HK1073146B - Liquid driven downhole drilling machine - Google Patents

Description

Liquid driven underground drilling machine

Technical Field

The invention relates to a liquid-driven downhole drilling machine having a casing, a drill bit mounted in a guide bushing in an angularly fixed but axially limited manner, a piston hammer for striking a drill bit shank, and a valve for controlling the reciprocating movement of the piston hammer, which valve alternately pressurizes and depressurizes a pressure chamber in which there is a piston face for driving the piston hammer forward when the chamber is pressurized.

Background

This type of liquid driven downhole drilling machine is often used with a drill string connected one by one, whereby the drill string connected by the drill string is rotated, whereby the drilling machine and its drill bit are guided between each impact of the piston hammer. The drill bit is fixed in the sleeve at an angle. In drilling deep wells, friction between the drill pipe and the wall of the well sometimes causes the rotation of the lower portion of the drill pipe to become uneven, although the rotation of the upper portion of the drill pipe is continuous. The drill rod becomes non-uniformly guided between impacts of the piston hammer, like a torsion spring, and when there are multiple impacts, the drill cannot rotate and then rotates quickly. This slip-stick effect reduces drilling speed and increases wear on the drill bit.

In a fluid-driven drilling machine, power fluid is supplied through the drill pipe, the return stroke of the piston hammer is hydraulically blocked, and a pressure spike is generated as the piston hammer forces fluid into the drill pipe. This results in higher stresses and a reduction in energy efficiency. Attempts have been made to create an accumulator directly connected to the drilling machine, but to date there has been no good solution to this problem.

Disclosure of Invention

It is an object of the present invention to improve the indexing between impacts of the liquid-driven drilling machine used. Another object of the invention is to reduce the pressure peaks at the entry of the power fluid into the drill rig while at the same time improving energy efficiency.

In particular, according to the present invention there is provided a liquid driven downhole drilling machine comprising drill pipe and outer pipe, a drill bit which is angularly fixed but axially limited movably mounted in guide bushings, a piston hammer for striking a drill bit shank, and a valve for controlling the reciprocating movement of the piston hammer, the valve alternately pressurising and depressurising a cylindrical chamber in which there is a piston face which causes the hammer piston to drive forward when the chamber is pressurised, characterised in that: the guide bushing is rotatably guided within the outer tube and coupled by a one-way coupling to a rotating sleeve having axial ridges that form boundaries of a plurality of cavities with the ridges in the drill pipe and forming a rotating piston for reciprocally rotating the rotating sleeve, some of the plurality of cavities being coupled to the cylinder cavity so as to be compressed and decompressed along with the cylinder cavity with the piston face driving the piston hammer forward.

These objects are achieved by arranging the guide bushing to be rotationally guided in the sleeve and by coupling it to the rotating sleeve by means of a one-way coupling, the rotating sleeve having an axial ridge bounding a pressure chamber and forming a rotary piston for reciprocating rotation of the rotating sleeve, the chambers being coupled and compressed and decompressed together with said pressure chamber having a piston face for driving the piston hammer forward.

The invention is defined by the claims.

Drawings

FIG. 1a is a longitudinal cross-sectional view through the front of a downhole drilling rig in accordance with the present invention;

FIG. 1b is a longitudinal cross-sectional view through the tail of the same downhole rig;

FIG. 2 is a cross-sectional view taken along line 2-2 of FIG. 1 a;

FIGS. 3 and 4 are the same cross-sectional views as FIG. 2, but they show some of the components in other mutual positions;

FIG. 5 is a cross-sectional view taken along line 5-5 in FIG. 1 a.

Detailed Description

The liquid driven downhole drilling machine shown in the figure has a drilling machine casing comprising a drill pipe 11, with a not shown rear portion (back head) in the upper part of the drill pipe 11 arranged to engage the drill pipe for supplying a driving liquid, typically water or a suspension of bentonite in water. The middle of the downhole drilling rig is not shown in the figure. An outer tube 12 is screwed to the front of the drill pipe and the drill bit 13 with its shank 14 extends into the outer tube. A terminal sleeve 15 is screwed onto the outer tube 12 and clamps a follower cylinder 16 against a thrust bearing 17 supporting an internal shoulder 18 in the outer tube 12. The follower cylinder is journalled for rotation in the outer tube 12. The forward end of the drill pipe 11 has a reduced diameter and it has a set of ridges 20 as shown in figure 2. A rotating sleeve 22 is journalled between the forward end of the drill pipe 11 and the outer pipe 12 and has an inwardly directed ridge 24. A set of sealed cavities 25, 26, 27 is defined between the ridge 20 and the ridge 24. The axial portion of the drill pipe radially inside the ridge 20 forms a short positive guide for guiding the piston hammer 30.

The toggle member 29 is incorporated between the follower cylinder 16 and the rotary sleeve 22 to form a one-way coupling preventing reverse rotation.

The shank 14 of the drill bit 13 has a splined connection with a guide bushing 31 which is screwed onto the follower cylinder 16 and clamps a stop ring 32 axially against a shoulder of the follower cylinder. The stop ring 32 is axially split to prevent the drill bit from falling, but allows limited axial movement of the drill bit. The drill bit has a not shown central passage for conveying flushing water to the recess at the front end of the drill bit.

At the forward end of the drill pipe 11 there is a valve 40 located in a valve housing 41 and the valve housing has a tube 42 which extends into a longitudinal channel 43 of the piston hammer 30. The outer door plate of the drilling machine, not shown, clamps the valve sleeve against an isolation sleeve 44 which supports the front end of the valve sleeve against a shoulder of the drill pipe 11. The spacer sleeve 44 tightly seals the drill pipe 11 and has longitudinal grooves forming a plurality of passages 25a between the spacer sleeve and the drill pipe. The piston hammer has a ram 45 which is guided outside the spacer sleeve 44 and inside the tube 42. The piston is thus guided only by a short guiding area at its end, while the main length of the piston is not guided, since an annular space, i.e. a cylindrical cavity 49, is present between the piston and the spacer sleeve 44. Behind the hammer head 45 of the piston hammer, an annular piston surface 46 is formed in an annular cylinder chamber 47 (pressure chamber), and the hammer head forms a smaller annular piston surface 48 in an annular cylinder chamber 49 (pressure chamber), the annular cylinder chamber 49 being formed in the space between the two guide regions of the piston hammer. The cylinder chamber 49 is always coupled with the high pressure liquid through a passage parallel to the passage 25a to constantly provide a rearward force on the piston, whereas the valve 40 alternately connects the cylinder chamber 47 with the high pressure liquid and the pipe 42, which pipe 42 is connected with the flushing channel in the drill bit through the through passage 43 of the piston. Thus, the tube 42 is always at a low pressure and the outflowing liquid is used to flush debris out of the wellbore. Since the piston face 46 is much larger than the piston face 48, the piston hammer will strike the drill bolt reciprocally at a frequency of, for example, 100 Hz.

From the cylindrical chamber 47, channels 25a lead to the six chambers 25 shown in fig. 2, so that these chambers 25 are alternately pressurized and depressurized. The bore 26a shown in figure 1a leads from the constantly pressurised cylindrical cavity 49 to the two cavities 26 shown in figure 2, so these cavities 26 are constantly pressurised and the bore 27a connects the 4 cavities 27 to the cavity 50 at the end face of the drill bolt. The 4 chambers 27 are constantly depressurized.

Fig. 3 shows the rotational position of the rotating sleeve 22 when the cavity 25 has a low pressure. The two cavities 26 are the only cavities that are under pressure, and therefore the rotating sleeve 22 is rotated anticlockwise to its end position in which the ridge 24 bears on the ridge 20 of the drill pipe 11.

Fig. 4 shows the rotational position of the rotating sleeve 22 when not only two cavities 26 but also 4 cavities 25 are pressurized. Two cavities 26 tend to rotate counterclockwise and six cavities 25 tend to rotate clockwise so that the force generated by the 4 cavities rotates the rotating sleeve 22 clockwise to its extreme position where the ridges bear on the ridges of the drill pipe.

The rotating sleeve 22 is thus rotated and stopped to and fro by the pressure of the trailing piston face of the piston hammer, that is to say by the cyclic impact of the piston hammer. Since the one-way coupling couples the rotating sleeve 22 to the follower cylinder 16, the latter rotates clockwise relative to the drill pipe 11. The follower cylinder follows the rotating sleeve to rotate clockwise, but is stationary when the rotating sleeve rotates counterclockwise. The drill bit 13 is thus angled (indexed) between impacts so that the buttons embedded in the drill bit shift the point of contact with the rock between impacts, which effectively breaks the rock. Thus, the drill rod does not have to be rotated and, instead of using telescopic tubes, flexible tubes, i.e. bendable drill rods without joints, can be used, which can be straightened out from the coiled state.

When the piston is in the return stroke and the valve 40 is switched to the position of pressurization of the cylinder chamber 47, the piston hammer is stopped by this pressure. And goes to the forward stroke. During the piston arrest, the volume of the cylinder chamber 47 becomes smaller, so that the driving liquid is pressed out of the chamber, which results in a pressure rise and energy loss due to the flow. The 6 chambers 25 of the rotating device are combined with the cylindrical chamber 47 and they can force the liquid out of the cylindrical chamber, thus reducing losses while at the same time making the rotation efficient. The need for an accumulator at the inlet of the impact motor is also reduced.

In selecting the patterns of the chambers 25, 26, 27 serving as pressure chambers and the rotary piston forming 12 chambers, they should be made symmetrical with respect to the rotational force and the radial force so that the supporting force can be reduced. Another version may also be selected, and the cavity of the rotary device may be coupled to the pressure chamber of the forward-driving piston hammer. The present invention can be used with piston hammers driven by other principles than using alternating pressure for the working stroke and constant pressure for the return stroke.

Claims (1)

1. A fluid driven downhole drilling machine comprising a drill pipe (11) and an outer pipe (12), a drill bit (13) fixed at an angle but axially limited movably mounted in a guide bushing (31), a piston hammer (30) for striking a drill bit shank (14), and a valve (40) for controlling the reciprocating movement of the piston hammer, the valve alternately pressurizing and depressurizing a cylindrical chamber (47) having a piston face (46) in the cylindrical chamber for driving the hammer piston forward when the chamber is pressurized, characterized in that:

the guide bush (31) is rotationally guided within the outer tube (12) and is coupled by a one-way coupling (29) to a rotary sleeve (22) having an axial ridge (24) which, together with the ridge (20) in the drill pipe (11), delimits a plurality of chambers (25, 26, 27) and forms a rotary piston for reciprocating rotation of the rotary sleeve, a part (25) of these chambers being coupled to the cylinder chamber (47) so as to be compressed and decompressed together with the cylinder chamber (47) having a piston face (46) which drives the piston hammer (30) forward.