SE1950045A1 - A rock drilling system for geothermal drilling, a method and use of such a rock drilling system - Google Patents

Abstract

The invention relates to a rock drilling system (10) for geothermal drilling. The rock drilling system (10) comprises a drilling rig (2) with a drill string (22) and a drilling hammer (4) for drilling a borehole (9); at least one air compressor (1) configured for driving the drilling hammer (4) and supplying compressed air into the borehole (9) via the drill string (22); a conveying chamber arrangement (3) configured to be arranged at a ground surface (12), wherein the conveying chamber arrangement (3) is configured to encircle the drill string (22) and to be connected to a borehole casing (44). The rock drilling system (10) further comprises an extraction device (5) connected to the conveying chamber arrangement (3) to draw air containing drill cuttings from the borehole (9), thereby controlling the flow of air upwards through the borehole (9). The invention also relates to a use of such a rock drilling system (10) for generation of geothermal energy and a method for geothermal drilling with such a rock drilling system (10).

Description

A rock drilling system for geothermal drilling, a method and use of such a rock drilling system TECHNICAL FIELD The present invention relates to a rock drilling system for geothermal drilling anda method for geothermal drilling with such a rock drilling system. The inventionalso relates to a use of such a rock drilling system for generation of geothermal energy.

BACKGROUND Geothermal energy is thermal energy generated and stored in the Earth. lt is aclean and sustainable source of energy. Many regions of the world are alreadytapping geothermal energy as an affordable and sustainable solution to reducingdependence on fossil fuels. Thereby, global warming and public health risks thatresult from the use of fossil fuels are also reduced. Hence, geothermal energyis becoming more and more important in the global environment as the supplyof fossil fuels diminish and the demand for energy increases. The Earth'sgeothermal resources are theoretically more than adequate to supply humanity'senergy needs. Still, only a very small fraction is profitably exploited, since drillingfor deep resources is very expensive and technically demanding.

Shallow geothermal boreholes, 50 - 200 meters, are commonly used as heatsource or sink for heat pumping systems for heating of for example smallerresidential buildings. When drilling deeper, the temperature increases and moregeothermal energy can be extracted. However, drilling to greater depths, suchas 2000-3000 metres or more, to reach high-temperature geothermal resources,becomes a challenge due to increasing pressure and temperature.

Thus, geothermal energy has great potential as an environmentally friendlysource of energy in many parts ofthe world, but expansion has been constrainedby technical difficulties and high costs related to drilling deep in hard rock.

One known solution for drilling deep boreholes is disclosed in document US4653593 A. The document discloses a method for controlling the operation of acompressed air operated down-the-hole percussive rock drill when drilling deepboreholes.

SUMMARY OF THE INVENTIONAn object of the present invention is to achieve an advantageous rock drillingsystem for enabling extraction of high-temperature geothermal resources.

Another object of the invention is to reduce the cost of investment in geothermal energy.

The herein mentioned objects are achieved by: - a rock drilling system for geothermal drilling, - a use of such a rock drilling system for generation of geothermal energy, and - a method for geothermal drilling with such a rock drilling system, according to the appended independent c|aims.

Hence, according to an aspect of the present disc|osure a rock drilling systemfor geothermal drilling is provided. The rock drilling system comprises: a drillingrig with a dri|| string and a drilling hammer for drilling a borehole; at least one aircompressor configured for driving the drilling hammer and supp|yingcompressed air into the borehole via the drill string; and a conveying chamberarrangement configured to be arranged at a ground surface, wherein theconveying chamber arrangement is configured to encircle the dri|| string and tobe connected to a borehole casing. The rock drilling system further comprisesan extraction device connected to the conveying chamber arrangement to drawair containing dri|| cuttings from the borehole, thereby controlling the flow of airupwards through the borehole.

According to another aspect of the present disclosure a use of a rock drilling system as disclosed herein is provided for generation of geothermal energy.

According to another aspect of the present disclosure, a method for geothermaldrilling with a rock drilling system as disclosed herein is provided. The methodcomprises the steps of: driving the drilling hammer and supplying compressedair into a borehole via the drill string by means of the at least one air compressor;and drawing air containing dri|| cuttings from the borehole via the conveyingchamber arrangement, by means of the extraction device.

Thus, by means of supplying compressed air down the borehole by at least oneair compressor and drawing air up from the borehole by means of the extractiondevice, the flow of air upwards through the borehole may be controlled. Bycontrolling and maintaining an efficient flow of air upwards in the borehole, anefficient penetration rate of drilling, cooling of the drilling equipment and removalofdrill cuttings is achieved, despite high temperatures and increasing pressurein the earth's interior. Thereby, an advantageous rock drilling system isachieved, which enables deep drilling such that high-temperature geothermalresources may be extracted. Thus, green energy may be harvest in a time- and cost-efficient manner. ln conventional borehole drilling, a drilling fluid is generally pumped downwardthrough a dri|| string or outside the dri|| string along the borehole annulus. Thefluid is then circulated upward to the surface with cuttings along the boreholeannulus or inside the dri|| string. Common drilling fluids may be water, a mix ofair and water, or others. When using water or other viscous fluid, the fluid hasto be transported to and from the drilling site, which has a negative impact onthe environment in the form of emissions and consumption of fossil fuels. lnaddition, in some part of the world, water is scarce. ln these regions, drinking water must be prioritized, not drilling fluid. ln the present disclosure, compressed air is used as drilling fluid. Air is astrategic choice of fluid as it is cheap, always available in all part of the world,and there is no need for transportation of air to or from the drilling site.Accordingly, air is a cost-efficient and advantageous drilling fluid for environmental reasons. ln rock drilling systems, the removal ofdrill cuttings from the borehole is crucial.A constant removal of boring debris from the bottom of the borehole as drillingprogresses is utterly important as the drill bit will getjammed and the flow in theborehole get clogged, without an efficient removal of drill cuttings. lf the flow inthe borehole is obstructed, the penetration rate of drilling will be reduced andthe drilling equipment may also be damaged due to blockage. The penetrationrate, or drill rate, is the speed at which a drill bit breaks the rock under it todeepen the borehole. ln addition to functioning as flushing means, the drillingfluid also operates as cooling means. Thus, if the removal of drill cuttings doesnot function properly, the drilling equipment may be damaged due tooverheating. The drilling fluid also ensures the stability of the borehole, i.e. the drilling fluid prevents that the borehole collapses. ln known apparatus for drilling deep boreholes into the earth, the drillingmechanisms may comprise a drill bit and a pressure fluid motor that directlydrives the drill bit, which motor is located at the bottom of the borehole beingdrilled. The pressurized fluid may be fed to the motor through a tubular shaft orduct inside a drill string that is supported from the surface of the earth at themouth of the borehole. When deep holes are to be drilled, in particular holes thatare several hundred meters deep, the pressure in the ground will be so high thatit must be compensated for. To compensate for the increasing pressure, thesupply of pressurized fluid fed to the apparatus may be varied in accordancewith various rules of thumb. lf the supply of pressurized fluid fed to the apparatusis too small, the penetration rate becomes very low and there is risk that the drill bit and borehole get jammed. On the other hand, if the supply of pressurized fluid is too high, there is risk that the impact velocity may damage the drilling equipment, or at least drastically reduce the life span of the drilling equipment. lncreasing the supply of pressurized fluid significantly increases the cost ofdrilling. ln order to achieve an increase of the supply of pressurized fluid, morepowerful and/or multiple sources of pressurized fluids are required. These typesof sources are very expensive, and also consume fossil fuels in order to producethe pressurized fluid. Thus, an increase in power output also entails an increaseof fossil fuel. Fossil fuels, such as diesel or petrol, is expensive and not anenvironmentally friendly choice. lt is also difficult to get a hold of fossil fuels inmany parts of the world.

By means of supplying compressed air down the borehole by at least one aircompressor and drawing air up from the borehole by means of the extractiondevice according to the present disclosure, less power is required to achieve anefficient flow of air in the borehole. Fewer air compressors, and/or less powerfulair compressors may be needed, which save initial investment costs, reduce fuelconsumption and are favourable in view of transport and logistics. The extractiondevice is relatively cheap and consumes a lot less power compared to attemptsto obtain an efficient flow upward by adding additional, or extra powerful, aircompressors. Thus, the solution of using an extraction device drawing airupwards in combination with the at least one air compressor forcing airdownwards according to the present disclosure is superior in many wayscompared to conventional methods, wherein only air compressors are used toforce air down the borehole.

By means of the rock drilling system according to the present disclosure, thecost of investment in geothermal energy is reduced, in respect to both financialand environmental assets. Thus, by the present disclosure, an advantageousand sustainable way of achieving green and clean energy in the form ofgeothermal energy is obtained.

Further objects, advantages and novel features of the present invention willbecome apparent to one skilled in the art from the following details, and also byputting the invention into practice. Whereas the invention is described below, itshould be noted that it is not restricted to the specific details described.Specialists having access to the teachings herein will recognise furtherapplications, modifications and incorporations within other fields, which arewithin the scope of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS For fuller understanding of the present invention and further objects andadvantages of it, the detailed description set out below should be read togetherwith the accompanying drawings, in which the same reference notations denote similar items in the various drawings, and in which: Figure 1 schematically illustrates a rock drilling systemaccording to an example of the present disclosure; Figure 2 schematically illustrates a conveying chamberarrangement according to an example of the presentdisclosure; Figure 3 schematically illustrates a conveying chamber arrangement according to an example of the presentdisclosure; andFigures 4 and 5 schematically illustrate block diagrams of methods according to examples of the present disclosure.

DETAILED DESCRIPTION The rock drilling system will be described in further detail below. lt is understoodthat all the various examples of the rock drilling system also applies for the useof such a rock drilling system for generation of geothermal energy and methodsfor geothermal drilling with such a rock drilling system.

According to an aspect of the present disclosure, a rock drilling system forgeothermal drilling is provided. The rock drilling system comprises: a drilling rigwith a dri|| string and a drilling hammer for drilling a borehole; at least one aircompressor configured for driving the drilling hammer and supplyingcompressed air into the borehole via the drill string; and a conveying chamberarrangement configurd to be arranged at a ground surface, wherein theconveying chamber arrangement is configured to encircle the dri|| string and tobe connected to a borehole casing. The rock drilling system further comprisesan extraction device connected to the conveying chamber arrangement to drawair containing dri|| cuttings from the borehole, thereby contro||ing the flow of airupwards through the borehole.

The rock drilling system as disc|osed is adapted for geothermal drilling. Thismeans that the rock drilling system is designed for drilling deep boreholes. Thetrajectory of the borehole may be straight, as for vertical drilling. However, thepresent disclosure is also suitable for directional drilling, which is the practise ofdrilling non-vertical boreholes.

The rock drilling system comprises a drilling rig with a dri|| string and a drillinghammer for drilling a borehole. The drilling rig may be a conventional dri|| rigwith a feed beam or mast. The dri|| string may comprise multiple clriii pibes whichare ecrewed together or joinecl in some other way. The drilling hamrner may bea conventional driiiing hamnter, driven by compressed air. The driiiing hamrnermay be driven by cornpressed air oniy. lt may be favorabie to use a clriilinghammer driven merely by compressed air at greater deptn, as no electronicsetc. rnay be needed in such drilling hantmers. Ûther types of driiling harnrnerscontprising sensitive rnateriai such as piastic or eiectronic components rnay bedamagecl due to the increase of ternperattirte in deep boreholes.

The drilling hammer may be a pneuntaticaiiy potvered rock hamrner. The driiiingharnrner rnay be a pneumatic percussiort rock clriii. The driiiing itammer may bernounted to the lower' end of the driii string. The driiiing hammer may be a down» the-iteie (BTH) pneumatic hammer. A down-the-hole drill, usually called DTH, isa pneumatic powered rock or ground drill, in which the percussive hammer islocated directly behind the drill bit, so the percussion mechanism follows the drillbit down into the borehole. Compared to other geothermal drilling methods,down-the-hole hammers may have an increased penetration rate. Thus, the drilling procedure may be relatively quick.

The drill string may transfer the necessary feed force and rotation to the drillinghammer and drill bit, as well as compressed air for driving the drilling hammer.Drill pipes may be added to the top of the drill string as the borehole gets deeper.The driiiihg hammer may itave a piston hammer that delivers impact to the driiibit either directiy or through ah ahvii block. The piston hammer may directlystrike the impact surface of the drill bit, while a hammer casing gives guidanceto the drill bit. The drilling hammer impact may break hard rock into smallparticles, i.e. drilling cuttings, which may be blown upwards in the borehole bythe air exhaust from the drill hammer.

The rock drilling system comprises at least one air compressor configured fordriving the drilling hammer and supplying compressed air into the borehole viathe drill string. The at least one air compressor may be of any type, driven by forexample a diesel, gasoline or electric motor. The at least one air compressorforces, by means of the motor, more and more air into a storage tank, increasingthe pressure. The pressurized air, i.e. the compressed air, may be used to drivethe drilling hammer. Cempressed air rtiay be supplied from the air campressarto the drilling hammer through the driii string via ah air duct. Such air dticts maycomprise heses, pipes, tubes etc. The compressed air may also be used to flushthe borehole. The compressed air may remove drill cuttings from the borehole.A constant removal of boring debris from the bottom of the borehole as drillingprogresses is very important as the drill bit will get jammed and the flow in theborehole get clogged, without an efficient removal of drill cuttings. ln addition,the compressed air cools down the drilling equipment. The compressed air alsoensures the stability of the borehole. By means of the at least one air compressor, the flow of air downwards through the dri|| string may be controlled. For example,by adjusting the supply of compressed air, the airflow and/or the air pressure inthe channel in the dri|| string may be adjusted. By adjusting the airflow and/or airpressure in the channel, the drive of the dri|| hammer and the amount of exhaustair from the dri|| hammer may be adjusted. Thereby may for example the penetration rate and the amount of flushing air in the borehole be adjusted.

The rock drilling system comprises a conveying chamber arrangementconfigured to be arranged at a ground surface, wherein the conveying chamberarrangement is configured to encircle the dri|| string and to be connected to aborehole casing. The conveying chamber may facilitate connection of differentparts in the rock drilling system. The configuration of the conveying chamberarrangement may separate and guide airflows in, out and within the mouth ofthe borehole at the ground surface. By means of the conveying chamberarrangement, the airflow in the borehole may be controlled. The configuration ofthe conveying chamber arrangement enables the dri|| string with compressedair to enter the borehole, and air and dri|| cutting to exit the borehole, whilemaintaining the flow in the borehole. The configuration of the conveyingchamber arrangement counteract air leaks and unfavourable airflows. Theconfiguration of the conveying chamber arrangement also impedescontamination of the surroundings around the borehole, as air and dri|| cuttings may be prevented from leaking out to the ambient air or at the ground surface.

The conveying chamber arrangement is configured to be connected to aborehole casing. A borehole casing is a large diameter pipe that is lowered andusually cemented in place in order to line the borehole of an open well. Theborehole casing may be strategically sized and placed into the borehole so thatdrilling operations can reach desired depths. The borehole ntay extend from theground surface through a top layer of softer material, such as soil or gravol, to arock layer. The borehole casing may line the borehole from the ground surfaceinto the rock layer. The oorehote casing may thus ensure the stability of borehole, i.e. prevent that the upper part of the borehole collapses. The borehole casing also supports the flow of air upwards through the borehole.

The rock drilling system further comprises an extraction device connected to theconveying chamber arrangement to draw air containing drill cuttings from theborehole. The extraction device may be any type of suction device, suitable forextracting air and drill cuttings. The extraction device may be a tank comprisingan inlet, an outlet and a pump. The extraction device may be a vacuum truck orvacuum tanker. By means of the extraction device, air and drill cuttings mayefficientiy be removed from the borehole. By means of the extraction device, theflow of air upwards through the borehole may be controlled. For example, byadjusting the force of suction of the extracting device, the airflow in the passagebetween the drill string and the inner circumference of the borehole may beadjusted. By keeping the air flowing fast enough upwards in the passagebetween the the drill string and the inner circumference of the borehole, an aircurtain may be created. The air curtain may comprise air moving at increasedvelocity, i.e. accelerated air. The air curtain may be beneficial for the transportation of drill cuttings up to the ground surface.

Thus, by means of the supply of compressed air down the borehole by at leastone air compressor, the configuration of the conveying chamber arrangementand the drawing of air from the borehole by means of the extraction device, theflow of air upwards through the borehole may be controlled. The airflow in theborehole may be further controlled by adjusting at least one of the following twoparameters: the supply of air from the at least one air compressor and thesuction force of the extraction device. By altering and optimizing these twoparameters for different applications, an efficient penetration rate and removalof drill cuttings may be achieved.

By controlling and maintaining an efficient flow of air upwards in the borehole,an efficient penetration rate of drilling, cooling of the drilling equipment andremoval of drill cuttings is achieved, despite high temperatures and increasing 11 pressure in the ground. Thereby, an advantageous rock drilling system isachieved, which enables deep drilling such that high-temperature geothermalresources may be extracted.

According to an example, the rock drilling system may be configured so that theair flows in a direction towards the bottom of the borehole in a channel insidethe drill string and in a direction towards the ground surface in a passage formedbetween the drill string and an inner circumference of the borehole. Thisconfiguration of airflow in the borehole is advantageous, as the supply ofcompressed air driving the drilling hammer may be efficiently distributed to thedrilling hammer through the drill string, while the removal of drill cuttings maysimultaneously be efficiently removed through the passage between the drillstring and the inner circumference of the borehole.

According to an example, the rock drilling system may further comprise airjettingmeans with at least one nozzle arranged along the drill string above the drillinghammer, wherein the at least one nozzle is configured to eject airfrom a channelinside the drill string to a passage formed between the drill string and an innercircumference of the borehole.

The at ieast one riozzie ntay be arranged aiong the driii string to forward airfiowing 'ironi the bottom oi the borehoie. The at ieast one itozzie may thus assistin driii cutting removat up the borehoie. The at ieast one nozzie may be arrangedto eject air in in direction upwards towards the ground surface. The at ieast onenozzie may aiternativeiy be arranged to eject air in a radiai direction of theborehoie. The at ieast ene nozzie may be arranged above the driiiing hammer.This mean that the at ieast one nozzie may be arranged aieng the driii stringbetween the driiiing hammer and the ground surface. The at ieast one nozzientay be arranged directiy above the driiiing hammer.

The air ietting means aiiow iarge tfoiumes oi compressed air to be sent downthe driii string for fitishing, ohanneiing no ntore air to the driiiing hamnter than is 12 needed for efficient operation. Mottipie riozzies piaoeo throughout the driit stringaiiow excess air at various points to assist evacuation of driit settings in theborehoie. This is espeešaiiy important in for exanipte turns or horizontai driitšngsitoations. Use ot airjetting rneans atso prevent ovenpressuring of the hainrnerenvironment in deep rock apptioations. Even when iarge voinmes of cornpressedair is soppiied to the driii string in order to aohieve an efficient rernotfai of driftouttings, onty the antount of air needed to drive the driiiing hantrner is transferredto the driiiirig hannmer. The excess air, vvhioh may have negative impact on theoperation of the driiiing harniner, rnay be discharged by the nozzies into thepassage between the driit string and the inner ciroumferenee of the borehoie,before reachtng the driiiing hammer. The excess air may form a curtain of air inthe passage, which may enhance the speed of the airflow moving upwards theborehole.

The air jetting means may be passively controlled by the airflow and/or the airpressure in the channel inside the drill string. The air jetting means may bepassively controlled by the difference in air pressure between the air pressurein the channel inside the drill string and the air pressure in the passage formedbetween the drill string and the inner circumference of the borehole. The term“passively controlled” means that the airjetting means may act without the needof any external power supply. The passive control of the airjetting means maybe achieved by means of mechanically actuated valves, such as check valvesor similar devices. The ejection by the airjetting means may be adjusted by e.g.changing the type or number of nozzles, altering the size, shape and/or angle ofthe discharge opening, the positioning of the nozzles along the drill string, andthe configuration of when and where in the drilling process the nozzles areopened and closed etc. The airjetting means may be manually actuated and/oradjusted by an operator. lt may be suitable to perform such manual procedures,such as actuating and/or adjusting the air jetting means, in conjunction withchanging or sharping the drill bit. Alternatively, the air jetting means may beelectronically controllable. 13 Thus, the airflow in the borehole may be controlled not only by adjusting thesupply of air from the at least one air compressor and the suction force of theextraction device. The ejection by the air jetting means is a third parameter,which may be used to control the airflow in the borehole. Hence, by altering andoptimizing these three parameters for different applications, an efficient penetration rate and removal of drill cuttings may be achieved.

According to an example, the rock drilling system may further comprise a drillcuttings separator for separating the drill cuttings from the air containing drillcuttings.

The driti setting separator may be ef any sert that separate drift cuttings frem theair. The drift setting separator may ceiiect the driii ettttirwgs and reiease the airinte the atntesphere. The air may be cieaned before the air is reieased inte theatmesphere hy means ef an air fiiter. The air fitter may for exampie comprise astainiess steei mesh artci/er HEPA-fiiters (high-efficiency partieuiate air fiiters).The driii cutting separator may comprise a tank with an intet for air and driiicuttings, an air etitiet and a fiiter eiement arranged between the iniet and theeuttet. Atternativeiy, the drâii cutting separator may be a cyfeiene separater. Thedršii cuttšng separator rriay be a separate unit or integrated yvith fdr exampie theextraction device. The driii eutting separator may be mevahie. The driti cuttângseparator may be arranged en a vehieie.

According to an example of the present disclosure, the rock drilling system maybe configured for drilling boreholes that are at least 1500 meters deep.According to an example, the rock drilling system may be configured for drillingboreholes that are at least 2000 meters deep, or at least 3000 meters deep. Dueto the configuration of the rock drilling system according to the presentdisclosure, drilling very deep bereheies inte the earth to deeths, greater than1500 meters, 2000 meters andíer 3000 meters, may be aeeempiished. Symeans of a sintpie and efficient rock driiiing system, a mere efficient airflow in 14 the borehoie is achieved. Tiiereby, deep drilling may be acccmpiisiied quickiyand at iovv cost.

According to an example, the drilling rig, the at least one air Compressor andthe extraction device may be mobile. By means of the equipment being mobile,the equipment may be easily transported to the drilling site. This enables drillingat places hard to reach, far from railroads and other types of infrastructure. Thismay be useful especially for sustainable development in countries suffering fromsevere structural impediments. The drilling rig, the at least one air compressorand the extraction device may be arranged on vehicles. The different units maybe arranged on different vehicles, or one or more units may share the samevehicle. The vehicles may comprise wheels or continuous tracks (i.e. tank orcaterpillar treads).

According to an example, the conveying chamber arrangement may beconfigured to be airtight, in order to maintain the flow of air upwards through theborehole. That the conveying chamber arrangement may be configured to beairtight means that the borehole is sealed for pressurization by means of the atleast one air compressor and the extraction device. By means of the conveyingchamber being airtight, the airflow directed downwards through the drill stringmay efficiently be separated from the airflow directed upwards through theborehole. The configuration of the conveying chamber arrangement to beairtight, also impedes air leaks in and out of the convening chamberarrangement. lt is important that the extraction device draws air from theborehole, and not ambient air from the outside of the conveying chamberarrangement. Air leaks of ambient air may affect the airflow upwards in theborehole negatively. The configuration of the conveying chamber arrangementto be airtight, also impedes contamination of the surroundings around theborehole, as air and drill cuttings may be prevented to leak out in the ambientair or at the ground surface.

By means of an airtight conveying chamber arrangement, the airflow in theborehole may be properly controlled. The airtight configuration of the conveyingchamber arrangement enables the dri|| string with compressed air to enter theborehole, and air and dri|| cutting to exit the borehole, while maintaining anefficient airflow in the borehole.

According to an example, the conveying chamber arrangement may comprise:a top cover with an opening for the dri|| string; a dri|| string sleeve connected tothe top cover and arranged to encircle the dri|| string; chamber walls connectedto the top cover and encirc|ing the dri|| string sleeve, wherein the chamber wallsare configured to be connected to the borehole casing at a bottom end; and anextraction opening configured to be connected to the extraction device. Bymeans of this configuration, the conveying chamber arrangement may facilitate connection of different parts in the rock drilling system.

The dri|| string may be slidingly engaged with the opening in the top cover. Thedri|| string sleeve may be fixedly connected to the top cover by welding.Alternatively, the dri|| string sleeve may be connected to the top cover byattachment means, such as threaded parts, bayonet connectors or any othersuitable type of coupling or connector. The chamber walls may be connected tothe top cover and the borehole casing by means of bolts, screws and nuts orother types of durable engagement part, suitable for engagement anddisengagement. The extraction opening may be formed in the chamber walls ofthe conveying chamber arrangement. The extraction opening is configured tobe connected to the extraction device by means of clamping jaws, clawcouplings, bayonet connectors, quick coupling or other types of suitable couplingfor connecting a suction hose, pipe or similar to the extraction opening.

According to an example, the conveying chamber arrangement may comprisesealing elements between the top cover and the chamber walls and/or at theopening for the dri|| string, and/or at the extraction opening, and/or at the bottomend of the chamber walls. 16 The sealing elements may be of any type suitable for sealing the differentcomponents to each other, such that an airtight conveying chamberarrangement is achieved. The sealing elements may comprise gaskets, O-ringsor other e|astic parts. The sealing elements may comprise clamping plates,sealing flanges etc. By means of these sealings, the air pressure and airflowwithin the borehole may be controlled. By means of the sealing means, air leaksin and out of the conveying chamber arrangement may be impeded. Air leaks of ambient air may affect the airflow upwards in the borehole negatively.

The conveying chamber arrangement may comprise sealing elements betweenthe top cover and the chamber walls. The sealing elements may comprisegaskets, O-rings or other e|astic parts. The top cover may be connected to thechamber walls by means of fastening means. The fastening means maycomprise clamping bolts and nuts, or other types ofdurable engagement part,suitable for engagement and disengagement.

The conveying chamber arrangement may comprise sealing elements at theopening for the drill string. These sealing elements may comprise gaskets, O-rings or other e|astic parts and clamping plates, sealing flanges etc. Thesesealing members may be arranged above the top cover. These sealingmembers may comprise at least one flat gasket, covering the entire top cover.The flat gasket may tightly seal any small gap between the drill string and thedrill string sleeve, about the opening in the top cover. The drill string may beslidingly engaged with a flat gasket and the opening in the top cover. By meansof the flat gasket, the entrance of the drill string into the drill string sleeve maybe airtight. The at least one flat gasket may be clamped between the top coverand for example a clamping plate by means of fastening means. The fastening means may comprise clamping bolts and nuts, or other similar fastening devices.

The fastening means may be the same as mentioned above. 17 The conveying Chamber arrangement may comprise sealing elements at theextraction opening, and/or at the bottom end of the chamber walls. The sealingelements may comprise gaskets, O-rings or other elastic parts. The sealingelement arranged at the extraction opening, may be arranged between theextraction opening of the conveying chamber arrangement and a suction hose,connecting the conveying chamber arrangement to the extraction device. Thesealing elements may be clamped between the extraction opening and thesuction hose by means of clamping jaws, claw couplings, bayonet connectors,quick coupling or other types of suitable coupling for connecting a suction hoseor similar to the extraction opening. The sealing element at the bottom end, maybe arranged between the bottom end and the borehole casing. The sealingelement arranged between the bottom end and the borehole casing may beclamped by means of fastening means. The fastening means may compriseclamping bolts and nuts, or other types ofdurable engagement part, suitable forengagement and disengagement.

According to an example, the drilling hammer may be configured to be arrangedat the bottom of the borehole at an end of the drill string. Arranging the drillinghammer te the lower end of the drill string may be advantageous En manydifferent xfvaye ae previously' described. Fer example, a down-the-hole hammermay have an increased penetration rate compared to for example pneumatic tophammers. Also, at deeper levels, the weight of the drill string becomes highlysignificant and the number of joints between drill pipes numerous. As anexample, a 2000 meters long drill string may weigh 45 tons, i.e. 45 000 kg.Consequently, the drill string may collapse if, for example, a pneumatic tophammer drill is used. ln top hammer drilling, the hammer produces a percussiveforce on top of the drill string, which is transferred to the drill bit through the drillstring. Thus, by using a drilling hammer arranged at the bottom of the boreholeat the end of the drill string, a more efficient and robust configuration is achieved for drilling of deep holes. 18 According to an example, the rock drilling system may further comprise a controldevice configured to control the drilling rig and/or the at least one air compressorand/or the extraction device and/or the airjetting means. The control device maybe implemented as a separate entity or distributed in two or more physicalentities. The control device may comprise one or more control units and/orcomputers. The control device may thus comprise control units comprised in theat least one air compressor, the drilling rig and/or the extraction device. Thecontrol device may be implemented or realised by the control device comprisinga processor and a memory. The memory may comprise instructions, which when executed by the processor causes the control device to perform method steps.

By means of the control device controlling the drilling rig, the drill rig may transferthe necessary feed force and rotation to the drill string. The drill string may thentransfer the feed force and rotation to the drilling hammer and drill bit. By meansof the control device controlling the at least one air compressor, the driving ofthe drilling hammer and supply of compressed air into the borehole may becontrolled. By means of the control device controlling the extraction device, thedrawing of air containing drill cuttings from the borehole may be controlled.Thereby, the flow of air upwards through the borehole may be controlled. Bymeans of the control device controlling the airjetting means, the ejection of airby means of air jetting means may be controlled. The air jetting means mayassist the flow of air and drill cuttings upwards through the borehole. Thereby,the flow of air upwards through the borehole may be controlled.

By means of the control device, the airflow in the borehole may be controlled byadjusting at least some of the following three parameters: the supply of air fromthe at least one air compressor, the suction force of the extraction device and/orthe ejection by the air jetting means. By altering and optimizing theseparameters for different applications, an efficient penetration rate and removal of drill cuttings may be achieved. 19 According to an axampäa, suitabta air fältara and ahäaiaing alarnants may baprovided at tha air iniats and air autiats ofthe rack dräiišng systern. Air fältars andahtaldäng alamanta may kaap dust and dirt aut af tha anaurnatia maahaniams.Acoardäng to an example, guardäng atarnants, än tha form af grids, ntash, natsata., may ba arrangad at tha toa of tha barahota ta prataat tha drilting aquäainantän tha barahaäa fram falling atanas and tha äika. Tha guardirtg arrangamartt mayba arrangad in tha paranoia casäng.

According to an aspect of the present disclosure, use of a rock drilling system as disclosed herein is provided, for generation of geothermal energy.

By the use of the rock drilling system for generation of geothermal energy, thecost of investment in geothermal energy is reduced, in respect to both financialand environmental assets. By the use of the rock drilling system for generationofgeothermal energy, an advantageous and sustainable way of achieving greenand clean energy is obtained.

According to an aspect of the present disclosure, a method for geothermaldrilling with a rock drilling system as disclosed herein is provided.

The method comprises the steps of: driving the drilling hammer and supplyingcompressed air into a borehole via the drill string by means of the at least oneair compressor; and drawing air containing drill cuttings from the borehole viathe conveying chamber arrangement, by means of the extraction device.

By means of steps of driving the drilling hammer and supplying compressed airinto a borehole via the drill string by means of the at least one air compressor;and drawing air containing drill cuttings from the borehole via the conveyingchamber arrangement, by means of the extraction device, the flow of airupwards through the borehole may be controlled. By controlling and maintainingan efficient flow of air upwards in the borehole, an efficient penetration rate ofdrilling, cooling of the drilling equipment and removal of drill cuttings is achieved,despite high temperatures and increasing pressure in the ground. Thereby, an advantageous rock drilling system is achieved, which enables deep drilling such that high-temperature geothermal resources may be extracted.

The step of drawing of air containing drill cuttings by means of the extractiondevice may be initiated when reaching a depth of about 200-300 meters, i.e.when the air pressure in the borehole increases. At smaller depth, a sufficientflow of air upwards through the borehole may be achieved by means of the atleast one air compressor only.

According to an example, the method as disclosed above further comprising thestep of ejecting air by means of airjetting means to assist the flow of air and drillcuttings upwards through the borehole. By means of the step of ejecting air bymeans of airjetting means, iarger voiunfies of carnpressed air may be sent downthe driii string for fiushing, without affecting the operation of the driii hanfrnernegativeiy. Excess air, net needed te Ope-rate the driii hartimer, may be ejectedby the airjetting means and improve the fiew of air in the passage between thedriii string and the inner cireurnference ei the boreheie. Consequently, the flowof air in the passage may be controlled and the removal of drill residuals fromthe borehole may be improved.

According to an aspect of the disclosure, a conveying chamber arrangement fora rock drilling system is provided. The conveying chamber arrangement isconfigured to be arranged at a ground surface, wherein the conveying chamberarrangement is configured to encircle a drill string and to be connected to aborehole casing. The conveying chamber arrangement comprises: a top coverwith an opening for the drill string; a drill string sleeve connected to the top coverand encircling the drill string; chamber walls connected to the top cover andencircling the drill string and the drill string sleeve; wherein the chamber wallsare configured to be connected to a borehole casing at a bottom end; and an extraction opening configured to be connected to an extraction device. 21 The conveying chamber arrangement may facilitate connection of different partsin a rock drilling system. The configuration of the conveying chamberarrangement may separate and guide airflows in, out and within the mouth of aborehole at the ground surface. By means of the conveying chamberarrangement, the airflow in the borehole may be controlled. The configuration ofthe conveying chamber arrangement enables a dri|| string with compresses airto enter the borehole, air and dri|| cutting to exit the borehole, while maintainingthe flow in the borehole. The configuration of the conveying chamber alsoimpedes contamination of the surroundings around the borehole, as air and dri|| cuttings may be prevented to leak out in the ambient air or at the ground surface.

According to an example, the conveying chamber arrangement as disclosedherein, comprises sealing elements between the top cover and the chamberwalls and/or at the opening for the dri|| string, and/or the extraction opening,and/or the bottom end of the chamber walls. The sealing elements may be ofany type suitable for sealing the different components to each other such anairtight conveying chamber arrangement is achieved. The sealing elements maycomprise gasket, O-rings or other elastic parts. The sealing elements maycomprise clamping plates, sealing flanges etc. By means of these sealings, theconveying chamber arrangement may be connected airtight to the dri|| string,borehole casing and the extracting device. Thereby, air pressure and airflowswithin the borehole may be controlled.

According to an aspect of the disclosure, a method performed by a controldevice, for geothermal drilling with a rock drilling system as disclosed herein isprovided. The method comprising the steps of: controlling the at least one aircompressor to drive the drilling hammer and supply compressed air into aborehole via the dri|| string; controlling the extraction device to draw aircontaining dri|| cuttings from the borehole via the conveying chamberarrangement. The control device performing the method is comprised in the rockdrilling system. 22 lt is to be understood that the control device may be implemented as a separateentity or distributed in two or more physical entities. The control device maycomprise one or more control units and/or computers. The control device maythus be implemented or realised by the control device comprising a processorand a memory, the memory comprising instructions, which when executed bythe processor causes the control device to perform the above disclosed methodsteps.

The control device may allow monitoring and controlling of the different units inthe rock drilling system. By means of monitoring drilling processes during drillingof boreholes, data and parameters may collected and stored. The collected datamay thus be analysed and used to control upcoming drilling procedures. Thedrilling procedure may thus be optimized, based on the collected data fromprevious drilling procedures. The control device may allow remote monitoringand controlling of the different units in the rock drilling system via lnternet,Bluetooth, mobile phone network data service or similar.

According to an example, the method above may further comprise the step ofcontrolling airjetting means to eject air in order to assist the flow of air and drillcuttings upwards through the borehole. ln this event, the airjetting means maybe electronically controllable. Alternatively, the air jetting means may bemanually actuated and/or adjusted on the initiative of a signal given by thecontrol device to an operator. Thus, an actuation procedure of the air jettingmeans as such may be manually operated, but monitored and controlled by thecontrol device. Thus, the control device may notify the operator when a manualprocedure is suitable to be carried out, e.g. when reaching a certain depth, orwhen the flow of air upwards in the borehole decreases. lt may be suitable toperform such manual procedures, such as actuating and/or adjusting the airjetting means, in conjunction with changing or sharping the drill bit. By means ofthe control device controlling the airjetting means, the ejection of air by meansof airjetting means may be controlled. The airjetting means may assist the flow 23 of air and dri|| cuttings upwards through the borehole. Thereby, the flow of air upwards through the borehole may be controlled.

By means of the control device, the airflow in the borehole may be controlled byadjusting at least one of the following three parameters: the supply of air fromthe at least one air compressor, the suction force of the extraction device and,when applicable, the ejection by the air jetting means. By adjusting andoptimizing these parameters for different applications, an efficient penetrationrate and removal ofdrill cuttings may be achieved. Thereby, deep holes may beefficiently drilled.

The altering and optimizing of these parameters for different applications maybe based on collected data from previously performed drilling processes. Thealtering and optimizing of these parameters for different applications may forexample be based on the current drilling depth and/or the material being drilled(such as the type of rock) and other relevant parameters for the currentapplication. When the drilling depth increases, so does the pressure inside theborehole. The supply of air from the at least one air compressor and the suctionforce of the extraction device, and the ejection by the air jetting means whenapplicable, may then be automatically increased by means of the control device.The method steps of controlling the at least one air compressor, controlling theextraction device and controlling the air jetting means may be performedcontinuously throughout the drilling process, in order to efficiently control and regulate the drilling process.

According to an aspect of the disclosure, a computer program comprisinginstructions which, when the program is executed by a computer, causes thecomputer to perform the method as disclosed above is provided. By means ofthe computer program, an increased control of the drilling process may beobtained. The computer program causes the rock drilling system to perform the above methods steps when executed, with increased predictability and 24 reproducibility compared to performing the method manually and/or in accordance with various rules of thumb.

According to an aspect of the disclosure, a computer-readable mediumcomprising instructions, which when executed by a computer causes thecomputer to carry out the method as disclosed above is provided. The computer-readable medium may be any tangible and/or non-transitory medium that maycontain or store a program for execution by a processor.

The present disclosure will now be further illustrated with reference to theappended figures, wherein for the sake of clarity and understanding of thedisclosure some details of no importance are deleted from the figures. Moreover,the figures shall not be considered drawn to scale as some features may be exaggerated in order to more clearly illustrate the invention.

Figure 1 schematiceliy iliustrates e side view of e rock driiliiwg systern ti)according te en exampie ef the present disciosure. A deep, verticetly extendihgborehole ä of circuier cross section is iiiustreted. Hewever, the presentdisclosure is also suitable for directional drilling. The bcreheie 9 may extendfrem the ground surface 12 through e top tag/er "i ef softer htateriai, such es soilcr gravel, to e. rock iayer 8. A borehole casing 44 may line the borehole 9 from the ground surface 12 into the rock layer 8.

The rock drilling system 10 for geothermal drilling as schemeticeiiy iiiustrated inFigure 1 comprises: a drilling rig 2 with a drill string 22 and a drilling hammer 4for drilling a borehole 9; at least one air compressor 1 configured for driving thedrilling hammer 4 and supplying compressed air into the borehole 9 via the drillstring 22; a conveying chamber arrangement 3 arranged at the ground surface12, wherein the conveying chamber arrangement 3 is configured to encircle thedrill string 22 and to be connected to a borehole casing 44. An extraction device5 is connected to the conveying chamber arrangement 3 to draw air containing dri|| cuttings from the borehole 9, thereby controlling the flow of air upwardsthrough the borehole 9.

The driiiing rig 2 has a 'feed bearn or mast 21 and a drive unit 20 viihich mayrotate and feed the driii string 22. The drive unit 20 ntay be a dieeei, gasoline orelectric motor. The ciriii string 22 rnay consiet ot nttiitipie driii pipes which arescrewed together or joined in some other way. The dri|| string 22 may transferthe necessary feed force and rotation to the drilling hammer 4 and a dri|| bit 42,as well as compressed air for driving the drilling hammer 4. The drilling hammer4 may comprise the dri|| bit 42. Dri|| pipes are added to the top of the dri|| string22 as the borehole 9 gets deeper. The rtriiiing hammer 4 may comprise a pistonharriiner »tt that deiivera impact to the driii bit 42 either directiy or through ananvii bicck. The piston hammer 41 may directly strike the impact surface of thedri|| bit 42, while a hammer casing gives guidance to the dri|| bit. The drillinghammer 4 impact may break hard rock into small particles, i.e. drilling cuttings,which may be blown upwards in the borehole 9 by air exhaust from the dri|| hammer 4.

The driiiing hammer 4 inay be a conventionai driiiing hantrner, driven bycompressed air. According to an exarnpie, the driiiing haminer 4 may bearranged at the bottom of the borehole 9 at an end of the dri|| string 22.According to an exarnpie, the ciriiiing hammer 4 may be a pneiirnatic down~the~hoie percussive rock driii. Compressed air niay be suppiied frorn the aircompressor t to the driiiing rig 2 via an air compressor hose tt, Frorn the driiiingrig 2, the compressed air niay be transported to the driiiing harnrrier 4 throughthe driii string 22.

During a driiiihg operation, the at least one air compressor 1 may drive thedrilling hammer 4 and supply compressed air into the borehole 9 via the dri||string 22. When reaching a depth of about 200-300 meters, when the airpressure in the borehole 9 increases, the drawing of air containing dri|| cuttingsby means of the extraction device 5 may be initiated. At minor depths, a 26 sufficient flow of air upwards through the borehole 9 may be achieved by means of the at least one air Compressor 1 only.

According to an example, the rock drilling system 10 may be configured so thatthe air flows in a direction downwards towards the bottom of the borehole 9 in achannel 23 inside the drill string 22 and upwards in a direction towards theground surface 12 in a passage 24 formed between the drill string 22 and aninner circumference of the borehole 9. The direction of the airflow isschematically illustrated by arrows in figure 1.

According to an example, the rock drilling system 10 may comprise air jettingmeans 6 with at least one nozzle arranged along the drill string 22 above thedrilling hammer 4. The at least one nozzle may be configured to eject air fromthe channel 23 inside the drill string 22 to the passage 24 formed between thedrill string 22 and the inner circumference of the borehole 9. The air jettingmeans 6 may assist the flow of air and drill cuttings upwards through theborehole 9.

According to an example, the rock drilling system 10 may comprise a drillcuttings separator 55 for separating the drill cuttings from the air containing drillcuttings. The driii cuiting separator 55 rnay be a separate unit er integrated withfor exampie the extractien device 5 as ecnennaticaiiy iiiusirated in 'figure i. Thedriii cutting separator 55 may be niovabie. The driii cutting separator 55 may be arranged on a venicie.

According to an example, the rock drilling system 10 may be configured fordrilling boreholes 9 that are at least 1500 meters deep. According to an example,the rock drilling system is configured for drilling boreholes 9 that are at least2000 meters deep, or at least 3000 meters deep. According to an example, thedrilling rig 2, the at least one air compressor 1 and the extraction device 5 maybe mobile. The different units 2,1,5 may be arranged on different vehicles, orone or more units 2,1 ,5 may share the same vehicle. The vehicles may comprise 27 wheels or continuous tracks (i.e. tank or caterpillar treads). ln figure 1, the drillingrig 2, the at least one air Compressor 1 and the extraction device 5 are illustratedas separate vehicles. The drilling rig 2 is schematically illustrated with continuous tracks.

According to an example, the conveying chamber arrangement 3 may beconfigured to be airtight, in order to maintain the flow of air upwards through theborehole 9.

According to an example, the rock drilling system 10 may further comprise acontrol device 100 configured to control the drilling rig 2 and/or the at least oneair compressor 1 and/or the extraction device 5 and/or the airjetting means 6.The control device 100 may allow remote monitoring and controlling of thedifferent units in the rock drilling system 10 via Internet, Bluetooth, mobile phonenetwork data service or similar. The control device 100 may be implemented asa separate entity or distributed in two or more physical entities. The controldevice 100 may comprise one or more control units and/or computers. Thecontrol device 100 may thus be implemented or realised by the control device100 comprising a processor and a memory. The memory may compriseinstructions, which when executed by the processor causes the control device100 to perform method steps. According to an example, the controll device 100may comprise a computer program P. The computer program P may compriseinstructions which when the program is executed by a computer, causes thecomputer to perform method steps as disclosed herein.

According to an aspect of the present disclosure, the rock drilling system 10 asillustrated in figure 1 may be intended for use for generation of geothermalenergy.

Figure 2 and figure 3 schematically illustrate details of the rock drilling system10. Figure 2 and figure 3 illustrates examples of a conveying chamberarrangement 3. The conveying chamber arrangement 3 may comprise: a top 28 cover 36a with an opening 31 for the dri|| string 22; a dri|| string sleeve 33connected to the top cover 36a and encircling the dri|| string 22; chamber walls38 connected to the top cover 36a and encircling the dri|| string 22 and the dri||string sleeve 33, wherein the chamber walls 38 are configured to be connectedto the borehole casing 44 at a bottom end 32; and an extraction opening 39 configured to be connected to the extraction device 5.

The conveying chamber arrangement 3 may according to an example comprisesealing elements 34a, 34b, 34c, 34d, 36b between the top cover 36a and thechamber walls 38 and/or at the opening 31 for the dri|| string 22 and/or at theextraction opening 39, and/or at the bottom end 32 of the chamber walls 38.

The conveying chamber arrangement 10 may be configured as disc|osed infigure 3. ln figure 3, the dri|| string sleeve 33 is more e|ongated than in figure 2.When the dri|| string sleeve 33 is longer, a supporting structure 37 may bearranged to support the dri|| string sleeve 33. The supporting structure 37 maycomprise struts, or some sort of supporting legs, attached to the chamber walls38. A more e|ongated dri|| string sleeve 33 may be beneficial for achieving anairtight conveying chamber arrangement. ln figure 3, it is schematicallyillustrated that the diameter of the borehole casing 44 varies. The diameter ofthe borehole casing 44 may be varied in order to obtain an efficient airflow upwards in the borehole 9.

As illustrated in figure 2 and figure 3, the conveying chamber arrangement 3may comprise sealing elements 34b, 36b at the opening 31 for the dri|| string 22.These sealing elements 34b, 36b may comprise gaskets, O-rings or other elasticparts and clamping plates, sealing flanges etc. For example, the sealingelements 34b, 36b are arranged above (on top of) the top cover 36a and maycomprise at least one flat gasket 34b. The at least one flat gasket 34b may havea similar shape and size as the top cover 36a. However, the opening in the atleast one flat gasket 34b for the dri|| string may be smaller than the opening 31of the top cover 36a. Due to this configuration, the at least one flat gasket 34b 29 may tightly seal any small gap between the dri|| string 22 and the dri|| stringsleeve 33 at the opening 31 in the top cover 36a. The dri|| string 22 may beslidingly engaged with the at least one flat gasket 34b and the opening 31 in thetop cover 36a. By means of the at least one flat gasket 34b, the entrance of thedri|| string 22 into the dri|| string sleeve 33 may be airtight. The at least one flatgasket 34b may be clamped between the top cover 36a and for example aclamping plate 36b by means of fastening means 35a. The clamping plate 36bmay comprise a flat circular plate with an opening for the dri|| string 22.According to an example, there may be two flat gaskets 34b between the topcover 36a and the clamping plate 36b. The fastening means 35a may compriseclamping bolts and nuts, or other similarfastening devices. The fastening means35a may be the same as mentioned above.

The conveying chamber arrangement 3 may comprise sealing elements 34c,34d at the extraction opening 39 and/or at the bottom end 32 of the chamberwalls 38. The sealing elements 34c, 34d may comprise gaskets, O-rings or otherelastic parts. The sealing element 34c arranged at the extraction opening 39,may be arranged between the extraction opening 39 of the conveying chamberarrangement 3 and a suction hose 51, connecting the conveying chamberarrangement 3 to the extraction device 5. The sealing elements 34c may beclamped between the extraction opening 39 and the suction hose 51 by meansof clamping jaws, claw couplings, bayonet connectors, quick coupling or othertypes of suitable coupling for connecting a suction hose or similar to theextraction opening 39. The sealing element 34d at the bottom end 32, may bearranged between the bottom end 32 and the borehole casing 44. The sealingelement 34d arranged between the bottom end 32 and the borehole casing 44may be clamped by means of fastening means 35b. The fastening means 35bmay comprise clamping bolts and nuts, or other types of durable engagementpart, suitable for engagement and disengagement.

Figure 4 schematically illustrates a block diagram of a method for geothermaldrilling with a rock drilling system 10 according to an example. The methodrelates to the rock drilling system 10 as disclosed in figure 1.

The method comprises the steps of: driving s10 the drilling hammer 4 andsupplying compressed air into a borehole 9 via the drill string 22 by means ofthe at least one air compressor 1; and drawing s20 air containing drill cuttingsfrom the borehole 9 via the conveying chamber arrangement 3, by means of theextraction device 5. The method may further comprise the step of: ejecting s30air by means of air jetting means 6 to assist the flow of air and drill cuttingsupwards through the borehole 9.

Figure 5 schematically illustrates a block diagram of a method performed by acontrol device 100, for geothermal drilling with a rock drilling system 10according to an example. The method relates to the rock drilling system 10 asdisclosed in figure 1. The method may thus be performed by the control device100 as disclosed in figure 1.

The method comprising the steps of: controlling s110 the at least one aircompressor 1 to drive the drilling hammer 4 and supply compressed air into aborehole 9 via the drill string 22; controlling s120 the extraction device 5 to drawair containing drill cuttings from the borehole 9 via the conveying chamber arrangement 3.

The method may optionally comprise the step of controlling s130 air jettingmeans 6 to eject air in order to assist the flow of air and drill cuttings upwardsthrough the borehole 9. lt is to be understood that the control device 100 may be implemented as aseparate entity or distributed in two or more physical entities. The control device100 may comprise one or more control units and/or computers. The control device 100 may thus be implemented or realised by the control device 100 31 comprising a processor and a memory, the memory comprising instructions,which when executed by the processor causes the control device 100 to performthe above disclosed method steps.

According to an example, a computer program P comprising instructions which,when the program is executed by a computer, causes the computer to performthe method as disclosed above is provided. The computer program P isschematically i||ustrated in figure 1. According to an example, a computer-readable medium comprising instructions, which when executed by a computer causes the computer to carry out the method as disclosed above is provided.

The foregoing description of the preferred examples of the present disclosure isprovided for illustrative and descriptive purposes. lt is not intended to beexhaustive or to restrict the invention to the variants described. Manymodifications and variations will obviously be apparent to one skilled in the art.The examples of the present disclosure have been chosen and described inorder best to explain the principles of the invention and its practical applications and hence make it possible for specialists to understand the invention for various embodiments and with the various modifications appropriate to the intended use.

Claims (14)

32 Claims

1. A rock drilling system (10) for geothermal drilling, the rock drilling system (10) comprising:a drilling rig (2) with a dri|| string (22) and a drilling hammer (4) for drillinga borehole (9);at least one air Compressor (1) configured for driving the drilling hammer(4) and supplying compressed air into the borehole (9) via the dri|| string(22):a conveying chamber arrangement (3) configured to be arranged at aground surface (12), wherein the conveying chamber arrangement (3) isconfigured to encircle the dri|| string (22) and to be connected to aborehole casing (44);characterized by thatan extraction device (5) is connected to the conveying chamberarrangement (3) to draw air containing dri|| cuttings from the borehole (9),thereby contro||ing the flow of air upwards through the borehole (9).

2. The rock drilling system (10) according to claim 1,wherein the rock drilling system (10) is configured so that the airflows ina direction towards the bottom of the borehole (9) in a channel (23) insidethe dri|| string (22) and in a direction towards the ground surface (12) in apassage (24) formed between the dri|| string (22) and an innercircumference of the borehole (9).

3. The rock drilling system (10) according to claim 1 or 2, further comprising:airjetting means (6) with at least one nozzle arranged along the dri|| string(22) above the drilling hammer (4), wherein the at least one nozzle is configured to eject air from a channel (23) inside the dri|| string (22) to a passage (24) formed between the dri|| string (22) and an inner circumference of the borehole (9). 33

4. The rock drilling system (10) according to any one of the preceding claims, further comprising:a drill cuttings separator (55) for separating the drill cuttings from the aircontaining drill cuttings.

5. The rock drilling system (10) according to any one of the preceding claims,wherein the rock drilling system (10) is configured for drilling boreholesthat are at least 1500 meters deep.

6. The rock drilling system (10) according to any one of the preceding claims,wherein the drilling rig (2), the at least one air compressor (1) and theextraction device (5) are mobile.

7. The rock drilling system (10) according to any one of the preceding claims,wherein the conveying chamber arrangement (3) is configured to beairtight, in order to maintain the flow of air upwards through the borehole (9).

8. The rock drilling system (10) according to any one of the preceding claims, wherein the conveying chamber arrangement (3) comprises:a top cover (36a) with an opening (31) for the drill string (22);a drill string sleeve (33) connected to the top cover (36a) and arranged toencircle the drill string (22);chamber walls (38) connected to the top cover (36a) and encircling thedrill string sleeve (33), wherein the chamber walls (38) are configured tobe connected to the borehole casing (44) at a bottom end (32); andan extraction opening (39) configured to be connected to the extractiondevice (5).

9. The rock drilling system (10) according to claim 8,wherein the conveying chamber arrangement (3) comprises sealingelements (34a, 34b, 34c, 34d, 36b) between the top cover (36a) and the 34 Chamber walls (38) and/or at the opening (31) for the drill string (22)and/or at the extraction opening (39), and/or at the bottom end (32) of thechamber walls (38).

10. The rock drilling system (10) according to any one of the preceding claims,wherein the drilling hammer (4) is configured to be arranged at the bottomof the borehole (9) at an end of the drill string (22).

11. The rock drilling system (10) according to any one of the preceding claims,further comprising a control device (100) configured to control the drillingrig (2) and/or the at least one air compressor (1) and/or the extractiondevice (5) and/or the airjetting means (6).

12. Use of a rock drilling system (10) according to any one of claims 1-11,for generation of geothermal energy.

13. A method for geothermal drilling with a rock drilling system (10) according toany ofclaims 1-11, wherein the method comprises the steps of: - driving (s10) the drilling hammer (4) and supplying compressed air into aborehole (9) via the drill string (22) by means of the at least one aircompressor (1 ); and - drawing (s20) air containing drill cuttings from the borehole (9) via theconveying chamber arrangement (3), by means of the extraction device (s).

14. The method according to claim 13 further comprising the step of:- ejecting (s30) air by means of airjetting means (6) to assist the flow of airand drill cuttings upwards through the borehole (9).