A sandblaster for oilfield formation fracturing

Abstract

The present application relates to the technical field of oilfield fracturing, and discloses a sand blaster for oilfield formation fracturing. The sand blaster mainly comprises an upper column body, an intermediate column body and a lower column body. A pressure feedback cavity in the upper column body is communicated with a Helmholtz resonance cavity in the intermediate column body through a throttle hole; an adjusting column in the lower column body can extend into the Helmholtz resonance cavity, and the position of the adjusting column is controlled by a pressure feedback driving mechanism. During operation, the sand-carrying liquid pressure drives the adjusting column to move, and the volume of the Helmholtz resonance cavity is changed, so that the frequency of the pulsed jet flow is adaptively adjusted: when the pressure is high, the frequency tends to be low, and the hard formation is impacted with high energy; when the pressure is low, the frequency tends to be high, and the soft formation is impacted rapidly. The present application realizes the generation of pulses and the adaptive adjustment of frequency through a pure mechanical structure, solves the problems of poor pulse effect, low reliability and the inability to adapt in the prior art, and the movement of the adjusting column has a dynamic self-cleaning function, effectively prevents sand blockage, and improves the fracturing efficiency and the reliability of the tool.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oilfield fracturing technology, and particularly relates to a sandblaster for oilfield formation fracturing. BACKGROUND

[0002] In the development of oil and gas fields, hydraulic fracturing is a key engineering technology for improving low-permeability reservoirs and increasing single-well production. As one of the core tools of the fracturing string, the sandblaster functions to inject the sand-carrying liquid from the surface high-pressure pump into the formation at high speed, press open the fractures and provide support for the fractures. Its performance directly determines the efficiency of the fracturing operation and the ultimate recovery rate.

[0003] At present, the continuous jet sandblaster is widely used in oilfield sites, which is mainly divided into two types according to its structure and working principle:

[0004] Fixed sandblaster: the size and geometry of its jet channel (sandblasting port or nozzle) are fixed and unchangeable. During construction, the sand-carrying liquid is continuously injected at a constant flow rate and pressure. Although this structure is simple and reliable, it has obvious defects: first, the constant jet flow has a single impact on the formation, and the energy utilization rate is low, a large amount of hydraulic energy is dissipated as heat energy; second, the high-speed sand-carrying fluid causes serious erosion and wear of the nozzle and flow channel, and the service life is short; third, the fixed jet parameters cannot adapt to the fracture characteristics of different depths and different lithology formations, and the process adaptability is poor.

[0005] Ball sliding sleeve sandblaster: used for multi-layer staged fracturing. By throwing different sizes of sealing balls from the wellhead, it opens the sliding sleeves of each stage sandblaster in turn to realize selective fracturing. Although this type of tool solves the process problem of multi-layer operation, the jet flow is still continuous, and the fundamental problems of energy utilization rate and formation adaptability have not been solved.

[0006] In order to improve the fracturing effect, the technical personnel in the field recognize that pulsed jet flow has significant advantages over continuous jet flow. Pulsed jet flow can produce stronger water hammer effect and rock fatigue damage through periodic pressure peaks, which is beneficial to form longer and more complex fracture networks. There are mainly two ways to generate pulsed jet flow in the prior art:

[0007] Surface pump group modulation: the flow and pressure fluctuations are generated by controlling the start-stop or frequency of the surface fracturing pump. However, this fluctuation signal needs to be transmitted through a fracturing string several kilometers long, and is seriously attenuated, distorted and delayed due to the influence of fluid compressibility, pipe string elasticity and friction, and is very weak when it reaches the downhole, which cannot form effective pulse impact, and has high requirements for surface equipment and low reliability.

[0008] Downhole mechanical or hydraulic pulse devices: These devices integrate mechanical moving parts such as valve cores and rotary valves into downhole tools, generating pulses through their periodic opening and closing. These devices have complex structures, and in high-pressure, highly abrasive sand-carrying fluid environments, the moving parts are extremely prone to wear and jamming, resulting in a very short lifespan. Their reliability cannot meet the requirements of long-term, large-scale industrial fracturing operations.

[0009] Therefore, the following technical problems urgently need to be solved in the existing technology: 1. The continuous jet fracturing efficiency is low and the energy utilization rate is poor; 2. The existing pulse generation method (surface modulation) has serious signal attenuation and cannot form an effective pulse at the bottom of the well; 3. The existing downhole pulse device has a complex structure and poor reliability and cannot adapt to harsh working conditions; 4. The working parameters of the sandblaster are fixed and cannot be adaptively adjusted according to formation conditions. Summary of the Invention

[0010] The purpose of this invention is to overcome the shortcomings of the prior art and to provide an adaptive sandblaster with a simple and reliable structure that can directly generate high-intensity pulse jets downhole and automatically adjust the pulse frequency according to downhole pressure changes, thereby overcoming the deficiencies of the prior art.

[0011] To achieve the above objectives, the present invention adopts the following technical solution: a sandblasting device for oilfield formation fracturing, comprising:

[0012] The upper column has a pressure feedback chamber inside. The bottom of the pressure feedback chamber is provided with a throttling hole and a slide hole that run vertically through it. A drive column is slidably installed in the slide hole.

[0013] The intermediate column has a Helmholtz resonant cavity inside. The surface of the intermediate column has a sandblasting nozzle that communicates with the Helmholtz resonant cavity. The intermediate column is threaded to the bottom of the upper column.

[0014] The lower column has an adjusting column that can be slidably installed inside it and can extend into the Helmholtz resonant cavity. The bottom end of the driving column is fixedly connected to the adjusting column. A pressure feedback driving mechanism is provided at the bottom of the lower column. The pressure feedback driving mechanism automatically adjusts the position of the adjusting column according to the fluid pressure in the pressure feedback cavity.

[0015] The fluid pressure within the pressure feedback chamber can drive the adjustment column to move via the drive column, thereby adaptively adjusting the volume of the Helmholtz resonant cavity according to changes in the fluid pressure.

[0016] Preferably, the pressure feedback chamber is connected to the Helmholtz resonant chamber through the throttling orifice, so that when the sandblasting nozzle is in operation, the throttling pressure drop generated by the throttling orifice makes the pressure in the pressure feedback chamber higher than the back pressure of the sandblasting nozzle.

[0017] Preferably, the pressure feedback drive mechanism includes a column-shaped seat, an annular groove is provided on the inner wall of the lower column, the column-shaped seat is slidably installed in the annular groove, a damping cavity is provided in the column-shaped seat, a lower connecting rod is slidably installed in the damping cavity, the top end of the lower connecting rod is fixedly connected to the adjusting column, and a return spring is provided in the damping cavity to press the lower connecting rod upward.

[0018] Preferably, a shearing pin is fixedly installed on the surface of the lower column, and the column base is fixed to the lower column by the shearing pin. The return spring is in a compressed state. Under the action of the return spring, the top of the adjusting column presses against the bottom of the upper column and closes the sandblasting nozzle by the adjusting column.

[0019] A separator plug is slidably installed inside the damping cavity. An overflow groove is formed on the surface of the separator plug. The separator plug divides the damping cavity into upper and lower chambers, which are connected through the overflow groove. Both chambers of the damping cavity are filled with viscous damping fluid. The bottom end of the lower connecting rod is fixedly connected to the separator plug. The return spring is arranged on the lower side of the separator plug. An end plug for sealing the bottom port of the damping cavity is threaded onto the cylindrical seat.

[0020] Preferably, the regulating column has a first flow channel hole that runs vertically through the throttle orifice along the same axis, and the column base has a second flow channel hole that runs vertically through the throttle orifice along the same axis. The throttle orifice, the first flow channel hole, and the second flow channel hole form a hollow flow channel that runs vertically through the sandblaster, allowing fluid to pass through to operate downstream downhole tools.

[0021] Preferably, the sandblaster further includes a sealing ball, the orifice diameter of the throttling orifice is d1, the orifice diameter of the first flow channel orifice is d2, the diameter of the sealing ball is d3, and d1 > d3 > d2;

[0022] When a sealing ball is thrown into the pressure feedback chamber and blocks the first flow channel hole, the fluid pressure reaches the first threshold, the shearing pin is sheared and fails, and the column seat moves downward away from the upper column, causing the sandblasting nozzle to change from a closed state to an open state.

[0023] Preferably, a flow guide sleeve is fixedly installed inside the upper column. The inner hole of the flow guide sleeve is a funnel-shaped structure with a larger upper diameter and a smaller lower diameter, and the lower end of the flow guide sleeve is coaxial with the throttling orifice. The upper end of the upper column is a threaded interface, and the lower end of the lower column is a threaded interface. The threaded interfaces are used to connect the fracturing tubing string.

[0024] The present invention has the following beneficial effects:

[0025] 1. The sandblasting device proposed in this invention converts a continuous sand-carrying fluid flow into a high-frequency, high-pressure pulse jet through a built-in Helmholtz resonant cavity. This pulse jet, by concentrating energy release (increasing instantaneous impact force) and utilizing dynamic water hammer and rock fatigue effects, can more efficiently break rocks. This not only facilitates the formation of deep-penetrating main fractures but also increases the complexity of the fractures, thereby achieving a larger reservoir stimulation volume and higher conductivity under the same construction scale.

[0026] Compared to existing technologies that use ground pumps to generate pressure fluctuations, this invention directly generates high-frequency, high-amplitude, and stable pure fluid dynamic pulses at the sandblasting nozzle. The pulse frequency and intensity far exceed the range achievable by ground pumps, and the energy transfer efficiency is extremely high. This solves the technical problem of severe attenuation, distortion, and delay in pulse signals generated on the ground after being transmitted over long distances through tubing.

[0027] 2. The sandblasting device proposed in this invention combines a pressure feedback mechanism with the volume adjustment of a Helmholtz resonant cavity, achieving adaptive adjustment of the sandblasting device's operating frequency to formation pressure. When the operating pressure is high, it automatically tends towards low-frequency, high-energy impact, which is beneficial for fracturing hard formations; when the operating pressure is low, it automatically tends towards high-frequency, dense impact, which is beneficial for forming complex fracture networks in soft formations. This adaptive capability greatly enhances the tool's adaptability to different operating conditions and its fracturing effect.

[0028] 3. The sandblasting device proposed in this invention provides adjustable damping force for the movement of the adjusting column through the design of a damping cavity and viscous damping fluid in the pressure feedback drive mechanism. This design not only ensures smooth movement of the adjusting column and prevents component damage caused by high-frequency oscillations, but also effectively isolates the interference of high-frequency pressure pulsations in the Helmholtz resonant cavity on the adjusting mechanism, thereby ensuring the stability and reliability of the adaptive adjustment process and extending the tool's service life.

[0029] 4. The sandblaster proposed in this invention achieves both the sandblasting nozzle opening and adaptive adjustment functions through a purely mechanical structure, requiring no electronic sensors or external control circuitry. Its core pressure sensing, signal transmission, and execution adjustment are all accomplished through the physical interaction of fluid pressure with springs and damping fluid. Compared to existing rotary valve-type pulsers, it has fewer moving pairs and no high-speed rotating parts. It exhibits strong resistance to high temperature, high pressure, and strong vibration. Furthermore, by disturbing the flow field through the moving adjustment column, it can promptly flush away any sand particles that may be attached or initially deposited within the Helmholtz resonant cavity. It is particularly suitable for the extremely harsh working environment of oilfield downholes, offering high reliability and low maintenance requirements. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the three-dimensional structure of the sandblasting device proposed in this invention. Figure 1 .

[0031] Figure 2This is a schematic diagram of the three-dimensional structure of the sandblasting device proposed in this invention. Figure 2 .

[0032] Figure 3 This is a three-dimensional structural diagram of the upper column proposed in this invention.

[0033] Figure 4 This is a partial cross-sectional three-dimensional structural diagram of the sandblaster proposed in this invention.

[0034] Figure 5 This is a schematic diagram of the cross-sectional structure of the sandblaster proposed in this invention.

[0035] Figure 6 for Figure 5 A schematic diagram of the structure of the central column type base.

[0036] Figure 7 for Figure 5 Schematic diagram of the structure of the central adjustment column and column base Figure 1 In this process, after the sealing ball is released, the pressure feedback chamber drives the regulating column to move downward with pressure P1.

[0037] Figure 8 for Figure 5 Schematic diagram of the structure of the central adjustment column and column base Figure 2 In this process, after the sealing ball is released, the pressure feedback chamber drives the regulating column to move downward with pressure P2.

[0038] Figure 9 This is a time-domain waveform diagram of the sandblasting nozzle pressure of the sandblaster in Embodiment 3 of the present invention.

[0039] Figure 10 This is a Fast Fourier Transform (FFT) spectrum of the sandblasting nozzle pressure signal of the sandblaster in Embodiment 3 of the present invention.

[0040] Figure 11 This is a comparison chart of the theoretical calculation value and the measured value of the relationship between the working pressure and the resonant frequency of the sandblaster in Embodiment 3 of the invention.

[0041] Figure 12 This is a comparison chart of the theoretical calculation value and the measured value of the relationship between the working pressure of the sandblaster and the displacement of the regulating column in Embodiment 3 of the invention.

[0042] In the picture:

[0043] 100. Upper column; 101. Pressure feedback chamber; 102. Throttling orifice; 103. Drive column; 104. Guide sleeve;

[0044] 200. Intermediate column; 201. Helmholtz resonant cavity; 202. Sandblasting nozzle;

[0045] 300. Lower column; 301. Adjusting column; 302. Shear pin; 303. First flow channel hole;

[0046] 400. Column base; 401. Damping cavity; 402. Lower connecting rod; 403. Separator plug; 404. Overflow groove; 405. End plug; 406. Second flow channel hole; 407. Return spring;

[0047] 500, Sealed ball. Detailed Implementation

[0048] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0049] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0050] Example 1

[0051] Reference Figure 1 , Figure 2 This invention provides a sandblasting device for oilfield formation fracturing, which mainly consists of three modules: an upper column 100, a middle column 200, and a lower column 300. The upper column 100 contains a pressure feedback chamber 101 responsible for sensing fluid pressure; the middle column 200 contains a Helmholtz resonant cavity 201 responsible for generating pulsed jets; and the lower column 300 integrates a pressure feedback drive mechanism for automatically adjusting the volume of the Helmholtz resonant cavity 201 according to pressure.

[0052] For details, please refer to Figure 3 , Figure 5 The upper column 100 has a threaded interface at its top for connecting to the upper fracturing tubing. The bottom of the pressure feedback chamber 101 inside the upper column 100 has a through-hole throttling orifice 102 and a slide hole. A guide sleeve 104 is installed inside the upper column 100. The inner hole of the guide sleeve 104 is funnel-shaped, wider at the top and narrower at the bottom, and its lower end is coaxial with the throttling orifice 102, guiding the sand-carrying fluid towards the throttling orifice 102. A drive column 103 is slidably installed in the slide hole at the bottom of the pressure feedback chamber 101.

[0053] refer to Figure 7 , Figure 8 The surface of the intermediate column 200 is provided with a sandblasting nozzle 202 that communicates with the Helmholtz resonant cavity 201, and the intermediate column 200 is threadedly connected to the bottom of the upper column 100.

[0054] refer to Figure 5 , Figure 6 The lower end of the lower column 300 has a threaded interface for connecting the lower fracturing tubing. An adjusting column 301, which extends into the Helmholtz resonant cavity 201, is slidably installed inside the lower column 300. The bottom end of the drive column 103 is fixedly connected to the adjusting column 301. A pressure feedback drive mechanism is provided at the bottom of the lower column 300, which automatically adjusts the position of the adjusting column 301 according to the fluid pressure in the pressure feedback cavity 101.

[0055] Among them, such as Figure 6 As shown, the pressure feedback drive mechanism includes a column base 400, an annular groove is provided on the inner wall of the lower column 300, the column base 400 is slidably installed in the annular groove, a damping cavity 401 is provided in the column base 400, a lower connecting rod 402 is slidably installed in the damping cavity 401, the top end of the lower connecting rod 402 is fixedly connected to the adjusting column 301, and a return spring 407 is provided in the damping cavity 401 to press the lower connecting rod 402 upward.

[0056] A shear pin 302 is fixedly installed on the surface of the lower column 300, and the column base 400 is fixed to the lower column 300 by the shear pin 302. The return spring 407 is in a compressed state. Under the action of the return spring 407, the top of the adjusting column 301 presses against the bottom of the upper column 100, and the sandblasting nozzle 202 is closed by the adjusting column 301. Figure 5 As shown.

[0057] like Figure 6 As shown, a partition plug 403 is slidably installed in the damping cavity 401. An overflow groove 404 is provided on the surface of the partition plug 403. The partition plug 403 divides the damping cavity 401 into upper and lower chambers, and the upper and lower chambers are connected through the overflow groove 404. Both upper and lower chambers of the damping cavity 401 are filled with viscous damping fluid. The bottom end of the lower connecting rod 402 is fixedly connected to the partition plug 403. A return spring 407 is arranged on the lower side of the partition plug 403. An end plug 405 that seals the bottom port of the damping cavity 401 is threaded onto the cylindrical seat 400.

[0058] It should be noted that, as a preferred option, the viscous damping fluid is high-viscosity methyl silicone oil, with a dynamic viscosity in the range of 1000-5000 cSt. This choice is based on its excellent thermal stability, chemical inertness, and wide temperature range operation capability, ensuring long-term reliable operation of the damping mechanism under high-temperature and high-pressure downhole environments. When changes in downhole construction pressure cause a change in pressure within the pressure feedback chamber 101, the drive column 103 drives the adjustment column 301 and the separator plug 403 to move. During this process, the viscous damping fluid is forced to flow between the upper and lower chambers through the overflow groove 404 on the surface of the separator plug 403. Due to the high viscosity of the damping fluid and the limited flow area of ​​the overflow groove 404, significant viscous resistance is generated. This resistance effectively suppresses the oscillation tendency of the adjustment column 301, allowing it to move smoothly and slowly to a new equilibrium position, thus achieving stable adjustment of the volume of the Helmholtz resonant cavity 201.

[0059] like Figure 5 As shown, the regulating column 301 has a first flow channel hole 303 that is coaxial with the throttle hole 102 and passes through vertically, and the column base 400 has a second flow channel hole 406 that is coaxial with the throttle hole 102 and passes through vertically. The throttle hole 102, the first flow channel hole 303 and the second flow channel hole 406 form a hollow flow channel that passes through the sandblaster vertically, which is used to allow fluid to pass through to operate downstream downhole tools (such as packers).

[0060] like Figure 7 As shown, the sandblaster also includes a sealing ball 500, the orifice diameter of the throttling orifice 102 is d1, the orifice diameter of the first flow channel orifice 303 is d2, and the diameter of the sealing ball 500 is d3, where d1 > d3 > d2. When the sealing ball 500 is thrown into the pressure feedback chamber 101 and the sealing ball 500 blocks the first flow channel orifice 303, when the fluid pressure in the pressure feedback chamber 101 reaches the first threshold (P = 25 MPa), the shear pin 302 is sheared and fails. After the shear pin 302 fails, the column seat 400 loses its radial fixation and moves downward away from the upper column 100, causing the sandblasting port 202 to change from the closed state to the open state.

[0061] Since the pressure feedback chamber 101 is connected to the Helmholtz resonant chamber 201 through the throttling orifice 102, when the sandblasting nozzle 202 is open, the throttling pressure drop generated by the throttling orifice 102 makes the pressure in the pressure feedback chamber 101 higher than the back pressure of the sandblasting nozzle 202. The fluid pressure in the pressure feedback chamber 101 can drive the adjusting column 301 to move via the driving column 103, thereby adaptively adjusting the volume of the Helmholtz resonant chamber 201 according to changes in fluid pressure, as detailed below:

[0062] like Figure 7 , Figure 8As shown, after the sandblasting nozzle 202 is opened, the high-pressure sand-carrying fluid is mainly ejected from the sandblasting nozzle 202. At the same time, due to the throttling effect of the throttling orifice 102, the pressure feedback chamber 101 always maintains a fluid pressure (P1 or P2) that is higher than the back pressure of the sandblasting nozzle 202.

[0063] This pressure P1 or P2 acts continuously on the end face of the drive column 103, generating a downward force (F1). This force is transmitted through the drive column 103 to the adjusting column 301, attempting to compress the return spring 407 and cause it to move downward. At the same time, the return spring 407 provides a restoring force in the opposite direction (F2). The final equilibrium position of the adjusting column 301 is determined by the equilibrium point of these two forces (F1=F2).

[0064] When the strata are hard and the construction pressure is high, the pressure of the high-pressure sand-carrying fluid rises to P1 or P2, where F1 > F2, breaking the balance and forcing the regulating column 301 to move downward. This causes the upper end of the regulating column 301 to withdraw more from the Helmholtz resonant cavity 201, increasing the effective volume (V) of the Helmholtz resonant cavity 201. According to the Helmholtz resonant frequency formula (f∝√(A / (VL))), with the throat cross-sectional area (A) and length (L) remaining unchanged, the increase in the volume (V) of the Helmholtz resonant cavity 201 will lead to a decrease in the system's natural resonant frequency (f).

[0065] Pulse generation principle: When the high-pressure sand-carrying fluid flows through the throat (throttle orifice 102) and is injected into the Helmholtz resonance cavity 201, it generates violent vortices and pressure disturbances within the cavity. These disturbances are reflected and superimposed within the cavity. When their frequency approaches the inherent Helmholtz resonance frequency f of the structure (f is determined by the cavity volume V, the throat cross-sectional area A, and the length L, satisfying the relationship f ∝√(A / (V·L))), resonance will occur, forming a stable, high-amplitude pressure oscillation. This pressure oscillation is transmitted from the sand-jet nozzle 202, thus converting the continuous inlet flow into a high-frequency, high-pressure pulse jet. It is worth mentioning that the core of this pulse generation mechanism is based on the Helmholtz resonance principle, which is also applicable in liquid media and can generate strong pressure oscillations. For details, see the reference: Wang Zefeng, Hu Yongming, Xiong Shuidong, et al. Influence of cavity wall elasticity on the resonant frequency of underwater small cylindrical Helmholtz resonator [J]. Acta Physica Sinica, 2009, 58(04):2507-2512.

[0066] The engineering effect of varying the pulse frequency of the 202 blasting nozzle:

[0067] like Figure 8As shown, low-frequency pulses (at high V): When the strata are hard (high construction pressure P2) leading to an increase in volume V and a decrease in frequency f, the resulting pulses have longer periods, longer durations of single injections, more concentrated energy, and larger impulses. This "hammer-like" impact is more conducive to initiating and extending cracks in hard rock.

[0068] like Figure 7 As shown, high-frequency pulses (at low V): In softer formations (low construction pressure P1), the volume V decreases and the frequency f increases. This results in pulses with short periods and high frequency, with even higher impact frequencies. This "impact drill" effect can more effectively utilize the fatigue failure mechanism of rocks, generating more microcrack networks at and around the fracture tip, thereby increasing fracture complexity and reservoir stimulation volume (SRV). For details on the mechanism, see the reference: Chen Jiangzhan, Cao Han, Wu Jingjing. Study on the time effect of coal and rock fracture creation under pulsed hydraulic fracturing [C] / / Proceedings of the 18th National Academic Conference on Exploration Engineering (Rock and Soil Drilling Engineering) Technology, Proceedings of the Exploration Engineering Professional Committee of the Geological Society of China. Key Laboratory of Nonferrous Metal Metallogenic Prediction, Ministry of Education, Central South University; School of Earth Sciences and Information Physics, Central South University; Hunan Provincial Key Laboratory of Shale Gas Resource Utilization; 2015: 559-565.

[0069] The working principle of the sandblasting device proposed in this invention is as follows:

[0070] Initial state and ball drop initiation: When the tool is lowered into the well, the force of the return spring 407 moves the adjusting column 301 upward, closing the sandblasting port 202, opening the central flow channel, and allowing fluid to flow down to the next stage tool. When fracturing of this layer is required, a sealing ball 500 (whose diameter d3 satisfies d1>d3>d2) is dropped. The ball sets on the upper end of the first flow channel hole 303, blocking the flow channel. The pressure increases and shears the shear pin 302.

[0071] Enable and adaptive adjustment: such as Figure 7 and Figure 8 As shown, after the shearing nail 302 cuts, the column base 400 loses its fixation and moves downward under the action of fluid pressure, driving the adjusting column 301 to move downward, thereby opening the sandblasting nozzle 202. Afterward, the tool enters an adaptive working mode: the pressure in the pressure feedback chamber 101 is maintained through the throttling orifice 102 and is always higher than the back pressure of the sandblasting nozzle 202. This pressure difference acts on the driving column 103, generating a downward force F1, which balances with the force F2 of the return spring 407. When changes in the stratum cause fluctuations in construction pressure, the balance between F1 and F2 is broken, and the adjusting column 301 will automatically move to a new position, changing the volume V of the Helmholtz resonant cavity 201, thereby adjusting the pulse frequency f (f∝1 / √V), achieving intelligent self-adaptation.

[0072] It should be noted that the pressures P, P1, and P2 of the sand-carrying fluid are controlled by the ground pump unit, which directly generates high-frequency, high-amplitude, and stable pure fluid dynamic pulses at the sand-spraying nozzle 202. The pulse frequency and intensity far exceed the range that can be achieved by the ground pump adjustment, and the energy transfer efficiency is extremely high. This solves the technical problem of severe attenuation, distortion, and delay that exists after the pulse signal generated on the ground is transmitted through a long-distance tubing.

[0073] Example 2

[0074] The difference between this embodiment and Embodiment 1 is that the lower column 300 is a closed end (not fully shown in the figure, but this can be achieved by omitting the second flow channel hole 406 and closing the lower end). Therefore, this tool does not have a through flow channel and is usually used as the end tool of a fracturing string for single-layer fracturing.

[0075] Workflow: During construction, all fluid is ejected from the sandblasting nozzle 202. Its adaptive adjustment principle is exactly the same as that of Example 1: the pressure in the pressure feedback chamber 101 drives the adjustment column 301 to change the volume of the Helmholtz resonant chamber 201, thereby adjusting the pulse frequency of the sand-carrying flow ejected from the sandblasting nozzle 202 to meet the usage requirements of different construction scenarios.

[0076] It is worth noting that in Embodiments 1 and 2 above, the axial movement of the regulating column 301 within the Helmholtz resonant cavity 201 constitutes a dynamic self-cleaning mechanism. The periodic movement of the regulating column 301 in response to downhole pressure changes continuously alters the instantaneous geometric volume and inner wall profile of the Helmholtz resonant cavity 201. This dynamic change effectively disrupts the flow field environment required for stable deposition of proppant (sand particles) in the proppant-carrying fluid. Simultaneously, the relative motion and local flow field disturbance generated between the surface of the moving regulating column 301 and the fixed inner wall of the Helmholtz resonant cavity 201 promptly flush away any sand particles that may have adhered or initially deposited. This mechanism, in conjunction with the main pulse jet ejected from the jet nozzle 202, jointly prevents the accumulation of sand particles inside the Helmholtz resonant cavity 201, thereby reducing the risk of blockage and further improving the long-term operational reliability of the tool under harsh well conditions.

[0077] Example 3

[0078] To verify that the sandblaster of the present invention can generate a stable pressure pulse during sandblasting operations and can adaptively adjust the pulse frequency according to the pressure, the following bench test was conducted.

[0079] 1. Key parameters of the sandblaster: Orifice 102: Diameter dh=45 mm, length Lh=40 mm, effective length Leff=Lh+0.8dh;

[0080] • Helmholtz resonant cavity 201 (cylindrical cavity): inner diameter Dc=100 mm, effective length range L=92-180 mm, corresponding effective volume range V=0.72-1.41 L;

[0081] • Single blasting nozzle 202: Single-hole structure (hole diameter can be selected according to displacement), blasting nozzle 202 is connected to Helmholtz resonant cavity 201;

[0082] • Damping chamber 401: filled with viscous damping fluid (methyl silicone oil 1000~5000cSt);

[0083] • Reset spring 407: stiffness k=1.2×106 N / m, preload F0=50 kN.

[0084] 2. Experimental Apparatus and Methods

[0085] The experiment employed a high-pressure circulating test bench, using fracturing fluid (which could be water / slickwater) as the working medium. After the shear pin 302 was sheared, detection was performed. A high-frequency dynamic pressure sensor was placed at the blast nozzle 202 to collect the pressure pulsation signal p(t) near the nozzle, with a sampling frequency of at least 500Hz. After mean removal and windowing of p(t), a Fast Fourier Transform (FFT) was used to obtain the spectrum |P(f)|, with the frequency corresponding to the main peak of the spectrum taken as the pulse frequency f. Simultaneously, a displacement sensor recorded the displacement x of the regulating column 301 to establish the pressure-displacement relationship.

[0086] 3. Experimental Results and Analysis

[0087] (1) Time-domain characteristics of pressure pulsation

[0088] like Figure 9 As shown, the pressure signal p(t) near the sandblasting nozzle 202 exhibits obvious periodic pulsation with good waveform repeatability, indicating that the sandblaster can generate stable pressure pulse output under sandblasting conditions.

[0089] (2) Frequency domain dominant frequency and harmonic characteristics

[0090] like Figure 10 As shown, for Figure 9 The spectrum obtained after performing FFT on p(t) shows a clear dominant frequency peak and harmonic components, indicating that the pressure pulsation energy is concentrated near the dominant frequency, and the pulse is not a random fluctuation but has stable resonance characteristics.

[0091] (3) Pressure-frequency relationship (comparison between theory and practice)

[0092] like Figure 11As shown, the extracted main frequency f under different pressure conditions changes continuously with pressure, and the measured data points are generally consistent with the theoretical curve calculated based on the Helmholtz resonance relationship. This result demonstrates that the present invention achieves the technical effect of adaptively adjusting the pulse frequency with pressure by adjusting the effective volume of the Helmholtz resonant cavity 201 through pressure feedback, and that this frequency modulation law is predictable and designable.

[0093] (4) Pressure-displacement relationship (effectiveness of drive mechanism)

[0094] like Figure 12 As shown, the displacement x of the regulating column 301 has a monotonic relationship with the pressure change. The measured data is basically consistent with the theoretical relationship, indicating that the pressure feedback drive mechanism can stably convert the pressure change into the axial displacement of the regulating column 301, thereby changing the effective volume of the Helmholtz resonant cavity 201 and realizing the linkage adjustment of "pressure-displacement-frequency".

[0095] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A sandblasting device for oilfield formation fracturing, characterized in that, include: The upper column (100) has a pressure feedback chamber (101) inside. The bottom of the pressure feedback chamber (101) is provided with a throttling hole (102) and a slide hole that run vertically through it. A drive column (103) is slidably installed in the slide hole. The intermediate column (200) has a Helmholtz resonant cavity (201) inside. The surface of the intermediate column (200) is provided with a sandblasting nozzle (202) communicating with the Helmholtz resonant cavity (201). The intermediate column (200) is threadedly connected to the bottom of the upper column (100). The lower column (300) has an adjusting column (301) that can extend into the Helmholtz resonant cavity (201) slidably installed inside it. The bottom end of the driving column (103) is fixedly connected to the adjusting column (301). The bottom of the lower column (300) is provided with a pressure feedback driving mechanism. The pressure feedback driving mechanism automatically adjusts the position of the adjusting column (301) according to the fluid pressure in the pressure feedback cavity (101). The fluid pressure in the pressure feedback chamber (101) can drive the adjustment column (301) to move through the drive column (103), thereby adaptively adjusting the volume of the Helmholtz resonant chamber (201) according to the change of the fluid pressure.

2. A sandblasting device for oilfield formation fracturing according to claim 1, characterized in that: The pressure feedback chamber (101) is connected to the Helmholtz resonant chamber (201) through the throttling orifice (102), so that when the sandblasting port (202) is in operation, the throttling pressure drop generated by the throttling orifice (102) makes the pressure in the pressure feedback chamber (101) higher than the back pressure of the sandblasting port (202).

3. A sandblasting device for oilfield formation fracturing according to claim 1 or 2, characterized in that: The pressure feedback drive mechanism includes a column base (400), the inner wall of the lower column (300) is provided with an annular groove, the column base (400) is slidably installed in the annular groove, a damping cavity (401) is opened in the column base (400), a lower connecting rod (402) is slidably installed in the damping cavity (401), the top end of the lower connecting rod (402) is fixedly connected to the adjusting column (301), and a return spring (407) is provided in the damping cavity (401) to press the lower connecting rod (402) upward.

4. A sandblasting device for oilfield formation fracturing according to claim 3, characterized in that: A shear pin (302) is fixedly installed on the surface of the lower column (300), and the column base (400) is fixed to the lower column (300) by the shear pin (302). The return spring (407) is in a compressed state. Under the action of the return spring (407), the top of the adjusting column (301) presses against the bottom of the upper column (100), and the sandblasting nozzle (202) is closed by the adjusting column (301).

5. A sandblasting device for oilfield formation fracturing according to claim 4, characterized in that: A separator plug (403) is slidably installed inside the damping cavity (401). An overflow groove (404) is provided on the surface of the separator plug (403). The separator plug (403) divides the damping cavity (401) into two chambers, and the two chambers are connected through the overflow groove (404). Both chambers of the damping cavity (401) are filled with viscous damping fluid. The bottom end of the lower connecting rod (402) is fixedly connected to the separator plug (403). The reset spring (407) is arranged on the lower side of the separator plug (403). The cylindrical seat (400) is threaded with an end plug (405) that seals the bottom port of the damping cavity (401).

6. A sandblasting device for oilfield formation fracturing according to claim 5, characterized in that: The regulating column (301) has a first flow channel hole (303) that is coaxial with the throttle hole (102) and extends vertically through it. The column base (400) has a second flow channel hole (406) that is coaxial with the throttle hole (102) and extends vertically through it. The throttle hole (102), the first flow channel hole (303), and the second flow channel hole (406) form a hollow flow channel that extends vertically through the sandblaster, which allows fluid to pass through to operate downstream downhole tools.

7. A sandblasting device for oilfield formation fracturing according to claim 6, characterized in that: The sandblaster also includes a sealing ball (500), the orifice (102) has a diameter of d1, the first flow channel orifice (303) has a diameter of d2, the sealing ball (500) has a diameter of d3, and d1 > d3 > d2; When a sealing ball (500) is thrown into the pressure feedback chamber (101) and the sealing ball (500) blocks the first flow channel hole (303), when the fluid pressure reaches the first threshold, the shearing nail (302) is sheared and fails, and the column seat (400) moves downward away from the upper column (100), so that the sandblasting nozzle (202) changes from the closed state to the open state.

8. A sandblasting device for oilfield formation fracturing according to claim 1, characterized in that: A flow guide sleeve (104) is fixedly installed inside the upper column (100). The inner hole of the flow guide sleeve (104) is a funnel-shaped structure with a larger upper part and a smaller lower part, and the lower port of the flow guide sleeve (104) is coaxial with the throttling hole (102).

9. A sandblasting device for oilfield formation fracturing according to claim 1, characterized in that: The upper end of the upper column (100) is an upper threaded interface, and the lower end of the lower column (300) is a lower threaded interface. The upper threaded interface and the lower threaded interface are used to connect the fracturing tubing.

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