Natural gas hydrate depressurization exploitation sand control screen pipe

Abstract

The invention provides a natural gas hydrate depressurization exploitation sand control screen pipe which sequentially comprises an unobstructed protective sleeve, a buffer layer, a control layer, a first supporting layer, a second supporting layer and a base pipe from outside to inside, and the unobstructed protective sleeve, the buffer layer, the control layer, the first supporting layer, the second supporting layer and the base pipe are all tubular. The buffer layer, the control layer, the first supporting layer and the second supporting layer are filled with annular low-density microspheres to form a filtering assembly of the sand control screen pipe for depressurization exploitation of the natural gas hydrate, the particle sizes are configured according to the sequence of medium-small-large-large-large, and fluid sequentially penetrates through the filtering assembly in a seepage mode in the radial direction. According to the sand control screen pipe for depressurization exploitation of the natural gas hydrate, the problems that the continuous pilot production period is short, the daily average gas production rate is small and a pilot production process scheme of'small-step jogging 'is not adopted for the sand control problem in the current pilot production of the natural gas hydrate are solved, and an implementation scheme of'thick and thin prevention', long-period stable pilot production and great improvement of the daily average gas production rate is provided.

Description

Technical Field

[0001] The invention relates to the technical field of sand production control in natural gas hydrate depressurization production wells, and in particular to a sand control screen pipe for natural gas hydrate depressurization production. Background Art

[0002] The natural gas hydrate reservoirs in the South my country Sea are characterized by shallow burial, weak consolidation, undiagenetic, and difficult seepage. Analysis of sediment cores taken from the Shenhu Sea area shows that the hydrate saturation can reach 64%, and the horizontal permeability coefficient of the sediment is (0.96-3.70)×10 -9 The median particle size of the sediment is 7.57 μm, of which the mud component accounts for about 36.0%, the silt component content is about 63.0%, the sand component content is less than 1.0%, the sediment sorting coefficient is 2.24, and the uniformity coefficient is 7.86, which is an extremely poorly sorted inhomogeneous sediment.

[0003] Based on the experience of the three recent offshore natural gas hydrate trials (i.e., Japan AT1-P2, China SHSC4, and China SHSC2-6), reservoir sanding is one of the biggest engineering geological challenges that natural gas hydrate production must face. The reservoir is shallow and the sediment cementation strength is poor. When depressurizing the production, the decomposition of natural gas hydrates can easily lead to reservoir and well wall instability and serious sanding. The main problems in controlling sand in natural gas hydrate production wells in the South China Sea are:

[0004] (1) The reservoir sand particle size is extremely low (median particle size is less than 20 μm), and the strong heterogeneity and poor sorting make it difficult to control sand in the full size range. Traditional sand control media cannot meet the sand control accuracy requirements;

[0005] (2) Ultra-high mud content (over 40% in some areas), especially high content of montmorillonite (36% to 41%) and kaolinite, clay minerals can easily lead to blockage of sand control media;

[0006] (3) During the test production process, gravel particles settle to form a deficit in the upper part of the gravel-filled section. The gas-liquid mixture produced by the formation carries sand particles and directly impacts the screen, eroding the screen and damaging it, resulting in sudden large-scale sand production at the bottom of the well.

[0007] (4) During the depressurization process, the gravel filling and metal sand control screen used in the production layer have a void structure, and natural gas hydrates are easily regenerated, causing ice blockage and hindering continuous production;

[0008] (5) When using gravel pre-packed screens or gravel pre-packed bypass screens, the thickness of the filter layer material is one order of magnitude greater than that of conventional mechanical screens, which greatly increases the risk of integrity damage when passing through a wellbore with a small curvature radius. The main natural gas hydrate reservoirs in the South China Sea are generally only 100 to 300 mbsf (mbsf is the depth below the seafloor). When drilling and completing long horizontal wells, the curvature radius of the inclination section is small. The gravel pre-packed screen must reduce the thickness of the gravel layer to pass safely, which greatly reduces the sand control performance of the screen.

[0009] (6) Based on the experience of natural gas hydrate production trials conducted at home and abroad and the results of indoor research, it is shown that the engineering geological risks that may be faced under the conditions of long-term decomposition and production of hydrates include well wall instability and collapse, wellbore settlement and deformation, stratum settlement, submarine landslides and damage to underwater wellheads. The existing sand control pipes used in conventional oil and gas well production do not have a flexible design to compensate for deformation. Therefore, they cannot adapt to the conditions of geological deformation during long-term production trials of natural gas hydrates.

[0010] (7) In 2020, the Shenhu area of ​​the South China Sea used the “formation fluid extraction method” to test the production of natural gas hydrate for the second time. The sand control process of “pre-filled bypass screen + light sand circulation filling double sand control” was adopted. A three-level composite sand control of “coarse + fine” gravel filling + high-precision pre-filled screen was formed in the wellbore to achieve sand tolerance and reduce blockage, effectively delaying the time point when the wellbore was blocked by mud and sand, and maintaining a high production capacity (average daily gas production of 2.87×10 4 m 3 / d).

[0011] During the entire trial production process, although the sand control technology always maintained the mud and sand output in a controllable state, due to the limited trial production time, low water production, and rapid gas production decline, the contradiction between sand control and mud control and production increase was prominent. Whether this sand control technology can be applied and promoted to the industrialized exploitation of natural gas hydrates in the South China Sea needs further verification.

[0012] In addition, this type of sand control technology is complex, difficult to construct, and costly, and does not meet the economic goal of low-cost exploitation of natural gas hydrates in the South China Sea.

[0013] (8) According to the basic theory and technology research on marine natural gas hydrate exploitation in my country in recent years and the summary of the practice of the secondary production test of natural gas hydrate in Shenhu area of ​​South China Sea, in order to increase the daily average production of a single well, it is advisable to adopt a "coarse and fine" sand control scheme, but it also means that there will inevitably be a large amount of mud output in the formation, the risk of sand burial in the wellbore will increase, and long-term stable production test cannot be guaranteed. In order to alleviate the contradiction between the production increase and sand production of this reservoir, domestic experts and scholars have proposed a "small step and slow jogging" production test process scheme to reduce the production pressure difference, prevent large-scale sand production in the reservoir, and prevent secondary hydrate accumulation and blockage at the bottom of the well.

[0014] At present, the trial production period and daily average gas production of all offshore natural gas hydrates are far from the trial production period and daily average production capacity threshold required for industrial exploitation (5.0×10 5 m 3 / d) There is a huge gap. The trial mining process plan of "small steps and slow jogging" for the sake of sand control is not in line with the strategic goal of industrialized exploitation of natural gas hydrates in the South China Sea.

[0015] In the Chinese patent application with application number: 201810176099.9, a multi-layer, multi-grade composite pre-filled screen suitable for fine sand sand control is involved, and the multi-layer, multi-grade composite pre-filled screen suitable for fine sand sand control includes, from inside to outside, a base pipe; an inner wire layer, sleeved on the outer surface of the base pipe; a multi-grade composite filling layer, sleeved outside the inner wire layer, the multi-grade composite filling layer is three layers, the interlayers are filled with gravel, each layer has different thickness, and the gravel particle size between the layers is different; an outer wire layer, sleeved outside the multi-grade composite filling layer; and an outer protective cover of the outermost layer. The overall outer diameter of the screen is large, and there are problems such as erosion and secondary generation.

[0016] In the Chinese patent application with application number: 202110314940.8, a modified composite cavity sand control completion screen with a diversion effect is involved, and the sand control completion screen includes, from the inside to the outside: a base pipe, a diversion hole connected to the inside of the base pipe is opened on the base pipe; an inner filter screen sleeved on the outside of the base pipe; an outer filter screen sleeved on the outside of the base pipe; a modified multi-grade pre-filling layer between the inner filter screen and the outer filter screen; an outer protective cover sleeved on the outside of the outer filter screen; the modified multi-grade pre-filling layer includes a first pre-filling layer and a second pre-filling layer, the first pre-filling layer and the second pre-filling layer are separated and arranged in an alternating manner along the axial direction of the base pipe, the first pre-filling layer and the second pre-filling layer are respectively filled with expanded clay, and the particle sizes of the expanded clay in the two filling layers are different. The patented modified composite cavity sand control completion screen has 8 partition support strips, with a 45° cavity between adjacent partition support strips, and each cavity is alternately filled with a single layer of ceramsite with a hydrophilic coating and a hydrophobic coating. The single-layer filling of ceramsite to block sand is prone to blockage and production reduction, and the hydrophilic coating ceramsite layer has the risk of water channeling and flooding.

[0017] In the Chinese patent application with application number: 202110168612.1, a variable density pre-filled screen is involved, including a hollow base pipe, a plurality of first flow holes radially penetrating the base pipe are arranged on the side wall of the base pipe at intervals, characterized in that the outer side of the base pipe is provided with a protective sleeve structure, an axially penetrating filling annulus is arranged in the protective sleeve structure, the filling annulus can be tightly filled with ultra-low density proppant, the two ends of the filling annulus are open, and the two ends of the base pipe located at the protective sleeve structure are respectively provided with unlocking structures, each of which can close the filling annulus from the corresponding end, and each of which can move in the direction away from the protective sleeve structure under the blocking pressure of the annulus after blocking. The variable density pre-filled screen of this invention patent controls the compaction or reverse movement of the filling gravel by spring force in the axial direction, but due to the resistance of complex conditions downhole, the spring force is difficult to effectively control, and there is still a risk of deficit or blockage of the filling gravel. Moreover, in the radial direction, the patent still uses a single filling layer for sand control, and the single-layer sand control has low permeability and is easy to be blocked.

[0018] The above existing technologies are greatly different from the present invention and fail to solve the technical problem we want to solve. Therefore, we have invented a new sand control screen for depressurizing and mining natural gas hydrate. Summary of the invention

[0019] The purpose of the present invention is to provide a sand control screen for natural gas hydrate depressurization production, which provides sand control technology guarantee for long-term trial production of natural gas hydrate and ensures stable and high production of gas wells on the basis of accurately controlling the sand particle size produced by the formation.

[0020] The object of the present invention can be achieved through the following technical measures: a natural gas hydrate pressure reduction production sand control screen pipe, which comprises a non-obstructive protective sleeve, a buffer layer, a control layer, a first supporting layer, a second supporting layer and a base pipe from the outside to the inside, the non-obstructive protective sleeve, the buffer layer, the control layer, the first supporting layer, the second supporting layer and the base pipe are all tubular, and the buffer layer, the control layer, the first supporting layer and the second supporting layer are filled with annular low-density microspheres to form a filtering component of the natural gas hydrate pressure reduction production sand control screen pipe, the particle size is arranged in the order of medium-small-relatively coarse-coarse, and the fluid seeps through in radial direction in sequence.

[0021] The purpose of the present invention can also be achieved by the following technical measures:

[0022] The natural gas hydrate pressure reduction production sand control screen pipe also includes a plurality of unobstructed filter jackets, which are used to separate the buffer layer and the control layer, the control layer and the first support layer, the first support layer and the second support layer, and the second support layer and the base pipe.

[0023] The non-obstructed filter jacket is made by stamping a stainless steel sheet, and the connection form adopts a locking structure of a spiral continuous corrugated pipe.

[0024] The entire surfaces of the annular low-density microspheres, the non-obstructive protective sleeve, the non-obstructive filter jacket and the base tube are coated with low surface energy or ultra-low surface energy coating materials.

[0025] The coating materials used on the entire surface of the annular low-density microspheres, the non-obstruction protective sleeve, the non-obstruction filter jacket, and the base tube include modified polytetrafluoroethylene and nano-composite ceramics.

[0026] The non-obstructive protective sleeve is made of stainless steel sheet stamping, and the connection form adopts the locking structure of the spiral continuous corrugated pipe.

[0027] The non-obstructive protective sleeve and the non-obstructive filter jacket are both made of 304L or 316L metal material.

[0028] The openings or filter gap sizes of the unobstructed filter jacket are designed and determined according to the particle sizes of the annular low-density microspheres of the spaced filling layers.

[0029] The annular low-density microspheres are made of low-density and ultra-low-density materials such as lightweight ceramsite, glass, and polystyrene.

[0030] The annular low-density microspheres are hollow glass microspheres with particle sizes of 80, 200, 250, and 350 um.

[0031] The particle size of the annular low-density microspheres filled in the control layer is designed to be 5-6 times the d60 particle size of the formation sand.

[0032] The sand control screen pipe for depressurizing and mining natural gas hydrate in the present invention mainly has the following technical advantages:

[0033] 1. Using microbeads as sand control filter media solves the problem of selecting sand control media for natural gas hydrate reservoirs.

[0034] By controlling the relatively large particle size of micro-beads, the difficulty of sand control in natural gas hydrate reservoirs with extremely low particle size (median particle size less than 20μm), strong heterogeneity and poor sorting is solved.

[0035] According to the horizontal comparative experimental research on the plugging rules of different sand control media in the field of sand control of marine natural gas hydrate exploitation in recent years, pre-filled ceramsite has the highest plugging equilibrium permeability among a variety of commonly used sand retaining media, which is 6 to 8 times higher than the wire-wound screen commonly used in oil and gas wells. This also shows that microbeads are the preferred material for pre-filled sand retaining media in natural gas hydrate exploitation.

[0036] 2. The use of inorganic or organic lightweight or ultra-light microbeads solves the problem of natural sedimentation and integrity failure of sand control media.

[0037] Low-density and ultra-low-density micro-beads will not naturally settle during production and use, causing local deficiencies in the filling layer. The dense and stable micro-bead filling layer ensures the integrity of the sand control screen.

[0038] 3. The filter components of the sand control screen are composed of a buffer layer, a control layer and a support layer filled with micro beads, which solves the implementation difficulties of the "coarse and fine prevention" sand control scheme.

[0039] The control layer beads d1 ensure the target particle size d of the sand control in the production well; the buffer layer beads d2 sort the formation sand D and block the scouring and impact of the gas-liquid mixed fluid and the formation sand D on the control layer d1; the support layer beads d3 (or d3, d4) support and stabilize the control layer d1 to prevent the loss of the control layer beads d1; sand particles smaller than the target particle size d, including ultra-high mud and clay minerals, can be mined through the pores of the beads in the buffer layer, control layer and support layer, preventing the gaps of the beads in each layer from being blocked and reducing the permeability.

[0040] 4. The non-obstructive protective sleeve and non-obstructive filter jacket serve as the spacing and fixing materials of each micro-bead filling layer, solving the integrity problem of each micro-bead filling layer during filling production, downhole operation, and production and use.

[0041] The non-blocking protective sleeve and the non-blocking filter jacket both adopt a spiral corrugated pipe structure with continuous spiral waveform, which has excellent flexibility, and its anti-twisting, anti-bending and thermal shock resistance are particularly outstanding. The non-blocking protective sleeve and the non-blocking filter jacket can not only ensure the safety of the thick sand control filter assembly composed of 3 to 4 layers of micro-bead filling layers passing through the small curvature radius deflection section when going down the well, but also ensure the integrity of the sand control screen when the ambient temperature changes greatly (such as different ambient temperatures during production, downhole use, and downhole operations).

[0042] The non-blocking protective sleeve and non-blocking filter jacket adopt the high-flexibility structure of spiral corrugated pipe, so that the sand control screen can automatically compensate for thermal expansion and contraction deformation during long-term use, and automatically absorb the settlement deformation of the wellbore or casing in the long horizontal well section, thereby greatly extending the trial production period of the natural gas hydrate production well.

[0043] 5. Use surface coating technology to solve the problem of secondary formation of natural gas hydrates blocking the sand control screen.

[0044] All materials of the sand control screen, including each layer of filling micro beads and the non-blocking protective sleeve, non-blocking filter jacket, and the entire surface of the base pipe are coated with low surface energy or ultra-low surface energy coating materials. The coating not only destroys the conditions for the secondary generation of natural gas hydrate nuclei in the porous material gaps of the decomposed methane and water phases in the sand control screen, but also prevents the natural gas hydrate microcrystals from being adsorbed on the surface of the porous material and growing to block the gaps.

[0045] The low surface energy or ultra-low surface energy coating also prevents hydrophilic, negatively charged clay minerals and montmorillonite and kaolinite particles in the sediment from adhering and depositing on the surface and internal porous materials of the sand control screen and causing blockage.

[0046] 6. Use corrosion-resistant materials to solve long-term test mining and production problems

[0047] The microbeads in each filling layer of the sand control screen are made of inorganic or organic materials, including but not limited to ceramsite, glass, polystyrene plastic, etc. The metal materials used are 304L or 316L stainless steel, and the coatings used are polymer materials with stable chemical properties. These materials are resistant to acid and alkali corrosion and are suitable for long-term trial production and production conditions of natural gas hydrate mining wells.

[0048] 7. Sand control screen solved the problem of significantly increasing the average daily production of a single well in the natural gas hydrate trial production

[0049] In summary, this sand control screen solves the difficulties faced by the current South China Sea natural gas hydrate trial production, such as short continuous trial production cycle, small daily average gas production, and the "small steps and slow running" trial production process scheme that has to be adopted to solve the sand control problem, from the aspects of sand control principle, mechanical structure, physical and chemical materials.

[0050] The sand control screen provides an implementation plan for the exploitation of natural gas hydrates in the South China Sea to "prevent coarse and fine particles", conduct long-term stable trial production, and significantly increase the average daily gas production.

[0051] 8. Sand control screens meet the technical advantages of low-cost industrial exploitation of natural gas hydrates in the South China Sea

[0052] This sand control screen is made of common materials (excluding expensive raw materials), and the domestic supply of raw materials is sufficient and the price is stable. The manufacturing process of the sand control screen and its parts is simple, and they are all made by mechanization or automation to achieve standardized and efficient production of batch products. The sand control screen has a great low-cost advantage and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 It is a structural diagram of a specific embodiment of the sand control screen pipe for depressurization production of natural gas hydrate of the present invention;

[0054] In the figure, 1-obstruction-free protective cover B, 2-buffer layer microbead filling d2, 3-obstruction-free filter jacket B1, 4-control layer microbead filling d1, 5-obstruction-free filter jacket B2, 6-support layer microbead filling d3, 7-obstruction-free filter jacket B3, 8-support layer microbead filling d4, 9-obstruction-free filter jacket B4, 10-base tube. DETAILED DESCRIPTION

[0055] It should be noted that the following detailed descriptions are exemplary and are intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0056] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations and / or combinations thereof.

[0057] The sand control screen pipe for depressurized production of natural gas hydrates of the present invention comprises: a non-obstructive protective sleeve-a buffer layer-a non-obstructive filter jacket 1-a control layer-a non-obstructive filter jacket 2-a support layer (1)--a non-obstructive filter jacket 3-a support layer (2)--a non-obstructive filter jacket 4-a base pipe.

[0058] The tubular non-blocking filter jacket is made of stainless steel sheet stamping, and the connection form adopts the lock structure of spiral continuous corrugated pipe. It adopts tubular non-blocking filter jacket and spiral continuous corrugated pipe structure. It has high strength, super flexibility, large flow and non-blocking characteristics.

[0059] The tubular non-blocking protective sleeve is made by stamping stainless steel thin plates, and the connection form adopts the locking structure of the spiral continuous corrugated pipe.

[0060] The cross section of the screen is filled with 3-4 layers of annular low-density microspheres, which are made of low-density and ultra-low-density materials such as lightweight ceramsite, glass, and polystyrene. The purpose is to solve the problem of natural sedimentation and integrity failure of the sand control medium. The ultra-low-density materials used in this patent application, such as hollow glass microspheres, have particle sizes of 80, 200, 250, 350um and other specifications, and the compressive strength must reach more than 35MPa. The existing domestic technology cannot achieve this, and the corresponding production process needs to be specially developed.

[0061] Buffer layer - control layer - support layer (1-2 layers), the particle size is arranged in the order of "medium-small-relatively coarse-coarse", and the fluid seeps through in radial direction in sequence.

[0062] The control layer is located in the middle of the second layer, and the particle size of the microbeads in this layer is designed to be 5-6 times the particle size of the formation sand d60. Usually, the filling microbead particle size d1 of the control layer can be designed according to the Saucier theory method, and d1 can be corrected through gravel filling sand control evaluation experiments when necessary.

[0063] The non-blocking protective sleeve and the non-blocking filter jacket both adopt the high-flexibility lock connection structure of the spiral continuous corrugated pipe. The purpose is to enable the sand control pipe to automatically compensate for thermal expansion and contraction deformation during long-term use, and automatically absorb the settlement deformation of the wellbore or casing in the long horizontal well section, thereby greatly extending the trial production period of the natural gas hydrate production well.

[0064] The above-mentioned filling layer micro beads, non-blocking protective sleeve, non-blocking filter jacket, and base pipe are all coated with low surface energy or ultra-low surface energy coating materials. The coating materials include but are not limited to modified polytetrafluoroethylene, nano-composite ceramics, etc. The purpose of the surface coating is to prevent the secondary generation of natural gas hydrates.

[0065] The sand control screen pipe for natural gas hydrate depressurization production of the present invention has the following technical features:

[0066] (1) From the flow direction of the fluid from outside to inside, the sand control filtration component is composed of 1 buffer layer, 1 control layer, 1 to 2 support layers, and a total of 3 to 4 microbead filling layers.

[0067] (2) The microbeads in each filling layer are made of inorganic or organic light or ultra-light materials, and the microbeads are filled to form a porous filter medium.

[0068] (3) The particle size d1 of the control layer microbeads must be designed and determined based on the target particle size d of the production well, that is, formation sand larger than the target particle size d is blocked, while sand particles smaller than the target particle size d can flow out through the pores of the control layer microbeads d1.

[0069] (4) The particle size d2 of the buffer layer microbeads is designed and determined based on the particle size d1 of the control layer microbeads and the particle size distribution D of the formation sand. That is, the formation sand and the control layer microbeads with a particle size greater than or equal to d1 of the control layer microbeads are blocked (regardless of forward and reverse flow), while sand particles smaller than the target particle size d can flow out through the pores of the buffer layer microbeads d2.

[0070] (5) The support layer can be one layer or two layers, the outer and inner layers. The particle size d3 of the outer layer microbeads is designed and determined based on the particle size d1 of the control layer microbeads, that is, the control layer microbeads d1 are completely blocked, while sand particles smaller than the target particle size d can flow out through the pores of the outer layer microbeads d3. Similarly, the particle size d4 of the inner layer microbeads is designed and determined based on the particle size d3 of the outer layer microbeads, that is, the outer layer microbeads d3 are completely blocked, while sand particles smaller than the target particle size d can flow out through the pores of the inner layer microbeads d4.

[0071] (6) In order to ensure the dense filling of the microbeads in the buffer layer, control layer and support layer and maintain the integrity of the filling structure, the surface layer of the sand control screen adopts a high-strength, ultra-flexible, large-flow, non-obstructive protective cover, and the internal layers of the filling microbeads are separated by high-strength, ultra-flexible, large-flow, non-obstructive filter jackets.

[0072] (7) The opening or filtering gap size B of the unobstructed protective cover is smaller than the particle size d2 of the microbeads in the buffer layer to ensure the structural integrity of the buffer layer during the manufacturing and use process.

[0073] (8) The opening or filter gap size B1-B4 of each unobstructed filter jacket is designed and determined according to the particle size of the microbeads of the filling layer to ensure the structural integrity of the filling layer during production and use.

[0074] (9) The non-blocking protective cover and each non-blocking filter jacket are made of 304L or 316L metal material.

[0075] (10) To prevent the secondary hydrate formation of natural gas hydrate inside and outside the sand control screen and adsorption on the sand control screen material to cause blockage, the entire surface of all materials of the sand control screen is coated with low surface energy or ultra-low surface energy coating materials.

[0076] The following are several specific embodiments of the present invention.

[0077] Example 1

[0078] In a specific embodiment 1 of the present invention, the natural gas hydrate production sand control screen pipe is as follows: Figure 1 As shown, from outside to inside it is composed of 1-obstruction-free protective cover B, 2-buffer layer microbead filling d2, 3-obstruction-free filter jacket B1, 4-control layer microbead filling d1, 5-obstruction-free filter jacket B2, 6-support layer microbead filling d3, 7-obstruction-free filter jacket B3, 8-support layer microbead filling d4, 9-obstruction-free filter jacket B4, 10-base tube.

[0079] (1) The production fluid (including formation sand particles) seeps from the wellbore into the oil pipe, passes through the buffer layer d2 (1st layer), control layer d1 (1st layer) and support layer d3, d4 (1-2 layers) micro-bead filling filter media in the sand control pipe in turn, and then enters the oil pipe.

[0080] (2) The control layer d1 is a fine filter layer that plays a role in gap control, so as to intercept particles of a certain size distribution (≥d) while allowing smaller sand particles (<d) to pass through the filter medium and enter the downstream.

[0081] According to the target value d of sand control accuracy of the production well, the filling microbead particle size d1 of the control layer can usually be designed according to the Saucier theory method. If necessary, d1 can be corrected through gravel filling sand control evaluation experiments.

[0082] (3) The buffer layer d2 is a safety protection layer. It is filled with coarse microbeads d2 to form larger gaps, which provide external protection for the control layer d1 and prevent the fluid from directly scouring the control layer d1. At the same time, the buffer layer d2 also plays the role of screening the formation sand, blocking the formation sand that is easy to block the control layer d1, and allowing smaller sand particles (<d) to pass through the filter medium and enter the downstream.

[0083] (4) The support layer is a filter medium with larger gaps filled with coarse beads d3 and coarse beads d4, so that smaller sand particles (<d) can quickly pass through the filter medium and enter the downstream. At the same time, the support layer filled with coarse and coarse beads enables the sand control pipe to achieve a higher overall mechanical strength.

[0084] The microbeads in each of the above filling layers are all made of low-density and ultra-low-density materials such as lightweight ceramsite, glass, and polystyrene.

[0085] (5) The base pipe is made by drilling holes in oil and casing according to API or GB standards. Conventional materials and opening forms can be used according to the fluid production and the requirements for the use of the base pipe.

[0086] (6) The upstream side of the control layer filled with micro beads d1 is clamped and fixed with a non-obstruction filter jacket B1, and the downstream side is clamped and fixed with a non-obstruction filter jacket B2. The upstream side of the buffer layer filled with micro beads d2 is clamped and fixed with a non-obstruction protective sleeve B, and the downstream side is clamped and fixed with a non-obstruction filter jacket B1. The supporting layer (outer) filled with micro beads d3 is clamped and fixed with a non-obstruction filter jacket B2 on the upstream side, and the downstream side is clamped and fixed with a non-obstruction filter jacket B3 on the downstream side. The supporting layer (inner) filled with micro beads d4 is clamped and fixed with a non-obstruction filter jacket B3 on the upstream side, and the downstream side is clamped and fixed with a non-obstruction filter jacket B4.

[0087] The non-obstruction protective sleeve and the non-obstruction filter jacket are used as the spacing and fixing materials of each microbead filling layer. Both adopt a spiral bellows structure with a continuous spiral waveform and are made of 304L or 316L stainless steel.

[0088] (7) The entire surface of the above-mentioned filling layer microbeads, non-obstruction protective sleeve, non-obstruction filter jacket, and base pipe is coated with low surface energy or ultra-low surface energy coating materials. The specific coating materials are determined according to the optimization experiment of the secondary generation and blockage of natural gas hydrate in porous filter materials.

[0089] Example 2

[0090] Taking the sand control pipe (length 4800mm) in the 9-5 / 8" casing and 2-7 / 8" oil pipe of the natural gas hydrate production well as an example, the sand control accuracy is based on the formation sand particle size d 60 =12um design. The relevant technical indicators of each filling bead layer, non-blocking protective sleeve, each non-blocking filter jacket, and base tube are as follows:

[0091] 1. Non-blocking protective cover B

[0092]

[0093] 2. Buffer layer microbead filling d2

[0094] Microbead size d2(um) 200

[0095] Filling length (mm) 3850

[0096] Material: Polystyrene, coated with super hydrophobic coating material

[0097] 3. Unobstructed filter jacket B1

[0098]

[0099] 4. Control layer microbead filling d1

[0100] Microbead size d1(um) 80

[0101] Filling length (mm) 3850

[0102] Material: Polystyrene, coated with super hydrophobic coating material

[0103] 5. Unobstructed Filter Jacket B2

[0104]

[0105] 6. Support layer (outer) microbead filling d3

[0106] Microbead size d3(um) 250

[0107] Filling length (mm) 3850

[0108] Material: Polystyrene, coated with super hydrophobic coating material

[0109] 7. Unobstructed Filter Jacket B3

[0110]

[0111] 8. Support layer (inner) microbead filling d4

[0112] Microbead size d4 (um) 350

[0113] Filling length (mm) 3850

[0114] Material: Polystyrene, coated with super hydrophobic coating material

[0115] 9. Unobstructed Filter Jacket B4

[0116]

[0117]

[0118] 10. Base pipe API 5CT PSL1

[0119]

[0120] Example 3

[0121] This patent is also applicable to sand control in high-mud natural gas wells. The purpose of applying super-hydrophobic coating materials under such conditions is to prevent scaling and clogging of high-mineralized formation water in the wellbore and sand control pipe. Taking the sand control pipe (length 4800mm) in the 5.5" casing (inner diameter 121.4mm) and 2-3 / 8" oil pipe of a shallow well as an example, the sand control accuracy is based on the formation sand particle size d 60 = 20um design. The relevant technical indicators of each filling bead layer, non-blocking protective sleeve, each non-blocking filter jacket, and base tube are as follows:

[0122] 1. Non-blocking protective cover B

[0123]

[0124] 2. Buffer layer microbead filling d2

[0125] Microbead size d2(um) 500

[0126] Filling length (mm) 3850

[0127] Material: Polystyrene, coated with super hydrophobic coating material

[0128] 3. Unobstructed filter jacket B1

[0129]

[0130] 4. Control layer microbead filling d1

[0131] Microbead size d1(um) 120

[0132] Filling length (mm) 3850

[0133] Material: Polystyrene, coated with super hydrophobic coating material

[0134] 5. Unobstructed Filter Jacket B2

[0135]

[0136] 6. Support layer microbead filling d3

[0137] Microbead size d3(um) 600

[0138] Filling length (mm) 3850

[0139] Material: Polystyrene, coated with super hydrophobic coating material

[0140] 7. Unobstructed Filter Jacket B3

[0141]

[0142] 8. Base pipe API 5CT PSL1

[0143]

[0144] Finally, it should be noted that the above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art can still modify the technical solutions recorded in the aforementioned embodiments or replace some of the technical features therein with equivalents. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

[0145] Except for the technical features described in the specification, all other technical features are known technologies to those skilled in the art.

Claims

1. A sand control screen for depressurizing natural gas hydrate production, characterized in that: The natural gas hydrate pressure reduction and production sand control screen pipe comprises, from outside to inside, a non-blocking protective sleeve, a buffer layer, a control layer, a first supporting layer, a second supporting layer and a base pipe in sequence; the non-blocking protective sleeve, the buffer layer, the control layer, the first supporting layer, the second supporting layer and the base pipe are all tubular; the buffer layer, the control layer, the first supporting layer and the second supporting layer are filled with annular low-density microspheres to form a filter component of the natural gas hydrate pressure reduction and production sand control screen pipe; the particle sizes are arranged in the order of medium-small-relatively coarse-coarse, and the fluid seeps through in sequence in the radial direction.

2. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 1, characterized in that: The natural gas hydrate pressure reduction production sand control screen pipe also includes a plurality of unobstructed filter jackets, which are used to separate the buffer layer and the control layer, the control layer and the first support layer, the first support layer and the second support layer, and the second support layer and the base pipe.

3. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 2, characterized in that: The non-obstructed filter jacket is made by stamping a stainless steel sheet, and the connection form adopts a locking structure of a spiral continuous corrugated pipe.

4. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 3, characterized in that: The entire surfaces of the annular low-density microspheres, the non-obstructive protective sleeve, the non-obstructive filter jacket and the base tube are coated with low surface energy or ultra-low surface energy coating materials.

5. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 4, characterized in that: The coating materials used on the entire surface of the annular low-density microspheres, the non-obstruction protective sleeve, the non-obstruction filter jacket, and the base tube include modified polytetrafluoroethylene and nano-composite ceramics.

6. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 3, characterized in that: The non-obstructive protective sleeve is made of stainless steel sheet stamping, and the connection form adopts the locking structure of the spiral continuous corrugated pipe.

7. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 6, characterized in that: The non-obstructive protective sleeve and the non-obstructive filter jacket are both made of 304L or 316L metal material.

8. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 2, characterized in that: The openings or filter gap sizes of the unobstructed filter jacket are designed and determined according to the particle sizes of the annular low-density microspheres of the spaced filling layers.

9. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 1, characterized in that: The annular low-density microspheres are made of low-density and ultra-low-density materials such as lightweight ceramsite, glass, and polystyrene.

10. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 9, characterized in that: The annular low-density microspheres are hollow glass microspheres with particle sizes of 80, 200, 250, and 350 um.

11. The sand control screen for depressurizing and exploiting natural gas hydrate according to claim 1, characterized in that: The particle size of the annular low-density microspheres filled in the control layer is designed to be 5-6 times the d60 particle size of the formation sand.

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