DIRECTIONAL DRILLING CONTROL

Abstract

Drilling means for directional drilling in a bore hole comprising a drill pipe and a drilling head, including a slippable clutch device linking the drill pipe and said drilling head such that torque due to rotation of said drill pipe can be controllably applied to said drilling head through at least partial engagement of said clutch, and control means operable to sense an actual orientation angle of said drilling head and compare said actual orientation angle with a required orientation angle adjustably set in said control means and to control said slippable clutch such that when the actual orientation angle and the required orientation angle are the same, the slip torque of the slipping clutch equals the motor reaction torque, so maintaining the orientation angle of the drilling tool at said required orientation angle.

Description

The invention will now be described by way of example only and with reference to the accompanying drawings in which:

FIG. 1 is a schematic diagram showing a general arrangement of drilling means according to the invention, and

FIG. 2 is a schematic diagram of part of the control means for the drilling means of the invention.

Claims

1. Drilling means for directional drilling in a bore hole comprising a drill pipe and a drilling head, including a slippable clutch device linking the drill pipe and said drilling head such that torque due to rotation of said drill pipe can be controllably applied to said drilling head through at least partial engagement of said clutch, and control means operable to sense an actual orientation angle of said drilling head and compare said actual orientation angle with a required orientation angle adjustably set in said control means and to control said slippable clutch such that when the actual orientation angle and the required orientation angle are the same, the slip torque of the slipping clutch equals the motor reaction torque, so maintaining the orientation angle of the drilling tool at said required orientation angle.

2. Drilling means as claimed in claim 1, in which the slipping clutch is an hydraulically loaded multi-plate clutch.

3. Drilling means as claimed in claim 1 in which the motor is powered by relative motion between said drill pipe and said drilling head.

4. Drilling means as claimed in claim 3, in which electrical power is generated by a generator disposed in said drilling head and driven by relative rotation of said drill pipe relative to said drilling head.

5. Drilling means as claimed in claim 3, in which there is provided an hydraulic pump and relative motion between said drill pipe and said drilling head is used to drive said pump, which generates hydraulic power to drive said tool.

6. Drilling means as claimed in claim 1, wherein electrical energy for said control means is provided by batteries in said drilling head.

7. Drilling means as claimed in claim 1, in which there is provided a swash plate hydraulic pump used to drive a load piston of the clutch device, return of the hydraulic fluid being made via an electrically controlled spool valve which has a fourth feedback piston arranged such that a force on the spool of the valve is balanced by the feedback piston, the valve spool is driven from an electromagnetic force motor such that the clutch load is proportional to the force motor current.

8. Drilling means as claimed in claim 1, in which the control means includes flux gates and accelerometers.