Boring or penetrating the earth – Processes – Boring horizontal bores
Reexamination Certificate
1999-09-27
2002-11-26
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Processes
Boring horizontal bores
C175S007000, C175S325100, C175S010000, C166S355000
Reexamination Certificate
active
06484820
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a process and an apparatus for sinking drill holes, in particular for exploration and extraction and drill holes.
Exploration drill holes are made for the purpose of prospecting deposits and should permit the taking of samples of the material present in the deposit. Exploration drill holes are sunk, in particular, when the deposit is located at great depth and/or when water that is present above the deposit, e.g. an ocean or sea, does not permit the sinking of exploration shafts.
Extraction drill holes serve to extract the deposit content from bottom layers. An example of extraction drill holes is the mining of marine sediments with diamond inclusions present on the ocean floor.
The deposits containing the diamonds have generally been formed in front of river mouths in the form of not very thick layers spread out on a rock base. To mine the diamond-containing sediment material, apparatuses are used which are lowered onto the ocean floor from ships on an extendible drill-pipe. Such apparatuses may have drill heads which are designed for drill holes with a large diameter. Several such drill holes are made close to one another so as to be able to extract as much as possible of the diamond containing material.
When the drill head fastened to a drill-pipe which may have a great length encounters the ocean floor, the problem occurs that at the place on the ocean floor where the drill hole is to be made, the drill head of the drilling tool does not penetrate immediately, but tends to slip and move around spiral-shaped in a circle, especially when the ocean floor has even the slightest slope.
DESCRIPTION OF THE RELATED ART
To prevent this slipping sideways of the drill head, it is already known to arrange a centering guide point underneath the drill head, which under the drilling force exerted in the operating direction of the drill head penetrates into the surface of the sediment layer and, in particular in the initial phase of the drilling, provides a guidance that prevents a slipping sideways of the drill head at the start of the drilling operation, i.e. when the drill head is not yet guided at is sides by the drill hole walls.
When the drill head has passed nearly completely through the sediment layer, the projecting guide point is the first to encounter the generally rocky base located underneath, into which it cannot penetrate or only very slowly and with great wear. The drill head than cannot penetrate further into the sediment layer.
As the profitability of the extraction process depends on the quick sinking of a large number of adjacent drill holes, the respective drilling operation until now is greatly delayed when the guide point encounters the bedrock located underneath the sediment, and accordingly becomes uneconomical.
From the U.S. Pat. No. 3,277,972 an apparatus is known with which the drill head is moved down during the penetrating into a soft sediment layer. The drill head is arranged movable in the drill-pipe direction relative to the housing, so that it can be moved down separately from the housing as soon as the front end of the housing encounters a layer of hard rock.
From the AT-PS 379 863 a drill-pipe is known, which for the guiding in the drill hole comprises a guide sleeve that partly radially surrounds the drill-pipe, the outside diameter of which guide sleeve corresponds approximately to that of the advancing drill head.
BRIEF SUMMARY OF THE INVENTION
It is the objective of the invention to develop further a process and an apparatus for sinking drill holes, in particular exploration and extraction drill holes, of the described type in such a way that a deposit can mined through less hard rock layers up to the generally rocky primary rock located underneath, without in this case the process becoming uneconomical. Furthermore the apparatus should stand out by an adaptability to the most varying drilling conditions and depths and require the lowest possible production costs.
This problem associated with the process is solved by the subject of claim
1
.
According to the invention, a drill-pipe which at its end facing the floor to be mined is provided with a guide point fixed in the longitudinal direction of the drill pipe, is lowered to the place where the drill hole is to be made. When doing so, normally the guide point will penetrate at least slightly into the sediment layer. Next a drill head, which on its side facing the floor has at least on cutting element that can be moved in the longitudinal direction of the drill pipe between a top position, in which the guide point projects beyond the at least one cutting element, and a bottom position in which the at least one cutting element is positioned at the same height as the end of the guide point or projects beyond same in the operating direction, is moved from its top position assumed during the lowering of the drill pipe into its bottom position. Seeing that the guide point has penetrated by a certain amount into the sediment layer, the at least one cutting element of the drill head produces in the sediment layer a drill hole start which will guide the drill head laterally before the guide point assumes a decreasing laterally guiding effect of the drill head. When the drill head penetrates further into the sediment layer, the at least one cutting element is, therefore, positioned on the same plane as the end of the guide point or even moves ahead of same, so that according to the invention drill holes up to the bedrock located underneath the sediment layer can be made without any problems. Seeing that as a rule during the drilling operation the guide point need not penetrate into the rock layer located underneath the sediment layer, its wear is reduced considerably.
With a first variant of the process according to the invention, during the drilling operation the drill pipe is made to rotate around its longitudinal axis and as a result thereof, both the drill head fixed rotationally rigid to the drill pipe and also the guide point fixed rotationally rigid to the drill pipe and also the guide point fixed rotationally rigid to the drill pipe, are made to rotate. With this variant of the process, therefor, a “drilling” of the guide point into the sediment layer takes place.
It may, however, also be advantageous, to drive the drill pipe and to transmit the turning momentum to the rotationally fixed drill head, but not to the guide point which is mounted rotating around the longitudinal axis of the drill pipe. This ensures that the guide point does not rotate in the sediment. It is true that as a result thereof no drilling of the guide point into the sediment layer takes place, but it was found that in many cases an adequate guiding function of the guide point is obtained when it is pushed over a short length into the sediment layer exclusively by the mass bearing on it. As no relative movement takes place between the sediment layer and the guide point, the guide point is subjected to less wear compared to the aforementioned variant of the process according to the invention.
Particularly advantageous is the further development of the process with which the drill pipe is mounted rotationally rigid and the drill head is made to rotate relative to the longitudinal axis of the drill pipe, as by this measure the drive unit normally provided on the side of the drill pipe opposite the drill head side as well as possible complicated rotary transmission lead-throughs can be dispensed with. In this case it is possible to arrange the guide point rotationally rigid on the drill pipe.
However, in the case of a relatively hard sediment layer it may be advantageous to arrange the guide point rotating around the longitudinal axis of the drill pipe and to make it rotate around it longitudinal axis together with the drill head, as this permits a “drilling” of the guide point into the sediment layer in order to increase the initial guiding effect.
In another, particularly preferred variant of the process the guide point is again mounted rotating around the longitudinal axis of
Tibussek Fritz
Von Wirth Hermann-Josef
Bagnell David
Gay Jennifer H
Wirth Maschinen-Und Bohrgeraete Fabrik GmbH
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