Natural gas hydrate depressurization and sand control screen

Abstract

This invention provides a sand control screen pipe for pressure reduction and extraction of natural gas hydrates. From the outside in, it comprises an unobstructed protective sleeve, a buffer layer, a control layer, a first support layer, a second support layer, and a base pipe. All components—the unobstructed protective sleeve, buffer layer, control layer, first support layer, second support layer, and base pipe—are tubular. The filter assembly of this screen pipe consists of annular low-density microspheres filled in the buffer layer, control layer, first support layer, and second support layer. The particle size is configured in a medium-small-relatively coarse-large order, allowing fluid to seep through radially. This sand control screen pipe for pressure reduction and extraction of natural gas hydrates solves the current predicament of short continuous trial production cycles, low daily gas production, and the "small-step, slow-paced" trial production process required to address sand control challenges. It provides an implementation scheme that "prevents coarse-to-fine sand," enables long-term stable trial production, and significantly increases daily gas production.

Description

Technical Field

[0001] This invention relates to the field of sand control technology in natural gas hydrate depressurization wells, and in particular to a sand control screen pipe for natural gas hydrate depressurization wells. Background Technology

[0002] The natural gas hydrate reservoirs in the South my country Sea are characterized by shallow burial, weak consolidation, lack of diagenesis, and difficult seepage. Analysis of sediment cores from the Shenhu area shows hydrate saturation reaching 64%, with horizontal permeability ranging from (0.96 to 3.70) × 10⁻⁶. -9 The median grain size of the sediments is 7.57 μm, with muddy components accounting for approximately 36.0%, silt components accounting for approximately 63.0%, and sandy components accounting for less than 1.0%. The sediment sorting factor is 2.24, and the evenness factor is 7.86, indicating that the sediments are poorly sorted and heterogeneous.

[0003] Based on the experience of the three recent offshore natural gas hydrate trial productions (i.e., Japan AT1-P2, China SHSC4, and China SHSC2-6), reservoir sand production is one of the biggest engineering geological challenges inevitably faced in natural gas hydrate extraction. Shallow reservoir depths and poor sediment cementation strength make it extremely easy for natural gas hydrates to decompose during depressurization extraction, leading to reservoir and wellbore instability and severe sand production. The main challenges in sand control for natural gas hydrate extraction wells in the South China Sea include:

[0004] (1) The reservoir sand has extremely low particle size (median particle size less than 20 μm), and its 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) The clay content is extremely high (more than 40% in some areas), especially the content of montmorillonite (36% to 41%) and kaolinite. The clay minerals can easily cause the sand-controlling medium to become blocked.

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

[0007] (4) During the depressurization mining process, the gravel and metal sand control screens used in the production zone have a void structure, and natural gas hydrates are easily generated again, which can cause ice blockage and hinder the continuous production.

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

[0009] (6) Based on the experience of previous natural gas hydrate trial production both domestically and internationally, as well as the results of laboratory studies, the engineering geological risks that may be faced under long-term decomposition and extraction conditions for hydrates include wellbore instability and collapse, wellbore subsidence and deformation, formation subsidence, submarine landslides, and damage to the subsea wellhead. Existing sand control pipes used in conventional oil and gas well production lack a flexible design to compensate for deformation. Therefore, they cannot adapt to the geological deformation conditions that occur during long-term natural gas hydrate trial production.

[0010] (7) In 2020, the second trial production of natural gas hydrate in the Shenhu area of ​​the South China Sea was conducted using the "formation fluid extraction method." A sand control process of "pre-filled bypass screen + lightweight sand circulation filling dual sand control" was adopted. This formed a three-stage composite sand control system in the wellbore, consisting of "coarse + fine" gravel filling and high-precision pre-filled screens, achieving sand retention and reducing blockage. This effectively delayed the time when the wellbore would be blocked by mud and sand, maintaining a high production capacity (average daily gas production of 2.87 × 10⁻⁶) during the trial production period (lasting 30 days). 4 m 3 / d).

[0011] Although the sand control technology maintained sand and mud production under control throughout the trial production process, the limited trial period resulted in low water production and a rapid decline in gas production, highlighting the significant conflict between sand control and mud production improvement. Whether this sand control technology can be applied to the industrial-scale exploitation of natural gas hydrates in the South China Sea requires further verification.

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

[0013] (8) Based on the basic theoretical and technical research on marine natural gas hydrate exploitation in my country in recent years and the summary of the secondary trial production project of natural gas hydrate in the Shenhu area of ​​the South China Sea, the "anti-coarse and fine" sand control scheme should be adopted to increase the average daily production of a single well. However, this also means that a large amount of mud will be produced in the formation, increasing the risk of sand burial in the wellbore and making it impossible to guarantee long-term stable trial production. In order to alleviate the contradiction between production increase and sand production in this reservoir, domestic experts and scholars have proposed a "small step and slow jog" trial production 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] Currently, the trial production cycle and average daily gas production of all marine natural gas hydrates are far from the trial production cycle and average daily production capacity threshold required for industrial-scale exploitation (5.0 × 10⁻⁶). 5 m 3 There is a huge gap between / d) and the pilot production process, which is a "small-step, slow-paced" approach to sand control, is not in line with the strategic goal of industrial-scale exploitation of natural gas hydrates in the South China Sea.

[0015] Chinese patent application No. 201810176099.9 discloses a multi-layer, multi-grade composite pre-filled screen pipe suitable for sand control of fine sand. This multi-layer, multi-grade composite pre-filled screen pipe, from the inside out, comprises: a base pipe; an inner wire-wound layer sleeved on the outer surface of the base pipe; a multi-grade composite filling layer sleeved outside the inner wire-wound layer, consisting of three layers filled with gravel between each layer, each layer having varying thickness and different gravel particle sizes between layers; an outer wire-wound layer sleeved outside the multi-grade composite filling layer; and an outermost protective cover. This screen pipe has a large overall outer diameter, leading to problems such as erosion and secondary formation.

[0016] Chinese patent application No. 202110314940.8 discloses a modified composite cavity sand-controlling completion screen with diversion function. The sand-controlling completion screen comprises, from the inside out: a base pipe with a guide hole communicating with the inside of 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 and outer filter screens; and 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, which are arranged alternately along the axial direction of the base pipe. The first and second pre-filling layers are respectively filled with ceramic particles, and the ceramic particles in the two filling layers have different particle sizes. This patented modified composite cavity sand-control completion screen has eight partition support plates, with adjacent partition support plates forming cavities at a 45° angle. Each cavity is alternately filled with a single layer of ceramsite with both hydrophilic and hydrophobic coatings. Single-layer ceramsite sand control is prone to clogging and reduced production, and the hydrophilic coating ceramsite layer poses a risk of water channeling and flooding.

[0017] Chinese patent application No. 202110168612.1 discloses a variable-density pre-filled screen pipe, comprising a hollow base pipe with multiple first flow holes radially penetrating the sidewall of the base pipe at intervals. The key feature is that a protective sleeve structure is fitted around the outside of the base pipe, and an axially penetrating filling annulus is provided within the protective sleeve structure. The filling annulus can be tightly filled with ultra-low density proppant, and both ends of the filling annulus are open. Unlocking structures are respectively fitted on both ends of the base pipe at the protective sleeve structure. Each unlocking structure can close the filling annulus from its corresponding end, and each unlocking structure can move away from the protective sleeve structure under the pressure of the blocked annulus. This invention uses a spring force to control the compaction or reverse movement of the filled gravel in the axial direction. However, due to the resistance caused by complex downhole conditions, this spring force is difficult to control effectively, and there is still a risk of gravel shortage or blockage. Furthermore, the patent still uses a single filling layer for sand prevention in the radial direction. Single-layer sand prevention has low permeability and is prone to clogging.

[0018] The above-mentioned existing technologies are all quite different from the present invention and have failed to solve the technical problem we want to solve. Therefore, we have invented a new type of sand control screen pipe for depressurization mining of natural gas hydrates. Summary of the Invention

[0019] The purpose of this invention is to provide a sand control screen for long-term trial production of natural gas hydrates, which provides sand control technology support and ensures stable and high production of gas wells based on precise control of the sand particle size produced in the formation.

[0020] The objective of this invention can be achieved through the following technical measures: a natural gas hydrate depressurization and sand control screen pipe, which comprises, from the outside to the inside, an unobstructed protective sleeve, a buffer layer, a control layer, a first support layer, a second support layer, and a base pipe. The unobstructed protective sleeve, the buffer layer, the control layer, the first support layer, the second support layer, and the base pipe are all tubular. The buffer layer, the control layer, the first support layer, and the second support layer are filled with annular low-density microspheres to form the filter assembly of the natural gas hydrate depressurization and sand control screen pipe. The particle size is configured in the order of medium-small-coarse-large, and the fluid seeps through in the radial direction in sequence.

[0021] The objective of this invention can also be achieved through the following technical measures:

[0022] The natural gas hydrate depressurization and sand control screen pipe also includes multiple unobstructed filter jackets. 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 are all separated by the unobstructed filter jackets.

[0023] The unobstructed filter jacket is made of stainless steel sheet by stamping, and the connection method adopts a locking structure of spiral continuous corrugated tube.

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

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

[0026] This unobstructed protective sleeve is made of stainless steel sheet by stamping, and the connection adopts a locking structure of spiral continuous corrugated tube.

[0027] Both the unobstructed protective sleeve and the unobstructed filter jacket are made of 304L or 316L metal material.

[0028] The opening or slit size of the unobstructed filter jacket is designed and determined according to the particle size of the annular low-density microspheres in the spaced filling layers.

[0029] The annular low-density microspheres are made of lightweight ceramic particles, glass, polystyrene, and other low-density and ultra-low-density materials.

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

[0031] The annular low-density microspheres filling the control layer are designed to have a particle size 5-6 times that of the d60 particle size of the formation sand.

[0032] The natural gas hydrate depressurization and sand control screen pipe of this invention has the following main technical advantages:

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

[0034] By controlling microspheres with relatively large particle sizes, the problem of sand control in natural gas hydrate reservoirs with extremely low particle size (median particle size less than 20 μm), strong heterogeneity, and poor sorting has been solved.

[0035] Based on comparative experimental studies of the clogging patterns of different sand-controlling media in the field of sand production control in domestic marine natural gas hydrate extraction in recent years, pre-filled ceramsite exhibits the highest clogging equilibrium permeability among various commonly used sand-controlling media, which is 6 to 8 times higher than that of wire-wound screens commonly used in oil and gas wells. This also indicates that microspheres are the preferred material for pre-filled sand-controlling media in natural gas hydrate extraction.

[0036] 2. The use of inorganic or organic lightweight or ultralight microspheres solves the problems of natural sedimentation and integrity failure of sand control media.

[0037] Low-density and ultra-low-density microspheres will not naturally settle during production and use, thus preventing local voids in the filling layer. The dense and stable microsphere filling layer ensures the integrity of the sand control screen.

[0038] 3. The filter assembly of the sand control screen tube is composed of a buffer layer, a control layer, and a support layer filled with microspheres, which solves the implementation problem of the "anti-coarse and anti-fine" sand control scheme.

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

[0040] 4. The unobstructed protective sleeve and the unobstructed filter jacket serve as spacers and fixing materials for each microsphere filling layer, solving the problem of the integrity of each microsphere filling layer during filling, well operation, and production use.

[0041] Both the unobstructed protective sleeve and the unobstructed filter jacket adopt a continuous spiral corrugated tube structure, which has excellent flexibility, making its resistance to torsion, bending, and thermal shock particularly outstanding. The unobstructed protective sleeve and the unobstructed filter jacket can ensure the safety of the thick sand control filter assembly composed of 3-4 layers of microsphere filling when it is run into the well through the small radius of curvature directional section, and can also ensure the integrity of the sand control screen pipe when the ambient temperature changes significantly (such as different ambient temperatures during manufacturing, well use, and downhole operations).

[0042] The unobstructed protective sleeve and unobstructed filter jacket adopt a highly flexible spiral corrugated pipe structure, which enables the sand control screen pipe to automatically compensate for thermal expansion and contraction deformation and automatically absorb the settlement deformation of the wellbore or casing in long horizontal well sections during long-term use, thereby significantly extending the trial production cycle of natural gas hydrate production wells.

[0043] 5. Solve the problem of secondary formation of natural gas hydrates clogging the sand control screen tube using surface coating technology.

[0044] All materials in the sand control screen tube, including each layer of microsphere filling, the unobstructed protective sleeve, the unobstructed filter jacket, and the entire surface of the base tube, are coated with a low or ultra-low surface energy coating material. The coating not only disrupts the conditions for the secondary formation of natural gas hydrate crystal nuclei from the decomposed methane and water phases in the porous material pores within the sand control screen tube, but also prevents natural gas hydrate microcrystals from adsorbing and growing on the surface of the porous material, thus preventing them from clogging the pores.

[0045] Low or ultra-low surface energy coatings also prevent hydrophilic, negatively charged clay minerals and montmorillonite and kaolinite particles in the sediment from adhering to and depositing on the surface and internal porous material of the sand control screen tube, thus preventing clogging.

[0046] 6. Solve the problems of long-cycle trial mining and production using corrosion-resistant materials.

[0047] The microspheres used in each filling layer of the sand control screen are made of inorganic or organic materials, including but not limited to ceramsite, glass, and polystyrene plastic. All metal materials used are 304L or 316L stainless steel, and the coatings are all chemically stable polymer materials. These materials all possess resistance to acid and alkali corrosion, making them suitable for long-term trial production and production conditions in natural gas hydrate extraction wells.

[0048] 7. The sand-controlling screen pipe solved the problem of significantly increasing the average daily production of a single well in the trial production of natural gas hydrates.

[0049] In summary, this sand control screen has solved the current predicament faced by natural gas hydrate pilot production in the South China Sea, namely, short continuous pilot production cycle, low daily gas production, and the need to adopt a "small steps and slow pace" pilot production process due to sand control problems, by addressing issues such as sand control principle, mechanical structure, and physical and chemical materials.

[0050] This sand control screen provides an implementation plan for the exploitation of natural gas hydrates in the South China Sea, which includes "preventing coarse and fine sand," long-term stable trial production, and significantly increasing the average daily gas production.

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

[0052] This sand control screen is made of common materials (excluding expensive raw materials), which are readily available and reasonably priced domestically. The manufacturing process for the sand control screen and its components is simple, employing mechanized or automated processing to achieve standardized and efficient mass production. The sand control screen offers significant low-cost advantages and has broad application prospects. Attached Figure Description

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

[0054] In the figure, 1-Unobstructed protective sleeve B, 2-Buffer layer microsphere filling d2, 3-Unobstructed filter jacket B1, 4-Control layer microsphere filling d1, 5-Unobstructed filter jacket B2, 6-Support layer microsphere filling d3, 7-Unobstructed filter jacket B3, 8-Support layer microsphere filling d4, 9-Unobstructed filter jacket B4, 10-Base tube. Detailed Implementation

[0055] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

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

[0057] The natural gas hydrate depressurization and sand control screen pipe of the present invention includes: unobstructed protective sleeve - buffer layer - unobstructed filter jacket 1 - control layer - unobstructed filter jacket 2 - support layer (1) - unobstructed filter jacket 3 - support layer (2) - unobstructed filter jacket 4 - base pipe.

[0058] The tubular, unobstructed filter jacket is made of stamped stainless steel sheet, and the connection uses a locking structure of a spiral continuous corrugated tube. It features a tubular, unobstructed filter jacket with a spiral continuous corrugated tube structure. It possesses high strength, ultra-flexibility, high flow rate, and unobstructed characteristics.

[0059] The tubular, unobstructed protective sleeve is made of stainless steel sheet by stamping, and the connection adopts a locking structure of spiral continuous corrugated tube.

[0060] The cross-section of the sieve tube is filled with 3-4 layers of annular low-density microspheres, made of lightweight ceramic particles, glass, polystyrene, and other low-density and ultra-low-density materials. The aim is to solve the problems of natural settling and integrity failure in sand control media. The ultra-low-density materials used in this patent application, such as hollow glass microspheres, have particle sizes including 80, 200, 250, and 350 μm, and all have compressive strengths exceeding 35 MPa. Current domestic technology cannot achieve this, requiring the development of specialized manufacturing processes.

[0061] The buffer layer, control layer, and support layer (1-2 layers) are configured with particle sizes of "medium-small-coarse-large", and the fluid seeps through them in sequence in the radial direction.

[0062] The control layer is located in the middle of the second layer, and the microsphere size of this layer is designed to be 5-6 times the d60 particle size of the formation sand. The microsphere size d1 of the control layer can usually be designed according to the Saucier theory method, and d1 can be corrected by gravel backfill sand control evaluation experiments if necessary.

[0063] Both the unobstructed protective sleeve and the unobstructed filter jacket adopt a highly flexible locking connection structure using a spiral continuous corrugated pipe. The purpose is to enable the sand control pipe to automatically compensate for thermal expansion and contraction deformation and automatically absorb the settlement deformation of the wellbore or casing in long horizontal well sections during long-term use, thereby significantly extending the trial production cycle of natural gas hydrate production wells.

[0064] All of the aforementioned filling layers, including the microspheres, the unobstructed protective sleeve, the unobstructed filter jacket, and the entire surface of the base tube, are coated with a low- or ultra-low-surface-energy coating material. The coating material includes, but is not limited to, modified polytetrafluoroethylene (PTFE) and nanocomposite ceramics. The purpose of the surface coating is to prevent the secondary formation of natural gas hydrates.

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

[0066] (1) From the direction of fluid flow from the outside to the inside, the sand control filter assembly consists of 1 buffer layer, 1 control layer, 1 to 2 support layers, and a total of 3 to 4 microsphere filling layers.

[0067] (2) Each filling layer of microspheres is made of inorganic or organic lightweight or ultralight materials, and the microspheres fill to form a porous filter medium.

[0068] (3) The control layer microsphere particle size d1 must be designed and determined according to the sand control 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 microsphere d1.

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

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

[0071] (6) In order to ensure that the microbeads of the buffer layer, control layer and support layer are densely filled and to maintain the integrity of the filling structure, the surface of the sand control screen tube is equipped with a high-strength, ultra-flexible, high-flow and unobstructed protective sleeve, while the microbeads of each layer inside are separated by high-strength, ultra-flexible, high-flow and unobstructed filter jackets.

[0072] (7) The opening or filter gap size B of the unobstructed protective sleeve is smaller than the microsphere size d2 of the buffer layer to ensure the structural integrity of the buffer layer during manufacturing and use.

[0073] (8) The opening or slit size B1 to B4 of each unobstructed filter jacket is designed and determined according to the particle size of the microspheres in the filling layer, so as to ensure the structural integrity of the filling layer during manufacturing and use.

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

[0075] (10) In order to prevent the formation of secondary hydrates in the sand control screen tube inside and outside, and to prevent them from adsorbing onto the sand control screen tube material and causing blockage, all materials of the sand control screen tube are coated with low surface energy or ultra-low surface energy coating material.

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

[0077] Example 1

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

[0079] (1) The production fluid (including formation sand particles) seeps from the wellbore into the tubing, and passes through the buffer layer d2 (1 layer), control layer d1 (1 layer), and support layers d3 and d4 (1 to 2 layers) in the sand control pipe in sequence. The microspheres fill the filter medium before entering the tubing.

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

[0081] Based on the target value d for sand control accuracy of the production well, the particle size d1 of the filling microspheres in 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 coarser microspheres d2 to form larger gaps, which provides external protection for the control layer d1 and prevents the fluid from directly scouring the control layer d1. At the same time, the buffer layer d2 also plays a role in screening the formation sand, blocking the formation sand that is prone to clogging the control layer d1, while 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 pores filled with coarser microspheres d3 and coarse microspheres d4, which allows smaller sand particles (<d) to quickly pass through the filter medium and enter the downstream. At the same time, the support layer filled with coarser and coarse microspheres enables the sand control pipe to achieve higher overall mechanical strength.

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

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

[0086] (6) The control layer filled with microbeads d1 is clamped and fixed upstream using an unobstructed filter jacket B1 and downstream using an unobstructed filter jacket B2. The buffer layer filled with microbeads d2 is clamped and fixed upstream using an unobstructed protective sleeve B and downstream using an unobstructed filter jacket B1. The support layer (outer) filled with microbeads d3 is clamped and fixed upstream using an unobstructed filter jacket B2 and downstream using an unobstructed filter jacket B3. The support layer (inner) filled with microbeads d4 is clamped and fixed upstream using an unobstructed filter jacket B3 and downstream using an unobstructed filter jacket B4.

[0087] The unobstructed protective sleeve and the unobstructed filter jacket, which serve as spacers and fixing materials for each microbead filling layer, both adopt a continuous spiral wave structure and are made of 304L or 316L stainless steel.

[0088] (7) All the microspheres in the filling layers, the unobstructed protective sleeve, the unobstructed filter jacket, and the entire surface of the base tube are coated with a low surface energy or ultra-low surface energy coating material. The specific coating material was determined based on the optimization experiment of secondary formation and clogging of natural gas hydrates in porous filter materials.

[0089] Example 2

[0090] Taking the sand control pipe (4800mm in length) of a 9-5 / 8" casing and 2-7 / 8" tubing in a 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 specifications of each filling microbead layer, unobstructed protective sleeve, each unobstructed filter jacket, and base tube are as follows:

[0091] 1. Unobstructed Protective Cover B

[0092]

[0093] 2. Buffer layer filled with microbeads d2

[0094] Microbead particle size d2 (um) 200

[0095] Filling length (mm): 3850

[0096] Material: Polystyrene, coated with a superhydrophobic coating

[0097] 3. Unobstructed Filter Jacket B1

[0098]

[0099] 4. Control layer microsphere filling d1

[0100] Microbead particle size d1 (um) 80

[0101] Filling length (mm): 3850

[0102] Material: Polystyrene, coated with a superhydrophobic coating

[0103] 5. Unobstructed Filter Jacket B2

[0104]

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

[0106] Microsphere particle size d3 (um) 250

[0107] Filling length (mm): 3850

[0108] Material: Polystyrene, coated with a superhydrophobic coating

[0109] 7. Unobstructed Filter Jacket B3

[0110]

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

[0112] Microbead particle size d4 (um) 350

[0113] Filling length (mm): 3850

[0114] Material: Polystyrene, coated with a superhydrophobic coating

[0115] 9. Unobstructed Filter Jacket B4

[0116]

[0117]

[0118] 10. Base tube API 5CT PSL1

[0119]

[0120] Example 3

[0121] This patent also applies to sand control in high-mud content natural gas wells. The purpose of applying a superhydrophobic coating material under these conditions is to prevent high-salinity formation water from scaling and clogging the wellbore and sand control pipe. Taking a shallow well with 5.5" casing (inner diameter 121.4mm) and 2-3 / 8" tubing as an example, the sand control accuracy is based on the formation sand particle size d... 60 =20um design. The relevant technical specifications of each filling microbead layer, barrier-free protective sleeve, each barrier-free filter jacket, and base tube are as follows:

[0122] 1. Unobstructed Protective Cover B

[0123]

[0124] 2. Buffer layer filled with microbeads d2

[0125] Microbead particle size d2 (um) 500

[0126] Filling length (mm): 3850

[0127] Material: Polystyrene, coated with a superhydrophobic coating

[0128] 3. Unobstructed Filter Jacket B1

[0129]

[0130] 4. Control layer microsphere filling d1

[0131] Microbead particle size d1 (um) 120

[0132] Filling length (mm): 3850

[0133] Material: Polystyrene, coated with a superhydrophobic coating

[0134] 5. Unobstructed Filter Jacket B2

[0135]

[0136] 6. Support layer microsphere filling d3

[0137] Microbead particle size d3 (um) 600

[0138] Filling length (mm): 3850

[0139] Material: Polystyrene, coated with a superhydrophobic coating

[0140] 7. Unobstructed Filter Jacket B3

[0141]

[0142] 8. Base tube API 5CT PSL1

[0143]

[0144] Finally, it should be noted that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

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

Claims

1. A sand control screen for use in the depressurization of natural gas hydrates, the screen comprising: The natural gas hydrate depressurization exploitation sand control screen comprises, from outside to inside, a non-blocking protective sleeve, a buffer layer, a control layer, a first support layer, a second support layer and a base pipe, the non-blocking protective sleeve, the buffer layer, the control layer, the first support layer, the second support layer and the base pipe are all tubular, annular low-density microspheres are filled in the buffer layer, the control layer, the first support layer and the second support layer to form a filter assembly of the natural gas hydrate depressurization exploitation sand control screen, the particle sizes are configured in the order of medium, small, relatively coarse and coarse, and fluid flows through in the radial direction; The natural gas hydrate depressurization exploitation sand control screen further comprises a plurality of non-blocking filter jackets, 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 are all spaced apart by the non-blocking filter jackets; The annular low-density microspheres, the non-blocking protective sleeve, the non-blocking filter jackets and the base pipe are all coated with a low-surface-energy or ultra-low-surface-energy coating material on the full surfaces; The non-blocking protective sleeve and the non-blocking filter jackets adopt a spiral corrugated pipe high-flexibility structure; The non-blocking filter jackets are made of stainless steel sheet stamping and adopt a lock buckle structure of a spiral continuous corrugated pipe; The coating material used on the full surfaces of the annular low-density microspheres, the non-blocking protective sleeve, the non-blocking filter jackets and the base pipe comprises modified polytetrafluoroethylene and nano-composite ceramic; The non-blocking protective sleeve is made of stainless steel sheet stamping and adopts a lock buckle structure of a spiral continuous corrugated pipe; The particle size of the annular low-density microspheres filled in the control layer is designed as 5-6 times the d60 particle size of formation sand.

2. The NGH depressurization production sand control screen of claim 1, wherein, The non-blocking protective sleeve and the non-blocking filter jackets both adopt 304L or 316L metal materials.

3. The NGH depressurization production sand control screen of claim 1, wherein, The sizes of the openings or filter gaps of the non-blocking filter jackets are designed and determined according to the particle sizes of the annular low-density microspheres of the filled layers.

4. The NGH depressurization production sand control screen of claim 1, wherein, The annular low-density microspheres are made of one of low-density or ultra-low-density materials such as lightweight ceramsite, glass and polystyrene.

5. The NGH depressurization production sand control screen of claim 4, wherein, The annular low-density microspheres are made of hollow glass microbeads, and the particle sizes include 80, 200, 250 and 350 um.

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