a pre-filled component. Both the inner and outer sheaths are alternating composite sheaths. These alternating composite sheaths are arranged axially with alternating wire-wound and bridge-type structures. In the alternating composite sheath, the bridge-type structure area accounts for 70% of the total sheath area, and the wire-wound structure area accounts for 30%. Correspondingly, the length of the bridge-type structure area in each alternating repeating unit is 0.7m, and the length of the wire-wound structure area is 0.3m. In the bridge-type structure area, the seam width is 0.3~0.5mm, the seam length is 50~100mm, the bridge width is 0.3mm, and the opening rate is 75%. In the wire-wound structure area, the wire diameter is 0.3mm, the gap is 0.2mm, and the error is ≤±0.05mm. (3) The central base tube (Φ73mm, material 316L stainless steel) is fixedly connected to the pre-filling component described in step (2) to obtain an adaptive unblocking pre-filling sand screen tube based on a hydrophobic-negative dual-function coating.

[0041] Example 2 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating. The preparation method includes the following steps: (1) Take 100g of spherical ceramic particles with a particle size D50 of 0.45mm, ultrasonically clean them with deionized water for 30 minutes, and dry them at 80℃ for 2 hours; dissolve 20g of polydimethylsiloxane (PDMS) in 100mL of toluene, add 10g of silane coupling agent (KH-580) containing sulfonic acid group, and magnetically stir at 100rpm for 6 hours at 40℃ to obtain a uniform and transparent coating solution; The dried ceramsite is completely immersed in the above coating solution for surface coating for 30 minutes, during which it is slowly stirred to ensure uniform coating. After coating, the ceramsite is removed, excess solution is drained, and it is placed in a forced-air drying oven to dry and cure at 60°C for 6 hours to obtain multifunctional pre-filled granules with a hydrophobic-negative dual-function coating on the surface. Among them, the performance of the prepared multifunctional pre-filled particles was characterized; (i) hydrophobicity test: using a contact angle meter, the water contact angle of the multifunctional pre-filled particle tablet surface was measured to be 125°±3°, showing strong hydrophobicity; (ii) surface electrical property test: using a Zeta potential analyzer, the Zeta potential of the particle suspension was measured to be -42mV±2mV, confirming that strong negative charge was successfully introduced into the surface; (2) Prepare and assemble the inner sheath, outer sheath, first annular end cap, and second annular end cap. Fill the formed pre-filled cavity with the multifunctional pre-filled particles described in step (1), with a filling density of 1.5 g / cm³. 3 Then, the whole assembly is sintered and fixed. The temperature is raised to 400°C at a rate of 10°C / min, and held for sintering for 3 hours. The assembly is then cooled to room temperature in the furnace to form a pre-filled component. Both the inner and outer sheaths are alternating composite sheaths. These alternating composite sheaths are arranged axially with alternating wire-wound and bridge-type structures. In the alternating composite sheath, the bridge-type structure area accounts for 60% of the total sheath area, and the wire-wound structure area accounts for 40%. Correspondingly, the length of the bridge-type structure area in each alternating repeating unit is 0.6m, and the length of the wire-wound structure area is 0.4m. In the bridge-type structure area, the seam width is 0.3~0.5mm, the seam length is 50~100mm, the bridge width is 0.3mm, and the opening rate is 75%. In the wire-wound structure area, the wire diameter is 0.3mm, the gap is 0.2mm, and the error is ≤±0.05mm. (3) The central base tube (Φ73mm, material 316L stainless steel) is fixedly connected to the pre-filling component described in step (2) to obtain an adaptive unblocking pre-filling sand screen tube based on a hydrophobic-negative dual-function coating.

[0042] Example 3 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating. The preparation method includes the following steps: (1) Take 100g of spherical ceramic particles with a particle size D50 of 0.90mm, ultrasonically clean them with deionized water for 30 minutes, and dry them at 80℃ for 2 hours; dissolve 5g of polydimethylsiloxane (PDMS) in 100mL of toluene, add 1g of silane coupling agent containing sulfonic acid group (KH-580), and magnetically stir at 500rpm for 0.5 hours at 80℃ to obtain a uniform and transparent coating solution; The dried ceramsite is completely immersed in the above coating solution for surface coating for 30 minutes, during which it is slowly stirred to ensure uniform coating. After coating, the ceramsite is removed, excess solution is drained, and it is placed in a forced-air drying oven and dried and cured at 120°C for 2 hours to obtain multifunctional pre-filled granules with a hydrophobic-negative dual-function coating on the surface. Among them, the performance of the prepared multifunctional pre-filled particles was characterized; (i) hydrophobicity test: using a contact angle meter, the water contact angle of the multifunctional pre-filled particle tablet surface was measured to be 113°±3°, showing strong hydrophobicity; (ii) surface electrical property test: using a Zeta potential analyzer, the Zeta potential of the particle suspension was measured to be -36mV±2mV, confirming that strong negative charge was successfully introduced into the surface; (2) Prepare and assemble the inner sheath, outer sheath, first annular end cap, and second annular end cap. Fill the formed pre-filled cavity with the multifunctional pre-filled particles described in step (1), with a filling density of 2.0 g / cm³. 3 Then, the whole assembly is sintered and fixed. The temperature is raised to 200°C at a rate of 2°C / min, and the sintering is held for 3 hours. The assembly is then cooled to room temperature in the furnace to form a pre-filled component. Both the inner and outer sheaths are alternating composite sheaths. These alternating composite sheaths are arranged axially with alternating wire-wound and bridge-type structures. In the alternating composite sheath, the bridge-type structure area accounts for 80% of the total sheath area, and the wire-wound structure area accounts for 20%. Correspondingly, the length of the bridge-type structure area in each alternating repeating unit is 0.8m, and the length of the wire-wound structure area is 0.2m. In the bridge-type structure area, the seam width is 0.3~0.5mm, the seam length is 50~100mm, the bridge width is 0.3mm, and the opening rate is 75%. In the wire-wound structure area, the wire diameter is 0.3mm, the gap is 0.2mm, and the error is ≤±0.05mm. (3) The central base tube (Φ73mm, material 316L stainless steel) is fixedly connected to the pre-filling component described in step (2) to obtain an adaptive unblocking pre-filling sand screen tube based on a hydrophobic-negative dual-function coating.

[0043] Example 4 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand screen based on a hydrophobic-negative dual-functional coating. Compared with Embodiment 1, the only difference is that the inner sheath in step (2) is a simple wire-wound structure sheath (wire diameter 0.3mm, gap 0.2mm, error ≤ ±0.05mm), and the outer sheath is a simple bridge structure sheath (gap width 0.3~0.5mm, gap length 50~100mm, bridge width 0.3mm, opening rate 75%).

[0044] Example 5 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand screen based on a hydrophobic-negative dual-functional coating. Compared with Embodiment 1, the only difference is that the bridge structure area accounts for 50% of the total area of ​​the sheath in the alternating distribution composite sheath, and the wire winding structure area accounts for 50% of the total area of ​​the sheath.

[0045] Example 6 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand screen based on a hydrophobic-negative dual-functional coating. Compared with Embodiment 1, the only difference is that both the inner and outer sheaths in the composite sheath adopt a bridge structure (slit width 0.3~0.5mm, slit length 50~100mm, bridge width 0.3mm, and opening rate 75%).

[0046] Example 7 This embodiment provides a method for preparing an adaptive unblocking pre-filled sand screen pipe based on a hydrophobic-negative dual-functional coating. Compared with Embodiment 1, the only difference is that both the inner and outer sheaths in the composite sheath adopt a wire winding structure (wire diameter 0.3mm, gap 0.2mm, error ≤ ±0.05mm).

[0047] Comparative Example 1 This comparative example provides a method for preparing a pre-filled sand-proof screen tube. Compared with Example 1, the only difference is that spherical ceramic particles with a particle size D50 of 0.60 mm are directly filled, and the surface of the ceramic particles is no longer coated with a hydrophobic-negative dual-functional coating. Among them, the performance of the prepared pre-filled particles was characterized; (i) hydrophobicity test: using a contact angle meter, the water contact angle of the multifunctional pre-filled particle tablet surface was measured to be 50°±3°, showing strong hydrophobicity; (ii) surface electrical property test: using a Zeta potential analyzer, the Zeta potential of the particle suspension was measured to be -10mV±2mV, confirming that strong negative electrical property was successfully introduced into the surface.

[0048] Comparative Example 2 This comparative example provides a method for preparing a pre-filled sand-proof screen tube. Compared with Example 1, the only difference is that the silane coupling agent (KH-580) containing sulfonic acid group in the coating solution in step (1) is completely omitted. That is, the functional coating of the functional pre-filled particles used for filling is only hydrophobic.

[0049] Among them, the performance of the prepared pre-filled particles was characterized; (i) hydrophobicity test: using a contact angle meter, the water contact angle of the multifunctional pre-filled particle tablet surface was measured to be 110°±3°, showing strong hydrophobicity; (ii) surface electrical property test: using a Zeta potential analyzer, the Zeta potential of the particle suspension was measured to be -12mV±2mV, confirming that strong negative electrical property was successfully introduced into the surface.

[0050] Comparative Example 3 This comparative example provides a method for preparing a pre-filled sand-proof screen tube. Compared with Example 1, the only difference is that the polydimethylsiloxane (PDMS) in the coating solution in step (1) is completely omitted, that is, the functional coating of the functional pre-filled particles used for filling only has negative charge.

[0051] Among them, the performance of the prepared pre-filled particles was characterized; (i) hydrophobicity test: using a contact angle meter, the water contact angle of the multifunctional pre-filled particle tablet surface was measured to be 52°±3°, showing strong hydrophobicity; (ii) surface electrical property test: using a Zeta potential analyzer, the Zeta potential of the particle suspension was measured to be -36mV±2mV, confirming that strong negative charge was successfully introduced into the surface.

[0052] The pre-filled sand-control screens prepared in the above examples and comparative examples were tested. The test conditions included: simulating hydrate reservoir conditions in the Shenhu area of ​​the South China Sea (containing pressure 12 MPa, temperature 12℃) in a high-temperature and high-pressure core displacement device; the displacement fluid was simulated formation brine containing 30% silt (D50=50μm) and 5% sodium-based montmorillonite clay; continuous displacement was carried out at a constant flow rate of 0.5 mL / min for 60 hours; and the pressure difference (ΔP) between the inlet and outlet of the screen was monitored and recorded in real time. After the test was completed...

[0053] The relevant test results of the above embodiments and comparative examples are summarized in Table 1.

[0054] Table 1 As can be seen from Table 1: (1) By comparing the inlet and outlet pressure difference of the screen tubes, the pressure difference of the pre-filled sand-proof screen tube (with both hydrophobic and negatively charged functions) in Example 1 of the present invention increased extremely slowly. After 60 hours, ΔP only increased to 1.25 times the initial value, and the curve was stable. In contrast, the pressure difference of the pre-filled sand-proof screen tube (unmodified) in Comparative Example 1 increased sharply to more than 4 times the initial value within 15 hours, indicating that the screen tube was severely blocked. The pressure difference growth trends of Comparative Example 2 (hydrophobic only) and Comparative Example 3 (negatively charged only) were between the two, but both were significantly faster than that of Example 1. After 60 hours, ΔP was approximately 2.8 times and 3.2 times the initial value, respectively. After testing and dissection analysis, the pre-filled layer of the pre-filled sand-proof screen tube in Example 1 maintained good pores and the particle surface was clean, with only slight adhesion on the outer sheath surface. In contrast, a dense muddy filter cake was formed inside Comparative Example 1, and the pores were heavily blocked.

[0055] (2) The pre-filled sand-proof screen pipe of the present invention (with both hydrophobic and negative electrical functions) exhibits the best anti-mud clogging performance, verifying the effectiveness of its "passive adaptive unclogging" function. Although single-function modification (hydrophobic only or negative electrical only) has some improvement, the effect is far less than the synergistic effect of dual functions.

[0056] (3) The alternating distribution composite sheath of the present invention did not deform or break during the test, providing effective support for the functional particle layer. Specifically, comparing Example 1 with Example 4, although Example 4 used multifunctional pre-filled particles with a hydrophobic-negative dual-functional coating on the surface for pre-filling, the inner and outer sheaths did not use an alternating distribution composite sheath, causing fine particles to directly enter the pre-filled layer, accelerating internal blockage, and preventing the anti-blocking function of the multifunctional pre-filled particles from being fully utilized. That is, the alternating distribution composite sheath in the present invention plays the role of "pre-filtration + liquid distribution + support", which is an important part of the structure-material synergy effect in the present invention.

[0057] (4) In the alternating distribution composite sheath of the present invention, the bridge structure provides a high flow area (its opening area is significantly higher than other filter pipes), ensuring continuous production capacity, reducing fluid entry velocity, and reducing erosion and wear on the particulate coating. The wire-wound structure plays a fine filtration role, forming a pre-filtration layer and uniform liquid distribution function by providing wire-wound V-shaped gaps, protecting the internal pre-filled layer. In addition, the wire-wound structure has a "self-cleaning and anti-clogging" characteristic, with a gap structure that is narrow on the outside and wide on the inside, which can maintain a stable filtration efficiency during long-term operation.

[0058] (5) Neither pure wire-wound nor pure bridge-type sheaths can achieve the 1.25 times pressure differential ratio of composite sheaths (70 / 30) when used alone. Although pure bridge-type sheaths have lower initial pressure, they accelerate clogging in the later stages; pure wire-wound sheaths have good self-cleaning properties but high initial flow resistance. The performance advantage of composite sheaths stems from the balance between flow capacity and precision, the gradient matching between structural gaps and particle size, and the synergy between self-cleaning function and active repulsion capability.

[0059] (6) In the alternating distribution composite sheath of this invention, when the bridge structure accounts for about 70%, it can utilize the large-area flow of the bridge structure and the effective interception of fine muddy silt by the winding structure, together providing the most ideal hydrodynamic environment for the internal hydrophobic-negative dual-function particles. If the bridge ratio is too high (e.g., 80%), although the flow area is larger, the "protective umbrella" effect of the winding area is weakened, and the particle layer will be blocked prematurely; if the winding ratio is too high (≥40%), the flow resistance is too large, affecting the production capacity and reducing the economic efficiency. The layered structure (outer bridge / inner winding) scheme is not as good as the alternating type due to the flow matching problem of the inner and outer sheaths.

[0060] In summary, this invention relates to well completion technology in the field of underground resource extraction such as oil and gas fields and natural gas hydrates. Specifically, it relates to a pre-filled sand-control screen for reservoirs prone to sand production and high clay content, and more particularly to a sand-control screen through the synergy of surface functionalization of pre-filled materials and composite structure. This screen can achieve anti-mud clogging and adaptive unclogging without external energy, belonging to the interdisciplinary field of oilfield chemistry and well completion engineering technology. Specifically, this invention provides an adaptive unclogging pre-filled sand-control screen based on a hydrophobic-negatively charged dual-functional coating and its preparation method. The specific objectives are: (1) to effectively prevent the migration and physical clogging of fine silt and clay particles in high clay content reservoirs within the pre-filled layer; (2) to achieve "passive adaptive unclogging" without external energy or complex control systems through the functional characteristics of the material itself; and (3) to significantly improve the long-term permeability stability and service life of the sand-control screen through the synergy of functional materials and optimized structure, ensuring long-term and efficient extraction of complex reservoirs.

[0061] The present invention has been illustrated with the above embodiments to illustrate its detailed structural features. However, the present invention is not limited to the above detailed structural features, that is, it does not mean that the present invention must rely on the above detailed structural features to be implemented. Those skilled in the art should understand that any improvements to the present invention, equivalent substitutions for the components used in the present invention, additions of auxiliary components, and selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

[0062] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0063] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0064] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. An adaptive unblocking pre-filled sand-proof screen pipe based on a hydrophobic-negatively charged dual-functional coating, characterized in that, The adaptive unblocking pre-filled sand-control screen pipe includes a central base pipe, an inner sheath, an outer sheath, a first annular end cap, a second annular end cap, and multifunctional pre-filled particles. The inner sheath and the outer sheath are sequentially fitted onto the outside of the central base pipe, and the first annular end cap and the second annular end cap are respectively attached to the two ends of the inner sheath and the outer sheath. A pre-filled chamber is formed between the inner sheath, the outer sheath, the first annular end cap, and the second annular end cap and filled with the multifunctional pre-filled particles. The multifunctional pre-filled particles have a core-shell structure, with the core consisting of pre-filled particles and the outer shell consisting of a hydrophobic-negative dual-functional coating; the hydrophobic-negative dual-functional coating is prepared from a coating solution containing a hydrophobic polymer and a negatively charged group modifier.

2. The adaptive unblocking pre-filled sand-proof screen pipe according to claim 1, characterized in that, Both the inner sheath and the outer sheath are alternating composite sheaths, and the alternating composite sheaths are arranged in an alternating configuration of a wire-wound structure and a bridge structure along the axial direction; Preferably, in the alternating distribution composite sheath, the bridge structure area accounts for 60%-80% of the total sheath area, and the wire winding structure area accounts for 20%-40% of the total sheath area.

3. A method for preparing an adaptive unblocking pre-filled sand-control screen pipe based on a hydrophobic-negatively charged dual-functional coating according to claim 1 or 2, characterized in that, The preparation method includes the following steps: (1) Prepare a coating solution containing a hydrophobic polymer and a negatively charged group modifier, immerse the pre-filled particles in the coating solution for surface coating, remove them and dry and cure them to obtain multifunctional pre-filled particles; (2) Prepare the inner sheath, outer sheath, first annular end cap, and second annular end cap and assemble them. The multifunctional prefilled particles described in step (1) are filled into the prefilled cavity and sintered and fixed as a whole to form a prefilled assembly. (3) The central base pipe is fixedly connected to the pre-filling component described in step (2) to obtain an adaptive unblocking pre-filling sand screen pipe based on a hydrophobic-negative dual-function coating.

4. The preparation method according to claim 3, characterized in that, The pre-filled particles in step (1) include any one or a combination of at least two of the following: quartz sand, ceramsite, or alumina particles; Preferably, the particle size D50 of the pre-filled particles is 0.45-0.90 mm.

5. The preparation method according to claim 3, characterized in that, In step (1), the coating solution containing a hydrophobic polymer and a negatively charged group modifier includes any one or a combination of at least two of polydimethylsiloxane, polytetrafluoroethylene, or fluorinated acrylate copolymers. The negatively charged group modifier includes a surface modifier containing negatively charged functional groups, which include any one or a combination of at least two of sulfonic acid groups, carboxyl groups, or phosphate groups. The surface modifier includes a silane coupling agent.

6. The preparation method according to claim 3, characterized in that, The preparation method of the coating solution containing hydrophobic polymer and negatively charged group modifier in step (1) includes: dissolving the hydrophobic polymer in an organic solvent, adding the negatively charged group modifier, and stirring evenly; Preferably, the uniform stirring includes: magnetic stirring at a speed of 100-500 rpm for 0.5-6 hours at a temperature of 40-80℃; Preferably, the organic solvent includes any one or a combination of at least two of toluene, acetone, or ethanol.

7. The preparation method according to claim 6, characterized in that, The ratio of the hydrophobic polymer to the organic solvent is (0.05-0.20):1 g / mL, and the ratio of the negatively charged group modifier to the organic solvent is (0.01-0.10):1 g / mL.

8. The preparation method according to claim 3, characterized in that, The immersion time in step (1) is 5-60 minutes, and stirring is carried out during the immersion process in step (1).

9. The preparation method according to claim 3, characterized in that, The drying and curing temperature in step (1) is 60-120℃, and the time is 2-6 hours.

10. The preparation method according to claim 3, characterized in that, In step (2), the filling density is 1.5-2.0 g / cm³. 3 ; Preferably, in step (2), the overall sintering fixation includes: heating to 200-400°C at a rate of 2-10°C / min, holding for sintering for 0.5-3 hours, and then cooling to room temperature with the furnace.

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