In the oil and gas industries a number of wells in close proximity are often constructed from a single installation. The direction of each well must be controlled to allow it to access a specific area of an oil or gas field.

Wells consist of a number of concentric, decreasing diameter tubes known as conductors, casings or liners. Tubes installed to a greater depth are generally smaller in diameter than those at lesser depths. It is common practice to install the first tubular string (a number of connected sections of pipe), known as a conductor or surface casing, by driving with a pile-driving hammer to depths of very approximately 50 m to 200 m below ground level or the seabed.

The main advantage of driving with respect to drilling is that soil disturbance is reduced, which is important to preserve the integrity of the foundations beneath a platform.

Additionally, driving is less damaging to the environment, as drilling fluid circulation is not required.

One of the disadvantages of driving, with respect to drilling, is that it is more difficult to accurately control the inclination and direction of the driven pipe. To create a vertical well it is desired to drive pipes as straight and vertical as possible, while to gain separation from nearby wells it is desired to drive pipes at a controlled inclination and direction.

Attempts to drive pipes straight and vertical are hampered in that the driven pipe experiences significant compressive forces, under which they may bend, thereby driving the pipe away from the desired axis. Alternatively, should the formation through which the pipe is driven not be homogeneous, the pipe may deviate to follow a path of least resistance.

Driving of pipes in a controlled direction and inclination is presently achieved by methods involving the modification of a piece of pipe prior to driving. In one such method, illustrated in Figure 1, a section (1) is removed from the end of a piece of pipe

(2), typically the lowest piece in the driven string, before being reattached at an angle to the main axis by welding (3). Upon driving, the pipe has a tendency to travel in a direction and inclination determined by the direction and angle of the reattached pipe end. In an alternative method, as illustrated in Figure 2, the pipe end (4) is cut at an angle, such that the main axis of the pipe is no longer normal to a plane formed by the pipe end. Both of these methods suffer from the disadvantage that a pipe cannot be adjusted in situ during the driving process to compensate for unexpected deviations from the desired path, such as a reduced or increased inclination of the driven pipe or an undesirable direction. A disadvantage of the angled end approach (of Figure 2), in comparison to the method involving the reattachment of a section of pipe (of Figure 1), is that it has a relatively small effect on the angle of inclination. However, the reattachment of a section of pipe is itself unreliable, as a result of the difficulties involved in controlling the reattachment angle with any accuracy and the tendency of this method to result in low rates of change of angle in soft formations and possibly unacceptably high rates of angle build as the driving resistance increases. An alternative method for driving pipes in a controlled direction and inclination involves the driving of a pipe closed with an asymmetrical shoe.

Additionally, manufacturing imperfections which may be present in a pipe, such as a slight natural bend or variation in wall thickness around the circumference of the pipe, can affect the direction and inclination of a driven pipe. As such, the first piece of pipe driven, which will form the bottom of the first tubular string, is often hand-picked for uniformity.

The present invention seeks to reduce or negate the difficulties inherent in the current state of the art, by providing improved control over the direction and inclination at which a driven pipe travels and with reduced need for the selection or modification of standard pieces of pipe.

According to the present invention there is provided a component for use in driving pipes which comprises a pipe having walls and a covered end and containing at or near its covered end a directional driving device which contacts the pipe at three or more points which are axially separated and which through three or more of the said points of contact exerts a bending moment on the pipe.

There is also provided a directional driving device for use in driving a pipe which has walls and a covered end, which device contacts the pipe at three or more points which are axially separated and which through three or more of the said points of contact is adapted to exert a bending moment on the pipe.

The term'axially separated', when used herein in respect of the three or more points of contact, means that at least one of the three or more points is axially separated from the remaining points of contact.

The term'bending moment'when used herein means the result of forces which act to maintain a pipe in a straight configuration as well as those which act to bend a pipe. A bending moment may therefore be the result of, but is not limited to, transitory forces which arise only during the period when the vertical driving force is applied.

The term'contacts the pipe'when used herein includes contacts with the pipe internal walls and contacts with the pipe end (for example with a pipe cover member if present).

The term'points of contact'when used herein, in relation to contacts between a directional driving device and a pipe, includes area contacts, as would be appropriate to the role of the contact in supporting the directional driving component in place or contributing to the bending moment.

A single area contact which contacts the pipe over a sufficiently large region may, in appropriate circumstances, be considered to fulfill the role of more than one point of contact (i. e. spatially separated regions of the area contact are considered to be individual points of contact). A single point of contact involving a rigid (i. e. a fixed) connection may also, in appropriate circumstances, be considered to fulfill the role of more than one point of contact. Appropriate circumstances in each of these cases are those where only a single further point of contact is required to enable the application of a bending moment.

The term'at or near'when used herein in relation to the proximity of a directional driving device to a pipe end, means that it must be sufficiently close to the pipe end such that a

bending moment exerted by the directional driving device is effective in controlling the movement of the driven pipe.

In use during straight or vertical driving, the invention provides a supporting structure intemally of the pipe such that upon application of the driving force bending of the pipe in the region of the directional driving device is reduced. Maintenance of the pipe in a straight configuration during driving, particularly in the region of the pipe end, ensures that the pipe moves in a direction which more closely follows the main axis. The invention may also compensate for manufacturing flaws, such as natural bends, variations in thickness or weaknesses in certain areas of the pipe wall.

During directional driving, the invention may be used to induce a bend in the pipe, in the region of the pipe end. Upon application of the driving force, the pipe end will tend to travel in a direction determined by the direction of the induced bend and at an inclination which may be related to the degree of bending.

Driven pipes of use in the oil and gas industries usually have an outer diameter in the range 50.8-91. 4 cm (20-36 inches), with common sizes being 50.8, 61.0, 66.0, 71.1, 76.2, 81.3 and 91.4 cm in diameter (20,24, 26,28, 30,32 and 36 inches respectively), pipes with a diameter of 76.2 cm (30 inches) being particularly common. Wall thicknesses typically range from 1.3-5. 1 cm (0.5-2 inches). Each piece of pipe is typically 12. 2 m in length (40 feet). The directional driving device will have a major dimension of its cross-section (for example the diameter) which is suitable for use in a given pipe ie the major dimension of its cross-section will be slightly less than the minor internal dimension of the pipe. Conveniently, a given directional driving device may be designed such that it is suitable for use with a range of pipe sizes, though more often will be designed for use with a small number of pipe diameters which are close in size.

Usually preferred are embodiments wherein the directional driving device is suitable for (ie optimised for) use only with a single diameter of pipe.

The term'slightly less'when used herein in relation to the major dimension of the cross- section of a directional driving device means that it is sufficiently smaller such that the device can be readily inserted and removed from position accounting for variations in

the effective minor dimension of the pipe which arise from manufacturing or from bends or imperfections in the pipe.

For typical applications, the region of the pipe within approximately 6 m of the pipe end is considered to be most crucial for the directional control of a pipe during driving. The conventional approach of removing and reattaching a section at the end of the pipe has been found to be effective when the joint is located about 2 m from the pipe end.

Analysis suggests that little effect would result if the joint were more than 5 m from the pipe end. Therefore, embodiments of the present invention should be sized and positioned accordingly, desirably the directional driving device being in the range of 1- 10 m in length, preferably in the range of 5-8 m in length, and positioned at or near to the pipe end. For directional driving purposes the points of contact should desirably be arranged such that a bending moment is applied across the lower 5 m of a pipe, preferably across the lower 3 m.

To protect the directional driving device and enable it to be maintained in place during driving of the component, the driven pipe is covered at the lower end. For example, the lower end may bear a cover member. The cover member may be permanently attached to the pipe end, by means such as welding. Alternatively the cover member may be separably attached to the pipe end. Examples of mechanisms by which the cover member can be separably attached include, but are not limited to, latch mechanisms or threads which interface with the pipe end.

It is not a requirement that the covered end is sealed (for example that the cover member forms a seal at the pipe end), although the pipe end must be substantially closed, for example such that there is not significant ingress of the formation through any aperture into the pipe. The covered end (for example the cover member) may incorporate openings, such as ports, valves or similar, which may for example be used in delivering small amounts of lubricating fluid into an annular space between the outside of the driven pipe and the formation through which it is driven. The purpose of such a fluid may be to reduce the resistance to driving or to alter the properties of the formation outside the pipe in some other way.

Thus, the term'covered end'when used herein in relation to the pipe embraces pipe ends which are sealed, pipe ends which are substantially closed and also pipe ends which are substantially closed but incorporate openings for valves or ports.

After the component has been utilised and the driven pipe is in final position, the directional driving device can be recovered along the bore of the driven pipe. It will generally be necessary, particularly in applications where the driven pipe will form the basis for an oil or gas well, that the cover member is also removed. Cover members which are formed from a suitable material can be removed by a drilling or milling action.

Suitable materials which may be drilled or milled out include materials softer than the steel normally used to make pipes, for example aluminium. Alternatively, if the cover member is separable, the cover member may be recovered by release of the attachment to the pipe end and removal through the internal bore of the driven pipe. In this situation it is desirable for the cover member to be fabricated from a material which is tougher than aluminium, desirably of the same material as the pipe, although it may be preferred to use particularly tough materials (eg hardened steel) to facilitate the driving process.

In an alternative embodiment, the cover member may be permanently attached to the directional drivingMdevice. In such cases the cover member would be reversibiyattached to the pipe end and would be recovered along the bore of the driven pipe with the directional driving device.

To exert a bending moment on the pipe the directional driving device applies a force through three or more axially separate points of contact. In directional driving applications, these three or more points will preferably form a plane in which the pipe axis lies.

The three or more points of contact through which force is applied may be on the pipe wall. However, more preferably one of the points of contact through which a force is applied will be at the covered end, with two or more points of contact on the pipe wall.

The term'contact'when used herein in reference to contact between the directional driving device and the cover member includes contact where the items are touching,

reversibly connected or permanently attached. Preferably a contact between the directional driving device and the cover member is a reversible connection. Reversible connection includes, but is not limited to, mechanisms such as latches or threads.

Should the rigid core contact the pipe wall or cover member through a rigid connection, either a permanently or reversible connection (such as a latch or thread), in such a manner that a bending moment can be exerted in conjunction with only one further axially separated point of contact, the rigid connection behaves as more than one point of contact and is considered as such.

Although three or more points of contact through which a bending moment can be exerted are sufficient for the present invention, in applications involving straight or vertical driving it is desirable that additional points of contact through which a bending moment can be applied are present and/or that the points of contact correspond to areas of contact which cover a large proportion of the circumference of the pipe, thus ensuring that the directional driving device provides resistance to bending of the driven pipe in all directions. In applications involving directional driving, it is preferable that the bending moment arises as a result of three points of contact between the pipe and the directional driving device through which forces are applied.

It is desirable, although not a required aspect of the present invention, that in addition to the three or more points of contact through which a bending moment is exerted a number of further points of contact between the pipe and directional driving device are present. Such further points of contact may aid the positioning and stability of the directional driving device within the pipe but are not involved (or at least not significantly involved) in the application of a bending moment.

In some embodiments of the invention, the three or more points of contact through which the bending moment is exerted are fixed relative to each other.

In other embodiments, the directional driving device is adjustable, for example in situ, such that the positions of the points of contact are variable relative to each other. The positions of the points of contact may, for example, be varied relative to each other within a plane eg a plane in which the pipe axis lies.

In some embodiments of the invention, the positions of the points of contact may be varied relative to each other through a system of pistons. In other embodiments of the invention, the positions of the points of contact may be varied relative to each other through a system of cams. Other mechanisms for effecting the variation in position may also be envisaged.

The directional driving device will preferably comprise a rigid core to which may be appended elements which make contact with the pipe. A range of designs for the rigid core are possible based on the use of a single member. Examples of such rigid cores include cylindrical, beam, or cross-shaped members (illustrated in Figure 3 which shows a pipe 2 containing a directional driving device with a rigid core having a cross-member 20 and making contact with the pipe wall at points 21), preferably cylindrical members.

Alternatively, the directional driving device can comprise a rigid framework, formed from the connection of a plurality of individual members to which may be appended elements which make contact with the pipe.

Contact between the directional driving device and the pipe may be directly between the rigid core or rigid framework, as appropriate, and the pipe. It is desirable that contact between the rigid core or rigid framework and the pipe is mediated by appended elements. Such appended elements may be attached to the rigid core or rigid framework, and/or may be attached to the internal wall of the pipe.

Appended elements on the pipe wall will preferably be proud shoulders which are usually radially symmetrical and serve to reduce the internal diameter of the pipe at the points of contact (see for example feature 9 in Figures 6-9). Appended elements on the rigid core or rigid framework include proud shoulders (see for example feature 8 in Figures 6-9), which for straight driving applications will preferably be radially symmetrical.

Appended elements which are part of the directional driving device may be fixed in position relative to the rigid core or rigid framework, or may be adjustable, either before locating the directional driving device within the pipe or in situ. Appended elements may be removable from the directional driving device and replaceable, either with an identical element or a different element such as may be required for the directional

driving device to be utilised to gain a different directional response, or to be used on a pipe of different diameter.

Appended elements may also serve to increase stiffness of the rigid core or framework.

Figure 4 shows an example of a mechanism by which appended elements (11) and (12) may be moved relative to a rigid core (6) by the rotation of an intermediate sleeve (13) which surrounds the rigid core in an off-axis manner. The elements are appended to an outer sleeve (14) which surrounds the intermediate sleeve in an off-axis manner. Such an arrangement of off-axis sleeves is commonly referred to as a cam. The directional driving device may be installed in the pipe with the points of contact concentric to the rigid core, followed by rotation of the intermediate sleeve to apply a lateral force through element 12, the magnitude and direction of the force and being dependent upon the positioning of the movable sleeves.

Figure 5 shows an example of a mechanism by which movable appended elements (15), in the form of pistons may be arranged relative to a rigid core (6) to which they are attached and around which is located the piston housing and chambers (16).

In one embodiment of the present invention, suitable for straight driving applications, appended elements on the directional driving device are fixed in place (ie non-movable), for example such as that illustrated in Figure 6. In an alternative embodiment, suitable for straight and directional driving applications, the relative positions of points of contact between the directional driving device and the pipe are variable by the movement of appending elements on directional driving device, for example by a mechanism such as a system of cams or pistons (for example as shown in Figures 4 or 5). The movement mechanism may be utilised to adjust the position of the movable appended elements and thereby adjust the forces applied to the pipe, such that the pipe may be bent to varying degrees or not bent at all.

Movable elements such as those illustrated in Figures 4 and 5 may be adjusted in situ to compensate for unexpected deviations of a driven pipe from a desired path, whether the desired path is straight or at a particular inclination and direction.

Although complex designs of the directional device which enable control over the movement of the pipe in all directions may be foreseen, in one embodiment of the invention the directional control device enables control only in a single direction.

Appended elements on the directional driving device and pipe wall may engage to prevent rotation of the two items relative to each another. The internal face of the cover member may also have elements which interface with the directional driving device to prevent rotation of the two items relative to each another.

The rigid core or rigid framework is constructed from suitable materials and is of a suitable design such that during use, either to bend the driven pipe or maintain the driven pipe in a straight configuration, the directional driving device does not itself experience very significant bending relative to the driven pipe.

The directional driving device will preferably leave a clear space along the central axis of the pipe of approximately 5.1 cm (2 inches) or more in diameter to enable access to the pipe end for directional surveying purposes. For this purpose, the core will either be hollow or contain a channel of the appropriate size.

It is preferable, although not a requirement of the invention, that the section of driven pipe used in proximity to the installed directional driving device is manufactured to a higher level of precision than that which is typical for driven pipes, so as to improve the degree of directional control which the invention provides.

As a further aspect of the present invention there is provided a process for driving a pipe which comprises (a) the provision of a component comprising a pipe having walls and a covered end and containing at or near its covered end a directional driving device which contacts the pipe at three or more points which are axially separated and which through three or more of the said points of contact exerts a bending moment on the pipe; and (b) driving the pipe.

There is also provided a process for driving a pipe which comprises (a) providing a pipe which has walls and a covered end; (b) inserting into the pipe a directional driving device which contacts the pipe at three or more points which are axially separated and

which through three or more of the said points of contact exerts a bending moment on the pipe; and (c) driving the pipe.

A process according to the present invention, where the three or more points of contact which exert a bending moment on the pipe cause the pipe to bend, may be utilised for driving a pipe away from the main axis of the pipe (ie directional driving).

A process according to the present invention, where the three or more points of contact which exert a bending moment on the pipe serve to maintain the pipe in a straight configuration, may be utilised for driving a pipe along the main axis of the pipe (ie straight or vertical driving).

Pipe driving may be achieved by any method known in the art, such as the use of a pile driving hammer which is typically hydraulic or diesel powered.

A range of hammers are available and are selected according to the formation conditions, pipe characteristics and the depth to which the pipe will be driven. For example, the impact energy of common pile driving hammers that may be selected for driving a 76. 2 cm (30 inch) diameter pipe in a typical application is very approximately 100 kNm. Pile driving hammers typically deliver 30. L90 blows per minute and require only a few blows per meter to drive the pipe initially, but up to approximately 500 blows per meter to drive the pipe at the point of refusal. The desired depth may be very approximately 50-200 m penetration below the seabed or ground level.

The degree of pipe bend that is expected to be required to initiate deflection is in the range of 0.1 to 0.5 degrees over the lower half of a 12. 2 m (40 feet) long piece of pipe.

This may require a bending moment of very approximately 1500 kNm on the internal walls of the driven pipe. For directional applications, the rate of build of angle is commonly measured in degrees per 30 m. A planned build rate would typically be in the range of 0.5 to 3 degrees per 30 m.

Depending on the design of the directional driving device and the location of the points of contact, for a 76. 2 cm (30 inch) diameter pipe with a 2. 5 cm (1 inch) wall thickness the forces exerted on the pipe would be approximately 500 kN. This will vary

significantly depending on the nature of the driven pipe and the desired deflection required.

As another aspect of the invention we provide the use of a component as herein before described in driving pipes, especially for oil and gas exploration and extraction. It is envisaged that the component may also be of use in driving pipes for exploration and extraction of other materials, for surveying purposes, or for the foundations of a structure or building.

The invention is illustrated by reference to the following Examples and Figures in which: Figure 1 shows a longitudinal section through a pipe which has been modified according to a conventional approach to directional driving, with a section of the pipe having been detached and reattached, by way of comparison to the present invention.

Figure 2 shows a longitudinal section through a pipe which has been modified according to a conventional approach to directional driving, with the end of the pipe cut at an angle, by way of comparison to the present invention.

Figure 3 shows a cross-section of the rigid core of a directional driving device according to the invention, which employs a cross shaped structure.

Figure 4 shows a cross-section through a mechanism according to the invention for adjusting the contact point between a driven pipe and a rigid core using a system of two offset circular cams.

Figure 5 shows a cross-section through a mechanism according to the invention for adjusting the contact point between a driven pipe and a rigid core using appended pistons.

Figure 6 shows a longitudinal section through the embodiment of Example 1, a component which is suitable for straight driving applications.

Figure 7 shows a longitudinal section through the embodiment of Example 2, a component which is suitable for directional driving applications.

Figure 8 shows a longitudinal section through the embodiment of Example 3, a component which is suitable for straight driving applications.

Figure 9 shows a longitudinal section through the embodiment of Example 4, a component which is suitable for directional driving applications.

Figure 10 shows a longitudinal section through Example 5, a component which is suitable for directional driving applications.

Example 1 A component suitable for straight driving, as illustrated by Figure 6.

A drillable or removable cover member (5) is positioned at the end of a pipe (2). A directional driving device with a rigid cylindrical core (6) is held in place close to the pipe end by a reversible connection (7) to the cover member. Three externally upset shoulders (8) on the cylindrical core contact the internal wall of the pipe via internat upset shoulders on the pipe wall (9).

The points of contact between the directional driving device are arranged so as to maintain the driven pipe in a straight configuration. The directional driving device is radially symmetrical and is located coaxially with the driven pipe.

Upon the application of a vertical driving force, bending of the pipe in the region of the directional driving device will be resisted due to the structural reinforcement which it provides by the exertion of forces on the pipe which counteract bending, thereby improving the level of control over the direction of pipe movement.

Example 2 A component suitable for directional driving, as illustrated by Figure 7.

A drillable or removable cover member (5) is positioned at the end of a pipe (2). A directional driving device with a rigid cylindrical core (6) is located close to the pipe end.

Externally upset shoulders (8) on the cylindrical core contact the internal wall of the pipe via internally upset shoulders on the pipe wall (9). The middle appended shoulders (10) are offset in relation to the main axis of the pipe, thereby exerting a bending moment on the pipe and causing the pipe to bend between the upper and lower shoulders such that the axis of the driven pipe is not concentric along its length.

Upon the application of a vertical driving force, the pipe will tend to travel in the direction of the bend, at an inclination determined by the angle of the bend (i. e. the magnitude of the bend).

Example 3 A component suitable for straight driving, as illustrated by Figure 8.

A drillable or removable cover member (5) is positioned at the end of a pipe (2). A directional driving device with a rigid cylindrical core (6) is held in place close to the pipe end by a reversible connection (7) to the cover member. Two externally upset shoulders (8) on the cylindrical core contact the internal wall of the pipe via internally upset shoulders on the pipe wall (9).

The points of contact between the directional driving device are arranged as to maintain the driven pipe in a straight configuration. The directional driving device is radially symmetrical and is located coaxially with the driven pipe.

Upon the application of a vertical driving force, bending of the pipe in the region of the directional driving device will be resisted due to the structural reinforcement which it provides by the exertion of forces on the pipe which counteract the bending, thereby improving the level of control over the direction of pipe movement.

Example 4 A component suitable for directional driving, as illustrated by Figure 9.

A drillable or removable cover member (5) is positioned at the end of a pipe (2). A directional driving device with a rigid cylindrical core (6) is held in place close to the pipe end by a reversible connection (7) to the cover member. Externally upset shoulders (8) on the cylindrical core contact the internal wall of the pipe via internally upset shoulders on the pipe wall (9). The upper appended shoulders (10) are offset in relation to the main axis of the pipe, thereby exerting a bending moment on the pipe and causing the pipe to bend between the upper shoulders and the cover member such that the axis of the driven pipe is not concentric along its length.

Upon the application of a vertical driving force, the pipe will tend to travel in the direction of the bend, at an inclination determined by the angle of the bend (i. e. the magnitude of the bend).

Example 5 A component suitable for directional driving, as illustrated by Figure 10.

A drillable or removable cover member (5) is positioned at the end of a pipe (2). A directional driving device with a rigid cylindrical core (6) is held in place close to the pipe end by a rigid reversible connection (7) to the cover member. An adjustable appended element (8) on the cylindrical core contacts the internal wall of the pipe via intemally upset shoulders on the pipe wall (9). Adjustment of the appended element (8) enables a bending moment to be applied. Upon the application of a vertical driving force, the pipe will tend to travel in the direction of the bend, at an inclination determined by the angle of the bend (i. e. the magnitude of the bend). This Example illustrates that the rigid connection between the directional driving device and the cover member may fulfil the role of more than one point of contact (i. e. the rigid connection in conjunction with a single further point of contact is sufficient for a bending moment to be applied).

Throughout the specification and the claims which follow, unless the context requires otherwise, the word'comprise', and variations such as'comprises'and'comprising', will be understood to imply the inclusion of a stated integer, step, group of integers or group of steps but not to the exclusion of any other integer, step, group of integers or group of steps.