The present invention relates to a method for arranging a collector conduit in a drilled energy well. The invention also relates to a collector conduit device for use in such an energy well.

Geothermal energy wells are used, among other things, in systems for geothermal heating and cooling. Such wells are comprised by drilled holes in the ground, and can be dry or filled with water. Typically, in such holes a heat carrier in the form of a liquid circulating in collector conduits is led down into the hole and then back up, along the longitudinal direction of the hole, whereby thermal energy is transferred between the heat carrier and the ground in the inner walls of the holes, so that the heat carrier is either heated or cooled by the ground. A problem in connection with such wells is that the thermal conductivity in the surrounding ground is often higher than the medium with which the well is filled, such as air or water. Therefore, it is desirable to arrange the collector conduit as close as possible to the inner walls of the hole in order to maximize the thermal exchange between the ground and the heat carrier.

Another problem is thermal leakage between a downwards run ^¬ ning and an upwards running part of the collector conduit in the well, since the heat carrier has different temperatures heading downwards into the well and heading back in an up ^¬ wards direction. Therefore, it is desirable to keep the dif ^¬ ferent parts of the collector conduit running along the well separated . It has turned out that a drilled energy well in which the collector conduits are arranged against one opposite respec ^¬ tive wall typically can be made between 30% and 40% shallower as compared to a corresponding well in which the collector conduits are arranged close together, and still achieve the same efficiency. Of course, shallower holes result in lower costs . Therefore, there have been proposed various ways to press apart the parts of the collector conduit inside the well, and at the same time to press the parts against the inner walls of the well. For example, there are devices in which preassembled distance elements separate the collector conduits at a certain con ^¬ stant predetermined distance, or in which a spring load is used to press the collector conduits apart from one another. Such a collector conduit has the disadvantage that it is difficult to introduce down into the hole, because of fric ^¬ tion against the inner walls, and that the collector conduit tends to stick to irregularities in the well. Moreover, a balancing is needed between the said distance or spring load and the final contact of the collector conduit with the inner walls of the hole.

Another solution is that the collector conduit is delivered with an unfoldable distance device between the conduit parts, which is folded in and locked using a water soluble material. As the collector conduits are brought down into the hole, and come into contact with the subsoil water therein, the materi ^¬ al is dissolved, and the distance device is unfolded, for instance using pressure springs. Such collector conduits suffer from the problem that once they have been brought down into the hole, and the distance device has been unfolded, it is often not possible to move them further upwards or down ^¬ wards. In case problems occur during the introduction of the conduit into the hole, it may thus happen that the collector conduit gets stuck before the problems have been solved.

It is also known, from the publication "TATNING AV BORRHAL MED GREEN COLLECTOR I KRISTALLINT BERG", published in November of 2010 by Geostrata HB in S Sandby, Sweden, to arrange a bag of water-filled material in a drilled energy well, with the purpose of sealing the interior of the well to the sur ^¬ rounding ground. A collector conduit is thereafter brought down into the well which has been provided with the bag. The present invention solves the above described problems.

Hence, the invention relates to a collector conduit device for use in a drilled energy well in the ground with an open ^¬ ing and a bottom as well as a longitudinal direction and a radial direction, which collector conduit device comprises at least a first conduit part, arranged to run along the longi ^¬ tudinal direction of the well and in the first conduit part carry a heat carrier in a direction towards the bottom of the well, as well as at least one second conduit part, arranged to run along the longitudinal direction of the well and in the second conduit part carry the heat carrier in a direction towards the opening of the well, and is characterised in that the collector conduit device also comprises a flexible con ^¬ tainer with side walls and an end opening, which container is arranged to be inserted into the well together with the said conduit parts to an inserted position, in which the container runs essentially in parallel with the first and the second conduit parts along the longitudinal direction of the well, in that the container is arranged to, in the said inserted position, be tillable from the opening of the well with a liquid, whereby the side walls of the container are pressed outwards in the radial direction of the well, as a result of the liquid pressure, towards the side walls, so that the side walls of the container as a result press the first conduit part away from the second conduit part, and in that the con ^¬ tainer comprises prefolded creases, arranged to accommodate the conduit parts in the creases during the insertion into the well, so that the container is kept in its position be- tween the conduit parts that are to be pressed apart.

Furthermore, the invention also relates to a method for achieving thermal exchange between a drilled energy well in the ground and a heat carrier, which method uses such a col- lector conduit device.

In the following, the invention will be described in detail, with reference to exemplifying embodiments of the invention and to the enclosed drawings, wherein:

Figures la and lb are respective overview sketches illustrat ^¬ ing, from the side and in cross-section, a collector conduit device according to the present invention, arranged in an energy well and in a non-filled and a filled state, respec- tively;

Figures 2, 3 and 4 are respective overview top cross- sectional sketches illustrating three different collector conduit devices according to the invention, arranged in a respective energy well;

Figure 5 is a cross-sectional view of a container which is folded together;

Figure 6 is a cross-sectional view of a collector conduit device according to the invention; and Figure 7 is an overview sketch which illustrates, from the side and in cross-section, the assembly process of a collec ^¬ tor conduit device according to the invention. Figures la and lb show, with common reference numerals, a collector conduit device according to the present invention, for use in a drilled energy well 100 in the ground. The ener ^¬ gy well 100 has an opening 102 and a bottom 103, as well as a longitudinal direction L and a radial direction R. The longi- tudinal direction L preferably has, but does not necessarily have, a vertical component, and is most preferably essential ^¬ ly vertical. It is preferred that the energy well is at least 100 meters of depth, more preferably at least 150 meters deep. Preferably, it has a shape of a cylinder of essentially uniform thickness, most preferably a cylinder with circular cross-section, which most preferably has a largest diameter of between 5 and 50 cm. Preferably, it is drilled in a hard material, such as rock, but it can also be drilled in porous material, such as earth, or in mixed materials. Preferably, the well is filled with subsoil water, but can also be dried out .

The collector conduit device comprises at least a first con ^¬ duit part 110, arranged to run along the longitudinal direc- tion L of the well 100 and to in the first conduit part 110 bring a heat carrier in a direction towards the bottom 103 of the well. Moreover, the collector conduit device comprises at least one second conduit part 111, arranged to run along the longitudinal direction L of the well 100 and to bring the said heat carrier in the second conduit part 111 in a direc ^¬ tion towards the opening 102 of the well 100. Hence, the heat carrier is circulated up and down in the well 100 in a con ^¬ duit system comprising conduit parts 110, 111. The conduit parts, which may be more than two in number, are intercon- nected so that the heat carrier can be circulated down into the well 100 towards the bottom 103, and then back up again to the opening 102 of the well 100 through at least one closed circuit, so that the heat carrier preferably is kept separated from the interior of the well 100. The input of the heat carrier into the conduit part 110, and the output out from the conduit part 111, can take place in a way which is conventional as such, such as that the conduit system consti ^¬ tutes a part of a device (not shown) , which is conventional as such, for geothermal heating and/or cooling, in which the heat carrier is circulated between the well 100 and a heat exchanger in a closed circuit by the use of a pump.

When the heat carrier is circulated in the well 100, in the conduit system, a thermal exchange takes place between the heat carrier and the surrounding ground, via any water 101 or air in the well 100 and the well walls. Therefore, the heat carrier which is led up and out from the well 100 has a tem ^¬ perature which is closer to the temperature of the surround- ing ground as compared to the heat carrier which is led down into the well 100, which hence results in a temperature dif ^¬ ference between the conduit parts 110 and 111. These circum ^¬ stances make it desirable to, during operation of the collec ^¬ tor conduit device, keep the conduit parts 110, 111 as far from each other as possible in a radial R direction, and also as close to the well wall as possible.

In order to achieve this, according to the invention the collector conduit device comprises a flexible container 120 with side walls 121 and an end opening 122. The container 120, which preferably is closed in an end 123 opposite to the end opening 122, is arranged to be introduced or to be brought down into the well 100 together with the conduit parts 110, 111 to an introduced position. In this introduced position, which is illustrated in figure la, the container 120 runs essentially in parallel with the conduit parts 110, 111 along the direction L of elongation of the well 100. When it is in the introduced position, the container 120 is further arranged to be filled, from the opening of the well 100 and via the end opening 122, with a liquid. The liquid is, but does not have to be (see below) water or a water solution which mainly consists of water but which may have additives such as anti-freezing agents.

When the container 120 is filled with the said liquid, its side walls will be pushed outwards in the radial direction R of the well 100, because of the liquid pressure towards the side walls, and the side walls of the container 100 will therefore press the conduit parts 110, 111 away from each other. Preferably, the conduit parts 110, 111 are thereby also pressed in a direction towards one respective opposite inner wall of the well 100 each, preferably so that direct contact with the respective inner wall is achieved. This is illustrated in figure lb.

Figures 2, 3 and 4 illustrate alternative conduit arrange ^¬ ments for which the invention is applicable. These figures are all illustrated in the above said introduced position and in respective cross-sections from above.

Figure 2 illustrates the case with two conduit parts 210, 211, where one 210 leads the heat carrier down into the well 200 and the other 211 leads the heat carrier again up from the well 200. The container 220 is arranged between the conduit parts 210, 211, and, when the container 220 is filled with liquid, presses them apart in a direction Dl . Figure 3 illustrates the case with four conduit parts 310, 311, 312, 313, running along the longitudinal direction of the well 300. Two 310, 312 of these are arranged to bring the heat carrier in a direction towards the bottom of the well 300, and the other two 311, 313 are arranged to bring the heat carrier in a direction towards the opening of the well 300. It is realized that the heat carrier then can be con ^¬ veyed either in two separate, parallel connected loops or in one single, serial-connected loop. In this case, the side walls of the container 320 are arranged to press at least two of said four conduit parts 310-313, or at least two groups of said four conduit parts 310-313, away from each other when the container 300 is filled with liquid. Preferably, all four conduit parts 310-313 are pressed away from each other, in directions D2, and towards one respective part of the inner wall of the well 300, preferably so that each one achieves direct contact with the respective part of the said inner wall . Figure 4 illustrates an alternative embodiment, in which a plurality of conduit parts are arranged to run along the longitudinal direction of the well 400. A central conduit part 410, which is arranged to be centrally arranged in the said introduced position, is arranged to bring the heat car- rier in a first direction in the longitudinal direction of the well 400. The other conduit parts 411, which are prefera ^¬ bly at least three of number, are arranged around the cen ^¬ trally arranged conduit part 410 in the introduced position and are then arranged to bring the heat carrier in the oppo- site direction. During filling with water, the side walls of the container 420 are arranged to press the peripheral con ^¬ duit parts 411 away from the centrally arranged conduit part 410, in a respective direction D3. The container 420 can, but does not have to, be fixed to the peripheral conduit parts 411.

In the proposed embodiments illustrated in figures 2-4, the container 220, 320, 420 is constituted by a respective elon ^¬ gated, flexible, baglike structure, which is arranged to, when introduced into the well, already have been arranged beforehand, or be arranged during said introduction, between the conduit parts 210, 211; 310, 311, 312, 313; 410, 411 that are to be pressed apart during filling with liquid of the container 220, 320, 420.

A first preferred way to keep the container in position be ^¬ tween the conduit parts is to provide the container with pre- folded creases or folds, arranged so that the conduit parts can be arranged in the creases during introduction into the well, and so that the container is held in position between the conduit parts that are to be pressed apart, even during the pressing apart itself. Such a container 500 is illustrat- ed in cross-section in figure 5, which also shows two oppositely arranged such pre-folded creases 510, 520. Such a folded together structure also makes the container flat, whereby it can easily be transported, for instance in a rolled-up state.

The present inventors have discovered that it is possible to arrange such a container 500 between conduit parts in an energy well in such a way so that the container is kept in position even during filling with liquid, so that the conduit parts are pressed apart without the container slipping out from its desired position between the conduit parts.

In certain cases, it is preferred that the structure illus ^¬ trated in cross-section in figure 5 is provided with more rigid material in the longitudinal direction of the container 500, at least at and in connection to the areas for the creases 510, 520, so that the container 500 in cross-section maintains its pre-folded creases 510, 520 in the form of indentations even when filled with liquid. This will result in that the respective conduit parts are better held in posi ^¬ tion in the creases 510, 520. It is realized that another number than two of pre-folded creases can be used, for in ^¬ stance can four pre-folded creases be used to hold four con- duit parts in position as illustrated in figure 3, in a way corresponding to that for two conduit parts.

Another preferred way to keep the conduit parts in position in relation to the container is that the collector conduit device comprises a plurality of fastening means 130, 230, 330, 730 (see figures la, lb, 2, 3 and 7) at different loca ^¬ tions along the length of the collector conduit device, which fastening devices are arranged, during the insertion, to be able to fasten the container to the conduit parts so that the position of the conduit parts in relation to the container, possibly except along the longitudinal direction L, is fixed. For example, such fastening devices can be comprised by cable ties fixed to the container, strings or other fastening means arranged to be fastened around a respective conduit part and thereby fix the conduit part in relation to the container.

Such fastening devices can advantageously be fastened in connection to the insertion of the collector conduit device in the energy well (see below in connection to figure 7) .

It is noted that no fastening devices, at least not between the container 420 and the central conduit part 410, are re ^¬ quired in the case with a central 410 and several peripheral 411 conduit parts, as shown in figure 4, since in that case the container 420 is arranged around the central conduit part 410.

According to a third preferred way to keep the conduit parts in position, which is illustrated in figure 6, the collector conduit device 601 comprises two conduit parts 610, 611 that are to be pressed apart during filling of liquid to a con ^¬ tainer 620, which container 620 in turn is kept fixed to the conduit parts 610, 611 using pre-manufactured or pre-mounted fastening means 630, so that the conduit parts 610, 611 by the use of the fastening means 630 are kept in position in relation to the container 620. Preferably, the fastening means 630 run along the main longitudinal direction of the container 620. They are either mounted at regular intervals, such as at least every twenty meters, preferably at least every five meters, along the longitudinal direction of the container 620, or are fixed along a continuously connected section of the length of the container 620 to the conduit parts 610, 611.

Figure 6 illustrates a preferred example of the latter case, namely that the conduit parts 610, 611 and the container 620 constitute integrated parts of the same material body, which material body is the essentially cylindrical body the cross- section of which is illustrated using hashes in figure 6. Hence, the cross-section encloses the interior 610a of the first conduit part 610, the interior 611a of the second con ^¬ duit part 611 as well as the interior 620a of the container 620. In other words, the container 620 constitutes an inte- grated part of the collector conduit device 601. Such an arrangement result both in simple mounting in the energy well and that the conduit parts 610, 611 are kept in position in relation to the container 620. It is noted that the invention, apart from the prefabricated combination of conduit parts and container, also relates to a collector conduit device in assembled state, ready for opera ^¬ tion, in the inserted position in an energy well.

Furthermore, figure 7 illustrates a method according to the present invention for achieving thermal exchange between a drilled energy well 700 in the ground and a heat carrier. In the well 700, which comprises an opening 702 and a bottom 703, as well as a longitudinal direction L and a radial di ^¬ rection R, a collector conduit system is mounted, comprising at least first 710 and second 711 conduit parts, together with a flexible container 720 having side walls 721 and an end opening (not shown, hidden by the roll 760) . In assembled state, the conduit parts 710, 711 and the container 720 hence run essentially in parallel, along the longitudinal direction L of the well 700.

The assembly itself is performed by inserting the conduit parts 710, 711 into, or down into, the well 700, together with the container 720. One way to achieve this is that a preassembled collector conduit system according to the invention, in which the container is fastened to the conduit parts or surrounds a central conduit part, is brought down into the well 700. Another way is that the assembly of the collector conduit device takes place in connection to its insertion into the well. It is this latter method which is illustrated in figure 7. Hence, on the one hand the container 720, which is stored in a folded together state on, and is rolled off from in a di ^¬ rection D5, a roll 760, and on the other hand the conduit parts 710, 711, are brought together above the opening 702 of the well 700, where the parts are also fastened together at regular intervals using fastening devices 730 as described above. Initially, the end 723 of the container 720 facing away from its opening is also fastened, using a fastening device 750, to a bottom weight 740, which is arranged to keep the container 720 extended in the longitudinal direction L. The feeding down and fastening process is then ongoing until the whole collector conduit device has been lowered to a desired depth in the well 700. Such a mounting method results in that a container 720 according to the invention can be used together with existing collector conduits 710, 711 and a possible existing weight 740 in order to simply, in a subsequent step, be able to separate the conduit parts 710, 711 and to press them apart by filling of the container 720. After the assembly of the collector conduit device has been finished, and when it is located in the above described in ^¬ serted position in which the container 720 runs essentially in parallel with the conduit parts 710, 711, heat carrier can then be circulated in the conduit parts 710, 711 according to the above, so that the heat exchange is achieved.

Once the collector conduit device is in the inserted posi ^¬ tion, the container 720 is thereafter filled, from its opening, with a liquid, whereupon the side walls of the container 720 are pressed outwards in the radial direction R of the well 700, as a consequence of the liquid pressure towards the side walls, and thereby pressing the conduit parts 710, 711 away from each other. What has been said above in connection to figures la-6 is also applicable to the method illustrated in figure 7, and vice versa.

The container 720 can be liquid tight or liquid permeable. According to a preferred embodiment, the liquid which is filled to the container 720 is constituted mainly by water. Preferably, it is constituted by substantially pure water, alternatively water with a suitable anti-freeze additive. In this latter case, it is preferred that the container 720 is liquid tight, so that the filled liquid remains in the con ^¬ tainer and so that the liquid pressure therein continues to press apart the conduit parts 710, 711 also after the filling has ceased and the upper opening of the container 720 possi ^¬ bly has been sealed.

The well 700 can be, but does not have to be, filled with water 701. In particular for such water-filled wells 700, it is preferred that the liquid is supplied so that an overpres ^¬ sure is formed in the container 720 in relation to the pres ^¬ sure in the well 700 at a certain depth. This results in that the walls of the container 720 can manage to press apart the conduit parts 710, 711, against the surrounding water pres- sure in the well 700.

Also in other cases it is preferred that such an overpressure is achieved. A preferred way of achieving such overpressure is to arrange a liquid surface 124 (see figure lb) at a suf- ficient height, preferably above, the water surface 101 so that the required overpressure is achieved. Another preferred way is to supply the liquid under overpressure, such as sup ^¬ plying water via the public water mains via a valve (not shown) while using the water pressure supplied thereby, and to maintain the achieved overpressure, using a non-return valve or the corresponding means which is conventional as such, after the filling has been finished. An alternative, which is especially preferred for wells 700 drilled in earth- or porous grounds, is that the container 720 is water permeable, for instance by it being porous. In this case, the liquid is constituted mainly by earth, prefer- ably drilling masses, intermixed with a certain liquid. The certain liquid is preferably water. This way, solid material can be brought down into the drilled hole in a way which is both easy on the collector conduits and which is arranged to press them apart. The water will leak out from the container 720 and down into the surrounding ground, but the solid mate ^¬ rial will remain in the container 720. If and when the drilled hole collapses, by the surrounding ground closing in around the container 720, the conduit parts 710, 711 will then not be pressed together again.

Also in another preferred embodiment, the container 720 is porous, namely in the case when the liquid is constituted by a liquid substance which can be hardened or stiffen to solid consistence, such as bentonite slurry that can harden to bentonite clay. In this case, it is preferred that the con ^¬ tainer is permeable to the liquid, but only so much so that liquid during filling leaks out through the walls of the container 720 sufficiently slowly for a sufficient pressure gradient to be present between the interior of the container 720 and the surrounding well 700 in order to prevent that the conduit parts 710, 711 are pressed together before the slurry has hardened and the whole construction thereby has been fixed. Before final hardening, it is also preferred that sufficient amounts of slurry have time to penetrate the per- forations of the container in order to fill out the remaining space in the well, so that the end result is a well filled with bentonite clay and with separated conduit parts. This results in that an energy well can be sealed with clay, which is often desirable for environmental reasons, at the same time as good separation between the conduit parts can be guaranteed .

In this context, it is preferred that the container 720 has a cross-sectional area in its completely liquid-filled state which is sufficiently large in order for, as seen in cross- section, essentially completely fill the well 700. This re ^¬ sults in that the slurry can fill the container 720 and thereby also essentially the whole well 700. Because the container is permeable to the slurry, a certain share of the slurry can then leak out and seal any remaining air pockets in the well 700.

In case the filled container 720 in cross-section is smaller than the well 700, it is preferred to fill the container with slurry in stages, starting from the bottom 703 of the well 700. In this case, the slurry is hence filled and allowed to harden or stiffen in steps of about 1-10 meter at a time, and any air pockets outside of the container 720 are sealed with slurry supplied directly to the well 700, outside of the container 720, before the next stage is commenced.

Preferably, the conduit parts are manufactured from a plastic material. The container can in other cases for instance be manufactured from a liquid tight or perforated, flexible plastic- or rubber material, alternatively a textile materi ^¬ al.

Above, preferred embodiments have been described. However, it is apparent to the skilled person that many modifications can be made to the described embodiments without departing from the basic idea of the invention. For example, more than four conduit parts can be used in the corresponding way as the one illustrated in figure 3, and more or less than 8 peripheral conduit parts can be used in a collector conduit device according to figure 4.

Moreover, the energy well can have another longitudinal di ^¬ rection than vertical, such as a well which has been drilled aslant downwards.

Hence, the invention is not to be limited to the described embodiments, but can be varied within the scope of the en ^¬ closed claims.