Coal mine underground staged hydraulic fracturing regionalization stress field measuring method

Abstract

The invention belongs to the technical field of coal mine underground hydraulic fracturing, and relates to a coal mine underground staged hydraulic fracturing regionalization stress field measuring method. Comprising the following steps: S1, determining segment parameters and position parameters of a hydrofracture drill hole fracturing segment needing to be measured; s2, designing a measuring point arrangement scheme of each fracturing section; s3, a stress detection special roadway used for burying stress detection equipment is constructed for each fracturing section; s4, a stress detection special drill hole used for burying stress detection equipment is buried in the stress detection special roadway; s5, stress detection equipment is installed in the special drill hole for stress detection, and the special drill hole for stress detection is blocked; and S6, collecting and analyzing detection data of the stress detection equipment. According to the method, the regionalized stress field of staged hydraulic fracturing can be accurately measured, the accuracy and the reliability of measurement of the stress field of hydraulic fracturing are improved, and a more scientific guidance basis is provided for implementation of an underground coal mine staged hydraulic fracturing technology.

Description

Technical Field

[0001] The invention belongs to the technical field of hydraulic fracturing in coal mines, and relates to a method for measuring regionalized stress fields of segmented hydraulic fracturing in coal mines. Background Art

[0002] The rapid development of directional long-hole drilling technology in coal mines has provided effective solutions to many technical problems in the coal mining process. In particular, in the fields of regionalized modification, pressure relief and anti-bumping of thick and hard roof, gas permeability extraction in coal seams, and increasing the venting of thick and hard top coal, directional long-hole segmented hydraulic fracturing technology in coal mines has shown significant advantages. The widespread application of this technology has not only improved the efficiency of coal mining, but also helped to ensure the safety of coal mine production.

[0003] In the process of hydraulic fracturing, in order to verify the fracturing effect and guide subsequent construction, some key parameters are usually examined. However, the current parameters for segmented hydraulic fracturing are mainly concentrated on the hydraulic fracturing radius, and the investigation of the hydraulic fracturing stress field is relatively small. In fact, due to the fracture of the rock mass and the injection of high-pressure water during hydraulic fracturing, stress concentration or pressure relief will inevitably occur in a certain area of ​​the coal rock mass. Especially in segmented hydraulic fracturing, the stress interference phenomenon between segments is particularly obvious, which has an important impact on the expansion of the cracks and the fracturing effect. Therefore, accurately determining the regionalized stress field of segmented hydraulic fracturing is of great significance for guiding the implementation of fracturing technology.

[0004] However, in the field of oil and gas development, since it is impossible to actually enter the underground space to install test sensor instruments, only indirect testing methods can be used to infer the stress field. In contrast, the conditions for constructing tunnels and drilling holes at any location in the coal mines under mining are available, which provides a rare engineering foundation for measuring the stress field. However, the existing stress field measurement methods still have many shortcomings, especially in terms of accuracy, which needs to be further improved.

[0005] At present, a commonly used stress field determination method is to deduce and calculate through microseismic signals. However, this method has obvious inaccuracies. On the one hand, the microseismic signal formed by the coal rock fracture signal is not completely equivalent to the stress transfer signal, and there is a certain difference between the two; on the other hand, when fracturing in soft coal seams, there are often no microseismic signals or weak microseismic signals, which makes it impossible to accurately explore the relationship between the distribution of microseismic signals and the distribution of stress fields. Therefore, a more accurate and reliable stress field determination method is urgently needed to meet the needs of underground staged hydraulic fracturing technology in coal mines. Summary of the invention

[0006] In view of this, the purpose of the present invention is to provide a method for measuring the regionalized stress field of staged hydraulic fracturing in underground coal mines, accurately measure the regionalized stress field of staged hydraulic fracturing, improve the accuracy and reliability of hydraulic fracturing stress field measurement, and provide a more scientific guiding basis for the implementation of staged hydraulic fracturing technology in underground coal mines.

[0007] To achieve the above object, the present invention provides a method for measuring the regionalized stress field of staged hydraulic fracturing in underground coal mines, comprising the following steps:

[0008] Step S1, determining the segmentation parameters and position parameters of the hydraulic fracturing drilling fracturing section to be measured;

[0009] Step S2, designing a measurement point arrangement plan for each fracturing stage;

[0010] Step S3, constructing a special stress detection tunnel for burying stress detection equipment in each fracturing stage;

[0011] Step S4, burying a special drilling hole for stress detection in the special lane for stress detection for burying stress detection equipment;

[0012] Step S5, installing a stress detection device into the special borehole for stress detection and sealing the special borehole for stress detection;

[0013] Step S6: collecting and analyzing the detection data of the stress detection equipment.

[0014] Optionally, step S2 further includes:

[0015] Step S21, starting from the center of the fracturing section to be measured, a plurality of measuring points are arranged along the extension direction of the hydraulic fracturing borehole and in a direction perpendicular to the extension path of the hydraulic fracturing borehole, the plurality of measuring points are overall arranged in a cross shape, and the distance between every two adjacent measuring points is x, where x is 5 to 15 m.

[0016] Step S22: Calculate the number of measuring points according to the following formula:

[0017] The number of measuring points in the extension direction of the hydraulic fracturing borehole is c1, c1 = d1 / x;

[0018] The number of measuring points in the direction perpendicular to the extension path of the hydraulic fracturing borehole is c2, c2 = d2 / x;

[0019] The total number of measuring points is c, c = c1 + c2;

[0020] Among them, d1 is the expected fracturing range value of the fracturing section in the extension direction of the hydraulic fracturing borehole, and d2 is the expected fracturing range value of the fracturing section perpendicular to the extension path of the hydraulic fracturing borehole; the final calculated value of the total number of measuring points c is rounded to the nearest integer.

[0021] Optionally, in step S3, a special stress detection tunnel for burying stress detection equipment is arranged in the rock stratum below the coal seam in the hydraulic fracturing area corresponding to each fracturing stage in a manner perpendicular to the extension path of the hydraulic fracturing borehole. The special stress detection tunnel passes through the projection of the center of the fracturing stage on the horizontal plane, and the vertical distance between the special stress detection tunnel and the coal seam is 20 to 30 meters.

[0022] Optionally, in step S4, a special stress detection borehole for burying stress detection equipment is constructed in the special stress detection tunnel in a stop-at-coal manner toward the measuring point, and the actual depth k of each special stress detection borehole is recorded. n .

[0023] Optionally, step S5 further includes:

[0024] Step S51: prepare u number of oil pillow stress gauges and u number of electronic pressure transmitters.

[0025] When c1 and c2 are both odd, u=c-1,

[0026] When at least one of c1 and c2 is an even number, u = c;

[0027] The length y of the oil pipe of the oil pillow stress gauge is related to the actual depth of the special drilling hole for stress detection, y = k n +2(m).

[0028] Step S52: Push the oil pillow stress gauges one by one to the bottom of the corresponding special borehole for stress detection, and use cement slurry to seal the entire special borehole for stress detection.

[0029] Step S53: 10 days later, an electronic pressure transmitter is installed at the opening of each special borehole for stress detection, and the pressure in the oil pipe of the oil pillow stress gauge is supplemented to 3 MPa.

[0030] Step S54, prepare a set of networked substations with a channel number greater than u, connect all electronic pressure transmitters to the networked substations, and debug them so that the signals can be transmitted to the ground computer.

[0031] Optionally, in step S6, the ground computer records stress data before hydraulic fracturing, stress data during hydraulic fracturing, and data after hydraulic fracturing, and calculates and analyzes to obtain the distribution of the stress field over time and space.

[0032] The beneficial effects of the present invention are:

[0033] The technical effect of the present invention is remarkable, and a practical solution is proposed for the technical problem of measuring the regionalized stress field of segmented hydraulic fracturing in underground coal mines.

[0034] First, the present invention effectively solves the problem of single stress test point and ineffective combination of stress test and hydraulic fracturing by arranging multiple sensors in close proximity. Compared with the traditional microseismic signal measurement method, the present invention can more accurately reflect the true distribution of coal rock stress field during hydraulic fracturing. This is because the arrangement of multiple sensors can cover a wider area and capture more information about stress field changes, thereby improving the accuracy and reliability of the measurement.

[0035] Secondly, the method of the present invention has a significant regional measurement feature. By scientifically and rationally designing the measurement point layout and sensor embedding process, the present invention can accurately measure the stress field of any section of the segmented hydraulic fracturing. This regional measurement method not only improves the comprehensiveness of the stress field measurement, but also provides a more scientific guiding basis for subsequent hydraulic fracturing construction.

[0036] In addition, the present invention also makes full use of the convenient conditions of underground construction in coal mines, and realizes the close-range measurement of stress fields by burying special lanes and special boreholes for stress detection through the construction of stress sensors. This measurement method not only reduces the measurement cost, but also improves the efficiency and accuracy of the measurement. At the same time, the present invention also adopts advanced technical means such as electronic pressure transmitters and networked substations to realize real-time transmission and remote monitoring of stress data, providing a strong guarantee for safe production in coal mines.

[0037] In summary, the technical effects of the present invention are mainly reflected in improving the accuracy and reliability of hydraulic fracturing stress field measurement, realizing regional measurement, making full use of the convenient conditions for underground coal mine construction, reducing measurement costs and improving measurement efficiency, etc. It not only provides a more scientific guiding basis for the implementation of underground segmented hydraulic fracturing technology in coal mines, but also provides strong support for safe production and efficient mining of coal mines.

[0038] Other advantages, objectives and features of the present invention will be described in the following description to some extent, and to some extent, will be obvious to those skilled in the art based on the following examination and study, or can be taught from the practice of the present invention. The objectives and other advantages of the present invention can be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention will be described in detail below in conjunction with the accompanying drawings, wherein:

[0040] Figure 1 A flow chart of the method for determining the regionalized stress field of underground segmented hydraulic fracturing in a coal mine provided by the present invention;

[0041] Figure 2A plan view of the drilling arrangement of the method for determining the regionalized stress field of the underground segmented hydraulic fracturing in a coal mine provided by the present invention;

[0042] Figure 3 A cross-sectional view of the drilling arrangement along the Ι-Ι direction for the method for determining the regionalized stress field of underground segmented hydraulic fracturing in a coal mine provided by the present invention. DETAILED DESCRIPTION

[0043] The following describes the embodiments of the present invention by specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that the illustrations provided in the following embodiments only illustrate the basic concept of the present invention in a schematic manner, and the following embodiments and features in the embodiments can be combined with each other without conflict.

[0044] Among them, the drawings are only used for illustrative explanations, and they only represent schematic diagrams rather than actual pictures, and should not be understood as limitations on the present invention. In order to better illustrate the embodiments of the present invention, some parts of the drawings may be omitted, enlarged or reduced, and do not represent the size of actual products. For those skilled in the art, it is understandable that some well-known structures and their descriptions in the drawings may be omitted.

[0045] The same or similar numbers in the drawings of the embodiments of the present invention correspond to the same or similar parts; in the description of the present invention, it should be understood that if the terms "upper", "lower", "left", "right", "front", "rear", etc. indicate the orientation or position relationship, they are based on the orientation or position relationship shown in the drawings, which is only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operate in a specific orientation. Therefore, the terms describing the position relationship in the drawings are only used for illustrative purposes and cannot be understood as limiting the present invention. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to specific circumstances.

[0046] In view of the many defects of the prior art, the present invention proposes a method for measuring the regionalized stress field of staged hydraulic fracturing in underground coal mines, which not only solves the problems of the original single stress test point and the ineffective combination of stress test and hydraulic fracturing, but also improves the accuracy and reliability of stress field measurement, thereby more effectively guiding the implementation of staged hydraulic fracturing technology and improving the efficiency and safety of coal mining.

[0047] like Figure 1 As shown, the method for determining the regionalized stress field of underground segmented hydraulic fracturing in a coal mine of the present invention specifically comprises the following steps:

[0048] Step S1, determining the segmentation parameters and position parameters of the hydraulic fracturing drilling fracturing section to be measured;

[0049] Step S2, designing a measurement point arrangement plan for each fracturing stage;

[0050] Step S3, constructing a special stress detection tunnel for burying stress detection equipment in each fracturing stage;

[0051] Step S4, burying a special drilling hole for stress detection in the special lane for stress detection for burying stress detection equipment;

[0052] Step S5, installing a stress detection device into the special borehole for stress detection and sealing the special borehole for stress detection;

[0053] Step S6: collecting and analyzing the detection data of the stress detection equipment.

[0054] Further, step S2 includes:

[0055] Step S21, determine the distribution range: Figure 2 As shown, taking the center of the fracturing section to be measured as a reference, measuring points with a spacing of x are designed along the extension path of the hydraulic fracturing borehole and in the direction perpendicular to the extension path of the hydraulic fracturing borehole. The shape of the measuring points is a cross, the center of the cross is at the center of the fracturing section, and the distance x between two adjacent measuring points is 5 to 15 m;

[0056] Step S22, calculate the number of measuring points c: according to the expected fracturing range value d1 of the hydraulic fracturing borehole extension and the expected fracturing range value d2 in the direction perpendicular to the hydraulic fracturing borehole extension path, respectively calculate the number of measuring points c1 on the hydraulic fracturing borehole extension path = d1 / x, the number of measuring points c2 in the direction perpendicular to the hydraulic fracturing borehole extension path = d2 / x, the calculated value is rounded to an integer, c = c1 + c2

[0057] Specifically, in step S3, Figure 2 , Figure 3 As shown, in the rock layer below the coal seam in the hydraulic fracturing area, a special stress detection tunnel perpendicular to the fracturing drilling direction is constructed. The special stress detection tunnel is projected through the center of the fracturing section, and the vertical distance between the special stress detection tunnel and the coal seam is 20-30m.

[0058] Specifically, in step S4, a special borehole for stress detection is constructed toward the designed measuring point in the special tunnel for stress detection, and the special borehole for stress detection is constructed until coal is seen, and the actual depth k of each special borehole for stress detection is recorded. n .

[0059] Further, step S5 includes:

[0060] Step S51, determine the type, quantity and parameters of the stress sensing equipment: prepare u number of oil pillow stress gauges and u number of electronic pressure transmitters, when c1 and c2 are both odd numbers, u=c-1 (center repeat), otherwise u=c, the length y of the oil pillow stress gauge oil pipe is prepared according to the actual depth of the special drilling hole for stress detection, y=k n +2(m);

[0061] Step S52, installing the stress gauge: after pushing the oil pillow stress gauges one by one to the bottom of the corresponding special borehole for stress detection, cement slurry is used to seal the entire special borehole for stress detection;

[0062] Step S53, installing the electronic pressure transmitter: 10 days later, installing the electronic pressure transmitter at the opening of the special drilling hole for stress detection, and replenishing the pressure in the oil pipe of the oil pillow stress gauge to 3MPa;

[0063] Step S54, install other supporting equipment: prepare a set of networked substations with a channel number greater than u, connect all electronic pressure transmitters to the networked substations, and debug so that the signals can be transmitted to the ground computer.

[0064] Specifically, in step S6, the ground computer records stress data before hydraulic fracturing, stress data during hydraulic fracturing, and data after hydraulic fracturing, and analyzes the distribution of the stress field over time and space.

[0065] The present invention proposes a method for measuring regionalized stress field of underground coal mine staged hydraulic fracturing. Through the close arrangement of multiple sensors and the scientific and reasonable design of measuring points and sensor burying process, accurate and comprehensive measurement of the stress field is achieved, and the problems of inaccurate traditional microseismic signal measurement methods and unclear stress field distribution are effectively solved. The convenient conditions for underground coal mine construction are fully utilized, the measurement cost is reduced, the measurement efficiency and safety are improved, and strong support is provided for the implementation of underground coal mine staged hydraulic fracturing technology and safe production in coal mines.

[0066] Finally, it should be noted that the above embodiments are only used to illustrate the technical solution of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present invention can be modified or replaced by equivalents without departing from the purpose and scope of the technical solution, which should be included in the scope of the claims of the present invention.

Claims

1. A method for determining regionalized stress field of staged hydraulic fracturing in underground coal mines, characterized in that: The following steps are involved: Step S1, determining the segmentation parameters and position parameters of the hydraulic fracturing drilling fracturing section to be measured; Step S2, designing a measurement point arrangement plan for each fracturing stage; Step S3, constructing a special stress detection tunnel for burying stress detection equipment in each fracturing stage; Step S4, burying a special drilling hole for stress detection in the special lane for stress detection for burying stress detection equipment; Step S5, installing a stress detection device into the special borehole for stress detection and sealing the special borehole for stress detection; Step S6, collecting and analyzing the detection data of the stress detection equipment; Wherein, the step S2 further includes: Step S21, starting from the center of the fracturing section to be measured, a plurality of measuring points are arranged along the extension direction of the hydraulic fracturing borehole and in a direction perpendicular to the extension path of the hydraulic fracturing borehole, the plurality of measuring points are distributed in a cross shape as a whole, and the distance between every two adjacent measuring points is x, where x is 5 to 15 m; Step S22: Calculate the number of measuring points according to the following formula: The number of measuring points in the extension direction of the hydraulic fracturing borehole is c1, c1=d1 / x; The number of measuring points in the direction perpendicular to the extension path of the hydraulic fracturing borehole is c2, c2 = d2 / x; The total number of measuring points is c, c = c1 + c2; Among them, d1 is the expected fracturing range value of the fracturing section in the extension direction of the hydraulic fracturing borehole, and d2 is the expected fracturing range value of the fracturing section perpendicular to the extension path of the hydraulic fracturing borehole; the final calculated value of the total number of measuring points c is rounded to an integer.

2. The assay method according to claim 1, characterized in that: In the step S3, a special stress detection tunnel for burying stress detection equipment is arranged in the rock layer below the coal seam in the hydraulic fracturing area corresponding to each fracturing stage in a manner perpendicular to the extension path of the hydraulic fracturing borehole. The special stress detection tunnel passes through the projection of the center of the fracturing stage on the horizontal plane, and the vertical distance between the special stress detection tunnel and the coal seam is 20 to 30 meters.

3. The measuring method according to claim 1, characterized in that: In step S4, a special borehole for burying stress detection equipment is constructed in the special tunnel for stress detection toward the measuring point in a stop-as-coal manner, and the actual depth k of each special borehole for stress detection is recorded. n .

4. The measuring method according to claim 1, characterized in that: The step S5 further comprises: Step S51: prepare u number of oil pillow stress gauges and u number of electronic pressure transmitters. When c1 and c2 are both odd, u=c-1, When at least one of c1 and c2 is an even number, u = c; The length y of the oil pipe of the oil pillow stress gauge is related to the actual depth of the special drilling hole for stress detection, y=k n +2(m).

5. The assay method according to claim 4, characterized in that: The step S5 further comprises: Step S52: Push the oil pillow stress gauges one by one to the bottom of the corresponding special borehole for stress detection, and use cement slurry to seal the entire special borehole for stress detection.

6. The assay method according to claim 5, characterized in that: The step S5 further comprises: Step S53: 10 days later, an electronic pressure transmitter is installed at the orifice of each of the special boreholes for stress detection, and the pressure in the oil pipe of the oil pillow stress gauge is supplemented to 3 MPa.

7. The assay method according to claim 6, characterized in that: The step S5 further comprises: Step S54, prepare a set of networked substations with a channel number greater than u, connect all the electronic pressure transmitters to the networked substations, and debug them so that the signals can be transmitted to the ground computer.

8. The determination method according to claim 7, characterized in that: In step S6, the surface computer records stress data before hydraulic fracturing, stress data during hydraulic fracturing, and data after hydraulic fracturing, and calculates and analyzes the distribution of hydraulic fracturing stress field over time and space.

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