DRILLING ASSEMBLY FOR DRILLING HOLES IN SUBSURFACE FORMATIONS

Abstract

 The drill bit assembly comprises: a drill bit (10), suited to be fixed to the distal end of a drill string (20); a casing shoe (12), for being mounted at the distal end of a casing column (14); and a ring bit (16), supported in its rotation by the casing shoe (12). The drill bot (10) and the ring bot (16) mutually axially slide inside one another, so that the drill bit (10) is configured to take on a cooperating condition and an independent condition. In the cooperating condition, the ring bit (16) surrounds the drill bit (10) and is integral in rotation to the drill bit (10); the ring bit (16) is operated in rotation, when the drill bit (10) is rotated. In the independent condition, the drill bit (10) axially exceeds the ring bit (16) and the ring bit (16) is independent, in its rotation, of the drill bit (10); the drill bit (10) is capable of rotating independently of the ring bit (16).

Description

Technical field

[0001] The present invention relates to a drill bit assembly or boring rig to drill soil.

Technological background

[0002] In the drilling or boring field, drill bit assemblies or drilling tools are known, having a drill bit or pilot bit, which is caused to rotate through a drill string, a ring bit, which is supported in its rotation by a hose or casing shoe, which can be connected to a casing column.

[0003] In some examples of known drill bit assemblies, the ring bit and the casing shoe are not constrained in their rotation movement, but they are constrained in their forward movement, for example by means of abutments axially resting against one another, along the drilling axis of the hole. Therefore, when the drill bit stresses the casing column, the latter moves forward in the axial direction of the drilling or boring, substantially as one with the drill bit. Some types of known drill bit assemblies or boring rigs are described in patents WO2006017414A2 and WO2010071563A1.

[0004] Known drill bit assemblies or boring rigs are affected by some drawbacks.

[0005] One drawback lies in the fact that the constraint, in their forward movement, between the drill bit and the ring bit necessary determines a not very versatile operation of the whole system, which, as a consequence, is not capable of adjusting to the different drilling situations that may occur, in particular based on the type of soil to be drilled. and the soil in connection with the same.

Summary of the invention

[0006] An object of the present invention is to provide a drill bit assembly which is able to solve this and other drawbacks of the prior art and which, at the same time, can be produced in a simple and economic fashion.

[0007] According to the present invention, this and other objects are reached by means of a assembly having the features set forth in the appended independent claims.

[0008] The appended claims are an integral part of the technical teaches provided in the following detailed description concerning the present invention. In particular, the appended dependent claims define some preferred embodiments of the present invention and describe optional technical features.

Brief description of the drawings

[0009] Further features and advantages of the present invention will be best understood upon perusal of the following detailed description, which is provided by way of example and is not limiting, with reference, in particular, to the accompanying drawings, wherein:

• figure 1 is a partial longitudinal section view of a drill bit assembly or boring rig according to an exemplary embodiment of the present invention;
• figure 2 is an exploded, longitudinal or axial section view of some components of the system shown in figure 2; and
• figures 3 and 4 are cross section views of a drill bit and a ring bit belonging to the system shown in the previous figures.

Detailed description of the invention

[0010] Figure 1 shows, as a whole and in a schematic manner, a drill bit assembly or boring rig according to an explanatory embodiment of the present invention.

[0011] The system comprises:

• a drill bit 10, for being fixed to the distal end of a drill string 20;
• a casing shoe 12, for being mounted at the distal end of a casing column 14; and
• a ring bit 16, supported in its rotation by said casing shoe 12.

[0012] Drill bit 10 and ring bit 16 can mutually axially slide inside one another, so that drill bit 10 is configured to take on:

• a cooperating operating condition, in which ring bit 16 surrounds drill bit 10 and is integral in rotation to said drill bit 10; in this way, ring bit 16 is operated in rotation, when drill bit 10 is rotated; and
• at least one independent operating condition, in which drill bit 10 and ring bit 16 are axially offset and mutually independent in their rotation.

[0013] In the embodiment shown herein, there is a first independent operating condition, in which drill bit 10 axially exceeds ring bit 16 and ring bit 16 is independent, in its rotation, of drill bit 10; in this way, drill bit 10 is capable of rotating independently of ring bit 16.

[0014] Knowingly, drill bit 10 is designed to drill the soil in the central part of the hole; on the other hand, ring bit 16 is designed to drill the soil in the peripheral part of the hole, so as to the enable the penetration of casing column 14. In this way, one can choose whether to have the system operate, along the drilling direction, in the cooperating operating condition or in the first independent operating condition. This aspect proves itself to be advantageous, since is allows the system to be more flexible and to adjust to the different conditions of the soil to be drilled or bored.

[0015] In particular, let's consider the first independent operating condition of drill bit 10, when ring bit 16 is associated with casing column 14. If drill bit 10 is extracted and it is not integral in rotation relative to ring bit 16, drill bit 10 remains located on the outside of casing column 14 in the direction of the hole bottom.

[0016] Preferably, drill bit 10 is designed to take one a second independent operating condition, in which it is inactive. In particular, in the second independent operating condition, ring bit 16 axially exceeds the drill bit 10 and is independent, in its rotation, of the drill bit 10; in this way, ring bit 16 (and casing column 14) is capable of acting independently of drill bit 10.

[0017] In particular, let's consider the second independent operating condition of drill bit 10, when ring bit 16 is associated with casing column 14. If drill bit 10 is retracted and it is not integral in rotation relative to ring bit 16, drill bit 10 is surrounded by casing column 14 and is located on the inside thereof.

[0018] These aspects prove themselves to be advantageous, since they allow drill bit 10 and ring bit 16 (as well as, if necessary, casing column 14 associated therewith) to move forward and to operate independently of one another along the drilling direction.

[0019] With reference, in particular, to figure 1, the system is designed to be used in a drilling or boring rig (regardless of whether it is stationary or self-moving).

[0020] In the embodiment shown herein, the drilling rig comprises a rotary unit 18, for generating a torque, and a drill string 20 (comprising one or more drill pipes connected to one another in series), for transmitting the torque generated by rotary unit 18 to drill bit 10. In particular, the drilling axis is straight and it is indicated by the broken line x. In the example shown herein, drilling axis x is substantially vertical. Therefore, rotary unit 18 causes a rotation of drill string 20 and of drill bit 10 around axis x.

[0021] Casing column 14 comprises one or more casing pipes connected to one another. Knowingly, as the drilling or boring progresses, casing column 14 becomes longer, the casing pipes being connected to one another, for example by means of joints (typically through threaded screwing coupling).

[0022] Figure 2 shows, in detail, the conformation of ring bit 16 and of drill bit 10, which have a radially inner portion and a radially outer portion, which cooperate with one another and are complementary so as to enable a mutual sliding movement in an axial direction and a mutual constraint in rotation. In particular, ring bit 16 and drill bit 10 have respective complementary profiles, which are such as to be integral in rotation around drilling axis x, but, at the same time, enable a mutual sliding movement along said axis x.

[0023] As a person skilled in the art can easily understand, the conformation shown in figures 3 and 4 should be considered as merely explanatory and as non-limiting.

[0024] In the embodiment shown herein, the radially inner portion or profile of ring bit 16 has recesses 22, for mechanically cooperating with complementary projections 24 of the radially outer portion or profile of drill bit 10. According to a possible alternative embodiment (not shown herein), this arrangement can be inverted, for example making the projections on the ring bit and the recesses on the drill bit. Generally speaking and by mere way of example, the ring bit can comprise at least one between a projection and a recess, for cooperating with at least one respective recess and projection available on the drill bit.

[0025] Preferably, projections 24 include axial or longitudinal ribs, whereas recesses 22 include axial or longitudinal grooves.

[0026] In the embodiment shown herein, the cooperation between projections 22 and recesses 24 enables a guided sliding movement between drill bit 10 and ring bit 16 along longitudinal drilling axis x and covering a predetermined length (drill bit 10 being in the cooperating operating condition), without any relative rotation between drill bit 10 and ring bit 16.

[0027] With reference, in particular, to the embodiment shown in figures 3 and 4, more specifically, ring bit 16 has a plurality of recesses 22 (for example, three), which are angularly equally spaced apart from one another (in this example, by 120°), and drill bit 10 has a plurality of projections 24 (for example, three), which are angularly equally spaced apart from one another (in this example, by 120°) and adapted to engage the corresponding recesses 22.

[0028] Preferably, the drill bit assembly comprises a vibrating unit 25, for imparting vibrations to the casing column 14, thus allowing ring bit 16 to move autonomously relative to drill bit 10 (in particular, when drill bit 10 is in the first or second cooperating operating condition).

[0029] Preferably, vibrating unit 25 transmits vibrations through at least one bracket 26, which is constrained to casing column 14. Bracket 26 comprises a hole 18, or opening, for being engaged by a respective mechanical engaging means of said vibrating unit. Figure 1 shows a pair of said brackets 26.

[0030] Preferably, vibrating unit 25 imparts vibrations mainly along a direction that is substantially parallel to drilling axis x. With reference to the example shown herein, drilling axis x is substantially vertical and vibrating unit 25 generates substantially vertical vibrations. Alternatively, vibrating unit 25 can impart vibrations in other directions. Conveniently, the vibration frequency ranges from 80 to 200 Hz; more preferably from 120 to 150 Hz.

[0031] In a further variant, not shown herein, of the embodiment described above, the drilling rig also comprises a further known rotary unit, for generating a torque and transmitting it to casing column 14. For example, the further rotary unit can be mounted in the area of the proximal end of casing column 14 (namely, in a position far from ring bit 16 - and, therefore, from the soil to be subjected to the drilling).

[0032] This variant can be used when users need to control the sole rotation of casing column 14 (and, hence, if necessary, of ring bit 16) separately from the control of the rotation of drill string 20. For example, the control of the sole rotation of casing column 14 can be particularly useful to connect a further casing shoe 12 to the bottom of casing column 14 (typically, through a threaded coupling between the last casing shoe located at the bottom of the casing column and the further casing shoe to be fixed to said casing column).

[0033] Furthermore, the variant described above can also be used when the action of vibrating unit 25 needs to be combined with a rotation of casing column 14 (in particular, when the rotation of the casing column needs be controlled without having to use the cooperating operating condition between drill bit 10 and ring bit 16).

[0034] Therefore, this variant ensures a high use versatility of the drill bit assembly.

[0035] According to an advantageous aspect of the present invention, drilling fluids are pushed through drill string 20 and flow out in hollow space 30 between drill string 20 and casing column 14. Therefore, drill string 20 conveniently is hollow.

[0036] Conveniently, casing column 14 comprises a draining valve 32 to let out the drilling fluids. Valve 32 is preferably located on the surface, so as to be accessible to users.

[0037] Preferably, the system comprises a delivery pipe 34 and a return pipe 36 for the drilling fluids, which are obtained on at least one between said drill bit 10 and said ring bit 16. In this way, the drilling fluids reach the bottom of the hole, thus making the drilling easier. With reference to the variant of figures 3 and 4, delivery pipe 34 is arranged at the center of drill bit 10, which, as a consequence, is hollow. Return pipes 36 are obtained through recesses made on the radially outer surface of drill bit 10, which face the radially inner surface of ring bit 16. Therefore, these recesses 36 create a hollow space between ring bit 16 and drill bit 10, which creates a passage for the drilling fluids.

[0038] With reference to the variant shown, the in-flowing fluids flow into the drill string in the direction of the hole bottom. Drill string 20 is in fluid communication with delivery pipe 34 of drill bit 10. The fluids come into contact with the bottom of the hole; after that, the fluids, carrying debris and impurity due to the drilling, flow through return pipes 36, through which the fluids reach hollow space 30. From hollow space 30, the fluids flow back up the drill string until they reach draining valve 32, from the which they flow out.

[0039] Optionally, rotary unit 18 can possibly be designed to impart percussions to drill string 20, so as to make the drilling easier (in this case, rotary unit 18 acts as a rotation-percussion unit). By so doing, drill bit 10, connected to the lower end of drill string 20, is subjected to rotation-percussion actions.

[0040] According to a further embodiment of the invention, the drill bit assembly or boring rig comprises a hole bottom hammer or (not shown), which is capable of generating an impact on drill bit 10 in order to make the drilling easier. In other words, the hole bottom hammer creates a mechanism known as down-the-hole drill.

[0041] Conveniently, ring bit 16 and/or drill bit 10 comprise known crushing means, which brake and crush the soil during the drilling of the hole. In the embodiment shown, both ring bit 16 and drill bit 10 are provided with crushing means, in particular a plurality of button inserts 38. Alternatively, the drill bit can have tricone crushing means.

[0042] With reference, in particular, to figure 2, the lower end of casing column 14 comprises an inner radial recess 140, for housing the upper end 120 of casing shoe 12. Casing shoe 12 and casing column 14 are axially constrained along drilling axis x. The upper end of ring bit 16 comprises an inner radial recess 160, for housing lower end 122 of casing shoe 12. Casing shoe 12 and ring bit 16 are axially constrained along drilling axis x, bit they are independent in their rotation.

[0043] Naturally, the principle of the present invention being set forth, embodiments and implementation details can be widely changed relative to what described above and shown in the drawings as a mere way of non-limiting example, without in this way going beyond the scope of protection provided by the accompanying claims.

Claims

1. Drill bit assembly or boring rig to drill soil comprising:

- a drill bit (10), for being fixed to the distal end of a drill string (20);

- a casing shoe (12), for being mounted at the distal end of a casing column (14); and

- a ring bit (16), supported in its rotation by said casing shoe (12);

characterized in that said drill bit (10) and said ring bit (16) can mutually axially slide inside one another, so that said drill bit (10) is configured to take on:

- a cooperating operating condition, in which said ring bit (16) surrounds said drill bit (10) and is integral in rotation to said drill bit (10); said ring bit (16) being operated in rotation, when said drill bit (10) is rotated; and

- at least one independent operating condition, in which said drill bit (10) and said ring bit (16) are axially offset and mutually independent in their rotation.

2. Assembly according to claim 1, wherein, in said at least one independent operating condition, said drill bit (10) axially exceeds said ring bit (16) and is able to rotate independently of said ring bit (16).

3. Assembly according to claim 1 or 2, wherein, in said at least one independent operating condition, said ring bit (16) axially exceeds said drill bit (10) and is able to rotate independently of said drill bit (10).

4. Assembly according to any of the claims from 1 to 3, wherein said drill bit (10) and said ring bit (16) having, respectively, a radially inner portion (24) and a radially outer portion (22), which are complementary to one another and cooperate with one another to create a mutual sliding movement in an axial direction and a mutually integral in rotation, when they are in said cooperating operating condition.

5. Assembly according to claim 4, wherein said radially inner portion (24) and said radially outer portion (22) are uncoupled from one another, when said drill bit (20) is in said at least one independent operating condition.

6. Assembly according to claim 4 or 5, wherein said radially inner portion of said ring bit (16) has at least one between a recess (22) and a projection, for mechanically cooperating with at least one complementary projection (24) or recess of said radially outer portion of said drill bit (10).

7. Assembly according to claim 6, wherein said radially inner portion of said ring bit (16) has a plurality of said recesses (22) or projections and said radially outer portion of said drill bit (10) has a plurality of said projections (24).

8. Assembly according to claim 7, wherein said recess (22) and said projections (24) are equally spaced apart from one another.

9. Assembly according to any of the previous claims comprising, furthermore, a rotary unit (18), for generating a torque, and a drill string (20), on which distal end there is fixed said drill bit (10) and which is capable of transmitting said torque to said drill bit (10).

10. Assembly according to any of the previous claims comprising, furthermore, a casing column (14), on which distal end there is supported in rotation said ring bit (16) .

11. Assembly according to claim 10 comprising, furthermore, a vibrating unit (25), for imparting vibrations in an axial direction to said casing column (14) .

12. Assembly according to claim 11, wherein said vibrating unit (25) is located close to the proximal end of said casing column (14).

13. Drill bit assembly according to claim 11, wherein said vibrating unit is located close to the distal end of said casing column (14).

14. Assembly according to any of claims from 11 to 13, wherein the frequency of vibration of said vibrating unit (25) ranges from 80 Hz to 200 Hz, preferably from 120 Hz to 150 Hz.

15. Assembly according to any of claims from 10 to 14 comprising, furthermore, a rotary unit, for generating and transmitting a torque to said casing column (14).

Drawing