Drilling structure and drilling system suitable for carbonate rock stratum

Abstract

The utility model discloses a drilling structure suitable for a carbonate rock stratum and a drilling system. The drilling structure and the drilling system aim at solving the technical problems that an existing drilling structure for the carbonate rock stratum is unstable, and drill jamming and drill burning are easily caused. The drilling structure comprises a covering layer hole body, a carbonate rock stratum hole body, a wall protecting sleeve and a wall protecting floral tube. The drilling system comprises a drilling machine, a mud pit, a clean water pool, a mud pump, a filter and a water pressure sensor, wherein the mud pit and the clean water pool are arranged on the ground; the filter is arranged at the connecting position of the drill rod and the drill bit; according to the drilling structure and the drilling system, reliable and safe drilling of the exploration drilling hole in the carbonate rock stratum can be achieved, clear water replaces mud, the construction cost can be reduced, the adverse effect on the original stratum environment is reduced, and the accuracy and credibility of geological exploration data are ensured.

Description

Technical Field

[0001] The present application relates to the technical field of mineral resource exploration, and in particular to a drilling structure and a drilling system suitable for carbonate rock formations. Background Art

[0002] Carbonate rocks are primarily formed by carbonate minerals such as calcite and dolomite through long periods of sedimentation, solidification, and chemical reactions under specific geological conditions. Carbonate rocks themselves are valuable minerals and often coexist with many solid sedimentary mineral deposits. Their reservoirs primarily consist of pores and fractures. Numerous fractures often develop within carbonate formations, potentially caused by various factors such as tectonic movement, groundwater activity, and rock weathering. These fractures provide crucial pathways for the storage and transport of mineral resources. Karstification refers to the dissolution and erosion of soluble rocks (such as carbonates) by groundwater. Karstification is particularly pronounced in carbonate formations with developed fractures. The karst landforms and caves formed by karstification not only provide important clues and indicators for mineral exploration and development but may also directly serve as mineral storage spaces.

[0003] However, the cracks, caves and karst crevices developed in the carbonate rock formations result in good water conductivity in the formation and large local underground space. When conventional mud circulation drilling is used for exploration drilling, due to the presence of cracks, karst crevices and caves in the carbonate rock formations, circulating mud leakage often occurs during drilling construction in such formations, and the leakage speed is fast and the penetration volume is large. On the one hand, the leakage of mud will lead to increased mud usage and increased construction costs; on the other hand, due to the good water conductivity of the carbonate rock formation, the leaked mud has a long penetration distance and is eventually retained in the rock voids, resulting in blockage of the water conduction channel and affecting the original natural state of the formation, thereby causing the hydrogeological parameters obtained by drilling to be inconsistent with the actual situation of the original formation. Furthermore, because the mud cannot be circulated to the surface mud pool, it cannot carry cuttings. The accumulation of cuttings in the borehole can easily lead to drill sticking. Heat generated during drilling accumulates at the drill bit and cannot be dissipated with mud circulation, creating the risk of drill burning at the bottom of the hole. Drilling into fractured zones in carbonate formations can also lead to hole collapse, hampering the normal drilling of the exploration hole.

[0004] The information disclosed in this background technology section is only used to deepen the understanding of the background technology of the present disclosure and should not be regarded as an admission or any form of suggestion that the information constitutes the prior art known to those skilled in the art. Summary of the Invention

[0005] In view of at least one of the above technical problems, the present disclosure provides a drilling structure and a drilling system suitable for carbonate formations, aiming to solve the technical problems that the existing drilling structure in carbonate formations is unstable and easily causes drill sticking and burning.

[0006] According to one aspect of the present disclosure, a drilling structure suitable for carbonate rock formations is provided, which includes a covering layer hole body drilled in a loose covering layer above the carbonate rock formation, a carbonate rock layer hole body drilled coaxially with the covering layer hole body in the carbonate rock formation, a wall protection casing arranged in contact with the covering layer hole body, and a wall protection flower pipe arranged at the hole wall of the carbonate rock layer hole body within the fracture zone; a plurality of water-permeable holes are opened in a corresponding array on the pipe wall of the wall protection flower pipe.

[0007] In some embodiments of the present disclosure, the diameter of the pores in the covering layer is greater than the diameter of the pores in the carbonate rock layer, and the junction between the pores in the covering layer and the pores in the carbonate rock layer is correspondingly step-shaped.

[0008] In some embodiments of the present disclosure, the diameter of the water-permeable holes is 8-12 mm, and the hole spacing is 280-320 mm.

[0009] According to another aspect of the present disclosure, a drilling system suitable for carbonate rock formations is provided for implementing the above-mentioned drilling structure, which includes a drilling rig for drilling the overburden layer pores and the carbonate rock layer pores and including a drill rod and a drill bit, a mud pool and a clean water pool provided on the ground, a mud pump for extracting mud or clean water from the mud pool or the clean water pool respectively and pumping it into the drill rod, a filter provided at the connection position of the drill rod and the drill bit for filtering water when drilling the carbonate rock layer pores, and a water pressure sensor fixed at the connection position of the drill rod and the drill bit.

[0010] In some embodiments of the present disclosure, the drilling system further includes a groundwater level observation meter for monitoring the water level in the hole during the drilling process of the carbonate rock formation hole.

[0011] In some embodiments of the present disclosure, the clean water storage in the clean water tank satisfies the clean water supply flow rate of not less than 60.0m 3 / h.

[0012] In some embodiments of the present disclosure, the filter includes a backwash module.

[0013] One or more technical solutions provided in the embodiments of this application have at least the following technical effects or advantages:

[0014] 1. The wall casing can stabilize the overburden hole body and avoid the collapse of the hole wall. The step at the junction of the overburden hole body and the carbonate rock layer hole body can support the wall casing and prevent the leakage of cement.

[0015] 2. While effectively supporting the pore walls of the carbonate rock formation within the fracture zone, the wall-protecting flower pipe can ensure the water permeability of the pore bodies of the carbonate rock formation within the fracture zone through the array of water-permeable holes on its pipe wall, thereby avoiding affecting the diffusion of rock debris and heat carried by clean water.

[0016] 3. During the drilling process of carbonate rock formations, replacing the mud in the mud pool with clean water from the clean water pool can effectively avoid the increase in construction costs and geological environmental pollution caused by large-scale leakage of mud in the carbonate rock formation. At the same time, only the mud pump inlet pipeline needs to be switched, and there is no need to significantly modify the drilling system, which can improve construction convenience and efficiency.

[0017] 4. The groundwater level observation meter can be used to observe the head height of clean water in the pores of carbonate rock formations, thereby ensuring that the head height of clean water is at a high groundwater level, thereby ensuring that the clean water can carry the rock debris and spread smoothly to the surrounding formations. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of a drilling structure in one embodiment of the present application.

[0019] Figure 2 Schematic diagram of the structure of a borehole drilling system in one embodiment of the present application.

[0020] In the above figures, 11 is a loose covering layer, 12 is a carbonate rock layer, 13 is a broken zone, 2 is a covering layer hole, 3 is a wall casing, 4 is a carbonate rock layer hole, 5 is a wall casing, 6 is a drilling rig, 61 is a drill pipe, 62 is a drill bit, 7 is a clear water tank, 8 is a mud pump, and 9 is a filter. DETAILED DESCRIPTION

[0021] In the description of the present application, it should be understood that the terms "up", "down", "front", "back", "left", "right", "top", "bottom", "inside", "outside", "vertical", "horizontal", "clockwise", "counterclockwise", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0022] In order to better understand the technical solution of the present application, the above technical solution will be described in detail below with reference to the accompanying drawings and specific implementation methods.

[0023] This example uses a geothermal drilling hole for feasibility exploration of geothermal resources in a section of the Liaolan Fault as an example to disclose a drilling structure suitable for carbonate rock formations. Figure 1The designed borehole depth is 2150m. The upper loose overburden 11 is 1085m thick. The bedrock beneath the loose overburden is Ordovician limestone with well-developed fractures and karst. To ensure the stability of the borehole structure and accurately detect hydrogeological information related to geothermal resources, in this embodiment, the borehole structure includes an overburden hole 2 drilled within the upper loose overburden 11 of the carbonate rock formation. In order to ensure the stability of the covering layer hole body 2 and to avoid problems such as hole collapse during drilling, in this example, a wall protection casing 3 is set under the covering layer hole body 2, wherein the diameter of the wall protection casing 3 matches the diameter of the covering layer hole body 2, and the outer wall of the wall protection casing 3 is filled with cementing cement between the loose covering layer soil. The cementing cement seals the borehole mouth and maintains the stability of the hole wall, and can effectively isolate the formation liquid to prevent the liquid in the formation from escaping to the ground. At the same time, it can also provide support for the wall protection casing 3 to ensure the stability and safety of the casing.

[0024] In this embodiment, the overburden hole 2 is drilled using a mud-walled positive circulation rotary drilling method. Since the carbonate stratum has cracks and karst, its water conductivity is relatively good. When obvious slurry leakage occurs during the drilling of the overburden hole 2, it means that the current drill bit has drilled into the carbonate stratum. If mud is used as the drilling circulation fluid, a large amount of mud will be lost. The lost mud will spread into the stratum and affect the original stratum environment. For this reason, see Figure 1 The borehole also includes a carbonate rock formation body 4 drilled within the carbonate rock formation, with the central axis of the carbonate rock formation body 4 being collinear with the central axis of the overburden layer body 2. In this embodiment, during the drilling of the carbonate rock formation body 4, clean water is used instead of mud to carry rock debris and diffuse into the surrounding strata. The diameter of the carbonate rock formation body 4 is smaller than that of the overburden layer body 2, and the junction between the carbonate rock formation body 4 and the overburden layer body 2 is correspondingly stepped. As a result, the retaining wall casing 3 in the overburden layer body 2 can be placed on this step, providing support for the retaining wall casing 3 and preventing the retaining wall casing 3 from shifting relative to the overburden layer body 2 during the drilling of the carbonate rock formation body 4, thereby affecting the structural stability of the overburden layer body 2. In addition, the step at the junction of the carbonate rock formation body 4 and the overburden layer body 2 can also block the cement outside the retaining wall casing 3, preventing the loss of a large amount of cement, which would increase construction costs and affect the drilling of the carbonate rock formation body.

[0025] Due to the presence of a fracture zone in the carbonate rock layer, problems such as hole collapse may occur during the drilling of the carbonate rock layer hole body 4, affecting the normal hole body structure construction. Figure 1A wall protection pipe 5 is provided at the location of the broken zone in the carbonate rock formation; specifically, in order to prevent the wall protection pipe 5 from affecting the transportation of drill cuttings by clean water, a number of water-permeable holes are evenly arrayed on the wall of the wall protection pipe 5, the aperture of the water-permeable holes is 8-12 mm, and the hole spacing is 280-320 mm. In this embodiment, the aperture of the water holes is 10 mm and the hole spacing is 300 mm. Therefore, on the one hand, the pipe body of the wall-protecting flower tube 5 can support the structure of the broken zone to avoid problems such as collapse; on the other hand, the water holes arranged in an array on the wall of the wall-protecting flower tube 5 can ensure good water permeability and avoid adverse effects on the water permeability of the carbonate rock layer pore body, thereby allowing the use of clean water as a drilling medium during the drilling process to carry away the rock debris and heat generated during the drilling process; according to the specific geological information of the broken zone, the aperture and hole spacing of the water holes are reasonably selected to avoid the aperture being too small and affecting the permeability required for normal drilling, and to avoid the aperture being too large, where a large amount of gravel on the hole wall within the broken zone falls into the borehole and affects the drilling of the drill tool, and even causes the problem of drill stuck.

[0026] In addition, this example also discloses a drilling system suitable for carbonate rock formations, which is used for drilling the above-mentioned drilling structure. Figure 2 It includes a drilling rig 6 placed on the ground, which includes a drill rod 61 and a drill bit 62 installed at the end of the drill rod 61. In this embodiment, the drill bit adopts a three-cone drill bit, and the drilling rig is used to realize the drilling of the overburden layer hole 2 and the carbonate rock layer hole 4.

[0027] In this embodiment, when drilling the overburden hole 2 in the loose overburden layer above the carbonate rock layer, a mud pool is set up on the ground because of the positive circulation of mud wall protection. The mud pool is used as the circulating fluid, which is transported to the drill pipe through a mud pump and circulated back to the mud pool after being discharged from the drill bit. During the mud circulation process, the mud carries the rock debris and drill bit heat generated by drilling at the bottom of the hole during drilling and returns to the mud pool. After sedimentation treatment, the mud is recycled. However, when facing carbonate rock formations, due to the development of cracks and karst in the carbonate rock formation, a large amount of mud will be lost. For this reason, in this embodiment, a clear water pool is dug on the ground and connected to a clear water source. Clear water is stored in the clear water pool. In this embodiment, the clear water reserve in the clear water pool satisfies the clear water supply flow rate of not less than 60.0m 3 When a large amount of mud is lost during drilling of the overburden hole 2, it means that the drilling has reached the carbonate layer. Figure 2, switch the mud to clean water, extract clean water from the clean water pool 7 through the mud pump 8, and transport it to the drill pipe 61 through the pipeline. The clean water in the drill pipe 61 is discharged from the drill bit as the drill bit 62 drills, replacing the mud to carry the rock slag and heat. The difference is that the clean water can directly utilize the good water conductivity of the carbonate rock formation to carry the rock slag to the surrounding formations without causing damage or pollution to the surrounding geological environment. It only uses clean water sources, and the cost is lower than that of mud construction.

[0028] Among them, in order to prevent rock debris from flowing back into the drill pipe and clogging the drill pipe, in this embodiment, a filter 9 is provided at the connection position of the drill bit 62 and the drill pipe 61, wherein the filter mesh diameter of the filter is 1 to 1.5 mm. And in order to monitor the water pressure at the bottom of the hole, in this embodiment, a water pressure sensor is also provided at the connection position of the drill bit 62 and the drill pipe 61, and the filter 9 includes a backwash module. The pressure value of the water pressure sensor is used to determine whether there is a blockage problem at the filter, and the backwash module is activated accordingly to perform a backwash operation on the filter. In some other embodiments, in order to clean the clogged drill debris, the rock debris is discharged by lifting the drill bit and shaking it.

[0029] In addition, considering that the water in the formation has a certain pressure, in order to ensure that the clean water can effectively carry the drilling cuttings and diffuse into the surrounding formations, in this embodiment, during the drilling process of the carbonate rock formation hole body 4, a groundwater level observation meter is placed in the carbonate rock formation hole body 4 to achieve the observation of the water level in the hole. In this embodiment, during the drilling process of the carbonate rock formation hole body 4, the mud pump 8 is regulated so that the water supply speed is 45.0 m 3 / h or so, and through the groundwater level observation meter, ensure that the clean water level in the carbonate rock layer hole 4 is at least 2.0m higher than the normal groundwater level, that is, maintain a head height of 2.0m for the clean water in the hole, so that the clean water carrying rock debris can smoothly diffuse to the surroundings under the action of the head height, thereby realizing the drilling of the carbonate rock layer hole.

[0030] Although some preferred embodiments of the present application have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present application.

[0031] Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of the inventive concept. Thus, if such changes and modifications fall within the scope of the claims of this application and their equivalents, this application is intended to include such changes and modifications.

Claims

1. A drilling structure suitable for carbonate rock formations, characterized in that: It includes a covering layer hole body drilled in the loose covering layer above the carbonate rock formation, a carbonate rock layer hole body drilled coaxially with the covering layer hole body in the carbonate rock formation, a wall protection casing arranged in contact with the covering layer hole body, and a wall protection flower pipe arranged at the hole wall of the carbonate rock layer hole body within the fracture zone; a plurality of water-permeable holes are opened in a corresponding array on the pipe wall of the wall protection flower pipe.

2. The drilling structure according to claim 1, characterized in that: The diameter of the pores in the covering layer is greater than that of the pores in the carbonate rock layer, and the junction between the pores in the covering layer and the pores in the carbonate rock layer is in a step-like shape.

3. The drilling structure according to claim 1, characterized in that: The diameter of the water-permeable holes is 8-12 mm, and the hole spacing is 280-320 mm.

4. A drilling system suitable for carbonate formations, used to implement the drilling structure according to claim 1, characterized in that: The invention comprises a drilling rig for drilling the overburden hole and the carbonate rock layer hole and comprising a drill rod and a drill bit, a mud pool and a clean water pool arranged on the ground, a mud pump for extracting mud or clean water from the mud pool or the clean water pool respectively and pumping them into the drill rod, a filter arranged at the connection position of the drill rod and the drill bit for filtering water when drilling the carbonate rock layer hole, and a water pressure sensor fixed at the connection position of the drill rod and the drill bit.

5. The drilling system according to claim 4, characterized in that It also includes an underground water level observation meter for monitoring the water level height in the hole during the drilling of the carbonate rock layer.

6. The drilling system according to claim 4, characterized in that The clean water storage in the clean water tank meets the requirement of clean water supply flow rate of not less than 60.0m 3 / h.

7. The drilling system according to claim 4, characterized in that The filter includes a backwash module.

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