Section 1 Drilling Structure and Concept
Drilling structure refers to the change of drilling diameter from opening to final hole. The more times the diameter is changed, the more complicated the drilling structure is, and vice versa. The selection of drilling structure should fully consider the rock properties, hydrogeological conditions, final aperture, drilling depth, drilling method, drilling purpose and other factors in the mining area.
Second, determine the general principles of drilling structure
Taking the final well diameter as the standard for drawing up the drilling structure, according to the ideal rock profile, the caliber and opening diameter of each section are drawn up from bottom to top. On the premise of ensuring the quality and safety of drilling, protect the borehole with mud as much as possible, so as to reduce casing or casing running, reduce diameter change and simplify the drilling structure to the greatest extent.
Three, drilling structure selection example
When exploring metal deposits, the design hole is 700 meters deep and diamond drilling is used. The geological profile includes the following horizons: (1)0 to100m is rock, and the drillability is 1-7, which is completely lost and has no circulation; (3)100-700m is a stable rock with drillability of 9-10; (4) Geological sampling requires 59mm final hole. Try to determine the drilling structure. [Resolution] According to the known conditions, the hole is suitable for running all the way from160m to the bottom without casing. Through the analysis of geological profile, drilling pipe and a layer of casing are enough; To seal the plugging layer, run the casing to the depth of120-130m, and the casing shoe extends into the stable layer of10-20m. The casing diameter is 73mm, and a 76mm interval must be drilled. The length of orifice tube is 18 to 20m. The diameter is 89 mm, so the opening is 9 1 or 1 10 mm. Based on this, the drilling structure diagram as shown above can be made.
In the design of drilling technology in mining area, it is worth noting that the drilling structure in mining area should be divided into simple drilling structure and complex drilling structure, and all elements such as diameter and reducing depth should be indicated when drawing.
Section III Drilling Methods At present, in core drilling, the layered drilling method of alloy and diamond is often adopted according to the mechanical characteristics, structure and structure of strata in various mining areas, combined with drilling equipment and wall protection and plugging measures. Generally, alloy is used to drill holes to the complete rock surface for 3 to 5 meters, and then reaming pipes are used to isolate unstable strata such as upper loose layers and overburden layers, and then diamond is used to drill holes to the final hole. Therefore, only these two drilling methods are introduced here.
First, the concept of cemented carbide drilling 1 cemented carbide with certain strength and shape is fixed on the drill bit according to the drilling requirements, and under certain technical conditions, it is used as a drilling method for cutting tools to break rocks.
2 Requirements for cemented carbide in drilling Alloy drilling relies on cemented carbide fixed on the bit body to break rocks. All kinds of rocks have certain strength and abrasiveness, and the stress on the bit during drilling is also very complicated. Therefore, the cemented carbide used should have the following characteristics:
① High hardness and strong wear resistance. It is convenient for the drill bit to cut into or press into the rock effectively, and it can resist the wear of cemented carbide by the rock.
② High bending strength and good toughness. It is convenient to bear all kinds of loads in the process of rock breaking, and there will be no edge collapse and breakage.
③ Good thermal hardness and high thermal conductivity. High temperature will be generated at the bottom of the drilling hole, so it requires high thermal hardness and is easy to release heat in the washing liquid. (4) Good formability, easy to insert and weld on the bit body.
Tungsten-cobalt alloy is the main cemented carbide used in geological exploration, and its properties meet the above requirements.
Whether the structure of cemented carbide bit for drilling is reasonable directly affects drilling efficiency, bit life, drilling quality and material cost, so attention should be paid to the research and selection of structural elements of cemented carbide bit. Generally, it can be divided into two categories: coring bit and all-round bit. Generally speaking, only coring bits are used in geological exploration.
① Bit body: it is the matrix of embedded tool and is made of D35 or D45 seamless steel pipe. The inner and outer edges of the needle-shaped alloy bit should be consistent with the corresponding diamond bit, and the length of the bit body should be not less than 95mm, in which the length of the threaded part is 40mm, and the wall thickness of the steel body of the bit is 7-9 mm. If it is too thick, it will bring a large area of rock and consume a lot of power, while if it is too thin, it will affect the strength and be easily deformed. Under the condition of ensuring sufficient strength and rigidity, the wall thickness should be reduced as much as possible to reduce the coring area and improve drilling efficiency.
② The number and arrangement of alloy mosaic welding: it should be determined according to rock properties, drill bit diameter, alloy quality, drilling tool strength, equipment power and other factors. When the bit has large diameter, deep hole, high rock hardness and high abrasiveness, the amount of alloy should be appropriately increased. The quantities commonly used in geological exploration are shown in the following table.
Specification of drill bit (mm)
Alloy quantity (unit)
Rock properties 36 46 59 76 911010130150.
3-43-44-666-88-10/0-1412-14 has strong abrasiveness.
Weakly abrasive stratum 3-43-444-666-88 10
Generally, uniform single circle arrangement is adopted in the arrangement form.
(3) Cutting edge: There are three kinds of cutting edges: bottom, inside and outside. Among them, the bottom cutting edge plays the role of cutting into and breaking rocks, and the larger cutting edge is beneficial to the circulation of broken rocks and washing liquid, but it is easy to cause blade collapse and fracture if it is too large; The inner and outer blades mainly form an annular gap to ensure the circulation of washing liquid. Larger inner and outer blades will increase the rotary resistance of the drill bit, which is easy to collapse, but it is beneficial to discharge powder and reduce the chance of plugging. If it is too small, it is easy to block the core, affect the powder discharge effect, and even lead to bad phenomena such as paste drilling. Therefore, the size of the cutting edge should be considered according to the rock properties, and the following table can be referenced for selection in practical work.
Rock properties Inner edge (mm) Outer edge (mm) Bottom edge (mm)
Soft, weak to medium ground rock 1.5-2.5 2.5-3 2-3
Medium hard and strong abrasive rock1-21-21.5-2.5
(4) Inlay welding angle: The angle between alloy particles and the lip surface of the drill bit is generally fillet welding, which has self-grinding effect and is beneficial to powder discharge, but the required axial pressure is greater than other methods.
⑤ Nozzle and water tank: It plays the role of circulating cooling the drill bit with flushing fluid and carrying rock powder, and its shape and size should be considered according to different rock properties, drill bit structure and types of flushing fluid. Generally, the sum of nozzle areas is larger than the annular area between the drill bit and the core or between the drill bit and the hole wall to reduce the circulating resistance.
4 alloy drilling technical parameters
The technical parameters of alloy drilling mainly include WOB, rotating speed and flushing fluid volume. They are directly related to drilling efficiency, drilling quality, abrasive consumption and construction safety. In the process of operation, it is necessary to reasonably grasp the physical and mechanical properties of rocks, bit structure, the possibility of drilling equipment and drilling tools, drilling quality requirements and other conditions, and make corrections in practice to sum up the best drilling technical parameters suitable for mining areas.
① WOB: A reasonable WOB should not only ensure the durability of the bit, but also obtain the maximum average ROP. When other conditions remain unchanged, within a certain range, with the increase of WOB, the proportion of drilling speed increases. Practice has proved that the improvement of ROP mainly depends on the improvement of WOB. However, excessive pressure will lead to accidents such as edge collapse, drilling tool fracture, borehole bending and easy burning of soft rock drilling. WOB can be calculated by the following formula:
Total bit pressure = the pressure to be added on each cutting tool (such as columnar alloy 70- 120kgf/ piece) x the number of cutting tools on the bit.
In practical work, the types of alloy cutters, the arrangement and quantity of drill bits should be selected according to the nature of the drilled rock strata, and the best WOB should be continuously summarized in construction.
② Rotational speed: There are two ways to express the rotational speed of drilling tools, one is the revolutions per minute (rpm) of the drill bit, and the other is the circumferential speed v (m/s) of the drill bit. V = [π(D + D 1)n ]/(2X60)
The production practice shows that under certain conditions, increasing the bit speed can improve the ROP, but after exceeding the optimal value, it will decrease with the increase of the speed. Generally speaking, when drilling in soft to medium hard rocks, a higher rotating speed can be used; When drilling in hard and abrasive rocks or rocks with uneven and developed cracks, the rotation speed should be reduced; Deep hole or large diameter drilling should also reduce the speed.
③ Flushing fluid volume: The flushing fluid volume should be determined according to factors such as rock properties and well diameter. Generally speaking, when drilling in soft rock, a large amount of flushing fluid is selected because of the large amount of rock powder produced by fast penetration; When drilling in a rock stratum with a large proportion of coarse particles and coarse particles, the flushing fluid should also be increased accordingly; When drilling large-diameter holes and deep holes, if the drill pipe and hole wall leak a lot, the amount of flushing fluid should also be increased; However, in order to prevent core erosion and hole wall erosion when drilling in loose and broken formations, a small amount of flushing fluid should be selected. Generally, the empirical formula is used to calculate the flushing fluid q:q = kdk- empirical coefficient (6- 15l/cm. min)d- bit diameter (cm).
There is a close relationship between these parameters in actual drilling work. To achieve reasonable cooperation, the cooperative relationship is roughly as follows:
WOB rotational speed flushing fluid volume of rock
Hard rocks with high abrasiveness are large and small.
The fractured stratum is very small, and correspondingly, it is also very small.
Small and soft rocks are correspondingly large.
The design can be based on the data range of the following technical parameter table and the lithologic characteristics of the mining stratum, and at the same time, the optimal technical parameters suitable for the mining stratum can be explored in practical work.
Table of drilling technical parameters in different formations
Technical parameters of horizontal drilling in rock
Bit pressure speed
(rpm/min) Pump capacity
(liter/minute)
Core bit
(kg/granule) drag bit
(kg/cm)
1 ~ 4 grade 50 ~ 60100 ~120 200 ~ 350 > 80
Part 5 ~ 6, level 7, 80 ~ 120, 120 ~ 150, 150 ~ 250 > 80.
Note: (1) Each needle-shaped cemented carbide block can bear pressure150 ~ 200 kg;
(2) The pumping capacity of100 drilling rig is given by the maximum effective displacement of the pump.
(3) The cm (kg/cm) in the unit pressure of the bit refers to the bit diameter.
5 Matters needing attention in alloy drilling
Using alloy drilling, in addition to reasonable selection of bit structure and drilling technical parameters, correct operation methods are needed to improve drilling efficiency and service life of bit. Therefore, we should pay attention to the following aspects:
(1) Put the new drill bit into the hole, which should be more than 0.5m away from the bottom of the hole and turn it gently and slowly to the bottom of the hole to prevent the new drill bit from being squeezed. When sweeping holes, the speed should be slow to avoid the alloy collapsing or being blocked by the core left at the bottom of the hole.
② Always keep the bottom of the hole clean. The rock powder and caving alloy in the hole must be fished out in time. When the residual core in the hole exceeds 0.5m or there are fallen cores, no new drill bit can be run.
(3) In order to keep the aperture consistent, the drill bit should be used in a straight line. The principle is to use the one with large outer diameter and small inner diameter first, and then use the one with small outer diameter and large inner diameter.
(4) The normal WOB should be uniform, drilling tools should not be lifted without reason, and the pressure should gradually increase as the alloy becomes dull. If the core is blocked, it should be handled in time. If it is ineffective, it should be lifted immediately to prevent accidents in the hole.
⑤ Grasp the footage time reasonably. In the process of alloy drilling, the diameter reduction and penetration rate gradually decrease because the abrasive becomes dull. Therefore, in order to avoid the next drilling and tripping time and improve the return efficiency, a reasonable return footage time should be determined, which is one of the effective measures to improve the ROP. It can be determined on site by calculation method or drawing method, and the strata in each mining area are different, so specific data cannot be given here.
Return penetration rate = (cumulative footage per return)/(cumulative drilling time+tripping time)
Second, diamond drilling.
Advantages of 1 diamond drill: Compared with other methods, it has the following advantages:
① High drilling efficiency; ② The drilling quality is good (the recovery rate can reach more than 90%, the core is representative, the core is smooth and complete, there is no selective wear, loss and pollution of rich ore, and the drilling bending is small); ③ Less accidents; ④ Low labor intensity; ⑤ Low cost; ⑥ Wide application range.
2 diamond bit
Here, we need to know and master the composition, type, specification and structure of diamond bit, so as to evaluate whether the bit selected in the mining area is reasonable when designing or reviewing the design.
① Composition of drill bit: It consists of diamond, matrix and bit body.
Diamond: A diamond with a bottom, a side and a side. When the bottom edge is used to extract rocks, diamond with better crystal shape should be selected; The blade is mainly used to take stones and keep the inner diameter and outer diameter. So choose the best quality diamond; The side is only used to keep the inner diameter and outer diameter, and inferior diamonds can be selected.
Matrix: It is a circle of false alloy with diamonds embedded in the bottom of the drill. By powder metallurgy or electroplating, it is made into various required shapes to embed diamond particles and weld them firmly with the bit body. The housing part is provided with a water nozzle for circulation of washing liquid. The hardness of diamond bit matrix is generally between HRC 20-50 and 50, so the hardness of diamond bit matrix should be reasonably selected according to the abrasiveness and crushing degree of mining lithology.
Bit body: the steel body of the bit is made of medium carbon steel, and the upper part is threaded for connecting with the reamer.
3. Reasonable selection of diamond bits and abrasives
Production practice has proved that not all kinds of rocks can be successfully drilled by diamond bits, and in some rock formations (such as "sliding strata"), the penetration rate is very low or even no footage. Therefore, reasonable selection must be made according to the hardness, strength, abrasiveness and integrity of the rock, and the drill bit should be selected in layers, so as to give full play to the advantages of diamond drilling. If the selection is improper, it will not only fail to exert its effectiveness, but also increase the consumption of diamonds, increase drilling costs, accidents, low efficiency and poor quality. So we must attach importance to this work in design and practical work.
3. 1 Selection principle of layered drilling
① In medium-hard to hard rock stratum, medium-strong abrasive rock stratum and broken rock stratum, impregnated bit drilling should be adopted.
3.2 Basic principles of diamond bit selection
3.2. 1 bit type selection principle
The selection should be based on the abrasiveness, integrity and drillability of the rock. The invention is suitable for drilling in soft and medium hard complete strata; The impregnated drill head is suitable for drilling hard, hard, broken, uneven hardness and broken rock strata.
3.2.2 Selection principle of drill bit matrix: When drilling in highly abrasive, extremely broken, soft and coarse-grained rock stratum, the hardness of the selected matrix should be high; On the other hand, the matrix hardness used in the stratum with weak abrasiveness, complete uniformity, high hardness and fine particle size should be soft; However, the soft matrix should not be selected in the rock stratum with strong abrasiveness and extremely hard hardness, but the extremely hard matrix should be selected, otherwise the matrix will soon be worn by the rock stratum and the bit will lose its working ability.
3.3.3 Specific selection conditions: According to the above principles, for the specific design and use of diamond concentration, particle size and matrix hardness of commonly used artificial impregnated diamond bits, bits suitable for mining strata can be selected from bits produced by different manufacturers according to the following table.
Rock is hard, medium hard and soft.
Fine diamond particle size
100 mesh 80-46 mesh thick
46 orders
Low diamond concentration
50% higher than 50-75%
100%
The hardness of the matrix is soft.
Hrc30 hrc40 is hard.
HRC 40-50
4 rational use of diamond bit and reamer
The purpose is to achieve the highest penetration rate and the longest service life of the drill bit with the least amount of diamond, thus reducing the cost. The principle is: use the large outer diameter first, and then use the small outer diameter. At the same time, we should also consider using small inner diameter before using large inner diameter. The advantages of this are:
4. 1 Make the outer diameter of the drill bit match the hole bottom diameter as much as possible to avoid hole sweeping;
4.2 Make the inner diameter of the drill bit match the inner diameter of the clamp spring and the outer diameter of the residual core as much as possible to prevent the core from being blocked or damaged by core sweeping;
4.3 Prevent the drill bit and reamer from getting stuck and causing accidents;
4.4 It can prevent a single drill bit from continuously drilling for many times to form a "trumpet-shaped" drilling hole, resulting in long-distance hole sweeping;
4.5 The drill bit and reamer can be evenly worn, which can prolong the service life and reduce the cost.
5 drill bit with reamer and clamping spring.
5. 1 Matching of reamer outer diameter and bit outer diameter
The outer diameter of the reamer is too large, resulting in "stepped" drilling, and the reamer is prone to edge collapse or premature wear, resulting in low drilling efficiency; However, if the outer diameter of the reamer is too small, it will not play the role of reaming, resulting in premature wear of the bit. Therefore, the reasonable matching size of the outer diameter of the reamer and the outer diameter of the bit is: the outer diameter of the reamer is 0.3-0.5 mm larger than the outer diameter of the bit, and it should not be larger than 0.3mm in hard rock stratum.
5.2 Reasonable cooperation between the inner diameter of drill bit and the free inner diameter of clamp spring
The inner diameter of the clamp spring is the first "gateway" for the core to enter the inner tube. If the inner diameter of the clamp spring is too large, the core cannot be taken out or clamped, resulting in the core falling off or the residual hole bottom being too long. However, if the inner diameter of the clamping spring is too small, the core will be blocked or the clamping spring will be forced to lift the drill bit. Therefore, the fit size between them is: the free inner diameter of the clamp spring is 0.3-0.4 mm smaller than the inner diameter of the drill bit. When using the field machine, there should be two or three kinds of circlips for the machine to choose from. When using, use the small inner diameter first, and then use the large inner diameter. It is worth noting that the nipple is in transition fit with the circlip seat, and there should be a gap of 4-5 mm between the lower end of the circlip seat and the inner step of the drill bit (to prevent the core from being blocked).
6 preventive measures for common accidents in diamond drilling
6. 1 How to prevent core plugging
In actual drilling, when there are some factors such as joint development, rock fragmentation, unreasonable technological procedures, improper operation and poor coordination of drilling tools, it is easy to cause core blockage. Prevent the use of single-acting double-tube drilling tools or special coring tools. The inner tube of single-acting double-tube has the functions of centralizing the core, reducing the looseness of drilling tools and containing the core. At the same time, there must be a gap of 3 ~ 4mm between the clamp spring seat and the inner step of the drill bit to ensure that the inner tube can freely centralize the core and prevent plugging. However, special coring tools, such as containment tube or piston, should be designed in rock and mineral beds with developed joints and large crushing inclination. In addition, the main measures to ensure the core to enter the inner tube smoothly are: the inner tube is smooth and straight; A damping mechanism or a semi-closed tube is arranged in the double tube; Good fit between the free inner diameter of clamp spring and the inner diameter of drill bit; Careful operation, stable technical parameters and no unreasonable lifting of drilling tools.
6.2 How to prevent drilling burning accident
Insufficient cooling of the bottom hole bit will burn, and in severe cases, it will be accompanied by vicious drilling sticking and drill pipe fracture, so preventive work should be done.
The main causes of drilling burning accidents are: the drill pipe leaks halfway and the flushing fluid reaching the bottom of the hole is insufficient; The water pump is not working properly; If the core is blocked, it cannot be lifted in time; Water leakage in the rock stratum at the bottom of the hole; Drilling speed is too fast, and rock powder is not removed in time, which will cause drilling burning accident.
Accident signs: the pump pressure suddenly rises and the backwater becomes smaller; Turning resistance increases, and footage slows down or remains unchanged; Mechanical operation is not normal; Abnormal noise of diesel engine or rising ammeter value of motor are all signs of drilling accident.
Preventive measures: ① Prevent the flushing fluid from leaking from the drill pipe. Carefully check the wear of drill pipe when lifting, and replace it in time if it is unqualified; Measures such as winding cotton yarn on the thread of drill pipe joint when tripping in.
(2) to prevent the pump capacity is insufficient. It can be realized by checking the water pump regularly, using variable displacement pump and seismic pressure gauge with good seismic performance, and checking whether the water hole and waterway are unblocked at any time;
(3) Control the ROP in the soft stratum, and don't blindly push the footage. When the formation changes from hard to soft, the pressure will decrease accordingly.
(4) Always repair the grinding nozzle and sink. It is required that the nozzle height is not less than 3mm and the depth of the tank is not less than1.5 mm.
⑤ Careful operation. Operators should observe the changes of pump pressure gauge, bottom hole pressure gauge, ammeter (when using motor), backwater in hole, footage speed and power machine load at any time, and lift the drill immediately if any abnormality is found.
6. When tripping in, you can't reach the bottom of the well at one time. Pumping must be started at a distance of more than 0.5m from the bottom of the hole. After the circulation is smooth, slowly rotate and lower the drilling tool to the bottom of the hole.
⑦ When the core is blocked or the pump is stuck, it should be lifted immediately. Don't increase the pressure or speed up to deal with it.
⑧ Keep the hole clean, and the residual rock powder at the bottom of the hole shall not exceed 0.3m At the same time, regularly remove impurities, foreign bodies and sediments in the cleaning solution purification system.
8 diamond drilling technical parameters
Under the correct selection of diamond bit, the drilling efficiency of diamond depends on the reasonable adjustment of drilling adjustment parameters, that is, the axial load of bit, the rotation speed of bit and the amount of flushing liquid. Many variables have direct influence on the specification parameters, such as rock physical and mechanical properties, bit type, drilling diameter and depth, equipment and drilling tools used, etc. Diamond drilling adopts drilling rules with high rotation speed as the main body, and the change of rotation speed parameters has obvious influence on drilling effect. The rationality of the selected drilling regulations is evaluated mainly on the basis of drilling speed, bit footage and diamond consumption per unit footage (carat/meter), among which the diamond consumption per unit footage and bit footage are particularly important. In practical work, we should comprehensively choose the technical parameter range of construction in this mining area according to the lithologic characteristics of the mining area and the selected equipment, aperture and depth, instead of blindly applying the standard parameters in the design.
8. 1 WOB
Refers to the axial pressure directly acting on the drill bit during drilling. Suitable WOB can ensure that the diamond bit can effectively crush rocks, with high efficiency, more footage and less diamond consumption. When WOB is lower than the compressive strength of the rock, the diamond can't take away the rock, but slides on the rock and is quickly polished. Excessive WOB will lead to the accumulation of drill cuttings at the bottom of the well, which will lead to the rapid wear of the bit matrix and the large consumption of diamond, which will lead to low ROP and even sticking and burning of the bit.
When selecting pressure, drillability, abrasiveness, integrity, bit type, quality, quantity and granularity of diamond, and the area of rock annulus occupied by the bit should be considered. Generally speaking, it is not comprehensive to recommend WOB according to the bit diameter. Generally speaking, from the point of view of rock properties, small WOB is used for soft or weakly abrasive rock layers; In complete, medium hard to hard or medium abrasive rock strata, WOB； is appropriately increased; In fractured and heterogeneous rocks, WOB should be reduced appropriately (25-50%) according to the degree of fracture. From the type of drill bit, when the diameter is large, the wall thickness is thick and the matrix is hard, the larger WOB is used and the smaller WOB is used. It is worth noting that the WOB used when using the inlaid bit is larger than that of the impregnated bit, so that the diamond can be pressed into the drilled rock, resulting in volume crushing. From the composition of drill bits, when all diamond drill bits are of high grade, good quality, large quantity and large particle size, WOB should be larger, otherwise it should be smaller. At the same time, in practical work, when determining the WOB, we should also consider the old and new degree of the bit and estimate the loss of the bit at the bottom of the well. In the initial grinding stage, after applying a small WOB (200-300 kgf) and other normal cutting edges, the new bit can use normal WOB. Bottom hole loss is mainly affected by hole depth and pump pressure. With the increase of hole depth, the friction between drill string and hole wall and the increase of pump pressure offset a part of WOB, so WOB should be increased accordingly to ensure that the bit can effectively break the rock.
When designing, it can be calculated according to the following formula:
Pressure for installing the drill bit on the ground: p = (0.66—0.76) g m p.
Where p refers to the total pressure (kgf) of the surface-mounted drill bit;
G refers to the number of carats of diamonds on the drill bit;
M- diamond granularity (grain/carat);
P- empirical unit pressure (1.5-2.5 kgf/ granule);
0.66-0.76 is the coefficient, indicating that the actual amount of diamonds extracted from rocks accounts for 66-76% of the total carats of the drill bit. Calculation of WOB during injection: P = F p where: P- total WOB (KGF); F—— area of bit annulus (cm2), f = π/4 (d2–d2).
D- bit outer diameter (cm) D- bit inner diameter (cm)
8.2 speed
Rotating speed is one of the main technical parameters. When the diamond drills into the broken rock, the cutting depth is small (1% to11000 mm), so it is necessary to adopt a higher rotational speed to obtain a higher ROP. The production test shows that in a certain range, the higher the rotating speed, the higher the ROP. Therefore, in practical work, when the rock formation is relatively complete, the pipeline has sufficient strength and stability, is equipped with lubricant, and the equipment capacity allows, a higher rotation speed should be selected. It is worth noting that when the rotational speed exceeds a certain limit, the ROP will decrease and the life of the bit will be seriously affected. Domestic long-life bits are generally obtained at 800 rpm. Generally speaking, the cutting edge of impregnated drill head is very small, and the depth of cutting into rock is smaller. In order to obtain a higher penetration rate, the linear speed is required to reach1.5-3.0m/s; The cutting edge of the facing bit is larger than that of the impregnated bit, and the high rotation speed is easy to cause vibration and damage the diamond, so the linear speed of the facing bit is required to be1.0-2.0m/s.
The selection of rotating speed should be comprehensively considered from the aspects of drilling depth, equipment capacity, drilling structure and rock properties. When drilling deep holes, the weight of drilling tools is heavy, the stress situation is complicated, and the power consumed by drilling tool rotation is also large. Due to the limitation of power and drilling tool strength, when the pump pressure and pump quantity are insufficient, the rotation speed should be reduced. Higher rotating speed can be selected for drilling shallow holes; When the drilling structure is simple and the drilling tool classification is reasonable, it is appropriate to adopt high rotation speed; On the other hand, when the drilling structure is complex and the gap between the drill pipe and the hole wall is large, the drilling tool has poor stability and is not suitable for high speed driving. High rotation speed should be adopted in complete rock stratum; When the rock stratum is broken, the fracture is developed and the hardness is uneven, the drilling tool vibrates greatly, which is easy to damage the diamond, so the rotation speed should be reduced. The rotational speed is divided into three grades: high, medium and low. The maximum speed is generally above 700-800 rpm, or even 1000 rpm. The medium speed is generally 400-600 rpm; The low speed is generally 200-300 rpm, and the lowest speed is about 100 rpm. Then, in design and practical work, according to the above-mentioned selection principle, we can first determine how much linear speed to adopt, and then convert the rotational speed n through V = πDn/60, where v is linear speed (m/s), average diameter of D bit (m) and n is bit rotational speed (rpm/min). At the same time, according to the drilling depth, equipment capacity and rock properties, determine the reasonable speed.
8.3 Flushing fluid volume
Generally speaking, diamond drilling needs small pump capacity and high pump pressure, but it also needs uniform and continuous pump capacity and high flow rate. The reason is that the gap between the bottom of the hole and the wall of the hole is small, and the rock powder particles are fine, which requires higher upward flow and greater washing liquid pressure to overcome the flow resistance. Therefore, it is necessary to use variable displacement pump as the conveying equipment of flushing fluid in drilling operation. The main factors to be considered when determining the pumping capacity are rock properties, annular gap between drill pipe and borehole, bit type, diamond particle size, matrix performance and so on. The determination principle of pump capacity is as follows:
From the rock properties: when drilling into hard and fine-grained strata, a small amount of flushing fluid can be used because of low penetration rate and little fine-grained rock powder; Soft, medium hard and coarse-grained strata. Because of the high penetration rate, the flushing fluid is used earlier; When drilling in broken and slightly lost rock strata, a large amount of flushing fluid should be used to compensate for some losses; When drilling into abrasive rock strata, friction generates a lot of heat, which requires a lot of flushing fluid. However, it should be noted that if it is too large, it will erode the bit matrix under the action of strong liquid flow, so that diamond particles will be exposed prematurely and the edges will fall off.
Judging from the types of drill bits, impregnated drill bits use a lot of flushing fluid when drilling. Because of the high rotating speed, it is necessary to cool the matrix in time to avoid diamond damage and excessive wear of the matrix. The cutting edge of surface embedded drill bit is larger than that of impregnated drill bit, and the conditions of powder discharge and cooling are better than that of impregnated drill bit, and the amount of flushing liquid is smaller than that of impregnated drill bit.
Seen from the annulus, the sinking speed of rock powder in the borehole annulus is generally 0. 1m/s, and rock powder can be brought to the orifice only when the upward flow speed of flushing liquid exceeds the sinking speed. Therefore, when drilling diamond, it is required that the upward flow rate of the washing liquid is 0.3-0.5m/s. When the return flow rate of the washing liquid exceeds 0.5m/s, the rocks and unstable rocks on the hole wall will be washed away, and accidents will easily occur.
From the perspective of drilling depth: with the increase of well depth, the leakage at the joint of drill pipe also increases, so the pump capacity should be increased appropriately.
The empirical formula can be used to calculate the capacity of the pump: q = k d.
Where: q-displacement of the pump (liter/minute); D—— Diameter of drill bit (cm); K- empirical coefficient, from 5 to 8.
According to the above, in the design or practical work, the flushing fluid volume can be calculated initially from the diameter, and then the reasonable flushing fluid volume can be determined by comprehensively considering the factors such as the properties of drilling rocks, drilling depth, bit type and drilling tool classification in the mining area.
About pump pressure: diamond drilling has small annular clearance, narrow bit nozzle and small cross section, so the flow resistance is large and the pump pressure is high. Pump pressure loss includes ground pipeline, drill pipe inner diameter, double pipe, drill bit and annulus, in which the pressure loss of ground pipeline (including high-pressure hose, faucet, movable drill pipe, etc.). ), the double pipe and drill bit are about 8 atmospheres; Every 100 meter of drill pipe loses about 2 atmospheres. These factors should be considered when selecting equipment during design. At the same time, in practical work, we can judge the situation in the hole according to the change of pump pressure and make corresponding treatment countermeasures. Usually, the slight increase or decrease of pump pressure during drilling is a sign of formation change at the bottom of the well. At this time, pay attention to the footage and drilling tool noise, and adjust the drilling parameters (including three parameters) if necessary to prevent plugging the core; If the pump pressure is greatly increased, it is a reflection of serious blockage, and the drilling tool should be lifted to the bottom of the hole as soon as possible to prevent burning; If the pump pressure drops obviously, mainly because the drill pipe breaks or trips, stop immediately for inspection. Therefore, the change of pump pressure should be observed frequently during drilling to prevent water loss in the middle. At the same time, a pump pressure gauge with good performance should be equipped to help quickly judge the situation in the well.
8.4 Reasonable cooperation of technical parameters
WOB, rotational speed and pump displacement are mutually coordinated and restricted. Under certain conditions, there is an optimal matching relationship, which is called the optimal drilling program. Only drill under the best procedure. Only in this way can we obtain the highest drilling speed and longer bit life with minimum diamond consumption, and achieve the goals of high quality, high efficiency, low cost and safety.
Generally speaking, when drilling in soft formation, high rotation speed, large pump capacity and appropriate pressure are adopted; When drilling in hard and abrasive rock formations, use a larger WOB and appropriate rotation speed and pumping capacity; Minimum WOB, medium and low rotation speed and appropriate pump quantity are adopted when drilling in broken rock stratum and abrasive rock stratum; When drilling in "sliding layer", large WOB, medium and low rotation speed and appropriate pump capacity should be adopted.
In short, according to the actual situation, we should explore and summarize the reasonable cooperation of various parameters, accumulate experience, and gradually enrich and improve the drilling technical regulations in mining areas.
The parameters of wireline coring drilling procedure are larger than those of ordinary diamond drilling, which is mainly caused by the different lip surfaces of the drill bit. WOB is larger than the ordinary one outside, and the rotating speed is higher when the power conditions permit, while the water volume is smaller than that of the ordinary double pipe (generally 35-35 liters/minute) because of the small annular gap, so I won't talk about it here.
9 Selection of drilling tools
At present, in addition to single-pipe drilling in our area, double-pipe drilling tools are generally used after reducing the diameter. Double-pipe drilling tools are divided into single-acting double-pipe drilling tools and double-acting double-pipe drilling tools, and each mining area can be flexibly selected according to the lithologic characteristics of the drilled strata and the difficulty of coring.
.................. writes a design-you can't write the rest!