A method and device for measuring moisture content based on an inductive eddy current sensor

Abstract

The present application belongs to the field of oil logging, and particularly relates to a kind of water cut measurement method and device based on inductive eddy current sensor.The device comprises a sensor module and a signal conditioning circuit module.The sensor module comprises an insulating layer, a magnetic ring, two turns of excitation coil, one turn of detection coil and a fluid conduit;The signal conditioning circuit module comprises an excitation source, an amplification circuit, a filter circuit and an acquisition circuit.The method is: by the excitation source, a certain frequency of alternating current is applied to the two turns of excitation coil, when a certain conductivity of oil-water two-phase flow flows in the fluid conduit, the detection coil outputs the induced voltage reflecting the conductivity of the mixed phase fluid, and the useful information reflecting the conductivity of the mixed phase fluid is extracted by processing through the amplification acquisition circuit, so as to calculate the water cut.

Description

Technical fields:

[0001] This invention belongs to the field of oil well logging, specifically relating to a water cut measurement method and device based on an inductive eddy current sensor. Background technology:

[0002] With the development of oilfields, most onshore oilfields in China have entered the high water-cut and ultra-high water-cut development stage. Oil well production is characterized by high water cut, medium to low production, and complex multiphase flow patterns. Multiphase flow measurement technology can determine the most important oil well production parameters, which is of great significance for optimizing oilfield production operations and production equipment parameters. In recent years, in order to further tap the remaining oil potential beyond waterflooding, chemical flooding technologies such as polymer flooding and multi-component composite flooding have been widely used in domestic oilfields. This has led to more complex chemical compositions of the well fluids, enrichment of flocculent matter, and a tendency for corrosion and scaling of sensor electrodes, seriously affecting the accuracy and reliability of water cut measurements.

[0003] Existing, mature water cut measurement sensors are simple in structure, have no moving parts or flow obstructions, and possess high reliability. However, they are all contact measurements, with the sensor's metal parts in direct contact with the fluid, making them susceptible to contamination, scaling, and corrosion. This significantly reduces the sensor's performance and reliability, and increases production costs. This makes the measurement of water cut in multiphase flow oil wells even more challenging.

[0004] To address the aforementioned issues, an inductive eddy current sensor-based moisture content measurement system is proposed, featuring non-contact operation, high reliability, and small size. The key research objective is to design a novel, non-contact sensor with a high magnetic induction intensity dual-excitation structure. Summary of the Invention:

[0005] The main objective of this invention is to provide an inductive eddy current sensor moisture content measurement system to solve the problems of direct contact between the fluid and the sensor, as well as the effects of scaling and corrosion in the prior art, thereby achieving the characteristics of non-contact, high precision, no moving parts, and simple structure.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: an inductive eddy current sensor moisture content measurement system, comprising a sensor module and a signal conditioning circuit module. The sensor module includes: a sensor insulating layer (3), a magnetic ring (1), a magnetic ring insulating layer (2), a first-turn excitation coil (7), a second-turn excitation coil (8), a detection coil (6), a fluid pipe insulating layer (4), and a fluid pipe (5). The conditioning circuit module includes: an excitation circuit, an amplification circuit, a filtering circuit, and a data acquisition circuit. The system, from left to right, comprises an excitation circuit, a sensor body, an amplification circuit, a filtering circuit, and a data acquisition circuit. The excitation circuit is connected in series with the two-turn excitation coil, and the detection coil is connected to the amplification circuit, the filtering circuit, and the data acquisition circuit. The sensor body's insulating layer surrounds the outside of a magnetic ring. The magnetic ring surrounds the two-turn excitation coil and the detection coil, and its top view is divided into N equal parts, with each adjacent part filled by the magnetic ring's insulating layer. The excitation coil employs a structure with two independent, unidirectional turns, with the first turn located below the fluid pipe and the second turn located above it. The detection coil is located at the center of the distance between the two turns of the excitation coil. The fluid pipe's insulating layer is located between the fluid pipe and the coil.

[0007] When oil and water two-phase flows with different conductivity enter the fluid pipeline from bottom to top, they first pass through the first excitation coil, then the detection coil, and finally the second excitation coil. After the fluid passes through the two excitation coils, the excitation magnetic fields on both sides are superimposed and enhanced, acting on the detection coil. The voltage ε output by the detection coil is sensitive to the conductivity σ of the mixed-phase fluid. m Using Maxwell's relation, the conductivity σ of the miscible fluid m Sensitive to moisture content Y w The moisture content Y can be measured based on the effective value ε of the voltage output by the detection coil. w .

[0008] Step 1: Apply a sinusoidal alternating current of a certain frequency, I, to the dual excitation coils. J To determine the magnitude B of the magnetic induction intensity generated by the excitation coil itself. J .

[0009] B J =μNI J

[0010] In the formula, μ is the relative permeability of the magnetic shield; N is the number of turns of the excitation coil.

[0011] Step 2: Because the induced magnetic field generated by the excitation coil penetrates the pipe and has a certain conductivity σ mof the multiphase fluid, the pipeline fluid can be regarded as a series of thin fluid layers with gradually varying radii, each thin fluid layer forming a closed loop on its own, in which eddy currents are generated, and the eddy currents vary with the radius r. In the pipeline fluid, take a thin fluid layer with radius r (0<r<D / 2) and thickness dr, whose resistance is dR=(2πr) / (σ m hdr), then the effective value of the induced eddy current excited inside the fluid medium is -(dφ / dt) / [(2πr) / (σ m hdr)], and then the magnitude of the magnetic induction intensity B generated by the fluid medium itself is determined S .

[0012]

[0013] where D is the diameter of the fluid pipeline; φ is the magnetic flux of the induced magnetic field of the fluid medium; h is the equivalent length of the fluid.

[0014] Step 3: The magnitude of the magnetic induction intensity B generated by the dual excitation coils J and the magnitude of the magnetic induction intensity B generated by the fluid medium S are superimposed on the detection coil. Then the detection coil outputs the effective value ε of the induced voltage reflecting the fluid conductivity σ m .

[0015] ε=-d(B J +BS)S / dt=-4×μNπ 2 r 2 fI J +4×(D 2 / 8)μ 2 N 2 π 2 σ m hf 2 I J

[0016] That is where f is the excitation frequency of the excitation coil; S is the area of the conductor perpendicular to the direction of the magnetic line of force.

[0017] Step 4: The conductivity σ of the multiphase fluid can be known from the effective value ε of the induced voltage output by the detection coil m . Under the condition that the two-phase flow is a fine bubbly flow, the water cut Y w and the multiphase conductivity σ m satisfy the Maxwell relationship, where σ w is calibrated according to the field environment. Further, the water cut Y is obtained w .

[0018]

[0019] where σw The total electrical conductivity of water.

[0020] The beneficial effects of this invention are as follows: It proposes an inductive eddy current sensor method for measuring the water content of two-phase flow. In this sensor, the excitation coil and the detection coil are respectively wound around the outside of the fluid pipe. Based on the principle of electromagnetic induction, the fluid is measured in a non-contact manner, which overcomes the problem that existing two-phase flow measurement equipment is in direct contact with the fluid and is easily affected by contamination, scaling and corrosion. Attached image description:

[0021] Figure 1 This is a three-dimensional schematic diagram of the inductive eddy current sensor in Embodiment 1;

[0022] Figure 2 Top view of an inductive eddy current sensor;

[0023] Figure 3 This is a front view of an inductive eddy current sensor.

[0024] Figure 4 This is a schematic diagram of the overall experimental structure of the inductive eddy current sensor measurement system.

[0025] Figure 5 This is a schematic diagram of linear fitting of three experimental data points for an inductive eddy current sensor. Detailed implementation method:

[0026] Example 1

[0027] Reference Figures 1-3 This invention provides an inductive eddy current sensor for measuring the water content of a high-water-content oil-water two-phase flow. The structural features are as follows: a sensor insulating layer (3), a magnetic ring (1), a magnetic ring insulating partition layer (2), a first-turn excitation coil (7), a second-turn excitation coil (8), a detection coil (6), a fluid pipe insulating layer (4), and a fluid pipe (5). The sensor insulating layer surrounds the magnetic ring, providing isolation and protection. The magnetic ring is located outside the two-turn excitation coil and the detection coil, and is made of a high-permeability material to amplify the sensor's own magnetic field and shield external interference magnetic fields. Its top view is divided into N equal parts, with each adjacent part filled by the magnetic ring insulating partition layer to reduce eddy currents generated inside the magnetic ring and minimize losses. The excitation coil uses an independent, unidirectional winding structure with two turns, which maximizes the generation of the induced magnetic field and the induced eddy currents in the fluid medium. The detection coil is located at the center of the distance between the two-turn excitation coils, and the axial distance between the detection coil and each turn of the excitation coil is L, where L is selected from 1 / 2 to 2 times the pipe diameter. Within this range, the spacing L ensures that the useful information in the detected signal is maximized while maximizing the excitation magnetic field.

[0028] Example 2

[0029] Reference Figure 4 , the excitation circuit applies an excitation signal of alternating current at a specific frequency to the excitation coil to ensure the normal operation of the sensor. Since the signal directly output from the detection coil is relatively weak and mixed with high-frequency interference signals, it is necessary to amplify and filter this signal, filter out irrelevant interference signals, and extract the flow noise signal of the measured fluid. The filtered signal is subjected to relevant processing such as digitization by the acquisition circuit, so as to obtain a more accurate water content.

[0030] An inductive eddy current sensor water content measurement system comprises the following steps:

[0031] Step 1: Applying a sinusoidal alternating current with a certain frequency and an effective value I to the dual excitation coils J , to determine the magnitude B of the magnetic induction intensity generated by the excitation coils themselves J .

[0032] B J =μNI J

[0033] where μ is the relative magnetic permeability of the magnetic shield; N is the number of turns of the excitation coil.

[0034] Step 2: Since the induced magnetic field generated by the excitation coil penetrates the multiphase fluid with a certain electrical conductivity σ in the pipeline, the pipeline fluid can be regarded as a series of thin fluid layers with gradually changing radii, each thin fluid layer forms a closed loop by itself, in which eddy current is generated, and the eddy current varies with the radius r. Taking a thin fluid layer with a radius of r (0<r<D / 2) and a thickness of dr in the pipeline fluid, its resistance is dR=(2πr) / (σ m hdr), then the effective value of the induced eddy current excited inside the fluid medium is -(dφ / dt) / [(2πr) / (σ m hdr)], and then the magnitude B of the magnetic induction intensity generated by the fluid medium itself is determined m . S .

[0035]

[0036] where D is the diameter of the fluid pipeline; φ is the magnetic flux of the induced magnetic field of the fluid medium; h is the equivalent length of the fluid.

[0037] Step 3: The magnitude B of the magnetic induction intensity generated by the dual excitation coils J and the magnitude B of the magnetic induction intensity generated by the fluid medium S are superimposed on the detection coil. Then the detection coil outputs the effective value ε of the induced voltage reflecting the electrical conductivity σ of the fluid m .

[0038] ε=-d(B J +BS S / dt=-4×μNπ 2 r 2 fI J +4×(D 2 / 8)μ 2 N 2 π 2 σ m hf 2 I J

[0039] Right now In the formula, f is the excitation frequency of the excitation coil; S is the area of ​​the conductor perpendicular to the direction of the magnetic field lines.

[0040] Step 4: The conductivity σ of the mixed-phase fluid can be determined by detecting the effective value ε of the induced voltage output by the detection coil. m Under the condition that the two-phase flow is a fine bubble flow, the water cut Y w With the mixed-phase conductivity σ m It also satisfies the Maxwell relation, where σ w Calibration was performed based on the site conditions. The moisture content Y was then calculated. w .

[0041]

[0042] In the formula, σ w The total electrical conductivity of water.

[0043] As can be seen from the above formula, the effective value ε of the induced voltage output by the detection coil can reflect the conductivity σ of the miscible fluid in the pipe. m The conductivity σ of the miscible fluid m The required moisture content Y w There is a certain relationship, which is the principle of inductive eddy current sensor for measuring moisture content. Theoretical reasoning can prove that this method is feasible.

[0044] Reference Figure 5Three repeatable water cut measurement experiments were conducted using this device, and the experimental data are shown below. A linear fitting graph of the three experiments using the inductive eddy current sensor is provided. The relative response shown at each point in the graph is the effective value of the induced voltage output by the detection coil at the current water cut in the fluid pipeline relative to the effective value of the induced voltage output by the detection coil when the pipeline is in full oil phase. It can be seen that the relative response is higher under high water cut conditions, making it suitable for current oil well conditions. Furthermore, data analysis was performed on the effective values ​​of the induced voltage output by the sensor in the three repeatable experiments. The average values ​​of the effective induced voltage output in each experiment were 6.9V, 7.0V, and 6.8V, with standard deviations of 0.21V, 0.22V, and 0.19V. It can be seen that the data from the three experiments are stable, the overall experimental repeatability is good, and the sensor stability is ideal, meeting the requirements for sensor use. Therefore, this invention is effective.

[0045] This device utilizes the principle of electromagnetic induction to measure the water cut of two-phase flow. It employs a clever structure where both the excitation coil and the detection coil are placed outside the fluid pipe, avoiding measurement errors caused by corrosion and adhesion due to direct contact between the sensor probe and the fluid, thus saving production costs. It fundamentally solves the current problems faced in measuring the water cut of two-phase flow in producing wells. Therefore, this invention is of great significance.

[0046] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention shall still fall within the scope of the technical solution of the present invention.

Claims

1. A method for measuring moisture content based on an inductive eddy current sensor, characterized in that... The measurement device used in the measurement method includes a sensor module and a signal conditioning circuit module. The sensor module includes a sensor insulating layer (3), a magnetic ring (1), a magnetic ring insulating partition layer (2), a first-turn excitation coil (7), a second-turn excitation coil (8), a detection coil (6), a fluid pipe insulating layer (4), and a fluid pipe (5). The signal conditioning circuit module includes an excitation circuit, an amplification circuit, a filtering circuit, and a data acquisition circuit. The excitation circuit is connected in series with the two-turn excitation coil, and the detection coil is connected to the amplification circuit, the filtering circuit, and the data acquisition circuit. The sensor insulating layer surrounds the outside of the magnetic ring. The magnetic ring surrounds the outside of the two-turn excitation coil and the detection coil, and its top view direction is divided into multiple parts on an even basis. Each two adjacent parts are filled with the magnetic ring insulating partition layer. The excitation coil adopts a structure of two independent and unidirectional windings, wherein the first-turn excitation coil is located on the lower side of the fluid pipe, and the second-turn excitation coil is located on the upper side of the fluid pipe. The detection coil is located at the center of the distance between the two-turn excitation coil. The fluid pipe insulating layer is located between the fluid pipe and the coil. The measurement method includes the following steps: Step 1: Apply a sinusoidal alternating current of a certain frequency to the two-turn excitation coil. To determine the magnitude of the magnetic induction intensity generated by the excitation coil itself. : ； In the formula, The relative permeability of the magnetic ring is given by N; N is the number of turns of the excitation coil. Step 2: Since the induced magnetic field generated by the excitation coil penetrates through the pipeline, the multiphase fluid with a certain conductivity in the pipeline can be regarded as being composed of a series of thin fluid layers with gradually changing radii. Each thin fluid layer forms its own closed loop, in which eddy current is generated, and the eddy current varies with the radius r; a thin fluid layer with a radius of r (0<r<D / 2) and a thickness of dr is taken in the pipeline fluid, and its resistance is , then the effective value of the induced eddy current excited inside the fluid medium is - , and further the magnitude of the magnetic induction intensity generated by the fluid medium itself is determined : ； In the formula, D is the diameter of the fluid pipe; denoted as , where is the magnetic flux of the induced magnetic field in the fluid medium; and h is the equivalent length of the fluid. Step 3: The magnitude of the magnetic induction intensity generated by the two-turn excitation coil The magnitude of magnetic induction intensity generated by the fluid medium The combined effects of these factors on the detection coil result in an output from the detection coil reflecting the fluid conductivity. RMS value of induced voltage : ； Right now ; In the formula, is the excitation frequency of the excitation coil; S is the area of ​​the conductor perpendicular to the direction of the magnetic field lines; Step 4: Detect the effective value of the induced voltage output by the detection coil. The conductivity of the miscible fluid can be determined. Under the condition that the two-phase flow is fine bubble flow, the water content is With mixed-phase conductivity It also satisfies the Maxwell relation, where The moisture content was determined by calibrating the equipment based on the on-site environment. : ； In the formula, The total electrical conductivity of water.

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