Rock core measuring device and sound wave correction algorithm

Abstract

The invention belongs to the technical field of core measurement, and discloses a core measurement device and a sound wave correction algorithm. The device comprises a sleeve, a fixing assembly, a resistivity measuring assembly and a sound wave measuring assembly. A test cavity is formed in the sleeve, a to-be-measured rock core sample is located in the test cavity, and part of the rock core sample is located in the effective nuclear magnetic signal detection area. The fixing assembly comprises a first fixing piece and a second fixing piece which are arranged on the two sides of the core sample at intervals, the power supply electrode is arranged between the core sample and the first fixing piece, the measuring electrode is arranged between the core sample and the second fixing piece, the power supply electrode can provide electric signals, and the measuring electrode can receive the electric signals sent by the power supply electrode. Therefore, the resistivity is measured. According to the device, by increasing the length of the rock core sample, interference of magnetic fields of the resistivity measurement assemblies at the two ends of the rock core sample on effective nuclear magnetic signals in the nuclear magnetic resonance cabin is effectively avoided, and simultaneous measurement of sound waves, nuclear magnetism and resistivity of the natural gas hydrate rock core sample is achieved.

Description

Technical Field

[0001] The invention relates to the technical field of core measurement, and in particular to a core measurement device and an acoustic wave correction algorithm. Background Art

[0002] Natural gas hydrates are ice-cage-like compounds formed by natural gas and water under high pressure and low temperature conditions. The development of natural gas hydrate resources requires basic research on the physical, chemical and mechanical properties of natural gas hydrate reservoirs. The basic research is mainly based on natural gas hydrate core samples, and in-situ or quasi-in-situ testing of the physical properties of natural gas hydrate reservoirs is carried out.

[0003] At present, by placing a traditional gas hydrate core measurement device in a nuclear magnetic resonance chamber, the acoustic wave and nuclear magnetic signal of the core can be detected simultaneously. Since the power supply electrode and measurement electrode of the resistivity measurement component will interfere with the nuclear magnetic signal, resulting in errors in the measurement results, the traditional gas hydrate core measurement device does not have a resistivity measurement component, and thus cannot achieve simultaneous measurement of acoustic waves, resistivity and nuclear magnetic signals. Summary of the invention

[0004] The object of the present invention is to provide a core measurement device and an acoustic wave correction algorithm, wherein the measurement device can realize simultaneous measurement of acoustic waves, resistivity and nuclear magnetic signals, and the acoustic wave correction algorithm can eliminate the influence of the resistivity measurement equipment on the acoustic wave signal and truly reflect the comprehensive function of the sample.

[0005] To achieve this object, the present invention adopts the following technical solutions:

[0006] On the one hand, a core measurement device is provided, which is used in a nuclear magnetic resonance chamber, wherein an effective nuclear magnetic signal detection area is provided in the nuclear magnetic resonance chamber;

[0007] The core measurement device comprises:

[0008] A sleeve is provided with a test cavity, a core sample to be measured is located in the test cavity and in the effective nuclear magnetic signal detection area, and both ends of the core sample extend to the outside of the effective nuclear magnetic signal detection area; the test cavity is filled with a constant temperature liquid, and both ends of the sleeve are provided with a plugging piece, the plugging piece can seal the test cavity, and the plugging piece is made of a conductive material; the plugging piece is provided with a displacement channel connected with the core sample;

[0009] A fixing assembly, comprising a first fixing member and a second fixing member which are spaced apart and arranged on both sides of the core sample;

[0010] A resistivity measurement assembly, comprising a power supply electrode and a measuring electrode, wherein the power supply electrode is arranged between the core sample and the first fixing member, and the measuring electrode is arranged between the core sample and the second fixing member;

[0011] The acoustic wave measurement component includes an ultrasonic transducer and a detector. The ultrasonic transducer is arranged on the first fixing member and can provide a sound source for acoustic wave measurement. The detector is arranged on the second fixing member and can receive the sound source emitted by the ultrasonic transducer.

[0012] As an optional solution for the core measurement device, the size of the nuclear magnetic signal detection area is 10 cm, and the size of the core sample is 14 cm.

[0013] As an optional solution of the core measuring device, the blocking piece is made of copper material.

[0014] As an optional solution of the core measurement device, one of the blocking members is provided with a displacement inlet, and the other blocking member is provided with a displacement outlet, and both the displacement inlet and the displacement outlet are communicated with the corresponding displacement channel.

[0015] As an optional solution for the core measurement device, a constant temperature liquid inlet is provided on one of the sealing parts, and a constant temperature liquid outlet is provided on the other sealing part. Both the constant temperature liquid inlet and the constant temperature liquid outlet are connected to the test cavity, and the position height of the constant temperature liquid inlet is lower than the position height of the constant temperature liquid outlet.

[0016] As an optional solution of the core measurement device, the constant temperature liquid is a fluorinated liquid.

[0017] As an optional solution of the core measurement device, the temperature of the isothermal liquid is the same as the temperature of the formation where the core sample is located.

[0018] On the other hand, an acoustic wave correction algorithm is provided for correcting the results collected by the core measurement device described above, comprising the following steps:

[0019] S1: Data collection;

[0020] Using the acoustic wave signal collected by the core measurement device as test data;

[0021] The resistivity measurement assembly in the core measurement device is removed, and the collected acoustic wave signal is used as the baseline data;

[0022] S2: data preprocessing and feature extraction;

[0023] The test data and the reference data are filtered, noise is eliminated, and then standardized so that the test data and the reference data have the same amplitude range;

[0024] Extract key features from standardized test data and standardized benchmark data;

[0025] S3: Model building;

[0026] Combined with the benchmark data and test data, a mathematical model was established to describe the effect of the resistivity measurement component on the acoustic wave signal;

[0027] S4: Correction algorithm and verification optimization;

[0028] According to the established mathematical model, the error correction term is calculated and the correction algorithm is established. The test results of multiple tests are used to verify the effectiveness of the correction algorithm.

[0029] As an optional solution of the sound wave correction algorithm, the filtering process in step S2 uses a filter.

[0030] As an optional solution of the sound wave correction algorithm, the error range of the error correction item in step S4 does not exceed 5%.

[0031] Beneficial effects of the present invention:

[0032] The present invention provides a core measurement device, which increases the length of the core sample so that both ends of the core sample extend to the outside of the effective nuclear magnetic signal detection area, so as to avoid the magnetic field of the power supply electrode and the measuring electrode clamped at both ends of the core sample interfering with the nuclear magnetic signal in the effective nuclear magnetic signal detection area in the nuclear magnetic resonance chamber, thereby being able to achieve simultaneous measurement of acoustic waves, resistivity and nuclear magnetic resonance, and the core sample can be measured without moving the core sample multiple times, effectively avoiding the measurement error caused by the decomposition of hydrates during the movement of the core sample. In addition, the present invention also provides an acoustic wave correction algorithm, which can correct the acoustic wave signal obtained by the core measurement device to eliminate the influence of the resistivity measurement component on the acoustic wave signal, avoid the distortion of the acoustic wave detection signal, and thus ensure that an accurate acoustic wave signal is obtained, truly reflecting the comprehensive function of the sample. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is an overall schematic diagram of a core measurement device provided in a specific implementation example of the present invention.

[0034] In the figure:

[0035] 100. Core samples;

[0036] 1. Sleeve; 10. Test chamber; 11. Blocking piece; 111. Displacement channel; 112. Displacement inlet; 113. Displacement outlet; 114. Constant temperature liquid inlet; 115. Constant temperature liquid outlet;

[0037] 21. a first fixing member; 22. a second fixing member;

[0038] 31. Power supply electrode; 32. Measuring electrode;

[0039] 41. Ultrasonic transducer; 42. Detector. DETAILED DESCRIPTION

[0040] The present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It is to be understood that the specific embodiments described herein are only used to explain the present invention, rather than to limit the present invention. It should also be noted that, for ease of description, only parts related to the present invention, rather than all structures, are shown in the accompanying drawings.

[0041] In the description of the present invention, unless otherwise clearly specified and limited, the terms "connected", "connected", and "fixed" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0042] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0043] In the description of this embodiment, the terms "upper", "lower", "right", etc., directions or positional relationships are based on the directions or positional relationships shown in the drawings, and are only for the convenience of description and simplification of operation, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used to distinguish in the description and have no special meaning.

[0044] The technical solution of the present invention is further described below with reference to the accompanying drawings and through specific implementation methods.

[0045] like Figure 1As shown, this embodiment provides a core measurement device for use in a nuclear magnetic resonance chamber. An effective nuclear magnetic signal detection area is provided in the nuclear magnetic resonance chamber for detecting nuclear magnetic signals in the core. The core measurement device includes a sleeve 1, a fixing assembly, a resistivity measurement assembly, and an acoustic wave measurement assembly. Among them, a test chamber 10 is provided in the sleeve 1, and a core sample 100 to be measured is located in the test chamber 10 and in the effective nuclear magnetic signal detection area, and both ends of the core sample 100 extend to the outside of the effective nuclear magnetic signal detection area. The test chamber 10 is filled with a constant temperature liquid to simulate the environment in the formation where the core sample 100 is located. A plugging member 11 is provided at both ends of the sleeve 1, and the plugging member 11 can seal the test chamber 10, and the plugging member 11 is made of a conductive material. A displacement channel 111 connected to the core sample 100 is provided on the plugging member 11 to deliver the displacement liquid to the core sample 100 to ensure the smooth progress of the measurement. The fixing assembly includes a first fixing member 21 and a second fixing member 22 which are spaced apart and arranged on both sides of the core sample 100 .

[0046] Specifically, in this embodiment, the first fixing member 21 and the second fixing member 22 are both made of ceramic material. The ceramic material is heat-resistant and pressure-resistant and has good insulation properties. At the same time, it does not contain hydrogen signals and will not affect the measurement results.

[0047] The resistivity measurement assembly includes a power supply electrode 31 and a measuring electrode 32. The power supply electrode 31 is disposed between the core sample 100 and the first fixing member 21, and the measuring electrode 32 is disposed between the core sample 100 and the second fixing member 22. The power supply electrode 31 can provide an electrical signal, and the measuring electrode 32 can receive an electrical signal sent by the power supply electrode 31. Based on Ohm's law and the relationship between electric field distribution, in a material, the electric field strength is proportional to the potential difference and inversely proportional to the current strength. By measuring the potential difference and the current strength, the resistivity can be determined.

[0048] Specifically, the power supply electrode 31 , the measuring electrode 32 and the resistivity measurement principle are all prior arts and will not be described in detail herein.

[0049] The acoustic wave measurement assembly includes an ultrasonic transducer 41 and a detector 42. The ultrasonic transducer 41 is disposed on the first fixing member 21 and can provide a sound source for acoustic wave measurement; the detector 42 is disposed on the second fixing member 22 and can receive the sound source emitted by the ultrasonic transducer 41. Since geological factors such as the lithology and water content of the core sample 100 can cause changes in the velocity, amplitude and frequency of the acoustic wave, the geological conditions of the core sample 100 can be understood through the velocity, amplitude and frequency of the acoustic wave received by the detector 42, and certain mechanical parameters and other engineering geological property indicators of the core sample 100 can be obtained.

[0050] Specifically, the ultrasonic transducer 41 and the detector 42 are both existing devices that have been disclosed in the prior art. Their specific structures and principles refer to the prior art and will not be described in detail here.

[0051] The core measurement device effectively avoids the interference of the magnetic field of the resistivity measurement components at both ends of the core sample 100 on the effective nuclear magnetic resonance signal in the nuclear magnetic resonance chamber by increasing the length of the core sample 100, and realizes the simultaneous measurement of the acoustic wave, nuclear magnetic resonance and resistivity of the natural gas hydrate core sample 100.

[0052] Optionally, the size of the nuclear magnetic signal detection area is 10 cm, and the size of the core sample 100 is 14 cm. The length of the core sample 100 is slightly larger than the length of the nuclear magnetic signal detection area, which can effectively avoid the interference of the magnetic field of the resistivity measurement component on the nuclear magnetic signal detection area, and at the same time, the core sample 100 will not be broken due to the excessive length of the core sample 100.

[0053] Optionally, the blocking member 11 is made of copper material, which is corrosion-resistant and has good electrical conductivity. Alternatively, in other embodiments, the blocking member 11 can also be made of a material that is more conductive, such as silver or gold, but this will greatly increase the cost.

[0054] Optionally, a displacement inlet 112 is provided on one of the plugging members 11, and a displacement outlet 113 is provided on the other plugging member 11, and both the displacement inlet 112 and the displacement outlet 113 are connected to the corresponding displacement channel 111. Methane and water enter the displacement channel 111 through the displacement inlet 112 and are transported to the core sample 100 to provide power. Methane and water then enter the displacement channel 111 on the other side through the core sample 100, and then flow out through the displacement outlet 113. The above arrangement facilitates the entry and exit of methane and water, ensuring smooth measurement.

[0055] Optionally, a constant temperature liquid inlet 114 is provided on one sealing member 11, and a constant temperature liquid outlet 115 is provided on the other sealing member 11. The constant temperature liquid inlet 114 and the constant temperature liquid outlet 115 are both connected to the test chamber 10, and the position height of the constant temperature liquid inlet 114 is lower than the position height of the constant temperature liquid outlet 115. In other words, the constant temperature liquid enters from the bottom and exits from the top, and the constant temperature liquid enters the sleeve 1 from the constant temperature liquid inlet 114, so that the surrounding of the core sample 100 is filled with constant temperature liquid, and heat exchange occurs, and the temperature of the constant temperature liquid that completes the heat exchange increases. Since the specific gravity of water decreases with the increase of temperature, the constant temperature liquid that completes the heat exchange will float upwards. Therefore, the position height of the constant temperature liquid outlet 115 is higher than the position height of the constant temperature liquid inlet 114, which can make it easier to discharge the constant temperature liquid.

[0056] Further, the temperature of the isothermal liquid is the same as the temperature in the stratum where the core sample 100 is located. Specifically, the temperature of the isothermal liquid is -20°C-20°C, and the specific setting depends on the temperature of the stratum area under study.

[0057] On the other hand, this embodiment also provides an acoustic wave correction algorithm for correcting the results collected by the above core measurement device, including the following steps:

[0058] S1: Data collection;

[0059] The acoustic wave signal collected by the core measurement device is used as test data; the resistivity measurement component in the core measurement device is removed, and the acoustic wave signal collected is used as reference data.

[0060] S2: data preprocessing and feature extraction;

[0061] The test data and the reference data are filtered to eliminate noise, and then normalized to make the test data and the reference data have the same amplitude range.

[0062] Optionally, the filtering process adopts filter processing. Exemplarily, the filter is a device disclosed in the prior art, which may be a low-pass filter, a high-pass filter or other types of filters.

[0063] Assume x(t) is the original sound wave signal, x filtered (t) is the sound wave signal after filtering, x filtered (t) = Filter(x(t)).

[0064] x norm (t) is the normalized sound wave signal, Where μ is the mean value of the sound wave signal and σ is the standard deviation of the sound wave signal.

[0065] Then extract key features such as frequency, amplitude, etc. from the standardized test data and standardized benchmark data.

[0066] Assume that f(x) is a feature extracted from the sound wave signal, such as the average value, maximum value or other statistical features of the sound wave signal.

[0067] f(x norm )=Feature(x norm (t)), where Feature is the feature extraction function.

[0068] S3: Model building;

[0069] Combining the benchmark data with the test data, a mathematical model is established to describe the effect of the resistivity measurement component on the acoustic wave signal.

[0070] Specifically, a model can be established using linear regression, neural network or other machine learning methods. Assume that M is a model that describes the effect of the resistivity measurement component on the acoustic wave signal, and y(t) is the corrected acoustic wave signal. The model establishment equation is: y(t) = x norm (t)+M(x norm (t)). Among them, M may be a linear model, that is, M(x norm (t)) = αx norm (t)+β.

[0071] S4: Correction algorithm and verification optimization;

[0072] According to the established mathematical model, the error correction term is calculated and the correction algorithm is established. The test results of multiple tests are used to verify the effectiveness of the correction algorithm.

[0073] Specifically, y corrected (t) = y(t) - Error(y(t)), where Error(y(t)) is the error correction term calculated by model M.

[0074] Furthermore, when the error range of the error correction term does not exceed 5%, the correction algorithm is effective.

[0075] The above-mentioned acoustic wave correction algorithm can be integrated into the control module, that is, the above-mentioned acoustic wave correction algorithm is compiled in the control module. The test results collected by the core measurement device are input into the control module, and the control module, in combination with the acoustic wave correction algorithm, can output accurate test data about the core sample 100, and realize the in-situ measurement of the natural gas hydrate in-situ core sample 100. In other words, the acoustic, electrical and magnetic signals of the core sample 100 can be obtained without moving the core sample 100 multiple times, which effectively avoids the measurement error caused by the decomposition of hydrates during the movement of the core sample 100.

[0076] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, various obvious changes, readjustments and substitutions can be made without departing from the protection scope of the present invention. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A core measurement device, used in a nuclear magnetic resonance chamber, wherein an effective nuclear magnetic signal detection area is provided in the nuclear magnetic resonance chamber; It is characterized in that The core measurement device comprises: A sleeve (1) is provided with a test cavity (10), a core sample (100) to be measured is located in the test cavity (10) and in the effective nuclear magnetic signal detection area, and both ends of the core sample (100) extend to the outside of the effective nuclear magnetic signal detection area; the test cavity (10) is filled with a constant temperature liquid, and both ends of the sleeve (1) are provided with a plugging piece (11), the plugging piece (11) can seal the test cavity (10), and the plugging piece (11) is made of a conductive material; and a displacement channel (111) is provided on the plugging piece (11) and is connected to the core sample (100); A fixing assembly, comprising a first fixing member (21) and a second fixing member (22) which are spaced apart and arranged on both sides (100) of the core sample; A resistivity measurement assembly, comprising a power supply electrode (31) and a measuring electrode (32), wherein the power supply electrode (31) is arranged between the core sample (100) and the first fixing member (21), and the measuring electrode (32) is arranged between the core sample (100) and the second fixing member (22); The acoustic wave measurement component comprises an ultrasonic transducer (41) and a detector (42), wherein the ultrasonic transducer (41) is arranged on the first fixing member (21) and can provide a sound source for acoustic wave measurement, and the detector (42) is arranged on the second fixing member (22) and can receive the sound source emitted by the ultrasonic transducer (41).

2. The core measurement device according to claim 1, It is characterized in that The size of the nuclear magnetic signal detection area is 10 cm, and the size of the core sample (100) is 14 cm.

3. The core measurement device according to claim 1, It is characterized in that The blocking piece (11) is made of copper material.

4. The core measurement device according to claim 1, It is characterized in that One of the blocking members (11) is provided with a displacement inlet (112), and the other blocking member (11) is provided with a displacement outlet (113), and both the displacement inlet (112) and the displacement outlet (113) are in communication with the corresponding displacement channel (111).

5. The core measurement device according to claim 1, It is characterized in that A constant temperature liquid inlet (114) is provided on one of the blocking pieces (11), and a constant temperature liquid outlet (115) is provided on the other blocking piece (11); the constant temperature liquid inlet (114) and the constant temperature liquid outlet (115) are both connected to the test cavity (10), and the position height of the constant temperature liquid inlet (114) is lower than the position height of the constant temperature liquid outlet (115).

6. The core measurement device according to claim 1, It is characterized in that The constant temperature liquid is a fluorinated liquid.

7. The core measurement device according to claim 6, It is characterized in that The temperature of the isothermal liquid is the same as the temperature of the formation where the core sample (100) is located.

8. An acoustic wave correction algorithm for correcting the results collected by the core measurement device according to any one of claims 1 to 7, It is characterized in that The steps include: S1: Data collection; Using the acoustic wave signal collected by the core measurement device as test data; The resistivity measurement assembly in the core measurement device is removed, and the collected acoustic wave signal is used as the baseline data; S2: data preprocessing and feature extraction; The test data and the reference data are filtered, noise is eliminated, and then standardized so that the test data and the reference data have the same amplitude range; Extract key features from standardized test data and standardized benchmark data; S3: Model building; Combined with the benchmark data and test data, a mathematical model was established to describe the effect of the resistivity measurement component on the acoustic wave signal; S4: Correction algorithm and verification optimization; According to the established mathematical model, the error correction term is calculated and the correction algorithm is established. The test results of multiple tests are used to verify the effectiveness of the correction algorithm.

9. The acoustic wave correction algorithm according to claim 8, It is characterized in that The filtering process in step S2 uses a filter.

10. The acoustic wave correction algorithm according to claim 8, It is characterized in that The error range of the error correction term in step S4 does not exceed 5%.

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