A method for calculating negative pressure of a borehole

Abstract

The present application relates to the technical field of coal mining, and particularly relates to a negative pressure calculation method of a drill hole. The present application provides a negative pressure calculation method of a drill hole, comprising the following steps: inserting a plurality of test tubes into the drill hole, each of the test tubes comprising a suction end and a test end, and the plurality of test ends being arranged at different depths of the drill hole; for each of the test tubes, the following steps are performed: connecting an extraction system with the drill hole; connecting one end of a negative pressure gauge with the suction end and sealing the other end of the negative pressure gauge; starting the extraction system and recording a first negative pressure value of the negative pressure gauge; establishing a negative pressure calculation model according to a plurality of the first negative pressure values and depths of the plurality of test ends; and calculating a negative pressure value at any drill hole depth by using the negative pressure calculation model. The present application provides a negative pressure calculation method of a drill hole, which can provide a method for calculating the negative pressure of the drill hole, and thus improves the efficiency of gas extraction.

Description

Technical Field

[0001] This invention relates to the field of coal mining technology, and in particular to a method for calculating negative pressure in boreholes. Background Technology

[0002] During coal mining, the methane content in the borehole is high. If the methane is not extracted in time, it will affect the safe mining of coal.

[0003] In related technologies, gas extraction mainly relies on extraction systems to remove gas from boreholes. However, the negative pressure in the borehole varies with the depth of the borehole, and if the negative pressure in the borehole cannot be determined, the efficiency of gas extraction will be reduced.

[0004] Therefore, in order to address the above shortcomings, there is an urgent need for a method to calculate the negative pressure of the borehole. Summary of the Invention

[0005] This invention provides a method for calculating the negative pressure of a borehole, thereby improving the efficiency of gas extraction.

[0006] This invention provides a method for calculating negative pressure in boreholes, including:

[0007] Multiple test tubes are inserted into the borehole, each test tube including an air extraction end and a test end, and the multiple test ends are disposed at different depths of the borehole;

[0008] For each of the test tubes, the following steps are performed:

[0009] Connect the extraction system to the borehole;

[0010] Connect one end of the negative pressure gauge to the suction end, and seal the other end of the negative pressure gauge;

[0011] Turn on the extraction system and record the first negative pressure value of the negative pressure gauge;

[0012] A negative pressure calculation model is established based on multiple first negative pressure values ​​and the depths of multiple test terminals;

[0013] The negative pressure value at any drilling depth is calculated using the aforementioned negative pressure calculation model.

[0014] One possible design also includes:

[0015] For each of the test tubes, the following steps are performed:

[0016] The extraction system is connected to the borehole and the extraction end respectively; wherein, a negative pressure gauge is provided between the extraction end and the extraction system;

[0017] Turn on the extraction system and record the second negative pressure value of the negative pressure gauge;

[0018] For each of the test tubes, a first theoretical value is determined based on the second negative pressure value measured by the test tube and the tube diameter ratio of the test tube;

[0019] The step of establishing a negative pressure calculation model based on multiple first negative pressure values ​​and multiple test depths includes:

[0020] Multiple first negative pressure values ​​are verified using multiple first theoretical values ​​to obtain multiple first verification negative pressure values;

[0021] A negative pressure calculation model is established based on multiple first theoretical values, multiple first verification negative pressure values, and multiple test terminal depths.

[0022] In one possible design, the step of verifying multiple first negative pressure values ​​using multiple first theoretical values ​​to obtain multiple first verification negative pressure values ​​includes:

[0023] The first difference value is obtained by subtracting the first theoretical value and the first negative pressure value measured in the same test tube;

[0024] The first difference value that is higher than the first preset value is marked;

[0025] Delete the first negative pressure value corresponding to the first difference with the mark;

[0026] The first negative pressure value that was not deleted is determined as the first verification negative pressure value.

[0027] In one possible design, the first theoretical value is obtained using the following formula:

[0028] Δp=λ×l / d×(ρv 2 / 2)

[0029] L1=Δp-f2

[0030] Where Δp is the pressure drop, λ is the friction coefficient, l is the length of the test tube, d is the diameter of the test tube, ρ is the density of the fluid in the test tube, L1 is the first theoretical value, and f2 is the second negative pressure value.

[0031] One possible design also includes:

[0032] For each of the test tubes, the following steps are performed:

[0033] Connect the extraction system to the borehole;

[0034] Connect one end of the negative pressure gauge to the air extraction end, and connect the other end of the negative pressure gauge to the outside of the borehole;

[0035] Turn on the extraction system and record the third negative pressure value of the negative pressure gauge;

[0036] For each of the test tubes, a second theoretical value is determined based on the third negative pressure value measured by the test tube and the tube diameter ratio of the test tube;

[0037] The step of establishing a negative pressure calculation model based on multiple first negative pressure values ​​and multiple test depths includes:

[0038] Multiple second theoretical values ​​are used to verify multiple first negative pressure values ​​to obtain multiple second verification negative pressure values;

[0039] A negative pressure calculation model is established based on multiple second theoretical values, multiple second verification negative pressure values, and multiple test terminal depths.

[0040] In one possible design, the step of verifying multiple first negative pressure values ​​using multiple second theoretical values ​​to obtain multiple second verification negative pressure values ​​includes:

[0041] The second difference value is obtained by subtracting the second theoretical value and the first negative pressure value measured in the same test tube.

[0042] The second difference, which is higher than the second preset value, is marked;

[0043] Delete the first negative pressure value corresponding to the marked second difference;

[0044] The first negative pressure value that was not deleted is determined as the second verification negative pressure value.

[0045] In one possible design, the second theoretical value is obtained using the following formula:

[0046] Δp=λ×l / d×(ρv 2 / 2)

[0047] L2=Δp-f3

[0048] Where Δp is the pressure drop, λ is the friction coefficient, l is the length of the test tube, d is the diameter of the test tube, ρ is the density of the fluid in the test tube, L2 is the second theoretical value, and f3 is the third negative pressure value.

[0049] In one possible design, two extraction systems are included, with the two extraction systems respectively disposed on both sides of the borehole;

[0050] Connecting the extraction system to the borehole includes:

[0051] The two extraction systems are respectively connected to the two ends of the borehole;

[0052] The step of activating the extraction system and recording the first negative pressure value of the negative pressure gauge includes:

[0053] Turn on both of the extraction systems respectively and record the first negative pressure value of the negative pressure gauge respectively;

[0054] Simultaneously activate both of the aforementioned extraction systems and record the first negative pressure value of the negative pressure gauge.

[0055] In one possible design, two extraction systems are included, with the two extraction systems respectively disposed on both sides of the borehole;

[0056] The step of connecting the extraction system to the borehole and the extraction end respectively includes:

[0057] One of the extraction systems is connected to the first end of the borehole and the extraction end, respectively.

[0058] Connect another of the aforementioned extraction systems to the second end of the borehole;

[0059] The step of activating the extraction system and recording the second negative pressure value of the negative pressure gauge includes:

[0060] Simultaneously activate both of the aforementioned extraction systems and record the second negative pressure value of the negative pressure gauge;

[0061] Disconnect the first end from the extraction system, and simultaneously turn on both extraction systems and record the second negative pressure value of the negative pressure gauge;

[0062] Disconnect the second end from the extraction system, and simultaneously turn on both extraction systems and record the second negative pressure value of the negative pressure gauge.

[0063] In one possible design, two extraction systems are included, with the two extraction systems respectively disposed on both sides of the borehole;

[0064] Connecting the extraction system to the borehole includes:

[0065] The two extraction systems are respectively connected to both ends of the borehole;

[0066] The step of activating the extraction system and recording the third negative pressure value of the negative pressure gauge includes:

[0067] Turn on both of the aforementioned extraction systems and record the third negative pressure value of the negative pressure gauge respectively;

[0068] Simultaneously activate both of the aforementioned extraction systems and record the third negative pressure value of the negative pressure gauge.

[0069] Compared with the prior art, the present invention has at least the following beneficial effects:

[0070] In this embodiment, multiple test tubes are set up, each including an extraction end and a test end. The test tubes have different lengths, and the test ends of the multiple test tubes are inserted into the borehole, placing them at different positions within the borehole. For each test tube, the following test operations are performed: the extraction system is connected to one end of the borehole; one end of a negative pressure gauge is connected to the extraction end, and the other end of the negative pressure gauge is sealed; the extraction system is turned on to extract gas from the borehole. Since the extraction end is connected to one end of the negative pressure gauge, the other end of the negative pressure gauge is sealed, and the test end is located in the borehole, the gas in the borehole is continuously extracted. Therefore, the first negative pressure value displayed by the negative pressure gauge is the negative pressure value of the test tube at that depth. After measuring the first negative pressure value of each test tube, different negative pressure values ​​(first negative pressure values) at different depths (depth of the test section) in the borehole are obtained, thus obtaining the mapping relationship between borehole depth and negative pressure value, i.e., the negative pressure calculation model. After obtaining the negative pressure calculation model, the negative pressure value at any borehole depth can be calculated. Attached Figure Description

[0071] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0072] Figure 1 This is a flowchart of a borehole negative pressure calculation provided by an embodiment of the present invention;

[0073] Figure 2 This is a schematic diagram of the structure of a drilling test system provided in one embodiment of the present invention;

[0074] Figure 3 This is a schematic diagram of a drilling test system provided in another embodiment of the present invention;

[0075] Figure 4 This is a schematic diagram of another drilling test system provided in one embodiment of the present invention;

[0076] Figure 5 This is a schematic diagram of the structure of another drilling test system provided in one embodiment of the present invention;

[0077] Figure 6 This is a schematic diagram of another drilling test system provided in another embodiment of the present invention;

[0078] Figure 7 This is a schematic diagram of another drilling test system provided in another embodiment of the present invention. Detailed Implementation

[0079] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are some embodiments of the present invention, but not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0080] like Figure 1 and Figure 2 As shown, this embodiment of the invention provides a method for calculating negative pressure in boreholes, including:

[0081] Multiple test tubes are inserted into the borehole. Each test tube includes an air extraction end and a test end. The multiple test ends are set at different depths in the borehole.

[0082] For each test tube, perform the following steps:

[0083] Connect the extraction system to the borehole;

[0084] Connect one end of the negative pressure gauge to the suction end and seal the other end of the negative pressure gauge.

[0085] Start the extraction system and record the first negative pressure value of the negative pressure gauge;

[0086] A negative pressure calculation model is established based on multiple first negative pressure values ​​and the depth of multiple test terminals;

[0087] The negative pressure value at any borehole depth is calculated using a negative pressure calculation model.

[0088] In this embodiment, multiple test tubes are set up, each including an extraction end and a test end. The test tubes have different lengths, and the test ends of the multiple test tubes are inserted into the borehole, placing them at different positions within the borehole. For each test tube, the following test operations are performed: the extraction system is connected to one end of the borehole; one end of a negative pressure gauge is connected to the extraction end, and the other end of the negative pressure gauge is sealed; the extraction system is turned on to extract gas from the borehole. Since the extraction end is connected to one end of the negative pressure gauge, the other end of the negative pressure gauge is sealed, and the test end is located in the borehole, the gas in the borehole is continuously extracted. Therefore, the first negative pressure value displayed by the negative pressure gauge is the negative pressure value of the test tube at that depth. After measuring the first negative pressure value of each test tube, different negative pressure values ​​(first negative pressure values) at different depths (depth of the test section) in the borehole are obtained, thus obtaining the mapping relationship between borehole depth and negative pressure value, i.e., the negative pressure calculation model. After obtaining the negative pressure calculation model, the negative pressure value at any borehole depth can be calculated.

[0089] In this embodiment, the flow meter can also be connected in series with the negative pressure gauge, and the flow meter can measure the flow rate of the test tube.

[0090] It is understandable that, such as Figure 2 As shown, closing the valve between the extraction system and the flow meter achieves the effect of sealing the extraction end in this embodiment.

[0091] It should be noted that the gas extraction end can be connected through a gas extraction single bundle tube. In addition to being connected to the extraction system, the gas extraction single bundle tube is also connected to the extraction pump. Then, a gas sampler is connected to the extraction pump to obtain the changes in negative pressure and concentration at each monitoring point (test end) of the extraction borehole over time during the extraction cycle, as well as the changes in negative pressure and concentration along the extraction borehole.

[0092] like Figure 2 As shown, in some embodiments of the present invention, it further includes:

[0093] For each test tube, perform the following steps:

[0094] The extraction system is connected to the borehole and the extraction end respectively; a negative pressure gauge is installed between the extraction end and the extraction system.

[0095] Start the extraction system and record the second negative pressure value of the negative pressure gauge;

[0096] For each test tube, the first theoretical value is determined based on the second negative pressure value measured by the test tube and the tube diameter ratio of the test tube;

[0097] A negative pressure calculation model is established based on multiple initial negative pressure values ​​and the depth of multiple test terminals, including:

[0098] Multiple first theoretical values ​​are used to verify multiple first negative pressure values, resulting in multiple first verification negative pressure values;

[0099] A negative pressure calculation model is established based on multiple first theoretical values, multiple first verification negative pressure values, and the depth of multiple test terminals.

[0100] Since the first negative pressure value measured in the above embodiment is the actual negative pressure value measured at the test end, any problem with any device or component in the test system will affect the first negative pressure value, causing a large deviation between the measured first negative pressure value and the negative pressure value in the borehole. Therefore, this embodiment is designed to find the large deviation value in the first negative pressure value.

[0101] In this embodiment, for each test tube, the extraction system is connected to both the borehole and the extraction end, and the extraction system simultaneously extracts gas from both ends. Since the extraction system directly extracts gas from the extraction end, while indirectly extracting gas from the test end through the borehole, the negative pressure at the extraction end is higher, causing gas to flow from the test end to the extraction end. At this point, the test tube forms a negative pressure system, and the second negative pressure value displayed on the negative pressure gauge is the negative pressure value of this system. Further, the theoretical negative pressure value at the test end of the test tube, i.e., the first theoretical value, can be determined by the ratio of the second negative pressure value to the tube diameter. The first negative pressure value is verified using the first theoretical value of the same test tube. If the first theoretical value and the first negative pressure value deviate significantly, then the first negative pressure value is incorrect. After deleting the incorrect first negative pressure value, the remaining value is the correct first verification negative pressure value. In addition to verifying the first negative pressure value, the first theoretical value can also participate in the establishment of the negative pressure calculation model. The negative pressure calculation model established based on multiple first theoretical values, multiple first verified negative pressure values, and the depth of multiple test terminals is more accurate.

[0102] It should be noted that when the sampling system is connected to the same test tube, the first negative pressure value and the second negative pressure value of the test tube can be tested at the same time to improve the testing efficiency.

[0103] It is understandable that, such as Figure 2 As shown, opening the valve between the extraction system and the flow meter allows the extraction system in this embodiment to simultaneously extract from the borehole and the extraction end.

[0104] In some embodiments of the present invention, multiple first negative pressure values ​​are verified using multiple first theoretical values ​​to obtain multiple first verification negative pressure values, including:

[0105] The first difference value is obtained by subtracting the first theoretical value and the first negative pressure value measured in the same test tube.

[0106] Mark the first difference that is higher than the first preset value;

[0107] Delete the first negative pressure value corresponding to the first difference marked with the label;

[0108] The first negative pressure value that was not deleted is determined as the first verification negative pressure value.

[0109] In this embodiment, the first theoretical value and the first negative pressure value of the same test tube are first subtracted to obtain the first difference value. Each first difference value is compared with the first preset value, and the first difference values ​​that are higher than the first preset value are marked. The first negative pressure value with the marked first difference value is the error value. After removing the error value, the remaining first negative pressure value is the first verification negative pressure value.

[0110] It should be noted that the first preset value can be an empirical value or determined by averaging multiple first differences. Specifically, 1.4 to 2 times the average can be used as the first preset value.

[0111] In some embodiments of the present invention, the first theoretical value is obtained by the following formula:

[0112] Δp=λ×l / d×(ρv 2 / 2)

[0113] L1=Δp-f2

[0114] Where Δp is the pressure drop, λ is the friction coefficient, l is the length of the test tube, d is the diameter of the test tube, ρ is the density of the fluid in the test tube, L1 is the first theoretical value, and f2 is the second negative pressure value.

[0115] In this embodiment, the pressure drop is obtained by considering the aspect ratio of the test tube, the fluid density, and the friction coefficient. The difference between the pressure drop and the second negative pressure value is the theoretical negative pressure value (first theoretical value) at the test end. The friction coefficient can be determined experimentally, and the fluid density can be determined by the gas concentration of the gas flowing through the test tube.

[0116] like Figure 3 As shown, in some embodiments of the present invention, it further includes:

[0117] For each test tube, perform the following steps:

[0118] Connect the extraction system to the borehole;

[0119] Connect one end of the negative pressure gauge to the suction end, and connect the other end of the negative pressure gauge to the outside of the borehole;

[0120] Turn on the extraction system and record the third negative pressure value of the negative pressure gauge;

[0121] For each test tube, the second theoretical value is determined based on the third negative pressure value measured by the test tube and the tube diameter ratio of the test tube;

[0122] A negative pressure calculation model is established based on multiple initial negative pressure values ​​and the depth of multiple test terminals, including:

[0123] Multiple second theoretical values ​​are used to verify multiple first negative pressure values ​​to obtain multiple second verification negative pressure values;

[0124] A negative pressure calculation model is established based on multiple second theoretical values, multiple second verification negative pressure values, and the depth of multiple test terminals.

[0125] In order to verify the first negative pressure value through multiple methods and angles, and to provide more data for establishing a negative pressure calculation model, this embodiment is designed to obtain the third negative pressure value and the second theoretical value.

[0126] In this embodiment, for each test tube, an extraction system is connected to the borehole, with the extraction end open to the external environment of the borehole (i.e., the extraction end is not sealed and not connected to the extraction system). The extraction system extracts gas from the borehole. Because the extraction system extracts gas from the test end through the borehole, a large negative pressure is created at the test end. Since the extraction end is open to the external environment of the borehole, gas flows from the extraction end to the test end. At this time, the test tube forms a negative pressure system, and the third negative pressure value displayed by the negative pressure gauge is the negative pressure value of this system. Further, the theoretical negative pressure value of the test end of the test tube can be determined by the ratio of the third negative pressure value to the tube diameter, i.e., the second theoretical value. The second theoretical value of the same test tube is used to verify the first negative pressure value. If the second theoretical value and the first negative pressure value deviate significantly, then the first negative pressure value is incorrect. After deleting the incorrect first negative pressure value, the remaining value is the correct second verification negative pressure value. In addition to verifying the first negative pressure value, the second theoretical value can also participate in the establishment of the negative pressure calculation model. The negative pressure calculation model established based on multiple second theoretical values, multiple first verification negative pressure values, and the depth of multiple test terminals is more accurate.

[0127] It should be noted that when the sampling system is connected to the same test tube, the first negative pressure value and the third negative pressure value of the test tube can be tested at the same time to improve the testing efficiency.

[0128] It should be noted that because the flow direction of the gas in the test tube changes, the connection of the negative pressure gauge needs to be changed.

[0129] In some embodiments of the present invention, multiple first negative pressure values ​​are verified using multiple second theoretical values ​​to obtain multiple second verification negative pressure values, including:

[0130] The second difference value is obtained by subtracting the second theoretical value and the first negative pressure value measured in the same test tube.

[0131] Mark the second difference that is higher than the second preset value;

[0132] Delete the first negative pressure value corresponding to the marked second difference;

[0133] The first negative pressure value that was not deleted is determined as the second verification negative pressure value.

[0134] In this embodiment, the second theoretical value and the first negative pressure value of the same test tube are first subtracted to obtain a second difference value. Each second difference value is compared with a second preset value, and the second difference values ​​that are higher than the second preset value are marked. The first negative pressure value with the marked second difference value is the error value. After removing the error value, the remaining second negative pressure value is the second verification negative pressure value.

[0135] It should be noted that the second preset value can be an empirical value or determined by averaging multiple second differences. Specifically, 1.4 to 2 times the average can be used as the second preset value. The first preset value can be the same as or different from the second preset value.

[0136] In some embodiments of the present invention, the second theoretical value is obtained by the following formula:

[0137] Δp=λ×l / d×(ρv 2 / 2)

[0138] L2=Δp-f3

[0139] Where Δp is the pressure drop, λ is the friction coefficient, l is the length of the test tube, d is the diameter of the test tube, ρ is the density of the fluid in the test tube, L2 is the second theoretical value, and f3 is the third negative pressure value.

[0140] In this embodiment, the pressure drop is obtained by considering the aspect ratio of the test tube, the fluid density, and the friction coefficient. The difference between the pressure drop and the third negative pressure value is the theoretical negative pressure value (second theoretical value) at the test end. The friction coefficient can be determined experimentally, and the fluid density can be determined by the gas concentration of the gas flowing through the test tube.

[0141] like Figure 2 , 4 As shown in Figure 5, in some embodiments of the present invention, two extraction systems are included, which are respectively arranged on both sides of the borehole.

[0142] Connecting the extraction system to the borehole includes:

[0143] Two extraction systems were connected to the two ends of the borehole, respectively.

[0144] Turn on the extraction system and record the first negative pressure value of the negative pressure gauge, including:

[0145] Start the two sampling systems separately and record the first negative pressure value of the negative pressure gauges respectively;

[0146] Simultaneously activate two sampling systems and record the first negative pressure value of the negative pressure gauge.

[0147] To ensure the measured data more closely approximates real-world data, extraction systems are installed at both ends of the borehole. Specifically, when measuring the first negative pressure value, extraction is performed at both ends of the borehole, and then simultaneously at both ends. These three extractions yield three first negative pressure values. This setup improves the accuracy of the first negative pressure value, reduces errors, and increases the data available for establishing the negative pressure calculation model.

[0148] It should be noted that in order to ensure that the negative pressure inside the extraction borehole reaches a balanced state, the extraction interval should be at least 6 days.

[0149] In this embodiment, Figure 2 , 4 The extraction valve in section 5 is in the closed state.

[0150] like Figure 2 , 4 As shown in Figure 5, in some embodiments of the present invention, two extraction systems are included, which are respectively arranged on both sides of the borehole.

[0151] The extraction system is connected to both the borehole and the extraction end, including:

[0152] Connect a extraction system to the first end and the extraction end of the borehole, respectively;

[0153] Connect another extraction system to the second end of the borehole;

[0154] Turn on the extraction system and record the second negative pressure value of the negative pressure gauge, including:

[0155] Simultaneously activate two extraction systems and record the second negative pressure value of the negative pressure gauge;

[0156] Disconnect the first end from the sampling system, and simultaneously turn on both sampling systems and record the second negative pressure value of the negative pressure gauge;

[0157] Disconnect the second end from the sampling system, and simultaneously turn on both sampling systems and record the second negative pressure value of the negative pressure gauge.

[0158] To ensure the measured data more closely approximates real-world data, extraction systems are installed at both ends of the borehole. Specifically, when measuring the second negative pressure value, extraction is performed separately at both ends of the borehole, and then simultaneously at both ends. This three-stage extraction process yields three second negative pressure values. This setup improves the accuracy of the second negative pressure value, reduces errors, and increases the data available for establishing the negative pressure calculation model.

[0159] In this embodiment, regardless of which end of the borehole is being pumped from, a pumping system must be connected to the pumping end. When one pumping system is pumping air through the pumping end and another pumping system is pumping air at one end of the borehole, it must be ensured that the power of the two pumping systems is the same.

[0160] It should be noted that in order to ensure that the negative pressure inside the extraction borehole reaches a balanced state, the extraction interval should be at least 6 days.

[0161] In this embodiment, Figure 2 , 4 The extraction valve in section 5 is in the open state.

[0162] like Figure 3 , 6As shown in Figure 7, in some embodiments of the present invention, two extraction systems are included, which are respectively disposed on both sides of the borehole;

[0163] Connecting the extraction system to the borehole includes:

[0164] Connect the two extraction systems to the two ends of the borehole respectively;

[0165] Turn on the extraction system and record the third negative pressure value of the negative pressure gauge, including:

[0166] Turn on the two sampling systems separately and record the third negative pressure value of the negative pressure gauge respectively;

[0167] Simultaneously activate two extraction systems and record the third negative pressure value of the negative pressure gauge.

[0168] To ensure the measured data more closely approximates real-world data, extraction systems are installed at both ends of the borehole. Specifically, when measuring the third negative pressure value, extraction is performed at both ends of the borehole separately, and then simultaneously at both ends. This three-stage extraction process yields three third negative pressure values. This setup improves the accuracy of the third negative pressure value, reduces errors, and increases the data available for establishing the negative pressure calculation model.

[0169] It should be noted that in order to ensure that the negative pressure inside the extraction borehole reaches a balanced state, the extraction interval should be at least 6 days.

[0170] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for calculating negative pressure in boreholes, characterized in that, include: Multiple test tubes are inserted into the borehole, each test tube including an air extraction end and a test end, and the multiple test ends are disposed at different depths of the borehole; For each of the test tubes, the following steps are performed: Connect the extraction system to the borehole; Connect one end of the negative pressure gauge to the suction end, and seal the other end of the negative pressure gauge; Turn on the extraction system and record the first negative pressure value of the negative pressure gauge; A negative pressure calculation model is established based on multiple first negative pressure values ​​and the depths of multiple test terminals; The negative pressure value at any drilling depth is calculated using the aforementioned negative pressure calculation model; Specifically, it includes: The extraction system is connected to the borehole and the extraction end respectively; wherein, a negative pressure gauge is provided between the extraction end and the extraction system; Turn on the extraction system and record the second negative pressure value of the negative pressure gauge; For each of the test tubes, a first theoretical value is determined based on the second negative pressure value measured by the test tube and the tube diameter ratio of the test tube; The step of establishing a negative pressure calculation model based on multiple first negative pressure values ​​and multiple test depths includes: Multiple first negative pressure values ​​are verified using multiple first theoretical values ​​to obtain multiple first verification negative pressure values; A negative pressure calculation model is established based on multiple first theoretical values, multiple first verification negative pressure values, and multiple test terminal depths; The first theoretical value is obtained by the following formula: Δp=λ×l / d×(ρv 2 / 2) L1=Δp-f2 Where Δp is the pressure drop, λ is the friction coefficient, l is the length of the test tube, d is the diameter of the test tube, ρ is the density of the fluid in the test tube, L1 is the first theoretical value, and f2 is the second negative pressure value.

2. The negative pressure calculation method according to claim 1, characterized in that, The step of verifying multiple first negative pressure values ​​using multiple first theoretical values ​​to obtain multiple first verification negative pressure values ​​includes: The first difference value is obtained by subtracting the first theoretical value and the first negative pressure value measured in the same test tube; The first difference value that is higher than the first preset value is marked; Delete the first negative pressure value corresponding to the first difference with the mark; The first negative pressure value that was not deleted is determined as the first verification negative pressure value.

3. The negative pressure calculation method according to claim 1, characterized in that, Also includes: For each of the test tubes, the following steps are performed: Connect the extraction system to the borehole; Connect one end of the negative pressure gauge to the air extraction end, and connect the other end of the negative pressure gauge to the outside of the borehole; Turn on the extraction system and record the third negative pressure value of the negative pressure gauge; For each of the test tubes, a second theoretical value is determined based on the third negative pressure value measured by the test tube and the tube diameter ratio of the test tube; The step of establishing a negative pressure calculation model based on multiple first negative pressure values ​​and multiple test depths includes: Multiple second theoretical values ​​are used to verify multiple first negative pressure values ​​to obtain multiple second verification negative pressure values; A negative pressure calculation model is established based on multiple second theoretical values, multiple second verification negative pressure values, and multiple test terminal depths.

4. The negative pressure calculation method according to claim 3, characterized in that, The process of verifying multiple first negative pressure values ​​using multiple second theoretical values ​​to obtain multiple second verification negative pressure values ​​includes: The second difference value is obtained by subtracting the second theoretical value and the first negative pressure value measured in the same test tube. The second difference, which is higher than the second preset value, is marked; Delete the first negative pressure value corresponding to the marked second difference; The first negative pressure value that was not deleted is determined as the second verification negative pressure value.

5. The negative pressure calculation method according to claim 3, characterized in that, The second theoretical value is obtained using the following formula: Δp=λ×l / d×(ρv 2 / 2) L2=Δp-f3 Where Δp is the pressure drop, λ is the friction coefficient, l is the length of the test tube, d is the diameter of the test tube, ρ is the density of the fluid in the test tube, L2 is the second theoretical value, and f3 is the third negative pressure value.

6. The negative pressure calculation method according to claim 1, characterized in that, It includes two extraction systems, which are respectively disposed on both sides of the borehole; Connecting the extraction system to the borehole includes: The two extraction systems are respectively connected to the two ends of the borehole; The step of activating the extraction system and recording the first negative pressure value of the negative pressure gauge includes: Turn on both of the extraction systems respectively and record the first negative pressure value of the negative pressure gauge respectively; Simultaneously activate both of the aforementioned extraction systems and record the first negative pressure value of the negative pressure gauge.

7. The negative pressure calculation method according to claim 1, characterized in that, It includes two extraction systems, which are respectively disposed on both sides of the borehole; The step of connecting the extraction system to the borehole and the extraction end respectively includes: One of the extraction systems is connected to the first end of the borehole and the extraction end, respectively. Connect another of the aforementioned extraction systems to the second end of the borehole; The step of activating the extraction system and recording the second negative pressure value of the negative pressure gauge includes: Simultaneously activate both of the aforementioned extraction systems and record the second negative pressure value of the negative pressure gauge; Disconnect the first end from the extraction system, and simultaneously turn on both extraction systems and record the second negative pressure value of the negative pressure gauge; Disconnect the second end from the extraction system, and simultaneously turn on both extraction systems and record the second negative pressure value of the negative pressure gauge.

8. The negative pressure calculation method according to claim 3, characterized in that, It includes two extraction systems, which are respectively disposed on both sides of the borehole; Connecting the extraction system to the borehole includes: The two extraction systems are respectively connected to both ends of the borehole; The step of activating the extraction system and recording the third negative pressure value of the negative pressure gauge includes: Turn on both of the aforementioned extraction systems and record the third negative pressure value of the negative pressure gauge respectively; Simultaneously activate both of the aforementioned extraction systems and record the third negative pressure value of the negative pressure gauge.

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