A comprehensive control system and method for curved directional long drilling of target coal seams

Abstract

This application discloses a comprehensive management and control system and method for a long, curved directional borehole in a target coal seam. The comprehensive management and control system includes a negative pressure extraction module, a high-pressure nitrogen injection module, an intelligent control module, and a multi-effect collaborative pipeline. The multi-effect collaborative pipeline first performs drainage operations in the depressions of the internal extraction pipe, then performs nitrogen injection and displacement operations in the external nitrogen injection pipe, and finally performs gas extraction operations in the internal extraction pipe. This achieves integrated management and control of drainage of accumulated water in depressions, nitrogen injection and displacement, and gas extraction within the same borehole and pipeline. This can improve the effect of nitrogen injection to increase flow and promote extraction while shortening the construction cycle, optimizing resource allocation, and reducing construction costs.

Description

Technical Field

[0001] This application relates to the field of coal mine gas extraction technology, and in particular to a comprehensive control system and method for a target coal seam curved directional long borehole. Background Technology

[0002] As my country's coal resources gradually move towards deeper mining, the "three highs and one low" characteristics of coal seams are becoming increasingly apparent. Traditional borehole pre-drainage methods struggle to overcome the low permeability of coal seams, as they are time-consuming and exhibit rapid methane flow decay, failing to meet the demands of mining succession and safe production. With continuous advancements in science and technology, gas injection for methane displacement technology has achieved breakthroughs from theory to field implementation. This technology increases the internal gas pressure of the coal seam, accelerating the seepage velocity of the mixed gas, injecting strong momentum into the coal seam flow field, and forming reliable gas migration channels. This effectively reduces the effective partial pressure of methane and promotes the desorption of adsorbed methane, thereby solving the problem of insufficient pressure drop in the later stages of mining. Therefore, gas injection for methane displacement technology has become a key technical means to improve methane extraction efficiency and address the challenges of deep coal seam mining.

[0003] However, for directional long boreholes in coal seams, nitrogen injection for regional drainage is often not uniformly stable along the strike due to sedimentary and tectonic influences. For mineable coal seams, the following situations mainly exist: 1) The coal seam thickness is relatively stable, but due to folds or faults, it exhibits a wavy or undulating pattern along the strike, following the coal-bearing strata; 2) Due to sedimentary or tectonic influences, the coal seam thickness varies wavy or undulating along the strike; 3) For long-distance borehole construction, excessively long drill rods can cause borehole deflection. Therefore, under the condition that the coal seam exhibits a wavy or undulating pattern along the strike, the trajectory of regional directional long boreholes for nitrogen injection along the strike will inevitably also exhibit wavy or undulating patterns, which is the so-called curved directional long borehole for nitrogen injection for regional drainage.

[0004] Currently, water accumulation in the depressions of directional, curved long boreholes used for regional nitrogen injection displacement presents the following problems. Firstly, it affects the displacement effect. On one hand, it reduces displacement efficiency. Water accumulation or blockage of the depressions at low points in the borehole affects nitrogen injection displacement efficiency and may even prevent high-pressure nitrogen injection. The space occupied by the water reduces the contact area between nitrogen and methane in the coal seam, making it difficult for nitrogen to effectively displace methane from the coal seam. This leads to reduced displacement efficiency and prolonged displacement time. On the other hand, it also affects nitrogen distribution. The presence of water alters the fluid distribution within the borehole, interfering with the seepage, diffusion, and adsorption processes of nitrogen in the coal seam. This may result in uneven distribution of nitrogen throughout the coal seam, thus affecting the displacement effect. Secondly, it also affects coal seam characteristics. On one hand, it alters the pore structure of the coal seam. Water accumulation in the borehole may have a certain impact on the pore structure of the coal seam, such as causing pore blockage or changing pore size. This affects the coal seam's adsorption capacity for methane, thereby affecting the displacement effect. On the other hand, it affects the permeability of the coal seam. The presence of water reduces the permeability of the coal seam, making it difficult for nitrogen to flow smoothly within it. This leads to increased pressure loss during nitrogen displacement, thereby reducing displacement efficiency. These problems all result in poor gas extraction performance and also pose certain safety issues. Improperly handled water accumulation in the borehole may cause safety accidents, such as borehole wall collapse or other geological disasters. Furthermore, it may corrode or damage drilling equipment, increasing the cost of maintenance and replacement, and also deteriorating the working environment, increasing the difficulty and danger of operations.

[0005] In summary, resolving the issue of water accumulation in depressions of long, curved boreholes requiring nitrogen injection for directional drainage is particularly important and urgent. However, current industry technologies for borehole drainage primarily target downward-facing conventional boreholes, including gas-lift water methods, orifice drainage, and in-hole deep well pump drainage. For water accumulation in long, curved boreholes, existing technologies employ the addition of branch boreholes, but this approach also has several drawbacks. First, the construction of branch boreholes is limited by geological conditions, impacting drilling efficiency and success rates. Second, controlling the borehole trajectory during branch borehole construction presents challenges, potentially leading to deviations from the designed path, which affects drainage effectiveness and the quality of subsequent work. Furthermore, adding branch boreholes may increase safety risks during construction, such as drill pipe bending and borehole collapse. Additionally, it significantly increases construction costs. Summary of the Invention

[0006] This application provides a comprehensive management and control system and method for a target coal seam curved directional long borehole. This system integrates the management and control of water accumulation in depressions, nitrogen injection for displacement, and gas extraction in the same borehole and pipeline. It can improve the effect of nitrogen injection to increase flow and promote extraction, while shortening the construction cycle, optimizing resource allocation, and reducing construction costs.

[0007] To achieve the above objectives, the technical solution of this invention is as follows:

[0008] In a first aspect, embodiments of the present invention provide a comprehensive control system for a curved directional long borehole in a target coal seam, comprising: a negative pressure extraction module, a high-pressure nitrogen injection module, an intelligent control module, and a multi-effect collaborative pipeline; the multi-effect collaborative pipeline is arranged within the curved directional long borehole, including an inner inner extraction pipe and an outer outer nitrogen injection pipe; wherein, the inner extraction pipe is used to extract water and perform gas extraction operations within the borehole, and the outer nitrogen injection pipe is used to inject nitrogen into the borehole; the negative pressure extraction module is used to generate a negative pressure environment and to extract water and gas from the borehole through the inner extraction pipe; the high-pressure nitrogen injection module is used to provide high-pressure nitrogen and to inject nitrogen into the borehole through the outer nitrogen injection pipe to achieve the displacement effect of nitrogen and enhance the gas flowability in the target coal seam; the intelligent control module... The control module is connected to the negative pressure extraction module, the high-pressure nitrogen injection module, and the multi-effect collaborative pipeline, respectively, and is used to intelligently control the working status of the negative pressure extraction module and the high-pressure nitrogen injection module. The specific process of intelligent control includes: first, starting and controlling the negative pressure extraction module to extract water from the borehole through the inner extraction pipe, and shutting down the negative pressure extraction module after the water is extracted; then starting and controlling the high-pressure nitrogen injection module to perform nitrogen injection and displacement operations through the outer nitrogen injection pipe, and shutting down the high-pressure nitrogen injection module after the nitrogen injection and displacement operations reach the preset conditions; finally, starting and controlling the negative pressure extraction module again to extract gas from the borehole through the inner extraction pipe, thereby realizing the integrated management and control of water discharge, nitrogen injection and displacement, and gas extraction in the depression of the curved directional long borehole.

[0009] In some possible implementations, the internal extraction pipe and the external nitrogen injection pipe are connected by a separation connection device. The number of separation connection devices is determined according to the length of the curved directional long borehole. The main body of the separation connection device is a double-sleeve ventilation pipe, with a one-way valve at each of the upper and lower ports. The outer ends of the two one-way valves are equipped with filters.

[0010] In some possible implementations, a high-pressure nitrogen injection shut-off valve and a negative-pressure extraction shut-off valve are installed between the multi-effect collaborative pipeline and the intelligent control module. The high-pressure nitrogen injection shut-off valve is used to control the flow and stop of high-pressure nitrogen in the external nitrogen injection pipe, and the negative-pressure extraction shut-off valve is used to control the flow and stop of water or gas in the internal extraction pipe. When the negative-pressure extraction module is working, the high-pressure nitrogen injection shut-off valve is closed and the negative-pressure extraction shut-off valve is open; when the high-pressure nitrogen injection module is working, the high-pressure nitrogen injection shut-off valve is open and the negative-pressure extraction shut-off valve is closed.

[0011] In some possible implementations, sensors are installed at the ends of the multi-effect collaborative pipeline to monitor the pressure and concentration data inside the borehole in real time; the intelligent control module determines whether to perform re-nitrogen injection or re-drainage operations based on the monitored pressure and concentration data.

[0012] In some possible implementations, the curved directional long borehole includes multiple boreholes, each with a multi-effect co-operating pipeline arranged inside; a connection regulator is set between the multiple multi-effect co-operating pipelines and the intelligent control module, and the intelligent control module can control the connection regulator to realize the replacement of the connection point with each multi-effect co-operating pipeline end.

[0013] In some possible implementations, the connecting regulator is also used to indirectly achieve the effect of pulsed nitrogen injection during nitrogen displacement operations.

[0014] In some possible implementations, the head of the internal extraction pipe is in a closed state; the density of nitrogen injection ports on the external nitrogen injection pipe gradually increases from the outside to the inside of the borehole.

[0015] In some possible implementations, the sealing section of the curved directional long borehole is arranged between the elastic zone of the stress concentration zone and the original stress zone.

[0016] Secondly, embodiments of the present invention provide a comprehensive management and control method for a curved directional long borehole in a target coal seam, applied to the comprehensive management and control system for a curved directional long borehole in a target coal seam provided in the first aspect. The method includes: designing a curved directional long borehole trajectory based on a preset nitrogen injection displacement flow enhancement and extraction target, the strike and occurrence conditions of the coal and rock strata at the target working face, and the performance of the directional drilling equipment; performing drilling according to the designed curved long borehole trajectory; arranging a multi-effect synergistic pipeline within the long borehole after drilling is completed; sealing the borehole between the elastic zone and the original stress zone in the stress concentration area; opening the negative pressure extraction shut-off valve, closing the high-pressure nitrogen injection shut-off valve, and starting the process. The system controls the operation of the negative pressure extraction module to discharge accumulated water in the borehole through the internal extraction pipe. When the water extraction is complete, based on the flow rate data from the internal extraction pipe, the negative pressure extraction module and the negative pressure extraction shut-off valve are closed. The high-pressure nitrogen injection shut-off valve is opened, and the high-pressure nitrogen injection module is started and controlled to perform nitrogen injection and displacement operations through the external nitrogen injection pipe. After the nitrogen injection and displacement operations reach the preset conditions, the high-pressure nitrogen injection module is closed, the negative pressure extraction shut-off valve is opened, and the high-pressure nitrogen injection shut-off valve is closed. The negative pressure extraction module is then started and controlled to perform gas extraction operations through the internal extraction pipe, achieving integrated management and control of water discharge, nitrogen injection and displacement, and gas extraction in the curved directional long borehole depression.

[0017] One or more technical solutions provided in the embodiments of the present invention have at least the following technical effects or advantages:

[0018] In this embodiment of the invention, the multi-effect synergistic pipeline is applicable to most curved long boreholes, flexibly adapting to various complex and changing geological environments. It ensures efficient implementation of nitrogen injection and drainage projects regardless of whether the borehole is winding or facing extreme geological challenges, thus meeting the diverse needs of geological exploration and engineering implementation. Furthermore, it avoids the need for additional branch boreholes in traditional curved directional long borehole drainage operations, reducing potential damage to geological structures and effectively improving overall construction efficiency. By reducing unnecessary drilling operations, it not only protects the natural state of underground resources but also promotes the practice of environmentally friendly construction concepts. Moreover, the multi-effect synergistic pipeline first performs drainage operations in the depressions of the internal extraction pipe, then nitrogen injection and displacement operations in the external nitrogen injection pipe, and finally gas extraction operations in the internal extraction pipe, achieving integrated management of drainage of accumulated water in depressions, nitrogen injection and displacement, and gas extraction within the same borehole and pipeline. The multi-effect drilling operation approach solves the problem of wasted time caused by laying out the pumping pipeline first and then the nitrogen injection pipeline in traditional operations, which greatly shortens the overall construction cycle of the project. By efficiently integrating the construction steps, it not only significantly reduces the time that construction equipment occupies, but also effectively optimizes resource allocation, further reduces construction costs, and improves the economic benefits of the project. Attached Figure Description

[0019] To more clearly illustrate the embodiments of the present invention, the accompanying drawings used in the embodiments of the present invention will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 A schematic diagram of a long, curved borehole and water accumulation in a depression.

[0021] Figure 2 A schematic diagram of a comprehensive control system for a curved directional long borehole in a target coal seam, provided for the implementation of this invention;

[0022] Figure 3 This is a schematic diagram of the main component of the separation and connection device in an embodiment of the present invention;

[0023] Figure 4 This is a schematic diagram of the structure of the separation connection device in the multi-effect synergistic pipeline according to an embodiment of the present invention;

[0024] Figure 5 This is a schematic diagram of the structure of the sealing hole position inside the borehole in an embodiment of the present invention;

[0025] Figure 6 This is a schematic diagram of another integrated control system for a curved directional long borehole targeting a coal seam, as described in an embodiment of the present invention.

[0026] Figure 7 This is a schematic flowchart of an embodiment of a comprehensive control method for a curved directional long borehole in a target coal seam according to an invention.

[0027] Figure 8 This is a schematic diagram of the structure at the start of the multi-effect synergistic pipeline pumping process in an embodiment of the present invention;

[0028] Figure 9 This is a schematic diagram of the multi-effect synergistic pipeline pumping process in an embodiment of the present invention;

[0029] Figure 10 This is a schematic diagram of the multi-effect synergistic pipeline nitrogen injection displacement process in an embodiment of the present invention;

[0030] Figure 11 This is a schematic diagram of the multi-effect synergistic pipeline gas extraction process in an embodiment of the present invention. Detailed Implementation

[0031] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are within the scope of protection of this application.

[0032] In the relevant descriptions of this embodiment, the terms "including," "containing," and "possessing" are all open terms and are generally understood to include but not be limited to; the term "at least one" is generally understood to mean one or more, where "multiple" refers to two or more; the term "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items, for example, "at least one of a, b, or c", or "at least one of a, b, and c", which can all mean: a, b, c, ab (i.e., a and b), ac, bc, or abc, where a, b, and c can be single or multiple; the symbol "A / B" is used to describe the selection relationship of associated objects, generally indicating an "or" relationship.

[0033] In the following description of the embodiments, the terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The singular forms "a" and "the" as used in the embodiments of this application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise.

[0034] Those skilled in the art should understand that, in the following description of the embodiments of this application, the sequence of numbers does not imply the order of execution. Some or all steps may be executed in parallel or sequentially. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of this application.

[0035] Those skilled in the art will understand that the numerical ranges in the embodiments of this application should be understood to specifically disclose each intermediate value between the upper and lower limits of the range. Any stated value or intermediate value within a stated range, as well as any other stated value or each smaller range between intermediate values ​​within a range, are also included within this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0036] Unless otherwise stated, the technical / scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. While this application describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this application. All references to this specification are incorporated by way of citation to disclose and describe the methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0037] To illustrate the technical solution of the present invention, specific embodiments are described below.

[0038] As my country's coal resources gradually move towards deeper mining, the "three highs and one low" characteristics of coal seams are becoming increasingly apparent. Traditional borehole pre-drainage methods struggle to overcome the low permeability of coal seams, as they are time-consuming and exhibit rapid methane flow decay, failing to meet the demands of mining succession and safe production. With continuous advancements in science and technology, gas injection for methane displacement technology has achieved breakthroughs from theory to field implementation. This technology increases the internal gas pressure of the coal seam, accelerating the seepage velocity of the mixed gas, injecting strong momentum into the coal seam flow field, and forming reliable gas migration channels. This effectively reduces the effective partial pressure of methane and promotes the desorption of adsorbed methane, thereby solving the problem of insufficient pressure drop in the later stages of mining. Therefore, gas injection for methane displacement technology has become a key technical means to improve methane extraction efficiency and address the challenges of deep coal seam mining.

[0039] However, for directional long boreholes in coal seams, nitrogen injection for regional drainage is often not uniformly stable along the strike due to sedimentary and tectonic influences. For mineable coal seams, the following situations mainly exist: 1) The coal seam thickness is relatively stable, but due to folds or faults, it exhibits a wavy or undulating pattern along the strike, following the coal-bearing strata; 2) Due to sedimentary or tectonic influences, the coal seam thickness varies wavy or undulating along the strike; 3) For long-distance borehole construction, excessively long drill rods can cause borehole deflection. Therefore, under the condition that the coal seam exhibits a wavy or undulating pattern along the strike, the trajectory of the regional nitrogen injection directional long boreholes arranged along the strike will inevitably also exhibit wavy or undulating changes, which is the so-called curved nitrogen injection directional long borehole. For example... Figure 1 As shown, Figure 1 This is a schematic diagram of a long, curved borehole and a depression filled with water.

[0040] Currently, the following problems exist with water accumulation in the long, curved borehole depressions caused by directional nitrogen injection displacement (mainly including primary water accumulation caused by borehole hydraulicing and secondary dynamic water accumulation from slow seepage from water-bearing coal and rock strata or other water-bearing geological bodies). See also Figure 1 The curve-shaped borehole shows different amounts of water accumulation in the depressions.

[0041] First, it affects the displacement effect. On one hand, it reduces displacement efficiency. Water accumulation or slag blockage in low-lying areas of the borehole can affect nitrogen injection displacement efficiency and even prevent high-pressure nitrogen injection. The space occupied by water reduces the contact area between nitrogen and methane in the coal seam, making it difficult for nitrogen to effectively displace methane from the coal seam. This leads to reduced displacement efficiency and prolonged displacement time. On the other hand, it also affects nitrogen distribution. The presence of water alters the fluid distribution within the borehole, interfering with the seepage, diffusion, and adsorption processes of nitrogen in the coal seam. This may result in nitrogen not being evenly distributed throughout the coal seam, thus affecting the displacement effect. Furthermore, it affects coal seam characteristics. On one hand, it alters the pore structure of the coal seam. Water accumulation in the borehole may have a certain impact on the pore structure of the coal seam, such as causing pore blockage or changing pore size. This affects the coal seam's adsorption capacity for methane, thus affecting the displacement effect. On the other hand, it affects coal seam permeability. The presence of water reduces the permeability of the coal seam, making it difficult for nitrogen to flow smoothly within the coal seam. This leads to increased pressure loss during nitrogen displacement, thus reducing displacement efficiency. These problems all result in poor gas extraction performance and pose safety risks. Improperly handled water accumulation in the borehole can cause accidents such as borehole wall collapse or other geological disasters. Furthermore, it can corrode or damage drilling equipment, increasing maintenance and replacement costs, and worsening the working environment, thus increasing operational difficulty and danger.

[0042] In summary, resolving the issue of water accumulation in depressions of long, curved boreholes requiring nitrogen injection for directional drainage is particularly important and urgent. However, current industry technologies for borehole drainage primarily target downward-facing conventional boreholes, including gas-lift water methods, orifice drainage, and in-hole deep well pump drainage. For water accumulation in long, curved boreholes, existing technologies address this by adding branch boreholes, but this approach also has some drawbacks. First, the construction of branch boreholes is limited by geological conditions, affecting drilling efficiency and success rates. Second, controlling the borehole trajectory during branch borehole construction presents challenges, potentially leading to deviations from the designed path, which impacts drainage effectiveness and the quality of subsequent work. Furthermore, adding branch boreholes may increase safety risks during construction, such as drill pipe bending and borehole collapse. Additionally, it increases construction costs.

[0043] Based on this, the present invention provides a comprehensive management and control system and method for a target coal seam curved directional long borehole, which realizes integrated management and control of pit water discharge, nitrogen injection displacement and gas extraction in the same borehole and pipeline. It can improve the effect of nitrogen injection to increase flow and promote extraction, while shortening the construction cycle, optimizing resource allocation and reducing construction costs.

[0044] Figure 2 A schematic diagram of a comprehensive control system for a curved directional long borehole in a target coal seam, provided for implementation of the present invention, is shown below. Figure 2 As shown, the aforementioned integrated control system for curved directional long boreholes in the target coal seam may include:

[0045] The negative pressure extraction module 11, the high-pressure nitrogen injection module 12, the intelligent control module 13, and the multi-effect collaborative pipeline 14; their connection relationships are as follows: Figure 2 As shown.

[0046] The multi-effect synergistic pipeline 14 is arranged in a curved directional long borehole. The multi-effect synergistic pipeline 14 includes an inner inner extraction pipe 141 and an outer external nitrogen injection pipe 142. The inner extraction pipe 141 is used to extract water in the borehole and carry out gas extraction operations, while the external nitrogen injection pipe 142 is used to inject nitrogen into the borehole.

[0047] The negative pressure extraction module 11 is used to generate a negative pressure environment and to extract water and gas from the borehole through the inner extraction pipe 141.

[0048] The high-pressure nitrogen injection module 12 is used to provide high-pressure nitrogen and inject nitrogen into the borehole through the external nitrogen injection pipe 142 to achieve the displacement effect of nitrogen and enhance the gas flowability in the target coal seam.

[0049] The intelligent control module 13 is connected to the negative pressure extraction module 11, the high pressure nitrogen injection module 12 and the multi-effect collaborative pipeline 14 respectively, and is used to intelligently control the working status of the negative pressure extraction module 11 and the high pressure nitrogen injection module 12.

[0050] The specific process of intelligent control module 13 includes the following:

[0051] First, the negative pressure extraction module 11 is started and controlled to extract water from the borehole through the inner extraction pipe 141. After the water is extracted, the negative pressure extraction module 11 is shut down. Then, the high-pressure nitrogen injection module 12 is started and controlled to perform nitrogen injection and displacement operations through the outer nitrogen injection pipe 142. After the nitrogen injection and displacement operations reach the preset conditions, the high-pressure nitrogen injection module 12 is shut down. Finally, the negative pressure extraction module 11 is started and controlled again to extract gas from the borehole through the inner extraction pipe 141, thereby achieving integrated management and control of water discharge, nitrogen injection and displacement, and gas extraction in the curved directional long borehole depression.

[0052] In some embodiments, the internal extraction pipe 141 and the external nitrogen injection pipe 142 can be connected by a separation connection device 15.

[0053] The main body of the separation and connection device is a double-sleeve ventilation tube. Figure 3 This is a schematic diagram of the main component of the separation and connection device 15 in an embodiment of the present invention. See also... Figure 3 As shown, the double sleeve of the separation connection device 15 includes two independent channels, inner and outer, with one port at the top and one at the bottom, respectively as shown in the figure. Figure 3 Ports 151 and 152 are shown. (The rest of the text appears to be incomplete and requires further context.) Figure 3 The separation and connection device of the ventilation double-tube structure shown allows the inner extraction tube 141 and the outer nitrogen injection tube 142 to pass through the two independent channels of the double tube, thereby realizing the spatial separation of the two. At the same time, the necessary connection can be achieved through the upper and lower ports 151 and port 152.

[0054] Figure 4 This is a schematic diagram of the separation and connection device 15 in the multi-effect synergistic pipeline 14 according to an embodiment of the present invention. See also Figure 4 As shown, a one-way valve 16 is provided at each of the upper and lower ports of the separation connection device 15, and a filter screen 161 is provided at the outer end of the two one-way valves 16.

[0055] Understandably, the design of the one-way valve 16 ensures that gas or liquid can only flow in one direction, thus preventing water from flowing back into the borehole during drainage. The filter screen 161 installed at the outer end of the one-way valve 16 controls and prevents impurities or particles from entering the separation connection device from inside or outside the borehole, thus preventing them from affecting the normal operation of the one-way valve or causing blockage. The filter screen 161 effectively filters out these impurities or particles, ensuring the cleanliness and unobstructed flow inside the separation connection device 15.

[0056] In some embodiments, the number of separation connection devices 15 is determined according to the length of the curved directional long borehole;

[0057] Specifically, if the borehole is long, more separation and connection devices 15 need to be installed in the borehole to ensure that the inner extraction pipe 141 and the outer nitrogen injection pipe 142 can maintain stable connection and connection throughout the entire borehole length, while ensuring the efficiency of extraction and nitrogen injection operations. If the borehole is short, the number of separation and connection devices 15 can be reduced accordingly.

[0058] In some embodiments, the end of the internal extraction pipe 141 located inside the borehole is in a closed state; thus, the water pumped by the negative pressure extraction module 11 into the borehole is all through a one-way valve, improving drainage efficiency.

[0059] Understandably, when the negative pressure extraction module 11 starts working, it creates a negative pressure environment inside the borehole. Because the pipe head is sealed, water in the borehole can only enter the pipeline through a pre-installed one-way valve. This effectively prevents fluid backflow or the entry of external impurities into the borehole. Since water can only enter the inner extraction pipe 141 through the one-way valve, the unidirectional and stable flow of fluid is ensured, reducing the risk of reduced extraction efficiency or equipment damage due to fluid backflow or impurities, and improving drainage efficiency.

[0060] In some embodiments, the density of nitrogen injection ports on the external nitrogen injection pipe 142 gradually increases in the direction from the outside to the inside of the borehole. That is, as the borehole depth increases, the distance between the nitrogen injection ports becomes shorter and shorter, and the nitrogen injection ports are arranged more and more densely.

[0061] Understandably, nitrogen pressure gradually decreases as it flows through a pipeline. If the nitrogen injection ports are unevenly distributed, especially if there are insufficient ports at deeper boreholes, the furthest ports may not be able to effectively inject nitrogen into the borehole due to insufficient pressure, thus affecting nitrogen displacement throughout the entire borehole area. Increasing the density of nitrogen injection ports through components can homogenize the nitrogen injection density throughout the borehole, thereby improving the effectiveness of nitrogen displacement operations.

[0062] In some embodiments, the nitrogen injection port can take any same or different shape, such as conical, circular, trumpet-shaped or other shapes that can increase the nitrogen diffusion area and velocity, thereby improving the uniformity and coverage of nitrogen distribution in the borehole.

[0063] In some embodiments, a high-pressure nitrogen injection shut-off valve 51 and a negative-pressure extraction shut-off valve 52 are provided between the multi-effect collaborative pipeline 14 and the intelligent control module 13 (see...). Figure 5 (As shown).

[0064] Among them, the high-pressure nitrogen injection shut-off valve 51 is used to control the flow and stop of high-pressure nitrogen in the external nitrogen injection pipe 142, and the negative pressure extraction shut-off valve 52 is used to control the flow and stop of water or gas in the internal extraction pipe 141.

[0065] Specifically, when the negative pressure extraction module 11 is working, the intelligent control module 13 can automatically control the high pressure nitrogen injection 51 shut-off valve to close and the negative pressure extraction shut-off valve 52 to open; when the high pressure nitrogen injection module is working, the intelligent control module 13 can automatically control the high pressure nitrogen injection shut-off valve 51 to open and the negative pressure extraction shut-off valve 52 to close.

[0066] In some embodiments, when the multi-effect synergistic pipeline 14 is arranged in a curved directional long borehole, the borehole opening needs to be sealed. The borehole sealing section is arranged between the elastic zone and the original stress zone within the stress concentration zone.

[0067] Understandably, in order to ensure effective nitrogen injection and stable gas extraction, and to prevent unnecessary exchange of gas or liquid inside and outside the borehole, it is necessary to perform strict sealing treatment at the borehole opening, which is crucial for maintaining the stability and safety of the borehole's internal environment.

[0068] For example, to achieve borehole sealing, the existing "two-plug-one-injection" sealing method can be used. The core of this method lies in placing two sealing plugs (usually called "plugs") at specific locations within the borehole, forming a closed space between them—the sealing section. This sealing section is positioned between the elastic zone and the original stress zone within the stress concentration area to ensure optimal borehole sealing. Specifically, the first plug is typically placed near the borehole opening, its main function being to initially prevent external gas or liquid from entering the borehole. The second plug is placed at a certain distance from the first plug, forming a relatively closed area. Within this area, a special sealing material (such as cement grout, polyurethane foam, etc.) can be injected into the borehole using grouting equipment. After curing, this material forms a strong and dense sealing layer, further preventing gas leakage and exchange. By arranging the sealing section between the elastic zone and the original stress zone within the stress concentration area, the stress state of the rock strata is relatively stable and not easily disturbed by external factors. This provides a good curing environment for the sealing material, ensuring the durability and reliability of the sealing effect.

[0069] For example, see also [link / reference] Figure 5 As shown, Figure 5 This is a schematic diagram of the borehole sealing position in an embodiment of the present invention. 53 represents the coal seam fracture zone, 54 is a double-plug-one-injection bag used to achieve sealing using the "double-plug-one-injection" method, and 55 is a nitrogen injection port located on the external nitrogen injection pipe 142.

[0070] It should be noted that the coal seam at the borehole opening usually has a fractured zone of a certain depth, such as... Figure 5 The coal seam fracture zone 53 shown is typically accompanied by numerous fissures and faults. These fissures are not only numerous but also widely distributed. The presence of these fissures severely compromises the integrity of the formation, creating channels for gas and liquid flow. Due to the development of these fissures, the permeability of the coal seam fracture zone 53 is usually very high. This means that gas or liquid inside and outside the borehole can easily exchange through these fissures, increasing the difficulty of borehole sealing. Therefore, when sealing the borehole, it is necessary to avoid areas such as... Figure 5 The fracture zone 53 region shown is selected between the elastic zone and the original stress zone within the stress concentration zone as described above.

[0071] In some embodiments, a sensor is provided at the end of the multi-effect co-operation pipeline 14 for real-time monitoring of pressure and concentration data inside the borehole;

[0072] The intelligent control module 13 can determine whether to perform nitrogen re-injection or drainage operations based on the monitored pressure and concentration data.

[0073] Specifically, if the intelligent control module 13 detects that the extracted gas concentration is reduced or the concentration distribution is uneven, or the nitrogen concentration in the borehole is reduced or the pressure distribution is uneven, it indicates that the nitrogen displacement effect may be weakened. At this time, the intelligent control module 13 will promptly trigger the re-injection of nitrogen to ensure that nitrogen can continuously and effectively displace the gas from the coal seam.

[0074] In some embodiments, curved directional long boreholes may include multiple boreholes. For example Figure 6 As shown, Figure 6 This is a schematic diagram of another integrated control system for a curved directional long borehole targeting a coal seam, according to an embodiment of the present invention. See also... Figure 6 As shown, the target coal seam includes three curved directional long boreholes 17 (where the boreholes are actually curved in practical applications, but are represented by straight lines in the illustration for ease of representation). Each borehole contains a multi-effect coordinating pipeline 14 as described above. A connecting regulator 62 is installed between the end 61 of each multi-effect coordinating pipeline 14 and the intelligent control module 13. During water drainage, nitrogen injection displacement, and gas extraction operations, the intelligent control module 13 can control the connecting regulator 62 to change the connection point with the end 61, thereby enabling gas extraction in each borehole.

[0075] In some embodiments, the intelligent control module 13 determines whether to perform renitrogen injection or re-drainage operations based on pressure and concentration data monitored by sensors. Alternatively, it can determine which borehole requires renitrogen injection or re-drainage operations separately.

[0076] Specifically, the intelligent control module 13 determines whether the extraction effect has deteriorated and whether nitrogen injection should be performed again based on the real-time pressure and concentration data detected by the sensors at the end 61 of the multi-effect co-operation pipeline 14. When the number of boreholes with deteriorating extraction effect is 0, it indicates that no secondary nitrogen injection displacement operation is needed for any borehole, and no adjustment of the connection regulator 62 is required. When the number of boreholes with deteriorating extraction effect is 1, it indicates that one borehole requires secondary nitrogen injection displacement operation. In this case, the connection regulator 62 is adjusted to connect the high-pressure nitrogen injection module 12 to the end 61 of the multi-effect co-operation pipeline 14 in the corresponding borehole. When the number of boreholes with deteriorating extraction effect is greater than 1, it indicates that multiple boreholes require secondary nitrogen injection displacement operation, and the connection regulator 62 needs to be adjusted sequentially to connect the end 61 of the multi-effect co-operation pipeline 14 in the corresponding borehole. The principle of "heavy first, light last" can be adopted simultaneously, first connecting the multi-effect co-operation pipeline 14 in the borehole with the worst extraction effect, and then connecting the multi-effect co-operation pipeline 14 in the other boreholes in sequence.

[0077] In some embodiments, the connection regulator 62 is also used to indirectly achieve the effect of pulsed nitrogen injection during nitrogen displacement operations.

[0078] For details, see Figure 6 As shown, the connection regulator 62 can periodically or randomly select the end 61 to establish a connection relationship among the three multi-effect coordinating pipelines 14 according to a preset program or according to the instructions transmitted by the intelligent control module 13, so that nitrogen gas is injected into the borehole and coal seam in the form of pulses.

[0079] Under the influence of nitrogen pulses, the pores and fractures in the coal seam are forced to undergo a dynamic process of expansion-contraction-re-expansion-re-contraction. This periodic stress change leads to fatigue damage within the coal seam, which in turn promotes the interconnection of internal pores and the development, expansion, and formation of new fractures. These changes significantly improve the gas transport channels and reduce the transport resistance of mixed gas, thereby accelerating the diffusion and seepage rate of coal gas and achieving a considerable effect in promoting gas drainage / extraction. Furthermore, pulsed nitrogen injection also helps to achieve a uniform distribution of nitrogen in the coal seam. By periodically injecting nitrogen, local accumulation of nitrogen in the coal seam can be avoided, ensuring that nitrogen can fully contact and effectively displace the gas in the coal seam. This uniform nitrogen distribution not only improves the displacement efficiency but also shortens the displacement time.

[0080] Secondly, embodiments of the present invention also provide a comprehensive management and control method for a target coal seam with curved directional long boreholes, which can be applied to the comprehensive management and control system for a target coal seam with curved directional long boreholes provided in the first aspect. Figure 7 This is a schematic flowchart of an embodiment of a comprehensive control method for curved directional long boreholes in a target coal seam according to an invention. See also... Figure 7 As shown, the above method may include:

[0081] S701, based on the preset nitrogen injection displacement flow enhancement and pumping target, the coal and rock strata strike and occurrence conditions of the target working face, and the performance of the directional drilling equipment, a curved directional long borehole trajectory is designed.

[0082] Among these, clearly defined pre-set nitrogen injection displacement and flow enhancement targets form the basis of the entire design process. These targets include specific indicators such as the desired gas extraction volume, the degree of gas concentration reduction, and the effectiveness of nitrogen injection displacement. These targets directly guide the design of the borehole trajectory, ensuring that the borehole accurately targets the coal seam and achieves the expected gas extraction effect.

[0083] The strike and occurrence conditions of the coal and rock strata at the target working face are crucial factors that must be considered when designing the borehole trajectory. The dip angle, thickness, joint development, and geological structure of the coal and rock strata directly affect the drilling difficulty and gas extraction efficiency. Therefore, during the design process, it is necessary to fully understand the geological conditions of the target working face and conduct a comprehensive analysis based on the actual situation to determine the optimal borehole trajectory.

[0084] Furthermore, the performance of the directional drilling equipment is also an indispensable factor when designing the drilling trajectory. The equipment's drilling capacity, guiding accuracy, and stability directly affect the quality and efficiency of the drilling. Therefore, when designing the drilling trajectory, it is necessary to fully consider the performance characteristics of the equipment to ensure that the drilling trajectory can be achieved within the equipment's capabilities and to maximize construction efficiency and quality as much as possible.

[0085] Taking all the above factors into account, when designing a curved directional long borehole trajectory, scientific methods and means, such as geological exploration, numerical simulation, and optimization design, should be adopted to ensure that the borehole trajectory can meet the preset nitrogen injection displacement flow enhancement and pumping target.

[0086] S702, drilling is carried out according to the designed modular curved directional long drilling trajectory. After drilling is completed, the modular multi-effect collaborative pipeline is arranged in the long borehole.

[0087] In some embodiments, the multi-effect co-operating pipeline can be pre-placed inside the drill pipe. During drilling, the multi-effect co-operating pipeline can enter the curved directional borehole synchronously with the drill pipe. After drilling is completed, the drill pipe and drill bit are removed, leaving the multi-effect co-operating pipeline inside the borehole. This greatly simplifies the construction process and avoids the complexity and potential risks of installing pipelines after drilling is completed.

[0088] In other embodiments, multi-effect co-location piping can also be installed within the borehole after the curved directional long borehole construction is completed. Understandably, although this approach requires additional construction steps and may face greater technical challenges compared to synchronously built-in piping, it offers flexibility in handling special terrain, adjusting piping layout, or responding to emergencies.

[0089] It should be noted that laying pipelines after drilling requires additional construction work, and laying pipelines inside the borehole is quite difficult. Therefore, in a preferred embodiment of the present invention, the multi-effect synergistic pipeline can be directly and synchronously introduced into the borehole along with the drill rod and drill bit.

[0090] S703, sealing the borehole between the elastic zone and the original stress zone in the stress concentration area;

[0091] Specifically, the "two-plug-one-injection" method described above can be used. After each borehole is drilled, it is immediately sealed with casing, using materials such as expansive cement. The sealing length can be determined based on experience, for example, not less than 30m. Using the "two-plug-one-injection" sealing method, the sealing sections of the boreholes are arranged between the elastic zone of the stress concentration area and the original stress zone. A pressure gauge is used to measure the pressure inside the borehole, and the integrity of the airtightness is checked.

[0092] S704: Open the negative pressure extraction shut-off valve, close the high-pressure nitrogen injection shut-off valve, start and control the negative pressure extraction module to discharge the water accumulated in the borehole through the internal extraction pipe; when the water pumping is completed according to the flow data of the internal extraction pipe, close the negative pressure extraction module, close the negative pressure extraction shut-off valve, open the high-pressure nitrogen injection shut-off valve, start and control the high-pressure nitrogen injection module to perform nitrogen injection and displacement operations through the external nitrogen injection pipe; after the nitrogen injection and displacement operations reach the preset conditions, close the high-pressure nitrogen injection module, open the negative pressure extraction shut-off valve, close the high-pressure nitrogen injection shut-off valve, start and control the negative pressure extraction module to perform gas extraction operations through the internal extraction pipe, realizing integrated management and control of water discharge, nitrogen injection and displacement, and gas extraction in the depression of the curved directional long borehole.

[0093] For example, the state changes of the multi-effect synergistic pipeline during the processes of water drainage, nitrogen injection displacement, and gas extraction using the aforementioned integrated control method for curved directional long boreholes in the target coal seam can be seen in [reference needed]. Figures 8 to 11 As shown, where, Figure 8 This is a schematic diagram of the structure at the start of the multi-effect synergistic pipeline pumping process in an embodiment of the present invention; see also Figure 8 As shown, the water accumulated in the borehole enters the inner extraction pipe 141 through the one-way valve 16. Figure 9 This is a schematic diagram of the multi-effect synergistic pipeline pumping process in an embodiment of the present invention; see also Figure 9 As shown, the accumulated water is pumped out through the internal extraction pipe 141.

[0094] Figure 10 This is a schematic diagram of the multi-effect synergistic pipeline nitrogen injection displacement process in an embodiment of the present invention; see also Figure 10 As shown, nitrogen gas enters the borehole from the nitrogen injection port 55 of the external nitrogen injection pipe 142, thereby displacing the gas in the coal seam.

[0095] Figure 11 This is a schematic diagram of the multi-effect synergistic pipeline gas extraction process in an embodiment of the present invention. See also... Figure 10 As shown, after the nitrogen injection displacement is completed, the gas extraction also enters the inner extraction pipe 141 through the one-way valve 16, and is then extracted through the inner extraction pipe 141.

[0096] In some embodiments, the nitrogen injection displacement operation reaching the preset conditions can be achieved by allowing the nitrogen to remain in the coal seam for a period of time after the nitrogen injection displacement operation is completed, so that nitrogen can fully exert its displacement effect in the coal seam and release as much gas as possible from the coal seam. Alternatively, the nitrogen injection displacement operation reaching the preset conditions can also be achieved by directly detecting the gas concentration in the flowing state. When the gas concentration in the flowing state reaches the preset value, gas extraction can then be carried out.

[0097] The purpose of achieving the preset conditions during nitrogen injection displacement is primarily to determine whether nitrogen injection displacement is complete, serving as a criterion for determining whether gas extraction can proceed. The selection of these preset conditions does not limit the scope of protection of this invention; therefore, this embodiment of the invention does not specifically limit them.

[0098] It should be noted that the specific execution process and functions of the integrated management and control method for curved directional long boreholes in target coal seams can be found in the description of the functions of each module in the integrated management and control system for curved directional long boreholes in target coal seams. This embodiment of the invention will not elaborate on these details.

[0099] In this embodiment of the invention, the multi-effect synergistic pipeline is applicable to most curved long boreholes, flexibly adapting to various complex and changing geological environments. It ensures efficient implementation of nitrogen injection and drainage projects regardless of whether the borehole is winding or facing extreme geological challenges, thus meeting the diverse needs of geological exploration and engineering implementation. Furthermore, it avoids the need for additional branch boreholes in traditional curved directional long borehole drainage operations, reducing potential damage to geological structures and effectively improving overall construction efficiency. By reducing unnecessary drilling operations, it not only protects the natural state of underground resources but also promotes the practice of environmentally friendly construction concepts. Moreover, the multi-effect synergistic pipeline first performs drainage operations in the depressions of the internal extraction pipe, then nitrogen injection and displacement operations in the external nitrogen injection pipe, and finally gas extraction operations in the internal extraction pipe, achieving integrated management of drainage of accumulated water in depressions, nitrogen injection and displacement, and gas extraction within the same borehole and pipeline. The multi-effect drilling operation approach solves the problem of wasted time caused by the traditional method of first laying out water pumping pipelines and then nitrogen injection pipelines, greatly shortening the overall construction cycle of the project. By efficiently integrating construction steps, it not only significantly reduces the time spent on construction equipment but also effectively optimizes resource allocation, further reducing construction costs and improving the project's economic benefits. Furthermore, through the linkage between the intelligent control module and the connecting regulator, pulsed nitrogen injection can be indirectly achieved, improving gas extraction efficiency. The multi-functional integration of the integrated management and control system for water drainage, nitrogen injection displacement, and gas extraction reduces manual operation time and the time that downhole workers are exposed to potentially hazardous environments, thereby effectively reducing the risk of accidents during operations.

[0100] The various embodiments in this specification are described in a progressive manner. For the same or similar parts between the various embodiments, please refer to each other. Each embodiment focuses on describing the differences from other embodiments.

[0101] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit this application. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of this application.

Claims

1. A comprehensive control system for curved directional long boreholes targeting coal seams, characterized in that, include: Negative pressure extraction module, high-pressure nitrogen injection module, intelligent control module, and multi-effect collaborative pipeline; The multi-effect synergistic pipeline is arranged within a curved directional long borehole, including an inner inner extraction pipe and an outer external nitrogen injection pipe. The inner extraction pipe is used to extract water and perform gas extraction within the borehole, while the external nitrogen injection pipe is used to inject nitrogen into the borehole. The curved directional long borehole is designed based on a preset nitrogen injection displacement flow enhancement and extraction target, the coal and rock formation occurrence conditions of the target working face, and the performance of the directional drilling equipment. The inner extraction pipe and the external nitrogen injection pipe are connected by a separation connection device, the number of which is determined by the length of the curved directional long borehole. The main body of the separation connection device is a double-sleeved venting pipe, with a one-way valve at each of the upper and lower ports, and filters installed at the outer ends of the two one-way valves. The negative pressure extraction module is used to generate a negative pressure environment and to extract water and gas from the borehole through the inner extraction pipe. The high-pressure nitrogen injection module is used to provide high-pressure nitrogen and inject nitrogen into the borehole through the external nitrogen injection pipe to achieve the displacement effect of nitrogen and enhance the gas flowability in the target coal seam. The intelligent control module is connected to the negative pressure extraction module, the high-pressure nitrogen injection module, and the multi-effect collaborative pipeline, respectively, and is used to intelligently control the working status of the negative pressure extraction module and the high-pressure nitrogen injection module. The specific process of intelligent control includes: first, starting and controlling the negative pressure extraction module to extract water from the borehole through the inner extraction pipe, and shutting down the negative pressure extraction module after the water extraction is completed; then, starting and controlling the high-pressure nitrogen injection module to perform nitrogen injection and displacement operations through the outer nitrogen injection pipe, and shutting down the high-pressure nitrogen injection module after the nitrogen injection and displacement operations reach the preset conditions; finally, starting and controlling the negative pressure extraction module again to extract gas from the borehole through the inner extraction pipe, thereby realizing integrated management and control of water discharge, nitrogen injection and displacement, and gas extraction in the curved directional long borehole depression.

2. The integrated control system according to claim 1, characterized in that, A high-pressure nitrogen injection shut-off valve and a negative-pressure extraction shut-off valve are installed between the multi-effect collaborative pipeline and the intelligent control module. The high-pressure nitrogen injection shut-off valve is used to control the flow and stop of high-pressure nitrogen in the external nitrogen injection pipe, and the negative-pressure extraction shut-off valve is used to control the flow and stop of water or gas in the internal extraction pipe. When the negative-pressure extraction module is working, the high-pressure nitrogen injection shut-off valve is closed and the negative-pressure extraction shut-off valve is open. When the high-pressure nitrogen injection module is working, the high-pressure nitrogen injection shut-off valve is open and the negative-pressure extraction shut-off valve is closed.

3. The integrated control system according to claim 2, characterized in that, The multi-effect collaborative pipeline is equipped with a sensor at its end for real-time monitoring of pressure and concentration data within the borehole; the intelligent control module determines whether to perform re-nitrogen injection or re-drainage operations based on the monitored pressure and concentration data.

4. The integrated control system according to claim 3, characterized in that, The curved directional long boreholes include multiple boreholes, and the multi-effect synergistic pipeline is arranged in each borehole; A connection regulator is provided between the multiple multi-effect collaborative pipelines and the intelligent control module. The intelligent control module can control the connection regulator to realize the replacement of the connection point with each of the multi-effect collaborative pipeline ends.

5. The integrated control system according to claim 4, characterized in that, The connection regulator is also used to indirectly achieve the effect of pulsed nitrogen injection during nitrogen displacement operations.

6. The integrated control system according to claim 5, characterized in that, The head of the internal extraction pipe is in a closed state; the density of nitrogen injection ports on the external nitrogen injection pipe gradually increases from the outside to the inside of the borehole.

7. The integrated control system according to claim 6, characterized in that, The sealing section of the curved directional long borehole is arranged between the elastic zone and the original stress zone of the stress concentration area.

8. A comprehensive control method for a target coal seam curved directional long borehole, applied to the comprehensive control system described in any one of claims 2 to 7, characterized in that, include: Based on the preset nitrogen injection displacement flow enhancement and pumping target, the coal and rock strata strike and occurrence conditions of the target working face, and the performance of the directional drilling equipment, a curved directional long borehole trajectory is designed. Drilling is carried out according to the designed curved directional long borehole trajectory. After drilling is completed, the multi-effect synergistic pipeline is arranged in the long borehole. The borehole is sealed between the elastic zone and the original stress zone in the stress concentration area; Open the negative pressure extraction shut-off valve, close the high-pressure nitrogen injection shut-off valve, start and control the negative pressure extraction module to discharge the accumulated water in the borehole through the inner extraction pipe; when the water pumping is completed according to the flow data of the inner extraction pipe, close the negative pressure extraction module, close the negative pressure extraction shut-off valve, open the high-pressure nitrogen injection shut-off valve, start and control the high-pressure nitrogen injection module to perform nitrogen injection displacement operation through the outer nitrogen injection pipe; after the nitrogen injection displacement operation reaches the preset conditions, close the high-pressure nitrogen injection module, open the negative pressure extraction shut-off valve, close the high-pressure nitrogen injection shut-off valve, start and control the negative pressure extraction module to perform gas extraction operation through the inner extraction pipe, realizing integrated management and control of water discharge, nitrogen injection displacement, and gas extraction in the depression of the curved directional long borehole.

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