EP3827156A1

EP3827156A1 - Borehole sealing device

Info

Publication number: EP3827156A1
Application number: EP19756105.3A
Authority: EP
Inventors: Sascha ZIPP
Original assignee: Zipp Industries Co Kg GmbH
Current assignee: Zipp Industries Co Kg GmbH
Priority date: 2018-07-26
Filing date: 2019-07-25
Publication date: 2021-06-02
Anticipated expiration: 2039-07-25
Also published as: EP3827156B8; EP3827156B1; DE102018118121A1; WO2020021002A1

Abstract

The invention relates to a borehole sealing device for performing drilling in a borehole while controlling the water outlet from the borehole, having a basic pipe (1) and a sleeve (7) which is located longitudinally movably on the outer face of the basic pipe (1). A spring (11) is arranged between the basic pipe (1) and the sleeve (7) such that a longitudinal displacement of the sleeve (7) relative to the basic pipe (1) in one of the longitudinal directions is possible only by overcoming the spring force. A radially expandable elastomeric element (24) is fixed on the outer face of the borehole sealing device such that the elastomeric element is axially connected to or adjoins the sleeve (7), such that a displacement of the sleeve (7) in the longitudinal direction against the spring force brings about a reduction in the radial dimensions of the elastomeric element (24) and a displacement of the sleeve (7) in the longitudinal direction corresponding to the spring force brings about a radial expansion of the elastomeric element (24), which effects sealing relative to an outer pipe (25) arranged around the borehole sealing device. The wall of the basic pipe (1) has one or more radial passages (3) which open into a piston chamber (14) between the outer face of the basic pipe (1) and the inner face of the sleeve (7). The piston chamber (14) is closed on both sides in the longitudinal direction, and the displacement of the sleeve (7) in the longitudinal direction against the spring force can be brought about by a fluid which was supplied during the drilling entering the piston chamber (14) between the outer face of the basic pipe (1) and the inner face of the sleeve (7).

Description

Borehole closure device The invention relates to a borehole closure for carrying out bores in a borehole while controlling the water leakage from the borehole.

Various drilling methods for rock and soil are known from the prior art. Such bores are used, for example, in civil engineering, for setting anchors, which introduce tensile forces into the ground or rock, and in geothermal energy. In this context, a general distinction is made between dry drilling and rinsing drilling processes. While the drilling material is conveyed to the surface periodically during dry drilling, the drilling material is conveyed continuously during flush drilling in the flushing stream, air or a fluid, in particular water, being used to generate the flushing stream. Additives are often added to the water, for example bentonite to increase viscosity or cement. A further distinction is made between cased and uncased bores.

Particular problems arise when drilling below the groundwater table, because in this case water presses into the borehole, which must be drained off in a controlled manner without allowing more soil to be discharged from the borehole. Uncontrolled discharge from the ground is fundamentally undesirable, as this can make the rock unstable and, in the worst case, cause a bottom break. The problem of pressing water can also occur with diagonal or horizontal drilling. Drilling below the water table is mostly done in outer pipes. Downhole hammers are often used in this context Use, especially if the drilling has to be carried out in relatively hard rock. Only on light soils can rinsing holes be made without a down-the-hole hammer. The holes are often carried out as double-headed holes. The object of the invention was to provide a borehole closure with which, on the one hand, the space between the drill pipe and the outer pipe can be effectively sealed against water pressing from below or from other directions, but which, on the other hand, permits flushing drilling processes in which the supplied Fluid continuously transports the cuttings out of the borehole.

This object is achieved according to the invention by a borehole closure device for carrying out bores in a borehole under the control of the water outlet from the borehole, with a base tube and a sleeve which is longitudinally displaceable on the outside of the base tube, with a spring in the manner between the base tube and the sleeve is arranged that a longitudinal displacement of the sleeve relative to the base tube in one of the longitudinal directions is only possible by overcoming the spring force, a radially expandable elastomer element being fixed on the outside of the borehole closure device in such a way that it is axially connected to the sleeve or on this adjoins, so that a displacement of the sleeve in the longitudinal direction against the spring force leads to a decrease in the radial expansion of the elastomer element and a displacement of the sleeve in the longitudinal direction in accordance with the spring force brings about a radial expansion of the elastomer element, which seals against an outer tube arranged around the borehole closure device, and wherein the wall of the base tube has one or more radial passages which open into a piston space between the outside of the base tube and the inside of the sleeve, the piston space being closed on both sides in the longitudinal direction , and the displacement of the sleeve in the longitudinal direction against the spring force can be brought about in that a fluid supplied during the bore reaches the piston space between the outside of the base tube and the inside of the sleeve. According to the invention, an elastomer element fixed on the outside of the base pipe is designed such that it can seal the intermediate space between the borehole closure device belonging to the drill pipe and the outer pipe. The elastomer element is normally arranged radially around the borehole closure device, in particular around the base pipe. It can have the shape of a ring cylinder or a tubular sleeve. However, the elastomer element can be stretched such that there is no longer a seal with respect to the outer tube, and a fluid, in particular water, can penetrate through the intermediate space to the outside. In order to bring about this stretching, the elastomer element can in any case be connected to the sleeve at one axial end, preferably directly, whereby the displacement of the sleeve in the longitudinal direction counter to the spring force causes the elastomer element to stretch. Alternatively, the elastomer element can also abut only a portion of the sleeve, so that the longitudinal movement of the sleeve allows the elastomer element to expand in the longitudinal direction, the radial expansion simultaneously decreasing. The elastomer element can be made of rubber or another elastic material, for example. The rigidity of the elastomer element can be adjusted depending on the pressures used by a suitable choice of shape and material. With regard to the material, the term elastomer is to be interpreted broadly. In principle, materials are suitable which allow the elastomer element to be deformed in such a way that there is a radial expansion in the longitudinal direction and a decrease in the radial expansion in the longitudinal direction. A certain deformability is necessary for this.

Essentially, two different operating states can be distinguished for the borehole closure device according to the invention. In the idle state, in which there is no drilling and no flushing with fluid, the elastomer element is expanded and seals the space between the borehole closure device and the outer tube. In this condition, the drill pipe can be removed and extended, for example. This effectively prevents groundwater or other pressurized water from escaping. If, on the other hand, a drilling takes place, the entire borehole closure device is pressurized, ie fluid flows through the inside of the base pipe in the drilling direction in order to take the comminuted drillings (cuttings) through the outer pipe during drilling and herauszufördern. In this pressurized state, the fluid passes through the radial passages in the wall of the base tube into the piston space between the outside of the base tube and the inside of the sleeve. The pressure of the fluid causes the sleeve to be displaced in the longitudinal direction, the pressure exerted by the fluid acting against the spring force of the spring. Since the sleeve is also connected to the elastomer element or abuts against it, the latter is stretched or given space for stretching in the longitudinal direction. This is associated with a decrease in the radial expansion of the

Elastomer element and the space between the well closure device and the outer tube is released, d. H. the supplied fluid can flow out through the space between the borehole closure device and the outer pipe and in the process can transport the conveyed drilling material to the outside. As soon as the pressure through the fluid decreases again because there is no longer any pressurization with fluid, the spring ensures that the sleeve moves axially in the opposite direction, in which case the sleeve compresses the

Elastomer element in the longitudinal direction ensures that the elastomer element expands radially and brings about a closure of the space between the outer tube and the borehole closure device. The uncontrolled escape of pressing water is prevented. This is in the idle state of

Significance when not drilling, especially when removing the drill pipe.

Typically, the sleeve moves in the opposite direction to the drilling direction when fluid enters the piston chamber and accordingly expands the elastomer element in the same direction. In principle, however, there is also a displacement of the sleeve in the opposite direction, i. H. Direction of drilling, conceivable with appropriate stretching of the elastomer element.

The piston chamber is preferably sealed in the longitudinal direction by means of groove sealing rings. So that the sleeve is longitudinally displaceable, the groove sealing ring should be attached to the sleeve at least in one direction so that a

Longitudinal displacement relative to the base pipe is possible, but at the same time the sealing of the piston chamber remains guaranteed. The longitudinally displaceable, spring-side limitation of the piston chamber normally abuts the spring directly or indirectly, ie when the piston chamber is pressurized by means of supplied fluid, a force is exerted on the spring by the limitation of the piston space, which compresses the spring; if, on the other hand, the pressure in the piston chamber decreases, the relaxation of the spring ensures that the piston chamber is reduced again by pressing the spring against the limitation and displacing the sleeve in the longitudinal direction.

The fluid is usually a water-based fluid, although water with certain additives can also be used, for example bentonite. With the water, the rock crushed by the drill and soil in the space between the borehole closure device and the outer pipe surrounding it are simultaneously conveyed out of the borehole. It is also possible to use gases as a fluid, for example air. The use of a mixture of air, water and a cement water suspension as a fluid is particularly preferred.

The fluid, which preferably contains water, is used for cooling during drilling and for discharging the dissolved drilling material. During operation, a fluid is pumped through the interior of the base pipe to the drill, which ensures that the shredded drillings are flushed out of the borehole through the outer pipe. According to the invention, the fluid takes on a further role and passes through the passages in the wall of the base tube into the piston space between the outside of the base tube and the inside of the sleeve in order to ensure that the sleeve builds up in the longitudinal direction with the pressure built up here the spring force shifts and thereby expands the elastomer element. If drilling is interrupted, the fluid supply is reduced or stopped. The release of the fluid pressure causes the spring to expand and the fluid to be pressed out of the piston chamber and the sleeve to move in the opposite direction, as a result of which the elastomer element expands radially and seals the gap between the borehole closure device and the outer tube. Discharge of drillings in this state is naturally not necessary due to the lack of a hole, but at the same time, undesired and uncontrolled leakage of groundwater is effectively prevented, particularly in the case of holes below the water table. The same applies to horizontal or diagonal drilling if there is pressing water. The drill can be a hydraulically driven drill. Preferred drills are known in the prior art as down-the-hole hammers, which are used in particular in bores in solid rock and have an impact mechanism for generating an impact movement. In principle, however, the invention can also be practiced with other drills, for example with lighter soils. Examples of other drills are (lost) ram tips, possibly with spade cutting. The invention can also be used in connection with HDI (high-pressure injection process), ie jet spray processes, in which a fluid is fed under high pressure, which cuts open the rock or soil. In this case, a mostly cement-containing suspension can also be added to produce a concrete-like body. According to the terminology used here, such methods are also interpreted as "drilling", and an HDI injection lance is accordingly interpreted as a drill. It makes sense to mount the drill at the end of the drilling direction

Connect the borehole closure device, in particular via a closure sleeve arranged at the end of the base pipe on the drilling direction side. This sealing sleeve should have a flow channel running in the longitudinal direction, which connects to the flow channel of the base pipe, in other words be connected to the interior of the base pipe. The connection between the base tube and the closure sleeve can be established, for example, by the base tube having a corresponding external thread and the closure sleeve having a corresponding internal thread, which can be screwed together. However, embodiments are also conceivable in which, for example, the drill is connected directly to the base pipe or the drill is a direct component of the

Borehole closure device is. The elastomer element can adjoin the locking sleeve on the drilling direction side, so that the longitudinal stretching is limited by the locking sleeve. Alternatively, the borehole closure device can also have another limitation for the elastomer element in the drilling direction.

In order to control the pressure build-up by the fluid, it makes sense to arrange a baffle plate in the flow path of the fluid leading to the passages, preferably on the drilling direction side. Such a baffle plate ensures for the fact that a certain pressure must first build up before a sufficient amount of fluid reaches the piston space between the base pipe and the sleeve through the radial passages in order to build up a pressure here that is sufficiently large to displace the sleeve against the spring force. However, smaller pressures that are already exerted by groundwater or other pressurized water are not sufficient to move the sleeve. The elastomer element accordingly remains in its expanded configuration and closes the space between the borehole closure device and the outer tube. The baffle plate regulates the desired overpressure and is preferably exchangeable, ie the desired overpressure, from which the sleeve is displaced and thus the gap between the outer tube and the borehole closure device opens, can be adjusted on site depending on requirements and conditions.

The baffle plate can expediently be arranged in the closure sleeve. The closure sleeve can have an area with a smaller inner diameter in which the baffle plate is arranged. At the end of the closure sleeve on the direction of drilling, this can have a receptacle for which the receptacle of the drill, for example a pin of the drill, is suitable.

The spring, which ensures that the sleeve remains in its rest position without fluid pressure and the elastomer element has an expanded shape, must be arranged in such a way that it can fulfill its role. It is expedient to use a helical spring, in particular a compression spring, which is loaded and compressed by the application of pressure. A compression spring, in particular a helical compression spring, has the advantage of being able to be arranged in such a way that it is sufficiently spaced from the elastomer element.

In principle, however, embodiments are also conceivable in which, for example, a plate spring or a tension spring, in particular a coil tension spring, is used.

The spring, in particular the compression spring, is preferably arranged in a space between the outside of the base tube and the inside of the sleeve. This intermediate space, separated by a longitudinally displaceable spring-side limitation of the piston chamber in the longitudinal direction, can adjoin the piston chamber which is filled by the fluid in the operating state. The above The aforementioned spring-side limitation of the piston chamber thus compresses the spring when the fluid flows into the piston chamber. As a rule, the piston chamber is arranged behind the intermediate space, as seen in the drilling direction, ie the piston chamber is located on the drilling direction side towards the intermediate space. At the spring end of the piston chamber opposite end of the

Compression spring should be provided with a limitation or fixation that fixes this end of the compression spring, so that the force exerted by the spring-side limitation of the piston chamber results in compression of the compression spring. For example, the base tube can have a step on its outside which serves as a limitation for the spring lying opposite the drilling direction. In the case of a tension spring, one end of the tension spring should of course be fixed in such a way that the pressurization of the fluid causes the tension spring to be pulled apart.

In order to limit the longitudinal movement of the sleeve, the outside of the base tube can have a stop which interacts with a spacer attached to the sleeve. The stop can be, for example, a one-part or multi-part bounce ring, which is preferably designed to run radially all round. The baffle ring in turn adjoins the piston chamber, if necessary also separately sealing groove seals which are sealed off by the piston chamber. At the same time, the spacer can serve as a stop for the elastomer element, with either a connection, for example an adhesive connection, to the elastomer element, or the spacer merely limiting the longitudinal expansion of the elastomer element. The spacer can be a radially circumferential spacer ring over the inner circumference of the sleeve, the z. B. can be fixed on the sleeve via a locking ring. The locking ring can be partially embedded in a radially circumferential recess on the inside of the sleeve.

In addition to the borehole closure device according to the invention, the invention also relates to a drilling device as a whole, which is composed of the borehole closure device, as described above, an outer tube through which the borehole closure device extends, and a drill which is connected to the borehole closure device. In this context, it is also possible for the drill itself to be part of the borehole closure device. Finally, the invention also relates to a Method for performing bores, in which the borehole is temporarily sealed against leakage of liquid using the borehole closure device according to the invention.

The invention is explained in more detail by way of example with reference to the figures. It should be pointed out that the figures show preferred embodiment variants of the invention, but the invention is not restricted to this. In particular, as far as it makes technical sense, the invention encompasses any combinations of the technical features that are listed in the claims or described in the description as relevant to the invention. Show it:

Fig. 1, the base pipe of the invention

Borehole closure device in longitudinal section;

Fig. 2, the sleeve of the invention

Borehole closure device in longitudinal section; Fig. 3 shows the base pipe of the invention

Borehole closure device with attached sleeve in longitudinal section;

Fig. 4, the sleeve on the base pipe in the unpressurized

Condition in longitudinal section;

Figure 5 shows the sleeve on the base tube in the pressurized state in longitudinal section.

Fig. 6, the closure sleeve of the invention

Borehole closure device in longitudinal section;

7 shows the borehole closure device according to the invention within an outer tube in the unpressurized state in longitudinal section;

8 shows the borehole closure device according to the invention within an outer tube in the pressurized state in longitudinal section; 9 shows the borehole closure device according to the invention within an outer tube in the unpressurized state in longitudinal section according to an alternative embodiment, and FIG. 10 shows the borehole closure device according to the invention within an outer tube in the pressurized state in longitudinal section according to the alternative embodiment.

In Figure 1, the base tube 1 is shown in longitudinal section, the drilling direction being on the right, as in the following figures, i. H. the drill, not shown here, is arranged on the right. The base pipe 1 has an interior space 2 as a passage in the longitudinal direction, through which a fluid can be directed in the direction of the drill. The base tube 1 has passages 3 in its wall through which the fluid can reach the outside. In addition, the base pipe 1 has an external thread 4, via which a screw connection with a sealing sleeve is possible, a step 5 as a stop for a spring, and a radially circumferential groove 6 for a first locking ring.

In Figure 2, the sleeve 7 of the borehole closure device according to the invention is shown in longitudinal section. The sleeve 7 is essentially hollow on the inside, so that it can be plugged onto the base tube 1. The sleeve 7 also has a radially circumferential recess 8 for a groove sealing ring, a radially circumferential recess 9 for a second retaining ring and a radially circumferential groove 10 for an O-ring.

In Figure 3, the base tube 1 is shown with the sleeve 7 attached. Between base tube 1 and sleeve 7 there is an intermediate space 16 in which a helical compression spring 11 is accommodated, which adjoins step 5 on the side facing away from the drilling direction. The sleeve 7 is arranged on the base tube 1 so as to be longitudinally displaceable, in the illustration chosen here to the left, ie counter to the drilling direction, a spring-side limitation 26 of the piston chamber compressing the spring 11. There is also a radially circumferential O-ring 13 between sleeve 7 and base tube 1. In FIG. 4, the sleeve 7 is shown again in the state attached to the base pipe 1, but here the radially surrounding bouncing ring 15 is also shown, which is fixed on the base pipe 1 with the aid of a first retaining ring 17. The baffle ring 15 can be in several parts and sealed by further groove sealing rings 27. This results in a piston chamber 14, which is connected to the passages 3 and is closed in the longitudinal direction, but by supplying a fluid through the passages 3 under pressure into the piston chamber 14, a longitudinal displacement of the sleeve 7 on the base tube 1 counteracts the Drilling direction (to the left in the selected illustration) is possible. The spring 11 is compressed by the spring-side boundary 26 of the piston chamber 14. This movement is limited by a spacer 18 fixed to the sleeve 7 by means of a second securing ring 19, which abuts the bouncing ring 15 when the sleeve 7 is displaced to the maximum extent. The spacer 18 and the second locking ring 19 are also arranged radially circumferentially.

Figure 5 shows the same representation as Figure 4, but in the pressurized state. It can be seen that the piston chamber 14 has become significantly larger and the sleeve 7 has shifted to the left, the spring 1 having been compressed. Since the spacer 18 is connected to the sleeve 7, this also moves against the drilling direction.

In Figure 6, the closure sleeve 20 is shown in longitudinal section. This has an internal thread 21 which can be screwed to the external thread 4 on the base tube 1. A baffle plate 22 is arranged in the closure sleeve 20, which regulates the desired overpressure and can be changed if necessary. Furthermore, the closure sleeve 20 has a receptacle 23 for the drill.

In Figure 7, the entire system is shown in the depressurized state. The borehole closure device is located within an outer tube 25. In comparison to FIG. 4, one can also see the elastomer element 24 adjoining the spacer 18 and possibly connected to it, which adjoins the closure sleeve 20 on the drilling direction side. The elastomer element 24 is radially circumferential and has the shape of a ring cylinder. In the depressurized state, the elastomer element 24 is radial therefore expands and seals the space 28 between the borehole closure device and the outer tube 25. In other words, no liquid indicated by the arrows, for example groundwater, can escape through the intermediate space 28. FIG. 8 shows the situation in the pressurized state. Here, a fluid is guided in the direction of the arrow through the interior 2 of the base pipe 1 to the drill, not shown here, in order to cool it. In addition, the fluid ensures that the drilling material is discharged. The fluid passes through the passages 3 into the piston chamber 14, the pressure being regulated via the baffle plate 22. Due to the pressurization of the piston chamber 14, the sleeve 7 moves counter to the drilling direction, ie to the left in the illustration chosen here, and compresses the spring 11. To the same extent, the spacer 18 also moves counter to the drilling direction, as a result of which the elastomer element 24 moves in the longitudinal direction stretches and at the same time its radial expansion decreases. Correspondingly, the space 28 between the outer tube 25 and the borehole closure device is released, ie the fluid can flow through the outer tube 25 and discharge drill material. If the drilling process is interrupted, the fluid supply is interrupted, the compression spring 11 expands and moves the sleeve 7 again in the drilling direction (to the right), the spacer 18 being taken along and causing the elastomer element 24 to expand radially. The space 28 between the borehole closure device and the outer tube 25 is sealed again accordingly.

An alternative embodiment, which differs with regard to the elastomer element 24, is shown in FIGS. 9 and 10, FIG. 9 showing the unpressurized state, FIG. 10, however, the pressurized state. FIG. 9 shows the elastomer element 24, which is also formed radially circumferentially here and which is connected on the drilling direction side to the closure sleeve 20 and on the side facing away from the drilling direction to the sleeve 7. In this case, the elastomer element 24 is in the form of a tubular sleeve, the tubular sleeve being compressed in the unpressurized state in such a way that a sealing of the intermediate space 28 between the borehole closure device and the outer tube 25 is ensured. The elastomer element 24 is connected to the sleeve 7 via a driver ring 29, so that the axial Movement of the sleeve 7 is transmitted to the elastomer element 24. The elastomer element 24 is connected to the closure sleeve 20 via a further ring 30, for example in the form of a half-shell. The driver ring 29 and the further ring 30 are fixed to the sleeve 7 or the closure sleeve 20 via one or more, for example two grub screws 31. In contrast to the embodiment according to FIG. 7 or 8, the inside of the elastomer element 24 does not lie completely against the base tube 1, but instead bulges radially outward in the longitudinal direction in order to bring about the sealing. FIG. 10 shows the state when the pressure in the piston chamber 14 increases by supplying fluid through the passages 3. The increase in pressure causes the sleeve 7 to be displaced counter to the drilling direction against the force exerted by the spring 11. Since the sleeve 7 is connected to the elastomer element 24 via the driving ring 29, the elastomer element 24 is stretched in the longitudinal direction with a simultaneous decrease in the radial expansion and the passage 28 between the borehole closure device and the outer tube 25 is released.

Claims

claims

1. Borehole closure device for performing bores in a borehole under the control of the water outlet from the borehole, with a base pipe (1) and a sleeve (7) which is longitudinally displaceable on the outside of the base pipe (1), a spring (11) is arranged between the base tube (1) and the sleeve (7) such that a longitudinal displacement of the sleeve (7) relative to the base tube (1) in one of the longitudinal directions is only possible by overcoming the spring force, a radially expandable elastomer element (24) is fixed on the outside of the borehole closure device in such a way that it is axially connected to or adjoins the sleeve (7), so that a displacement of the sleeve (7) in the longitudinal direction against the spring force reduces the radial expansion of the elastomer element (24) and a displacement of the sleeve (7) in the longitudinal direction in accordance with the spring force a radial expansion of the elastomer element (24) which seals against an outer tube (25) arranged around the borehole closure device, and wherein the wall of the base tube (1) has one or more radial passages (3) which lead into a piston space (14) between the outside of the base tube ( 1) and the inside of the sleeve (7) open, the piston chamber (14) being closed on both sides in the longitudinal direction, and the displacement of the sleeve (7) in the longitudinal direction against the spring force being brought about by the fact that a fluid supplied during the drilling into the Piston chamber (14) between the outside of the base tube (1) and the inside of the sleeve (7).

2. Borehole closure device according to claim 1, characterized in that the fluid contains water.

3. Borehole closure device according to claim 1 or 2, characterized in that a drill can be connected to the end of the borehole closure device on the drilling direction side.

4. Borehole closure device according to one of claims 1 to 3, characterized in that the drill is an in-hole hammer, a lost ram tip or one or more high-pressure injection nozzles.

5. Borehole closure device according to one of claims 2 to 4, characterized in that the drill can be connected via a closure sleeve (20) arranged at the end of the base tube (1) on the drilling direction side, the closure sleeve (20) having a longitudinally extending flow channel which connects to the flow channel (2) of the base pipe (1).

6. Borehole closure device according to one of claims 1 to 5, characterized in that a baffle plate (22) is arranged in the flow path of the fluid leading to the radial passages (3), preferably on the drilling direction side, which controls the pressure with which the fluid flows through the radial passages (3) flow and can act on the spring (11).

7. Borehole closure device according to claim 5 and 6, characterized in that the baffle plate (22) is arranged in the closure sleeve (20).

8. Borehole closure device according to one of claims 5 to 7, characterized in that the base tube (1) has at its end on the drilling direction end an external thread (4) and the closure sleeve (20) has an internal thread (21), via which the closure sleeve (20 ) can be connected to the base pipe (1).

9. Borehole closure device according to one of claims 6 to 8, characterized in that the baffle plate (22) is interchangeable.

10. Borehole closure device according to one of claims 1 to 9, characterized in that the spring (11) is arranged in an intermediate space (16) between the outside of the base tube (1) and the inside of the sleeve (7).

11. Borehole closure device according to claim 10, characterized in that the piston chamber (14) seen in the drilling direction behind the

Intermediate space (16) is arranged.

12. Borehole closure device according to one of claims 1 to 11, characterized in that the outside of the base tube (1) has a stop (15) which cooperates with a spacer (18) attached to the sleeve (7) and the longitudinal movement of the sleeve (7) limited.

13. Borehole closure device according to one of claims 1 to 12, characterized in that the base pipe (1) has on its outside at least one step (5), which serves as a limitation for the spring (11) lying opposite the drilling direction.

14. Drilling device with a borehole closure device according to one of claims 1 to 13, an outer tube (25) and a drill.

15. A method for performing bores, in which the borehole is temporarily sealed with a borehole closure device according to one of claims 1 to 13 against leakage of liquid.