NO20230521A1

NO20230521A1 -

Info

Publication number: NO20230521A1
Application number: NO20230521A
Authority: NO
Priority date: 2023-04-21
Filing date: 2023-05-04
Publication date: 2024-09-02
Also published as: WO2024219978A1; AU2024259304A1; NO348130B1

Description

A SYSTEM AND A METHOD FOR DOWN HOLE CONTROL OF DEVICES WITHIN ROTARY STEERABLE DRILLING ASSEMBLY.

Technical Field of the Invention

This invention relates to a rotary steerable drilling assembly for drilling directional boreholes in the bed rock, more particularly the invention relates to a system and a method for controlling a “point the bit” steering device within a drilling assembly, said steering device being responsible for the borehole deviation provided by the drilling assembly during drilling as well as drilling direction.

Background of the Invention

Prior art rotary steerable drilling assemblies also known as rotary steerable systems (or just RSS) typically comprise a drilling assembly having a main body that are kept substantially rotationally fixed relative to the borehole wall, wherein a rotatable drive shaft is running through the said main body, the drive shaft at one end being connected to a drill bit, and at the other end thereof a coupling for connection to a drill string driven by a drill rig at surface. The drilling assembly further comprise a steering device adapted to provide means for deviating the borehole in a desired direction, said steering device typically being integrated into forward section of the drilling assembly main body. One of the most common engineering principles for such a steering device is known as “point the bit”, wherein the steering device is adapted to introduce an angular deviation to the drill bit axis, relative to the axis of the drilling assembly, thus also the borehole. By adjusting the degree of said angular deviation of the drill bit axis, degree of borehole deviation provided by the drilling assembly during drilling can be controlled. Drilling direction can be controlled by adjusting the rotational position of the said angular deviation of the drill bit axis.

The main body of the drilling assembly may also comprise a navigation instrument commonly referred to as a measure while drilling (MWD) unit and a system control device. In one embodiment the operator at surface may communicate to the system control device downhole to initiate adjustment of the steering device based on data the operator has received from the navigation instrument and other sensors. In another embodiment the system control device may initiate adjustment of the steering device semi or fully autonomously, based on data the system control device has received from the navigation instrument and other sensors downhole, thus acting without interference from the operator at surface. The latter require that the operator gives the system control device operational parameters to work within, typically according to a drilling plan. To manually initiate the said adjustments while the drilling assembly is downhole or adjusting operational parameters for an autonomously working system control device downhole, it is known to use different kinds of means for communication transmitted along the drill sting, such as telemetry, acoustics, or mud pulses (hydraulic pressure pulses).

It is also common with drilling assemblies having a “point the bit” steering device wherein adjustment of the angular deviation of the drill bit axis provided by the said steering device is done manually at surface, thus the whole drilling assembly must be brought to surface every time the operator wants to make an adjustment Steering devices of this type is typically used within the mining and infrastructure industry and are in some cases adapted to take core samples.

The navigation instrument comprises different sensors such a magnetometers, accelerometers, and gyros for at least measuring the rotational position of the angular deviation given to the drill bit axis by means of the steering device, typically relative to a known reference such as earth gravity, said rotational position commonly being known as orientation or tool face and related to the drilling direction. The navigation instrument may also measure the directional position of the drilling assembly thus also the borehole at a given depth, relative to a known reference such as true or geographic north or a local grid.

Several systems are known for keeping the said orientation thus also the drilling direction fixed during drilling, such as anti-rotation devices engaging the borehole wall or steering devices adaptive to rotation. To overcome the friction that occur when the anti-rotation device engages the borehole wall, it is known to use axially working bearings transferring load from the drill string to the main body of the drilling assembly to push it forward without the main body rotating along with the drive shaft within the main body or the drill string thereof. It is emphasized that the weight on the bit in most cases are transferred directly from the drill sting to the drill bit by means of the drive shaft and couplings thereof.

In GB1139908 a solution is described where the pressure on the anti-rotation pads is used to push the whole drilling assembly radially relative to the borehole wall to change the drilling direction. This is performed using an insert capable of controlling the pressure on the pads selectively. The orientation of the said anti-rotation pads is found by using a separate retrievable orientation instrument which is inserted into the drilling assembly at need to measure the said orientation.

The present invention relates to rotary steerable drilling assembly having a “point the bit” steering device. A brief explanation of “point the bit” concept follows below.

Point the bit

A “point the bit” steering device comprises typically a bearing having an axis that can be adjusted to be offset relative to the axis of the drilling assembly. The said offset can among other be achieved by means of two eccentric rings that can be rotated relative to each other, wedges, or adjustment screws. In one embodiment the steering device is located at the forward section of the drilling assembly main body, between a tiltable front bearing having its center point coinciding with the axis of the drilling assembly, and a fixed rear bearing having an axis coinciding the drilling assembly. In another embodiment the steering device is a located at the very front of the drilling assembly main body, wherein a rear bearing having an axis coinciding with the axis of the drilling assembly is placed some distance further back. A drive shaft having a drill bit attached to its front end is running through the bearings, thus a structural bend is imposed to the drive shaft. Consequently, the axis of the drive shaft as it protrudes out of the main body of the drilling assembly and wherein the drill bit is mounted, will have an angular deviation relative to the axis of the drilling assembly. The degree of borehole deviation provided by the steering device during drilling can be adjusted by changing the offset given to the bearing within the steering device, while drilling direction can be adjusted by changing the rotational position of the said angular deviation

It is also known in prior art to have a drive shaft comprising one or more universal joints adapted to facilitate angular deviation of drill bit axis, without the need for structural bending of the drive shaft.

US6244361 describes rotary steerable drilling assembly having a “point the bit” steering device that can be adjusted downhole by means of a system control device, and wherein the system also involves use of MWD and communication along the drill sting.

NO20171838 and CA2749316C describes steerable core drilling assembly having a “point the bit” steering device that require the whole drilling assembly to be brought to surface for adjusting the steering device.

There are several major disadvantages related to prior art for downhole adjustment of a “point the bit” steering device within a rotary steerable drilling assembly, said adjustment being related to the borehole deviation provided by the steering device during drilling. In one embodiment prior art requires the complete drilling assembly to be brought to surface when adjustments of the steering device are needed. This represents inefficient and expensive operations. In another embodiment prior art comprise systems for adjustments of the steering device downhole, but wherein the complexity and high cost of said systems makes it not commercially viable for markets with considerably lower margins than found in the oil and gas industry, such as the mining and infrastructure sector.

Objects of the Invention

The main object of the present invention is to provide a system and a method for downhole adjustment of the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by a “point the bit” steering device within a rotary steerable drilling assembly, that is easy to use, less complex and costly than prior art.

Another object of the invention is to provide a solution that can be used for adjusting the angular deviation of the drill bit axis relative to the axis of the drilling assembly provided by a steering device downhole without retrieving the drilling assembly, thus providing a possibility for active steering while drilling.

Yet another object of the present invention is to provide a system and a method for controlling the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by a “point the bit” steering device downhole, wherein the system and method involves bringing the controlling means to surface for adjustment, thus it can be achieved without surface to downhole communication and the main body of the drilling assembly does not need to comprise a power source. Yet another object of the present invention is to provide a system and a method for controlling the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by a “point the bit” steering device downhole, wherein the execution of the said controlling is not limited by the length of the borehole.

Yet another object of the present invention is to provide a system and a method for controlling the drill fluid pressure within a rotary steerable drilling assembly, that is less flow dependent than prior art.

Yet another object of the present invention is to provide a system and a method for controlling drill fluid pressure within a rotary steerable drilling assembly, wherein the said pressurized drill fluid is involved in control of the steering device in the drilling assembly.

Yet another object of the present invention is to provide a system and a method for controlling drill fluid pressure within a rotary steerable drilling assembly, wherein the system can be configured to send information from the drilling assembly downhole to the operator at surface, said information being related to operation of the drilling assembly.

Yet another object of the present invention is to provide a system and a method according to the above-mentioned objects, wherein parts of the system, such as a navigation unit, pressure control device and system control device can be brought to surface for repair and maintenance work, without bringing the whole drilling assembly to surface. It’s emphasized that this also provides means for adjusting operational parameters of the drilling assembly downhole without the use of surface to downhole communication.

Yet another object of the invention is to provide a steerable drilling assembly wherein the retrievable inner assembly may also be configured to collect core samples as well as carrying other instruments, such as instruments for core orientation. This way core samples may be retrieved without retrieving the whole drilling assembly.

Finally, there is an object of the present invention is to provide a system and a method according to at least some of the above-mentioned objects, wherein the system and method is compatible with both coring and non-coring rotary steerable drilling assemblies.

The objects stated above are achieved by means of a system and a method as further defined by the independent claims, while embodiments, variants and alternatives are defined by the dependent claims.

Summary of the Invention

The main principle of the present invention describes a system and a method for downhole adjustment of the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided a “point he bit” steering device within a rotary steerable drilling assembly, by using a retrievable inner assembly.

As disclosed in the claims the present invention relates to a rotary steerable drilling assembly having a steering device utilizing “point the bit” principle for drilling directional boreholes where degree of borehole deviation can be controlled by using pressure control means, which provides a more efficient drilling operation, and wherein the system is capable of controlling the drilling operation downhole, and in some cases may be semi or fully autonomously operated based on pre-set parameters as well as data collected downhole. This may be realized in different ways, where especially two embodiments are discussed as examples below.

In one embodiment the present innovation describes a retrievable inner assembly comprising at least a navigation instrument and a pressure control device, making the solution suitable for a wide range of drilling tools. The navigation instrument being adapted to at least monitor the rotational position of the steering device, thus also the rotational position of the drill bit axis relative to a known reference such as earth gravity. Said rotational position of the drill bit axis being related to the drilling direction. The pressure control device comprises means adapted to cause the drill fluid to be pressurized when drill fluid is pumped through. The pressure control device further comprises one or more external fluid conductor outlet port seals, wherein the position of the said seal/s can be adjusted manually at surface to direct pressurized drill fluid to specific fluid conductor inlet port/s inside the drive shaft running through the drilling assembly, said fluid conductor inlet port/s represents a specific angular deviation given to the drill bit axis relative to the axis of the drilling assembly, by means of the steering device. The borehole deviation provided by the steering device during drilling can thus be adjusted by changing which fluid conductor inlet port/s is pressurized, said adjustment being effective when the inner assembly is re-seated inside the drilling assembly.

It is emphasized that a valve can be configured to provide same functionality as described above. In that case the said seals may be used to provide exclusive communication between one or more fluid conductor outlet port/s in the pressure control device and the corresponding fluid conductor inlet port/s in the drive shaft, wherein the valve is used to direct the pressurized drill fluid to a specific fluid conductor inlet port/s. By adjusting the position of the said valve manually at surface, the adjustment will become effective when the inner assembly is re-seated inside the drilling assembly.

In another embodiment the present innovation describes a retrievable inner assembly comprising at least a navigation instrument, a pressure control device, and a system control device. The navigation instrument being adapted to at least monitor the rotational position of the steering device, thus also the rotational position of the drill bit axis relative to a known reference such as earth gravity. Said rotational position of the drill bit axis being related to the drilling direction. The pressure control device comprises means adapted to cause the drill fluid to be pressurized when drill fluid is pumped through. The pressure control device further comprises external fluid seals that provide exclusive communication between one or more fluid conductor outlet port/s in the pressure control device and the corresponding fluid conductor inlet port/s in the drive shaft, said fluid conductor inlet port/s represents a specific angular deviation given to the drill bit axis relative to the axis of the drilling assembly, by means of the steering device. Preferably a valve within the pressure control device is used to direct the pressurized drill fluid to a specific fluid conductor inlet port/s, alternatively the said external fluid seals can be re-positioned. The said system control device being adapted to at least control the pressure control device, based on data collected from sensors within the inner assembly such as but not limited to data from sensors associated with the drill fluid pressure and the navigation instrument. Adjustment of the borehole deviation provided by the steering device may be initiated according to pre-set parameters given by the operator when the inner assembly is at surface. The adjustment may also be executed semi-or fully autonomously downhole.

It is to be understood that at least the system control device and the pressure control device according to the present invention may also be used for semi- or fully autonomous downhole control of other system devices and/or parameters within an rotary steerable drilling assembly, such as but not limited to an anti-rotation device, as a part of the system for controlling a steering device, or separately without involving control of a steering device.

According to the present invention the pressure control device may also be used for establishing several different pressure levels, one at a time at need, wherein the said pressure levels individually represent a specific angular deviation given to the drill bit axis relative to the axis of the drilling assembly.

According to the present invention the pressure control device may also comprise means for producing mud-pulse signals, said signals being initiated and controlled by the system control device and actuated by the pressure control device. The signals can be related to events downhole, such as but not limited to core block in a rotary steerable core drilling assembly, landing indication for the inner assembly, or giving the operator data about orientation of the steering device (drilling direction) or actual directional position of the drilling assembly.

According to the invention a solution is achieved where an inner assembly, e.g., a wireline solution is be used to control and monitor the drilling direction, thus not being dependent on communication along the drill string and limited by the depth of the drilling operation.

Preferably, the rotary steerable drilling assembly or the steering device thereof, should also comprise a system for adjusting the orientation of the steering device.

Preferably the navigation instrument is adapted to at least measure the rotational position of the steering device i.e., where the drill bit axis is pointing, relative to earth gravity or another known reference. An example of such a system is described in international patent application WO2023280480, Norwegian Patent application NO20210892 or European patent EP3180496B1.

It should be emphasized that the navigation instrument, system control device, and pressure control device respectively can be any device or unit suitable or adapted to perform the described task of the said device. Furthermore, they do not need to appear as individual units or devices as long as one single component or a combination of components within the inner assembly perform the described task of the said device or devices.

Moreover, its emphasized that the “main body” of the drilling assembly is to be understood as the non-rotational outer section of the drilling assembly wherein the steering device is mounted.

Moreover, its emphasized that “angular deviation” in relation to an axis is to be understood as a difference in angular direction between two axes.

Moreover, its emphasized that the drill bit axis coincide with the axis of the drive shaft, at the point where the drive shaft axis protrudes out of main body of the drilling assembly.

Moreover, its emphasized that “adjust, adjusting or adjustment”, it is primarily to be understood as the operation of giving a device new working parameter/s.

Moreover, its emphasized that the word “downhole” is to be understood as any place below surface and in a location where the device such as a steering device is not directly accessible by hand.

Moreover, its emphasized that “rotational position” of where the drill bit axis is pointing relates to where angular deviation of the drill bit axis is pointing, when seen along the axis of the drilling assembly with the rear end of the drilling assembly as viewpoint. Said rotational position also being known as “orientation” or “tool face” of the drilling assembly, and typically being relative to earth gravity if nothing else is specified.

Moreover, it is emphasized that “drilling direction” is related to the rotational position of where the drill bit axis is pointing.

Moreover, it is emphasized that a “universal joint” is a common reference for a drive shaft coupling connecting two drive shafts together, wherein the said drive shaft coupling can transfer torque from one drive shaft to the other drive shaft. The drive shaft coupling according to the present invention is also adapted to transfer an axial force through the drive shaft coupling.

Moreover, it is emphasized that “retrievable or retrieve” in relation to the inner assembly, can preferably be done by standard of the shelf wire line technology, but available solutions may also be contemplated.

Moreover, it is emphasized that in a side view “front” of the drilling assembly is the side where the drill bit is located, and “rear” of the drilling assembly is the side where the coupling for the drill sting is located.

BRIEF DESCRIPTION OF THE DRAWINGS

For detailed understanding of the disclosure, references should be made to the following description taken in conjunction with the accompanying drawings illustrating the invention by way of examples and in which corresponding elements are generally designated by like numerals, and wherein;

Figure 1 illustrates simplified version of a rotary steerable drilling assembly according to prior art, comprising a steering device located between a front and a rear bearing.

Figure 2 illustrates simplified version of a rotary steerable drilling assembly according to prior art, comprising a steering device located at the very front of the main body of the drilling assembly wherein a rear bearing is located further back.

Figure 3 illustrates simplified version of a rotary steerable drilling assembly according to prior art similar fig 2, but wherein the drive shaft has a universal joint.

Figure 4 illustrates simplified version of a rotary steerable drilling assembly according to prior art similar fig.1, but wherein the drilling assembly also comprise a retrievable inner assembly, and wherein the inner assembly also comprise a core tube.

Figure 5 illustrates simplified version of a retrievable inner assembly as seen in fig.4.

Figure 6 illustrates a longitudinal section of a rotary steerable drilling assembly according to one embodiment of the present invention, comprising a “point the bit” steering device shown to provide minimum angular deviation of the drill bit axis and wherein the retrievable inner assembly comprises a pressure control device and a navigation instrument.

Figure 7 illustration similar Fig.6, but wherein the steering device is shown to provide maximum angular deviation of the drill bit axis.

Figure 8 illustrates a longitudinal section of a rotary steerable drilling assembly according to one embodiment of the present invention, comprising a “point the bit” steering device shown to provide maximum angular deviation of the drill bit axis.

Figure 9 illustrates a simplified axial section of a rotary steerable drilling assembly according to prior art, wherein the rotational position of the angular deviation given to the drill bit axis is shown to point at 12 o’clock (seen along the axis of the drilling assembly, with rear as viewpoint).

Figure 10 illustration similar fig 9, but wherein the rotational position of the angular deviation given to the drill bit axis is shown to point at 3 o’clock.

Figure 11 illustrates a longitudinal section of a rotary steerable drilling assembly according to another embodiment of the present invention, comprising a “point the bit” steering device shown to provide minimum angular deviation given to the drill bit axis and wherein the pressure control device is controlled by a system control device.

Figure 12 similar illustration as fig.11, but wherein the steering device shown at maximum angular deviation given to the drill bit axis.

Figure 13 illustrates a longitudinal section of a rotary steerable drilling assembly according to another embodiment of the present invention, comprising a “point the bit” steering device, wherein the system includes a sperate ring piston for adjustment the steering device, and wherein the movement of the ring piston is limited by stop bars.

FIG.14 illustrates a simplified longitudinal section of a pressure control device according to the present invention, wherein the pressure control device shown in fig.10, 11 and 12 additionally is adapted to facilitate control of the system pressure as well as generating mud pulses.

FIG.15 illustrates a simplified longitudinal section of an anti-rotation device and a pressure control device according to the present invention, wherein the pressure control device is adapted to facilitate control of the system pressure as well as generating mud pulses.

It should be emphasized that the drawings do not include all foreseeable or possible embodiments according to the present invention, but merely a selection of embodiments that can be used to achieve the objects of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

Referring to FIG.1-3, a rotary steerable drilling assembly includes as a minimum the following prior art embodiments;

- a drilling assembly (2a) that houses a steering device (10a), and

- a drive shaft (3a) running through the main body of the drilling assembly (2a), said drive shaft (3a) having a drill bit (1) at its front end and a coupling (5) for drill string at its rear end thereof.

In Fig.1 a drilling assembly (2a) according to prior art is shown to have a main body wherein the forward section comprises a steering device (10a) located between a front bearing (4a) and a rear bearing (4b). The steering device (10a) has an internal bearing (10b) with an axis that are offset relative to the axis (6) of the drilling assembly (2a), whereas the front bearing (4a) has an axis (7) that can be tilted, said tilt having its center point coinciding with the axis (6) of the drilling assembly (2a), and the rear bearing (4b) an axis that fixedly coincides with the axis (6) of the drilling assembly (2a). In Fig 2 a drilling assembly (2a) according to prior art is shown to have a main body wherein the forward section comprises a steering device (10a) located at the very front, and wherein a rear bearing (4b) is located at some distance behind. The steering device (10a) has an internal bearing (10b) with an axis (7) that are offset relative to the axis (6) of the drilling assembly (2a), and the rear bearing (4b) an axis that fixedly coincides with the axis (6) of the drilling assembly (2a). A drive shaft (3a) having a drill bit (1) at its forward end and a coupling for drill string (not shown) at the other end thereof is running thru the bearings shown in Fig 1 and Fig 2, thus the drive shaft (3a) is subject to structural bending. In Fig.3 a drilling assembly (2a) similar to Fig.2 shown but wherein the drive shaft (3a) is equipped with a universal joint (12), said universal joint being located before the drive shaft (3a) enters the steering device (10a), thus the drive shaft (3a) will not be subject to structural bending. Any suitable universal joint (12) adapted to transfer both torque and thrust can be used for this purpose.

Now referring to Fig 1-3 collectively. The center line (7) of the drive shaft (3a) as it protrudes out of the main body of the drilling assembly (2a) and wherein the drill bit (1) is mounted is shown to have an angular deviation relative to the axis (6) of the drilling assembly (2a), said angular deviation being a consequence of the bending of the drive shaft (3a) by means of the steering device (10a).

Furthermore, an anti-rotation device (2b) can be seen located behind the rear bearing (4b). The said anti-rotation device (2b) are shown to have gripping means in form of wheels that can engage the borehole wall (30) for keeping the main body of the drilling assembly (2a) thus also the steering device (10a) substantially rotationally fixed during drilling while allowing the drilling assembly (2a) to slide up/down in the borehole. The gripping means should preferably be actuated by pressurized hydraulic fluid and comprise knifes or rollers to ensure that they engage the borehole wall (30) properly. Mechanical actuation solutions are also known in prior art. The rotational position of where the drill bit axis (7) is pointing i.e., drilling direction is thus kept fixed during drilling, until the rotational position is changed by the operator. It is however anticipated that the anti-rotation device (2b) may slip or have some rotational drift over time, thus the rotational position of the main body carrying the steering device (10a) may have to be corrected from time to time. In another embodiment the anti-rotation device is not needed or comprise flat pads that may give relatively high rotational drift, wherein the steering device has an internal mechanism that continuously correct the drilling direction according to the said drift, to keep the drilling direction fixed.

In FIG.4 a rotary steerable drilling assembly (2a) according to prior art is shown to comprise a retrievable inner assembly (13c). In this specific embodiment the inner assembly (13c) shown to also carry a core tube (13b) for collecting core samples during drilling. The retrievable inner assembly (13c) is located inside the drive shaft (3a) and the coupling thereof and are releasably locked inside the drilling assembly (2a) by means of a lock and release mechanism (13e). The retrievable inner assembly (13c) can be retrieved to surface by means of a wire line operated fishing tool (not shown) or similar means and reseated inside the drilling assembly (2a) downhole at need. It’s emphasized that the drilling assemblies shown in Fig.1 -3 may also be adapted to comprise a retrievable inner assembly (13c), with or without the inner assembly carrying a core tube (13b). The drilling assembly shown in Fig.3 requires however that the universal joint (12) is hollow if the drilling assembly includes a core tube (13b).

In FIG.5 a retrievable inner assembly (13c) carrying a core tube (13b) according to prior art is shown separately. The retrievable inner assembly (13c) according to this specific embodiment comprise at least a core catcher (13a) adapted to grip the core sample in such way that it will break off from the rock formation when the drilling assembly (2a) thus also the core tube (13b) is lifted off bottom, a core tube (13b) adapted to collect and store core samples continuously during drilling, wherein the said core samples can be brought to surface by hoisting the inner assembly (13c) thus also the core tube (13b) to surface for inspection and storage, a navigation instrument (15a) adapted to monitor the rotational position of the steering device (10a), thus also the drilling direction, and a releasable locking mechanism (13e) adapted to facilitate locking and releasing of the inner assembly (13c) inside the drilling assembly. It is emphasized that the core catcher (13a) and the core tube (13b) shown in Fig.4 and Fig.5 is complementary elements not relevant for the definition or scope of the present patent.

FIG.6 and FIG.7 shows a simplified partial sectional view of a rotary steerable drilling assembly according to a first embodiment of the present invention. It can be mentioned that only Fig 6 has a complete set of part numbers since Fig.7 is identical component wise.

Nevertheless, at least the components that have shifted position are denoted.

The steering device (10a) is here shown be located at the font of the forward section of the drilling assembly (2a) main body, wherein a rear bearing (4b) is located some distance further back. The steering device (10a) is shown to comprise a bearing (10b) having an inclined guide structure at its outer surface, wherein the said inclined guide structure is engaging a matching wedge or ramp (10c) internally the steering device. The bearing (10b) and the wedge (10c) engage each other in such manner that when the bearing (10b) moves forward from position A1 shown in Fig.6 towards position A2 shown in Fig.7, the bearing (10b) will climb on the wedge or ramp (10c). Consequently, an offset is given to the axis (7) of the bearing (10b) relative to the axis (6) of the drilling assembly, said offset giving the drive shaft axis (7) as it protruded out of the steering device (10a) and wherein the drill bit is mounted, an angular deviation relative to the axis (6) of the drilling assembly. It’s emphasized that this will impose a structural bend to the drive shaft (3a). In another embodiment (not shown) the bearing (10b) is seated inside a suitable support structure that carries the bearing (10b), wherein the said bearing support structure comprise means for engaging the wedge or ramp (10c). It is emphasized that a skilled professional understands that the said guide structure and the matching wedge or ramp (10c) may be located at any suitable place around the circumference of the bearing (10b) or bearing support structure thereof, such as but not limited to each of the sides. It’s thus emphasized that the specific embodiment shown in Fig 6 and 7 is not intended to define or limiting the scope of the patent. Furthermore, it is emphasized that a skilled professional understands that the same outcome can be achieved by keeping the bearing (10b) in an axially fixed position, wherein the wedge or ramp is moved axially, without this defining or limiting the scope of the patent.

Other solutions than using a wedge and a ramp may also be contemplated, such as one or more expanding, pressurized pads on one side of the drilling assembly pushing a bearing in the radial direction, e.g., based on the solutions in the prior art discussed above, or individually hydraulic actuators distributed along the circumference of the drilling assembly applying a pressure in the radial direction.

The angular deviation imposed on the drill bit axis (7), will be at its minimum (as shown in fig.

6), when the bearing (10b) is fully retracted to position A1 with an initial pressure P0 applied to the bearing (10b). Likewise, the angular deviation imposed on the drill bit axis (7) will be at its maximum (as shown in fig.7) when the bearing (10b) is in fully forward position A2 by applying an increased pressure P1 to the bearing (10b). It is to be understood that the said angular deviation is directly linked to the position of the bearing (10b) relative to the ramp (10c) and that either the bearing (10b) or the ramp (10c) preferably should comprise means for selfalignment of the bearing axis, relative to axis of the drive shaft (3a) as it runs thru the bearing (10b), and that this alignment comes to effect at any given position the bearing (10b) has on the ramp (10c). Such an alignment can readily be solved by implementing a spherical support structure for the ramp (10c) or having a bearing (10b) comprising a spherical shaped structure.

In the specific embodiments shown in Fig.6-8, the stiffness of the drive shaft (3a) will act as a spring, forcing the bearing (10b) to slide down the ramp (10c) and back to fully retracted position A1 when no other forces are working on the bearing (10b). The force of the said spring functionality of the drive shaft (3a) can readily be adjusted by altering the distance between the bearing (10b) and the rear bearing (4b), likewise the inclination given to the ramp is relevant for the retracting force working on the bearing (10b). In another embodiment retraction of the bearing (10b) back to position A1 involves a spring or hydraulic fluid pressure pushing the bearing (10b).

The bearing (10b) is tightly fitted inside the steering device, the same tight fit can be said to apply for the drive shaft (3a) and the bearing (10b). Consequently, the bearing (10b) will obtain similar functionality as a ring piston that can be moved axially between position A1 and A2 by means of pressurized hydraulic fluid alone or in combination with a mechanical force such as a spring force, working on one or the other side of bearing (10b), said bearing (10b) working as a ring piston. Without sealing means some leakage will occur and act as an efficient system for cleaning and cooling the bearing (10b). If needed the bearing (10b), sleeve or support structure thereof may be equipped with one or more seals (not shown) sealing at least the outer surface while leaving only the narrow clearance between the bearing (10b) and the drive shaft (3a) open, alternatively sealing means can be applied there as well. To accommodate for miss alignment between the surfaces that are going to be sealed, such as the misalignment between the axis of the drive shaft (3a) and the axis of the steering device (10a) that will occur when the bearing (10b) is in position A2, the seal/s can be made of a flexible material such as but not limited to elastomer, or the seal/s can be seated in a cartridge allowing some degree of misalignment. One-way or two-way seal/s can be chosen based on the functionality of the steering system.

The drive shaft (3a) in this specific embodiment acts also as a drill fluid conductor providing a pressurized drill fluid with a chosen pressure P1, where the drive shaft is shown to have at least two fluid conductor inlet ports (3b, 3c) for drill fluid communication, said fluid conductor inlet ports constitute transverse holes going from interior of the drive shaft (3a) to outer surface of the drive shaft. A first fluid conductor inlet port (3c) is leading to a chamber axially confined by two shaft seals (16a,16b), below the anti-rotation element (2b). When the chamber is hydraulicly pressurized the anti-rotation element (2b) will protrude outward until it engages the borehole wall, thus the main body of the drilling assembly (2a) and the steering device (10a) becomes rotationally locked relative to the borehole wall (30). The anti-rotation element (2b) or an underlaying piston is preferable equipped with one or more seals (not shown) preventing drill fluid to leak out from the circumferences of the anti-rotation element (2b). Alternatively, the chamber involves a bellow with the same purpose. A second fluid conductor inlet port (3b) leads to a chamber axially confined by the shaft seal/s (16a), wherein the said chamber communicates thru a hydraulic fluid conductor (19a) with the steering device (10a).

Still referring to Fig.6 and Fig.7 collectively, a retrievable inner assembly (13c) can be seen seated inside the drive shaft (3a) and a coupling thereof, comprising at a core tube (13b), a pressure control device (17a) adapted to at least provide means for directing pressurized drill fluid to specific fluid conductor inlet ports (3a,3b) in the drive shaft and a navigation instrument (15a) adapted to at least monitor the orientation of the steering device (10a), thus also the drilling direction.

The inner assembly (13c) are shown to create an annulus between the outer diameter of the retrievable inner assembly (13c) and the inner diameter of the drive shaft (3a), said annulus being the flow conductor for conducting drill fluid going to the drill bit (1). The origin of the drill fluid is a hydraulic fluid pump at surface supplying drill fluid through the drill string. A seal (18a) located on the circumference of pressure control device (17a) is shown to block the said annulus at one point, thus forcing the drill fluid to enter an fluid conductor inlet port (17c) in the pressure control device (17a), wherein a pressure building element (17d) is adapted to cause a buildup of fluid pressure P1 upstream the pressure building element (17d), when drill fluid is pumped through. Drill fluid downstream the pressure building element (17d) will remain unpressurized (P0) during drilling, thus a differential pressure is created that can be used to actuate force exerting means needed for control of the steering device (10a) as well as the anti-rotation device (2b). The drill fluid will further continue through fluid conductor outlet port (17b) to the drill bit.

In this specific embodiment the pressure building element (17d) constitutes a nozzle or constriction, without this defining or limiting the scope of the patent, thus its emphasized that any suitable means for building up hydraulic fluid pressure can be utilized such as a valve shown in Patent NO344679B1 or a combination of a valve/s and nozzles or similar.

The navigation instrument (15a) is at least monitoring the rotational position of the reference element (15b), to measure the orientation of the main body of the drilling assembly thus also the steering device (10a) as discussed in abovementioned WO2023280480 and EP3180496B1.

The system described herein provides the necessary means for controlling at least the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by the steering device (10a) and the anti-rotation device (2b). In Fig.6 the pressure control device seal/s (18a) is shown in position B1, i.e. upstream fluid inlet port (3b) in the drive shaft (3a), thus pressurized drill fluid (P1) will not be able to communicate with the steering device (10a), and the bearing (10b) will stay in position A1 providing minimum angular deviation of the drill bit axis (7), relative to the axis (6) of the drilling assembly (2a). In Fig.7 the pressure control device seal/s (18a) is shown in position B2, i.e., downstream fluid inlet port (3b) in the drive shaft (3a), thus pressurized drill fluid (P1) will be able communicate through inlet port (3b). A fluid conductor (19a) further allows the pressurized (P1) drill fluid to engage the rear-end surface of bearing (10b) causing the bearing (10b) to move to position A2, providing maximum angular deviation of the drill bit axis (7) relative to the axis (6) of the drilling assembly (2a). To switch between bearing position A1 and A2, the inner assembly (13c) is brought to surface by wireline, wherein the seal (18a) is manually moved to a predetermined position on the outer surface of pressure control device (17a) that represent either position B1 or position B2. The change will come to an effect as soon as the inner assembly (13c) is reseated downhole, and drilling resumed. Consequently, the operator is given an easy and convenient way of downhole adjustment of the angular deviation of the drill bit axis (7) relative to the axis (6) of the drilling assembly, thus also obtained borehole deviation during drilling.

In another embodiment (not shown) adjustment of the steering device may involve exposing one side of the bearing (10b) or a bearing support structure to different pressure levels, wherein each pressure level represents a specific angular deviation given the drill bit axis relative to the axis of the drilling assembly. As described the fluid pressure may work on one side of the bearing (10b) while the other side subject to a mechanical force such as a spring force. Movement of the bearing (10b) from position A1 towards position A2 will cause the spring to be compressed causing the force needed to actuate the said movement to increase. Consequently, a specific fluid pressure levels may be used to place the bearing 10b) in a specific position on the ramp (10c), thus downhole adjustment of the angular deviation of the drill bit axis (7) relative to the axis (6) of the drilling assembly may be achieved. It’s emphasized that the spring force may be replaced by a fluid pressure, and that this would involve controlling the fluid pressure at both sides of the bearing (10b) to achieve the same functionality.

It is emphasized that the anti-rotation device (2b) will be pressurized through fluid conductor inlet port (3c) in the drive shaft regardless of the position of the seal/s (18a), thus the steering device (10a) will stay rotationally locked to the bore hole wall when the system is operational.

It’s furthermore emphasized that the bearing (10b) can be of any type, such as but not limited to a sliding bearing or a rolling bearing engaging the drive shaft directly or indirectly, likewise whether the drive shaft is comprising a universal joint or carries a core tube is not defining or being relevant for the scope of the invention.

FIG.8 shows a simplified partial sectional view of a rotary steerable drilling assembly according to an embodiment of the invention. The steering device is here shown to comprise a bearing (10b) engaging a wedge or ramp (10c), wherein the said bearing (10b) is placed between a front bearing (4a) having focal seating and a rear bearing (4b) having a fixed seating. The bearing (10b) and the wedge (10c) is interacting like what is described for Fig.6 and Fig.7, but in this embodiment the drive shaft (3a) is subject to structural bending between the front bearing (4a) and a rear bearing (4b) to achieve an angular deviation of the drive shaft axis (7) as it protrudes out of the front bearing (4a), thus also the drill bit axis, relative to the axis (6) of the drilling assembly (2a). When the bearing (10b) is at position A1 the offset imposed to the shaft is at its minimum (as shown in fig.6), likewise when the bearing (10b) is at position A2, the offset imposed to the shaft is at its maximum (as shown in fig.7). The angular deviation given to the drill bit axis (7) relative to the axis (6) of the drilling assembly is directly linked to the position of the bearing (10b) relative to the ramp (10c). To adjust the position of the bearing (10b) on the ramp, the same method as described in Fig.6-7 may be used. The drive shaft (3b) is in this embodiment also shown to carry a core tube (13b), without this defining or being relevant for the scope of the present invention.

FIG.9 shows a simplified schematic illustration of an axial section of a rotary steerable drilling assembly according to the invention and prior art, wherein the rotational position of the angular deviation given to the drill bit axis (7) is shown to point at 12 o’clock seen with base of viewpoint at the rear of the drilling assembly (2a), thus the drilling direction in this case is upwards.

FIG.10 shows a simplified partial sectional view of a rotary steerable drilling assembly according to the invention and prior art, wherein the rotational position of the angular deviation given to the drill bit axis (7) is shown to point at 3 o’clock seen with base of viewpoint at the rear of the drilling assembly (2a), thus the drilling direction in this case is to the right.

FIG.11-12 shows a simplified partial sectional view of a rotary steerable drilling assembly according to an embodiment of the invention. The steering device (10a) utilize similar principles as described for Fig.6 and Fig 7, for establishing an angular deviation of the drill bit axis (7), relative to the axis (6) of the drilling assembly (2a), as well as for control of the antirotation device (2b), thus it is referred to Fig 6 and Fig.7 for detailed description. The steering device (10a) in Fig.11 and Fig.12 is additionally shown to comprise a shaft seal (16c) located in the front of the bearing (10b), said seal (16c) creating a chamber axially confined by the seal (16c) at one end, and the bearing (10b) at the other end. It is also shown a hydraulic fluid conductor (19b) leading to the said chamber. Furthermore, a universal joint (12) is incorporated into the drive shaft like what can be seen in Fig.3, wherein the universal joint is adapted to facilitate an angular deviation of the drill bit axis (7), without the need for structural bending of the shaft (3a). The universal joint (12) is adapted to transfer both torque and axial load to the drill bit during drilling. It emphasized that if the drilling assembly (2a) should carry core tube for collection core samples, the said universal joint (12) need to comprise an internal bore large enough for the core tube. In an alternative embodiment the drive shaft does not comprise a universal joint, thus the drive shaft (3a) could be similar to what is described in Fig.6, 7 or 8, i.e., having a structural bend.

The drive shaft (3a) is in this specific embodiment shown to have at least three fluid conductor inlet ports (3b, 3c and 3d) for drill fluid communication, said fluid inlet ports constitutes transverse holes going from interior of the drive shaft (3a) to outer surface of the drive shaft. The first fluid conductor inlet port (3c) is leading to a chamber axially confined by two shaft seals (16a,16b) below the anti-rotation element (2b), thus similar principle as described in Fig. 6 and Fig.7 is utilized for operation of the anti-rotation element/s (2b) that engage the borehole wall to rotationally lock the main body of the drilling assembly (2a) and the steering device (10a) thereof, relative to the borehole wall (30) during drilling. It is referred to Fig 6 and Fig.7 for detailed description. The second fluid conductor inlet port (3b) leads to a chamber axially confined by two shaft seals (16a,16d), wherein the said chamber communicates thru a hydraulic fluid conductor (19b) with the steering device (10a). The third fluid conductor inlet port (3d) leads to a chamber axially confined by shaft seal (16d), wherein the said chamber communicates thru a hydraulic fluid conductor line (19a) with the steering device (10a).

Still referring to Fig.11 and Fig.12 collectively a retrievable inner assembly (13c) can be seen seated inside the drive shaft (3a), comprising a pressure control device (17a) adapted to at least provide means for directing the pressurized drill fluid to specific fluid conductor inlet ports in the drive shaft, a system control device (25) adapted to at least providing means for collecting and processing data from sensors as well as means for exerting necessary force to actuate the said means for controlling the fluid pressure, and a navigation instrument (15a) adapted to at least monitor the orientation of the steering device (10a), thus also the drilling direction.

The inner assembly (13a) are shown to create an annulus between the outer diameter of the retrievable inner assembly (13a) and the inner diameter of the drive shaft (3a), said annulus being the flow path for drill fluid going to the drill bit (1). The origin of the drill fluid is a hydraulic fluid pump at surface supplying drill fluid through the drill string. A seal (18a) located on the circumference of pressure control device (17a) is shown to block the said annulus at one point, thus forcing the drill fluid to enter an fluid conductor port (17c) in the pressure control device (17a), wherein a pressure building element (17d) is adapted to cause a buildup of fluid pressure P1 upstream the pressure building element (17d), when drill fluid is pumped through. Drill fluid downstream the pressure building element (17d) will remain unpressurized (P0) during drilling, thus a differential pressure is created that can be used to actuate force exerting means. The drill fluid will further continue to the drill bit.

In this specific embodiment the pressure building element (17d) is shown to constitute a nozzle or constriction, without this defining or limiting the scope of the patent, thus its emphasized that any suitable means for building up hydraulic fluid pressure can be utilized such as a valve shown in Patent NO344679B1 or a combination of a valve/s and nozzles or similar, and that the pressure building element (17b) may be located other suitable places as a separate component independent of the valve spool.

The pressure control device (17a) further comprises two fluid conductor outlet ports (17g, 17h) leading to chambers outside the pressure control device, said chambers being axially confined by the fluid seals (18a, 18b) and (18b, 18c) respectively. A valve spool (17e) within the pressure control device (17a) is adapted to selectively direct pressurized drill fluid to one or the other chamber through a fluid conductor outlet port (17f). It’s emphasized that number of fluid conductor outlet ports is not defining or limit the scope of the invention, thus the valve spool may be adapted to direct pressurized drill fluid to a range of chambers or ports. In this specific embodiment the valve spool is being adjusted manually when the inner assembly (13a) is at surface or actuated by a system control device (25) comprising among other a force exerting device such as but not limited to a motor being controlled by a processor within the system control device (25). It is emphasized that in one embodiment the valve spool (17e) may move axially to shift what chamber to pressurize (as shown), and in another embodiment (not shown) it may rotate. A combination of both axial movement and rotational movement may also be feasible.

The navigation instrument (15a) is at least monitoring the rotational position of the reference element (15b), to provide means for measuring the orientation of the main body of the drilling assembly thus also the steering device (10a) as discussed in abovementioned WO2023280480 and EP3180496B1.

The system described herein provides the necessary means for at least controlling the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by the steering device (10a). In Fig.11 the fluid conductor outlet port/s (17f) of valve spool (17e) is shown to align with fluid conductor outlet port/s (17g) in the housing carrying the said valve spool, thus pressurized drill fluid (P1) may communicate through fluid conductor inlet port (3b) in the drive shaft (3a) whereas fluid conductor inlet port (3d) in the drive shaft is kept closed. A fluid conductor (19b) further allows the pressurized (P1) drill fluid to engage the front-end surface of bearing (10b) causing the bearing (10b) to move to position A1, providing minimum angular deviation of the drill bit axis (7) relative to the axis (6) of the drilling assembly. In Fig. 12 the fluid conductor outlet port/s (17f) of valve spool (17e) is shown to align with fluid conductor outlet port/s (17h) in the housing carrying the said valve spool, thus pressurized drill fluid may communicate through fluid conductor inlet port (3d) in the drive shaft (3a) whereas fluid conductor inlet port (3b) in the drive shaft is kept closed. A fluid conductor (19a) further allows the pressurized (P1) drill fluid to engage the rear-end surface of bearing (10b) causing the bearing (10b) to move to position A2, providing maximum angular deviation to drill bit axis (7) relative to the axis (6) of the drilling assembly (2a). Preferably the end-surface of the bearing (10b) not being pressurized should be vented to an unconfined and unpressurized area to avoid problems related to leakage over the seals.

The system control device (25) is adapted to control which fluid conductor inlet ports (3b, 3d) to communicate pressurized frill fluid through, said control involving the system control device (25) processing data received from the navigation instrument (15a) alone or in combination with data from other sensors relevant for the operation of the drilling assembly (2a). A change in position of the valve spool (17e) leading to an adjustment of the angular deviation of the drill bit axis (7) relative to the axis (6) of the drilling assembly (2a) by means of the steering device (10a) may be executed according to operator specified working parameters given to the system control device (25) when at surface. If the said working parameters need to be changed the inner assembly (13c) is once again brought to surface for re-programming, wherein the said changes will come to an effect as soon as the inner assembly (3c) is reseated downhole, and drilling resumed. It’s emphasized that in another embodiment, control of the steering device (10a) may be carried without the use of data from the navigation instrument, thus the operator may instruct the system control device (25) to actuate a specific angular deviation of the drill bit axis (7), relative to the axis (6) of the drilling assembly. The borehole deviation obtained during drilling can thus be controlled semi- or fully autonomously. It’s emphasized that adjustment of the steering device may also involve use of different fluid pressure levels similar to what is described in Fig.6 and Fig.7 wherein the said fluid pressures is controlled by the system control device (25).

In another embodiment (not shown) the pressure control device (17a) comprises at least one pair of fluid conductor outlet port seals similar to (18a, 18b) and/or (18b, 18c), wherein the axial position of the said seals may be adjusted to provide exclusive communication of the pressurized fluid between one or more fluid conductor outlet port/s similar to (17g, 17h) in the pressure control device (17a) and corresponding fluid connector inlet port/s such as ports (3b, 3d) in the drive shaft (3a). Said adjustment being controlled by the system control device (25).

It is emphasized that the positioning of the valve spool (17e) or positioning of fluid conductor outlet port seals such as seals (18a, 18b) and/or (18b, 18c), may also be executed manually at surface without involving the system control device (17a) or other instruments, the said adjustment will become effective when the inner assembly is re-seated inside the drilling assembly. This embodiment provides a very rudimentary and simple system with low user threshold for adjusting the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by the “point the bit” steering device.

It is emphasized that the anti-rotation device (2b) will be pressurized through conductor inlet port (3c) in the drive shaft regardless of the position of valve spool (17a), thus the steering device (10a) will stay rotationally locked to the bore hole wall when the system is operated.

FIG.13 shows a simplified partial sectional view of a steering device within a rotary steerable drilling assembly according to an embodiment of the invention. The steering device (10a) utilizing similar principles as described for Fig 6 and Fig 7, for establishing an angular deviation of the drill bit axis (7), relative to the axis (6) of the drilling assembly (2a), thus it is referred to Fig 6 and Fig.7 for detailed description. The steering device (10a) in Fig.13 is additionally shown to comprise a separate ring piston (21a) connected to the bearing (10a), said ring piston being adapted to exert the necessary force to move the bearing (10b) or a bearing support structure thereof between position A1 and position A2. In this specific embodiment the steering device (10a) is further shown to comprise two stop bars (21b, 21c) adapted to limit the movement of the ring piston (21a) thus also the bearing (10b). The position of the bars (21b, 21c) can be adjusted axially in both directions by means of a screw/s or other suitable adjustment mechanism (not shown) such as but not limited to a hydraulicly operated mechanism or a gear, to give the steering device (10a) a specific working range. Said working range being the minimum and maximum angular deviation of the drill bit axis (7), relative to the axis (6) of the drilling assembly (2a) provided by the steering device (10a) during drilling. It is emphasized that the stop bars (21b, 21c) may be adapted to engage the bearing (10b) or a bearing support structure thereof directly regardless of the steering device comprising a separate ring piston or not.

FIG.14 shows a simplified partial sectional view of an inner assembly (13c) according to an embodiment of the invention. In this embodiment the means for controlling the steering device additionally include the pressure control device (17a) being adapted to at least control the system pressure (P1). Furthermore, the pressure control device (17a) provides means for downhole to surface communication. The pressure control device (17a) has a pressure building element (17d) comprising an orifice (23) and a constriction element (22) located partially inside the said orifice (23). The constriction element (22) is connected to the valve spool (17e) which is actuated by a motor or other suitable force exerting means being a part of the system control device (25), thus means are provided to move the valve spool (17e) and the constriction element (22) both axially and rotationally at need. This can readily be achieved by connecting the valve spool (17e) to a lead screw driven by the said motor or similar force exerting means. It is emphasized the axial position of the constriction element (22) relative to the orifice (23) is directly related to the flow area through the orifice (23), thus also the drill fluid pressure that builds up at a given flow frate.

In another embodiment the orifice (23) may be integrated into a valve having similar purpose as the one described in patent EP3710669B1, wherein the valve piston or ball comprises an orifice running through the said piston or ball, and the constriction element (22) is used to facilitate an adjustment of the flow area thru the said orifice. Alternatively, a valve having similar purpose as the one described in patent EP3710669B1 can be set up to run in parallel with the orifice (23) and the constriction element (22). In both cases the orifice (23) and the constriction element (22) will facilitate control of pressure levels below the opening pressure of the valve described in patent EP3710669B1, as well as providing a more stable fluid pressure by compensating for the spring quotient associated with the valve spring at high flow rates.

It is empathized that the pressure building element (17d) comprising an orifice (23) and a constriction element (22) may be configured differently, thus the illustration is not intended to define or limit the scope of the patent. As an example, in one embodiment the pressure building element (17d) may comprise a first sleeve having a transverse opening with similar purpose as orifice (23), wherein a second sleeve also having a transverse opening is fitted inside the said first sleeve and acting as a constriction element, thus it will have similar purpose as constriction element (22). It’s emphasized that degree of alignment between the two transverse openings decide the flow area through the pressure building element (17d), thus means adapted to cause fluid pressure to build up inside the drive shaft when drill fluid is pumped through is provided, and wherein the means are adjustable. To use a constriction element that are adjusted rotationally rather than axially may be beneficial for reducing the force needed to actuate an adjustment of the pressure building element (17d). It’s emphasized that system described in Fig.14 may comprise one or more additional valves such as but not limited to safety valves or similar used for controlling specific fluid pressures related to operation of the drilling assembly.

The system control device (25) is adapted to receive data from fluid pressure sensors (not shown) to monitor the drill fluid pressure (P1) upstream the pressure building element (17d) as well as the drill fluid pressure (P0) downstream the pressure building element (17d) and use such data to control the axial position of the constriction element (22) relative to the orifice (23). Said control being related to provide a specific differential fluid pressure over the pressure building element (17d), wherein the said differential fluid pressure may communicate with devices in the drilling assembly through fluid conductor inlet ports in the drive shaft (3a). The system will thus be able to operate semi- or fully autonomously based on parameters given by the operator when the inner assembly (13c) is at surface. It is emphasized that the system control device (25) may also receive data from the navigation instrument (15a) and use such data in combination with the data from the said fluid pressure sensors to control the fluid pressure (P1).

As an example, the system control device (25) may automatically initiate the pressure control device (17a) to increase the fluid pressure (P1) applied to the anti-rotation device (2b) and its gripping means, if the system control device (25) receives data from the navigation instrument (15a) about the steering device (10a) having rotational drift, to avoid or limit the said rotational drift. If the said rotational drift has left the steering device in a rotational position that is not according to the drill plan, i.e. the drilling directions is not correct the system control device (25) may automatically initiate the pressure control device (17a) to reduce the fluid pressure (P1), to allow further rotational drift, wherein the fluid pressure (P1) is increased when the steering device enters the correct rotational position. It’s emphasized that the operator may give input to the system control device (25) regarding parameters the system control device should work within when the inner assembly are at surface.

To facilitate downhole control of the steering device (10a) by means of this system, the fluid conductor outlet ports (17f) in the valve spool (17e) may be adjusted to rotationally to align with one or the other of fluid conductor outlet ports (17g, 17h) to direct pressurized drill fluid to specific fluid conductor inlet ports (3d, 3b) in the drive shaft (3a). Said fluid conductor inlet ports (3d, 3b) having same purpose as described in Fig.11 and Fig.12. The adjustment is initiated by the system control device (25) based on data collected from the navigation instrument (15a) alone or in combination with data from other sensors (not shown. As an example, the system control device (25) may initiate an adjustment of the steering device (10a) to reduce the obtained borehole deviation during drilling, if the system control device (25) detects that the current hole deviation is too high. Said adjustment being initiated semior fully autonomously downhole based on working parameters given to the system control device (25) when the inner assembly (13c) is at surface. The adjustment may be permanent until the system control device (25) initiates a new adjustment, periodically or a one-time event over a given timeframe. The system control device (25) may also receive data from other sensors (not shown) and use the collected sensor data to initiate actions down hole semi- or fully autonomously.

It’s emphasized that the described system herein also provides means for actuating pressure pulses that can be detected by the operator at surface. The pulses can readily be actuated by moving the constriction element (22) relative to the orifice (23) in such manner that the flow area change repeatedly between fully open and closed, alternatively to a specific pressure level or between specific pressure levels. The system control device (25) may be configured to initiate actuation of the said pressure pulses if it receives data relevant for the operation of the drilling assembly, such as downhole events, measured data of interest or operational parameters within the drilling assembly (2a) such as but not limited to core block in a core tube carried by the inner assembly, seating verification for the inner assembly, the borehole deviation being too high or too low, orientation of the steering device, or the drilling direction not being according to plan. As an example, in the case of core block, a load cell (not shown) can monitor the load applied the inner assembly and communicate such data to the system control device (25), that in turn initiate pressure pulses if the said load becomes too high.

FIG.15 shows a simplified partial sectional view of an inner assembly (13c) adapted to control an anti-rotation device (2b) and according to the invention as described in Fig.6 and Fig.7. It can be referred to Fig.6 and Fig.7 for description of the system controlling the steering device (10a) and the anti-rotation device (2b), while it can be referred to Fig, 14 for description of the means for controlling the fluid pressure (P1) and means for downhole to surface communication, with the exception of the constriction element (22) in this embodiment being connected directly to the actuating means since there is no valve spool involved.

It’s however emphasized that the functionality related to controlling the steering device (10a) is optional in this embodiment, thus the system can be used solely for controlling the fluid pressure (P1) that actuates the anti-rotation device (2b) as well as for downhole to surface communication. Said communication being related to events, measured data of interest or operational parameter within the drilling assembly (2a) such as but not limited to core block in a core tube carried by the inner assembly, seating verification for the inner assembly, the borehole deviation being too high or too low, orientation of the steering device, or the drilling direction not being according to plan.

To summarize the present invention relates to a rotary steerable drilling assembly having a rotatable drive shaft running through where the drive shaft is at one end being connected to a drill bit and at the other end to a coupling for connection to a drill string. The drive shaft also comprises or constitutes a fluid conductor and comprises one or more fluid conductor ports for interconnecting pressurized drill fluid within the drive shaft with system devices outside the drive shaft.

In addition, the drilling assembly includes an anti-rotation device configured to keep the steering device substantially rotationally fixed relative to the borehole during drilling, for example being operated through the pressurized drilling fluid through the drive shaft and fluid conductor ports.

The drilling assembly also comprises a steering device at its forward end being adopted to facilitate adjustment of the borehole deviation provided by the drilling assembly as well as drilling direction. More in detail the steering device includes a radially working bearing engaging the drive shaft, where the steering device comprise means for imposing an adjustable offset to the said bearing axis, thus also the drive shaft, relative to the axis of the drilling assembly. The offset provides an angular deviation to the drill bit axis relative the axis of the drilling assembly, where the said offset of the bearing axis is configured to be hydraulicly actuated by means of the pressurized drill fluid conducted through the drive shaft.

The drill assembly according to the invention also includes a retrievable inner assembly being seated and locked in a predetermined position inside the drive shaft a coupling thereof during drilling, wherein the said inner assembly can be released from the drilling assembly and reseated at need, for example using wireline or other available tools. The retrievable inner assembly further comprising a pressure building element causing the drill fluid to be pressurized when the drill fluid is pumped through it and a fluid conductor system for directing pressurized drill fluid conducted from the drive shaft to at least one of said fluid conductor ports in the drive shaft to the steering device, where the steering device is configured to provide a specific angular deviation given to the drill bit axis relative to the axis of the drilling assembly based on that a specific fluid conductor port or a specific fluid pressure is supplied through the inner assembly. The inner assembly also includes a navigation instrument being adapted to at least monitor the rotational position of the steering device relative to earth gravity, thus also the drilling direction, enabling a measure and control over the orientation and direction of the deviation in the drilling axis.

The pressure building element in the inner assembly may include an adjustable constriction such as a nozzle or valve being configured to build up a chosen pressure in the fluid flow. The pressure building element may also include an orifice and a constriction element wherein the position of the constriction element relative to the orifice may be adjusted, said adjustment being related to the flow area through orifice and consequently the fluid pressure within the drive shaft that are conducted to the devices outside the drive shaft at need.

As well as controlling the steering device the pressurized fluid caused by the pressure building element also causes the anti-rotation device to hold the steering device substantially rotationally fixed during drilling.

As an alternative the orifice and constriction element where the pressure is depending on the relative position of the constriction element relative to the orifice, and wherein a system control device is adapted to semi or fully autonomously control the constriction element for a controlled pressurization of the drill fluid. In this embodiment the control involves at least the system control device being configured to sample and process data from at least a pressure sensor downstream the orifice and a pressure sensor upstream the pressure building element orifice and a means for actuating the position of the constriction element relative to the orifice, thus also the flow area through the orifice while building up a defined pressure.

The navigation instrument is adapted to measure the rotational position of the steering device thus, also the rotational position of the drill bit axis relative to the axis of the drilling assembly, at any time, also during drilling.

The steering device may also comprise means for establishing a predefined range or a set of values for the angular deviation of the drill bit axis relative to the axis of the drilling assembly, that can be provided by the steering device. The range may preferably be set by adjustable stop bars limiting the drive shaft offset providing by the steering device.

The means for controlling the steering device may include one or more seals adapted to direct pressurized drill fluid to one or more specific fluid conductor inlet ports inside the drive shaft. It may also be possible to change the position of the seals seated in the circumference of the inner assembly.

The inner assembly may also include one or more valve/s adapted to direct the pressurized drill fluid to one or more specific fluid conductor inlet ports inside the drive shaft, preferably including external seals that provide exclusive communication of the pressurized fluid between one or more fluid conductor outlet port/s and corresponding fluid connector inlet port/s in the drive shaft.

In operation a preferred embodiment of the present invention may therefore involve directing pressurized drill fluid by means of the provided fluid ports, seals and valve etc., to the means associated with adjustment of the angular deviation given to the drill bit axis relative to the axis of the drilling assembly provided by a “point the bit” steering device, said pressurized drill fluid being used for moving a wedge, bearing, pad etc., adapted to impose an offset to a limited section of the drive shaft axis, relative to the axis of the drilling assembly, wherein the said offset result in the drill bit axis obtaining an angular deviation to relative to the axis of the drilling assembly by means of said steering device.

This may involve bringing the inner assembly to surface for manually adjustment of the means for directing the drill fluid, wherein the adjustment comes to effect when the inner assembly thereafter is re-seated inside the drilling assembly, but will preferably involve a system control device operating semi or fully autonomous, which is configured to control the means directing the drill fluid, thus also the angular deviation of the drill bit axis relative to the axis of the drilling assembly. The latter implies that the system control device can be given operational parameters to work within when the inner assembly are at surface, as well as utilize data collected downhole, such as but not limited to data from the navigation instrument. Preferably the system control device, using the pressure building element is configured to initiate actuation of pressure pulses within the drill fluid by means of the pressure control device when certain events or operational parameters occur downhole during drilling, and wherein the said pressure pulses can be observed by the operator at surface. In this case the pressure building element preferably includes an orifice and a constriction element where the fluid pressure is dependent on the position of the constriction element relative to the orifice and where the pressure control unit is configured to regulate the pressure by changing the position of the constriction element relative to the orifice, and in this way generate the pressure pulses by changing the available flow area through the orifice.

In operation the preferred embodiment of the present invention may also include using the pressurized drill fluid to actuate pads, knifes etc., associated with the anti-rotation device, said knifes or pads engaging the into the rock formation surrounding the borehole and rotationally lock the main body of the drilling assembly thus also the steering device to the borehole wall, while the drill bit and the drive shaft as well as the coupling thereof is rotational. If an adjustment of the orientation of the steering device is needed, the fluid pressure may be lowered to withdraw the anti-rotation pads and release the locking to the borehole wall, and thereby facilitate adjustment of the steering device orientation and then increasing the fluid pressure for to re-establish the rotational locking of the steering device to the borehole wall, thus also the direction of the drill bit. It’s emphasized that the reduction of fluid pressure may be obtained by increasing the flow area through the inner assembly, alternatively reducing, or shutting down the flow through the system.

In operation the preferred embodiment of the present invention may also include the retrievable inner assembly comprising a navigation instrument capable of measuring the orientation of the drilling assembly main body thus also the steering device during drilling, wherein the said orientation data is utilized in the process of controlling the anti-rotation device and/or the steering device.

As discussed above the inner assembly may also include means for changing or shifting what fluid conductor inlet ports shall communicate pressurized drill fluid to the steering device, wherein the said fluid conductor inlet port/s represent a specific angular deviation given to the drill bit axis relative to the axis of the drilling assembly.

Claims

1. A rotary steerable drilling assembly, the drilling assembly having a rotatable drive shaft running through, said drive shaft at one end being connected to a drill bit, and at the other end thereof a coupling for connection to a drill string, the drive shaft is conducting pressurized drill fluid pumped through the drive shaft to one or more fluid conductor ports for interconnecting pressurized drill fluid within the drive shaft with system devices outside the drive shaft, and an anti-rotation device configured to keep the steering device substantially rotationally fixed relative to the borehole during drilling,

the drilling assembly further comprising a steering device, the steering device having a radially working bearing engaging the drive shaft, wherein the said steering device comprise means for imposing an adjustable offset to the said bearing axis, thus also the drive shaft, relative to the axis of the drilling assembly, said offset providing directly or indirectly an angular deviation to the drill bit axis relative the axis of the drilling assembly,

and wherein the said offset of the bearing axis is configured to be hydraulicly actuated by means of the pressurized drill fluid,

w h e r e i n drill assembly also includes,

- a retrievable inner assembly being seated and locked in a predetermined position inside the drive shaft during drilling, wherein the said inner assembly can be released from the drilling assembly and re-seated at need,

- the retrievable inner assembly further comprising a pressure building element causing the drill fluid to be pressurized when the drill fluid is pumped through and a fluid conductor system configured for directing the pressurized drill fluid within the drive shaft to specific fluid conductor port/s in the drive shaft at need wherein the specific fluid conductor port and/or a specific fluid pressure represents a specific angular deviation given to the drill bit axis relative to the axis of the drilling assembly by means of said steering device,

- the inner assembly further comprising a navigation instrument being adapted to at least monitor the rotational position of the steering device relative to earth gravity, thus also the drilling direction.

2. Drilling assembly according to claim 1, wherein the fluid conductor system for directing pressurized drill fluid within the drive shaft to specific fluid conductor port/s in the drive shaft, includes changing the position of one or more seals seated on the circumference of inner assembly.

3. Drilling assembly according to claim 1, wherein the fluid conductor system for directing pressurized drill fluid within the drive shaft to specific fluid conductor port/s in the drive shaft, includes one or more valve/s having external seals that provide exclusive communication between one or more fluid conductor outlet port/s and the corresponding fluid conductor inlet port/s in the drive shaft

4. Drilling assembly according to claim 1, wherein the fluid conductor system for directing pressurized drill fluid within the drive shaft to specific fluid conductor port/s in the drive shaft involves bringing the inner assembly to surface for manually adjustment of the means for directing the drill fluid, wherein the adjustment comes to effect when the inner assembly thereafter is re-seated inside the drilling assembly.

5. Drilling assembly according to claim 1, wherein the fluid conductor system for directing pressurized drill fluid within the drive shaft to specific fluid conductor port/s in the drive shaft involves a system control device being at least adapted to semi or fully autonomously control the means directing the drill fluid, thus also the angular deviation of the drill bit axis relative to the axis of the drilling assembly.

6. Drilling assembly according to claim 1, wherein the steering device comprise means for establishing a predefined range or a set of values for the angular deviation of the drill bit axis relative to the axis of the drilling assembly, that can be provided by the steering device.

7. Drilling assembly according to claim 6, wherein the means for establishing a predefined range or a set of values for the angular deviation of the drill bit axis relative to the axis of the drilling assembly involves adjustable stop bars limiting the drive shaft offset provided by the steering device.

8. Drilling assembly according to claim 1, wherein the pressure building element involves an adjustable constriction such as a nozzle or a valve.

9. Drilling assembly according to claim 8, wherein the pressure building element involves an orifice, and a constriction element being adjustable relative to the opening in the orifice, thus providing means for adjusting the flow area through the said orifice.

10. Drilling assembly according to claim 8, wherein the pressure building element includes an orifice and a constriction element, the pressure being dependent on the position of the constriction element relative to the orifice, and wherein the system control device is adapted to semi or fully autonomously control the constriction element causing the drill fluid to be pressurized, wherein the said control involves at least the system control device being configured to sample and process data from at least a fluid pressure sensor downstream the orifice and a fluid pressure sensor upstream the orifice and a means for actuating the position of the constriction element relative to the orifice, thus also the flow area through the orifice.

11. Drilling assembly according to claim 1 wherein the inner assembly also comprise a system for directing fluid pressure to the anti-rotation device holding the steering device substantially rotationally fixed during drilling.

12. Drilling assembly according to claim 1, wherein the navigation instrument is adapted to measure the rotational position of the steering device thus also the rotational position of the angular deviation given to the drill bit axis relative to the axis of the drilling assembly at any time, also during drilling.

13. Drilling assembly according to claim 3 or 10, wherein system control device can be given parameters to work within when the inner assembly are at surface, as well as utilize data collected downhole, such as but not limited to data from the navigation instrument.

14. Drilling assembly according to claim 5 or 10, wherein system control device by means of a pressure building element is configured to initiate actuation of pressure pulses within the drill fluid that can be observed at surface, said pressure pulses being initiated by the system control device when certain events or operational parameters occur downhole during drilling.

15. Drilling assembly according to claim 14, wherein the pressure building element includes an orifice and a constriction element, the fluid pressure being dependent on the position of the constriction element relative to the orifice, the pressure control unit being configured to regulate the pressure by changing said position of the constriction element relative to the orifice, thus generating pressure pulses by changing the available flow area through the said orifice.