GB2091322A

GB2091322A - Turbodrill

Info

Publication number: GB2091322A
Application number: GB8201130A
Authority: GB
Original assignee: Ruhrkohle AG
Current assignee: RAG AG
Priority date: 1981-01-15
Filing date: 1982-01-15
Publication date: 1982-07-28
Also published as: GB2091322B; DE3101052C2; DE3101052A1

Abstract

Two rotors 2, 3 having spirals 4, 5 rotate in opposited directions in a drill pipe 1. Each rotor carries a bit 6, 7. The rotors are mounted on pinions 14 and slide bearings 17. <IMAGE>

Description

SPECIFICATION Turbodrill The invention relates to a turbodrill, in particular for cable core boreholes, comprising a rotor which carries a bit and rotates with respect to a casing forming the drill pipe, the rotor being provided on its surface with passive drive elements, such as blade wheels or spirals, to be acted upon within an annular space by, for example, a drilling fluid.

Such turbodrills drill an annular space when making a core and the remaining rock core is raised to the surface in the core barrel for test purposes. In comparison with a conventional drill drive, turbines which are driven by drilling fluids have the disadvantage of only being able to apply a slight torque. What is desired is a turbodrill which permits, in a simpe manner, a considerable increase in the drilling torque.

The present invention provides a turbodrill in which two rotors which are arranged one inside the other, rotate in'opposite directions, and comprise corresponding passive drive elements are provided inside the drill pipe.

It has proved particularly advantageous, within the scope of the invention, for the rotors to be provided with respective bits, at least the outer bit being of annular construction. It has also proved advantageous for the rotors to be provided at the end remote from the bit or bits with a guide formed by a plurality of pinions distributed over the circumference and projecting into an annular space between the rotors.

Oppositely rotating rotors assist one another as regards their effect, and pinions whose axles are mounted on a non-rotating feed-pipe cause retroaction of the moments of reaction arising when moments of action are applied at the face.

Owing to the opposite direction of the tangential cutting forces, the changes in direction caused by the tangential cutting forces and the reaction forces resulting therefrom are reduced.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a schematic side view of a turbodrill, partly cut open; Figure 2 is a section along line X-X in Figure 1; Figure 3 is a section along line Y-Y in Figure 1;and Figure 4 is a section along line Z-Z in Figure 1.

The turbodrill illustrated has two rotors 2 and 3 rotating in opposite directions and surrounded by a drill pipe 1. In Figure 1 the turbodrill is shown in a borehole sunk in rock 12.

Both the inner rotor 3 and the outer rotor 2, which together define an annular space 8, are provided on their external surface with so-called passive drive elements. The drive elements are spirals 4, 5 which are attached to the respective rotors 2, 3 such that the rotors rotate in opposite directions under the action of a pressurized drilling fluid.

The rotors 2, 3 are mounted on pinions 14 at the end remote from the hole bottom, the axles 1 6 of which pinions are mounted in holders 1 5 which are rigidly connected to the non-rotating drill pipe 1. On account of the mounting of the rotors 2, 3 on the pinions 14, which are distributed over the circumference, the rotors 2, 3 assist one another as regards their direction of rotation, as can be seen from Figure 2, where the directions of rotation are indicated by arrows.

The inner rotor 3 and the outer rotor 2 are provided with bits 6 and 7, respectively. In the embodiment shown in the drawings, particularly according to Figure 1, the inner bit is one which is required to drill out a core. However, it is possible for a cutting drill head to be driven instead. The bit 6 and the bit 7, which rotate in opposite directions in accordance with the rotors 2,3 are in each ease of annular construction. The fiushing fluid, which drives the rotors 3, 2 by means of the spirals 4, 5, is guided via the annular spaces 8, 9 in the direction of the hole bottom and the pressure in the region of the bits 6, 7 is reduced by the delivery of energy to the spirals 4, 5.

The fluid is conveyed via the annular space 8 in the region of the bits 6, 7 via holes 22 and 23, respectively, through the bits 6, 7 and, on its return journey, as indicated by the arrows in the region of the bits 6, 7, brings the drillings to the surface via the annular space 10 which is formed between the drill pipe 1 and the borehole wall 11.

An annular space 25 is formed between the bits 6, 7 to ensure constant removal of the drillings with the flushing fluid. If, for example, there is no possibiiity of through-flow between the outer bit 7 and the borehole 1 the fluid is removed via the space 25 and holes 24 in the bit 7. The annular space 8 has openings 20 provided behind the bits 6, 7 and at right angles to the feed direction, which is indicated by the arrow A. In the same direction and in the same plane the annular space 9 is provided with openings 21 in the direction of the borehole wall 11. The openings 21 have a larger cross-section than the openings 20.

The openings 20, 21 ensure that the fluid can be removed when the holes 22, 23 are clogged.

Since, if clogging occurs, additional fluid has to be taken into account in the region of the annular space 9 owing to the fluid leaving the annular space 8, the opening to the outer annular space 10 has an even greater cross-section, as otherwise a reflux via the annular spaces 8, 9 is to be expected and the operation of the turbine cannot therefore be guaranteed.

The rotors 2, 3 are mounted in the region of the bits 6, 7 by guide bearings in the form of slide bearings 17. In order to ensure that the position of the rotors 2, 3 is stable, the outer rotor 2 comprises a special bearing surface 18 in the transition to the outer bit 7. Seals 1 9 are arranged opposite this bearing surface 1 8 on the drill pipe 1. The inner bit 6 is also mounted so as to be rotatable with respect to the outer core bit 7, as indicated by the bearing 26 in Figure 1.

The section of Figure 3 along the line Y-Y in Figure 1 shows how the rotors 2,3 are mounted with respect to the drill pipe 1 in the region behind the bits 6, 7. The section in Figure 4 along the line Z-Z in Figure 1 shows the arrangement of the holes 22, 23, 24 for removing the drilling fluid and the drillings.

The turbodrill described above is very suitable for making boreholes in coal seams, on account of the opposite direction of the tangential cutting forces. In such cases, when a turbodrill is required to operate in seams, it is advisable to construct this according to the known principles of drilling technology in seams.

Claims

CLAIMS.

1. A turbodrill comprising two rotors inside a drill pipe, the rotors having passive drive elements and being arranged to rotate in opposite directions during drilling, at least one of the rotors carrying a bit.

2. A turbodrill as claimed in claim 1, in which the rotors are provided with respective bits, at least the outer bit being of annular construction.

3. A turbodrill as claimed in claim 1 or 2, in which the rotors are provided at the end remote from the bit or bits with a guide formed by a plurality of pinions distributed over the circumference and projecting into an annular space between the rotors.

4. A turbodrill as claimed in claim 3, in which the pinions have axles mounted in holders disposed inside the drill pipe.

5. A turbodrill as claimed in any preceding claim, in which slide bearings are provided between the rotors in an end part of the rotors adjacent the bit or bits.

6. A turbodrill as claimed in any preceding claim, in which the end part of the outer rotor adjacent the bit or bits is formed as a bearing surface cooperating with the drill pipe.

7. A turbodrill as claimed in any preceding claim, in which openings are provided from the annular space between the rotors and from the annular space between the rotor and the drill pipe as a connection to the annular space between the drill pipe and the borehole wall, which openings are arranged in the same transverse plane, the outer opening having the larger cross-section.

8. A turbodrill as claimed in any preceding claim, in which the annular space between the rotors communicates with holes passing through the bit or bits.

9. A turbodrill as claimed in claim 8, including holes arranged so as to extend in an axial extension of the said annular space in the direction of the hole bottom in a bit carried by the inner rotor.

10. A turbodrill as claimed in claim 8 or 9, including holes arranged so as to extend from the said annular space in the direction of the hole bottom in a bit carried by the outer rotor.

1 A turbodrill as claimed in any preceding claim, in which each rotor carries a bit, and holes are provided from a space between the borehole wall and the drill pipe.

12. A turbodrill substantially as described with reference to, and as shown in, the accompanying drawings.