A through-casing resistivity logging tool

Abstract

The present invention provides a through-casing resistivity logging instrument, belonging to the field of well logging instruments. The through-casing resistivity logging instrument comprises a first measuring device, a power module, and a loop current electrode. The first measuring device includes a first probe system, a first high-voltage energy storage and discharge system, a first processor, and a first acquisition system. The circuit structure is relatively simple. The first processor controls the power module to supply power to electrical components within the first measuring device, supporting the first probe system on the inner wall of the casing. The first high-voltage energy storage and discharge system allows for instantaneous emission of high-power, sharp pulsed, high-frequency alternating current. The first processor collects the discharge voltage via the first acquisition system and receives formation current response characteristics at different angles. This high-resolution measurement results in more accurate calculated formation resistivity.

Description

Technical Field

[0001] The invention relates to a through-casing resistivity well logging instrument, belonging to the field of well logging instruments. Background Art

[0002] Through-casing resistivity logging is a new technology developed in recent years for resistivity measurement in cased wells. This technology has unique advantages in remaining oil monitoring, tapping the potential of old wells, determining the waterlogging status of oil reservoirs, and monitoring oil reservoir production dynamics. It supplies high-power current to the casing of the development well and detects the weak potential difference formed by the "leakage current" flowing into the formation through the casing wall, thereby determining the resistivity of the reservoir. In the through-casing measurement mode, the voltage between the electrodes is on the order of microvolts (10 -6 V), the voltage after differential is in the nanovolt level (10 -9 V), so what is measured through the bushing is an ultra-low frequency (0.1 Hz) and extremely weak (about 30 nV) electrical signal.

[0003] There are two main types of traditional through-casing resistivity logging tools, using monopolar and bipolar power supply methods, respectively. The monopolar power supply method is exemplified by the Schlumberger CHFR. The tool primarily consists of top and bottom current electrodes, a set of measuring electrodes, and a hydraulic system. The top current electrode serves as the power supply electrode, while the bottom current electrode serves as the return electrode, both of which are pushed into contact with the casing by a spring arm. There are four measuring electrodes, spaced equidistantly (0.6 m), each consisting of three plates angled 120 degrees from each other and connected in parallel. During logging, the tool stops at each measuring point and contacts the casing inner wall via the hydraulic push system. A high-power current source on the surface is connected to the power supply electrode, which injects low-frequency alternating current (AC) into the casing in the frequency range of 0.25-10 Hz. Part of the current flows along the casing, while the remaining part leaks out of the casing into the formation. The test is a two-step process: the first step measures the voltage drop caused by the current leaking into the formation, and the second step measures the voltage loss caused by the casing resistivity. According to the electrode measurement results combined with the apparent resistivity formula, the resistivity of formations at different depths can be calculated. This type of instrument has the following main problems: First, the injection current can only generate a leakage current of a few milliamperes. The leakage current generated in high-resistance formations is even smaller. Due to the limitation of the logging cable, the injection current cannot be too large, generally around 6A. Therefore, the electrical signal that can reflect the formation information is extremely weak. At the same time, it is affected by factors such as the wellbore, formation, casing and cement ring. The measured formation information data is highly interfered and requires further correction. Second, when the instrument has poor contact with the inner wall of the casing, no current is injected into the formation, which will cause measurement failure. Third, the electrode spacing is 1.2m. The limitation of the circuit source distance results in a vertical resolution of 1.2m for through-casing resistivity logging, and the interpretation accuracy of thin interlayers is low.

[0004] The bipolar power supply method, exemplified by the Russian ECOS, consists primarily of a power supply electrode, a potential electrode, a measuring electrode, and a hydraulic system. The power supply electrode, also known as a current transmitter electrode, consists of an upper and lower power supply electrode. These electrodes are a pair of spring-loaded, uncontrollable electrodes that maintain close contact with the inner wall of the casing and apply the transmitter current, supplied by a current source, to the casing string. The potential electrode measures the potential from the depth point to the return electrode. Three measuring electrodes are arranged at equal intervals (0.5 m) between the upper and lower power supply electrodes. The measuring electrodes are connected by a flexible steel cable, which allows for some flexing to ensure close contact with the casing even when slight deformation occurs. During fixed-point measurements, current is injected into the casing from the upper and lower power supply electrodes, respectively. The voltage difference between the measuring electrodes is recorded, and the resistivity of the formation is then calculated. This type of instrument has the following major issues: First, the flexible connection design between the measuring electrodes allows the instrument to bend slightly to accommodate slight casing deformation, allowing the electrodes to adhere tightly to the casing even in irregularly shaped casing. However, during actual logging, the instrument may become misaligned, resulting in uneven spacing between the measuring electrodes. This increases the error in the measured second-order potential difference and reduces the accuracy of the calculation. Second, the limited 1m electrode spacing and circuit source spacing result in a 1m vertical resolution for through-casing resistivity logging, resulting in low accuracy in interpreting thin interbeds.

[0005] Chinese patent CN102102513A discloses a through-casing resistivity logging instrument, comprising a cable-connected downhole measuring device, a surface control unit, and a computer. Similar to the Russian ECOS bipolar power supply method, this instrument primarily consists of an upper measuring unit, an electrode pushing unit, electrodes, and a lower measuring unit. The electrodes include two current electrodes and a plurality of parallel measuring electrodes. The two current electrodes are located on either side of the plurality of measuring electrodes and are connected to the upper measuring unit on either side, forming two power supply circuits. A cavity fluid is provided between the electrode pushing unit and the electrodes. The electrode pushing unit's electrode pushing function has two functions: first, using the cavity fluid to lift the two current electrodes and drive them into the inner wall of the metal casing; second, using the cavity fluid to press the plurality of measuring electrodes against the inner wall of the metal casing. The lower measuring unit measures the differential pressure and secondary differential pressure of the plurality of measuring electrodes, as well as the potential of the intermediate measuring electrode. The upper measuring unit measures the two power supply currents and the circuit current. The instrument uses a flexible connection, allowing each probe to be adjusted for close contact with the casing wall. However, during actual logging, the instrument may not be centered, resulting in uneven spacing between the measuring electrodes. This increases the error in the measured second-order potential difference and reduces the calculation accuracy. Furthermore, the complex structure and large number of measuring electrodes lead to high maintenance costs and unstable reliability. Summary of the Invention

[0006] The object of the present invention is to provide a through-casing resistivity logging instrument for solving the problems of weak electrical signals, low resolution, complex circuit structure and low reliability of existing through-casing resistivity logging instruments.

[0007] To achieve the above-mentioned object, the present invention provides a through-casing resistivity logging tool, comprising a first measuring device, a power module, and a loop current electrode for forming a measuring loop, wherein the first measuring device comprises a first probe system for being supported on the inner wall of the casing, a first high-voltage energy storage and discharge system, a first processor, and a first acquisition system for acquiring a discharge voltage and a probe current passing through the formation;

[0008] The power supply module supplies power to the first high-voltage energy storage and discharge system, and the first high-voltage energy storage and discharge system is connected to the first probe system to enable the first probe system to discharge toward the bushing;

[0009] The first acquisition system measures the probe current passing through the formation through the first probe system, and the first acquisition system is also connected to the first high-voltage energy storage discharge system to collect the discharge voltage;

[0010] The first processor controls the first probe system to support or disconnect the inner wall of the casing, controls the first high-voltage energy storage and discharge system to store or discharge energy, and connects to the first acquisition system.

[0011] The through-casing resistivity logging instrument includes a first measuring device, a power supply module and a loop current electrode. The first measuring device includes a first probe system, a first high-voltage energy storage and discharge system, a first processor and a first acquisition system, and the circuit structure is relatively simple; the first processor controls the power supply module to supply power to the electrical components in the first measuring device, so that the first probe system is supported on the inner wall of the casing, and high-power sharp pulse high-frequency alternating current can be instantly emitted through the first high-voltage energy storage and discharge system. The first processor collects the discharge voltage through the first acquisition system and receives the formation current response characteristics at different angles. The measurement resolution is high, so that the calculated formation resistivity is more accurate.

[0012] Furthermore, the above-mentioned logging instrument further includes a second measuring device, which includes a second probe system for supporting on the inner wall of the casing, a second high-voltage energy storage and discharge system, a second processor, and a second acquisition system for collecting the discharge voltage and the probe current passing through the formation;

[0013] The power supply module supplies power to the second high-voltage energy storage and discharge system, and the second high-voltage energy storage and discharge system is connected to the second probe system to enable the second probe system to discharge toward the bushing;

[0014] The second acquisition system measures the probe current passing through the formation through the second probe system, and the second acquisition system is also connected to the second high-voltage energy storage discharge system to collect the discharge voltage;

[0015] The second processor controls the second probe system to support or disconnect the inner wall of the casing, controls the second high-voltage energy storage and discharge system to store or discharge energy, and connects to the second acquisition system.

[0016] Adding a second measuring device to the through-casing resistivity logging instrument can realize the dual-transmitter and dual-receiver working mode of the through-casing resistivity logging instrument. That is, the upper and lower measuring devices send current to the casing at the same time, and the corresponding acquisition system simultaneously collects the discharge voltage and the probe current passing through the formation. This can offset the influence of the casing and cement sheath, improve the resolution of formation current acquisition, and thus improve the accuracy of the measurement.

[0017] Furthermore, in the above-mentioned logging instrument, the first high-voltage energy storage and discharge system and the second high-voltage energy storage and discharge system both include a capacitor group, and also include a commutation group for controlling the capacitor group to output forward or reverse current, and a switch group for controlling the charging or discharging of the capacitor group. The first processor controls the commutation group and the switch group connected to the first high-voltage energy storage and discharge system, and the second processor controls the commutation group and the switch group connected to the second high-voltage energy storage and discharge system.

[0018] The high-voltage energy storage and discharge system is powered by a power module. The commutation group transmits positive and negative pulse voltages to the capacitor bank, and the switch group controls the charging and discharging of the high-voltage energy storage. When the switch is closed, the capacitor charges, and when the switch is open, the capacitor discharges. The length of time the switch is closed determines the amount of transmitted power, achieving controllable discharge into the bushing.

[0019] Furthermore, in the above-mentioned logging instrument, the first acquisition system and the second acquisition system both include a voltage acquisition module and a probe acquisition module. The voltage acquisition module samples and connects to the capacitor group in the corresponding high-voltage energy storage and discharge system, and the probe acquisition module is used to connect to the probe in the corresponding probe system to collect the current passing through the formation.

[0020] Furthermore, in the above-mentioned logging instrument, the first probe system and the second probe system each include a probe unit and a pushing motor module; the pushing motor module drives the probe unit to compress or stretch in the axial direction;

[0021] When the probe unit is axially compressed, the probe in the probe unit contacts the inner wall support of the sleeve; when the probe unit is axially extended, the probe in the probe unit is disconnected from the inner wall support of the sleeve.

[0022] The probes, when in contact or disconnected from the casing inner wall, enable continuous resistivity measurements at varying depths and accurately measure the casing inner diameter. When the upper and lower probe units are fully extended, reliable contact between the probes and the casing inner wall is ensured, while also providing a positive centering function to ensure the through-casing resistivity logging tool remains centered downhole for safe raising or lowering.

[0023] Furthermore, in the above-mentioned logging instrument, the probe unit includes a first rotating shaft group and a second rotating shaft group, the first rotating shaft group and the second rotating shaft group are connected by a pushing rod group, each pushing rod group includes two pushing rods hinged to each other, and each pushing rod is hinged to the corresponding rotating shaft in the corresponding rotating shaft group; a probe for supporting the inner wall of the contact casing is formed or arranged at the pushing rod hinge of each pushing rod group; the pushing motor module is used to push and pull the first rotating shaft group and the second rotating shaft group.

[0024] Furthermore, in the above-mentioned logging instrument, the probes are arranged at equal angles along the circumferential direction.

[0025] The probes are evenly arranged along the circumference, which can fully receive the current response signal of the formation and measure the change of the inner diameter, further improving the angular resolution and ensuring the accuracy of the measurement.

[0026] Furthermore, in the above-mentioned logging instrument, the pushing motor module includes a motor and a screw system, and the pushing motor module drives the screw system through the motor to push and pull the first rotating shaft group and the second rotating shaft group.

[0027] A pushing motor module is formed by the motor and the lead screw system to realize the push-pull movement of the first rotating shaft group and the second rotating shaft group. The structure is simple and easy to implement.

[0028] Furthermore, in the above-mentioned logging instrument, when performing resistivity logging, a pulse current is sent to the casing through the first measuring device, and the discharge voltage and probe current are simultaneously acquired through the first acquisition system to calculate the resistivity;

[0029] Alternatively, a pulse current is sent to the casing by the first measuring device, and the discharge voltage and probe current are simultaneously acquired by the first acquisition system and the second acquisition system to calculate the resistivity;

[0030] Alternatively, a pulse current is sent to the casing by the first measuring device and the second measuring device, and the discharge voltage and probe current are obtained by the first acquisition system and the second acquisition system to calculate the resistivity.

[0031] In the working mode in which a pulse current is sent to the casing by the first measuring device and the discharge voltage and probe current are obtained by the first acquisition system to calculate the resistivity, the instrument has the highest vertical resolution and is more suitable for measuring thin interlayers; in the working mode in which a pulse current is sent to the casing by the first measuring device and the discharge voltage and probe current are obtained by the first and second acquisition systems to calculate the resistivity, better correction of factors affecting remote exploration and near-wellbore areas can be achieved; in the working mode in which a pulse current is sent to the casing by the first and second measuring devices and the discharge voltage and probe current are obtained by the first and second acquisition systems to calculate the resistivity, the influence of the casing and cement sheath can be offset, focusing on the far end can be achieved, the resolution of formation current acquisition can be improved, and the accuracy of measurement can be enhanced.

[0032] The acquisition system uses each probe to synchronously receive the formation current response characteristics at different angles, transmitting and receiving at the same time, shortening the single acquisition cycle and reducing the deviation between the start and end angles of recording for each probe. It can also ensure measurement accuracy even when the instrument rotates, meeting the requirements for accurate identification of weak signals in casing formations and ensuring on-site logging efficiency.

[0033] Furthermore, in the above-mentioned logging instrument, the pulse current is a pulse current with periodic forward and reverse intervals.

[0034] Emitting periodic forward and reverse spike pulse currents into the casing can greatly increase the current leaking into the formation, enhancing the effective identification of formation information through the casing; the same magnitude of the current emitted in the forward and reverse directions can offset the influence of the casing resistance and improve the accuracy of resistivity measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 Schematic diagram of the structure of a through-casing resistivity logging tool according to an embodiment of the present invention;

[0036] Figure 2 This is a structural diagram of a first pushing motor module in an embodiment of the present invention;

[0037] Figure 3 Schematic diagram of the structure of the first probe system in an embodiment of the present invention;

[0038] Figure 4 Schematic diagram of a single discharge circuit of each functional module in an embodiment of the present invention;

[0039] Figure 5 Schematic diagram of the structure of the second probe system in an embodiment of the present invention;

[0040] Figure 6 Schematic diagram of the connection of various functional modules in an embodiment of the present invention;

[0041] Figure 7 : is a waveform diagram of a spike pulse signal in an embodiment of the present invention;

[0042] Figure 8 4 is a flowchart of resistivity logging in an embodiment of the present invention.

[0043] In the figure: 1 is the host computer, 2 is the data power cable, 3 is the through-casing resistivity logging tool, 301 is the first housing, 302 is the first push motor module, 30201 is the motor, 30202 is the ball screw, 30203 is the sliding shaft, 30204 is the push shaft, 3021 is the first connecting shaft group, 30211, 30212, 30213 are the first connecting shaft, the second connecting shaft, the third connecting shaft in the first connecting shaft group respectively. 303 is a first probe system, 3032 is a first probe group, 30321, 30322, 30323 are respectively the first probe, the second probe, the third probe in the first probe group, 3033 is a first push rod group, 30331, 30332, 30333 are respectively the first push rod, the second push rod and the third push rod, 304 is a second housing, 3040 is a second connecting shaft group, 3041 is a third connecting shaft group, 30 5 is the first switch group, 3051 is the first switch, 3052 is the second switch, 3053 is the third switch, 306 is the first capacitor group, 3061 is the first capacitor, 3062 is the second capacitor, 3063 is the third capacitor, 307 is the first reversing group, 3071 is the first reversing module, 3072 is the second reversing module, 3073 is the third reversing module, 308 is the power supply module, 309 is the second reversing group, 310 is the second capacitor group, 311 is the second switch group, 312 is the second probe system, 3122 is the second probe group, 3123 is the second pushing rod group, 313 is the second pushing motor module, 3131 is the fourth connecting shaft group, 314 is the third housing, 4 is the first processor, 401 is the data bus, 5 is the first acquisition system, 501 is the voltage acquisition module, 502 is the probe acquisition module, 6 is the second processor, 7 is the second acquisition system, and 101 is the loop current electrode. DETAILED DESCRIPTION

[0044] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0045] Example 1 of through-casing resistivity logging tool:

[0046] The through-casing resistivity logging instrument in this embodiment includes a first processor 4 and a first acquisition system 5. The first processor 4 and the first acquisition system 5 are both arranged inside the through-casing resistivity logging instrument 3. The first acquisition system 5 respectively collects voltage and probe current, transmits them to the first processor 4 for processing via the data bus 401, and then uploads the processed information to the host computer 1 via the data power cable 2. The host computer 1 processes and analyzes the signals to ultimately determine the resistivity information of the formation.

[0047] like Figure 1 As shown, the through-casing resistivity logging tool 3 also includes a first push motor module 302, a first probe system 303, a first switch group 305, a first capacitor group 306, and a first reversing group 307. The first push motor module 302 is disposed in a first housing 301, while the first switch group 305, the first capacitor group 306, the first reversing group 307, the power module 308, the first processor 4, and the first acquisition system 5 are all disposed in a second housing 304. The first housing 301 and the second housing 304 can prevent wear on the various devices and mutual interference between the modules. In this embodiment, the first housing 301 and the second housing 304 are both cylindrical. As other embodiments, the specific shapes of the first housing 301 and the second housing 304 are not limited, as long as they match the shape of the production well casing and do not affect the measurement.

[0048] The first pushing motor module 302 is as follows Figure 2 As shown, the system includes a motor 30201, a ball screw 30202, a sliding shaft 30203, and a pushing shaft 30204. The output shaft of the motor 30201 is connected to the sliding shaft 30203 via the ball screw 30202, and the sliding shaft 30203 is further connected to the pushing shaft 30204. The pushing shaft 30204 drives the first connecting shaft assembly 3021 to move up and down. The first probe assembly 3032 of the first probe system 303 is hinged to the corresponding connecting shafts of the first connecting shaft assembly 3021 via the pushing rods of the first pushing rod assembly 3033. When the motor 30201 is powered on, the motor 30201 drives the ball screw 30202 and the push shaft 30204 to move back and forth, thereby driving the first connecting shaft group 3021 to move back and forth, and then realizing the opening of each push rod in the first push rod group 3033, so that each probe in the first probe group 3032 is supported on the inner wall of the sleeve.

[0049] The first probe system 303 is disposed between the first housing 301 and the second housing 304 and is connected to the first pushing motor module 302 and the first switch group 305 via a connecting shaft. Figure 3As shown, the first probe system 303 includes a first probe group 3032 and a first pushing rod group 3033. The first probe group 3032 includes a plurality of probes, for example, a first probe 30321, a second probe 30322, a third probe 30323, etc., and the first pushing rod group 3033 includes pushing rods corresponding to the probes, for example, a first pushing rod 30331, a second pushing rod 30332, a third pushing rod 30333, etc.

[0050] Each probe corresponds to two pushing rods in the first pushing rod group 3033. Specifically, each probe is connected to the first pushing motor module 302 in the first housing 301 through a corresponding pushing rod, and is also connected to the first switch group 305 in the second housing 304 through another corresponding pushing rod. The first pushing motor module 302 is articulated to the pushing rod on the side of the first probe system 303 close to the first pushing motor module 302 through each connecting shaft in the first connecting shaft group 3021, and the second housing 304 is articulated to the pushing rod on the side of the first probe system 303 close to the first switch group 305 through each connecting shaft in the second connecting shaft group 3040. The first connecting shaft group 3021 includes a first connecting shaft 30211, a second connecting shaft 30212, a third connecting shaft 30213, etc. For example, the first probe 30321 is connected to the first pushing motor module 302 via one of the first pushing rods 30331 and the first connecting shaft 30211 in the first connecting shaft group 3021, and is further connected to the second housing 304 via another first pushing rod 30321 and a connecting shaft in the second connecting shaft group 3040. After being powered, the first pushing motor module 302 can control the pushing rods in the first pushing rod group 3033 to contract or expand, thereby supporting each probe of the first probe group 3032 against the inner wall of the casing.

[0051] In this embodiment, the first probe group 3032 includes 12 probes, which are evenly rotated and arranged at equal angles along the circumferential direction, and the corresponding first pushing rod group 3033 has 12 pairs of pushing rods. According to the principle that one circle is 360°, it can be calculated that the resolution of the first probe system 303 is 360° / 12=30°. As another embodiment, the number of probe groups can also be 24, then the resolution of the first probe system 303 is 360° / 24=15°. There is no limit to the number of probe groups, as long as it is ensured that the probes in the first probe system 303 can be evenly arranged in the casing. The more probes there are, the higher the angular resolution and the more accurate the result.

[0052] In this embodiment, the first processor 4 is a DSP processor that includes multiple acquisition chips, each of which is equipped with a small-capacity memory and a large-capacity memory. The signal input of each acquisition chip is connected to the signal output of each probe in the first probe group 3032 to obtain the current signal collected by the probe. The acquisition chip stores the collected current signal in the small-capacity memory, waiting for the DSP processor to read it sequentially. The DSP processor reads the digital signal stored in the small-capacity memory and stores it in the large-capacity memory. The data is then uploaded to the host computer 1 via the data power cable 2. The host computer 1 analyzes the data and calculates the resistivity of the formation.

[0053] The power module 308 in the through-casing resistivity logging instrument 3 is connected to the first pushing motor module 302 and the first processor 4. The power module 308 is connected to the power supply equipment set on the ground. When the through-casing resistivity logging instrument 3 reaches the designed depth, the first processor 4 issues an instruction to control the power module 308 to power the first pushing motor module 302, so that the first pushing motor module 302 works and acts on the first pushing rod group 3033, so that each probe in the first probe group 3032 is supported on the inner wall of the casing.

[0054] like Figure 6 As shown, the power module 308 is connected to the first commutation group 307, the first capacitor group 306, the first switch group 305, and the first probe group 3032 in sequence. In this embodiment, the capacitors in the first capacitor group 306 are non-polar capacitors, and their main function is to provide sharp pulse high-power current for instantaneous emission. Figure 4 The figure shows a unidirectional discharge circuit of the through-casing resistivity logging tool 3. When the switch in the switch group is closed, the power module charges the capacitor group through the commutation group; when the switch in the switch group is opened, the capacitor group discharges to the probe.

[0055] The first processor 4 is connected to the first commutation group 307 and the first switch group 305 via a data bus 401, and is also connected to the first acquisition system 5. The voltage acquisition module 501 of the first acquisition system 5 is connected to each capacitor in the first capacitor group 306 to acquire the voltage across each capacitor; the probe acquisition module 502 of the first acquisition system 5 is connected to each probe in the first probe group 3032 to obtain current information collected by each probe.

[0056] Since the number of probes in the first probe group 3032 in this embodiment is 12, the first switch group 305 includes 12 switches corresponding to the probes, the first capacitor group 306 includes 12 corresponding capacitors, and the first commutation group 307 includes 12 corresponding commutation modules. The first switch group 305 includes a first switch 3051, a second switch 3052, and a third switch 3053, and the first commutation group 307 includes a first commutation module 3071, a second commutation module 3072, and a third commutation module 3073. The first processor 4 controls the connection of each switch and commutation module, and the voltage acquisition module 501 samples the voltage of each connected capacitor.

[0057] The first processor 4 is connected to the power module 308 and the data bus 401. The data bus 401 is connected to the switches of the first switch group 305 and the commutation modules of the first commutation group 307. The first processor 4 controls the first commutation group 307 to cause the power module 308 to transmit positive and negative pulses to the first capacitor group 306. The first processor 4 controls the on and off of the switches in the first switch group 305 to charge or instantaneously discharge the capacitors in the first capacitor group 306. The first processor 4 also controls the probes to synchronously collect current signals.

[0058] The through-casing resistivity logging tool 3 also includes a loop current electrode 101. This electrode is connected to the surface power supply and the host computer 1, forming a test loop with each probe through the formation. The host computer 1 and the surface power supply are located in a logging vehicle, which is connected to the surface system. The loop current electrode 101 is located on the surface, typically connected to the casing string wellhead of an adjacent well.

[0059] The through-casing resistivity logging tool in this embodiment can realize a single-shot single-receive working mode. In the single-shot single-hand working mode, the instrument has the highest vertical resolution and is more suitable for resistivity measurement of thin interbeds. The workflow in this mode is as follows: Figure 8 As shown, the following steps are included:

[0060] (1) The ground power supply equipment, i.e., the high-power current source on the ground, supplies power to the downhole through-casing resistivity logging instrument 3, so that the first pushing motor module 302 is powered.

[0061] (2) The motor 30201 of the first pushing motor module 302 is started, and the pushing shaft 30204 is pushed to move through the ball screw 30202, and then the corresponding probe is supported on the inner wall of the sleeve through the pushing rod, and each probe is evenly rotated and arranged at equal angles along the circumferential direction.

[0062] (3) The first processor 4 receives the command to start emitting current given by the upper computer 1, controls each switch in the first switch group 305 to close, and enables the ground power supply equipment to provide high voltage to the first reversing group 307 through the power module 308, thereby charging the first capacitor group 306 with positive or negative current.

[0063] (4) The voltage acquisition module 501 acquires the voltage information of each capacitor in the first capacitor group 306. When it is detected that the capacitor voltage reaches the set value, the first processor 4 controls each switch in the first switch group 305 to open, and each capacitor in the first capacitor group 306 discharges, and sends a signal to the corresponding probe. Figure 7 The periodic spike pulse signal shown. In this embodiment, the periodic spike pulse signal recording period includes a transient emission period and a collection period, typically 3000V to 5000V. The forward and reverse emission currents are consistent, offsetting the effects of casing resistance. Spike pulse transmission does not require a continuous surface power supply and can be performed underground using a single-core cable for energy storage transmission, offering a wider range of applications and greater reliability.

[0064] When each switch in the first switch group 305 is turned on, the first probe system 303 is turned on. Each probe in the first probe system 303 acts as a receiver to receive the current response characteristics of the casing formation in each sector. The first processor 4 sends a common clock signal to each probe in the first probe system 303, so that each probe synchronously collects electrical signals. The probe acquisition module 502 of the first acquisition system 5 obtains the current information collected by each probe in the first probe system 303.

[0065] (5) The first acquisition system 5 stores the data packets of the currently acquired voltage information and current information in the first processor 4 and waits for an upload command.

[0066] (6) After receiving the upload command, the first processor 4 sends the stored data packet to the host computer 1.

[0067] (7) The host computer 1 analyzes the received data packets and displays the data in the form of a waveform curve.

[0068] (8) The host computer 1 automatically determines whether the data is abnormal or normal according to the set judgment conditions. If the data is abnormal, the staff is prompted to modify the settings and then measure again; if the data is normal, the data packet is stored.

[0069] (9) After the data packet is stored, the next depth point is measured.

[0070] Example 2 of Through-Casing Resistivity Logging Tool:

[0071] The difference between this embodiment and Example 1 is that the through-casing resistivity logging tool in this embodiment further includes a second probe system 312 and a second push motor module 313. The second probe system 312 also includes 12 probes. Therefore, in this embodiment, the first switch group 305 has 24 corresponding switches, the first capacitor group 306 has 12 corresponding capacitors, and the first reversing group 307 has 24 corresponding reversing modules. The first processor 4 controls the connection between the switches and reversing modules, and the probe acquisition module 502 of the first acquisition system 5 also samples the probes connected to the second probe system 312.

[0072] The structure of the second pushing motor module 313 is similar to that of the first pushing motor 302. It is arranged in the third shell 314. The third shell 314 is cylindrical. As other embodiments, the shape of the third shell 314 is not limited, as long as it matches the shape of the production well casing and does not affect the measurement.

[0073] The second probe system 312 is disposed between the second housing 304 and the third housing 314, and its structure and configuration are similar to those of the first probe system 303. The probes in the second probe system 312 are connected to corresponding connecting shafts in the third connecting shaft assembly 3041 via corresponding push rods. They are also connected to the second push motor module 313 via another corresponding push rod. When the motor in the second push motor module 313 is powered, it controls the push rods in the second probe system 312 to retract or expand, thereby supporting the probes of the second probe system 312 against the inner wall of the cannula.

[0074] Example 3 of Through-Casing Resistivity Logging Tool:

[0075] The difference between this embodiment and the first embodiment is that the through-casing resistivity logging tool in this embodiment further includes a second probe system 312, a second pushing motor module 313, a second reversing group 309, a second capacitor group 310, a second switch group 311, a second processor 6 and a second acquisition system 7. Figure 2 As shown, the first pushing motor module 302 is arranged in the first shell 301, the first switch group 305, the first capacitor group 306, the first commutation group 307, the power supply module 308, the second commutation group 309, the second capacitor group 310, the second switch group 311 and the first processor 4, the first acquisition system 5, the second processor 6, the second acquisition system 7 are arranged in the second shell 304, and the second pushing motor module 313 is arranged in the third shell 314.

[0076] The first, second, and third housings 301, 304, and 314 prevent wear and tear on the various devices and interference between modules. In this embodiment, the first, second, and third housings 301, 304, and 314 are cylindrical. In other embodiments, the specific shapes of the first, second, and third housings 301, 304, and 314 are not limited, as long as they match the shape of the production well casing and do not affect measurement.

[0077] The first processor 4 is connected to the first acquisition system 5 via the data bus 401. The voltage acquisition module 501 of the first acquisition system 5 is connected to each capacitor in the first capacitor group 306 to acquire the voltage across each capacitor; the probe acquisition module 502 of the first acquisition system 5 is connected to each probe in the first probe system 303 to obtain current information collected by each probe.

[0078] The second processor 6 is connected to the second acquisition system 7 via a data bus. The voltage acquisition module of the second acquisition system 7 is connected to each capacitor in the second capacitor bank 310 to acquire voltage information across each capacitor. The probe acquisition module of the second acquisition system is connected to each probe of the second probe system 312 to obtain current information collected by each probe in the second probe system 312.

[0079] The first acquisition system 5 transmits the collected capacitor voltage and probe current to the first processor 4 for data processing, and the second acquisition system 7 transmits the collected capacitor voltage and probe current to the second processor 6 for data processing. Then the first processor 4 and the second processor 6 upload the processed voltage and current information to the host computer 1 through the data power cable 2. The host computer 1 analyzes and processes the signals and finally determines the resistivity information of the formation.

[0080] The first probe system 303 is provided between the first housing 301 and the second housing 304, and is connected to the first pushing motor module 302 and the first switch group 305. The second probe system 312 is provided between the second housing 304 and the third housing 314, and is connected to the second pushing motor module 313 and the second switch group 311, respectively. Figure 5 As shown, the second probe system 312 includes a second probe group 3122 and a second pushing rod group 3123. Each probe in the second probe group 3122 is connected to the two pushing rods in the second pushing rod group 3123. The probe is connected to the connecting shaft in the fourth connecting shaft group 3131 through one of the corresponding pushing rods, and is also connected to the corresponding connecting shaft in the third connecting shaft group 3041 through another corresponding pushing rod.

[0081] In this embodiment, the first probe system 303 includes 12 probes, and the second probe system 312 also includes 12 probes. Therefore, there are 12 corresponding switches in the first switch group 305, 12 corresponding capacitors in the first capacitor group 306, and 12 corresponding reversing modules in the first reversing group 307. The first processor 4 is respectively connected to each switch in the first capacitor group 305 and each reversing module in the first reversing group 307; there are 12 corresponding switches in the second switch group 311, 12 corresponding capacitors in the second capacitor group 310, and 12 corresponding reversing modules in the second reversing group 309. The second processor 6 is respectively connected to each switch in the second switch group 311 and each reversing module in the second reversing group 309.

[0082] In this embodiment, both the first processor 4 and the second processor 6 are DSP processors, each comprising multiple acquisition chips, each of which is supplemented with a small-capacity memory and a large-capacity memory. The signal input of the acquisition chip of the first processor 4 is connected to the signal output of each probe in the first probe system 303 to acquire the current signals collected by each probe in the first probe system 303; the signal input of the acquisition chip of the second processor 6 is connected to the signal output of each probe in the second probe system 312 to acquire the current signals collected by each probe in the second probe system 312. The acquisition chip stores the collected current signals in the small-capacity memory, awaiting sequential reading by the DSP processor. The DSP processor reads the digital signals stored in the small-capacity memory, stores them in the large-capacity memory, and then uploads them to the host computer 1 via the data power cable 2. The host computer 1 analyzes the data and subsequently calculates the resistivity of the formation.

[0083] One end of the power module 308 is connected to the ground power supply equipment, and the other end is respectively connected to the first pushing motor module 302 and the second pushing motor module 313. The first processor 4 controls the power supply module 308 to supply power to the first pushing motor module 302. The first processor 4 issues a power supply instruction, and the power module 308 supplies power to the first pushing motor module 302, causing the motor of the first pushing motor module 302 to operate and act on the first pushing rod group 3033, thereby supporting each probe in the first probe group 3032 on the inner wall of the casing. The second processor 6 controls the power supply module 308 to supply power to the second pushing motor module 313. The second processor 6 issues a power supply instruction, and the power module 308 supplies power to the second pushing motor module 313, causing the motor of the second pushing motor module 313 to start, thereby supporting each probe of the second probe system 312 on the inner wall of the casing.

[0084] The first processor 4 is connected to each switch of the first switch group 305 and each commutation module of the first commutation group 307 through the data bus 401, and realizes that the power supply module 308 transmits positive and negative pulses to the capacitors in the first capacitor group 306 by controlling the first commutation group 307, and realizes the charging or instantaneous discharge of each capacitor in the first capacitor group 306 by controlling the on and off of the switches in the first switch group 305, and also controls each probe in the first probe system 303 to synchronously collect current signals.

[0085] The second processor 6 is connected to each switch in the second switch group 311 and each reversing module in the second reversing group 309 through a data bus, and realizes that the power supply module 308 transmits positive and negative pulses to the capacitors in the second capacitor group 310 by controlling the second reversing group 309, and realizes that each capacitor in the second capacitor group 310 is charged or instantly discharged by controlling the on and off of the switches in the second switch group 311, and also controls each probe in the second probe system 312 to synchronously collect current signals.

[0086] The through-casing resistivity logging tool in this embodiment can realize dual-transmit and dual-receive operation mode or single-transmit and dual-receive operation mode. When using the dual-transmit and dual-receive operation mode, the influence of the casing and cement sheath can be offset, and the focus can be achieved at the far end, thereby improving the resolution of formation current acquisition. The specific working process in this mode is as follows:

[0087] (1) When the through-casing resistivity logging instrument reaches a certain depth, the surface power supply equipment supplies power to the downhole through-casing resistivity logging instrument 3, so that the first pushing motor module 302 and the second pushing motor module 313 are powered.

[0088] (2) The motor of the first pushing motor module 302 is started, and acts on the pushing rod through the corresponding transmission components, so that the probes of the first probe system 303 are supported on the inner wall of the casing. The motor of the second pushing motor module 313 is started, and acts on the pushing rod through the corresponding transmission components, so that the probes of the second probe system 312 are supported on the inner wall of the casing. The probes are evenly rotated and arranged at equal angles along the circumferential direction.

[0089] (3) The first processor 4 receives the command to start transmitting current given by the host computer 1, controls the closure of each switch in the first switch group 305, and enables the ground power supply equipment to provide high voltage to the first reversing group 307 through the power module 308, thereby charging the first capacitor group 306 with positive or negative current; the second processor 6 receives the command to start transmitting current given by the host computer 1, controls the closure of each switch in the second switch group 311, and enables the ground power supply equipment to provide high voltage to the second reversing group 309 through the power module 308, thereby charging the capacitors 310 in the second capacitor group with positive or negative current.

[0090] (4) The voltage acquisition module 501 acquires the voltage information of each capacitor in the first capacitor group 306. When it is detected that the capacitor voltage reaches the set value, the first processor 4 controls each switch in the first switch group 305 to open, and each capacitor in the first capacitor group 306 discharges, and sends the corresponding probe in the first probe system 303 as shown in FIG. Figure 7 The voltage acquisition module of the second acquisition system 7 collects voltage information of each capacitor in the first capacitor group 306. When it detects that the capacitor voltage reaches a set value, the second processor 6 controls the switches of the second switch group 311 to open, causing the second capacitor group 310 to generate positive and negative spike pulse signals, which are sent to the corresponding probes of the second probe system 312.

[0091] When the first switch group 305 is turned on, the first processor 4 sends a common clock signal to the first acquisition system 5, and the probe acquisition module 502 synchronously acquires the current signal of each probe through each probe in the probe system 303 as the current response characteristics of the casing formation in each sector.

[0092] When the second switch group 305 is turned on, the second processor 6 sends a common clock signal to the second acquisition system 7. The probe acquisition module of the second acquisition system 7 synchronously acquires the current signal of each probe through the second probe system 312 as the current response characteristics of the casing formation in each sector.

[0093] (5) The first acquisition system 5 and the second acquisition system 7 store the data packets of the currently acquired voltage information and current information in the corresponding first processor 4 and second processor 6, and wait for the upload command.

[0094] (6) After receiving the upload command from the host computer 1 , the first processor 4 and the second processor 6 send the stored data packet to the host computer 1 .

[0095] (7) The host computer 1 analyzes the received data packets and displays the data in the form of a waveform curve.

[0096] (8) The host computer 1 automatically determines whether the data is abnormal or normal according to the preset judgment conditions. If the data is abnormal, the staff is prompted to modify the settings and then measure again; if the data is normal, the data packet is stored.

[0097] (9) After the data packet is stored, the current measurement is terminated and the measurement of the next depth point is carried out.

[0098] When using the single-transmit dual-receive working mode, through the two groups of receivers, better correction of factors affecting the long-range exploration and near-wellbore areas can be achieved. The working process in this mode is as follows:

[0099] (1) When the through-casing resistivity logging instrument reaches a certain depth, the surface power supply equipment supplies power to the downhole through-casing resistivity logging instrument 3, so that the first pushing motor module 302 and the second pushing motor module 313 are powered.

[0100] (2) The motor of the first pushing motor module 302 is started, and acts on the pushing rod through the corresponding transmission components, so that the probes of the first probe system 303 are supported on the inner wall of the casing. The motor of the second pushing motor module 313 is started, and acts on the pushing rod through the corresponding transmission components, so that the probes of the second probe system 312 are supported on the inner wall of the casing. The probes are evenly rotated and arranged at equal angles along the circumferential direction.

[0101] (3) The first processor 4 receives the command to start emitting current given by the upper computer 1, controls each switch in the first switch group 305 to close, and enables the ground power supply equipment to provide high voltage to the first reversing group 307 through the power module 308, thereby charging the first capacitor group 306 with positive or negative current.

[0102] Alternatively, the second processor 6 receives a command from the host computer 1 to start emitting current, controls each switch in the second switch group 311 to close, and enables the ground power supply equipment to provide high voltage to the second reversing group 309 through the power module 308, thereby charging each capacitor 310 in the second capacitor group with positive or negative current.

[0103] (4) When the first processor 4 receives the command from the host computer 1 to start emitting current in step (3) and controls the charging of the first capacitor group 306, the voltage acquisition module 501 of the first acquisition system 5 acquires the voltage information of the capacitors in the first capacitor group 306. When it is detected that the capacitor voltage reaches the set value, the first processor 4 controls each switch in the first switch group 305 to open, and each capacitor in the first capacitor group 306 discharges, and sends the corresponding probe in the first probe system 303 as shown in FIG. Figure 7 The periodic spike signal shown.

[0104] When the switch in first switch group 305 is turned on, first probe system 303 and second probe system 311 are activated. The probes in first probe system 303 and second probe system 311 act as receivers to receive the current response characteristics of the cased formation in each sector. First processor 4 sends a common clock signal to each probe in first probe system 303, and second processor 6 sends the same common clock signal to each probe in second probe system 312, enabling each probe to synchronously collect electrical signals. Probe collection module 502 of first collection system 5 acquires the current signals collected by each probe in first probe system 303, while probe collection module 502 of second collection system 7 acquires the current signals collected by each probe in second probe system 311.

[0105] (5) The first acquisition system 5 stores the currently acquired voltage information and current information as a data packet in the first processor 4, and the second acquisition system 7 stores the acquired current information as a data packet in the second processor 6, waiting for an upload command.

[0106] (6) After receiving the upload command from the host computer 1 , the first processor 4 and the second processor 6 send the stored data packet to the host computer 1 .

[0107] (7) The host computer 1 analyzes the received uploaded data packets and displays the data in the form of a waveform curve.

[0108] (8) The host computer 1 automatically determines whether the data is abnormal or normal according to the set judgment conditions. If the data is abnormal, the staff is prompted to modify the settings and then measure again; if the data is normal, the data packet is stored.

[0109] (9) After the data packet is stored, the measurement of the next depth point is carried out.

Claims

1. A through-casing resistivity logging tool, characterized in that: The device comprises a power supply module, a loop current electrode for forming a measurement loop, and two measuring devices, each of which comprises a probe system for supporting on the inner wall of the casing, a high-voltage energy storage and discharge system, a processor, and a collection system for collecting the discharge voltage and the probe current passing through the formation; The power module supplies power to the high-voltage energy storage and discharge systems in the two measuring devices; In each measuring device, the processor controls the probe system to support or disconnect the inner wall of the casing, and also controls the high-voltage energy storage and discharge system to store or discharge energy, and is also connected to the acquisition system; when the probe system supports and contacts the inner wall of the casing, the probes in the probe system are arranged at equal angles along the circumferential direction of the casing, and the high-voltage energy storage and discharge system is connected to the probe system to send a periodic sharp pulse signal to the corresponding probe to realize the discharge of the probe system into the casing. The recording period of the periodic sharp pulse signal includes an instantaneous emission period and an acquisition period; the processor sends a common clock signal to each probe in the probe system, and each probe acts as a receiver to synchronously receive the current response characteristics of the casing formation in each sector. The acquisition system obtains the current information collected by each probe in the probe system through the probe acquisition module. The acquisition system is also connected to the high-voltage energy storage and discharge system to collect the discharge voltage; The logging instrument can realize single-transmit and single-receive, single-transmit and dual-receive, and dual-transmit and dual-receive working modes; in the single-transmit and single-receive mode, one of the measuring devices sends a pulse current to the casing, and simultaneously obtains the discharge voltage and probe current through the acquisition system in the measuring device, and calculates the resistivity based on the discharge voltage and probe current obtained by the acquisition system; in the single-transmit and dual-receive mode, one of the measuring devices sends a pulse current to the casing, and simultaneously obtains the discharge voltage and probe current through the acquisition systems in the two measuring devices, and calculates the resistivity based on the discharge voltage and probe current obtained by the two acquisition systems; in the dual-transmit and dual-receive mode, both measuring devices send a pulse current to the casing, and simultaneously obtain the discharge voltage and probe current through the acquisition systems in the two measuring devices, and calculates the resistivity based on the discharge voltage and probe current obtained by the two acquisition systems.

2. The through-casing resistivity logging tool according to claim 1, characterized in that: The high-voltage energy storage and discharge systems in the two detection devices both include a capacitor group, a commutation group for controlling the capacitor group to output forward or reverse current, and a switch group for controlling the charging or discharging of the capacitor group. The processors in the two measuring devices control the commutation group and switch group corresponding to the two high-voltage energy storage and discharge systems.

3. The through-casing resistivity logging tool according to claim 1, characterized in that: The acquisition systems in the two measuring devices both include a voltage acquisition module and a probe acquisition module. The voltage acquisition module samples and connects to the capacitor group in the corresponding high-voltage energy storage and discharge system, and the probe acquisition module is used to connect to the probe in the corresponding probe system to collect the current passing through the formation.

4. The through-casing resistivity logging tool according to claim 1, characterized in that: The probe systems in the two measuring devices both include a probe unit and a pushing motor module; the pushing motor module drives the probe unit to compress or stretch in the axial direction; When the probe unit is axially compressed, the probe in the probe unit contacts the inner wall support of the sleeve; when the probe unit is axially extended, the probe in the probe unit is disconnected from the inner wall support of the sleeve.

5. The through-casing resistivity logging tool according to claim 4, characterized in that: The probe unit includes a first rotating shaft group and a second rotating shaft group, and the first rotating shaft group and the second rotating shaft group are connected by a pushing rod group. Each pushing rod group includes two pushing rods hinged to each other, and each pushing rod is hinged to the corresponding rotating shaft in the corresponding rotating shaft group; a probe for supporting the inner wall of the contact sleeve is formed or arranged at the pushing rod hinge of each pushing rod group; the pushing motor module is used to push and pull the first rotating shaft group and the second rotating shaft group.

6. The through-casing resistivity logging tool according to claim 4, characterized in that: The pushing motor module includes a motor and a screw system. The pushing motor module drives the screw system through the motor to push and pull the first rotating shaft group and the second rotating shaft group.

7. The through-casing resistivity logging tool according to claim 1, characterized in that: The pulse current is a pulse current with periodic forward and reverse intervals.

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