Offshore subsea drilling

Abstract

A subsea vertical drill is disclosed having a drill assembly and a vertical feed system, the drill assembly formed from a riser pipe and a drill body, the riser pipe having a first end, a second end, and a length extending between the first end and the second end, the drill body including a drill bit and coupled to the first end of the riser pipe, the vertical feed system configured to advance the drill assembly in a first direction. The riser pipe is provided with at least one rack extending along at least a portion of the length of the riser pipe, and the vertical feed system includes a motor coupled to a pinion gear, the pinion gear arranged to mesh with the rack to advance the drill assembly.

Description

TECHNICAL FIELD

[0001] The present invention relates to a subsea vertical drilling machine and related method for seabed drilling, in particular a method of installing a pile or casing and drilling into the seabed to form an offshore foundation. The invention is particularly suitable for near shore applications, for example for forming a foundation pile for a wind energy device. BACKGROUND

[0002] Interest in renewable energy systems has led to various offshore energy applications, such as offshore wind farms. As the field of offshore wind farms has developed, it has been observed that it is desirable to move to locations further from the shore, to marine locations with greater water depth.

[0003] To achieve this, the energy device, such as a wind turbine, must have a stable foundation in the seabed, and / or be anchored to the seabed. Developing towards increasing water depth and increasing distance from the shore presents challenges when forming the foundation. At the same time, the impact on the marine environment, for example noise and vibrations that can disturb marine life, must be kept under control when drilling and piling on the seabed.

[0004] In "Bauer Maritime Technologies", "Seabed Drilling for Marine Energy", Bauer Maschinen GmbH 1.2016 and downloadable via http: / / www.bauerrenewables.co.uk / export / shared / documents / pdf / bst / print / 905_042_2_Seabed-Drilling-for-Marine-Energy.pdf, various systems for seabed drilling are shown.

[0005] A subsea pile drilling tool for release drilling of a driven pile is described in http: / / www.tms.nl / documents / news-items / subsea-pile-drilling-tool.xml?lang=en.

[0006] However, they all have limited production rates and push-down capacity and are not able to provide the possibility to carry out sufficient drilling depth under a range of different ground conditions, such as rock. Furthermore, typically these drilling tools require a casing to be clamped thereto during the drilling operation, which casing has been installed into the ground or drilled into the ground during the drilling operation. SUMMARY

[0007] It is an object of the present invention to provide a subsea drilling machine with increased drilling rate.​

[0008] It is a further object of the present invention to provide a subsea drill rig providing increased productivity in setting a pile or shaft in the seabed and drilling into the seabed.

[0009] It is a further object of the present invention to provide a subsea drill rig enabling large drilling depths at larger water depths.

[0010] At least some of these objects are achieved by a subsea drill rig.

[0011] In a first aspect, there is provided a subsea drill rig, comprising:

[0012] a drill assembly comprising:

[0013] a riser pipe having a first end, a second end and a length extending between the first end and the second end; and

[0014] a drill rig body coupled to the first end of the riser pipe, the drill rig body comprising a drill head; and

[0015] a feed system configured to advance the drill assembly in a first direction;

[0016] wherein the riser pipe is provided with at least one rack extending along at least a portion of the length of the riser pipe; and wherein the feed system comprises a motor coupled to a pinion gear, the pinion gear being arranged to engage with the rack to advance the drill assembly.

[0017] The rack and pinion gear cooperation enables substantially continuous advancement of the drill head into the seabed and retraction of the drill head from the seabed. There is no need to interrupt the drilling action for re-setting the system or similar solutions such as at the end of a stroke. Moreover, the rack and pinion system enables increased push force of the drill head into the seabed. Thus, increased drilling rate can be achieved.

[0018] The feed system enables fine feed control of the drilling rate and drilling force exerted at the cutting surface of the drill head. This enables the drill rig to be applied to a range of different ground conditions, from loose sand to hard clay and hard rock.

[0019] In an alternative, the cooperating rack and pinion can be replaced with a hydraulic arrangement, as will be described in further detail below with reference to a second aspect of the invention.

[0020] The drill rig body comprising a drill head is suspended to the riser pipe and driven by the riser pipe, as defined above.

[0021] With a drilling assembly as defined herein, the riser receives, reacts and / or transmits operational drilling torque, crown force and pullback force. It also reacts to environmental wave, wind and current loads. Torque from the drill bit is transmitted via the riser to the feed system and further to the structure to which the feed system is fixed, e.g. by clamping means.

[0022] The rack is preferably formed as an integral structure of the riser.

[0023] The length of the riser and the extension of the rack along the riser define the drilling depth, which can be achieved without interruption of the operation. The subsea drilling machine is therefore referred to as a single-trip system.

[0024] The at least one rack preferably extends over substantially the entire length of the riser. The drilling depth that can be achieved by the machine can thus be maximized.

[0025] Preferably, the riser is provided with a plurality of said racks, which are distributed along the circumference of the riser, each rack extending along at least a portion of the length of the riser, and wherein the feed system comprises a corresponding plurality of pinions or pinion sets, each pinion or pinion set being arranged to cooperate with one rack. The racks preferably extend along substantially the entire length of the riser and are symmetrically distributed along the circumference of the riser. Preferably, 2, 3 or 4 racks are provided on the riser. Stable positioning and movement of the riser relative to the feed system can thus be achieved.

[0026] The vertical feed system can comprise a plurality of pinions for each rack. By arranging a plurality of pinions to mesh with each rack, the stability and / or reliability of the propulsion action can be increased.

[0027] When the desired drilling depth has been reached, the vertical feed system can also be operated in reverse to retract the drilling assembly at the end of the drilling operation. Also, the vertical feed system can be operated in reverse for partially retracting the drill bit during the operation, e.g. when a casing is provided and the casing is drilled into the seabed (as will be described in further more detail below).

[0028] The feed system is typically a vertical feed system and the first direction is a vertical direction. The subsea drilling machine can then also be referred to as a vertical drilling machine, since it is designed for drilling substantially vertically into the ground or seabed. However, the drilling machine can be arranged to drill in a direction other than vertical, e.g. for setting a framed pile on an offshore or near-shore structure.

[0029] The drill bit is provided with a drill unit and / or a cutter, which can be selected depending on the soil or ground conditions at the drilling location. The drill bit can thus be adapted to different ground conditions within a range.

[0030] The drill bit can comprise a down-the-hole reamer. When activated, the down-the-hole reamer extends radially outwards from the drill bit, thereby extending the cutting diameter of the seafloor drilling machine. A brake device is typically provided in the drill bit to activate the down-the-hole reamer (e.g. to power the down-the-hole reamer).

[0031] The drill bit (in particular the drill machine unit and / or the cutter) can be locally driven via a seafloor gearbox and motor arranged in the drilling machine body.

[0032] The drill bit is preferably designed such that the diameter of the drill bit can be varied. The diameter is typically in the range of 2 to 3.5 meters, or even larger. In many applications, a nominal or default diameter of 3 meters is used.

[0033] Furthermore, the outer diameter of the drilling machine body can be adjustable in order to match the drilling diameter. To this end, the drilling machine body can be provided with adjustable and / or interchangeable outer skids. By setting these in accordance with the drilling diameter, stability of the drilling machine body during drilling machine propulsion can be provided.

[0034] Hydraulic and / or electrical umbilicals, cables or wiring for providing control, power supply and / or other services to components arranged in the drilling machine body can be arranged inside the riser. They can thus be protected from environmental and / or operational elements.

[0035] Further advantageously, the riser is equipped at its second or upper end with a docking feature or docking station for coupling to a lifting tool for lifting the drill machine assembly into and out of the water.

[0036] The riser preferably comprises a plurality of riser modules, each riser module being provided with at least one rack extending along its length; the riser modules being coupled to each other such that the at least one rack of different modules are substantially aligned with each other. The length of the riser can thus be set to substantially correspond to the length of the pile foundation. The riser can be assembled such that the length of the riser corresponds to the length of the pile foundation. The modules are preferably bolted together prior to the drilling operation, thereby forming the complete riser. There will thus be no need to add riser modules or sections during the drilling operation. The length of the riser modules or sections is in the range of 5 to 15 meters, preferably 10 meters.

[0037] The feeding system can be coupled to a pipe (also referred to as a fishing pipe) that is configured to be coupled to a second entity (such as a drilling machine receiving portion of a rig) and substantially fix the feeding system relative to the second entity. To this end, the pipe can be provided with a collar, which can also be referred to as a landing interface. Thus, the feeding system can be fixedly coupled to a rig (such as a seabed rig, conductor rig and / or pile gate) in a clamping manner and / or in other ways to be driven into the seabed. The sleeve can be configured to clamp the rig externally for sleeve casing sleeve drilling and open hole sleeve drilling, or to clamp the pile internally for pile release drilling. Thus, drilling loads and environmental loads can be transferred to the rig or the pile being drilled. By this arrangement, the rotational cutting speed can be increased, thereby providing a high drilling productivity. The rotational torque can be increased, thereby providing a high drilling power. For sleeve casing installation, a high push down capacity can be achieved. Thus, a higher productivity than for prior art systems can be achieved.

[0038] The fishing pipe further protects the drill bit before and / or after the drilling operation. The fishing pipe encloses the drill bit before and during insertion of the drill machine into the rig. After the drilling operation, the drill bit can be retracted into the fishing pipe before being lifted out of the rig and / or a sacrificial casing that is inserted into the seabed during the drilling operation.

[0039] In some embodiments, the seabed drilling machine further preferably comprises a waste removal system; the waste removal system comprises a conduit extending through the drill bit and the upflow pipe, and a waste discharge outlet provided at the second end of the upflow pipe. Thus, a solid waste pipe is provided inside the upflow pipe and the drill bit, thereby being protected by the upflow pipe. The waste pipe is arranged to transfer the waste cuttings away from the drill bit and the drill machine cutting face provided on the drill bit, and to the waste discharge outlet. The seabed drilling machine preferably comprises a pump (also referred to as a mud pump) arranged in the drilling machine body, in particular in or near the drill bit, the pump being arranged to pump the waste from the drill bit to the waste discharge outlet. Thus, compared to an air lift waste removal system, the waste removal capacity can be increased, thereby increasing the drilling rate.

[0040] Optionally, in other embodiments, the drill machine can be configured to use an air lift waste removal.

[0041] According to the above, the components of the drill machine (i.e. the upflow pipe, the drill machine body comprising the drill bit, and the feeding system, which are advantageously composed of multiple parts or modules that are bolted together) are assembled together so as to form a single unit that can be lifted from the vessel by a crane, and positioned and lowered relative to the rig, and subsequently released from the crane. During the drilling operation, the crane is not required. Thus, the crane of the vessel can be used for other operations performed on or from the vessel.

[0042] The seafloor drill rig can further comprise one or more control units configured to control operation of one or more of the feed system, the drill rig (in particular the drill bit drive system), and / or the waste removal system. The control units can be configured to control operation of one or more parts or components of the feed system, the drill rig, and / or the waste removal system. Thus, the seafloor drill rig, or at least a part thereof, can be configured to operate independently (semi-) autonomously.

[0043] According to a second aspect, there is provided a seafloor drill rig comprising:

[0044] a drill assembly comprising:

[0045] a riser pipe having a first end, a second end, and a length extending between the first end and the second end; and

[0046] a drill rig body coupled to the first end of the riser pipe, the drill rig body comprising a drill bit; and

[0047] a feed system configured to advance the drill assembly in a first direction,

[0048] wherein the feed system comprises:

[0049] a first feed subsystem comprising a first set of hydraulic actuators arranged to cause a first gripper to move in the first direction, the first gripper comprising a first gripping device that, upon actuation of the first gripping device, grips and / or clamps the riser pipe; and

[0050] a second feed subsystem comprising a second set of hydraulic actuators arranged to cause a second gripper to move in the first direction, the second gripper comprising a second gripping device that, upon actuation of the second gripping device, grips and / or clamps the riser pipe.

[0051] The feed system of the drill rig according to the second aspect forms an alternative to the feed system of the drill rig of the first aspect and the one or more racks provided on the riser pipe. The first gripping device and the second gripping device can comprise a bladder device that can be hydraulically and / or pneumatically operated to grip or clamp the riser pipe with a force sufficient to carry the weight of the riser pipe and to exert a thrust force to advance the drill assembly into the ground or seabed.

[0052] By operating the first and second feed sub-systems in an alternating manner, the drill assembly, in particular the drill bit, can be substantially continuously advanced. While the first set of hydraulic actuators is operating to move the riser in a first direction via the first clamping device being activated to clamp or grip the riser, the second clamping device is in a deactivated state such that there is no clamping or gripping of the riser, and when the first set of hydraulic actuators reaches the end of its stroke or actuation interval, the second set of hydraulic actuators is set or reset to an initial state such that it is ready to be activated. When the first set of hydraulic actuators reaches the end of its stroke (i.e. the end of the range of movement of the first set of hydraulic actuators), the second clamping device is actuated and the first clamping device is deactivated, and the second set of hydraulic actuators is actuated, thereby continuing the advancement of the riser. Thus, by operating the first and second feed sub-systems in an alternating manner, the drill assembly can be advanced in a substantially continuous manner.

[0053] Thus, the advantages described for the first aspect as being achieved by the rack and pinion can at least to a large extent be achieved alternatively by using hydraulic actuators.

[0054] Various embodiments of the drill rig of the first aspect can be applied to the drill rig of the second aspect.

[0055] According to a third aspect, there is provided a subsea drill rig comprising:

[0056] a drill assembly comprising:

[0057] a riser having a first end, a second end, and a length extending between the first end and the second end; and

[0058] a drill rig body coupled to the first end of the riser, the drill rig body comprising a drill bit;

[0059] a feed system configured to advance the drill assembly in a first direction, and

[0060] a waste removal system comprising a conduit extending through the drill bit and the riser, and a waste exit port provided at the second end of the riser.

[0061] As described above with reference to the waste removal system of the drill rig according to the first aspect, the internal waste removal system enables efficient waste removal, thereby facilitating an increased rate of drilling.

[0062] The drill rig preferably comprises a pump (also referred to as a mud pump) arranged in the drill rig body, the pump being arranged to pump the waste from the drill bit to the waste exit port.

[0063] The subsea drill rig of the third aspect can further comprise any one or more features and / or embodiments of the subsea drill rig of the first aspect.

[0064] The seabed drill of the first, second and third aspects can each comprise respective features and / or embodiments as described above, and their respective technical effects and advantages.

[0065] According to a fourth aspect, there is provided a method of drilling a hole in a seabed, the method comprising the steps of:

[0066] providing a drill assembly comprising a riser pipe and a drill rig body coupled to a first end of the riser pipe, the drill rig body comprising a drill bit;

[0067] providing a feed system configured to advance the drill rig in a first direction;

[0068] assembling the drill assembly with the feed system to form a drill rig;

[0069] arranging a drill floor on the seabed, the drill floor comprising one or more drill rig receiving portions;

[0070] arranging the drill rig in one of the drill rig receiving portions;

[0071] fixing the feed system relative to the drill floor;

[0072] advancing the drill bit into the seabed by operating the feed system to move the riser pipe substantially continuously relative to the feed system while operating the drill bit; and

[0073] after reaching a final depth of the vertical borehole, retracting the drill rig from the borehole.

[0074] The method according to the fourth aspect is advantageously performed using the seabed drill according to the first or second aspect. Thus, the technical effects and advantages as described above are achieved with this method.

[0075] The step of advancing the drill bit is advantageously performed by rotating a pinion gear in mesh with a rack extending along at least a portion of the length of the riser pipe. This can be performed by the seabed drill of the first aspect.

[0076] Optionally, the step of advancing the drill assembly can be performed by alternatingly operating the first and second feed subsystems; wherein operating one of the first and second feed subsystems to advance the drill assembly while resetting the other of the first and second feed subsystems. This can be performed by the seabed drill of the second aspect.

[0077] The method can further comprise the steps of:

[0078] Before the step of arranging the drill rig in one of the drill rig receiving portions, a casing is arranged substantially around the drill rig body.

[0079] Since the drill rig according to the application does not require a casing or a cased hole to advance the drill bit into the ground, the length of the casing does not need to correspond to the drilling depth. The length of the casing can be chosen such that the borehole is stabilized during the drilling operation and during subsequent operations, such as introducing a pile into the borehole. Thus, a casing length corresponding to the depth of an unstable layer of the ground or seabed can be sufficient. When left in the hole after the drilling operation, the casing can be referred to as a sacrificial casing.

[0080] The casing can advantageously be clamped or fixed relative to the drill rig body by means of a clamping unit, e.g. in the form of a bladder, provided on the drill rig body. By inflating / deflating the bladder, the casing can be clamped / loosened relative to the drill rig body.

[0081] The casing can be arranged on the drill rig by lowering the rig assembly over the casing, thereby bringing the drill rig body into the casing. Once a certain relationship between the casing and the drill rig body has been achieved, the clamping unit can be activated in order to temporarily lock the casing relative to the drill rig body. The casing and the drill rig can be lowered into the seabed simultaneously. The casing and the drill rig can be simultaneously advanced into the seabed at least a certain depth as one unit.

[0082] In embodiments where the rig assembly is provided with a washpipe as described above with reference to the first aspect, the casing is preferably arranged between the washpipe and the drill rig body in such a way that the casing is substantially completely arranged between the washpipe and the drill rig body when the drill rig is lowered into the water.

[0083] The casing can advantageously be advanced into the seabed together with the rig assembly.

[0084] The position of the drill bit relative to the outer end of the casing can be set in dependence of the ground conditions at the rig location. Thus, the drill rig according to the application is suitable for a wide range of different ground conditions. If desired, the position of the drill bit relative to the casing can be adjusted during the drilling operation.

[0085] During the step of advancing the rig assembly into the seabed, the drill bit can protrude in front of the casing. This is advantageous when drilling in rock. By protruding the drill bit outside the casing, the drill bit can be moved in front of the casing so that the casing can be advanced into the hole formed by the operation of the drill bit. Thus, by means of the drill bit in a rock ground, the casing can be advanced into the ground.

[0086] Optionally, during said step of advancing the drill assembly into the seabed, the drill bit can be arranged within the casing. This is advantageous when drilling in unstable layers, such as sand and / or clay layers. Operating the drill bit within the casing facilitates stable drilling operations when drilling in sand and / or clay.

[0087] The method can comprise the step of further advancing the drill bit into the ground when the casing has been inserted into the seabed to a casing depth. As mentioned above, the depth can be set such that an unstable layer at the drilling location is covered, thereby stabilizing the borehole.

[0088] The step of advancing the drill bit can comprise activating and operating an underreamer cutter of the drill bit so as to drill with a diameter equal to or larger than the outer diameter of the casing.

[0089] The method can comprise removing waste via a waste return pipe arranged within the drill rig body and the riser pipe, and discharging the waste at a waste discharge outlet arranged at the second end of the riser pipe.

[0090] The step of retracting can advantageously be performed by reversing the feed system.

[0091] The feed system can also be reversed during part of the drilling operation, for example if a boulder or similar is hit when advancing the drill assembly. In this case, the advancement of the drill assembly can be interrupted, and the drill assembly is subsequently reset or repositioned before continuing the advancement of the drill assembly.

[0092] When advancing the drill assembly provided with the casing, the feed system can be reversed, as mentioned above, for example in order to adjust the position and / or orientation of the casing before resuming the advancement of the drill assembly and the casing.

[0093] The method described above can advantageously be performed semi-autonomously. One or more of the steps described above can be performed (semi-) autonomously or automatically.

[0094] The seabed drill rig described herein (also referred to as a vertical seabed drill rig) can advantageously be applied for pile drilling and driving, for example to form a foundation for an offshore energy device, such as an offshore wind farm. The seabed drill rig described herein is equally applicable for other types of marine energy devices, such as tidal turbines.

[0095] The drill rig as described herein will be expected to be used at water depths of 50 to 100 meters, for example 70 meters, and drill depths of up to 50 meters. However, the drill rig as described herein can be used at water depths of up to 200 meters.

[0096] As mentioned above, the drill rig provides open hole sleeve drilling, cased sleeve drilling, and pile release drilling.

[0097] By assembling the riser pipe to match the drilling depth and providing a rack that mates with the pinion of the vertical feed system, a single pass drilling system has been achieved.

[0098] As mentioned above, the drilling machine can be configured to operate in an independent, semi-autonomous manner.

[0099] The drilling machine can be used in various ground conditions, including unstable layers such as sand and gravel, where a foundation pile can be set with high stability and drilled into the seabed. The machine and method as described above can be used to set a cased hole and drill into unstable layers and underlying bedrock. BRIEF DESCRIPTION OF DRAWINGS

[0100] Further features and advantages of the present application will become apparent from the description of the application, given by way of non-limiting and non-exclusive example. These examples should not be interpreted as limiting the scope of protection. The skilled person will recognize that other alternative and equivalent embodiments of the application can be conceived and simplified to practice without departing from the scope of the present application. Embodiments of the present application will be described with reference to the accompanying drawings, in which similar or identical reference numerals designate similar, identical or corresponding parts, in which:

[0101] Figure 1 schematic illustration of an offshore wind energy installation is shown;

[0102] Figure 2a a perspective view of a seabed drilling machine according to an embodiment is shown;

[0103] Figure 2b a schematic cross-section of Figure 2a is shown;

[0104] Figure 3a a detail of Figure 2a the drilling machine shown is shown;

[0105] Figure 3b a schematic cross-section of Figure 3a is shown, showing a detail of a feed system according to an embodiment;

[0106] Figure 4 a detail of a drill bit according to an embodiment is shown;

[0107] Figure 5 a schematic illustration of a seabed drilling machine according to an alternative embodiment is shown;

[0108] Figure 6a a seabed drilling platform arranged on a seabed is shown schematically;

[0109] Figure 6bA part of a sea floor rig is shown in which a subsea drill is arranged according to an embodiment;

[0110] Figure 7a A jacket is shown mounted on the drill body; and

[0111] Figure 7b to 7d The feed process of a drill according to an embodiment of the invention is schematically shown. DETAILED DESCRIPTION

[0112] Figure 1 An energy device in the form of a windmill 1 mounted in or anchored into the sea floor via a foundation 2 is schematically shown. Figure 1 Different types of foundations 2 are shown, all of which include piles 4 drilled into and formed in the sea floor 6. The windmill is located at a water depth di in the sea, the piles 4 have a drilling depth d2. As mentioned above, there is an increasing interest in positioning offshore windmills in deeper water, which leads to various challenges, including drilling to greater water depths and reaching greater drilling depths even in poor ground conditions. The invention provides a subsea drill that drills to a water depth of typically about 70 to 100 meters or even up to 200 meters with a high drilling or production rate.

[0113] Figure 2a and 2b An embodiment of a subsea drill 8 according to the invention is shown (also referred to as a vertical subsea drill). Figure 2a A perspective view of the drill 8 is shown, whereas Figure 2b A schematic cross-section of the drill 8 is shown. Although a vertical subsea drill is described herein, it can be noted that the same concept can also be applied to a drill that drills in a direction that is inclined relative to the vertical direction.

[0114] As can be seen in Figure 2a , Figure 2b The drill includes a riser pipe 10 and a drill body 12 including a drill bit 14. The drill body 12 is arranged at a lower end 16 (also referred to as a first end) of the riser pipe 10. The riser pipe and the drill body are assembled together, thereby forming what is referred to herein as a rig assembly.

[0115] At an upper end 18 (also referred to as a second end) of the riser pipe 10, a spoil outlet 20 is provided, which is connected to a spoil pipe 48 arranged inside the riser pipe. Further, a docking station 22 for lifting arrangements is provided and / or coupled to the upper end 18 of the riser pipe.

[0116] The drilling rig 8 further comprises an upright feed system 24 arranged for causing movement of the riser 10 in order to advance the rig assembly in a vertical direction relative to the upright feed system. Thus, the drill bit is advanced into the seabed during drilling operations.

[0117] As can be seen in more detail in Figure 3a and Figure 3b , the riser 10 is provided with a plurality of racks 26 extending substantially along the entire length of the riser 10. The upright feed system 24 comprises a respective plurality of pinions 27 each driven by a motor 28. The pinions 27 are in mesh with the racks 26 in order to advance the rig assembly.

[0118] The racks 26 are distributed symmetrically around the circumference of the riser. The upright feed system 24 comprises a plurality of pinion sets 27 and associated motors 28, each pinion set being associated with one of the racks 26. In the illustrated embodiment, four racks and four pinion sets have been seen to provide stable and accurate advancement of the rig assembly. The pinion sets comprise four pinions associated with each rack. However, other numbers are possible.

[0119] The drilling rig body 12 is suspended to the riser 10 and is advanced into the seabed during drilling operations by means of the cooperating rack and pinion system, which can be seen in detail in Figure 3b . By means of the racks 26 extending along the length of the riser 10 and the pinions 27 in mesh with the racks 26, the drilling rig body can be advanced in a substantially continuous manner. The drilling depth is mainly limited by the length of the riser 10, in particular by the extension of the racks 26 provided on the riser 10.

[0120] As can be seen in Figure 2b , the riser 10 is composed of a plurality of riser modules (or sections) 30 bolted together, thereby forming one riser 10. The different modules 30 are oriented relative to each other such that the racks are aligned. By this arrangement, the length of the riser 10 can be set according to the intended drilling depth d2. The modules are installed together before the drilling operation starts.

[0121] As shown in Figure 2a and Figure 2b , the upright feed system 24 is coupled to a fishing pipe 32 provided with a collar 34 configured to be coupled to a rig receiving portion of a drilling rig deck, as will be described further below. The collar 34 can also be referred to as a landing and locking collar. Thus, the upright feed system 24 can be substantially fixed relative to the seabed rig deck and / or the casing.

[0122] The rig assembly, including the riser 10 and the drill rig body 12, can be assembled with the vertical feed system 24 and the fish pipe 32, such as to form a single rig. The single rig can be lifted from the vessel via the docking station 22 and lowered into the sea, and subsequently onto a seafloor rig table, as will be further described below. The fish pipe is also used to protect the drill bit 14 before and / or after the drilling operation, in particular when lowering the rig assembly into the seafloor rig table.

[0123] Figure 4 Details of the drill bit 14 are shown.

[0124] As can be seen in Figure 4 , the drill bit 14 comprises a plurality of cutters 38 (also referred to as rig units) that form a cutting and / or gouging action during the drilling operation. The cutters are selected depending on the ground conditions at the drilling site. The drill bit 14 can also comprise a plurality of underreamers 40 that can be activated during the drilling operation to extend in a radial direction, thereby increasing the drilling diameter.

[0125] A drill bit drive system can be provided in the drill rig body for controlling and operating the drill bit (i.e. operating the cutters 38), and, if applicable, for operating the underreaming cutters 40.

[0126] The drill rig can also comprise one or more control units (not shown) for controlling the operation of one or more components of the drill rig, in particular the feed system 24, the drill rig body 12 including the drill bit 14, and / or a waste removal system (described below). The drill rig can thus be configured for semi-autonomous operation.

[0127] As shown in Figure 2b , the subsea drill rig also comprises a waste removal system comprising a waste pipe 48 arranged inside the drill bit 14, the drill rig body 12 and the riser 10 and extending at least partially through the drill bit 14, the drill rig body 12 and the riser 10. A metering pump is arranged for pumping drill cuttings or waste into a waste inlet 46 arranged in or near the drill bit, thereby passing the drill cuttings or waste through the waste pipe for discharge via a waste outlet 20.

[0128] According to an alternative, the feed system described above with reference to Figure 2a , Figure 2b , Figure 3a and Figure 3b may be replaced with a hydraulic arrangement, which is shown in Figure 5 .

[0129] Figure 5A portion of a subsea rig 108 including an alternative feed system based on a hydraulic arrangement is shown. The subsea rig 108 includes a riser 110 that need not necessarily be provided with a rack. Other features of the rig 108 are similar to those described above with reference to Figure 2a , 2b , 3a and 3b. The feed system (in particular the vertical feed system) includes a first feed subsystem 126 and a second feed subsystem 128.

[0130] The first feed subsystem 126 includes a first set of hydraulic actuators 130 or hydraulic cylinders arranged to cause movement of a first gripper 132 in a vertical direction. The first gripper includes a first gripping device (not shown) for gripping and / or clamping the riser 110 when the first gripping device is actuated.

[0131] The second feed subsystem 128 includes a second set of hydraulic actuators or hydraulic cylinders 134 arranged to cause movement of a second gripper 136 in a vertical direction. The second gripper 136 includes a second gripping device (not shown) for gripping and / or clamping the riser when the second gripping device is actuated.

[0132] The first and second gripping devices can include a hydraulic or pneumatic operated bladder device for gripping or clamping the riser with a force sufficient to carry the weight of the riser and for applying a thrust force to propel the rig assembly into the ground or seabed.

[0133] When the first set of hydraulic actuators is operating to move the riser in a first direction via the first gripping device being activated to grip or clamp the riser, the second gripping device is in a deactivated state so that the riser is not gripped or clamped and, when the first set of hydraulic actuators reaches its end of stroke or actuation interval, the second set of hydraulic actuators is set or reset to an initial state so that it is ready to be activated. When the first set of hydraulic actuators reaches its end of stroke (i.e. the end of the range of movement of the first set of hydraulic actuators), the second gripping device is actuated and the first gripping device is deactivated and the second set of hydraulic actuators is actuated, thereby continuing to propel the riser. Thus, by operating the first and second feed subsystems in an alternating fashion, the rig assembly can be propelled in a substantially continuous manner.

[0134] The subsea rig is configured to be used during drilling operations with a rig floor, such as the seabed rig floor 50 shown in Figure 6a The rig floor 50 is typically lifted by a crane located on a vessel and lowered onto the seabed and then leveled in a known manner.

[0135] The seabed rig floor 50 includes one or more rig receiving portions 52 for receiving the rig assembly and the vertical feed system. When the rig has been lowered into one of the portions 52, actuators 54 provided on the rig floor (shown in Figure 7b FIG. 1 1 ) are activated to position and orient the rig in a manner known in the art. Once the rig has been properly positioned, the actuators of the rig floor are deactivated and the feed system 24 is fixed relative to the rig floor via the collar 34.

[0136] Figure 6b A rig receiving portion 52 of the seabed rig floor is shown schematically, with the subsea rig 8 disposed in the rig receiving portion 52 and the rig receiving portion 52 having drilled into the seabed 6 a distance. The collar 34 is engaged with the portion 52 of the seabed rig floor.

[0137] Operation of the subsea rig and the subsea drilling system, such as lowering of the rig toward the seabed rig floor, coupling of the rig to the seabed rig floor, and operation of the drill bit, is typically operated from an operator console located on a vessel that deploys the rig.

[0138] A machine monitoring system is also provided for monitoring and / or displaying various parameters associated with the operation of the subsea rig. These parameters can include drilling depth, drilling advance rate, drilling advance force, cutting face rotational speed, mud pump pressure, rig diagnostics, etc. The machine monitoring system can include one or more control units, as described above, that configure the rig for autonomous or semi-autonomous operation.

[0139] Figure 7a to 7d Initial steps of a method of drilling a vertical hole or bore into a seabed using the subsea rig described above are shown. Although described herein with reference to the rig according to the first embodiment using a feed means via a rack and pinion system, the following method can be similarly applied to the rig according to the second embodiment using a hydraulic feed system. For ease of illustration, Figure 7b to 7d Only one rig receiving portion 52 is shown. It will be appreciated by the skilled person that the seabed rig floor can include one or more such portions 52.

[0140] Figure 7a An arrangement of a jacket 64 on the rig body that can be used as a sacrificial jacket is shown. As described above, this jacket can drill into the ground while the drill bit is being advanced into the ground, in particular to a depth, in order to stabilise unstable ground layers around the hole being drilled. As also described above, the position of the drill bit relative to the outer end of the jacket can be adjusted based on ground conditions at the drilling location.

[0141] As Figure 7aAs shown on the left, the drilling rig 8, equipped with the retrieval pipe 32, is lowered above the casing 64. This operation is typically performed on vessels conducting drilling operations.

[0142] Figure 7a The middle section shows the casing 64, which is substantially fully inserted between the drilling rig body 12 and the retrieval pipe 32. The casing is temporarily clamped or fixed relative to the drilling rig body by a clamping unit (e.g., in the form of a bladder-like device) provided on the drilling rig body.

[0143] like Figure 7a As shown on the left, after the casing has been installed and secured to the main body of the drilling rig, the drilling rig with the casing can be lifted as a single unit and thus mobilized into the water.

[0144] like Figure 6a As shown, a seabed drilling rig has been positioned on the seabed and is preferably leveled relative to the seabed so that the central axis of section 52 has a substantially vertical orientation. Therefore, holes or piles can be drilled substantially vertically to, for example, form a vertically oriented base.

[0145] In the first step of the drilling operation, such as Figure 7b As shown, the drilling rig 8 descends vertically 56 toward the drilling rig receiving section 52, thereby being positioned within the receiving section 52. During and / or after the drilling rig is descended into the receiving section, the position and orientation of the drilling rig can be adjusted by an actuator 54 disposed in the seabed drilling rig, such as positioning the drilling rig at the center of the receiving section and orienting the drilling rig in the vertical direction.

[0146] Although not in Figure 7b As shown, however, before lowering the drilling rig toward the drilling rig receiving section 52, the drilling rig may be configured as referenced. Figure 7a The described shell 64. However, this may not be necessary for all applications, and the following description applies regardless of whether such a shell is set.

[0147] Once correctly positioned and oriented, the vertical feed system 24 is fixed relative to the seabed drilling rig, as described above.

[0148] like Figure 7c As shown, during drilling operations, the drill bit 14 (together with the casing 64, if applicable) is advanced vertically 56 into the seabed 6 using the rack and pinion system described above. During vertical advancement, the drill bit is operated, for example, by rotating the drill bit unit in the rotation direction 58, to perform excavation operations. Waste generated during drilling is removed by the waste removal system described above.

[0149] like Figure 7dAs shown, the drilling operation and the associated advancement of the drill bit 14 into the seabed 6 can be continuous (substantially continuous) over a distance set by the length of the riser 10 and the extension of the rack along the riser.

[0150] Once the intended drilling depth has been achieved, and / or if required during the drilling operation, the drill bit 14 can be retracted from the borehole by reversing the operation of the vertical feed system (i.e. by driving the pinion in a reverse direction). The retraction of the drill bit (and indeed the rig assembly) can thus also be performed in a substantially continuous manner.

[0151] It will be clear to a person skilled in the art that the scope of the application is not limited to the examples discussed in the foregoing, but that several modifications and embodiments thereof are possible without departing from the scope of the application as defined by the appended claims. The application has been described in detail with particular references to certain embodiments thereof, but it will be understood that variations and modifications can be effected within the scope of the application. The application is not limited to the disclosed embodiments, but includes any combination of the disclosed embodiments which can bring advantages.

[0152] Variations to the disclosed embodiments can become apparent to those of ordinary skill in the art upon reading and understanding the present application. By way of example, one or more of the following changes can be made to the disclosed embodiments without departing from the scope of the application. In the description and claims of the application, each of the words "comprise" and "comprising" are not used as limiting, and do not exclude the addition of further elements or steps. The terms "a" and "an" and "the" preceding an element do not, unless the context dictates otherwise, exclude the presence of a plurality of such elements. Indeed, the use of the term "a" or "an" preceding an element or step does not exclude the presence of a plurality of such elements or steps. The use of the term "at least one" preceding an element or step does not exclude the presence of a plurality of such elements or steps. The application is not limited to the embodiments disclosed but can be used in any number of applications without departing from the scope of the application. The disclosure of the application is not a disclaimer of any prior art incorporated herein in its entirety by reference. Any statement herein that a prior art is incorporated by reference is not to be construed that the prior art is already known in the art. Any statement herein that a prior art is incorporated by reference is not to be construed that the prior art is already known in the art.

Claims

1. A subsea drill rig comprising: a rig assembly comprising: a riser having a first end, a second end, and a length extending between the first end and the second end; and a drill rig body coupled to the first end of the riser, the drill rig body comprising a drill head; and a feed system configured to advance the rig assembly in a first direction; wherein the riser is provided with at least one rack extending along at least a portion of the length of the riser; and wherein the feed system comprises a motor coupled to a pinion gear arranged to mesh with the rack to advance the rig assembly in the first direction, wherein the subsea drill rig further comprises: a waste removal system; wherein the waste removal system comprises a waste pipe extending through the drill head and the riser, and a waste discharge outlet provided at the second end of the riser; and a mud discharge pump arranged in or adjacent to the drill head for pumping waste from the drill head to the waste discharge outlet.

2. The seafloor drill rig of claim 1, wherein, The at least one rack extends along the entire length of the riser.

3. The seafloor drill rig of claim 1, wherein, The riser is provided with a plurality of the racks, the racks being distributed along a circumference of the riser, each rack extending along at least a portion of the length of the riser, and wherein the feed system comprises a corresponding plurality of pinion gears or pinion gear sets, each pinion gear or pinion gear set being arranged to cooperate with one rack.

4. The seafloor drill rig of any one of claims 1-3, wherein, The feed system comprises a plurality of pinion gears for each rack.

5. The seafloor drill rig of any one of claims 1-3, wherein, The feed system is a vertical feed system and the first direction is a vertical direction.

6. The seafloor drill rig of any one of claims 1-3, wherein, The riser comprises a plurality of riser modules, each riser module being provided with at least one rack extending along a length of the riser module; The riser modules are coupled to each other such that the at least one rack of different modules are aligned with each other.

7. The seafloor drill rig of any one of claims 1-3, wherein, The feed system is coupled to a pipe configured to be coupled to a second entity and to fix the feed system relative to the second entity.

8. The subsea drill rig of claim 7, wherein, The second entity is a drill rig receiving portion of a drill floor.

9. The seafloor drill rig of any one of claims 1-3, wherein, The drill rig body further comprises a drill head drive system for operating the drill head.

10. The subsea drill rig of any one of claims 1-3, further comprising a control unit configured to control operation of one or more of the feed system, the drill rig body, and the waste removal system.

11. The seafloor drill rig of claim 10, wherein, The drill rig body is a drill head drive system.

12. A subsea drill rig comprising: a rig assembly comprising: a riser having a first end, a second end, and a length extending between the first end and the second end; and a drill rig body coupled to the first end of the riser, the drill rig body comprising a drill head; and a feed system configured to advance the rig assembly in a first direction, wherein the feed system comprises: a first feed subsystem comprising a first set of hydraulic actuators arranged to cause a first gripper to move in the first direction, the first gripper comprising a first gripping device that grips and / or clamps the riser when the first gripping device is actuated; and a second feed subsystem comprising a second set of hydraulic actuators arranged to cause a second gripper to move in the first direction, the second gripper comprising a second gripping device that grips and / or clamps the riser when the second gripping device is actuated. a second feed sub-system comprising a second set of hydraulic actuators arranged to cause movement of a second clamp along said first direction, said second clamp comprising a second clamping device which, upon actuation of said second clamping device, clamps and / or grips said riser; wherein the subsea rig further comprises: a waste removal system; wherein the waste removal system comprises a waste pipe extending through the drill bit and the riser, and a waste discharge outlet provided at the second end of the riser, and a mud discharge pump arranged in or near the drill bit for pumping waste from the drill bit to the waste discharge outlet.

13. The seafloor drill rig of claim 12, wherein, The feed system is coupled to a pipe configured to be coupled to a second entity and to fix the feed system relative to the second entity.

14. The seafloor drill rig of claim 13, wherein, The second entity is a rig receiving portion of a drilling rig.

15. A subsea rig comprising: a rig assembly comprising: a riser having a first end, a second end, and a length extending between the first end and the second end; and a rig body coupled to the first end of the riser, the rig body comprising a drill bit; a feed system configured to advance the rig assembly along a first direction, and a waste removal system comprising a waste pipe extending through the drill bit and the riser, and a waste discharge outlet provided at the second end of the riser, and a mud discharge pump arranged in or near the drill bit for pumping waste from the drill bit to the waste discharge outlet.

16. A method of drilling a hole in a seabed, the method comprising the steps of: providing a rig assembly comprising a riser and a rig body coupled to a first end of the riser, the rig body comprising a drill bit; providing a feed system configured to advance the rig assembly along a first direction; assembling the rig assembly with the feed system to form a rig; arranging a drilling rig on the seabed, the drilling rig comprising one or more rig receiving portions; arranging the rig in one of the rig receiving portions; fixing the feed system relative to the drilling rig; continuously moving the riser relative to the feed system by operating the feed system to advance the rig assembly into the seabed while operating the drill bit; and retracting the rig assembly from the vertical borehole after reaching a final depth of the vertical borehole; characterized in that the method further comprises the steps of: removing waste via a waste pipe arranged within the rig body and extending through the drill bit and the riser, and discharging the waste at a waste discharge outlet arranged at the second end of the riser, wherein a mud discharge pump is arranged in or near the drill bit for pumping waste from the drill bit to the waste discharge outlet.

17. The method of claim 16, wherein, said advancing the rig assembly is performed by rotating a pinion gear in mesh with a rack extending along at least a portion of the length of the riser.

18. The method of claim 16, wherein, The feeding system comprises a first feeding sub-system and a second feeding sub-system, the advancing of the rig assembly being performed by alternately operating the first feeding sub-system and the second feeding sub-system; wherein one of the first feeding sub-system and the second feeding sub-system is operated to advance the rig assembly while the other of the first feeding sub-system and the second feeding sub-system is reset.

19. The method according to any one of claims 16 to 18, further comprising the step of: arranging a casing around the drill body prior to the step of arranging the drilling machine in one of the drill machine receiving portions.

20. The method of claim 19, wherein, The casing is advanced into the seabed together with the rig assembly.

21. The method of claim 20, wherein, During the step of advancing the rig assembly into the seabed, the drill bit protrudes in front of the casing.

22. The method of claim 20, wherein, During the step of advancing the rig assembly into the seabed, the drill bit is arranged inside the casing.

23. The method of claim 20, comprising: When the casing has been inserted into the seabed to a casing depth, the drill bit is further advanced into the ground.

24. The method of any one of claims 16 to 18, wherein, The feeding system is a vertical feeding system, the retracting being performed by operating the vertical feeding system in reverse.

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