WO2021008229A1 - Testing method for non-contact measurement of rock wave velocity in fidelity environment - Google Patents

Abstract

Disclosed is a testing method for non-contact measurement of the rock wave velocity in a fidelity environment. A cylindrical container (3) is selected; a sound wave emission probe (5) and a sound wave reception probe (6) are respectively and fixedly arranged inside the cylindrical container by means of two fixing devices (4); a sound wave testing system (1) provided with a waveform signal generator and a signal acquisition card is selected; the sound wave testing system is connected to the sound wave reception probe (6) and the sound wave emission probe (5); and a liquid sound-wave transmission medium (2) is injected into the cylindrical container (3). Non-contact measurement of the rock wave velocity can be achieved in the fidelity environment, and the required apparatuses are simple in structure, low in construction cost, and simple in measurement method. Non-contact rock sound wave testing can be achieved by using a conventional sound emission testing system, and the testing efficiency of rock sound waves can be greatly improved, support can also be provided for subsequent continuous integration work of rock petrophysical property testing, and an important significance is achieved for in-depth research into the mechanical properties of deep in situ rock masses.

Description

A test method for non-contact measurement of rock wave velocity under fidelity environment Technical field

The invention relates to the field of rock mechanics and engineering technology, in particular to a test method for non-contact measurement of rock wave speed in a fidelity environment.

Background technique

The in-situ rock mechanics behavior law of the rock layers with different depths is the leading science and important theoretical basis for deep drilling, deep resource development and utilization, and earth application science. The core and key is how to obtain the in-situ rock core under deep environmental conditions. Real-time load testing and analysis. Wave speed is an important physical parameter of the core, which can be inverted with the mechanical parameters such as elastic modulus. At the same time, acoustic wave testing has become an important parameter for exploring the internal structure of the core.

In the process of conventional rock acoustic wave testing, the acoustic wave probe needs to be closely attached to the core, and a coupling agent needs to be applied between the acoustic wave probe and the core contact surface to eliminate the influence of the gap at the contact surface on the acoustic emission signal. Simple, but the preparation is complicated. More importantly, the deep in-situ environment has been destroyed during the preliminary work such as placing the probe, and the test results obtained are also distorted. The fidelity environment is collected when the rock is intercepted in the deep in-situ environment. The environment where the rock is located, and throughout the experiment, ensure that the temperature, pressure, and humidity of the sample rock and the deep in-situ are basically the same. According to deep rock mechanics and engineering needs, if non-contact rock sonic testing can be realized, it can not only greatly improve the efficiency of rock sonic testing, but also provide support for the integrated work of continuous core physical testing in the later stage. Therefore, this test device is in-depth Exploring the non-contact rock acoustic wave velocity test under the fidelity environment has important theoretical and engineering practical significance.

Summary of the invention

In view of the above-mentioned technical deficiencies, the purpose of the present invention is to provide a non-contact measurement method for rock wave velocity in a fidelity environment, which not only takes into account the in-situ environmental conditions of the test sample, but also uses non-contact measurement. The efficiency of acoustic emission measurement of rock wave velocity is greatly improved, and the characteristics of the in-situ environment of the specimen are also guaranteed.

To solve the above technical problems, the present invention adopts the following technical solutions:

The invention provides a test method for non-contact measurement of rock wave velocity in a fidelity environment, which includes the following steps:

It includes the following steps:

S1. Choose a cylindrical container, and set two sound wave transmitting probes and sound wave receiving probes of equal height in its interior through two fixing devices;

S2. Select a sound wave test system equipped with a waveform signal generator and a signal acquisition card, connect it to the preamplifier and the sound wave emission probe, and connect the sound wave receiving probe to the sound wave test system;

S3. Connect the output interface of the waveform signal generator to the signal acquisition card as a synchronization signal for monitoring the sound wave signal;

S4. Fill the cylindrical container with liquid acoustic wave transmission medium;

S5. Seal the cylindrical container with a sealing lid, then apply hydrostatic pressure to the target pressure through an external pressurizing pump, the pressure range is 0～150MPa, and heat to the target temperature through an external electric heating ring, at room temperature～150℃, at room temperature and normal pressure The test can skip this step;

S6. Turn on the acoustic wave test system and waveform signal generator without inserting the rock core. The acoustic wave test system uses the acoustic wave transmitting probe and the acoustic wave receiving probe to collect the acoustic wave signal propagated through the liquid acoustic wave transmission medium while recording the acoustic signal. , After transmitting several times of sound wave signal, stop transmitting signal;

S7. Use the sound wave test system to read the sound wave synchronization signal and the sound wave signal propagating between the two probes, and find the sound wave time difference t _p1 between the two signals;

S8. Comparing the distance a ₁ between the two probes with the difference between t _{p1 –} t _o , obtain the longitudinal wave velocity v _{p1 of the} acoustic wave propagating in the liquid acoustic wave transmission medium; t _o is the system error, which is analyzed by software and actual The time error of the waveform take-off point is calculated;

S9. Adjust the external pressure pump to relieve the pressure and cool to room temperature. Open the sealing cover and place the sample rock stored in the fidelity environment in the middle of the sound wave emitting probe and the sound wave receiving probe, so that the center line of the two probes passes through The center of the core section;

S10. Refer to step S5 for sealing, pressurizing and heating, and refer to steps S7 and S8 to measure the total time t _p2 of sound wave propagation;

S11. The speed of sound wave propagating in the rock v _p2 = a ₂ /t, a ₂ is the maximum lateral distance of the rock in the direction of the center line of the two probes, t = t _p2 -t _o -t _l , t is the sound wave propagating in the rock Time, t _l is the propagation time of the liquid acoustic wave transmission medium, t _l =(a ₁ -a ₂ )/v _p1 .

Preferably, the material of the fixing device in step S1 is PVC material.

Preferably, both the acoustic wave transmitting probe and the acoustic wave receiving probe in step S2 are packaged, and the package is processed with a high temperature resistance of 150° C. and a high pressure of 150 MPa.

Preferably, hydraulic oil is selected as the liquid acoustic wave transmission medium.

Preferably, in step S6, the number of times of transmitting the acoustic wave signal is 6 to 8 times.

The beneficial effects of the present invention are: the non-contact rock wave velocity can be measured in a fidelity environment, the required equipment structure is simple, the cost is low, and the measurement method is simple; the non-contact rock of the present invention can be realized by using an ordinary acoustic wave test system Acoustic testing can not only greatly improve the efficiency of rock acoustic testing, but also provide support for the subsequent integration of continuous rock physical property testing, which is of great significance for in-depth study of the role of rock masses.

Description of the drawings

In order to explain the embodiments of the present invention or the technical solutions in the prior art more clearly, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are only These are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative work.

FIG. 1 is a schematic diagram of the connection of various components in a test method for non-contact measurement of rock wave velocity in a fidelity environment provided by an embodiment of the present invention.

Description of reference signs:

1. Acoustic wave test system; 2. Liquid acoustic wave transmission medium; 3. Cylindrical container; 4. Fixing device; 5. Acoustic emission probe; 6. Acoustic wave collection probe, 7. Sealed cover; 8. Pressurized pump; 9. Electricity J.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative work shall fall within the protection scope of the present invention.

Embodiment 1. A test method for non-contact measurement of rock wave velocity in a fidelity environment. The core test under normal temperature and pressure includes the following steps:

S1. As shown in Fig. 1, a cylindrical container 3 is selected, and two sound wave transmitting probes 5 and sound wave receiving probes 6 of equal height are respectively fixed in its inside through two fixing devices 4, and the distance between the two probes is set to 103.9mm;

S2. Select the Disp sound wave test system 1 installed with a waveform signal generator and a signal acquisition card, connect it to the preamplifier and the sound wave emission probe 5 in turn, and connect the sound wave receiving probe 6 to the Disp sound wave test system 1;

S3. Connect the output interface of the waveform signal generator to the signal acquisition card as a synchronization signal for monitoring the acoustic emission signal;

S4. Fill the cylindrical container 3 with hydraulic oil;

S5. Turn on the Disp acoustic wave test system 1 and the waveform signal generator without putting the rock core, use the ARB-1410 arbitrary waveform signal generator as the signal source, set the excitation voltage to 150V, the excitation frequency to 300hz, and the Disp sound wave The test system 1 uses the sound wave transmitting probe 5 and the sound wave receiving probe 6 to collect the sound wave signal propagated through the hydraulic oil while recording the sound signal, and stops transmitting the signal after transmitting 6 to 8 sound wave signals;

S6. Use the Disp acoustic wave test system 1 to read the acoustic synchronization signal and the acoustic wave signal propagating between the two probes, and obtain the acoustic wave time difference t _p1 between the two signals, which is measured by the Disp acoustic wave test system 1 multiple times and averaged t _p1 = 71.3μs;

S7. Comparing the distance a ₁ between the two probes with the difference between t _p1- t _o , obtain the longitudinal wave velocity v _{p1 of the} sound wave propagating in the hydraulic oil, and t _o is the system error, which is analyzed by the software and taken off by the actual waveform. The time error of the point is calculated to obtain t _o =0, v _p1 ＝103.9mm/(71.3μs-0)=1457.22m/s in this case;

S8. Place the sample core at the center of the sound wave transmitting probe 5 and the sound wave receiving probe 6, so that the center line of the two probes passes through the center of the core section circle. In order to facilitate the comparison with the contact rock sound wave test, the columnar rock is selected. In this embodiment, granite, marble, and medium sandstone are selected as the test objects. The error of diameter does not exceed 0.03cm, and the error of non-parallelism on both ends of the sample does not exceed 0.005cm. The following table shows the sample number;

Sample serial number	Lithology	Diameter/mm	Length/mm	Test items
1	granite	47.5	100.30	Longitudinal wave velocity
2	Marble	49.2	100.20	Longitudinal wave velocity
3	Medium sandstone	49.4	99.70	Longitudinal wave velocity

S9. Refer to steps S6 and S7 to measure the total time t _p2 of sound wave propagation;

S10. The speed of the sound wave propagating in the rock v _p2 = a ₂ /t, a ₂ is the maximum lateral distance of the rock in the direction of the center line of the two probes, t is the propagation time of the sound wave in the rock, t = t _p2 -t _o -t _l , t _l is the propagation time in hydraulic oil, t _l = (a ₁ -a ₂ )/v _p1 ;

(1) Granite: Disp acoustic wave test system 1 test result t _p2 = 48.8μs,

According to a ₁ =103.9mm, a ₂ =47.5mm, t _p2 =48.8μs, t _o = 0μs, v _p1 =1457.22m/s, t = t _p2 -t _o -t _l =48.8μs–0μs–[( 103.9–47.5)/1457.22] = 10.1μs The velocity of sound waves propagating in granite v _p2 =a _{2 /} t =47.5mm/10.1μs =4702.97m/s

(2) Marble: Disp acoustic wave test system test 1 result t _p2 = 48.7μs,

According to a ₁ =103.9mm, a ₂ =49.2mm, t _p2 =48.7μs, to =2μs, v _p1 =1457.22m/s, t =t _p2 -t _o -t _l =48.7μs-2μs–[(103.9 –49.2)/1457.22]=9.2μs The velocity of sound wave propagating in marble vp2=a2/t=49.2mm/9.2μs=5347.82m/s

(3) Medium sandstone: Disp acoustic wave test system 1 test result t _p2 = 67.8μs

According to a ₁ =103.9mm, a ₂ =49.4mm, t _p2 =67.8μs, to =10μs, v _p1 =1457.22m/s, t=t _p2 -t _o -t _l =67.8μs-10μs–[(103.9 –49.4)/1457.22] = 20.4μs velocity of sound wave propagating in medium sandstone v _p2 =a ₂ /t=49.4mm/20.4μs=2421.56m/s where the sandstone sample is the rock sample after the mechanical experiment test. There are cracks inside the sample, so the wave velocity is low

S11. Move the rock sample, keeping the center of the two probes connected by the center of the rock sample in this plane unchanged, measure the rock sample close to the acoustic wave emission probe 5 once, and move the rock sample close to the acoustic wave acquisition probe 6 for another test.

S12. Move the rock sample to gradually deviate from the center line and test twice.

The fixing device 4 in step S1 is made of PVC material.

Both the acoustic wave transmitting probe and the acoustic wave receiving probe in step S2 are packaged, and the package is processed with a high temperature resistance of 150° C. and a high pressure of 150 MPa.

Step S8 tests the wave velocity of the rock sample under normal temperature and pressure. Therefore, there is no heating and pressure step. Place the sound wave transmitting probe 5 and the sound wave receiving probe 6 close to the rock surface, and apply a proper amount of sound wave couplant to the contact between the probe and the rock. Disp acoustic wave test system 1, refer to the measurement steps S6-S7 to measure the acoustic wave velocity of granite, marble and medium sandstone, and compare the obtained results with the non-contact rock wave velocity test as shown in Table 1 and Table 2:

Sonic test data summary table 1

Note: The medium sandstone rock is the rock after the mechanical experiment test. There are cracks in the rock, so the wave speed is low.

Sonic test data summary table 2

The following conclusions can be preliminarily drawn through experimental data:

(1) When measuring the speed of hydraulic oil only, the measured sound wave time difference is 71.3μs. When the rock is placed between the sound wave transmitting probe 5 and the sound wave receiving probe 6, the sound wave time difference is less than 71.3μs, and the sound wave propagates in the rock. The speed at time is much greater than the speed of propagation in hydraulic oil, which indicates that when testing the sound wave speed of rock under non-contact conditions, the sound wave signal received by the sound wave receiving probe 6 must be the sound signal passing through the rock. Therefore, the sound wave probe and It is feasible to measure rock wave velocity in a non-contact manner.

(2) Observe the above experimental data. In this experiment, the experimental results of contact measurement and non-contact measurement of acoustic wave velocity are basically consistent, verifying that under non-contact conditions, the acoustic signal is generated from the acoustic wave emission probe 5 and passes through the rock along the center line. Behind the surface, the sound wave propagates inside the rock according to the centerline path. After passing through the surface of the other side of the rock, the sound wave still propagates along the centerline and reaches the sound wave receiving probe 6.

Example 2, a test method for non-contact measurement of rock wave velocity in a fidelity environment. The core is tested in a fidelity environment. Refer to Example 1. In step S4, a pressurized part is added: a sealing cap 7 is used to seal the cylindrical volume. Then, the external pressure pump 8 passes through the sealing cover 7 and the external electric heating ring 9 to apply hydrostatic pressure to the hydraulic oil to a target pressure of 60MPa and heating to a target temperature of 80°C; a pressure relief part is added in step S8 : When the external pressurizing pump 8 is adjusted to relieve the pressure and the hydraulic oil is cooled to room temperature, the sealing cover 7 is opened and then the sample rock is put in; the pressurizing part is added in step S9. In addition to the above-mentioned additional steps, the embodiment 2 Other steps are the same as those in Example 1; the test results are compared with Example 1 as shown in Table 3:

Sonic test data summary table 3

Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. In this way, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these modifications and variations.

Claims (5)

1. A test method for non-contact measurement of rock wave velocity in a fidelity environment is characterized in that it comprises the following steps:

   S1. Choose a cylindrical container, and set two sound wave transmitting probes and sound wave receiving probes of equal height in its interior through two fixing devices;

   S2. Select a sound wave test system equipped with a waveform signal generator and a signal acquisition card, connect it to the preamplifier and the sound wave emission probe, and connect the sound wave receiving probe to the sound wave test system;

   S3. Connect the output interface of the waveform signal generator to the signal acquisition card as a synchronization signal for monitoring the sound wave signal;

   S4. Fill the cylindrical container with liquid acoustic wave transmission medium;

   S5. Seal the cylindrical container with a sealing cap, and then apply hydrostatic pressure to the target pressure through an external pressurizing pump and heat the external electric heating ring to the target temperature. This step can be skipped for testing at room temperature and normal pressure;

   S6. Turn on the acoustic wave test system and waveform signal generator without inserting the rock core. The acoustic wave test system uses the acoustic wave transmitting probe and the acoustic wave receiving probe to collect the acoustic wave signal propagated through the liquid acoustic wave transmission medium while recording the acoustic signal. , After transmitting several times of sound wave signal, stop transmitting signal;

   S7. Use the sound wave test system to read the sound wave synchronization signal and the sound wave signal propagating between the two probes, and find the sound wave time difference t _p1 between the two signals;

   S8. Comparing the distance a ₁ between the two probes with the difference between t _{p1 –} t _o , obtain the longitudinal wave velocity v _{p1 of the} acoustic wave propagating in the liquid acoustic wave transmission medium; t _o is the system error, which is analyzed by software and actual The time error of the waveform take-off point is calculated;

   S9. Adjust the external pressure pump to relieve the pressure and cool to room temperature. Open the sealing cover and place the sample rock stored in the fidelity environment in the middle of the sound wave emitting probe and the sound wave receiving probe, so that the center line of the two probes passes through The center of the core section;

   S10. Refer to step S5 for sealing, pressurizing and heating, and refer to steps S7 and S8 to measure the total time t _p2 of sound wave propagation;

   S11. The speed of sound wave propagating in the rock v _p2 = a ₂ /t, a ₂ is the maximum lateral distance of the rock in the direction of the center line of the two probes, t = t _p2 -t _o -t _l , t is the sound wave propagating in the rock Time, t _l is the propagation time of the liquid acoustic wave transmission medium, t _l =(a ₁ -a ₂ )/v _p1 .
2. The test method for non-contact measurement of rock wave velocity in a fidelity environment according to claim 1, wherein the fixing device in step S1 is made of PVC material.
3. The test method for non-contact measurement of rock wave velocity in a fidelity environment according to claim 1, wherein the acoustic wave transmitting probe and the acoustic wave receiving probe in step S2 are both packaged, and the package is processed for high temperature and high pressure resistance .
4. The testing method for non-contact measurement of rock wave velocity in a fidelity environment according to claim 1, characterized in that, in step S4, hydraulic oil is selected as the liquid acoustic wave transmission medium.
5. The test method for non-contact measurement of rock wave velocity in a fidelity environment according to claim 1, wherein in step S6, the number of times of transmitting the acoustic wave signal is 6 to 8 times.

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