A borehole electrical source time domain electromagnetic measurement apparatus and method

Abstract

The application belongs to the technical field of petroleum physical exploration, and particularly discloses a wellbore electric source time-domain electromagnetic measurement device and method. The device comprises a ground collection system, a cable, a remote transmission short section, an array electric source receiving sensor and a transmitting device. The ground collection system is connected with the remote transmission short section through the cable. The remote transmission short section is connected with the array electric source receiving sensor. The array electric source receiving sensor is connected with the transmitting device. The measurement mode of electric source excitation and array electric source receiving is adopted, the manufacturing process difficulty of three-dimensional magnetic source in the limited space of the wellbore is reduced, the problem of difficult quick shutdown of the multi-turn coil is solved, and the ultra-long detection of the radial geological information beside the well is realized.

Description

Technical Field

[0001] This invention belongs to the field of petroleum physical exploration technology, specifically relating to a time-domain electromagnetic measurement device and method for wellbore electrical sources. Background Technology

[0002] As resource exploration shifts towards deeper earths, deep seas, and unconventional areas, the targets faced in resource exploration are becoming increasingly complex. Seismic detection, with a resolution range of only tens of meters, is no longer sufficient to meet the needs of refined exploration and development. Conventional logging can only detect geological information 1-2 meters away from the wellhead. Complex (fractured, thin-layered, fault-block, etc.) and unconventional resource exploration requires breakthroughs in traditional measurement models to detect complex stratigraphic interfaces, accurately describe reservoir structures, finely characterize the shape and size of reservoirs and the distribution of fluids within them, improve reserve prediction for risky blocks, and enhance the description of geological sedimentary environments and the evaluation of oil and gas reservoirs. Currently, long-range borehole detection technology provides an effective means to solve these problems, filling the gap in spatial evaluation scales between conventional logging and seismic exploration. However, frequency-domain electromagnetic long-range detection technology suffers from long instrument strings that are prone to bending and twisting, significant challenges in signal synchronization and measurement data processing, high manufacturing and transportation costs, and compromised reliability, making it impossible to achieve long-boundary detection with short transmit / receive distances. Time-domain electromagnetic remote sensing technology measures the secondary induced electromagnetic field that decays over time after a current pulse is turned off, enabling well-side geological information detection. It achieves the same level of remote well-side detection previously only achievable with longer frequency-domain instruments, using a shorter instrument length. However, time-domain electromagnetic remote well-sounding technology offers a rich array of signal frequency components and is sensitive to formation interfaces, presenting significant drawbacks in addressing issues such as numerous short instrument sections, large instrument length, and high cost. Summary of the Invention

[0003] The purpose of this invention is to provide a time-domain electromagnetic measurement device and method for a borehole electrical source, so as to solve the technical problems in existing borehole remote detection technology, such as the difficulty in manufacturing three-component magnetic sources and the difficulty in quickly shutting them off.

[0004] To achieve the above objectives, the present invention employs the following technical solution:

[0005] In a first aspect, a borehole electrical source time-domain electromagnetic measurement device includes a ground acquisition system, a cable, a remote transmission sub, an array-type electrical source receiving sensor, and a transmitting device. The ground acquisition system is connected to the remote transmission sub via the cable, the remote transmission sub is connected to the array-type electrical source receiving sensor, and the array-type electrical source receiving sensor is connected to the transmitting device.

[0006] A further improvement of the present invention is that the launching device is a first launching mode device and / or a second launching mode device.

[0007] A further improvement of the present invention is that the first emission mode device includes a first insulating rod, and the first insulating rod is provided with a first emission electrode and a second emission electrode.

[0008] A further improvement of the present invention is that: the second emission mode device includes a second insulating rod, the second insulating rod is provided with a third emission electrode, and the second emission mode device also includes a fourth emission electrode disposed on the ground at the wellhead.

[0009] A further improvement of the present invention is that the cable is a seven-core cable.

[0010] A further improvement of the present invention is that the array-type electrical source receiving sensor is a plurality of array-type acquisition electrodes disposed on a third insulating rod.

[0011] A further improvement of the present invention is that the ground acquisition system is an acquisition vehicle.

[0012] Secondly, a time-domain electromagnetic measurement method for a borehole electrical source, based on the aforementioned time-domain electromagnetic measurement device for a borehole electrical source, specifically includes the following steps:

[0013] A pulse waveform is applied to the transmitting device to excite a circumferential magnetic field in the formation. After the pulse excitation is turned off, the formation generates a secondary electromagnetic induction signal that decays over time.

[0014] The array-type electrical source receiving sensor receives a secondary electromagnetic induction signal that decays over time.

[0015] The array-type electrical source receiving sensor receives secondary electromagnetic induction signals and transmits them to the ground acquisition system through a remote transmission stub and cable;

[0016] The ground acquisition system evaluates the geological information near the well based on the secondary electromagnetic induction signal that decays over time.

[0017] A further improvement of the present invention is that it specifically includes the following steps:

[0018] A pulse waveform is applied to the first transmission mode device. After the pulse excitation is turned off, a first and second electromagnetic induction signal that decays over time is generated in the formation.

[0019] A pulse waveform is applied to the second transmission mode device. After the pulse excitation is turned off, a second and secondary electromagnetic induction signal that decays over time is generated in the formation.

[0020] The first and second transmission mode devices are controlled to work alternately, so that the array-type electrical source receiving sensor alternately receives the first and second electromagnetic induction signals that decay over time and the second electromagnetic induction signals that decay over time. As the logging device moves along the wellbore, the signal superposition measurement is achieved for a preset number of times.

[0021] The secondary electromagnetic induction signal, which is obtained by superimposing signals after a preset number of times and received by the array-type electrical source receiving sensor, is transmitted to the ground acquisition system through a remote transmission stub and cable.

[0022] The ground acquisition system performs well-side reservoir and geological evaluation by superimposing secondary electromagnetic induction signals after a preset number of signal superpositions.

[0023] A further improvement of the present invention is that: based on the secondary electromagnetic induction signals superimposed a preset number of times, an inversion method is used to process and evaluate the reservoir and geology near the well.

[0024] Compared with the prior art, the present invention has at least the following beneficial effects:

[0025] 1. The present invention adopts a measurement mode of electrical source excitation and array-type electrical source reception, which reduces the manufacturing difficulties of three-dimensional magnetic sources in the confined space of wellbore and solves the problem of difficulty in rapid turn-off of multi-turn coils.

[0026] 2. The present invention can flexibly combine different measurement modes through the first and second launch mode devices to realize radial far-hole geological information detection.

[0027] 3. In this invention, only one of the first and second launch mode devices is needed to meet the measurement requirements, which is lower in cost and more convenient to manufacture and use compared to existing technologies. Attached Figure Description

[0028] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0029] In the attached diagram:

[0030] Figure 1 This is a schematic diagram of the structure of a wellbore electrical source time-domain electromagnetic measurement device according to the present invention;

[0031] Figure 2 This is a schematic diagram of the structure of the first transmission mode device in the time-domain electromagnetic measurement device for a wellbore electrical source according to the present invention;

[0032] Figure 3 This is a schematic diagram of the second emission mode device in a wellbore electrical source time-domain electromagnetic measurement device of the present invention;

[0033] Figure 4 This is a schematic diagram of the array-type electrical source receiving sensor structure in a wellbore electrical source time-domain electromagnetic measurement device of the present invention;

[0034] Figure 5This is a schematic diagram of the transmitted pulse waveform in a wellbore electrical source time-domain electromagnetic measurement device according to the present invention;

[0035] Figure 6 This is a schematic diagram of the electromagnetic field excited by the electrical source in the time-domain electromagnetic measurement device of the wellbore electrical source according to the present invention.

[0036] In the diagram: 1. Ground acquisition system; 2. Cable; 3. Remote transmission sub; 4. Array-type electrical source receiving sensor; 5. First transmission mode device; 51. First transmitting electrode; 52. Second transmitting electrode; 53. First insulating rod; 6. Second transmission mode device; 61. Third transmitting electrode; 62. Fourth transmitting electrode; 63. Second insulating rod; 7. Third insulating rod. Detailed Implementation

[0037] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that, unless otherwise specified, the embodiments and features described herein can be combined with each other.

[0038] The following detailed description is exemplary and intended to provide further detailed explanation of the invention. Unless otherwise specified, all technical terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art. The terminology used in this invention is for describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention.

[0039] Example 1

[0040] like Figure 1 As shown, a borehole electrical source time-domain electromagnetic measurement device includes a ground acquisition system 1, a cable 2, a remote transmission sub 3, an array-type electrical source receiving sensor 4, a first transmission mode device 5, and a second transmission mode device 6. The remote transmission sub 3 is connected to the ground acquisition system 1 via the cable 2, which is a seven-core cable. The ground acquisition system 1 is a data acquisition vehicle. The array-type electrical source receiving sensor 4 and the transmitting device are located below the remote transmission sub 3. The transmitting device employs a dual-mode electrical source excitation mode, including the first transmission mode device 5 and the second transmission mode device 6.

[0041] like Figure 2 As shown, the first emission mode device 5 includes a first insulating rod 53, a first emission electrode 51 and a second emission electrode 52. The first emission electrode 51 and the second emission electrode 52 are both disposed on the first insulating rod 53, and the first emission electrode 51 and the second emission electrode 52 disposed on the first insulating rod 53 form a circuit.

[0042] like Figure 3As shown, the second emission mode device 6 includes a second insulating rod 63, a third emission electrode 61 and a fourth emission electrode 62. The third emission electrode 61 is disposed on the second insulating rod 63, and the fourth emission electrode 62 is disposed on the ground around the wellhead. A circuit is formed by the cable 2, the third emission electrode 61 and the fourth emission electrode 62.

[0043] like Figure 4 As shown, the array-type electrical source receiving sensor 4 is configured as an array of acquisition electrodes placed on the third insulating rod 7, with the number of acquisition electrodes set as needed. The transmitting electrode excites a bipolar pulse time-domain signal, such as... Figure 5 As shown, after the transmitting current is turned off, the array-type electrical source receiving sensor 4 collects the secondary electromagnetic field signal induced in the stratum.

[0044] When performing time-domain electromagnetic measurements of the borehole electrical source, one or more of the first transmission mode device 5 or the second transmission mode device 6 may be selected as needed.

[0045] Example 2

[0046] A time-domain electromagnetic measurement method for a borehole electrical source, based on the aforementioned time-domain electromagnetic measurement device for a borehole electrical source, specifically includes the following steps:

[0047] The borehole electrical source time-domain electromagnetic measurement employs time-division multiplexing for transmission and reception. The first transmission mode device 5 consists of two (pair) transmitting electrodes placed on the first insulating rod 53 inside the well, equivalent to a pair of electric dipoles. The second transmission mode device 6 consists of a third transmitting electrode 61 placed on the second insulating rod 63 and a fourth transmitting electrode 62 placed on the surface at the wellhead. These electrodes form a loop via cable 2, creating a pair of transmitting electrodes, equivalent to a grounded long conductor source. The electrical source excites a circumferential magnetic field in the formation, i.e., a circumferential magnetic field surrounding the well axis. This measurement method is beneficial for detecting geological information such as well-side geological interfaces, water-drive fronts, and concealed geological structures.

[0048] The first transmission mode device 5, the second transmission mode device 6, and the array-type electrical source receiving sensor 4 are all independent short sections that can be arbitrarily combined to form different transmit and receive distances according to engineering operation needs. The first transmission mode device 5, the second transmission mode device 6, and the array-type electrical source receiving sensor 4 are connected by a 31-pin plug.

[0049] A pulse waveform is applied to the first transmission mode device 5 via the transmitting circuit, such as... Figure 4 As shown, an electrical source induces a circumferential magnetic field in the strata, such as... Figure 6As shown, the array-type electrical source receiving sensor 4 receives the secondary electromagnetic induction signal that decays over time. A pulse waveform is applied to the second transmission mode device 5 via the transmitting circuit, and the array-type electrical source receiving sensor 4 receives the secondary electromagnetic induction signal that decays over time excited by the second transmission mode. As the transmitting and receiving devices move from the bottom of the well to the wellhead within the borehole, the two transmitting devices transmit alternately, and the array-type electrical source receiving sensor 4 receives the secondary electromagnetic induction signal that decays over time, achieving a multiple superposition measurement mode.

[0050] The propagation mode of the electromagnetic field in the time domain of the wellbore is similar to that in the half-space time domain. As time goes by, the electromagnetic field spreads to distant places. The secondary electromagnetic induction signal received by the array-type electrical source receiving sensor 4, which decays over time, is related to geological information such as geological interfaces, water drive fronts, and hidden structures near the well.

[0051] By utilizing the time-decreased secondary induced electromagnetic field information collected by the array-type electrical source receiving sensor 4, the well-side electrical parameters can be obtained through inversion, thereby achieving a fine evaluation of the well-side geology.

[0052] As is known from common technical knowledge, this invention can be implemented through other embodiments that do not depart from its spirit or essential characteristics. Therefore, the disclosed embodiments described above are merely illustrative in all respects and are not the only ones. All modifications within the scope of this invention or its equivalents are included in this invention.

[0053] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A time-domain electromagnetic measurement device for a borehole electrical source, characterized in that, The device includes a ground acquisition system (1), a cable (2), a remote transmission section (3), an array-type electrical source receiving sensor (4), and a transmitting device. The ground acquisition system (1) is connected to the remote transmission section (3) via the cable (2), the remote transmission section (3) is connected to the array-type electrical source receiving sensor (4), and the array-type electrical source receiving sensor (4) is connected to the transmitting device. The launching device adopts a dual-mode electrical source excitation mode, including a first launching mode device (5) and a second launching mode device (6). The first emission mode device (5) includes a first insulating rod (53), a first emission electrode (51) and a second emission electrode (52). The first emission electrode (51) and the second emission electrode (52) are both disposed on the first insulating rod (53). The first emission electrode (51) and the second emission electrode (52) disposed on the first insulating rod (53) form a circuit. The second emission mode device (6) includes a second insulating rod (63), a third emission electrode (61) and a fourth emission electrode (62). The third emission electrode (61) is disposed on the second insulating rod (63), and the fourth emission electrode (62) is disposed on the ground around the wellhead. A circuit is formed by the cable (2), the third emission electrode (61) and the fourth emission electrode (62). The array-type electrical source receiving sensor (4) includes an array of acquisition electrodes placed on a third insulating rod (7); The first transmission mode device (5), the second transmission mode device (6), and the array-type electrical source receiving sensor (4) are all independent short sections that can be arbitrarily combined according to engineering operation needs to form different transmission and reception distances. The first transmission mode device (5), the second transmission mode device (6), and the array-type electrical source receiving sensor (4) are connected by a 31-pin plug. The pulse waveform is loaded onto the first transmission mode device (5) by the transmitting circuit, and the array-type electrical source receiving sensor (4) receives the secondary electromagnetic induction signal that decays over time; the pulse waveform is loaded onto the second transmission mode device (6) by the transmitting circuit, and the array-type electrical source receiving sensor (4) receives the secondary electromagnetic induction signal that decays over time excited by the second transmission mode; as the transmitting and receiving devices move from the bottom of the well to the wellhead in the wellbore, the two transmitting devices transmit alternately, and the array-type electrical source receiving sensor (4) receives the secondary electromagnetic induction signal that decays over time, thus realizing the multiple superimposed measurement mode.

2. The wellbore electrical source time-domain electromagnetic measurement device according to claim 1, characterized in that, The cable (2) is a seven-core cable.

3. The wellbore electrical source time-domain electromagnetic measurement device according to claim 1, characterized in that, The ground acquisition system (1) is an acquisition vehicle.

4. A time-domain electromagnetic measurement method for a borehole electrical source, based on the time-domain electromagnetic measurement device for a borehole electrical source according to any one of claims 1-3, characterized in that, Specifically, the following steps are included: A pulse waveform is applied to the transmitting device to excite a circumferential magnetic field in the formation. After the pulse excitation is turned off, the formation generates a secondary electromagnetic induction signal that decays over time. The array-type electrical source receiving sensor (4) receives the secondary electromagnetic induction signal that decays over time; The array-type electrical source receiving sensor (4) receives secondary electromagnetic induction signals and transmits them to the ground acquisition system (1) through the remote transmission stub (3) and cable (2). The ground acquisition system (1) evaluates the geological information near the well based on the secondary electromagnetic induction signal that decays over time.

5. The time-domain electromagnetic measurement method for a borehole electrical source according to claim 4, characterized in that, The method also includes: A pulse waveform is loaded onto the first transmission mode device (5). After the pulse excitation is turned off, a first and second electromagnetic induction signal that decays over time is generated in the formation. A pulse waveform is loaded onto the second emission mode device (6). After the pulse excitation is turned off, a second electromagnetic induction signal that decays over time is generated in the formation. Control the first transmission mode device (5) and the second transmission mode device (6) to work alternately, so that the array-type electrical source receiving sensor (4) alternately receives the first secondary electromagnetic induction signal and the second secondary electromagnetic induction signal that decays with time. As the logging device moves along the well hole, the preset number of signal superposition measurements are achieved. The secondary electromagnetic induction signal, which is superimposed on the signal after a preset number of times and received by the array-type electrical source receiving sensor (4), is transmitted to the ground acquisition system (1) through the remote transmission short section (3) and the cable (2). The ground acquisition system (1) performs well-side reservoir and geological evaluation by superimposing a secondary electromagnetic induction signal after a preset number of signal superpositions.

6. The time-domain electromagnetic measurement method for a borehole electrical source according to claim 4, characterized in that, Based on the secondary electromagnetic induction signals superimposed a preset number of times, the inversion method is used to process and evaluate the reservoir and geology near the well.

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