WO2011018432A1

WO2011018432A1 - Conductor casing deployment control system for oil or gas wells

Info

Publication number: WO2011018432A1
Application number: PCT/EP2010/061548
Authority: WO
Inventors: Mikkel L Hvidsteen
Original assignee: Mikkel L Hvidsteen
Priority date: 2009-08-11
Filing date: 2010-08-09
Publication date: 2011-02-17
Also published as: GB0914022D0

Abstract

Apparatus for establishing a wellhead and a method for performing active directional adjustment of a conductor casing as it is being driven into the substratum using a retrievable tool having pivoting body parts 1, 2 configured to cooperate with a jointed conductor casing 50, 52, 53 is described. The tool incorporates anchor means, e.g. actuators 11, 21 arranged to anchor the tool body 1 in the conductor casing, and further actuators 14, 23 for selectively effecting a movement of the pivoting body parts by reaction against an inner surface of the casing, whereby the casing is deflected to cause a change in angle or azimuth of a driving direction.

Description

Conductor Casing Deployment Control System for Oil or Gas Wells Field of the Invention

This invention relates to drilling and well completion operations and provides a tool that is useful to the oil and gas industry for the purpose of stabilising unconsolidated surface formations for the purposes of establishing a wellhead for example.

More specifically, the present invention relates to the directional adjustment of conductor casings during deployment. In particular, the invention provides an apparatus and a method for active directional adjustment of an offshore conductor casing as it is being driven below the mud-line of the substratum.

Background to the Invention

During the initial stages of drilling, especially at a subsea location, the surface encountered may be typically of a sedimentary deposit character, i.e. relatively soft, unstable, loose and susceptible to movement. In order to stabilise the initial penetration of such a surface for the purpose of subsequent operations, it is known to insert a relatively large diameter casing string referred to commonly as "conductor" casing. The conductor can be driven into the surface at onshore or shallow offshore sites by a pile-driving technique, whilst at deeper locations; the conductor can be delivered on the end of a work string equipped with a reciprocating driving means (pile hammer) and a shoe for assisting the penetration of the surface. The operation may be initiated by a drilling operation e.g. using a drill ahead BHA, in which case the work string would be a drill string. Optionally, the driving of the conductor can be facilitated by fluid-jetting to displace sedimentary material dislodged during the driving operation. Since very few wells are driven vertically in current practice, there is often a requirement for a deviated or directionally controlled borehole or indeed a number of diverging boreholes. There are numerous proposals for deviated drilling operations by deflecting the drill string after it leaves the conductor. Thus generally, in past practice, it would be usual to deliver the conductor casing directly to initially confront and penetrate the surface, more or less vertically. However, there have been proposals to seek to influence the driving of the conductor to angle it towards a desired direction for the borehole. This is achievable onshore or in shallow locations, but much more difficult to achieve at deep water operational sites where all operations are significantly more challenging.

There is a need to control the angle of entry of the conductor casing especially in a deep water location, since it is via this casing that each subsequent operation is conducted and from which the stability of the well head including support for subsequent borehole casing strings is derived.

Directional drilling of oil and gas production wells has become an established practice in view of the many potential benefits which, inter alia, include: (i) increasing the exposed section length through a reservoir; (ii) bypassing difficult formations that surround a reservoir; (iii) allowing new wells to be drilled in close proximity to existing wells; (iv) increasing the lateral reach of a well; and (v) facilitating the grouping of wellheads closer together with wells diverging through the substrata to predetermined depths and locations around a reservoir.

With particular reference to point (v) above, multi-slot platforms can have 24-60 slots spaced 2-3 metres apart at the surface. Given the natural tendency for driven conductors to deviate and follow the path of least soil resistance, directional control is required to avoid the collision of adjacent conductors. Known techniques for providing such directional control (as described below) can result in dog-legs (i.e. significant changes in angle and/or directional azimuth) resulting in high stresses along the conductor and its connections. Such stresses may exceed the mechanical limits of the conductor or its connections, resulting in a failure and a redundant slot which therefore has to be junked.

Past proposals for influencing the direction of the conductor installation have included suggestions to bend the conductor casing e.g. by passing the conductor casing through formers before deployment from the drilling structure. These early techniques for influencing the extent of deviation of a driven conductor casing typically employed either pre-curved conductor pipes or pipes which were forcibly curved through introducing them via offset guides. More recent solutions utilise drive-shoe members attached to the distal end of the conductor casing, the drive-shoe either having a distal end with an asymmetric surface profile and/or being attached to the conductor casing at a fixed offset angle relative to vertical. Such solutions are disadvantageous insofar as the degree of deviation is often

unpredictable and difficult to control once the conductor casing has penetrated the substratum.

More sophisticated solutions employ bevelled drive-shoes connected by hinge means to the distal end of the conductor casing. Devices of this type may utilise shear pins for retaining the central longitudinal axis of the drive-shoe in a coaxial relationship with that of the conductor casing, thus ensuring its vertical insertion into the substratum. Once sub-surface resistive forces impinging on the bevelled surface of the drive-shoe exceed a threshold level, the pivoting motion of the drive-shoe about the hinge causes the shear pin to rupture. Through selection of shear pins with appropriate rupture threshold values, this arrangement allows deviation of the conductor casing to be initiated at a depth below the mud- line. Whilst offering some advantages over early designs, this passive solution is heavily dependent on the accuracy of soil surveys aimed at predicting the depth at which sufficient resistive forces will occur to rupture a given shear pin. Often, shear pins will rupture prematurely with the result that deviation commences at an undesired depth. Moreover, apparatus of this type fails to react predictably where soil characteristics fluctuate below the mud-line, or when passing through areas of disrupted soil (i.e. proximate template wells).

The aforementioned solutions each suffer from the problem that soil strength starts at zero at the mud-line, and increase with depth up to values of 600 psi (~ 42 kg m^"2) or higher. Conventional apparatus will typically under perform in the shallow soil, perform close to what is predicted at the mid point, and then begin to over perform in deeper soil having higher soil resistance.

A further suggestion has been to attach an open-ended angled section at the leading end of the conductor which forms an offset or "dog-leg" that is said to influence the direction of the conductor as it is driven into the surface below the mudline.

A still further proposal involves modifying the conductor by provision of a bevel cut partially through a circumferential section of casing, which section is attached to the main body of the casing by a hinge. It is intended thereby that upon driving of the conductor, the bevel section is forced to close, thereby displacing the unhinged end to create an offset leading section which in turn causes the conductor to be deviated at an angle from the axis of the driven main body of the conductor as driving operations below the mudline are continued.

An object of the invention is to provide improvements in or relating to installation of conductor casing, and to provide a tool useful for such a purpose. Summary of the Invention

According to an aspect of the present invention there is provided a method for performing active directional adjustment of a conductor casing

("steering") as it is being driven into the substratum, wherein the conductor casing is provided in sections connected by flexible joints allowing one section to pivot with respect to the next, and one section is equipped with a drive shoe, and the method comprises remote operation of actuators deployed within jointed sections of conductor casing above the drive shoe, whereby that end of the conductor casing may be deflected from an original path aligned with the central longitudinal axis of the conductor casing towards a deviated angle path with respect to said original path by a predetermined amount by control of the actuators and the apparatus for causing deviation of the drive path of conductor casing will be described more fully hereinafter. The invention in one aspect provides at least one retrievable tool body having at least first and second parts connected end to end by a flexible joint, wherein the first part is adapted to be anchored within a jointed conductor casing, and the second part thereof is provided with actuators configured for contact with an inner surface of the jointed conductor casing to cause the second part to deflect a corresponding part of the conductor casing whereby a change in angle or azimuth of a driving direction can be effected by selective operation of the actuators. Such an actuator- movable part of the jointed tool body will be generally referred to herein as a "deflector body". According to another aspect of the invention, apparatus for establishing a wellhead at a subsea location is provided which comprises a retrievable flexible jointed tool body and a corresponding flexible jointed conductor casing, wherein the tool body is configured to be introduced into the conductor casing, and adapted in one part to be anchored within the jointed conductor casing, and in another part flexibly joined to the first part there are provided actuators configured for contact with an inner surface of the jointed conductor casing to cause deflection of a corresponding part of the conductor casing whereby a change in angle or azimuth of a driving direction can be effected by selective operation of the actuators.

Various ways of implementing a suitable flexible joint or coupling between the parts are contemplated and no limitation is intended on this aspect. For practical considerations, the joint between the conductor casing sections which may be for example a simple hinge or pivot will be designed to remain clear of the bore to allow passage of tools, so that for example trunnions would be within or very close to the wall dimensions of the conductor casing section.

Optionally, the apparatus may be configured to provide angular deviation in more than one plane with respect to the central longitudinal axis so that deviation in the driving path can be achieved in the full range of angle or azimuth options.

The actuators may be operated by remote control means including hydraulic control lines connected to a hydraulic pump. Preferably, a soil remould or plough ring is connected concentrically to the outer wall of the drive shoe proximate its distal end.

In a representative embodiment for implementing the method of the invention, the conductor casing includes two flexible joints axially spaced upon the longitudinal axis of the conductor casing and oriented at 90 degrees with respect to each other to provide for deviation of one conductor casing part in one direction and deviation of the other conductor casing part in a direction that is perpendicular to the first. In this way the conductor casing can be directed into a surface at an angle of inclination to vertical and also deviated with respect to azimuth angle.

The invention further provides a retrievable articulated tool configured to cooperate with an articulated conductor in order to provide directional control during driving of the conductor into a surface. The articulated parts of the conductor are forced to deviate by deflection under control of the articulated parts of the tool when inserted into the conductor. The deflection of the articulated parts of the casing is achievable by use of tool actuators acting upon internal surfaces of the articulated conductor. In a typical embodiment, at least one deflector body equipped with actuators for effecting a deflection in angle and azimuth is inserted into the casing and anchored within a first part of the casing close to a joint so that the actuators are positioned within a second contiguous part of the casing to that joint to enable deflection of that second part of the casing with respect to the first part of the casing. It will be understood that by appropriate use of multiple actuator configurations within a single steerable deflector body it is possible to provide for deflection at 90 degree phasing to achieve deviation angle and azimuth with that body.

In an alternative embodiment, two such tools each including a deflector body are deployed in tandem upon a fishing neck e.g. on work string, and introduced to a jointed conductor casing of this invention and comprising parts which are pivotal in first and second directions that are typically at 90 degrees to each other. Each body is configured to land on surfaces within the corresponding conductor casing parts and deploy anchors or slips to lock the respective bodies into the conductor casing parts. Once anchored in place, then actuators provided upon the bodies can be selectively deployed to push the conductor casing in a selected direction. In this way a retrievable tool comprising two steerable deflector bodies can be used to alter the angular configuration of respective pivotally connected sections of a conductor casing.

The steerable deflector bodies can be located in the conductor using a separate running tool the design of which is not critical provided that it can be run to lower the deflector bodies into the conductor, land same and achieve correct orientation for deployment of anchors, slips or a fastening mechanism, or by way of surface configuration be adapted to engage with the conductor and react the moment generated when actuators are deployed to effect a directional adjustment to the conductor. According to another aspect of the present invention there is provided a retrievable apparatus for installing a flexible jointed conductor casing comprising a first body section adapted for deployment and retrieval on a work string, and a second body section dependent from and connected to the first body section, each body section incorporating actuator means disposed to provide for directional control with respect to at least one of angle and azimuth,

said first body incorporating anchor means for locating the first body within a conductor casing, Thus these bodies serve as deflector bodies for directing the installation of jointed conductor casing sections. The second body may also incorporate anchor means for locating the second body within a conductor casing.

The connection between the body sections may be a tie bar to space the bodies apart by a predetermined amount. The bar may be pivotally connected to the body sections. The anchor means may be realised for any aspect of this invention by corresponding surface configuration of the respective bodies and casing. For example, a threaded connection of sufficient length to react moments generated is one option. The deviation controlling body may have an external (male) thread and the casing may have a corresponding internal (female) thread. Alternatively, an internal land surface extending inwardly and axially within the conductor casing is configured to cooperate with a corresponding surface of a deviation controlling body. This provides a narrow bore that is close fitting to the body allowing reaction against bore wall of the conductor casing without the need for additional anchoring means. Spaced landing shoulders providing two reaction points spaced sufficiently far apart and of sufficient width to support the generated moment may be used.

The shoulders may be arranged as a circumferential or part circumferential seating for landing of the deviation controlling body. The shoulders may be provided as a series of landing pads or spaced segments of a

circumferential landing configuration. A J-slot or T-slot locking mechanism can be used to provide anchoring means for the tool within the conductor casing, wherein the deviation controlling body is locked into the conductor casing by appropriate rotation applied through the running tool optionally with reciprocation as may be required. In such an arrangement, the conductor casing may be provided with slots of the desired configuration, and pins designed to engage the slots can be provided upon the deviation controlling body. Such pins may be in different planes and greater moments can be handled when the pins are axially spaced apart.

Other locking means include an hydraulic lock utilising dogs or pads which can be radially driven outwardly from the tool body to brace same against an inner wall of the conductor bore. Alternatively, a similar bracing system can be operated electrically or mechanically in the latter case using a weight set down procedure for locking and being releasable by use of fasteners designed to yield at a certain loading e.g. shear pins.

The first and second bodies may be landed in tandem or sequentially.

The first and second body sections may have pivot axes mutually disposed orthogonally to permit tortuous deviation paths to be

accommodated.

The first and second body sections may have parallel pivot axes in the case where a significant deviation requires more than one articulation to achieve the bend. A third or more deflector body sections connected in series can be used, but generally two deflector body sections would be sufficient for practical use.

Various means for effecting the articulation of the parts are contemplated, including hinges, pivots, spherical seat connections (ball and socket type joints) and these options will be generally referred to herein as joints.

Tandem arrangements where articulated deflector bodies are spaced apart and are connected by a double pivot connecting rod are also contemplated. This connecting rod allows for linear and angular movement of the bodies and transmits rotation from one body to the other. Thus the bodies can be run in together as if a single tool and thereafter operated individually to perform a required path deviation (inclination angle / azimuth adjustment) by effecting a deflection upon a corresponding conductor casing part.

According to an embodiment, the upper body can be considered to be the main body that allows for retrieval and the lower body can be regarded as a secondary or slave body which is equivalent in function and adapted for connection to the first retrievable body. Alternatively, the deflector bodies may be attached to a retrievable running tool body of any suitable design.

Preferably, each body is of similar construction and is configured for orientation and landing upon land surface profiles within the jointed conductor casing sections.

Corresponding articulated joint conductor casings are required for the intended field use of all aspects of the invention to be more fully described hereinbelow. In each instance of use, the retrievable articulated deviation bodies for deflection of the corresponding conductor section is internal with respect to the conductor, leading to lack of interference with driving of the conductor casing, and ease of recovery of the tool.

Orientation of the tools may be achieved by use of an internal shoulder, a ramp or cam surface in cooperation with a key profile, wherein the cam surface defines an angular path around the longitudinal axis of the tool body e.g. a helical path of sufficient length to allow satisfactory alignment and orientation of the tool within a conductor casing.

The anchor means may comprise actuators operatively connected to surface engaging members for locating the body within a conductor casing. The actuators of the anchor means may be disposed in an arrangement comprising opposed pairs configured to contact the inner surface of a conductor when the anchor means are deployed. Two pairs of opposed actuators may be oriented to provide contact points at 90 degrees intervals around the inner surface of a conductor casing. The pairs of opposed actuators can be arranged in the same horizontal plane or axially spaced apart. The internal drive means for deflecting a section of conductor casing may comprise actuators operatively connected to surface engaging members for contacting the inner surface of a conductor casing to be deflected.

The actuators of the internal drive means may be disposed in an arrangement comprising opposed pairs configured to be selectively and independently operable to contact an inner surface of a conductor casing to be deflected.

Each of the aforesaid actuators may comprise a cylinder and a rod which can be displaced from the cylinder along a radius of the conductor casing to contact an inner surface thereof.

The actuators may comprise double acting cylinders.

A suitable rod may be of a length that permits it to be stowed within a body portion of the tool until a need for same to be deployed for contact with an inner surface of the conductor casing. The invention will be described herein with reference to hydraulic actuators but other actuators such as electromagnetic linear actuators may be used.

Furthermore, an electric motor together with appropriate reduction gearing can be used to drive mechanical actuating means to effect a deviation in driving path by deflection of the casing upon one or more deflector bodies controlled by the actuating means.

The actuators may be connected to a system that is controllable from a surface installation.

The actuators may be controlled wirelessly from a surface installation. The invention further provides apparatus for establishing a wellhead, comprising a work string, a running tool and a retrievable body including anchor means and at least one dependent body section pivotally connected to said retrievable body and including actuators for effecting a deflection of the dependent body section, a conductor casing comprising flexible jointed sections, wherein the jointed sections are configured to pivot in different directions, and said bodies are configured to engage surfaces within the conductor casing, such that a first section of casing receives the retrievable body and anchor means, and a further section of casing receives the dependent body section enabling that further section to be deflected during driving of the conductor casing to effect a deviation in driving path.

According to a still further aspect of the invention, there is provided a method of installing a conductor casing at a subsea interface where a wellhead is to be established,

which comprises

providing a retrievable tool on a work string, said tool having or being attached to a body having a longitudinal axis normally aligned with the work string and being adapted to adopt a predetermined orientation when retrievably positioned within a conductor casing,

the tool comprising a retrievable tool main body providing anchor means for engaging an inner surface of a conductor casing, and pivotally attached thereto a first deviation body dependent from the main body, said first deviation body housing actuators adapted to effect a deflection of the body from the longitudinal axis by a predetermined angle, and pivotally attached thereto a second deviation body dependent from the first deviation body, said second deviation body housing actuators adapted to effect a deflection of the body from the longitudinal axis by a predetermined angle, providing conductor casing sections connected to form at least two flexible joints therein, and providing a closed end shoe for an end of the jointed conductor casing sections

running the conductor sections to the interface where the wellhead is to be established,

landing and orienting the tool within the conductor casing sections actuating the anchor means and selectively operating actuators to effect a deflection in angle or azimuth of the jointed conductor sections by a predetermined amount, and

driving the conductor sections to the required depth.

Preferably, the method further comprises the step of retrieving the tool. The tool may be retrieved by disengaging the anchor means and releasing all deflector devices from contact with the conductor section surfaces and pulling the drill string out, optionally with reverse rotation thereof.

The aforesaid deflector devices may be linear actuators configured to provide anchor devices with respect to the tool main body, and reaction devices for deflection of the deflector bodies.

Description of the Drawings

The invention will now be further described by way of illustration by reference to the accompanying drawings in which:

Fig. 1 a illustrates a longitudinal side view of an embodiment of a steerable deflector body with hydraulic actuators for selectively contacting and deflecting a conductor casing into a deviated path during driving into a subsea surface;

Fig. 1 b is a cross-section [A - A] through the hydraulic actuator part of the body shown in Fig. 1 a; Fig. 1 c illustrates a further longitudinal side view of the embodiment of the steerable body shown in Fig. 1 a rotated by 90 degrees about its longitudinal axis;

Fig. 2 is a schematic representation of a longitudinal side view of a jointed conductor casing in three sections with two joints arranged one with respect to the other at 90 degree phasing;

Fig. 3a illustrates the conductor casing of Fig. 2 with two deflector bodies such as illustrated in Fig. 1 a anchored within the casing in tandem wherein deflection is effected by use of the upper one of the bodies by selective use of one of the actuators;

Fig. 3b shows an enlarged detail cross-section [X - X] through the hydraulic actuator part of the deflector body shown in Fig. 3a;

Fig. 3c shows an end view of the deflected conductor casing as viewed from the actuator section of the deflector body of Figs. 3a, 3b. Fig. 4 shows a schematic longitudinal section through jointed conductor casing sections before introduction of deflector bodies;

Fig. 5 shows a schematic longitudinal section as in Fig. 4, at the orientation and alignment stage of introduction of a tool assembly of deflector bodies in tandem for landing on respective shoulders within the jointed conductor casing;

Fig. 6 shows a schematic longitudinal section as in Fig. 5, at the stage of landing the oriented and aligned jointed bodies within the conductor casing;

Fig. 7 shows a schematic longitudinal section as in Fig. 6, at the stage of anchoring the jointed bodies within the conductor casing when appropriate orientation and alignment has been completed; Fig. 8 shows a schematic longitudinal section as in Fig. 7, at the stage of effecting a first deviation reaction upon one of the jointed sections of conductor casing in one direction (angle build);

Fig. 9 shows a schematic longitudinal section as in Fig. 7, at the stage of effecting a deviation reaction upon a one of the jointed sections of conductor casing in the opposite direction from that of Fig. 8 (angle drop);

Fig. 10 shows a schematic longitudinal section as in Fig. 7 (view axially rotated by 90°), at the stage of effecting a first deviation reaction upon another of the jointed sections of conductor casing in one direction

(azimuth turn right);

Fig. 11 shows a schematic longitudinal section as in Fig. 7 (view axially rotated by 90°), at the stage of effecting a first deviation reaction upon another of the jointed sections of conductor casing in the opposite direction from that of Fig. 10 (azimuth turn left); and and

Fig. 12 shows a schematic longitudinal section as in Fig. 4, at the stage of retracting anchors and actuators in preparation for retrieval of the deflector bodies upon a fishing neck on a suitable work string.

Description of Embodiments of the Invention Referring to Figs. 1 a, 1 b, and 1 c, a deflector body 1 comprises an actuator assembly 11 including actuator cylinders 13 and rods 12 configured to be deployed in opposite directions.

Referring now to Fig.2 a jointed conductor casing 10 comprising three casing sections 50, 52, 53, is shown, with one section 53 deflected at an angle from the normal longitudinal axis through the casing sections as initially aligned for run in to the subsea surface. Turning to Fig. 3a, a jointed conductor casing as in Fig.2 has two sections 52, 53 similarly deflected by means of an actuator rod 12 on a deflector body 1 forming part of an assembly of deflector bodies introduced to the conductor casing sections in tandem. The actuators of the second deflector body 2 are not deployed at this stage.

It is to be understood that in the use of the invention, hydraulic lines, electrical power lines and control system lines are run in internally from the surface with the running tool as is generally considered in the art for downhole control of operations, and thus the arrangement of the hydraulic lines, electrical power lines and control systems are not further described herein.

The typical steps required for deploying a jointed conductor casing with deflector bodies providing means for "steering" the casing on a deviated path during the driving of the casing into a subsea surface for the purpose of establishing a well head is illustrated in a "storyboard" provided by the series of Figs. 4 to 12, and will now be described with reference thereto. It will be understood that unless otherwise stated each figure has the same parts as first shown in Fig. 4 and so all call out numerals are not repeated in subsequent figures. In Fig. 4, a conductor casing 5 consisting of three sections 50, 52, and 53 with joints 22, 32 allowing the casing to flex about the joint and be deflected in use is shown as aligned for deployment to the surface into which it is to be driven. The casing sections 50 and 52 are respectively provided with inner shoulders 51 , 54. The lower end of the casing is provided with a shoe 112, and a soil-reforming or plough ring 113.

Turning to Fig. 5, a retrievable tool assembly comprising first and second deflector bodies 1 , 2 connected in tandem by hinged connector rod 3 is shown deployed within a jointed conductor casing as shown in Fig. 4. The first deflector body 1 houses an assembly of actuators 11 arranged to anchor the main tool body 1 when required by extending a bearing surface to contact a surface to which the tool body is to be anchored. A further assembly of actuators 14 is located at the other end of the body The second deflector body 2, similarly houses actuators 21 , 23 for equivalent purposes.

In this embodiment the actuator assembly 14 comprises double acting cylinders 13 with linear extending rods 12 providing reaction surfaces for contact with a corresponding surface within the conductor to be installed. The conductor 5 comprises articulated casing sections 50, 52, 53 connected at joints 22, 32, and configured to allow angular deviations to be developed by cooperation with actuator assemblies 14, 23 of the respective deflector bodies 1 , 2.

The conductor 5 is also configured to receive the tool bodies so as to properly orientate and align the deflector bodies 1 , 2 to allow proper control of the deflection of the articulated casing sections 52, 53 in the intended direction. An inwardly extending shoulder 51 is presented within the conductor section 50 for landing of deflector body 1 , and similarly shoulder 54 is presented in conductor section 53 for landing of the deflector body 2.

In a subsea use, the articulated conductor 5 equipped with closed end shoe is run to the mudline where a well head is to be established.

The deflector body tool assembly 1 , 2, is run in the conductor on a worksthng composed of drill pipe usually. The main deflector tool body 1 lands upon shoulder 51 (Fig. 6), and is properly oriented and aligned by use of the work string and similarly the dependent deflector body 2, is also aligned as a consequence of manipulating work string.

The work string can be released from the deflector body assembly and retrieved. The actuators 11 within the deflector body 1 are operated to deploy the extendible rods 12 in opposite directions as anchoring means (Fig. 7) to contact the inner surface of the conductor casing 50.

Thereafter, the actuator assemblies 14 and 23 in the deflector bodies 1 , 2 are operated to effect "steering" of the corresponding casing sections 52, 53 by deploying extendible rods in a similar way to the anchoring means, but in a chosen single direction to cause a deflection of the articulated casing sections 52, 53 in the opposite direction to permit deviated driving of the conductor into the surface at the mudline.

An angle build step (Fig. 8) can be initiated by the upper deviation body through operation of an actuator deploying a rod serving as a deflector device pushing against an internal surface of the conductor assembly and when sufficient deviation is achieved the actuator rod can be retracted.

An angle drop step (Fig. 9) can be initiated by operating an opposite actuator in a similar fashion In order to effect an azimuth turn (Fig. 10), the lower deviation body can be used to effect a deflection through operation of an actuator deploying a rod serving as a deflector device pushing against an internal surface of the conductor assembly and when sufficient deviation is achieved the actuator rod can be retracted. Similarly in order to effect an azimuth turn in the opposite direction (Fig. 11 ), the lower deviation body can be used to effect a deflection through operation of an opposing actuator.

The conductor is driven into place by a driving tool e.g. a pile hammer with ongoing adjustment of the articulated sections 52, 53 as required.

When the conductor is driven to the required depth, the actuators are reversed to release anchors within the conductor casing 5 and contact with the dependent articulated casing sections 52, 53.

The worksthng is again run in to latch onto the tool assembly, and the tool assembly is retrieved by pulling out the workstring, whilst recovering associated control and instrumentation lines.

Whereas the illustrative embodiment has been described with respect to hydraulic systems and actuators, it will be understood that any means of powering the deflector body to contact the conductor casing jointed part and effect a deflection of the casing during driving of the conductor casing and leading to a deviation in driving path can be used. Thus mechanical actuators driven by electric motors through reduction gearing can be used. Use of electromagnetic linear actuators to effect the required deviation in driving path by driving the deflector body against the jointed conductor casing section may also be used.

The invention as described above can achieve effective deviation in the driven conductor casing by selective remote control of the actuators.

Taking as an example a pivot angle relative to the opposing surface of the drive shoe of five degrees, based on a drive shoe length between its distal ends of six metres, a relative lateral displacement of the first pivot axis of up to 522.9 mm (20.6 inches) can be achieved as indicated in the table below.

Claims

Claims:

1. A retrievable tool comprising body parts connected by a flexible joint and configured to engage with a conductor casing comprising sections connected by a flexible joint in order to provide directional control during driving of the conductor casing into a surface, wherein actuating means is provided in at least one body part of the tool for effecting movement of said at least one body part, such that in use when the tool is located in the conductor casing, the corresponding section of the conductor is deflected and forced to deviate in angle and or azimuth of a driven direction by controlled movement of said at least one body part and resulting contact with the corresponding section of conductor casing.

2. A retrievable tool as claimed in claim 1 , wherein at least one tool body part is provided with anchor means for locating the tool body in a first section of conductor casing.

3. A retrievable tool for installing a conductor casing comprising a first body adapted for deployment and retrieval on a work string, and a second body pivotally connected to the first body section to allow deflection thereof in angle and or azimuth,

said first body incorporating anchor means for locating the first body within a conductor casing, and said second body housing actuators adapted to effect a deflection of the body from the longitudinal axis by a

predetermined angle for selectively deflecting a section of conductor casing in a predetermined direction during installation of the conductor casing.

4. A retrievable tool as claimed in any one of claims 1 to 3, wherein a body of the tool is configured to engage a landing shoulder within a conductor casing.

5. A retrievable tool as claimed in claim 4, wherein the body is equipped with an orientation key for alignment of the body within the conductor casing.

6. A retrievable tool as claimed in any one of claims 2 to 5, wherein the anchor means comprises actuators arranged to deploy contact members against an internal surface of a conductor casing.

7. Apparatus for establishing a wellhead, comprising a work string, a running tool and a retrievable body including anchor means and at least one dependent body section pivotally connected to said retrievable body and including actuators for effecting a deflection of the dependent body section, a conductor casing comprising flexible jointed sections, wherein the jointed sections are configured to pivot in different directions, and said bodies are configured to engage surfaces within the conductor casing, such that a first section of casing receives the retrievable body and anchor means, and a further section of casing receives the dependent body section enabling that further section to be deflected during driving of the conductor casing to effect a deviation in driving path.

8. A method of installing a conductor casing at a subsea interface where a wellhead is to be established,

which comprises

the tool comprising a retrievable tool main body providing anchor means for engaging an inner surface of a conductor casing, and pivotally attached thereto a first deviation body dependent from the main body, said first deviation body housing deflector devices adapted to deflect the deviation body from the longitudinal axis by a predetermined angle, and pivotally attached thereto a second deviation body dependent from the first deviation body, said second deviation body housing deflector devices adapted to deflect the deviation body from the longitudinal axis by a predetermined angle,

providing conductor casing sections connected to form at least two joints therein, and providing a closed end shoe for an end of the jointed conductor casing sections

landing and orienting the tool within the conductor casing sections actuating the anchor means and actuating the deflector devices to deflect the jointed conductor sections by a predetermined angle, and

driving the conductor sections to the required depth.