United States Patent 3697940

A borehole telemetering apparatus comprises a protective casing coaxially mounted to the drill pipe. The casing includes a magnetostrictive or electrostrictive acoustic transducer which is in acoustic contact with the drill pipe, a silicon controlled rectifier and power supply for controlling the activation of the transducer. The transducer is coupled to the drill pipe preferably by means of an acoustic transformer and the lengths of individual drill pipes are adjusted to the transducer frequency.

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Publication Date:
Filing Date:
Primary Class:
International Classes:
E21B47/16; (IPC1-7): G01V1/40
Field of Search:
340/18NC,18LD,8MM,18 166
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Primary Examiner:
Bennett Jr., Rodney D.
Assistant Examiner:
Buczinski S. C.
Parent Case Data:

This is a continuation-in-part application of application Ser. No. 530,246, filed Feb. 15, 1966, entitled Signalling Device for Bore Logging, and now abandoned.
What is claimed is

1. A signalling device for bore logging including a sonic transmitter unit attached to a lower section of the drill string disposed in a borehole, and a sonic receiver unit disposed on the earth's surface and secured to an upper section of the drill string, said sonic transmitter unit comprising at least an electroacoustic transducer having a body mechanically deformable by the effects of electricity and capable of vibration, an acoustic transformer having an upwardly converging conical configuration, said transformer being of a length substantially equal to the half of the wave length of said vibrations, the upper base of said transformer being integral with said upper section of said drill string, said body being acoustically connected to the lower base of said accoustic transformer to transmit vibrations to said receiver unit, electric power pulse generating means electrically connected to said transducer for generating damped vibrations in said transducer, power supply means for feeding said power pulse generating means, switch means connected between said power pulse generating means and said power supply means, and a survey instrument coupled with said switch means for activating said transducer as a function of a predetermined condition of said borehole, said sonic receiver unit comprising an electroacoustic pick-up element, filter means coupled to said pick-up for separating said damped vibrations from accidental noise, amplifier means coupled to said filter means, and indicating means electrically connected to said amplifier means.

2. The signalling device according to claim 1 wherein said survey instrument is a radiation detector adapted for actuating said switch means when detecting radiation in said borehole.

3. A sonic transmitter unit for a signalling device for bore logging comprising a drill section, a hermetically sealed casing concentrically surrounding said drill section, an acoustic transformer having an upwardly converging conical configuration, said transformer being integral with said drill section, said casing being secured to said acoustic transformer, said casing including an electrical power supply with two output terminals; a power pulse generator comprising a capacitor connected to one power supply output terminal via a resistor, a semiconductor switching device having a switching control circuit actuated by said switch means; an electroacoustic transducer having two electrical input terminals,, said transducer being terminated by an upper vibrating surface acoustically connected with said acoustic transformer, one of said transducer terminals being connected to said capacitor and the second transducer terminal being connected to the second power supply output terminal to charge said capacitor via said resistor, whereby said semiconductor switching device being connected for abruptly discharging said capacitor through said transducer; and a pendulum inclinometer the pendulum of which forms one contact of said switch means,, the second contact of said switch means being adjustably supported in the path of said pendulum to provide a connection when the angular position of the pendulum resulting from the inclination of the borehole corresponds to a preset angular position of said second contact.

4. The sonic transmitter for a signalling device according to claim 3 wherein said semiconductor switching device is a silicon controlled rectifier the gate of which forms said switching control circuit.

5. The sonic transmitter for a signalling device according to claim 4 wherein said switching device control circuit further comprises a trigger circuit for producing a train of trigger pulses of a definite frequency.

The present invention relates in general to signalling systems for bore logging.

In particular, the present invention relates to a sonic transmitter attached to a drill string at the bottom of a borehole for transmitting sonic signals upwardly through the acoustically adjusted drill string when a joined survey instrument, such as an inclinometer or detector of radioactive radiation, is actuated.

Known signalling devices generate sonar signals by striking a movable metal rod of an electromagnet against a body attached to the drill pipe through which vibrations are transmitted to the earth's surface. However, these sound generating mechanisms are based on a mechanical striking of the drill pipe and can be used for short distance signalling only because of the fact that the resulting effective energy is low. In addition, it is difficult to separate these signals from accidental vibrations.

In other known devices, an electroacoustic transducer is actuated by a signal generator for continuous wave operation at frequencies which are different than its own characteristic resonant frequency. A disadvantage of such devices resides in the fact that associated battery power supplies becomes very quickly exhausted and, due to the continuous energization, the transducer cannot be constantly operated at its peak power.

Therefore, a primary object of the present invention is to provide a signalling system for bore logging having a sonic transmitter unit possessing a compact structure without movable parts and including a homogenous unitary casing.

Another object of the present invention is to provide a sonic transmitter circuit which is immediately responsive to a predetermined condition in the borehole, the signal of which can be coded and easily separated from accidental noises and/or noises which are unrelated to said condition.

A still further object of this invention is to provide a transmission path in a drill string which has a reduced acoustic resistance, especially with respect to joints of individual drill string sections.

Yet another object of the invention is to provide a battery powered transmitter unit for use with the above system having a minimum power consumption at peak transducer efficiency.

Another object of the present invention is to provide receiver means by which proper sonic signals are detected and/or indicated and/or recorded.

The present invention fulfills the aforementioned objects and overcomes limitations and disadvantages of prior art solutions to drilling problems. According to one aspect of the invention, a borehole transmitting apparatus includes a protective casing coaxially supported by a drill pipe. Within this casing, an electrostrictive acoustic transducer is supported in acoustic contact with the drill pipe. A power pulse generator and associated power supply are cooperatively connected to the transducer, and said transducer is responsive to this pulse generator. An acoustic transformer couples the transducer with the drill pipe.

The invention will be more clearly understood from the following description of specific embodiments of the invention, together with the accompanying drawings, wherein similar reference characters denote similar elements throughout the several views, and in which:

FIG. 1 is a sectional schematic elevational view of a sonic transmitter unit according to this invention;

FIG. 2 is a schematic electrical diagram of a sonic transmitter unit according to this invention;

Fig. 3 is a schematic elevational view of a complete signalling system of this invention for use in orientating a deflection wedge in a borehole;

FIG. 4 is a fragmentary sectional elevational view of a portion of the unit shown in FIG. 1 utilizing a radiation detector; and

FIG. 5 is a schematic sectional elevational view of another preferred embodiment of the invention.

Referring now to FIG. 1, a sonic transmitter unit is shown including a cylindrical protective casing 10 coaxially mounted to a drill string or pipe 3 such as by welding. Casing 10 is provided at one end thereof with a removable lid 18 which is hermatically sealed by means of a seal 51. Within casing 10, a sonic transmitter and a survey means are located. The survey means includes an inclinometer 16 having a hollow toroid or ring of insulating material wherein a quantity of mercury preferably in the shape of a ball 163 is free to move circumferentially around the axis of symmetry of the drill string. Two spaced contacts 161 and 162 are arranged in the path of movement of mercury ball 163 such that electrical connection is made therewith when the drill string is inclined and turned until the contacts attain a lowermost stable position with the mercury ball. Mercury ball inclinometer 16 is removable and may be replaced with another kind of survey means, such as a detector of radioactive radiation, or a thermometer which actuates switching means. The mercury ball inclinometer may be replaced by a hinged pendulum.

Regardless of the form of the survey means, the sonic transmitter is actuated when contacts such as 161 and 162 are electrically connected.

The transmitter includes an acoustically active element in the form of an electroacoustic transducer 11 of magnetostrictive or electrostrictive material and of a suitable geometric configuration which causes the radiating surface of transducer 11 to acoustically contact the upper portion of drill pipe 3. In the embodiment shown in FIG. 1, a magnetostrictive transducer 11 includes an excitation winding 111. Transducer 11 is acoustically connected at point 52 with a shoulder of a recess in drill pipe 3.

The transmitter further includes a power supply 17, a low voltage to high voltage converter 15, a rectifier 13 and a power pulse generator 12.

As shown in a block circuit diagram in FIG. 2, the power supply 17, which preferably includes low voltage batteries or shock resistant accumulators, is connected to a low direct current voltage-to-high alternating current voltage convertor in one branch, and in another branch through switch means 161, 162 and 163 to the input of a transistorized trigger pulse generator 14. The high alternating current voltage output of convertor 15 is rectified by a rectifier 13. Rectifier 13 is electrically connected to power pulse generator 12 as follows: A first output terminal of rectifier 13 is connected through a resistor 123 with one outlet of a storage capacitor 122 and is further connected with the anode of a silicon controlled rectifier 121. A second output terminal of rectifier 13 is connected directly to the cathode of the silicon controlled rectifier 121. The second outlet of capacitor 122 is connected to a cathode of silicon controlled rectifier 121 through winding 111 of transducer 11. Of course, trigger pulse generator 14 is not necessary for the present invention to be operative where other than the disclosed type of power pulse generator is used.

FIG. 3 schematically shows the complete assembly of the signalling system for bore logging according to the present invention, whereby the adjustment of individual pipes of the entire drill string 3 enables an optimum transmission path for acoustic energy, as later explained with reference to FIG. 5. The aforementioned transmitter unit is hermetically sealed in casing 10 and is situated at the lower end of drill string 3 within the illustrated borehole. An electroacoustic pick-up means 21 is acoustically connected to uppermost portion of string 3 and is coupled to a receiver unit consisting of an electric signal filtering means 22, an amplifier 23 and an indicator or alarm device 24. Filtering means 22 is of any suitable conventional design that will insure that the electric signal transformed from the transmitted acoustic signal by the pick-up means 21 is separated from disturbing electric signals resulting due to the accidental noise in the drill string.

Describing now the operation of the signalling device, in order to transmit sonic pulses from transducer 11 at its maximum permissible load and with the least amount of current drain of the batteries in power supply 17, transducer 11 is activated by discharge pulses from the storage condenser 122 to generate damped sonic vibrations at the transducer's own frequency. The direct current high voltage from the output of rectifier 13 charges the storage capacitor 122 slowly through resistor 123, and winding 111 of transducer 11. The silicon controlled rectifier 121 is electrically dimensioned so as to stay in a non-conductive condition even at the maximum charge of condenser 122. Only in the event that the switch 161, 162 and 163 connects trigger pulse generator 14 to power supply 17, will generator 14 start to generate trigger pulses which abruptly turn the silicon control rectifier into a conductive state. Condenser 122 is very rapidly discharged through winding 111. The resulting high voltage and high current pulse of very short duration excites the magnetostrictive transducer 11 into damped vibrations of a predetermined signal frequency which is a function of parameters which include the mechanical structure and configuration of the transducer 11. Since transducer 11 is in acoustic contact with drill string 3 at point 52, these short-time powerful vibrations propagate upwardly in the form of an acoustic pulse through the walls of drill string 3, and are detected and converted back into electrical signals by the pick-up means 21. These signals are separated from accidental noises by the filter means 22, and are amplified and indicated by a suitable indicating device, generally designated 24. After the voltage on condenser 122 has dropped to zero, and the silicon controlled rectifier has returned to its non-conductive state during the interval between two successive trigger pulses, condenser 122 becomes fully charged again until the next pulse from the trigger generator 14 initiates a discharge.

One of many applications of the above-described signalling system includes its use with the orientation and releasing of a deflecting wedge commonly used in an inclining borehole for correcting the inclination of the borehole. In the event that the borehole is inclined and the drill assembly is brought to rest, the mercury ball of inclinometer 16 will remain in the lowest point within the circumferential channel of inclinometer 16 due to gravity. Consequently, the desired orientation of the guiding surface of a deflecting wedge 41 can be ascertained from indicator 24. Since the angular position of contacts 161 and 162 with respect to the angular position of deflecting wedge 41 is predetermined and thus known in advance, the final position and orientation of wedge 41 may be set. For this purpose the inclinometer is made integral with rotatable lid 18 by means of a locking nut 32 which matingly engages a thread 31 on the drill pipe 3. The orienting operation is thus simplified, since the drilling crew above ground merely slowly turns the drill string 3 until contacts 161 and 162 reach the mercury ball which has sought the lowermost portions of the hollow inclinometer. The transmitter is thereby actuated and an alarm signal from the receiver is generated. Since the guiding surface of wedge 41 is preset at 180 degrees from contacts 161 and 162, the sloping guiding surface is correctly oriented for biasing the drilling tool against the inclined wall of the borehole in order to restore the desired drilling borehole angle. The wedge 41 can subsequently be released by increasing fluid pressure in conventional types of shear means designated 4.

Another preferred embodiment of the present invention employed for the detection of radioactive layers during the drilling process is shown in FIG. 4. Instead of an inclinometer, a solid state detector of radioactive radiation 16' is used to control switching in a transmitter circuit. The output signal from detector 16' is applied to a base 163' of a transistor. The emitter 162' and collector 161' of the transistor are analagous to switch contacts 162 and 161, respectively, of the switch described for FIG. 2, and connect the trigger pulse generator to the power supply.

FIG. 5 shows a preferred embodiment of a transmitter unit according to this invention, wherein the vibrating member is an electrostrictive transducer 11', preferably made of lead titanate zirconate with electrodes 111' and 111", the transducer being acoustically coupled to drill pipe 3 by means of an acoustic transformer 6. The acoustic transformer 6 has an upwardly tapered conical shape and is of the same material as the drill pipe 3 and is adapted for being joined thereto through an intermediate joint piece 3'. A ring-shaped transducer 11' is coaxially mounted on drill string 3, and is acoustically coupled to the base of cone 6 which in turn, concentrates the acoustic energy radiated from the relatively large top surface of transducer 11' to the relatively small sectional surface of drill string 3.

A protective casing 10 of the type already described for FIG. 1 is connected to cone 6 at a point which is a distance designated λ'/4 from the vibrational radiating or excitation source comprising an upper surface of transducer 11'. This point coincides with a first nodal point at which there is zero deflection due to vibration. The wave length of vibration is designated λ for purposes of illustration.

The difference between λ and λ' results from the conical shape of acoustic transformer 6 slightly altering the position of the first nodal point, which would lie at a distance of λ/4 if the cross section of transformer 6 were uniform. Thus, λ'/4 in magnitude than λ/4.

Provided that no acoustic transformer is employed, as shown in FIG. 1, the maximum amplitude of the vibrational signal occurs at a distance λ/2 from the vibrational source. It is therefore advantagous to connect the transmitter unit at the latter point (λ'/2 ) to the upper portion of drill string 3 in FIG. 5. The intermediate connecting joint piece 3' is of a length λ/4 or of a magnitude of a whole integer multiple thereof.

To create a reliable acoustic connection between respective drill string sections, a thin metal (e.g. aluminum) ring 5 or grease, is disposed in each joint 30, as illustrated in FIG. 1. To further minimize transmission losses resulting from undesirable reflections of energy, the lengths of individual drill pipes with adjacent joint pieces are equal to whole integer multiples of λ/4. Since electrostrictive transducer 11' has no excitation winding but rather includes electrodes 111' and 111" it is possible to connect same in parallel to storage condenser 122 charged through the resistor 123. The operation of the transmitter circuit will remain the same as that previously described.

The embodiments of the invention particularly disclosed are presented merely as examples of the invention. Other embodiments, forms and modifications of the invention coming within the proper scope of the appended claims, will of course readily suggest themselves to those skilled in the art.