EP3357069B1

EP3357069B1 - Waste disposal system, bop and method for disposing a waste into a drilled borehole in a subtending tectonic plate

Info

Publication number: EP3357069B1
Application number: EP16760817.3A
Authority: EP
Inventors: Rudolf Johannes Gerardus Antonius Van Der Hoorn; Wilhelmus Hubertus Paulus Maria Heijnen; Dirk SWART
Original assignee: Ruwidic BV
Current assignee: Ruwidic BV
Priority date: 2015-09-28
Filing date: 2016-08-16
Publication date: 2020-03-25
Anticipated expiration: 2036-08-16
Also published as: EP3357069A1; NL2015515B1; WO2017058005A1

Description

The present invention relates to the field of repositories for waste material, in particular nuclear waste material, and relates to a waste disposal system, blowout preventer and method for disposing a waste into a drilled borehole in a subtending tectonic plate.
US 4.178.109 discloses a method for permanent disposal of nuclear or toxic waste materials by placing these materials in a descending tectonic plate at the edge of a subduction zone. The waste material is placed in a borehole made in a basement rock of an oceanic plate. The descending tectonic plate carries the waste material into the centre of the earth. A re-entry tower is used that is centred over the borehole for disposing the waste material into the borehole. The waste material is stored in an elongated waste cylinder which is to be introduced into the borehole. A revolving cylinder is housed in the re-entry tower and has a plurality of cylindrical openings for receiving a plurality of waste cylinders. The revolving cylinder is rotatably mounted in an offset position in the re-entry tower such that an innermost opening is positioned directly in a centre of the tower and is directly over the borehole. The revolving cylinder can be rotated by the drill string to bring another waste cylinder above the borehole. The waste cylinders are released one by one into the borehole.
A problem to the disclosed method is that it is difficult to relocate a drilled borehole. Once, the drilled borehole opening is found, it is difficult to bring the revolving cylinder or a hopper at a tip of a drill string exactly at a position of the borehole. Depositing waste material would require manipulation of the waste by an apparatus located on the seabed to position the revolving cylinder on the borehole and to fill the borehole. In an accident during such a positioning operation, the waste material might scatter radioactive debris over the seabed, which will cause an environmental disaster.
The general object of the present invention is to at least partially eliminate the above mentioned drawback and/or to provide a useable alternative. More specific, it is an object of the invention to provide a method and system which increases safety during a disposal of waste into a drilled borehole.
According to the invention, this object is achieved by a method for disposing a waste into a drilled borehole in a subtending tectonic plate according to claim 1.
According to the invention, the method comprises a step of drilling a borehole in a tectonic plate. The borehole is drilled in a conventional manner by a deep sea drilling method. The drilling method comprises a step of installing a wellhead at a seabed of the tectonic plate. The wellhead comprises a borehole channel. The borehole channel extends in an axial direction. The borehole channel has a lower end and an upper end. The lower end faces the seabed. The borehole channel extends away from the seabed in an upwards direction. The upper end faces upwards to a sea surface. The wellhead is provided with a subsea blowout preventer, also called a BOP, to be able to close off the borehole channel in case of an emergency.
The drilling method comprises a step of connecting a riser to the upper end of the borehole channel of the wellhead. In a step of the drilling method, a drill string is guided from sea level through the riser and through the borehole channel of the wellhead. The drill string is used for drilling the borehole into the tectonic plate. After drilling the borehole, the drill string is removed and taken out of the riser. After removing the drill string, preferably, a liner is introduced into the borehole via the riser to prevent the borehole from collapsing.
According to the invention, the method comprises a step of providing a docking station on the wellhead. The docking station may be integral with the wellhead, in particular integral with the blowout preventer, or mounted as a separate component. The docking station is arranged for docking a carrier to the docking station. The docking station has a docking member for docking the carrier to the docking station. In an assembly, the docking member is positioned alongside the upper end of the borehole channel of the wellhead, such that the upper end of the borehole channel remains free for maintaining a connecting of the riser in alignment with the borehole channel. The docking member is positioned radially with respect to the borehole channel. The borehole channel further comprises a waste inlet opening which is positioned in between the lower and upper end of the borehole channel. Preferably, the waste inlet opening is positioned in between the blowout preventer and the upper end of the borehole channel. The docking station comprises waste displacement means for taking out a waste from the carrier, moving the waste in a radial direction and introducing the waste from aside into the waste inlet opening of the borehole channel of the wellhead.
According to the invention, the method comprises a step of lowering a carrier from sea level to the docking station. The carrier is arranged to store at least one waste. The carrier comprises at least one storage for storing a waste. Further, the carrier comprises a shutter which can be moved in an open or closed position for unloading a waste from a storage.
According to the invention, the method comprises a step of docking the carrier to the docking member of the docking station.
According to the invention, the method comprises a step of opening the carrier at the docking station and unloading a waste from the carrier. The waste is handled by the waste displacement means. The waste displacing means places the waste into the borehole channel via the waste inlet opening. While displacing the waste towards the borehole channel, the waste moves in a radial direction. Preferably, the riser remains connected to the upper end of the borehole channel during the introduction of the waste into the waste inlet opening.
According to the invention, the method comprises a step of lowering the waste from the borehole channel into the borehole.
According to the invention, the method comprises a step of sealing the borehole by a stopper. A stopper may be a plug, a so called packer, or a seal may be provided by introducing a hardening substance into the borehole. The hardening substance is e.g. a cement material.
The method according to the invention may provide several advantages.
The method according to the invention allows the waste to be disposed in a safe manner. Waste is transported from sea level to the seabed by a carrier and introduced into a drilled borehole by using a docking station. The presence of the docking station and the waste inlet opening in the borehole channel allows a riser to remain connected to the wellhead during the introduction of the waste into the borehole. Herewith, a closed system is provided in that the riser shuts off the borehole channel at the upper end and the docked carrier shuts off an opening to the borehole channel which is formed by the docking member at the docking station which increases operational safety. Advantageously, the riser can be used as a guidance for the carrier. Additionally, the riser can be used after introducing the waste e.g. to seal the borehole or to introduce a dart to push waste further into the borehole.
In an embodiment of the method according to the invention, the waste displacement means comprises a waste passageway. The waste passageway is preferably a pipe-conduit for guiding a waste. Preferably, the waste passageway pipe-conduit has a closed conduit wall, such that a waste is wholly enclosed during a transport from the carrier to the borehole channel. Preferably, the waste passageway is shielded to prevent an emission of nuclear radiation. The waste passageway extends from the docking member to the waste inlet opening of the borehole channel. The waste passageway extends under an acute angle with respect to the axial direction of the borehole channel. Preferably, the acute angle is at most 45°, but preferably at most 30°. Herewith, the waste passageway advantageously allows an introduction of a waste into the borehole channel by gravity, which may advantageously make driving components to actively handle the waste redundant.
In an alternative embodiment of the method according to the invention, the waste displacement means may comprise at least one robot arm. At a distal end, the robot arm has a grip which is arranged to grip a waste. After gripping the waste, the waste is radially moved by the robot arm and introduced into the borehole channel. Subsequently, the waste is released, such that the waste moves down into the borehole.
In an embodiment of the method according to the invention, the drilled borehole is drilled along a curved path. The curved path includes a part of section which extends in an imaginary plane. The imaginary plane is substantially in parallel with a dividing plane in between the sub tending tectonic plate and a continental plate. In this context, the wording 'in parallel' and 'substantially in parallel' means 'in parallel' seen from a technical point of view and not from a pure mathematical point of view. From a technical point of view some tolerances are foreseen, e.g. an angle of deviation of about 10° from pure parallel in a mathematical sense. Advantageously, in comparison with vertical drilling, a curved path allows a longer borehole which provides more available space to dispose waste. In particular, the curved path includes a slanted section. Preferably, the curved path comprises a path section which extends in a direction under an acute angle with respect to a horizontal reference of most 45°, in particular at most 30°, and preferably at most 15°. A horizontal reference is for example defined by a plane substantially in parallel with a sea surface. Advantageously, in comparison with vertical drilling, horizontal drilling may provide a longer borehole which provides a larger disposal for waste.
In an embodiment of the method according to the invention, the drilled borehole is drilled along a curved path which at least partly extends in the imaginary plane in parallel with the dividing plane, wherein a path section extends in a horizontal direction along at least 5 km, more in particular at least 10 km.
In an embodiment of the method according to the invention, a plurality of boreholes is drilled, wherein said plurality of boreholes comprise a plurality of borehole sections which extend in parallel with each other. The plurality of borehole sections form a borehole matrix. Advantageously, the borehole matrix provides a large space for a disposal for waste.
In an embodiment of the method according to the invention, the waste is unloaded from the carrier by opening the shutter by a remote control. Advantageously, the waste can be maintained in a shielded space inside the carrier to protect an environment from a radiation. In an embodiment of the method according to the invention, the carrier is lowered from sea level by a hoisting line. In comparison with an underwater vehicle which can be used to lower the carrier, the hoisting line provides a more safe transport of the carrier to a great depth of e.g. 2000 m in that a risk of losing contact with the carrier is minimised.
Preferably, the riser is connected to the wellhead during the lowering of the carrier, such that the carrier can be lowered along the riser.
In an embodiment of the method according to the invention, the carrier engages the riser during to the step of lowering the carrier. Advantageously, the riser guides the carrier to the docking station at the seabed.
In an embodiment of the method according to the invention, the borehole is sealed by introducing the hardening substance into the borehole through the riser. The presence of the riser allows a reliable introduction of the hardening substance. Advantageously, no reconnection of the riser is necessary. The riser is connected during a drilling operation and may remain connected during a step of introducing a waste into the borehole.
In an embodiment of the method according to the invention, the borehole is drilled by a deep sea drilling method. In the deep sea drilling method, the wellhead is installed at a seabed at a depth under sea level of at least 2000 m, in particular at least 3000 m. Typically, a conventional deep sea drilling method is available to install a wellhead at a seabed at a depth of at most 4000 m. Preferably, the borehole is drilled by a horizontal drilling method.
Further preferred embodiments are defined in the dependent claims.
Further, the invention relates to a waste disposal system for disposing a waste into a subsea drilled borehole. To carry out the above described method according to the invention, the waste disposal system according to the invention comprises several devices.
The waste disposal system according to the invention comprises a wellhead to provide an entrance to the borehole. The wellhead includes a borehole channel which extends in an axial direction. In operation, the borehole channel of the wellhead is in alignment with the drilled borehole. The borehole channel has an upper end which is connectable to a riser. The borehole channel is connectable in fluid communication with the riser via the upper end of the borehole channel. The borehole channel has a lower end which is in operation in fluid communication and aligned with the drilled borehole.
The waste disposal system according to the invention comprises a riser which is connectable to the upper end of the borehole channel.
The waste disposal system according to the invention comprises a subsea blowout preventer, a so-called BOP, for closing the borehole channel in an emergency situation. In an embodiment, the blowout preventer may be mounted on top of the wellhead as a separate component. The blowout preventer provides an extension of the borehole channel. The blowout preventer is positioned in between the riser and the wellhead. Alternatively, the blowout preventer may be incorporated in the wellhead.
The waste disposal system according to the invention comprises a carrier for underwater transporting at least one waste form a sea level to the wellhead at a seabed. The carrier comprises at least one storage which are each arranged to store a waste. Further, the carrier comprises a shutter to open or close a storage and to unload a waste from the carrier.
The waste disposal system according to the invention comprises a docking station including a docking member for docking the carrier to the docking station. The docking member is in an assembled condition with the wellhead radially spaced apart from the borehole channel. The docking member is positioned at a radial position outside the borehole channel, such that a docked carrier is eccentrically positioned at a position outside the borehole channel. Advantageously, a carrier can be docked at a position beside the riser. Advantageously, the riser can remain connected to the wellhead during a step of introducing a waste into the borehole. The docking station comprises a waste displacement means for displacing a waste in a radial direction from a docked carrier towards the borehole channel of the wellhead, which borehole channel is aligned with the riser.
In an embodiment of the waste disposal system according to the invention, the docking station is connectable to the wellhead. The docking station may be connectable to the blowout preventer on top of the wellhead to connect the docking station to the wellhead. In an alternative embodiment of the waste disposal system according to the invention, the docking station and the wellhead are integrated as a one piece item. In a further embodiment, the docking station may be incorporated in the blowout preventer which can be installed in between a riser and a wellhead.
In an embodiment of the waste disposal system according to the invention, the waste displacement means is a waste passageway which is arranged to guide a waste by gravity. The waste passageway extends in an inclined direction with respect to the axial direction of the borehole channel. The waste passageway is a passive device without driving components. The waste passageway may be trough-shaped, but is preferably formed by a pipe-conduit with a fully closed circumferential wall which is in fluid communication with the borehole channel.
In particular, the waste passageway is a branched off passageway of the borehole channel. At an intersection, the waste passageway and the borehole channel together define a Y-connection. In an embodiment, the waste passageway is a pipe-conduit and the borehole channel is a pipe-conduit, wherein the waste passageway pipe-conduit is connected, in particular welded, to an outer wall of the borehole channel pipe-conduit under an acute angle.
Preferably, the borehole channel extends in a linear axial direction, in particular in a substantially vertical direction. In particular, the waste passageway extends in a linear direction under an acute angle with respect to the axial direction of the borehole channel.
In particular, at an intersection of the borehole channel and the waste passageway, the waste passageway extends in a direction under an acute angle of at most 20°, in particular at most 10° with respect to the axial direction of the borehole channel. Advantageously, such a small acute angle allows a smooth and reliable introduction of waste from the waste passageway into the borehole channel.
In an embodiment of the method and waste disposal system according to the invention, the waste is packaged in a container, a so-called waste container. The container may comprise a box or cylinder with sidewalls including lead or other radiation shield material. The container may be a glass container. In an embodiment, the waste container comprises an elongated body including at least one flexible body section to allow the waste container to curve when guided along a curved waste passageway. Preferably, the waste container further comprises at least one roller e.g. a ball bearing at an outer circumference of the body. Preferably, the at least one roller is provided at a tip of the body. Advantageously, the at least one roller reduces a friction of the waste container when guided along the waste passageway.
In particular, the waste is a nuclear waste. In an embodiment of the waste disposal system according to the invention, the carrier is arranged for transporting at least one nuclear waste container. The carrier comprises a nuclear shield for shielding emitting nuclear radiation.
In an embodiment of the waste disposal system according to the invention, the carrier comprises at least one storage, preferably a plurality of storages for storing each a volume of waste.
In an embodiment of the waste disposal system according to the invention, the carrier comprises an elongated carrier body, which carrier body has a front end and a back end. The front end of the carrier body is arranged for the docking the carrier to the docking member of the docking station. The front end comprises a shutter for opening and closing the carrier body for unloading a waste.
In an embodiment of the waste disposal system according to the invention, the system further comprises a riser which is connectable to the upper end of the wellhead. Advantageously, the riser can be used to seal off the borehole after introducing at least one volume of waste.
In an embodiment of the waste disposal system according to the invention, the riser of the system comprises an external rail which extends along an outer surface of the riser which is arranged to guide a carrier along the riser.
In an embodiment of the waste disposal system according to the invention, the wellhead comprises a blowout preventer for closing the borehole channel in an emergency situation. In particular, the blowout preventer is mounted in between the wellhead and the riser. Advantageously, herewith, the waste disposal system according to the invention is arranged to be used in a deep sea drilling method.
Further, the invention relates to a blowout preventer which is arranged to close a borehole in case of an emergency situation. The blowout preventer is configured to be installed in between a wellhead and a riser. The blowout preventer comprises a blowout channel which extends in an axial direction and a blowout shutter to close the blowout channel in case of emergency. According to the invention, the blowout preventer further incorporates a docking station comprising a waste passageway and a docking member. The waste passageway is configured for guiding a waste. The waste passageway is connected to the blowout channel, such that a waste can be supplied from the waste passageway into the blowout channel. Subsequently, the waste can be lowered into the drilled borehole which is aligned with the blowout channel. The docking member is configured for docking a carrier which carrier stores at least one waste. The docking member is connected to and arranged in communication with the waste passageway, such that a waste which is released from the carrier can be transported by the waste passageway into the blowout channel. Advantageously, the blowout preventer according to the invention can be installed as a separate item onto the wellhead and incorporates a docking station for receiving a carrier and for transferring the waste to the borehole.
The above-mentioned features of the waste passageway embodied in the wellhead can in a same manner be embodied in the blowout preventer. For example, the acute angle in between the borehole channel and the waste passageway can be equally arranged in between the blowout channel and the waste passageway.
The invention will be explained in more detail with reference to the appended drawings. The drawings show a practical embodiment according to the invention, which may not be interpreted as limiting the scope of the invention. Specific features may also be considered apart from the shown embodiment and may be taken into account in a broader context as a delimiting feature, not only for the shown embodiment but as a common feature for all embodiments falling within the scope of the appended claims, in which:

Fig. 1 shows in a schematic view a location with a subduction zone;
Fig. 2 shows the subduction zone of fig. 1 in further detail, wherein a waste disposal system according to the invention is arranged at a location nearby;
Fig. 3 shows the waste disposal system of fig. 2 in further detail, wherein a carrier carrying at least one waste is lowered from a vessel to a wellhead with a docking station at a seabed;
Fig. 4 shows the wellhead of fig. 3 in further detail, wherein a waste passageway provides an interconnection between the docking station and a borehole channel of the wellhead and
Fig. 5 shows the wellhead of fig. 3, wherein the carrier is embodied as a toroidal carrier including a ringshaped inner space for storing waste.

Fig. 1 illustrates in a schematic view a location for a permanent disposal of a waste. The location is situated at a subduction zone 6. The subduction zone 6 is characterised by a spot of compacting sediment 9, which is positioned in between a continental tectonic plate 7 and a subtending tectonic plate 4. A sediment layer 3 is situated on top of the subtending tectonic plate 4. A top surface of the sediment layer 3 provides a seabed 2 under a sea level 1 of an ocean surface.
The subtending tectonic plate 4 moves on earth mantle 5 towards the continental tectonic plates 7 and is forced downwards into the earth between the mantle parts 5 and 8. This movement forms a more or less steep trench while the sediment layer 3 on top of the plate 4 is at least partly stopped by the continental plate 7 and compacted near the spot indicated 9. A distance in between the ocean surface 1 and the top surface 2 of the sediment layer 3 is mostly about 3000 m in case of normal subduction zones. The trench itself could be more than 6000 to 8000 m deep. A preferred location to carry out the method according to the invention for disposing a waste at a subduction zone 6, has a depth of at most 4000 m, preferably at most 3000 m which allows a conventional subsea drilling method to be carried out.
Fig. 2 shows the location of fig. 1 in further detail and further illustrates a waste disposal system according to the invention. The waste disposal system is arranged to dispose at least one waste into a subsea drilled borehole. The waste disposal system is positioned close to, but outside the region of the compacted sediment 9. Advantageously, the method according to the invention is carried out in a region near the region of the compacted sediment 9, because in this region, the hardness of the sediment is relatively low. In this region, the sediment is not yet compacted to a soft rock. A boundary of the region of compacted sediment 9 is provided at a foot of the rising sediment. Preferably, the method according to the invention is carried out in a region at a distance of at most 100 km away from the boundary of the region of compacted sediment 9.
As illustrated in fig. 2 and in further shown in detail in fig. 3, the waste disposal system is installed from a vessel 10. The vessel 10 is floating at the ocean surface 1. The waste disposal system comprises a wellhead 13 which is installed at a conventional manner at the seabed 2. The waste disposal system further comprises a riser 11 which extends from the wellhead 13 in an upwards direction to the vessel 10. Borehole 14, 15, 16 is drilled underneath the wellhead 13 at a conventional manner. The borehole is drilled along a curved path. The curved path comprises a substantially vertical first section 14, a curved intermediate section 15 and a substantially horizontal end section 16. The curved intermediate section 15 is curved to an angle of at least 75° to at most 85° with respect to a horizontal reference, such that the following substantial horizontal end section 16 has an inclination under an acute angle of about 15° to 5° with respect to the horizontal reference. Practically, a sea surface defines such a horizontal reference. Preferably, the end section 16 extends in an imaginary plane which is in parallel with a dividing plane in between the subtending tectonic plate 4 and the continental plate 7. Preferably, the end section 16 extends in a direction in the imaginary plane under an acute angle with respect to the horizontal reference. Herewith, the end section 16 extends in a direction transverse of the cross section which is illustrated in figure 2.
The wellhead 13 provides an entrance to the borehole 14,15,16 by a borehole channel. The borehole channel of the wellhead 13 extends in a linear direction. The borehole channel defines an axial direction. The borehole channel is aligned with the borehole. The borehole channel has a lower end which is centred on top of the borehole. The lower end of the borehole channel provides an access to borehole. The borehole channel has an upper end which is connected to the riser 11. The upper end of the borehole channel provides access to the borehole channel.
Further, the wellhead 13 comprises a blowout preventer. The blowout preventer is arranged as a safety device to shut off the borehole in case of an emergency situation. The blowout preventer is mounted on top of the wellhead 13. The blowout preventer is mounted in between the wellhead 13 and the riser 11.
Further, the waste disposal system comprises a docking station 12 to dock a carrier 17. The carrier 17 is lowered by a hoisting line 18 from the vessel 10 at the ocean surface 1. The carrier 17 engages with the riser 11, such that the riser 11 pilots the carrier to the wellhead 13. The riser 11 comprises a rail at an outer surface to guide the carrier 17.
Fig. 4 shows the wellhead 13 including a docking station 12 in a schematic view in further detail. The wellhead 13 has a borehole channel 131. The borehole channel 131 extends through the wellhead 13. The riser 11 is connected to an upper end 138 of the borehole channel 131. The borehole channel 131 is aligned with the borehole 14. A lower end 137 of the borehole channel 131 is centrally positioned above the borehole 14.
The docking station 12 comprises a docking member 120. The docking member 120 is positioned radially at a distance away from the upper end of the borehole channel 131. The docking member is positioned at a radial position alongside the borehole channel 131. The docking member is positioned besides the riser 11. The borehole channel 131 has a waste inlet opening which is positioned in between the lower and upper end 137, 138. The waste inlet opening is arranged to provide an entrance of waste into the borehole channel. The waste inlet opening is located in a circumferential wall which defines the borehole channel. The docking station 12 further comprises a waste passageway 121 to displace a waste about a radial distance from the docking member via the waste inlet opening 139 into the borehole channel. The waste passageway 121 is a pipe-conduit which extends from the docking member 120 to the borehole channel 131. The waste passageway 121 is connected under an acute angle to the borehole channel 131 at a position in between the upper end and end the lower end. A waste can be loaded from a docked carrier 17 and transported through the waste passageway to the borehole channel 131. Subsequently, the waste can be further lowered into the borehole 14. After sealing the borehole 14 by inserting a plug or supplying a hardening substance through the riser 11 into the borehole 14, the waste is deposit in a safe manner in the subtending tectonic plate 4.
Fig. 5 shows an embodiment of the carrier 17 in which the carrier comprises a ringshaped carrier body 171, in particular a toroidal carrier body. The carrier body 171 is ring shaped. The carrier body 171 has a through pass which is arranged for allowing the riser 11 to pass through. The trough pass is centrally positioned at a carrier body 171.
The carrier body 171 includes a storage for storing waste during a transportation of the waste from the vessel 10 to the docking station 12. Preferably, the storage extends along a full circumference of the carrier body 171 in which the storage is ring shaped. The storage circumvents the centrally positioned through pass. Particularly, the storage comprises at least one storage compartment.
The carrier 17 is lowered by at least one, but preferably a number of hoisting lines 18 from the vessel 10 at the ocean surface 1. The carrier 17 engages with the riser 11, such that the riser pilots the carrier to the wellhead 13. Preferably, the riser 11 comprises at least one external rail connected at an outer surface of the riser 11 for guiding the carrier 17.
The invention includes an aspect in that the borehole is drilled along a curved path as defined in dependent claim 3, 4 and 5 which aspect is considered also to be advantageous in combination with other waste disposal methods, e.g. prior art methods, than currently claimed in claim 1.
Thus, according to the invention a method and waste disposal system is provided for disposing a waste into a drilled borehole in a subtending tectonic plate which allow to dispose waste in a safe manner. The waste is transported from sealevel to the seabed by a carrier and introduced into a drilled borehole by using a docking station. The docking station allows a riser to remain connected to a wellhead during the introduction of the waste. Advantageously, the riser can be used in a first instance as a guidance for the carrier. Additionally, the riser can be used after introducing the waste into the bore hole, e.g. to seal the borehole or to introduce a dart to push waste further into the borehole. A further advantage provided by the invention is that at least one borehole is drilled along a curved path including a substantially horizontal section which in comparison with a vertical drilling method increases a maximum length of the borehole which advantageously allows an increase in storage of waste.

Claims

Method for disposing a waste into a drilled bore hole in a subtending tectonic plate (4) which preferably moves towards a subduction zone (6), comprising the step of:
- drilling a bore hole (14,15,16) in the subtending tectonic plate (4), including the following steps:
- installing a well head (13) at a seabed (2) above the subtending tectonic plate (4), which wellhead (13) has a borehole channel (131) comprising a lower end (137) and an upper end (138), which borehole channel extends in an axial direction, wherein the borehole channel further comprises a waste inlet opening (139) which is positioned in between the lower and upper end (137,138);

- providing a subsea blowout preventer (BOP) to be able to close off the borehole channel (131);

- connecting a riser (11) to the upper end of the borehole channel (131) of the well head (13);

- guiding a drill string through the riser (11) and through the well head (13) and drilling the bore hole into the tectonic plate;

- removing the drill string out of the riser;

wherein the method further comprises the steps of:
- providing a docking station (12) on the well head, wherein the docking station is adapted to dock a carrier, wherein the docking station comprises a docking member (120) for docking the carrier to the docking station (12) which docking member is radially positioned with respect to the upper end of the borehole channel (131) of the wellhead and wherein the docking station has a waste displacement means (121), preferably a waste passageway, for radially displacing the waste and introducing said waste into the borehole channel (131) of the well head;

- lowering a carrier (17), preferably along the riser (11), from sea level (1) to the docking station (12), wherein the carrier (17) comprises at least one storage for the waste and a shutter to unload the waste from the at least one storage;

- docking the carrier (17) to the docking member (120) of the docking station (12), such that the carrier is positioned radially outside the borehole channel (131);

- opening the shutter of the carrier (17) at the docking station (12);

- unloading a waste from the carrier (17);

- radially moving and placing the waste into the borehole channel (131) via the waste inlet opening (139) by the waste displacement means;

- lowering the waste from the borehole channel (131) into the bore hole (14,15,16);

- sealing the bore hole (14,15,16) by introducing a stopper, e.g. a hardening substance or a plug, into the bore hole.
Method according to claim 1, wherein the waste is transported through the waste passageway (121) via the waste inlet opening (139) into the borehole channel by gravity.
Method according to any of the preceding claims, wherein the drilled bore hole is drilled along a curved path which curved path includes a path section which extends in an imaginary plane which is substantially in parallel with a dividing plane defined by the subtending tectonic plate (4) and a continental plate (7).
Method according to claim 3, wherein said path section, which is in particular an end section (16), extends in a direction under an acute angle with respect to a horizontal reference of at most 45°, in particular at most 30°, and preferably at most 15°.
Methods according to claim 3 or 4, wherein a plurality of boreholes is drilled, wherein said plurality of boreholes comprise a plurality of borehole sections which extend substantially in parallel with each other to define a borehole matrix which serves as a disposal for waste.
Method according to any of the preceding claims, wherein the waste is unloaded from the carrier (17) by opening the shutter by a remote control.
Method according to any of the preceding claims, wherein the carrier (17) is lowered from sea level (1) by a hoisting line (18) and, wherein in particular the carrier engages the riser (11) during the step of lowering the carrier (17), such that the carrier is guided by the riser to the docking station.
Method according to any of the preceding claims, wherein the borehole is sealed by introducing the hardening substance through the riser (11) into the borehole.
Waste disposal system for disposing a waste into a subsea drilled bore hole (14,15,16) comprising:
- a wellhead (13) for providing an entrance to the borehole, which well head (13) includes a borehole channel (131) which extends in an axial direction and which borehole channel (131) includes an upper end (138) which is in operation in fluid communication with a riser (11) and a lower end (137) which is in operation in fluid communication with the drilled borehole, in which the borehole channel (131) is in operation in alignment with the borehole (14,15,16), wherein the borehole channel further comprises a waste inlet opening (139) which is positioned in between the lower and upper end;

- a riser (11) which is connectable to the upper end of the borehole channel (131);

- a subsea blowout preventer (BOP) for closing the borehole channel (131) in an emergency situation;

- a carrier (17) for underwater transporting at least one waste from a sea level (1) to the wellhead (13) at a seabed (2);

- a docking station (12) comprising a docking member (120) for docking the carrier (17) to the docking station (12), wherein the docking station comprises a waste displacement means (121) for displacing a waste in a radial direction from the carrier (17) towards and into the waste inlet opening (139) of the borehole channel (131) of the wellhead (13).
Waste disposal system according to claim 9, wherein the waste displacement means comprises a waste passageway (121) for guiding a waste, wherein the waste passageway (121) is in communication with the borehole channel (131) of the well head (13) and extends from the docking member (120) to the waste inlet opening (139) in an inclined direction with respect to the axial direction of the borehole channel, such that a waste can be guided and supplied to the borehole channel (131) via the waste passageway (121).
Waste disposal system according to claim 10, wherein the waste passageway is a pipe-conduit for guiding the waste, wherein the waste passageway pipe-conduit is connected to the borehole channel (131) of the wellhead (13) under an acute angle with respect to the axial direction at a position in between the upper and lower end of the borehole channel (131).
Waste disposal system according to any of the claims 9-11, wherein the carrier (17) comprises a nuclear shield for shielding an emission of nuclear radiation from the waste.
Waste disposal system according to any of the claims 9-12, wherein said riser (11) comprises an external rail for guiding the carrier (17) along the riser (11), which rail is connected to an external surface of the riser.
Waste disposal system according to any of the claims 9-12, in particular according to claim 13, wherein the carrier (17) comprises a ring-shaped carrier body (171) including a through pass to allow a riser (11) to pass through.
Blowout preventer system arranged to shut off a borehole in case of an emergency situation, wherein the blowout preventer is a subsea blowout preventer which is configured to be installed in between a wellhead (13) and a riser (11), wherein the blowout preventer comprises a blowout channel which extends in an axial direction and which blowout channel forms an extension for a borehole channel of the wellhead (13) and wherein the blowout preventer further comprises a blowout shutter to close the borehole channel in case of emergency, wherein the blowout preventer further incorporates a docking station (12) comprising:
- a waste passageway (121) for guiding a waste, wherein the waste passageway is connected to the blowout channel, such that a waste can be supplied from the waste passageway via a waste inlet opening (139) into the blowout channel;

- a docking member (120) for docking a carrier (17) which carrier is arranged for storing at least one volume of waste, wherein the docking member is connected to the waste passageway (121), such that a waste which is released from the carrier can be transported along the waste passageway via the waste inlet opening (139) into the blowout channel.