Downhole cavitation device and downhole cavitation jet stimulation and injection enhancement process

Abstract

The application discloses a downhole cavitation device and a downhole cavitation jet flow stimulation and injection increase process, and particularly relates to the technical field of oil exploitation, and comprises the following steps: preparation before construction, transporting the device to the site, determining the construction point and filling the layer table; wellbore preparation, deepening the sand face of the pipe string, washing the well with the oil pipe with the scraper after the original pipe string is pulled out; construction pipe string configuration, assembling the pipe string and the cavitation device and checking the depth; ground pipeline pressure test, completing the connection cleaning and the sectional pressure test; processing point by point from bottom to top; and pulling out the tool to complete the well completion and deliver the oil well. The downhole cavitation device and the downhole cavitation jet flow stimulation and injection increase process realize efficient and safe stimulation and injection increase reconstruction of the oil well, effectively improve the production capacity of the oil well, prolong the service life of the oil well, and provide strong support for efficient development of the oil field.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil extraction, particularly to a downhole cavitation device and downhole cavitation jet stimulation and injection enhancement process. BACKGROUND

[0002] In the field of oil extraction, as the time of oil well production increases, the formation energy gradually decreases, and the oil well production and injection capacity often face the problem of reduction, which seriously affects the overall production efficiency and economic benefit of the oilfield. In order to maintain the stable production of oil wells, stimulation and injection enhancement technology has become a key link in the process of oil extraction. Traditional stimulation and injection enhancement methods cannot meet the increasingly complex reservoir condition requirements.

[0003] At present, conventional stimulation and injection enhancement technologies mainly include acidification, fracturing, etc. Acidification technology is to dissolve the blockage and rock minerals in the formation by injecting acid liquid into the formation, so as to expand the pore and fracture and improve the formation permeability. Fracturing technology is to inject liquid into the formation by high pressure to form cracks in the formation and increase the oil flow channel. In addition, there are some physical stimulation methods, such as acoustic stimulation technology, which improves the flowability of crude oil by emitting acoustic waves to the formation. However, the existing stimulation and injection enhancement technologies still have the following defects in the use process:

[0004] During the acidification process, the reaction of acid liquid and formation rock may produce precipitates, which will re-block the formation pore and reduce the acidification effect. At the same time, the acid liquid has strong corrosiveness to the downhole equipment, which can easily shorten the service life of the equipment and increase the production cost. Moreover, the action range of acidification technology is limited, and the treatment effect on deep formation is not good;

[0005] Fracturing construction requires high pressure, which is harsh on equipment and formation conditions. If the pressure is not properly controlled, it may cause excessive formation rupture and cause problems such as formation collapse. In addition, the fracture shape and extension direction generated by fracturing are difficult to accurately control, which may not effectively connect the oil flow channels in the reservoir, affecting the stimulation and injection enhancement effect. At the same time, the fracturing construction process is complex, the cost is high, and it may cause certain pollution to the environment;

[0006] The energy of acoustic waves attenuates quickly during propagation, and the action distance is limited, which makes it difficult to effectively treat deep formation. Moreover, the stimulation effect of acoustic waves is greatly affected by the formation lithology, and the stimulation effect is not obvious for some complex lithology formations. In addition, the stability and reliability of the existing acoustic stimulation equipment need to be improved, and the operation process is also complex. SUMMARY

[0007] The main purpose of the present application is to provide a downhole cavitation device and downhole cavitation jet stimulation and injection enhancement process, which can effectively solve the problems of poor effect and high cost of the existing stimulation and injection enhancement process.

[0008] To achieve the above object, the technical scheme adopted by the present application is:

[0009] A downhole cavitation device, comprising a high-pressure pump truck, an instrument truck and a well control device arranged at the wellhead, the output end of the high-pressure pump truck is connected with the well control device through a high-pressure pipeline, the input side of the high-pressure pump truck is provided with a sand mixing truck, the input side of the sand mixing truck is provided with a liquid tank, the input side of the liquid tank is connected with the well control device, the detection probes of the instrument truck are arranged at the input and output sides of the sand mixing truck and the high-pressure pump truck respectively, the cavitation device further comprises a cavitation jet tool installed at the lower end of the well control device and an instrument truck arranged at the construction site;

[0010] The well control device comprises a casing head connected with a tubing, a four-way valve, a single-gate blowout preventer and a self-sealing device are sequentially arranged at the upper end of the casing head, the two sides of the four-way valve are respectively connected with a kill line and an inner control line communicated with the cavitation device, the inner control line passes through a liquid filling pipeline, a pressure gauge and a blowout pipeline, the liquid filling pipeline is connected with the liquid tank, and the kill line is connected with the high-pressure pump truck.

[0011] Preferably, the instrument truck 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 device and the PID algorithm to dynamically optimize the jet pump rotating speed and nozzle opening degree parameters;

[0012] The instrument truck is integrated with a multi-sensor system, which is arranged at the jet device, fluid pipeline and wellhead, and provides downhole pressure, temperature, flow rate and HS concentration data support for the closed-loop control system;

[0013] 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 matching threshold values in combination with real-time acquisition data;

[0014] The process is matched with an emergency shutdown system, which automatically shuts off the power supply of the jet pump and the fluid supply at the wellhead when the parameters exceed the called matching threshold values;

[0015] The process is provided with a remote emergency platform, which transmits downhole parameters and equipment state data through 4G / 5G, and remotely guides emergency treatment.

[0016] A downhole cavitation jet stimulation and injection enhancement process using the above downhole cavitation device, comprising the following steps:

[0017] S1 Preparation before construction: transport the workover rig, well control device, cavitation device and instrument truck to the construction site; determine the cavitation construction interval position according to the oil well basic data and perforation data, determine the construction point, fill in the construction interval table, and fill the circulating construction liquid into the liquid tank;

[0018] S2 wellbore preparation: deepen the original well pipe column hard sand face, after the original well pipe column is lifted, the oil pipe with the scraper is lowered to the artificial well bottom, and the well is washed for two weeks;

[0019] S3 construction pipe column configuration: assemble and configure the construction pipe column and the cavitation device, lower the construction pipe column to the predetermined depth; the depth of the cavitation device is calibrated through the magnetic positioning device to ensure the accurate position thereof;

[0020] S4 ground pipeline pressure test: after the ground pipeline is connected, it is cleaned and the segmented pressure test is completed;

[0021] S5 construction operation: start the high-pressure pump truck, and sequentially perform cavitation treatment from the lowermost construction point to the uppermost construction point;

[0022] After the spraying is completed, the pump is stopped and the cavitation device is lifted to the next construction point through the workover machine;

[0023] S6 construction completion: after all the construction points are completed, the downhole tool is lifted, the completion operation is completed, and the oil well is delivered.

[0024] Preferably, the circulating construction liquid in the step S1 is circulated in a closed mode through the high-pressure pump truck, the liquid tank, the sand mixing truck, the liquid filling pipeline, the internal control pipeline, the oil well and the well killing pipeline.

[0025] Preferably, the circulating construction liquid in the step S1 is prepared according to the formula of “formation leakage amount x volume coefficient + wellbore volume” and contains 0.2% (by weight) of a drag reduction agent and 0.2% (by weight) of a surfactant, wherein the formation leakage amount is obtained according to the original production data of the oil well, and the volume coefficient is 1.1-1.5.

[0026] The drag reduction agent is one of polyacrylamide, polyethylene oxide and surfactant.

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

[0028] Preferably, the construction pipe column fixed combination in the step S3 is sequentially arranged from bottom to top as follows: cavitation jet tool, 2-3 oil pipes and 1-2 positioning short joints.

[0029] When the magnetic positioning device is calibrated in the step S3, the positioning short joint and the oil pipe form a depth reference point according to the construction pipe column fixed combination, the position of the cavitation jet tool is calibrated in real time in combination with the wellbore magnetic signal, and the vertical error range of the cavitation jet tool and the target layer is ensured to be within ±0.1 m.

[0030] Preferably, the specific pressure and pressure holding time of the step S4 is that: 30-60 MPa pressure is applied to the high-pressure pipeline for 10-15 min, 10-20 MPa pressure is applied to the outlet pipeline for 10-15 min, and the pressure drop of the pipeline during pressure holding is ≤0.7 MPa.

[0031] Preferably, the tubing is connected with the pump group before the cavitation jet operation in the step S5, and the well is washed for 10 min under a pressure less than 10 MPa to determine the construction pressure during the cavitation operation.

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

[0033] Preferably, the parameters such as the flowback fluid volume, the flowback fluid pressure, the high-pressure pump truck output pressure, the sand mixing truck output pressure and the H2S concentration at the outlet of the liquid pipeline are monitored in real time during the construction operation in the step S5.

[0034] 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.

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

[0036] 1. The present application aims at the problems of extensive traditional process construction scheme and low transformation efficiency, and precise oil well data are obtained through a multi-sensor system and magnetic positioning data acquisition, and the jet flow parameters are dynamically optimized by combining the PID algorithm of the closed-loop control system, so that the construction scheme is customized for each well, the positioning accuracy of the operation point is improved, the reservoir is not excessively transformed or insufficiently transformed, the reservoir transformation efficiency and the oil well productivity are finally improved, the stable production cycle of the oil well is prolonged, and support is provided for efficient development of the oil field.

[0037] 2. The present application aims at the problems of unstable wellbore system and high safety risk of the traditional process, and the wellbore cleanliness and the pipe string sealing are improved by fine processing of the original well pipe string, accurate assembly of the construction pipe string and high-pressure pressure test of the ground pipeline, and the leakage risk is reduced; at the same time, the H2S concentration is monitored in real time by relying on the double sensor, and the safety threshold adjustment mechanism and the emergency shutdown system are matched, so that the risk parameter control speed is greatly improved, the personnel safety risk is eliminated, and the safety and reliability of the whole construction cycle are ensured.

[0038] 3.The present application aims at the problem of uncontrolled cavitation operation and difficult quality traceability of traditional process, adopts a bottom-up point-by-point cavitation treatment method, combines with a closed-loop control system to collect construction parameters in real time, ensures that there is no blind area in reservoir reconstruction, and through automatic parameter storage and standardized data recording, replaces manual recording, realizes whole-process traceability of construction quality, can accurately judge the reservoir liquid absorption capacity to adjust parameters, avoids construction rework, and improves construction efficiency.

[0039] 4.The present application aims at the problem of lagging emergency response and poor whole-process cooperation of traditional process, through linkage of a remote emergency platform and a closed-loop control system, realizes real-time transmission of downhole parameters and remote instruction sending, shortens emergency response time, at the same time, forms a closed loop with multi-sensor data, equipment state data and emergency instructions, improves fault diagnosis accuracy, reduces downtime, enhances construction risk resistance and continuity, and ensures that construction is carried out according to the plan. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a whole process flowchart of the present application;

[0041] Figure 2 is a cavitation device swing illustration of the present application;

[0042] Figure 3 is a well control device installation schematic diagram of the present application;

[0043] Figure 4 is a stimulation and injection operation mode schematic diagram of the present application;

[0044] Figure 5 is an oil well construction horizon schematic diagram of the present application;

[0045] Figure 6 is a cavitation construction pipe string schematic diagram of the present application;

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

[0047] The drawing label: 1, self-sealing device;2, single-gate blowout preventer;3, kill line;4, four-way;5, casing head;6, internal control line;7, pressure gauge;8, blowout line;9, liquid filling line;10, instrument car;11, construction pipe string;12, positioning nipple;13, oil pipe;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 liquid pipe;22, cavitation modulator;23, centralizer;24, steady flow pipe;25, cyclone eliminator;26, high-pressure pipeline. DETAILED DESCRIPTION

[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 matched with an emergency shutdown system, and when the parameters exceed the matching threshold of the call, the system automatically shuts off the jet pump power supply and the wellhead fluid supply.

[0061] The closed-loop control system is provided with a remote emergency platform, which transmits downhole parameter and equipment state data through 4G / 5G and remotely guides emergency treatment.

[0062] In the specific implementation process of the present application, through the pre-construction preparation step, the workover rig 17, well control equipment 16 and the like are transported to the construction site, the construction point is determined according to the oil well data, and the construction layer table is filled in, laying the foundation for subsequent operation; in the wellbore preparation stage, the original well pipe column hard sand face is deepened, after the original pipe column is pulled out, the well is washed for two weeks with a scraper-equipped oil pipe 13 to ensure the cleanliness of the wellbore; when the construction pipe column 11 is configured, the pipe column is precisely assembled and lowered to the predetermined depth, and the position of the cavitation equipment is accurately corrected by using a magnetic positioning device; the ground pipeline pressure test is completed, and the circulation cleaning and segmented pressure test are carried out; the work operation starts the high-pressure pump truck 18, and the cavitation treatment is carried out point by point from bottom to top; finally, through the above steps, the cavitation treatment of the oil well is realized, and the construction safety and efficiency are improved by means of closed-loop control, multi-sensor and the like, so that efficient and safe stimulation and injection augmentation reconstruction is achieved.

[0063] Based on this, the present application realizes efficient and safe stimulation and injection augmentation reconstruction of oil wells through a complete and systematic downhole cavitation jet flow stimulation and injection augmentation process, controls the whole process from pre-construction preparation to completion delivery, effectively improves the production capacity of oil wells, prolongs the service life of oil wells, provides strong support for efficient development of oil fields, and the operation process of the present application is further disclosed in combination with specific data.

[0064] In example one, the equipment and materials required for construction are further disclosed based on step S1.

[0065] Specifically, as shown in Figure 2 The downhole cavitation equipment includes a high-pressure pump truck 18, an instrument truck 10 and a well control equipment 16 arranged at the wellhead, the output end of the high-pressure pump truck 18 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 probes of the instrument truck 10 are arranged at the input and output sides of the sand mixing truck 19 and the high-pressure pump truck 18 respectively, and the cavitation equipment further includes a cavitation jet tool 14 installed at the lower end of the well control equipment 16 and an instrument truck 10 arranged at the construction site.

[0066] Further, the above-mentioned high-pressure pump truck 18 is a group of two high-pressure pump trucks 18, and another high-pressure pump truck 18 is configured as a backup.

[0067] Further, as shown in Figure 3As shown, the well control equipment 16 in step S1 includes a casing head 5 connected with the tubing 13, the upper end of the casing head 5 is sequentially provided with a four-way valve 4, a single-gate blowout preventer 2, and a self-sealing device 1, the two sides of the four-way valve 4 are respectively connected with a blowout control pipeline 3 and an inner control pipeline 6, 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 a liquid tank 20, and the blowout control pipeline 3 is connected with a high-pressure pump truck 18.

[0068] The above equipment is transported to the construction site and assembled as shown in Figure 4 Further, the construction pump group is placed in the upwind or crosswind direction of the construction well, and a safety and emergency evacuation passage is left, and in particular, the placement of the liquid storage tank 20 needs to ensure that the tank can be replaced quickly and timely, and the placement area of the construction pump group should be free of flammable materials.

[0069] In step S1, the circulating construction liquid is prepared according to "formation leakage volume x 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; and the surfactant is a fatty alcohol polyoxyethylene ether nonionic surfactant or a sulfonate anionic surfactant.

[0070] In step S1, the circulating construction liquid is circulated in a closed loop through the high-pressure pump truck 18, the liquid tank 20, the sand mixing truck 19, the liquid filling pipeline 9, the inner control pipeline 6, the oil well, and the blowout control pipeline 3, and the construction liquid is recycled, the inlet and outlet flow rates are monitored in real time, and the leakage volume is counted, and if the formation leakage is serious during cavitation construction, sufficient construction liquid needs to be prepared to supplement the leakage volume in time.

[0071] In example two, the basic data, production data, and perforation data table of the oil well are collected based on step S1, and thus the construction operation point is determined:

[0072] According to the construction environment data, the well basic data is assumed as follows:

[0073]

[0074] It needs to be further explained that the sand sticking pipe refers to a special pipe material for enhancing well cementing quality by sticking sand particles on the surface of the metal casing, which is mainly applied to well cementing operations in deep wells, ultra-deep wells, and complex lithology formations in the field of oil drilling, and is especially suitable for casing string cementing construction in shale, mudstone, and other easy-collapsing formations and high-porosity, high-permeability reservoirs.

[0075] Further, the above floating collar is also called a cementing floating collar, which is a key component for preventing backflow and ensuring cementing quality during the process of casing string lowering and cement slurry pouring, mainly used for preventing cement slurry backflow, realizing pressure release after cementing pressure impact, and helping to improve the cementing quality of the cement sheath and the casing. The above two components are conventional technical equipment in the oil drilling technical equipment.

[0076] The well production data are as follows:

[0077]

[0078] The well perforation data are as follows:

[0079]

[0080] The cavitation construction layer position judgment method in step S1 is specifically as follows:

[0081] S1.1: The key indicators for judgment are determined, including permeability K, formation coefficient F, and thickness H. According to the geological conditions, oil well characteristics, and historical data, the threshold values of each indicator are set, respectively denoted as , , ;

[0082] S1.2: The K, F, and H data of each small layer are extracted from the table, and the actual indicator values of each small layer are calculated, respectively denoted as , , ;

[0083] S1.3: For each small layer, it is judged whether , , is established;

[0084] S1.4: The number of indicators meeting the threshold value of each small layer is counted, and the small layer meeting at least two indicators is listed as a candidate layer;

[0085] S1.5: In combination with the oil well production data, geological structure, and surrounding strata and other factors, the candidate layer is verified in detail to determine the final small layer for cavitation construction.

[0086] In combination with the above judgment method, the data of each small layer in the well perforation data table are analyzed, and it is assumed that the threshold values in the current production environment are , , ;

[0087] Based on the above data analysis, the conditions of each small layer are as follows:

[0088] PI1: permeability , , formation coefficient , effective thickness meters, satisfy three indexes;

[0089] PI3: permeability , formation coefficient , effective thickness meters, satisfy three indexes;

[0090] PI4: permeability , formation coefficient , effective thickness meters, satisfy three indexes;

[0091] Therefore, the cavitation construction layer section of the well includes three layer numbers, and the small layer numbers are PI1, PI3 and PI4. The sandstone thickness of the perforation section is 1.6 m, 2.9 m and 3.5 m, the effective thickness is 0.4 m, 0.7 m and 2.4 m, and a total of 5 cavitation jetting operations are performed. The construction point table of the construction layer position is shown in Table 1 and Table 2: Figure 5 and Figure 6

[0092]

[0093] Example three, on the basis of example one and example two, the original well pipe column is processed and washed;

[0094] Specifically, before pulling out the original well pipe column, the hard sand face of the original well pipe column is deepened to ensure that the wellbore depth meets the construction requirements, and then the original well pipe column is pulled out to prepare for the subsequent running of the construction pipe column 11.

[0095] The well pipe column is run to the artificial well bottom with the scraper and the oil pipe 13, and the well washing operation is performed for 2 weeks to ensure the wellbore cleaning and create good conditions for the running of the construction pipe column 11.

[0096] Then, the construction pipe column 11 is configured and assembled according to the sequence in step S3, and the fixed combination from bottom to top is: cavitation jet tool 14, 2-3 oil pipes 13, 1-2 positioning short sections 12, and the uppermost oil pipe 13 is connected with the casing head 5. During the assembly process, it is ensured that each component is connected tightly, the threads are evenly coated, and leakage is prevented.

[0097] As shown in Figure 6 and Figure 7 ​As 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, the circulating cleaning is performed to clean the impurities in the high-pressure pump truck 18, the circulating device and the ground pipeline, so as to prevent the large particles from entering the reservoir cavitation jet tool 14 to cause the cavitation jet tool 14 to be worn and blocked.

[0107] Further, after the circulating cleaning is completed, the pipeline is subjected to the sectional pressure test, so as to ensure that the pipeline is stable in pressure during the cavitation operation. Specifically, the sectional pressure test is performed on the high-pressure pipeline 26 and the outlet pipeline, and the pressure and pressure maintaining time are as follows: the high-pressure pipeline 26 is subjected to the pressure of 30-60 MPa for 10-15 min, and the outlet pipeline is subjected to the pressure of 10-20 MPa for 10-15 min. During the pressure maintaining process, the pressure drop of the pipeline is less than or equal to 0.7 MPa.

[0108] In the fifth embodiment, the specific process of the cavitation operation for the oil well is further disclosed based on the first to fourth embodiments.

[0109] Specifically, in step S5, the tubing 13 is connected with the pump group before the cavitation jet operation, and the well is washed for 10 min under the pressure less than 10 MPa, so as to determine the construction pressure during the cavitation operation.

[0110] The high-pressure pump truck 18 is started, and the cavitation treatment is sequentially performed on the points from the lowermost construction point (such as the PI4 layer construction point at 1472.8 m) to the uppermost construction point. During the cavitation treatment, the high-pressure pump truck 18 is gradually lifted to the displacement of 2-2.5 m3 / min, the jet pressure is less than or equal to 50 MPa, and the single-point jet time is 1.5-2.0 hours.

[0111] Further, in step S5, the parameters such as 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 are monitored in real time by the instrument truck 10. When the H2S concentration at the outlet of the liquid pipeline is greater than or equal to 10 ppm, the audible and light alarms are automatically triggered, and the displacement of the pump truck is reduced, so as to ensure the safety of the construction personnel.

[0112] Specifically, the flowback fluid volume refers to the total volume of the working fluid (including the fracturing fluid, the proppant mixed fluid and the like) injected into the wellbore and the reservoir production fluid (including the crude oil, the formation water and the like) mixed after the cavitation jet operation, which is collected by the flow sensor on the pipeline in real time by the instrument truck 10. The data is mainly used to determine whether the reservoir is normally liquid-absorbed. If the flowback fluid volume is continuously lower than the injection volume and the difference is too large, it is indicated that the reservoir has too strong liquid-absorbing capacity or there is a leakage, and the wellbore sealing property needs to be checked in time. If the flowback fluid volume suddenly increases, it is indicated that the reservoir has a crack, and the jet parameter needs to be adjusted to avoid excessive modification.

[0113] Flowback pressure: refers to the pressure of the flowback fluid at the outlet of the surface flowback manifold, which is collected by a pressure sensor on the manifold. Changes in the value of this parameter can reflect whether the flow regime in the wellbore is stable. If the flowback pressure fluctuates frequently, it indicates that there may be a pipe column blockage or fluid mis-mixing anomaly in the wellbore, and the operation needs to be suspended for investigation. If the pressure continues to rise, it may be due to poor ground pipeline, which needs to be cleaned in time to avoid the risk of pressure build-up.

[0114] High-pressure pump truck 18 output pressure: refers to the outlet pressure of the high-pressure pump truck 18 that provides power for the working fluid. The instrument truck 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 has increased, and the pump truck speed needs to be reduced to reduce the output pressure to prevent damage to the pipe string. When the pressure is lower than the preset value, the pump truck operating status needs to be checked to ensure that the fluid injection amount meets the cavitation operation requirements.

[0115] Sand mixing truck 19 output pressure: refers to the outlet pressure of the sand mixing truck 19 that mixes proppants and fracturing fluid. Monitoring this pressure can ensure stable delivery of the mixed fluid. If the difference between the sand mixing truck 19 output pressure and the high-pressure pump truck 18 output pressure is too large, it indicates that there is a throttling loss in the delivery pipeline of the mixed fluid, and the pipeline diameter or flow rate needs to be adjusted. If the pressure drops suddenly, it may be due to insufficient supply of the sand mixing truck 19, and proppants or fracturing fluid need to be supplemented to avoid affecting the cavitation modification effect.

[0116] H2S concentration at the outlet of the liquid pipeline: refers to the concentration of hydrogen sulfide gas at the outlet of the main fluid delivery pipeline on the ground, which is collected by a special gas sensor. This parameter is a safety core monitoring item. When the concentration is ≥10 ppm, the closed-loop control system of the instrument truck 10 will automatically trigger an audible and visual alarm, and send a signal to the high-pressure pump truck 18 to reduce the displacement. The reduction in displacement is adjusted according to the extent of the concentration exceeding the standard. The higher the concentration, the greater the reduction. Reducing the output of H2S can reduce the risk of poisoning for construction personnel and ensure the safety and reliability of the entire construction cycle.

[0117] Further, the pump injection pressure and displacement are recorded every 3 minutes; the loss and flowback fluid temperature are recorded once during the construction of each cavitation operation point, and the cavitation pump injection operation personnel are responsible for recording. Finally, the construction files are formed by summarizing.

[0118] After the injection is completed, the pump is stopped and the pressure is released. The cavitation jet tool 14 is lifted to the next construction point by the workover rig 17 to continue the cavitation operation. After all the operation points have been completed, all the downhole tools are pulled out, all the equipment is removed, the oil production device and the production pipeline are connected to the initial state, and the oil well is handed over to the oil production plant. At the same time, all the data during the construction process, such as pressure, displacement, and liquid volume records, are submitted to ensure that the data is complete, accurate, and reliable.

[0119] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application 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 the stimulation of a well by cavitation jetting downhole using the apparatus of 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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