High oil-gas ratio shale oil well plug removal, gas and sand removal, recycling treatment system

Abstract

The application discloses a high oil-gas ratio shale oil well plug sweeping, gas and sand removing and recycling processing system and relates to the technical field of shale oil and gas exploitation. The system comprises a wellhead liquid receiving processing unit, a double-path switching valve group, a sand and gas removing tank, a simple sand and gas removing tool, a blowdown sedimentation system and a recycling unit. The oil nozzle manifold outlet is connected with a high gas content path and a low gas content path through high-pressure switching valves one and two respectively. In the high gas content path, the return liquid enters the sand and gas removing tank for three-phase separation. In the low gas content path, the return liquid enters the simple sand and gas removing tool for rotary centrifugal separation. The liquid and solid outlets of the two paths are connected with the blowdown sedimentation system which is composed of four blowdown tanks connected in series. The water outlet in the lower part of the third blowdown tank is connected with a dosing booster pump and a coiled tubing to return to the high-pressure well to form a closed cycle. The application is suitable for different gas content conditions through double-path switching, simultaneously realizes gas removing, sand removing and liquid recycling, and is suitable for the on-site instant processing of the return liquid of shale oil plug sweeping operation.

Description

Technical Field

[0001] This invention relates to the field of shale oil and gas extraction technology, and more specifically, to a treatment system for degassing, desanding, recovering, and recycling the returned fluid during coiled tubing cleaning operations in high oil-to-gas ratio shale oil wells. Background Technology

[0002] Shale oil wells commonly employ staged volumetric fracturing technology for reservoir stimulation. After fracturing, a plugging operation is performed via coiled tubing to achieve full-bore production, increase wellhead pressure, and improve production enhancement. During the plugging operation, a large amount of sand-laden, gas-containing return fluid is continuously discharged from the wellhead, and its treatment directly affects the safety and economy of the operation. Currently, the treatment of plugging return fluid mainly faces the following technical challenges.

[0003] Firstly, the returned fluid has a complex composition and large discharge volume, making direct transportation or discharge costly and risky. The discharge rate for single-well fracturing is typically 24–30 m³ / h, with an average daily fluid production of 576–720 m³. The returned fluid contains not only a large amount of fracturing sand (approximately 1 m³ of sand per 120–150 m³ of returned fluid, with a cumulative sand removal of up to 20 m³ per well), but also a large amount of natural gas (some wells produce over 20,000 m³ of gas per day). Transporting it by tanker truck would be extremely costly and pose significant traffic safety risks. Direct discharge of the gas-containing returned fluid would be dangerous, as natural gas concentrations of 5%–15% in the air can ignite upon contact with an open flame, posing a serious safety threat. Furthermore, the returned fluid contains oil and sand; direct reuse without treatment would affect the performance of fracturing agents such as drag reducers. Therefore, comprehensive treatment involving oil removal, degassing, and sand removal is urgently needed to achieve fluid recycling.

[0004] Secondly, existing separation equipment struggles to simultaneously address the needs of sand removal and degassing, and its adaptability to blockage-clearing operations is poor. Conventional three-phase separators cannot handle sand-containing fluids; sand particles rapidly erode and wear down internal components, occupying effective separation space and severely reducing gas-liquid separation efficiency. Furthermore, the market lacks specialized processing equipment tailored to the characteristics of blockage-clearing operations: large discharge volume, high sand content, high gas content, and short cycle time. Specifically, Chinese patent CN218953292U discloses a "sand removal device for shale oil and gas development," which achieves preliminary sand-liquid separation through cyclone separation and incorporates a stirring mechanism within the sand storage tank to assist in sand discharge, thus alleviating the problem of material blockage to some extent. However, the device has a single function, only capable of removing sand, and lacks a gas separation and collection structure, making it unable to handle high-gas-content return liquid. Its sand removal operation needs to be started before discharge, and it cannot continuously remove sand during device operation. The continuous deposition of sand particles will still affect the separation efficiency and effective volume. At the same time, the device does not involve the design of returning liquid recycling, making it difficult to meet the requirements of comprehensive treatment and resource recovery under high oil-gas ratio conditions.

[0005] Chinese patent CN223136108U discloses an "integrated high-pressure desanding and fluid drainage system for shale gas wellheads," which employs a cyclone desanding mechanism connected in series with a desanding and fluid drainage mechanism, exhibiting a high degree of integration and capable of desanding and fluid drainage of gas well products. However, this system is primarily designed for stable high-pressure production processes in the early stages of gas well commissioning. The equipment structure is fixed, the system is complex, and it focuses on high-pressure desanding and fluid drainage under multi-well confluence conditions. It does not employ a skid-mounted design, making rapid disassembly and relocation inconvenient. Similarly, the system does not address the recycling of sludge return fluid and does not consider control strategies to reduce gas intrusion at the process source. Its applicable scenarios and processing objectives differ significantly from the actual needs for immediate treatment and liquid reuse of sludge return fluid. In summary, existing technologies either lack functionality, failing to simultaneously remove sand and gas, or are misaligned with application scenarios, making it difficult to meet the urgent needs of shale oil sludge removal operations for safe, efficient, and mobile equipment.

[0006] Third, the short construction cycle and frequent site relocation of scavenging operations, coupled with the high gas-liquid ratio and large velocity fluctuations of the returned fluid, place higher demands on the on-site adaptability of the treatment equipment. Single-well scavenging operations typically last only 3-7 days, requiring highly modular and skid-mounted treatment equipment for rapid disassembly, transportation, and on-site pressure testing. Furthermore, due to the high gas-liquid ratio and large velocity fluctuations at the returned fluid outlet, direct discharge into the atmospheric pressure storage tank can easily cause liquid splashing and natural gas accumulation, further increasing on-site safety and environmental risks. Simultaneously, current scavenging processes, in order to enhance sand-carrying capacity, often result in an outlet discharge rate greater than the inlet discharge rate, leading to the large-scale removal of formation gas, further increasing the difficulty of treating the returned fluid.

[0007] In summary, there is an urgent need to develop an integrated, skid-mounted specialized treatment system that can simultaneously achieve efficient sand and gas removal and support the recycling of returned fluid, in order to meet the pressing needs of safe, efficient, and mobile equipment for shale oil well cleaning operations with high oil-gas ratios. Summary of the Invention

[0008] The purpose of this section is to outline some aspects of embodiments of the present invention and to briefly describe some preferred embodiments. Simplifications or omissions may be made in this section, as well as in the abstract and title of this application, and such simplifications or omissions should not be construed as limiting the scope of the invention.

[0009] In view of the problems existing in the above and / or prior art, the present invention is proposed.

[0010] This invention addresses the aforementioned shortcomings in the treatment of returned fluid during coiled tubing plugging operations in high-oil-gas-ratio shale oil wells, aiming to provide an integrated, skid-mounted plugging, sand removal, degassing, and recycling system. This system simultaneously solves the following key technical problems: First, it ensures efficient and synchronous separation of fracturing sand and natural gas in the returned fluid, avoiding separation failure due to sand erosion in conventional equipment; second, the treated aqueous phase can be online mixed with drag-reducing agents and injected into the wellbore, achieving closed-loop recycling of the plugging fluid and eliminating the costs and risks of large-scale fluid transportation; third, the device features rapid assembly and disassembly, online sand removal, self-cleaning, and pressure testing functions, adapting to the characteristics of short single-well construction cycles and frequent site relocations; fourth, it can adapt to different gas content conditions and can suppress formation gas intrusion from the process source, reducing the downstream processing load.

[0011] To address the aforementioned technical problems, this invention provides a high-oil-gas-ratio shale oil well cleaning, degassing, and sand removal recycling system. Its core concept lies in constructing a dual-path processing flow of "high gas content – ​​low gas content," with a sand and gas removal tank equipped with a rotary desander, multi-stage baffle sedimentation, two-stage mist capture, and automatic liquid level control as the core processing unit. A uniquely structured, simple sand and gas removal tool serves as an auxiliary processing unit, complemented by a multi-stage sludge discharge tank group and a chemical dosing booster pump skid, forming an integrated closed-loop circulation system of "separation – sedimentation – recovery – liquid preparation – reinjection."

[0012] Specifically, the system includes a wellhead fluid treatment unit, a dual-path switching valve assembly, a desanding and degassing tank, a simple desanding and degassing tool, a sewage settling system, and a recycling unit. The wellhead fluid treatment unit comprises a high-pressure well, a high-pressure valve assembly, a cuttings collection manifold, and an oil nozzle manifold connected in sequence. The dual-path switching valve assembly includes a high-pressure switching valve one and a high-pressure switching valve two. The outlet of the oil nozzle manifold is connected to a high-gas-content treatment path and a low-gas-content treatment path via the dual-path switching valve assembly.

[0013] Furthermore, in the high-gas content treatment path, the high-pressure switching valve is connected to the desanding and degassing tank via a gate valve. The desanding and degassing tank has a primary mist eliminator at the top of its inlet for preliminary gas-liquid separation of the returned liquid; multiple upward-extending baffles along the length of the tank bottom divide the bottom into multiple settling chambers to guide liquid flow and promote sand sedimentation; each settling chamber is equipped with a jet desander, whose inlet is connected to an external water source via a bottom flushing water supply pipe, and whose outlet is connected to a main drain pipe via a tank drain valve, for continuously or periodically discharging sand particles deposited at the bottom of the tank during system operation; a secondary mist eliminator is located at the top of the tank outlet for further gas-liquid purification; a liquid outlet with a liquid discharge control valve is located at the lower part of the tank outlet; and a radar level gauge is installed at the top of the tank, which, in conjunction with the liquid discharge control valve signal, forms an automatic level control loop. The outlet of the sand and gas removal tank is connected to the sewage settling system, and the exhaust port is connected to the natural gas collection device and / or combustion storage tank.

[0014] Furthermore, in the low-gas content treatment path, the high-pressure switching valve two is connected to the simple sand and gas removal tool. The simple sand and gas removal tool includes a coaxial central tube, an intermediate tube rotatably fitted around the central tube, and an outer tube fixedly fitted around the intermediate tube. The central tube has a central tube slot outlet at its bottom, the intermediate tube has multiple oblique outlets circumferentially, and the outer tube has an exhaust port at its top and a drain port at its bottom. After the returned liquid enters the tool, it flows through the central tube slot outlet into the annular space between the intermediate tube and the central tube, and is ejected from each oblique outlet, generating a rotating centrifugal force field. The gas gathers upwards and is drawn by an exhaust fan to the combustion storage tank, while the liquid and sand are discharged from the bottom drain port. The gas outlet of the simple sand and gas removal tool is connected to the combustion storage tank, and the liquid-solid outlet is connected to the sewage settling system.

[0015] Furthermore, the wastewater settling system includes a primary wastewater tank, a second wastewater tank, a third wastewater tank, and a final wastewater tank connected in series. The primary wastewater tank is placed on a base, the height of which is no less than half the height of the primary wastewater tank body, to lower the liquid level inside the tank and facilitate smooth overflow to the second wastewater tank. The liquid-solid mixture from the desanding and degassing tank or simple desanding and degassing tools settles and separates in the four-stage wastewater tanks. The separated gas is led out from the exhaust port at the top of each wastewater tank, and the recovered floating oil is transported away by tanker truck.

[0016] Furthermore, the recycling unit includes a water pump, a chemical dosing booster pump skid, and coiled tubing. The outlet at the lower part of the third sewage tank is connected to the inlet of the chemical dosing booster pump skid via the water pump, and the outlet of the chemical dosing booster pump skid is connected to the coiled tubing, which returns to the high-pressure well, forming a closed-loop circulation circuit.

[0017] Furthermore, the upper part of the inner cavity of the desanding and degassing tank is equipped with a rotary tank cleaner, whose inlet is connected to a water source via an upper flushing pipe and a gate valve for cleaning the inner wall of the tank after the operation. A pressure testing water pipe is also provided, connected to the desanding and degassing tank via a gate valve for on-site pressure testing. During the plugging operation, the injection volume of the coiled tubing and the flow rate of the return fluid from the high-pressure wellhead are monitored, and the wellhead nozzle opening or pump speed is dynamically adjusted to ensure that the injection volume is equal to or slightly greater than the return fluid discharge volume, with the difference controlled within 0–50 L / min, thus suppressing formation gas intrusion from the source.

[0018] Compared with the prior art, the present invention achieves the following beneficial effects: 1. Achieving closed-loop recycling of returned fluid, significantly reducing costs and increasing efficiency. This invention constructs an integrated closed-loop circulation system of "separation-sedimentation-recovery-liquid preparation-reinjection." The treated aqueous phase is directly injected into the coiled tubing after being mixed with drag-reducing agent via a booster pump skid for downhole plugging. This completely avoids the huge tanker rental and transportation costs incurred from transporting large quantities of fluid, saving more than 60% of transportation costs per well. Simultaneously, it significantly reduces the frequency of on-site vehicle traffic, lowering traffic congestion and safety risks at the well site. Furthermore, the closed-loop system significantly reduces the consumption of fresh industrial water and the discharge of waste fluid, meeting the environmental protection requirements of energy conservation, emission reduction, and green development, resulting in excellent economic and environmental benefits.

[0019] 2. Synchronous and efficient sand and gas removal, ensuring inherent safety and equipment lifespan. This invention uses a sand and gas removal tank as the core processing unit, integrating cyclone separation, gravity settling, baffle sand capture, and two-stage mist capture into one unit. It can simultaneously complete the efficient separation of solid, liquid, and gas phases within the same tank, effectively eliminating the safety hazard of natural gas accumulation in atmospheric pressure storage tanks and causing explosions. Crucially, the tank is equipped with a cyclone separator and a bottom flushing water supply pipe. This allows for continuous or timed discharge of fracturing sand settled at the bottom of the tank using an external pressurized water flow, without system shutdown or pressurization. This avoids large amounts of sand particles accumulating and occupying effective separation space, eroding and wearing internal tank components and mist capture device parts, ensuring continuous and stable gas-liquid separation efficiency, and significantly extending the equipment's continuous operation cycle and service life. This online sand removal mechanism overcomes the shortcomings of traditional units that require shutdown for sand removal, ensuring the continuity and reliability of the entire scavenging operation.

[0020] 3. Dual-path adaptive processing with strong adaptability to various operating conditions. This invention sets up two independent processing paths for high and low gas content, supplemented by a high-pressure switching valve group for flexible switching: the high gas content path uses a desanding and degassing tank as the core for deep gas-liquid-solid separation. Natural gas can enter a natural gas collection device for grid connection and external transmission or enter a combustion storage tank for on-site combustion, depending on the gas volume and pressure, adapting to gas production fluctuations under different well conditions; the low gas content path directly uses a simple desanding and degassing tool for rapid rotary centrifugal separation, resulting in a short process, low energy consumption, and high processing efficiency. This dual-path design allows the system to flexibly adjust the processing mode according to the real-time gas content of the returned liquid, avoiding the problem of insufficient processing capacity of simple equipment under high gas content conditions, and avoiding the energy waste caused by using large equipment under low gas content conditions. The applicable scope covers diverse operating conditions with different gas-oil ratios and different scavenging stages.

[0021] 4. Modular skid-mounted design for rapid and flexible on-site deployment. The core processing units of this invention all adopt a skid-mounted, modular design. Each functional module can be prefabricated and debugged in the factory and then shipped to the site as a whole. Pipeline connections are completed via quick-connect fittings, achieving "immediate installation and immediate use." Combined with the integrated pressure testing water pipeline system of this invention, the entire desanding and degassing tank can be pressure tested on-site without disassembling any internal components, significantly shortening the construction preparation cycle. After single-well plugging is completed, each skid can be quickly disassembled and transported to the next well site, perfectly matching the "short, flat, and fast" operation characteristics of shale oil plugging, significantly improving plugging efficiency and reducing the construction cycle.

[0022] 5. Rotational deceleration and splash prevention improve the on-site working environment. This invention features a simple sand and gas removal tool at the inlet of the primary sewage tank. This tool employs a three-layer casing structure: a central pipe, an intermediate pipe, and an outer pipe. Returning liquid flows into the annular space through the slotted outlet of the central pipe, and then is ejected at high speed through the evenly distributed oblique outlets on the circumference of the intermediate pipe. This generates a rotating centrifugal force field to enhance gas-liquid separation. Simultaneously, the fluid reaction force drives the intermediate pipe to rotate in the opposite direction, converting the fluid's kinetic energy into rotational mechanical energy, achieving energy dissipation and deceleration buffering. This allows liquid and sand to flow smoothly out from the slotted outlet at the bottom of the outer pipe, effectively preventing splashing caused by high-pressure, high-velocity fluid directly impacting the tank wall. Combined with the elevated installation of the primary sewage tank to lower the liquid level and facilitate stable overflow, this eliminates the on-site safety and environmental risks caused by droplet splashing and instantaneous gas release at the source, providing a cleaner and safer operating environment for workers.

[0023] 6. Source-level degassing reduces downstream processing load. During the plugging operation, this invention dynamically adjusts the wellhead nozzle opening or pump speed by real-time monitoring of the coiled tubing injection volume and the return fluid flow rate from the wellhead casing gate valve. This ensures the injection volume is equal to or slightly greater than the return fluid discharge rate (0–50 L / min), effectively maintaining a positive pressure differential at the bottom of the well and suppressing the passive intrusion of formation fluids, especially natural gas. This process control strategy significantly reduces the natural gas content in the return fluid at the source, keeping it in a "low gas content" state under most operating conditions. This not only ensures that the simple desanding and degassing tools can meet the processing needs of most operating conditions but also significantly reduces the operating load on the desanding and degassing tank and gas treatment unit, lowering the overall system energy consumption and improving the overall operational safety and economy.

[0024] 7. Online self-cleaning eliminates the need to open the tank, reducing maintenance costs. This invention features multiple rotating tank cleaners installed in the upper part of the desanding and degassing tank. After operation, no personnel need to enter the tank. Simply switch the gate valve to introduce clean water to drive the rotating nozzles for 360° cleaning of oil stains and residual sand particles adhering to the tank wall. The cleaning wastewater is discharged through the tank's drain valve, achieving rapid and thorough cleaning of the tank interior without opening the tank or entering personnel. This avoids the safety risks of confined space operations and high cleaning costs associated with traditional manual tank cleaning, significantly reducing the difficulty and cycle of equipment maintenance. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. The drawings are provided for reference and illustration only and are not intended to limit the present invention. Wherein: Figure 1 This is a process flow diagram of the high oil-gas ratio shale oil well cleaning, degassing, desanding, and recycling system of the present invention. Figure 2 This is an enlarged view of the sand and gas removal tank in this invention; Figure 3 This is a front view of the simple sand and gas removal tool of the present invention; Figure 4 This is an enlarged cross-sectional view of the simple sand and gas removal tool of the present invention.

[0026] Explanation of reference numerals in the attached figures: 1. High-pressure well; 2. High-pressure valve assembly; 3. Cuttings collection manifold; 4. Oil nozzle manifold; 5. Sand and gas removal tank; 5a. Primary mist eliminator; 5b. Baffle; 5c. Secondary mist eliminator; 5d. Rotary jet sand remover; 5e. Rotary tank cleaner; 6. Natural gas collection equipment; 7. Combustion storage tanks; 8. Simple sand and gas removal tools; 8a. Central pipe; 8a1. Central pipe slot outlet; 8a2. Blind plug; 8b. Intermediate pipe; 8b1. Angled outlet; 8c. Outer pipe; 8c1. Outer pipe slot vent; 8c2. Outer pipe slot drain. 9. Exhaust fan; 10. Dosing booster pump skid; 11. Continuous tubing; S1. High-pressure switching valve one; S2. High-pressure switching valve two; F1. First flow meter; F2. Second flow meter; F3. Third flow meter; LT1. Radar level gauge; LT2. Magnetic plate level gauge; V1. Gate Valve 1; V2. Gate Valve 2; V3. Gate Valve 3; V4. Gate Valve 4; V5. Discharge Control Valve; V6. Exhaust Regulating Valve Assembly; V7. Connecting Valve; V8. Safety Valve; V9. Tank Drain Valve; G1. High-gas-content flushing return pipe; G2. Gas pipeline; G3. Bottom sand flushing water supply pipe; G4. Main sewage pipe; G5. Test pressure water pipe; G6. Upper flushing pipe; T1. Primary sewage tank; T1a. Base; T2. Secondary sewage tank; T3. Third sewage tank; T4. Final sewage tank; T5. Tanker truck. Detailed Implementation

[0027] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, the invention is further described below with reference to specific illustrations. Obviously, the described embodiments are merely some embodiments of this invention, not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] Unless otherwise defined, 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. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention.

[0029] I. Overall System Composition like Figures 1 to 4 As shown, the high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system of the present invention mainly includes: a high-pressure well 1, a high-pressure valve group 2, a cuttings collection manifold 3, an oil nozzle manifold 4, a sand and gas removal tank 5, a simple sand and gas removal tool 8, a first-stage sludge tank T1, a second-stage sludge tank T2, a third-stage sludge tank T3, a final-stage sludge tank T4, and a chemical dosing booster pump skid 10. Among these, the sand and gas removal tank 5 is the core processing unit of the present invention, the simple sand and gas removal tool 8 is an auxiliary processing unit, and the first-stage sludge tank T1 to the final-stage sludge tank T4 constitute a four-stage series sedimentation and separation system.

[0030] The outlet of the casing gate valve at the wellhead of high-pressure well 1 is connected to the inlet of the cuttings collection manifold 3 via high-pressure valve group 2. The fluid outlet of the cuttings collection manifold 3 is connected to the inlet of the nozzle manifold 4. The outlet of the nozzle manifold 4 is connected to two pipelines, and the inlets of the two pipelines are respectively equipped with high-pressure switching valve one S1 and high-pressure switching valve two S2.

[0031] II. Core Processing Unit – Sand and Degassing Tank and its Auxiliary Systems 2.1 High-Gas-Containing-Length Inlet Liquid Feed and Gas-Liquid Pre-Separation The outlet of the high-pressure switching valve S1 is connected to the inlet of the high gas content scavenging plug return liquid pipe G1 via the first flow meter F1. The outlet of the high gas content scavenging plug return liquid pipe G1 is equipped with a gate valve V1. The outlet of the gate valve V1 is connected to the inlets of the gate valves V3 and V4 respectively. The outlet of the gate valve V4 is connected to the tank inlet of the sand and gas removal tank 5.

[0032] The desanding and degassing tank 5 has a primary mist eliminator 5a at the top of its inlet. The outlet of gate valve V4 is connected to the side wall inlet of the primary mist eliminator 5a. The primary mist eliminator 5a is a cyclone gas-liquid separation structure used for preliminary gas-liquid separation of the liquid returning from the continuous tubing scavenging. After the returning liquid enters the primary mist eliminator 5a tangentially, it generates a cyclone. Under the action of centrifugal force, the denser droplets and solid particles are thrown against the tank wall and flow downwards into the tank, while the less dense gas rises from the top, achieving pre-separation of the gas, liquid, and solid phases.

[0033] 2.2 In-tank settling and baffle sand-catching structure Multiple upward-extending baffles 5b are arranged along the length of the tank at the bottom, dividing the bottom of the tank into multiple settling chambers. Preferably, at least three settling chambers are provided to guide the liquid flow and promote the settling of sand particles. The upper end of each baffle 5b is inclined towards the liquid inlet, with an inclination angle preferably between 15° and 30°. This inclined structure has a dual function: firstly, it can block fine sand particles that float with the liquid flow, causing them to fall back to the bottom of the settling chamber; secondly, it facilitates the smooth downward flow of the overflow liquid phase along the inclined surface, avoiding noise and secondary entrainment caused by the liquid flow falling.

[0034] A secondary mist eliminator 5c is installed at the top of the tank outlet end to further separate the gas and liquid in the exhaust gas from the primary mist eliminator 5a and the gas escaping from inside the tank, ensuring exhaust quality. The secondary mist eliminator 5c can adopt a wire mesh or blade type demisting structure, with a wire mesh type mist eliminator preferred to balance high collection efficiency and low resistance drop.

[0035] 2.3 Liquid Level Monitoring and Automatic Control A radar level gauge LT1 is installed on the top of the tank for remote continuous monitoring of the liquid level inside the tank; a magnetic level gauge LT2 is installed on the side wall of the tank for on-site observation of the liquid level. The two complement each other to ensure the reliability of the liquid level monitoring. A liquid outlet is located at the lower part of the tank's outlet end, and a liquid outlet control valve V5 is installed at the outlet to control the liquid flow rate. The liquid outlet control valve V5 is linked to the signal of the radar level gauge LT1 to form an automatic liquid level control loop, ensuring that the liquid level inside the tank is always maintained within the set range.

[0036] Preferably, the liquid level control logic is as follows: a lower liquid level limit a and an upper liquid level limit b are set, where a < b; when the liquid level in the tank reaches the upper limit b, the liquid outlet control valve V5 is automatically opened to drain liquid; when the liquid level drops to the lower limit a, the liquid outlet control valve V5 is automatically closed, so that the liquid level in the tank is stably maintained between a and b during operation. If the liquid level exceeds b+300mm or drops below a-100mm, the system will trigger an audible and visual alarm to remind the operator to check the equipment status. This liquid level control strategy ensures that there is sufficient gas space in the tank for gas-liquid separation, and also prevents gas from entraining liquid caused by excessively high liquid level or flow interruption of drainage caused by excessively low liquid level.

[0037] 2.4 On-line sand removal system Each settling chamber at the bottom of the inner cavity of the tank is respectively provided with a rotary-jet sand remover 5d, and the water inlet of each rotary-jet sand remover 5d is connected to an external bottom sand flushing water supply pipe G3 and a booster water pump. The rotary-jet sand remover 5d can adopt a jet-type cyclone structure well known in the art. After booster water enters from the tangential inlet, it forms a high-speed rotating jet, which disturbs the accumulated sand at the bottom of the settling chamber and brings it into the sand collecting chamber.

[0038] The sand outlet of each rotary-jet sand remover 5d is connected to the tank drain valve V9 outside the tank through a blow-off pipe, and the outlet of each tank drain valve V9 is connected to the main blow-off pipe G4. The outlet of each settling chamber at the tank bottom is also provided with a tank drain valve V9 and the outlet thereof is connected to the main blow-off pipe G4, which is used for continuously or periodically discharging the sand-water mixture after cleaning. In actual operation, the blowdown strategy can be flexibly formulated: the most sand deposits in the settling chamber closest to the inlet end of the tank, which can be set for continuous blowdown; the intermediate settling chamber can be set for intermittent blowdown (for example, discharging once every 2 to 4 hours); the settling chamber closest to the outlet end of the tank has the least sand deposits, which can be set for timed blowdown (for example, discharging once every 8 hours), so as to save water while ensuring the sand removal effect.

[0039] The outlet of the main blow-off pipe G4 is connected to multi-stage series-connected blow-off tanks, which are used for receiving and further settling the sand-water mixture discharged from the tank drain valve V9 and the main blow-off pipe G4.

[0040] 2.5 Degassing system The gas outlet at the top of the first-stage mist catcher 5a is connected to the sidewall inlet of the second-stage mist catcher 5c through the gas pipeline G2, and the second-stage mist catcher 5c performs further liquid removal and purification on the gas after the first-stage mist capture. The outlet of the second-stage mist catcher 5c is divided into three paths: First path: connected to the natural gas collection device 6 through the gas outlet at the top of the second-stage mist catcher 5c via the exhaust regulating valve group V6. This path is suitable for working conditions with large gas volume, and the treated natural gas can enter the gathering and transportation pipeline network for recovery and utilization. The exhaust regulating valve group V6 preferably comprises an electric regulating valve and a stop valve, which can automatically adjust the opening according to the system pressure and gas volume, and maintain the micro-positive pressure (preferably 5 to 20kPa) operation in the tank.

[0041] The second route: The gas outlet at the top of the secondary mist eliminator 5c is connected to the inlet of the combustion storage tank 7 via the connecting valve V7. This route is suitable for applications with smaller gas volumes or where on-site combustion is required.

[0042] The third route connects to the combustion storage tank 7 via the side wall outlet of the secondary mist eliminator 5c. A safety valve V8 is installed in this connection line. The set pressure of the safety valve V8 is preferably 1.05 to 1.1 times the tank's design pressure, used for system overpressure protection. When the system pressure exceeds the set value, the safety valve V8 automatically opens to release pressure to the combustion storage tank 7, ensuring the safety of the tank and pipeline.

[0043] 2.6 Tank Self-Cleaning and Pressure Testing System The outlet of gate valve V3 is connected to the inlet of the upper flushing pipe G6. A rotary tank cleaner 5e is installed in the upper part of the tank's inner cavity. Multiple rotary tank cleaners 5e are arranged along the tank's axial direction, and the inlet of each rotary tank cleaner 5e is connected to the outlet of the upper flushing pipe G6. The rotary tank cleaner 5e preferably adopts a self-rotating three-dimensional nozzle, which can automatically rotate under the pressure of the flushing water, achieving 360° cleaning of the inner wall of the sand and gas removal tank 5 without dead angles.

[0044] The outlet of the test water pipe G5 is connected to the inlet of gate valve 2 V2, and the outlet of gate valve 2 V2 is connected to the outlet of gate valve 1 V1. This test pipeline setup allows for overall water or air pressure testing of the tank without disassembling any internal components of the desanding and degassing tank 5, greatly simplifying on-site pressure testing operations.

[0045] III. Auxiliary Processing Unit – Simple Sand and Gas Removal Tools like Figure 3 and Figure 4 As shown, a simple sand and gas removal tool 8 is installed at the inlet of the primary sewage tank T1. This tool is horizontally set and mainly consists of a three-layer sleeve structure consisting of a coaxial central pipe 8a, an intermediate pipe 8b, and an outer pipe 8c.

[0046] One end of the central tube 8a is an open inlet end, and the other end is sealed by a blind plug 8a2. The bottom of the central tube 8a is provided with a central tube slot outlet 8a1 along the length direction for liquid to flow out. The width of the central tube slot outlet 8a1 is preferably 5 to 15 mm, and its length extends to most of the total length of the central tube 8a to ensure that the fluid is evenly distributed along the axial direction.

[0047] The intermediate tube 8b is fitted around the outer circumference of the central tube 8a. Both ends of the intermediate tube 8b are equipped with closed end plates. The inner circumference of the end plates is supported on the outer wall of the central tube 8a by ball bearings or other bearings, allowing the intermediate tube 8b to rotate freely around the central tube 8a. Multiple oblique outlets 8b1 are centrally symmetrically arranged on the circumference of the intermediate tube 8b, and these outlets 8b1 are evenly distributed along both the circumferential and length directions of the intermediate tube 8b. The axes of the oblique outlets 8b1 form an angle of 20° to 45° with the radial direction of the intermediate tube 8b, generating a tangential jetting force to drive the intermediate tube 8b to rotate.

[0048] The outer tube 8c is fitted around the outer periphery of the intermediate tube 8b. Both ends of the outer tube 8c extend beyond the ends of the intermediate tube 8b, and both ends of the outer tube 8c are equipped with closed end plates. The inner periphery of the end plates is welded to the outer wall of the central tube 8a, thus fixing the outer tube 8c in place. The top of the outer tube 8c has a slit exhaust port 8c1 along its length for gas phase outflow. An exhaust fan 9 is located at the outer tube inlet of the slit exhaust port 8c1, and the outlet of the exhaust fan 9 is connected to the combustion storage tank 7. The bottom of the outer tube 8c has a slit drain port 8c2 along its length for liquid outflow.

[0049] The returned liquid enters from the inlet end of the central pipe 8a, flows into the annular space between the intermediate pipe 8b and the central pipe 8a from the central pipe slot outlet 8a1, and then sprays out from each inclined outlet 8b1, entering the annular space between the intermediate pipe 8b and the outer pipe 8c. The fluid generates tangential velocity when sprayed from the inclined outlet 8b1, forming a rotating flow field within the annular space, enhancing gas-liquid centrifugal separation; simultaneously, the reaction force of the sprayed fluid drives the intermediate pipe 8b to rotate in the opposite direction, further promoting the gas-liquid separation effect. Under the action of the rotating centrifugal force, the gas contained in the returned liquid rises to the top of the outer pipe 8c and is drawn to the combustion storage tank 7 by the exhaust fan 9; the liquid and sand fall to the bottom of the outer pipe 8c and flow smoothly into the primary sewage tank T1 from the outer pipe slot outlet 8c2, avoiding high-speed fluid directly impacting the liquid surface inside the tank, causing splashing and instantaneous gas release.

[0050] IV. Four-stage sewage settling system The primary sewage tank T1, the secondary sewage tank T2, the tertiary sewage tank T3, and the final sewage tank T4 are connected in series to form a four-stage sedimentation separation system. Each sewage tank is a sealed storage tank under normal pressure, with an exhaust port on the top and baffles and overflow weirs inside.

[0051] The primary sewage tank T1 receives a sand-water mixture (high gas content path) from the sand and degassing tank 5 or a liquid-solid mixture (low gas content path) from the simple sand and degassing tool 8. Preliminary three-phase separation is carried out inside the tank: the separated gas is led out from the top exhaust port and supplied to the combustion storage tank 7 as fuel; the sand particles settle downwards to the bottom of the tank; and the liquid phase overflows from the upper side wall into the second sewage tank T2.

[0052] To lower the liquid level in the primary sewage tank T1 and facilitate a smooth overflow to the secondary sewage tank T2, the primary sewage tank T1 is placed on a base T1a with a height not less than half its own height. Preferably, the height of the base T1a is 0.5 to 0.8 times the height of the primary sewage tank T1 to ensure that the overflow liquid level is higher than the inlet height of the secondary sewage tank T2, achieving pump-free gravity flow.

[0053] The second wastewater tank T2 is mainly used for further sedimentation. After the liquid phase overflowing from the primary wastewater tank T1 enters the second wastewater tank T2, the residual fine sand continues to settle, and the liquid phase overflows from the top into the third wastewater tank T3.

[0054] The third wastewater tank T3 is mainly used for gravity sedimentation separation of water and oil. In the third wastewater tank T3, the aqueous phase, due to its higher density, is located at the bottom, while the floating oil, due to its lower density, is located at the top, forming a clear water-oil interface. The floating oil overflowing from the third wastewater tank T3 is collected in the final wastewater tank T4 and then extracted and recovered by the oil tanker T5; the aqueous phase accumulating in the lower part of the third wastewater tank T3 is extracted and pumped out for use in circulating liquid preparation.

[0055] The final sewage tank T4 serves as the final oil collection tank, where floating oil from the third sewage tank T3 is allowed to settle and stored, and is periodically transported and recycled by tanker truck T5.

[0056] V. System Workflow 5.1 Upstream process source control (entire operation process) During the scavenging operation, the injection volume at the inlet (coiled tubing 11) and the flow rate of the returned fluid at the wellhead casing gate outlet are monitored. The wellhead nozzle opening or the coiled tubing injection pump speed is dynamically adjusted to ensure that the injection volume of high-pressure well 1 is equal to or slightly greater than the returned fluid discharge volume, with the difference controlled between 0 and 50 L / min. This process control strategy effectively maintains a positive pressure differential at the bottom of the well, suppressing the passive intrusion of formation fluids, especially natural gas, thereby significantly reducing the natural gas content in the returned fluid from the source, alleviating the burden on downstream gas processing units, and improving the safety and economy of system operation. Simultaneously, this strategy ensures that the returned fluid is in a "low gas content" state under most operating conditions, allowing it to directly follow a low gas content path and reducing processing energy consumption.

[0057] 5.2 Route Selection The fluid returned from the coiled tubing plugging process flows out from the wellhead casing valve of high-pressure well 1, and then flows out through high-pressure valve group 2, cuttings catcher manifold 3, and nozzle manifold 4. The operator selects either a high-gas-content treatment path or a low-gas-content treatment path based on the real-time gas content of the returned fluid. High gas content path: Open high pressure switching valve S1 and close high pressure switching valve S2. The fluid enters the desanding and degassing tank 5 through the first flow meter F1, gate valve V1 and gate valve V4 for deep three-phase separation.

[0058] Low gas content path: Close high pressure switching valve one S1, open high pressure switching valve two S2, and the fluid enters the simple sand and gas removal tool 8 directly through the second flow meter F2 for rapid rotational centrifugal separation.

[0059] 5.3 High Gas Content Pathway – Processing Liquid Flow The liquid returning from the blockage removal process enters the primary mist eliminator 5a via gate valve V1 and gate valve V4, where initial gas-liquid separation is achieved through swirling flow. Liquid and solid particles flow downwards into the tank, passing through baffles 5b in stages. Sand particles settle to the bottom of each settling chamber under gravity. Liquid overflows between the baffles. When the overall liquid level in the tank reaches the upper limit b set by the radar level gauge LT1, the discharge control valve V5 automatically opens to drain the liquid; when the liquid level drops to the lower limit a, the discharge control valve V5 automatically closes, thus ensuring that the liquid level in the tank remains stable between a and b. If the liquid level exceeds the safe range (exceeding b + 300 mm or falling below a - 100 mm), the system triggers an audible and visual alarm.

[0060] 5.4 High Gas Content Pathway – Gas Flow Most of the gas is separated in the primary mist eliminator 5a and then enters the secondary mist eliminator 5c for further purification via gas pipeline G2. A small amount of gas that enters the tank with the liquid rises to the space above the liquid level and then enters the secondary mist eliminator 5c through the top space of the tank. The purified gas, depending on the pressure and flow rate, is controlled by the exhaust regulating valve group V6 to either enter the natural gas collection device 6 (suitable for large gas flow conditions) or enter the combustion storage tank 7 through the connecting valve V7 (suitable for small gas flow or emergency conditions). The safety valve V8 automatically opens to release pressure when the system pressure exceeds the set value, ensuring operational safety.

[0061] 5.5 High Gas Content Pathway – Solids Treatment (Online Continuous Sand Removal) When it is necessary to remove the fracturing sand deposited at the bottom of the desanding and degassing tank 5, the external booster water pump is started to draw the separated aqueous phase from the lower middle part of the third drain tank T3 as the desanding water source and pressurize it. The water then enters each jet desander 5d through the bottom flushing water supply pipe G3. The pressurized water is ejected tangentially, forming a local rotating flow field at the bottom of each settling chamber in the tank. This disturbs the settled sand particles and carries them into the vortex center. Under the action of the pressure difference between the inside and outside of the tank, the sand-water mixture is discharged through the tank drain valve V9 and the main drain pipe G4, and then enters the subsequent drain tanks in sequence to achieve further solid-liquid separation. This process can be carried out under normal operating conditions of the desanding and degassing tank 5, achieving continuous sand removal without interrupting production and effectively ensuring the long-term stability of the effective separation volume in the tank.

[0062] 5.6 Low Gas Content Pathway When the gas content of the returned liquid is very low due to upstream process control, the high-pressure switching valve S1 is closed and the high-pressure switching valve S2 is opened. The fluid then enters the simple sand and gas removal tool 8 directly through the second flow meter F2. Inside the tool, a small amount of gas is separated from the fluid through the three-layer sleeve structure and the centrifugal action. The gas is led to the combustion storage tank 7 by the exhaust fan 9 as fuel. The liquid and sand flow gently into the first-stage sewage tank T1 from the bottom slotted drain port of the outer pipe, and then enter the second sewage tank T2, the third sewage tank T3, and the final sewage tank T4 for further separation and recovery, as described above.

[0063] 5.7 Liquid Recycling The separated aqueous phase drawn from the lower part of the third sewage tank T3 is metered by the third flow meter F3 and then enters the chemical dosing booster pump skid 10. Utilizing the online liquid preparation function of the chemical dosing booster pump skid 10, the required drag-reducing agent (and other agents such as drainage aids and clay stabilizers can also be added as needed) is added according to the process formula. After the drag-reducing agent and aqueous phase are evenly mixed in the skid, they are injected under high pressure into the coiled tubing 11 and returned to the tubing gate inlet of the high-pressure well 1 for use in downhole plugging operations, forming a complete closed-loop circulation circuit.

[0064] VI. Auxiliary Operation Procedures 6.1 Pressure Testing Procedure After the sand and gas removal tank 5 is installed or during regular maintenance, a pressure test is required to verify the tank's sealing performance and pressure-bearing capacity. The specific procedure is as follows: Close gate valves V1, V3, and all external valves on the tank (including drain valves V9 and safety valves V8). Open gate valves V2 and V4. Inject water or gas into the tank through the test water pipe G5, slowly increasing the pressure to the design test pressure. After maintaining the pressure for the specified time, check all connections on the tank for leaks and abnormal deformation. After the pressure test is completed, release the pressure and drain the liquid through drain valve V9. The entire pressure test process does not require disassembling any internal components of the tank, greatly simplifying the on-site pressure testing operation.

[0065] 6.2 Tank Cleaning Process After the single-well scavenging operation is completed, the inside of the desanding and degassing tank 5 needs to be cleaned. The specific operation is as follows: close gate valve 1 V1 and gate valve 4 V4, open gate valve 2 V2 and gate valve 3 V3, introduce clean water into the upper flushing pipe G6 through the pressure test water pipe G5, and then drive each rotating tank cleaner 5e to rotate automatically, performing 360° high-pressure water jet cleaning on the oil stains and residual sand particles attached to the inner wall of the tank. The cleaned dirt is discharged through the tank drain valve V9, realizing rapid cleaning of the inside of the tank, avoiding the safety risks of confined space operation and high cleaning costs caused by manual cleaning by opening the tank.

[0066] VII. Other variations of the implementation method Those skilled in the art should understand that the above description is merely a preferred embodiment of the present invention and does not limit the scope of the patent. In practical applications, appropriate modifications can be made to the following aspects according to specific working conditions and site conditions: Number of sewage tank stages: Four-stage series sewage tanks are the preferred solution of the present invention. In practical applications, the number of stages can be adjusted to three or five stages according to the processing capacity and site area. All of these are equivalent substitutions of the present invention. Number of settling chambers: The number of baffles and settling chambers in the desanding and degassing tank 5 can be appropriately increased or decreased according to the tank length and treatment requirements. At least three settling chambers are required to achieve the baffle settling effect of this invention. Number of rotary tank cleaners: The number and spacing of the rotary tank cleaners 5e can be adjusted according to the diameter and length of the tank to ensure cleaning coverage. Types of chemicals added: The chemicals added online by the chemical dosing booster pump skid 10 are not limited to drag reducers. They can also include commonly used fracturing fluid additives such as drainage aids, demulsifiers, bactericides, and clay stabilizers, depending on geological conditions and fluid preparation requirements. Natural gas destination: The natural gas collection device 6 can be a mobile CNG / LNG recovery skid or directly connected to a nearby gas collection pipeline network, and the combustion storage tank 7 can be an atmospheric pressure buffer tank connected to a ground burner or a flare.

[0067] Any equivalent structural or procedural transformations made based on the description and drawings of this invention, or any direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this invention.

Claims

1. A recycling and reuse system for high-oil-gas ratio shale oil wells, characterized in that: include: Wellhead fluid treatment unit, dual-path switching valve group, desanding and degassing tank (5); The wellhead fluid treatment unit includes a high-pressure well (1), a high-pressure valve group (2), a cuttings collection manifold (3), and an oil nozzle manifold (4) connected in sequence. The dual-path switching valve group includes a high-pressure switching valve one (S1) and a high-pressure switching valve two (S2). The outlet of the oil nozzle manifold (4) is connected to the high gas content treatment path and the low gas content treatment path respectively through the dual-path switching valve group. In the high gas content treatment path, the high pressure switching valve (S1) is connected to the sand and gas removal tank (5) via a gate valve. The outlet of the sand and gas removal tank (5) is connected to the sewage settling system. The exhaust port of the sand and gas removal tank (5) is connected to the natural gas collection device (6) and / or the combustion storage tank (7). In the low-gas treatment path, the high-pressure switching valve (S2) is connected to the simple sand and gas removal tool (8), the gas outlet of the simple sand and gas removal tool (8) is connected to the combustion storage tank (7), and the liquid-solid outlet of the simple sand and gas removal tool (8) is connected to the sewage settling system.

2. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that: The sewage settling system includes a primary sewage tank (T1), a second sewage tank (T2), a third sewage tank (T3), and a final sewage tank (T4) connected in series.

3. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 2, characterized in that: It also includes a recycling unit, which includes a water pump, a chemical booster pump skid (10) and a coiled tubing (11). The outlet of the lower part of the third sewage tank (T3) is connected to the inlet of the chemical booster pump skid (10) via the water pump. The outlet of the chemical booster pump skid (10) is connected to the coiled tubing (11). The coiled tubing (11) returns to the high-pressure well (1), forming a closed-loop circulation circuit.

4. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The sand and gas removal tank (5) is equipped with a primary mist eliminator (5a) at the top of the tank inlet and a secondary mist eliminator (5c) at the top of the tank outlet.

5. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The bottom of the desanding and degassing tank (5) is provided with multiple upward-extending baffles (5b) along the length direction. The upper end of each baffle (5b) is inclined towards the liquid inlet end, with an inclination angle of 15° to 30°.

6. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The top of the desanding and degassing tank (5) is equipped with a radar level gauge (LT1), and a liquid discharge control valve (V5) is installed at the liquid outlet of the desanding and degassing tank (5). The liquid discharge control valve (V5) is linked with the radar level gauge (LT1) to form an automatic liquid level control loop.

7. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The simple sand and gas removal tool (8) includes a coaxial central tube (8a), an intermediate tube (8b) rotatably fitted around the outer periphery of the central tube (8a), and an outer tube (8c) fixedly fitted around the outer periphery of the intermediate tube (8b). The central tube (8a) has a central tube slot outlet (8a1) at the bottom, the intermediate tube (8b) has multiple oblique outlets (8b1) in the circumferential direction, the outer tube (8c) has an exhaust port (8c1) at the top and a drain port (8c2) at the bottom.

8. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 7, characterized in that, The axis of the inclined outlet (8b1) forms an angle of 20° to 45° with the radial direction of the intermediate tube (8b).

9. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 2, characterized in that, The primary sewage tank (T1) is placed on a base (T1a), and the height of the base (T1a) is not less than half the height of the primary sewage tank (T1).

10. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The bottom of the desanding and degassing tank (5) is divided into multiple settling chambers by the partition (5b). Each settling chamber is equipped with a rotary jet desander (5d). The inlet of the rotary jet desander (5d) is connected to an external water source through the bottom sand flushing water supply pipe (G3). The sand outlet of the rotary jet desander (5d) and the outlet of each settling chamber at the bottom of the tank are connected to the main drain pipe (G4) through the tank drain valve (V9).

11. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The upper part of the inner cavity of the sand and gas removal tank (5) is provided with a rotary tank cleaner (5e), ​​and the water inlet of the rotary tank cleaner (5e) is connected to the water source through the upper flushing pipe (G6) and the gate valve (V3).

12. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, It also includes a test pressure water pipe (G5), which is connected to the desanding and degassing tank (5) via gate valve two (V2).

13. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 4, characterized in that, The outlet of the secondary mist eliminator (5c) is divided into three paths: the first path is connected to the natural gas collection device (6) via the exhaust regulating valve group (V6), the second path is connected to the combustion storage tank (7) via the connecting valve (V7), and the third path is connected to the combustion storage tank (7) via the safety valve (V8) through the side wall outlet of the secondary mist eliminator (5c).

14. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, During the scavenging operation, the injection volume of the high-pressure well (1) is equal to or slightly greater than the return fluid discharge volume, and the difference is controlled between 0 and 50 L / min.

15. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 4, characterized in that, The side wall of the sand and gas removal tank (5) is equipped with a magnetic plate level gauge (LT2), and the secondary mist eliminator (5c) is a wire mesh mist eliminator.

16. The high oil-to-gas ratio shale oil well cleaning, degassing, and sand removal recycling system according to claim 1, characterized in that, The bottom of the desanding and degassing tank (5) is divided into multiple settling chambers by the partition (5b), and there are at least three settling chambers.

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