Downhole cavitation equipment and downhole cavitation jet flow yield and injection increasing technology

Abstract

The invention discloses underground cavitation equipment and an underground cavitation jet flow yield increasing and injection increasing process, and particularly relates to the technical field of oil exploitation blockage removing and yield increasing. The underground cavitation equipment and the underground cavitation jet flow yield increasing and injection increasing process comprise the following steps that preparation before construction is conducted, equipment is transported to a site, a construction point position is determined, and a horizon table is filled in; preparing a shaft, deepening a pipe column sand exploring surface, pulling out an original pipe column, and putting an oil pipe with a scraper to wash a well; configuring a construction pipe column, assembling the pipe column and cavitation equipment, and checking the depth; performing pressure test on a ground pipeline, and completing connection cleaning and segmented pressure test; performing point-by-point treatment from bottom to top; the tool is pulled out to complete well completion and oil well delivery. According to the underground cavitation equipment and the underground cavitation jet flow yield-increasing and injection-increasing technology, through the complete and systematic underground cavitation jet flow yield-increasing and injection-increasing technology, the whole process from preparation before construction to well completion delivery is controlled, efficient and safe yield-increasing and injection-increasing transformation of an oil well is achieved, the production capacity of the oil well is effectively improved, and the production efficiency of the oil well is improved. The service life of an oil well is prolonged and powerful support is provided for efficient development of oil fields.

Description

Technical Field

[0001] This invention relates to the field of oil extraction unblocking and production enhancement technology, and particularly to a downhole cavitation equipment and a downhole cavitation jet production enhancement and injection process. Background Technology

[0002] In the field of oil extraction, as the time of oil well operation increases, the formation energy gradually decreases, and the production and injection volume of oil wells often face the problem of reduction. This seriously affects the overall extraction efficiency and economic benefits of oil fields. In order to maintain the stable production of oil wells, production enhancement and injection technology has become a key link in the oil extraction process. Traditional production enhancement and injection methods are difficult to meet the increasingly complex reservoir conditions.

[0003] Currently, conventional production enhancement and injection technologies mainly include acidizing and fracturing. Acidizing involves injecting acidic fluids into the formation to dissolve blockages and rock minerals, thereby expanding porosity and fractures and increasing formation permeability. Fracturing uses high pressure to inject fluids into the formation, creating fractures and increasing oil flow channels. In addition, there are some physical enhancement methods, such as acoustic enhancement, which improves crude oil fluidity by emitting sound waves into the formation. However, existing production enhancement and injection technologies still have the following drawbacks in use:

[0004] During acidizing, the reaction between the acid and the formation rock may produce precipitation. This precipitation can re-clog formation pores, reducing the acidizing effect. At the same time, the acid is highly corrosive to downhole equipment, which can shorten the equipment's service life and increase mining costs. Moreover, the acidizing technology has a limited range of application and is not effective in treating deep formations.

[0005] Fracturing requires high pressure, which places stringent demands on equipment and formation conditions. Improper pressure control can lead to excessive formation fracturing and cause formation collapse. In addition, the morphology and extension direction of the fractures generated by fracturing are difficult to control precisely, which may prevent the effective connection of oil flow channels in the reservoir and affect the production and injection effects. At the same time, fracturing is a complex and costly process that may also cause some environmental pollution.

[0006] Sound waves attenuate rapidly during propagation and have a limited range, making them difficult to effectively treat deep strata. Moreover, the effectiveness of sound wave enhancement is greatly affected by the lithology of the strata, and the enhancement effect is not significant for some complex strata. In addition, the stability and reliability of existing sound wave enhancement equipment need to be improved, and the operation process is also relatively complicated. Summary of the Invention

[0007] The main objective of this invention is to provide a downhole cavitation device and a downhole cavitation jet enhancement and injection process, which can effectively solve the problems of poor performance, side effects, and high costs of existing enhancement and injection processes.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] A downhole cavitation device includes a high-pressure pump truck, an instrument truck, and well control equipment installed at the wellhead. The output end of the high-pressure pump truck is connected to the well control equipment via a high-pressure pipeline. A sand-mixing truck is installed on the input side of the high-pressure pump truck, and a liquid tank is installed on the input side of the sand-mixing truck. The input side of the liquid tank is connected to the well control equipment. The detection probes of the instrument truck are respectively installed on the input and output sides of the sand-mixing truck and the high-pressure pump truck. The cavitation device also includes a cavitation jet tool installed at the lower end of the well control equipment and an instrument truck installed at the construction site.

[0010] The well control equipment includes a casing head connected to the tubing. A four-way valve, a single-gate blowout preventer, and a self-sealing device are sequentially installed on the upper end of the casing head. The four-way valve is connected to a kill line and an internal control line that are connected to the cavitation equipment, respectively. The internal control line is connected to a fluid injection line, a pressure gauge, and a blowout line through the four-way valve. The fluid injection line is connected to a fluid tank, and the kill line is connected to a high-pressure pump truck.

[0011] Preferably, the instrument vehicle is equipped with a closed-loop control system, which includes a PLC controller, a parameter acquisition module and an execution adjustment module. The system combines the positioning data of the magnetic positioning device with the PID algorithm to dynamically optimize the jet pump speed and nozzle opening parameters.

[0012] The instrument vehicle integrates a multi-sensor system, which is deployed in the downhole jet device, fluid pipeline and wellhead, to provide downhole pressure, temperature, flow rate and HS concentration data support for the closed-loop control system;

[0013] The closed-loop control system includes a safety threshold adjustment mechanism. This mechanism pre-stores multiple sets of well depth-formation corresponding threshold tables and calls the matching threshold in combination with real-time acquired data.

[0014] The process is equipped with an emergency shut-off system. When the parameters exceed the matching threshold, the system automatically cuts off the power supply to the jet pump and the fluid supply to the wellhead.

[0015] The process includes a remote emergency platform that transmits downhole parameters and equipment status data via 4G / 5G to remotely guide emergency response.

[0016] A downhole cavitation jet enhancement and injection process using the above-mentioned downhole cavitation equipment includes the following steps:

[0017] Preparations before S1 construction: Transport the workover rig, well control equipment, cavitation equipment, and instrument vehicle to the construction site; determine the location of the cavitation construction layer based on the oil well foundation data and perforation data, determine the construction point, fill in the construction layer table, and fill the liquid tank with circulating construction fluid;

[0018] S2 wellbore preparation: Deepen the original well string to harden the sand surface. After pulling out the original well string, run the tubing with a scraper to the bottom of the artificial well and flush the well for two weeks.

[0019] S3 Construction Pipeline Configuration: Assemble and configure the construction pipeline and cavitation equipment, and lower the construction pipeline to the predetermined depth; use magnetic positioning equipment to calibrate the depth of the cavitation equipment to ensure its accurate position;

[0020] S4 Ground pipeline pressure test: After connecting the ground pipeline, circulate and clean it, and complete the segmented pressure test;

[0021] S5 construction operation: Start the high-pressure pump truck and carry out cavitation treatment point by point from the bottom to the top, starting from the lowest construction point.

[0022] After the injection is completed, the pump is stopped and the pressure is released. The cavitation equipment is then lifted to the next work site using a workover rig.

[0023] S6 Construction Completed: After all construction points have been completed, downhole tools are retrieved, well completion operations are completed, and the well is handed over.

[0024] Preferably, in step S1, the circulating construction fluid undergoes closed-loop circulation via a high-pressure pump truck, liquid tank, sand mixing truck, injection pipeline, internal control pipeline, oil well, and well kill pipeline.

[0025] Preferably, in step S1, the circulating construction fluid is specifically prepared according to the formula of "formation leakage × volume coefficient + wellbore volume" and contains 0.2% (by weight) drag reducer and 0.2% (by weight) surfactant. The formation leakage is obtained based on the original production data of the oil well, and the volume coefficient is 1.1-1.5.

[0026] The drag-reducing agent is one of polyacrylamide, polyethylene oxide, or surfactant-based drag-reducing agents.

[0027] The surfactant is a nonionic surfactant of fatty alcohol polyoxyethylene ether or an anionic surfactant of sulfonate.

[0028] Preferably, in step S3, the construction pipe column fixing assembly from bottom to top consists of: cavitation jet tool, 2-3 oil pipes, and 1-2 positioning short sections;

[0029] In step S3, when calibrating the magnetic positioning equipment, the positioning short section and the tubing are fixedly combined according to the construction string to form a depth reference point. The position of the cavitation jet tool is calibrated in real time in conjunction with the wellbore magnetic signal to ensure that its vertical error with the target layer is within ±0.1m.

[0030] Preferably, the specific pressure and holding time for the segmented pressure test in step S4 are as follows: apply 30-60MPa pressure to the high-pressure pipeline and stabilize for 10-15 minutes, apply 10-20MPa pressure to the outlet pipeline and stabilize for 10-15 minutes, and the pressure drop of the pipeline during the pressure holding process is ≤0.7MPa.

[0031] Preferably, in step S5, the tubing is connected to the pump set before the cavitation jetting operation, and the well is circulated and flushed for 10 minutes at a pressure of less than 10 MPa to determine the construction pressure during the cavitation operation.

[0032] In step S5, during the cavitation spraying operation, the high-pressure pump truck is gradually increased to a displacement of 2-2.5 m³ / min, the spraying pressure is ≤50 MPa, and the single-point spraying time is 1.5-2.0 hours.

[0033] Preferably, during the construction operation in step S5, the parameters monitored in real time by the instrument vehicle are the return liquid volume, return liquid pressure, high pressure pump truck output pressure, sand mixing truck output pressure, and H2S concentration at the outlet of the liquid pipeline.

[0034] When the H2S concentration at the outlet of the liquid pipeline is ≥10ppm, an audible and visual alarm will be automatically triggered and the pump truck's discharge rate will be reduced.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1. This invention addresses the problems of extensive and inefficient traditional construction methods. It acquires precise well data through a multi-sensor system and magnetic positioning data acquisition, and dynamically optimizes jet parameters using a PID algorithm in a closed-loop control system. This enables customized construction plans for each well, improving the accuracy of work site positioning and avoiding over- or under-modification of the reservoir. Ultimately, this improves reservoir modification efficiency and well productivity, extends the stable production cycle of wells, and provides support for efficient oilfield development.

[0037] 2. This invention addresses the issues of instability and high safety risks in traditional wellbore systems by refining the original well tubing, precisely assembling the construction tubing, and conducting high-pressure testing of the surface pipelines. This improves wellbore cleanliness and tubing sealing, reducing leakage risks. Simultaneously, relying on dual sensors to monitor H2S concentration in real time, coupled with a safety threshold adjustment mechanism and an emergency shut-off system, it significantly improves the speed of risk parameter control, eliminates personnel safety risks, and ensures safety and reliability throughout the entire construction cycle.

[0038] 3. This invention addresses the problems of uncontrolled cavitation operations and difficulty in quality traceability in traditional processes by adopting a bottom-up, point-by-point cavitation treatment method, combined with a closed-loop control system to collect construction parameters in real time, ensuring no blind spots in reservoir stimulation; at the same time, by automatically storing parameters and recording standardized data, it replaces manual recording, realizes full traceability of construction quality, and can accurately judge the reservoir's liquid absorption capacity to adjust parameters, avoid construction rework, and improve construction efficiency.

[0039] 4. This invention addresses the problems of delayed emergency response and poor overall coordination in traditional processes. By linking a remote emergency platform with a closed-loop control system, it enables real-time transmission of downhole parameters and remote command transmission, shortening emergency response time. At the same time, it allows multi-sensor data, equipment status data, and emergency commands to form a closed loop, improving the accuracy of fault diagnosis, reducing downtime, enhancing the resilience and continuity of construction, and ensuring that construction proceeds as planned. Attached Figure Description

[0040] Figure 1 This is a flowchart illustrating the overall process flow of the present invention.

[0041] Figure 2 This is a schematic diagram showing the placement of the cavitation equipment of the present invention;

[0042] Figure 3 This is a schematic diagram of the installation of the well control equipment of the present invention;

[0043] Figure 4 This is a schematic diagram of the production increase and injection increase operation method of the present invention;

[0044] Figure 5 This is a schematic diagram of the oil well construction layers according to the present invention;

[0045] Figure 6 This is a schematic diagram of the cavitation construction tubing of the present invention;

[0046] Figure 7 This is a schematic diagram of the cavitation jet tool assembly of the present invention.

[0047] Reference numerals: 1. Self-sealing device; 2. Single-gate blowout preventer; 3. Kill line; 4. Four-way connector; 5. Casing head; 6. Internal control line; 7. Pressure gauge; 8. Venting line; 9. Fluid filling line; 10. Instrument vehicle; 11. Work string; 12. Positioning sub; 13. Tubing; 14. Cavitation jet tool; 15. Cavitation jet; 16. Well control equipment; 17. Workover rig; 18. High-pressure pump truck; 19. Sand mixing truck; 20. Liquid tank; 21. Return fluid pipe; 22. Cavitation modulator; 23. Centralizer; 24. Flow stabilizer; 25. Swirl eliminator; 26. High-pressure line. Detailed Implementation

[0048] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below in conjunction with specific embodiments.

[0049] like Figure 1 As shown, a downhole cavitation equipment and a downhole cavitation jet production enhancement and injection process include the following steps:

[0050] Preparations before S1 construction: Transport the workover rig 17, well control equipment 16, cavitation equipment, and instrument vehicle 10 to the construction site; determine the location of the cavitation construction layer based on the oil well foundation data and perforation data, determine the construction point, fill in the construction layer table, and fill the liquid tank 20 with circulating construction fluid.

[0051] S2 wellbore preparation: Deepen the original well string to harden the sand surface. After pulling out the original well string, run tubing 13 with a scraper to the bottom of the artificial well and flush the well for two weeks.

[0052] S3 Construction Pipeline 11 Configuration: Assemble and configure the construction pipeline 11 and cavitation equipment, and lower the construction pipeline 11 to the predetermined depth; calibrate the depth of the cavitation equipment using a magnetic positioning device to ensure its accurate position;

[0053] S4 Ground pipeline pressure test: After connecting the ground pipeline, circulate and clean it, and complete the segmented pressure test;

[0054] S5 Construction Operation: Start the high-pressure pump truck 18 and carry out cavitation treatment point by point from the bottom to the top, starting from the lowest construction point.

[0055] After the injection is completed, the pump is stopped and the pressure is released. The cavitation equipment is then lifted to the next work site using workover rig 17.

[0056] S6 Construction Completed: After all construction points have been completed, downhole tools are retrieved, well completion operations are completed, and the well is handed over.

[0057] Furthermore, the instrument vehicle 10 is equipped with a closed-loop control system, which includes a PLC controller, a parameter acquisition module, and an execution adjustment module. Combining the positioning data of the magnetic positioning device with the PID algorithm, the system dynamically optimizes the jet pump speed and nozzle opening parameters.

[0058] The instrument vehicle 10 integrates a multi-sensor system, which is deployed in the downhole jet device, fluid pipeline and wellhead, to provide downhole pressure, temperature, flow rate and H2S concentration data support for the closed-loop control system;

[0059] The closed-loop control system includes a safety threshold adjustment mechanism. This mechanism pre-stores multiple sets of well depth-formation corresponding threshold tables and calls the matching threshold in combination with real-time acquired data.

[0060] The closed-loop control system is equipped with an emergency shut-off system. When the parameters exceed the matching threshold, the system automatically cuts off the power supply to the jet pump and the fluid supply to the wellhead.

[0061] The closed-loop control system is equipped with a remote emergency platform, which transmits downhole parameters and equipment status data via 4G / 5G to remotely guide emergency response.

[0062] In the specific implementation of this invention, the pre-construction preparation steps involve transporting the workover rig 17, well control equipment 16, etc., to the construction site, determining the construction location based on oil well data, and filling in the construction layer table to lay the foundation for subsequent operations. During the well preparation stage, the original well string is deepened to harden the sand surface. After the original string is pulled out, the well is washed for two weeks with tubing 13 equipped with a scraper to ensure the wellbore is clean. When configuring the construction string 11, it is precisely assembled and lowered to the predetermined depth, and the position of the cavitation equipment is accurately calibrated using magnetic positioning equipment. The surface pipeline pressure test completes the circulation cleaning and segmented pressure test. During the construction operation, the high-pressure pump truck 18 is started to perform cavitation treatment point by point from bottom to top. Finally, through the above steps, the cavitation treatment of the oil well is achieved, and the construction safety and efficiency are improved by using closed-loop control, multi-sensor and other technologies, thereby achieving efficient and safe production and injection enhancement.

[0063] Based on this, the present invention achieves efficient and safe production enhancement and injection transformation of oil wells through a complete and systematic downhole cavitation jet production enhancement and injection process, controlling the entire process from pre-construction preparation to well completion and delivery. This effectively improves the production capacity of oil wells, extends their service life, and provides strong support for the efficient development of oil fields. The operation process of this process is further disclosed below with specific data.

[0064] Example 1: This example further discloses the equipment and materials required for construction based on step S1;

[0065] Specifically, such as Figure 2 As shown, the downhole cavitation equipment includes a high-pressure pump truck 18, an instrument truck 10, and a well control device 16 installed at the wellhead. The output end of the high-pressure pump truck 18 is connected to the well control device 16 via a high-pressure pipeline 26. A sand mixing truck 19 is installed on the input side of the high-pressure pump truck 18, and a liquid tank 20 is installed on the input side of the sand mixing truck 19. The input side of the liquid tank 20 is connected to the well control device 16. The detection probes of the instrument truck 10 are respectively installed on the input and output sides of the sand mixing truck 19 and the high-pressure pump truck 18. The cavitation equipment also includes a cavitation jet tool 14 installed at the lower end of the well control device 16 and an instrument truck 10 installed at the construction site.

[0066] Furthermore, the aforementioned high-pressure pump truck 18 consists of two high-pressure pump trucks 18 as a group, with an additional high-pressure pump truck 18 configured as a backup.

[0067] Furthermore, such as Figure 3As shown, in step S1, the well control equipment 16 includes a casing head 5 connected to the tubing 13. The upper end of the casing head 5 is sequentially equipped with a four-way valve 4, a single-gate blowout preventer 2, and a self-sealing device 1. The four-way valve 4 is connected to a kill line 3 and an internal control line 6 connected to the cavitation equipment on both sides. The internal control line 6 integrates a fluid injection line 9, a pressure gauge 7, and a blowout release line 8 through the four-way valve 4. The fluid injection line 9 is connected to the fluid tank 20, and the kill line 3 is connected to the high-pressure pump truck 18.

[0068] Transport the aforementioned equipment to the construction site, and according to... Figure 4 As shown in the diagram, the construction pump set should be placed upwind or crosswind from the wellhead, with safety and emergency evacuation routes provided. In particular, the placement of the storage tank 20 should ensure rapid and timely tank replacement, and the area where the construction pump set is placed should be free of flammable materials.

[0069] In step S1, the circulating construction fluid is specifically prepared according to the formula of "formation leakage × volume coefficient + wellbore volume", containing 0.2% (by weight) drag-reducing agent and 0.2% (by weight) surfactant. The formation leakage is obtained based on the original production data of the oil well, and the volume coefficient is 1.1-1.5. The drag-reducing agent is one of polyacrylamide, polyethylene oxide, or surfactant-based drag-reducing agents. The surfactant is either a nonionic surfactant of fatty alcohol polyoxyethylene ether or an anionic surfactant of sulfonate.

[0070] In step S1, the circulating construction fluid is circulated in a closed loop through the high-pressure pump truck 18, liquid tank 20, sand mixing truck 19, injection pipeline 9, internal control pipeline 6, oil well, and kill well pipeline 3. The construction fluid is recycled, and the inlet and outlet discharge rates are monitored in real time and the leakage is counted. If the cavitation construction formation leakage is serious, sufficient construction fluid must be prepared to replenish the leakage in a timely manner.

[0071] Example 2: This example is based on the basic data, production data, and perforation data table of the oil well collected in step S1, thereby determining the location of the construction operation:

[0072] Based on the construction environment data, the following table shows the assumed well foundation data:

[0073]

[0074] It should be further explained that the aforementioned sand-bonded pipe refers to a special type of pipe that enhances cementing quality by bonding sand particles to the surface of a metal casing. It is mainly used in cementing operations for deep wells, ultra-deep wells, and complex lithological formations in the oil drilling field, and is especially suitable for casing string cementing construction in easily collapsible formations such as shale and mudstone, as well as high-porosity and high-permeability reservoirs.

[0075] Furthermore, the aforementioned floating collar, also known as a cementing floating collar, is a key component for preventing backflow and ensuring cementing quality during casing string running and cement slurry injection. It is mainly used to prevent cement slurry backflow, realize pressure release and waiting for solidification after cementing impact, and help improve the bonding quality between cement sheath and casing. Both of these components are conventional technical equipment in oil drilling technology.

[0076] Well production data are shown in the table below:

[0077]

[0078] The well perforation data is shown in the table below:

[0079]

[0080] The specific method for determining the location of the cavitation construction layer in step S1 is as follows:

[0081] S1.1: Define the key indicators used for judgment, including permeability K, formation coefficient F, and thickness H. Based on geological conditions, well characteristics, and historical data, set threshold values ​​for each indicator, denoted as follows: , , ;

[0082] S1.2: Extract the K, F, and H data for each sub-layer from the table, calculate the actual indicator values ​​for each sub-layer, and then use... , , express;

[0083] S1.3: For each sub-layer, determine... , , Is it valid?

[0084] S1.4: Count the number of indicators that meet the threshold in each sub-layer, and list the sub-layers that meet at least two indicators as candidate layers;

[0085] S1.5: Combining oil well production data, geological structure and surrounding strata, the candidate layers are verified in detail to determine the final sub-layers for cavitation construction.

[0086] Based on the above judgment method, analyze the data of each sub-layer in the well perforation data table, assuming that the thresholds in the current production environment are... , , ;

[0087] Based on the above data analysis, the situation of each sub-layer is as follows:

[0088] PI1: Penetration Rate , stratum coefficient , Effective thickness rice, It meets three criteria;

[0089] PI3: Penetration Rate , stratum coefficient , Effective thickness rice, It meets three criteria;

[0090] PI4: Penetration Rate , stratum coefficient , Effective thickness rice, It meets three criteria;

[0091] Therefore, the cavitation construction section of this well includes three layers, with sub-layers PI1, PI3, and PI4. The sandstone thickness in the perforated sections is 1.6m, 2.9m, and 3.5m, with effective thicknesses of 0.4m, 0.7m, and 2.4m. A total of five cavitation injection operations were carried out, which can be summarized as follows: Figure 5 and Figure 6 Construction point location table for the indicated construction layer:

[0092]

[0093] Example 3: This example is based on Examples 1 and 2, where the original well tubing is processed and the well is cleaned.

[0094] Specifically, before pulling out the original well string, the hard sand surface of the original well string is deepened to ensure that the well depth meets the construction requirements. Then the original well string is pulled out to prepare for the subsequent installation of the construction string 11.

[0095] The wellbore string, along with the scraper and tubing 13, is lowered to the bottom of the artificial well for a well-washing operation. The well is washed for two weeks to ensure the wellbore is clean, creating favorable conditions for the lowering of the construction string 11.

[0096] Then, the construction pipe string 11 is configured and assembled in the order of construction pipe string 11 in step S3. Its fixed combination from bottom to top is as follows: cavitation jet tool 14, 2-3 oil pipes 13, 1-2 positioning short sections 12. The uppermost oil pipe 13 is connected to the casing head 5. During the assembly process, ensure that all components are tightly connected and the threads are evenly coated to prevent leakage.

[0097] like Figure 6 and Figure 7As shown, the cavitation jet tool 14 includes a cavitation modulator 22 located at the bottom, a centralizer 23 located on the outer surface of the cavitation modulator 22, a flow stabilizer 24 and a swirl eliminator 25 installed sequentially on the upper side of the cavitation modulator, and the upper end of the swirl eliminator 25 is connected to two oil pipes 13 located on the lower side.

[0098] In its specific use, the high-pressure liquid flows in from the upper oil pipe 13 and first passes through the vortex eliminator 25 to eliminate the vortex that may be generated during the transportation process in the oil pipe 13, so that the liquid flow is initially stabilized.

[0099] Next, the liquid enters the flow stabilizing tube 24, where the flow state of the fluid after the swirling is further stabilized and eliminated;

[0100] Subsequently, the liquid enters the cavitation unit. Under the action of the special structure of the cavitation unit, cavitation begins to occur. The liquid with initial cavitation bubbles continues to flow downward through the cavitation modulator 22, where the cavitation phenomenon is further intensified. Finally, a high-intensity cavitation jet is formed and ejected from the lower end of the cavitation modulator 22. The cavitation effect is used to cavitate and transform the reservoir rock and crude oil.

[0101] All of the above components are conventional equipment in the prior art. In this invention, their cavitation effect is used to perform cavitation impact, crushing or cleaning operations on target media, such as rocks and material surfaces, in order to increase the production and injection of oil wells. In this invention, their specific internal structure and operating principle will not be shown or explained in detail.

[0102] Following step S3, the magnetic positioning device is used for calibration. The positioning section 12 and tubing 13 are fixedly combined with the construction string 11 as the depth reference point. The position of the cavitation jet tool 14 is calibrated in real time by combining the wellbore magnetic signal, so that the working range of the cavitation jet 15 is within the reservoir, and the vertical error range between it and the target layer is within ±0.1m.

[0103] according to Figure 4 After all the equipment is assembled, the construction string 11 is lowered into the wellbore to the predetermined depth. Based on the data measured in Example 2, the predetermined depth is 1472.8m. During the process of the construction string 11 entering the predetermined layer, the positioning is calibrated in real time by the magnetic positioning device until the lower end of the cavitation jet tool 14 is located at 1472.8m ± 0.1m.

[0104] Example 4 further discloses the process for handling ground pipelines before cavitation operations, based on Examples 1 and 2.

[0105] Specifically, after connecting the ground pipelines, check the connection status of the ground pipelines to ensure that each link meets the safety and operating procedure requirements;

[0106] Then, a circulation cleaning process is performed to clean the impurities in the high-pressure pump truck 18, circulation equipment, and ground pipelines, preventing large particles from entering the reservoir cavitation jet tool 14 and causing wear and blockage of the cavitation jet tool 14.

[0107] Furthermore, after completing the cyclic cleaning, the pipeline is subjected to segmented pressure testing to ensure stable pressure bearing during cavitation operations. Specifically, the pressure and holding time for the S4 segmented pressure test are as follows: apply 30-60 MPa pressure to the high-pressure pipeline 26 and stabilize for 10-15 minutes; apply 10-20 MPa pressure to the outlet pipeline and stabilize for 10-15 minutes; and ensure that the pressure drop in the pipeline during the pressure holding process is ≤0.7 MPa.

[0108] Example 5 further discloses the specific process for oil well cavitation construction operations based on Examples 1 to 4.

[0109] Specifically, in step S5, before the cavitation jetting operation, the tubing 13 is connected to the pump set, and the well is circulated and flushed for 10 minutes at a pressure of less than 10 MPa to determine the construction pressure during the cavitation operation.

[0110] Start the high-pressure pump truck 18 and begin cavitation treatment from the lowest construction point (such as the PI4 layer construction point at 1472.8m) in a bottom-up sequence. During the cavitation treatment, the high-pressure pump truck 18 is gradually increased to a displacement of 2-2.5m³ / min, a spray pressure of ≤50MPa, and a single-point spray time of 1.5-2.0 hours.

[0111] Furthermore, during the construction operation in step S5, the instrument vehicle 10 monitors parameters in real time, including the return liquid volume, return liquid pressure, output pressure of the high-pressure pump truck 18, output pressure of the sand mixing truck 19, and H2S concentration at the outlet of the liquid pipeline. When the H2S concentration at the outlet of the liquid pipeline is ≥10ppm, an audible and visual alarm is automatically triggered and the pump truck discharge is reduced to ensure the safety of construction personnel.

[0112] Specifically, the flowback volume refers to the total volume of fluid returned to the surface from the wellbore after the working fluid (including fracturing fluid, proppant mixture, etc.) injected into the wellbore and the reservoir produced fluid (including crude oil, formation water, etc.) are mixed during cavitation jet operations. The instrument vehicle 10 collects this data in real time through flow sensors on the pipeline, mainly to determine whether the reservoir is absorbing fluid normally. If the flowback volume is consistently lower than the injection volume and the difference is too large, it indicates that the reservoir's fluid absorption capacity is too strong or there is leakage, and the wellbore sealing needs to be checked in time. If the flowback volume increases sharply, it may indicate that the reservoir has fractures that have been connected, and the jet parameters need to be adjusted to avoid excessive modification.

[0113] Backflow fluid pressure: refers to the pressure of the backflow fluid at the outlet of the surface backflow manifold. It is collected by a pressure sensor on the manifold, and its value changes can reflect whether the flow state in the wellbore is stable. If the backflow fluid pressure fluctuates frequently, it indicates that there may be a blockage in the tubing or abnormal fluid miscibility in the wellbore, and the operation needs to be suspended for investigation. If the pressure continues to rise, it may be that the surface pipeline is blocked, and the pipeline needs to be cleared in time to avoid the risk of pressure buildup.

[0114] High-pressure pump truck 18 output pressure: refers to the outlet pressure of the high-pressure pump truck 18 that provides power to the working fluid. The instrument vehicle 10 monitors this pressure in real time to control the fluid injection power. When the pressure is higher than the preset value, it indicates that the injection pipeline may be blocked or the reservoir resistance is increased. It is necessary to reduce the pump truck speed to reduce the output pressure and prevent damage to the tubing. When the pressure is lower than the preset value, it is necessary to check the pump truck's working status to ensure that the fluid injection volume meets the cavitation operation requirements.

[0115] Output pressure of mixing truck 19: This refers to the outlet pressure of mixing truck 19, which mixes proppant and fracturing fluid. Monitoring this pressure can ensure the stable delivery of the mixed fluid. If the output pressure of mixing truck 19 is too large and the output pressure of high-pressure pump truck 18 is too large, it indicates that there is a throttling loss in the delivery pipeline, and the pipeline diameter or flow rate needs to be adjusted. If the pressure drops suddenly, it may be that the supply of material from mixing truck 19 is insufficient, and proppant or fracturing fluid needs to be added to avoid affecting the cavitation transformation effect.

[0116] H2S concentration at the outlet of the liquid pipeline: This refers to the concentration of hydrogen sulfide gas at the outlet of the main ground fluid transport pipeline, which is collected by a dedicated gas sensor. This parameter is a core safety monitoring item. When the concentration is ≥10ppm, the closed-loop control system of the instrument vehicle 10 will automatically trigger an audible and visual alarm and send a signal to the high-pressure pump truck 18 to reduce the discharge rate. The reduction rate is adjusted according to the degree of concentration exceeding the standard. The higher the concentration, the greater the reduction rate, thus reducing the amount of H2S produced. If the concentration continues to rise to 20ppm, the emergency shut-off system will be further triggered to ensure that construction personnel are away from the risk of poisoning and to fully guarantee the safety and reliability of the entire construction cycle.

[0117] Furthermore, the pumping pressure and discharge rate are recorded every 3 minutes; the leakage and return fluid temperature are recorded once during the construction of each cavitation operation point, and the cavitation pumping personnel are responsible for recording them. Finally, the records are compiled into a construction file.

[0118] After the injection is completed, the pump is stopped and the pressure is released. The cavitation jet tool 14 is then lifted to the next work point using the workover rig 17 to continue the cavitation operation until all work points have been cavitation treated. All downhole tools are then retrieved, all equipment is dismantled, and the oil production unit and production pipeline are connected to their initial state. The oil well is then handed over to the oil production plant. At the same time, all data from the construction process, such as pressure, displacement, and fluid volume records, are submitted to ensure that the data is complete, accurate, and reliable.

[0119] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A downhole cavitation apparatus comprising a high pressure pump truck (18), a gauging truck (10) and well control equipment (16) provided at the well head, characterised in that, The high-pressure pump truck (18) output end is connected with the well control equipment (16) through a high-pressure pipeline (26), the input side of the high-pressure pump truck (18) is provided with a sand mixing truck (19), the input side of the sand mixing truck (19) is provided with a liquid tank (20), the input side of the liquid tank (20) is connected with the well control equipment (16), the detection probe of the instrument vehicle (10) is respectively arranged at the input and output sides of the sand mixing truck (19) and the high-pressure pump truck (18), and the cavitation equipment further comprises a cavitation jet tool (14) installed at the lower end of the well control equipment (16) and an instrument vehicle (10) arranged at the construction site; The well control equipment (16) comprises a casing head (5) connected with a tubing (13), a four-way valve (4), a single-gate blowout preventer (2) and a self-sealing device (1) are sequentially arranged at the upper end of the casing head (5), the two sides of the four-way valve (4) are respectively connected with a well killing pipeline (3) and an inner control pipeline (6) which are communicated with the cavitation equipment, the inner control pipeline (6) is integrated with a liquid filling pipeline (9), a pressure gauge (7) and a blowout pipeline (8) through the four-way valve (4), the liquid filling pipeline (9) is connected with the liquid tank (20), and the well killing pipeline (3) is connected with the high-pressure pump truck (18).

2. A downhole cavitation apparatus according to claim 1, characterized in that: The instrument vehicle (10) is provided with a closed-loop control system, which comprises a PLC controller, a parameter acquisition module and an execution adjustment module, and combines the positioning data of the magnetic positioning equipment and the PID algorithm to dynamically optimize the jet pump rotating speed and the nozzle opening degree parameters; The instrument vehicle (10) is integrated with a multi-sensor system, which is arranged at the jet device, the fluid pipeline and the wellhead, and provides the closed-loop control system with downhole pressure, temperature, flow rate and H2S concentration data support; The closed-loop control system comprises a safety threshold adjustment mechanism, which pre-stores a plurality of sets of well depth-formation corresponding threshold tables, and calls the matching threshold in combination with the real-time acquisition data; The closed-loop control system is matched with an emergency shutdown system, which automatically shuts off the power supply of the jet pump and the fluid supply of the wellhead when the parameters exceed the called matching threshold; The closed-loop control system is provided with a remote emergency platform, which transmits downhole parameters and equipment state data through 4G / 5G, and remotely guides emergency treatment.

3. A process for stimulation of a well by cavitation jetting downhole using the cavitation device according to any one of claims 1-2, characterized in that, The method comprises the following steps: S1: preparation before construction: transporting the workover rig (17), the well control equipment (16), the cavitation equipment and the instrument vehicle (10) to the construction site; determining the cavitation construction layer position according to the oil well basic data and the perforation data, determining the construction point, filling the construction layer table, and filling the circulating construction liquid into the liquid tank (20); S2: wellbore preparation: deepening the original well pipe column hard sand face, after the original well pipe column is pulled out, the tubing (13) with a scraper is lowered to the artificial well bottom, and the well is washed for two weeks; S3: configuration of the construction pipe column (11): assembling and configuring the construction pipe column (11) and the cavitation equipment, and lowering the construction pipe column (11) to the predetermined depth; the depth of the cavitation equipment is calibrated through the magnetic positioning equipment to ensure the accurate position; S4: ground pipeline pressure test: after the ground pipeline is connected, it is circulated and cleaned, and the segmented pressure test is completed; S5: construction operation: starting the high-pressure pump truck (18), starting from the lowermost construction point, and performing cavitation jetting operation in the order from bottom to top. The jetting is finished, the pump is stopped to unload pressure, and the cavitation equipment is lifted to the next operation point by the workover rig (17); S6: After the operation of all operation points is completed, the downhole tool is lifted, the well completion operation is completed, and the oil well is delivered.

4. The downhole cavitation jetting stimulation process of claim 3, wherein: The circulating construction liquid in step S1 is circulated in a closed mode through the high-pressure pump truck (18), the liquid tank (20), the sand mixing truck (19), the liquid filling pipeline (9), the internal control pipeline (6), the oil well, and the well killing pipeline (3).

5. The downhole cavitation jetting stimulation process of claim 3, wherein: The circulating construction liquid in step S1 is prepared according to the formula of "formation leakage volume × volume coefficient + wellbore volume", and contains 0.2% (by weight) of a drag reduction agent and 0.2% (by weight) of a surfactant, the formation leakage volume is obtained according to the original production data of the oil well, and the volume coefficient is 1.1-1.

5. The drag reduction agent is one of polyacrylamide, polyethylene oxide, and a surfactant type drag reduction agent. The surfactant is a fatty alcohol polyoxyethylene ether nonionic surfactant or a sulfonate anionic surfactant.

6. The downhole cavitation jetting stimulation process of claim 3, wherein: The fixed combination of the construction string (11) in step S3 comprises, from bottom to top, the cavitation jet tool (14), 2-3 oil pipes (13), and 1-2 positioning nipples (12). When the magnetic positioning equipment is calibrated in step S3, the positioning nipple (12) and the oil pipe (13) form a depth reference point according to the fixed combination of the construction string (11), and the position of the cavitation jet tool (14) is calibrated in real time in combination with the wellbore magnetic signal to ensure that the vertical error range of the cavitation jet tool (14) and the target layer is within ±0.1 m.

7. The downhole cavitation jetting stimulation process of claim 3, wherein: The specific pressure and pressure holding time of the segmented pressure test in step S4 are as follows: 30-60 MPa pressure is applied to the high-pressure pipeline (26) for 10-15 min, and 10-20 MPa pressure is applied to the outlet pipeline for 10-15 min, and the pressure drop of the pipeline during the pressure holding process is ≤0.7 MPa.

8. The downhole cavitation jetting stimulation process of claim 3, wherein: The oil pipe (13) is connected with the pump group before the cavitation jet operation in step S5, and the well is washed for 10 minutes at a pressure of less than 10 MPa to determine the construction pressure during the cavitation operation. The high-pressure pump truck (18) is gradually lifted to a displacement of 2-2.5 m³ / min during the cavitation jet operation in step S5, the jetting pressure is ≤50 MPa, and the single-point jetting time is 1.5-2.0 hours.

9. The downhole cavitation jetting stimulation process of claim 3, wherein: The parameters are monitored in real time by the instrument truck (10) during the construction operation in step S5, including the flowback fluid volume, the flowback fluid pressure, the output pressure of the high-pressure pump truck (18), the output pressure of the sand mixing truck (19), and the H2S concentration at the outlet of the liquid pipeline. When the H2S concentration at the outlet of the liquid pipeline is ≥10 ppm, an audible and light alarm is automatically triggered, and the pump truck displacement is reduced.

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