Boring or penetrating the earth – Processes – Boring with specific fluid
Reexamination Certificate
2001-08-27
2003-07-15
Bagnell, David (Department: 3672)
Boring or penetrating the earth
Processes
Boring with specific fluid
C175S016000, C175S017000, C299S014000
Reexamination Certificate
active
06591920
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national stage of PCT/EP00/01015 filed Feb. 9, 2000 and based upon a German national application 199 09 836.0 of Mar. 5, 1999 under the International Convention.
FIELD OF THE INVENTION
The present invention relates to a fusion drilling process for the placement of dimensionally accurate borings, particularly those of large diameter, in rock, in which the waste melt is pressed into the surrounding rock, which is cracked—due to the effects of temperature and pressure, and in which a borehole lining is produced during boring by solidifying melt.
BACKGROUND OF THE INVENTION
The placement of borings in rock by means of melting the rock to be removed is generally known. Thus, for example, U.S. Pat. No. 3,357,505 discloses a boring head with which the melting of rock is performed.
This known boring head, which consists of a metal resistant to high temperatures, such as molybdenum or tungsten, is heated by means of heating elements to a temperature above the melting temperature (1000-2000° C.) of the rock and pressed at high pressure by means of costly extendable propulsion rods into the rock, which then melts.
The problems associated with transporting away the waste rock melt occurring in the boring process are solved in this case in that the rock melt enters into an opening of the boring head and is then conveyed to the surface within a conductor pipe by a rapid gas stream.
In spite of the resistant material, the boring head is subject to great wear due to the corrosive effects of the molten rock, so that it occasionally has to be replaced.
Furthermore, solving the problems associated with the waste by subjecting the melt to a high pressure, in addition to the naturally prevailing extremely high temperature gradients between the rock melt and the surrounding solid rock at the boring head, in order to cause the formation of cracks and splits of the surrounding solid rock into which the waste rock melt can be pressed through temperature and pressure stress is also known. It is thus no longer necessary to convey the waste material to the surface due to this process.
Also known is the pressing of the rock melt around the boring head during the production of fusion drilling borings, so that the melt solidifies above and around the fusion drilling head, particularly due to additional cooling measures which are provided, and the borehole is lined with a uniform glassy melt layer.
A device of this type, in which the rock is melted by an H2/O2 flame, is known from DE 2,554,101.
A fusion drilling device and a process for the operation of the device, which utilizes the pressing of the waste into the surrounding stone and the borehole lining, is known from DE 195 01 437 Al. The device described here is used in salt galleries and uses the molten salt itself as the boring medium.
In the known devices, there is a problem in that, due to the melt solidifying above and around the boring device, adhesion occurs between the wall of the boring device and the lining of the borehole, which typically must be overcome through special hydraulic propulsion and lifting facilities in order to bore further.
Correspondingly, a continuous hydraulic pressure must be used when operating with the known process, which makes the boring facility as a whole very costly, because it must be designed for enormous pressures of up to several thousand tons.
A boring device known from U.S. Pat. No. 5,168,940 uses a metal ceramic mixture for the boring head in order to reduce wear and more easily overcome the adhesive forces between the boring head surface and the rock melt.
The known facilities must be equipped with costly supply lines in order to supply the enormous quantities of energy for heating to the boring head over several kilometers of bore depth.
Due to the melting around the boring head, the later lifting of the boring device is also problematic in this case.
OBJECTS OF THE INVENTION
An object of the invention is to provide an energy-saving, universally usable boring process with which extremely deep borings, shafts, and tunnels, both horizontal and vertical, particularly those with large borehole diameters of, for example, more than 1 m, can be made, ready for use, in any rock substrate.
Furthermore, it is an object of the invention to provide a process and a device for performance of this process with which the fusion drilling process can be performed economically and easily without additional cooling measures, without time-consuming drill pipe assembly, without moving components, without changing of the boring head, without waste transport, and without subsequent lining and casing work.
A further object of the invention is to provide special materials for general use in fusion drilling processes.
SUMMARY OF THE INVENTION
These objects are achieved according to the invention by, among other things, supplying, as the boring medium, a melt containing metal through pipeline elements to the base of the borehole, which is to be removed through melting.
According to the invention, to perform the boring process, a heated melt containing metal, which is also understood to mean a pure metal melt, e.g. an iron melt at a pouring temperature of approximately 2000° C., is poured as a low viscosity boring medium into the first pipeline element in the direction of boring, so that the metal melt comes out of the last pipeline element directly over the base of the borehole and melts and removes the rock from the base of the borehole.
The removal of the molten waste rock is hereby promoted in that the rock has a significantly lower density than the metal melt, so that the rock melt automatically floats on the metal melt. The base of the borehole is thus automatically and continuously freed from the molten rock melt.
Due to the high static pressure which results from the metal melt column standing in the pipeline elements, the metal melt coming out of the lowermost pipeline element is guided with the waste material (rock melt), in the process according to the invention, between the outer side of the pipeline elements and the inner wall of the borehole, where they solidify as the boring progresses. Because the boring process is performed without further cooling measures, energy and cost savings of over 50% relative to known fusion drilling processes result.
The solidified melt, which can also be a mixture of melts made of metal and rock, forms a pressure seal between the pipeline element and the inner wall of the borehole, so that, due to the extremely high temperature gradients in the rock and the pressure generated, splitting of the rock material occurs automatically, whereby above all the lighter waste melt is pressed into the surrounding rock.
The loss of metal melt which results due to the compression and solidification can be compensated at the beginning of the boring at the first pipeline element through addition of metal melt. This addition can be performed continuously or discontinuously, because the volume of the melt column resting on the base of the borehole acts as a reservoir.
In this way, it is possible according to the invention to produce a dimensionally stable lined borehole, particularly lined with cast metal, which can have a large diameter, e.g. of more than 1 m, and essentially any desired profile, with this borehole able to be supplied for its intended use without any further post-processing, due to the automatic cast metal lining. The boring can hereby be performed not only vertically, but also horizontally or at other angles to the surface of the earth, so that borings for greatly differing intended uses such as, e.g., geothermal power stations, supply lines, or tunnels can be produced.
This means that, in the metal melt boring process according to the invention, in one single work cycle a borehole is melted, the borehole melt is pressed into the surrounding rock, and a compressed, stable borehole lining is made from the cooled rock melt which is simultaneously also lined with a seamless metal wall.
The process according to the invention thus adva
Bagnell David
Dubno Herbert
Gay Jennifer H.
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