WO2022081020A1

WO2022081020A1 - Establishing sidetracks in a well

Info

Publication number: WO2022081020A1
Application number: PCT/NO2021/050211
Authority: WO
Inventors: Gaute GRINDHAUG; Tore Weltzin; Morten HOVLAND; Morten EIDEM; Frode Berge; Stephen Mark Williams; Brian Dahl KRISTENSEN
Original assignee: Equinor Energy As
Priority date: 2020-10-15
Filing date: 2021-10-12
Publication date: 2022-04-21
Also published as: GB2599931A; GB202016353D0

Abstract

The present invention provides various means for establishing multiple sidebranches from a main wellbore using a single or reduced number of trips. For example, a means may utilise a wellbore tubular for lining a well, used in the production of hydrocarbons, the wellbore tubular comprising a main body formed by connection of a plurality of tubular sections, and a plurality of deflector plates axially spaced along the main body, each deflector plate being attached to the main body by one or more hinges so that deflector plate is moveable between a non-deployed position in which the deflector plate lies substantially flush with the main liner body and a deployed position in which the deflector plate provides an axially extending ramp within the main body.

Description

ESTABLISHING SIDETRACKS IN A WELL

Technical Field

The present invention relates to establishing sidetracks in a well such as a hydrocarbon reservoir producing or injection well.

Background

For a variety of reasons it is often desirable to establish sidetrack running away from a main hydrocarbon reservoir completed well. Presently, this may be achieved by running a so-called whipstock into the well and securing it at a location where a sidetrack is to be established. The whipstock has an angled surface such that it provides deflection of a milling tool to allow a window to be milled through the surrounding tubing (assuming the main wellbore has been completed - nb. sometimes sidebranches may be drilled prior to completing the main wellbore). Thereafter a drilling Bottom Hole Assembly (BHA) is run into the well and is similarly deflected by the whipstock allowing the sidetrack to be drilled. Running of a whipstock and milling of a window is a relatively time-consuming process in an industry where time has enormous cost implications. This is especially problematic where multiple sidetracks need to be established (this often being the case).

Research Disclosure database number 675001 , “One-trip Multilateral Openhole Completion System”, 26 May 2020, describes the use of a re-locatable whipstock which can be pulled up by a drill string and re-set to allow the drilling of multiple sidetracks with a single trip into the well, with the lowermost sidetrack being drilled first.

Summary

It is an object of the present invention to provide methods and apparatus to facilitate the establishment of multiple sidetracks from a well whilst requiring only a single trip, or at least a reduced number of trips, into the well.

Various aspects of the present invention are set out in the appended claims. The term “wellbore tubular” used here encompasses both “liner” and “casing” as those terms are commonly understood, as well as other suitable tubulars.

Brief Description of the Drawings

Figures 1 a to 1c illustrate schematically the use of deflector plates in a main well liner to provide multiple sidebranch kick-offs;

Figures 2a to 2f illustrate an alternative mechanism for providing multiple kick-offs within a main well liner and comprising pass-through ramps machined within the liner;

Figures 3a to 3c illustrate a further alternative mechanism for providing multiple kickoffs within a main well liner and comprising a moveable whipstock and multiple whipstock latches;

Figures 4a to 4h illustrate a further alternative mechanism for providing multiple kickoffs within a main well liner and comprising a plurality of borehole assemblies deployed within the liner;

Figures 5a to 5f illustrate a procedure for deploying completion liners into multiple sidebranches with a single run into the main well; and

Figure 6 illustrates a possible mechanism for using a drill pipe to move a whipstock between multiple locations.

Detailed Description

As has been outlined above, it is desirable to be able to establish multiple sidebranches extending laterally, or in any other direction and/or angle, away from a main wellbore with only a single trip into the well, or at least with a reduced number of trips. This means that it is necessary to provide a means that allows for deflection of a drill bit (where it is assumed that the drill bit is also able to mill through part of the liner if necessary) at multiple locations along the main wellbore. This can be achieved in three ways; a first relies on a moveable deflection mechanism and a second of which relies upon providing multiple deflection means spaced along the wellbore and which allow for pass-through of the drill bit and/or other tools. A third approach is to include a deflector device as part of the drill string itself. Various embodiments adopting one or other of these approaches will now be described.

Multiple integrated and deflectable whipstocks in liner Figure 1 a illustrates a wellbore tubular 1 , in this case a liner, made up of a plurality of connected liner sections, with multiple integrated whipstocks 2 (where the left most end in the drawing represents the lower part of the liner and the right most end represents the upper part of the liner (i.e. the part closest to the surface)). This liner is run into the main borehole during completion of the main borehole. Figure 1 b shows in more detail a short section of the liner 1 including one of the integrated whipstock 2, again with the rightmost end in the drawings representing the end closest to the surface. The whipstock 2 comprises a deflector 3 which forms a part of the liner joint which is coupled to the main body of the liner via a pair of circumferentially spaced hinges 4 at the lower most end of the deflector. [NB. Other hinge mechanisms may be used and the term “hinge” is defined accordingly. For example, a “hinge” may be provided by way of a score or weakened area connecting the deflector to the main body of the liner.] The deflector is curved in transverse cross-section such that it generally conforms to the circumference of the liner and may be formed of a relatively strong material, e.g. a steel of the same or similar grade to that from which the liner is formed. The deflector may also be formed of a material that, whilst sufficiently strong, is dissolvable by a suitable fluid. The deflector is oriented as required and located within a cut-out window 5 of the liner. During running in of the liner 1 and prior to activation, the uppermost end of the deflector 3 is secured in place and prevented from falling into the inside of the liner by a moveable sleeve 6.

The insets in Figure 1c show cross-sections through the liner and deflector plate as viewed from the right, i.e. from the surface, in the non-deployed (right) and deployed (left) configurations. It will be appreciated that the curvature of the deflector plate when in the deployed configuration is not necessarily optimal for guiding the drill bit. A drill bit guide 7 may therefore be provided on a surface of the deflector such that it projects into the interior of the liner when the deflector is deployed. The guide 7 may extend axially along the length of the deflector, on one side thereof. As the drill bit is conventionally rotated in a clockwise direction during drilling, the drill bit tends to move towards the right side of the deflector. It will therefore push against the guide and be guided thereby. The skilled person will appreciate that the liner sections generally have male and female ends that allow for threaded connection of the sections. The female end will generally have a collar that projects radially outward by a small amount. The projecting collars will provide a degree of protection for the guide when the deflector is in the non-deployed configuration.

Having installed the liner 1 , a new drilling Bottom Hole Assembly (BHA) is run in hole on a drill string. The BHA is lowered to just above the location of the lowermost whipstock 2, and may comprise a rotary steerable system having pads that are used to “grab” the movable sleeve 6 and drag it upwards. This releases the uppermost end of the deflector 3 which is pushed inward into the interior of the liner by a spring load or other biasing mechanism (not shown), creating a ramp within the liner and leaving an opening in the liner wall. This activated configuration of the whipstock 2 is illustrated in Figure 1c. Figure 1c also shows cross-sectional details of the deflector 3 at the lowermost and uppermost ends. It is also possible to have a dedicated sub to grab and move the sleeve, or maybe a battery powered mechanism in the liner joint which is activated by a signal from the surface.

Drilling of the lowermost sidetrack is then commenced. The drill bit and the drill string (which has a degree of flexibility) is deflected outwardly by the deflector 3 as it is pushed downwards, exiting the liner through the cut-out window 5, with the deflector presenting a much greater resistance than the formation surrounding the liner. Drilling is continued until the sidetrack is completed. Having drilled the sidetrack, the BHA is pulled up to the location of the next whipstock 2 and the procedure is repeated creating another sidetrack, and so on.

Multi-branch drilling single run kick-off system

In an alternative approach, rather than having multiple deflectable whipstocks, a plurality of "whipstock ramps" are formed integrally on the inside wall of the a specially designed "kick-off casing/liner joint". The approach is illustrated in Figure 2a which shows a liner section 10 having an internally machined ramp 11 shown with broken lines. Figure 2b is a cross-section of the liner section 10 taken along the plane X-X from which it can be seen that the ramp 11 comprises a pair of ramp sections 11 a, 11b on opposite sides of the liner section. The ramps may be linear with an angle of the order of 5-25 degrees, or may be curved or change in a stepwise manner. A window 12 is provided above the ramps, but is “filled” with a plate of aluminium, fibreglass or other relatively easily drillable material. The kick-off joint is used in conjunction with a specially designed bottom hole 13 assembly (BHA) illustrated in Figure 2c and which may have a specially modified polycrystalline diamond compact (PDC) drill bit 14, a specially modified hydraulic drilling motor 15 and an orientation sub 16. The BHA is coupled to a drill pipe 17 through which mud is pumped to drive the hydraulic motor and the drill bit. Figure 2d is a cross-section through the drill pipe on the plane A-A, showing that the cross-section is circular and narrow relative to the inside diameter of the liner (the drill pipe may be of standard dimensions). Cross-sections through the motor 15 and bit 14 on the planes B-B and C-C are shown in Figures 2e and 2f respectively, and illustrate the rectangular cross-section of these components.

The drill bit 14 is driven by the motor 15 and is capable of both milling through the window 12 above the kick-off joint, and drilling a sidebranch through the formation to a distance of a few tens of meters to several kilometers. From a consideration of the cross-sectional views of Figures 2, it will be appreciated that in one rotational orientation the drill bit 14 and motor 15, as well as the drill pipe 17, are able to pass through the slot formed between ramp sections 11 a,11b without deflection. However, when rotated, e.g. by 90 degrees, the long axis of the bit and motor cause them to engage the ramp 11 , deflecting them and the drill pipe away from the main well axis. The ramp 11 ends short of the end of the window 12. At this point the motor, which remains on the ramp, is operated to rotate the drill bit. The drill bit will commence drilling of the window and then on into the formation. At the point where the motor leaves the end of the ramp, the drill bit is already within the formation so drilling will continue along the desired trajectory.

Multiple kick-off joints can be provided in the liner string enabling multiple sidebranches to be drilled. The orientation of these joints can be set up to allow any kick-off direction in the reservoir by including an orientation collar in the kick off joint. In addition, the orientation of the entire liner string needs to be set during running to allow the required kick-off direction. This may be done using similar methods deployed in the multilateral technology (MLT) window placement in current MLT wells.

This approach can provide flexibility to enter specific branches or pass though along the mother bore as desired simply by orienting the bottom hole assembly to either engage the ramp or pass through the kick-off joint. The approach is flexible in that sidebranches can be formed from the bottom up, or the top down, or in any desired pattern. Sidebranches can be added later as required.

It should be noted that, with this approach, conventional cementing of the casing/liner may not possible because the internal profile of the kick-off joints prevents cementing plugs passing through. Liner top squeeze or running a small outside diameter pipe through the kick-off joints to the casing shoe track assembly may be feasible alternatives.

A modification of this approach involves replacing the rectangular bit/ with a conventionally shaped bit of smaller size, followed by a hydraulically activated underreamer or other component behind the bit. This component may be activated when the BHA approaches a kick-off joint where a sidebranch is to be established so that the BHA is deflected. Following drilling of the sidebranch and withdrawal of the BHA, the component may be withdrawn allowing the BHA to pass through the joint.

Multi-set whipstock top-down

Figure 3a to 3c illustrate a further approach to establishing multiple sidebranches with only a single trip into the well or a reduced number of trips. This approach employs a single whipstock 20 with multiple whipstock latches 21 spaced along the liner 22 at the locations where sidebranches are to be established. The latch 21 is for example a spring loaded or otherwise inwardly biased latch which holds the whipstock in place when deployed. A drill bit 23 is, as usual, deflected by the latched whipstock causing it to mill through the liner and into the formation. Located just behind the drill bit, e.g. on the motor, is a latch release mechanism 24 that engages the latch 21 when the drill bit enters the formation, causing the latch to be pulled outwardly, thereby releasing the whipstock. The whipstock is released and can fall under gravity, or be pushed by the drill bit, to the location of the next latch. The latch release might also be achieved by the bit itself removing a latch lock device or the release may be a mechanism that can be “grabbed” (e.g. by pads, friction or "ledge" on backside of bit) ) when pulling out after having drilled the sidebranch. This approach therefore provides for top down sidebranch establishment. In an alternative approach the latch release mechanism allows the latch to be released upon withdrawal of the drill bit from the sidebranch. In a modification to the approach of Figures 3a to 3c, prior to drilling the sidebranches, a mainbore completion string may be run to the total depth of well. The completion string may consist of a predefined number of sidetracking locations that can consist of special tubular that is made from a material that is easy to drill with a drill bit that also allows drilling of the formation. The sidetracking tubular internals can be “slick” or have a “slot” or a “latch” which is used to land, lock and/or orient a deflector device. A drilling BHA is then run into the mainbore completion string, with the whipstock attached to it. At a sidetrack location, which can be a“sidetracking tubular” or anywhere else, depending on use, the whipstock is oriented and then set using the drillstring. A hole is milled in the tubular and a sidebranch is drilled with the same drilling assembly. Upon completing drilling of the sidebranch, the drilling BHA is pulled back and reconnected to the whipstock and the whipstock is released. The string with the reattached whipstock is then relocated to another/next location and the setting, release, milling, drilling and reconnecting steps repeated. This continues until a defined number of branches are drilled.

Potential methods for connection between the drilling assembly and the resettable whipstock can be mechanical solutions such as a “collar” with a smaller inside diameter than a device on the drilling BHA, slots, “j-slots”, threaded (left or right) etc. It may also utilise a hydraulic system that uses string pressure to release, connect etc. or a combination of mechanic and hydraulic operations. Solutions may also use a Measurement While Drilling tool with a "grabbing" device having arms or other means that are activated to grab hold of the whipstock or release it on demand by surface signal.

Multi branch drilling and completion in one run using multiple drill bits

This approach is illustrated by the sequence of Figures 4a to 4h:

Figure 4a. The main bore completion 30 is run prior to drilling the branches. The completion consist of two different joints for each future branch to be drilled, namely (1 ) a drill bit with a mud motor 31 temporarily mounted inside the joint and (2) a permanent whipstock 32 mounted inside the joint that allows the drill string to pass through but not the drill bit. Figure 4b. The drill string 33 is run in hole and connected to the first drill bit I mud motor 31 . A known latching mechanism may be used to connect the parts together. The drill string wall includes axially spaced one-way valves of a known type that prevent the outflow of fluid whilst allowing inflow, under certain conditions.

Figure 4c. A first, uppermost side branch 34 is drilled to the terminal destination (TD).

Figure 4d. The main body of the drill string 33 is detached from a terminal section 35 at a junction, leaving the terminal part 35 and the connected drill bit with mud motor 31 in the first sidebranch.

Figure 4e. The drill string is run through the first whipstock 32 and connected to the second drill bit with a mud motor 31 , and the process is repeated.

Figure 4f. The process continues until all branches are drilled. The drill string 33 is detached from the final drill bit with a mud motor 31 and is pulled to the surface.

Figure 4g. The drill string is opened for tubing flow through inflow valves 36. The drill pipe therefore does not provide any significant restriction of fluid flow from the sidebranch to the main well.

Figure 4h. Alternatively or additionally a packer element (not shown) can be part of each BHA and can be used to facilitate a fluid induced pressure at the TD of each branch to facilitate fracturing of the formation. This can be done prior to disconnection of each branch such that the drill string can be used to supply fluid pressure.

Single trip completion of multiple sidebranches

Following the establishment of a main well with multiple sidebranches, whether carried out using one of the approaches described above or using a conventional approach, completion of the sidebranches may be required. Again, it is desirable to be able to complete all of the sidebranches with a single trip into the well, or with a reduced number of trips. On possible approach to achieve this is illustrated in Figures 5a to 5f. Figure 5a. An expandable liner 40 is run into main bore with sealing capabilities 41 against the formation at branch kick-off for zonal control. Drill pipe 42 is then run into the sidebranches in turn, from bottom to top. A re-locatable whipstock 43 is used to cause deflection for the drill pipe. The whipstock and the movement mechanism may be similar to that described with reference to Figures 3a to 3c. Packers (e.g. a dual packer system) 44 are used to isolate end sections of the branches to allow fractures 45 to be formed there using pressurised fluid pumped through the drill pipe. Excess gravel is washed out.

Figure 5b. Screens are run in all / several branches in one run. The screen 46 is assembled from detachable screen sections 47 and is run in on a drill pipe 48 that passes through the centre of the screen. This allows clean-out ahead of the screen. Again, a movable whipstock mechanism is used to provide deflection for the screen into the sidebranches.

Figure 5c. With the movable whipstock located at the lowermost sidebranch, the end of the screen 46 is run into that sidebranch. The lowermost screen section is then detached from the main screen. This may be achieved using using a release mechanism that is activated when the drill pipe is pulled back through the screen section.

Figure 5d. The drill pipe 42 is then pulled further up the main well. The BHA 48 of the drill pipe is configured to engage the movable whipstock and pull it up the well to the location of the next side branch, where the whipstock is latched to the main liner. NB. A mechanism may be required to allow for rotation of the whipstock so that it can be correctly aligned with the sidebranch.

Figure 5e. The various procedures are repeated until liner sections have been located in all sidebranches.

Figure 5f. An inner completion string 49 is then run in the main bore including inflow control valve/ pressure-temperature gauge and fibre for rate and inflow estimation.

Figure 6 illustrates a further possible mechanism for allowing a BHA to move a whipstock between a plurality of liner locations. This involves a whipstock 50 comprising a hydraulically or mechanically operated anchor 51 allowing the whipstock to be releasable secured at a desired position within the liner 52. The whipstock further comprises a sleeve portion 53 comprising an internal recess or recesses 54 for receiving hydraulically operated dogs 55 provided on the BHA 56. In use, the BHA is secured to the whipstock using the dogs and is lowered into the liner to the desired position. The anchor is then activated to secure the whipstock in place. The dogs are then released allowing the BHA to move down the whipstock, being deflected as it does so and allowing milling of the liner and drilling of the sidebranch into the formation. The BHA is then pulled back and the dogs re-engaged with the recess(es) of the sleeve. The anchor is released and the whole assembly lowered to the next location where the process is repeated.

It will be appreciated that various modifications may be made to the above described embodiments without departing from the scope of the present invention.

Claims

1 . A wellbore tubular for lining a well, used in the production of hydrocarbons, the wellbore tubular comprising: a main body formed by connection of a plurality of tubular sections; a plurality of deflector plates axially spaced along the main body, each deflector plate being attached to the main body by one or more hinges so that the deflector plate is moveable between a non-deployed position in which the deflector plate lies substantially flush with the main liner body and a deployed position in which the deflector plate provides an axially extending ramp within the main body.

2. A wellbore tubular according to claim 1 , wherein said deflector plates have a generally curved transverse cross-section that conforms substantially to the curvature of the tubular sections.

3. A wellbore tubular according to claim 2, wherein the main body defines a plurality of cut-out windows within which respective deflector plates are accommodated.

4. A wellbore tubular according to any one of the preceding claims and comprising a guide member extending axially along each deflector plate, the guide member projecting into the main body when the associated deflector plate is in the deployed position so that it provides a guide for the drill bit.

5. A wellbore tubular according to any one of the preceding claims and comprising, for each deflector plate: a biasing mechanism for biasing the deflector plate towards said deployed position; and a latching mechanism for latching the deflector plate in said non-deployed position against the urging of said biasing mechanism, the latching mechanism being releasable upon engagement by a bottom hole assembly of a drill string.

6. A wellbore tubular according to claim 5, wherein said latching mechanism comprises a substantially tubular sleeve that can be raised upon said engagement to release the deflector plate.

7. A method of establishing multiple sidebranches from a main well using the wellbore tubular of any one of the preceding claims and comprising; a) running the wellbore tubular into the main well; b) running a drill string having a bottomhole assembly (BHA) comprising a drill bit into the wellbore tubular to a location of a lowermost deflector plate; c) placing the deflector plate at that location into the deployed position; d) lowering the BHA into the well causing it to be deflected by the deflector plate whilst operating the drill bit; e) drilling a sidebranch into a formation surrounding the main well; f) raising the BHA to the next deflector plate location and repeating steps c) to e); and g) repeating step f) until all required sidebranches have been established.

8. A wellbore tubular for lining a well, used in the production of hydrocarbons, the wellbore tubular comprising: a main body formed by connection of a plurality of tubular sections; and a plurality of axially inclined ramps spaced axially along the main body, each ramp being configured to allow a drill pipe and an attached bottomhole assembly, BHA, comprising a drill bit, to pass axially when the BHA is in a first rotational orientation or otherwise non-deployed state and to deflect the BHA laterally when the BHA is in a second rotational orientation or otherwise deployed state, thereby allowing milling through the main body and drilling of a sidebranch into a surrounding formation when the BHA is in said second rotational orientation or otherwise deployed state.

9. A wellbore tubular according to claim 8, wherein each ramp comprises a pair of axially inclined ramp sections, the ramp sections being diametrically spaced and defining a central passage through which the drill pipe and BHA can pass when the BHA is in said first rotational orientation.

10. A wellbore tubular according to claim 8 or 9, the main body defining a plurality of cut-out windows adjacent respective ramps, and comprising panels located within respective windows, the panels being of a material that is soft relative to the material of the remainder of the main body.

11. A bottomhole assembly, BHA, for use with the wellbore tubular of any one of claims 8 to 10 and having a generally asymmetric cross-section .

12. A bottomhole assembly according to claim 11 , wherein said cross-section is substantially rectangular.

13. A bottomhole assembly, BHA, for use with the wellbore tubular of claim 8 and comprising one or more components movable radially with respect to a main body of the BHA, whereby radially outward movement puts the BHA in said deployed state and radially outward movement puts the BHA in said non-deployed state.

14. A bottomhole assembly according to claim 13, wherein said one or more movable components is or are hydraulically operable.

15. A method of establishing multiple sidebranches from a main well using the wellbore tubular of any one of claims 8 to 10 and the bottomhole assembly, BHA, of any one of claims 11 to 14 and comprising; a) running the wellbore tubular into the main well; b) running a drill string having said bottomhole assembly (BHA) to a location above a first of said ramps; c) placing said BHA into said second rotational orientation or otherwise deployed state; d) lowering the BHA into the well causing it to be laterally deflected by said first ramp; e) operating the BHA to drill into a formation surrounding the main well; f) raising the BHA and placing it in said first rotational orientation or otherwise non-deployed state; g) raising or lowering the BHA through said first ramp to a location above a second ramp; and h) repeating step c) to g) one or more times until the required sidebranches have been established.

16. A wellbore tubular for lining a well, used in the production of hydrocarbons, the wellbore tubular comprising: a main body formed by connection of a plurality of tubular sections; and a plurality of whipstock latches spaced axially along the main body, each whipstock latch being configured to releasably latch a moveable whipstock within the main body and each latch being configured to release a latched whipstock upon contact with a bottomhole assembly, BHA, being withdrawn from a sidebranch established using the whipstock or entering into a formation when establishing the sidebranch.

17. A system comprising the wellbore tubular of claim 16 and a moveable whipstock, the moveable whipstock configured to be held in place axially by each of the latch mechanisms until release by a BHA.

18. A method of establishing multiple sidebranches from a main well using the system of claim 17 and comprising; a) running the wellbore tubular into the main well; b) running a drill string having said bottomhole assembly (BHA) to a location of a first of said whipstock latches; c) latching the moveable whipstock to said first whipstock latch; d) lowering the BHA into the well causing it to be laterally deflected by said first whipstock; e) operating the BHA to drill into a formation surrounding the main well to establish a sidebranch; f) releasing the moveable whipstock using the BHA either before or after step (e); g) moving the moveable whipstock to a location of a second whipstock latch and repeating step c) to f) one or more times until the required sidebranches have been established.

19. A method of establishing multiple sidebranches from a main well and comprising: a) running a wellbore tubular into the main well, the wellbore tubular containing a plurality of axially spaced borehole assemblies (BHAs) each comprising a drill bit, and the BHAs being located above respective whipstocks provided within the wellbore tubular; b) running a drill pipe to a location of an uppermost one of said BHAs and coupling the drill pipe to that BHA; c) lowering the BHA and using the drill pipe to operate the drill bit of the coupled BHA, whereby the BHA is deflected by the associated whipstock and a sidebranch established in the surrounding formation; d) detaching a terminal section of the drill pipe and the coupled BHA from the remainder of the drill pipe and raising the remainder of the drill pipe to leave the terminal section and the coupled BHA in the sidebranch; e) running the drill pipe through the whipstock associated with the now detached BHA to a next BHA in the wellbore tubular, coupling the drill pipe to that next BHA and repeating steps c) and d) to establish a further sidebranch; and f) repeating step e) until the required sidebranches have been established.

20. A method of completing a well comprising a main wellbore and a plurality of sidebranches and comprising running a completion string into the main well and a first sidebranch, detaching a terminal part of the completion string and leaving it in the first sidebranch, running the remainder of the completion string into a second sidebranch and detaching a further terminal part of the completion string and leaving it in the second sidebranch, and repeating the procedure until all sidebranches are completed.

21 . A method of completing a well used in the production of hydrocarbons, the well comprising a main well and a plurality of sidebranches extending laterally from the main well, the method comprising: a) running a length of screen into the well on a drill pipe, the drill pipe having a moveable whipstock attached to its terminal end and the screen comprising a plurality of connected screen sections; b) using the drill pipe to locate and secure the whipstock at a location of a lowermost one of the sidebranches, and detaching the drill pipe from the whipstock to leave the whipstock secured within the main well; c) lowering the drill pipe and a lowermost screen section into the sidebranch adjacent to the whipstock; d) detaching said lowermost screen section from the remainder of the screen and raising the drill pipe and said remainder of the screen to leave said lowermost screen section in the adjacent sidebranch; e) reconnecting the whipstock to the terminal end of the drill pipe and raising the drill pipe, the remainder of the screen, and the whipstock until the whipstock is adjacent to a next sidebranch; f) again detaching the drill pipe from the whipstock to leave the whipstock secured within the main well; g) repeating steps c) and d) to leave a next lowermost screen section in said next sidebranch; and g) repeating step e) to g) until all required sidebranches are provided with a screen section.