Ecological coal mining based on optical fiber sensing and slurry blocking prevention monitoring method in filling pipe

Abstract

The application discloses a kind of ecological coal mining based on optical fiber sensing with the method for preventing and monitoring slurry blockage in casing pipe, based on distributed optical fiber strain measurement, vibration measurement principle, in the slurry conveying process, sediment blockage is generated at the turning place and horizontal section of the casing pipe, at this time, the sensing optical cable arranged outside the casing pipe can real-time response to the event, the monitoring host can intelligently assess the blockage degree, and locate the blockage section;When the blockage exceeds 20%, the reamer bit is lowered through the orifice, the monitoring host real-time locates the bit advancing position, when the bit advances to the blockage section, the bit waterway pressure is increased according to the blockage degree to ream hole.The application solves the problems of slurry blockage prevention and monitoring in the casing pipe during the casing process, and ensures normal slurry conveying in the casing pipe in the later period.

Description

Technical Field

[0001] This invention belongs to the field of coal mining technology and relates to a method for monitoring the prevention of slurry blockage in the casing during ecological coal mining based on optical fiber sensing. Background Technology

[0002] The horizontal long borehole-based, continuous filling method for coal seam roof mining is gaining increasing attention as a novel technological approach to address overburden subsidence in mining areas. Before continuous filling, a horizontally oriented long borehole is first drilled in the immediate roof stratum above the coal seam of the longwall face to be mined, and a casing is then lowered. During continuous filling, filling slurry is injected into the goaf in real time until the entire longwall face operation is completed. However, the slurry used in the filling process mainly consists of coal gangue, cement, sand, loess, and water. Poor slurry proportion control can easily lead to large particle sedimentation and coagulation during casing transportation, especially at casing bends. This can cause blockages in the pipeline before the slurry reaches the goaf, potentially leading to a complete casing shutdown. Therefore, monitoring and preventing blockages in the casing slurry during the filling process is crucial. Summary of the Invention

[0003] To address the shortcomings of existing technologies, the present invention aims to provide a method for monitoring and preventing slurry blockage in the casing during ecological coal mining based on fiber optic sensing. This method solves problems such as monitoring and preventing slurry blockage in the casing during the charging process, and ensures the normal transportation of slurry in the casing in the later stages.

[0004] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0005] A method for monitoring slurry blockage prevention in the casing of ecological coal mining based on fiber optic sensing includes the following steps:

[0006] Step 1: Before lowering the charging sleeve into the hole, first arrange the sensing optical cable along the axial direction of the charging sleeve in the groove on the upper side of the outer wall of the charging sleeve, and seal it with glue to protect it, so that the sensing optical cable is coupled with the charging sleeve; the sensing optical cable is lowered into the hole in one go along with the charging sleeve, and the ground end of the sensing optical cable is connected to the monitoring host to enter the measurement state.

[0007] Step 2: During the slurry filling process, the monitoring host adopts the strain measurement mode. By monitoring the strain signal of the sensing optical cable in real time, the degree of blockage D of each section of the filling sleeve is evaluated.

[0008] Step 3: When the blockage degree D of a certain section exceeds 20%, stop the slurry delivery and locate the blockage area based on the location information of the strain signal of the optical fiber sensor.

[0009] Step 4: The monitoring host adopts the vibration measurement mode. The high-pressure water jet reaming drill bit is lowered into the orifice. The monitoring host locates the forward position of the reaming drill bit in real time. After reaching the blockage position, the jet reaming mode is turned on. After the reaming is completed, the reaming drill bit is withdrawn and the slurry filling continues.

[0010] The present invention also includes the following technical features:

[0011] Specifically, the sensing optical cable is a common communication optical cable.

[0012] Specifically, in step 2, the pulsed laser of the monitoring host emits a highly coherent laser pulse signal through modulation, which is then sent into the sensing optical cable through a circulator. Due to the transport of the slurry, the optical signal is disturbed in the sensing optical cable, generating a backscattered Rayleigh signal, which is then sent to the photodiode of the monitoring host through the circulator again. The phase information of the disturbance signal modulated onto the sensing optical cable is linearly demodulated, and the strain information along the axial direction of the sensing optical cable is obtained through a signal processing algorithm. The position is determined by the optical signal transmission delay, thereby realizing the localization of the strain event.

[0013] Specifically, the degree of blockage D is the ratio of the volume of slurry sediment in the filled sleeve to the volume of the empty sleeve in that section.

[0014] Specifically, in step 2, the slurry flows through the horizontal section of the charging sleeve at a fixed flow rate. Sedimentation and blockage occur at the bend and horizontal section of the charging sleeve. At this time, the orifice continues to deliver slurry, and the overall flow rate of the slurry remains unchanged. The slurry flow rate at the blockage point increases. At this time, the strain signal is sensed in real time by the sensing optical cable arranged on the outside of the charging sleeve. The signal is transmitted to the ground monitoring host through reflected light. The monitoring host demodulates and processes the data to assess the degree of blockage D.

[0015] Specifically, the assessment of the degree of blockage D includes:

[0016] Let the axial direction of the casing be the x-axis and the radial direction be the y-axis. Based on the Hagen-Poiseuille flow principle, the slurry flows inside the casing, and the fluid velocity profile U(y) is expressed as:

[0017]

[0018] In the formula, μ is the first viscosity coefficient of the slurry fluid, a is the radius of the filling sleeve, and G=-ΔP represents the pressure gradient;

[0019] According to Newton's principle of fluid dynamics, the slurry is a viscous fluid, and a shear stress τ(y) exists as it moves within the filling sleeve, expressed as:

[0020]

[0021] From equations (1) and (2), we obtain:

[0022]

[0023] When the slurry becomes clogged, it settles and accumulates on the lower side of the casing due to gravity, increasing the slurry fluid pressure gradient ΔP on the upper side of the casing. This also increases the shear stress τ(y). The sensing optical cable arranged on the outer wall of the upper side of the casing can detect the shear stress τ(y) in the casing in real time. The pressure gradient ΔP of this section can be calculated using equation (3). A prediction model for the pressure gradient ΔP and the degree of clog D is established.

[0024]

[0025] In the formula, ΔP0 is the pressure gradient of the section under unblocked conditions, and a, b, and c are model constants.

[0026] Specifically, the model constants a, b, and c are calculated through simulation experiments as follows: A laboratory simulation platform is built, a 2-meter section of the charging sleeve is cut, and the slurry delivery pressure at the orifice is controlled by a mud pump. Different degrees of blockage D are simulated by solidifying slurry at the middle of the charging sleeve. A pressure sensor is placed at the charging sleeve directly above the blockage to monitor the pressure gradient ΔP with the orifice in real time. By simulating different degrees of blockage D, the corresponding pressure gradient ΔP is measured, a large number of sample values ​​are established, and the curve trend is obtained based on the interpolation method. The model constants a, b, and c are obtained through fitting analysis.

[0027] Specifically, in step 4, after the high-pressure water jet reaming drill bit is lowered into the horizontal section, the water pump is turned on to make the reaming drill bit advance steadily in the slurry. During this process, the monitoring host adopts the vibration measurement mode to receive the reflected signal of the sensor optical cable outside the charging sleeve in real time. The real-time position of the reaming drill bit in the charging sleeve is located by vibration monitoring. When the drill bit reaches the blockage area, the water pressure is increased according to the different degrees of blockage D to complete the reaming.

[0028] Compared with the prior art, the present invention has the following technical effects:

[0029] 1. This invention delivers the delivery casing and sensing optical cable into the immediate top rock layer in one go through a horizontally directional long borehole, eliminating the need for secondary sensor deployment. Furthermore, the downhole monitoring section uses distributed optical fiber and is entirely passive, avoiding the flammable and explosive hazards during the mining process.

[0030] 2. In the process of ecological coal mining and charging, this invention monitors the flow of slurry in the charging casing in real time through a sensor optical cable, and the monitoring host assesses the degree of blockage in the casing in real time and locates the blockage area. At the same time, it can track the position of the reaming drill bit and accurately locate the reaming section. By using one set of monitoring equipment with two measurement methods, it can solve two monitoring problems. It is the most effective monitoring mode in the limited working conditions of mining and charging. Attached Figure Description

[0031] Figure 1 This is a schematic diagram illustrating the principle of slurry monitoring during filling.

[0032] Figure 2 This is a diagram illustrating the principle of slurry flow.

[0033] Figure 3 This is a schematic diagram of a high-pressure water jet orifice expansion.

[0034] The meanings of the labels in the diagram are as follows:

[0035] 1. Coal mining face, 2. Direct roof stratum, 3. Casing with charging, 4. Optical fiber sensor, 5. Monitoring host, 6. Slurry pump, 7. Reamer bit. Detailed Implementation

[0036] Ecological coal mining process of horizontal long borehole for mining and filling: Before mining and filling, a horizontal directional long borehole is first formed in the direct roof stratum above the coal seam of the longwall mining face to be mined, and a filling casing is lowered. During the mining and filling process, filling slurry is injected into the goaf in real time until the entire longwall mining face operation is completed.

[0037] This invention proposes a method for monitoring and preventing slurry blockage in the casing during ecological coal mining based on fiber optic sensing. This method can monitor the flow of slurry in the entire casing, locate the blockage area, and assess the degree of blockage. When the blockage in a certain area of ​​the casing exceeds 20%, a drill bit is lowered and a high-pressure water jet is used to enlarge the hole. Since the high-pressure hose will bend during the lowering process, it is impossible to accurately control the position of the enlarging drill bit. Therefore, fiber optic sensing can locate the enlarging drill bit to the blockage location. Before the slurry finally sets, the high-pressure water jet is used to clear the blockage, ensuring the normal transportation of slurry in the casing in the later stage.

[0038] Specifically, this method is based on the principle of distributed optical fiber strain and vibration measurement. During slurry transportation, sedimentation and blockage are easily generated at bends and horizontal sections of the charging sleeve. At this time, the slurry is continuously transported through the orifice, and the slurry flow at the blockage point increases, forming a large flow velocity. This event can be detected in real time by the sensing optical cable arranged on the outside of the charging sleeve. The monitoring host can intelligently assess the degree of blockage and locate the blockage section. When the blockage exceeds 20%, a reaming drill bit is lowered through the orifice. When the drill bit passes through the slurry in the horizontal section with a small water pressure, it generates vibration. The sensing optical cable can detect the vibration signal in real time, and the monitoring host can locate the forward position of the drill bit in real time. When the drill bit advances to the blockage section, the water pressure in the drill bit is increased according to the degree of blockage to expand the hole.

[0039] The following are specific embodiments of the present invention. It should be noted that the present invention is not limited to the following specific embodiments. All equivalent modifications made based on the technical solutions of this application fall within the protection scope of the present invention.

[0040] Example 1:

[0041] This embodiment provides a method for monitoring the prevention of slurry blockage in the casing during ecological coal mining based on fiber optic sensing, including the following steps:

[0042] Step 1: Before lowering the charging sleeve into the hole, first arrange the sensing optical cable along the axial direction of the charging sleeve in the groove on the upper side of the outer wall of the charging sleeve, and seal it with adhesive to ensure coupling between the sensing optical cable and the charging sleeve. The sensing optical cable is a standard communication cable. It is lowered into the hole in one go along with the charging sleeve. The ground end of the sensing optical cable is connected to the monitoring host, entering measurement mode. The monitoring host determines the zero-coordinate starting point position of the sensing optical cable based on the relevant parameters of the charging sleeve and the sensing optical cable, and sets the sampling resolution. For example... Figure 1 As shown, a horizontally oriented long borehole is formed in the direct roof stratum 2 above the coal mining face 1 and a charging casing 3 is lowered in. The sensing optical cable 4 on the outer wall of the charging casing 3 is connected to the monitoring host 5, and the charging casing 3 is connected to the slurry pump 6 at the ground end.

[0043] Step 2: During the slurry filling process, the monitoring host adopts the strain measurement mode. By monitoring the strain signal of the sensing optical cable in real time, the degree of blockage D of each section of the filling sleeve is evaluated.

[0044] Specifically, the pulsed laser of the monitoring host emits a highly coherent laser pulse signal through modulation, which is sent into the sensing optical cable through a circulator. Due to the transport of slurry, the optical signal is disturbed in the sensing optical cable, generating a backscattered Rayleigh signal, which is then sent to the photodiode of the monitoring host through the circulator again. The phase information of the disturbance signal modulated on the sensing optical cable is linearly demodulated, and the strain information along the axis of the sensing optical cable is obtained through signal processing algorithms. The position is determined by the optical signal transmission delay, thus realizing the localization of the strain event (resolution 1 meter).

[0045] During the charging process, the monitoring host monitors the strain signal of the sensing optical cable in real time and intelligently assesses the degree of blockage D in each section of the charging sleeve: The slurry flows through the horizontal section of the charging sleeve at a fixed flow rate. However, when the slurry ratio is uneven, there are many solid particles, and the concentration is high, sedimentation blockage is very likely to occur at the bend and horizontal section of the charging sleeve. At this time, the orifice continues to deliver slurry, the overall flow rate of the slurry remains unchanged, and the slurry flow rate at the blockage point increases. At this time, the sensing optical cable arranged on the outside of the charging sleeve senses the information in real time and transmits it to the ground monitoring host through reflected light. After the monitoring host demodulates and processes the data, it assesses the degree of blockage D. D is the blockage percentage, which refers to the proportion of the volume of slurry sediment in the charging sleeve in this section (1 meter) to the volume of the empty sleeve.

[0046] The method for assessing the degree of congestion D is as follows:

[0047] like Figure 2Let the axial direction of the casing be the x-axis and the radial direction be the y-axis. Based on the Hagen-Poiseuille flow principle, the slurry flows inside the casing, and the fluid velocity profile U(y) is expressed as:

[0048]

[0049] In the formula, μ is the first viscosity coefficient of the slurry fluid, a is the radius of the filling sleeve, and G=-ΔP represents the pressure gradient;

[0050] According to Newton's principle of fluid dynamics, the slurry is a viscous fluid, and a shear stress τ(y) exists as it moves within the filling sleeve, expressed as:

[0051]

[0052] From equations (1) and (2), we obtain:

[0053]

[0054] When the slurry becomes clogged, it settles and accumulates on the lower side of the casing due to gravity, increasing the slurry fluid pressure gradient ΔP on the upper side of the casing. This also increases the shear stress τ(y). The sensing optical cable arranged on the outer wall of the upper side of the casing can detect the shear stress τ(y) in the casing in real time. The pressure gradient ΔP of this section can be calculated using equation (3). A prediction model for the pressure gradient ΔP and the degree of clog D is established.

[0055]

[0056] In the formula, ΔP0 is the pressure gradient of the section under non-blockage conditions, and a, b, and c are model constants calculated through simulation experiments. A laboratory simulation platform is built, and a 2-meter section of the casing is cut off. The slurry delivery pressure at the orifice is controlled by a mud pump. Different blockage degrees D are simulated by solidifying slurry at the middle of the casing. A pressure sensor is placed at the casing directly above the blockage to monitor the pressure gradient ΔP at the orifice in real time. By simulating different blockage degrees D, the corresponding pressure gradient ΔP is measured, a large number of sample values ​​are established, and the curve change trend is obtained based on the interpolation method. The parameters a, b, and c in formula (4) are obtained through fitting analysis to complete the prediction of the blockage degree D model.

[0057] Step 3: When the blockage degree D of a certain section exceeds 20%, stop the slurry delivery and locate the blockage area based on the location information of the strain signal of the optical fiber sensor.

[0058] Step 4: The monitoring host adopts the vibration measurement mode. The high-pressure water jet reaming drill bit is lowered into the orifice. The monitoring host locates the forward position of the reaming drill bit in real time. After reaching the blockage position, the jet reaming mode is turned on. After the reaming is completed, the reaming drill bit is withdrawn and the slurry filling continues.

[0059] likeFigure 3 The high-pressure water jet reaming drill bit 7 is lowered into the horizontal section. After the reaming drill bit 7 is lowered into the horizontal section, the water pump is turned on to ensure that the drill bit moves forward at a steady speed in the slurry with a relatively small water pressure. During this process, the monitoring host adopts the vibration measurement mode to receive the reflected signal of the sensor optical cable outside the charging sleeve in real time. The real-time position of the drill bit in the charging sleeve is located by vibration monitoring. When the drill bit reaches the blockage area, the water pressure is increased according to the degree of blockage D, and the jet reaming mode is turned on. After the reaming is completed, the drill bit is withdrawn and the slurry filling continues.

Claims

1. An ecological coal mining based on optical fiber sensing method for preventing blocking of slurry in the inner material of the casing pipe, characterized by, The method comprises the following steps: Step 1, before the follow-up sleeve is lowered into the hole, first arrange the sensing optical cable on the outer wall of the follow-up sleeve in the groove on the upper side of the follow-up sleeve in the axial direction, and then glue seal and protect the sensing optical cable, so that the sensing optical cable is coupled with the follow-up sleeve; the sensing optical cable is lowered into the hole together with the follow-up sleeve, the ground end of the sensing optical cable is connected to the monitoring host, and the sensing optical cable enters a measurement state; Step 2, in the process of slurry filling, the monitoring host adopts a strain measurement mode, and the blocking degree D of each section of the follow-up sleeve is evaluated through real-time monitoring of the strain signal of the sensing optical cable by the monitoring host; Step 3, when the blocking degree D of a section exceeds 20%, stop slurry transportation, and locate the blocked area according to the position information of the strain signal of the sensing optical cable; Step 4, the monitoring host adopts a vibration measurement mode, a high-pressure water jet reamer is lowered into the hole, the monitoring host real-time locates the advancing position of the reamer, after reaching the blocked position, the jet reaming mode is started, and after reaming is completed, the reamer is withdrawn, and slurry filling is continued; The evaluation of the blocking degree D comprises: Let the axial direction of the filling sleeve be the x-axis and the radial direction be the y-axis. Based on the Hagen-Poiseuille flow principle, the slurry flows in the sleeve, and the fluid velocity profile is is represented as: (1) wherein is the first viscosity coefficient of the slurry fluid, a is the radius of the sleeve, represents the pressure gradient; According to the principle of Newtonian fluid, the slurry belongs to viscous fluid, and there is shear stress in the movement of the slurry in the charging sleeve , which is expressed as: (2) The formula (1) and the formula (2) are obtained as follows: (3) When the slurry produces a blockage, the slurry is accumulated on the lower side of the casing due to gravity, and the fluid pressure gradient of the slurry on the upper side of the casing will increase , at this time, the shear stress will also increase, and the sensing optical cable arranged on the outer wall of the upper side of the casing can sense the shear stress in the casing in real time , and the pressure gradient of the section can be solved through formula (3) ; a prediction model of the pressure gradient and the blockage degree D is established. (4) In the formula, is the pressure gradient of the section under the non-plugging state, and a, b, and c are model constant terms.

2. The optical fiber sensing based ecological coal mining with in-situ pipe filling slurry anti-blocking monitoring method according to claim 1, characterized in that, The sensing optical cable adopts a common communication optical cable.

3. The optical fiber sensing based ecological coal mining with in-situ pipe filling slurry anti-blocking monitoring method according to claim 1, characterized in that, In step 2, the pulsed laser of the monitoring host emits highly coherent laser pulse signals through modulation, the signals are sent into the sensing optical cable through a circulator, the slurry transportation causes disturbance of the optical signals in the sensing optical cable, backscattering signals are generated, the signals are again sent to the photodiode of the monitoring host through the circulator, the phase information of the disturbance signals modulated on the sensing optical cable is linearly demodulated, the strain information along the axial direction of the sensing optical cable is obtained through a signal processing algorithm, the position of the sensing optical cable is determined according to the transmission delay of the optical signals, and the location of the strain event is realized.

4. The optical fiber sensing based ecological coal mining with in-situ pipe filling slurry anti-blocking monitoring method according to claim 1, characterized in that, The blocking degree D is the ratio of the volume of the slurry precipitate in the section of the follow-up sleeve to the volume of the follow-up sleeve.

5. The optical fiber sensing based ecological coal mining with in-situ pipe filling slurry anti-blocking monitoring method according to claim 1, characterized in that, In step 2, the slurry passes through the horizontal section of the follow-up sleeve at a fixed flow rate, and the slurry is deposited and blocked at the turning part and the horizontal section of the follow-up sleeve, at this time, the hole continuously transports the slurry, the overall flow rate of the slurry is unchanged, the flow rate of the slurry at the blocked part is increased, at this time, the strain signal is sensed in real time through the sensing optical cable arranged outside the follow-up sleeve, the reflected light is transmitted to the ground monitoring host, and the monitoring host evaluates the blocking degree D after demodulation and processing of the data.

6. The optical fiber sensing based ecological coal mining with in-situ pipe filling slurry anti-blocking monitoring method according to claim 1, characterized in that, The model constant terms a, b, c are calculated through a simulation test process: a laboratory simulation platform is built, 2 meters of the random filling pipe is intercepted, the slurry conveying pressure is controlled by the mud pump through the orifice, the different blockage degrees D are simulated by the solidified slurry in the middle of the random filling pipe, the pressure sensor is arranged at the random filling pipe directly above the blockage to monitor the pressure gradient with the orifice in real time ; by simulating different blockage degrees D, the corresponding pressure gradient is measured , a large number of sample values are established, the curve change trend is obtained based on the interpolation method, and the model constant terms a, b, c are obtained through fitting analysis.

7. The optical fiber sensing based ecological coal mining with in-situ pipe filling slurry anti-blocking monitoring method according to claim 1, characterized in that, In step 4, after the high-pressure water jet reamer is lowered into the horizontal section, the water pump is started, the reamer advances at a constant speed in the slurry, in this process, the monitoring host adopts a vibration measurement mode, the reflected signal of the sensing optical cable outside the follow-up sleeve is received in real time, the real-time position of the reamer in the follow-up sleeve is located through vibration monitoring, and when the reamer reaches the blocked area, the water pressure is increased according to different degrees of the blocking degree D, and reaming is completed.

Images