RU2319009C2 - Method for rock drilling with electrical pulsed discharges and drilling tool - Google Patents

Abstract

FIELD: mining, particularly methods or devices for dislodging, particularly by electricity.

SUBSTANCE: method involves transferring high-voltage pulses with frequency defined by head rotation rate on rotary drilling head. Drilling tool includes serially connected drilling string 9, drilling head 1, high-voltage pulse source 11 arranged directly in drilling tool over drilling head 1 and charging means 12. The charging means 12 is arranged in drilling tool over high-voltage pulse source 11.

EFFECT: increased drilling efficiency due to increased operational drilling tool reliability.

3 cl, 6 dwg, 1 tbl

Description

The invention relates to mining and is intended for drilling wells and shafts during exploration, in the oil and gas industries, for mining, during construction work, as well as in other areas.

A known method of drilling wells by electric pulsed discharges (Yutkin L.A. Electro-hydraulic effect and its application in industry. - L .: Mashinostroenie, 1988. - S. 61-64).

According to the known method, high voltage pulses are applied to the electrodes of a drill bit mounted on a rock that is coated with a flushing fluid. A discharge occurs between the electrodes. The discharge channel passes either over the surface of the rock, or the discharge channel is introduced into the rock, which is typical for very porous rocks with low dielectric strength. The energy stored in the source of high-voltage pulses is explosively released in the discharge channel, which leads to the destruction of the rock in the channel passage zone.

The disadvantage of this method is the low efficiency of the drilling process, because there is no relationship between the rotation speed of the drill bit and the frequency of supply of high voltage pulses.

A well-known drill (Yutkin L.A. Electro-hydraulic effect and its application in industry. - L .: Mashinostroenie, 1986. - p. 171-173) that implements the above method. It consists of an external drill pipe - housing, a high-voltage input, a drill bit - an external electrode, a central high-voltage rotating electrode, an electric motor for rotating the central electrode.

The work of the drill is as follows: flushing fluid is supplied to the drill; an electric motor is turned on to rotate the central high-voltage electrode, to which high voltage pulses are supplied, rock is destroyed at the bottom of the well; destroyed rock - the sludge is carried out by the flow of washing liquid into the sludge collector.

The disadvantages of the known drill are due to the fact that the source of high voltage pulses and the charger are located separately from the drill, which leads to a decrease in drilling efficiency due to energy losses and distortion of the parameters of the high voltage pulse in the transmission system - a high voltage cable from the source of high voltage pulses to the drill and the drill itself of varying lengths while drilling a well.

The prototype of the proposed method is an electropulse method of rock destruction (RF patent No. 2232271, IPC 7 Е21С 37/18, publ. 10.07.04). The method consists in the fact that high voltage pulses are supplied to the moving 2-electrode device. The step of moving the electrodes of the device between two electrical pulses is selected from the following conditions:

moreover

where m is the step of moving the electrodes of the device, mm;

W _s - energy stored source of pulses, J;

L is the interelectrode gap, mm;

W _opt1 — optimal fracture energy per pulse for a rock with a propodyakonov coefficient of 5 J;

n is the number of pulses on the interelectrode gap.

The disadvantage of this method is the lack of conditions for choosing the optimal frequency of supply of high voltage pulses depending on the speed of movement of the electrode device.

The prototype of the proposed drill is the projectile described in the description of the invention "Electropulse drill" (copyright certificate SU No. 730022, IPC 4 E21C 37/18, publ. 30.12.87 Bull. No. 48). The drill consists of a high-voltage input, a metal drill string, inside which there is a conductive system centered by the insulators, and a high-voltage pulse generator is mounted, which is secured with insulators between the pipe string and the drill bit.

The work of the drill is as follows. Energy is transmitted through a conductive system to a high-voltage pulse generator from a direct current source. High voltage pulses are formed directly on the drill bit without any transmission through the conductive system of the drill. The destruction process is carried out by a drill bit, followed by the removal of sludge from the destruction zone.

The disadvantage of a drill selected for the prototype of the drill is the need to supply a high constant charging voltage from the earth's surface through the conductive system of the drill, which is associated with the difficulty of isolating the conductive system. For example, you need a high voltage cable for a working charging voltage. In addition, the rotation of the drill bit is not provided for this drill, which significantly affects the efficiency of drilling. It increases losses during the transfer of energy from the surface-mounted charger through the drill pipe conductive system to the high-voltage pulse generator located directly above the drill bit, increases the metal consumption of the drill bit and, as a result, the load on the high-voltage pulse generator, and also prevents the use of combined destruction methods.

The main technical result of the proposed method and the drill is to select the optimal frequency of supply of high voltage pulses depending on the speed of movement (rotation) of the electrode device along the bottom of the well and the location of the source of high voltage pulses and the charger directly in the shell, which eliminates the above disadvantages of the known technical solutions: low efficiency of the drilling process, as there is no relationship between the rotation speed of the drill bit and the frequency of supply of high voltage pulses; the device is located separately from the drill. In addition, the presence of a jacket at the source of high-voltage pulses and a charger (according to claims 2 and 3 of the claims) allows them to be intensively cooled by a flow of washing liquid, it is technically simple to carry out their maintenance and replacement if necessary.

The main technical result is achieved by the fact that in the proposed method for drilling wells using electrical impulse discharges, high voltage pulses are supplied to the rotating drill bit according to the proposed solution with a frequency

where f is the frequency of the pulses, imp./s;

V is the peripheral speed of rotation of the drill bit, mm / s;

m is the step of movement of the drill bit between two pulses, mm / imp.

To achieve the main technical result, a drill for drilling by electric pulse discharge is also proposed, which, like the prototype, contains a series of drill pipe string, drill bit, a source of high-voltage pulses located directly in the drill over the drill bit, and according to the proposed solution, a charger source of high voltage pulses located directly above this source.

It is also advisable to supply the source of high voltage pulses and the charger with a jacket, which forms a channel for the flow of flushing fluid between the drill pipe string and the jacket.

An example of a specific implementation of the proposed method. In figure 1, 2, 3 and 4 presents shells with drill bits in 2- and 3-electrode versions that implement the proposed method. A two-electrode drill bit (Figs. 1 and 2) is designed for core drilling. It consists of a housing 1, a core insulator 2 with openings 3 for the passage of the washing liquid flow, a high voltage current lead 4, a high voltage electrode 5 and a grounded electrode 6.

The method is as follows. Flushing fluid is supplied to the drill, which fills the internal cavity of the drill, passes through the holes 3 of the core insulator 2 of the drill bit 1 to the bottom 8 of the well 7 and fills the annulus between the walls of the well and the drill pipe string. The device for rotating the drill at a given speed is turned on. The source of high-voltage pulses is switched on with a pulse supply frequency determined from the expression:

where f is the frequency of the pulses, imp./s;

V is the peripheral speed of rotation of the drill bit, mm / s;

m is the step of movement of the drill bit between two pulses, mm / imp.

At the bottom 8 of the well 7 between the electrodes 5 and 6, an electric discharge occurs in the rock mass, which leads to its separation and destruction. The destroyed rock-sludge is picked up by flushing fluid and carried to the surface. While waiting for the next voltage pulse, the drill bit moves a distance equal to step m, and the next discharge occurs. The discharge channel passes in a solid dielectric (rock), as the least electrically durable. Therefore, it is introduced into the rock mass both at the bottom of the well and in its walls. The development of the walls of the well and core takes place, which contributes to the free rotation of the tip and the absence of its hovering on the wall of the well. As a result, a two-electrode drill bit drills a gap, and a core remains in the center of the well.

Three-electrode drill bit (Fig.3, 4) is designed for continuous drilling (without core). It consists of a housing 1, a core insulator 2 with holes 3 for the passage of the flow of flushing fluid, high-voltage conductor 4, high-voltage electrodes 5 and a grounded electrode 6.

The operation of this drill bit is similar to that of a two-electrode bit. The difference lies in the fact that the use of the third central high-voltage electrode causes the development of discharge channels both between it and the grounded electrode, and between the peripheral high-voltage and grounded electrodes, which leads to core destruction, and drilling is carried out by a continuous slaughter.

The results of a specific drilling tip, which had two electrodes (Fig.1, 2): a high voltage electrode of positive polarity and a grounded electrode. The outer diameter of the tip D _nak = 98 mm As a sample, fine-grained sandstone with a specific mechanical compressive strength σ _cr = 86 MPa was used (the coefficient of strength on the scale of Prof. M. M. Protodyakonov is 5). The washing liquid was water with a specific resistance ρ = 8 · 10 ³ Ohm · cm. The drill bit electrical resistance was 530 ohms. The distance between the electrodes is 25 mm. The rotation of the tip was carried out from an external drive with a given speed of movement of the electrodes v = 33 mm / s. In this case, the displacement step changed with a change in the pulse repetition rate in accordance with the expression

Wells 160 mm deep were drilled in sandstone samples.

Table 1 shows the drilling results, where

f is the frequency of the pulses, imp./s;

m is the step of movement of the drill bit between two pulses, mm / imp;

W _beats - specific energy consumption for the destruction of a unit volume of rock, J / cm ³ ;

D _SLE - the average diameter of the drilled well, mm

The most objective and informative characteristic of rock destruction during drilling by electric impulse discharges is specific energy consumption W _beats (J / cm ³ ). Comparison of the drilling efficiency at different frequencies of the pulse supply was carried out by specific energy consumption W _beats .

Table 1 No. p / p f, imp./s m, mm / imp. W _beats , j / cm ³ _SLE mm one 1.7 19 332 one hundred 2 2,3 fourteen 210 105 3 3.3 10 255 107 four 4.0 8.3 410 108

Уменьшение частоты менее чем

при v=const (строка 1, табл.1), увеличивает шаг перемещения электродов m по забою скважины, что вызывает увеличение W_уд в 1,58 раза, т.к. уменьшается объем разрушения, из-за снижения затраченной энергии на разрушение при перемещении электродной системы на длину межэлектродного промежутка. Кроме того, уменьшение частоты подачи импульсов меньше оптимальной при v=const приводит к уменьшению среднего диаметра скважины. При диаметре бурового наконечника 98 мм разработка среднего диаметра скважины для строки 1, табл.1 составляет 2 мм, т.е. 1 мм на сторону. Поскольку разрушение горной породы электрическими импульсными разрядами происходит крупным сколом, то стенки скважины оказываются с выступами и впадинами, что приводит к зацеплению бурового наконечника за выступы стенок скважины и, как следствие, к затратам дополнительной энергии на вращение бурового снаряда и даже «зависанию» его на стенках скважины, что дополнительно снижает эффективность бурения. Увеличение частоты подачи импульсов более чем

при v=const (строка 3, 4, табл.1) уменьшает шаг перемещения электродов по забою скважины, что приводит также к увеличению удельных энергозатрат в 1,21÷1,95 раза, которые тратятся на переизмельчение продуктов разрушения - шлама и увеличение среднего диаметра скважины. Разработка среднего диаметра скважины для строки 3, табл.1 составляет 9 мм, т.е. 4,5 мм на сторону. Увеличение среднего диаметра скважины - положительный эффект, который способствует более свободному вращению наконечника на забое скважины, отсутствию «зависания» бурового снаряда на стенках скважины, возможности регулирования диаметра скважины с изменением частоты, улучшению выноса на поверхность крупных частиц шлама.From table 1 it is seen that with increasing frequency of the supply of pulses, the specific energy consumption W _beats varies with a minimum (row 2 of table 1). The minimum value of W _beats corresponds to the most efficient drilling process and, as a consequence, to the optimal pulse feed frequency, i.e. condition

Frequency reduction less than

at v = const (line 1, Table 1), increases the step of moving the electrodes m along the bottom of the well, which causes an increase in W _{beats by} 1.58 times, because the volume of destruction is reduced due to a decrease in the energy consumed for destruction when moving the electrode system to the length of the interelectrode gap. In addition, a decrease in the frequency of the pulse supply is less than optimal at v = const leads to a decrease in the average diameter of the well. With a drill bit diameter of 98 mm, the development of the average well diameter for line 1, table 1 is 2 mm, i.e. 1 mm per side. Since rock destruction by electric impulse discharges occurs as a large cleavage, the walls of the borehole are ledges and depressions, which leads to the engagement of the drill bit over the bumps of the borehole walls and, as a result, to the cost of additional energy for the rotation of the drill string and even its “freezing” on the walls of the well, which further reduces the efficiency of drilling. An increase in pulse frequency of more than

at v = const (line 3, 4, Table 1) it reduces the step of moving the electrodes along the bottom of the well, which also leads to an increase in specific energy consumption by 1.21 ÷ 1.95 times that are spent on regrinding of fracture products - sludge and an increase in the average borehole diameter. The development of the average borehole diameter for line 3, table 1 is 9 mm, i.e. 4.5 mm per side. An increase in the average borehole diameter is a positive effect that contributes to a more free rotation of the tip at the bottom of the borehole, the absence of a “hang” of the drill string on the borehole walls, the possibility of controlling the borehole diameter with a change in frequency, and the improvement of the removal of large particles of sludge to the surface.

An example of a specific implementation of the proposed drill. Figure 5 shows the drill, consisting of a string of drill pipes 9, which are attached to the tip 1 using an insulator 2.

The charger 12 and the source of high-voltage pulses 11 are placed inside the drill pipe string 9 and directly above the drill bit 1. On the surface of the earth on the drilling site are located: a power cabinet 13, from which a charger 12 is powered by a power cable 14 to a voltage of 380 V, a collection tank sludge 19, pumping equipment, pressure hoses, etc. (not shown).

Drill works as follows. The drill string 9 and well 7 are filled with flushing fluid, which is pumped through a fitting 16 to the top of the drill. The fluid through the holes 3 of the insulator 2 (FIGS. 2, 4, 5) enters the drill bit 1 and through the annulus 17, the conductor 10 and the nozzle 18 are discharged into the tank 19. At the moment the fluid exits the nozzle 18, the rotation device of the drill string is turned on (on the drawing is not shown) and the charger 12 and the source of high-voltage pulses 11 are turned on. Pulses with an amplitude of 350 kV come from the source of high-voltage pulses 11 to the high-voltage electrodes 5 of tip 1. In the face zone 8, rock breakdown occurs between grounded 6 and high-voltage electric by rods 5 and the chipped sludge is carried out upward by the flushing liquid. In accordance with the optimal mode of operation according to claim 1 of the claims, uniform production (destruction and removal of the rock) of the face zone 8 is carried out and the projectile is immersed in the rock mass. After turning off the source of high-voltage pulses 11, the flushing process is carried out until all the cuttings are removed from the well.

The advantage of the proposed design of the drill according to claim 2 of the claims is as follows. Until now, in electric-pulse drilling, the charger was located outside the drill on the surface of the earth (see prototype), and the source of high-voltage pulses located in the drill pipe string was connected to the charger with a high-voltage cable (1.5 ÷ 40 kV). In the proposed design of the drill, the power from the power cabinet 13 to the charger 12 is transmitted by a cable 14 designed for an operating voltage of 380 V, which simplifies the power supply process, increases the reliability of the projectile and, as a result, increases the drilling efficiency due to even more reliable operation of the drill string pipes.

Figure 6 shows the drill, in which the charger 12 and the source of high-voltage pulses 11 are placed inside the drill pipe 9 directly above the drill bit 1. The principle of flushing the drill is similar to that shown in figure 5, with the only difference being that in the lower part projectile, the fluid flows between the jacket, in which the charger and the source of high-voltage pulses 11 are enclosed, and the wall of the drill pipe (according to claim 3).

Drill works as follows. After completing the procedure for filling drilling pipe string 9 and well 7 with drilling fluid, the device rotates the projectile (not shown) and the charger 12 and the source of high-voltage pulses 11 are turned on.

In accordance with claim 3 of FIG. 6, the charger 12 and the source of high voltage pulses 11 are placed in the jacket 20 of the source of high voltage pulses 11. The gap between the charger 12, the source of high voltage pulses 11 and the jacket 20 of the source of high voltage pulses 11 is filled with dielectric material. When flushing fluid is supplied through the nozzle 16 to the drill pipe string 9, a fluid flow passes between the drill pipe string 9 and the jacket 20 of the high-voltage pulse source 11. This design provides cooling efficiency of the charging device 12 and the high-voltage pulse source 11 and increases drilling efficiency by increasing the reliability of operation drill shell.

Claims (3)

1. The method of drilling wells by electrical impulse discharges, in which high voltage pulses are fed to a rotating drill bit, characterized in that the pulses are fed with a frequency

where f is the frequency of the pulses, imp./s; V is the peripheral speed of rotation of the drill bit, mm / s; m is the step of movement of the drill bit between two pulses, mm / imp. 2. A drill for drilling by electric impulse discharges, consisting of series-connected drill pipe columns, a drill bit, a source of high voltage pulses located directly in the drill above the drill bit, and its charging device, characterized in that the charger of the source of high voltage pulses is located directly above the source of high voltage pulses. 3. The drill according to claim 2, characterized in that the source of high voltage pulses and the charger are equipped with a jacket, which forms a channel for the flow of flushing fluid between the drill pipe string and the jacket.

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