Rock uniaxial compressive strength in-situ determination method based on acoustic logging data

Abstract

The invention provides a rock uniaxial compressive strength in-situ measurement method based on acoustic logging data, and relates to the technical field of rock strength in-situ measurement, and the rock uniaxial compressive strength in-situ measurement method comprises the following steps: according to the area of an exploration area, arranging logging and carrying out rock core sampling on a reference well; measuring wave velocities of compression waves of rock stratums with different depths; measuring the uniaxial compressive strength of the rock through the rock samples with different depths; carrying out data fitting on the wave velocities of the compression waves and the uniaxial compressive strength of different rock stratums, and determining the fitting relationship; according to the method, a test well is drilled, the wave velocities of compression waves of rock stratums of different depths are measured, the uniaxial compressive strength of the rock is determined through the fitting relation, well logging arrangement, rock sampling and sound wave propagation velocity measurement are standardized, and more accurate in-situ measurement is conducted on the uniaxial compressive strength of the rock through the propagation velocity of sound waves in the stratums; the uniaxial compressive strength of the rock is measured by measuring the sound wave propagation velocity in the stratum, tedious steps are reduced, and the method is more convenient and efficient.

Description

Technical Field

[0001] The invention belongs to the technical field of in-situ determination of rock strength, and relates to an in-situ determination method of rock uniaxial compressive strength based on sonic logging data. Background Art

[0002] Well logging is an important part of the oil exploration and development process. By measuring and analyzing the formations around the wellbore, various important geological and fluid information can be obtained, thus providing reliable data support for oil and gas exploration and development. Therefore, the design and implementation of well logging is particularly critical.

[0003] The uniaxial compressive strength of rock is an important mechanical indicator for the analysis of wellbore stability and an important basis for wellbore design and support. The methods for determining the uniaxial compressive strength of rock can be roughly divided into two categories, namely direct measurement and indirect measurement. The direct measurement method requires the use of a coring machine to take samples during logging; then the rock samples are brought back to the laboratory and subjected to uniaxial compression by a uniaxial compression testing machine until the samples are destroyed, thereby obtaining the uniaxial compressive strength of the samples. However, the direct measurement method requires sampling, sample preparation on site, and bringing the samples back to the laboratory. This process is cumbersome and requires a lot of time and effort.

[0004] The indirect measurement method measures certain physical and mechanical properties of rocks, such as sound wave propagation velocity, density, point load intensity, etc., and obtains the uniaxial compressive strength of rocks through conversion relationships. Among them, measuring the uniaxial compressive strength of rocks by using the sound wave propagation velocity is a common indirect measurement method for the uniaxial compressive strength of rocks. Existing studies have found that the conversion relationship between the uniaxial compressive strength of rocks and the sound wave propagation velocity is regional. At the same time, under high sound wave propagation velocity conditions, the uniaxial compressive strength of rocks is highly discrete. How to use the sound wave propagation velocity to measure the uniaxial compressive strength of rocks in a specific engineering area is a challenging task. Summary of the invention

[0005] The purpose of the present invention is to provide a method for in-situ determination of the uniaxial compressive strength of rock based on acoustic logging data, so as to solve the technical problems of the in-situ determination method in the prior art that the steps are complicated and the accuracy is low.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] An in-situ determination method for uniaxial compressive strength of rock based on sonic logging data, comprising:

[0008] Arrange test wells and reference wells according to the area of ​​the exploration area, and obtain rock samples by core sampling from the reference wells;

[0009] Determine the compression wave velocity of rock layers at different depths, and determine the uniaxial compressive strength of rocks at different depths based on rock samples;

[0010] By fitting the data of compression wave velocity and uniaxial compressive strength of different rock formations, the fitting relationship between compression wave velocity and uniaxial compressive strength is clarified;

[0011] The test well is drilled and the compression wave velocity of rock layers at different depths is measured. The uniaxial compressive strength of the rock is determined by the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0012] Preferably, the ratio of the reference well to the test well is 1:4; the test wells are arranged at intervals of 20 m according to the area of ​​the exploration region; and the reference well is arranged at the center of the four test wells.

[0013] Preferably, the core sampling of the reference well to obtain the rock sample comprises:

[0014] The reference well was drilled using a drilling rig. After 100 cm of excavation, a core sampling machine was used to take core samples with a length of 60 cm.

[0015] The reference well is drilled and sampled in a cycle according to the above process until the predetermined depth is reached.

[0016] Preferably, the compression wave velocity of rock formations at different depths is measured using an acoustic logging instrument.

[0017] Preferably, the method of measuring the compression wave velocity of rock formations at different depths by using an acoustic logging instrument specifically includes:

[0018] Lower the sonic logging instrument to the predetermined core sampling depth;

[0019] The sound wave is emitted by the sound wave transmitter and received by the sound wave receiver;

[0020] The sound wave velocity V of the rock formation is recorded and predicted by the propagation distance and propagation time of the sound wave.

[0021] Preferably, the uniaxial compressive strength of rock at different depths is determined based on rock samples and is obtained by performing uniaxial compression tests on rock samples at different depths.

[0022] Preferably, the uniaxial compressive strength of rock is determined by performing uniaxial compression tests on rock samples at different depths, including:

[0023] Select complete rock samples without obvious joints and cracks from the cored rock samples and prepare cylindrical rock samples with a diameter of 50 mm and a height of 100 mm;

[0024] The cylindrical rock sample was subjected to axial displacement loading at a loading rate of 0.02 mm / s using a compression testing machine until the sample was damaged, and the uniaxial compressive strength σ of the sample under uniaxial compression conditions was obtained. c .

[0025] Preferably, the compression wave velocity of the different rock layers is exponentially related to the uniaxial compressive strength, that is,

[0026] σ c =Ke a·V

[0027] Among them, K and a are constants.

[0028] Preferably, data fitting is performed on the compression wave velocity and uniaxial compressive strength of different rock formations through an exponential relationship to obtain fitting parameters K and a, and to clarify the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0029] Preferably, a test well is drilled and the compression wave velocity of rock layers at different depths is measured, and the uniaxial compressive strength of the rock is determined by a fitting relationship between the compression wave velocity and the uniaxial compressive strength, including:

[0030] S401: Drilling a test well using a drilling rig until the well reaches a predetermined depth;

[0031] S402: lowering the sonic logging instrument to a predetermined core sampling depth;

[0032] S403: generating sound waves by using a sound wave transmitter, and receiving the sound waves by using a sound wave receiver;

[0033] S404: Record and predict the acoustic wave velocity V of the rock layer based on the propagation distance and propagation time of the acoustic wave;

[0034] S405: Determine the uniaxial compressive strength of the rock through the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] 1) This patent regulates the logging arrangement, rock sampling and the measurement of the acoustic wave propagation velocity, and can achieve a more accurate in-situ measurement of the uniaxial compressive strength of rock through the propagation velocity of the acoustic wave in the formation.

[0037] 2) The uniaxial compressive strength of rock can be measured by measuring the propagation velocity of sound waves in the formation, which reduces the tedious steps of core drilling, sampling, and indoor test measurement, making it more convenient and efficient. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0039] Figure 1 is a flow chart of the method of the present invention;

[0040] Figure 2 A schematic diagram of the well logging arrangement position according to an embodiment of the present invention;

[0041] Figure 3 A schematic diagram of an acoustic logging instrument according to an embodiment of the present invention;

[0042] Figure 4 4 is a fitting relationship diagram between the compression wave velocity and the uniaxial compressive strength of an embodiment of the present invention.

[0043] Among them: 1-test well; 2-reference well; 3-formation; 4-well wall; 5-sonic generator; 6-sonic generator A; 7-sonic generator B; 8-sonic generator C; 9-sonic generator D. DETAILED DESCRIPTION

[0044] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in various different configurations.

[0045] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0046] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0047] In the description of the embodiments of the present invention, it should be noted that if the terms "upper", "lower", "horizontal", "inner", etc. indicate an orientation or positional relationship based on the orientation or positional relationship shown in the drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use, it is only for the convenience of describing the present invention and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0048] In addition, if the term "horizontal" appears, it does not mean that the component must be absolutely horizontal, but can be slightly tilted. For example, "horizontal" only means that its direction is more horizontal than "vertical", which does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0049] In the description of the embodiments of the present invention, it is also necessary to explain that, unless otherwise clearly specified and limited, the terms "set", "install", "connect", and "connect" 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 it can be indirectly connected through an intermediate medium, or it can be the internal connection of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0050] The present invention is further described in detail below in conjunction with the accompanying drawings:

[0051] See also Figure 1 The present application discloses a method for in-situ determination of uniaxial compressive strength of rock based on acoustic logging data, comprising:

[0052] S1: Arrange test well 1 and reference well 2 according to the area of ​​the exploration area, and take core samples from reference well 2 to obtain rock samples;

[0053] S2: Determine the compression wave velocity of rock layers at different depths, and determine the uniaxial compressive strength of rocks at different depths based on rock samples;

[0054] S3: By fitting the data of compression wave velocity and uniaxial compressive strength of different rock formations, the fitting relationship between compression wave velocity and uniaxial compressive strength is clarified;

[0055] S4: Drilling the test well 1 and measuring the compression wave velocity of rock layers at different depths, and determining the uniaxial compressive strength of the rock through the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0056] In some embodiments, a method for in-situ determination of uniaxial compressive strength of rock based on sonic logging data is characterized by comprising:

[0057] Well logging shall be arranged reasonably according to the area of ​​exploration; well logging shall be divided into two categories, namely reference well 2 and test well 1, with the ratio of the two wells being 1:4; test well 1 shall be arranged at an interval of 20m according to the area of ​​exploration; reference well 2 shall be arranged at the center of four test wells 1; reference well 2 shall be sampled in situ and the uniaxial compressive strength shall be measured, and the fitting relationship between the compression wave velocity and the uniaxial compressive strength of different rock formations shall be clarified by data fitting of the compression wave velocity and the uniaxial compressive strength of different rock formations; test well 1 shall only measure the compression wave velocity of different rock formations, and the uniaxial compressive strength of rock shall be determined by the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0058] Drilling the reference well 2 with a drilling rig and taking core samples with a coring machine;

[0059] The compression wave velocity of rock formations at different depths is measured using an acoustic logging instrument;

[0060] The uniaxial compressive strength of rock is determined by conducting uniaxial compression tests on rock samples at different depths;

[0061] By fitting the data of compression wave velocity and uniaxial compressive strength of different rock formations, the fitting relationship between compression wave velocity and uniaxial compressive strength is clarified;

[0062] Test well 1 is drilled and the compression wave velocities of rock layers at different depths are measured. The uniaxial compressive strength of the rock is determined through the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0063] In some embodiments, the reference well 2 is drilled using a drilling rig, and a core sampling machine is used to take core samples, including:

[0064] The reference well 2 was drilled using a drilling rig. After 100 cm of excavation, a core sampling machine was used to take core samples. The length of the sample was 60 cm.

[0065] According to the above process, the reference well 2 is subjected to a drilling-sampling cycle operation until the predetermined depth is reached.

[0066] In some embodiments, using an acoustic logging instrument to measure the compression wave velocity of rock formations at different depths includes:

[0067] Lower the sonic logging instrument to the predetermined core sampling depth;

[0068] The sound wave is emitted by the sound wave transmitter and received by the sound wave receiver;

[0069] The sound wave velocity V of the rock formation is recorded and predicted by the propagation distance and propagation time of the sound wave.

[0070] In some embodiments, the uniaxial compressive strength of rock is determined by performing uniaxial compression tests on rock samples at different depths, including:

[0071] Select complete rock samples without obvious joints and cracks from the cored rock samples and prepare cylindrical rock samples with a diameter of 50 mm and a height of 100 mm;

[0072] The cylindrical rock sample was subjected to axial displacement loading at a loading rate of 0.02 mm / s using a compression testing machine until the sample was damaged, and the uniaxial compressive strength σ of the sample under uniaxial compression conditions was obtained. c .

[0073] In some embodiments, by performing data fitting on the compression wave velocity and the uniaxial compressive strength of different rock formations, the fitting relationship between the compression wave velocity and the uniaxial compressive strength is clarified, including:

[0074] According to existing research, the compression wave velocity of different rock formations is exponentially related to the uniaxial compressive strength, that is, σ c =Ke a·V , where K and a are constants;

[0075] The data of compression wave velocity and uniaxial compressive strength of different rock formations were fitted through exponential relationship, and the fitting parameters K and a were obtained to clarify the fitting relationship between compression wave velocity and uniaxial compressive strength.

[0076] In some embodiments, the test well 1 is drilled and the compression wave velocity of rock layers at different depths is measured, and the uniaxial compressive strength of the rock is determined by the fitting relationship between the compression wave velocity and the uniaxial compressive strength, including:

[0077] Drilling the test well 1 by using a drilling rig until the drilling reaches a predetermined depth;

[0078] Lower the sonic logging instrument to the predetermined core sampling depth;

[0079] The sound wave is generated by a sound wave transmitter and received by a sound wave receiver;

[0080] The sound wave velocity V of a certain rock layer is recorded and predicted through the propagation distance and propagation time of the sound wave;

[0081] The uniaxial compressive strength of rock is determined by the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0082] [Example]

[0083] In view of the shortcomings of the existing in-situ determination method of the uniaxial compressive strength of rock, the present invention provides an in-situ determination method of the uniaxial compressive strength of rock based on sonic logging data, which specifically includes the following steps:

[0084] S1, reasonably arrange well logging according to the area of ​​exploration, including:

[0085] Specifically, the implementation process of S1 is as follows: the well logging is divided into two categories, namely, reference well 2 and test well 1, and the ratio of the two wells is 1:4;

[0086] According to the area of ​​the exploration area, test wells 1 are arranged at a spacing of 20 m;

[0087] like Figure 2 As shown, a reference well 2 is arranged at the center of each of the 4 test wells 1;

[0088] The reference well 2 needs to be sampled in situ and the uniaxial compressive strength measured. The fitting relationship between the compression wave velocity and the uniaxial compressive strength of different rock formations is clarified by fitting the data.

[0089] Test well 1 only needs to measure the compression wave velocity of different rock layers, and determine the uniaxial compressive strength of the rock through the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0090] S2, drilling the reference well 2 with a drilling rig and taking core samples with a coring machine, including:

[0091] Specifically, the implementation process of S2 is as follows: using a drilling rig to drill the reference well 2, after excavating 100 cm, using a coring machine to take core samples, the sampling length is 60 cm;

[0092] According to the above process, the reference well 2 is subjected to a drilling-sampling cycle operation until the predetermined depth is reached.

[0093] S3, using sonic logging to measure the compression wave velocity of rock formations at different depths, including:

[0094] Specifically, the implementation process of S3 is: lowering the sonic logging instrument to a predetermined core sampling depth;

[0095] like Figure 3 As shown, a sound wave transmitter is used to transmit sound waves, and sound waves are received by sound wave receivers A, B, C, and D;

[0096] The sound wave generator emits sound waves at a frequency of 20kHz and at a time interval of 0.1s.

[0097] The distance between adjacent sound wave receivers is 20 cm. The sound wave velocity V of the rock layer between two adjacent sound wave receivers can be calculated by the propagation distance and propagation time of the sound wave. The calculation formula is:

[0098]

[0099] Among them, d i→jis the distance from the acoustic wave receiver i to j; t i→j is the time it takes for the sound wave to propagate from sound wave receiver i to sound wave receiver j.

[0100] S4, by conducting uniaxial compression tests on rock samples at different depths, the uniaxial compressive strength of rock is determined, including:

[0101] Specifically, the implementation process of S4 is as follows: selecting complete rock samples without obvious joints and cracks from the cored rock samples, and preparing cylindrical rock samples with a diameter of 50 mm and a height of 100 mm;

[0102] The cylindrical rock sample was subjected to axial displacement loading at a loading rate of 0.02 mm / s using a compression testing machine until the sample was damaged, and the uniaxial compressive strength σ of the sample under uniaxial compression conditions was obtained. c .

[0103] S5, by fitting the data of compression wave velocity and uniaxial compressive strength of different rock formations, the fitting relationship between compression wave velocity and uniaxial compressive strength is clarified, including:

[0104] Specifically, the implementation process of S5 is as follows: According to existing research, the compression wave velocity of different rock formations is exponentially related to the uniaxial compressive strength, that is, σ c =Ke a·V , where K and a are constants;

[0105] like Figure 4 As shown, the compression wave velocity and uniaxial compressive strength of different rock formations are fitted by exponential relationship, and the fitting parameters K and a are obtained, and the fitting relationship between the compression wave velocity and the uniaxial compressive strength is clarified.

[0106] S6, drilling the test well 1 and measuring the compression wave velocity of rock layers at different depths, and determining the uniaxial compressive strength of the rock through the fitting relationship between the compression wave velocity and the uniaxial compressive strength, including:

[0107] Specifically, the implementation process of S6 is: drilling the test well 1 by using a drilling rig until the drilling reaches a predetermined depth;

[0108] Lower the sonic logging instrument to the predetermined core sampling depth;

[0109] The sound wave is generated by a sound wave transmitter and received by a sound wave receiver;

[0110] The sound wave velocity V of a certain rock layer is recorded and predicted through the propagation distance and propagation time of the sound wave;

[0111] The uniaxial compressive strength of rock is determined by the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

[0112] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for in-situ determination of uniaxial compressive strength of rock based on sonic logging data, characterized in that: include: Arranging a test well (1) and a reference well (2) according to the area of ​​the exploration region, and taking core samples from the reference well (2) to obtain rock samples; Determine the compression wave velocity of rock layers at different depths, and determine the uniaxial compressive strength of rocks at different depths based on rock samples; By fitting the data of compression wave velocity and uniaxial compressive strength of different rock formations, the fitting relationship between compression wave velocity and uniaxial compressive strength is clarified; A test well (1) is drilled to measure the compression wave velocity of rock layers at different depths, and the uniaxial compressive strength of the rock is determined through the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

2. The in-situ determination method of rock uniaxial compressive strength based on acoustic logging data according to claim 1 is characterized in that: The ratio of the reference well (2) to the test well (1) is 1:4; the test wells (1) are arranged at intervals of 20 m according to the area of ​​the exploration region; and the reference well (2) is arranged at the center of the four test wells (1).

3. The in-situ determination method of rock uniaxial compressive strength based on acoustic logging data according to claim 1 is characterized in that: The core sampling of the reference well (2) to obtain a rock sample comprises: The reference well (2) is drilled using a drilling rig. After 100 cm of excavation, a core sampling machine is used to take core samples. The length of the sample is 60 cm. According to the above process, the reference well (2) is subjected to a drilling-sampling cycle until the predetermined depth is reached.

4. The in-situ determination method of rock uniaxial compressive strength based on acoustic logging data according to claim 1 is characterized in that: The compression wave velocity of rock formations at different depths is measured using an acoustic logging instrument.

5. The in-situ determination method of rock uniaxial compressive strength based on acoustic logging data according to claim 4 is characterized in that: The method of measuring the compression wave velocity of rock formations at different depths by using an acoustic logging instrument specifically includes: Lower the sonic logging instrument to the predetermined core sampling depth; The sound wave is emitted by the sound wave transmitter and received by the sound wave receiver; The sound wave velocity V of the rock formation is recorded and predicted by the propagation distance and propagation time of the sound wave.

6. The in-situ determination method of rock uniaxial compressive strength based on sonic logging data according to claim 1 is characterized in that: The uniaxial compressive strength of rocks at different depths is measured based on rock samples and is obtained by performing uniaxial compression tests on rock samples at different depths.

7. The in-situ determination method of rock uniaxial compressive strength based on sonic logging data according to claim 6 is characterized in that: The uniaxial compressive strength of rock is determined by conducting uniaxial compression tests on rock samples at different depths, including: Select complete rock samples without obvious joints and cracks from the cored rock samples to prepare cylindrical rock samples with a diameter of 50 mm and a height of 100 mm; The cylindrical rock sample was subjected to axial displacement loading at a loading rate of 0.02 mm / s using a compression testing machine until the sample was damaged, and the uniaxial compressive strength σ of the sample under uniaxial compression conditions was obtained. c .

8. The in-situ determination method of rock uniaxial compressive strength based on sonic logging data according to claim 1 is characterized in that: The compression wave velocity of the different rock layers is exponentially related to the uniaxial compressive strength, that is, σ c =I am a·V Among them, K and a are constants.

9. The in-situ determination method of rock uniaxial compressive strength based on sonic logging data according to claim 8 is characterized in that: The compression wave velocity and uniaxial compressive strength of different rock formations were fitted through exponential relationship, and the fitting parameters K and a were obtained to clarify the fitting relationship between the compression wave velocity and uniaxial compressive strength.

10. The in-situ determination method of rock uniaxial compressive strength based on sonic logging data according to claim 1, characterized in that: The test well (1) is drilled and the compression wave velocity of rock layers at different depths is measured, and the uniaxial compressive strength of the rock is determined by the fitting relationship between the compression wave velocity and the uniaxial compressive strength, including: S401: Drilling the test well (1) using a drilling rig until the drilling reaches a predetermined depth; S402: lowering the sonic logging instrument to a predetermined core sampling depth; S403: generating sound waves by using a sound wave transmitter, and receiving the sound waves by using a sound wave receiver; S404: Record and predict the acoustic wave velocity V of the rock layer based on the propagation distance and propagation time of the acoustic wave; S405: Determine the uniaxial compressive strength of the rock through the fitting relationship between the compression wave velocity and the uniaxial compressive strength.

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