WO2013000024A1

WO2013000024A1 - Fluid drilling head with powered swivel assembly

Info

Publication number: WO2013000024A1
Application number: PCT/AU2012/000762
Authority: WO
Inventors: Scott Christopher Adam
Original assignee: Cmte Development Limited
Priority date: 2011-06-30
Filing date: 2012-06-29
Publication date: 2013-01-03

Abstract

A fluid drilling head of the type adapted to cut a bore hole in rock by the rotation of a swivel assembly (5) within a body (1) typically has high pressure fluid nozzles providing cutting and reaming jets at the leading end (7) with the reaming jets angled to provide reaction forces to rotate the swivel assembly (5). The invention provides a positive displacement fluid driven motor (3) coupled to the swivel assembly (5) to control the rotational speed of the swivel assembly by restricting fluid flow to the motor through a metering nozzle (8).

Description

FLUID DRILLING HEAD WITH POWERED SWIVEL ASSEMBLY Field of the Invention

[0001] This invention relates a fluid drilling head with a powered swivel assembly and has been devised particularly though not solely for the drilling of lateral bore holes in horizontal rock seams.

Background of the Invention

[0002] It has become known to use fluid drilling heads of the type adapted to cut a bore hole in rock by the rotation of a swivel assembly at the leading end of a tool body. The swivel assembly typically has a plurality of nozzles arranged to provide cutting and reaming jets of fluid with the swivel assembly being rotated by reaction forces from one or more of the reaming jets. Such fluid drilling heads have the disadvantage that when the tool is lightly loaded in operation, the reaction forces from the reaming jets can produce high levels of torque driving the rotation of the swivel assembly. This torque can significantly exceed the drag generated by various sources of friction within the tool resulting in an unabated speed increase in the rotation of the swivel assembly which can lead to seal or bearing failure within the tool.

Summary of the Invention

[0003] Accordingly, the present invention provides a fluid drilling head operable by the rotation of a swivel assembly at the leading edge of a tool body and having a plurality of nozzles arranged to provide cutting and reaming jets of fluid in use, the swivel assembly being driven to rotate at least partially by reaction forces from one or more of the reaming jets, wherein the swivel assembly is coupled to a positive displacement fluid driven motor arranged to control the rotational speed of the swivel assembly.

[0004] Preferably, fluid is supplied to the motor through a flow rate control device. [0005] Preferably, the flow rate control device comprises a metering nozzle configured to deliver fluid to the motor at a pressure significantly less than the pressure of the fluid supplied to the nozzles in the swivel assembly.

[0006] Preferably, the positive displacement fluid driven motor is a water powered vane motor.

Brief Description of the Drawings

[0007] Notwithstanding any other forms that may fall within its scope, one prefenred form of the invention will now be described by way of example only with reference to the accompanying drawings in which:

[0008] Figure 1 is an end view of a powered swivel assembly on a fluid drilling head according to the invention;

[0009] Figure 2 is a longitudinal cross-section on the line A-A of Figure 1 ; and

[0010] Figure 3 is an exploded perspective view of key components of the powered swivel assembly shown in Figures 1 and 2.

Preferred Embodiments of the Invention

[001 1] In the preferred form of the invention a fluid drilling head is provided with a powered swivel assembly at the leading end of the drilling head having a generally cylindrical body assembly 1 on which is typically mounted a shroud ring 2 designed to control the forward progress of the fluid drilling head as a bore hole is formed in the rock as is well known in the art of fluid drilling.

[0012] The fluid drilling head incorporates a swivel assembly 5 rotatable in bearings within the body of the tool and designed for the mounting of a cutting head on the leading end 7 which is provided with a plurality of nozzles arranged to provide cutting and reaming jets of fluid in use.

[0013] In the fluid drilling head according to the invention, the rotating shaft and bearing pack of the swivel assembly 5 is coupled to a positive displacement fluid driven motor 3 arranged to control the rotational speed of the swivel assembly. The motor is typically a water powered vane motor where the rotational speed is directly proportional to the flow rate of fluid through the motor.

[0014] The drive shaft through the motor and to the swivel assembly is sealed by a seal assembly 6 incorporated within the swivel body rear end 4.

[0015] A proportion of the fluid normally provided to the fluid drilling head at high pressures of up to 15,000 psi. is diverted through a flow rate control device in the form of a metering nozzle 8 configured to deliver fluid to the motor 3 at a pressure significantly less than the fluid supply pressure. In the preferred form of the invention the metering nozzle 8 incorporated within the swivel body rear end 4 is sized to deliver water flow to the motor 3 at approximately 10 litres per minute compared with the general flow rate within the tool of approximately 240 litres per minute.

[0016] The flow rate to the motor 3 is set by the metering nozzle diameter and the supply pressure.

[0017] The fluid supply line to the motor 3 also incorporates a relief valve in passage 9 set for example to 1 ,000 psi. which is much lower than the supply pressure of 10,000 - 15,000 psi. This means that if the positive displacement motor 3 stops rotating due to external loading, the relief valve will actuate and protect the motor from destruction.

[0018] It will be appreciated by those skilled in the art that some quantity of torque is required to rotate the shaft 5 at the nominal speed. This torque is the sum of friction from the high pressure seal 6, friction from the oil seals in the bearing pack assembly, and friction from the bearings in the bearing pack. The high pressure of the supply fluid generates high axial loads on the shaft 5 so the bearing loads are correspondingly very high.

[0019] All up, this friction typically adds up to about 1 - 2 Nm of torque. However, it is easy to configure a water jet head so that up to 4 Nm of torque is generated. The problem with existing fluid drilling heads is that this torque is generated regardless of the speed. Without a braking or speed regulating mechanism, if the reactive torque generated by the cutting and reaming jets exceeds the drag generated by the various sources of friction, the rotational speed of the shaft 5 would increase unabated, resulting in seal or bearing failure.

[0020] The use of a positive displacement water powered motor 3 means that when used in conjunction with a torque generating cutting head, the motor acts as a brake, spinning at near or no load or even acting as a pump. This has been found to be an excellent way of minimising wear in the motor as for most of the time there would be no net load on the motor.

[0021] However, should the cutting head contact the rock at the end of the hole, the motor will be loaded up and supply positive torque to maintain rotation.

[0022] One other advantage of the present invention is that the waste water from the motor 3 is clean, and is useful for the purpose of keeping environmental water (typically laden with e.g. coal fines) away from the oil seals in the bearing pack. It is directed around the bearing pack and released between the sizing ring and the rotating shaft in a thin gap. This thin gap generates a slight back pressure (e.g. 50 psi.) in the bearing housing void, and stops environmental water from getting in and around the bearing seals.

[0023] The waste water can also be used in the sliding shroud ring 2 in order to keep the shroud ring clean.

Claims

Claims :-

1. A fluid drilling head operable by the rotation of a swivel assembly at the leading end of a tool body and having a plurality of nozzles arranged to provide cutting and reaming jets of fluid in use, the swivel assembly being driven to rotate at least partially by reaction forces from one or more of the reaming jets, wherein the swivel assembly is coupled to a positive displacement fluid driven motor arranged to control the rotational speed of the swivel assembly.

2. A fluid drilling head of the type claimed in claim 1 , wherein fluid is supplied to the motor through a flow rate control device.

3. A fluid drilling head as claimed in claim 2, wherein the flow rate control device comprises a metering nozzle configured to deliver fluid to the motor at a pressure significantly less than the pressure of fluid supplied to the nozzles in the swivel assembly.

4. A fluid drilling head as claimed in any one of the preceding claims, wherein the positive displacement fluid driven motor is a water powered vane motor.

5. A fluid drilling head as claimed in any one of the preceding claims, wherein waste fluid from the motor is directed to keep environmental water away from oil seals in bearings of the swivel assembly.

6. A fluid drilling head as claimed in any one of the preceding claims when fitted with a shroud ring, wherein waste water from the motor is directed to keep the shroud ring clean.

7. A fluid drilling head when constructed, arranged and operable substantially as described herein with reference to the accompanying drawings.