Boring or penetrating the earth – Below-ground impact members – Fluid-operated
Reexamination Certificate
2000-09-28
2003-02-11
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Below-ground impact members
Fluid-operated
C175S061000, C175S075000
Reexamination Certificate
active
06516902
ABSTRACT:
BACKGROUND
1. Field of the Invention
This application generally relates to drilling, and more particularly to a method and apparatus for directional drilling.
2. Description of Related Art
For many years, directional drilling has been a cost efficient and less complex alternative to traditional methods of laying pipelines and tubing in open construction. In directional drilling, a special drill head with a guidance piece is used to produce a pilot hole. The guidance piece may be formed either by an end face of the drill head inclined to the axial direction of the drill head or by a guide body bent at a small angle (less than 5°) in the axial direction of the drill head behind the drill head. Due to the inclined face or the bend in the guide body, the drilling produced with this drill head runs along a circular line with a large radius of curvature. The order of magnitude of the radius of curvature may be, for example, more than 10 meters, or with long drillings, may be more than 100 meters.
The drill column carrying the drill head may be rotated about its longitudinal axis during the forward advance. In this way, the orientation of the inclined surface of the drill head and the bend of the guide piece, and thus the plane of curvature, may be altered. The course of the drilling may be controlled by altering the plane of curvature.
The pilot drill head may include a magnetic probe with which the position of the drill head may be determined accurately. Passive probes may be used at drilling depths of less than fifteen meters in which their positions may be monitored by a monitoring system at the earth's surface. At greater drilling depths, active probes may be used. Active probes may be supplied with electric power over an electric connection line running in the drill column. Signals may be exchanged with the monitoring system at the earth's surface over this line. The position of the drill head may be known by means, for example, such as these probes, so that the course of drilling may be controlled accurately by rotating the drill head about its axis.
Setting and maintaining a certain angle of rotation of the drill column may be essential for controlling the course of drilling. Thus, it is not usually possible to apply rotational movements with the drill column to the drill head to increase drilling capacity. Material removed in producing the pilot hole may be carried away primarily by a wash fluid to which a mud forming additive, such as bentonite in particular, is added. The wash fluid comes out of fluid nozzles in the drill head at a high pressure, such as 100 bar. To increase the capacity for removing cut material, rotation of the drill head may be induced through the wash fluid by means of a turbine-like drive, also known as a mud motor, in particular when a bent or angled control element is used behind the drill head for the control. The wash fluid may also provide support for the pilot hole due to the admixed bentonite while also lubricating the drill column. Bentonite mixed with water may have a pasty gelatinous consistency and therefore may reduce friction on the drill column arranged behind the drill head in the pilot hole.
The axial advance of the drill head may be produced by a driving device at the point of entry of the drill head into the ground, exerting a compressive force on the drill column. Despite the wash fluid (also called a supporting fluid) in the pilot hole, there may be considerable friction on the drill column, in particular with lengthy drilling, such as with distances of more than 100 meters. Therefore, a limited axial pressure may be applied to the drill head over the drill column. Because of the limited axial pressure that may be transferred over the drill column, it may be possible to a limited extent to drill by breaking rocks, for example, by means of drill bits on the drill head that are in contact with the material to be removed with an axial pressure and remove this material because of movements of the drill head. Even with drill heads having a rotational drive, the removal of material may take place mainly through a high-pressure supply of the wash fluid and to a limited extent through the mechanical action of drill bits, such as a rotary cutter. Thus, in producing pilot holes, it is may be difficult to penetrate through harder materials, such as for example, in areas of rock and gravel.
After producing the pilot hole, the drill head coming out of the exit hole of the drilling may be removed from the drill column. It may be necessary to widen the diameter of the hole. To accomplish this, an enlargement bit mounted on the drill column may advanced by the drill column through the pilot hole, for example, by means of the driving device, enlarging the diameter in the process. The wash fluid or supporting fluid also supplied to the enlargement bit under pressure through the channel in the drill column may be responsible for removing most of the material. When working with an enlargement bit, the drill head of the enlargement bit may also be set in rotational motion by the drill column. A supporting pipe which supports the drilling with an expanded diameter may be mounted on the rear end of the head of the enlargement bit. The supporting pipe may also be formed by the pipe which is actually to be laid. The supporting pipe may be pulled passively through the hole due to the force applied to the drill column by the driving device.
SUMMARY OF THE INVENTION
In accordance with principles of the invention is a device for directional drilling which increases removal of material and drilling through hard materials. This may be achieved according to this invention by providing a housing between the drill column and the drill head having a receptacle for an axially movable piston and a piston drive to generate strokes of the piston acting on the drill head. A connecting link permits an axial movement between the drill head and the drill column and the channel for the wash medium is sealed at least with respect to the end faces of the piston.
The term “drill head” refers to the part which is in contact at an axial end face with the material to be removed. Axial strokes on the drill head are generated by the axially movable piston in the housing, producing a brief increase in surface pressure between the drill head and the material to be removed. The teeth and tips also provided on traditional drill heads for directional drilling remove larger amounts of material, especially hard material, due to the stroke. The efficiency in removal of material is increased greatly by the percussion mechanism. A connecting link provides for axial movements between the drill head and the drill column transmitting the axial force. In the absence of such a connecting link, strikes would be applied to the drill column mounted on the drill head in addition to the end face of the drill head. Consequently, this would reduce the impact energy for removal of material, because the drill column, which may be several hundred meters long, and the drill head would have to be accelerated together. Additionally, the risk of damage to the drill column would be increased.
The fact that the channel for the wash medium may be separated at least from the end faces of the piston may be taken into account. A wash medium, in particular a supporting medium consisting of bentonite mixed with water flowing around the piston at the end face may prevent a rapid axial movement of the piston. When creating the pilot hole in which a drill column is connected to one side of the drill head, the wash fluid may be transported to the drill head exclusively axially through this drill column. In this case, special measures may be taken to prevent the wash fluid from entering the spaces bordering the end faces of the piston. On the peripheral face of the piston, the wash fluid may optionally flow around it because the wash fluid here may not interfere with the axial movement of the piston. Thus, for example, the wash fluid may be used to induce a rotational movement in the piston at its peripheral face
Choate Hall & Stewart
Dougherty Jennifer R
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