Retractable drill bit to allow insertion of a thick tube

Abstract

Retractable drill bit (1) for drilling a well comprising at least one body (2) provided with at least one arm (3), said arm (3) being movable between a retracted position, in which the arm (3) forms an angle (α) with a drilling rotation axis (A) included in a first angle value range, and a deployed position in which the arm (3) forms an angle (β) with the drilling rotation axis (A) included in a second angle value range, the at least one arm (3) being movable about a deployment rotation axis (32), characterized in that when the arm (3) is in the deployed position, the deployment rotation axis (32) and a free end (33) of the arm (3) are positioned on either side of a median axis (M) of the body (2). Figure 3

Description

Title of the invention: Retractable drill bit for allowing insertion of a thick tube

[0001] The invention relates to the field of civil engineering and more particularly to a retractable drill bit and a method of using such a drill bit.

[0002] To drill a borehole, it is known to use a mechanical drill that rotates an auger into the ground. The auger comprises an endless screw equipped at one end with a drilling head or bit.

[0003] Hereinafter, the axis along which the drill bit is inserted into the ground is called the drilling rotation axis. The drilling rotation axis corresponds to an elongation axis of the worm screw when the drill bit is fixed on the worm screw.

[0004] Subsequently, a diameter of the drill bit is called the diameter of the circle drawn by the drill bit when it is rotating around the drilling rotation axis. We distinguish the drilling diameter of the drill bit which corresponds to a diameter of the drilling well produced by the rotation of the drill bit by the worm screw.

[0005] The drill bit, generally equipped with tungsten teeth, has the function of breaking the soil so as to create pieces that can be brought to the surface by the auger. The pieces of soil are also called drilling residues or cuttings in English.

[0006] Some drilling techniques require a tube to be inserted into the wellbore while the drill bit is in operation. To do this, the tube is positioned around the auger, with the drill bit drilling beneath the tube. The tube follows the progress of the drill bit and is driven into the ground.

[0007] In order to be able to remove the auger and recover the drill bit at the end of drilling, it is known to use retractable drill bits. A retractable drill bit comprises at least one arm movable between a retracted position and a deployed position, the arm having the function of breaking the ground.

[0008] When the arm is in the extended position, the diameter of the drill bit corresponds to the drilling diameter.

[0009] When the arm is in the retracted position, the diameter of the drill bit is less than the diameter of the drill bit in the extended position. More specifically, the diameter of the drill bit in the retracted position, hereinafter referred to as the handling diameter, allows insertion or withdrawal of the drill bit into the tube.

[0010] Document US2002070051 describes a retractable drill bit comprising two arms movable around an axis of rotation extending perpendicular to the axis of elongation of the worm screw and oriented radially relative to the circle drawn by the drill bit when the latter is rotating along the axis of the worm screw.

[0011] The disadvantage of this drill bit is that it has low resistance to a cutting force exerted on a free end of the arms. Thus, this drill bit cannot be used to drill a well with a tube whose external diameter is much greater than an internal diameter, i.e. having a significant thickness, or a well in a ground having significant mechanical resistance.

[0012] The invention aims to overcome all or part of the aforementioned drawbacks by proposing a retractable drill bit for drilling a well comprising at least one body provided with at least one arm, said arm being movable between a retracted position, in which the arm forms an angle with a drilling rotation axis included in a first angle value range, and a deployed position in which the arm forms an angle with the drilling rotation axis included in a second angle value range, the at least one arm being movable about a deployment rotation axis, characterized in that when the arm is in the deployed position, the deployment rotation axis and a free end of the arm are positioned on either side of a median axis of the body.

[0013] The body comprises at least one arm, and in particular two arms, movable in rotation between a retracted position and a deployed position. The arm is therefore fixed to the body at one end and comprises a free end. The arm is configured to drill the ground when the drill bit is rotated along the drilling rotation axis.

[0014] In the retracted position, the arm forms an angle with the drilling rotation axis within a first angle value range. The first angle value range is [0°, 60°], preferably [0°, 30°] and in particular 24°. Thus, the diameter of the drill bit in the retracted position is less than the diameter of the drill bit in the deployed position. More precisely, the diameter of the drill bit in the retracted position, hereinafter called the handling diameter, allows insertion or withdrawal of the drill bit into the tube, i.e. the handling diameter is less than or equal to the inside diameter of the tube positioned on a worm screw rotating the drill bit.

[0015] In the deployed position, the arm forms an angle with the drilling rotation axis within a second angle value range. The second angle value range is [60°, 130°], preferably [80°, 100°] and in particular 90°, that is to say that the arm extends perpendicular to the drilling rotation axis. Thus the diameter of the drill bit corresponds to the drilling diameter which is greater than the handling diameter. More precisely, the drilling diameter corresponds substantially to that of the external diameter of a tube inserted into the well.

[0016] Furthermore, the drill bit is configured so that in the deployed position, the deployment rotation axis of the arm and the free end of the arm are positioned on either side of a median axis of the body. The median axis of the body passes through the center of rotation of the drill bit when the latter is rotated by the worm screw, i.e. it is secant with the drilling rotation axis, and extends parallel to the deployment rotation axis so as to separate the body into two zones. Preferably, the two zones are substantially identical, or symmetrical.

[0017] Thus the arm comprises a contact portion configured to be in contact with the body and a drilling portion at the free end making it possible to increase the drilling diameter in the deployed position. The specific position of the deployment rotation axis makes it possible to ensure better transmission of the cutting forces exerted on the free end of the arm. The cutting forces are transmitted from the arm, via the contact portion, to the body.

[0018] Thus, the invention makes it possible to produce a well equipped with a tube whose external diameter is much greater than an internal diameter, that is to say having a significant thickness, such as for example a concrete tube or a well in a ground having significant mechanical resistance.

[0019] The invention may also have one or more of the following features taken alone or in combination.

[0020] According to one embodiment, the deployment rotation axis is positioned in a plane forming an angle between [50°, 110°], preferably [80°, 100°], and in particular 90° with the drilling rotation axis.

[0021] According to one embodiment, the deployment rotation axis is not coincident with the drilling rotation axis.

[0022] In other words, the deployment rotation axis is not a radius or does not intersect the drilling rotation axis. Therefore, there is a non-zero distance between the deployment rotation axis and the drilling rotation axis.

[0023] Thus, it is possible to increase the dimension of the contact part of the arm on the body so as to promote transmission of cutting forces.

[0024] According to one embodiment, a ratio of the diameter of the drill bit in the deployed position to the diameter of the drill bit in the retracted position is between [1; 5], preferably [1; 3] and in particular 2.

[0025] Thus it is possible to insert a tube having a significant thickness such as for example a concrete tube.

[0026] According to one embodiment, the drill bit comprises at least one device for locking the at least one arm in the deployed position.

[0027] The locking device allows the arm to be held in the deployed position.

[0028] According to one embodiment, the drill bit comprises a fixing base intended to fix the drill bit on a worm screw, a locked position of the arm being achieved by a rotation of the body relative to the base.

[0029] The worm screw is a rod extending along an elongation axis, one orientation of which indicates the orientation of the well to be drilled. The worm screw makes it possible to put in rotation of the drill bit. The axis of rotation of the auger corresponds to the drilling axis.

[0030] The base is a mechanical part intended to be fixed in a removable manner on the worm screw so that there is no possible relative movement between the base and the worm screw. Alternatively, the base is fixed in a non-removable manner on the worm screw, for example by welding.

[0031] According to one embodiment, the base extends substantially along a first plane forming an angle with the elongation axis of the worm screw of between [60°, 120°], preferably [80°, 100°] and in particular 90°.

[0032] The body is fixed on the base.

[0033] The rotation of the body relative to the base is carried out by means of the worm screw. The rotation is therefore carried out along the drilling rotation axis. Thus, the locking device is simple to implement. Locking is carried out by rotating the worm screw in one drilling direction, while unlocking is carried out by rotating the worm screw in the opposite direction.

[0034] According to one embodiment, in the retracted position the diameter of the drill bit is less than or equal to that of the drill bit comprising only the base.

[0035] In other words, in the retracted position, the diameter of the drill bit corresponds to that of the base, i.e. the diameter of the circle drawn by the base when the latter is rotating along the drilling rotation axis.

[0036] According to one embodiment, the base comprises a locking surface configured to come into contact with the at least one arm in the locked position.

[0037] In the unlocked position, the locking surface is not in contact with the arm. The latter is therefore movable between the retracted position and the deployed position. When the locking surface is brought into contact with the arm, the latter is locked in the deployed position.

[0038] According to one embodiment, the locked position is achieved by a rotation along the drilling axis of between [0°, 180°], preferably [60°, 120°] and in particular 70°.

[0039] According to one embodiment, the body has a flat contact surface with the arm in the deployed position.

[0040] The contact surface of the body is configured to come into contact with the contact portion of the arm. This contact allows for the absorption of cutting forces exerted on the free end of the arm.

[0041] The invention also relates to a method of using a drill bit according to any one of the preceding claims, comprising: - a step of fixing a worm screw on the drill bit - a step of deployment of at least one arm of the body - a step of locking the at least one arm in the deployed position.

[0042] According to one embodiment, the step of opening the arm is carried out when the drill bit comes into contact with the ground.

[0043] In other words, the arm opens when it meets the resistance of the ground. The ground causes the arm to open.

[0044] According to one embodiment, the method comprises an unlocking step in which the worm screw is turned in a direction opposite to the drilling direction.

[0045] The invention will be better understood, thanks to the following description, which relates to an embodiment according to the present invention, given by way of non-limiting example and explained with reference to the appended schematic drawings, in which:

[0046] [Fig-1] is a side view of a drill bit according to the invention in the deployed position towards rusty;

[0047] [Fig.2] is a bottom view of the drill bit of [Fig.l];

[0048] [Fig.3] is a perspective view of the drill bit of [Fig.l];

[0049] [Fig.4] is a side view of the drill bit according to the invention in the retracted unlocked position rusty;

[0050] [Fig.5] is a perspective view of the drill bit of [Fig.4];

[0051] [Fig.6] is a perspective view of a drilling installation implementing a drill bit according to the invention;

[0052] The invention relates to a retractable drill bit 1 for drilling a well. The drill bit 1 comprises in particular a body 2 forming a central block of the drill bit 1.

[0053] The body 2 is provided with two arms 3 allowing the ground to be drilled when the drill bit 1 is rotated along a drilling rotation axis A.

[0054] According to one embodiment, the two arms 3 are identical. Thus, the remainder of the description relates to a single arm 3.

[0055] The arm 3 comprises a plurality of tungsten teeth 31 whose geometry is known to those skilled in the art. The arm 3 has a substantially blade shape.

[0056] The arm 3 comprises an end fixed to the body 2. This end is fixed by means of a deployment rotation axis 32. Thus, the arm 3 is movable in rotation around the deployment rotation axis 32 between a retracted position, visible in Figures 4 and 5, and a deployed position, visible in Figures 1 to 3.

[0057] The arm 3 comprises, opposite the deployment rotation axis, a free end 33. The free end 33 is provided with a drilling projection 331.

[0058] The arm 3 comprises two substantially planar faces 332, 333 extending along an axis perpendicular to the deployment rotation axis 32. The arm 3 has a thickness, along the deployment rotation axis 32, which is constant and along an axis perpendicular to the deployment rotation axis 32, decreasing between the deployment rotation axis 32 and the free end 33.

[0059] According to one embodiment, the deployment rotation axis 32 is positioned in a plane forming an angle between [50°, 110°], preferably [80°, 100°], and in particular 90° with the drilling rotation axis A. in other words, the deployment rotation axis is perpendicular to the drilling rotation axis A.

[0060] According to one embodiment, the deployment rotation axis 32 is not coincident with the drilling rotation axis A, i.e. the deployment rotation axis 32 is not a radius or does not intersect the drilling rotation axis A. There is therefore a non-zero distance d between the deployment rotation axis 32 and the drilling rotation axis A.

[0061] In the retracted position, the arm 3 forms an angle α with the drilling rotation axis A within a first angle value range. The first angle value range is [0°, 60°], preferably [0°, 30°] and in particular 24°. Thus, the diameter DI of the drill bit 1 in the retracted position, subsequently called the handling diameter D1, is less than the diameter D2 of the drill bit in the deployed position.

[0062] In the deployed position, the arm 3 forms an angle [3 with the drilling rotation axis A included in a second angle value range. The second angle value range is [60°, 130°], preferably [80°, 100°] and in particular 90°, that is to say that the arm 3 extends perpendicular to the drilling rotation axis A. Thus the diameter D2 of the drill bit corresponds to the drilling diameter D2 which is greater than the handling diameter DL

[0063] The drill bit 1 is configured so that in the deployed position, the deployment rotation axis 32 of the arm 3 and the free end 33 of the arm 3 are positioned on either side of a median axis M of the body 2. The median axis M of the body 2 passes through the center of rotation of the drill bit 1 when the latter is rotated by a worm screw 5, that is to say it intersects with the drilling rotation axis A, and extends parallel to the deployment rotation axis 32 so as to separate the body 2 into two zones. Preferably, the two zones are substantially identical, or symmetrical.

[0064] Thus the arm 3 comprises a contact portion, at the face 333, configured to be in contact with the body 2, at a flat contact surface 21, and a drilling portion at the free end 33 making it possible to increase the drilling diameter D2 in the deployed position. The specific position of the deployment rotation axis 32 makes it possible to increase the dimension of the contact portion of the arm 3 on the body 2 and thus promote the transmission of cutting forces to the end of the arm.

[0065] By the specific geometry of the drill bit, a ratio of the diameter D2 of the drill bit in the deployed position to the diameter D1 of the drill bit 1 in the retracted position is between [1; 5], preferably [1; 3] and in particular 2.

[0066] The drill bit 1 also comprises a fixing base 4 intended to fix the drill bit 1 on the worm screw 5.

[0067] The worm screw 5 is a rod extending along an elongation axis of which one orientation indicates the orientation of the well to be drilled. The elongation axis of the auger 5 therefore corresponds to the drilling rotation axis A. The auger 5 allows the drill bit 1 to rotate.

[0068] The fixing base 4 is a mechanical part intended to be fixed in a removable manner on the endless screw 5 so that there is no possible relative movement between the fixing base 4 and the endless screw 5. Alternatively, the fixing base 4 is fixed in a non-removable manner on the endless screw 5, for example by welding.

[0069] According to one embodiment, the base 4 extends substantially along a first plane forming an angle with the drilling rotation axis A of between [60°, 120°], preferably [80°, 100°] and in particular 90°.

[0070] The body 2 is fixed in a movably manner on the base 4, and more particularly movable in rotation.

[0071] The drill bit 1 comprises a device for locking the arm 3 in the deployed position.

[0072] According to one embodiment, a locked position of the arm 3 is achieved by a rotation of the body 2 relative to the base 4. The locked position is achieved by a rotation along the drilling axis (A) between [0°, 180°], preferably [60°, 120°] and in particular 70°.

[0073] According to one embodiment, the base 4 comprises a locking surface 41 configured to come into contact with the at least one arm 3 in the locked position.

[0074] The rotation of the body 2 relative to the base 4 is carried out by means of the worm screw 5. The rotation is therefore carried out along the drilling rotation axis A. During the rotation, the locking surface 41 is moved in order to be positioned in contact with the arm 3. The latter is then locked in the deployed position. Thus, the locking device is simple to implement. Locking is carried out by rotating the worm screw 5 in a drilling direction, while unlocking is carried out by rotating the worm screw 5 in the opposite direction.

[0075] According to one embodiment, in the retracted position the diameter DI of the drill bit 1 is less than or equal to that of the drill bit 1 comprising only the base 4. In other words, in the retracted position, the diameter DI of the drill bit 4 corresponds to that of the base 4, that is to say the diameter of the circle drawn by the base 4 when the latter is rotating along the drilling rotation axis A.

[0076] The drill bit 1 according to the invention is more particularly intended to allow the insertion of a tube during drilling, that is to say a tube positioned around the endless screw 5 while the drill bit is digging the well.

[0077] With the drill bit according to the invention, the diameter DI of the drill bit 1 in the retracted position allows insertion or removal of the drill bit 1 from the tube, i.e. the handling diameter D1 is less than or equal to the diameter of the worm screw 5 driving in rotation of the drill bit 1. The drilling diameter D2 corresponds approximately to that of the external diameter of the tube inserted into the well.

[0078] Thus, the invention makes it possible to drill a well equipped with a tube whose external diameter is much greater than an internal diameter, that is to say having a significant thickness, such as for example a concrete tube or a well in a ground having significant mechanical resistance.

[0079] Furthermore, the drill bit according to the invention makes it possible to improve the transmission of cutting forces between the body and the arms 3, due to the non-zero distance between the deployment rotation axis and the drilling rotation axis, in the opposite direction to the end of the arm. It is thus possible, on a drill bit 1 having a drilling diameter of 600 mm and a handling diameter of 300 mm, to transmit a drilling torque of 6 t.m to an arm 3.

[0080] The invention also relates to a use of the drill bit 1 implementing a method comprising a step of fixing the worm screw 5 on the drill bit 1, as illustrated in [Fig.6].

[0081] Then, a tube 6 is inserted around the worm 5, intended to remain in the well. The drill bit 1 is then in the retracted position.

[0082] When drilling begins, the free end 33 of the arms 2 touches the ground. The worm screw 5 is rotated, which causes the drill bit 1 to rotate in the drilling direction. The arms rub the ground and are rotated. By friction and pressure on the ground, the arms gradually deploy during a deployment step. Only the friction and the pressure of the arms 3 on the ground cause the arms 3 to deploy. The drill bit 1 moves from the retracted position to the unlocked deployed position.

[0083] When deployment is fully completed, the worm screw 5 continues to rotate but it only rotates the base 4 during a locking step. Indeed, friction prevents rotation of the body 2 and the arms 3. Thus, there is a relative rotation of the base 4 with respect to the body 2. This rotation makes it possible to position the locking surface 41 of the base 4 in contact with the arm 3. The arm 3 is then in the deployed and locked position.

[0084] A drilling step can then begin in which the worm screw 5 continues to rotate and drives the entire drill bit 1 and therefore the arms 3 in rotation. The drill bit is driven into the ground as well as the tube 6 which is positioned around the worm screw 5. The well comprising the tube 6 is then created.

[0085] To obtain a well of great length it is possible to position a new tube 6 after the initial tube around the worm screw 5.

[0086] When the well is finished, and in order to recover the drill bit, the method comprises an unlocking step in which the worm screw 5 is turned in a direction opposite to the drilling direction. In this way, the base 4, and more particularly the surface of locking 41, is rotated relative to the body 2 so that there is only contact between the surface 41 and the arm 3. The drill bit 1 is then in the deployed and unlocked position.

[0087] When the worm screw 5 is withdrawn, the arms 3 of the drill bit 1 fold back under the action of gravity and possibly by contact with the tube 6. The drill bit 1 then takes the retracted position and can pass into the tube so as to be extracted from the borehole.

[0088] By this method, it is possible to position thick tubes in the borehole, such as concrete tubes.

[0089] Of course, the invention is not limited to the embodiments described and shown in the attached figures. Modifications remain possible, in particular from the point of view of the constitution of the various elements or by substitution of technical equivalents, without departing from the scope of protection of the invention.

Claims

Claims

1. Retractable drill bit (1) for drilling a well comprising at least one body (2) provided with at least one arm (3), said arm (3) being movable between a retracted position, in which the arm (3) forms an angle (a) with a drilling rotation axis (A) included in a first angle value range, and a deployed position in which the arm (3) forms an angle (|3) with the drilling rotation axis (A) included in a second angle value range, the at least one arm (3) being movable about a deployment rotation axis (32), characterized in that when the arm (3) is in the deployed position, the deployment rotation axis (32) and a free end (33) of the arm (3) are positioned on either side of a median axis (M) of the body (2) and in that the drill bit comprises at least one locking device for the at least one arm (3) in the deployed position and a fixing base (4) intended to fix the drill bit (1) on a worm screw (5),a locked position of the arm (3) being achieved by a rotation of the body (2) relative to the base (4).,

2. Drill bit (1) according to claim 1, wherein the deployment rotation axis (32) is positioned in a plane forming an angle between [50°, 110°], preferably [80°, 100°], and in particular 90° with the drilling rotation axis (A).

3. A drill bit (1) according to claim 2, wherein the deployment rotation axis (32) is not coincident with the drilling rotation axis (A).

4. Drill bit (1) according to any one of claims 1 to 3, in which a ratio of the diameter (D2) of the drill bit (1) in the deployed position to the diameter (D1) of the drill bit (1) in the retracted position is between [1; 5], preferably [1; 3] and in particular 2.

5. A drill bit (1) according to claim 1, wherein the base (4) comprises a locking surface (41) configured to come into contact with the at least one arm (3) in the locked position.

6. Drill bit (1) according to any one of the preceding claims, in which the locked position is achieved by a rotation along the drilling axis (A) of between [0°, 180°], preferably [60°, 120°] and in particular 70°.

7. A drill bit (1) according to any preceding claim, wherein the body (2) has a flat contact surface (21) with the arm (3) in the deployed position.

8. A method of using a drill bit (1) according to any one of the claims- previous instructions, including: - a step of fixing a worm screw (5) on the drill bit (1); - a step of deploying at least one arm (3) of the body (2); - a step of locking the at least one arm (3) in the deployed position.

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