A method for detecting the progress of underground coal gasification in deep underground

Abstract

This invention relates to a method for detecting the underground gasification process of deep coal, comprising: drilling an injection well, an underground furnace, and a production well into a deep coal seam; connecting a temperature-measuring fiber optic cable to a drill bit and drilling a first temperature-measuring well and a second temperature-measuring well on both sides of the production well; lowering the drill bit down the production well to the lower part of the well, and then drilling a third temperature-measuring well above the furnace, with the tail ends of the three temperature-measuring wells extending to the corresponding furnace head ends; connecting a coiled tubing to a drill bit and drilling a first monitoring well and a second monitoring well on both sides of the injection well, with the tail ends of the two monitoring wells extending to the corresponding furnace tail ends; and then placing a detection device into the monitoring well along the coiled tubing for installing a microseismic probe inside the monitoring well.

Description

Technical Field

[0001] This invention belongs to the field of deep coal gasification detection technology, specifically relating to a method for detecting the underground gasification process of deep underground coal. Background Technology

[0002] With the gradual depletion of shallow coal resources, researchers in this field have begun in-depth studies on the development and utilization of deep coal. Underground coal gasification (UCG) at depths of over 1,000 meters has enormous potential, but it also faces new technical challenges. Extreme environments—high ground stress, high rock temperature (reaching geothermal gradient anomaly zones), and high pore / fracture pressure—lead to complex rock mechanics, making the surrounding rock of the combustion chamber more prone to unsteady fractures and dynamic disasters. Therefore, detecting parameters such as formation temperature and ground stress during deep underground gasification is crucial for understanding the underground gasification process and formation anomalies. However, the strong coupling between the high-temperature underground combustion (thermal field) and the aforementioned "three-high" geological environment increases the difficulty of detecting underground formation parameters. Moreover, deep strata are far from the surface, and traditional surface geophysical methods (such as seismic and electromagnetic methods) suffer from long propagation paths, severe energy attenuation, extremely low signal-to-noise ratios, and low accuracy at depth. Summary of the Invention

[0003] To address the above problems, this invention provides a method for detecting the underground gasification process of deep coal, comprising:

[0004] S1: Drill injection wells, extraction wells and underground furnaces into deep coal seams. The first end of the furnace is connected to the bottom of the injection well, and the last end of the furnace is connected to the bottom of the extraction well.

[0005] S2: Connect the temperature measuring fiber to the drill bit and run it down to a position near the bottom of the well. Drill the first temperature measuring well on one side of the well. Using the same method, drill the second temperature measuring well on the other side of the well with another drill bit. The tail ends of both temperature measuring wells extend to the bottom of the corresponding injection well.

[0006] S3: Following the method in step S2, lower the drill bit down to the bottom of the production well, and drill the third temperature measurement well from the side of the production well. The third temperature measurement well is located above the furnace, and the tail end of the third temperature measurement well extends to the corresponding head end of the furnace.

[0007] S4: The drill bit is connected to the continuous tubing and runs down to the middle of the injection well. The drill bit drills the first monitoring well on one side of the injection well. Following the above method, another drill bit drills the second monitoring well on the other side of the injection well. The tail ends of both monitoring wells extend to the corresponding furnace tail ends.

[0008] Then, a detection device is placed into the monitoring well along the coiled tubing to install a microseismic probe in the monitoring well so as to monitor underground vibration in real time.

[0009] S5: A gas pipe is lowered into the injection well to introduce the gasifying agent into the furnace; a gas production pipe is lowered into the production well to transport the gas obtained from gasification in the furnace to the surface.

[0010] This invention improves upon the conventional configuration of injection wells, underground furnaces, and production wells by setting up a near-field temperature measurement well system and a medium- to long-field microseismic monitoring system around the furnace. The two complement each other and work together to monitor the real-time changes in underground temperature and vibration during the furnace gasification process.

[0011] Because the furnace is located deep within the coal seam, the traditional method involves drilling several monitoring wells from the ground. Drilling these wells deep into the coal seam is costly, has a limited monitoring range, and fails to obtain comprehensive data. In this invention, existing injection and extraction wells are used directly as channels for the drill bit to penetrate the underground strata, eliminating the need for additional vertical shafts leading directly to the surface, thus saving significant costs. In step S2, using the extraction well as a vertical shaft, a first and a second temperature measuring well are drilled twice, on either side of the bottom of the extraction well. Both of these temperature measuring wells extend along the furnace to its head, monitoring the changes in underground temperature during gasification along the length of the furnace. In step S3, again using the extraction well, a third temperature measuring well is drilled above the furnace. Combined with the first two temperature measuring wells, this forms a three-dimensional monitoring network around the furnace, simultaneously monitoring the temperature of the corresponding external strata at various locations within the furnace. The temperature at the corresponding location within the furnace is then deduced, avoiding direct measurement of the furnace temperature. The temperature-sensing optical fiber of the present invention does not need to be placed directly inside the furnace, thus avoiding the influence of the high-temperature environment on the temperature-sensing optical fiber, improving the detection accuracy of the temperature-sensing optical fiber, avoiding the adverse effects of the mixed airflow of gasifying agent and coal gas inside the furnace on temperature detection, and avoiding the problem of failure to detect due to ash covering the temperature-sensing optical fiber inside the furnace.

[0012] In step S4, using the injection well as a vertical shaft, a first monitoring well and a second monitoring well are drilled twice, on either side of the middle of the injection well. Both monitoring wells extend along the furnace to its end, monitoring changes in ground vibration or damage during gasification along the length of the furnace. Because the monitoring wells are farther from the furnace than the temperature measuring wells, the influence of the "three highs" (high temperature, high humidity, and high temperature) of the deep coal seam is further reduced, significantly improving the accuracy of probe detection. Furthermore, the ground changes caused by coal gasification within the furnace are very significant; even at a distance from the furnace, these changes can be detected by a high-precision probe.

[0013] Optionally, step S2 specifically includes:

[0014] (1) The tail of the first drill bit is connected to a continuous tubing, and a temperature measuring fiber is installed inside the continuous tubing. The top of the temperature measuring fiber is connected to a monitoring device on the ground.

[0015] (2) Lower the first drill bit along the well until it is close to the bottom of the well. The first drill bit is facing downwards and drills out from the left side of the well. After drilling a section of the directional section, the first drill bit is at the same depth as the furnace. Then, the first drill bit gradually turns to be parallel to the length of the furnace and drills along the length of the furnace to the corresponding furnace head position to complete the first temperature measurement well.

[0016] (3) Following the method in step (2), lower the second drill bit along the well until it reaches the same depth as the top of the first temperature measuring well. The second drill bit is drilled out from the right side of the well, with the well as the center. The first temperature measuring well and the second temperature measuring well are set symmetrically on the left and right.

[0017] Optionally, step S3 specifically includes:

[0018] (4) The tail of the third drill bit is connected to the coiled tubing, and a temperature measuring fiber is installed inside the coiled tubing. The top of the temperature measuring fiber is connected to a monitoring device on the ground.

[0019] (5) Lower the third drill bit along the production well until the lower part of the production well; the third drill bit is facing downwards and drills out from the side of the production well. The third drill bit is directly above the furnace. Drill a section of the inclination section so that the third drill bit gradually turns to be parallel to the length direction of the furnace. Then drill along the length direction of the furnace to the position of the corresponding furnace head to complete the third temperature measurement well.

[0020] This invention features three temperature measuring wells, one on each side and one above the furnace, parallel to the furnace. This facilitates real-time monitoring of the ongoing gasification process within the furnace. Coal on the furnace wall begins gasification at the beginning of the injection well and gradually moves along the length of the furnace towards the end of the extraction well. The temperature-sensing optical fiber is not located inside the furnace, thus avoiding the influence of the high-temperature and high-pressure environment. Furthermore, the optical fiber is situated inside the coiled tubing, preventing it from being scraped by the well wall strata during its insertion into the temperature measuring well by the drill bit. This better protects the optical fiber, ensuring stable operation within the temperature measuring well and resulting in higher accuracy and a more realistic reflection of temperature changes at various locations within the well.

[0021] Although this invention does not directly measure the temperature at various points inside the furnace, research has led to the establishment of a reasonable distance between the temperature measuring well and the furnace. This distance is relatively small, falling within the scope of short-range detection. The temperature inside the furnace is very high and can be transmitted outwards through the strata. As long as there are no aquifers or significant faults in the transmission space, the temperature transmission process can be relatively stable. This ensures that the temperature difference between the temperature measuring well and the furnace is proportional to the distance between them. This allows researchers to obtain the relationship between the temperature of the temperature measuring well and the temperature inside the furnace through ground-based simulation experiments, and thus infer the temperature at the corresponding location inside the furnace based on the temperature measured by the temperature measuring well.

[0022] The first and second temperature measuring wells of this invention are located on opposite sides of the furnace, equivalent to two parallel temperature measuring channels, enabling parallel monitoring and mutual verification. Simultaneously, considering that heat is more easily transferred upwards, the third temperature measuring well is located above the furnace, capable of detecting the heat transferred upwards from the furnace. Working in conjunction with the other two temperature measuring wells, this forms a three-dimensional detection system around the outside of the furnace, allowing for multi-directional detection.

[0023] Optionally, step S4 specifically includes:

[0024] (6) The tail of the fourth drill bit is connected to the continuous tubing. The fourth drill bit is lowered along the injection well until the middle of the injection well. The fourth drill bit is facing downwards and drills out from the left side of the injection well. After drilling a section of the directional section, the fourth drill bit gradually turns to be parallel to the length of the furnace. Then it is drilled along the length of the furnace to the corresponding position at the tail end of the furnace to complete the first monitoring well.

[0025] (7) Following the method in step (6), lower the fifth drill bit along the injection well until it reaches the same depth as the top of the first monitoring well. The fifth drill bit is facing downwards and drills out from the right side of the injection well. With the injection well as the center, the first monitoring well and the second monitoring well are set symmetrically on the left and right.

[0026] (8) The corresponding detection devices are placed into the two monitoring wells one after another. The detection devices travel along the corresponding monitoring well to the corresponding drill bit, and then back along the edge of the monitoring well while installing microseismic probes. Each microseismic probe is connected to the detection device through a line.

[0027] (9) The detection device retracts to the top of the monitoring well and receives data from the corresponding microseismic probes; the detection device is connected to the monitoring device on the ground via a line and continues to transmit the collected data back to the ground.

[0028] In traditional technology, microseismic probes are used to monitor ground vibrations or ruptures at the surface or in shallow underground layers. However, for ground vibrations caused by the gasification process in deep strata, the signal is too weak due to the great distance, and the changes in the strata cannot be transmitted to the surface in a timely and accurate manner. Therefore, for a long time, microseismic probes have played a limited role in the field of monitoring underground gasification in deep strata.

[0029] In this invention, two monitoring wells are installed above the third temperature measuring well, extending along the length of the furnace. Several microseismic probes are installed within each monitoring well, enabling close-range monitoring of ground vibrations. The detection device is responsible for installing the microseismic probes and then acts as a signal relay station, receiving signals transmitted from the microseismic probes and transmitting them back to the ground via wired transmission, thus improving the accuracy of data transmission.

[0030] Optionally, the detection device includes a storage section, an installation section, a connector section, and a main control section. The storage section stores a number of microseismic probes. The two ends of each microseismic probe are slidably connected to the inner walls on both sides of the storage section and can move to the bottom of the storage section. A door is provided between the bottom of the storage section and the installation section. The microseismic probes fall into the lower part of the installation section through the door.

[0031] The installation section includes a pressing section and a lowering section. The pressing section and the connector section are arranged sequentially on the outside of one side of the storage section. The main control section is located above the storage section. The connector section contains several movable connectors, which are connected to the main control section for communication.

[0032] One side of the lowering section is connected to the lowering section, and the other side is equipped with a retractable connecting chain. The tail end of the microseismic probe in the installation section is detachably connected to the head of the connecting chain, and the head end can be connected to a connector. The gradually elongating connecting chain lowers the tail end of the probe to the bottom of the monitoring well. The rotating lifting device of the lowering section presses the probe into the soil through the connector, thereby installing the microseismic probe.

[0033] Further optionally, the storage unit is a cuboid, with two opposite vertical wide sides each provided with an identical S-shaped meandering first guide rail, and the two first guide rails correspond to each other; several openable clamping parts are slidably connected on each first guide rail, and the clamping parts on the two first guide rails are arranged in pairs, with each pair of clamping parts clamping the two ends of the microseismic probe respectively.

[0034] Further optionally, the lower part is provided with a winding motor at its tail end, the winding shaft of the winding motor is perpendicular to the length direction of the microseismic probe, the connecting chain is wound on the winding shaft, and the head of the connecting chain can face the tail end of the microseismic probe; the head of the connecting chain is provided with an openable snap ring for detachably connecting to the tail end of the microseismic probe.

[0035] The bottom surface of the lower part has a small groove, and the bottom of the winding motor is slidably connected to the groove, so that the winding motor can move along the length of the microseismic probe, which facilitates the docking of the connecting chain, connector and the two ends of the microseismic probe.

[0036] Optionally, the pressing part is provided with a rotating lifting device, and the rotating lifting motor can control the rotating shaft to rotate and lift, with the rotating shaft pointing vertically downward; the side of the lowering part is provided with an openable rotating ring, which is perpendicular to the width direction of the storage part, and the rotating ring is connected to the side through an angle controller, which can drive the rotating ring to rotate in place, and the rotating ring is a hollow ring.

[0037] Optionally, the connector is a cuboid, with its length direction parallel to the width direction of the storage section; a second guide rail is provided on the long side of the connector away from the storage section, and the structure of the second guide rail is the same as that of the first guide rail, which is also an S-shaped bend.

[0038] Several sliders are slidably connected on the second guide rail. The number of sliders is equal to the number of microseismic probes. Connecting heads are movably connected to the sliders, and the sliders lead the connecting heads to move along the second guide rail.

[0039] Optionally, the connector is a cylinder. When the connector is connected to the slider, the central axis of the connector is horizontal. The circular side of the connector away from the slider is the bottom surface, and the circular side closer to the slider is the top surface. A recessed slot is provided at the center of the top surface. The protruding rod on the side of the slider can be inserted into the slot, thereby movably connecting the connector. The bottom surface of the connector is provided with a quick-connect fitting. The head of the quick-connect fitting is connected to a communication component. The communication component is located inside the connector and is wirelessly connected to the main control unit. Attached Figure Description

[0040] Figure 1 A schematic diagram of the production well and three temperature measurement wells (I);

[0041] Figure 2 Schematic diagram of the production well and three temperature measurement wells (II);

[0042] Figure 3 This is a schematic diagram of the third temperature measurement well, the first monitoring well, and the second monitoring well;

[0043] Figure 4 A schematic diagram of the injection well and two monitoring wells;

[0044] Figure 5 This is a schematic diagram of the detection device;

[0045] Figure 6 This is a schematic diagram of the storage section;

[0046] Figure 7 This is a schematic diagram of connecting a microseismic probe to a connector.

[0047] Among them, 1-injection well, 2-production well, 3-furnace, 4-first temperature measuring well, 5-second temperature measuring well, 6-third temperature measuring well, 7-first monitoring well, 8-second monitoring well, 9-gate number one, 10-slot, 11-quick connector, 12-front part, 13-middle part, 14-rear part, 15-detection device, 16-storage unit, 17-microseismic probe, 18-pressing part, 19-lowering part, 20-connector part, 21-main control unit, 22-connector head, 23-connecting chain, 24-first guide rail, 25-second guide rail, 26-winding motor, 27-slide groove, 28-rotating lifting device, 29-rotating ring, 30-slider. Detailed Implementation

[0048] This embodiment provides a method for detecting the underground gasification process of deep underground coal, such as... Figures 1-4 As shown, it includes:

[0049] S1: Drill an injection well 1, a production well 2 and an underground furnace 3 into the deep coal seam. The front end of the furnace 3 is connected to the bottom of the injection well 1 and the rear end of the furnace 3 is connected to the bottom of the production well 2.

[0050] S2: The drill bit is connected to the temperature measuring fiber and goes down along the extraction well 2 to a position near the bottom of the well. The drill bit drills the first temperature measuring well 4 on one side of the extraction well 2. Following the above method, another drill bit is used to drill the second temperature measuring well 5 on the other side of the extraction well 2. The tail ends of the two temperature measuring wells extend to the bottom of the corresponding injection well 1.

[0051] S3: Following the method in step S2, lower the drill bit along the extraction well 2 to the lower part of the extraction well 2, and drill out the third temperature measuring well 6 from the side of the extraction well 2. The third temperature measuring well is located above the furnace 3, and the tail end of the third temperature measuring well 6 extends to the corresponding head end of the furnace 3.

[0052] S4: The drill bit is connected to the continuous tubing and goes down to the middle of the injection well 1. The drill bit drills the first monitoring well 7 on one side of the injection well 1. Following the above method, the other drill bit drills the second monitoring well 8 on the other side of the injection well 1. The tail ends of the two monitoring wells extend to the corresponding tail end of the furnace 3.

[0053] Then, a detection device 15 is placed into the monitoring well along the coiled tubing to install a microseismic probe in the monitoring well so as to monitor underground vibration in real time.

[0054] S5: A gas pipe is lowered into injection well 1 to input gasifying agent into furnace 3; a gas extraction pipe is lowered into production well 2 to transport the gas obtained from gasification in furnace 3 to the surface.

[0055] Optionally, step S1 is based on existing technology. Using existing geological exploration technology, site selection is carried out to determine the specific locations of injection well 1, extraction well 2 and underground furnace 3. The bottom of injection well 1, the bottom of extraction well 2 and underground furnace 3 are all located in deep underground coal seams, generally at a depth of 1000-1500 meters. Furnace 3 is basically horizontal.

[0056] Optionally, step S2 specifically includes:

[0057] (1) The tail of the first drill bit is connected to a continuous tubing, and a temperature measuring fiber is installed inside the continuous tubing. The top of the temperature measuring fiber is connected to a monitoring device on the ground to transmit the data detected in the first temperature measuring well 4 back to the ground.

[0058] (2) Lower the first drill bit along the production well 2 until it is close to the bottom of the production well 2. The first drill bit is facing downwards and drills out from the left side of the production well 2. After drilling a section of the directional section, the first drill bit is at the same depth as the furnace 3. Then, the first drill bit gradually turns to be parallel to the length direction of the furnace 3 and drills along the length direction of the furnace 3 to the position of the corresponding furnace 3 head, thus completing the first temperature measuring well 4.

[0059] (3) Following the method in step (2), lower the second drill bit along the extraction well 2 until it reaches the same depth as the top of the first temperature measuring well 4. The second drill bit is drilled out from the right side of the extraction well 2 at an angle downward. With the extraction well 2 as the center, the first temperature measuring well 4 and the second temperature measuring well 5 are set symmetrically on the left and right.

[0060] Further optionally, in step (1), the first drill bit is equipped with a positioning device that can guide the drilling direction of the first drill bit according to a predetermined direction; the coiled tubing is outside the temperature-sensing optical fiber, which can protect the temperature-sensing optical fiber during drilling, avoid damage or breakage of the optical fiber, and ensure normal subsequent detection. The temperature-sensing optical fiber is a conventional high-temperature resistant optical fiber with temperature measurement function, and the detected data can be transmitted back to the monitoring device on the ground through the temperature-sensing optical fiber for data processing and recording. The top of the coiled tubing is on the ground.

[0061] Further optional, in step (2), the first temperature measuring well 4 includes a front part 12, a middle part 13 and a rear part 14. The front part is on the same vertical plane as the extraction well 2. This vertical plane is perpendicular to the length direction of the furnace 3. The front part is an inclined section that slopes downward.

[0062] The middle and rear sections are at the same depth. The middle section is a horizontal directional section, which causes the first drill bit to gradually turn to be parallel to the length direction of the furnace 3. The rear section is parallel to the length direction of the furnace 3. The end point of the rear section is on the same straight line as the beginning of the furnace 3 (i.e. the bottom of the injection well 1), and this straight line is perpendicular to the length direction of the furnace 3.

[0063] Further optional, in step (3), the structure and usage of the second drill bit are the same as those of the first drill bit; the coiled tubing and temperature measuring fiber connected to the second drill bit are also the same as in step (1).

[0064] The second temperature measuring well 5 has the same structure as the first temperature measuring well 4. The front part of the second temperature measuring well 5 is on the same vertical plane as the front part of the first temperature measuring well 4 and the extraction well 2. The middle part and the rear part of the second temperature measuring well 5 are at the same depth as the furnace 3. The end point of the second temperature measuring well 5 is on the same straight line as the end point of the first temperature measuring well 4 and the beginning of the furnace 3.

[0065] Optionally, step S3 specifically includes:

[0066] (4) The tail of the third drill bit is connected to the coiled tubing, and a temperature measuring fiber is installed inside the coiled tubing. The top of the temperature measuring fiber is connected to a monitoring device on the ground to transmit the data detected in the third temperature measuring well 6 back to the ground.

[0067] (5) Lower the third drill bit along the production well 2 until the lower part of the production well 2; the third drill bit is facing downwards and drills out from the side of the production well 2. The third drill bit is directly above the furnace 3. Drill a section of the inclined section so that the third drill bit gradually turns to be parallel to the length direction of the furnace 3. Then drill along the length direction of the furnace 3 to the position of the corresponding furnace 3 head end to complete the third temperature measuring well 6.

[0068] Further optional, in step (4), the third drill bit has the same structure and usage as the first drill bit; the coiled tubing and temperature measuring fiber connected to the third drill bit are also the same as in step (1).

[0069] Further optional, in step (5), the third temperature measuring well 6 includes a front part and a rear part. The front part is on the same vertical plane as the extraction well 2. This vertical plane is perpendicular to the vertical plane formed by the extraction well 2 and the front parts of the first and second temperature measuring wells. The front part of the third temperature measuring well 6 is an inclined section that slopes downward.

[0070] The rear part of the third temperature measuring well 6 is located directly above the furnace 3 and parallel to the length direction of the furnace 3, and the end point of the rear part does not contact the injection well 1.

[0071] The first, second, and third drill bits remain at the end of their respective temperature measurement wells and are not retrieved. The coiled tubing in the three temperature measurement wells extends into production well 2 and continues along production well 2 to the surface.

[0072] Optionally, the distance between the rear part of the first temperature measuring well 4 and the furnace 3 is equal to the distance between the rear part of the second temperature measuring well 5 and the furnace 3, and also equal to the distance between the rear part of the third temperature measuring well 6 and the furnace 3; the distance between the rear part of the first temperature measuring well 4 and the furnace 3 is 40-50m.

[0073] Optionally, step S4 specifically includes:

[0074] (6) The tail of the fourth drill bit is connected to the continuous tubing. The fourth drill bit is lowered along the injection well 1 until the middle of the injection well 1. The fourth drill bit is oriented diagonally downward and drills out from the left side of the injection well 1. After drilling a section of the directional section, the fourth drill bit gradually turns to be parallel to the length direction of the furnace 3. Then, it is drilled along the length direction of the furnace 3 to the corresponding tail end of the furnace 3 to complete the first monitoring well 7.

[0075] (7) Following the method of step (6), lower the fifth drill bit along the injection well 1 until it reaches the same depth as the top of the first monitoring well 7. The fifth drill bit is drilled out from the right side of the injection well 1 at an angle downward. With the injection well 1 as the center, the first monitoring well 7 and the second monitoring well 8 are set symmetrically on the left and right.

[0076] (8) The corresponding detection devices 15 are successively lowered into the two monitoring wells. The detection devices 15 travel along the corresponding monitoring well to the corresponding drill bit, and then back along the edge of the monitoring well while installing microseismic probes. Several microseismic probes are evenly distributed along the length of the monitoring well, and each microseismic probe is connected to the detection device 15 through a line.

[0077] (9) The detection device 15 retracts to the top of the monitoring well and receives the data detected by the corresponding microseismic probes; the detection device 15 is connected to the monitoring device on the ground through a line and continues to transmit the collected data back to the ground.

[0078] Alternatively, the fourth and fifth drill bits have the same structure and usage as the first drill bit; the coiled tubing connected to the fourth and fifth drill bits also refers to step (1).

[0079] Further optional, in step (6), the first monitoring well 7 includes a front part, a middle part and a rear part. The front part is on the same vertical plane as the injection well 1. This vertical plane is perpendicular to the length direction of the furnace 3. The front part is a downward inclined section.

[0080] The middle and rear sections are at the same depth. The middle section is a horizontal directional section, which causes the fourth drill bit to gradually turn to be parallel to the length direction of the furnace 3. The rear section is parallel to the length direction of the furnace 3. The end point of the rear section is on the same plane as the production well 2 and the front part of the first temperature measuring well 4, but the first monitoring well 7 does not contact the production well 2 or any of the temperature measuring wells.

[0081] Further optional, in step (7), the second monitoring well 8 has the same structure as the first monitoring well 7, the front part of the second monitoring well 8 is on the same vertical plane as the front part of the first monitoring well 7 and the injection well 1; the middle part and the rear part of the second monitoring well 8 are at the same depth as the middle part and the rear part of the first monitoring well 7; the rear part of the second monitoring well 8 and the rear part of the first monitoring well 7 are parallel to each other in the length direction of the furnace 3; the end point of the second monitoring well 8 corresponds to the end point of the first monitoring well 7.

[0082] The fourth and fifth drill bits remained at the end of their respective monitoring well sections and were not retrieved. The coiled tubing in both monitoring wells extended into injection well 1 and continued along injection well 1 to the surface.

[0083] Optionally, the rear part of the first monitoring well 7 and the rear part of the second monitoring well 8 are respectively located obliquely above the two sides of the furnace 3, and both are higher than the third temperature measuring well 6; the vertical distance between the rear part of the first monitoring well 7 and the furnace 3 is equal to the vertical distance between the rear part of the second monitoring well 8 and the furnace 3, and this vertical distance is 200-300 meters.

[0084] Optional, such as Figures 5-7 As shown, the detection device 15 includes a storage section 16, an installation section, a connector section 20, and a main control section 21. The storage section 16 stores a plurality of microseismic probes 17. The two ends of each microseismic probe are slidably connected to the inner walls on both sides of the storage section 16, and can move to the bottom of the storage section 16. A door 9 is provided between the bottom of the storage section 16 and the installation section. The microseismic probes fall into the lowering section 19 of the installation section through the door 9.

[0085] The installation part includes a pressing part 18 and a lowering part 19. The pressing part 18 and the connector part 20 are arranged sequentially on the outside of one side of the storage part 16. The main control part 21 is located above the storage part 16. The connector part 20 is provided with a number of movable connectors 22, and the connectors 22 are communicatively connected to the main control part 21.

[0086] One side of the lowering section 19 is connected to the pressing section 18, and the other side is provided with a retractable connecting chain 23. The tail end of the microseismic probe in the installation section is detachably connected to the head of the connecting chain 23, and the head end can be connected to a connector 22. The gradually elongating connecting chain 23 lowers the tail end of the probe to the bottom of the monitoring well. The rotating lifting device 28 of the pressing section 18 presses the probe into the soil through the connector 22, thereby installing the microseismic probe.

[0087] Further optionally, the storage unit 16 is a cuboid, and its two opposite vertical wide sides are respectively provided with S-shaped meandering first guide rails 24 with the same structure, and the two first guide rails 24 correspond to each other; each first guide rail 24 is slidably connected with a number of openable clamping parts, and the clamping parts on the two first guide rails 24 are arranged in pairs, with one microseismic probe corresponding to a pair of clamping parts, that is, a pair of clamping parts clamp the two ends of the microseismic probe respectively;

[0088] The uppermost and lowermost ends of the first guide rail 24 are close to the same long side. A connecting rail is provided between the upper and lower ends of the first guide rail 24, so that the clamping part can move cyclically along the first guide rail 24 and the connecting rail.

[0089] Further optionally, the wide side corresponding to the front end of the microseismic probe is close to the pressing part 18, and the wide side corresponding to the rear end of the microseismic probe is corresponding to the lowering part 19. The length of the first door is not less than the length of the microseismic probe, and the first door is located in the center of the bottom of the storage part 16.

[0090] Based on the length of the furnace 3 and the lengths of the middle and rear sections of the monitoring well, the required number of microseismic probes is determined. Within the storage section 16, the two ends of each microseismic probe are clamped between a pair of clamping parts. Several microseismic probes are arranged along the first guide rail 24, allowing the storage section 16 to store the required number of probes for one monitoring well. The pair of clamping parts guides the microseismic probes along the two first guide rails 24 until they reach the first door. An infrared sensor can be installed next to the first door. When the sensor detects that a microseismic probe has moved above the first door, the first door opens, the clamping parts release, and the microseismic probe falls into the installation section. The first door closes, awaiting the arrival of the next microseismic probe. A rubber pad can be installed on the bottom surface of the lowering section 19 to prevent damage to the microseismic probes.

[0091] Door No. 1 is a conventional sensor-operated door. Door No. 2 and the clamping unit can both be connected to the main control unit 21 for control. To prevent the microseismic probes in the storage unit 16 from misleading and affecting Door No. 1, a barrier can be installed between the bottommost microseismic probe and the adjacent topmost microseismic probe. The barrier is connected to the two wide sides of the storage unit 16, so that the infrared sensor of Door No. 1 can only detect the bottommost microseismic probe.

[0092] Further optionally, the mounting part is L-shaped, the pressing part 18 is vertical, the lowering part 19 is horizontal, the bottom of the pressing part 18 is connected to the top of the head of the lowering part 19, and the tail of the lowering part 19 is provided with a connecting chain 23; the side of the head of the lowering part 19 is connected to the side of the connector part 20, and the connector part 20 is parallel to the width direction of the storage part 16.

[0093] The mounting part is located in the middle of the detection device 15, that is, the lowering part 19 corresponds to the middle of the storage part 16 below, and the pressing part 18 corresponds to the middle of the side of the storage part 16.

[0094] Further optionally, the lower part 19 is provided with a winding motor 26 at its tail end. The winding shaft of the winding motor 26 is perpendicular to the length direction of the microseismic probe. The connecting chain 23 is wound on the winding shaft, and the head of the connecting chain 23 can face the tail end of the microseismic probe. The head of the connecting chain 23 is provided with an openable snap ring for detachably connecting the tail end of the microseismic probe.

[0095] The bottom surface of the lower part 19 is provided with a small groove 27. The bottom of the winding motor 26 is slidably connected to the groove 27, so that the winding motor 26 can move along the length of the microseismic probe, which facilitates the docking of the connecting chain 23, the connector 22 and the two ends of the microseismic probe.

[0096] Optionally, the bottom surface of the lowering part 19 is provided with an openable second door, below which is the internal environment of the monitoring well, so that the microseismic probe can be lowered and installed into the strata at the bottom of the monitoring well.

[0097] The microseismic probe is lowered from Gate 1 into Lowering Section 19, and Gate 1 closes. The locking ring opens, and the winding motor 26 moves along the slide 27 towards the pressing section 18. An infrared sensor on the inner wall of the locking ring detects the tail end of the microseismic probe, causing the locking ring to close and engage the tail end. At this time, the head end of the microseismic probe is aligned with the opening of the head section 20. The winding motor 26 continues to move along the slide 27, pushing the microseismic probe towards the connector section 20. The head end of the microseismic probe can enter the connector section 20 through the opening, thus engaging with a connector 22 corresponding to the opening. Then, the winding motor 26 moves in the opposite direction along the slide 27, and the head end of the microseismic probe, along with the connector 22, exits the connector section 20. Gate 2 opens, and the winding motor 26 unwinds the connecting chain 23, pulling the tail end of the microseismic probe downwards. The head end of the microseismic probe rotates within Lowering Section 19, causing the microseismic probe to gradually change from a horizontal to a vertical position. When the tail end of the microseismic probe is lowered to the bottom of the monitoring well, the locking ring opens, the winding motor 26 winds up the connecting chain 23 and resets, and the winding motor 26 also resets along the slide groove 27.

[0098] Door No. 2 is a conventional sensor-operated door. Door No. 2, the locking ring, the winding motor 26, and the slide 27 are all connected to the main control unit 21 and controlled in the manner described above.

[0099] Optionally, the pressing part 18 is provided with a rotating lifting device 28, and the rotating lifting motor can control the rotation and lifting of the rotating shaft, which is vertically downward; the side of the lowering part 19 is provided with an openable rotating ring 29, which is perpendicular to the width direction of the storage part 16. The rotating ring 29 is connected to this side through an angle controller, which can drive the rotating ring 29 to rotate in place. The rotating ring 29 is a hollow ring.

[0100] After the microseismic probe falls into the lowering section 19, its tip does not contact the rotating ring 29. At this time, the rotating ring 29 closes into a circle, with its circular plane perpendicular to the length of the microseismic probe. The microseismic probe is directly opposite the center of the rotating ring 29. When the microseismic probe is pushed by the connecting chain 23, the rotating ring 29 opens, and the tip and front part of the microseismic probe pass through it. After the tip of the microseismic probe aligns with the connector 22, it returns to the lowering section 19, and the rotating ring 29 closes, clamping the outer side of the microseismic probe. At this time, the connector 22 and the connecting chain 23 are on opposite sides of the rotating ring 29. Then, the connecting chain 23 lowers the tail end of the microseismic probe, while the angle controller controls the rotation of the rotating ring 29, causing the microseismic probe to rotate downwards around the rotating ring 29 as a fulcrum, and the connector 22 to rotate upwards. After the microseismic probe is rotated to a vertical position, the connector 22 of the microseismic probe is directly below the rotating shaft. The rotating shaft descends and abuts against the connector 22, the rotating ring 29 opens, and the rotating lifting motor rotates and presses the microseismic probe down to the bottom of the monitoring well through the rotating shaft, so that the tail end of the microseismic probe is inserted into the soil by more than ten centimeters, so that the microseismic probe can stand up on its own and can detect the ground vibration below the monitoring well.

[0101] Then the rotating shaft retracts, the second door closes, and preparations are made for the installation of the next microseismic probe. The connector 22 of the newly installed microseismic probe is connected to the main control unit 21 of the detection device 15 via a circuit. The detection device 15 then retracts away from the newly installed microseismic probe to install the next microseismic probe.

[0102] The rotating ring 29 and the angle controller are conventional components, both connected to the main control unit 21 and controlled in the manner described above.

[0103] Optionally, the connector 20 is a cuboid, with its length direction parallel to the width direction of the storage section 16. The length of the connector 20 is equal to the width of the storage section 16, and the height of the connector 20 is equal to the sum of the heights of the storage section 16 and the lowering section 19. A second guide rail 25 is provided on the long side of the connector 20 away from the storage section 16. The structure of the second guide rail 25 is the same as that of the first guide rail 24, which is also an S-shaped meandering curve.

[0104] Several sliders 30 are slidably connected on the second guide rail 25. The number of sliders 30 is equal to the number of microseismic probes. Connectors 22 are movably connected to the sliders 30, and the sliders 30 lead the connectors 22 to move along the second guide rail 25.

[0105] Further optionally, one long side of the connector 20 near the storage section 16 is the inner long side, and the other long side is the outer long side. The second guide rail 25 is disposed on the outer long side, and an opening is provided at the position of the corresponding lowering section 19 on the inner long side for connecting the lowering section 19 and the connector 20. The tip of the microseismic probe in the lowering section 19 can enter the connector 20 through the opening so as to connect the corresponding connector 22.

[0106] Optionally, the connector 22 is a cylinder. When the connector 22 is connected to the slider 30, the central axis of the connector 22 is horizontally set. The circular side of the connector 22 away from the slider 30 is the bottom surface, and the circular side close to the slider 30 is the top surface. A recessed slot 10 is provided at the center of the top surface. The protruding rod on the side of the slider 30 can be inserted into the slot 10, thereby movably connecting the connector 22. A quick-connect connector 11 is provided on the bottom surface. The head of the quick-connect connector 11 is connected to the communication component. The communication component is located inside the connector 22 and is wirelessly connected to the main control unit 21.

[0107] Alternatively, the protruding rod is horizontal and parallel to the length direction of the storage section 16, with the free end of the protruding rod pointing towards the storage section 16, and a small gap between the free end and the inner long side of the connector section 20, to prevent the connector 22 from falling off from the free end of the protruding rod.

[0108] The slider 30 leads the connector 22 along the second guide rail 25. When the tip of the microseismic probe aligns with the opening of the connector 20, one connector 22 also moves to the corresponding position and remains there. When the winding motor 26 pushes the microseismic probe through the snap-fit ​​ring, the tip of the microseismic probe inserts into the quick-connect connector 11, connecting the circuit, and the tip of the microseismic probe is snapped into the quick-connect connector 11 (not easily disengaged). When the winding motor 26 drives the microseismic probe out of the connector 20, it brings the connector 22 out to the lowering section 19. At this time, the slider 30 of the second guide rail 25 continues to move, preparing to deliver the next connector 22.

[0109] After the connector 22 rotates to a position directly below the rotating shaft following the rotation of the microseismic probe, the bottom end of the rotating shaft moves downward and inserts into the slot 10 on the top surface of the connector 22. The inner wall of the slot 10 may be provided with internal threads, and the outer side of the bottom of the rotating shaft may be provided with external threads. The rotating shaft can rotate to connect to the slot 10, thereby driving the microseismic probe to rotate and descend. When the tail end of the microseismic probe is inserted into the soil layer to a certain depth, the rotating shaft can then rotate to loosen the slot 10 without affecting the fixation of the microseismic probe.

[0110] Optionally, the storage section 16 and the lower surface of the connector section 20 of the detection device 15 are provided with a traveling mechanism. The traveling mechanism includes four wheels, and the wheel rotation is controlled by existing technology to drive the detection device 15 to move. The traveling mechanism is positioned away from the lowering section 19 so as not to affect the installation of the microseismic probe. The wheels have a certain height to allow the lowered microseismic probe to stand upright.

[0111] Alternatively, the top of the detection device 15 is provided with at least two hanging rings arranged in a row, and a continuous oil pipe passes through the row of hanging rings, so that the detection device 15 can move along the continuous oil pipe, and the continuous oil pipe plays the role of guiding the detection device 15.

[0112] When lowering the detection device 15, a rope is connected to the tail of the device, and a wiring connection is made to the main control unit 21. This wiring connects to a monitoring device on the ground, transmitting the detection data signals received by the main control unit 21 back to the ground via a wired connection to ensure signal strength and accuracy. The rope and wiring are lowered together with the detection device 15. The detection device 15 is lowered along the coiled tubing, guided to avoid frequent collisions with the inner wall of the well 1. After reaching the middle section of the monitoring well, the detection device 15, under the weight of its wheels, can touch the ground and then move forward along the coiled tubing using a walking mechanism until it reaches the corresponding drill bit. A rangefinder can be installed on the head of the detection device 15 to measure the distance between the head of the detection device 15 and the drill bit, thereby determining the location for installing the microseismic probe. The detection device 15 begins ranging and installing the microseismic probe from near the drill bit (i.e., near the end point of the monitoring well), using a reverse installation method. Depending on monitoring needs, a microseismic probe may or may not be installed in the middle section of the monitoring well. The detection device 15 is pushed to the middle or front section and then stops retracting. At this position, it receives data signals from the microseismic probe. The main control unit 21 performs preliminary processing and signal amplification before transmitting the signal back to the ground via a line. The monitoring well is relatively far from the furnace 3, thus experiencing less influence from underground gasification. The environment inside the monitoring well is relatively stable and mild, which is conducive to wireless data transmission. Furthermore, the furnace 3 is typically on the order of hundreds of meters in length, while the monitoring well has a limited length, allowing for wireless transmission.

[0113] The detection device 15 provided by this invention makes it possible to bury microseismic probes deep underground. Compared with the current microseismic probes that can only be buried at the surface or in shallow underground locations, this invention installs the microseismic probes underground at a medium distance from the furnace 3, which can measure more realistic underground vibrations and understand the changes in the strata. This is a major advancement.

Claims

1. A method for detecting the underground gasification process of deep coal, characterized in that, include: S1: Drill injection wells, extraction wells and underground furnaces into deep coal seams. The first end of the furnace is connected to the bottom of the injection well, and the last end of the furnace is connected to the bottom of the extraction well. S2: Connect the temperature measuring fiber to the drill bit and run it down to a position near the bottom of the well. Drill the first temperature measuring well on one side of the well. Using the same method, drill the second temperature measuring well on the other side of the well with another drill bit. The tail ends of both temperature measuring wells extend to the bottom of the corresponding injection well. S3: Following the method in step S2, lower the drill bit down to the bottom of the production well, and drill the third temperature measuring well from the side of the production well. The third temperature measuring well is located above the furnace, and the tail end of the third temperature measuring well extends to the corresponding head end of the furnace. S4: The drill bit is connected to the continuous tubing and runs down to the middle of the injection well. The drill bit drills the first monitoring well on one side of the injection well. Following the above method, another drill bit drills the second monitoring well on the other side of the injection well. The tail ends of both monitoring wells extend to the corresponding furnace tail ends. Then, a detection device is placed into the monitoring well along the coiled tubing to install a microseismic probe in the monitoring well so as to monitor underground vibration in real time. S5: A gas pipe is lowered into the injection well to introduce the gasifying agent into the furnace; a gas production pipe is lowered into the production well to transport the gas obtained from gasification in the furnace to the surface.

2. The detection method according to claim 1, characterized in that, Step S2 is as follows: (1) The tail of the first drill bit is connected to a continuous tubing, and a temperature measuring fiber is installed inside the continuous tubing. The top of the temperature measuring fiber is connected to a monitoring device on the ground. (2) Lower the first drill bit along the well until it is close to the bottom of the well. The first drill bit is facing downwards and drills out from the left side of the well. After drilling a section of the directional section, the first drill bit is at the same depth as the furnace. Then, the first drill bit gradually turns to be parallel to the length of the furnace and drills along the length of the furnace to the corresponding furnace head position to complete the first temperature measurement well. (3) Following the method in step (2), lower the second drill bit along the well until it reaches the same depth as the top of the first temperature measuring well. The second drill bit is drilled out from the right side of the well, with the well as the center. The first temperature measuring well and the second temperature measuring well are set symmetrically on the left and right.

3. The detection method according to claim 1, characterized in that, Step S3 is as follows: (4) The tail of the third drill bit is connected to the coiled tubing, and a temperature measuring fiber is installed inside the coiled tubing. The top of the temperature measuring fiber is connected to a monitoring device on the ground. (5) Lower the third drill bit along the production well until the lower part of the production well; the third drill bit is facing downwards and drills out from the side of the production well. The third drill bit is directly above the furnace. Drill a section of the inclination section so that the third drill bit gradually turns to be parallel to the length direction of the furnace. Then drill along the length direction of the furnace to the position of the corresponding furnace head to complete the third temperature measurement well.

4. The detection method according to claim 1, characterized in that, Step S4 is as follows: (6) The tail of the fourth drill bit is connected to the continuous tubing. The fourth drill bit is lowered along the injection well until the middle of the injection well. The fourth drill bit is facing downwards and drills out from the left side of the injection well. After drilling a section of the directional section, the fourth drill bit gradually turns to be parallel to the length of the furnace. Then it is drilled along the length of the furnace to the corresponding position at the tail end of the furnace to complete the first monitoring well. (7) Following the method in step (6), lower the fifth drill bit along the injection well until it reaches the same depth as the top of the first monitoring well. The fifth drill bit is facing downwards and drills out from the right side of the injection well. With the injection well as the center, the first monitoring well and the second monitoring well are set symmetrically on the left and right. (8) The corresponding detection devices are placed into the two monitoring wells one after another. The detection devices travel along the corresponding monitoring well to the corresponding drill bit, and then back along the edge of the monitoring well while installing microseismic probes. Each microseismic probe is connected to the detection device through a line. (9) The detection device retracts to the top of the monitoring well and receives data from the corresponding microseismic probes; the detection device is connected to the monitoring device on the ground via a line and continues to transmit the collected data back to the ground.

5. The detection method according to claim 1, characterized in that, The detection device includes a storage section, an installation section, a connector section, and a main control section. The storage section stores several microseismic probes. The two ends of each microseismic probe are slidably connected to the inner walls on both sides of the storage section and can move to the bottom of the storage section. A door is provided between the bottom of the storage section and the installation section. The microseismic probes fall into the lower part of the installation section through the door. The installation section includes a pressing section and a lowering section. The pressing section and the connector section are arranged sequentially on the outside of one side of the storage section. The main control section is located above the storage section. The connector section contains several movable connectors, which are connected to the main control section for communication. One side of the lowering section is connected to the lowering section, and the other side is equipped with a retractable connecting chain. The tail end of the microseismic probe in the installation section is detachably connected to the head of the connecting chain. The head end of the microseismic probe can be connected to a connector. The gradually elongating connecting chain lowers the tail end of the probe to the bottom of the monitoring well. The rotating lifting device of the lowering section presses the probe into the soil through the connector, thereby installing the microseismic probe.

6. The detection method according to claim 5, characterized in that, The storage unit is a cuboid, with two opposite vertical wide sides each provided with an identical S-shaped meandering first guide rail, and the two first guide rails correspond to each other; several openable clamping parts are slidably connected on each first guide rail, and the clamping parts on the two first guide rails are arranged in pairs, with each pair of clamping parts clamping the two ends of the microseismic probe respectively.

7. The detection method according to claim 5, characterized in that, The lower part is equipped with a winding motor at its tail end. The winding shaft of the winding motor is perpendicular to the length direction of the microseismic probe. The connecting chain is wound on the winding shaft, and the head of the connecting chain can face the tail end of the microseismic probe. The head of the connecting chain is equipped with an openable snap ring for detachably connecting the tail end of the microseismic probe. The bottom surface of the lower part is provided with a slide groove, and the bottom of the winding motor is slidably connected to the slide groove, so that the winding motor can move along the length of the microseismic probe, which facilitates the docking of the connecting chain, connector and the two ends of the microseismic probe.

8. The detection method according to claim 5, characterized in that, The pressing section is equipped with a rotating lifting device. The rotating lifting motor can control the rotation and lifting of the rotating shaft, which is vertically downward. The side of the lowering section is equipped with an openable rotating ring. This side is perpendicular to the width direction of the storage section. The rotating ring is connected to this side through an angle controller. The angle controller can drive the rotating ring to rotate in place. The rotating ring is a hollow circular ring.

9. The detection method according to claim 6, characterized in that, The connector is a cuboid, with its length direction parallel to the width direction of the storage section. A second guide rail is provided on the long side of the connector away from the storage section. The structure of the second guide rail is the same as that of the first guide rail, which is also an S-shaped meandering curve. Several sliders are slidably connected on the second guide rail. The number of sliders is equal to the number of microseismic probes. Connecting heads are movably connected to the sliders, and the sliders lead the connecting heads to move along the second guide rail.

10. The detection method according to claim 9, characterized in that, The connector is cylindrical. When the connector is connected to the slider, the central axis of the connector is horizontal. The circular side of the connector away from the slider is the bottom surface, and the circular side closer to the slider is the top surface. A recessed slot is provided at the center of the top surface. The protruding rod on the side of the slider can be inserted into the slot, thereby movably connecting the connector. The bottom surface of the connector is provided with a quick-connect connector. The head of the quick-connect connector is connected to the communication component. The communication component is located inside the connector and is wirelessly connected to the main control unit.

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