FR2777595A1 - Information transmission for ground drilling machine includes inductive magnets transmitting data via support cables between control and drill head - Google Patents

Abstract

The ground drill uses the support cables as a transmission to convey information to the drill head. The transmission is for information to and from a drilling head suspended to drill into the ground. The head is suspended by supports (210) which are at least partially electrically conducting. A first electro magnet (220) is mounted near to the drilling head to transmit or receive a current which flows in a closed loop. A second electromagnet (222) is mounted near the surface to operate in similar manner. Both units are mounted to be in electromagnetic contact with one of the electrically conducting suspension wires (210) to enable communication between them. Further circuits convert the information to be transmitted into a series of pulses, with a control signal being produced as a function of this control signal.

Description

 The present invention relates to an installation for transmitting information in a drilling excavation between the drilling tool and the ground surface, this installation using at least part of said drilling tool.

 To carry out more or less deep drilling of substantially circular section, drilling tools are used which are mounted at the end of a train of drilling tubes, the tubes being assembled to each other as and when I tool down. The tubes which are made of an electrically conductive material serve on the one hand to exert the necessary pressure under the drilling tool and on the other hand to allow the transmission of the rotational movement of the drilling tool. It is also known that for such a type of drilling, drilling mud which has a certain electrical conductivity is injected and fills the borehole as it progresses. It is used to reassemble debris cut by the tool.

 During these operations, it is very useful to be able to bring information to the ground surface on, for example, the direction relative to the vertical of the drilling tool in order to be able to possibly modify the direction, as well as possibly d other information taken by sensors mounted on this tool.

 When it is desired to make trench-shaped excavations, drilling rigs of the bucket bucket type or similar are most often used. The positioning in the ground of such a machine must be constantly checked in order to correct in real time, if necessary, a deviation from its trajectory relative to the vertical. For this purpose, inclinometers and orientation members such as pushers actuated by actuators are provided on the drilling rig. It is important to be able to bring all this information to the surface in order to be able to check on the surface the proper functioning of the drilling rig and the conformity of the trench drilled with the predefined shape.

 In both cases, for the transmission of this information, it has been proposed to mount an electrical transmission cable between measuring or detection devices mounted on the drilling tool and on the ground surface.

However, this technique has drawbacks, in particular linked to the risks of breaking or damaging the cable.

 Another solution to this problem is to use radio transmission between the measuring devices and sensors mounted on the drilling tool and the ground surface. However, when the drilling has a significant depth, the conditions for transmission of the radio signal become very difficult to implement.

 There is therefore a real need to develop an installation for transmitting information between the drilling tool and the ground surface which is not likely to be damaged during drilling operations and which is compatible with large boreholes. depth.

To achieve this object, according to the invention, the installation for transmitting information in a drilling excavation equipped with a drilling tool serving to carry out this excavation between the bottom of the excavation and the ground surface, said tool being suspended from elements at least partially electrically conductive, and the content of said excavation including said elements being capable of constituting a closed loop conducting electricity, is characterized in that it comprises:
- a first electrical device disposed near said tool for emitting and / or receiving an electric current flowing in said closed loop;
- a second electrical device disposed near the surface of the ground for emitting and / or receiving an electric current flowing in said closed loop;
means for converting information to be transmitted in the form of a series of pulses;
- Means for developing an electrical signal for controlling the predetermined frequency modulated as a function of said pulses;
- Means for applying to one of said devices said electric control signal so that it emits an electric current corresponding to said electric control signal; and
- Means for receiving from one of said electrical devices said electrical current which has passed through said closed loop.

According to a first embodiment of the invention applied to the case where the drilling machine is suspended from cables and hoses,
The installation is characterized in that said drilling tool is suspended from elements at least partly conductive comprising at least metallic cables or flexible pipes at least partly conductive;
in that said closed electrical loop is constituted by two of said elements at least partly conductive; and
in that said first and second electrical devices are each mounted on one of said elements.

 It is understood that in this embodiment, a modulated alternating current which carries the information is circulated in a closed conductive loop constituted by the cables or the hoses. Using the second electrical device, the current flowing in the current loop is detected and received, whereby the corresponding information can be collected.

In a second embodiment of the invention more particularly suited to the case of drilling using a tool fixed to the end of a train of tubes, the installation is characterized in that said drilling tool is suspended from the lower end of a train of electrically conductive drilling tubes, the inner face of which is covered with an insulating layer and in that the drilling excavation is filled with a mud of electrically conductive drilling also filling the interior of said train of tubes;
in that said closed loop is formed on the one hand by the drilling mud filling said drilling tubes and on the other hand by the tube string and by drilling mud in said excavation outside said drilling tubes; and
in that said first electrical device is mounted near the upper end of the tube string and said second measuring device near the bottom end of the tube string.

 In this second embodiment, it is understood that the internal and external zones filled with the conductive drilling mud limited by the drilling tubes whose internal face has been coated with an insulator are used as closed conductive loop. It goes without saying that in this case, special measures are taken to ensure an electrical connection between the internal and external zones filled by the drilling mud at the lower and upper ends of the wellbore.

Other characteristics and advantages of the invention will appear better on reading the following description of several embodiments of the invention given by way of nonlimiting examples. The description refers to the appended figures in which:
- Figure 1 is an elevational view of a first embodiment of the installation applied in the case where the drilling tool is suspended from a lifting machine;
- Figure 2 is a schematic view of the closed electrical circuit corresponding to the first embodiment;
- Figure 3 is a diagram showing an embodiment of the electronic circuit associated with the transmission and reception coils;
- Figure 4 is a diagram showing a form of alternating current usable in the invention;
- Figure 5 is a vertical sectional view of a second embodiment of the installation applied to drilling by a drill pipe; and
- Figure 6 is a partial view showing the mounting in the drilling tubes of the detection and emission coils.

 Referring first to Figures 1 to 4, we will describe a first embodiment of the invention applied to the case where the drilling tool is of the type suspended from a lifting device.

 In Figure 1, there is shown a lifting device 200 which supports a drilling tool 202 for example of the bucket bucket type. This tool makes a trench 204. The orientation of the drilling tool 202 is given by a muffle 206 suspended from the end of the boom of the lifting machine. A cable 208 connects the upper end of the drilling tool 202 to the muffle 206.

 Flexible hydraulic lines 210 which are wound on drums 212 integral with the muffle 206 serve to convey a hydraulic fluid to the drilling tool to control in particular the movement of its buckets 216. As is known, the flexible lines are reinforced by a continuous metallic braid over its entire length. Consequently, flexible pipes constitute an electrical conductor. It is understood that thus, the assembly constituted by the drilling machine 202, the flexible conduits 210 and the muffle 206 constitute a closed electrical circuit in which it is possible to circulate an electric current used to transmit information.

 The information transmission installation comprises a first electrical device 220, essentially consisting of coils as will be explained later, arranged on a flexible pipe near the drilling machine. Similarly, near the muffle 206, there is a second electrical appliance 222 essentially consisting of coils as will be explained. The lower coil group 220 is electrically connected to a first set of electrical circuits 224 on board the drilling tool 202 and the upper coil group 222 is connected to electric circuits 226 on board, for example in the cabin of the vehicle. lifting.

 In the particular example considered, the drilling tool 202 comprises one or more verticality control inclinometers, not shown, which are connected to the electrical circuits 224 and which make it possible to measure the inclination of the tool. In addition, the drilling rig is equipped for example with pushers such as 230 which can be actuated by actuators not shown to correct the position of the drilling rig. In addition, as is known, the trench being excavated is filled with drilling mud 232.

 As best shown in FIG. 2, each group of lower 220 and upper coils 222 is constituted by a magnetic toroid, for example made of ferrite 240 which surrounds the conductive element constituted for example by flexible pipe 210. mounted two coils 242 and 244 wound on the torus and which serve respectively, as will be explained later, for the emission of electric current and for the reception of electric current possibly circulating in the closed conductive loop.

 Before describing in detail the circuits connected to the coils 220 and 222, it should be noted that the information is converted into binary digital form, that is to say into a series of pulses corresponding to l or absence of pulse corresponding to 0. These pulses are used to modulate an electrical signal of predetermined frequency, preferably less than 20 kHz. In FIG. 4, the lower diagram shows the pulses (S) and the upper diagram shows the corresponding modulated alternating control signal.

 Referring now to FIG. 3, there will be described in detail the electrical circuits making it possible to develop the electrical control signal to be applied to a coil in transmission or to process the signal collected by a coil in reception.

 On the left part (A), the circuit 224 is shown associated with the lower coils 220 and on the right part (B), the circuit 226 is represented associated with the upper coils 222. The difference lies in the mode of power supply of the various components of these circuits.

 Circuit 224 will first be described. This circuit is connected to the terminals of the transmission coil 242 and of the reception coil 244. The circuit 224 is controlled by a microcontroller 58 of which a first series of inputs 60 receives the information delivered by the sensors mounted on the drilling tool and a series of inputs-outputs 62 connected to the actuators of the drilling tool. The microcontroller 58 is programmed to convert the information to be transmitted received from the sensors into analog form in binary digital form. The corresponding pulses of the digital signal are applied to its output 64. The microcontroller 58 is also programmed to decode the binary pulses which it receives on its input 66.

 The components of circuit 224 are supplied by a battery 68 which is permanently connected to a power supply unit 70 and to a carrier detection circuit 72. When the detection coil 244 receives a signal, a modulated alternating voltage appears on its terminals and the presence of this voltage is detected by the circuit 72 which controls the activation of the power supply unit 70. All the components of the circuit 224 are then supplied. The electrical signal collected by the detection coil 244 is applied to an input circuit 74 and to a filter 76 which is tuned to the frequency of the alternating signal. The filtered signal is applied to the input of a demodulator 78 which is set to the predetermined frequency of the alternating signal. The demodulator 78 delivers on its output 78a the binary digital signal containing the information which is applied to the input 66 of the microcontroller 58. Following the reception phase, the power supply unit is controlled to reset the circuit 224 standby state.

 When the circuit 224 must transmit a transmission signal to the coil 242, the power supply unit 70 controls the supply of the components of the circuit.

 The alternating signal of predetermined frequency is delivered by an oscillator 82 which delivers on its output 84 the electrical signal of frequency.

The output 84 is connected to the terminal A of an electrically controllable switch 86 whose output 88 is connected to the input of an output amplifier 80 itself connected to the supply coil 242. The terminal B of the switch 86 is connected to ground. The control signal of the switch 86 is delivered by the output 64 of the microcontroller58 and therefore consists of a binary digital signal S corresponding to the information to be transmitted. The microcontroller 58 contains the programming elements which make it possible to convert the analog information received from the sensors into this digital signal.

 When the signal S corresponds to a 1 (presence of a pulse), the terminal A of the switch is connected to its output 88. Throughout the duration of this pulse, the amplifier 80 receives the alternating signal delivered by the oscillator 82 .

 On the other hand, when the signal S corresponds to a 0 (absence of pulse), the output terminal of the switch 86 is connected to ground and the amplifier 80 receives a zero voltage.

 The amplifier 80 therefore applies to the transmission coil 242 an alternating signal of predetermined frequency which is modulated by the logic levels of the signal S. This modulated alternating control signal which is applied to the coil 242 will produce in the closed conducting loop an electric current having the same form.

 It is understood that, at the end of an S pulse, the frequency signal can have any amplitude between its maximum and zero. To avoid lag phenomena, it would be interesting for the frequency signal to be interrupted when it passes through zero. For this, provision can be made for the microcontroller to receive information representative of the amplitude of the frequency signal delivered by the oscillator. As soon as the digital signal S passes from the value 1 to the value, the control signal of the switch 86, to pass from the terminal A to the terminal B will be emitted only at the moment when the frequency signal passes through the zero value.

Thus, the alternation train corresponding to the numerical value 1 will effectively end when it passes through zero.

 However, when the conductive properties of the closed electrical loop are poor, for example in the case where the tool is at a great depth, it may be advantageous to increase the electrical energy of the alternation packet of the corresponding alternating signal. to a 1. For this, the microcontroller 58 can be programmed so that during the passage from 1 to O, the alternating signal is interrupted on the first passage thereof by a maximum which follows the transition from 1 to 0.

Advantageously, the microcontroller 58 is programmed to allow the control of the implementation of one or the other of these modes of modulation of the alternating signal.

 The circuit 226 shown in part B of FIG. 3 is identical to the circuit 34 except as regards the electrical supply of the components. Indeed, this circuit being on the surface, it is not useful to seek to limit the consumption of electrical energy. The power supply 70 therefore permanently connects the battery 68 to the components of the circuit and the carrier detection circuit 72 can therefore be omitted.

 Referring now to Figures 5 and 6, we will describe a second embodiment of the transmission installation applied in the case of drilling by a tool mounted at the lower end of a drill pipe train.

 In Figure 5, there is shown in vertical section a wellbore 10 opening into the ground 12 and a drilling tool 14 mounted at the end of a train of drill tubes 16 formed by the drill tubes 18 The head of the wellbore 20 is also shown schematically allowing the assembly of the drilling tubes to one another, as well as the rotation of these tubes for the activation of the drilling tool 14. In addition, as is well known, the wellbore 10 is filled as it advances with an electrically conductive drilling mud, this drilling mud firstly filling the axial passage 24 defined by the tubes drilling, as well as the annular space 26 extending between the tube string 16 and the wall of the wellbore 10.

 The internal wall of each tube which is referenced 1 8a is covered by a layer 28 of an insulating material as shown in Figure 6. This insulating layer can be produced for example using an insulating resin or a relatively resistant special paint, by rylsanisation, or by a specific heat treatment of the internal face of the metal constituting the drill pipe. The entire train of tubes thus constitutes an insulating sleeve in which the conductive drilling mud is contained.

 The internal insulation 28 of the tubes 18 therefore separates the electrically conductive media 24 and 26 over the entire length of the train of tubes.

In order to produce a closed loop that conducts electricity, a conductive connection is created at the lower end and at the upper end of the conductive media 24 and 26. For this, as shown in Figure 6, it is provided that the internal insulation layer 28 of the tube 18i on which is mounted the drilling tool is removed at the lower end 18 'of this tube. Thus, an electrical connection is made between the lower ends of the conductive media 24 and 26. At the upper end of the conductive media 24 and 26, an electrical connection is also made by any suitable means. An electrically conductive closed loop is thus obtained, formed firstly by the column 24 of conductive mud and secondly by the train of tubes 18 and the external annular zone of drilling mud.

 The installation also includes a first electrical device 100 for injecting an electrical current into the closed conductive loop or for collecting a current which circulates therein and mounted at the lower end of the train of tubes and a second electrical device 102 having the same functions as the first but maintained at the upper end of the closed conductive loop. More specifically, the apparatus 100 is mounted in the lower tube 18i above the end portion 18 'devoid of internal insulation and the apparatus 102 is maintained in the train of tubes at a level slightly lower than the upper level of the conductive medium 26.

 Each device 100 or 102 is constituted by a magnetic toroid 104, preferably made of ferrite, and by two coils 106 and 108 whose turns are wound on the torus. The coil 106 is used to inject current into the closed conductive loop and the coil 108 is used to collect the current flowing in the closed conductive loop. The coils 106 and 108 of the device 100 are connected to an electrical circuit 34 while the coils 106 and 108 of the device 102 are connected to the surface circuit 36.

 The circuits 34 and 36 associated with the electrical devices 100 and 102 are respectively identical to the circuits 224 and 226 described in conjunction with FIG. 3. It is therefore not useful to describe them again.

Claims (10)

 1. Installation for transmitting information in a drilling excavation (204, 10) equipped with a drilling tool (202, 14) used to carry out this excavation between the bottom of the excavation and the ground surface, said tool being suspended from elements at least partially electrically conductive (210, 18), and the content of said excavation including said elements being capable of constituting a closed loop conducting electrically, characterized in that it comprises :  - a first electrical device (220, 100) disposed near said tool for emitting and / or receiving an electric current flowing in said closed loop;  - a second electrical device (222, 102) arranged near the surface of the ground for emitting and / or receiving an electric current flowing in said closed loop;  - means (58) for converting information to be transmitted in the form of a series of pulses,  - means (85) for producing an electrical signal for controlling the predetermined frequency modulated as a function of said pulses,  - means (80, 34) for applying to one of said devices said electric control signal so that it emits an electric current corresponding to said electric control signal; and  - Means (22, 36) for receiving from said second electrical appliance said electrical current which has passed through said closed loop.  2. Installation for transmitting information according to claim 1, characterized in that said drilling tool (202) is suspended from elements (210) at least partially conductive comprising at least metal cables or flexible pipes at least in conductive parts;  in that said closed electrical loop is constituted by two of said elements (210) at least partly conductive; and  in that said first and second electrical devices (220, 222) are each mounted on one of said elements.  3. Installation according to claim 2, characterized in that each device (220, 222) comprises a magnetic toroid (240) surrounding one of said elements at least partly conductive (21 0), a first emitting coil (242, 244) mounted on said torus and a second receiving coil (244, 242) mounted on said torus.  4. Installation for transmitting information according to claim 1, characterized in that said drilling tool (14) is suspended from the lower end of a train of electrically conductive drilling tubes (18), the face of which internal (18a) is covered with an insulating layer (28) and in that the drilling excavation is filled with an electrically conductive drilling mud also filling the interior of said train of tubes;  in that said closed loop is constituted on the one hand by the drilling mud (24) filling said drilling tubes and on the other hand by the train of tubes (18) and by drilling mud (26) in said excavation outside of said drill pipes; and  in that said first electrical device (102) is mounted near the upper end of the tube string and said second measuring device (100) near the lower end of the tube string.  5. Installation according to claim 4, characterized in that each electrical device comprises a magnetic toroid (l04) mounted inside the tube train, a first transmitting coil (106) mounted on said torus and a second receiving coil (108 ) mounted on said torus.  6. Installation according to claim 1, characterized in that it comprises, on the first device (100, 220), analog / digital conversion means (58) for converting the data to be transmitted into a series of pulses, a transmitting coil (106, 242), an alternating current generator (82) connected to the transmitting coil, a switch (86) mounted between the alternating current generator and the transmitting coil and actuated by the converter means so as to pass the alternating current (I) in the transmitter coil in the presence of a pulse (1) and not to pass it in the absence of pulse (0), and, on the second device, a receiver coil (244, 108 ) to collect said sequence of pulses, and means (58) connected to the take-up reel to reconstruct said sequence of pulses (S).  7. Installation according to claim 6, characterized in that it comprises a standby module (78) which is capable of activating all of the electrical modules present on one of the devices when an induced current (I) circulates in the closed electrical circuit and to deactivate these modules after a predetermined time interval has elapsed since the last detection of an induced current (I) in the closed electrical circuit.  8. Installation according to any one of claims 6 and 7, characterized in that it also comprises, on the second device, an analog / digital converter (58), a transmitting coil (242), a current generator (82 ) connected to the transmitter coil, a switch (86) mounted between the alternating current generator and the transmitter coil and actuated by the converter so as to pass the alternating current (I) through the transmitter coil in the presence of a pulse ( 1) and not to pass it in the absence of a pulse (0) and, on the first device, a take-up reel (244) and means connected to the take-up reel to reconstruct said sequence of pulses.  9. Installation according to any one of claims 7 and 8, characterized in that it comprises means (58) of phase detection of the signal delivered by the alternating current generator (82) for actuating the switch (86) for that it does not pass into the switching position (B) between the alternating current generator and the zero potential until the current delivered by the generator is canceled during its alternation, during the passage of a pulse ( 1) no pulse (0).  10. Installation according to claim 9, characterized in that it comprises a phase detection module (58) connected to the alternating current generator (82), which actuates the switch (86) so that it does not pass into position ( B) switching between the alternating current generator and the zero potential, only at the moment when the current delivered by the generator is maximum during its alternation during the passage of a pulse (1) to an absence of pulse ( 0).