Fork-based downhole flowmeter

Abstract

The present invention provides a downhole flowmeter based on a tuning fork. The downhole flowmeter based on a tuning fork includes a tuning fork vibration generator, an optical fiber vibration sensor, and an optical fiber signal transmission device. The tuning fork vibration generator is composed of a plurality of tuning forks, and generates vibrations with corresponding frequencies according to different fluid flow rates. The optical fiber vibration sensor is connected to the optical fiber signal transmission device, receives the vibration signal from the tuning fork vibration generator, and transmits the vibration signal to the optical fiber signal transmission device. The optical fiber signal transmission device receives the vibration signal from the optical fiber vibration sensor and transmits the vibration signal to an external wellhead ground analyzer. The downhole flowmeter based on a tuning fork establishes a corresponding relationship between the resonance frequencies of a plurality of circular tuning forks and the fluid flow rate to achieve downhole flow measurement without electronic equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield development, and particularly to a downhole flowmeter based on a tuning fork. Background Art

[0002] A large number of downhole intelligent devices use electronic components. However, due to the high temperature downhole, the electronic devices age and are damaged, shortening the life of the intelligent string. Therefore, it is considered to use mechanical and optical fiber testing devices without electronic components downhole and apply them to downhole testing technology to achieve the purpose of extending the life of downhole intelligent devices and amplifying useful signals.

[0003] In the petroleum industry, a large number of downhole intelligent devices in oil and water wells use electronic components. However, due to the high temperature downhole and the self-heating of the electronic devices after being powered on, the electronic devices age and are damaged. This greatly shortens the service life of downhole intelligent devices and reduces the life of downhole intelligent strings. Therefore, it is considered to use mechanical and optical fiber testing devices without electronic components downhole and apply them to downhole testing technology to achieve the purpose of extending the life of downhole intelligent devices and amplifying useful signals.

[0004] In the Chinese patent application with the application number: CN201880068893.X, it relates to a multiphase flowmeter with a tuning fork for measuring flow rate and components. The fluid flows from bottom to top; a Venturi flowmeter is used to generate turbulence; the vibration frequency of the tuning fork is used to determine the fluid density value of the multiphase fluid; an electric resonator is applied to the tuning fork to vibrate the tuning fork at the first frequency; the tuning fork vibrates at the second frequency under the action of turbulent flow, and the second frequency is related to the fluid density; the fluid density is also determined by means of temperature; a ground controller is used to analyze the signals transmitted from downhole.

[0005] In the Chinese patent application with the application number: CN201821938848.9, it relates to a mine explosion-proof and intrinsically safe ultrasonic flowmeter, belonging to the field of ultrasonic flowmeters. The mine explosion-proof and intrinsically safe ultrasonic flowmeter includes a test tube, and the left end of the test tube includes a secondary sound generating tube. Through the coordinated setting of the sound receiving funnel, the sound transmission block, the sound guiding spring, the sound guiding needle, the sound amplifying groove, the rotating connecting piece, the connecting rod, the round hammer, the inner tube, the bearing spring, the fixing block, the tuning fork and the sound guiding fluid, the external sound can be transmitted to the sound transmission block through the sound receiving funnel, so that the sound guiding needle and the sound guiding spring on the sound transmission block can be affected by the sound vibration and start to vibrate, so that the vibration is transmitted to the sound amplifying groove through the sound transmission block, so that the connecting rod in the sound amplifying groove is shaken up and down in the sound amplifying groove through the rotating connecting piece under the influence of the vibration, so that the round hammer on the connecting rod hammers up and down in the tuning fork, so that the tuning fork emits sound waves.

[0006] In the Chinese patent application with the application number: CN201610579578.6, it relates to a parallel U-tube mass measurement system, which is characterized by including a parallel U-tube, a flow distributor, an electromagnetic vibrator, and a displacement signal sensor. The flow inlet end of the parallel U-tube is connected to the inlet end of the flow distributor, and the flow outlet end of the parallel U-tube is connected to the outlet end of the flow distributor. The electromagnetic vibrator is installed at the top of the parallel U-tube. There are two displacement signal sensors, and the two displacement signal sensors are respectively installed on both sides of the parallel U-tube.

[0007] In the Chinese patent application with the application number: CN201911189028.3, it relates to a method and device for determining the phase components of a multiphase fluid flow. Specifically, the present invention discloses a method for determining the phase components of a multiphase fluid flow in a fluid pipeline. The method includes: using a vibration sensor 22 to obtain a vibration signal from the fluid flow. The vibration sensor 22 includes a target disposed in the fluid flow, and the target vibrates in response to the fluid flow in the fluid pipeline. Analyzing the vibration signal to determine a first energy parameter related to the energy of the vibration signal in a first frequency band and a second energy parameter related to the energy of the vibration signal in a second frequency band; and using the first and second energy parameters to determine a phase component parameter (such as a dryness parameter) related to the phase components of the fluid flow.

[0008] In the Chinese patent application with the application number: CN201911189028.3, it relates to a method and device for determining the phase components of a multiphase fluid flow. Specifically, the present invention discloses a method for determining the phase components of a multiphase fluid flow in a fluid pipeline. The method includes: using a vibration sensor 22 to obtain a vibration signal from the fluid flow. The vibration sensor 22 includes a target disposed in the fluid flow, and the target vibrates in response to the fluid flow in the fluid pipeline. Analyzing the vibration signal to determine a first energy parameter related to the energy of the vibration signal in a first frequency band and a second energy parameter related to the energy of the vibration signal in a second frequency band; and using the first and second energy parameters to determine a phase component parameter (such as a dryness parameter) related to the phase components of the fluid flow.

[0009] The above prior arts are all quite different from the present invention and fail to solve the technical problems we want to solve. Therefore, we have invented a new tuning fork-based downhole flowmeter. Summary of the Invention

[0010] The object of the present invention is to provide a downhole flowmeter that establishes a corresponding relationship between the resonant frequencies of multiple circular tuning forks and the fluid flow velocity and has no electronic devices.

[0011] The object of the present invention can be achieved by the following technical measures: a downhole flowmeter based on a tuning fork, which includes a tuning fork vibration generator, an optical fiber vibration sensor, and an optical fiber signal transmission device. The tuning fork vibration generator consists of multiple tuning forks, which generate vibrations with corresponding frequencies according to different fluid flow rates. The optical fiber vibration sensor is connected to the optical fiber signal transmission device, receives the vibration signal from the tuning fork vibration generator, and transmits the vibration signal to the optical fiber signal transmission device. The optical fiber signal transmission device receives the vibration signal from the optical fiber vibration sensor and transmits the vibration signal to an external wellhead ground analyzer.

[0012] The object of the present invention can also be achieved by the following technical measures:

[0013] The tuning fork vibration generator is installed inside the tubing, and the optical fiber vibration sensor is installed outside the tubing and embedded in the outer wall of the tubing.

[0014] The optical fiber signal transmission device is composed of communication optical fibers.

[0015] The multiple tuning forks are all circular, and the two fork arms of the same tuning fork are exactly the same; the diameters of the multiple tuning forks are all the same as D, and the size of the opening is g, and the g of each tuning fork can be different.

[0016] The multiple tuning forks are fixed on a connection line coaxially at a certain interval. The connection line is a straight line or a spiral line with the same radius as the circular tuning fork.

[0017] The lengths and thicknesses of the fork arms of different tuning forks are different, and they gradually taper from the fixed point to the suspended point. The natural vibration frequencies of different tuning forks are different, and the fixed point of the tuning fork is the corresponding position of the opening.

[0018] The multiple tuning forks are fixed on a straight strip of metal at a certain interval. The straight strip of metal is connected to the inner wall of the pipe string and transmits the vibration of the tuning fork to the tubing.

[0019] The cross-section of the multiple tuning forks is trapezoidal, where the lower base of the trapezoid is the upstream-facing surface, the upper base of the trapezoid is the downstream-facing surface, the long waist of the trapezoid is close to the central axis of the tubing string, and the short waist of the trapezoid is close to the inner wall of the tubing. When the fluid flows through the downhole flowmeter based on the tuning fork, behind the upstream-facing surface of each tuning fork, that is, at the long waist of the trapezoid, turbulence is generated. The frequency of the turbulence is proportional to the fluid flow rate, and the relationship between the frequency and the flow rate is:

[0020] f = Sx * V / d Formula 1

[0021] Where, f: vortex frequency; V: fluid velocity; d: width of the upstream-facing surface of the vortex generator; Sx: correction coefficient;

[0022] Moreover, the turbulence will further disturb the subsequent tuning forks, causing the subsequent tuning forks to be vibrated by the turbulence. Among them, the tuning fork with the natural vibration frequency consistent with the turbulence vibration frequency generates the largest vibration amplitude.

[0023] The downhole flowmeter based on tuning forks in the present invention realizes the response and amplification of signals such as downhole flow velocity and components, and transmits them to the downhole optical fiber sensor. The present invention adopts a downhole non-electronic device and a tuning fork with a specific shape to realize the response and amplification of signals such as downhole flow velocity and components, and transmits them to the downhole optical fiber sensor.

[0024] The innovation of the present invention lies in the adoption of a mechanical structure. This mechanical structure can generate responses with specific frequencies and amplitudes to different flow velocities of downhole fluids. This response is received by the optical fiber sensor and transmitted to the wellhead. It not only realizes no electronic components downhole, effectively avoiding the aging and damage of downhole testing equipment at high temperatures and extending the service life, but also can specifically amplify the downhole flow-related signals, solving the problems of over-sensitivity of optical fiber sensors and high signal complexity. It is a downhole flow testing device with low complexity, long service life, and high reliability. Brief Description of the Drawings

[0025] Figure 1 It is a structural diagram of a specific embodiment of the downhole flowmeter based on tuning forks of the present invention;

[0026] Figure 2 It is a schematic diagram of the circular tuning fork structure in a specific embodiment of the present invention;

[0027] Figure 3 It is a schematic diagram of the cross-section of the tuning fork in the pipe string in a specific embodiment of the present invention. Detailed Description of the Embodiment

[0028] It should be noted that the following detailed description is exemplary and is intended to provide further illustration of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which the present invention belongs.

[0029] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, and / or combinations thereof.

[0030] The downhole flowmeter based on a tuning fork according to the present invention consists of three parts: a tuning fork vibration generator, an optical fiber vibration sensor, and an optical fiber signal transmission device. Among them, the tuning fork vibration generator is the core component: multiple tuning forks are fixed on a connection line in a coaxial manner at a certain interval. This connection line is usually a straight line or a spiral line with the same radius as the circular tuning fork (which can ensure the homogeneity in the circumferential direction). The principle is as follows: when the fluid flows, it pushes the tuning forks and forms eddy currents behind each tuning fork. The frequency of the eddy current is proportional to the velocity of the fluid. The eddy current pushes the tuning forks to vibrate, and the tuning fork with the resonant frequency consistent with the eddy current frequency has the largest vibration amplitude. The vibration is transmitted to the optical fiber vibration sensor and then transmitted to the ground through the optical fiber;

[0031] The following are several specific embodiments of applying the present invention.

[0032] Embodiment 1:

[0033] In a specific Embodiment 1 of applying the present invention, the flowmeter structure consists of three parts: a tuning fork vibration generator 1, an optical fiber vibration sensor 2, and an optical fiber signal transmission device 3, as Figure 1 . The tuning fork vibration generator 1 is installed inside the oil pipe and consists of multiple tuning forks, which can generate vibrations with corresponding frequencies according to different fluid flow velocities; the optical fiber vibration sensor 2 is installed outside the oil pipe and embedded in the outer wall of the oil pipe, and is used to receive the vibrations from the tuning fork vibration generator 1; the optical fiber signal transmission device 3 consists of communication optical fibers and is used to transmit the vibration signals sent from the optical fiber vibration sensor 2 and transmit them to the wellhead ground analyzer.

[0034] Among them, the tuning fork vibration generator 1 is the core component: multiple tuning forks are fixed on a connection line in a coaxial manner at a certain interval. This connection line is usually a straight line or a spiral line with the same radius as the circular tuning fork (which can ensure the homogeneity in the circumferential direction). The principle is as follows: when the fluid flows, it pushes the tuning forks and forms eddy currents behind each tuning fork. The frequency of the eddy current is proportional to the velocity of the fluid. The eddy current pushes the tuning forks to vibrate, and the tuning fork with the resonant frequency consistent with the eddy current frequency has the largest vibration amplitude. The vibration is transmitted to the optical fiber vibration sensor and then transmitted to the ground through the optical fiber.

[0035] Embodiment 2:

[0036] In a specific Embodiment 2 of applying the present invention, the structure of the tuning fork vibration generator is as Figure 2As shown in the figure: Each tuning fork has a circular diameter of D, and the size g of the opening can be set artificially; the fork arms of each tuning fork are circular, and the two fork arms of the same tuning fork are exactly the same; the fork arms of different tuning forks have different lengths and different thicknesses, and can also gradually taper from the fixed point to the suspended point, and the natural vibration frequencies of different tuning forks are different. The fixed point of the tuning fork is the corresponding position of the opening. A downhole flowmeter provided by the present invention has a tuning fork vibration generator composed of a plurality of circular tuning forks with the same radius fixed on a straight metal strip in a coaxial manner at a certain interval. The straight metal strip is connected to the inner wall of the pipe string and transmits the vibration of the tuning fork to the oil pipe. To achieve corresponding differences, the vibration signal generated by the tuning fork with a certain vibration frequency in the fluid flow rate is the strongest;

[0037] Embodiment 3:

[0038] In a specific Embodiment 3 of applying the present invention, as Figure 3 shown in the figure: The cross-section of the tuning fork is trapezoidal, where the lower base of the trapezoid is the flow-facing surface, the upper base of the trapezoid is the backflow surface, the long waist of the trapezoid is close to the center of the pipe string, and the short waist of the trapezoid is close to the inner wall of the pipe string; the working principle of such a structure is that when the fluid flows through the tuning fork type flowmeter, behind the flow-facing surface of each tuning fork, that is, at the long waist of the trapezoid, turbulence is generated, and the frequency of this turbulence is proportional to the flow velocity of the fluid, as shown in Formula 1, and this turbulence will further disturb the subsequent tuning fork, causing the subsequent tuning fork to be vibrated by the turbulence; among them, the tuning fork with the natural vibration frequency consistent with the turbulence vibration frequency generates the largest vibration amplitude. This realizes the association between the flow velocity of the fluid and the vibration of the tuning fork. That is also the key point of the present invention.

[0039] Relationship formula between frequency and flow velocity:

[0040] f = Sx * V / d Formula 1

[0041] f: Vortex frequency; V: Fluid velocity; d: Width of the flow-facing surface of the vortex generator; Sx: Correction coefficient;

[0042] The optical fiber vibration sensor is based on the currently common downhole optical fiber vibration sensor. For the convenience of reliable signal reading, the optical fiber vibration sensor should be embedded in the outer wall of the oil pipe.

[0043] The optical fiber signal transmission device is a common downhole high-temperature optical cable on the market, which is used to transmit downhole signals to the ground signal analyzer.

[0044] The ground signal analyzer is used to transmit and receive optical signals to the downhole optical fiber vibration sensor and analyze the optical signals transmitted from downhole.

[0045] When the present invention is used, one or more downhole flowmeters are connected to the part of the oil pipe string that needs to test the flow rate (such as near the production layer), and are lowered into the well together with the pipe string, asFigure 3 As shown. Multiple downhole flowmeters can share a set of optical fiber signal transmission devices, usually optical cables.

[0046] When the downhole fluid flows, for oil wells, the fluid flows from bottom to top, and for water wells, the fluid flows from top to bottom; the fluid flows through the downhole flowmeter, the tuning fork vibrator generates vibrations, the optical fiber sensor receives the vibrations, and then the optical fiber transmission transmits the signal to the ground for analysis by the ground signal analyzer.

[0047] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or perform equivalent replacements for some of the technical features. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

[0048] Except for the technical features described in the specification, they are all well-known technologies to those skilled in the art.

Claims

1. A downhole flowmeter based on a tuning fork, characterized in that The downhole flowmeter based on a tuning fork includes a tuning fork vibration generator, an optical fiber vibration sensor, and an optical fiber signal transmission device. The tuning fork vibration generator consists of multiple tuning forks, which generate vibrations with corresponding frequencies according to different fluid flow rates. The optical fiber vibration sensor is connected to the optical fiber signal transmission device, receives the vibration signal from the tuning fork vibration generator, and transmits the vibration signal to the optical fiber signal transmission device. The optical fiber signal transmission device receives the vibration signal from the optical fiber vibration sensor and transmits the vibration signal to an external wellhead surface analyzer. The tuning fork vibration generator is installed inside the tubing, and the optical fiber vibration sensor is installed outside the tubing and embedded in the outer wall of the tubing. The optical fiber signal transmission device consists of communication optical fibers. The multiple tuning forks are all circular, and the two fork arms of the same tuning fork are exactly the same. The diameters of the multiple tuning forks are all the same as D, the size of the opening is g, and the openings g of each tuning fork are different. The lengths and thicknesses of the fork arms of different tuning forks are different, and they gradually taper from the fixed point to the suspended point. The natural vibration frequencies of different tuning forks are different, and the fixed point of the tuning fork is the corresponding position of the opening. The multiple tuning forks are fixed on a straight metal strip in a coaxial manner at a certain interval. The straight metal strip is connected to the inner wall of the pipe string and transmits the vibration of the tuning fork to the tubing. The cross-sections of the multiple tuning forks are trapezoidal, where the lower base of the trapezoid is the flow-facing surface, the upper base of the trapezoid is the backflow surface, the long waist of the trapezoid is close to the center of the tubing string, and the short waist of the trapezoid is close to the inner wall of the tubing.

2. The downhole flowmeter based on a tuning fork according to claim 1, wherein When the fluid flows through the downhole flowmeter based on a tuning fork, turbulence is generated behind the flow-facing surface of each tuning fork, that is, at the long waist of the trapezoid. The frequency of the turbulence is proportional to the fluid flow rate. The relationship between the frequency and the flow rate is: f = Sx * V / d Formula 1 Where, f: vortex frequency; V: fluid velocity; d: width of the flow-facing surface of the vortex generator; Sx: correction coefficient. And the turbulence will further disturb the subsequent tuning forks, causing the subsequent tuning forks to be vibrated by the turbulence. Among them, the tuning fork with the natural vibration frequency consistent with the turbulence vibration frequency generates the largest vibration amplitude.

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