The present invention relates to a radial clamping/sealing system for a drilling system for (semi)-continuous drilling a borehole. Such drilling system is used in exploration and production drilling relating to oil and gas production at sea or on land.

Conventional drilling systems are based on a Kelly-drive rotary approach. This approach is well established in practice. In this approach the top of the drilling rig is connected to a swivel that is hung in a travelling block. This travelling block is suspended by steel cables to the crown block at the top of a so-called derrick. The hoisting system is used to raise and lower the drill string and to vary the weight on the drill bit during drilling. Drilling fluid enters the swivel through a gooseneck. A bearing in the lower part of the swivel allows the Kelly and the drill string to rotate, while the other part of the swivel remains stationary. A so-called Kelly section is provided between the top of the drill string and the swivel. The outer surface of the Kelly is used to exert torque on the drill string and can be of various shape including square and hexagonal shapes. The Kelly section is capable of moving vertically through a matching bushing with the bushing transmitting rotary power to the Kelly. This bushing is locked into a rotary table that is hydraulically or electrically powered. When a new drill pipe or drill pipe section is needed the Kelly needs to be disconnected from the drill string and has to be connected to the new section after which this new pipe section is connected to the drill string. Therefore, the Kelly, which is connected by a threaded connection to the top of the drill string, executes all the required functions for the drilling operation. This disconnecting and reconnecting requires additional labor in the field and results in a standstill of the operation.

Another conventional system uses a topdrive rotary drilling approach. In this approach a topdrive is connected with a threaded connection/quill to the top of the drill string. The topdrive is used to rotate, apply torque and hoist the drill string. In addition, drilling fluid can be injected into the drill string. In case a new pipe section is needed the topdrive needs to be disconnected, and as a next step, to be connected to the new pipe section. After connecting the new pipe section to the drill string, the drilling operation can continue.

Besides problems associated with the requirement of additional labor in the field and standstill of the operation during connection of a new pipe section, other problems may occur during such standstill. For example, a drill string can get stuck in the borehole due to the standstill. Also, the interruption of the drilling fluid during connection of a new pipe section limits control of the downhole pressure and dropping cuttings. These problems restrict the areas and types of formation that can be explored for oil and gas, for example. WO 2011/093716 discloses a device and method for drilling with continuous tool rotation and continuous fluid supply. The invention comprises a topdriven drilling machine and a second drilling machine which is arranged between the topdriven drilling machine and the borehole. This second drilling machine is vertically movable along a guide track and includes a rotary table that is able to take the weight of the drill string and a rotary drive unit for continuous rotation of the drill string. The fluid chamber is sealed by pressure seals that directly seal the drill pipe with the stationary second drilling housing. Due to the drilling fluid pressures, the roughness of the pipe surface and the relative movement of the drill pipe section in radial and axial direction to the stationary housing to which the pipe is sealed, seal erosion and lifetime are challenging. Also this document describes the use of polygonal drive pipe sections for executing the function of applying torque to the drill string, which requires non-standard drill pipe sections.

US 2739790 describes a rotary oil well drilling apparatus. It consists of a driven rotatable housing which is placed in a stationary housing. In the rotatable housing a gripping system is capable of clamping the drill string so that it is fixed in radial direction with respect to the rotatable housing. This device is able to couple and uncouple drill pipe sections, however, fluid injection has to be done with an additional device. This apparatus is not appropriate for continuous drilling with fluid injection.

WO 99/51852 describes the invention of a subsea diverter and rotating drilling head which is placed at the wellhead on the sea floor. It uses an upper housing that is lowered during installation in an alignment funnel on top of the diverter housing assembly. During operation the drill string moves vertically through both primary and secondary sealing systems, leading to seal erosion. The apparatus is not able to hoist the drill string or to couple and/or uncouple drill pipe sections.

US5178215 discloses a rotary blowout preventer adaptable for use with both Kelly and overhead drive mechanisms with a rotatable housing with an annular sealing system that is designed for sealing the drill pipe with the rotatable housing, in such a manner that vertical movement of the drill pipe remains possible during operation. The preventer is not suited for hoisting the drill string or to couple and/or uncouple drill pipe sections.

US6315051 discloses the invention of a continuous circulation drilling method. This invention comprises a method with a number of sealing systems located above each other, which can alternately seal a drill pipe section with the surrounding housing. In US6591916 a technically more detailed invention based on the described continuous circulation drilling method is disclosed. This continuous circulation system itself does not rotate, apply torque or hoist the drill string, but purely focuses on the continuous circulation and injection of drilling fluid. The other functions are executed by external existing drilling systems, such as rotary slips and power tongs. Since the seals are fixated in axial direction, during the coupling and uncoupling the rough drill pipe moves in axial and radial direction relative to the seal, leading to seal erosion.

The described apparatuses provide partial solutions for the design of a continuous drilling system. However, these conventional apparatuses and methods will still experience relatively high seal erosion and low seal lifetime due to the sealing design that has to cope with rough drill pipe surfaces that move relative to the seal and erode the seal. Some conventional apparatuses even require the use of custom made polygonal pipe sections in order to function instead of standard circular pipe sections and some of them would require additional equipment for executing one or more of the drilling functions, which limits room at the drill floor. None of the above systems is able to combine the main drilling functions in such a way that continuous drilling and continuous tripping is possible with standard pipe equipment and a high sealing lifetime.

For the tripping process, when the drill string has to be pulled out of the wellbore, similar problems arise with the present technology.

The present invention has for its object to obviate or at least reduce the above stated problems. The present invention provides a radial clamping/sealing system for a drilling system for continuous and/or semi-continuous drilling a borehole according to the invention, the drilling system comprising:

a first stationary housing;

a rotatable housing comprising a longitudinal opening for receiving a drill string;

- a radial clamping system configured for holding and clamping a box end of the drill

string in a substantially radial direction with respect to the rotatable housing;

a first direct sealing system in use arranged between a drill pipe and the rotatable housing; a second indirect sealing system in use arranged between the rotatable housing and the stationary housing;

- a mechanical and/or hydraulic transmission configured for radial activation of the radial clamping system; and

a first drive configured for rotating the rotatable housing with the drill string.

For drilling a borehole in the subsurface four main functions need to be executed, which are hoisting the drill string, rotating the drill string, applying torque to the drill string and inject drilling fluid into the drill string. The weight on the drill bit is regulated by the hoisting function, and in order to drill through the formation a certain rotational speed and torque are required.

Finally the drilling fluid transports rock cuttings to the surface, provides a certain hydrostatic pressure in the well and lubricates and cools the drill bit. In order to design a drilling system, this system has to at least be able to execute these functions.

When drilling a borehole with a system according to the present invention all four essential drilling functions are fulfilled in such a way that continuous and/or semi-continuous drilling is possible. The invention enables hoisting and rotation of the drill string, as well as applying torque and the continuous injection of drilling fluid. An additional advantage of the invention is that due to the compactness of the invention relative to other inventions and conventional drilling equipment, the system is installable on current rigs and provides more room for drilling before reaching the drill floor.

By having at least the first clamping means clamping and holding the box end of the drill string in a substantially radial direction of the drill string such that the upper end of the drill string is approachable for other equipment, including the positioning of an additional pipe section, a continuous or semi-continuous/near continuous operation with continuous drilling fluid injection is achieved. By clamping the drill string in a radial direction instead of its upper end a standstill for connection of an additional drill pipe section is not required. Conventional systems require an axial (threaded) connection for hoisting the drill string, such that a standstill is required having the aforementioned problems that are obviated or at least reduced by the present invention.

The system according to the present invention enables continuous drilling and continuous tripping while obviating the aforementioned disadvantages of the conventional drilling methods. The preferred system is capable of executing all four main drilling functions in a manner such that continuous drilling with continuous fluid injection is possible.

In a presently preferred embodiment according to the present invention therefore all drilling functions are to be executed from a radial direction in order to enable continuous drilling. The stationary housing together with the rotatable housing is capable of hoisting the drill string with a drill bit such that the entire weight of the drill string is supported. The drill string is rotated by one or two or even more drives of which at least one drive associated with the rotatable housing is a rotational drive acting from a rotational direction onto the drill string. The support of the drill string can be achieved by the clamping means. In a presently preferred embodiment the clamping means comprise clamping parts and support parts that cooperate with each other.

According to the present invention the rotatable housing comprises a first direct seal between the drill string and the rotatable housing, and a second indirect seal between the rotatable housing and the stationary housing. A direct seal is here defined as sealing the drill pipe section directly, whereas an indirect seal is defined as not directly sealing the drill pipe section but sealing a secondary housing for example which does directly seal the drill pipe section.

The sealing function is performed by an indirect sealing between the rotatable housing and a stationary housing. A first direct sealing seals the rotatable housing against the jointly rotating drill string or pipe section. This enables an optimal design of the sealing function without the constraints of the drill string or pipe section. For example, the surface areas of the sealing means can be designed for optimal sealing such that also relatively rough surfaces of the drill string can be sealed. Also due to this preferred sealing method, seal erosion is minimized, in contrast to conventional solutions. The seal in a preferred embodiment according to the present invention between the drill pipe and the rotatable housing is a radial seal that is activated by a ring of flexible material that surrounds it. This ring of flexible material is preferably deformable but not compressible and may in an alternative embodiment be replaced by a hydraulic fluid. The ring of flexible material is locked inside the rotatable housing by an outer circular wall and an upper wall. When a pressure is applied on the underside of the ring, the flexible material will deform. Due to the surrounding housing, it will activate the first direct seal in a radial direction. This activation is preferably combined with the activation system of the clamping system and the support system.

In a presently preferred embodiment the drilling system comprises an axial support system configured for longitudinally fixating the drill string on a deviated area of a drill pipe. According to a presently preferred embodiment of the invention, the drill string is preferably supported at the elevator shoulder. This elevator shoulder is an angled section of the drill string that can be supported by the supporting means.

In a presently preferred embodiment, the first direct and/or second indirect seals comprise seal parts. The use of seal parts enables an integrated design of the clamping parts and the seal parts.

In a further preferred embodiment the first and and/or second seals comprise a number of sub-seals. By providing sub-seals it is possible to deal with the relatively high pressures in a rather gradual way. A number of sub-seals, placed in series, jointly provide the sealing function. This reduces the constraints on an individual subseal.

In an advantageous preferred embodiment according to the present invention, the first clamping means comprise a number of clamping parts that move relative to each other in at least a radial direction for clamping and unclamping the drill string or pipe section.

By providing the clamping means from a number of separable clamping parts, for example two or four clamping parts, the clamping means can be separated to release the drill string or pipe section. This enables an easy positioning of the clamping means around the drill string or pipe section. The supporting means may preferably also be provided from a number of separable supporting parts, providing similar advantages. In a presently preferred embodiment the clamping means and supporting means consist of three clamping parts and three supporting parts, ensuring radial fixation and centering of the drill pipe inside the rotational housing.

Furthermore, by providing the clamping means with clamping parts, the clamping and sealing functions can be separated. The clamping parts directly clamp the drill string or pipe section. The clamping parts rotate together with the drill string during a drilling operation. This enables an optimal design of the clamping parts.

The mechanical transmission preferably comprises a lever system that converts an axial movement to a radial clamping movement of the clamping parts. By providing a lever the clamping force acting on the drill string can be controlled. In a presently preferred embodiment the lever is provided with a lever arm to increase the force acting on the drill string or pipe section.

In an alternative embodiment the transmission system activates the clamping system through axial compression of a flexible material placed in a casing. Due to the axial compression of the flexible material and the casing the axial compression is converted to a radial movement, which is used to activate the clamping system. In another alternative embodiment the mechanical transmission system comprises a geared transmission, where the clamping system in the rotatable housing is activated through gears, of which the first activating gear is situated in the stationary housing.

In yet another alternative embodiment the mechanical transmission system is replaced by a hydraulic transmission system, wherein the activation of the clamping system is activated through fluid pressure flowing from the stationary housing to the rotatable housing through a fluid chamber sealed in a radial direction.

In yet another alternative embodiment the clamping means are activated by an electric actuating system or a magnetic actuating system.

In a presently preferred embodiment the transmission system also activates the support system and the first direct sealing system between the drill pipe and the rotatable housing.

In an alternative embodiment the clamping mechanism is activated automatically from the interaction between the clamping parts and the elevator shoulder. This obviates the need for a separate control system to activate the clamping force. The clamping force is activated by a support pad with the clamping force being such that torque can be transferred to the drill string, and preferably the sealing is also activated automatically. Alternatively, or in combination, an external system is used to provide additional clamping force. By providing the lever such that clamping forces increase in presence of an axial operating load the structure contributes to the overall safety of the system.

In a further advantageous preferred embodiment according to the present invention, the first and/or second clamping means of the drilling system comprise inserts enabling the handling of different drill string diameters/dimensions.

The use of inserts enables application of the drilling system according to the invention over a range of pipe dimensions by switching and/or removing/adding inserts. The range of pipe dimensions may involve different pipe diameters, different elevator shoulder angles, etc. Providing inserts increases the flexibility of the system to handle different pipe diameters/dimensions without requiring structural changes to the system. Preferably the use of inserts is combined with releasable and/or replaceable inner or first seals to enable coping with different piping diameters.

In an alternative embodiment the clamping means, supporting means and sealing system can be constructed such that also the handling of polygonal pipe sections is enabled. In an alternative embodiment the clamping means, supporting means and sealing system can be constructed such that also casing well drilling is enabled with the drilling system according the invention.

The invention also relates to a drilling system for continuous and/or semi -continuous drilling a borehole comprising a radial clamping system as described above as first clamping means, and further comprising:

a second rotatable housing, comprising:

a second stationary housing wherein in use the rotatable housing is axially fixed;

a radial clamping system configured for holding and clamping the pin end of a drill pipe in substantially radial direction with respect to the rotatable housing; and

wherein the second stationary housing is longitudinally movable within the first stationary housing and comprises a third sealing system between the first and second stationary housing.

The first and second rotatable housing are preferably located above each other in a first stationary housing in a preferred embodiment according to the present invention, the system further preferably comprising:

a separating sealing system configured for creating two pressure chambers between the first and second rotatable housing; and

radial located fluid inlets in the first stationary housing configured for regulating the fluid pressure in aforementioned created fluid chambers.

Providing two separate drives enables the rotation of the drill string with one drive while the other drive is connected to another pipe section. This preferably enables a continuous drilling system, or at least a semi-continuous or near continuous drilling system, for drilling a borehole. Providing two separate drives omits undesired standstill of the drilling operation for connecting a new pipe section. More specifically, the system according to the invention is capable of performing the required functions also during connection and disconnection. This enables a faster drilling process and allows for continuous circulation of drilling fluid leading to an improved control of downhole pressure, so that more difficult formations of subterranean structures can be drilled, and drill cuttings are not dropping to the bottom of the borehole.

The first and second rotatable housings according to a preferred embodiment of the system according to the invention, inside the first stationary housing, enable the continuous execution of the hoisting, rotating, applying torque and injecting drilling fluid function during the coupling and uncoupling of drill pipe sections, so that continuous drilling and tripping is possible. For the coupling process the drill string is supported by the support means in the lower first rotatable housing, after which it is clamped by the clamping means at the box end of the pipe. Then the drill string is sealed with the first direct sealing system and the separating sealing system between both rotatable housings is closed, so that drilling fluid can be injected in the lower fluid chamber that is created. During the process the lower rotatable housing rotates and applies torque to the drill string so that drilling is continued. The second rotatable housing clamps a new drill pipe section at the pin end, which is sealed with the first direct sealing system to the second rotatable housing. Fluid pressure is built up in the upper fluid chamber until there is no pressure difference between the upper and lower fluid chamber. At that point the separating seal is opened, after which the second rotatable housing rotates the new pipe section. The second rotatable housing is now lowered within the first stationary housing, so that the pin end of the new pipe section meets the box end of the drill string, after which both are coupled. Coupling torque is applied by the rotatable housing and when the coupling is completed, the fluid injection is taken over by the injection system from the topdrive that is connected to the upper end of the newly attached drill pipe section.

In a presently preferred embodiment the separating seal system between the two rotatable housings comprises a ram seal system in which two hydraulically activated ram seals seal the fluid chamber in the stationary housing. In an alternative embodiment the separating seal system comprises a sealing system connected to the second rotatable housing. This sealing system is opened when the drill fluid pressure in the stationary housing is equal to the drill fluid pressure in the new drill pipe section. The opening of the sealing system is constructed such that the sealing system does not block the vertical movement of the second rotatable housing, enabling a connection between the box end of the drill string and pin end of the new pipe section while continuously executing the main drilling functions, including fluid injection.

In a presently preferred embodiment the ram seals comprise a flexible material on the top side of the seal on which the pin end of the new drill pipe section can rest before coupling when the ram seals are closed. This enables exact longitudinal alignment of the new pipe section in the second rotatable housing and reduces pipe damage at the pin end.

In another presently preferred embodiment the two fluid chambers that are separated with the separating sealing system comprise fluid and gas inlets and outlets. These inlets are positioned in the fluid chambers preferably such that when filling the fluid chamber with drilling fluid no gas is left in the fluid chamber. On the other hand when emptying the fluid chamber the fluid inlet may function as outlets and are positioned such that all fluid is removed from the chamber. It is also possible to provide the fluid chambers with multiple and/or separate fluid and gas inlets and outlets.

In a presently preferred embodiment a gearbox is used for executing the rotating function of both the first rotatable housing and the second rotatable housing using one drive. This gearbox is designed such that the rotation function can be executed continuously during drilling operation, which means that also during the vertical movement of the second rotatable housing for coupling or uncoupling the drill pipe sections both the first and second rotatable housings are rotated. This invention further relates to a drilling rig comprising a continuous and/or semi- continuous drilling system as described above for drilling a borehole with a first stationary housing comprising a first and second rotatable housing as described above, further comprising;

a topdrive; and

- a guide track, enabling translation of the stationary housing in the axial direction of the drill string under the topdrive,

wherein the above system is installed on a drilling rig.

In case the first drive comprises the first clamping means and the second drive comprises a conventional drive system, such as a so-called topdrive, the first drive rotates the drill string. The rotatable housing directly engages the drill string and rotates at the same rotational speed. When the upper end of the drill string with the rotatable housing reaches a working platform, or other structural part of the rig, the topdrive connects a new pipe section. In case of a topdrive this involves a threaded connection. The second drive may rotate the drill string for a period of time after the additional pipe section is connected to the drill string. The first drive and the rotatable housing are repositioned. After the first clamping means start clamping the drill string the first drive again takes over the function of rotating the drill string from the second drive. The second drive is then available for providing a further additional pipe section. This enables a continuous or semi-continuous drilling operation.

In a presently preferred embodiment the guide track installed on the drilling rig for the topdrive is also used as a guiding means for the drilling system.

An alternative embodiment of the drilling system may comprise a divisible drilling system, which is comprised of two or more main parts which can move away from the drill string in radial direction, such that the drilling system can be moved away from the drill string.

An alternative embodiment the drilling system may apply a so-called "hand-over-hand" approach. The first drive of the first rotatable housing rotates the drill string. When the upper end of the drill string with the first rotatable housing associated with the first drive reaches the working platform, or other structural part of the rig, the second drive associated with a second rotatable housing comprising second clamping means positions an additional pipe section. After the additional pipe section is connected to the drill string the second drive may rotate the drill string. The first drive is then available for providing a further additional pipe section and to position this pipe section to the drill string. This further pipe section is connected to the drill string, preferably before the upper end of the drill string with the second rotatable housing of the second drive reaches the working platform or other structural part of the rig. This enables a continuous or semi- continuous drilling operation. This is achieved by performing the sealing, supporting and rotating functions by the rotatable housing in a substantially radial direction relative to the drill string. In a embodiment of the invention the clamping means comprises parts or sections that can be separated from each other to enable repositioning of the clamping means relative to the drill string or pipe section. This "hand-over-hand" drilling method approach comprises a divisible drilling system.

Preferably, the guiding means are configured such that at least one of the first or second clamping means are capable of positioning an additional pipe section on the drill string by performing the clamping in a direction with a substantial radial component. Even more preferably, both the first and second clamping means are capable of positioning the additional pipe section on the drill string. In this latter case a so-called "hand-over-hand" system for holding and driving the drill string can be achieved. In such system, both the first and second drives act from a radial direction onto the drill string and perform the relevant functions of sealing, supporting and rotating in a substantial radial direction relative to the drill string. The first and second drives can be changed in position with the second drive for placing a new pipe section on the drill string.

Preferably, in such embodiment both the first and second clamping means are associated with a separate rotatable housing such that the first and second drives can preferably be separated.

The present invention further relates to a drilling rig comprising a drilling system as described above. Such drilling rig provides the same effects and advantages as described for the drilling system.

The present invention further also relates to a method for continuous and/or semi- continuous drilling a borehole, the method comprising providing a drilling system according to the invention. Preferably, the method comprises the steps of:

- injecting drilling fluid and rotating the drill string with the topdrive, in use starting at the top of the derrick and moving down, with the continuous drilling system deactivated such that the drill string moves through the longitudinal opening;

clamping the continuous drilling system to the topdrive connection with the drill string, with the first rotatable housing clamping, sealing and supporting the box end of the drill string and the second rotatable housing, clamping and sealing the pin end of the topdrive, and executing the said drilling functions;

the continuous drilling system taking over the functions of hoisting the drill string, rotating the drill string and applying torque to the drill string of the topdrive with the first rotatable housing, filling the fluid chamber between the first and second rotatable housing with drilling fluid with a pressure equal to the injected drilling fluid by the topdrive;

the second rotatable housing uncoupling the connection between the drill string and the topdrive, whereafter the separating seal system seals is activated, the drilling fluid injection is taken over by the drilling system, and the drilling fluid injection by the topdrive is stopped; removing the drilling fluid from the upper fluid chamber, the second rotatable housing deactivating the clamping and sealing function on the pin end of the topdrive, and the topdrive connecting to a new pipe section;

inserting the new pipe section in the continuous drilling system, and the second rotatable housing clamping and sealing the pin end of the new pipe section, filling the upper fluid chamber with drilling fluid with a pressure equal to the injected drilling fluid by the drilling system;

deactivating the separating seal system and the second rotatable housing rotating the new drill pipe section, wherein the drilling fluid injection is taken over by the topdrive and stopping the drilling fluid injection by the drilling system ;

coupling the drill string and the new drill pipe section, while the first rotatable housing is still executing the functions of hoisting the drill string, rotating the drill string and applying torque to the drill string, and after completion removing the drilling fluid from the fluid chamber; and

the topdrive taking over the functions of hoisting the drill string, rotating the drill string and applying torque to the drill string, in addition to the injection of drilling fluid, and the drilling system deactivating the clamping, sealing and supporting means.

Such a method provides the same effects and advantages as described for the drilling system and/or drilling rig. The method according to the invention preferably enables a continuous or semi-continuous or near continuous operation of the drilling and tripping. This is achieved by performing the different functions that are described earlier, to a large extent in a substantially radial direction. This may involve the use of a rotational drive, clamping the drill string and/or the pipe sections in a substantially radial direction and providing an indirect seal that is positioned at a radial distance from the drill string.

The present invention further also relates to a method for continuous and/or semi- continuous tripping while preferably continuously injecting drilling fluid, which provides a system as described above. This method provides the advantage of increased downhole pressure control during tripping. The method further preferably comprises the steps of:

moving the drilling system upwards starting at a drill floor, and rotating, sealing and hoisting the drill string at the upper box end, and injecting drilling fluid, wherein the topdrive is located above the drill string in a derrick and is inserted in the deactivated second rotatable housing;

the continuous drilling system clamping and sealing the pin end of the topdrive with the second rotatable housing, filling the upper fluid chamber with drilling fluid with a pressure equal to the injected drilling fluid by the continuous drilling system; opening the separating seals and rotating the pin end of the topdrive, the second rotatable housing moving down in the first stationary housing, enabling the coupling of the topdrive and the drill string, and stopping he drilling fluid injection from the drilling system and taking over by the topdrive;

taking over the functions of hoisting and rotating the drill string by the topdrive and deactivating the clamping, supporting and sealing means of the first and second rotatable housing;

moving down the drilling system to a following drill pipe connection, and the first rotatable housing clamping, supporting and sealing the box end of the connection, while the second rotatable housing clamping and sealing the pin end of the connection;

taking over the functions of hoisting and rotating the drill string from the topdrive by the drilling system, and filling the fluid chamber with drilling fluid with a pressure equal to the injected drilling fluid by the topdrive;

the second rotatable housing delivering the break out torque to enable the decoupling of the drill string and the upper drill pipe section, closing the separating seals and taking over the function of injecting drilling fluid by the drilling system; and

removing the drilling fluid from the upper fluid chamber in the continuous drilling system, the second rotatable housing deactivating the clamping and sealing function on the pin end of the topdrive, and the topdrive relocating the decoupled pipe section.

The present invention further also relates to an alternative embodiment for (serni)- continuous tripping without continuously injecting drilling fluid. This method provides the advantage of increased tripping speed compared to the above method since no threaded connections are required between the topdrive and the drill string. The method for tripping without circulation comprises:

the topdrive lifting the drill string out of the borehole with the elevator until at least two pipe sections are above the drill floor;

clamping the box end and pin end of the pipe section connection just above the drilling floor by the first and second rotatable housing, respectively;

the second rotatable housing delivering a break out torque for uncoupling the upper drill pipe section;

the topdrive lifting and storing the uncoupled pipe section, the drilling system taking over the hoisting function of the rotary slips and lifting the drill string further out of the borehole;

supporting the drill string in rotary slips on a drill floor and moving the drilling system downward to the drill floor;

relocating the topdrive above the drill string and connecting topdrive to the upper pipe section of the drill string with the elevator; and

the topdrive taking over the hoisting function of the continuous drilling system.

In a presently preferred embodiment the invention comprises a control system enabling the automated handling of one or more of the above described methods with the drilling system.

When drilling a borehole periodically additional pipe sections are required. The described method for continuous drilling and the described method for continuous tripping with or without fluid injection can also be executed by adding or removing more than one drill pipe section at a time. Further advantages, features and details of the invention will be elucidated on the basis of preferred embodiments thereof, wherein reference is made to the accompanying drawings, in which:

fig. 1 A-B show a schematic representation of a drilling rig with a drilling system according to the invention;

fig. 2 A-C show a schematic representation of stationary and rotatable housings that contact the drill string;

fig. 3 A-B show the clamping function in a clamped and undamped state;

fig. 4 A-D show parts of the housing;

fig. 5 shows a side view of the rotatable housing;

fig. 6 shows a schematic representation of a continuous drilling system according to the invention;

fig. 7 shows a schematic representation of stationary and rotatable housings that contact the drill string;

fig. 8 A-C show a schematic representation of the first rotatable housing, the separating sealing system and the second rotatable housing;

fig. 9 A-C show the clamping, sealing and supporting means of the first rotatable housing; fig. 10 A-C show the clamping and sealing means of the second rotatable housing;

fig. 11 A-D show a schematic representation of the continuous drilling system in the different states of activation;

fig. 12 A-E show a schematic representation of the method for continuous drilling a borehole according to the invention;

fig. 13 A-C show a schematic representation of the method for tripping without continuous circulation according to the invention.

Drilling rig 2 (Fig. 1 A) comprises a drilling system 4 with working platform/floor 6. A drill string 8 is with one end positioned in borehole 12 and with the other end connected to drill bit 14. Pipe section 10 is to be connected with drill string 8 to enable advancing pipe 8 into borehole 12. In the illustrated embodiment first drive 16, which in the illustrated state makes contact with the top of drill string 8, is associated with first stationary and rotatable housing configuration 18. Configuration 18 comprises with first clamping means 20 to connect configuration 18 is connected to drill string 8. First guide means 22 enable axially positioning radial drilling drive 16 in a substantially vertical direction. Second drive or topdrive 24 with second clamping means 26, for example the topdrive with a threaded connection, is in the illustrated embodiment connected to the pipe section 10 that is to be connected to drill string 8. Second guiding means 28 enable positioning drive 24 in a substantially direction allowing co-operation with first drive 16.

Fluid supply system 30 supplies drilling fluid to drilling system 4, and in the illustrated embodiment specifically to drive 16. The other drive may also comprise a fluid supply system. Fluid supply system 30 comprises a first and second fluid chamber 32, 34. Fluid supply system 30 can be any conventional and/or commercially available fluid supply system.

When drilling borehole 12 drilling system 4 advances drill string 8 in an underground formation using drill bit 14. Drill string 8 is connected to radial drilling device 16 by first clamping means 20 and may be rotated by first drive 16. In this embodiment the drill string 8 may be rotated by first drive 16 while second drive 24 is connected to additional pipe section 10 that is to be connected to drill string 8. After connecting pipe section 10 to drill string 8 second drive 24 starts rotating drill string 8. In a next step first drive 16 is repositioned in an axial direction away from the drill floor. When the axial drilling device nears the drill floor, so there is a need for a new pipe section, the radial drilling device is connected to the top of drill string 8. After again clamping drill string 8 at the new position first drive 16 takes over the rotation. The second topdrive is ready to get an additional pipe section 10 that also needs to be connected to drill string 8 while drill string 8 is advancing into borehole 12.

Another embodiment drilling rig 42 (Fig. 1 B) comprises alternative drilling system 44. System 44 comprises a first drive 16 associated with first stationary and rotatable housing configuration 18 comprising first clamping means 20. In this embodiment second drive 46 is associated with second stationary and rotatable housing configuration 48 comprising second clamping means 50. In the illustrated embodiment drilling system 44 is provided with a second fluid supply system 52 for the second configuration 48. First configuration 18 is guided by guiding means 22 while second configuration 48 is guided by second guiding means 54. When drilling borehole 12 alternative drilling system 44 advances drill string 8 in an underground formation using drill bit 14. In system 44 first and second configuration 18, 48 take over in a so-called "handover-hand" approach, applying a divisible drilling system. First, drill string 8 is supported by first configuration 18. When configuration 18 is about to reach platform 6 the second configuration 48 positions pipe section 10 and connect section 10 to drill string 8. First configuration 18 is released or in other words unclamps and second configuration 48 takes over the clamping and rotating functions. Then first configuration 18 is ready to get a further additional pipe section 10. Configuration 18, 48 (Fig. 2 A-C) comprises a divisible drilling system comprising a stationary housing 56 and rotatable housing 58. Rotatable housing 58 rotates relative to stationary housing using first and second bearings 60, 62. Rotatable housing 58 is rotated using gear 64 by the first drive 16. In this embodiment drive 16 is a so-called rotational drive. Clamping element 86 is activated by supporting element 84 when the elevator shoulder 48 makes contact with insert 98 of support element 84 and the weight is supported by configuration 18. Additional clamping force can be generated by moving clamping actuator 68 in an axial direction A.

In the illustrated embodiment mechanism 66 comprises a first link 70 that with hinge 72 is connected to second link 74. Second link 74 is connected with hinge 76 to third link 78. At the upper part third link 78 is connected with hinge 80 to fourth link 82. First supporting element 84 supports drill string 8. Fourth link 82 is connected to clamping element 86. Clamping element 86 is functionally connected to first suporting element 84 with lever 90 and coupling element 92, 94. Together with mechanism 66 clamping elements 84, 86 establish first clamping means 96.

When drill string 8 provides a downward axial force on clamping element 84 at insert 98 lever 90 intends to rotate around joint or hinge 100 second clamping element 86 is forced against drill string 8 with increased force. This constitutes a self-supporting structure.

First seal 102 seals drill string 8 against rotatable housing 58. In fact, first seal 102 is pressed against the drill pipe 8 by the clamping element 86. Clamping element 86 is equipped with an insert 104. First seal 102 is pressed against the drill string by insert 104 that is mounted on element 86. Second seal 108 comprises first/bottom and second/upper seal units 110, 112.

Optionally, between units 110, 112 a number of sealing rings 114 placed in series is provided. It will be understood that other sealing components can also be applied in addition to, or alternative to, seal unit 110, 112 and sealing rings 114. Sealing part 110 comprises fluid channel 116 for providing fluid to the inner part of drill string 8. First link 70 rotates with rotatable housing 58 relative to stationary housing 56 over bearing 118. Additional bearing 120 of stationary housing 56 provides support to rotatable housing 56. Clamping mechanism moves between an undamped state (Fig. 3 A) and a clamped state (Fig. 3 B) by moving first link 70 in an axial direction. Bottom part 122 with constructional part 124 of rotatable housing 58 rotates relative to stationary housing 56 over bearing 120.

In the illustrated embodiment hinge 76 comprises a number of pins 126 and corresponding openings 128 (Fig. 4 A16-D and 5). In this embodiment other hinges also comprise a number of pins and openings or holes.

In a presently preferred embodiment continuous drilling system 130 (Fig. 6) comprises a first rotatable housing 58 and a second rotatable housing 132 with a longitudinal opening for receiving drill string 8. The first rotatable housing 58 is arranged in a first stationary housing 56 and is fixated in axial direction by bearings 120 and bearings 60. The second rotatable housing 132 is arranged in a second stationary housing 134 and is fixated in axial direction with respect to the second stationary 134 housing by bearings 136 and bearings 138. The second stationary housing 134 is longitudinally movable within first stationary housing 56. The continuous drilling system 130 enables the coupling or uncoupling of the drill string 8 with another drill pipe section 12. The separating seals 140 comprise two ram seals which move in a fixed housing 146.

The clamping, sealing and supporting function of the first rotatable housing 58 are activated by actuating element 68 in a direction A. The axial movement and force required for the activation is provided by hydraulic cylinders 150, but may alternatively be enabled by other activation means. In the figure the first rotatable housing 58 is seen in an activated state, clamping, sealing and supporting the drill string 8. The clamping and sealing function of the second rotatable housing 132 is activated by the actuating element 148 in a direction B. The axial movement and force required for the activation is provided by hydraulic cylinders 152, but may alternatively be enabled by other activation means. The axial movement of the second rotatable housing 132 and the second stationary housing 134 within the first stationary housing 56 is guided by guiding means 154. This axial movement is actuated by activation means 156 in a direction C, attached both to the second stationary housing 134 and to the first stationary housing 56, preferably by hydraulic cylinders. The continuous drilling system 130 also comprises a gearbox 158 for driving first rotatable housing 58and/or second rotatable housing 132 and a construction arranged such that the continuous drilling system 130 is connected to the guiding means on the drilling rig. Also the continuous drilling system 130 comprises lifting eyes 160 for the attachment to the lifting means in the drilling rig.

The continuous drilling system 130 (Fig. 7) enables continuous drilling and fluid injection during coupling and uncoupling of the drill string 8 and pipe section 10. The first rotatable housing 58 comprises support element 84, clamping element 86 and first direct seal 102 as well as a flexible material 162 that activates the direct seal 102 when compressed by actuating means 68.

The first rotatable housing 58 is driven by gear 64. The separating seals 140, when closed as in the figure, enable the creation of a lower fluid chamber 142 and an upper fluid chamber 144 for drilling fluid. The second rotatable housing 132 comprises a direct seal 164, which is activated by compression of flexible material 166, and clamping element 168, both activated by actuating means 148. The second rotatable housing 132 is driven by gear 170. Seals 172 seal the second stationary housing 134 and the first stationary housing 56.

The first rotatable housing 58 (Fig. 8 A) comprises the actuating means 68, comprising first link 70 which is locked between bearing 118 and bearing 172 and which activates the clamping element 86, support element 84 and first direct seal 102. The second indirect seal 174 between the first rotatable housing 58 and the first stationary housing 56 comprises a face seal which is activated by spring 176. The separating seals 140 (Fig. 8 B) are hydraulically activated with fluid inlets and outlets 178 and the fluid chamber 144 or 142 is filled or emptied using inlets 180. The second rotatable housing 132 (Fig. 8 C) comprises the actuating means 148, comprising link 182 which is locked between bearing 184 and bearing 186 and which activates clamping element 168 and first direct seal 164. The second indirect seal 188 comprises a face seal and is activated by spring 190.

The actuating system of the first rotatable housing 58 (Fig. 9 A-C) comprises a first link 70 which is axially moved and which indirectly rotates link 78 around hinge 218, which activates of clamping element 86 and link 192 for the compression of flexible material 162, which activates the first direct seal. Also first link 70 moves link 194, which moves link 196 around hinge 198, which activates support element 84.

The actuating system of the second rotatable housing 132 (Fig. 10 A-B) comprises a first link 182 which is axially moved and which rotates link 200 around hinge 202 via the connection with link 204. The rotation of link 200 activates the clamping element 168, comprising clamping insert 206, via link 208. Also the rotation of link 200 activates the compression of flexible material 166 for the activation of the first direct seal, via the connection with link 210.

The drilling system according to the invention comprises different states of activation (Fig. 11 A-D). In Figure 11 A the first rotatable housing 58 in the drilling system is rotating drill string 8, which is supported by supporting element 84 and which is clamped by clamping element 86 and sealed by seal 102. The separating sealing system 140 is closed, so that drilling fluid injection is done via the lower fluid chamber 142. The second rotatable housing 132 is deactivated, meaning that clamping element 168 and sealing element 164 are removed in a radial direction from a drill pipe section, creating an opening for receiving a new drill pipe section. In Figure 11 B the drilling system is still executing the drilling functions via rotatable housing 58. A new drill pipe section 10 is clamped with clamping element 86 and sealed with sealing element 84 in the second rotatable housing 132. Fluid chamber 144 is filled with drilling fluid until the fluid pressure is equal to the drilling fluid pressure in fluid chamber 142. In Figure 11 C the separating seals 140 have been opened and the second rotatable housing 132 in second stationary housing 134 is lowered in first stationary housing 56 in order to couple new pipe section 10 to the drill string 8. The fluid injection is now taken over by for example a topdrive. In Figure 11 D the drilling system is completely deactivated, resulting in a longitudinal opening through which the drill string 8 and pipe sections can travel. The drilling functions are executed by a second drilling system, for example a topdrive.

The method for continuous drilling (Fig. 12 A-E) comprises different steps according to the invention. In Figure 12 A the topdrive 24, installed on drilling rig 2, is drilling drill string 8 with drill head 14 into the borehole and is injecting fluid 212. The continuous drilling system 130 is deactivated. In Figure 12 B the continuous drilling system 130 takes over the drilling functions from the topdrive 24 and is injecting drilling fluid 212. The clamping means, support means and seal system in the first rotatable housing 58 are activated. The second rotatable housing 132 is used to uncouple the topdrive 24 from the drill string 8. In Figure 12 C the topdrive 24 delivers two new pipe sections 10 to the drill string 8. The second rotatable housing 132 is deactivated so that the pipe sections 10 can be placed inside the continuous drilling system 130 before coupling them to the drill string 8. The continuous drilling system 130 is still drilling and injecting drilling fluid 212. In Figure 12 D both the first rotatable housing 58 and the second rotatable housing 132 are activated and clamp and seal the drill string 8 and new pipe section 10 respectively. The separating seals in the continuous drilling system 130 are opened and the topdrive 24 injects drilling fluid 212. The continuous drilling system 130 is still executing the drilling functions of supporting, rotating and delivering torque to the drill string 8. In Figure 12 E the continuous drilling system 130 has connected the drill string 8 and the pipe section 10. After this the topdrive 24 takes over the drilling functions and the continuous drilling system is deactivated and moves upwards to continue the process as in Figure 12 A.

The method for tripping without continuous fluid injection according to the invention comprises different steps. In Figure 13 A the continuous drilling system 130 is hoisting the drill string 8 out of the borehole 12. During this action the continuous drilling system 130 uncouples pipe section 10, which is hoisted by elevator hinges 214, from drill string 8. The rotary slips 216 are opened. In Figure 13 B the continuous drilling system 130 has hoisted the drill string 8 such that one pipe section is above the rotary slips 216, which are closed to support the drill string 8 while the continuous drilling system 130 moves downward and topdrive 24 is storing the uncoupled pipe sections. In Figure 13 C the elevator hinges 214 have connected to the drill string 8 and hoist the drill string 8 out of the borehole. During this action continuous drilling system 130 is deactivated and moves downward. The rotary slips are opened.

The present invention is by no means limited to the above described embodiments thereof. The rights sought are defined by the following claims within the scope of which many

modifications can be envisaged. For example, the indirect sealing approach can also be used in conventional drilling systems.