A single-frequency harmonic detection method for underground directional holes and its application

Abstract

The present invention provides a single-frequency harmonic detection method for underground directional holes and its application. Before and after the fracturing-grouting construction in the emission borehole, harmonic signal acquisition is carried out once respectively. The quadruple-frequency harmonic algorithm is used to extract the average harmonic signal amplitude value from the collected data. After processing the average harmonic signal amplitude value, the difference in absorption attenuation coefficients before and after the fracturing-grouting construction is obtained. By using the difference in absorption attenuation coefficients before and after the fracturing-grouting construction, the fracture distribution range and the slurry diffusion range can be indirectly inferred. According to the fracture distribution range and the slurry diffusion range, the effect of the fracturing-grouting construction can be known. This method uses the quadruple-frequency harmonic algorithm to extract the average harmonic signal amplitude value from the collected data, greatly improving the detection accuracy of the signal intensity. Applying this method to the grouting construction or the fracturing construction can provide a basis for optimizing the process of the fracturing-grouting construction.

Description

Technical Field

[0001] The present invention belongs to the technical field of perspective detection, relates to detection in directional drilling, and specifically relates to a single-frequency harmonic detection method for underground directional holes and its application. Background Art

[0002] Before coal mining face is exploited, it is necessary to eliminate potential safety hazards during the exploitation process of the mining face. Water hazards and gas outbursts are the two biggest threat factors to coal mining projects. With the improvement of treatment means, directional drilling is used more and more in coal mines. Due to its high drilling footage and accurate trajectory, directional drilling has outstanding advantages in disaster treatment.

[0003] At present, the construction technology of directional drilling includes coal seam fracturing construction and floor grouting construction, that is, fracturing-grouting construction. The technological route of this fracturing-grouting construction is as follows: First, the directional drill is applied to a high-gas mining face, and the hydraulic fracturing method is used to increase and expand the extension range of coal seam fissures, which can reopen the originally closed fissures, expand the length and width of the original fissures, provide better conditions for pre-drainage of coalbed methane, improve the extraction efficiency of coalbed methane, reduce the gas concentration during mining, and ensure the safety of coal mining. Then, the floor grouting method is adopted to reinforce the coal seam floor, seal the original fissures. After grouting the water-conducting channels and fissures, during the coal mining process, the risk of water inrush caused by the fragmentation of the coal mine floor is greatly reduced, fully ensuring the safety of coal mining and excavation.

[0004] At present, the fracturing-grouting construction technology of directional drilling is mature, and the fracturing-grouting technology has a very broad application prospect. However, there is currently a lack of corresponding detection means for the effect of fracturing-grouting construction.

[0005] There are significant differences in the attenuation speed of harmonics in different media. When there are fissures in the rock, the fissures are generally filled with water, and the attenuation speed of harmonics in water increases greatly. Generally speaking, the existence of fissures causes the attenuation of electromagnetic waves to accelerate during propagation. After grouting construction, the fissures are filled with cement slurry, and after solidification, its electrical properties are close to those of the surrounding rock, and the attenuation speed of harmonics will be greatly reduced; for hydraulic fracturing projects, fissures are increased in the rock and filled with water, and the attenuation speed of harmonics increases. Whether it is a grouting project or a hydraulic fracturing project, there are significant changes in the harmonic attenuation degree between the drill holes before and after construction. From the above analysis, it can be seen that it is feasible to use harmonics to detect the effect of fracturing-grouting construction. Summary of the Invention

[0006] Aiming at the defects and deficiencies existing in the prior art, the purpose of the present invention is to provide a single-frequency harmonic detection method for underground directional holes and its application, so as to solve the technical problem of the lack of detection means for the effect of fracturing-grouting construction in the prior art.

[0007] To solve the above technical problems, the present invention is implemented by the following technical solutions:

[0008] A single-frequency harmonic detection method for underground directional holes. Before and after the fracturing-grouting construction in the emission borehole, harmonic signal acquisitions are respectively carried out once. The quadruple-frequency harmonic algorithm is adopted to extract the average harmonic signal amplitude value from the acquired data. After processing the average harmonic signal amplitude value, the difference in absorption attenuation coefficients before and after the fracturing-grouting construction is obtained.

[0009] The present invention also has the following technical features:

[0010] This method specifically includes the following steps:

[0011] Step 1, flush the directional borehole;

[0012] Step 2, determine the emission borehole and the receiving borehole, and design the positions of the emission points and the receiving points;

[0013] Step 3, carry out the harmonic signal acquisition before construction;

[0014] Step 3.1, perform time synchronization;

[0015] Step 3.2, carry out the harmonic signal acquisition during the drill pipe drilling;

[0016] Step 3.3, carry out the harmonic signal acquisition of the return shift during the drill pipe withdrawal;

[0017] Step 4, extract the average harmonic signal amplitude value

[0018] After completing the harmonic signal acquisition before construction in Step 3, the quadruple-frequency harmonic algorithm is adopted to extract the average harmonic signal amplitude value from the harmonic signal data before construction

[0019] The set of harmonic signals S during the drill pipe drilling is represented as follows, where n represents the number of emission points and m represents the number of receiving points:

[0020] S = [S (0，0) , S (0，1) , S (1，1) , S (1，2) , S (2，2) , S (2，3) ,......, S (n-1，m-1) , S (n-1，m) , S (n，m) , S (n，m-1) ;

[0021] In the set of harmonic signals S during the drill pipe drilling, each harmonic signal S (i , j)All contain k acquisition cycles, and each acquisition cycle contains four acquisition time points, and each acquisition time point corresponds to a harmonic data value λ;

[0022] Then the first harmonic signal S of the initial emission point F0 (0，0) is expressed as follows:

[0023]

[0024] The first harmonic signal S of the initial emission point F0 (0，0) The acquisition time tf (0，0) is expressed as follows:

[0025]

[0026] Then the first harmonic signal S of the initial emission point F0 (0，0) Among them, the four harmonic data values λ included in the first acquisition cycle are respectively expressed as follows;

[0027] The Harmonic data value collected at the acquisition time point As shown in Equation I:

[0028]

[0029] The Harmonic data value collected at the acquisition time point As shown in Equation II:

[0030]

[0031] The Harmonic data value collected at the acquisition time point As shown in Equation III:

[0032]

[0033] The Harmonic data value collected at the acquisition time point As shown in Equation IV:

[0034]

[0035] Then the first harmonic signal S of the initial emission point F0 (0,0) The amplitude value A of the harmonic signal can be calculated according to the following Equation V and / or Equation VI:

[0036]

[0037]

[0038] In Formula I, Formula II, Formula III, Formula IV, Formula V and Formula VI:

[0039] θ represents the phase of the harmonic signal corresponding to the initial acquisition time point;

[0040] A represents the amplitude value of the harmonic signal;

[0041] π represents the phase increase of the harmonic signal corresponding to half a period;

[0042] For the first harmonic signal S of the initial emission point F0 (0,0) Among the 4k harmonic data values λ included in it, a total of 2k harmonic signal amplitude values A can be obtained. By analogy with Formulas I to VI, according to the first harmonic signal S of the initial emission point F0 (0,0) The obtained harmonic signal amplitude value A (0,0) The set is represented as follows:

[0043]

[0044] Then for the first harmonic signal S of the initial emission point F0 (0,0) The corresponding average harmonic signal amplitude value Is obtained according to Formula VII:

[0045]

[0046] In the set of harmonic signals S of the drill pipe during drilling, for each harmonic signal S (i，j) The corresponding average harmonic signal amplitude value The calculation process is the same as that of the average harmonic signal amplitude value corresponding to the first harmonic signal S of the initial emission point F0 (0，0) The corresponding average harmonic signal amplitude value The calculation process is the same. By analogy, multiple average harmonic signal amplitude values corresponding to the harmonic signals S can be obtained

[0047] The set of return harmonic signals Q during the retraction of the drill pipe is represented as follows, where n represents the number of emission points and m represents the number of receiving points:

[0048] Q = [Q (n-1，m-3) , Q (n-1，m-4) , Q (n-2，m-4) , Q (n-2，m-5) , ……, Q (4，1) , Q (4，2) , Q (3，1) , Q (3，0) ;

[0049] In the set of back-migration harmonic signals Q for the drill pipe to withdraw, each back-migration harmonic signal Q contains k acquisition cycles. Each acquisition cycle contains four acquisition time points, and each acquisition time point corresponds to a back-migration harmonic data value ω;

[0050] Then the second back-migration harmonic signal Q of the emission point F3 (3，0) is expressed as follows:

[0051]

[0052] The second back-migration harmonic signal Q of the emission point F3 (3，0) The acquisition time tr (3，0) is expressed as follows:

[0053]

[0054] In the set of back-migration harmonic signals Q for the drill pipe to withdraw, the average harmonic signal amplitude value corresponding to each back-migration harmonic signal Q The calculation process of (0，0) is the same as the average harmonic signal amplitude value corresponding to the first harmonic signal S of the initial emission point F0 By analogy, the average harmonic signal amplitude values corresponding to multiple back-migration harmonic signals Q can be obtained

[0055] Step Five, perform harmonic signal acquisition and amplitude value extraction after construction;

[0056] After completing the harmonic signal acquisition before construction described in Step Three, perform fracturing-grouting construction on the emission borehole; after the construction is completed, repeat the above Steps 3.1 to 3.3 to complete the harmonic signal acquisition after grouting-fracturing construction, use the four-fold frequency harmonic algorithm to extract the harmonic signal amplitude value from the harmonic signal data after construction, and obtain the average harmonic signal amplitude value after construction;

[0057] Step Six, process the average harmonic signal amplitude value before construction obtained in Step Four and the average harmonic signal amplitude value after construction obtained in Step Five to obtain the difference in absorption attenuation coefficients before and after fracturing-grouting construction.

[0058] The specific content of Step Two is as follows: After flushing the directional borehole described in Step One, select and determine the emission borehole and the receiving borehole, design the initial emission point F0 in the emission borehole, and design the initial receiving point R0 in the receiving borehole; starting from the initial emission point F0, with a as the measuring point spacing, design n emission points at equal intervals, denoted as F1, F2, F3... F n; Starting from the initial receiving point R0, with a as the measurement point spacing, design m receiving points at equal measurement point intervals, denoted as R1, R2, R3... R m .

[0059] The specific steps of step 3.2 are as follows:

[0060] Step 3.2.1, collect the harmonic signals of the initial emission point F0;

[0061] After completing the time synchronization in step 3.1, synchronously and slowly push the transmitting probe and the receiving probe to the preset initial emission point F0 and initial receiving point R0 in step 2 respectively. After recording the start time of collection, collect and obtain the first harmonic signal S of the initial emission point F0 (0,0) , and then push the receiving probe to the receiving point R1, collect and obtain the second harmonic signal S of the initial emission point F0 (0,1) ;

[0062] Step 3.2.2, collect the harmonic signals of the emission point F1;

[0063] After completing the collection of the harmonic signals of the initial emission point F0 in step 3.2.1, push the transmitting probe to the emission point F1, collect and obtain the harmonic signal S of the emission point F1 (1,1) , and then push the receiving probe to the receiving point R2, collect and obtain the second harmonic signal S of the emission point F1 (1,2) ;

[0064] Step 3.2.3, push forward and collect the harmonic signals of the remaining emission points;

[0065] After completing the collection of the harmonic signals of the emission point F1 in step 3.2.2, repeat the operations in step 3.2.2 until the first harmonic signal S n-1 and the second harmonic signal S (n-1,m-1) of the emission point F (n-1,m) are collected. At this time, the receiving probe is located at the receiving point R m . Push the transmitting probe to the emission point F n , collect and obtain the first harmonic signal S n of the emission point F (n,m) , and then push the receiving probe back to the receiving point R m-1 , collect and obtain the second harmonic signal S n of the emission point F (n,m-1) , completing the collection of the harmonic signals during the drill pipe drilling.

[0066] The specific steps of step 3.3 are as follows:

[0067] Step 3.3.1, withdraw the drill pipe and conduct collection;

[0068] After the harmonic signal acquisition of the drill pipe drilling in step 3.2 is completed, push the transmitting probe back to the transmitting point F n-1 and push the receiving probe back to the receiving point R m-3 to collect and obtain the first harmonic signal Q of the back-movement at the transmitting point F n-1 ; then push the receiving probe back to the receiving point R (n-1,m-3) to collect and obtain the second harmonic signal Q of the back-movement at the transmitting point F m-4 ; n-1 (n-1,m-4) n-1 ;

[0069] Step 3.3.2, continue to withdraw the drill pipe and conduct the acquisition;

[0070] After the acquisition of the first harmonic signal Q of the back-movement at the transmitting point F n-1 and the second harmonic signal Q of the back-movement in step 3.3.1 is completed, push the transmitting probe to the transmitting point F (n-1,m-3) to collect and obtain the first back-movement harmonic signal Q at the transmitting point F (n-1,m-4) ; then push the receiving probe to the receiving point R n-2 to collect and obtain the second back-movement harmonic signal Q at the transmitting point F n-2 ; (n-2,m-4) m-5 n-2 (n-2,m-5) n-2 (3,1) (3,0) ;

[0071] Step 3.3.3, complete the harmonic signal acquisition;

[0072] After the acquisition of the back-movement harmonic signal at the transmitting point F n-2 in step 3.3.2 is completed, repeat the operations in step 3.3.2 until the acquisition of the first back-movement harmonic signal Q (3,1) and the second back-movement harmonic signal Q (3,0) at the transmitting point F3 is completed, and the harmonic signal acquisition during the withdrawal of the drill pipe is completed. Thus, the harmonic signal acquisition process before the entire construction ends.

[0073] In step two, the measuring point spacing a is taken as 3m to 6m.

[0074] In the said step two, it is also necessary to design the detection depth H1 of the transmitting borehole and the detection depth H2 of the receiving borehole, and the detection depth H1 of the transmitting borehole is equal to the detection depth H2 of the receiving borehole.

[0075] The number m of the transmitting points is equal to the detection depth H1 of the transmitting borehole divided by the measuring point spacing a, and the number m of the transmitting points is equal to the number n of the receiving points.

[0076] Step six is specifically as follows: perform CT imaging processing on the average harmonic signal amplitude value obtained before construction in step four to obtain the absorption attenuation coefficient data of the emission borehole and the receiving borehole before construction; perform CT imaging processing on the average harmonic signal amplitude value obtained after construction in step five to obtain the absorption attenuation coefficient data of the emission borehole and the receiving borehole after construction; subtract the absorption attenuation coefficient data after construction from the absorption attenuation coefficient data before construction to obtain the difference in absorption attenuation coefficient before and after the fracturing-grouting construction.

[0077] The present invention also protects the application of the downhole directional borehole single-frequency harmonic detection method as described above for evaluating the construction effect of the fracturing-grouting construction. The specific process of this application is: based on the difference in absorption attenuation coefficient before and after the fracturing-grouting construction, infer the slurry diffusion range and fracture distribution range during the fracturing-grouting construction, and then evaluate the construction effect of the fracturing-grouting construction.

[0078] Compared with the prior art, the present invention has the following beneficial technical effects:

[0079] (Ⅰ) For the downhole directional borehole single-frequency harmonic detection method of the present invention, harmonic signal acquisition is performed once before and after the fracturing-grouting construction in the emission borehole; the four-fold frequency harmonic algorithm is used to extract the average harmonic signal amplitude value from the collected data; after processing the average harmonic signal amplitude value, the difference in absorption attenuation coefficient before and after the fracturing-grouting construction is obtained. Using the difference in absorption attenuation coefficient before and after the fracturing-grouting construction, the fracture distribution range and slurry diffusion range can be indirectly inferred, and based on the fracture distribution range and slurry diffusion range, the construction effect of the fracturing-grouting construction can be known.

[0080] (Ⅱ) In the prior art, the conventional methods for extracting the single-frequency harmonic signal amplitude are the energy integration method and the Fourier spectrum analysis method. Among them, the energy analysis method cannot directly obtain the amplitude value, and the spectrum analysis method has poor anti-noise ability. For the downhole directional borehole single-frequency harmonic detection method of the present invention, the four-fold frequency harmonic algorithm is used to extract the average harmonic signal amplitude value from the collected data, which greatly improves the detection accuracy of the signal intensity.

[0081] (Ⅲ) For the downhole directional borehole single-frequency harmonic detection method of the present invention, its detection range can reach more than 500 m of the borehole depth, breaking through the distance limit of short-hole perspective exploration and improving the engineering application range of electromagnetic wave perspective.

[0082] (Ⅳ) Applying the downhole directional borehole single-frequency harmonic detection method of the present invention to the grouting construction or fracturing construction can provide a basis for optimizing the process of the fracturing-grouting construction. Description of the Drawings

[0083] Figure 1 It is a schematic diagram of a single harmonic signal S or a single migrated harmonic signal Q;Figure 1 Among them, the black dots represent the harmonic data values or the shifted-back harmonic data values for each acquisition cycle.

[0084] Figure 2 It is a schematic diagram of harmonic signal acquisition for drill pipe drilling.

[0085] Figure 3 It is a schematic diagram of harmonic signal acquisition for drill pipe withdrawal.

[0086] Figure 4 It is a comparison chart of harmonic signal data collected before and after the launch borehole fracturing - grouting construction in Example 1; Figure 4 Among them, the horizontal axis is the number of receiving points, and the vertical axis is the received voltage.

[0087] Figure 5 It is a distribution map of the absorption attenuation coefficient before the launch borehole fracturing - grouting construction in Application Example 1; Figure 5 Among them, the light color represents the normal background area, and the dark color represents the speculated fracture distribution area.

[0088] Figure 6 It is a distribution map of the absorption attenuation coefficient after the launch borehole fracturing - grouting construction in Application Example 1; Figure 6 Among them, the light color represents the normal background area, and the dark color represents the speculated fracture distribution area.

[0089] Figure 7 It is a distribution map of the difference in absorption attenuation coefficient before and after the launch borehole fracturing - grouting construction in Application Example 1.

[0090] Figure 8 It is a schematic diagram of the relationship between resistivity and attenuation coefficient.

[0091] The technical solution of the present invention will be further described below in conjunction with embodiments. Specific Embodiments

[0092] When the present invention performs harmonic signal acquisition, the transmitting probe is synchronously advanced and withdrawn. The storage synchronization technology ensures the synchronization of data in time. The storage synchronization system consists of three parts: an in - hole transmitting probe, an in - hole receiving probe, and a hole - mouth control host, and the crystal oscillator synchronization method is adopted to keep the time consistent. When the construction starts, the transmitting probe is started. The transmitting probe is connected to the hole - mouth host through a synchronization line. At this time, the transmitting probe and the hole - mouth host achieve recording time synchronization. Then the receiving probe is started, and the hole - mouth synchronization host gives time to the receiving probe. Through the above process, the time synchronization of the transmitting probe, the receiving probe, and the hole - mouth host is achieved.

[0093] In the downhole directional hole single - frequency harmonic detection method of the present invention, the quadruple - frequency harmonic algorithm is the core technology. This quadruple - frequency harmonic algorithm, as Figure 1As shown, four numbers are evenly collected in each waveform cycle. Two adjacent data form a mathematical orthogonal relationship, and the sum of their squares is the peak value of the signal. By using the mean value of the sum of squares of multiple groups of orthogonal data, the accuracy of detecting the signal intensity is greatly improved.

[0094] It should be noted that all the devices used in the present invention, without special instructions, are devices known in the art. For example, both the transmitting probe and the receiving probe are probes known in the prior art.

[0095] In compliance with the above technical solution, the following gives specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments, and all equivalent transformations made on the basis of the technical solution of this application fall within the protection scope of the present invention.

[0096] Embodiment 1:

[0097] This embodiment provides a single-frequency harmonic detection method for downhole directional holes. As Figures 1 to 4 shown, the specific steps of this method are as follows:

[0098] Step 1, flush the directional borehole;

[0099] After the directional borehole is drilled, all the drill pipes in the directional borehole are withdrawn, and the directional borehole is flushed during the drill pipe withdrawal process to carry out the cuttings and mud in the directional borehole, ensuring that there is no drill sticking or blockage during the probe feeding process.

[0100] Step 2, determine the transmitting borehole and the receiving borehole, and design the positions of the transmitting point and the receiving point;

[0101] After flushing the directional borehole in Step 1, according to the directional borehole trajectory plan, select the detection section, select and determine the transmitting borehole and the receiving borehole, design and determine the detection depth H1 of the transmitting borehole and the detection depth H2 of the receiving borehole, and design the initial transmitting point F0 and the initial receiving point R0.

[0102] In this embodiment, the depth of the initial transmitting point F0 in the transmitting borehole is HF0, and the depth of the initial receiving point R0 in the receiving borehole is HR0; HR0 is equal to the sum of HF0 and ΔH, and ΔH is taken as 6 - 10m, that is, the initial receiving point R0 is 6 - 10m deeper than the initial transmitting point F0.

[0103] Starting from the initial transmitting point F0, with a as the measuring point spacing, n transmitting points are designed at equal intervals, and are respectively denoted as F1, F2, F3... F n , the distance between F0 and F n is the detection depth H1 of the transmitting borehole; starting from the initial receiving point R0, with a as the measuring point spacing, m receiving points are designed at equal measuring point intervals, and are respectively denoted as R1, R2, R3... R m, the distance between R0 and R m is the detection depth H2 of the receiving borehole.

[0104] In this embodiment, the detection depth H1 of the emission borehole can be reasonably set according to the area to be understood. Generally, H2 is equal to H1; the measuring point spacing a is generally set to 3 m or 6 m, that is, an integer multiple of the length of one directional drill pipe. The number m of emission points is equal to the number n of receiving points, and m = n = H1 / a.

[0105] Step 3: Collect harmonic signals before construction;

[0106] Step 3.1: Perform time synchronization;

[0107] Install the emission probe and the receiving probe at the front ends of the drill pipes of two drilling rigs respectively. Start the emission probe and the receiving probe, and use the orifice control host to perform time synchronization on the emission probe and the receiving probe.

[0108] Step 3.2: Collect harmonic signals during the drilling of the drill pipe;

[0109] Step 3.2.1: Collect the harmonic signals of the initial emission point F0;

[0110] After completing the time synchronization in Step 3.1, slowly push the emission probe and the receiving probe forward synchronously at a uniform speed to the preset initial emission point F0 and initial receiving point R0 in Step 2 respectively. After recording the start time of collection, collect and obtain the first harmonic signal S of the initial emission point F0 (0,0) , and then push the receiving probe to the receiving point R1 to collect and obtain the second harmonic signal S of the initial emission point F0 (0,1) .

[0111] Step 3.2.2: Collect the harmonic signals of the emission point F1;

[0112] After completing the collection of the harmonic signals of the initial emission point F0 in Step 3.2.1, push the emission probe to the emission point F1 to collect and obtain the harmonic signal S of the emission point F1 (1,1) , and then push the receiving probe to the receiving point R2 to collect and obtain the second harmonic signal S of the emission point F1 (1,2) .

[0113] Step 3.2.3: Push forward and collect the harmonic signals of the remaining emission points;

[0114] After completing the collection of the harmonic signals of the emission point F1 in Step 3.2.2, repeat the operations in Step 3.2.2 until the first harmonic signal S of the emission point F n-1 and the second harmonic signal S (n-1,m-1) are completed. (n-1,m)After the acquisition, the receiving probe is located at the receiving point R m At this time, the transmitting probe is pushed to the transmitting point F n At this time, the first harmonic signal S of the transmitting point F is collected and obtained n After that, the receiving probe is pushed back to the receiving point R (n,m) At this time, the second harmonic signal S of the transmitting point F is collected and obtained m-1 Thereby, the harmonic signal acquisition during the drill pipe drilling is completed n (n,m-1)

[0115] Step 3.3, perform harmonic signal acquisition for the drill pipe withdrawal

[0116] Step 3.3.1, withdraw the drill pipe and perform acquisition

[0117] After completing the harmonic signal acquisition during the drill pipe drilling in Step 3.2, the transmitting probe is pushed back to the transmitting point F n-1 At this time, the receiving probe is pushed back to the receiving point R m-3 At this time, the first back-moving harmonic signal Q of the transmitting point F is collected and obtained n-1 After that, the receiving probe is pushed back to the receiving point R (n-1,m-3) At this time, the second back-moving harmonic signal Q of the transmitting point F is collected and obtained m-4 n-1 (n-1,m-4)

[0118] Step 3.3.2, continue to withdraw the drill pipe and perform acquisition

[0119] After completing the acquisition of the first back-moving harmonic signal Q n-1 and the second back-moving harmonic signal Q (n-1，m-3) (n-1，m-4) of the transmitting point F in Step 3.3.1, the transmitting probe is pushed to the transmitting point F n-2 At this time, the first re-back-moving harmonic signal Q of the transmitting point F is collected and obtained n-2 Then, the receiving probe is pushed to the receiving point R (n-2，m-4) At this time, the second re-back-moving harmonic signal Q of the transmitting point F is collected and obtained m-5 n-2 (n-2，m-5)

[0120] Step 3.3.3, complete the harmonic signal acquisition

[0121] After completing the acquisition of the back-moving harmonic signal of the transmitting point F in Step 3.3.2, repeat the operations in Step 3.3.2 until the first re-back-moving harmonic signal Q n-2 and the second re-back-moving harmonic signal Q (3，1) (3，0) ​​​​​​​​​​The acquisition is completed, and the harmonic signal acquisition for the drill pipe to withdraw is finished. Thus, the entire harmonic signal acquisition process before construction ends.

[0122] Step Four, extract the average harmonic signal amplitude value

[0123] After completing the harmonic signal acquisition before construction in Step Three, use the quadruple-frequency harmonic algorithm to extract the average harmonic signal amplitude value from the harmonic signal data before construction.

[0124] The set of harmonic signals S during drill pipe penetration is represented as follows, where n represents the number of emission points and m represents the number of receiving points:

[0125] S = [S (0，0) , S (0，1) , S (1，1) , S (1，2) , S (2，2) , S (2，3) ,......, S (n-1，m-1) , S (n-1，m) , S (n，m) , S (n，m-1) ;

[0126] In the set of harmonic signals S during drill pipe penetration, each harmonic signal S (i , j) contains k acquisition cycles, each acquisition cycle contains four acquisition time points, and each acquisition time point corresponds to a harmonic data value λ.

[0127] Then the first harmonic signal S (0，0) of the initial emission point F0 is represented as follows:

[0128]

[0129] The first harmonic signal S (0，0) of the initial emission point F0, the acquisition time tf (0，0) is represented as follows:

[0130]

[0131] Then in the first harmonic signal S (0,0) of the initial emission point F0, the four harmonic data values λ contained in the first acquisition cycle are respectively represented as follows;

[0132] The harmonic data value collected at the acquisition time point is as shown in Equation I:

[0133]

[0134] Harmonic data value collected at the acquisition time point As shown in Equation II:

[0135]

[0136] Harmonic data value collected at the acquisition time point As shown in Equation III:

[0137]

[0138] Harmonic data value collected at the acquisition time point As shown in Equation IV:

[0139]

[0140] Then, for the first harmonic signal S of the initial emission point F0 (0,0) the harmonic signal amplitude value A can be calculated according to the following Equation V and / or Equation VI:

[0141]

[0142]

[0143] In Equation I, Equation II, Equation III, Equation IV, Equation V and Equation VI:

[0144] θ represents the phase of the harmonic signal corresponding to the initial acquisition time point;

[0145] A represents the harmonic signal amplitude value;

[0146] π represents the phase increase of the harmonic signal corresponding to half a period.

[0147] For the first harmonic signal S of the initial emission point F0 (0，0) Among the 4k harmonic data values λ included, a total of 2k harmonic signal amplitude values A can be obtained. By analogy with Equation I to Equation VI, then based on the first harmonic signal S of the initial emission point F0 (0，0) the obtained harmonic signal amplitude value A (0，0) is represented by the following set:

[0148]

[0149] Then, for the first harmonic signal S of the initial emission point F0 (0，0) the corresponding average harmonic signal amplitude value is obtained according to Equation VII:

[0150]

[0151] In the set of harmonic signals S during drill pipe drilling, each harmonic signal S (i，j) The corresponding average harmonic signal amplitude value The calculation process of is the same as that of the first harmonic signal S corresponding to the initial emission point F0 (0，0) The corresponding average harmonic signal amplitude value The calculation process is the same, and so on. The average harmonic signal amplitude values corresponding to multiple harmonic signals S can be obtained

[0152] The set of return harmonic signals Q during drill pipe withdrawal is represented as follows, where n represents the number of emission points and m represents the number of receiving points:

[0153] Q = [Q (n-1，m-3) , Q (n-1，m-4) , Q (n-2，m-4) , Q (n-2，m-5) , ……, Q (4，1) , Q (4，2) , Q (3，1) , Q (3，0) ;

[0154] In the set of return harmonic signals Q during drill pipe withdrawal, each return harmonic signal Q contains k acquisition cycles, and each acquisition cycle contains four acquisition time points, and each acquisition time point corresponds to a return harmonic data value ω;

[0155] Then the second return harmonic signal Q of the emission point F3 (3，0) Is represented as follows:

[0156]

[0157] The second return harmonic signal Q of the emission point F3 (3，0) The acquisition time tr (3，0) Is represented as follows:

[0158]

[0159] In the set of return harmonic signals Q during drill pipe withdrawal, the average harmonic signal amplitude value corresponding to each return harmonic signal Q The calculation process of is the same as that of the first harmonic signal S corresponding to the initial emission point F0 (0,0) The corresponding average harmonic signal amplitude value The calculation process is the same, and so on. The average harmonic signal amplitude values corresponding to multiple return harmonic signals Q can be obtained

[0160] In this embodiment, it can be seen from Formula V and Formula VI that the sum of the squares of any two adjacent harmonic data values is the square of the harmonic signal amplitude value A. According to the invariance of the harmonic amplitude, after collecting multiple acquisition cycles, and so on, multiple harmonic signal amplitudes A can be calculated, and then multiple average harmonic signal amplitude values can be obtained. By continuously collecting multiple cycles and taking the average after superposition, the determination accuracy of the average harmonic signal amplitude value can be greatly improved. And there is no requirement for the start time of acquisition.

[0161] Step Five: Collect harmonic signals after construction and extract amplitude values.

[0162] After completing the harmonic signal acquisition before construction in Step Three, carry out construction on the emission borehole; after the construction is completed, repeat the above Steps 3.1 to 3.3 to complete the harmonic signal acquisition after the grouting-fracturing construction, then adopt the quadruple-frequency harmonic algorithm to extract the harmonic signal amplitude value from the harmonic signal data after construction, and obtain the average harmonic signal amplitude value after construction.

[0163] In Step Three and Step Five of this embodiment, after the harmonic signal acquisition is completed, according to the comparison between the time recorded by the hole mouth host and the time recorded inside the receiving probe, the data of each acquisition point is extracted to complete the correspondence between the acquisition point position and the harmonic signal. The comparison of the harmonic signal data before and after construction is as Figure 4 shown, and it can be seen from Figure 4 that after the emission borehole undergoes fracturing-grouting construction, the overall data of the received voltage increases, and the low-value measurement area before grouting is filled.

[0164] Step Six: Perform CT imaging processing.

[0165] Perform CT imaging processing on the average harmonic signal amplitude value obtained before construction in Step Four to obtain the absorption attenuation coefficient data of the emission borehole and the receiving borehole before construction; perform CT imaging processing on the average harmonic signal amplitude value obtained after construction in Step Five to obtain the absorption attenuation coefficient data of the emission borehole and the receiving borehole after construction; subtract the absorption attenuation coefficient data after construction from the absorption attenuation coefficient data before construction to obtain the difference in absorption attenuation coefficient before and after the fracturing-grouting construction. In this embodiment, the CT imaging processing adopts the conventional electromagnetic wave CT imaging processing technology known in the prior art.

[0166] Application Example 1:

[0167] This application example provides an application of using the single-frequency harmonic detection method for downhole directional holes in Example 1 to evaluate the construction effect of the fracturing-grouting construction. The specific process of this application is as follows: Based on the difference in the absorption attenuation coefficient before and after the fracturing-grouting construction obtained in Example 1, the diffusion range of the slurry and the fracture distribution range during the fracturing-grouting construction are speculated, and then the construction effect of the fracturing-grouting construction is evaluated, such as Figures 5 to 7 as shown

[0168] Figure 7 In, the different areas are the speculated fracture filling areas. The darker the color, the greater the difference before and after grouting. As can be seen from Figure 7 the diffusion range of the slurry in the directional borehole after the fracturing-grouting construction is large, the grouting volume in the directional borehole has increased significantly, and the fractures have been filled, indicating that the effect of the fracturing-grouting construction is good.

[0169] In this application example, the principle of speculating the diffusion range of the slurry and the fracture distribution range based on the difference in the absorption attenuation coefficient before and after the fracturing-grouting construction is as follows:

[0170] When the electromagnetic wave travels from the transmitting probe to the receiving probe, it will experience a certain path attenuation. The attenuation coefficient of the electromagnetic wave propagating in the rock formation is as shown in Equation VIII:

[0171]

[0172] In Equation VIII:

[0173] β represents the attenuation coefficient of the electromagnetic wave per unit distance;

[0174] ω represents the electromagnetic wave frequency;

[0175] μ represents the vacuum permeability;

[0176] ε r represents the relative permittivity of the medium;

[0177] ρ represents the resistivity of the medium.

[0178] For the limestone of the coal seam floor that needs to be grouted and reformed, since both μ and ε r are very stable and basically do not change before and after grouting, they are generally regarded as fixed values; ω is a parameter determined by the instrument and does not change before and after grouting. In the limestone of the coal seam floor after grouting and reforming, the original voids filled with water will be filled with cement slurry, resulting in an increase in the comprehensive resistivity of the rock. The relationship between the resistivity of the water-bearing rock and the porosity and the resistivity of the filler in the pores is as shown in Equation IX:

[0179]

[0180] In Equation IX:

[0181] ρ represents the resistivity of the rock;

[0182] α represents a proportionality coefficient. α is generally a constant, and the value of α varies between 0.6 and 1.5;

[0183] φ represents the porosity of the rock;

[0184] m represents the cementation coefficient of the rock. The value of m generally varies between 1.5 and 3, but it is a fixed value for rocks of the same age and deposited in the same location;

[0185] S represents the water saturation, that is, the ratio of the voids filled with water;

[0186] n represents the saturation index, which can generally also be regarded as a constant;

[0187] ρ0 represents the resistivity of the water filling the voids.

[0188] As can be seen from the above equations VIII and IX, after grouting, the parameter whose value directly decreases is the porosity φ; assuming that all the voids are connected, the water saturation S will remain unchanged. If there are non-connected pores, the water saturation S will also decrease; at the same time, the resistivity ρ0 will also increase due to the influence of the cement slurry. The changes in these three values will all lead to an increase in the resistivity ρ of the rock, and the increase in the resistivity ρ of the rock will directly cause the attenuation coefficient β of the electromagnetic wave to decrease rapidly.

[0189] In this application example, the relationship between the resistivity and the attenuation coefficient is as Figure 8 shown. It can be seen from Figure 8 that the grouting process changes the resistivity of the rock, and the electromagnetic wave penetration CT imaging technology can reflect this resistivity change on a plane. The grouting distribution range can be indirectly inferred through the CT imaging map.

Claims

1. A single-frequency harmonic detection method for downhole directional holes, characterized in that, Before and after the fracturing - grouting construction in the emission borehole, harmonic signal acquisition is carried out once respectively; the four - fold frequency harmonic algorithm is adopted to extract the average harmonic signal amplitude value from the collected data; after processing the average harmonic signal amplitude value, the difference in absorption attenuation coefficients before and after the fracturing - grouting construction is obtained; by using the difference in absorption attenuation coefficients before and after the fracturing - grouting construction, the fracture distribution range and the slurry diffusion range can be indirectly inferred, and according to the fracture distribution range and the slurry diffusion range, the effect of the fracturing - grouting construction can be known; The method specifically includes the following steps: Step 1, flush the directional borehole; Step 2, determine the emission borehole and the receiving borehole, and design the positions of the emission points and the receiving points: After flushing the directional borehole described in Step 1, select and determine the emission borehole and the receiving borehole. Design the initial emission point F0 in the emission borehole and the initial receiving point R0 in the receiving borehole. Starting from the initial emission point F0, design n emission points at equal intervals with a as the measurement point spacing, denoted as F1, F2, F3... F n ; Starting from the initial receiving point R0, design m receiving points at equal measurement point intervals with a as the measurement point spacing, denoted as R1, R2, R3... R m ; Step 3, carry out harmonic signal acquisition before construction: Step 3.1, perform time synchronization; Step 3.2, carry out harmonic signal acquisition during the drill pipe drilling: Step 3.2.1, acquire the harmonic signal of the initial emission point F0; After completing the time synchronization in step 3.1, the transmitting probe and the receiving probe are respectively and slowly advanced synchronously and uniformly to the preset initial transmitting point F0 and the initial receiving point R0 in step 2. After recording the start time of acquisition, the first harmonic signal S of the initial transmitting point F0 is collected and obtained. (0,0) Then, the receiving probe is moved to the receiving point R1, and the second harmonic signal S of the initial transmitting point F0 is collected and obtained. (0,1) ; Step 3.2.2, acquire the harmonic signal of the emission point F1; After collecting the harmonic signal of the initial emission point F0 in step 3.2.1, move the transmitting probe to the emission point F1, and collect and obtain the harmonic signal S of the emission point F1 (1,1) , then move the receiving probe to the receiving point R2, and collect and obtain the second harmonic signal S of the emission point F1 (1,2) ; Step 3.2.3, push forward and acquire the harmonic signals of the remaining emission points; After completing the acquisition of the harmonic signal of the emission point F1 in step 3.2.2, repeat the operation in step 3.2.2 until the acquisition of the harmonic signal of the emission point F1 is completed. n-1 The first harmonic signal S (n-1,m-1) and the second harmonic signal S (n-1,m) After the acquisition, the receiving probe is located at the receiving point R m Move the transmitting probe to the transmitting point F n At the point where the emission point F is collected and obtained n The first harmonic signal S (n,m) Then move the receiving probe back to the receiving point R m-1 At the point where the emission point F is collected and obtained n The second harmonic signal S (n,m-1) , complete the harmonic signal collection of drill pipe drilling; Step 3.3, carry out return - shift harmonic signal acquisition during the drill pipe withdrawal: Step 3.3.1, withdraw the drill pipe and carry out acquisition; After the harmonic signal acquisition of the drill pipe drilling in step 3.2 is completed, the transmitting probe is pushed back to the transmitting point F n-1 and the receiving probe is pushed back to the receiving point R m-3 . The first return harmonic signal Q n-1 of the transmitting point F is collected and obtained (n-1,m-3) . Then the receiving probe is pushed back to the receiving point R m-4 again, and the second return harmonic signal Q n-1 of the transmitting point F is collected and obtained (n-1, m-4) . Step 3.3.2, continue to withdraw the drill pipe and carry out acquisition; Complete the emission point F of step 3.3.1 n-1 The first shifted harmonic signal Q (n-1,m-3) And the second shifted harmonic signal Q (n-1,m-4) After acquisition, move the transmitting probe to the emission point F n-2 At this point, collect and obtain the first shifted harmonic signal Q of the emission point F n-2 Then move the receiving probe to the receiving point R (n-2, m-4) At this point, collect and obtain the second shifted harmonic signal Q of the emission point F m-5 ; n-2 ; (n-2, m-5) ; Step 3.3.3, complete the harmonic signal acquisition; Complete the emission point F in step 3.3.2 n-2 After the acquisition of the backward migration harmonic signal, repeat the operations in step 3.3.2 until the first backward migration harmonic signal Q (3,1) and the second backward migration harmonic signal Q (3,0) are acquired, and the acquisition of the harmonic signal for drill pipe withdrawal is completed. Thus, the acquisition process of the harmonic signal before the entire construction ends; Step 4, extract the average harmonic signal amplitude value Ā: After completing the harmonic signal acquisition before construction in Step 3, the four - fold frequency harmonic algorithm is adopted to extract the average harmonic signal amplitude value Ā from the harmonic signal data before construction; The set of the harmonic signals S during the drill pipe drilling is expressed as follows, where n represents the number of emission points and m represents the number of receiving points: ； In the set of harmonic signals S of the drill pipe drilling, each harmonic signal S （i,j） contains k acquisition cycles, each acquisition cycle contains four acquisition time points, and each acquisition time point corresponds to a harmonic data value λ; Then the first harmonic signal S of the initial emission point F0 is expressed as follows: (0,0) as follows: ； The acquisition time tf of the first harmonic signal S of the initial emission point F0 (0,0) is expressed as follows: (0,0) as follows ； Then the first harmonic signal S of the initial emission point F0 (0,0) Among them, the four harmonic data values λ included in the first acquisition period are respectively expressed as follows; The harmonic data value collected at the acquisition time point as shown in Formula I: Formula I; The harmonic data value collected at the acquisition time point as shown in Equation II: Formula II; The harmonic data value collected at the acquisition time point as shown in Equation III: Formula III; The harmonic data value collected at the acquisition time point as shown in Equation IV: Formula IV; Then, the harmonic signal amplitude value A of the first harmonic signal S of the initial emission point F0 (0,0) can be obtained by calculation according to the following formula V and / or formula VI: Formula V; Formula VI; In Equation I, Equation II, Equation III, Equation IV, Equation V and Equation VI: θ represents the phase of the harmonic signal corresponding to the initial acquisition time point; A represents the harmonic signal amplitude value; π represents the phase increase of the harmonic signal corresponding to half a period; The first harmonic signal S of the initial emission point F0 described (0,0) Among the 4k harmonic data values λ included in it, a total of 2k harmonic signal amplitude values A can be obtained. By analogy with the above formulas I to VI, then according to the first harmonic signal S of the initial emission point F0 (0,0) The obtained harmonic signal amplitude value A (0,0) The set is represented as follows: ； Then the first harmonic signal S of the initial emission point F0 (0,0) The corresponding average harmonic signal amplitude value Ā (0,0) Is obtained according to Equation VII: Formula VII; In the set of harmonic signals S of the drill pipe drilling, each harmonic signal S （i,j） The calculation process of the corresponding average harmonic signal amplitude value Ā is the same as that of the first harmonic signal S of the initial emission point F0 (0,0) The corresponding average harmonic signal amplitude value Ā (0,0) The calculation process is the same. By analogy, the average harmonic signal amplitude values Ā corresponding to multiple harmonic signals S can be obtained; The set of the return - shift harmonic signals Q during the drill pipe withdrawal is expressed as follows, where n represents the number of emission points and m represents the number of receiving points: ； In the set of the return - shift harmonic signals Q during the drill pipe withdrawal, each return - shift harmonic signal Q contains k acquisition cycles, and each acquisition cycle contains four acquisition time points, and each acquisition time point corresponds to a return - shift harmonic data value ω; Then the second return-moving harmonic signal Q of the emission point F3 (3,0) is expressed as follows: ； The acquisition time tr of the second back-migration harmonic signal Q of the emission point F3 (3,0) is as follows: (3,0) is expressed as follows: ； In the set of return migration harmonic signals Q for the drill pipe to withdraw, the calculation process of the average harmonic signal amplitude value Ā corresponding to each return migration harmonic signal Q is the same as that of the first harmonic signal S of the initial emission point F0 (0,0) corresponding to the average harmonic signal amplitude value Ā (0,0) The calculation process is the same. By analogy, the average harmonic signal amplitude values Ā corresponding to multiple return migration harmonic signals Q can be obtained; Step 5, carry out harmonic signal acquisition and amplitude value extraction after construction: After completing the harmonic signal acquisition before construction described in Step 3, carry out fracturing - grouting construction on the emission borehole; after the construction is completed, repeat the above Steps 3.1 to 3.3 to complete the harmonic signal acquisition after the grouting - fracturing construction, adopt the four - fold frequency harmonic algorithm to extract the harmonic signal amplitude value from the harmonic signal data after construction, and obtain the average harmonic signal amplitude value after construction; Step 6: Process the average harmonic signal amplitude value before construction obtained in Step 4 and the average harmonic signal amplitude value after construction obtained in Step 5 to obtain the difference in absorption attenuation coefficients before and after the fracturing-grouting construction: Conduct CT imaging processing on the average harmonic signal amplitude value before construction obtained in Step 4 to obtain the absorption attenuation coefficient data of the emission borehole and the receiving borehole before construction; conduct CT imaging processing on the average harmonic signal amplitude value after construction obtained in Step 5 to obtain the absorption attenuation coefficient data of the emission borehole and the receiving borehole after construction; subtract the absorption attenuation coefficient data after construction from the absorption attenuation coefficient data before construction to obtain the difference in absorption attenuation coefficients before and after the fracturing-grouting construction.

2. The downhole directional hole single-frequency harmonic detection method according to claim 1, wherein, In Step 2, the measuring point spacing a is taken as 3m to 6m.

3. The downhole directional hole single-frequency harmonic detection method according to claim 1, characterized in that In Step 2, it is also necessary to design the detection depth H1 of the emission borehole and the detection depth H2 of the receiving borehole, and the detection depth H1 of the emission borehole is equal to the detection depth H2 of the receiving borehole.

4. The downhole directional hole single-frequency harmonic detection method according to claim 3, wherein, The number m of the emission points is equal to the detection depth H1 of the emission borehole divided by the measuring point spacing a, and the number m of the emission points is equal to the number n of the receiving points.

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