A drilling and sampling apparatus and method for breaking up limestone formations

Abstract

The application provides a drilling and sampling device and method for breaking limestone strata. The sampling device comprises a drill rod joint, a blocking ball, a core barrel and a drill bit. The drill rod joint comprises an upper drill rod connecting part and a lower core barrel connecting part. A drilling fluid conversion cavity is arranged in the core barrel connecting part. A drilling fluid circulation port is arranged on the core barrel top cover. First and second drilling fluid circulation channels are arranged on the side walls of the core barrel and the drill bit respectively. Each drilling fluid circulation channel is communicated with the drilling fluid conversion cavity. When the blocking ball is arranged at the drilling fluid circulation port, the drilling fluid is circulated through the first and second drilling fluid circulation channels. When the blocking ball is removed, the drilling fluid is circulated normally through the core barrel. The application can realize the local function of the drilling fluid hole bottom, ensure that the cuttings are not accumulated at the hole bottom, and improve the drilling efficiency of the broken limestone strata. Meanwhile, the device can realize two drilling fluid circulation paths, and avoids the complexity of carrying multiple drilling tools by the survey drilling machine.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of geotechnical engineering investigation, and particularly relates to a drilling and sampling device and method for broken limestone stratum. BACKGROUND

[0002] In limestone areas, karst caves and fissures are developed, especially in broken limestone layers, the scale and width of the fissures are larger, and in this area, when drilling and investigation are carried out, when drilling to the broken limestone stratum, the drilling fluid is pumped into the drilling tool from the mud pool to the bottom of the hole, and due to the existence of the fissures, the drilling fluid cannot return to the hole from the bottom along the hole wall, but flows into the broken limestone stratum through the fissures, at this time, the drilling fluid is difficult to circulate, and cannot effectively carry the rock cuttings generated by the drill bit, and the rock cuttings are easy to accumulate at the bottom of the hole, thereby blocking the further cutting of the drill bit, in this case, the drilling efficiency of the drilling machine in the broken limestone stratum is low, and the time for the drilling to reach the designed hole depth is prolonged, and if the drilling in the broken limestone layer is carried out for a long time, the stratum cannot be penetrated as soon as possible, the disturbance to the stratum is larger, the probability of hole collapse and drill burying is higher, and the smooth development of the investigation engineering in the limestone area is seriously affected. SUMMARY

[0003] In order to solve the problem of low drilling and investigation efficiency in the limestone area, the present application provides a drilling and sampling device and method for broken limestone stratum, the sampling device can realize the local function of the drilling fluid at the bottom of the hole, and ensure that the rock cuttings are not accumulated at the bottom of the hole, so as to improve the drilling efficiency in the broken limestone stratum.

[0004] In order to achieve the above technical purpose, the present application provides a drilling and sampling device for broken limestone stratum, the sampling device comprises a drill rod joint, a blocking ball, a core tube and a drill bit, the drill rod joint comprises a drill rod connecting part at the upper side and a core tube connecting part at the lower side, a drilling fluid inlet matched with the drill rod is arranged in the drill rod connecting part, and a drilling fluid conversion cavity is arranged in the core tube connecting part;

[0005] The upper connecting port of the core tube is in sealed connection with the core tube connecting part of the drill rod joint, the top cover of the core tube is arranged in the drilling fluid conversion cavity after connection, a drilling fluid circulation port communicated with the drilling fluid conversion cavity is arranged in the top cover of the core tube, the size of the drilling fluid circulation port is matched with the blocking ball, and a plurality of first drilling fluid circulation channels penetrating along the axial direction of the core tube are arranged in the wall of the core tube, and the upper end of each drilling fluid circulation channel is communicated with the drilling fluid conversion cavity;

[0006] The drill bit is sealingly connected to the lower connecting port of the core barrel, a plurality of second drilling fluid circulation channels penetrating along the axial direction of the drill bit are arranged on the side wall of the drill bit, the number and position of the second drilling fluid circulation channels are matched with the number and position of the first drilling fluid circulation channels on the side wall of the core barrel, and each second drilling fluid circulation channel is in communication with the corresponding first drilling fluid circulation channel; the drilling surface of the drill bit is provided with a row of drill teeth, and a water outlet in communication with the second drilling fluid circulation channel is arranged on the inclined surface of the drill teeth.

[0007] When the drilling and sampling device drills in the overburden layer of limestone, the blocking ball is taken out, at this time, the drilling fluid enters the core barrel through the drilling fluid conversion cavity and the drilling fluid circulation port for normal circulation; when the drilling and sampling device drills into the limestone broken layer, the blocking ball is placed at the drilling fluid circulation port, at this time, the drilling fluid enters the first drilling fluid circulation channel and the second drilling fluid circulation channel through the drilling fluid conversion cavity and flows to the water outlet at the bottom end of the drill bit.

[0008] The preferred technical scheme of the present application is that the drill teeth of the drill bit are embedded with polycrystalline diamond compacts, and the water outlet arranged on the drill teeth is opposite to the polycrystalline diamond compacts on the drill teeth.

[0009] The preferred technical scheme of the present application is that the core barrel connecting portion of the drill rod joint is sleeved with the upper connecting port and the threaded sleeve of the core barrel, the core barrel connecting portion is sleeved outside the upper connecting port of the core barrel, the drilling fluid conversion cavity and the top cover of the core barrel are both arc-shaped and protrude upward, the arc-shaped channel is formed between the top cover of the core barrel and the arc-shaped cavity of the drilling fluid conversion cavity, the drilling fluid circulation port is located at the central part of the top cover of the core barrel, the diameter of the large opening of the drilling fluid circulation port is larger than the diameter of the blocking ball, and the diameter of the small opening of the drilling fluid circulation port is smaller than the diameter of the blocking ball.

[0010] The preferred technical scheme of the present application is that the drill bit is sleeved with the lower connecting port of the core barrel through threads, the drill bit is sleeved outside the lower connecting port of the core barrel, the arc-shaped groove in communication with the first drilling fluid circulation channel is arranged at the connecting portion of the drill bit, and the upper end of the second drilling fluid circulation channel is arranged on the bottom surface of the arc-shaped groove.

[0011] The preferred technical scheme of the present application is that the thicknesses of the pipe walls of the core barrel and the drill bit are matched and are both 1-2 cm, the first drilling fluid circulation channels and the second drilling fluid circulation channels are both annularly and equidistantly distributed along the side walls of the core barrel and the drill bit, the diameters of the first drilling fluid circulation channels and the second drilling fluid circulation channels are 0.5-1 cm and are not larger than half of the thicknesses of the pipe walls of the core barrel and the drill bit.

[0012] In order to achieve the above technical purposes, the present application further provides a drilling and sampling method for broken limestone strata, which uses the drilling and sampling device for broken limestone strata to drill and sample, and the specific steps are as follows:

[0013] (1) the drilling rig is positioned, the blocking ball of the drilling sampling device is taken out, and then the blocking ball is connected with the drill rod, drilling is started from the overburden layer of the limestone, at this time, the drilling fluid is pumped into the drill rod by the mud pump, and then is transported into the drill rod joint through the drill rod, and then is pumped into the core tube through the drilling fluid conversion cavity and the drilling fluid circulation port, and then flows out from the bottom of the core tube, and then flows back to the hole through the gap between the core tube and the hole wall, and then returns to the mud pool, and then the normal circulation of the drilling fluid is completed;

[0014] (2) during the drilling process, the circulation of the drilling fluid is observed, when the drilling speed decreases, and the drilling fluid return amount becomes smaller or stops, at this time, it is judged that the drilling sampling device drills to the limestone broken layer, and then the drilling is stopped, and the drilling sampling device is pulled out;

[0015] (3) after the drilling sampling device is pulled out, the drill rod joint is disassembled from the core tube, and the blocking ball is placed at the drilling fluid circulation port in the center of the core tube top cover, because the drilling fluid circulation is large at the top and small at the bottom, and the large port diameter is larger than the diameter of the blocking ball, and the small port diameter is smaller than the diameter of the blocking ball, the blocking ball is just clamped at the drilling fluid circulation port, the drilling fluid circulation port is blocked, and the drill rod joint is assembled with the core tube;

[0016] (4) then, the assembled drilling sampling device is placed into the borehole again to continue drilling, during the drilling process, the drilling fluid is pumped into the drill rod and the drill rod joint by the mud pump, the drilling fluid entering the drill rod joint provides downward pressure to the blocking ball, so that the blocking effect of the blocking ball is better, at this time, the drilling fluid flows to the water outlet at the bottom end of the drill bit along the first drilling fluid circulation channel of the core tube side wall and the second drilling fluid circulation channel of the drill bit side wall, and then flows out through the water outlet, and the drilling fluid flowing out carries the rock debris cut by the polycrystalline diamond compact together to flow into the fissures of the limestone broken layer.

[0017] The preferred technical scheme of the present application is that: after the drilling sampling of the limestone broken layer is completed, the drilling sampling device is pulled out, the drill rod joint is disassembled from the core tube, the blocking ball is taken out, the drill rod joint is assembled with the core tube, and then the assembled drill rod joint is placed into the borehole to continue drilling, at this time, the drilling fluid in the sampling device restores normal circulation, the drilling fluid flows out from the bottom of the core tube, carries the rock debris, and then flows back to the limestone broken layer, and then flows into the fissures.

[0018] The preferred technical scheme of the present application is that: when the drilling sampling device appears a shaking condition during the drilling process, the drilling sampling device is located in the limestone broken layer; when the drilling sampling device becomes stable from the shaking state, it is judged that the drilling sampling device drills to the limestone complete layer.

[0019] In this invention, during drilling in fractured limestone formations, the drilling fluid flows from inside the drill pipe to the drill pipe interface, enters the drilling fluid conversion chamber, and, due to the obstruction of the plug ball, flows downward along multiple drilling fluid circulation channels within the core tube sidewall. It flows through a groove, then from the drilling fluid circulation channel on the drill bit sidewall to the water outlet on the drill teeth, exits through the water outlet directly opposite the PDC at the bottom of the drill bit, and then flows into the fractures of the fractured limestone formation. The drill bit cutting the rock produces cuttings, which are cleaned away from the cutting contact surface between the drill bit and the limestone formation by the flushing action of the drilling fluid within the water outlet, ensuring continuous cutting of the limestone by the PDC at the bottom of the drill bit and improving drilling efficiency. In this invention, the drill pipe joint and core tube are detachable, and the internal plug ball can be removed. The drilling fluid in the drilling fluid conversion chamber can flow directly downward into the core tube, thus changing the drilling fluid flow path from the inside of the core tube to the bottom of the hole, as is conventional.

[0020] This invention has a simple structure and is easy to use. It can select different drilling fluid circulation paths according to different drilling formations, and can enable the drilling fluid to play a local role at the bottom of the hole, ensuring that rock cuttings do not accumulate at the bottom of the hole, thereby improving the drilling efficiency of fractured limestone formations. At the same time, the device in this invention can realize two drilling fluid circulation paths, serving two purposes in one device, avoiding the cumbersome task of carrying multiple drilling tools on exploration drilling rigs. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of the exploration and sampling device of the present invention;

[0022] Figure 2 for Figure 1 Sectional view of A1A1 in the middle;

[0023] Figure 3 for Figure 1 Sectional view of A2A2 in the middle;

[0024] Figure 4 for Figure 1 Sectional view of B1B1 in the middle;

[0025] Figure 5 for Figure 1 Sectional view of B2B2 in the middle;

[0026] Figure 6 This is a top view of the drill bit;

[0027] Figure 7 This is a schematic diagram of the drilling fluid flow direction when the drilling fluid circulation port is open in this invention;

[0028] Figure 8 This is a schematic diagram of the drilling fluid flow direction under the condition of the drilling fluid circulation port being blocked in this invention.

[0029] In the diagram: 1-Drill pipe connector, 100-Drilling fluid inlet, 2-Plug ball, 3-Core tube, 300-Drilling fluid circulation port, 4-Drill bit, 400-Drill teeth, 5-Polycrystalline diamond composite sheet, 6-Drilling fluid conversion chamber, 7-First drilling fluid circulation channel, 8-Arc-shaped groove, 9-Second drilling fluid circulation channel, 10-Water outlet. Detailed Implementation

[0030] The present invention will be further described below with reference to the accompanying drawings and embodiments. Figures 1 to 8 The drawings are simplified and are intended only to clearly and concisely illustrate the embodiments of the present invention. The technical solutions shown in the accompanying drawings are specific embodiments of the present invention and are not intended to limit the scope of the claimed invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0031] In the description of this invention, it should be understood that the terms "upper," "lower," "inner," "outer," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship commonly used when the product of this invention is in use, or the orientation or positional relationship commonly understood by those skilled in the art. They are only used to facilitate the description of this invention and to simplify the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0032] An embodiment provides a drilling and sampling device for fractured limestone formations, such as... Figures 1 to 5 As shown, the sampling device includes a drill pipe connector 1, a plugging ball 2, a core tube 3, and a drill bit 4. The drill pipe connector 1 includes an upper drill pipe connection part and a lower core tube connection part. A drilling fluid inlet 100 matching the drill pipe 1 is provided in the drill pipe connection part, and a drilling fluid conversion chamber 6 is provided in the core tube connection part. The upper connection port of the core tube 3 is threadedly connected to the core tube connection part of the drill pipe connector 1, and the core tube connection part is fitted over the outside of the upper connection port of the core tube 3, connecting... The top cover of the core tube 3 is placed inside the drilling fluid conversion chamber 6. Both the drilling fluid conversion chamber 6 and the top cover of the core tube 3 are upwardly convex arc-shaped, forming an arc-shaped channel between the top cover of the core tube 3 and the arc-shaped cavity of the drilling fluid conversion chamber 6. A drilling fluid circulation port 300 communicating with the drilling fluid conversion chamber 6 is opened at the center of the top cover of the core tube 3. The drilling fluid circulation port 300 is larger at the top and smaller at the bottom, with the larger diameter being larger than the diameter of the plugging ball 2 and the smaller diameter being smaller than the diameter of the plugging ball 2. Multiple first drilling fluid circulation channels 7 are opened on the wall of the core tube 3, running along the axial direction of the core tube. The upper end of each drilling fluid circulation channel 7 is connected to the drilling fluid conversion chamber 6.

[0033] The embodiment provides a drilling and sampling device for breaking limestone strata, which comprises a core barrel 3 and a drill bit 4. Figures 1 to 5 As shown in the figure, the drill bit 4 is threadedly connected with the lower connecting port of the core barrel 3, and the drill bit 4 is connected outside the lower connecting port of the core barrel 3, a plurality of second drilling fluid circulation channels 9 are arranged on the side wall of the drill bit 4 and penetrate along the axial direction of the drill bit 4, the number and position of the second drilling fluid circulation channels 9 are matched with the number and position of the first drilling fluid circulation channels 7 on the side wall of the core barrel 3, and each second drilling fluid circulation channel 9 is in communication with a corresponding first drilling fluid circulation channel 7; an arc-shaped groove 8 in communication with the first drilling fluid circulation channel 7 is arranged at the connecting position of the drill bit 4, and the upper end of the second drilling fluid circulation channel 9 is arranged on the bottom surface of the arc-shaped groove 8. A row of drill teeth 400 are arranged on the drilling surface of the drill bit 4, and a water outlet 10 in communication with the second drilling fluid circulation channel 9 is arranged on the inclined surface of the drill teeth 400; a polycrystalline diamond compact (PDC) 5 is embedded on the drill teeth 400 of the drill bit 4, and the water outlet 10 arranged on the drill teeth 400 is opposite to the polycrystalline diamond compact 5 on the drill teeth. The first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are arranged in a ring shape and equidistantly distributed along the side walls of the core barrel 3 and the drill bit 4.

[0034] The drilling and sampling device for breaking limestone strata in the embodiment has matched wall thicknesses of the core barrel 3 and the drill bit 4, both of which are 1-2 cm, the first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are arranged in a ring shape and equidistantly distributed along the side walls of the core barrel and the drill bit 4, the diameters of the first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are 0.5-1 cm and are not greater than half of the wall thicknesses of the core barrel 3 and the drill bit 4.

[0035] The drilling and sampling device for breaking limestone strata in the embodiment has matched wall thicknesses of the core barrel 3 and the drill bit 4, both of which are 1-2 cm, the first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are arranged in a ring shape and equidistantly distributed along the side walls of the core barrel and the drill bit 4, the diameters of the first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are 0.5-1 cm and are not greater than half of the wall thicknesses of the core barrel 3 and the drill bit 4. Figure 7 As shown in the figure, the drill bit 4 is threadedly connected with the lower connecting port of the core barrel 3, and the drill bit 4 is connected outside the lower connecting port of the core barrel 3, a plurality of second drilling fluid circulation channels 9 are arranged on the side wall of the drill bit 4 and penetrate along the axial direction of the drill bit 4, the number and position of the second drilling fluid circulation channels 9 are matched with the number and position of the first drilling fluid circulation channels 7 on the side wall of the core barrel 3, and each second drilling fluid circulation channel 9 is in communication with a corresponding first drilling fluid circulation channel 7; an arc-shaped groove 8 in communication with the first drilling fluid circulation channel 7 is arranged at the connecting position of the drill bit 4, and the upper end of the second drilling fluid circulation channel 9 is arranged on the bottom surface of the arc-shaped groove 8. A row of drill teeth 400 are arranged on the drilling surface of the drill bit 4, and a water outlet 10 in communication with the second drilling fluid circulation channel 9 is arranged on the inclined surface of the drill teeth 400; a polycrystalline diamond compact (PDC) 5 is embedded on the drill teeth 400 of the drill bit 4, and the water outlet 10 arranged on the drill teeth 400 is opposite to the polycrystalline diamond compact 5 on the drill teeth. The first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are arranged in a ring shape and equidistantly distributed along the side walls of the core barrel 3 and the drill bit 4. Figure 8 As shown in the figure, the drill bit 4 is threadedly connected with the lower connecting port of the core barrel 3, and the drill bit 4 is connected outside the lower connecting port of the core barrel 3, a plurality of second drilling fluid circulation channels 9 are arranged on the side wall of the drill bit 4 and penetrate along the axial direction of the drill bit 4, the number and position of the second drilling fluid circulation channels 9 are matched with the number and position of the first drilling fluid circulation channels 7 on the side wall of the core barrel 3, and each second drilling fluid circulation channel 9 is in communication with a corresponding first drilling fluid circulation channel 7; an arc-shaped groove 8 in communication with the first drilling fluid circulation channel 7 is arranged at the connecting position of the drill bit 4, and the upper end of the second drilling fluid circulation channel 9 is arranged on the bottom surface of the arc-shaped groove 8. A row of drill teeth 400 are arranged on the drilling surface of the drill bit 4, and a water outlet 10 in communication with the second drilling fluid circulation channel 9 is arranged on the inclined surface of the drill teeth 400; a polycrystalline diamond compact (PDC) 5 is embedded on the drill teeth 400 of the drill bit 4, and the water outlet 10 arranged on the drill teeth 400 is opposite to the polycrystalline diamond compact 5 on the drill teeth. The first drilling fluid circulation channels 7 and the second drilling fluid circulation channels 9 are arranged in a ring shape and equidistantly distributed along the side walls of the core barrel 3 and the drill bit 4.

[0036] The example given is a detailed survey of the Kunming Youth Science and Technology Cultural Tourism Practice Base project. The bedrock strata at the site consist of dolomitic limestone from the Lower Permian Qixia Formation, overlain by a red clay layer ranging from 0 to 6 meters. Below this layer, at depths of 5 to 15 meters, there is fractured limestone with well-developed fissures and occasional karst caves. When the exploration drilling rig performs core drilling at this location, once the drill bit penetrates the overlying clay layer, the drilling fluid cannot return to the borehole opening. Instead, it flows into the fissures of the fractured limestone layer at the bottom of the hole. The drilling fluid cannot form a loop circulation, and the rock cuttings generated by the drill bit cannot be carried to the surface by the drilling fluid. They accumulate at the bottom of the drill bit, hindering the drill bit's cutting of the strata, slowing down the drilling rate, and ultimately reducing the drilling efficiency of the rig. Even worse, the longer the borehole wall remains exposed due to low drilling efficiency, the greater the probability of the borehole wall collapsing and burying the drill bit.

[0037] To improve drilling efficiency in limestone fractured formations, the sampling drill string of this invention is used for drilling and sampling. This sampling drill string can select two drilling fluid circulation paths, and its specific drilling and sampling steps are as follows:

[0038] (1) Position the drilling rig and remove the sealing ball of the drilling sampling device. Then connect it to the drill rod and begin drilling from the overburden layer of limestone. First, remove the sealing ball 2. Figure 7 As shown, at this time, the drilling fluid enters the drill pipe through the mud pump and is transported to the drill pipe joint through the drill pipe. Then, it enters the core tube through the drilling fluid conversion chamber and the drilling fluid circulation port, flows out through the bottom of the core tube, and flows back up to the borehole opening along the gap between the core tube and the borehole wall, and then returns to the mud pit to complete the normal circulation of the drilling fluid.

[0039] (2) During the drilling process, observe the circulation of drilling fluid. When the drilling speed decreases and the amount of drilling fluid returned decreases or stops returning, it is determined that the drilling sampling device has reached the limestone fracture layer. Drilling should be stopped and the drilling sampling device should be pulled out.

[0040] (3) After pulling out the drilling sampling device, disconnect the drill pipe joint 1 from the core tube 3, and place the sealing ball 2 at the drilling fluid circulation port 300 in the center of the top cover of the core tube 3. Since the drilling fluid circulation is larger at the top and smaller at the bottom, and the diameter of the large opening is larger than the diameter of the sealing ball, and the diameter of the small opening is smaller than the diameter of the sealing ball, the sealing ball is just stuck at the drilling fluid circulation port to block the drilling fluid circulation port, and then install the drill pipe joint and the core tube.

[0041] (4) then put the assembled drilling sampling device into the borehole again to continue drilling, and in the drilling process, the drilling fluid is pumped into the drill pipe and the drill pipe joint through the mud pump, the drilling fluid entering the drill pipe joint gives the down pressure to the blocking ball, so that the blocking effect of the blocking ball is better, at this time the drilling fluid flows to the water outlet at the bottom end of the drill bit along the first drilling fluid circulation channel of the core tube side wall and the second drilling fluid circulation channel of the drill bit side wall, and flows out through the water outlet, and the drilling fluid flowing out carries the rock debris cut by the polycrystalline diamond compact together to flow into the fissure of the limestone broken layer;

[0042] (5) continue drilling, when drilling the limestone broken layer, the contact surface of the drill bit and the stratum is piece by piece and uneven, and it is usually shaken together with the drill pipe when drilling, and after drilling the complete layer, the drilling is relatively stable; therefore, the sampling device is observed during drilling, if it becomes stable from the shaking state, it is judged that the drilling sampling device drills to the limestone complete layer; drilling is stopped again, the drill pipe joint 1 and the core tube 3 are disassembled, the blocking ball 2 is taken out, the drill pipe joint 1 and the core tube 3 are assembled and put into the borehole to continue drilling, at this time the drilling fluid recovers normal circulation in the sampling device, the drilling fluid flows out from the bottom of the core tube, carries the rock debris and flows back to the limestone broken layer, and then flows into the fissure, and finally the sampling drill reaches the designed depth, and the hole drilling is completed.

[0043] In this process, the drilling fluid path is changed during the limestone broken layer drilling stage, so that the drilling fluid flows out from the drill bit water outlet, which can continue to play a role in removing the hole bottom debris, and also can cool the drill bit, ensure the direct contact of the drill bit with the stratum, speed up the efficiency of the drill bit cutting the limestone broken stratum, and improve the drilling efficiency. In addition, the overburden soil layer and the limestone complete layer drilling stage realizes the dual-purpose of the sampling drill by taking out the blocking ball and changing the drilling fluid circulation path without selecting other types of sampling drills, avoiding the complexity of carrying multiple drills by the survey drilling machine. The drill bit cuts the rock to produce rock debris, which is cleaned to the outside of the cutting contact surface of the drill bit and the limestone stratum by the flushing of the drilling fluid in the water outlet, ensuring the continuous cutting of the PDC at the bottom end of the drill bit, and improving the drilling efficiency.

[0044] The above is only one embodiment of the present application, which is described in more detail and in detail, but it cannot be understood as limiting the scope of the present application. It should be noted that for ordinary skilled persons in the art, without departing from the concept of the present application, a number of modifications and improvements can be made, which are within the scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A drilling and sampling method for fractured limestone strata, characterized in that: The drilling sampling method uses a drilling sampling device for fractured limestone formations to perform drilling sampling. The sampling device includes a drill pipe joint (1), a plugging ball (2), a core tube (3), and a drill bit (4). The drill pipe joint (1) includes an upper drill pipe connection part and a lower core tube connection part. A drilling fluid inlet (100) matching the drill pipe is provided in the drill pipe connection part, and a drilling fluid conversion chamber (6) is provided in the core tube connection part. The upper connection port of the core tube (3) is sealed to the core tube connection part of the drill pipe joint (1). After the connection, the top cover of the core tube (3) is placed in the drilling fluid conversion chamber (6), and a drilling fluid circulation port (300) communicating with the drilling fluid conversion chamber (6) is opened on the top cover of the core tube (3). The size of the drilling fluid circulation port (300) matches the plugging ball (2). Multiple first drilling fluid circulation channels (7) are opened on the pipe wall of the core tube (3) along the core tube axis. The upper end of each first drilling fluid circulation channel (7) is connected to the drilling fluid conversion chamber (6). The drill bit (4) is sealed and connected to the lower connection port of the core tube (3). Multiple second drilling fluid circulation channels (9) are provided on the side wall of the drill bit (4) along the drill bit axis. The number and position of the second drilling fluid circulation channels (9) are matched with the number and position of the first drilling fluid circulation channels (7) on the side wall of the core tube (3). Each second drilling fluid circulation channel (9) is connected to the corresponding first drilling fluid circulation channel (7). The drilling surface of the drill bit (4) is provided with a ring of drill teeth (400), and an outlet (10) connected to the second drilling fluid circulation channel (9) is opened on the inclined surface of the drill teeth (400). When the drilling and sampling device is drilling in the limestone overburden layer, the plugging ball (2) is taken out. At this time, the drilling fluid enters the core tube (3) through the drilling fluid conversion chamber (6) and the drilling fluid circulation port (300) for normal circulation. When the drilling and sampling device drills to the limestone fracture layer, the plugging ball (2) is placed at the drilling fluid circulation port (300). At this time, the drilling fluid enters the first drilling fluid circulation channel (7) and the second drilling fluid circulation channel (9) through the drilling fluid conversion chamber (6) and flows to the outlet (10) at the bottom of the drill bit (4). The drilling fluid circulation port (300) is located in the center of the top cover of the core tube (3), and the drilling fluid circulation port (300) is larger at the top and smaller at the bottom. Its large opening diameter is larger than the diameter of the plugging ball (2), and its small opening diameter is smaller than the diameter of the plugging ball (2). The specific steps of the sampling method are as follows: (1) The drilling rig is positioned, and the sealing ball of the drilling sampling device is removed and then connected to the drill pipe. Drilling begins from the overburden layer of limestone. At this point, drilling fluid enters the drill pipe through the mud pump and is then transported to the drill pipe joint. It then enters the core tube through the drilling fluid conversion chamber and the drilling fluid circulation port, flows out through the bottom of the core tube, and flows back up to the borehole opening along the gap between the core tube and the borehole wall, before returning to the mud pit, thus completing the normal circulation of drilling fluid. (2) During the drilling process, observe the circulation of drilling fluid. When the drilling speed decreases and the amount of drilling fluid returned decreases or stops returning, it is determined that the drilling sampling device has reached the limestone fracture layer. Drilling should then be stopped and the drilling sampling device should be pulled out. (3) After pulling out the drilling sampling device, disconnect the drill pipe joint from the core tube and place the sealing ball at the drilling fluid circulation port in the center of the core tube top cover. Since the drilling fluid circulation is larger at the top and smaller at the bottom, and the diameter of the large opening is larger than the diameter of the sealing ball and the diameter of the small opening is smaller than the diameter of the sealing ball, the sealing ball is just stuck at the drilling fluid circulation port to seal the drilling fluid circulation port. Then install the drill pipe joint and the core tube. (4) Then, the installed drilling sampling device is put back into the borehole to continue drilling. During the drilling process, the drilling fluid is pumped into the drill pipe and drill pipe joint by the mud pump. The drilling fluid entering the drill pipe joint gives the plugging ball downward pressure, making the plugging ball more effective. At this time, the drilling fluid flows along the first drilling fluid circulation channel on the side wall of the core tube and the second drilling fluid circulation channel on the side wall of the drill bit to the water outlet at the bottom of the drill bit, and flows out through the water outlet. The outflowing drilling fluid carries the rock cuttings from the polycrystalline diamond composite sheet to the fractures of the limestone fracture layer.

2. The drilling and sampling method for fractured limestone strata according to claim 1, characterized in that: The drill bit (4) has a polycrystalline diamond composite sheet (5) embedded in its drill teeth (400), and the water outlet (10) on the drill teeth (400) is directly opposite the polycrystalline diamond composite sheet (5) on the drill teeth.

3. A drilling and sampling method for fractured limestone strata according to claim 1 or 2, characterized in that: The core tube connection of the drill pipe joint (1) is threadedly connected to the upper connection port of the core tube (3), and the core tube connection is sleeved outside the upper connection port of the core tube (3). The top cover of the drilling fluid conversion chamber (6) and the core tube (3) are both upwardly convex arc-shaped, and an arc-shaped channel is formed between the top cover of the core tube (3) and the arc-shaped cavity of the drilling fluid conversion chamber (6).

4. A drilling and sampling method for fractured limestone strata according to claim 1 or 2, characterized in that: The drill bit (4) is threaded into the lower connection port of the core tube (3), and the drill bit (4) is sleeved outside the lower connection port of the core tube (3). An arc-shaped groove (8) communicating with the first drilling fluid circulation channel (7) is provided at the connection part of the drill bit (4). The upper port of the second drilling fluid circulation channel (9) is opened on the bottom surface of the arc-shaped groove (8).

5. A drilling and sampling method for fractured limestone strata according to claim 1 or 2, characterized in that: The wall thickness of the core tube (3) and the drill bit (4) is matched, both being 1-2 cm. The first drilling fluid circulation channel (7) and the second drilling fluid circulation channel (9) are distributed in a ring at equal intervals along the side walls of the core tube (3) and the drill bit (4), respectively. The diameter of the first drilling fluid circulation channel (7) and the second drilling fluid circulation channel (9) is 0.5-1 cm, and is not greater than half the wall thickness of the core tube (3) and the drill bit (4).

6. A drilling and sampling method for fractured limestone strata according to claim 1, characterized in that: After drilling and sampling of the fractured limestone layer is completed, once drilling reaches the intact limestone layer, the drilling and sampling device is pulled out. The drill pipe joint and core tube are then disconnected, the plugging ball is removed, the drill pipe joint and core tube are reinstalled, and the drill pipe is placed back into the borehole to continue drilling. At this time, the drilling fluid resumes normal circulation in the sampling device. The drilling fluid enters the drill pipe through the mud pump, flows out from the bottom of the core tube, and carries rock cuttings upward back to the fractured limestone layer, where it flows into the fissures.

7. A drilling and sampling method for fractured limestone strata according to claim 1, characterized in that: When the drilling and sampling device vibrates during drilling, it is located in a fractured limestone layer; when the drilling and sampling device becomes stable from the vibration state, it is determined that the drilling and sampling device has drilled into a complete limestone layer.

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