AU626528B2

AU626528B2 - Device for steering the direction of drilling

Info

Publication number: AU626528B2
Application number: AU19976/88A
Authority: AU
Inventors: Viktor Tokle
Original assignee: Sintef AS
Current assignee: Sintef AS
Priority date: 1987-03-16
Filing date: 1988-07-07
Publication date: 1992-08-06
Anticipated expiration: 2008-07-07
Also published as: AU1997688A; SE8800945D0; EP0391899A1; NO168962B; NO871068L; NO168962C; SE502676C2; WO1990000666A1; SE8800945L; NO871068D0

Description

Device for steering the direction of drilling

The invention applies to a device of the type indicate in Claim of Patent 1 for steering the direction of drilling when, for example drilling under fjords, and during the geological mapping of natural resources such as iron ore, minerals, oil and gas.

Priof art

Directional control is obtained at present by using wedges, or drilling is done with two drilling strings with an eccentric bearing located on the front pipe. Both these methods are costly and demanding in terms of labour. Holes with larger diameters can be steered using a turbomotor in the front pipe. Since this method is also expensive it is usually restricted to drilling for oil and gas.

Objectives:

The main objective with the invention is to design a means of steering the direction of drilling so that a hole can b drilled in any direction. The device required for this purpose must be simple and inexpensive to produce. It must be easy to use, be robust and require minimal maintenance.

Principle of the invention:

The principle of the invention is described in Claim o /00666

2 Patent 1 .

The subsidiary claims of patent state other advant¬ ageous features of the invention.

A device in accordance with the invention will represent considerable improvements compared with known equip¬ ment. The device, which is known as a directional drill is to be used in connection with known, standard drilling strings. This means that there are no restrictions on drilling depth apart fro the length of the drilling string and the capacity of the rig.

The device is not restricted to a particular diameter of hole. There is however a certain minimum diameter required to allow room for the components.

When using the device, the drilling string can be adjusted so that it is eccentric in relation to the axis of the hole that has already been drilled.

Example:

The invention will be described in more detail below with reference to the illustrations, where

Figure 1 shows an axial longitudinal section along the connection between the drilling string and a device in accordanc with the invention.

Figure 2 shows an equivalent section of a packer whic is attached to this connection and linked further to an outer pipe in the drilling device, whilst

Figure 3 shows the front end of the drilling device complete with an eccentric bearing and a bit. 3

Figure 4 shows a section along A-A, while

Figure 5 shows a section along B-B.

A drilling string 11 is screwed to a connection pipe 12 which is internally threaded at its lower end to connect with a drive shaft 13 which forms an extension to the drilling string. The drive shaft 13 is axially moveable in a lower bearing 14 and also supports an upper bearing 15 at the junction with connection pipe 12. Bearing 15 can be moved inside a housing 16 which stretches from the connection pipe 12 and downwards until it joins a packer 17.

The housing 16 has a number of functions. It encloses a helical spring 18 which is placed concentrically on the drive shaft 13 between bearings 14 and 15 to maintain tension in the direction of the lower end of the device when the drilling string 11 is pressed vertically downwards. The lower end of the housing 16 also has space for an inclinometer 19 which is used to register the angle of the housing 16 about its axis. The inclino¬ meter 19 is linked to a transmitter 20 which is powered by a battery 21, signals being transmitted to a control room about the angle of the housing 16.

The interior of the housing 16 is sealed by a packing box 22 and two more bearings, an upper bearing 23 and a lower bearing 24 located on each side of the packing box. The lower end of the housing 16 is threaded internally so that a packer 17 can be screwed into it. The connection between the housing 16 and the packer 17 is made by a pipe end or a nipple 25 with external threads. There is also a locking nut 26 on the housing 16.

The packer 17 is designed in known way with an expand- /00666

4 ing central element 27 with longitudinal ribs which form ducts 2

(Fig.4) . The packer's 17 pressure chamber 29 is connected to the interior of the drilling string through an orifice 30 in the wal of the drilling string. This orifice 30 is placed in a union 31 that links the drive shaft 13 to the lower drive shaft 32. The axial orifice in the union 31 forms a constriction or nozzle to ensure that there is sufficient operating pressure for the packe

17.

The lower end of the packer 17 has internal threads s that it can be joined to a connecting housing 33 which is screwe into an outer pipe 34 which protrudes downwards. This is the lower end of the device which extends towards the drilling bit

35. The outer pipe 34 is split into an upper part 34A and a low part 34B. An eccentric bearing 36 is located between the two elements in the outer pipe. The eccentric bearing 36 is mainly shaped as a connecting nipple with external threads on both end and an eccentric space 36A through it (Fig. 5) which is designe to house a core barrel 37.

The lower drive shaft 32 is connected to the core barrel 37 by means of a muff-like connecting sleeve 38 which is externally screwed onto the lower drive shaft 32 and internally screwed into the core barrel 37. The core barrel 37 is led through a slide bearing 39 and a sealing ring 40 to the bit 35 which is threaded internally. The sealing ring 40 and the slide bearing 39 are both contained in a housing 41 which is screwed into the lower end of the outer pipe 34B.

The eccentric bearing 36 ensures that the core barrel

37 is at an inclined angle in relation to the main axis of the 5 device. This makes it possible to define a drilling direction which is inclined in relation to the immediately overlying part of the hole.

Prior to use, the drill is placed in a jig so that it can be adjusted to the directional deviation required. The eccentric bearing 36 is set in the direction required and the components are locked. Then the inclinometer 19 is set so that this gives signals about the required direction ^of the eccentric bearing. The directional drill is screwed together with this turning ratio between the inclinometer and the eccentric bearing. The directional drill is then run into the bottom of the hole. Next, the driller slowly turns the drilling string 11 in the hol until it receives the signal indicating the correct direction from the inclinometer 1 . The water pressure is turned on in the drilling string. This will make the packer 17 hold the outer pip 34 still in relation to the hole wall and thereby position the eccentric bearing 36. The device is now correctly oriented and drilling can commence.

Drilling is then carried out to a predetermined depth, depending on how much deviation is required per metre. The maximal drilling length may for instance be 0.5 m.

When this predetermined section has been drilled, the water pressure is cut off. The packer 17 will then be released from the wall of the hole and the spring 18 in the housing will then press the packer and the components attached t it in the direction of the bottom of the hole. The driller slowl turns the drilling string once more until the signals from the inclinometer are registered. Everything is now ready for drillin 0/00666

6 a new section. This procedure is repeated until the core barrel

37 is full. Coring is then done in the usual way.

The annulus between the connecting housing 33 and the eccentric bearing 36 is topped up with oil to provide lubricatio for the eccentric bearing and the front bearing 39. The sealing ring 40 prevents any leakage of oil. This space is sealed agains the interior of the packer 17 by a packing box 42 in the lower end of the connecting housing 33, with bearings 43 and 44 at eac end.

Using an alternative means of design, grooves for return water are located inside the packer. These emerge on the outside of the drilling string above and below the packer.

Claims

7Claim of Patent:

1. A device for controlling the direction of a rock drill which consists of an outer pipe (34) and a core barrel (37) which is led through an eccentric bearing (36) in the outer pipe and which has a drilling bit (35) at its free end, and where a drilling fluid under pressure is fed through the interior of the core barrel, c h a r a c t e r i z e d by the outer pipe (34) being connected to a packer (17) to hold the device against the wall of the hole, and that connected to the packer in a fixed coupling there is an inclinometer (19) with a battery-powered transmitter (20) to facilitate the remote control of the eccen¬ tric bearing's (36) position by turning the drilling string.

2. A device in accordance with Claim of Patent 1, c h a r a c t e r i z e d by an adjustable means of setting the turning position of the inclinometer (19) in relation to the eccentric bearing.

3. A device in accordance with Claims of Patent 1 or 2, c h a r a c t e r i z e d by the supply of a pressure medium to the packer (17) being directed by leading the drilling fluid towards a constriction in the duct leading to the bit (35).

4. A device in accordance with one of Claims of Patent 1-3, c h a r a c t e r i z e d by the packer (17) being pressed downwards by a helical spring (18) which is held by a stop (15) on the core barrel or is attached to a connected component (13).

5. A device in accordance with Claim of Patent 4, c h a r a c t e r i z e d by the helical spring (18) which causes tension in the packer (17) being located between two axial bearings (14,15) .