DE2652043A1 - Simultaneous formation of two drill shafts - and part recovery of molten rock for heat content utilisation - Google Patents

Abstract

The recovery of geothermal heat energy from subterranean rock comprises: drilling the earth with a rock melting drill so as to form two distinct shafts; circulating heat absorbing fluid down one shaft, through the drill and up the other shaft; and recovering heat from the fluid. The appts. includes an electric heating element capable of withstanding a temp. of 1200 degrees C and a drill for forming two shafts and moving some of the rock. The drill is such as to allow passage of a circulating fluid between the shafts. Both shafts are drilled together and communicate without recourse to rock fracturing. Additional piping is not required for the circulating fluid nor for excess rock removal. Excessive mechanical force upon the drill is avoided so drill wear is reduced. The force on the heating element is minimal so they may be fabricated from materials which allow higher temps. to be attained.

Description

Equipment and method for drilling rock

formations The invention relates to a device and a method for drilling rock formations using a drill body and a Heating element; which by heating melts a volume of rock through which the Drill body is lowered.

It is generally accepted by geologists to be within a distance from about 30 to 35 km below any point on the surface of the earth including the ocean floor Temperatures can be reached necessary for the operation of high-performance heating machines would be particularly cheap. The only previous barrier to such energy sources tapping was the difficulty of finding suitable heat exchangers in those called geothermal Energy sources bring suitable depths. As soon as this difficulty at one given point of the earth's surface are to be overcome, this is particularly suitable to put a geothermal power plant into operation. It is believed accepted, that the previously easily accessible geothermal energy sources in the vicinity of the Earth's surface, which has been successfully exploited so far, the result of a natural Are heat exchange mechanism that extends to great depths. This however, natural heat exchange in these areas is very low Part of the energy available for within the 30 to 35 kilometer zone the yield free.

Exceeding all geothermal energy sources on earth by far the entire world energy demand, and not just for today, but also for the entire foreseeable future. However, these energy sources are so far almost inaccessible with the help of known methods and facilities, namely not because known drilling devices do not have a sufficiently high level of development have achieved, but because of the difficulties and limitations of both technological as well as of the economic nature that occur with the known drilling methods. It is desirable to overcome these difficulties and both a method as also to create facilities with which geothermal energy sources are accessible be to meet the world's need for energy environmentally friendly and without pollution to win.

Attempts have already been made to drill two separate holes with heat drills or to drive other drilling devices into massive rock formations, to then break up the rock formation hydraulically or atomically and passages to create for liquid flows.

One introduced through a borehole and circulated through the passages Fluid is then returned to the surface of the earth via the other borehole, to recover the thermal energy absorbed in the earth's interior. When using Nuclear explosive devices could be part of that triggered by the nuclear reaction Heat regained be won. Attempts have also been made to drill a single borehole, in which after removing the drilling equipment Pipes are inserted to carry heat through a fluid circulated over the depth (U.S. Patents 3,274,769, 3,470,943, and 3,521,699). For the drilling process were various devices are contemplated (U.S. Patents 3,396,806, 3,357,505, and 3 693 731).

These known methods and devices have disadvantages. In particular you need a separate drilling device and insertion for each borehole of pipes running the length of the borehole to drilling mud for removal of to be able to circulate excess rock. Furthermore, there are also considerable mechanical forces required to operate the drill head, the considerable wear and tear is subject and thereby irregularities in the drilling cross-sections in Borehole inevitably brings with it. It is also necessary to line the borehole, with a lining that extends from the surface to the bottom of the borehole to prevent collapse of the drill walls. Included the individual parts of the liner must fit into one another, so that you have a borehole receives, which has increasingly smaller diameter. This in turn requires that the Drilling device fits into the smallest diameter part at the bottom of the borehole, with further advancing the borehole of the drill in each case of the smaller-diameter lining must be adjusted. The drilling rigs themselves often have to be removed and replaced as they wear out. With these drilling operations it is hardly possible while useful to recover thermal energy from drilling, d. H. it stands no heat output is available until the drilling process is complete. Also, separate machining operations are necessary in addition to drilling to make the liner of the borehole to perforate so that liquid can pass through the borehole and the surrounding area Rock-stone formation can circulate. So such a Circulation through the rock formation is possible, apart from drilling rock blasting be carried out in the borehole area, so that the circulated for the heat transport Liquid comes into contact with the rock over the largest possible area. When using of fusible drills there are no convenient facilities to position or to control the orientation of the quarries, because it is quite desirable Avoiding breaks that go wrong within the rock.

There is also no suitable means of drilling two holes in the massive To connect rocks to one another, except by providing for rock fractures, which allow the passages for the fluid from one borehole to the other borehole. Furthermore, there is no suitable means of having a working geothermal spring to advance with two boreholes to a greater depth, without the connecting passages to seal between the boreholes. It is also necessary for fusion drills to exert a thrust on the heating surface to both the molten rock as well as to move the drill. Fusion drills that bring such a force to the heating surface that the used or usable Temperatures are limited by the structural strength of the material and not due to the material strength at higher temperatures.

The invention is based on the object of a method and a device for drilling solid rock, such as those mentioned above Disadvantages are overcome and the required goals are achieved.

This object is achieved according to the invention for a drilling device solved that the heating element is supported so that it is only part of the to be melted Rock melts directly that the remaining part of the part of the rock to be melted by dissipating heat from the directly melted rock is brought to melt, such that by the rapid mutual penetration a sharp rise in the mean temperature of the rock above the melting point is avoided, and that the drill body to divert part of the rock melt Is used.

Further refinements of the drilling device according to the invention are Subject of further claims.

The method according to the invention provides that the directly with parts of the rock that come into contact with the heating element directly through heat transfer to a temperature significantly higher than the melting temperature of the rock are heated and that they do not come into direct contact with the heating element adjacent pieces of rock melted by conduction from the molten rock be, reducing the mean temperature of the entire molten rock on a M elze maintained at a much lower temperature than the highest temperature of the partial melt will.

This method is further developed through features of further Expectations.

A particularly advantageous embodiment of the invention includes a Drill body with a special shape and a heating element with a certain Configuration attached to the lower end of the drill body and by melting of the rock penetrates into the ground.

Two separate boreholes are created in the earth at the same time.

These two boreholes are used for the supply and discharge of liquid, which is circulated in the form of drilling mud over the drill body to remove excess Remove rock. The heating element works at a temperature Temperature, which is significantly higher than the melting temperature of the rock. This will make before the drill body created a rock melt and the surrounding rock as well melted by convection so that they eventually melt in the Rock mass forms a mean temperature, which is much less above that Melting point of the rock. The molten rock mass can move forward of the drill body flow away in two ways. Either it flows inside of the drill body and mixes with the drilling mud to bring it to the surface to be brought. The other part of the mud flows around the exterior of the drill body around to the top, which forms the two boreholes in the molten rock. For this purpose, suitable devices are provided on the drill body on which the rock mass shifts along and gradually solidifies.

This creates the two boreholes in the desired manner. There are Devices are also provided which allow the boreholes to be located in exactly wind around each other in the intended manner.

The drilling mud leading down the borehole is with an or provided several recesses which extend over the entire length of the borehole and are preferably cut in a V-shape into the wall of the borehole. These Recesses are provided for breaking in a later process step of the surrounding rock to ease by removing thermal stresses on the front At the end of the V-shaped cutout to ensure that the Fractions proceed in the desired way. The one through the drill holes and the drill body circulated drilling mud absorbs heat which is recovered in appropriate Energies can be converted, which are used to sustain the drilling process Can be used. This absorbed heat can be used in the in the liquid column a so-called thermosiphon effect can be achieved by which a force acts on the liquid in the direction of the liquid movement and which can be sufficiently large to accommodate that necessary for the circulation of the liquid Apply pump power. With the help of heat exchange on the earth's surface the heat is recovered from the circulated drilling mud and put into one for the Recycling converted into desired form of energy.

Once the drill body has reached the desired depth, fractures will occur installed in the surrounding rock by introducing energy in a hydraulic way will. As already mentioned, these breaks preferably start from the V-shaped recesses the end. By introducing a suitable material, the fractures are partially closed, so that cells arise in which the heat exchange with the transport fluid takes place. If the boreholes are twisted together, they run from the fractures in the same direction emanating from the borehole conducting the fluid downward and with the same rotation as the drill holes, so that helical surfaces are created. The drilling mud or the liquid introduced instead of the drilling mud is used as a transport fluid for the thermal energy that it collects from the rock picks up when they get through the boreholes, the fractures and the cells in the rock as well the drill body circulates. As already mentioned, the thermosiphon effect is used a pumping power provided, which supports the circulation of the liquid Circulation speeds can be achieved using a turbine make necessary to adjust the liquid flow to the desired flow rate to limit. The turbine can be used in both downward and upward flow lie, but the downward current Downward current is preferred, because it does not carry any rock remnants with it because of the sieving on the surface of the earth. This turbine can also be used to supply energy.

It is also possible to use the drill body again at a later date to start up again to lower the drilling level further without it it is necessary to seal the fractures in the rock. The fractures caused by a borehole go out, have no connection to the other borehole, so that all the fluid, which is circulated through the boreholes, must flow over the drill body.

With the measures of the invention can be geothermal in an advantageous manner Obtaining heat from the earth's crust »whereby the measures are much more versatile and in much more different: geological formations than previously known methods can be used. It can drive drilling operations to very great depths that so far, if at all, only with extremely great efforts and economic Effort can be achieved. The measures are not just for use in solid rock, but also in ice, so that now also exploration these areas of the earth's surface is much lighter. It is also possible, that the oil and gas wells, which lately close to the surface in 5 edimentary Rock formations were found trapped by the deposition of chemical substances which may have originated from a greater depth the base rock has pushed upwards, so that through fractures in the solid rock usable quantities of these petrochemical substances obtained in sufficient depth can be. The invention is therefore also particularly advantageous for research unknown regions suitable to unknown knew raw material sources to find.

The advantages and features of the invention also emerge from the following description of an embodiment in connection with the claims and the drawing. They show: FIG. 1 a schematic perspective view a device for drilling solid rock as an example of implementation the invention; Fig. 2 is a section along the line II-II of FIG. 1 through a for example embodiment of a heating coil according to the invention; Fig. 3 the View of another heating element used in practicing the invention Can be found; Fig. 4 is a schematic view of formed in the outer wall of the bore Fractions; 5 shows a schematic perspective view of a further embodiment a device for carrying out soil boreholes; 6 shows a modified embodiment the embodiment according to FIG. 5; 7 shows detailed views of the embodiment according to Fig. 5; 8 shows a section through a device for applying a hydraulic hydraulic Pressure to create or expand breaks.

In Fig. 1 is a device for drilling rock formations and to facilitate the extraction of geothermal energy. The drilling device comprises a drill body 12 and a heating element 15, which preferably consists of a heat-resistant Material such as B. pyrolytic graphite or tungsten is made and consists from a number of straight or curved heating rods in the form of a heating grid or a heating coil 18 through which current flows. This heating grid is attached to the end points 17 on the drill body 12 according to FIG. 2 and has a certain Compliance in the direction of drilling. The heating elements can be shaped accordingly Enclosed housing. The drill body is preferably made of a heat-resistant one Made material that is electrically insulating, e.g. B. boron nitride. There is a greater number of materials that can be used for the drill body including Ceramic and baked brick materials. The drill body has an opening 20 on the underside, curved side walls with a lip-shaped tapering part 24, which merges into the upper end surface 26, as well as shaped elements 28, which on the upper End with a circumferential collar 25 are provided. With the help of the form elements Drill openings formed having a cross-sectional area of about the cross-sectional area the opening 20 have. This opening 20 stands with a curved pipe section 30 within the drill body 12 via a channel 23 and an opening 21 in connection.

The heating element 15 melts the rock in front of the drill body 12 and is operated at a temperature that is sufficient above the melting temperature of the surrounding rock. A rock that goes with the establishment according to the invention is preferably to be pierced, consists of granite. granite has a melting point of about 1200C. Therefore, the heating element must have a temperature be heatable from 1 2000C without melting itself or even with long-term Use to wear out. An expedient and advantageous operating temperature of the Heating element is about twice the melting temperature of the rock, i.e. in the given case at 2 700 C for granite. The heating element 15, which acts as a heating grid or heating coil is formed, the rock melts in a corresponding Pattern and penetrates only a fraction of the total volume of the melted Rock.

In doing so, it only displaces the rock by a certain distance as it penetrates in the order of magnitude of the diameter of the rod-shaped elements of the heating grid or the heating coil 18, so that the molten rock volume is only slightly The remaining solid rock is interspersed with greater than the volume of the displaced rock the openings in the heating grid or in the heating coil and is heated by the Rock outgoing conduction melted before the radiator 12 reached this area achieved. The process and the facility provided for its implementation connect three very important features that allow the heating element to penetrate the rock with a lower resistance than in previous attempts of the Case was. The molten rock had to be removed from the surface of the heating element be removed1 in order to add thermal energy to more rock. As long as melted Rock is located between the heating element and the solid rock, this acts as a Insulator. In the present invention, the molten rock need only be in orders of magnitude are displaced, which correspond to the diameter of the rod elements and not in the order of magnitude of the diameter of the drill body, as in known methods procedure the case is. Furthermore, the rock displaced by the heating element is much hotter than the rest of the rock melt and therefore has a lower viscosity resistance. Finally, the lower viscosity resistance acts on the heating element only during the relatively short time it takes to displace the rock mass will. These features make it possible to use the heating element at higher temperatures to use than before and to advance the hole faster because the heating element a relatively small resistance and thus correspondingly lower stresses learns. The total volume of the molten rock is only reduced to one Heated temperature that is the desired range above the melting temperature. This results in a very economic advantage in conjunction with a rapid Penetration of the rock at lower melting temperatures as a whole. The use of a heating grid or a heating coil for the heating element 15 would obviously also lead to the same benefits if instead of two Holes only one hole is driven.

The heating element can be resilient, so that it is when Penetrating the rock can deform up and down without permanent Assume deformation. However, provision is also made for the heating element to be rigid and to provide rods on which the heating element after the force of a spring is displaceable up and down, as can be seen from FIG. With the yielding one Embodiment results in a. greater radial concentration of the bars or loops in the area of the attachment points 17 (FIG. 2), at which the loops do not yield for pressure or tension absorption. There is also a larger radial Concentration of the rods or loops in the area of the outer diameter 19 what serves to protect the perimeter. The dimensions of the molten rock are important for the advancing Advance speed of the drill, wherein the resilient shape and the concentration of the rods, the heating coil and des Heating grid 18 on the outer periphery help that the occupied by the melt Space has a substantially constant cross-sectional shape. The area the cross-section decreases slightly when the element moves upwards, whereby the sink rate of the drill body is lower. This will make that Element is protected from damaging compressive stresses caused by too rapid sinking can be triggered. The measures mentioned prevent accidental pressure loads for the heating element 15 kept to a minimum »so that this one with a high Temperature can be operated at which the structural strength is proportionate is small, but in which the heating element is otherwise stable. Through the present Invention, the function of the heating element is separated from that of the drill body, so that the heating element only heats the rock and does not exert any force on it Exercises rock to move or deform it. The drill body 12 displaces and shapes the rock and is for adjusting the penetration speed of the Drill body in the rock responsible. Force through the measures of the invention neither the heating surfaces nor the drill body melted rock, between congruent Surfaces to flow through, the molten rock still has to flow over one another or penetrate the rock a substantial distance, being distances of about 1/10 of the diameter of the melt has in mind. Well-known fusion drills do not have these advantages and require considerable force to to propel the drill head forward. The lip-shaped terminating part 24 is the outer one Perimeter determines the shape of the perimeter of the cavity receiving the melt, lies at a short distance from the massive rock, d. H. the drill body touches the massive rock does not, as this this already melted is before the drill bit comes into the area. The heating element works at one almost constant temperature, so that the mean temperature of the molten rock essentially of the driving speed of the drill body and thus of the Depends on advancement of the heating element through the rock. This mean temperature determines the viscosity of the molten rock, which is its greatest change in the area the melting point of the rock. The drill body advances at one speed which is determined by the viscosity of the rock that is being penetrated got to. A speed is set at which the interacting Forces are in balance. As the speed increases, it decreases the mean temperature of the molten rock, making the viscosity greater and the drill body advances more slowly. Conversely, if on the other hand by the slower one Advancing the state of equilibrium is undershot, the mean temperature rises of the molten rock and leads to a lower viscosity, so that the further advancement of the drill body takes place at a greater speed. That The weight of the drill body can be determined by adding weights (not shown) be increased in order to increase the temperature range at which the equilibrium is reached adjusts to move. It is desirable that the state of equilibrium sets at a temperature at which, on the one hand, the rock is hot enough, to melt evenly and on the other hand is still cool enough to produce a to ensure rapid solidification along the form elements.

Although the drill body 12 is not in contact with the solid rock comes, the circumferential collars 25 provided as part of the form elements 28 are of this type designed to be used in the formation of the wellbores Wells are surrounded by liquid rock and the liquid rock by parts of the underlying push off solid rock.

The frets can also come into contact with the solid rock. The part of the heating element below the opening 20 heats the rock to a higher mean temperature and thus facilitates the drainage of the liquid rock through the channel 23 and the opening 21.

The channel 23 and the opening 21 can be pyrolytic through a layer Graphite be insulated, which prevents the liquid rock on the surfaces of the channel 23 or the opening 21 cools. This will close the rock of the surfaces kept at the highest temperature. Has pyrolytic graphite an anisotropic thermal conductivity that is very high along the crystalline basal planes is and very low in planes perpendicular to it. So this material has the ideal Combination of conductivity and insulating properties with regard to the necessities in the channel 23 and in the opening 21. The crystalline base planes of the graphite lie parallel to the walls of the channel and thus conduct the heat in the longitudinal direction of the Walls very good, but hardly through the walls. The greatest concentration of heat results located immediately below the opening 20, so that the along the walls upwards dissipated heat assumes a maximum value and thus the flow of the melt eased along the walls by the canal.

The curved pipe section 30 conducts within the drill body 12 the drilling mud through the drill body. It connects the supply line 32 with of lead 34. The dimensions of these leads are important in terms of shape the drill body, which isolates the pipes from the molten rock. The administration preferably has an oval cross-section with the largest diameter in the vertical Direction.

A A corridor made of molten material must connect the two pipe elements together, but it only needs to be wide enough to that the drill body can move through. However, it may be narrower than the dimensions be the pipe shafts. The speed of the drilling mud through the pipes is determined with the help of turbines placed on the surface of the earth. The flow rate is preferably only as great as it has to be in order to avoid excess To be able to discharge rock material without clogging the line. When the liquid If its direction of flow changes, a force is exerted on the drill body in the advancing direction exercised.

At the same time, an opposing force acts on the drill body due to the rock melt flowing through the channel 23. Both forces are however relatively small and orders of magnitude smaller than the weight of the drill body.

The stone mass melted with the drill body takes two different ones Paths when the drill body advances. Part of the mass flows through the opening 20 and the channel 23 and the opening 21 in the curved pipe section 30 and is carried away by the drilling mud. In the illustrated embodiment the melt receiving space consists of two non-communicating spaces Melting areas, which through the drill body in the area of the opening 20 heating element connected to the end points with the drill body and the massive rock are separated from each other below the heating element. So that is almost the entire Rock mass pressed into the channel 23 below the opening 20. Through this execution.

form becomes an essential constant part of the rock through which the drill body penetrates, removed with the help of the drilling mud.

The size and shape of the opening 21 depends on the drilling mud used addicted. The greater the surface tension of the molten rock in the drilling mud, the larger the opening can be. Through the opening becomes the rock discharged into the drilling mud in an area where the drilling mud already begins to flow upwards. This will remove the molten rock relieved.

The drilling mud is sifted at the surface of the earth to remove parts of a certain size to remove. Smaller parts can remain in the drilling mud and continue to circulate without causing a high level of wear and tear or impairment of the Tool is given.

The rock melt that has not been introduced into the drilling mud flows around the side walls 22 of the drill body 12 and on the lip-shaped tapering Part 24 up to the upper end face of the drill body. The rock melt flows from there around the form elements 28 so that two wells in the molten rock be formed. Parts of the wall of the wells consist of the solid rock, from which the molten rock is scraped off, perhaps a thin one Layer of molten rock remains on the surface of the solid rock. The density of the drilling mud is slightly greater than that of the molten rock, so that the wells, which are between the circumferential collars 25 and a Form sealing washer 35, are filled with drilling mud due to its weight the rock melt supports around the borehole and to maintain the shape contributes to the molten stone during cooling. The stone melt cools with a certain Speed due to the mud isolated in the borehole. This creates a crust on the surface that thickens as the melt cools. if this reaches the area of the borehole designated by 42 in FIG. 1, has the solidified melt the desired thickness and is capable of the. through the borehole flowing cooler drilling mud without breaking the surface. It may be, that be that individual rock areas for a longer period of time and thus remain in the molten state until well above the drill body before they solidify again. Most of that used to melt the rock Thermal energy is finally transferred to the drilling mud because it is in the most areas cooler than the surrounding rock and thus represents a heat sink after which the heat energy flows away.

In this way, two drill holes are created when the drill body is lowered with an inner surface 41 in the rock, with only a single drill body required will. The drilling mud continuously flows through the two boreholes. The drilling mud is within the boreholes 50 between the sealing disks 34 and enclosed in the drill body and acts like a thermal insulator that prevents cooling of the melt at a rate at which undesirable thermal stresses to be avoided in the rock.

This reduces unwanted break points to a minimum. However, the seal is not hermetic; the opening 39 in the supply line and the discharge line a renewal of the drilling mud too, if this is necessary. With the supply line on the one hand and the discharge line on the other hand connected damping washers 43, which between the circumferential collar 25 and the sealing disk 35 are arranged, prevent circulation of the drilling mud as a result of convection. The circumferential lines of this damping disk are proportionate close to the inner walls 41 of the drill holes.

The supply line 32 and the discharge line 34 have a specific one Length and usually do not extend to the surface of the earth, but only up far enough to create an area for drilling Borehole walls allowed to cool, and and about the direction of rotation of the drill body while advancing to be able to control. At its upper end, collapsible funnels 36 are attached, above which the borehole alone represents the line for the drilling mud. The drill holes are self-sustaining in all rock formations found at sufficient depth. A very important advantage of the present invention is the ability to use drilling mud without the need to bring down pipelines over the entire length of the borehole to be able to circulate, as is the case with all holes with a single borehole with the exception of narrow stratified areas is the case. The fact that a drill pipe can be dispensed with, which differs from the Surface extending from to depth also removes one of the main obstacles for drilling to great depths, seen in the cost and difficulty to pipe boreholes for kilometers into the earth. This possibility the abandonment of piping extending to the surface of the earth also a prerequisite that the drill holes rotate freely around one another because a tightly twisted borehole would jam standard drill pipes to lead. Furthermore, the boreholes according to the invention are essentially the same Diameter or at least have a smaller diameter tolerance, what the possibility offers the borehole in its entire length with a lining more constant Understanding diameter size, which is also not the case with known drilling methods is and what also allows the supply of liquids to a greater depth.

The supply line 32 and the discharge line 34 can be in the borehole with the help of suitable guides, e.g. B. centered with rollers 38 on a spring ring will. These rollers 38 lie on the wall 41 of the borehole in one area in which the rock is already again solidified again has and contributes to the positioning of the supply line and the discharge line within of the drill holes. Eccentric displacement or displacement creates a rotation of the drill body as it advances into the ground. The positioning of the lines in the borehole causes the change in the orientation of the borehole when traveling through the path between the form elements 28 and the rollers 38. If the rollers 38 position the tubes where they would be when the Device for drilling at a certain angle around the central vertical axis rotates, then this is the angle of rotation of the drilling device when advancing the distance from the rollers 38 to the shaped elements 28. The drill head moves primarily due to its own weight, so that it is therefore basically down emotional. If the drilling device executes a rotary movement, it follows all the more more of a vertical direction. It is possible to put the lines in the boreholes Orientate so that the drilling equipment moves slightly in one direction of moved away from the vertical, which may be desirable for special applications can, however, such an alignment is usually not provided. For the case that the drilling device when rotating from the vertical direction of movement shifts out, however, the rotation results in a self-alignment.

As can be seen from Figs. 1 and 2, the rock is in different Zones assigned to the drilling equipment. Zone A is the area in which the upper parts of the boreholes that lead to the surface of the earth, the zone B is the area between the sealing washers 35 and the upper end of the drill body, this includes the area in which the molten stone slowly solidifies, to go into zone A {. Zone C comprises the largest radial area in which the rock is melted by the action of the heating element 15 State and does not yet contain any solidified parts.

holds. Zone D represents the solid rock under the drill body, on which the heating element 15 acts. Finally, with the zones E, the area becomes denotes in which solid rock moves through the heating element and is in the state of melting.

Since the drilling device described according to the invention always from is penetrated by a liquid drilling mud during the drilling process, it is possible Heat absorbed by the drilling mud when it reaches the surface of the earth to win back. For this reason, a heat exchanger 45 is schematically shown in FIG. 1 indicated. Of course, other systems can also be provided in order to achieve the To use drilling mud located thermal energy. If from this thermal energy electrical Energy is obtained, this in turn can be used to generate the drilling process to deliver the required electrical energy or to make it available in part. It is quite possible that the drilling process without external energy or only with one very small proportion of external energy can be carried out.

This allows the limit of economic efficiency to be very low Move holes to more favorable areas. Due to the temperature dependent Density differences become kinetic due to the absorption of heat in the drilling mud Energy converted and can according to the thermosyphon effect, as it is with the Self-circulation cooling is known to be recovered. Because this effect is self-circulation maintains, significantly less pump power is required, so that possibly pumps can be dispensed with entirely and with the help of one that is switched on in the circuit electrical machine 46 according to FIG. 1 from the stored kinetic energy electrical energy can be obtained.

If the When the drill body is down to the desired When the depth is advanced, the electrical energy from the heating element is turned off and leave the drilling equipment in place. Appropriately, the electrical feed lines removed. The drilling mud can also be used if desired be removed, in particular with the help of the thermosyphon effect by a different liquid, in particular water, is gradually added to the drilling mud will. The drilling equipment can and possibly can remain in the depth forever be put into operation again at a later point in time.

In this case, they must be used for the supply of electrical energy necessary lines are reconnected to the drill body. When a drill body is to be put back into operation at a later date, it must be at Shutdown must be prepared accordingly. For this purpose, the advance speed slowed down and a liquid introduced into the liquid rock melt, which is heavier than the molten rock and therefore gradually replaces it, since the rock melt floats on this supplied liquid. This supplied However, the liquid must not solidify when the drill head is taken out of service is and is fed until all of it is located around the drill head 'Melt is replaced.

Then the drill head is fixed and put out of operation. The heavy one Replacement fluid is preferably supplied very slowly, including one of the following Reasons: 1. There must be enough time to move the molten rock in to exchange the cavern filled in by it; 2. by feeding this heavy Liquid increases the volume that is used in the manufacture of the boreholes accrues. Therefore, the amount of heavy liquid supplied is dosed in such a way that that the diameter of the drill holes is changed insignificantly. After a certain Time is then all of the molten rock, which the Heizdie Heating elements has penetrated, including Zone E and exchanged by the heavy liquid replaced. If the drill body is now taken out of operation, there is no risk of that it is jammed and crushed by the cooling of the surrounding rock. When restarting the drilling equipment at a later point in time reattached the electrical feed lines and reattached the heating element put into operation.

The drill body will only advance very slowly and slowly with it begin to melt the rock, if anything is still solidified Rock is located in front of the drill body or in the channel 23, which are first melted got to. The heavy liquid is gradually consumed over a period of time, where it can lay against the borehole and also partially mixed with the rock. When it is finally used up, the drill body can operate normally without hindrance Advance drilling operation. The electrical supply lines can be used as waveguides be designed and both for supplying the heavy liquid and for discharging serve the same when the drilling equipment is put back into operation.

When these electrical feed lines down to the bottom the cavern that absorbs the liquid can run through the heavy liquid removed relatively quickly when the drilling equipment is started up again will.

The energy required for drilling can be obtained from a high-frequency generator are generated on the earth's surface and are preferably transmitted by cables, as they are usual for high frequency transmission. This line resists that Thermal resistance, high pressure and corrosion and has a specific weight, which corresponds approximately to that of the drilling mud, so that it is relieved of weight. The advantage of the high-frequency current is that the current is due to the skin effect on the surface of the heating element element 15 flows. By this effect increases the resistance of the heating element and offers the possibility of to use higher voltages at lower currents in the transmission line. This means that the heating element can also do more in terms of strength and heating quality and less with regard to electrical resistance. However, it is likely that the heating element was made from a good electrical conductor is. The line to the heating element can also be used as a waveguide instead of a cable be carried out if very high frequencies are used.

Although the drilling process without creating undesirable fractures or high thermal stresses can be carried out in the rock, it is desirable to prepare the downwardly running borehole during the drilling process in such a way that that it favors the formation of fractures later. After the drilling process will be with the help of a special procedure in certain places in a certain way oriented fractures attached in the rock. Both the heating element 15 and the Form elements 28 devices can be provided with the help of which into the rock one or more indentations is cut while the drill body is moving lowers in depth. This makes it possible over the entire length of the borehole to make a recess in the wall. The devices connected to the heating element are placed in such a way that the greatest thermal stress in the rock is directly in front of the Place at which the recess is made, so that the later To favor breaking the rock. The recess is preferably V-shaped. In Fig. 3 shows a projection 116 on the heating element 115, with which a V-shaped Cut into the wall of the cavern receiving the molten rock can be. It is preferred that the drill body rotate as it enters the rock advances. In this this case will be due to the later breaking of the rock produces surfaces that resemble helical surfaces, what has certain advantages to be described below. There can also be devices be in place to control the setting of the rollers to allow the speed of rotation of the drill body can be adjusted while advancing.

The recesses and the concentrated thermal stress in the borehole, which are generated during the drilling process, are used later with the help of hydraulic Measures to apply the desired breaks. The breaks start in the recess and only extend radially outwards into the rock. It is also possible that To use the moment of the flowing drilling mud to generate the hydraulic pressure, by inserting a device 80 as shown in FIG. 8 into the wellbore developing the downward flow is introduced to close the borehole and the fluid flow with shock-like To apply shocks. In the event that the boreholes extend to great depths extend, carries the moment of the entire volume of liquid above such Device 80 contributes to the increase in pressure, which in this way in large Depth becomes greater than is the case with conventional hydraulic methods, which contribute to an equal increase in pressure in all depths.

The device 80 for introducing a hydraulic pressure and for The creation or enlargement of fractions is shown in FIG. 8 and consists of one upper part 81 and a lower part 82, which are rotatable against each other, wherein a screw 84 moves along a threaded spindle 83. The threaded spindle 83 is driven with the aid of a motor 85. The two parts 81 and 82 are piston-like slidable into one another and have a cylindrical seal in the area 86 "where piston rings can also be provided in this area. A Ring tube 87, which is filled with a liquid, lies both on the upper part 81 in the area 88 as well as on the lower part 82 in the area 89. When the two parts are shifted towards each other, the ringscia is also pushed outwards and lays adhere to the walls of the borehole. This creates a seal at the same time the outside of the device 80 opposite the borehole. With further Bringing the two parts 81 and 82 together is carried out by a valve piston 91 and a valve seat 92 formed valve slowly closed.

When the valve piston rests on the valve seat, no liquid can flow flow through the valve. The hydraulic fluid flows through openings in the upper Part 81 and lower part 82 according to the arrows in Fig. 8. The motor 85 is controlled so that a desired reduction in velocity for the flow is maintained and thus an increase in pressure due to the reduction in speed contributes to fracture formation.

The desired breaks can also be achieved by conventional means (U.S. Patents 3,303,883, 3,050,119, 3,018,095, and 2,368,424). In doing so, the breaks can also be attached before or after the B.

Another important step is in the space between the breaks to bring in horizontally dividing material. This material sets itself and divides the volume within the fractures into individual cells 62, like this is indicated in FIG. Convection currents arise in the individual cells because the liquid in the area of the borehole is cooler, which makes it possible to heat extract and dissipate energy from the deeper areas of the fractures.

When the fractures are open towards the borehole, it mixes the fluid in the Bohrloc h with the fluid in the fractures and contributes to wearing to facilitate heat dissipation. The convection currents arise regardless of whether the borehole is lined or not. Such a heat-conducting lining of the borehole is indicated by dashed lines in FIG. 1 with the reference numeral 47. In the ascending borehole is provided with a heat-insulating slide, such as this is indicated by the reference numeral 48 in dashed lines.

By this on the one hand thermally conductive and on the other hand thermally insulating The transfer of heat becomes particularly economical.

It should be noted that the breaks are positioned so that there are no flow bridges arise between the two boreholes and the flow through the earth is longitudinal the boreholes takes place. In this way it is possible to break the rock to be carried out during or alternating with the drilling process without the Removal of the rock with the aid of the drilling mud is impaired. By The flow flowing through the boreholes collects the heat either by convection, through Conduction or by mixing the fluid in the borehole with the fluid in Cells and is brought to the surface of the earth in order to be exploited there in the desired manner and also to contribute to the thermosyphon effect in the flow, which, as already mentioned, can be used to utilize energy.

A preferred form of the fracture are helical fracture surfaces, for a variety of reasons. First of all, the heat can be twisted in It is easier to collect running boreholes from all sides, since the heat dissipation is not takes place preferentially to one side. Also have helical Breaks the property of promoting vertical breaks in an important way. Helical surfaces are those created by a line that is perpendicular to an axis goes out to which the line rotates at constant speed when moving along the axis. The area swept over is almost vertical in the immediate vicinity of the axis running and becomes increasingly horizontal with increasing distance from the axis Course. The vertical distance between areas of the resulting surface is the same at different distances from the axis and if the helical one Surface has passed through a full revolution with an axis length of z. B. about 60 m, the vertical distance between associated areas of the helical Area also about 60 m, which means that all points between these areas at a distance of about 30 m from a surface, regardless of the radius the area. When generating geothermal heat, due to the heat conduction in the Rock dissipates heat the slowest. The distance between the points is within of the rock from which the heat is dissipated, very important for the extracted Heat share. Vertical breaks that are not helical will diverge but proportional to the distance from the borehole axis from which the The essential difference is that of the helical one in preference Breaks leads.

The cooling of the rock in the area of the fractures causes it to shrink. This process extends over long periods of time and over a wide range of changes the temperature, until finally a large part of the rock volume is essential has smaller dimensions. Thus, the process contributes to the enlargement of the fractures and of the volume present in the fractures. The fracture volume that is at great depths is generated, represents at least the amount of work that is required to to bring an equal volume of rock to the surface, and represents at most the considerable amount of work compared to elastic forces, which one deformation oppose the formation of the rock. However, if the Volume enlargement is the consequence of a shrinkage of the rock, is for this no special work is required and therefore it is particularly economical. The shrinkage can also cause fractures in all directions in the rock. Propping up the fractures to keep them open should be done repeatedly, what contributes to the settling of the rock during the continuous removal of geothermal Energy is decreased.

A modified device for drilling and heat recovery according to the invention is shown in FIG. In this embodiment, the Heating element 215 held at a distance from the opening 220 in the drill body 212 and thus does not automatically subdivide the molten rock into an outer and an inner flow area.

Rather, the molten rock flows due to the pressure difference between the molten rock and the drilling mud through channel 223. If excess molten rock through channel 223 and opening 221 in the through conduits 229 and 234 flowing drilling mud flows, the pressure in the molten rock must greater than the pressure in the drilling mud. In this case there will be no balance between the molten rock and the drilling mud in the boreholes. The heating element 215 is made up of rigid or flexible rods 203 in the embodiment according to FIG. 5 or

rigid rods 303, which bear against biasing springs 308, in the embodiment according to FIG. 6 supported. This makes it possible that the heating element 215 before Drill body 212 moved up and down. The drilling device is always moving. not due to their own weight, as is the case with the embodiment according to FIG. 1 may be the case, but is done with the help of mechanical, not shown devices postponed that for that which ensure that the drilling equipment shifts at a constant speed, which is only slightly dependent of the distance of the heating element 215 from the drill body 212 is variable. To this Purpose, not shown scanning devices are provided that this distance of the heating element 215 from the drill body 212 to determine as a function of these Values to control the feed rate. The shaped elements 228 according to FIG. 5 and 7 are preferably cylindrical and made up of overlapping resilient elements made of a non-stick material. The Elements surround spring elements 240, which are between the lines 229 and 234 and the shaped elements 228 are arranged.

There can also be provided spring elements 241 that are within the Form elements 228 are arranged. The spring elements 240 and 241 lie against the cylindrical shaped elements 228 and prevent compression. Practice doing this they exert a force to hold the form elements 228 in their working position. Excess pressure in the rock melt is absorbed by the spring. The solidifying rock is shaped by the shaped elements 228.

When the drilling rig is advanced beyond the range, on which the walls of the boreholes are solidified, these walls have a sufficient one high strength to withstand the differential pressure that develops between the molten Sets the rock and the drilling mud in the borehole. An overpressure in the melted Rock arises whenever the volume of the molten stone exceeds the value increases, which is required to create the boreholes, but is sufficient this overpressure is used to remove excess rock.

The drilling devices shown in Figs. 5 and 6 have both Advantages and disadvantages in comparison with the drilling device according to FIG. 1 Fig. 1. The disadvantages are that the drill body with the help of mechanical means must be moved, the feed is to be controlled separately. Also useful the form elements. In addition, the feed rate is not used as a definition the heat in the rock to a desired temperature range above the melting point. Furthermore, the cooling devices must be able to shape the borehole from the rock at a wider temperature range. In the end A precaution must be taken to reduce the rate of advance of the drill body depending on its distance from the heating elements. In general it is true that this modified form of the drilling device is more complex and more prone to failure is. However, the advantages can outweigh these disadvantages. There is a great advantage in that the drill body can also process rocks of different porosity, whereby the amount of rock to be removed depends on the porosity changes. In the embodiment according to FIG. 1, a constant fraction of the rock is used removed, making this very good both in solid rock and in rock with a certain porosity can be used. However, if the rock is very porous, it becomes too much Rock removed so that no well-formed boreholes are created. In the embodiment According to FIG. 5, only that portion of the rock is removed that is above the training of the boreholes, regardless of the porosity of the Rock. There are enough areas in the world for which there is easy accessibility to the massive base rock to meet the world's energy needs. Therefore the modified embodiment of the invention is not preferred, but may they are particularly advantageous in the creation of geothermal energy sources, if the rock formation is designed accordingly. This is especially true the case when there is a geothermal energy source in the near from concentrated consumption is to be tapped around in this area a less favorable rock formation is located.

It is easily possible to modify a drilling device to create the features of both the embodiment of FIG. 1 and the embodiment according to FIG. 5 combined. So z. B. a rigid heating element with the opening be connected to a drill body, which even when fed by spring force a up and down movement so that a constant fraction of the Rock is removed and with the help of scanning devices the weight of the drill body is set when the heating elements come too close.

Otherwise, such a configuration as the embodiment work according to Fig. 1. It is also possible to create a drilling device »which, as in FIG. 6, from the embodiment according to FIG. 5 to the embodiment according to FIG Fig. 1 is changeable. In this embodiment, cylindrical shaped elements enclose 228 the circumferential collars 25 according to the embodiment of FIG. 1. It can also Means may be provided that the shaped elements 228 from the drilling device peel off, so that they remain in the borehole at certain points and only the circumferential collar 25 would be used solely for shaping.

This embodiment could serve to make the detachment dependent takes place from the removal of the heating element 215 from the drill body 212, e.g. Am Dependence on the preload of the springs 318 in connection with the rods 303. Such a change in the drilling device would preferably take place when with a natural stratification of the rock, the porous rock over the massive Rock lies and thus the heating element 215 is further away from the drill body during operation is. As soon as the drilling equipment reaches the massive rock »the springs 318 compressed and the distance to the drill body reduced, which the detachment the form elements 228 would bring with it.

From the From the foregoing it follows that a given a large number of possible variations in the application of the invention is. So z. B. the shape of the heating elements, the drill body and the shape elements can be changed to suit specific conditions of use and of course changing Adapt rock formations. The present drilling device can also without difficulty be expanded further in order to produce three or more boreholes at the same time, by attaching several lines to the drill body and connecting each line to the necessary form elements for forming the drill holes is provided. In such a In this case, the circulating fluid or the circulating drilling mud can through two or more boreholes circulate and thereby different cooling areas be created by connecting corresponding lines in the drill body will. It is also evident that the flow of molten rock flows through it the inside of the drill body when it is introduced into the drilling mud with the aid of pumps can be supported, with z. B. use a flexible material for the channel walls can find and peristaltic attacking forces are used to melt the stone to push through the channel. You can also with the help of scanning devices that be set in an area where the borehole will be formed, the amount of Measure rock that is available to help with the formation of the borehole the aforementioned pumps the rock melt through the channel 23 more or less quickly to remove. The present invention can also be used with conventional Drilling devices are coupled »by, for example, initially in conventional Way from the surface of the earth a borehole was driven up to the rock formation is to use on which the drilling device according to the invention is particularly advantageous is. The method according to the invention and the devices are also for tapping drill suitable for geological formations other than rock, especially for drilling of ice. For all of the above-mentioned types of use, a method for Extraction of geothermal energy and for the recovery of waste heat during drilling Find use, regardless of whether there is only one drill hole or two or more drill holes (see U.S. Patent 3,396,806).

When designing the device for generating and enlarging Breaks according to FIG. 8, it is possible to provide a multitude of ring tubes 87, on the one hand to improve the seal and on the other hand to improve the individual To reduce ring hoses acting forces. There can also be several of the devices 8 are used one above the other and are operated synchronously to control the flow and to reduce the forces acting on the individual ring tubes.

In such a case, the stress on the individual would be reduced Distribute the ring hoses evenly over the number of devices.

It should be noted that the individual core windings or heating grids 18 can be made as small as possible in terms of diameter, with a Diameters of about 4.5 mm in the upper region and about 2.5 mm in the preferred Area would lie. The reason for this is that given a Temperature for the heating elements and a given feed rate the necessary force to move the drill head through the rock proportional to the is the fourth power of the diameter. Thus, if a force F to move the Drill body is required and the heating coils have a diameter of 2 cm, then for a heating coil with a diameter of only one cm at the same temperature and the same feed speed requires a force of F / 16.

Of the Of the variations and configurations described apart from that, further changes can also be made to the drilling device according to the invention be made within the scope of the inventive concept.

Patent claims

Claims (11)

Claims 1. Device for drilling rock formations with a drill body, a heating element and a device for heating the Heating element to a temperature that is significantly above the melting point of the rock lies, characterized in that the heating element (15, 115, 215) is held in this way is that only part of the rock to be melted melts directly that the remaining part of the rock to be melted by dissipating heat from the directly molten rock is melted in such a way that through the rapid interpenetration a sharp rise in the mean temperature of the Rock above the melting point is avoided, and that the drill body (12, 212) is used to derive part of the rock melt. 2. Device according to claim 1, characterized in that g e k e n n z e i c h n e t that the heating element (15) as a heating coil or heating grid (18) made of rod-like, is constructed at a distance from one another parts, and that the heating element is charged with electrical energy to generate the melting temperature. 3. Device according to claim 1 or 2, characterized in that the drill body (12) is designed such that it is ensured that the molten Rock does not flow along substantial distances between congruent surfaces got to. 4. Device according to one of claims 1 to 3, characterized in that that connected to the drill body (12) facilities are that out the molten stone at least two separate and different drill holes (41) train at the same time and in cooperation with the drill head, that part of the molten stone is removed, that further mold elements (28, 25) for Forming the wellbores that exist during the drilling operation substantially ensure a constant cross-sectional shape of the drill holes. 5. Device according to one of claims 1 to 4, characterized in that that the heating element (15, 115, 215) made of a heat-resistant material such as. B. Tungsten, pyrolytic graphite, molybdenum, tantalum or rhenium is made. 6. method of drilling rock using a drill body, whose heating element melts a volume of rock through which the drill body is displaced is characterized in that it is in direct contact with the heating element Coming parts of the rock directly through heat transfer to a substantially upper part the melting temperature of the rock lying temperature, and that the not in contact with the neighboring rock parts are melted by conduction from the molten rock, whereby the mean temperature of the entire molten rock at a much lower Temperature is maintained as the highest temperature of the partial melt. 7. The method according to claim 6, characterized in that the e i chne t molten rock lying in the path of the advancing element (15), is completely removed from this path in that it is a removal which is smaller than a tenth of the smallest diameter of the drill body, displaced will. 8. The method according to claim 6 or 7, characterized ge ke nn -z e i c hn e t that every point within the area of the earth through which the drill body penetrates, within a distance of less than 1/3 of the smallest diameter of the drill body of points through which the heating element is displaced. 9. The method according to any one of claims 6 to 8, characterized in that that by the advancement of the drill body two separate and separated from each other Boreholes (41) simultaneously with the penetration of the drill body through the rock melt are formed. 10. The method according to any one of claims 6 to 9, wherein a down penetrating borehole is created, thereby gelennz e i c h n e t that longitudinal the borehole is shaped in a certain way and positioned at a certain point Recess (60) is formed during the drilling process, with thermal stresses at the outermost end of the wedge-shaped cut into the wall of the borehole Recess can be concentrated to later with the help of hydraulic means from the extreme To attach the end of the recess from fractures extending into the rock, the below Formation of cells are supported. 11. The method according to one or more of claims 6 to 10, characterized characterized in that the hydraulic pressure introduced to generate the fractures by restricting the downward flow of flow to a particular one Bred flow path into effect and slowed down the flow in the borehole by narrowing and that the moment of flow is converted into pressure to break the rock will.