(a) percussive rotary drilling
Impact rotary drilling is a drilling method in which an impactor (also called DTH hammer) is connected to the upper part of the drilling tool (the upper part of the drill bit when drilling without core), so that the drill bit can break the rock by using longitudinal impact force and rotary cutting force on the basis of bearing a certain static load. The increase of impact load changes the rock breaking mechanism of pure rotary drilling and improves drilling efficiency. At the same time, due to the high-frequency vibration of the core tube, it is beneficial for the broken core to enter the coring tube smoothly, thus reducing the core blockage and increasing the footage length. Impact rotary drilling can be used for ordinary lifting coring or rope coring drilling.
The impactor is the key equipment for percussive rotary drilling. Impactor can be divided into hydraulic impactor, pneumatic impactor and mechanical impactor according to power mode. The hydraulic impactor takes high-pressure water or mud as the power medium; Pneumatic impactor uses compressed air as power medium, and can also be mixed with air and water. Mechanical impactor uses motor, electromagnetic device, turbine or special mechanism (such as jaw clutch) to make the impact hammer move up and down. In geological core drilling, hydraulic impactor is mainly used, pneumatic impactor is mainly used for large diameter shallow-medium deep hole drilling, and mechanical impactor is rare in geological drilling.
1. Types and working principles of hydraulic impactors
According to the working principle, China's hydraulic impactors mainly include valve-type positive action, valve-type reaction, valve-type double action, jet type, jet type and so on.
(1) valve type positive-acting hydraulic impactor
As shown in Figure 4- 1 1, the working principle of the valve-type positive-acting hydraulic impactor is that the hammer piston 5 is in the upper position under the action of the hammer spring 6, and its central hole is covered by the movable valve 4, so that the liquid flow is blocked instantly and the hydraulic pressure rises sharply, resulting in the water hammer effect. Under the action of hydraulic pressure, the hammer piston and the movable valve descend together to compress the valve spring 3 and the hammer spring; When the movable valve descends to a certain position, it is limited by the valve seat 9 and stops running, leaving the hammer piston. The liquid flows through the central hole of the hammer piston and flows to the bottom of the hole, and the hydraulic pressure drops, and the movable valve returns to its original position under the action of the valve spring. Under the action of kinetic energy, the piston of the impact hammer continues to run inertia and impacts the anvil 7. Impact energy is transferred to the drill bit through anvil-core pipe joint-core pipe, etc. After the impact, the piston of the impact hammer bounces back under the action of the hammer spring force. Contact the live valve again to complete an impact cycle.
The invention has the advantages of simple structure, stable performance and easy debugging. However, the spring of the impactor will offset the impact force generated by a part of high-pressure liquid flow; The spring is easy to be damaged at the working frequency of 1500 times/minute or higher.
(2) Valve type reaction hydraulic impactor
As shown in Figure 4- 12, the working principle of the valve-type reaction hydraulic impactor is as follows: high-pressure liquid flows into the impactor, and when the pressure difference between the upper and lower ends of the hammer piston exceeds the compression force of the working spring 1 and the mass of the hammer piston itself, the hammer piston is forced to move upward, compressing the working spring to store energy; At the same time, the water channel of anvil 4 flowing to the bottom of the hole is opened, the hydraulic pressure drops, and the impact hammer piston continues to move upward under the action of inertia; When it rises to the top dead center, the hammer piston moves down quickly under the action of its own gravity and spring, impacting the anvil; At the same time, due to the contact between the hammer piston and the anvil, the channel of liquid flowing to the bottom of the hole is closed, and the hydraulic pressure begins to rise. When it rises to a certain value, it acts on the hammer piston again to make it rise and start the second working cycle.
Fig. 4- Schematic diagram of valve-type positive-acting hydraulic impactor +0 1
1- shell; 2- Movable seat washer; 3- valve spring; 4- valve; 5— Impact hammer piston; 6— Hammer spring; 7- anvil; 8— Buffer washer; 9- Seat
Fig. 4- 12 schematic diagram of valve-type reaction hydraulic impactor
1- working spring; 2- shell; 3— Piston impact hammer; Four anvil
The advantages of this kind of impactor are strong adaptability to mud, small internal pressure loss and large single impact work. The main disadvantage is that the spring with high stiffness is needed, and its working life is only 40 ~100 h.
(3) Valve type double-acting hydraulic impactor
As shown in Figure 4- 13, the working principle of the impactor is that when the drilling tool reaches the bottom of the hole, the movable joint F is pressed to the position G on the jacket due to the self-weight of the drilling tool. At this time, the liquid flow in the working chamber D acts on the movable valve 2 and the tower hammer piston 6 respectively, and the movable valve is forced to move to the uppermost position due to the pressure difference between the upper and lower ends of the movable valve; Due to the pressure difference between the upper and lower ends of the impact hammer piston, it is forced to move upward; When the hammer piston rises and engages with the movable valve, the channel d 1 is closed, and the hammer piston and the movable valve quickly descend together. When descending h, the movable valve is limited by the support 4, the hammer piston is separated from the movable valve, and the inertia continues to decline. When descending s, it impacts the anvil 9, and the liquid flow resumes circulation because the central channel of the hammer piston is opened. Under the action of liquid flow pressure, the movable valve rises sharply, and the hammer piston also rises sharply, and so on.
Figure 4- 13 Working principle of valve-type double-acting hydraulic impactor
1- movable valve seat with hole; 2- valve; 3- coat; 4- support seat; 5-Guide seal; 6— Tower-shaped impact hammer piston; 7-Guide seal; 8— Throttle ring; 9- chopping block
The main advantages of double-acting hydraulic impactor are high energy utilization rate of liquid flow; The disadvantage is that the structure is complex and some parts wear quickly.
(4) Jet hydraulic impactor
As shown in fig. 4- 14, the working principle of jet hydraulic impactor is that the high-pressure water output by the water pump is ejected through the nozzle of jet element ①, resulting in wall attachment. If the wall is attached to the right side first, the high-pressure liquid flow enters the upper part of the cylinder ② through the right output channel C, pushing the piston ③ downward. At this time, the impact hammer ④ connected with the piston impacts the anvil ⑤, transferring the impact energy to the core tube and the drill bit, and completing one impact. While C outputs high-pressure water, a small stream of high-pressure liquid flow (called feedback signal liquid flow) enters the D control hole. At the end of the piston stroke, the feedback signal is very strong, which makes the jet flow switch from C to E, and the high-pressure liquid flow is output from the left channel and enters the lower chamber, pushing the piston to move upward. When the piston rises, the feedback signal returns to F, and the jet is switched to the right output channel. So as to repeatedly realize the impact action of the impact hammer. The backwater from the upper and lower cylinders returns to the vent hole through the C and E outlets, flows into the core pipe through the water joint and the inner hole of the anvil, reaches the bottom of the hole, and returns to the surface after washing the bottom of the hole.
Fig. 4- 14 working principle of jet hydraulic impactor
① Jet components; ② steel body; ③ piston; ④ Impact hammer; 5 chopping board; 6. Core tube; ⑦ snap spring; 8 drill bit; 1-upper connector; 2— Cylinder liner shell; 3- fishing pad; 4— Spring retaining ring; 5— Bolt; 6-O type sealing ring; 7-fishing line; 8-O type sealing ring; 9— Jet element; 10 O type sealing ring; 1 1- cylinder; 12- piston rod; 13-spring retaining ring; 14- sealing ring; 15-support ring; 16- copper bushing; 17 O type sealing ring; 18- gland; 19-support ring; 20— sealing ring; 2 1- copper pad; 22— Spring retaining ring; 23— Joint; 24- impact hammer; 25— Shell; 26- chopping block; 27- hexagon set; 28— Joint; 29— Core tube; 30- circlip seat; 31-circlip; 32— Drill bit; 33 stitches
Its main features are: no spring, water distribution valve and other parts, long service life; High energy utilization rate; It is not easy to cause water plugging when working, which can better prevent accidents such as burning drill bit and choking pump; The high-pressure water hammer produced during drilling is smaller than the valve impactor, and the drilling tool works smoothly, which can reduce the damage of pumps, impactors and high-pressure pipelines.
(5) Jet-suction hydraulic impactor
The impactor makes use of the entrainment effect caused by high-speed injection of liquid flow and the comprehensive feedback relationship of pressure and displacement between the valve and the impact hammer, and makes the impact hammer move repeatedly through the positive and negative exchange of liquid flow pressure difference between the valve and the impact hammer and between the upper and lower chambers of the piston. Working principle: both the valve and the hammer are at the lower limit of the static working position, as shown in Figure 4- 15(a). When the nozzle sprays high-speed jet, the pressure in the upper chamber of the valve and hammer piston is lower than that in the lower chamber, and the pressure difference pushes the valve and hammer to rise rapidly. Due to the small mass of the valve, the movement speed is faster than that of the impact hammer, and it reaches the upper limit of the working position first [Figure 4- 15(b)]. Immediately after the impact hammer rises at a high speed, when the valve and the conical surface on the impact hammer are closed [Figure 4- 15(c)], the liquid flow channel is suddenly cut off and water hammer occurs. The valve and the piston upper cavity, which were originally in the low pressure state, were suddenly in the high pressure state, while the lower cavity was in the low pressure state due to the inertia of liquid flow, so that the valve and the hammer were pushed down synchronously and quickly by the high pressure liquid flow [Figure 4- 15(d)]. After the valve reaches the upper limit of working position, the inertia of high-speed movement makes the impact hammer move down the impact anvil quickly to complete a stroke. At this point, the conical surface of the valve and hammer has left, and the valve and hammer re-enter the return journey of the next cycle. This cycle is repeated, forming a continuous impact.
Fig. 4- 15 working principle of jet-suction hydraulic impactor
(a) Initial state when no water is delivered; (b) Initial state at the time of water supply; (c) Return state when lifting the hammer; (d) Start of the stroke
1-nozzle; 2- superior cavity; 3 piston; 4- valve; 5- impact hammer; 6- inferior cavity; 7- chopping block; 8— Low pressure cavity; 9— High pressure cavity; 10- water hammer area; 1 1- decompression zone
The main characteristics of this impactor are: simple structure, few parts and no fragile spring, so the working life is longer; Wide range of input and output technical parameters, stable impact at high frequency and good back pressure resistance.
2. Type and working principle of pneumatic impactor
Pneumatic impactor, also known as pneumatic DTH hammer, uses compressed air as working medium. According to the gas distribution mode and structural characteristics of pneumatic impactors, they can be divided into two categories: valved impactors and valveless impactors. Pneumatic impactor is often used in geological core drilling.
The structural principles of valved impactor and valveless impactor are shown in Figure 4- 16 and Figure 4- 17. The structural principle of pneumatic impactor coring drilling tool is shown in Figure 4- 18. The drilling tool is mainly used for drilling microfractures or microfractures. During normal drilling, the axial pressure, rotating torque and impact force are transmitted to the joint, the outer core pipe and the drill bit through the pneumatic impactor, so that the rock at the bottom of the hole is broken and the inner pipe does not move; The compressed air flowing from the pneumatic impactor reaches the bottom of the hole through the inner hole of the joint, the annular gap between the inner and outer core pipes and the air hole of the drill bit, which cools the drill bit and returns the rock powder along the outer annular gap. When coring, the drilling tool is slowly lifted, the sliding sleeve compresses the spring, and the inner core tube and the circlip seat are partially moved down and located on the inner step of the drill bit, so that the outer tube bears a large clamping force, and the core can be clamped.
Fig. 4- 16 Structural Diagram of Pneumatic Impactor with Valve
1- connector; 2- steel washer; 3- adjusting ring; 4— Disc spring; 5— Throttle plug; 6— Valve cover; 7- valve plate; 8- valve seat; 8 '- valve stem; 9— Piston; 10- outer cylinder; 1 1- inner tube; 12- bushing; 13 needle; 14-spring; 15- clamp bushing; 16-steel wire; 17- round key; 18- protective cover; 19- sealing ring; 20- Check the plug; 2 1- spring; 22— Wear-resistant parts; 23— Drill bit
Fig. 4- 17 structural diagram of valveless pneumatic impactor
1-upper connector; 2- sealing ring; 3- spring; 4- check valve; 5— Sealing washer; 6— Air inlet seat; 7- inner cylinder; 8— outer cylinder; 9— Throttle plug; 10- impact hammer; 1 1- gasket; 12- guide sleeve; 13- round key; 14-lower connector; 15 bit
3. The application effect of impact rotary drilling in deep hole drilling and water wells.
China's percussive rotary drilling technology is becoming more and more mature, which has been widely used in scientific drilling, deep hole core drilling and water well drilling, and achieved good results.
Chinese mainland Scientific Drilling Engineering Department (1) drilled 1 well (CCSD- 1).
In the construction of Chinese mainland Scientific Drilling Engineering Department 1 Well, screw motor and hydraulic (valve or jet) DTH hammer were used for percussive rotary drilling coring. Borehole diameter φ 157mm, cumulative total footage 4043.25m, deepest hole section 5 129.33m, average ROP 1.65438+6.34m/. Compared with single screw motor coring drilling, the ROP is increased by 59% (1.13m/h: 0.71m/h) and the footage is increased by 178% (6.34: 2.28).
Fig. 4- 18cx- 120 pneumatic impactor coring drilling tool structure schematic diagram
1- connector; 2- cylindrical alloy; 3- bearing; 4— Sliding sleeve; 5— Outer core tube; 6- spring; 7— Inner pipe joint; 8— Nut; 9— Inner core tube; 10- righting ring; 11-circlip seat; 12-circlip; 13 bit
(2) The first scientific deep drilling of uranium mine in China.
The deep drilling of uranium mine constructed by Beijing CNNC Dida Mining Exploration and Development Co., Ltd. has a designed hole depth of 2500m, and the actual final hole depth is 28 18.88m. From the hole depth of 45.88 ~ 28 18.88 m, φ 122mm diameter rope coring double-acting hydraulic DTH hammer is used for percussive rotary drilling, and the average core recovery rate of the whole hole is 99. The average footage is 2.76m. Compared with conventional wireline coring drilling in the same layer, the ROP is increased by 83% (1.52m/h: 0.83m/h) and the footage length is increased by 38% (2.76m: 2.0m).
(3) Exploration of Yandian Iron Mine in Yanzhou, Shandong Province
The third geological brigade of Shandong Bureau of Geology and Mineral Exploration and Development drilled two special strata in ZK00 1 hole of Yandian Iron Mine in Yanzhou. One is cracks, fissures and caves, mainly dolomite and porphyritic limestone. The second layer is chlorite-sericite-phyllite stratum, with local time pulse. Rock is hard and fragile, with steep occurrence and easy to form pores. Conventional wireline coring drilling has some problems, such as low aging degree, less return times, short bit life and high deviation strength. After that,1121m ~1648m, the final hole was drilled by SYZX75 rope coring hydraulic percussion rotary drilling, with the aging increased by 30% and the return footage increased by 18. The strength of well deviation is reduced from 6.03/ 100 m to 1.75/ 100 m, and the full pipe return rate is 95%, and the monthly efficiency is increased by 40%.
(4) Application in water well drilling
The Engineering Investigation Institute of the First Hydrological Team of Anhui Bureau of Geology and Mineral Resources has successively drilled two bedrock water supply wells with the final aperture of φ 180mm in Dazhuang Town, Sixian County, Anhui Province and Mohekou Town, Bengbu City, with the depths of 230.40m and 280.00m respectively. Under the conditions of the same formation and the same caliber, the average aging of the two wells is 1.40m/h and 0.8m/h when conventional rotary drilling is used, while the average aging is 14.45m/h and 12.50m/h when pneumatic percussion rotary drilling is used, which improves the aging/h.
4. Key points of percussion rotary drilling technology
(1) General principles for selecting impactors (DTH hammer)
1) large diameter, shallow hole, medium-deep hole coreless drilling and dry and water-deficient areas should use pneumatic impactor;
2) Hydraulic impactor should be used for drilling geological cores above medium and deep holes;
3) Low-frequency high-power impactor should be selected for drilling cemented carbide and compact, and high-frequency low-power impactor should be selected for drilling diamond;
4) Spring-free valves and jet (or jet-suction) impactors should be selected for drilling small-diameter geological cores with deep holes.
(2) Selection of drilling equipment
1) Conventional drilling equipment can be used for hydraulic percussion rotary drilling. However, it is required that the mud pump has a wide flow range, the pump pressure is greater than 10MPa, and the high-pressure hose and faucet should also adapt to the pump pressure requirements.
2) The vertical shaft or rotary table drilling rig should be selected for pneumatic impact rotary drilling, with the rotating speed of 20 ~ 60r/min, the through hole of the main rod should be large, and the faucet, high-pressure pipeline and drill pipe should have good high pressure resistance and sealing performance; The displacement and pressure of air compressor should meet the requirements of drilling depth and diameter; The orifice should have dust removal, dust prevention and defoaming devices.
(3) Requirements of flushing medium
In hydraulic percussion rotary drilling, solid-free or low-solid mud should be selected as far as possible according to the formation characteristics and wall protection requirements to reduce the wear of the impactor. Mud is required to have low sand content (≤0. 1%) and good lubricity and rheology.
Pneumatic percussion rotary drilling can use washing media such as dry air, atomized gas, foam and gas-water mixture. Because dry air has relatively poor functions of carrying rock powder, cooling the drill bit and cleaning the bottom of the hole, the upward flow rate of gas should reach15 ~ 25m/s; During atomization drilling, in order to solve the problems of mud bag, mud plug and rock powder sticking to the hole wall in wetland drilling, the gas-water volume should reach 2000/1~ 3000/1; During foam drilling, in order to stabilize the pore wall of wetland layer and increase the powder carrying capacity, 0.3% ~ 1.0% pollution-free foaming agent should be added to make the gas-liquid volume ratio 200/1~ 300/1; When gas-water mixed drilling is carried out in water-bearing formation, in order to improve the chip removal ability, the air volume should account for 80% of the mixed medium.
(4) Selection of drill bit
According to the different drillability of rocks, cemented carbide bits, roller bits, composite bits and diamond bits can be selected for impact rotary drilling. It is required that the mouth of the bit lip and the cross section of the water tank are large to reduce the working back pressure of the impactor; The impact strength of the drill bit should be greater than the impact force output by the impactor.
(2) local reverse circulation drilling at the bottom of the hole
Local reverse circulation drilling at the bottom of the well is a technological method to generate negative pressure in the core tube by means of jet reaction elements, change the direction of bottom-hole liquid flow and improve the recovery rate of core crushing. It is divided into single-pipe reverse circulation drilling tools and double-pipe reverse circulation drilling tools. In the extremely broken stratum where cuttings are soft, fragile, powdery and easy to be eroded by water, single-acting double-tube jet reverse drilling tool is selected; When joints and bedding are developed, cracks are hard and brittle, and core disturbance is not strict, single pipe jet reverse drilling tool is selected.
1. Single-acting dual-tube jet reverse drilling tool
(1) drilling tool structure and working principle
In order to meet the needs of deep prospecting and engineering geological exploration, the 3 13 geological team of Anhui Bureau of Geology and Mineral Resources designed SX-type (77mm, 96mm, φ 1 10 mm) series of jet-suction bottom hole reverse circulation single-acting double-pipe drilling tools. The drilling tool structure is shown in Figure 4- 19.
Figure 4- 19SX Series Jet Suction Single-acting Double-tube Coring Drilling Tool Structure Schematic Diagram
1-external pipe joint; 2— Bearing upper gland; 3— Bearing bush; 4,5—sealing ring; 6-axis retaining ring; 7— Upper bearing; 8— hollow shaft; 9— Lower bearing; 10- gland bushing; 1 1- bearing lower gland; 12- adjust the lock nut; 13-upper connector; 14- nozzle; 15- Ejector shell; 16-transmitter; 17 head screw; 18-lower connector; 19-inner tube; 20— outer tube; 2 1- spring tongue coring device; 22— Inner pipe joint; 23— Bottom Jet Bit
During drilling, the outer tube assembly of SX drilling tool mainly transmits the axial pressure and rotating torque needed to break rocks. The inner tube single-action system ensures that the ejector assembly and the inner tube assembly do not rotate during drilling to protect the core. The main difference between the drilling tool and the common single-acting double-pipe is that an ejector component is added between the single-acting system of the inner pipe and the joint on the inner pipe, which realizes the reverse circulation at the bottom of the double-pipe hole (cooling the drill bit, suspending and carrying cuttings) and improves the recovery rate of broken loose cores.
During drilling operation, mud enters the conical nozzle of SX drilling tool injector along the drill string and is injected into the diffusion pipe at high speed. Under the action of high-speed jet, the liquid around the ejector composed of nozzle and diffuser is taken away by the jet, forming a negative pressure zone, which urges the liquid at the bottom of the hole to be sucked into the diffuser through the core tube. The high-speed liquid flow and the inhaled liquid flow are mixed in the mixing chamber, and the mixed liquid flows to the diffusion chamber through the throat and then is discharged through the water outlet. Under the action of residual pressure, a part of the discharged mud returns to the ground from the bottom jet bit or the side jet bit along the gap between the inner and outer pipes through the gap between the drilling tool and the hole wall (forming a positive circulation), while under the action of negative pressure, the other part is sucked into the inner pipe cavity, forming a reverse circulation at the bottom of the hole, which generates a floating adsorption force on the cores in the inner pipe, suspending the cuttings with larger particles and crushing the cores, and self-grinding does not occur between cores, thus effectively improving the core recovery rate.
The drilling tool is suitable for rotary drilling and percussive rotary drilling in hard, fragile, broken and gravel formations. Bottom-jet drill bit should be selected in extremely broken stratum, and it should be equipped with spring tongue or wire bundle coring device, as shown in Figure 4-20.
Figure 4-20 Bottom-injection bit and its matching coring device
(a) a bottom-jet diamond drill bit; (b) Bottom-sprayed composite bit; (c) spring tongue coring device; (d) Wire harness coring device
(2) Application effect
Experiments on ZK03 hole for deep prospecting in crisis mine of Langyashan copper mine in Chuzhou, Anhui Province, ZK44 hole in Huoqiu-Jiji iron mine area and new 5 holes in Cenozoic stereoscopic geology in Beijing Plain show that SX single-acting double-tube hole bottom local reverse circulation drilling tool has solved the coring problem in hard and brittle stratum and gravel stratum. The application effect is shown in Table 4-4, and the core samples taken out are shown in Figure 4-2 1.
Table 4-4 Comparison Table of SX Jet Suction Single-acting Double-tube Local Reverse Circulation Drilling Effect
Figure 4-2 1 reverse circulation continuous coring core sample
2. Single-pipe jet reverse drilling tool
Single-pipe jet reverse drilling has two structures: elbow type (Figure 4-22) and diversion joint type (Figure 4-23). Among them, the water diversion joint drilling tool has simple structure and convenient processing and installation.
Figure 4-22 Single pipe drilling tool with reverse circulation at the bottom of elbow jet
1- straightening pipe; 2— Nozzle joint; 3— Nozzle; 4- diffusion tube; 5- When water enters the water pipe; 6— Connecting pipe; 7— Elbow; 8-coupling; 9— Reducing joint; 10 core pipe; 11-direct positive cycle
Fig. 4-23 Single-pipe drilling tool with reverse circulation at the bottom of jet at diversion joint
1- straightening pipe; 2— Nozzle joint; 3— Nozzle; 4- diffusion tube; 5— Washer; 6— Connecting pipe; 7- Diversion joint; 8-core tube
(3) Full hole reverse circulation drilling
Whole hole reverse circulation drilling coring, also known as reverse circulation continuous coring, is a coring method that continuously transports cores (or cuttings) to the surface through the central passage of drill pipe without drilling. Full-hole reverse circulation coring can be divided into gas lift reverse circulation, pump suction reverse circulation and pump pressure reverse circulation according to different principles of transporting cores (or cuttings); According to different washing media, it can be divided into air reverse circulation and clear water (mud) reverse circulation; According to the different discharged samples, it can be divided into reverse circulation coring and reverse circulation chip removal. Full-hole reverse circulation continuous coring has the advantages of high drilling efficiency, high core recovery rate, improving the coring quality of loose and broken hole walls, clean hole bottom, easy passage through complex strata and low unit cost.
The working principle of full-hole reverse circulation continuous coring drilling is shown in Figure 4-24. Mud is pumped into the annular gap of the double-walled concentric pipe string by the pump 6 through a special water joint, and enters the inner pipe 3 through the drill bit 1 at a distance of 2 ~ 3 cm from the bottom of the hole. Mud carries the core and rock powder up to the core outlet hose 5 along the inner pipe and water joint 4, and flows with the rock powder to the core recovery tank 7 installed in the liquid collection tank 8. When drilling, the core breaker is installed at the lower part of the inner pipe of the drilling tool. When the drilled core reaches a certain length (about twice the diameter), it is blocked by the core breaker. In this way, the core is continuously transported from the bottom hole to the surface in sections.
Figure 4-24 Schematic Diagram of Reverse Circulation Continuous Coring Drilling Device
1 bit; 2— Outer pipe of double-arm drill string; 3- inner tube; 4-side water inlet connector; 5- catheter; 6— Mud pump; 7— Core recovery tank; 8— Liquid collection box