NL8102401A - APPARATUS AND METHOD FOR PROCESSING SIGNALS IN A DRILLING HOLE DURING DRILLING - Google Patents

Description

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Apparatus and method for processing signals in a borehole during drilling.

The invention relates to a device and a method for processing signals in a borehole during drilling. The invention also includes a drill gauge remote adapter.

Different systems of measurement during drilling (Measurements While Drilling = MWD) have been proposed for making measurements in a borehole while drilling and for transferring the measurement data to the earth's surface. Since no time is wasted stopping the drill and inserting a probe into the borehole in these systems, significant savings in drilling time are achieved and thereby a significant reduction in the total cost of drilling. The systems proposed so far belong to four basic types, namely purge pressure pulse systems, electromagnetic systems, metal wire systems and acoustic systems. A wide variety of electromagnetic (EM) systems have been proposed, all based on the transmission of electromagnetic data signals through the earth and / or through the drill string. However, none of these EM systems provide a reasonable signal-to-noise ratio for the signals observed at the surface, severely limiting the data transfer rate.

U.S. Patent 2354887 proposes an EM system 25 in which the measurement data signals are supplied in the form of pulses to a toroidal coil surrounding the drill string in proximity to the drill bit. A varying magnetic field is connected to the pulsating current in the coil and this field induces signals in the form of pulsating currents in the drill string. The return circuits 30 for currents flowing in the drill string as a result of this operation pass through the earth itself. The transmitted signals are sensed at the surface by a receiving station connected between the drill string and a grounded electrode at a distance from the drill string. However, due to the attenuation of the signals in the earth and the core losses in the coil, the signal-to-noise ratio of the observed signals is poor, so that the system is not satisfactory in practice.

The object of the invention is to provide a signal device which forms an EM system that is inexpensive and capable of transmitting signals at high speed and with an acceptable signal-to-noise ratio.

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The signal device according to the invention comprises a transformer whose winding is electrically connected between a first part of the drill string for drilling the borehole and a second part of the drill string which is electrically insulated from the first part, and means 5 for transmission and / or receiving signals electrically connected to the other winding of the transformer, the first part forming a current path for signals moving between the transformer and a signal receiving and / or transfer station located at a distance from the transformer along the drill string, while providing a return path between the transformer and the signal station through the second part of the drill string and the earth formations in which the borehole is drilled.

Preferably, said one winding is the secondary winding of the transformer and said other winding is the primary winding of the transformer, while the transmitters are electrically connected to the primary winding for transmitting signals to a remote receiving station.

With this system, the dimensions of the transformer and the number of turns of the primary and secondary windings of the transformer can be selected such that the core losses are reduced. In addition, the transformer, which is preferably a toroidal transformer, can be very small so that the transformer is inexpensive to manufacture and can be housed in a small chamber in the wall of the drill string. Since the core losses are small, the power required for the means for transmitting and / or receiving the signals is small, for example of the order of 1 W, and can be supplied by a battery.

In a preferred embodiment according to the invention, the first and the second parts of the drill string are the top part, respectively. the lower part of a special remote measurement adapter or telemetry adapter, the parts of which are separated by an electrical insulator, and the transformer is arranged in a chamber in the wall of the adapter, together with the means for transmitting the signals consisting of a battery and signal processing signals.

Since the degree of attenuation of the transmitted signals depends on the distance over which the signals are transmitted and on the electrical conductivity of the earth formations through which the borehole is drilled, it may be beneficial to have one or more repetitive sections between the adapter with the measuring instrument and the earth's surface. Each repeat adapter may include identical 8102401f-3 transmission and receiving means for the signals and amplifiers, the signal transmitting means being the same as in the adapter containing the measuring instrument. Since the adapters are relatively inexpensive to manufacture, a large number of repetitive adapters can be applied as needed along the drill string.

The invention also includes a method for processing signals in a borehole during drilling, using a drill string with a first and a second part which are electrically insulated from one another, which method consists of feeding signals between transmission and / or signal receiving means and a signal receiving and / or transferring station located at a distance from the means along the drill string, via a transformer whose winding is electrically connected between the first and second parts of the drill string and the other winding is electrically connected to the signal members, while the first drill string section provides a flow path for signals moving between the transformer and the signal station, and a return path is provided between the transformer and the signal station through the second part of the drill string and the nature formations in which the hole is being drilled.

The invention additionally includes a. drill string telemetry adapter, consisting of a first and a second part, which are electrically insulated from each other, a transformer with a winding being electrically connected between the first and the second part of the adapter, and means for transmission and / or collection of 25 signals are electrically connected to the other winding of the transformer, the first portion of the adapter providing a flow path for signals moving between the transformer and a signal station spaced along the drill string when the adapter is fitted in a drill string, and a return path is provided during drilling 30 between the transformer and the signal station through the second adapter portion and the earth formations in which the hole is drilled.

The invention will be explained in more detail below with reference to the drawing, which shows an embodiment of the device according to the invention.

Pig. 1 schematically shows a part of a drill string with a telemetry adapter according to the invention.

Fig. 2 is a longitudinal section through a telemetry adapter according to the invention.

In Figure 1 only the principle of the invention is shown 40 and not the detailed construction of the telemetry adapter.

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The adapter 1 is shown as arranged between two drill string sections 2, 3 in a borehole 10. The adapter 1 is coupled to the part 2 by means of a threaded coupling 4 with external thread to the adapter 1 and to the part 3 by means of a screw -5 threaded coupling 5 internally threaded to the adapter 1. The part 2 is connected to a surface (not shown) rotary table via other drill string sections and the part 3 is connected to a drill bit (not shown), preferably also through other drill string sections.

The reducer 1 consists of an upper part 6, which is electrically connected to the drill string part 2 and a lower part 7, which is electrically connected to the drill string part 3. The two reducer parts 6, 1 are electrically insulated from each other by an insulator 8 A chamber 9 is arranged in the side wall of the adapter, which contains an electronic circuit 11 and a toroidal output transformer 12, the second winding 15 of the transformer being connected between the upper part 6 and the lower part 7. At the In operation of the device, a signal with measurement data, in the form of pulses, is applied to the primary winding of the transformer 12 via the electronic circuit 11, the measurement data being, for example, the data coming from the instrument for measuring the direction borehole, as described in British Patent Specification 1,509,293. Thereby, a pulsating current signal is induced in the secondary winding of the transformer 12 and this signal is fed to the surface by the adapter part 2 and the further parts of the drill string between this part 2 and the surface. A return job for it.

25 signal is provided by the earth formations through which borehole 10 is drilled.

The telemetry adapter of FIG. 1 may be either only an adapter for transferring measurement data supplied thereto by an adjacent measuring instrument, or a repetition adapter, which. receives a signal that is fed to it via the drill string, processes this signal and further transfers the processed signal. In the latter case, the electronic circuit 11 includes a battery and a signal processing circuit for modulating the current supplied by the battery in accordance with the measurement data.

A repeat adapter is shown in longitudinal section in Figure 2. Corresponding parts have the same reference numerals as in Figure 1. The annular insulator 8 is located between the chamber 9 and the inner wall of the adapter in the vicinity of the chamber 9, insulator is substantially S-shaped in cross-section for reinforcing the connection 40 between the upper part 6 and the lower part 7.

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The chamber 9 is closed from the outside by a cover 13, which at its edges is sealed with a seal 14 and is electrically insulated such that this cover does not provide a current path between the two parts 6, 7. The piston contains, except the output transformer 12 , an input transformer 15, an input amplifier 16, a signal processing circuit 18 and an output amplifier 17. The input transformer 15 and the output transformer 12 can be replaced by a single transformer, the function of which is both to receive and transmit signals. The repeat adapter is arranged to receive and transmit signals in a multiplexed manner. In an initial period of, for example, 1 sec. an input signal transmitted by a transfer only adapter or by another repetitive adapter further down the drill string is sensed by the input transformer 15, the primary winding of which is connected between the lower parts of the drill string 15 and the return path through the earth, and is amplified by the input amplifier 16. In a second period, for example, 100 milliseconds. the signal is digitally processed by the error clearing circuit 18 and in a third period of e.g. 1 sec. the processed signal is amplified by the output amplifier 17 and transmitted by the output transformer 12, either to a surface receiver or to another repetition adapter further up along the drill string.

Since the telemetry adapters can be manufactured quite inexpensively and the bandwidth and thus the possible speed of transmitting the data of a signal decreases as a function of the distance over which it is transmitted, repetitive adapters can be arranged at a distance of 300 m along the drill stand: if necessary. This allows signals to be transferred at a rate of about 100 hfc / sec. with a power input of approximately 30 W per adapter and a bandwidth of approximately 100 Hz.

When, as in the system of U.S. Pat. environment, the core losses of that system and of the system according to the invention can be compared with each other.

When the cross sectional area of the toroidal core is A ^ and the flux density at maximum saturation for the core material is Β0, then clearly max <B .A ................. (i).

40 When the impedance of the secondary winding is Z, the 8102401 * · * - 6 - power input into the secondary winding can be written as P = ......... * .......... ....... (ii)

2ZS

5 The maximum value of the emk induced in the secondary winding can be written as V = N. f max CO ................... (iii), where Ng is the number of turns s s.

of the secondary winding and y max. is the maximum value of the magnetic flux through the toroidal core cross section and w = 2 TT. f, where 10f is the frequency of the primary drive. . , ¾

It follows from equations (i), (ii) and (iii) that Ac> -— 2.v 'fTi —.....

S * * * * SAT

As an example, values for silicon iron transformer core material can be taken: max = 1.2 Tesla 15 Core loss at 200 Hz = 5.5 W / kg -3

Core density = 7 g.cm.

From previous calculations at 200 Hz, the impedance Zg of the drill stand and earth can be set at 0.17 Ohm.

For a torus with an average diameter of 14 cm around the drill string, with a secondary winding with a single winding, these example values give a minimum value for the cross-sectional area 2 of the core of 3.9 cm and as a result a minimum core volume 3 of 156 cm, while the minimum mass of the core is calculated at 1.1 kg when the case of P = 1 W is considered. Before dispensing

O

Thus, of 1 W on the secondary circuit at 200 Hz, the resulting core loss is about 6 W. Furthermore, such a core is expensive in manufacture.

In contrast, when the toroidal transformer of the system according to the drawing has 100 turns of its secondary winding, the minimum value for the cross-sectional area of the core is about 4 mm and therefore the core can be extremely small, so that the core losses are negligible.

8102401

Claims (16)

1. Device for processing signals in a borehole during drilling, during operation signals being electromagnetically transferred along the drill string between means in the borehole for transmitting and / or receiving signals and a station for receiving and / or transmission of signals at a remote point along the drill string, a return path is provided for the signals via the earth formations in which the borehole is drilled, characterized in that a winding of a transformer (12) is electrically connected between a first part ( 6) of the drill string and a second part (7) of the drill string, which parts are electrically insulated from each other, the means (11, 15-18) for transmitting and / or receiving the signals being electrically connected to the other winding of the transformer (12), the first section (6) of the drill string providing a flow path for signals between the transformer (12) and the signal station, and the return 15 ba an between the transformer (12) and the signal station passes through the second drill string section (7) and the earth formations. 2. Device according to claim 1, characterized in that one winding is the secondary winding of the transformer (12) and the other winding is the primary winding of the transformer (12), while the signal transmitting means (11) are electric connected to the primary winding for transmitting signals to a remote station. Device according to claim 2, characterized in that the signal transmitting means (11) comprise signal processing means for modulating a carrier signal in accordance with the measuring data received from a measuring instrument. Device according to any one of the preceding claims, characterized in that the device comprises a number of signal units distributed over the drill string, each consisting of a transformer (12), a winding of which is electrically connected between the first drill string section (6). 30 and the second drill string section (7), and means (11; 15-18) for transmitting and / or receiving signals are electrically connected to the other winding, one of these units being adapted only for transmitting measurement data thereto supplied by a measuring instrument the or any other unit is a repetition unit for receiving a signal supplied thereto along the drill string, processing the signal and transmitting the processed signal. Device according to any one of the preceding claims, characterized in that the transformer (12) is toroidal in shape, 8102401-8 * V. transformer. Device according to any one of the preceding claims, characterized in that the transformer (12) and the means (11; 15-18) for transmitting and / or receiving signals are accommodated in a chamber (9) in the wall 5. of the drill string. Device according to any one of the preceding claims, characterized in that the means (11; 15-18) for transmitting and / or receiving signals are arranged to be powered by a battery. 8. Device according to any one of the preceding claims, characterized in that the first drill string section (6) and the second drill string section (7), respectively. the upper and lower parts are of a special telemetry adapter (1), which parts are separated from each other by an electrical insulator (8). 9. Drill string telemetry adapter incorporating means 15 for transmitting and / or receiving signals intended for the electromagnetic transmission of signals along the drill string between the adapter and a station for receiving and / or transmitting signals to a remote point along the drill string, a return path for the signals being provided by the earth formations 20 into which the borehole is drilled, characterized in that the adapter (1) consists of a first part (6) and a second part ( 7) which are electrically insulated from each other, and from a transformer (12), a winding of which is electrically connected between the first and second parts (6, 7), the means (11; 15-18) for transferring and / or reception of signals are electrically connected to the other winding of the transformer (12), while the first part (6) forms a current path for signals moving between the transformer (12) and the station, for reception and n / or transmitting signals when the adapter (1) is received in a drill string, and the return path is provided during drilling between the transformer (12) and the station for receiving and / or transmitting signals via the second part ( 7) of the reducer and earth formations. 10. Adapter according to claim 9, characterized in that this adapter serves only for the transmission of measurement data supplied thereto by a measuring instrument. A reducer according to claim 9, characterized in that it is a repeating adapter for receiving a signal fed thereto along the drill string, processing the signal and transmitting the processed signal. A reducer according to any one of claims 9 to 11, characterized in that the transformer (12) and the means (11; 15-18) for transmission and / or 8102401> - _ 1 ^ ^ Λ - 9 - receiving signals are contained in a chamber (9) in the wall of the adapter (1). Reducer according to claim 12, characterized in that the chamber (9) is closed on the outside by a lid (13). 14. Reducer according to any one of claims 9-13, characterized in that the first and second parts (6, 7) are insulated from each other by an annular insulator (8) which is substantially s-shaped in radial section is. 15. Method for processing signals in a borehole 10 during drilling, wherein signals are electrically transmitted along the drill string, between means for transmitting, and / or receiving signals in the borehole and a station for receiving and / or transmitting of signals at a remote point along the drill string, a signal return path being provided by the earth formations 15 into which the hole is drilled, characterized in that a drill string consisting of a first and a second part is used (6 7) which are electrically insulated from one another, with signals being conducted between the means (11; 15-18) for transmitting and / or receiving signals and the station for receiving and / or transmitting signals via a transformer (12), one winding of which is electrically connected between the first and second drill string sections (6, 7) and the other winding is electrically connected to the means (11; 15-18) for transmission e n / or receiving the signals, the first part) 6) forming a flow path for signals running between the transformer (12) and the station, and the return path being provided between the transformer (12) and the station by second part (7) and the earth formations. Method according to claim 15, characterized in that signals are successively fed between a number of signal units, each with a transformer (12), a winding of which is electrically connected between the first and second part (6, 7) of the drill string. and means (11; 15-18) for transmitting and / or receiving signals electrically connected to the other winding, the first of these units serving only for transmitting measurement data supplied thereto by a measuring instrument, and the or any other unit is a repeater that receives a signal fed to it by a previous unit, processes the signal and transmits the processed signal. 8102401 40 --- ++ ---