A low friction drag sand screen

Abstract

The application discloses a low-friction sand control screen pipe, and belongs to the technical field of oil and gas field development. The low-friction sand control screen pipe comprises a screen pipe body, a protection assembly, a friction reduction assembly and a magnetic coating, and a plurality of filter holes are formed through the screen pipe body. The protection assembly comprises an inner sheath and an outer sheath which are sleeved on the outer periphery of the screen pipe body, and a containing space is formed between the inner sheath and the outer sheath. The containing space is filled with a pre-filling layer which is composed of lightweight ceramic granules. The friction reduction assembly comprises a mounting sleeve and rolling bodies. The mounting sleeve is sleeved on the outer wall of the screen pipe body, and a plurality of rolling bodies are arranged on the outer wall of the mounting sleeve. The rolling bodies can rollingly contact the well wall. The outer surface of the inner sheath and / or the outer sheath is provided with the magnetic coating, and the magnetic coating is used for generating a magnetic field for adsorbing stratum particles. The sand control screen pipe realizes the comprehensive effects of low friction, light weight, anti-clogging and long-acting sand control through the functional complementation and structural compatibility between the components.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field development technology, and in particular to a low-friction sand-prevention screen pipe. Background Technology

[0002] In the process of oil and gas extraction, sand production is one of the main factors affecting the normal production of oil wells and the life of equipment. Therefore, it is usually necessary to install sand screens on the production tubing that is run into the well to prevent formation sand particles from entering the pump barrel or surface process.

[0003] Existing sand control screens typically employ structural forms such as wire-wound screens, slotted screens, or pre-filled gravel screens. Pre-filled gravel screens achieve sand control and sand retention by filling the space between the inner and outer casings with a gravel layer. After the pre-filled gravel screen is lowered into the wellbore, formation fluids enter the gravel layer through the flow holes on the outer casing. Sand particles are blocked by the gravel layer, while the fluids pass through the flow holes on the inner casing into the screen body and flow to the surface.

[0004] However, during actual installation, existing sand control screens often experience significant sliding friction resistance between the screen's outer wall and the wellbore due to the presence of curved, horizontal, or large-displacement sections in the wellbore trajectory, coupled with the rough wellbore surface and the presence of rock cuttings or mud cake. This excessive resistance not only makes it difficult to push the completion string to the predetermined depth but can also cause the string to jam or fail to be installed. Secondly, traditional pre-filled screens, filled with high-density gravel or ceramsite, result in excessive linear weight, increasing the requirements for drilling rig lifting capacity and string tensile strength. This excessive weight further exacerbates the installation friction. Furthermore, as production progresses, formation particles (such as clay particles, silt, and fine sand) can easily migrate and accumulate in the flow holes of the inner and outer casings and the pores of the pre-filled layer, causing blockages and premature screen failure. This can even lead to well shutdown or workover operations, reducing the lifespan of the sand control screen and production efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a low-friction sand-control screen pipe to solve the technical problems of existing sand-control screen pipes in the well running process, such as high frictional resistance, excessive linear weight, and easy clogging.

[0006] To achieve this objective, the present invention adopts the following technical solution: A low-friction sand-proof screen tube, comprising: The screen tube body has multiple filter holes extending through it. The protective assembly includes an inner sheath and an outer sheath, which are coaxially sleeved on the outer periphery of the screen tube body. An accommodating space is formed between the inner and outer sheaths, and the accommodating space is filled with a pre-filling layer. The pre-filling layer is formed by sintering and solidifying lightweight ceramic particles. The lightweight ceramic particles have a porous internal structure. Multiple flow holes are respectively opened through the inner and outer sheaths, and the flow holes are connected to the pre-filling layer. The friction reduction assembly includes a mounting sleeve and rolling elements. The mounting sleeve is fitted onto the outer wall of the screen pipe body. A plurality of rolling elements are provided on the outer wall of the mounting sleeve. The plurality of rolling elements are rotatably connected to the mounting sleeve and distributed along the circumference of the mounting sleeve. The rolling elements are able to make rolling contact with the well wall. A magnetic coating is provided on the outer surface of the inner sheath and / or the outer sheath, the magnetic coating being used to generate a magnetic field for adsorbing formation particles.

[0007] Preferably, the density of the lightweight ceramsite is 2.2–2.4 g / cm³. 3 The particle size of the lightweight ceramsite is 0.5 to 1.2 mm.

[0008] Preferably, the outer wall of the mounting sleeve is provided with a plurality of radially protruding ridges, the plurality of ridges are arranged at intervals along the circumference of the mounting sleeve, the ridges extend spirally along the axial direction of the mounting sleeve, and each ridge is provided with at least two rolling elements along its own extending direction.

[0009] Preferably, the multiple rolling elements on each of the convex ridges are distributed at equal intervals along the extending direction of the convex ridge.

[0010] Preferably, the protective assembly further includes a blocking member, with one blocking member provided for each of the flow holes. The blocking member is connected to the flow hole, and a flow gap is formed between the blocking member and the inner wall of the flow hole to allow fluid to pass through in a detour.

[0011] Preferably, the blocking member includes a straight section and inclined sections disposed at both ends of the straight section. The two inclined sections are respectively connected to the inner wall of the flow hole. The straight section and the inclined sections have an arched structure. The straight section is located on the side close to the screen tube body and is disposed at a distance from the flow hole to form the flow gap.

[0012] Preferably, the rolling element is at least one of a roller or a ball.

[0013] Preferably, a plurality of protective components are provided, and the plurality of protective components are distributed at intervals along the axial direction of the screen tube body, with at least one friction-reducing component provided between each two adjacent protective components.

[0014] Preferably, the magnetic coating is a resin-based coating containing nano-magnetic particles, wherein the nano-magnetic particles are uniformly dispersed in the magnetic coating.

[0015] Preferably, the particle size of the magnetic nanoparticles is 20–100 nm, and the dry film thickness of the magnetic coating is 50–100 μm.

[0016] The beneficial effects of this invention are: The low-friction sand-control screen proposed in this invention firstly involves fixing an installation sleeve to the outer wall of the screen body. Multiple rolling elements, circumferentially distributed on the outer wall of the installation sleeve, are rotatably connected to the sleeve. When the sand-control screen is lowered into the wellbore along with the completion string, the rolling elements directly contact the well wall and roll, thus transforming the sliding friction between the outer wall of the traditional sand-control screen and the well wall into rolling friction between the rolling elements and the well wall. Since the rolling friction coefficient is much lower than the sliding friction coefficient, the axial resistance to be overcome during lowering is effectively reduced, allowing the sand-control screen to pass more smoothly through curved sections, horizontal sections, and large displacement sections, improving the reliability and efficiency of well completion operations. Secondly, by filling the space between the inner and outer sheaths with a pre-filled layer formed by sintering and solidifying lightweight ceramic particles, the low bulk density of the lightweight ceramic particles compared to conventional solid or high-density filling materials, due to their porous structure, effectively controls the linear weight of the entire sand control screen. This not only reduces the requirements for drilling rig lifting capacity and the tensile strength of the sand control screen, but also reduces the normal pressure exerted by the sand control screen on the well wall during the lowering process. Combined with the rolling elements of the friction-reducing components, this further reduces the frictional resistance component caused by its own weight, achieving a synergistic effect of low friction and lightweight design. Simultaneously, the pre-filled layer formed by sintering and solidifying the lightweight ceramic particles maintains sufficient compressive strength and a stable pore structure, effectively preventing formation sand particles from entering the screen body and ensuring that the sand control function is not affected. Furthermore, a magnetic coating is applied to the outer surfaces of the inner and outer sheaths. The magnetic coating generates a magnetic field that adsorbs formation particles. When formation fluid carrying ferromagnetic or paramagnetic particles flows through the flow holes of the outer sheath into the pre-filled layer, and then through the flow holes of the inner sheath into the main body of the screen pipe, the particles are subjected to the magnetic field generated by the magnetic coating along their flow path. Because the magnetic coating is located on the outer surfaces of both the inner and outer sheaths, its magnetic field penetrates the pores of the flow holes and the pre-filled layer, actively capturing and adsorbing tiny magnetic or magnetizable particles in the fluid. These particles adhere to the surfaces of the inner and outer sheaths or the outer edge of the pre-filled layer, preventing them from migrating further into the pre-filled layer or accumulating at the flow holes. This effectively slows down the clogging process of the pre-filled layer pores, maintains the long-term unobstructed flow of the flow holes and the pre-filled layer, improves the anti-clogging ability of the screen pipe, and extends its service life.

[0017] In summary, this invention reduces the frictional resistance of the lowering component through rolling contact, reduces line weight through a lightweight ceramic pre-filling layer to indirectly reduce drag and lower equipment requirements, and solves the clogging problem by actively adsorbing microparticles through a magnetic coating. Furthermore, the components complement each other in function and are structurally compatible, thus achieving a comprehensive effect of low frictional resistance, lightweight design, and long-lasting sand protection. Attached Figure Description

[0018] Figure 1This is a schematic diagram of the low-friction sand-proof screen tube provided in Embodiment 1 of the present invention; Figure 2 This is an exploded structural diagram of the low-friction sand-proof screen tube provided in Embodiment 1 of the present invention; Figure 3 This is a schematic diagram of the friction-reducing component provided in Embodiment 1 of the present invention; Figure 4 This is a schematic diagram of the structure of the outer sheath provided in Embodiment 1 of the present invention; Figure 5 yes Figure 4 Enlarged view of point A in the middle; Figure 6 This is a cross-sectional view of the low-friction sand-proof screen tube provided in Embodiment 1 of the present invention.

[0019] In the picture: 1. Screen tube body; 11. Filter holes; 2. Protective components; 21. Inner sheath; 22. Outer sheath; 23. Accommodation space; 24. Pre-filled layer; 25. Flow hole; 26. Blocking component; 261. Flow gap; 262. Straight section; 263. Inclined section; 3. Friction-reducing components; 31. Mounting sleeve; 32. Raised rib; 33. Rolling element. Detailed Implementation

[0020] Embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0021] In the description of this invention, unless otherwise explicitly specified and limited, the terms "connected," "linked," and "fixed" should be interpreted broadly. For example, they can refer to a fixed connection or a detachable connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0022] In the description of this invention, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature being directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature being directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0023] The technical solution of the present invention will be further described below with reference to the accompanying drawings and specific embodiments.

[0024] Example 1 See Figures 1 to 6 The low-friction sand-proof screen tube provided in this embodiment of the invention includes a screen tube body 1, a protective component 2, a friction-reducing component 3, and a magnetic coating. The screen tube body 1 has multiple filter holes 11 extending through it. The protective component 2 includes an inner sheath 21 and an outer sheath 22, which are coaxially sleeved on the outer periphery of the screen tube body 1. A receiving space 23 is formed between the inner sheath 21 and the outer sheath 22, and the receiving space 23 is filled with a pre-filling layer 24. The pre-filling layer 24 is formed by sintering and solidifying lightweight ceramic particles, which have a porous internal structure. Multiple flow holes 25 are respectively extended through the inner sheath 21 and the outer sheath 22, and the flow holes 25 are connected to the pre-filling layer 24. The friction-reducing component 3 includes a mounting sleeve 31 and rolling elements 33. The mounting sleeve 31 is fitted onto the outer wall of the screen pipe body 1. Multiple rolling elements 33 are disposed on the outer wall of the mounting sleeve 31. These rolling elements 33 are rotatably connected to the mounting sleeve 31 and distributed circumferentially along the mounting sleeve 31, enabling them to roll and contact the well wall. The outer surfaces of the inner sheath 21 and / or the outer sheath 22 are coated with a magnetic coating, which generates a magnetic field to adsorb formation particles.

[0025] The screen body 1, as the load-bearing skeleton of the entire sand control screen, is made of metal materials with good mechanical strength and corrosion resistance, such as stainless steel, so that the screen body 1 can withstand high pressure, corrosive fluids and tensile and compressive loads in the complex downhole environment.

[0026] The screen tube body 1 has a cylindrical structure. The ratio of the wall thickness to the outer diameter of the screen tube body 1 can be optimized according to the actual well conditions. Generally speaking, the wall thickness is 3mm to 8mm, the outer diameter is 60mm to 180mm, and the length is set to 3 meters to 12 meters according to the well completion section requirements.

[0027] Multiple filter holes 11 are provided along the wall of the screen tube body 1. The filter holes 11 are used to introduce the formation fluid that has been filtered by the pre-filled layer 24 into the interior of the screen tube body 1, and then flow to the surface. The shape of the filter holes 11 can be circular, elliptical or narrow slit. Circular holes are easier to machine and have less stress concentration, so circular holes are preferred.

[0028] The pore size of the filter hole 11 is designed to be between 1 mm and 3 mm. This size range can ensure a high flow area and also form a secondary barrier against a small number of larger particles that may pass through the pre-filled layer 24.

[0029] The filter holes 11 are arranged in an array of multiple columns along the axis and evenly distributed around the circumference. The filter holes 11 in adjacent columns are staggered by half a hole spacing in the circumference to obtain the maximum flow area while ensuring the structural strength of the screen tube body 1.

[0030] Specifically, a ring of holes is provided at certain intervals along the axial direction of the screen tube body 1. Each ring of holes has 6 to 12 filter holes 11 evenly distributed in the circumferential direction. The filter holes 11 between adjacent rings of holes are staggered in the circumferential direction, thereby avoiding the formation of a continuous weakening zone on the tube wall and ensuring that the screen tube body 1 can withstand an internal or external pressure of not less than 50 MPa.

[0031] The screen tube body 1 is divided into multiple functional sections. Each functional section is provided with a protective component 2. Multiple protective components 2 are provided and distributed at intervals along the axial direction of the screen tube body 1. At least one friction-reducing component 3 is provided between each two adjacent protective components 2.

[0032] The protective component 2 includes an inner sheath 21, an outer sheath 22, and a pre-filling layer 24 between them. A certain length of bare pipe section is left between two adjacent protective components 2, and a friction-reducing component 3 is fixedly installed on the outer wall of the bare pipe section. Furthermore, the axial spacing between adjacent protective components 2 can be optimized according to the wellbore curvature radius and the distribution of running resistance, usually selected in the range of 0.5 meters to 2 meters, so that the rolling elements 33 are more uniformly distributed axially, ensuring that at least two to three friction-reducing components 3 are in contact with the lower well wall at the same time in the curved section, thereby effectively dispersing the contact pressure and maintaining a low friction state.

[0033] Both the inner sheath 21 and the outer sheath 22 are cylindrical metal sleeves coaxially arranged with the screen tube body 1. A gap of 0.5 mm to 1 mm is left between the inner diameter of the inner sheath 21 and the outer diameter of the screen tube body 1 to facilitate fitting during assembly. After assembly, they can be relatively fixed by end welding or threaded tightening. The inner diameter of the outer sheath 22 is larger than the outer diameter of the inner sheath 21, and the radial distance between the two is the thickness of the pre-filling layer 24.

[0034] Flow holes 25 are respectively opened through the pipe walls of the inner sheath 21 and the outer sheath 22. The shape of the flow holes 25 can be circular, square or oblong. The flow holes 25 can be arranged in an axially equidistant, circumferentially uniform form, or in a spiral arrangement, so that the flow path of the fluid in the pre-filled layer 24 is more tortuous, thereby improving the filtration effect.

[0035] To further prevent formation sand particles from directly passing through the flow holes 25 into the pre-filled layer 24 without reducing the flow capacity, the protective component 2 also includes a blocking member 26. One blocking member 26 is provided for each flow hole 25, connected to the flow hole 25. A flow gap 261 is formed between the blocking member 26 and the inner wall of the flow hole 25, allowing the fluid to pass through in a circuitous manner. The blocking member 26 does not completely seal the flow hole 25, but rather, together with the inner wall of the flow hole 25, forms one or more narrow and tortuous channels. When formation fluid carrying sand particles rushes towards the flow hole 25, larger sand particles are directly intercepted by the blocking member 26 and cannot enter the flow hole 25; the fluid, however, detours through the flow gap 261. During this process, the flow direction of the fluid changes multiple times, causing the fine particles it carries to collide with the blocking member 26 or the hole wall under inertia and settle, thus achieving pre-separation of the sand particles.

[0036] Preferably, the blocking member 26 includes a straight section 262 and inclined sections 263 disposed at both ends of the straight section 262. The two inclined sections 263 are respectively connected to the inner wall of the flow hole 25. The straight section 262 and the inclined section 263 have an arched structure. The straight section 262 is located on the side close to the screen tube body 1 and is disposed at a distance from the flow hole 25 to form a flow gap 261.

[0037] More specifically, the blocking member 26 can be formed by stamping a thin metal sheet, and its overall shape is similar to that of an arch bridge. The inclined sections 263 at both ends flare outwards, serving as connecting feet welded or riveted to the inner walls of opposite sides of the flow hole 25. The straight section 262 in the middle spans the central area of ​​the flow hole 25, is substantially perpendicular to the axis of the flow hole 25, and is positioned closer to the screen tube body 1 relative to the opening plane of the flow hole 25; that is, the straight section 262 is recessed into the hole. This creates a gap approximately parallel to the hole axis between the straight section 262 and the inner wall of the flow hole 25. The width of this gap is the flow gap 261, thus providing a primary sand-blocking function.

[0038] When fluid enters from outside the outer sheath 22 through the flow hole 25, it first encounters the obstruction of the straight section 262. The fluid is forced to flow around the perimeter of the straight section 262 and into the flow gap 261. Because the obstruction member 26 has an arched structure, the inclined sections 263 at both ends of the straight section 262 provide a smooth transition, avoiding excessive eddies and pressure loss during fluid flow. Simultaneously, this arched structure has high bending stiffness, resisting deformation caused by downhole pressure fluctuations. For the flow hole 25 on the inner sheath 21, a similar obstruction member 26 can be installed, but its straight section 262 should be located closer to the screen tube body 1, facing inwards towards the screen tube. This prevents sand particles that have entered the inner sheath 21 from flowing back into the pre-filled layer 24. Through the cooperation of the obstruction member 26 and the flow hole 25, the interception capacity for fine sand and silt is effectively improved without reducing the total area of ​​the flow hole 25, reducing the filtration burden on the pre-filled layer 24.

[0039] The accommodating space 23 formed between the inner sheath 21 and the outer sheath 22 is filled with a pre-filled layer 24, which is formed by sintering and solidifying lightweight ceramic particles. The lightweight ceramic particles have a porous internal structure.

[0040] Preferably, the density of the lightweight ceramsite is 2.2–2.4 g / cm³. 3 The particle size of lightweight ceramsite is 0.5–1.2 mm. It should be noted that the density of lightweight ceramsite here refers to the apparent density of the ceramsite particles, that is, the mass per unit volume including the closed pores within the particles. This is significantly higher than the silica sand or high-density ceramsite (whose density is typically 2.6–3.0 g / cm³) used in conventional sand control screens in existing technologies. 3 (Even higher), the lightweight ceramic particles selected in this invention have an advantage in density, which can effectively reduce the linear weight of the entire screen tube.

[0041] More preferably, the lightweight ceramsite can be ultra-lightweight high-strength ceramsite, whose density can be further reduced to 1.3–1.5 g / cm³. 3 Meanwhile, by optimizing the sintering process, its fracture resistance strength reaches over 25 MPa, thereby reducing the overall linear weight of the screen tube to 20 to 25 kg per meter while ensuring pressure resistance, which is about half the linear weight of traditional pre-filled screen tubes. The particle size of the lightweight ceramsite is controlled within the range of 0.5 to 1.2 mm. This particle size range has been optimized through gradation, that is, by mixing ceramsite of different particle sizes in a certain proportion, the smaller particle size fills the gaps between the larger particle size, thereby forming a porous filter medium with high bulk density, uniform pore distribution, and stability.

[0042] During the sintering and solidification process, the ceramic particles undergo local melting at their contact points and form sintering necks, connecting the discrete particles into a porous skeleton with overall strength. At the same time, the inherent microporous structure inside the particles is preserved, so that the pre-filled layer 24 has both high mechanical strength and good fluid permeability.

[0043] In practical use, when the formation fluid carrying sand particles flows through the pre-filled layer 24, the narrow and tortuous pore channels formed between the lightweight ceramic particles effectively intercept sand particles larger than the pore diameter on the outside or inside of the pre-filled layer 24, while the fluid can pass through smoothly. Simultaneously, the porous structure inside the lightweight ceramic particles increases their surface roughness, which is beneficial for forming stronger interparticle connections during sintering. Furthermore, these internal micropores also play a role in fluid buffering and particle capture, further delaying the clogging process of the pre-filled layer 24.

[0044] It is understood that those skilled in the art can make adaptive adjustments to the density and particle size of lightweight ceramsite based on the specific well conditions, such as temperature, pressure, and median formation sand particle size. For example, in deep well high-pressure environments, ceramsite with slightly higher density but greater strength can be preferred, while in shallow low-pressure wells, ultra-lightweight ceramsite with lower density can be selected to maximize the weight reduction effect. These adjustments do not depart from the core concept of this invention.

[0045] The outer surfaces of the inner sheath 21 and / or the outer sheath 22 are provided with a magnetic coating, which is used to generate a magnetic field to adsorb formation particles. In this embodiment, the outer surfaces of both the inner sheath 21 and the outer sheath 22 are provided with a magnetic coating to form a double adsorption barrier. It is understood that in other embodiments, the magnetic coating may be provided only on the outer surface of the inner sheath 21 or only on the outer surface of the outer sheath 22, depending on the particle size distribution and magnetic strength requirements of the formation particles, which will not be elaborated here.

[0046] Preferably, the magnetic coating is a resin-based coating containing nano-magnetic particles, which are uniformly dispersed within the magnetic coating. The resin-based coating can be made of materials with good corrosion resistance and adhesion, such as epoxy resin, polyurethane, or phenolic resin. Epoxy resin is preferred due to its low curing shrinkage and high bonding strength with the metal substrate.

[0047] The nanomagnetic particles can be made of high-permeability materials such as iron(III) oxide (Fe3O4) or γ-ferric oxide (γ-Fe2O3). These materials are superparamagnetic or ferromagnetic and can be magnetized under the influence of an external magnetic field, generating a residual magnetic field. During preparation, the nanomagnetic particles are added to liquid resin in a certain proportion (e.g., 30% to 60% of the resin mass). The nanomagnetic particles are uniformly dispersed using high-speed dispersion or ball milling. Then, the composite resin is applied to the outer surface of the inner sheath 21 and / or the outer sheath 22 by spraying, brushing, or dipping. After heating and curing, a firmly adhered magnetic coating is formed.

[0048] Furthermore, the particle size of the magnetic nanoparticles is 20–100 nm, and the dry film thickness of the magnetic coating is 50–100 μm. Controlling the magnetic nanoparticles within this particle size range ensures that the particles have a high specific surface area and magnetic response characteristics, while also facilitating uniform dispersion in the resin without agglomeration.

[0049] Dry film thickness refers to the actual thickness of the solid film remaining on the surface of the inner sheath 21 and / or outer sheath 22 after the magnetic coating has fully cured and the solvent or moisture has evaporated. In this embodiment, the dry film thickness is controlled between 50 and 100 micrometers. If it is too thin, the magnetic induction intensity will be insufficient; if it is too thick, it may affect the effective opening rate of the flow hole 25 on the sheath and increase the risk of coating cracking.

[0050] After being magnetized, the magnetic coating can generate a ring-shaped magnetic field of a certain strength in the space around it, for example, the magnetic induction intensity can reach 80 to 150 Gauss, which is sufficient to effectively attract ferromagnetic or paramagnetic particles carried in the formation fluid.

[0051] In actual production, when the formation fluid carrying clay particles, silt, and fine sand flows through the flow holes 25 of the outer sheath 22, the particles are first affected by the magnetic field of the magnetic coating on the surface of the outer sheath 22. Because the nano-magnetic particles are uniformly distributed in the magnetic coating, the resulting magnetic field is also continuous and uniform in space. The particles are attracted to the surface of the magnetic coating by magnetization in the magnetic field and gradually accumulate to form a loose, ordered soft protective layer. Due to the mutual repulsion or ordered arrangement between the magnetic particles, the soft protective layer has a high porosity, allowing the fluid to pass through smoothly, while finer particles are further adsorbed.

[0052] Meanwhile, since the magnetic coating is applied to the outer surface of the inner sheath 21 or the outer sheath 22, the adsorbed particles will not block the internal channels of the flow hole 25, but will adhere to the outside of the sheath. When the adsorption amount reaches a certain level, the flushing effect of the fluid can cause some of the loose particles to fall off and be carried out with the fluid, thus achieving a certain degree of self-cleaning.

[0053] In the case where a magnetic coating is also provided on the outer surface of the inner sheath 21, the extremely fine particles passing through the pre-filled layer 24 will be adsorbed a second time before entering the flow hole 25 of the inner sheath 21, thereby further preventing the particles from entering the interior of the screen tube body 1.

[0054] To further reduce the running resistance of the sand control screen pipe in complex wellbore trajectories, a friction-reducing component 3 is installed on the outer wall of the screen pipe body 1. As a preferred arrangement, a friction-reducing component 3 is fixedly installed every 2 to 3 meters along the axial direction of the screen pipe body 1. The selection of this spacing takes into account the radius of curvature of the wellbore bend and the flexible deformation capacity of the tubing string, ensuring that at least one friction-reducing component 3 is under load when passing through the build-up point or horizontal section.

[0055] The friction-reducing component 3 includes a mounting sleeve 31 and a rolling element 33. The mounting sleeve 31 has a cylindrical structure. The inner diameter of the mounting sleeve 31 is clearance-fitted with the outer diameter of the screen tube body 1 so that it can be smoothly fitted onto the outside of the screen tube body 1 during on-site assembly. After assembly, axial positioning and circumferential fixation are achieved by radially set set screws or end retaining rings to prevent relative rotation or axial movement of the mounting sleeve 31 during use.

[0056] To further improve the contact efficiency and load uniformity between the rolling elements 33 and the well wall, multiple ridges 32 are radially protruding on the outer wall of the mounting sleeve 31. These ridges 32 are spaced apart circumferentially along the mounting sleeve 31 and extend spirally along the axial direction of the mounting sleeve 31. Each ridge 32 has at least two rolling elements 33 arranged along its own extending direction. The spirally extending ridges 32 have a longer total length than straight ridges, allowing them to accommodate more rolling elements 33 within the limited axial length of the mounting sleeve 31. Simultaneously, the spiral direction ensures that the contact trajectory of the rolling elements 33 on the well wall is distributed spirally, preventing all rolling elements 33 from simultaneously passing through the same annular wear zone on the well wall, thereby reducing the risk of contact failure due to localized well wall depressions.

[0057] In this embodiment, each protrusion 32 is provided with two rolling elements 33, which are located near both ends of the protrusion 32 to ensure balanced force distribution.

[0058] Furthermore, the multiple rolling elements 33 on each convex ridge 32 are evenly distributed along the extension direction of the convex ridge 32, so that the projection of the rolling element 33 on any axial section can cover a wider circumferential angle range, thereby ensuring that when the screen pipe deflects or tilts in the wellbore, at least one rolling element 33 always keeps in contact with the lower or upper side of the well wall, avoiding local sliding contact caused by uneven distribution of the rolling elements 33.

[0059] Regarding the specific form of the rolling element 33, the rolling element 33 is at least one of a roller or a ball. In this embodiment, the rolling element 33 is a roller, which has a large contact area and high radial load-bearing capacity, and is particularly suitable for working conditions in horizontal wells with large displacement that need to withstand large lateral loads.

[0060] Each roller is rotatably mounted in a shaft hole on the convex rib 32 via a roller shaft, and the outer circumferential surface of the roller protrudes about 2 to 4 mm from the top surface of the convex rib 32.

[0061] The rollers can be made of high-performance polymer materials such as polyether ether ketone (PEEK) or polyimide (PI). These materials have self-lubricating properties, low coefficient of friction, high wear resistance and good low-temperature toughness, which can adapt to the low-temperature environment of deep-sea oil and gas fields or hydrate reservoirs, while avoiding electrochemical corrosion or cold welding that may occur between the metal rollers and the well casing.

[0062] During the screen pipe installation process, the rollers roll along the well wall as the tubing string advances, transforming traditional sliding friction into rolling friction. The coefficient of friction can be reduced from 0.3 to 0.5 for sliding friction to below 0.05 to 0.1 for rolling friction, thereby reducing pushing resistance. Simultaneously, due to the helical extension of the convex 32, the rollers generate a small axial force during rolling. This force helps guide the tubing string smoothly through curved sections, reducing additional resistance caused by tubing buckling.

[0063] Example 2 The following example illustrates the technical effects of this invention in a long horizontal well section of a silty mudstone hydrate reservoir in the South China Sea, but the application of this invention is not limited to this.

[0064] The scenario involves a water depth of 1200 meters, a horizontal section length of 1000 meters, a reservoir clay content of approximately 25%, a temperature of 5 to 10 degrees Celsius, and a pore pressure of approximately 12 MPa. The low-friction sand-control screen provided in Embodiment 1 of this invention was used for well completion operations.

[0065] The specific configuration is as follows: The main body 1 of the screen tube is made of 316L stainless steel with an outer diameter of 127mm and an inner diameter of 105mm. The tube wall is laser-drilled to form filter holes 11. The pre-filling layer 24 uses a density of 1.4g / cm³. 3Ultra-lightweight ceramic particles with an average particle size of 0.8 mm are sintered and cured after high-pressure filling. The pre-filling layer 24 is approximately 11 mm thick, and the entire screen tube weighs 22 kg per meter. Sleeves 31 are welded and installed every 3 meters along the screen tube axis. Rollers made of polyetheretherketone (PEEK) are installed on the sleeves 31. The outer diameter of the screen tube is 142 mm when the rollers are fully extended. An epoxy resin-based magnetic coating is applied to the inner and outer sheaths 22 using an electrostatic spraying process. 40% by mass of iron oxide nanoparticles with a particle size of approximately 50 nanometers are added to the coating. After curing, the dry film thickness is 80 micrometers, and the average magnetic field strength on the coating surface is 100 Gauss.

[0066] During the lowering operation, when the screen pipe passed through the directional drilling section (60° inclination angle) and the 1000-meter horizontal section, the measured lowering friction was reduced from the expected 18 tons for traditional screen pipes to 7 tons due to the rolling contact of the rollers. The lowering process was smooth and no jamming occurred. After 6 months of trial production monitoring, the fine sand content in the produced fluid remained stable, and the pressure differential outside the screen pipe increased slowly. After production was completed, the screen pipe was pulled out for inspection. The outer surface deposits were loose and easy to remove, and the internal flow channels remained in good condition. The permeability retention rate was greater than 90%, while the permeability retention rate of traditional screen pipes under the same conditions was less than 60%.

[0067] Example 3 This embodiment uses the exploitation of ultra-long horizontal sections in deep-water shallow gas reservoirs as an application scenario to further verify the applicability of the present invention under long-span and high-difficulty well conditions, but the application of the present invention is not limited to this.

[0068] The scenario involves a water depth of 1800 meters and a horizontal section length of 1500 meters. The reservoir consists of mudstone containing silt interlayers, presenting extremely challenging operational conditions. The low-friction sand-control screen pipe provided in Embodiment 1 of this invention was adopted and specifically optimized to meet the unique requirements of the ultra-long horizontal section.

[0069] The specific configuration is as follows: The 1500-meter-long sand control screen is divided into three 500-meter sections, connected by flexible anti-torsion joints. This joint can adapt to minor bending changes in the wellbore trajectory and transmit the necessary torque, facilitating the rotation of the tubing string to overcome local resistance when necessary.

[0070] The pre-filled layer 24 uses a density of 1.35 g / cm³. 3 The ultra-lightweight ceramsite reduces the total weight of the entire 1500-meter screen pipe by approximately 450 tons compared to traditional ceramsite, thus lowering the load requirements on the tensioner system of deep-water drilling vessels.

[0071] Regarding the arrangement of the friction-reducing components 3, the installation spacing is increased to one set every 2 meters in the horizontal section, with a total of approximately 750 sets of friction-reducing components 3 deployed throughout the entire section. This ensures that the sand-proof screen pipe is always supported by rollers throughout the entire ultra-long horizontal section, minimizing the contact friction between the tubing and the well wall. The magnetic coating and other structures use the materials and processes described in the aforementioned embodiments, and will not be repeated here.

[0072] During the running-in operation, the sand control screen string was successfully lowered to the predetermined depth, with the total running-in time shortened by approximately 50% compared to similar wells using conventional techniques. Throughout the process, the drilling rig load remained stable, and no overload alarms were triggered, indicating that the synergistic effect of the friction-reducing component 3 and the lightweight pre-filled layer 24 effectively controlled the axial resistance of the tubing string. This successful case fully demonstrates the feasibility of this invention for the safe running of ultra-long horizontal sections up to 1500 meters in length, providing reliable technical support for the efficient development of deep-water shallow gas reservoirs.

[0073] Example 4 This embodiment addresses the extremely high risk of particle migration and blockage in reservoirs with high clay content. It strengthens the magnetic coating provided in Embodiment 1 of the present invention and verifies its anti-blockage performance using a laboratory core flow apparatus. The simulated reservoir has a clay content as high as 35%, classifying it as a silty clay reservoir with a significant risk of particle migration and blockage.

[0074] The specific configuration is as follows: Based on the structure of Example 1, the magnetic coating was strengthened. The coating filler uses stronger magnetic γ-ferric oxide nanoparticles with a particle size of approximately 30 nanometers to replace conventional magnetite. This magnetic coating uses the same epoxy resin matrix as described above, with the nanoparticles added at a 40% mass ratio. The dry film thickness was increased to 100 micrometers by optimizing the spraying process, and the magnetic field strength on the coating surface was increased to 150 Gauss after magnetization. The remaining structures, including the lightweight ceramic pre-filled layer 24 and the friction-reducing component 3, are the same as in the aforementioned examples and will not be described again here.

[0075] To verify the anti-clogging effect of the reinforced magnetic coating, a comparative test was conducted in a laboratory core flow apparatus. Two sets of sieve tube samples were tested in parallel. The first set was the sand-proof sieve tube with reinforced magnetic coating provided in this embodiment, and the second set was a control sample, which had the same structure as the first set but was coated with a non-magnetic smooth coating (i.e., a pure resin coating without nano-magnetic particles).

[0076] During the test, simulated formation water containing kaolin particles was continuously injected into the device, and the change in inlet and outlet pressure difference over time was monitored.

[0077] The results showed that for the control sieve tube without a magnetic coating, the inlet and outlet pressure difference increased sharply within 48 hours of injection, indicating that the particles rapidly blocked the pre-filled layer 24 and the flow hole 25. However, for the sieve tube with the reinforced magnetic coating of this invention, the pressure difference increased slowly in the initial stage and then gradually stabilized, without a sharp increase.

[0078] After the test, the surface of the magnetic coating was observed using an electron microscope. It was observed that the adsorbed particles were arranged in an orderly manner, forming a loose particle layer rather than a dense filter cake, allowing fluid to pass through smoothly. Calculations showed that the stable flow capacity of the sand-control screen pipe of this invention is more than three times that of a sand-control screen pipe without a magnetic coating.

[0079] This embodiment fully demonstrates that by increasing the magnetic field strength of the magnetic coating, the present invention can effectively address the problem of particle migration in reservoirs with high clay content, slow down the clogging process, and extend the service life of the screen tube.

[0080] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the implementation of the present invention. Those skilled in the art can make other variations or modifications based on the above description. It is neither necessary nor possible to exhaustively describe all embodiments here. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A low-friction sand-proof screen pipe, characterized in that, include: The screen tube body (1) has multiple filter holes (11) through it. The protective component (2) includes an inner sheath (21) and an outer sheath (22). The inner sheath (21) and the outer sheath (22) are coaxially sleeved on the outer periphery of the screen tube body (1). An accommodating space (23) is formed between the inner sheath (21) and the outer sheath (22). The accommodating space (23) is filled with a pre-filling layer (24). The pre-filling layer (24) is formed by sintering and solidifying lightweight ceramic particles. The lightweight ceramic particles have a porous structure inside. Multiple flow holes (25) are respectively opened through the inner sheath (21) and the outer sheath (22). The flow holes (25) are connected to the pre-filling layer (24). The friction reduction component (3) includes an installation sleeve (31) and rolling elements (33). The installation sleeve (31) is sleeved on the outer wall of the screen pipe body (1). A plurality of rolling elements (33) are provided on the outer wall of the installation sleeve (31). The plurality of rolling elements (33) are rotatably connected to the installation sleeve (31) and distributed along the circumference of the installation sleeve (31). The rolling elements (33) can roll and contact the well wall. A magnetic coating is provided on the outer surface of the inner sheath (21) and / or the outer sheath (22), the magnetic coating being used to generate a magnetic field that adsorbs formation particles.

2. The low-friction sand-proof screen tube according to claim 1, characterized in that, The density of the lightweight ceramsite is 2.2–2.4 g / cm³. 3 The particle size of the lightweight ceramsite is 0.5 to 1.2 mm.

3. The low-friction sand-proof screen tube according to claim 1, characterized in that, The outer wall of the mounting sleeve (31) is provided with a plurality of protruding ridges (32) in the radial direction. The plurality of protruding ridges (32) are arranged at intervals along the circumference of the mounting sleeve (31). The protruding ridges (32) extend spirally along the axial direction of the mounting sleeve (31). Each protruding ridge (32) is provided with at least two rolling elements (33) along its own extension direction.

4. The low-friction sand-proof screen tube according to claim 3, characterized in that, The multiple rolling elements (33) on each of the protruding ridges (32) are distributed at equal intervals along the extension direction of the protruding ridge (32).

5. The low-friction sand-proof screen tube according to claim 1, characterized in that, The protective component (2) further includes a blocking member (26), one blocking member (26) is provided for each of the flow holes (25), the blocking member (26) is connected to the flow hole (25), and a flow gap (261) is formed between the blocking member (26) and the inner wall of the flow hole (25) for the fluid to pass through in a detour.

6. The low-friction sand-proof screen tube according to claim 5, characterized in that, The blocking member (26) includes a straight section (262) and inclined sections (263) disposed at both ends of the straight section (262). The two inclined sections (263) are respectively connected to the inner wall of the flow hole (25). The straight section (262) and the inclined section (263) have an arched structure. The straight section (262) is located on the side close to the screen tube body (1) and is disposed at a distance from the flow hole (25) to form the flow gap (261).

7. The low-friction sand-proof screen tube according to claim 1, characterized in that, The rolling element (33) is at least one of a roller or a ball.

8. The low-friction sand-proof screen tube according to claim 1, characterized in that, The protective components (2) are provided in multiple ways, and the multiple protective components (2) are distributed at intervals along the axial direction of the screen tube body (1). At least one friction-reducing component (3) is provided between each two adjacent protective components (2).

9. The low-friction sand-proof screen tube according to claim 1, characterized in that, The magnetic coating is a resin-based coating containing nano-magnetic particles, which are uniformly dispersed in the magnetic coating.

10. The low-friction sand-proof screen tube according to claim 9, characterized in that, The nano-magnetic particles have a particle size of 20–100 nm, and the dry film thickness of the magnetic coating is 50–100 μm.

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