CN106677766A - Experiment device for measuring low-frequency elastic wave response characteristic after liquid annular air cut - Google Patents

Abstract

The invention discloses an experiment device for measuring a low-frequency elastic wave response characteristic after liquid annular air cut and a corresponding experiment method. The experiment device comprises a mineshaft annular air simulation part, a liquid circulation control part, a bubble generation and circulation control part and an elastic wave response characteristic measurement part. According to the experiment device for measuring the low-frequency elastic wave response characteristic after liquid annular air cut, under the condition of annular liquid quiescence or flow, conditions of the pressure, the bubble size and the gas volume fraction are controlled, particularly stable control can be achieved in the range of low gas volume fraction (0.5-2%), the phase velocity and the reduction of an elastic wave after the annular air cut are measured, the structure is simple, the reliability of the measurement data is high, and the experiment cost is low.

Description

An experimental device for measuring the response characteristics of low frequency elastic waves after liquid ring air intrusion

technical field

The invention relates to an experimental measuring device, in particular to an experimental device for measuring the response characteristics of low-frequency elastic waves after liquid ring air intrusion. It belongs to the technical field of analysis and measurement control.

Background technique

In order to meet the needs of the national energy strategy, oil and gas drilling technology continues to develop. Currently, oil and gas drilling is developing towards deeper formations and deep ocean waters. During the drilling process, the pressure distribution of the wellbore annulus (the annular space between the drill pipe and the formation) is generally controlled by adjusting the drilling fluid density, so that the pressure of the liquid column in the annulus is greater than or equal to the pressure of the formation fluid, and the formation fluid is prevented from entering the annulus. null. Gas kick refers to the gas in the formation entering the annulus of the wellbore due to pressure difference or substitution, which is a common drilling complication. If gas intrusion is not handled properly, it will further develop into wellhead overflow, or even blowout accident, resulting in major safety accidents.

In the early stage of gas invasion, the intrusive gas exists in the annulus of the wellbore in the form of small bubbles, and migrates to the wellhead with the drilling fluid. According to Wood's equation (Wood, 1930), when a small amount of gas is intruded into the liquid, the phase velocity of the elastic wave propagating in the gas-liquid mixture will decrease rapidly. Considering the large attenuation of elastic waves in gas-liquid mixtures, it is an innovative technical solution to use the response characteristics of low-frequency elastic waves for early active monitoring of gas invasion downhole. Measuring and analyzing the response characteristics of low-frequency elastic waves after annular air intrusion by experimental methods has important theoretical significance for the early monitoring of downhole air intrusion.

To realize the experimental measurement of the low-frequency elastic wave response characteristics after annular air intrusion, the primary technology is to form stable bubbles in the annular liquid flow. For gas-liquid two-phase mixtures, gas hold-up is a basic concept, which refers to the volume percentage of gas in a unit volume of gas-liquid mixture. In the field of gas-liquid two-phase flow research, some mature gas-liquid two-phase flow experimental measurement devices have been formed over the years, but these devices cannot be used to complete the experimental measurement of low-frequency elastic wave response characteristics after annular air intrusion. The main reasons are: (1) In traditional experimental devices for studying gas-liquid two-phase flow, in order to form a stable flow state, the general experimental pipeline is long (>5m), and the gas content is generally greater than 5%. However, the elastic wave attenuates significantly in the gas-liquid mixture, and the measurement of its response characteristics must be completed in a short pipeline, otherwise the elastic wave signal attenuates seriously, and it is impossible to collect reliable and effective elastic wave signals; on the other hand, in order to facilitate early monitoring of gas It is especially necessary to form stable bubbles under the conditions of low gas content (<2%) and short pipelines (<2m), which cannot be realized in traditional gas-liquid two-phase flow experimental devices. (2) The traditional gas-liquid two-phase flow experimental device focuses on the control of convective flow, so in the state of bubbly flow, the ability to control the size of the bubble is weak, which is not suitable for retrofitting on the basis of this type of device to achieve annular air invasion. Experimental measurements of low frequency elastic wave response characteristics.

Contents of the invention

The object of the present invention is to overcome the deficiencies of the prior art above, and provide an experimental device for measuring the response characteristics of the low-frequency elastic wave after the air intrusion of the liquid ring, which can control the pressure, bubble size, Conditions such as gas content, especially in the range of low gas content (0.5-2%) can achieve stable control, measure the elastic wave phase velocity and attenuation after annular air intrusion, simple structure, high reliability of measurement data, and low experimental cost Low.

The present invention also provides an experimental method for measuring the response characteristics of the low-frequency elastic wave after liquid ring air intrusion by using the above-mentioned experimental device.

To achieve the above object, the present invention adopts the following technical solutions:

An experimental device for measuring the response characteristics of low-frequency elastic waves after liquid ring air intrusion, which includes the following four parts:

The simulation part of the wellbore annulus includes the inner pipe and the sealed outer pipe sleeved outside it. The bottom end of the inner pipe is fixedly connected with the base of the annular inner pipe, and the base of the annular inner pipe is provided with a liquid diversion port and a foaming needle-shaped hole , wherein the inner pipe simulates the wellbore, above the base of the annular inner pipe, seals the annular space formed between the outer pipe and the inner pipe to simulate the annulus of the wellbore;

The liquid circulation control part, including the liquid circulation pipe, one end is inserted into the inner pipe, and the other end is connected to the opening I opened on the top side of the sealed outer pipe, so that the liquid injected into the inner pipe flows through the liquid diversion port, the annular space, opening I and The liquid circulation pipe then flows back to the inner pipe through the liquid circulation pipe to form a circulation;

The bubble generation and circulation control part includes a gas injection structure located on the bottom side of the sealed outer tube, and its gas outlet is connected to the foaming needle-shaped hole. The top side of the sealed outer tube is provided with an opening II, which is connected to the gas recovery structure, and the position of opening II is higher than that of opening I; and

The elastic wave response characteristic measurement part includes a mobile measurement board, a pulse generator and an oscilloscope. The mobile measurement board is clamped between the sealed outer tube and the inner tube. The upper surface of the annular inner tube base and the lower surface of the mobile measurement board are respectively There are the same number of low-frequency piezoelectric sensors Ⅰ and low-frequency piezoelectric sensors Ⅱ aligned one by one; among them, the low-frequency piezoelectric sensor Ⅰ is connected to the pulse generator, and the input terminals of the oscilloscope are respectively connected to the pulse generator and the low-frequency piezoelectric sensor. Ⅱ, the output terminal of the oscilloscope is connected to the computer.

The inner diameter of the inner tube is preferably 25.4-76.2mm, and the length is 0.5-2m.

The inner diameter of the sealed outer tube is preferably 50.8-127mm, and the length is 0.5-2m.

The annular inner tube base includes an annular inner tube base base, on which four low-frequency piezoelectric sensors I, four liquid diversion ports and eight foaming needle-shaped holes are arranged, and their centers are located in the annular On the center line, the low-frequency piezoelectric sensor I and the liquid diversion port are evenly spaced, and the foaming needle-shaped hole is located in the middle between the low-frequency piezoelectric sensor I and the liquid diversion port.

Both the liquid diversion port and the foaming needle-shaped hole are through holes, and bubbles of different sizes are formed by selecting the diameter of the foaming needle-shaped hole and/or the gas injection displacement.

The diameter of the foamed needle-shaped pores is preferably 0.2-3.0 mm, and the size range of the formed bubbles is 1-6 mm.

The material of the inner tube and the sealed outer tube is preferably a transparent strengthened plexiglass tube, and the material of the base of the annular inner tube base is preferably a transparent plexiglass plate, so as to observe the bubble generation and cycle control during the experimental measurement .

Preferably, the components of the liquid circulation control part are sealed and connected through pressure-resistant circular tubes.

The liquid circulation pipeline is sequentially provided with: a liquid storage tank, a hydraulic pump, a booster tank, a pressure gauge I, a valve I, a liquid flow meter I and a liquid injection pipe. The liquid injection pipe penetrates into the inner pipe and seals the outer pipe There is an opening Ⅰ on one side of the top, which is connected to the valve Ⅱ, and the valve Ⅱ is connected to the liquid storage tank through the liquid flow meter Ⅱ.

Preferably, each component of the bubble generation and circulation control part is sealed and connected through a pressure-resistant circular tube.

The gas injection structure includes a gas cylinder, a pressure gauge II, a valve III, a gas flowmeter I and a gas injection pipe connected in sequence, the opening II is connected to the pressure gauge III, and the pressure gauge III is connected to the gas flowmeter II through the valve IV to the gas recovery tank.

Preferably, there are several foaming needle-shaped holes, and they are connected in parallel to the gas injection pipe in a sealed manner.

The moving measuring plate is fixedly connected with the limit rod, and the moving measuring plate is positioned at two known annular positions by lifting or lowering the limit rod.

The moving measuring plate includes a moving measuring plate base whose overall size is adapted to the inner diameter of the sealed outer tube, and a through hole is arranged in the center of the moving measuring plate base, the diameter of the through hole is adapted to the outer diameter of the inner tube, along the through hole Four branches are evenly arranged in the circumferential direction, and a low-frequency piezoelectric sensor II is respectively arranged on the lower surface of each branch.

Preferably, the low-frequency piezoelectric sensor I and the low-frequency piezoelectric sensor II are respectively pasted on the upper surface of the annular base base and the lower surface of the branch by epoxy resin.

The material of the base of the mobile measurement plate is preferably a transparent organic glass plate.

The operating frequency of the low-frequency piezoelectric sensor I and the low-frequency piezoelectric sensor II is 20-200 Hz.

An experimental method for measuring the response characteristics of low-frequency elastic waves after liquid ring air invasion by using the above-mentioned experimental device. After liquid filling and air inflation and pressurization are completed, the liquid circulation is established through the liquid circulation control part, and then the gas bubble generation and circulation control part is used to establish the gas flow. circulation, and then make bubbles generated at the foaming needle-shaped hole and distributed in the annular space, and finally, use the elastic wave response characteristic measurement part to complete the analysis and calculation of the elastic wave response characteristic.

The concrete steps of described experimental method are as follows:

(1) Before starting the experiment, close all valves; prepare a sufficient amount of liquid in the liquid storage tank.

(2) Turn on the power, turn on the hydraulic pump, and slowly pump liquid into the pressurized tank. After the pressure gauge Ⅰ reaches the predetermined pressure, turn off the hydraulic pump; slowly open the valve Ⅰ and valve Ⅱ, and directly inject liquid into the inner pipe; When the liquid level in the annular space reaches the height between valve II and valve IV, close valve I and valve II to complete filling;

(3) Slowly open the valve III, pay attention to the changes in the indication of the pressure gauge III, when the indication of the pressure gauge III reaches the set test pressure, close the valve III, and complete the inflation and pressurization;

(4) If measuring the elastic wave response characteristics of the annular liquid at rest, proceed directly to step (5); if measuring the elastic wave response characteristics of the annular liquid circulation, first slowly open the valve I, and then slowly open the valve Ⅱ, adjust valve Ⅰ and valve Ⅱ, so that the readings of liquid flow meter Ⅰ and liquid flow meter Ⅱ are the same, and establish liquid circulation;

(5) First slowly open valve III, then slowly open valve IV, adjust valve III and valve IV, so that the indications of gas flow meter I and gas flow meter II are the same, and establish a gas cycle; after the gas cycle is stable, slowly adjust the valve Ⅲ and valve Ⅳ, so that the size of the bubbles generated at the foaming needle hole is basically the same;

(6) After the gas circulation and the bubble size are stabilized, the distribution of the bubbles in the annular space is photographed by a digital camera, which is used to process and extract the actual size of the bubbles on the computer in the later stage;

(7) Lift or lower the limit rod, take two positioning points, record the positioning point closer to the low-frequency piezoelectric sensor I as A, and record the other as B, start the elastic wave response characteristic measurement part respectively, and record Excitation and reception signals of two positioning points: the pulse generator generates a voltage pulse of fixed frequency and width, which is recorded by the oscilloscope on the one hand, and on the other hand excites the low-frequency piezoelectric sensor Ⅰ to generate pulse vibration, forming an elastic wave source; After the elastic wave propagates through the gas-liquid mixture in the annular space, it is received by the low-frequency piezoelectric sensor II, and the elastic wave vibration is converted into a voltage signal, which is collected by the oscilloscope; the excitation pulse signal collected by the oscilloscope and the received signal are sent to the computer together, and the The analysis and calculation of the elastic wave response characteristics are completed.

The concrete method of the signal analysis in the step (7) and calculation is:

according to the formula Calculate the elastic wave phase velocity v, where L is the distance between two anchor points A and B; t _A is the arrival time of the first wave peak of the received signal when measured at anchor point A; t _B is the time measured at anchor point B , the arrival time of the first peak of the received signal;

according to the formula Calculate the elastic wave attenuation α, where L is the distance between two anchor points A and B; P _A is the peak value of the first wave peak of the received signal when measuring at anchor point A; P _B is when measuring at anchor point B, The peak value of the first peak of the received signal.

During the whole experiment, pay attention to observe the indications of pressure gauge Ⅰ and pressure gauge Ⅱ. When the indication of pressure gauge Ⅰ is close to the set test pressure, start the hydraulic pump in time to replenish the liquid in the booster tank; when the pressure gauge Ⅱ indicates When the number is close to the set test pressure, the gas cylinder should be replaced in time to replenish the gas source.

Beneficial effects of the present invention:

(1) The low-frequency piezoelectric sensor, liquid diversion port and foaming needle-shaped hole are centrally designed on the base of the annular inner tube, which not only simplifies the structure of the device, but also ensures that the bubbles are evenly distributed in the annular space and move up with the liquid at a constant speed. Improved reliability of measurement data;

(2) By receiving signals at two positioning points by moving the measuring board, the measurement and calculation of elastic wave phase velocity and attenuation can be completed simultaneously, saving a set of low-frequency piezoelectric sensors and reducing the cost of experiments;

(3) The liquid circulation and gas circulation of the experimental device are controlled independently. Through the flow control and the selection of the size of the foaming needle hole, the bubble size can be effectively controlled, especially at low gas content (0.5-2%) Range stability control.

Description of drawings

Fig. 1 is a schematic diagram of an experimental device for measuring the response characteristics of low-frequency elastic waves after liquid ring air intrusion of the present invention;

Fig. 2 is an enlarged view of part 3 in Fig. 1;

Fig. 3 is an enlarged view of part 4 in Fig. 1;

Among them, 1 is the sealed outer tube; 2 is the inner tube; 3 is the ring-shaped inner tube base; 4 is the mobile measuring plate; 5 is the limit rod; 6 is the pulse generator; 7 is the oscilloscope; 8 is the computer; 9 is the liquid injection 10 is a liquid flow meter; 11 is a valve Ⅰ; 12 is a pressure gauge Ⅰ; 13 is a booster tank; 14 is a hydraulic pump; 15 is a liquid storage tank; 16 is a valve Ⅱ; 17 is a liquid flow meter Ⅱ; 18 is Gas injection pipe; 19 is gas flowmeter I; 20 is valve III; 21 is pressure gauge II; 22 is gas cylinder; 23 is pressure gauge III; 24 is valve IV; 25 is gas flowmeter II; 26 is gas recovery tank ; 31 is the base of the inner tube base; 32 is the low-frequency piezoelectric sensor I; 33 is the liquid diversion port; 34 is the foaming needle-shaped hole; 41 is the base of the mobile measuring plate;

detailed description

The present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be noted that the following description is only for explaining the present invention and not limiting its content.

Example 1:

As shown in Figures 1 to 3, an experimental device of the present invention for measuring the response characteristics of low-frequency elastic waves after liquid annulus air invasion includes a wellbore annulus simulation part, a liquid circulation control part, a bubble generation and circulation control part, and an elastic wave The response characteristic measurement part has four parts, as follows:

Wellbore annulus simulation part: including the inner pipe 2 and the sealed outer pipe 1 sleeved outside it, the bottom of the inner pipe 2 is fixedly connected with the annular inner pipe base 3, and the annular inner pipe base 3 is provided with a liquid diversion port 33 and a foaming needle-shaped hole 34, wherein the inner pipe 3 simulates the wellbore, above the annular inner pipe base 3, seals the annulus formed between the outer pipe 1 and the inner pipe 2 to simulate the annulus of the wellbore;

The inner diameter of the inner tube 2 is 25.4 mm and the length is 1.5 m; the inner diameter of the sealed outer tube 1 is 76.2 mm and the length is 2 m.

The annular inner tube base 3 includes an annular inner tube base base 31, on which four low-frequency piezoelectric sensors I 32, four liquid diversion ports 33 and eight foaming needle-shaped holes 34 are arranged, and their centers They are all located on the center line of the ring, wherein the low-frequency piezoelectric sensor I32 and the liquid diversion port 33 are evenly spaced apart, and the foaming needle-shaped hole 34 is located in the middle between the low-frequency piezoelectric sensor I32 and the liquid diversion port 33 . Both the liquid guide port 33 and the foaming needle-shaped hole 34 are through holes, and bubbles of different sizes can be formed by selecting the diameter of the foaming needle-shaped hole 34 and/or the gas injection displacement. The diameter of the foaming needle-shaped hole 34 is 0.2 mm, the size range of the formed bubbles is 1.5-2.1 mm, and the gas content is 0.5-1.0%.

The material of the inner tube 2 and the sealed outer tube 1 is a transparent strengthened plexiglass tube, and the material of the annular inner tube base 31 is a transparent plexiglass plate, so as to observe the bubble generation and cycle control during the experimental measurement.

Liquid circulation control part: including liquid storage tank 15, hydraulic pump 14, booster tank 13, pressure gauge I12, valve I11, liquid flow meter I10 and liquid injection pipe 9 connected in sequence. The top side of the sealed outer tube 1 is provided with an opening I, which is connected to the valve II16, and the valve II16 is connected to the liquid storage tank 15 through the liquid flow meter II17. Various components of the liquid circulation control part are sealed and connected through pressure-resistant circular tubes. The liquid medium is distilled water.

The liquid circulation path is: liquid storage tank 15→hydraulic pump 14→boosting tank 13→valve Ⅰ11→liquid flow meter Ⅰ10→liquid injection pipe 9→inner pipe 2→liquid diversion port 33→wellbore annulus→valve Ⅱ16→liquid Flow meter II 17→fluid storage tank 15.

Bubble generation and circulation control part: including gas cylinder 22, pressure gauge II 21, valve III 20, gas flow meter I 19 and gas injection pipe 18 connected in sequence. There is an opening II on the top side of the pipe 1, and the position of the opening II is higher than that of the opening I. The opening II is connected to the pressure gauge III23, and the pressure gauge III23 is connected to the gas recovery tank through the valve IV24 and the gas flowmeter II25. The gas medium is nitrogen.

The gas circulation path is: gas cylinder 22 → valve III 20 → gas flow meter I 19 → gas injection pipe 18 → eight foaming needle holes 34 → wellbore annulus → valve IV 24 → gas flow meter II 25 → gas recovery tank 26. The gas flow rate is controlled at 240-270ml/min under standard conditions.

Elastic wave response characteristic measurement part: including low-frequency piezoelectric sensor Ⅰ32, low-frequency piezoelectric sensor Ⅱ42, mobile measurement board 4, pulse generator 6 and oscilloscope 7, the mobile measurement board 4 is clamped between the sealed outer tube 1 and the inner tube 2 , the upper surface of the annular inner tube base 3 and the lower surface of the moving measuring plate 4 are respectively provided with the same number of low-frequency piezoelectric sensors I32 and low-frequency piezoelectric sensors II42 aligned one by one; wherein, the low-frequency piezoelectric sensors I32 and the pulse generator The input terminal of the oscilloscope 7 is connected to the pulse generator 6 and the low-frequency piezoelectric sensor II42 respectively, and the output terminal of the oscilloscope 7 is connected to the computer 8 .

The moving measuring plate 4 is fixedly connected with the limit rod 5, and the moving measuring plate 4 is positioned at two known annular positions by lifting or lowering the limit rod 5. The mobile measuring plate 4 comprises a moving measuring plate base 41, and its overall size is adapted to the inner diameter of the sealed outer tube 1. The center of the moving measuring plate base 41 is provided with a through hole, and the diameter of the through hole is adapted to the outer diameter of the inner tube 2. Four branches are evenly arranged along the circumference of the through hole, and a low-frequency piezoelectric sensor II 42 is respectively arranged on the lower surface of each branch.

The low-frequency piezoelectric sensor I32 and the low-frequency piezoelectric sensor II42 are respectively pasted on the upper surface of the annular base base 31 and the lower surface of the branch by epoxy resin.

The material of the mobile measuring plate base 41 is a transparent organic glass plate.

The operating frequency of the low-frequency piezoelectric sensor I32 and the low-frequency piezoelectric sensor II42 is 150Hz.

An experimental method for measuring the response characteristics of low-frequency elastic waves after liquid ring air invasion by using the above-mentioned experimental device. After liquid filling and air inflation and pressurization are completed, the liquid circulation is established through the liquid circulation control part, and then the gas bubble generation and circulation control part is used to establish the gas flow. Circulation, then make bubbles generated at the foaming needle hole 34 and distributed in the annular space, finally, use the elastic wave response characteristic measurement part to complete the analysis and calculation of the elastic wave response characteristic.

Specific steps are as follows:

(1) Before the experiment starts, all valves are closed; a sufficient amount of liquid is prepared in the liquid storage tank 15 .

(2) Turn on the power, turn on the hydraulic pump 14, and slowly pump the liquid into the booster tank 13. After the pressure gauge I12 reaches the predetermined pressure, turn off the hydraulic pump 14; slowly open the valve I11 and the valve II16, and directly Inject liquid; when the liquid level in the annular space reaches the height between valve II16 and valve IV24, close valve I11 and valve II16 to complete liquid filling;

(3) Slowly open the valve III20, pay attention to the change of the indication of the pressure gauge III23, when the indication of the pressure gauge III23 reaches the set test pressure, close the valve III20, and complete the inflation and pressurization;

(4) If measuring the elastic wave response characteristics of the annular liquid at rest, proceed directly to step (5); if measuring the elastic wave response characteristics of the annular liquid circulation, first slowly open the valve I11, and then slowly open the valve Ⅱ16, adjust the valve Ⅰ11 and Ⅱ16, so that the readings of the liquid flow meter Ⅰ10 and the liquid flow meter Ⅱ17 are the same, and the liquid circulation is established;

(5) Slowly open valve III20 first, then slowly open valve IV24, adjust valve III20 and valve IV24, make the gas flowmeter I19 and gas flowmeter II25 show the same value, and establish gas circulation; after the gas circulation is stable, slowly adjust the valve Ⅲ20 and valve Ⅳ24, so that the size of the bubbles generated at the foaming needle hole 34 is basically the same;

(6) After the gas circulation and the bubble size are stabilized, the distribution of the bubbles in the annular space is photographed by a digital camera, which is used to process and extract the actual size of the bubbles on the computer in the later stage;

(7) Lift or lower the limit rod 5, take two positioning points, record the positioning point closer to the low-frequency piezoelectric sensor I32 as A, and record the other as B, start the elastic wave response characteristic measurement part respectively, respectively Record the excitation and reception signals of two positioning points: the pulse generator 6 generates a voltage pulse with a fixed frequency and width, which is recorded by the oscilloscope 7 on the one hand, and on the other hand excites the low-frequency piezoelectric sensor I32 to generate pulse vibrations to form elastic waves Vibration source; after the elastic wave propagates through the gas-liquid mixture in the annular space, it is received by the low-frequency piezoelectric sensor II42, and the elastic wave vibration is converted into a voltage signal, which is collected by the oscilloscope 7; the excitation pulse signal collected by the oscilloscope 7 is transmitted together with the received signal To the computer 8, the analysis and calculation of the elastic wave response characteristics are completed on the computer 8.

The concrete method of the signal analysis in the step (7) and calculation is:

according to the formula Calculate the elastic wave phase velocity v, where L is the distance between two anchor points A and B; t _A is the arrival time of the first wave peak of the received signal when measured at anchor point A; t _B is the time measured at anchor point B , the arrival time of the first peak of the received signal;

according to the formula Calculate the elastic wave attenuation α, where L is the distance between two anchor points A and B; P _A is the peak value of the first wave peak of the received signal when measuring at anchor point A; P _B is when measuring at anchor point B, The peak value of the first peak of the received signal.

During the whole experiment process, pay attention to observe the indications of pressure gauge I12 and pressure gauge II21. When the indication of pressure gauge I12 is close to the set test pressure, the hydraulic pump 14 should be started in time to replenish the liquid in the booster tank 13; When the indication of II 21 is close to the set test pressure, the gas cylinder 22 should be replaced in time to replenish the gas source.

Example 2:

The inner diameter of the inner tube 2 is 25.4 mm and the length is 1.5 m; the inner diameter of the sealed outer tube 1 is 101.6 mm and the length is 2 m. The diameter of the foaming needle-shaped hole 34 is 0.6mm, the gas flow rate is controlled at 310-360ml/min under standard conditions, the size range of the formed bubbles is 1.9-2.8mm, and the gas content is 1.8-2.7%. The operating frequency of the low-frequency piezoelectric sensor I32 and the low-frequency piezoelectric sensor II42 is 100Hz. All the other are with embodiment 1.

Example 3:

The inner diameter of the inner tube 2 is 50.8 mm and the length is 1.5 m; the inner diameter of the sealed outer tube 1 is 127 mm and the length is 2 m. The diameter of the foaming needle-shaped hole 34 is 2mm, the gas flow rate is controlled at 430-490ml/min under standard conditions, the size range of the formed bubbles is 2.3-4.5mm, and the gas content is 3.5-4.4%. The operating frequency of the low-frequency piezoelectric sensor I32 and the low-frequency piezoelectric sensor II42 is 50Hz. All the other are with embodiment 1.

Although the structure and method of use of the present invention have been described above in conjunction with the accompanying drawings, it does not limit the protection scope of the present invention. On the basis of the technical solution of the present invention, those skilled in the art can make various works without creative work. Such modifications or variations are still within the protection scope of the present invention.

Claims (10)

1. An experimental device for measuring the response characteristics of low-frequency elastic waves after liquid ring air intrusion is characterized in that it comprises the following four parts: The simulation part of the wellbore annulus includes the inner pipe and the sealed outer pipe sleeved outside it. The bottom end of the inner pipe is fixedly connected with the base of the annular inner pipe, and the base of the annular inner pipe is provided with a liquid diversion port and a foaming needle-shaped hole , wherein the inner pipe simulates the wellbore, above the base of the annular inner pipe, seals the annular space formed between the outer pipe and the inner pipe to simulate the annulus of the wellbore; The liquid circulation control part, including the liquid circulation pipe, one end is inserted into the inner pipe, and the other end is connected to the opening I opened on the top side of the sealed outer pipe, so that the liquid injected into the inner pipe flows through the liquid diversion port, the annular space, opening I and The liquid circulation pipe then flows back to the inner pipe through the liquid circulation pipe to form a circulation; The bubble generation and circulation control part includes a gas injection structure located on the bottom side of the sealed outer tube, and its gas outlet is connected to the foaming needle-shaped hole. The top side of the sealed outer tube is provided with an opening II, which is connected to the gas recovery structure, and the position of opening II is higher than that of opening I; and The elastic wave response characteristic measurement part includes a mobile measurement board, a pulse generator and an oscilloscope. The mobile measurement board is clamped between the sealed outer tube and the inner tube. The upper surface of the annular inner tube base and the lower surface of the mobile measurement board are respectively There are the same number of low-frequency piezoelectric sensors Ⅰ and low-frequency piezoelectric sensors Ⅱ aligned one by one; among them, the low-frequency piezoelectric sensor Ⅰ is connected to the pulse generator, and the input terminals of the oscilloscope are respectively connected to the pulse generator and the low-frequency piezoelectric sensor. Ⅱ, the output terminal of the oscilloscope is connected to the computer. 2. The experimental device according to claim 1, characterized in that, the annular inner tube base comprises an annular inner tube base base, four low-frequency piezoelectric transducers I and four liquid guides are arranged on the annular inner tube base base. There are eight foaming needle-shaped holes, and their centers are all located on the ring center line. Among them, the interval between the low-frequency piezoelectric sensor Ⅰ and the liquid guide port is evenly distributed, and the foaming needle-shaped holes are located between the low-frequency piezoelectric sensor Ⅰ and the liquid guide port. Midway between spouts. 3. The experimental device according to claim 1, characterized in that, the liquid circulation pipeline is sequentially provided with: a liquid storage tank, a hydraulic pump, a booster tank, a pressure gauge I, a valve I, a liquid flow meter I and a liquid An injection pipe, the liquid injection pipe protrudes into the inner pipe, and an opening I is provided on the top side of the sealed outer pipe, which is connected to the valve II, and the valve II is connected to the liquid storage tank through the liquid flow meter II. 4. The experimental device according to claim 1, wherein the gas injection structure comprises a gas cylinder, a pressure gauge II, a valve III, a gas flowmeter I and a gas injection pipe connected in sequence, and the opening II is connected to the pressure The gauge III is connected, and the pressure gauge III is connected to the gas recovery tank through the valve IV and the gas flow meter II. 5. The experimental device according to claim 4, characterized in that there are several foaming needle-shaped holes, and they are connected in parallel with the gas injection pipe in a sealed manner. 6. The experimental device according to claim 1, characterized in that, the moving measuring plate is fixedly connected to the limit rod, and the moving measuring plate is positioned at two known annular positions by lifting or lowering the limit rod . 7. experimental device according to claim 1, is characterized in that, described moving measuring plate comprises moving measuring plate base, and its overall size is adapted to the inner diameter of sealed outer tube, and the center of moving measuring plate base is provided with through hole, The diameter of the through hole is adapted to the outer diameter of the inner tube, four branches are evenly arranged along the circumference of the through hole, and a low-frequency piezoelectric sensor II is respectively arranged on the lower surface of each branch. 8. An experimental method utilizing the experimental device described in any one of claims 1 to 7 to measure the response characteristics of low-frequency elastic waves after liquid ring air invasion, characterized in that, after liquid filling and air inflation and pressurization are completed, the liquid circulation The control part establishes the liquid circulation, and then uses the bubble generation and circulation control part to establish the gas circulation, and then makes the bubbles generated at the foaming pinholes and distributed in the annular space, and finally, the elastic wave response characteristic measurement part is used to complete the analysis of the elastic wave response characteristics and calculate. 9. experimental method according to claim 8, is characterized in that, the concrete steps of described experimental method are as follows: (1) Before starting the experiment, close all valves; prepare a sufficient amount of liquid in the liquid storage tank. (2) Turn on the power, turn on the hydraulic pump, and slowly pump liquid into the pressurized tank. After the pressure gauge Ⅰ reaches the predetermined pressure, turn off the hydraulic pump; slowly open the valve Ⅰ and valve Ⅱ, and directly inject liquid into the inner pipe; When the liquid level in the annular space reaches the height between valve II and valve IV, close valve I and valve II to complete filling; (3) Slowly open the valve III, pay attention to the changes in the indication of the pressure gauge III, when the indication of the pressure gauge III reaches the set test pressure, close the valve III, and complete the inflation and pressurization; (4) If measuring the elastic wave response characteristics of the annular liquid at rest, proceed directly to step (5); if measuring the elastic wave response characteristics of the annular liquid circulation, first slowly open the valve I, and then slowly open the valve Ⅱ, adjust valve Ⅰ and valve Ⅱ, so that the readings of liquid flow meter Ⅰ and liquid flow meter Ⅱ are the same, and establish liquid circulation; (5) First slowly open valve III, then slowly open valve IV, adjust valve III and valve IV, so that the indications of gas flow meter I and gas flow meter II are the same, and establish a gas cycle; after the gas cycle is stable, slowly adjust the valve Ⅲ and valve Ⅳ, so that the size of the bubbles generated at the foaming needle hole is basically the same; (6) After the gas circulation and the bubble size are stabilized, the distribution of the bubbles in the annular space is photographed by a digital camera, which is used to process and extract the actual size of the bubbles on the computer in the later stage; (7) Lift or lower the limit rod, take two positioning points, record the positioning point closer to the low-frequency piezoelectric sensor I as A, and record the other as B, start the elastic wave response characteristic measurement part respectively, and record Excitation and reception signals of two positioning points: the pulse generator generates a voltage pulse of fixed frequency and width, which is recorded by the oscilloscope on the one hand, and on the other hand excites the low-frequency piezoelectric sensor Ⅰ to generate pulse vibration, forming an elastic wave source; After the elastic wave propagates through the gas-liquid mixture in the annular space, it is received by the low-frequency piezoelectric sensor II, and the elastic wave vibration is converted into a voltage signal, which is collected by the oscilloscope; the excitation pulse signal collected by the oscilloscope and the received signal are sent to the computer together, and the The analysis and calculation of the elastic wave response characteristics are completed. 10. experimental method according to claim 9 is characterized in that, the concrete method of the signal analysis in the step (7) and calculation is: according to the formula Calculate the elastic wave phase velocity v, where L is the distance between two anchor points A and B; t _A is the arrival time of the first wave peak of the received signal when measured at anchor point A; t _B is the time measured at anchor point B , the arrival time of the first peak of the received signal; according to the formula Calculate the elastic wave attenuation α, where L is the distance between two anchor points A and B; P _A is the peak value of the first wave peak of the received signal when measuring at anchor point A; P _B is when measuring at anchor point B, The peak value of the first peak of the received signal.