RU2471987C1 - Electric pulse drilling bit - Google Patents

Abstract

FIELD: mining.

SUBSTANCE: electric pulse drilling bit comprises cylindrical, coaxially arranged and separated with a high-voltage insulator outer and inner crowns made with side washing windows. The bottomhole part of the outer crown is equipped with evenly arranged radial ribs-electrodes, between every pair of which there is one outer radial rib-electrode of the inner crown installed in an equidistant manner. The value of the gap between the outer and inner crowns, in which a high-voltage bushing is installed, is more than electrode-to-electrode distance in the bottomhole part of the electric pulse drilling bit. As an option, width and height or diametre of upper washing windows of the inner crown are more than the maximum electrode-to-electrode distance. As an option, upper washing windows of the inner crown are arranged at height from its bottomhole end surface that is higher than height of largest core pieces.

EFFECT: increased service life of a bit and a high-voltage bushing included into its composition.

3 cl, 6 dwg

Description

The invention relates to technical means for electropulse drilling with backward internal flushing of continuous wells or coring. It can find application in exploration work, in the mining industry, in construction and other works where drilling is required in hard rocks.

A device for drilling (cutting) wells slit-shaped high-voltage pulsed discharges with reverse internal flushing (ed. Certificate for the invention SU No. 730033, IPC 5 E21C 37/18, priority from 01/14/1975, publ. 30.10.1993. Bull. No. 39-40), which contains a high-voltage and grounded system, mounted on an insulating casing having a channel for the removal of sludge in the central part, and channels for supplying flushing fluid to the bottom of the well in the lateral parts; the bottom-hole part of the body is wedge-shaped, and the electrodes attached to the body are in the form of plate-like parallel wedges.

The disadvantages of the known device are the inability to obtain core and low dielectric strength of solid-state insulation, because the thickness of the insulating casing is equal to the interelectrode distance, but the device does not structurally provide for the possibility of exceeding the thickness of the insulating casing over the interelectrode distance.

The first drawback allows you to eliminate the selected drill bit for the prototype, which is equipped with a shell for an electropulse method of drilling wells with backwash (ed. Certificate for invention SU No. 699837, IPC 5 E21C 37/18, priority from 09/13/1965, publ. 10/15/1993 Bull. No. 37-38). The projectile contains an outer and inner conductive pipe string with an outer and inner drill bit crowns; pipe columns and crowns are separated by insulators and are made with a system of side openings (windows).

The main disadvantage of the known drill bit is the low service life of solid-state insulation. This is due to the fact that its interelectrode distance is equal to or close to the gap between the outer and inner crowns above their bottom-hole portion. If, with a constant thickness of the core insulator, the interelectrode distance is reduced by decreasing the inner diameter of the bottom-hole portion of the outer crown and / or increasing the outer diameter of the inner crown, then the rock is only partially destroyed at the ends of the crowns, and the drill bit hangs on the walls of the well and / or core, t. to. such changes lead to such an increase in the length of the discharge channel that electric discharges do not develop in the rock, but along its surface or in the flushing fluid between the crowns.

The main technical result of the proposed device is a several-fold increase in the service life of high-voltage insulators due to the fact that the design of the device allows you to construct a drill bit with an interelectrode distance significantly smaller than the gap between the outer and inner crowns above their bottom-hole part, in which the high-voltage insulator is installed .

The specified technical result is achieved by the fact that in the electric pulse drill bit containing cylindrical coaxially located and separated by a high-voltage insulator outer and inner crowns made with side flushing windows, according to the proposed solution, the bottom-hole part of the outer crown is provided with uniformly distributed inner radial ribs-electrodes between each pair which are equidistantly installed along one outer radial rib-electrode of the inner crown, and led The reason for the gap between the outer and inner crowns, in which the high-voltage insulator is installed, is greater than the interelectrode distance in the bottomhole portion of the electric pulse drill bit.

It is advisable that the width and height or diameter of the washing windows of the inner crown be greater than the maximum interelectrode distance.

It is also advisable to wash the windows of the inner crown at a height from its bottomhole end surface, greater than the height of the largest pieces of core.

An example of a specific implementation of the proposed device is illustrated by six drawings. Figure 1 shows a longitudinal section of the proposed drill bit, figure 2 shows its end view, figure 3 shows the part of the drill located above the drill bit, figure 4 shows photographs of the inner crown (with a high-voltage insulator worn on it ) and the external crown, and Figs. 5 and 6 are photographs of sandstone blocks on calcareous cement and granite, in which experimental wells with core removal by backward internal washing were drilled with the proposed drill bit. The electric pulse drill bit contains (Fig. 1, Fig. 2 and Fig. 4) outer and inner crowns 2 and 3 separated by a high-voltage insulator 1. Subpacker windows 4 of the outer crown 2 are located above the high-voltage insulator 1, and upper flushing windows 5 of the inner crown are located under it 3. In the lower part of the outer crown 2, bottomhole flushing windows are arranged evenly around the circumference 6. The bottomhole inner part of the outer crown 2 is provided with uniformly distributed inner radial ribs-electrodes 7, between which pair are equal to Allen (15-16 mm) of them installed on one outer radial edge-electrode 8 of the inner crown 3. In order to ensure high mechanical strength both crowns are made from solid blanks for the production of ball bearing (SH-15 steel). However, to reduce the cost, they are also made from standard core pipes with the attachment of rib electrodes 7 and 8 using high-quality electric welding. The part of the drill (Fig. 3) located above the drill bit is connected to the outer crown 2 using the packer body 9, and to the inner crown 3 - adapter 10 of the high-voltage tubular current lead 11 (outer diameter 73 mm). The packer body 9 is made with packer holes 12, which serve to transfer the downward pressure of the flushing fluid to the packer jacket 13, mounted on the packer body 9. The packer body 9 is connected to the drill pipe string 14 (outer diameter 127 mm) onto which the insulating pipe is screwed 15. Below this pipe are parts of the drill string that are grounded during the well recess, and above that are under high voltage. A gland body 16 is attached to the insulating pipe 15 from above, to which an inlet fitting 17 is welded to the side. A tubular current lead 11 is passed through the upper central hole of the stuffing box housing 16 and through the nut 18 sealing the packing 19. To maintain a constant annular gap between the high-voltage tubular lead 11 and the drill pipe string 14, as well as the packer body 9, centering insulators 20 made with longitudinal flushing channels 21 are installed in this gap.

The operation of the proposed device is as follows. A rock block is placed in a tank and a pipe is installed vertically on this block (not shown in Figs. 1–6), which plays the role of a guide (and well walls — when drilling in the field). A drill shell equipped with the proposed electropulse drill bit is installed through a guide pipe to a rock block (or to the bottom of a well when drilling in the field). In this case, the dimensions of the guide tube are chosen so that the jacket of the packer 13 with force fully enters into it. At the top of the projectile, a hose is attached to the high-voltage tubular current lead 11, which ensures the upward flow of flushing fluid into the core and sludge collection tank. The drill pipe string 14 (FIG. 3), and through it the outer crown 2 (FIG. 1), are grounded, along the fitting 17 (FIG. 3), flushing fluid (diesel fuel) is fed into the annulus of the drill string, and to the high-voltage tubular pulses of positive polarity are fed to the current lead 11 from a source of high voltage pulses with a given frequency (5.6 cps / s for sandstone and 4.5 cps / granite). From the annular space of the projectile through the sub-packer windows 4 (Fig. 1), the downward flow of flushing fluid (600 l / min) enters the sub-packer annular space (below the packer jacket 13), then through the bottom-hole flushing windows 6 of the outer crown 2 enters the bottom-hole part between the outer crown 2 and internal 3, from where, having enriched with sludge generated during the introduction of high voltage pulses into the rock, it rises up under the high-voltage insulator 1 and through the upper washing windows 5 of the internal crown 3 enters the internal the south cavity of this crown, then into the adapter 10 and the high-voltage current lead 11 (Fig.3). Through a hose attached to the high-voltage current lead 11, the flushing fluid flows into the tank for collecting core and sludge. Coarse sludge under the high-voltage insulator 1 (figure 1) does not accumulate, because the width and height (17 mm) of the upper flushing windows 5 (or their diameter when they are round in shape) is greater than the interelectrode distance (16 mm) in the bottomhole portion of the electric pulse drill bit. The effectiveness of this solution is due to the fact that the sizes of the largest particles of sludge practically do not exceed the value of the interelectrode distance. The core does not overlap the upper flushing windows 5, because, as noted above, these windows are made at a height from the bottom end face of the inner crown 2, greater than the height of the largest core pieces (Fig. 5 and Fig. 6) formed in specific drilling conditions , which include rock properties, core diameter, drilling parameters and others. Of the drilling parameters, the important thing is the capacity of the source of high voltage pulses in the discharge, changing which they change the height of the core pieces (columns) (author's certificate for invention SU No. 854084, IPC5 E21 B25 / 10, priority from 03.19.73, publ. 15.10.93 Bull. No. 37-38). Pieces of core, torn from the bottom, are carried to the surface with flushing fluid along with the sludge. Part of this fluid acts on the core near the bottom, entering the inner crown 3 under its bottom end, because when electropulse drilling, the surface of the bottom of the well is covered with spalling funnels, the depth of which reaches 1/3 of the interelectrode distance. The height of the largest core piece (sandstone) is 53 mm, and the largest core diameter (65 mm) is close to the inner diameter of the inner crown 3 in its bottom end.

The table shows the results of a sieve analysis of drill cuttings.

Breed Sludge composition by fractions (in mm),% More than 10 7-10 5-7 Less than 5 Sandstone fourteen 21 21 44 Granite fifteen 17 eighteen fifty

Thus, in the prototype, the gap between the outer and inner crowns in which the high-voltage insulator is installed is approximately equal to the interelectrode distance; in the drill bit proposed by us and tested in the example of a specific embodiment, the value of this gap is 1.3 times greater than the interelectrode distance, i.e. and the wall thickness of the high-voltage insulator 1 (Fig. 1) is 1.3 times greater than this distance. Due to this, the service life of the high-voltage insulator 1 is increased several times, especially when drilling granite, in which, without electrical breakdowns of the insulator and its discharges over the surface, the maximum length of the drill bit is 0.6 m, the claimed bit is 7.9 m (this in total in several blocks of granite), and the high-voltage insulator 1 did not fail.

Claims (3)

1. Electropulse drill bit containing cylindrical, coaxially located and separated by a high-voltage insulator outer and inner crowns made with side flushing windows, characterized in that the bottom-hole part of the outer crown is provided with uniformly distributed inner radial ribs-electrodes, between each pair of which are equally spaced apart one outer radial rib-electrode of the inner crown, and the gap between the outer and inner crowns, in which tanovlen high voltage insulator longer the interelectrode distance in a near portion of electro drill bit. 2. Electric pulse drill bit according to claim 1, characterized in that the width and height or diameter of the upper washing windows of the inner crown is greater than the maximum interelectrode distance. 3. Electro-impulse drill bit according to claim 1, characterized in that the upper flush windows of the inner crown are made at a height from its bottom-end end surface, greater than the height of the largest core pieces.

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