Deviated borehole drilling assembly

An assembly for formation and completion of deviated wellbores is disclosed which includes a toolguide and a casing section which can be used together or separately. The toolguide includes a lower orienting section and a whipstock having a sloping face, commonly known as the directional portion of a whipstock. The toolguide is coated with a material such as epoxy or polyurethane to provide a repairable surface and one which can be removed to facilitate removal of the toolguide from the well bore. The lower orienting section has a latch which extends radially outwardly from the section and can be locked in the outwardly biased position. The casing section of the present invention includes a sleeve which can be moved between a first position in which access to the window opening of casing section is not affected and a second position in which the main casing is sealed from the liner section of a deviated wellbore to provide a hydraulic seal against passage of fluids from outside the casing of the wellbore into the main casing.

 

The embodiments of the invention in which an exclusive property privilege is claimed are defined as follows:

1. A system for securing a tieback hanger to a casing section, comprising:

a casing section including a window opening formed therethrough;

the window opening defining a first profiled area and a second profiled area;

a tieback hanger having a first end and a second end;

the first end including a first setting tab and a second setting tab; and

the first setting tab adapted to releasably engage the first profiled area and the second setting tab adapted to releasably engage the second profiled area;

wherein the tieback hanger extends through the casing window and engages to the casing section when the first setting tab is engaged to the first profiled area and the second setting tab is engaged to the second profiled area.

2. The system of claim 1, wherein:

the window opening includes a bottom and a top;

the first profiled area is formed adjacent the bottom of the window opening; and

the second profiled area is formed adjacent the top of the window opening.

3. The system of claim 1, wherein:

the window opening includes an edge; and

the first and second profiled areas are formed to taper gradually toward their respective edges thereby forming a beveled edge.

4. The system of claim 1, wherein the first and second setting tabs are formed to flare outwardly from the casing section.

5. The system of claim 1, wherein:

the first setting tab forms a tapering dovetail configuration;

the first profiled area forms a tapering dovetail mortise; and

the dovetail configuration enables the wedging engagement of the first setting tab and the first profiled area.

6. The system of claim 1, wherein:

the second setting tab forms a dovetail configuration;

the second profiled area forms a dovetail mortise; and

the dovetail configuration enables the wedging engagement of the second setting tab and the second profiled area.

7. The system of claim 1, wherein the second setting tab snaps into engagement with the second profiled area.

8. The system of claim 7, wherein the second profiled area includes a recess that receives an extension of the second setting tab once the second setting tab is snapped therein.

9. The system of claim 8, wherein the extension includes trailing edges that are chamfered to facilitate unsnapping of the second setting tab from the second profiled area.

10. The system of claim 1, wherein the width of the second setting tab is slightly greater than the width of the second profiled area.

11. The system of claim 1, wherein:

the tieback hanger further includes a plurality of flanges; and

the plurality of flanges are adapted to abut against the casing section when the first setting tab is engaged to the first profiled area.

12. The system of claim 1, wherein the engagement of the first setting tab and first profiled area and the engagement of the second setting tab and second profiled area are adapted to prevent the inward and outward movement of the tieback hanger in relation to the casing section.

13. A method of securing a tieback hanger to a casing section, comprising:

locating the casing section in the appropriate location in the wellbore;

sliding the tieback hanger at least partially through a window opening defined in the casing section;

engaging a first setting tab of the tieback hanger to a first profiled area of the window opening; and

engaging a second setting tab of the tieback hanger to a second profiled area of the window opening.

14. The method of claim 13, wherein the first setting tab engagement step comprises wedging the first setting tab with the first profiled area.

15. The method of claim 13, wherein the second setting tab engagement step comprises wedging the second setting tab with the second profiled area.

16. The method of claim 13, wherein the second setting tab engagement step comprises snapping the second setting tab into engagement with the second profiled area.

17. The method of claim 16, wherein the snapping step comprises snapping an extension of the second setting tab into a recess defined on the second profiled area.

18. The method of claim 17, wherein the second setting tab is disengaged from the second profiled area by unsnapping the extension from the recess.

19. The method of claim 13, further comprising after the engagement steps, disengaging the second setting tab from the second profiled area.

20. The method of claim 13, further comprising locating a plurality of flanges of the tieback hanger against the casing section when the first setting tab is engaged to the first profiled area.

21. The method of claim 13, wherein the engagement steps comprise preventing the inward and outward movement of the tieback hanger in relation to the casing section.

22. A system for tieing back a liner from a wellbore casing, comprising:

a wellbore casing including a window opening formed therethrough;

the window opening defined by edges extending between the outer surface of the casing and the inner surface of the casing;

the edges including beveled portions formed such that an acute angle is formed at the intersection of the edges and the outer surface of the casing;

a tieback hanger having an outboard end onto which a liner is attachable and an anchored end for attachment to the casing when the outboard end has been inserted through the window opening of the casing; and

the outboard end having thereon a flared tab for engaging against the beveled portions of the window opening edges.

23. The system of claim 22, wherein the beveled portions of the window opening are positioned on opposite sides of the window opening such that a dovetail mortise is formed therebetween and the flared tab is dovetailed to wedge into the dovetail mortise formed between the beveled portions.

24. The system of claim 22, wherein the edges of the window opening and the anchored end of the tieback hanger can be formed to snappingly engage with each other to prevent the tieback hanger from both passing outwardly through the window opening and moving back into the casing, once the parts are engaged together.

25. The system of claim 22, wherein the flared tabs are sized such that when they are engaged against the beveled portions, they substantially do not extend inwardly past the inner surface of the casing.

26. A system for securing a tieback hanger to a casing section, comprising:

a casing string including a casing section, the casing section including a window opening formed therethrough and having an interior surface;

at least one profiled area formed in the interior surface of the casing section;

a tieback hanger having at least one projection; and

the at least one projection adapted to releasably engage the at least one profiled area;

wherein the tieback hanger extends through the casing window and engages to the casing section when the at least one projection is engaged to the at least one profiled area.

27. The system of claim 26, wherein the at least one profiled area is formed to taper gradually toward its respective edges thereby forming a beveled edge.

28. The system of claim 26, wherein the at least one projection is formed to flare outwardly from the casing section.

29. The system of claim 26, wherein:

the at least one projection forms a tapering dovetail configuration;

the at least one profiled area forms a tapering dovetail mortise; and

the dovetail configuration enables the wedging engagement of the at least one projection and the at least one profiled area.

30. The system of claim 26, wherein the at least one projection comprises at least one tab.

31. The system of claim 26, wherein the at least one profile forms a recessed region in the interior surface.

32. The system of claim 31, wherein the at least one profile is adapted to cause the at least one projection to be substantially flush with the region of the interior surface outside of the recessed region when the at least one projection is engaged to the at least one profiled area.

FIELD OF THE INVENTION

The present invention is directed to a borehole drilling assembly and in particular to an assembly for drilling and completing deviated boreholes.

BACKGROUND OF THE INVENTION

Deviated boreholes are drilled using whipstock assemblies. A whipstock is a device which can be secured in the casing of a well and which has a tapered, sloping upper surface that acts to guide well bore tools along the tapered surface and in a selected direction away from the straight course of the well bore.

To facilitate the use of a whipstock, a section of casing is used which has premilled window openings through which deviated well bores can be drilled. The whipstock can be positioned relative to the window using a landing system which comprises a plurality of stacked spacers mounted on a fixed mounting device at the bottom of the casing and defining at the top thereof a whipstock retaining receptacle, or by use of a latch between the whipstock and the casing. A stacked landing system can cause difficulty in aligning the whipstock with the window opening as the distance between the mounting device and the window increases. The whipstock may also turn during the drilling or setting processes resulting in the deviated well bore being directed incorrectly and/or the well bore tools being stuck in the wellbore. Sometimes a latch system is used to overcome some of these disadvantages. However, the latch can sometimes disengage between the whipstock and the casing, allowing the whipstock to turn or move down in the casing. after the deviated wellbore is drilled, it can be left uncompleted or completed in any suitable way. To seal the deviated wellbore hydraulically from the main casing, a liner can be installed and cement can be pumped behind the liner. This is expensive and often creates obstructions in the main casing which complicates removal and run of the tools.

When the tools are used in horizontal primary bores, new problems arise. Running and retrieval tools which are useful for vertical tool manipulation are not always useful in horizontal applications.

SUMMARY OF THE INVENTION

An assembly for drilling and/or completing a deviated wellbore has been invented. In one aspect the assembly includes a toolguide which can be positioned relative to a window opening in a casing section and releasably locked in position. The toolguide or portions thereof can have applied thereto a coating which prevents damage to the metal components of the toolguide and facilitates removal of the toolguide from the wellbore after use.

A tool guide for creating deviated borehole branches from a wellbore includes a whipstock including a sloping face portion and a lower orienting section, including at least one latch biased radially outwardly from the orienting section and positioned in a known orientation relative to the sloping face portion and a latch locking means to releasably lock the latch in an extended position, the latch locking means being actuated to lock the latch by torsion of the mandrel within the lower orienting section.

Each latch of the orienting section is selected to fit within and lock into its own latch receiving slot formed in the casing. When the latch of the orienting section is locked into the latch receiving slot the toolguide will be maintained in position in the casing. Preferably, the casing includes at least one premilled window opening positioned in known relation relative to the latch receiving slot. Preferably, a removable liner can be positioned in the casing to close the window opening temporarily and to cover the latch receiving slot.

The orienting section can be releasably connected to the whipstock. Such connection is preferably by connectors such as, for example, shear pins to the whipstock so that these parts can be installed together into the casing. Preferably, the connectors are selected such that the sections can be separated by an application of force sufficient to overcome the strength of the connectors. This permits the whipstock and the lower section to be separated and removed separately should one part become stuck in the casing.

The sections are movable relative to one another and means are provided to translate such movement to actuate such means as a seal.

Preferably, the lower orienting section includes a mandrel engaged slidably and rotatably within an outer housing. The mandrel is releasably connected to the whipstock and moveable with the whipstock. Preferably, the latch locking means is an extension of the mandrel. The extension can be formed to fit behind the latch to lock it in the outwardly biased position.

Another toolguide for creating borehole branches from a wellbore, the toolguide having a longitudinal axis and comprising a whipstock including a sloping face portion, a lower orienting section, the whipstock and the lower orienting section being connected and moveable relative to each other along the longitudinal axis of the toolguide, and an annular sealing means mounted below the whipstock, the annular sealing means being actuatable to expand and retract upon movement of the whipstock and the lower orienting section relative to one another.

The whipstock is attached to a central mandrel of the lower orienting section. The central mandrel is engaged slidably and rotatably within an outer housing of the lower orienting section. The outer housing carries the annular sealing means which is actuatable to expand or retract by movement of the mandrel within the outer housing. Preferably, the outer housing includes a first section and a second section and disposed therebetween the annular sealing means. The first section is moveable toward the second section to compress the annular sealing means therebetween and cause it to expand outwardly. In this embodiment, preferably the mandrel has a shoulder positioned thereon to abut against the first section and limit the movement of the mandrel into the outer housing. Abutment of the shoulder against the first section causes the first section of the housing to be driven it towards the second section and the annular sealing means to be compressed and expanded outwardly.

Previous orienting tools were difficult to use because it was necessary to run the tool to a known depth and then search around for the position of the slot for accepting the latch on the tool. Because the latches of some orienting tools have to be biased outwardly on the trip down into the well, it has been difficult to use the orienting tools in wells, for example, having more than one lateral window and therefore more than one orienting slot for accepting the latch of the tool. To the problem of having the latch lock into the incorrect slot, where multiple slots are present, it has been necessary to shape the slots in the casing such that they will only accept one form of latch. This solution presents logistical problems, however, and limits the number of slots which can reasonably be positioned in the casing.

Thus, in accordance with one broad aspect of the present invention, there is provided an orienting tool for positioning in a well bore casing having a profile positioned therealong, the tool comprising: a body; at least one member mounted on the tool body and biased outwardly, at a selected pressure, therefrom, the selected pressure being great enough to permit determination of when the at least one member has moved past the profile but not being so great as to prevent the at least one member from moving past the profile using normal force.

The at least one member can be a spring loaded dog or an arm such as, for example, a part of a collet, a collar locator or any other means. In preferred embodiment, the at least one member is part of a ring of dogs mounted about a circumference of the tool body and biased outwardly therefrom. The at least one member preferably operates to position the tool at a selected pressure of 20,000 to 30,000 psi. At this pressure, when the member passes a profile, there will be a indicative overpull or decrease in drill string weight.

The at least one member can be biased outwardly by any desired means such as, for example, springs. In a preferred embodiment, the biasing means is selected to exert increased pressure as the depth of the tool is increased. This biasing means is preferred as it provides that less force is required to move the tool through the casing at shallower depths but requires greater force to be moved through the casing when it is at greater depths and, therefore, when there is greater available drill string weight to act on the tool. One such biasing means is sensitive to hydrostatic pressure and applies a pressure to the at least one member which increases with an increase in hydrostatic pressure of the fluids about the tool. It may be necessary to set an upper limit for the selected pressure applied to the at least one member.

The profile and the at least one member are preferably correspondingly positioned so that the at least one member will be affected by the profile regardless of the rotational orientation of the tool within the casing. To avoid forming a protrusion which extends inwardly from the casing inner surface and reduces the ID of the casing, preferably the profile is a groove sized to accept the at least one member therein. In a preferred embodiment, the groove is a radial groove extending about the ID of the casing.

There can be more than one profile along a length of casing. Where more than one profile is present along the casing, the at least one member will be affected by each profile in a similar manner. Preferably, the profiles are non-selective. The specific profile which is affecting the member can be determined using tool depth information, the measurement of which is well known in the art.

Where it is desired, in addition to positioning the tool at a selected orientation along the casing, to position the tool at a selected rotational orientation within the well, the tool can further comprise a latch for fitting into a slot positioned at a selected rotational position about the center axis of the casing. The tool is selected to provide for rotation of at least the portion of the tool carrying the latch to permit the latch to be located in its slot. In one embodiment, the tool body includes a first part carrying the at least one member, a second part carrying the latch and a joint positioned therebetween for permitting the second part to rotate relative to the first part and preferably also to move out of axial alignment with the first part.

The orienting sections according to the present invention can be used to orient whipstocks as well as other tools such as, for example, retrieval tools, sleeve shifting tools and lateral completion tools.

A whipstock for use in creating wellbore branches from a well bore can have a main body formed of a first material of reduced diameter to facilitate washover or engagement by die collars or overshots. The main body has extending out therefrom centralizers such as stand off rings or extensions the main body. Sometimes a coating material is disposed at least over a portion of the main body, the coating material being softer than the first material and being resistant to oil and gas.

In a whipstock having a main body of reduced diameter relative to centralizers formed thereon, it has been found that the width of the sloping face portion is greatly reduced. This reduces the surface area which is available to guide the drill bit or mill off the whipstock face and the mill or drill bit tends to roll off the sloping face portion in the direction of rotation of the drill.

To prevent roll off and to centralize and stabilize the upper tapered end of the whipstock, while continuing to facilitate washover procedures, a whipstock is provided including a main body having an outer surface, a sloping face portion formed on the main body and having a slope angle and an extension formed on the main body about the sloping face such that the diameter of the extension is greater than the diameter of the main body.

Preferably, the extension about the sloping face portion forms an effective diameter which is substantially equal to the drift diameter of the casing into which it is to be used. The extension preferably conforms to the slope angle of the sloping face portion and, where the sloping face portion has a curvature, follows and continues the curvature of the sloping face portion.

The whipstock can include centralizers extending out from the main body. Preferably, the effective diameter of the whipstock at the centralizers is substantially equal to the effective diameter of the whipstock at the extensions.

In one embodiment, the main body has applied thereto a coating, for example of polymeric material. The coating material can be applied against the extension and the centralizers, if any.

Running and retrieving tools are required for moving the tools through the well bore. Previous running tools for whipstocks used shear bolts for attachment between the running tool and the whipstock. These shear bolts are prone to shearing prematurely if the whipstock is bumped at surface while entering the will or sue to running the assembly through a tight area in the casing. The shear bolt may also shear prematurely if the assembly is rotated.

A new tool has been invented which is positively latchable to the whipstock in a manner that allows forces to be applied upwardly or downwardly as well as rotationally without risk of prematurely releasing the whipstock. At the desired time of release, hydraulic pressure is applied to the tool to unlatch it from the whipstock.

In accordance with a broad aspect of the invention, therefore, there is provided a running/retrieval tool for moving a well tool through a well bore casing, the running/retrieval tool comprising: a body; a latch for releasably engaging the well tool and being driven to move between a retracted position recessed in the body and an extended position in which a portion of the latch extends from the body; and a guide selected to act against the well tool to guide the latch into engagement with the well tool.

The latch can be driven between the retracted position and the extended position by any desired means. Preferably, the drive means for the latch can be controlled from surface and can be, for example, a hydraulic system.

The guide is formed on the tool and can be selected to engage with the well tool in such a way as to transmit rotational energy to the well tool. A key can be provided on the tool to assist in the location of the tool relative to a well tool to be retrieved. In a preferred embodiment, an outwardly biased key is provided which is engage able into an orienting slot formed on the casing section adjacent the mounting position of the well tool to be used with the running retrieval tool.

In another embodiment, the running/retrieval tool according to the present invention includes a outwardly extendable and retractable key useful for applying force against the casing in which the tool is positioned to urge it toward one side of the casing. The key can be extendable by a hydraulic system.

A casing section for a deviated wellbore junction comprises a cylindrical casing tube having a central axis and a window opening formed therein. A sleeve having an opening therein is mounted relative to the casing tube to move between a first position in which the opening of the sleeve is aligned with the window opening of the casing tube and a second position in which the opening of the sleeve is not aligned with the window opening of the casing tube.

Another casing section for a deviated wellbore junction includes a casing tube having a central axis and a window opening formed therein. A sleeve having a first opening and a second opening therein is mounted relative to the casing tube to move between a first position in which the first opening of the sleeve is aligned with the window opening of the casing tube and a second position in which the second opening of the sleeve is aligned with the window opening of the casing tube.

Preferably, sealing means are disposed between the casing tube and the sleeve. These sealing means are preferably selected to effect a hydraulic seal between the parts. In one embodiment, the sealing means are formed of deformable materials such as rubber or plastic and is disposed around the opening of the sleeve and along the top and bottom thereof.

In a preferred embodiment, the sleeve has formed therethrough two openings. The first opening is sized to allow access to the window opening of the casing section by deviated borehole tools and the second opening is smaller than the first opening.

In one embodiment, the sleeve is disposed within the casing tube in a counterbore formed therein such that the inner diameter of the sleeve is greater than or substantially equal to the inner diameter of the casing away from the position of the sleeve.

Preferably, the window of the casing is formed to accept a flange of a junction fitting such as, for example, a tieback hanger of a branched wellbore. In a preferred embodiment, the sleeve is selected to seal against the flange of the fitting.

BRIEF DESCRIPTION OF THE DRAWINGS

A further, detailed, description of the invention, briefly described above, will follow by reference to the following drawings of specific embodiments of the invention. These drawings depict only typical embodiments of the invention and are therefore not to be considered limiting of its scope. In the drawings:

FIG. 1 is a schematic representation of an embodiment of an assembly according to the present invention, the assembly being positioned in a wellbore;

FIG. 2 is a view showing the orientation of FIGS. 2a and 2b.

FIGS. 2a and 2b are a longitudinal section along a casing section for a deviated wellbore junction useful in the present invention;

FIG. 3A is a view showing the orientation of FIGS. 3A-a and 3A-b;

FIGS. 3A-a and 3A-b are a front elevation view, partly cutaway, of a whipstock of a toolguide according to the present invention;

FIG. 3B is a view showing the orientation of FIGS. 3B-a and 3B-b;

FIGS. 3B-a and 3B-b are a section along line 3B--3B of FIG. 3A;

FIG. 4A is a view showing the orientation of FIGS. 4A-a and 4A-b;

FIGS. 4A-a and 4A-b are a front elevation view, partly cutaway, of a whipstock of another toolguide;

FIG. 4B is a view showing the orientation of FIGS. 4B-a and 4B-b;

FIGS. 4B-a and 4B-b are a section along line 4B--4B of FIG. 4A;

FIGS. 4C and 4D are sectional views along line 4C--4C and 4D--4D, respectively, of FIG. 4B;

FIG. 4E is a bottom end view of FIG. 4A;

FIG. 4F is a top end view of FIG. 4A;

FIG. 5A is a front elevation view of a lower section of a toolguide according to the present invention, partly in section and in un-compressed configuration;

FIG. 5B is a front elevation view of the toolguide of FIG. 5A in compressed configuration;

FIG. 5C is a section along line 5C--5C of FIG. 5A;

FIG. 6A is a view showing the orientation of FIGS. 6Aa and 6Ab;

FIGS. 6Aa and 6Ab are longitudinal sections along another lower section of a toolguide in a set configuration;

FIG. 6B is a view showing the orientation of FIGS. 6Ba and 6Bb;

FIGS. 6Ba and 6Bb are longitudinal sections along another lower section of a toolguide;

FIG. 7 is a view showing the orientation of FIGS. 7A to 7C;

FIGS. 7A to 7C are longitudinal sections along a casing section for a deviated wellbore junction;

FIG. 8 is a view showing the orientation of FIGS. 8a and 8b;

FIGS. 8a and 8b are longitudinal sectional views along a running/retrieving tool;

FIG. 9 is a longitudinal section along another casing section for a deviated wellbore junction according to the present invention;

FIG. 10 is a rear plan view of a sleeve according to the present invention in flattened configuration;

FIG. 11A is a sectional view through a deviated wellbore junction using a casing section according to the present invention;

FIG. 11B is a front elevation view of a tieback hanger;

FIG. 11C is a front elevation view of a tieback hanger;

FIG. 12 is a front elevation view of another sleeve according to the present invention in flattened configuration;

FIG. 13 is a view showing the orientation of FIGS. 13a and 13b;

FIGS. 13a and 13b are elevation views of a casing section including a window opening;

FIG. 14 is a longitudinal sectional view along a liner positioning tool;

FIG. 15 is schematic representation of a system for imparting rotational force on a drill pipe;

FIG. 16A is a longitudinal sectional view along a sleeve shifting tool according to the present invention;

FIG. 16B is front elevation view of a portion of the sleeve shifting tool of FIG. 16A showing the sleeve engaging slips;

FIG. 17 is an elevation view of a casing section including a window opening according to the present invention;

FIG. 17A is a sectional view along line A--A of FIG. 17;

FIG. 17B is a sectional view along line B--B of FIG. 17;

FIG. 17C is an enlarged view of an edge of the window opening, as noted in FIG. 17A;

FIG. 18 is a front elevation view of a tieback hanger in accordance with another aspect of the present invention;

FIG. 18A is a sectional view along line A--A of FIG. 18 showing the lower setting tab;

FIG. 18B is a sectional view along line B--B of FIG. 18 showing the mid setting flanges;

FIG. 18C is a sectional view along line C--C of FIG. 18 showing the upper setting tab;

FIG. 19A is a sectional view through a casing section according to FIG. 17 having a tieback hanger according to FIG. 18 therein with the upper setting tab in unengaged position; and

FIG. 19B is a sectional view as in FIG. 19A with the upper setting tab in engaged position in the window of the casing section.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

For the purposes of clarity, in the Figures only reference numerals of the main components are indicated and like reference numerals relate to like components.

Referring to FIG. 1, there is a shown a tubular wellbore casing 2 for installation in a primary wellbore 4 drilled through a formation. Primary wellbore 4 can be a main wellbore directly opening to surface or a lateral wellbore drilled from a main wellbore. Primary wellbore can range between a vertical and a horizontal orientation. Casing 2 includes upper and lower sections of production casing 6 and secured therebetween a casing section 8 for use in deviated wellbore junctions. The deviated wellbores branch from wellbore 4.

Casing sections 6 and 8 are connected by standard connectors 9 or any other suitable means. A float collar 10 is provided at the lower end of casing 2 which allows fluids to flow out of the casing but prevents flow of fluid and debris back into wellbore casing 2. Any similar one way valve can be used in the place of float collar 10. By a completion procedure, cement 11 is disposed in the casing annulus.

Casing section 8 includes a window in the form of an elongated opening 12 extending in the longitudinal direction of casing 8. In use, opening 12 is oriented toward the desired direction of a deviated wellbore to be drilled, shown in phantom at 14. The window is sized and shaped with reference to the desired diameter and azimuth of the deviated wellbore to be drilled and the diameter of the casing, as is known in the art.

Casing section 8 further has formed therein a latch receiving slot 16a at a selected orientation relative to window opening 12. The latch receiving slot can be oriented at any point around the interior circumference of the casing section, so long as its position is known with respect to the window opening. Preferably, latch receiving slot 16a is aligned with the longitudinal axis of window 12, as shown, or is directly opposite window opening 12.

A toolguide 18 is installed in casing 2 with its latch 20 extending into slot 16a. Toolguide 18 includes a lower orienting section 22, also called a monopositioning tool, from which latch 20 is biased radially outwardly, and a whipstock 24 having a sloping face portion 26. Sections 22 and 24 are connected so that they are not free to rotate relative to each other, whereby face portion 26 is maintained in a fixed and known orientation relative to latch 20. In a preferred embodiment, as shown, latch 20 is aligned at the bottom of sloping face portion 26, so that the surface of the sloping face portion will be aligned opposite window opening 12, when latch 20 is in slot 16a.

An annular expandable seal 28 is disposed on toolguide 18 below sloping face portion 26. The seal 28 when expanded, acts to prevent debris and fluids from passing down the wellbore. Seal 28 is, therefore, selected to have an outer diameter, when expanded, which is greater than the inner diameter of the casing in which it is to be used.

Toolguide 18 is placed in casing 2 by use of a running tool 30 which releasably locks onto whipstock 24 and is shown in this drawing still attached to the whipstock. Running tool 30 is connected to a drill pipe 32.

To remove the toolguide from the wellbore, a retrieving tool can be used. FIGS. 8, show a tool that is useful for both running and retrieving operations.

To prepare for the drilling of a deviated borehole, such as that shown at 14, the wellbore casing 2 is installed and completed. FIGS. 2 shows apparatus useful for permitting completion of the well while preserving features used in the invention. Casing section 8 is milled to include a window opening 12 and a latch receiving slot 16a. Preferably, a slot 17 (FIGS. 2) for alignment of retrieval tools is also milled out in casing section 8. Preferably, window opening 12 and latch receiving slot 16a are aligned along the casing.

A liner 34 is positioned in casing 8 and seals 36a and 36b are provided between liner 34 and casing 8. A float collar 38 and an orienting subassembly 39 are attached above liner 34. Float collar 38 and orienting subassembly 39 can be positioned, as shown, or can be positioned further up the casing provided orienting subassembly is in a known configuration relative to window opining 12. Preferably, a removable filler 41 which is selected to withstand high downhole hydrostatic pressures, such as high density polyurethane or cement, is inserted between casing 8 and liner 34 between seals 36b to fill window opening 12 and the casing section 8 is wrapped in a rigid material 40, such as fibre glass or composite tape, to cover at least opening 12.

Preferably, slots 16a and 17 are filled with liquid or easily removable filling materials such as grease and/or foam to prevent materials from entering into the slots and the remainder of spaces 43, defined between casing 8, liner 34 and seals 36a, 36b, are filled with cement. To further prevent entry of materials into slots 16a, 17, caps 44 are welded onto the outer surface of casing 8 over the slots.

Casing 8, including the parts as noted hereinbefore, is connected to casing sections 6 to form casing string 2 and float collar 10 is attached. Casing string 2 is lowered into wellbore 4. The casing string is rotated until window opening 12 is oriented in the direction in which it is desired that the deviated wellbore 14 should extend. Suitable methods are well known in the oil and gas industry for orienting downhole tools. As an example, a surface reading gyro, a mule shoe or other suitable means can be used.

The cased wellbore is completed by forcing cement through the casing string and into the annulus between the casing and the wellbore. During completion, the cement is forced through float collar 38 and liner 34 but is prevented from moving behind liner 34 by seals 36a and the cement and fillers in spaces 43. As the cement fills the casing annulus, it is prevented from entering slot 16a by cap 44 and is prevented from entering window opening 12 by the filler 41 and rigid materials 40. The cement is allowed time to set.

After completion, a drill (not shown) of a diameter selected to be approximately equal to the inner diameter of the casing is run into the well to remove cement from the casing bore. The drill will also drill out liner 34, seals 36a, 36b, float collar 38 and cement in spaces 43. Thus, liner 34 is formed of a material such as, for example, aluminum, fibre glass, or carbon fibre-containing composite, which can be removed by drilling or by any other method without having to retrieve to surface. Where aluminum is used in the wellbore, preferably any aluminum surfaces which are exposed and will be contacted by the cement used in the completion operation, are coated with a suitable material, such as rubber cement, to improve the bond of the cement to the aluminum.

The casing is then ready for production or for drilling deviated wellbores. Where deviated wellbores are to be drilled a toolguide 18 will be run in and oriented in the casing as shown in FIG. 1.

In FIGS. 3A and 3B and FIGS. 4A to 4F, two embodiments of a whipstock are shown. Referring to FIGS. 3A and 3B, a whipstock 24 tapers toward its upper end to form a sloping, ramped face portion 26 which is formed to direct any tool pushed along it laterally outwardly at a selected angle. The face portion is machined to have a selected slope x or range of slopes with respect to long axis 52 of the section depending on the build radius desired for the deviated wellbore. As an example, when x is 4/, the build radius will be approximately 15.degree./30 meters drilled. Preferably, sloping face portion 26 is formed to be concave along its width.

An entry guide 49 is welded at the top of face portion 26. Entry guide 49 assists in centralization and tool retrieval and need only be used, as desired. A bore 50 extends a selected distance through the whipstock parallel to its central axis 52. Bore 50 is formed to engage a fishing spear device and provides one means of retrieving the toolguide from the wellbore. Extending back from face portion are slots 53 formed to accept and retain a retrieval tool having corresponding sized and spaced hooks thereon. Also formed on face portion 26 are apertures 54 formed to accept shear pins (not shown) for attachment to running tool 30 (FIG. 1).

Centralizers 56 are spaced about the whipstock. While only one centralizer is illustrated in the drawing, there are preferably at least three centralizers on the upper portion to center the whipstock in the hole. The centralizers can take other forms, as desired.

A socket 58 extends from the bottom of whipstock 24 parallel with central axis 52. Socket 58 is shaped to accept a male portion 68 on the lower orienting section 22, as will be discussed hereinafter with reference to FIGS. 5A and 5B. Preferably, socket 58 is faceted at 60 and male portion 68 is similarly faceted so that the parts lock together and male portion 68 cannot rotate within socket 58. Shear pins 61 are inserted through apertures 62 to secure male portion 68 in socket 58 and thereby, the whipstock to the lower section.

The whipstock is formed of hardened steel and has applied thereto a polymeric coating 64 (shown only in FIGS. 3B). Polymeric coating 64 is, preferably, formed of cured polyurethane but can be formed of other polymers such as epoxy. Coating 64 acts to prevent damage of the metal components of the whipstock and can be reapplied if it is removed during use. Coating 64 further facilitates wash over operations, should they become necessary, to remove the toolguide or whipstock from the casing. The coating is thick enough so that it will accommodate normal damage from, for example, abrasion and will prevent damage to the metal surfaces of the whipstock and is preferably also thick enough so that substantially only the coating will be removed by any washover operation. In a preferred embodiment, the coating is about 1/2 inch thick and is applied using a mold, so that the shape of the tool after coating is controllable. If damage occurs to the coating, it can be replaced.

The maximum outer diameter of the whipstock to the outer surface of the coating is selected to be smaller than the inner diameter of the casing in which it is to be used. In particular, the maximum effective outer diameter of the whipstock is selected to be as large as possible without exceeding the drift diameter (i.e. the maximum diameter permitted according to regulations for any tool for use in a casing of a particular id) for the casing.

Because coating 64 is easily abraded and, to a limited degree, deformable, the coating can interfere with tool centralization. Thus, to permit correct centralization of the whipstock within the casing, preferably centralizers 56 extend out from the metal portion of the whipstock a distance at least equal with the thickness of coating 64. In this way, centralizers 56 are either flush with the surface of the coating or extend out therefrom.

Referring to FIGS. 4A to 4F, another whipstock 24' is shown. Whipstock 24' includes a sloping face portion 26'. Generally, whipstocks are useful for producing deviated wellbores having only a selected one of a long, medium or short radius deviated wellbore. However, the profile of sloping face portion 26' of whipstock 24' is formed to allow flexibility to produce both medium and short radius laterals.

Whipstock 24' is selected to be useful with a running/retrieval tool as is described in more detail in FIGS. 8. In particular, whipstock 24' has formed at its upper end a dove-tail slot 51 and a second slot 55. These slots will be described in more detail with respect to FIGS. 8.

Centralizers 56' are formed integral with the metal portion of the whipstock. While six centralizers are shown, it is to be understood that only three centralizers are required for proper functioning.

Whipstock 24' includes a socket 58' which is generally similar to socket 58 described with reference to FIGS. 3B. Socket 58' includes a faceted portion 68. Apertures 62 extend through centralizers 56' and open into socket 58' for accepting shear pins (61' in FIGS. 6A) for securing the whipstock to the lower section.

A coating 64' of polymeric material is applied over selected portions of whipstock 24'. As noted with respect to FIGS. 3B, preferably coating 64' is applied to be flush with the outer, contact surface of centralizers 56'. The effective diameter of the whipstock to the outer surface of the coating is substantially the same as the effective diameter of the whipstock at the centralizers, which is selected to be equal to or just less than the drift diameter of the casing in which whipstock is to be used.

In using whipstocks that are of a reduced diameter and have applied thereover or attached thereto coatings or brass stand-off rings or that have been modified in other ways to facilitate washover or engagement by die collars or overshots, it has been found that the surface area of the sloping face portion is greatly reduced. This reduces the surface area which is available to guide the drill bit or mill off the whipstock face and the mill or drill bit tends to roll off the sloping face portion in the direction of rotation.

To prevent roll off and to centralize and stabilize the upper tapered end of the whipstock, while continuing to facilitate washover procedures, the surface area of face portion 26' is increased by an extension 65 which extends around face portion. Extension 65 acts to extend the width of face portion 26' such that the effective diameter of the whipstock at the extension 65 is equal to or just less than the drift diameter for the whipstock which is substantially equal to the effective diameter at the centralizers. A cavity is formed on the outer surface of the whipstock between the centralizers and the extension into which coating 64' is applied. The radial length of the whipstock relative to the long axis 52' is selected to be substantially equal along the length of the whipstock. As an example, in the preferred embodiment, the radial length r1 at the extension, the radial length to the outer surface of a coated area r2 and the radial length to the outer contact surface of a centralizer 56' r3 are each substantially equal. The extension is preferably 1/2" to 1" thick.

In FIGS. 5A and 5B, one embodiment of a lower orienting section 22 is shown. FIGS. 6A show another embodiment of a lower orienting section 22'. Orienting sections 22 or 22' can be utilized to position and orient any assembly in any desired depth profile included in the casing string. This may include whipstocks, for example as shown in FIGS. 3A or FIGS. 4A, packers, completion diverters or tubing splitters or any other completion tools required to be oriented in a particular location in the casing, such as for example, adjacent a lateral window.

Section 22 is shown uncompressed in FIG. 5A. In FIG. 5B, section 22 is shown in a compressed, set condition as would be the condition of the section when used in a toolguide which is locked in position in a wellbore ready for use. Lower orienting section 22 includes a male portion 68 shaped to fit into the sockets 58 or 58' on the whipstocks. Bores 70 (only one is shown) accept ends of shear pins 61.

Male portion 68 is connected to a central mandrel 72. Central mandrel 72 is mounted in a bore 73 in a housing 74. Mandrel 72 is both moveable through and rotatable within bore 73 as limited by movement of pin 76 on housing 74 in jay slot 78 formed in mandrel 72. Mandrel 72 can be releasably locked in position in housing by locking collet 77 frictionally engaging into knurled area 77a.

Housing 74 includes a top portion 80 and a lower portion 82. Each portion has a flange 84 which together retain an annular packing seal 28. Top portion 80 is moveable towards lower portion 82 as shown in FIG. 5B to compress packing seal 28 and cause it to expand outwardly.

Referring also to FIG. 5C, housing 74 at its lower end accommodates latch assembly 83. Latch assembly 83 includes latch 20, a latch retaining plate 85 and springs 86. Springs 86 act between latch 20 and latch retaining plate 85 to bias latch 20 radially outwardly from housing 74. Latch 20 is retained in a channel 88 through housing 74 which opens into bore 73. Latch 20 is prevented from being forced by the action of springs 86 out of the channel, by abutting flanges 90 which act against shoulders 92 on the latch. Latch 20 can be pushed into channel 88 by application of force on the latch toward plate 85.

Latch 20 is formed to fit into latch retaining slot 16a on casing 8 and has a ramped surface 94 on its upper edge, to ease removal from the slot, and an acute angle portion 96 which acts as a catch to resist against the latch moving out of the slot by any downward force.

Mandrel 72 is bifurcated at is lower end to form two arms 98a, 98b. Arms 98a, 98b are formed to be extendable through bore 73 on either side of latch 20. Arms 98a, 98b are generally wedge-shaped to permit rotation of mandrel 72 in bore 73. As mandrel rotates, arms 98a, 98b are driven from a position in which they do not restrict movement of the latch in the channel to a position in which arm 98a abuts against shoulder 99 of latch 20 and prevents it from moving back into channel 88. In this way arm 98a can be moved to act as a lock against retraction of latch 20 into channel 88. Arm 98b serves to stabilize the end of the mandrel, but, can be omitted from the mandrel, as desired.

In use, a toolguide is constructed by attaching a whipstock (ie. FIG. 3A or FIG. 4A) to lower section 22 by insertion of shear pins 61 through apertures 62 and 70. The toolguide is run into the well until the latch 20 is about 1 meter below the slot 16a in casing section 8. The toolguide is hoisted and rotated slowly, until latch 20 is located in slot 16a. When the latch is located in the slot, the torque load will suddenly increase. As the string torques up, jay pin 76 will release, allowing mandrel 72 to rotate in a direction indicated by arrow a. When the force on the toolguide is released, the mandrel will be free to move down in housing 74 (FIG. 5B). During rotation of the mandrel, arms 98a, 98b will be rotated so that arm 98a abuts against shoulder 99 of latch 20 and locks latch in the outwardly biased position. Mandrel arms can take other forms provided they are formed to lock behind the latch in response to rotation of the mandrel and/or movement of the mandrel through the housing.

A downward movement of the string allows the toolguide to travel down until portion 96 of the latch lands against the bottom of slot 16a. Latch 20 and housing 74 will support the weight of the tool and upper portion of the housing will be driven down by the weight of the whipstock to compress seal 28 allowing it to set. The set force is locked in by collet 77. The whipstock 24 is now aligned with window opening 12 and the directional drilling operations can begin.

After the directional drilling operations are completed, a retrieving tool is run in to retrieve the toolguide. Preferably, in the simplest retrieval procedure, a straight upward force, for example of about 20,000 psi on the toolguide will unlock locking collet 77 and permit mandrel 72 to be pulled up. This pulls arm 98a out of abutting engagement with the latch and releases seal 28. The toolguide can then be removed from the well.

If the toolguide gets stuck in the well, a force is applied which is sufficient to shear pins 61 so that the whipstock can be removed separately from the lower section.

Referring to FIGS. 6A, another lower section 22' is shown. Lower section 22' is illustrated connected to a whipstock 24'. Lower section 22' includes a male portion 68' shaped to fit into socket 58' of whipstock 24'. Bores 70' accept ends of shear pins 61'.

Male portion 68' is an extension of a mandrel 172 which is positioned in a bore 173 in housing 174. Mandrel 172 is slidably moveable through bore 173 along long axis 178 of the lower section, but can be releasably locked against longitudinal sliding movement by frictional engagement of locking collet 177 against knurled portion 177a of the mandrel. Mandrel 172 and bore 173 are correspondingly faceted along corresponding portions of their length to substantially prevent rotational movement of mandrel 172 within bore 173.

An annular packing seal 28 is retained on housing 174 and a tube 179 is positioned to ride over an upper surface of housing 174. Tube 179 is releasably secured through shear pins 179a to whipstock 24' to move therewith. Pressure of tube 179 against annular packing seal 28, for example when the weight of the whipstock is released onto the lower section, compresses the seal and causes it to expand outwardly.

Lower section 22' carries a latch assembly including a latch 20', a latch retaining plate 184 and latch biasing springs 186. Springs 186 act between latch 20' and plate 184 to bias latch 20' to extend radially outwardly from housing 174. Latch 20' is formed to fit into a latch retaining slot, such as slot 16a in FIG. 1.

Latch 20' is retained in a channel 188 which opens into bore 173. Latch 20' is prevented from being forced by the action of springs 186 out of channel 188 by abutting flanges 190 which act against shoulders 191 on the latch. Latch 20' has formed into its surface an upper cavity 192 and a lower cavity 193.

Mandrel 172 has an extension 198 on its lower end which is capable of fitting into cavity 192 when mandrel is moved toward the latch. When extension 198 of mandrel 172 fits into the cavity, latch 20' is prevented from moving back into channel 188 and, thereby is locked in an outwardly extending position. To strengthen the locking of latch 20' in the outward position, the latch preferably has formed thereon a cavity on each side thereof for accepting a pair of spaced extensions on the mandrel.

A rod 199 extends below latch 20 in a bore 200. Rod 199 is slidably moveable in bore 200 and the rod and the bore are correspondingly faceted along at least a portion of their lengths so that rod 199 is substantially prevented from rotating within the bore. Rod 199 has an end 199' which is capable of fitting into lower cavity 193 on latch 20'. End 199' is tapered to facilitate entry into lower cavity 193 even when the rod end and the cavity are not directly aligned, but cavity is formed such that when latch 20' is biased outwardly into a slot in the casing, end 199' will not align with and fit into the cavity. When end 199' is inserted into cavity 193, the latch is maintained in a recessed position in the channel and is prevented from being biased to extend fully outwardly. Thus, rod 199 acts as a lock for maintaining latch 20' in a recessed position within channel 188. Apertures 201 are formed through housing 174 for alignment with holes 202 on rod 199. Shear pins (not shown) can be inserted through apertures 201 into holes 202 to releasably lock rod 199 against slidable movement in bore 200. Other releasably lockable means can be used in place of shear pins such as spring biased pins or a locking collet. A releasable locking means which can be repeated locked and unlocked is preferred where the tool is to be repeatedly used downhole without being brought back to surface.

Rod 199 extends out of housing 174 and opposite rod end 199" is retained in a bore 204 formed in a lower housing 206. A portion of end 199" is enlarged so that rod is retained in the bore. However, bore 204 is selected to have a greater inner diameter, ID.sub.b, than the width, w, of end 199" so that rod 199 can move laterally within bore 204. This forms a wobble shaft arrangement and provides that housing section 206 can move out of axial alignment with axis 178 of housing 174.

Housing 206 houses an orienting assembly including a plurality of orienting dogs 208. Preferably, there are four orienting dogs spaced apart 90 degrees aligned around a circumference of the housing. Dogs 208 are retained in housing in any suitable way such as by abutting flanges, not shown. Dogs 208 are biased outwardly by springs 210, such as Belleville washers, which are actuated to apply various, selectable degrees of force to the dogs. Springs 210 are actuated to vary their biasing force by a hydrostatic piston assembly 212. In particular, piston 212 includes a piston 214 having a face 214' in communication with a chamber 216 opening though aperture 218 to the exterior of the tool. Op