Support casing for a boring head

[57] ABSTRACT

Drilling apparatus for installing casing while drilling in which a mobile head is connected to the lower end of a casing by bearing means. A drilling pipe string extends through the casing and is coupled to the casing at the upper end. A drilling bit is fixed to the lower end of the drill pipe and includes a plurality of retractable arms which cooperate with recesses in the mobile head to rigidly connect the drilling bit to the mobile head.

Claims, IS Drawing Figures

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3901,331

SUPPORT CASING FOR A BORING HEAD

The invention relates to a support casing apparatus for a drilling head applicable to all earth boring work and in particular to under-water petroleum drilling.

The need to protect bore holes and in particular petroleum drill holes leads to the use of a casing placed in position after drilling a pre-hole. For this purpose, the first drill hole is enlarged by means of a suitable tool and then after removal of this tool the casing is lowered into the hole. All these operations are lengthy and costly. They are still more so in the case of an underwater petroleum drill hole. Moreover, when drilling is carried out in soft ground, it is not unusual for cave-ins to occur between the moment of drilling and the location of the casing, thus necessitating further work.

According to the present invention there is provided a support casing apparatus for a drilling head comprising (1) a casing wherein the head is connected to the casing by a bearing connecting means permitting free rotation of the head about its axis, (2) first means for coupling the head to a lower portion of a pipe string carrying a drilling tool to drive the head, and (3) a second coupling means located at the upper portion of the casing for rigidly attaching it to a pipe string.

It is therefore sufficient for placing the casing in position in a single operation to select a drilling head and a drilling tool, a bit for example, suitable for the soils to be encountered. The combination of the bit, the head, and the casing fixed on its orientation relative to the soil forms in itself both a drilling tool of sufficient diameter for the introduction of the casing and a pipe for protection of the drill hole in which muds and drilled soil may subsequently be raised. Thus all the intermediate operations of lowering and lifting the tool, enlarging the first drill hole, and placing the casing in position are avoided.

To facilitate the actual drilling in the case of unforeseen change of the tool without having to raise the casing fitted with its drilling head, the coupling means of the head relative to the drilling tool may be arranged so that the head is set back relative to the tool and means may be provided on the upper part of the casing to rigidly connect the latter to guide means used for recovery of the original drilling tool after the casing has been placed in position and to guiding means for coupling the upper end of the casing to the pipe string.

The present invention will be more fully understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings, wherein:

FIGS, la and lb are diagrammatic views, partially in axial section, of an embodiment of casing apparatus according to the invention and including means for coupling to pipe string and to a bit;

FIG. 2 is an axial section of apparatus for control of means for coupling to the pipe string;

FIG. 3 is a section along the line ΠΙ-ΠΙ of FIG. la;

FIG. 4 is a section along the line 1V-IV of FIG. la; FIG. 5 is a section along the line V—V of FIG. la;

FIG. 6 is a sectional view of a detail of bearing means connecting the drilling head to the casing;

FIG. 7 is a view from below the head in the drilling position;

FIGS. 8 &amp; 9 are sections along the lines VIII—VIII and IX-fX of FIG. 7;

FIG. 10 is a section along the line X—X of FIG. lb;

FIG. 11 is a perspective view of a cutaway portion of a modification of the head;

FIG. 12 is a diagrammatic view of the outer portion of a bit co-operating with the head of FIG. 11;

FIG. 13 is a general view of the casing separated from the drilling tool, and

FIG. 14 is a diagrammatic representation of the well of a drilling barge.

In FIGS, la and lb, meeting along cut line 1, it will be seen that casing assembly 2 comprises a pipe or casing 3 provided at its lower portion with a head 4 and a bearing means 5, a detail view of which is given in FIG. 6. At its upper portion, casing 3 is shaped to receive an assembly 6 including a first coupling means having latches 8 and a plate 27 known as a base plate and supporting a guide assembly 7 acting as guide means for the reintroduction of bit 28-for example after tool changing to recommence drilling.

The coupling means of assembly 6 may be a conventional hydraulically controlled connector. To clarify the drawing, the latches 8 of the coupling means have been shown symbolically. As the conventional mechanism may be of any known type, it will not be further described. Only control pipe 37, which is used for unlocking the coupling means, has therefore been shown in the drawing. In the absence of pressure in control pipe 37, latches 8 extend into one of a plurality of circular grooves 3α in the upper portion of casing 3 rigidly attaching assembly 6 to the casing 3.

The upper end of assembly 6 is welded along the whole of its periphery to a castillated member 9, shown in plan in FIG. 3 and from below in FIG. 4. The weld line has been shown at 40 and 41. Member 9 has a central aperture which is castellated, the castellations or splines 9α engaging in three longitudinal grooves 42α in a threaded pipe 42. Threaded pipe 42 is attached to pipe string 45 by upper joint 38 and lower joint 26, shown in FIG. 2, so that rotation of assembly 6 locked on casing 3 relative to pipe string 45 is prevented.

The position of castellated member 9 on threaded pipe 42 is determined by a member 10, FIG. 5, having a central threaded aperture. In order to rigidly attach pipe string 45 to assembly 6, it is sufficient to screw member 10 onto threaded pipe 42 to the required height, i.e. to a height permitting latches 8 to penetrate one of the circular grooves 3α in the upper portion of casing 3 when castellated member 9 rests on member 10, and then to fix castellated member 9 on member 10.

In order to facilitate screwing of member 10 onto threaded pipe 42, a certain number of threaded holes 10α are provided in the peripheral surface of the member 10 permitting insertion of a bar having an end threaded with the same thread as these holes. After member 10 has been brought to the selected level and the above bars have been removed castellated member 9 is attached to member 10. For this purpose, castellated member 9 is provided with three openings 9b allowing passage of the shanks of bolts 43 therethrough and into threaded holes 10b of member 10, openings 9 b being of sufficient angular dimensions for at least one threaded hole 10b to be exposed to receive a bolt 43 whatever the angular position of member 10 relative to castellated member 9. The heads of the bolts 43 bear on the bases of grooves 9c bordering the openings 9b. A seal between the interior of casing 3 below castillated member 9 and the external environment is provided by

3901,331 annular elastic seals 44 in two circular grooves 10c in member 10 mating with two corresponding circular grooves 9d in castellated member 9.

The upper portion of threaded pipe 42 is connected to rod string 45 by lower joint 26, FIG. 2, which has an internal sleeve 36 normally retained by shear screws or pins 46. The internal sleeve 36 blocks a passage 26α extending control pipe 37, seals 53 ensuring the fluid tightness of the sleeve. The upper joint 38 rigidly attaches the lower joint 26 to rod string 45.

The upper portion 36α of internal sleeve 36 acts as a seat for a closure member 39 when the latter descends through rod string 45 to cause the automatic unlocking of assembly 6. When a frusto-conical portion 39α of closure member 39 rests on seat 36α, the pres- 1 sure inside rod string 45 increases until shear pins 46 are broken and internal sleeve 36 is driven until it comes to rest on seat 26b provided in lower joint 26. When internal sleeve 36 rests on seat 26b, internal sleeve 36 frees the passage 26α and thus causes the pressurisation of control pipe 37 causing unlocking of latches 8 of assembly 6. This action is sufficient to disconnect assembly 6 from the upper portion of casing 3.

The lower portion of threaded pipe 42 is connected to the drilling attachment, figures la and lb, by a pipe ²⁵string comprising a stem 11 supporting a turbine 12, the shaft 13 of which drives bit 28 through a diminishcr

14.

In the embodiment illustrated, the bit 28 includes three retractable arms 15 which are also visible in FIG. 10. The double-ended arrows in FIG. 10 are intended to illustrate the retractability of the retractable arms 15. The retractable arms 15 are driven by the bit 28 as it rotates, permitting angular coupling of the bit 28 to the head 4 by any known means. The head 4 may be of any type and have soil attacking zones 4α, FIGS. 7 to 9, of any suitable form, for example as shown in FIGS. 8 and 9. As shown in FIG. 10, the means for coupling bit 28 to head 4 may consist of recesses 46 provided in the head 4 and of the retractable arms 15 of bit 28 which enter these recesses.

The head is preferably mounted as shown in FIG. 6, in which the lower end of casing 3 comprises a lower housing for insertion of bearing means such as ballbearings 16 bearing directly on the upper portion of head 4 and a lateral housing for bearing means such as ball-bearings 17 retained by a ring or annular member 18. Ring 18, rigidly attached to head 4 by screws 19, ensures with seals 20 and 21. which may for example be lip seals, the fluid tightness of bearing means 5.

In the modified head 33, a portion of which is illustrated in FIG. 11, instead of the straight-edged recesses 46 of head 4, FIGS. 7 to 10, recesses 29 are provided, one of the edges 30 of which is extended by a ramp 31 and the other edge 32 of which extends up to the ramp 31 of the preceding recess 29.

Because of the relatively large number of recesses and the arrangement of the ramps, the structure of head 33 provides the advantage of being able to receive shoulders 34 of bit 35 shown in FIG. 12 and easily guiding them to the bases of recesses 29. A quick, strong, and efficient joint is thus formed, since it is sufficient for shoulders 34 to impinge either laterally on an edge 32 or vertically on a ramp 31 in order for the shoulder 34 to be guided to the base of recess 29.

When it is required to drill in an under-water environment with the above described apparatus, casing 3 is provided with its bearing means 5 and head 4 (or 33) and is lowered by means of derrick 47, FIG. 14, and rotary table 49 mounted on the upper deck 48 of the drilling barge 22. The rotary table 49 is used to form the 5 overall casing 3 progressively by adding additional sections of casing as each section is sunk into the soil 25. The length of casing 3 may vary depending on the nature of the soil 25 in which drilling is to be carried out. Base plate 27, on which guide assembly 7 rests, may be 10 fitted on the retractable floor plate 51 of the lower deck 50 inside wall 22α. Attachment of base plate 27 to casing 3 is effected by simple application of profile 27α of plate 27 to profile 3b of casting 3, followed by clamping, seals 52 being provided between these ele5 ments. For this purpose, the casing 3 is lowered by means of a handling pipe until profile 3b of the casing, FIG. la, reaches the level of profile 27α of base plate 27. The casing 3 is then rotated until it reaches the position shown in FIG. la, in which the base plate 27 is ³⁵ being

2θ locked on profile 3b of the casing, and the handling pipe is raised. It will be noted that in addition to guide assembly 7, plate 27 bears arms 23, FIG. 13, at the ends of which sonar reflectors 24 are provided for facilitating access to the well head-at a tool change for example.

When casing 3, still retained by the derrick 47, has been thus equipped, the drilling attachment comprising the stem 11, the turbine 12, the shaft 13, the diminisher 14, and the bit 28 (or 35) is lowered into casing 3. Thus ³⁰ the bit 28 (or 35) is attached to diminisher 14 driven by turbine 12 connted to stem 11, and the drilling attachment is lowered progressively into casing 3 until the bit 28 (or 35) reaches head 4 (or 33) and effects bit head interlocking as already described, interlocking carried out either by engaging retractable arms 15 in recesses 4b, FIG. 10, or bringing shoulders 34 into contact with the bases of recesses 29, FIG. 11. As described above, threaded pipe 42 is then placed in position, member 10 is then screwed onto the rod to act as an attachment means for castellated member 9 rigidly attached to assembly 6, which in turn is locked onto the upper portion of casing 3 after mounting of lower joint 26 and upper joint 38. It is clear that the length of the drilling attachment is such that when bit 28 (or 35) is engaged with head 4 (or 33) and member 10 has been screwed to the necessary height on threaded pipe 42, latches 8 fit into circular grooves 3a so that casing 3, the drilling attachment, and the pipe string 45 which is subsequently attached) form an assembly which can be lowered after complete opening of retractable floor plate 51 until the bit 28 (or 35) reaches the drilling location.

If the nature of the soils requires it, a plate similar to base plate 27 may optionally be lowered in advance to the actual point of drilling, and this plate may also carry sonar reflectors facilitating the start of the drilling.

When turbine 12 drives the diminisher 14 and therefore bit 28 (or 35), only head 4 (or 33) is rotated pipe string 45 and casing 3 being subjected only to a lowering motion. During this part of the drilling, the mud rises between the casing and the soil.

If for some reason or other the drilling attachment comprising elements 11-14 and 28 needs to be raised before casing 3 has been completely sunk into the ground, it is sufficient, after having caused the retraction of retractable arms 15, where bit 28 is being used, to introduce closure member 39 into the duct of pipe

3901,331 string 45 to cause breakage of shear pins 46, the drop of internal sleeve 36, and the application of pressure to control pipe 37, causing the withdrawal of latches 8. Where bit 35 is used, the process is obviously analogous. The rod string may then be raised with the drilling 5 attachment and, after possible changing of the tool, the assembly may be lowered after replacement of lower joint 26 and its internal sleeve 36. As the apparatus for guidance by sonar reflectors 24 may be of any conventional type, it has not been described, and it is evident ¹⁰that, although the preferred embodiment of the invention includes such means, other types of conventional guide means, such as anchor cables, could alternatively be used. When the bit reaches guide assembly 7, it is sufficient to lower the pipe string until the bit and the ¹⁵head interlock for assembly 6 to again be in the locking position on the upper portion of casing 3. Drilling is accomplished jointly by the bit and the head and is continued until the casing has been completely sunk in so that base plate 27 reaches its final operating position. ^2t&gt;Depending on the bit used, drilling may be pursued immediately without raising the drilling attachment, or else the tool changed as described above.

It is evident that when drilling is shallow and the na- ₂₅ture of the ground lends itself to it, member 10 may be dispensed with, and threaded pipe 42 may be replaced by a simple grooved rod, the castellated member 9 being rigidly attached to the said rod or otherwise. However, in other cases, the embodiment described is ₃₍₎particularly efficient, whatever may be the soils encountered and the vibrations due to the rotation of the tool.