WO2007063324A1

WO2007063324A1 - Method and apparatus for installing deflecting conductor pipe

Info

Publication number: WO2007063324A1
Application number: PCT/GB2006/004497
Authority: WO
Inventors: Louie Horvath; Charles Michael Webre
Original assignee: Frank's International, Inc.
Priority date: 2005-12-03
Filing date: 2006-12-01
Publication date: 2007-06-07
Also published as: NO20082927L; US20090266559A1; AU2006321380A1; AU2006321380B2; EP1954910A1; CA2631405A1

Abstract

Delivering an additional subterranean conduit (124) along a deflected path relative to an existing conduit (120) is used for installing additional conductor pipes (124) from an existing production platform (50). A deflecting member in the form of a shoe (114, 115; 214) has a coupling means in the form of a screwthread for coupling to a lowermost end of an additional conduit (124). The shoe (114, 115; 214) is arranged to deliver the additional conduit (124) along the deflected path when the shoe (114, 115; 214) contacts whipstock (126; 226) which has been installed on top of an existing conductor pipe (120). The method can include running in the whipstock (126; 226) as a first step on an elongate member such as a drill string (94) and then withdrawing the drill string (94) and then running in the additional conduit (124). The outer diameter of the additional conduit (124) is maximised as it passes through conductor guides (52) attached to the production platform(50).

Description

"Method and Apparatus"

The present invention provides a method and apparatus for delivering an additional subterranean conduit along a deflected path relative to an existing conduit. In particular, the invention relates to the installation of a subterranean conductor pipe along a deflected path relative to an existing conductor pipe that led to a hydrocarbon reservoir.

It is usual in the offshore hydrocarbon recovery and production industry to drill a number of wellbores and to use a respective number of conductor pipes leading downwards from a production platform through supporting conductor guides, wherein the conductor pipes transfer the produced hydrocarbons back to the production platform. Such wells are very expensive to drill and such production platforms are very expensive to maintain. Inevitably, each drilled well has a finite life and it is commercially and environmentally advantageous to be able to drill more wells from the existing production platform in order to tap previously undrilled reservoirs in the reachable vicinity of the platform. Accordingly, there is a need to be able to install additional conductor pipes from the existing production platform and conventionally this is achieved by removing an upper portion of an existing but dry conductor pipe and installing a new or additional conductor pipe along a deflected path from that of the existing but dry conductor. This is known as lost well slot.

There are two known methods for installing conductor pipe along a deflected path from an offshore platform: below the mud line (subsea well slot recovery) and at or above the seabed (seabed well slot recovery). These methods are shown schematically in Figures 1-4.

Figures 1-3 show the below mud-line method. This method is typically used when there is a conductor guide 22 close to the seabed, typically 2 to 8 feet (0.61 to 2.44 m) above the seabed.

The conventional method shown in Figure 1 involves cutting an existing pipe 20 leading from a platform (not shown in Figure 1 ) to a subterranean reservoir (not shown) that previously contained hydrocarbons. Firstly, the uppermost section (which may be in the region of 50-80 feet or so) of the existing conductor pipe is reamed out in order to create a large diameter hole 32 in the mud extending downwardly from the mouth of the borehole, and to leave the rest of the conductor pipe 20 in situ. In order to prevent the large diameter hole 32 from collapsing, a high viscosity mud can be pumped therein. An additional conductor pipe 24, with a whipstock 26 shear bolted thereto, is then run through the conductor guide 22 and it is this stage that is shown in Figure 1. The lower end of the whipstock 26 is provided with a landing ring 28 having a diameter greater than that of the existing pipe 20 such that when a spear 30 is landed in the bore of the existing pipe 20, the landing ring 28 abuts the upper end of the pipe 20 to ensure that the whipstock 26 is seated thereon. The landing ring 28 also bears the shock when the additional conductor pipe 24 is sheared off the whipstock 26.

Figure 2 shows an alternative method (known as overshot whipstock) of coupling the whipstock 26 to the upper end of the existing pipe 20, whereby the lower end of the whipstock 26 is provided with a large diameter portion 36, known in the art as an overshot. The inner diameter of the overshot 36 is greater than the outer diameter of the existing pipe 20 such that the overshot 36 accommodates the end of the existing pipe 20 therein.

Once the whipstock 26 of Figures 1 and 2 is respectively landed within or over the existing pipe 20, a force is applied to the new conductor pipe 24, typically by dropping the weight of the pipe 24, to shear the shear bolts coupling the new pipe 24 and the whipstock 26. Thus the new pipe 24 is deflected by the whipstock 26 and can be hammer driven from the platform to the required penetration depth along a deflected path 38, as shown in Figure 3.

The method of Figures 1 to 3 is discussed in more detail in US Patent number 4,733,732 to Inventor Samuel C. Lynch (Assigned to Atlantic Richfield Company - ARCO) and the paper titled "Submudline Drivepipe Whipstock: A Cost Effective Method of Reclaiming Platform Slots" by S.M. Provance of ARCO Oil & Gas Co. presented at the 1986 IADC/SPE Drilling Conference held in Dallas, TX from 10 to 12 February 1986 (publication ref IADC/SPE 14731).

Figure 4 shows a diagrammatic representation of the above seabed method. This method is utilised if there is no conductor guide 52 at least 60 feet (18.3 metres) above the seabed 34. The existing pipe 20 is cut at around 5 to 10 feet (1.5 to 3 metres) above the seabed 34. The new conductor pipe 24 is made up as previously described and is shear bolted to the whipstock 26. The new conductor 24 and coupled whipstock 26 is guided down through one or more conductor guides 52 incorporated in a platform structure 50. A force is then applied to the new conductor pipe 24 to shear the bolts coupling the conductor pipe 24 and the whipstock 26 and the whipstock 26 deflects the new conductor pipe 24 along a deflected path. The new conductor pipe 24 is then hammer driven from the platform 50 to a predetermined penetration depth.

The main drawback associated with both the below mud-line and above seabed methods is that it is only possible to install new conductor pipe 24 that is smaller in diameter than the inner diameter of the conductor pipe guides 22, 52. For example, if the inner diameter of the conductor guides 22, 52 is 32 inches (81.3 cm), a typical outer diameter for the new conductor pipe would be 30 inches (76.2 cm). This is due to the fact that the whipstock 26 has a wall thickness at the point that it is shear bolted to the conductor pipe 24 (as an example, the wall thickness could be in the region of ³A inch (1.9 cm)). Therefore, because the combination of the outer diameter of the conductor pipe 24 and the whipstock 26 must be smaller than the inner diameter of the conductor guides, the outer diameter of the conductor pipe 24 must be substantially smaller than the inner diameter of the conductor guides. By way of example only, if the outer diameter of the conductor pipe 24 is 30 inches (76.2 cm) and the wall thickness of the whipstock is % inch (1.9 cm), the total diameter of the assembly is 31.5 inches (80 cm), which is the maximum outer diameter possible for the assembly, while just enabling the assembly to run through the conductor guides 22, 52.

Furthermore, it is not generally possible to install a new conductor pipe using conventional techniques where existing conductor pipes have been cemented below the seabed, since the cement bonds the existing conductor pipe to its surroundings and therefore prevents the existing conductor pipe from being extracted from the ground, since the existing conductor with cement bonded thereto would not fit through the pipe guides. According to a first aspect of the invention, there is provided a method of delivering an additional subterranean conduit along a deflected path from an existing conduit, comprising the steps of:

(a) providing a deflecting member at a lower end of the additional conduit;

(b) installing a path diverting means at or towards an upper end of an existing conduit;

(c) delivering the lower end of the additional conduit towards the upper end of the existing conduit; and (d) deflecting the lower end of the additional conduit utilizing the the path diverting means to thereby urge the additional conduit along a deflected path relative to the existing conduit.

Preferably, the method further comprises step (e) of installing the additional conduit along the deflected path.

Step b) may be carried out simultaneously with step c). Alternatively, step b) may be carried out prior to step c).

According to the first aspect of the invention, there is also provided apparatus for delivering an additional subterranean conduit along a deflected path relative to an existing conduit, the apparatus comprising a deflecting member having a coupling means for coupling the deflecting member to a lowermost end of the additional conduit in use, wherein, in use, the deflecting member is arranged to deliver the additional conduit along the deflected path when the deflecting member contacts a predetermined structure.

The deflecting member can comprise a surface angled with respect to the longitudinal axis of the existing conduit. The angled surface can be planar. For example, the surface can be angled in the region of between 20° to 70°, and more preferably can be angled in the region of between 30° to 60°, and most preferably can be angled at 45° with respect to the longitudinal axis of the additional conduit although other angles, as conditions may warrant, will suffice.

Alternatively, the deflecting member can have an outer surface comprising an aerodynamically efficient shape and may be somewhat or substantially conical. The outer surface of the deflecting member is preferably in the form of a paraboloid or bullet shaped.

A portion of the deflecting member adjacent the lower end of the additional conduit can have a larger outer diameter than that of the conduit. The outer diameter of the portion of the deflecting member can be between 0.2 and 0.5 inches (0.51 and 1.27 cm) larger than that of the conduit. This provides the advantage that there is a minimised risk of the joint between the deflecting member and the additional conduit getting stuck on the predetermined structure during downward movement of the deflecting member and additional conduit.

The deflecting member can be formed from a drillable material and may be provided in the form of an aluminium or hard plastics or composite material shoe.

The deflecting member can be provided with one or more holes extending therethrough.

Preferably the deflecting member comprises a head portion and a collar portion wherein the collar portion is preferably generally tubular in cross section and more preferably is smaller in outer diameter than the head portion. Typically, a neck portion is provided between the head portion and the collar portion wherein the neck portion comprises an outwardly projecting shoulder, which preferably extends in a perpendicular direction with respect to the longitudinal axis of the deflecting member. Typically, a coupling means is provided on the outer surface of the neck portion which is adapted to couple to a coupling means provided on the internal surface of the lower end of the additional conduit. Typically, the said coupling means are corresponding screw threads.

The predetermined structure can comprise a path diverting means arranged for insertion in the upper end of the existing conduit. The path diverting means can comprise a whipstock.

The inner diameter of the path diverting means can be less than the outer diameter of the additional conduit.

The coupling means can be adapted to prevent rotation between the additional conduit and the deflecting member.

According to a second aspect of the present invention, there is provided a method of installing an additional subterranean conduit, comprising the steps of:

(a) installing a path diverting means at or towards an upper end of an existing conduit using a deployment means; (b) removing the deployment means following installation of the path diverting means;

(c) delivering a lower end of the additional conduit towards the upper end of the existing conduit; (d) deflecting the lower end of the additional conduit using the path diverting means to thereby urge the additional conduit along a deflected path relative to the existing conduit; and

(e) installing the additional conduit along the deflected path.

The method according to the second aspect has the advantage that the outer diameter of the additional conduit is maximised because it is run in separately from the path diverting means.

The method typically further relates to delivering an additional subterranean conduit along a deflected path from an existing conduit.

The method can include removing a portion of the existing conduit prior to commencing step (a).

Prior to step (c), the method may further comprise providing a deflecting member at the lower end of the additional conduit. Preferably, the deflecting member is coupled to the lower end of the additional conduit.

The deployment means may comprise an elongate member and, prior to step (a), the method can further comprise coupling the path diverting means to an elongate member via a connection means which may preferably comprise a threaded connection means.

Step (a) of the method can further comprise applying a longitudinal force to the elongate member thereby securing the path diverting means in the upper end of the existing conduit. Following step (a), the method preferably further comprises decoupling the elongate member and the path diverting means and withdrawing the elongate member.

The method can further comprise installing the path diverting means through the throughbore of one or more guide members. The method can include maximising the outer diameter of the path diverting means while enabling it to fit through the throughbore of the one or more guide members.

The method may further include providing the deflecting member with deflecting surfaces and shaping the deflecting surfaces and thereby urging the conduit on the deflected path.

The method may further include providing the deflecting member with an angled end member.

The method may include angling at least a portion of the deflecting member in the region of between 20° to 70°, and more preferably in the region of between 30° to 60°, and most preferably at 45° relative to a longitudinal axis of conduit, although other angles, as conditions may warrant, will suffice. Alternatively, the method can include shaping the deflecting member in an aero-dynamic manner such as in the shape of a paraboloid and thereby splaying at least a portion of the path diverting means during step (d).

According to another aspect of the present invention, there is provided a method of installing an additional subterranean conduit, comprising the steps of: (a) providing the additional conduit with a deflecting member coupled to an end thereof;

(b) detachably coupling an end of a path diverting means to a portion of the additional conduit; (c) installing the path diverting means and coupled additional conduit at or towards an end of an existing conduit;

(d) applying a longitudinal force to the additional conduit and thereby decoupling the additional conduit from the path diverting means;

(e) deflecting the additional conduit to thereby urge the additional conduit along a deflected path relative to the existing conduit; and

(f) installing the additional conduit along the deflected path.

The method preferably further includes orienting the path diverting means during installation with respect to the existing conduit such that the deflected path diverges away from the existing conduit and structures associated therewith.

In one preferred embodiment, the method preferably further includes deflecting the additional conduit around a structure which may be a pipe guide brace coupled to the existing conduit and the method can further include shaping the deflecting member such that it comprises a planar surface angled with respect to the longitudinal axis of the additional conduit.

However, in an alternative embodiment, the method can include shaping the deflecting member such that it comprises a somewhat or substantially conical outer surface such as in the shape of a paraboloid. Any feature of any aspect of any invention described herein may be combined with any feature of any aspect of any other invention described herein mutatis mutandis.

Embodiments of the invention will now be described with reference to and as shown in the accompanying drawings, in which:-

Figures 5 and 6 are side and front views respectively of a whipstock used in one embodiment according to the present invention; Figures 7 and 8 are side and front views of a conductor pipe having a deflecting end member and part of the whipstock shown in Figures 5 and 6 although the spear 130 is not shown in Figures 7 and 8;

Figure 9 is a side view of a conductor pipe deflected along a deflected path;

Figures 10 and 11 are side and front views of a whipstock and an additional conductor pipe with an end member used in a second embodiment in accordance with the present invention; Figure 12 shows the additional conductor pipe of Figures 10 and 11 along a deflected path;

Figures 13 and 14 are side and perspective views respectively of the end member of Figures 10 and 11 ; and Figures 15 and 16 are side and perspective views of the end member of Figures 7 and 8.

A whipstock is shown generally at 126 in Figure 5. The whipstock 126 has a trough 102 defined by the outer edges converging towards the lower end of the whipstock 126 and providing a gently curved surface 104 therebetween. The surface 104 is provided with an elongate hole 106 allowing an elongate member 94 such as a relatively slim drill string 94 to be accommodated therethrough. Within the whipstock 126, a connector 108 is provided with an open end 110 having an internal thread and is in the form of a 4 V≥ inch drill pipe box connector 110. The box connector 110 engages with thread 96 provided on a pin connection located at the lower end of the drill string 94.

Alternatively, the box connector 110 can be replaced by any other form of suitable connection means if a different type of connector is required, such as a "J"-latch, an annular groove with associated locking ring arrangement, etc. etc..

The whipstock 126 has a landing ring 128 and a spear 130. The outer diameter of the spear 130 is less than the inner diameter of an existing conductor pipe 120 in which the whipstock 126 is intended to be landed. The landing ring 128 is chosen to have a slightly greater inner diameter than the outer diameter of the existing conductor pipe 120 such that the landing ring 128 will abut the upper end of the existing conductor pipe 120 in use. However, depending upon the conditions, it may be preferable to replace the spear 130 with an overshot (not shown but similar to the overshot 36 of Figure 2).

As shown in Figures 7 and 8, an additional conductor pipe 124 having a diameter of 30 inches (76.2 cm) in this example is provided with a diverting end member in the form of a shoe 114. The shoe 114 is shown in greater detail in Figure 15 and is preferably formed from a drillable material such as aluminium, hard plastics such as polyurethane, a composite material or indeed any other suitable drillable material and is generally provided in two main portions, a head member 114 and a generally tubular collar 116 where there is a neck portion provided between the head member 114 and the collar 116, the neck portion providing a perpendicularly extending shoulder which can be torqued against the lower end of the replacement conductor 124, as will be subsequently described. The head member of the shoe 114 has a paraboloid or bullet shaped leading end having a curved substantially conical surface leading to a gently rounded point in which a central hole 118 is provided. The shoe 114 is coupled to the additional conductor pipe 124 via the collar 116 that is arranged for insertion into the end of the conductor pipe 124. A thread (not shown) is machined on an external surface of the collar 116 and the lower end of the conductor pipe 124 has an internal thread provided therein. The collar 116 of the shoe 114 is screwed into the conductor pipe 124 and can be secured with aluminium dowels to ensure that there is no rotation between the shoe 114 and the conductor pipe 124. The wide end of the head member of the bullet shaped shoe 114 has an outer diameter which is slightly larger (such as by VA inch) than the outer diameter of the conductor pipe 124. This prevents the joint between the shoe 114 and the conductor pipe 124 becoming stuck or separated as the shoe 114 contacts the surface 104 of the whipstock 126.

An alternative shoe 115 is shown in Figure 16. The end of the shoe 115 is also bullet shaped with a connector 116 at the other end. However, the head member of the shoe 115 has a plurality of holes 118 provided therein. The purpose of the holes 118 in the shoes 114, 115 is to allow fluid and muds therethrough to prevent a significant pressure building up behind the shoes 114, 115 as the shoes 114, 115 are drilled out (as will be subsequently described) and thus impeding the progress of the conductor pipe 124 as it is driven into the ground. Additionally, fluids can be pumped through the holes 118 via a drillstring (not shown) coupled to the shoe 115. The fluids can wash away obtrusive cuttings from the leading end of the shoe 115 if it becomes necessary. It should be noted that any dimensions stated hereinafter are given as an example only to aid understanding of the embodiments and that actual dimensions will vary depending upon the specific conditions such as the conductor pipe 120 being replaced, the outer diameter of the replacement conductor 124, the inner and outer diameters of the whipstock 126 and the inner and outer diameters of the platform conductor guides 122.

First Embodiment Case Example 1 A first example of a method according to one embodiment of the present invention will now be described with reference to Figures 5-9 of the drawings. The existing conductor pipe 120 in this example has a diameter of 30 inches (76.2cm) and is cut at least 60 feet (18.3 metres) below the seabed. Depending upon soil conditions, a hole 132 of approximately 48 inches (1.22 metres) in this example or larger is reamed in the mud above the cut conductor pipe 120; if the soil is relatively hard, it will likely be beneficial to drill a hole 132 larger than 48 inches (1.22 metres) in diameter. In order to prevent the hole from collapsing during whipstock 126 installation, heavy viscous mud can be pumped into the hole 132 before withdrawing the drilling assembly (not shown) used to ream the hole 132. The hole 132 can be drilled using a hole opener or under reamer.

The drill string 94 is coupled to the box connection 110 of the connector 108 within the whipstock 126. The drill string 94 passes through the hole 106 in the surface 104 of the whipstock 126. The whipstock 126 is then lowered through one or more conductor guides 122 and the spear 130 is landed within the end of the existing conductor pipe 120 with the whipstock trough 102 oriented in a predetermined location/direction. The drill string 94 is then rotated to decouple the threads 96 from the threads in the box connection 110 of the connector 108. Once the drill string 94 is decoupled from the whipstock 126, it can be withdrawn back to the platform floor.

Alternatively, different situations may mean that a different connection method (i.e. non-screwthread or non-high torque enabled connection) is preferred; in such cases, any other suitable connection means may be used such as a "J" slot and latch arrangement, an annular groove with locking ring arrangement etc. etc..

The additional conductor pipe 124 with the attached shoe 114 is deployed through the one or more guide members 122 towards the trough 102 of the whipstock 126. The inner diameter of the trough 102 in this example is 28.5 inches (72.4cm). At its widest point, the outer diameter of the shoe 114 in this example is 30¹/4 inches (76.8cm). However, since the shoe 114 is provided with a gently rounded point, this locates the shoe 114 and attached conductor pipe 124 correctly in the whipstock trough 102 and further downward movement of the shoe 114, which has a larger maximum outer diameter than the whipstock trough 102, forces the edges of the trough 102 to splay outwardly thereby accommodating the shoe 114 and the conductor pipe 124 within the trough 102. The contact between the shoe 114 and the surface 104 of the whipstock 126 causes the conductor pipe 124 to deflect relative to the longitudinal axis of the existing conductor pipe 120 as shown in Figure 9. The conductor pipe 124 can then be hammer driven to the required penetration depth such that the additional conductor pipe 124 can thereafter provide another well bore, in addition to the existing well bore provided by the existing conductor pipe 120, to provide another path for production fluids to flow from a reservoir to the surface. The above described method is also suitable where the closest conductor guide is above around 65 feet (19.8 metres) the seabed 134.

Running in the whipstock 126 separately from the additional conductor pipe 124 enables the maximum possible outer diameter of the conductor pipe 124 to be used with respect to the conductor guides 122. The diameter of the whipstock trough 102 can also be maximised with respect to the conductor guides 122. However, despite the inner diameter of the trough 102 being equal to or less than the outer diameter of the conductor pipe 124 it is still possible to deflect and install the conductor pipe 124 due to the shoe 114, which causes the whipstock 126 to splay thereby increasing the diameter of the whipstock trough 102 such that it can accommodate the end of the conductor pipe 124. Accordingly, embodiments of the present invention do not require that the additional conductor pipe 124 be 2 inches (5.1 cm) less in this example than the inner diameter of the conductor guides 122. This is a great advantage since it is always desirable to be able to use the maximum conductor pipe 124 possible in the circumstances in order to maximise potential hydrocarbon production rates or to enable twin well drilling from one conductor pipe.

First Embodiment Case Example 2

A second method of installing a conductor pipe 124, whilst using the bullet shaped shoe 114, will now be described.

The existing conductor pipe 120 is cut at least 60 feet (18.3 metres) below the sea bed as per example 1. The hole 132 is again reamed in the same manner as case example 1. However, in case example 2, the whipstock 126 is shear pinned to the lower end of the additional conductor pipe 124 with the attached shoe 114. Accordingly, in this example 2, the initial conductor pipe 124 and shoe 114 are run into the hole along with the whipstock 126 until the whipstock spear 130 is landed into the upper end of the existing conductor pipe 120. Further downward movement of the additional conductor pipe 124 shears the shear pins (not shown) causing the shoe 114 to enter in to the whipstock trough 102 and thus deflection of the shoe 114 and lower end of additional conductor pipe 124 occurs (as again shown in Figure 9). The conductor pipe 124 can then be hammer driven to the required penetration depth (either with the shoe 114 still attached or with the shoe 114 having been drilled out).

Running in the whipstock 126 simultaneously with the additional conductor pipe 124 has the advantage that only one trip is required to install the additional conductor pipe 124 as opposed to the two separate trips of the case example 1. However, case example 2 does not have the advantage of being able to maximise the outer diameter of the additional conductor pipe 124 with respect to the conductor guides 122.

Second Embodiment Case Example 1

Another embodiment of the invention is shown in Figures 10-12. The second described embodiment allows an additional conductor pipe 224 to be installed along a deflected path relative to an existing conductor pipe 220 in circumstances where there is a conductor guide relatively close to the seabed (say within 2 feet to 8 feet) with the existing conductor pipe 220 cemented into the seabed and providing the distance to the next conductor guide above that close to the seabed is at least 50 feet (15.2 metres) or so. The whipstock 226 is shown in Figures 10-12 and is generally of the same construction as that described for the previous embodiment. The whipstock 226 has a spear 230, a landing ring 228 and a trough 202 approximately 30 inches in length and defined by a surface 204. The conductor pipe 224 has a shoe 214 attached to its lower in use end. Furthermore, the lower in use end of the conductor pipe 224 is shear bolted to an upper end of the whipstock 226 via shear bolts 248 passing through holes 249 in the whipstock 226 and the conductor pipe 224. The shear bolts 248 shear capacity is determined from the tonnage of the conductor pipe 224 string weight.

The shoe 214 of the second embodiment is shown in more detail in Figures 13 and 14. The shoe 214 has an upper connector 216 for connecting the shoe 214 to the additional conductor pipe 224 in the same manner as previously described. The shoe 214 has a face 212 angled at 45° relative to the longitudinal axis of the conductor pipe 224, since this angle is likely to be the most used and therefore most preferred angle but other angles could be used depending upon the conditions but the angle is likely to be in the region between 20° to 70° with respect to the longitudinal axis of the additional conduit and more likely will be in the region between 30° to 60°. The shoe 214 is provided with a central hole 218 in the face 212. The hole 218 in the shoe 214 is also useful for guiding and centralising the tapered drill bit after the installation process when the shoe 214 is to be drilled off the leading end of the conductor pipe 224.

Figure 12 shows an upper and lower pipe guide 222U, 222L respectively. The lower pipe guide 222L is maintained in position by conductor guide bracings. A major guide brace 243 of the platform is shown in the left hand side of the conductor guide 222L in Figure 12 and a minor guide brace 242 having a smaller diameter than the major guide brace 242 is shown on the right hand side of the conductor guide 222L. In many embodiments, the cemented conductor pipe 220 is surrounded by four minor guide braces 242 spaced from one another by 90° and therefore there is no restriction on the orientation of the shoe 214.

The existing conductor pipe 220 is cut approximately 3 feet (91.4cm) above the lower conductor guide 222L. The additional conductor pipe 224 coupled to the whipstock 226 is then lowered through the upper conductor guide 222U. The whipstock 226 should be positioned within the existing conductor pipe 220 such that the trough 202 is angled towards the minor conductor guide brace 242, and markings applied to the conductor pipe 224 as it is lowered at the platform assists the operator to align the trough in the desired rotational position. The spear 230 is landed in the preexisting conductor pipe 220 so that the landing ring 228 abuts the upper edge of the existing conductor pipe 220. A force is then applied to the conductor pipe 224 to shear the shear bolts 248. Shearing the shear bolts 248 allows the conductor pipe 224 to deflect by virtue of the whipstock trough 202. The shoe 214 (angled at 45° in this specific example) allows the end of the pipe 224 to avoid minor conductor guide brace 242 which does not impede installation of the new conductor pipe 224 along its deflected path, in that if the angled face of the shoe 214 contacts the minor conductor guide brace 242, the angled face of the shoe 214 will ride over and around the minor conductor guide brace 242. The conductor pipe 224 is then hammer driven to the required depth along its deflected path.

Accordingly, case example 1 of the second embodiment has the advantage that only one trip is required to install the additional conductor pipe 224 because it is lowered along with the whipstock 226. However, case example 1 does have the disadvantage that the diameter of the new conductor pipe 224 is not maximised because of the shear pin attachment points 248.

Second Embodiment Case Example 2 The second embodiment case example 2 is largely similar to the second embodiment case example 1 with the exception that the whipstock 226 is run separately and is therefore not shear pinned to the new conductor pipe 224. In the second embodiment case example 2, the whipstock 226 is attached to a drill string 94 and is lowered through the upper conductor guide 222U until it is positioned within the existing conductor pipe 220. The trough 202 is angled in the same manner as second embodiment case example 1. The drill pipe is then decoupled from the whipstock 226 and is withdrawn back through the upper conductor guide 222U.

The new conductor pipe 224 with the attached shoe 214 is then lowered through the upper conductor guide 222U until the angled shoe 214 is located just above the whipstock 226. The new conductor pipe 224 and angled shoe 214 are rotated until the angled shoe 214 is in the desired rotational configuration with respect to the whipstock 226. The new conductor pipe 224 is then further lowered such that the conductor pipe

224 is deflected by virtue of the whipstock trough 202. The angled face of the shoe 214 again rides over and around the minor conductor guide brace 242 and the new conductor pipe 224 can then be hammer driven to the required depth along its deflected path.

The second embodiment case example 2 has the advantage that the diameter of the new conductor pipe 224 can be maximised because the new conductor pipe 224 is run separately from the whipstock 226 and therefore the outer diameter of the new conductor pipe 224 can be chosen to be as large as possible as long as it still fits through the upper conductor guide 222U.

The second embodiment has the great advantage that it can be used to install an additional conductor in circumstances where the existing conductor pipe has been cemented below the seabed, and where there is a conductor guide located just above the seabed; hitherto, it has not been possible to install an additional conductor in such a scenario.

In both embodiments it is possible, and likely desirable, to drill out the shoe 114, 214 just after the shoe 114, 214 has been stabbed into the subsea surface and immediately prior to hammer driving the conductor pipe 124, 224 into the desired position. In this scenario, the conductor pipe 124, 224 is temporarily secured to the rig and a smaller diameter drill pipe and drill bit (not shown) are run down into the conductor pipe 124, 224 and the shoe 114, 214 is drilled out. The smaller diameter drill pipe and drill bit are pulled out of the hole and hammer driving of the conductor pipe 124, 224 can commence until final depth of penetration is achieved. Alternatively, depending upon the formation, it may be more desirable to hammer drive the conductor pipe 124, 224 to the final depth of penetration and then drill out the shoe 114, 214.

The embodiments described herein have cost and time advantages over the prior art systems for installation of additional conductor pipes (124; 224) from an existing production platform (50); furthermore the outer diameter of the additional conductor pipe (124; 224) can be maximised.

Modifications and improvements can be made without departing from the scope of the invention. For instance, the shoe 114, 214 could be formed of a different drillable material such as a hard plastic which may be polyurethane. Also, the lower face of the landing ring 128 may be provided with teeth 129 shown in Fig. 4 which are adapted to bite into the upper end of the existing conductor 120, 220. The teeth 129 may point directly downwards or may point at an angle in one or both rotational directions in order to further prevent unwanted rotation occurring between the whipstock 126, 226. Furthermore, the various diameters and lengths of the components described herein can be varied in order to suit the particular platform involved.

Any feature of any aspect of any embodiment described herein may be combined with any feature of any aspect of any other embodiment described herein mutatis mutandis.

Claims

CLAIMS:-

1. Apparatus for delivering an additional subterranean conduit along a deflected path relative to an existing conduit, the apparatus comprising:- a deflecting member having a coupling means for coupling the deflecting member to a lowermost end of the additional conduit in use; wherein, in use, the deflecting member is arranged to deliver the additional conduit along the deflected path when the deflecting member contacts a predetermined structure.

2. Apparatus according to claim 1 , wherein a portion of the deflecting member adjacent the lower end of the additional conduit comprises a _t larger outer diameter than that of the conduit.

3. Apparatus according to either of claims 1 or 2, wherein the deflecting member can be formed from a drillable material.

4. Apparatus according to any preceding claim, wherein the deflecting member can be provided with one or more holes extending therethrough.

5. Apparatus according to any preceding claim, wherein the deflecting member comprises a head portion and a collar portion wherein the collar portion is generally tubular in cross section and is smaller in outer diameter than the head portion.

6. Apparatus according to claim 5, wherein a neck portion is provided between the head portion and the collar portion wherein the neck portion comprises an outwardly projecting shoulder which extends in a perpendicular direction with respect to the longitudinal axis of the deflecting member.

7. Apparatus according to claim 6, wherein a coupling means is provided on the outer surface of the neck portion which is adapted to couple to a coupling means provided on the internal surface of the lower end of the additional conduit.

8. Apparatus according to claim 7, wherein the said coupling means are corresponding screw threads.

9. Apparatus according to any preceding claim, wherein the predetermined structure comprises a path diverting means arranged for insertion in the upper end of the existing conduit.

10. Apparatus according to claim 9, wherein the path diverting means comprises a whipstock.

11. Apparatus according to any preceding claim, wherein the outer surface of the deflecting member is substantially conical.

12. Apparatus according to claim 9 or to either of claims 10 or 11 when dependent upon claim 9, wherein the inner diameter of the path diverting means is less than the outer diameter of the additional conduit.

13. Apparatus according to any of claims 1 to 10, wherein the deflecting member comprises a surface angled with respect to the longitudinal axis of the existing conduit.

14. Apparatus according to claim 13, wherein the surface is planar and is angled in the region of between 20° to 70° with respect to the longitudinal axis of the additional conduit.

15. A method of delivering an additional subterranean conduit along a deflected path from an existing conduit, comprising the steps of:

(a) providing a deflecting member at a lower end of the additional conduit; (b) installing a path diverting means at or towards an upper end of an existing conduit;

(c) delivering the lower end of the additional conduit towards the upper end of the existing conduit; and

(d) deflecting the lower end of the additional conduit utilizing the the path diverting means to thereby urge the additional conduit along a deflected path relative to the existing conduit.

16. A method according to claim 15, further comprising step (e) of installing the additional conduit along the deflected path.

17. A method according to either of claims 15 or 16, further comprising removing a portion of the existing conduit prior to commencing step (a).

18. A method according to any claims 15 to 17, wherein step (b) is completed prior to starting to carry out step (c).

19. A method according to claim 18, further comprising installing the path diverting means using a deployment means and yet further comprises the step of removing the deployment means following installation of the path diverting means.

20. A method according to claim 19, wherein the deployment means comprises an elongate member and, prior to step (b), the method further comprises coupling the path diverting means to the elongate member via a connection means.

21. A method according to claim 19, wherein step (b) of the method further comprises applying a longitudinal force to the elongate member thereby securing the path diverting means in the upper end of the existing conduit.

22. A method according to either of claims 20 or 21 , wherein following step (b), the method further comprises decoupling the connection means between the elongate member and the path diverting means and withdrawing the elongate member.

23. A method according to any of claims 15 to 22, wherein the method further comprises installing the path diverting means through the throughbore of one or more guide members.

24. A method according to claim 23, wherein the method includes maximising the outer diameter of the path diverting means while enabling it to fit through the throughbore of the one or more guide members.

25. A method according to any of claims 15 to 24, further comprising providing the deflecting member with deflecting surfaces and shaping the deflecting surfaces and thereby urging the conduit on the deflected path.

26. A method according to any of claims 15 to 25, further comprising shaping the deflecting member in an aero-dynamic manner such as in the shape of a paraboloid and thereby splaying at least a portion of the path diverting means during step (d).

27. A method according to any of claims 15 to 17, wherein step b) is carried out simultaneously with step c).

28. A method according to claim 27, further comprising:- coupling the path diverting means to the lower end of the additional conduit in a selectively breakable manner; running the path diverting means into the wellbore on the lower end of the additional conduit; installing the path diverting means in the upper end of the existing conduit; and breaking the coupling between the additional conduit and the path diverting means.

29. A method according to any of claims 15 to 25 or to claim 27, further comprising forming the deflecting surface with a planar angled end surface.

30. A method according to claim 29, further comprising angling at least a portion of the deflecting member in the region of between 20° to 70° relative to a longitudinal axis of the existing conduit.

31. A method of installing an additional subterranean conduit, comprising the steps of:

(a) installing a path diverting means at or towards an upper end of an existing conduit using a deployment means;

(b) removing the deployment means following installation of the path diverting means;

(c) delivering a lower end of the additional conduit towards the upper end of the existing conduit;

(d) deflecting the lower end of the additional conduit using the path diverting means to thereby urge the additional conduit along a deflected path relative to the existing conduit; and (e) installing the additional conduit along the deflected path.

32. A method according to claim 31 , wherein the method relates to delivering an additional subterranean conduit along a deflected path from an existing conduit to provide an additional well bore for production fluids to flow from a reservoir to the surface.

33. A method according to either of claims 31 or 32, further comprising removing a portion of the existing conduit prior to commencing step (a).

34. A method according to any of claims 31 to 33, further comprising providing a deflecting member at the lower end of the additional conduit prior to step (c).

35. A method according to claim 34, wherein the deflecting member is coupled to the lower end of the additional conduit.

36. A method of installing an additional subterranean conduit, comprising the steps of: (a) providing the additional conduit with a deflecting member coupled to an end thereof;

(b) detachably coupling an end of a path diverting means to a portion of the additional conduit;

(c) installing the path diverting means and coupled additional conduit at or towards an end of an existing conduit;

(e) deflecting the additional conduit to thereby urge the additional conduit along a deflected path relative to the existing conduit; and (f) installing the additional conduit along the deflected path.

37. A method according to claim 36, wherein the method relates to delivering an additional subterranean conduit along a deflected path from an existing conduit.

38. A method according to either of claims 36 or 37, further comprising orienting the path diverting means during installation with respect to the existing conduit such that the deflected path diverges away from the existing conduit and structures associated therewith.

39. A method according to any of claims 36 to 38, further comprising deflecting the additional conduit around a structure such as a pipe guide brace coupled to the existing conduit.