Concentric double-pipe continuous negative pressure sand washing device and process

Abstract

The invention discloses a concentric double-pipe continuous negative pressure sand washing device and process. The device comprises a pump truck and a sand washing pipe column structure. The pump truck is used for providing sand washing liquid pressure and displacement for the sand washing pipe column structure; the sand washing pipe column structure comprises a concentric double pipe column, a process pipe, a negative pressure injection pump and a sand washing nozzle. A process pipe; wherein an annular liquid return channel is formed between the outer-layer oil pipe of the concentric double-pipe column and the inner-layer oil pipe of the concentric double-pipe column; a negative-pressure injection pump and a sand washing nozzle are mounted at the bottom of the inner-layer oil pipe; the sand washing fluid shunting channel is divided into two channels; one part of sand washing fluid enters the well bottom through the self-sealing well mouth and the inner-layer oil pipe in sequence, and the sand washing fluid makes contact with the sand surface of the well bottom through the sand washing nozzle; and the other part of the sand washing fluid generates negative pressure through the negative pressure injection pump to discharge the formation produced fluid and mixed fluid of the sand washing fluid and shaft sand grains out of the ground through the annular fluid return channel and the process pipe, and through the concentric double-pipe structure and the negative pressure injection pump, internal circulation of the sand washing fluid and continuous negative pressure sand washing are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of oil production engineering, and in particular relates to a concentric double-tube continuous negative pressure sand flushing device and process. Background Art

[0002] During oilfield development and production in the petroleum industry, sand accumulation in wellbores has always been a key factor affecting the normal production and safety of oil wells. With the continuous advancement of oilfield development and the increasing difficulty of extraction, the accumulation of large amounts of sand in wellbores has become increasingly common. This sand primarily originates from the fragmentation of formation rocks during the extraction process, as well as the deposition of fine particles carried by fluids within the wellbore.

[0003] The accumulation of sand in wellbores can have a range of serious consequences. First, sand can clog pipelines, obstructing the normal flow of crude oil and significantly reducing well production. According to relevant statistics, in some wells with severe sand accumulation, production declines can reach 30%-50%, significantly impacting the economic profitability of the oilfield. Second, the friction and accumulation of sand in the wellbore can damage downhole equipment, increasing wear and tear on key components like pumps and valves, shortening equipment lifespan and increasing repair and replacement costs. More seriously, sand accumulation can also lead to serious safety incidents, such as sand stuck pump rod breakage and blowouts, posing a significant threat to personnel safety and oilfield production facilities.

[0004] Traditional sand flushing operations require stopping the pump when replacing a single tubing. This is affected by the operator's skills and formation conditions, and can easily cause sand burial and sand sticking accidents. In serious cases, a major overhaul is required. Secondly, due to the special wellbore structure of horizontal wells, extended reach wells, and highly deviated wells, traditional forward and reverse sand flushing methods are difficult to meet the needs, and there are problems such as complex operation, severe pollution, and high risk of sand sticking. In addition, although continuous tubing sand flushing can achieve continuous single-line circulation sand flushing, it has safety hazards such as wellhead suspension and ground switching of high-pressure valves. It is not suitable for underpressure formations and cannot meet the efficient, safe, and environmentally friendly production needs of modern oil fields. Summary of the Invention

[0005] In view of this, the purpose of the present invention is to provide a concentric double-tube continuous negative pressure sand washing device and process, which realizes the internal circulation of sand washing liquid and continuous negative pressure sand washing through the concentric double-tube structure and the negative pressure jet pump.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A concentric double-tube continuous negative pressure sand flushing device comprises: a power and circulation mechanism and a sand flushing pipe column structure;

[0008] The power and circulation mechanism includes: a pump truck for providing the sand flushing fluid pressure and displacement to the sand flushing pipe string structure to ensure that the sand flushing fluid is internally circulated;

[0009] The sand flushing string structure includes: a concentric double string and a process pipe; wherein the concentric double string includes: an outer oil pipe and an inner oil pipe; an annular liquid return channel is formed between the outer oil pipe and the inner oil pipe; a negative pressure jet pump and a sand flushing nozzle are installed at the bottom of the inner oil pipe; the process pipe is connected to the annular liquid return channel through a large four-way joint to form a diversion channel;

[0010] Among them, the sand flushing fluid diversion channel is divided into two channels; one part of the sand flushing fluid enters the bottom of the well through the self-sealing wellhead and the inner oil pipe in turn, and the sand flushing fluid contacts the sand surface at the bottom of the well through the sand flushing nozzle; the other part of the sand flushing fluid is discharged to the ground through the annular return channel and process pipe through the negative pressure generated by the negative pressure jet pump.

[0011] Furthermore, a casing and a leather cup packer are provided on the outside of the outer oil pipe;

[0012] The leather cup packer is arranged between the outer side of the outer oil pipe and the casing, and is used to seal the oil casing annulus and correct the eccentricity of the concentric double pipe strings.

[0013] Furthermore, the casing valve on one side of the large four-way valve is connected to the self-sealing device through flange bolts; the liquid inlet of the self-sealing device is connected to the liquid outlet pipe of the pump truck through a well washing pipeline to establish a continuous well washing process on the ground.

[0014] Furthermore, a reverse discharge pipeline is installed on the casing valve on the other side of the large four-way valve; the reverse discharge pipeline is connected to the liquid inlet of the ground liquid collecting tank; and the liquid outlet of the ground liquid collecting tank is connected to the suction pipe of the pump truck.

[0015] Furthermore, the device further comprises:

[0016] Flow meter, installed in the annular return channel, is used to monitor the sand flushing fluid discharge, pump pressure and sand return volume;

[0017] The pressure gauge is arranged in the negative pressure jet pump and is used for real-time monitoring of the negative pressure difference in the sand flushing string.

[0018] The present invention also provides a process for a concentric double-tube continuous negative pressure sand washing device, comprising the following steps:

[0019] S1. Collect geological data of the oil well and design the specifications of the power and circulation mechanism and the sand flushing string structure based on the geological data. The power and circulation mechanism includes a pump truck; the sand flushing string structure includes a concentric double string, process pipe, negative pressure jet pump and sand flushing nozzle;

[0020] S2. When the flushing work is carried out, the pump truck is turned on, and the sand flushing fluid enters the bottom of the well through the inner oil pipe in the sand flushing string structure, contacts the sand surface at the bottom of the well, and performs physical sand flushing;

[0021] S3. After the sand flushing fluid and sand particles are mixed, negative pressure is generated by a negative pressure jet pump to discharge the mixture of formation production fluid, sand flushing fluid and wellbore sand particles to the ground through the annular return channel and process pipe between the inner and outer oil pipes in the sand flushing string structure.

[0022] Furthermore, the geological data include: formation lithology, formation pressure, permeability, oil layer thickness, and formation fluid properties;

[0023] The specifications of the power and circulation mechanism and the sand flushing pipe string structure include: the pressure value of the pump truck and the sizes of the concentric double pipe strings, process pipes, negative pressure jet pumps and sand flushing nozzles.

[0024] Furthermore, in S2, the negative pressure difference range in the annular liquid return channel is determined by the oil layer permeability and the formation pressure coefficient.

[0025] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects: the present invention can quickly and effectively disperse the sand particles at the bottom of the well and carry them to the annular return channel by directly delivering the sand flushing fluid to the bottom of the well through the inner oil pipe and the sand flushing nozzle. At the same time, the use of a negative pressure jet pump can further enhance the carrying capacity of the sand flushing fluid, making it easier for the sand particles to be discharged from the ground, thereby significantly improving the efficiency of sand flushing; the sand flushing fluid is circulated and supplied through a pump truck to form an internal circulation system, which can achieve continuous sand flushing without the need to frequently stop the pump or replace equipment, reducing the frequency of operation interruptions and improving operation continuity and efficiency; the concentric double-tubing design forms an efficient liquid circulation path through the annular return channel between the outer oil pipe and the inner oil pipe, as well as the connection between the process pipe and the annular return channel. The mixture of the sand flushing fluid and the formation liquid can be quickly discharged from the ground through this path, avoiding the problems of liquid retention and blockage. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are merely embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying any creative work.

[0027] The following is a further description of a concentric double-tube continuous negative pressure sand washing device and process of the present invention in conjunction with the accompanying drawings;

[0028] Figure 1 This is a schematic structural diagram of the concentric double-tube continuous negative pressure sand flushing device provided by the present invention;

[0029] Figure 2 The present invention provides a schematic flow diagram of a concentric double-tube continuous negative pressure sand washing process.

[0030] Description of the drawings: 1. Safety helmet; 2. Self-sealing device; 3. Blowout preventer; 4. Large four-way valve; 5. Process pipe; 6. Self-sealing core pressure cap; 7. Self-sealing core; 8. Process pipe hanger; 9. Special joint; 10. Plug; 11. Oil pipe; 12. Sand flushing nozzle. DETAILED DESCRIPTION

[0031] The following embodiments of the present invention are described in further detail with reference to the accompanying drawings and examples. The following examples are used to illustrate the present invention but are not intended to limit the scope of the present invention.

[0032] In order to better understand the purpose, structure and function of the present invention, the present invention is further described in detail below with reference to the accompanying drawings.

[0033] Example 1

[0034] like Figure 1 As shown, the present invention provides a concentric double-tube continuous negative pressure sand flushing device, comprising: a power and circulation mechanism and a sand flushing pipe column structure;

[0035] The power and circulation mechanism includes: a pump truck for providing the sand flushing fluid pressure and displacement to the sand flushing pipe string structure to ensure that the sand flushing fluid is internally circulated;

[0036] The sand flushing string structure includes: a concentric double string and a process pipe 5; wherein the concentric double string includes: an outer oil pipe and an inner oil pipe; an annular fluid return channel is formed between the outer oil pipe and the inner oil pipe; a negative pressure jet pump and a sand flushing nozzle 12 are installed at the bottom of the inner oil pipe; the process pipe 5 is connected to the annular fluid return channel through a large four-way 4, forming a sand flushing liquid diversion channel;

[0037] Among them, the sand flushing fluid diversion channel is divided into two channels; one part of the sand flushing fluid enters the bottom of the well through the self-sealing wellhead and the inner oil pipe in turn, and the sand flushing fluid contacts the sand surface at the bottom of the well through the sand flushing nozzle 12; the other part of the sand flushing fluid is discharged to the ground through the annular return channel and the process pipe 5 through the negative pressure generated by the negative pressure jet pump.

[0038] The casing valve on one side of the large four-way valve 4 is connected to the self-sealing device via flange bolts; the liquid inlet of the self-sealing device is connected to the well-washing pipeline; the liquid outlet pipe of the pump truck is connected to the well-washing pipeline on the self-sealing device to establish a continuous surface well-washing process. The casing valve on the other side of the large four-way valve is installed with a backflow pipeline; the backflow pipeline is connected to the liquid inlet of the surface liquid collection tank; the liquid outlet of the surface liquid collection tank is connected to the suction pipe of the pump truck.

[0039] In this embodiment, the concentric double-tube structure is used to form a certain negative pressure difference in the sand flushing string, so that the formation fluid can enter the sand flushing string during the sand flushing process and return to the surface with the sand particles, thereby achieving a sand flushing process that removes sand particles in the wellbore and reduces pollution to the oil layer.

[0040] Among them, the negative pressure difference refers to the difference between the oil layer pressure and the pressure inside the sand flushing string. This difference should be reasonably determined based on the oil layer characteristics, formation fluid properties and sand flushing operation requirements.

[0041] Among them, the sand flushing fluid diversion channel is divided into two channels; one part of the sand flushing fluid enters the bottom of the well through the self-sealing wellhead and the inner layer oil pipe in turn, and the sand flushing fluid contacts the sand surface at the bottom of the well through the sand flushing nozzle 12; the other part of the sand flushing fluid generates negative pressure through the negative pressure jet pump to discharge the mixture of formation production fluid and sand flushing fluid and wellbore sand particles through the annular return channel and process pipe 5 to the ground.

[0042] The sand flushing string selection involves selecting an appropriately sized tubing 11 based on the well casing size, well depth, and sand flushing process requirements. The present invention utilizes 3.5-1 / 2 and 2.7-8 TBG tubing and a 1.9 TBG tubing in a concentric twin-tube structure. The strength of the tubing meets the tension, pressure, and torque requirements of the sand flushing operation, while also ensuring a safety factor that complies with relevant standards.

[0043] Connection requirements: The connection threads of the sand-blasting pipe column should be coated with sealing grease and tightened to ensure a reliable connection seal.

[0044] Material and connection: Use oil pipes that meet the inner diameter of downhole casing and have tensile strength that meets the well depth structure. The oil pipe strings are connected with threaded connections, and the thread sealing grease should have good temperature and pressure resistance.

[0045] Concentric pipe structure: The concentric pipe structure should meet the design requirements, including the specifications and connection methods of the inner and outer pipes, to ensure that the concentric pipe negative pressure sand flushing function can be achieved. The pipe string structure is generally selected (from bottom to top): sand flushing nozzle 12 + telescopic short circuit + negative pressure jet pump + pre-installed double oil pipe (the size of the oil pipe 11 is selected according to the actual situation of the casing in the well) + leather cup packer + variable buckle tee + oil pipe 11 to the wellhead, and the sand flushing pump core is put into the wellhead (due to the later installation of a single special joint 9, the pump core cannot be put into the wellhead). Note: The pipe string structure should be modified in time according to different downhole conditions or sand flushing requirements. The specific pipe string structure should be designed and constructed in accordance with the latest relevant downhole sand flushing process. The pipe string structure in this specification is only for reference. For downhole pipe string construction, this requirement is not a fixed criterion and should be changed accordingly based on actual conditions.

[0046] The outer side of the outer oil pipe is also provided with a casing and a leather cup packer;

[0047] The cup packer, installed between the outer tubing and the casing, is used to isolate the annulus between the tubing and casing and correct eccentricity within the concentric double string. The cup packer must meet technical parameter requirements, including maximum and minimum temperatures, operating medium, inner diameter, height, operating pressure, maximum sealing pressure, and connector type. The appropriate cup packer should be selected based on the specific downhole conditions to ensure isolation and eccentricity correction, meeting on-site operational requirements.

[0048] In this embodiment, before the power and circulation mechanism and the sand flushing string structure are installed, the following steps are also included:

[0049] 1) Ground installation: The lower flange of the self-sealing device 2 is bolted to the upper flange of the large four-way valve 4 at the wellhead, and the steel ring is sealed. The upper flange of the self-sealing device 2 is bolted to the flange below the blowout preventer 3, and the steel ring is sealed to keep the blowout preventer 3 in the fully open state.

[0050] 2) Seal Verification: Lower the high-pressure wire plug, tubing 11 (1-2 pieces), and cup packer into place, suspended by tubing 11 elevators. Close the blowout preventer 3 and the casing valve. Connect the flushing fluid outlet of the self-sealing device 2 to the pressure line and pressurize to the specified pressure for wellhead seal verification. After the seal verification is complete, release the pressure, fully open the blowout preventer 3, and lift the tubing out of the well to verify the seal.

[0051] 3) Lowering the tubing string: Connect the tubing string with the concentric double-tube jet pump negative pressure sand flushing string using the oil pipe 11, and lower the tubing string to the sand exploration surface;

[0052] 4) Sand handling: If sand is encountered during the lowering process, stop lowering the tubing string immediately, pull out the two oil pipes, and then proceed with the installation of the process pipes.

[0053] 5) Process pipe assembly installation: Connect the internal thread of the process pipe hanger 8 to the lifting joint. Pass the lower end of the tubing stub (1 meter) through the inner hole at the upper end of the lifting joint and connect it to the internal tubing 11. The length of the internal tubing 11 is 1 tubing + 2 meters. Lift the entire process pipe assembly with a large hook. Connect the lower end of the internal tubing 11 to the wellbore tubing and place it into the wellbore. Hang the process pipe 5 in the large spool 4. Remove the lifting joint connected to the internal thread of the process pipe hanger 8 at the upper end of the process pipe 5.

[0054] 6) Installation of the self-sealing core 7: Connect the outer reverse thread of one end of the lifting joint with the inner reverse thread of the self-sealing core pressure cap 6 and prepare to tighten. The lifting joint, the self-sealing core pressure cap 6 and the self-sealing core 7 are placed in the order of going into the well. An oil pipe is placed inside. An elevator is installed on the upper end of the oil pipe. The two elevators are lifted together and connected to the oil pipe that has been put into the well. As the pipe string is lowered, the self-sealing core pressure cap 6 and the self-sealing core 7 are brought into the self-sealing device. After they are in place, rotate the lifting joint forward to connect the outer thread of the self-sealing core pressure cap 6 with the inner thread of the self-sealing device housing and prepare to tighten. Continue to rotate the lifting joint forward to disengage it from the self-sealing core pressure cap 6, lift the oil pipe to remove the lifting joint, pour the oil pipe elevator, and unload the oil pipe above the oil pipe elevator;

[0055] 7) Installation of special connector 9: A special connector 9 is connected to the lower end of each oil pipe.

[0056] 8) Pipeline connection: Install the reverse discharge pipeline on the large four-way 4-valve to the ground liquid collecting tank, connect the liquid outlet of the liquid collecting tank to the suction pipe of the pump truck, and close the casing valve on the other side.

[0057] The liquid inlet of the self-sealing device 2 is connected to the well washing pipeline, and the liquid outlet pipe of the pump truck is connected to the well washing pipeline on the self-sealing device 2. The ground continuous well washing process is established and the flushing work is carried out. When the flushing is completed, the blowout preventer is removed first; then the self-sealing core pressure cap 6 is turned upside down and raised with the lifting joint, and the self-sealing core 7 is brought out of the self-sealing device 2 as the pipe string is lifted up; then the process pipe hanger 8 pressure cap is turned upside down and raised with the lifting joint, and the process pipe hanger 8 internal thread at the upper end of the process pipe 5 is connected to the lifting joint. The upper end of the lifting joint is suspended with a short circuit (1 meter) of the oil pipe, and the whole is lifted out of the well with a large hook. Normal oil pipe lifting: Finally, the oil pipe is lifted normally.

[0058] The concentric double-tube continuous negative pressure sand washing device of the present invention also has the following advantages:

[0059] (1) The negative pressure sand flushing pump can be placed below the packer to flush and suck the sand into the oil and gas layer. The sand flushing and suction are strong and thorough.

[0060] (2) It can realize the operation of sand flushing and lowering the pipe string at the same time, and the sand flushing effect is obvious.

[0061] (3) Since the casing annulus packer is a sand-proof leather cup structure and does not require setting, it can be used in highly deviated wells and horizontal wells and has a wide range of adaptability;

[0062] (4) Installing a pressure gauge on the pump core can monitor the negative pressure during sand flushing in real time, which is beneficial for data analysis;

[0063] (5) The negative pressure can be used to remove blockages while flushing sand.

[0064] (6) The sand flushing fluid is pressurized from the oil pipe, and the ground pressure is not restricted, which is conducive to the generation of ultra-low negative pressure.

[0065] (7) It requires a relatively low flow rate and has a certain ability to penetrate the sand bed, and can be used for sand flushing operations in oil and gas wells with extremely low downhole pressure.

[0066] Example 2

[0067] like Figure 2 As shown, the present invention also provides a sand washing process applied to a concentric double-tube continuous negative pressure sand washing device, comprising the following steps:

[0068] S1. Collect geological data of the oil well and design specifications of the power and circulation mechanism and the sand flushing string structure based on the geological data; the power and circulation mechanism includes a pump truck; the sand flushing string structure includes a concentric double string, a process pipe 5, a negative pressure jet pump, and a sand flushing nozzle 12; the geological data includes formation lithology, formation pressure, permeability, oil layer thickness, and formation fluid properties;

[0069] S2. When the flushing work is carried out, the pump truck is turned on, and the sand flushing fluid enters the bottom of the well through the inner oil pipe in the sand flushing string structure, contacts the sand surface at the bottom of the well, and performs physical sand flushing;

[0070] The negative pressure difference range in the annular return channel is determined by the oil layer permeability and the formation pressure coefficient.

[0071] In this embodiment, before flushing, the wellbore is first cleared using a clearing gauge. The outer diameter of the clearing gauge should be reasonably selected according to the casing size so that it can play a clearing role while avoiding various construction risks and obstacles caused by improper size. The clearing speed is controlled within a reasonable range, and the wellbore is checked for deformation, scaling, and fallen objects to ensure that the sand flushing string can be smoothly lowered to the predetermined position.

[0072] S3. After the sand flushing fluid and sand are mixed, a negative pressure jet pump generates negative pressure, discharging the mixture of formation fluid, sand flushing fluid, and wellbore sand to the surface through the annular return channel between the inner and outer tubing layers of the sand flushing string structure and process pipe 5. The wellbore flushing process continues. After the wellbore is cleared, the string is lowered at a controlled speed. Once the wellbore is fully flushed, the string is lowered, and backwashing is stopped. Continue flushing until the well is completely cleaned, then stop.

[0073] The sand washing fluid in this embodiment should have the following characteristics:

[0074] 1) Good sand carrying capacity. Viscosity and density should be determined based on the distribution of sand grain size in the formation. Viscosity should ensure that sand grains are effectively carried to the surface, and density should be within a reasonable range.

[0075] 2) Compatibility: It has good compatibility with formation fluids and oil layer rocks to prevent chemical reactions that may cause formation damage or blockage of the sand flushing string.

[0076] 3) Filtration loss: It has a low filtration loss, controls the filtration coefficient below a reasonable value, and reduces the depth of invasion of the sand flushing fluid into the oil layer.

[0077] The specifications of the power and circulation mechanism and the sand flushing pipe string structure include: the pressure value of the pump truck and the sizes of the concentric double pipe strings, process pipes, negative pressure jet pumps and sand flushing nozzles.

[0078] In this embodiment, the negative pressure difference range is determined based on parameters such as oil layer permeability, formation pressure coefficient, etc. During downhole sand flushing, the negative pressure difference should be ensured to be within the appropriate range.

[0079] During the sand flushing process, the negative pressure difference is monitored in real time, and the sand flushing parameters (such as sand flushing fluid displacement, pump pressure, etc.) are adjusted to keep it within the specified range. Real-time monitoring of the sand flushing speed: During the sand flushing process, the sand flushing speed should be reasonably controlled. The speed of lowering the sand flushing string should not be too fast to avoid sand agitation or damage to the sand flushing string caused by excessively fast sand flushing fluid flow rate, and the inability to effectively carry out sand particles due to too slow a flow rate. Real-time monitoring of the sand flushing fluid displacement: During positive and reverse circulation sand flushing, the sand flushing fluid displacement should be controlled within a reasonable range to ensure that the sand flushing fluid forms a sufficient flow rate in the wellbore to carry sand particles, but it must not exceed the fracture pressure of the formation. Real-time pump pressure monitoring: The pump pressure fluctuation range should be controlled within a reasonable range. If the pump pressure rises abnormally, the sand flushing should be stopped immediately, the cause should be analyzed, and corresponding measures should be taken.

[0080] In this embodiment, during the sand flushing process, the following sand return conditions need to be strictly recorded:

[0081] a. Amount of sand returned: It can be estimated and recorded through ground measuring equipment or other means. It should be recorded once every certain period of time (2 hours). The recorded data can be recorded in appropriate units (such as cubic meters) according to the actual situation.

[0082] b. Description of the returned sand status: including the particle size of the sand (which can be roughly described as fine sand, medium sand, coarse sand, etc.), the uniformity of the sand, whether it contains impurities and other information. A brief description should be given each time it is recorded.

[0083] c. Records of abnormal situations and treatment measures: Record abnormal situations that occur during the construction process, including the time and location of the abnormal situation (corresponding to the depth of the pipe or the location of the wellhead equipment, etc.), and description of the phenomenon (such as a sudden increase in pump pressure, poor sand return, pipe string stuck, etc.).

[0084] Records of treatment measures taken for abnormal situations, including the start time of the treatment measures, specific treatment methods (such as adjusting pump pressure, lifting and lowering the tubing string, changing tools, etc.), treatment results (such as whether the abnormal situation has been resolved, and continued observation after resolution, etc.).

[0085] Example 3

[0086] The present invention further provides a detailed experimental process using the process flow in Example 2:

[0087] First experiment:

[0088] On December 24, 2024, the sand flushing string was run into Well 28-19 to 2260m, and 0.5t of sand was lightly explored.

[0089] At 10:10, the first sand flushing string was lowered. Considering the feasibility of the process, the pump circulation was started in advance at 2222.41m, with a pump pressure of 8-12MPa and a displacement of 0.45-0.5m 3 / min;

[0090] 10:23 The discharge volumes of the inlet and outlet are basically the same, and the sand flushing column is gradually lowered;

[0091] At 12:10, all 20 sand flushing strings were put into the well and flushed to 2422.41m. On average, one sand flushing string was put into the well every 6 minutes. The outlet was black with little sand and circulated at a large displacement.

[0092] The pump was stopped at 13:50, all 20 sand flushing strings were pulled out, and the sealing packing of the sand flushing joints was replaced. 15 cubic meters of water were added that day, and the packer ran 200 meters downward and 200 meters upward. The hanging weight of the movable string was normal and there was no abnormality.

[0093] Second experiment:

[0094] On March 12, 2025, the first sand flushing string was run into Well 28-19 at 10:30. Considering the feasibility of the process, the pump circulation was started in advance at 2610.11m, with a pump pressure of 12-16MPa and a displacement of 0.40-0.45m 3 / min;

[0095] At 11:50, the discharge volume at the inlet and outlet was basically the same, and the sand flushing column was gradually lowered;

[0096] At 16:00, all 40 sand flushing strings were put into the well and flushed to 3008.02m. On average, one sand flushing string was put into the well every 7 minutes. The outlet was black with little sand and circulated at a large displacement.

[0097] The pump was stopped at 18:00 and all 40 sand flushing strings were pulled out. 30 cubic meters of water were added on the same day. The packer moved downward 1000m and upward 1000m. The hanging weight of the movable string was normal and there was no abnormality.

[0098] On March 13, 2025, the oil pipeline was lowered to 3000m. At 8:20, the first sand flushing string was lowered. The pump circulation was started in advance at 3000.82m. The pump pressure was 12-15MPa and the displacement was 0.4-0.45m. 3 / min;

[0099] At 15:15, all 36 sand flushing strings were put into the well and flushed to 3355m. On average, one sand flushing string was put in every 8 minutes. The outlet water was black and contained sand, and was circulated at a large flow rate.

[0100] The pump was stopped at 17:15 and all 36 sand flushing strings were pulled out. 40 cubic meters of water were added on the same day. The packer moved downward 1150 meters and upward 1150 meters. The hanging weight of the movable string was normal and there was no abnormality.

[0101] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein but is to be construed in the widest manner consistent with the principles and novel features disclosed herein.

Claims

1. A concentric double-tube continuous negative pressure sand washing device, characterized in that: include: Power and circulation mechanism and sand flushing string structure; The power and circulation mechanism includes: a pump truck for providing the sand flushing fluid pressure and displacement to the sand flushing pipe string structure to ensure that the sand flushing fluid is internally circulated; The sand flushing pipe string structure comprises: a concentric double pipe string and a process pipe (5); wherein the concentric double pipe string comprises: an outer oil pipe and an inner oil pipe; an annular fluid return channel is formed between the outer oil pipe and the inner oil pipe; a negative pressure jet pump and a sand flushing nozzle (12) are installed at the bottom of the inner oil pipe; the process pipe (5) is connected to the annular fluid return channel through a large four-way (4) to form a sand flushing liquid diversion channel; The sand flushing fluid diversion channel is divided into two channels; one part of the sand flushing fluid enters the bottom of the well through the self-sealing wellhead and the inner oil pipe in sequence, and the sand flushing fluid contacts the sand surface at the bottom of the well through the sand flushing nozzle (12); the other part of the sand flushing fluid is discharged to the ground through the negative pressure generated by the negative pressure jet pump, and the mixture of the formation production fluid and the sand flushing fluid and the wellbore sand particles is discharged through the annular return channel and the process pipe (5).

2. The concentric double-tube continuous negative pressure sand washing device according to claim 1, characterized in that: The outer side of the outer oil pipe is also provided with a casing and a leather cup packer; The leather cup packer is arranged between the outer side of the outer oil pipe and the casing, and is used to seal the oil casing annulus and correct the eccentricity of the concentric double pipe strings.

3. The concentric double-tube continuous negative pressure sand washing device according to claim 1, characterized in that: The casing valve on one side of the large four-way valve (4) is connected to the self-sealing device (2) through flange bolts; the liquid inlet of the self-sealing device (2) is connected to the liquid outlet pipe of the pump truck through a well washing pipeline to establish a continuous well washing process on the ground.

4. The concentric double-tube continuous negative pressure sand washing device according to claim 1, characterized in that: A reverse discharge pipeline is installed on the sleeve valve on the other side of the large four-way (4); the reverse discharge pipeline is connected to the liquid inlet of the ground liquid collecting tank; the liquid outlet of the ground liquid collecting tank is connected to the liquid suction pipe of the pump truck.

5. The concentric double-tube continuous negative pressure sand washing device according to claim 1, characterized in that: The device further comprises: Flow meter, installed in the annular return channel, is used to monitor the sand flushing fluid discharge, pump pressure and sand return volume; The pressure gauge is arranged in the negative pressure jet pump and is used for real-time monitoring of the negative pressure difference in the sand flushing string.

6. A concentric double-tube continuous negative pressure sand washing process, applied to the concentric double-tube continuous negative pressure sand washing device according to any one of claims 1 to 5, characterized in that: The following steps are involved: S1. Collect geological data of the oil well and design the specifications of the power and circulation mechanism and the sand flushing string structure based on the geological data; The power and circulation mechanism includes: a pump truck; the sand flushing pipe column structure includes: a concentric double pipe column, a process pipe (5), a negative pressure jet pump and a sand flushing nozzle (12); S2. When the flushing work is carried out, the pump truck is turned on, and the sand flushing fluid enters the bottom of the well through the inner oil pipe in the sand flushing string structure, contacts the sand surface at the bottom of the well, and performs physical sand flushing; S3. After the sand flushing fluid and the sand particles are mixed, a negative pressure is generated by a negative pressure jet pump, and the mixture of the formation production fluid, the sand flushing fluid and the wellbore sand particles is discharged to the ground through the annular return channel between the inner layer oil pipe and the outer layer oil pipe in the sand flushing pipe string structure and the process pipe (5).

7. The concentric double-tube continuous negative pressure sand blasting process according to claim 6, characterized in that: In said S2, the geological data include: formation lithology, formation pressure, permeability, oil layer thickness, and formation fluid properties; The specifications of the power and circulation mechanism and the sand flushing pipe column structure include: the pressure value of the pump truck and the sizes of the concentric double pipe columns, the process pipe (5), the negative pressure jet pump and the sand flushing nozzle (12).

8. The concentric double-tube continuous negative pressure sand blasting process according to claim 6, characterized in that: In the above-mentioned S2, the negative pressure difference range in the annular liquid return channel is determined by the oil layer permeability and the formation pressure coefficient.

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