Coalbed methane wellbore two-phase flow velocity sensor based on the principle of friction nanogenerator

Abstract

The present invention provides a coalbed methane wellbore two-phase flow velocity sensor based on the principle of a triboelectric nanogenerator. The sensor comprises a circuit board, a short-circuit housing, a connecting rod, and multiple sensor components. The sensor components include a PDMS housing and a first copper electrode, each sleeved on the connecting rod. The PDMS housing surrounds the first copper electrode. A second copper electrode and a PTFE membrane are provided on the inner wall of the PDMS housing. The outer side of the second copper electrode is fixedly bonded to the inner wall of the PDMS housing, and the inner side is bonded to the PTFE membrane. The PTFE membrane surrounds the first copper electrode without contact between the two electrodes. A circuit board connects the first and second copper electrodes. The circuit board calculates the time difference between a single bubble in the two-phase flow passing through the two sensor components based on the voltage detected by any two sensor components, thereby calculating the bubble's velocity. The present invention has the beneficial effect of enabling real-time measurement in situ underground, eliminating the need for long-distance signal output, and providing more accurate measurement data.

Description

Technical Field

[0001] The present invention relates to the technical field of geological instrumentation equipment, and in particular to a coalbed methane wellbore two-phase flow velocity sensor based on the principle of a friction nanogenerator. Background Art

[0002] Currently, there are two main methods for extracting coalbed methane: underground extraction and surface mining. Because coal reservoirs are multiphase fluids, gas and water are produced together. During the mining process, the coal reservoir near the wellbore is depressurized and drained, allowing gas to be released from the surface of the coal matrix and enter the cracks, thereby forming a two-phase seepage flow in the coal seam cracks, and finally migrated through the wellbore for production.

[0003] Determining the flow regime and parameters of two-phase flow is of great significance for the selection of coalbed methane (CBM) production methods and the analysis of gas well production dynamics. Starting from the velocity of the gas phase in two-phase flow, an analytical relationship between bubble volume and gas phase converted velocity is derived, and characteristic parameters of CBM in two-phase flow are constructed, providing data and theoretical support for the research and dynamic adjustment of CBM combined-layer production technology.

[0004] Currently, there are many methods for measuring the velocity of two-phase flow in underground wells, such as visual detection and indirect measurement with probes. However, due to their nature, traditional measurement methods cannot be accurately installed underground. Detection underground is limited to the ground and cannot be performed in situ in real time. The measurement data has large errors and poor reliability. Summary of the Invention

[0005] In view of this, the velocity measurement method of underground two-phase flow can only be limited to the ground, and cannot perform real-time in-situ detection. The measurement data has large errors and poor reliability. An embodiment of the present invention provides a coalbed methane wellbore two-phase flow velocity sensor based on the principle of friction nanogenerator.

[0006] An embodiment of the present invention provides a coalbed methane wellbore two-phase flow velocity sensor based on the principle of a friction nanogenerator, comprising a circuit board, a short-circuit housing, a connecting rod vertically arranged inside the short-circuit housing, and a plurality of sensor components spaced apart on the connecting rod, each of the sensor components comprising a PDMS housing and a first copper electrode respectively sleeved on the connecting rod, the PDMS housing surrounding the first copper electrode, the inner wall of the PDMS housing being provided with a second copper electrode and a PTFE membrane, the outer side of the second copper electrode being bonded and fixed to the inner wall of the PDMS housing, and the inner side being bonded to the PTFE membrane, the PTFE membrane surrounding the first copper electrode without contact therebetween, the PDMS housing being subjected to the alternating squeezing action of the liquid phase and the gas phase of the two-phase flow causing the PTFE membrane to contact or separate from the first copper electrode, the circuit board being respectively connected to the first copper electrode and the second copper electrode of each of the sensor components to detect the voltage between the first copper electrode and the second copper electrode of each of the sensor components, and the circuit board calculating the time difference between a single bubble in the two-phase flow passing through the two sensor components based on the voltage detected on any two of the sensor components, thereby calculating the bubble movement velocity in the two-phase flow.

[0007] Furthermore, the first copper electrode and the second copper electrode are both cylindrical copper sheets, and the axes of the first copper electrode and the second copper electrode coincide with each other.

[0008] Furthermore, a wire is provided in the connecting rod, and the circuit board is respectively connected to the first copper electrode and the second copper electrode of each sensor component through the wire.

[0009] Furthermore, the connecting rod is L-shaped, including a horizontal section and a vertical section, the horizontal section is fixedly connected to the inner wall of the short-circuit housing, and all sensor components are arranged at intervals on the vertical section.

[0010] Furthermore, a fixing element is provided at one end of the horizontal section, and the fixing element passes through the inner wall of the short-circuit housing and is connected and fixed through a waterproof joint.

[0011] Furthermore, a waterproof plug is provided at the end where the PDMS shell is connected to the connecting rod.

[0012] The beneficial effects brought about by the technical solution provided by the embodiments of the present invention are: compared with other traditional measurement methods, the coalbed methane wellbore two-phase flow velocity sensor based on the friction nanogenerator principle of the present invention calculates the bubble movement velocity in the two-phase flow by detecting the voltage changes in the two sensor components, and can perform real-time measurements in situ underground without the need for long-distance signal output. The measurement data is more accurate, providing more reliable theoretical support for the production process; since the interaction between the electrode charges is used to generate a potential difference during the measurement process, the circuit board can be powered. Compared with other traditional sensors, this sensor does not need to provide power, the sensor is reduced in size, and is more suitable for the underground environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 This is a schematic cross-sectional diagram of the installation of a coalbed methane wellbore two-phase flow velocity sensor based on the principle of a triboelectric nanogenerator according to the present invention;

[0014] Figure 2 yes Figure 1 Schematic diagram of the middle link 2 and the sensor component 3;

[0015] Figure 3 yes Figure 2 AA cross-sectional diagram of the sensor component 3;

[0016] Figure 4 is a schematic diagram of the movement of the first copper electrode, the PTFE membrane, and the second copper electrode;

[0017] Figure 5 This is a measurement principle diagram of a coalbed methane wellbore two-phase flow velocity sensor based on the principle of a friction nanogenerator of the present invention.

[0018] In the figure: 1-short-circuit housing, 2-connecting rod, 3-sensor component, 4-horizontal segment, 5-vertical segment, 6-PDMS housing, 7-first copper electrode, 8-second copper electrode, 9-PTFE membrane, 10-waterproof plug, 11-fixing element, 12-wire, 13-waterproof connector, 14-screw, 15-flange connector, 16-bolt hole. DETAILED DESCRIPTION

[0019] To make the objectives, technical solutions and advantages of the present invention more clear, the embodiments of the present invention will be further described below with reference to the accompanying drawings.

[0020] Please refer to Figure 1 and 2 An embodiment of the present invention provides a coalbed methane wellbore two-phase flow velocity sensor based on the principle of a friction nanogenerator, comprising a circuit board, a short-circuit housing 1, a connecting rod 2 vertically arranged inside the short-circuit housing 1, and a plurality of sensor components 3 spaced apart on the connecting rod 2.

[0021] Specifically, the shorting housing 1 is a cylindrical structure with flange joints 15 at both ends. The flange joints 15 are provided with multiple bolt holes 16. The shorting housing 1 is installed in a coalbed methane well, and the flange joints 15 at both ends of the shorting housing 1 are connected and fixed to the wellbore through the bolt holes 16.

[0022] The connecting rod 2 is L-shaped and includes a horizontal section 4 and a vertical section 5. The horizontal section 4 is fixedly connected to the inner wall of the shorting housing 1. One end of the horizontal section 4 is provided with a fixing element 11, which passes through the inner wall of the shorting housing 1. The exterior of the shorting housing 1 is provided with a waterproof joint 13, which is fixed to the outer wall of the shorting housing 1 and connected to the fixing element 11 via screws 14. All sensor components 3 are spaced apart on the vertical section 5.

[0023] At least two sensor components 3 are provided, and the specific number can be determined according to actual needs. In this embodiment, two sensor components 3 are provided, one sensor component 3 is provided at the lower end of the vertical section 5 of the connecting rod 2, and the other sensor component 3 is provided in the middle of the vertical section 5 of the connecting rod 2.

[0024] Please refer to Figure 1 、 2 Each sensor component 3 includes a PDMS shell 6 and a first copper electrode 7, each of which is respectively sleeved on the vertical section 5 of the connecting rod 2. The PDMS shell 6 surrounds the first copper electrode 7, and the inner wall of the PDMS shell 6 is provided with a second copper electrode 8 and a PTFE membrane 9. Here, the first copper electrode 7 and the second copper electrode 8 are both cylindrical copper sheets. The first copper electrode 7 is directly sleeved on the outer wall of the vertical section 5 of the connecting rod 2 and is fixedly connected to the vertical section 5 of the connecting rod 2.

[0025] The PDMS shell 6 is an elliptical, long, hollow shell, and the vertical section 5 of the connecting rod 2 penetrates the PDMS shell 6. In order to prevent liquid from penetrating into the interior of the PDMS shell 6, a waterproof plug 10 is provided at the end where the PDMS shell 6 is connected to the vertical section 5 of the connecting rod 2 for sealing and waterproofing. The inner wall of the PDMS shell 6, the second copper electrode 8 and the PTFE membrane 9 are laminated and laminated, that is, the outer side surface of the second copper electrode 8 is laminated and fixed to the inner wall of the PDMS shell 6, and the inner side surface is laminated to the PTFE membrane 9. The PTFE membrane 9 surrounds the first copper electrode 7 without contact therebetween. The PTFE membrane 9 is arranged around the first copper electrode 7 and an annular gap is left between the PTFE membrane 9 and the first copper electrode 7. The PDMS shell 6 is subjected to the alternating extrusion of the liquid phase and the gas phase of the two-phase flow, so that the PTFE membrane 9 contacts or separates from the first copper electrode 7. Preferably, the axes of the first copper electrode 7 and the second copper electrode 8 coincide.

[0026] The circuit board is respectively connected to the first copper electrode 7 and the second copper electrode 8 of each sensor component 3. Here, a wire 12 is provided in the connecting rod 2, and the circuit board is respectively connected to the first copper electrode 7 and the second copper electrode 8 of each sensor component 3 through the wire 12. The circuit board can detect the voltage between the first copper electrode 7 and the second copper electrode 8 of each sensor component 3.

[0027] Please refer to Figure 4 The working principle of the above-mentioned coalbed methane wellbore two-phase flow velocity sensor based on the principle of friction nanogenerator is as follows: in the initial state, when the two-phase flow has not yet flowed to the sensor component 3 at the lower end of the connecting rod 2, the PDMS shell 6 is not squeezed by the two-phase flow, the second copper electrode 8 and the PTFE film 9 remain stationary, and maintain a fixed distance from the first copper electrode 7. At this time, no potential difference (voltage) is generated between the first copper electrode 7 and the second copper electrode 8.

[0028] When the two-phase flow flows to the sensor component 3, the liquid phase and the gas phase of the two-phase flow alternately pass through the PDMS shell 6. When the liquid phase passes through the PDMS shell 6, the PDMS shell 6 is squeezed, so that the second copper electrode 8 and the PTFE film 9 are close to and in contact with the first copper electrode 7. Figure 4 As shown in ①→②, in order to balance the potential, negative charge is transferred from the first copper electrode 7 to the second copper electrode 8. The charge transfer generates a current and thus an electrical signal. When the contact area between the PTFE film 9 and the first copper electrode 7 reaches its maximum, the open circuit voltage reaches its maximum. As the gas phase passes through, the pressure decreases, resulting in a decrease in the contact area, until the second copper electrode 8 and the PTFE film 9 separate from the first copper electrode 7, as shown in FIG. Figure 4As shown in ②→③→④, the positive charge moves from the first copper electrode 7 to the second copper electrode 8, generating an opposite electrical signal again. At the same time, the open circuit voltage on the first copper electrode 7 and the second copper electrode 8 will also decrease. These voltage signals can be detected by the circuit board.

[0029] Theoretically, when a single bubble passes through the two sensor components 3 within a period of time, due to the same squeezing effect on the PDMS shell 6, the voltage between the first copper electrode 7 and the second copper electrode 8 of the two sensor components 3 is also the same. The time difference between a single bubble passing through the two sensor components 3 in the two-phase flow can be calculated. Since the distance between the two sensor components 3 is fixed, the movement speed of the bubble is calculated by the interval time between the two sensor components 3 and the distance between the two sensor components 3.

[0030] Please refer to Figure 5 For example, the velocity of the bubble can be calculated by measuring the voltage when the gas phase in the two-phase flow completely passes through the upper end of the PDMS shell 6. Specifically, when the gas phase completely passes through the upper end of the PDMS shell 6, the first copper electrode 7 and the second copper electrode 8 are completely separated, and the voltage U between them is zero. The time difference ΔT when the gas phase in the two-phase flow completely passes through the upper end of the PDMS shell 6 can then be determined. The velocity of the bubble can be calculated by dividing the distance between the two sensor components 3 by the time difference ΔT. Furthermore, parameters such as the bubble volume and the converted bubble velocity can be derived based on the bubble velocity to construct a downhole bubble migration model.

[0031] In this document, directional terms such as front, back, top, and bottom are defined based on the positions of components in the accompanying drawings and relative to each other, and are intended only for clarity and convenience in describing the technical solution. It should be understood that the use of these directional terms should not limit the scope of protection claimed in this application.

[0032] In the absence of conflict, the above embodiments and features in the embodiments may be combined with each other.

[0033] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A coalbed methane wellbore two-phase flow velocity sensor based on the principle of triboelectric nanogenerator, characterized by: The invention comprises a circuit board, a short-circuit housing, a connecting rod vertically arranged inside the short-circuit housing, and a plurality of sensor components spaced apart on the connecting rod, wherein each of the sensor components comprises a PDMS housing and a first copper electrode respectively sleeved on the connecting rod, the PDMS housing surrounds the first copper electrode, the inner wall of the PDMS housing is provided with a second copper electrode and a PTFE membrane, the outer side surface of the second copper electrode is fixedly bonded to the inner wall of the PDMS housing, the inner side surface of the second copper electrode is bonded to the PTFE membrane, the PTFE membrane surrounds the first copper electrode and the two are not in contact, the PDMS housing is subjected to the alternating squeezing action of the liquid phase and the gas phase of the two-phase flow so that the PTFE membrane contacts or separates from the first copper electrode, the circuit board is respectively connected to the first copper electrode and the second copper electrode of each sensor component to detect the voltage between the first copper electrode and the second copper electrode of each sensor component, and the circuit board calculates the time difference between a single bubble in the two-phase flow passing through the two sensor components based on the voltage detected on any two sensor components, thereby calculating the bubble movement speed in the two-phase flow; The first copper electrode and the second copper electrode are both cylindrical copper sheets, and the axes of the first copper electrode and the second copper electrode coincide with each other; A wire is provided in the connecting rod, and the circuit board is connected to the first copper electrode and the second copper electrode of each sensor component through the wire.

2. The coalbed methane wellbore two-phase flow velocity sensor based on the triboelectric nanogenerator principle according to claim 1, characterized in that: The connecting rod is L-shaped and includes a horizontal section and a vertical section. The horizontal section is fixedly connected to the inner wall of the short-circuit housing, and all sensor components are arranged at intervals on the vertical section.

3. The coalbed methane wellbore two-phase flow velocity sensor based on the triboelectric nanogenerator principle as claimed in claim 2, characterized in that: A fixing element is provided at one end of the horizontal section, and the fixing element passes through the inner wall of the short-circuit housing and is connected and fixed via a waterproof joint.

4. The coalbed methane wellbore two-phase flow velocity sensor based on the triboelectric nanogenerator principle according to claim 1, characterized in that: The end where the PDMS shell is connected to the connecting rod is provided with a waterproof plug.

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