Through-casing formation resistivity logging instrument, through-casing formation resistivity measuring method and storage medium

Abstract

The invention belongs to the technical field of oil exploration and development, and particularly relates to a through-casing formation resistivity logging instrument, a measuring method and a storage medium, the through-casing formation resistivity logging instrument is placed in a metal casing and comprises an electronic circuit module, an emission electrode, a loop electrode and a supervision electrode, every two supervision electrodes form a pair of supervision electrodes, the supervision electrodes are all arranged between the emission electrode and the loop electrode, and the emission electrode, the supervision electrodes and the loop electrode are all electrically connected with the electronic circuit module. The emission electrode, the monitoring electrode and the loop electrode are arranged on the instrument main body structure at intervals, and every two electrodes are insulated from each other. According to the through-casing stratum resistivity logging instrument, a non-contact measurement mode is adopted, emission current is spread along a casing in a wave mode and enters a stratum, and the resistivity information of the stratum outside the casing can be obtained by reasonably arranging a monitoring electrode and a loop electrode to measure current phase information.

Description

Technical Field

[0001] This invention belongs to the field of petroleum exploration and development technology, and specifically relates to a casing-through formation resistivity logging instrument, measurement method and storage medium. Background Technology

[0002] As oilfield exploration and production enter the mid-to-late stages, accurate evaluation of reservoir oil content and quantitative calculation of remaining oil saturation have become urgent needs in the oil and gas engineering field. Through-casing resistivity logging technology, as a high-tech method capable of measuring the resistivity of reservoirs outside the casing from within the steel casing, is of great significance for improving open-hole well data and locating lost oil layers in older wells.

[0003] Traditional contact-type through-casing resistivity logging methods primarily obtain formation resistivity by measuring the minute voltage drop across the casing. The working principle involves placing the instrument electrodes in close contact with the inner wall of the casing within the well. By measuring the voltage difference between the electrodes and the current leaking into the formation, the resistivity of the formation outside the casing is calculated. This method requires at least two measurement modes: casing resistance mode and leakage current mode. The former measures the casing resistance between the electrodes by setting specific current injection and return methods; the latter calculates the leakage current flowing into the formation by measuring the voltage difference between the electrodes, ultimately determining the formation resistivity. However, traditional methods have significant technical limitations. First, their measurement speed is slow, typically only 240 feet per hour, which greatly limits their efficiency in actual production applications. Second, this method has extremely stringent requirements for the wellbore environment, requiring all electrodes to be completely and tightly attached to the casing wall, free of oil and rust, to obtain accurate results. However, in oil wells that have been in operation for a long time, casing deformation and internal corrosion are unavoidable phenomena, and well washing cannot completely remove oil stains from the well wall. Therefore, traditional methods often fail to meet the measurement requirements in practical applications, severely limiting their widespread use.

[0004] In summary, although traditional contact-type through-casing resistivity logging methods can measure reservoir resistivity outside the casing to some extent, their application is greatly limited due to drawbacks such as slow measurement speed and stringent wellbore environmental requirements. Therefore, it is necessary to develop a novel through-casing resistivity logging technology to address the problems of existing technologies and improve the efficiency and accuracy of oilfield development. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a casing-through formation resistivity logging instrument, which adopts a non-contact measurement mode. The alternating current emitted by the transmitting electrode propagates along the casing in the form of a wave and enters the formation. By reasonably setting the monitoring electrode and the loop electrode to measure the current phase information, the resistivity information of the formation outside the casing can be obtained.

[0006] The technical solution adopted in this invention is: a through-casing formation resistivity logging instrument, wherein the through-casing formation resistivity logging instrument is placed inside a metal casing, the through-casing formation resistivity logging instrument includes an electronic circuit module, a transmitting electrode, a loop electrode, and a monitoring electrode, wherein an even number of monitoring electrodes are provided, and every two monitoring electrodes form a pair of monitoring electrodes, all of which are disposed between the transmitting electrode and the loop electrode, and the transmitting electrode, monitoring electrode, and loop electrode are all electrically connected to the electronic circuit module, and the transmitting electrode, monitoring electrode, and loop electrode are all spaced apart on the main structure of the instrument, and each pair of electrodes is insulated from each other.

[0007] Furthermore,

[0008] The through-casing formation resistivity logging instrument includes at least two pairs of monitoring electrodes, and multiple monitoring electrodes are arranged continuously at intervals. The two monitoring electrodes located in the middle form a first pair of monitoring electrodes, and the two monitoring electrodes adjacent to the first pair of monitoring electrodes form a second pair of monitoring electrodes, and so on, with each pair of monitoring electrodes arranged in sequence.

[0009] Furthermore,

[0010] When at least two pairs of monitoring electrodes are provided, the spacing between the multiple monitoring electrodes arranged in consecutive intervals is equal.

[0011] Furthermore,

[0012] The electronic circuit module includes a main control circuit, a transmitting circuit, and a data acquisition circuit. The main control circuit controls signal transmission, the transmitting circuit generates alternating current and transmits it outward through the transmitting electrode, and the data acquisition circuit is divided into a first data acquisition circuit and a second data acquisition circuit. The first data acquisition circuit is used to receive the data acquisition signal from the monitoring electrode and extract phase information from the data acquisition signal, and the second data acquisition circuit is used to receive the data acquisition signal from the loop electrode and extract phase information from the data acquisition signal.

[0013] This invention also provides a method for measuring formation resistivity through casing, using the aforementioned through-casing formation resistivity logging instrument, the method comprising:

[0014] Alternating current is emitted into the metal sleeve through the emitting electrode;

[0015] While the transmitting electrode emits alternating current, the monitoring electrode and the loop electrode start collecting current signals, and the transmission time and the acquisition time are strictly synchronized.

[0016] Signal acquisition between monitoring electrodes must be strictly synchronized;

[0017] Phase information is extracted from the signals acquired by the monitoring electrodes, and formation resistivity information is obtained from the phase difference between the two signals acquired by a pair of monitoring electrodes.

[0018] Furthermore,

[0019] When the launch time and acquisition time are strictly synchronized, a shared clock line is also used for calibration.

[0020] Furthermore,

[0021] The signal acquisition between the monitoring electrodes must be strictly synchronized. The accuracy of the acquired phase information must be less than 1°. If it is greater than 1°, the acquired signal is considered to be erroneous, and the signal acquisition will be resynchronized until the accuracy of the acquired phase information is stable again less than 1°.

[0022] Furthermore,

[0023] If the loop electrode is involved in the calculation, the signal acquisition between the monitoring electrode and the loop electrode is also strictly synchronized. The accuracy of the acquired phase information must be less than 1°. If it is greater than 1°, it is considered that the acquired signal is incorrect, and the signal acquisition begins to resynchronize until the accuracy of the acquired phase information is stable at less than 1° again.

[0024] Phase information is extracted from the signals acquired by the monitoring electrode and the loop electrode, and formation resistivity information is obtained from the phase difference generated by the three signals acquired by a pair of monitoring electrodes and a loop electrode.

[0025] Furthermore,

[0026] When multiple pairs of monitoring electrodes are set up, they form multiple sets of current phase difference measurements. The phase information extracted from the signals collected by each monitoring electrode is different. The extracted phase information is used to perform differential calculation, thereby completing the measurement data compensation and correction.

[0027] The present invention also provides a computer-readable storage medium storing one or more programs, which, when executed, can realize the aforementioned through-casing formation resistivity measurement method.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1. Compared with traditional contact measurement methods, this invention adopts a non-contact measurement mode, which eliminates the need to tightly attach the electrode to the inner wall of the casing, thereby completely eliminating the interference of casing deformation, inner wall corrosion and well wall oil stains on the measurement results, and significantly improving the stability and reliability of the measurement results.

[0030] 2. By rationally setting the monitoring electrode and loop electrode to measure the current phase information, the resistivity information of the formation outside the casing can be obtained. The monitoring electrode is used to monitor and collect the current signal. The monitoring electrodes are set in pairs to ensure the acquisition of current phase difference information. The monitoring electrodes are all set between the transmitting electrode and the loop electrode. The main function of the loop electrode is to serve as part of the current loop, ensuring that the current can effectively flow through the formation and return to the logging instrument, thereby accurately measuring the resistivity of the formation and other related parameters.

[0031] 3. The measurement method describes the specific measurement mode of the through-casing formation resistivity logging instrument. The measurement mode provides the specific principle and steps, as well as the clear electrode arrangement. According to the measurement mode, formation resistivity information can be obtained relatively quickly. In addition, the measurement method adopts the synchronous signal measurement mode, which can effectively improve the measurement accuracy.

[0032] 4. Increasing the number of monitoring electrode pairs can form multiple sets of current phase difference measurements and enable measurement data compensation and correction, thereby further improving the accuracy of the measurement. When multiple monitoring electrodes are set, the phase information extracted from the signals collected by each monitoring electrode is different. The extracted phase information can be used to perform differential calculations, thereby completing the compensation and correction.

[0033] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings.

[0034] The invention will now be further described with reference to the accompanying drawings. Attached Figure Description

[0035] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of a non-contact through-casing formation resistivity measurement mode according to an embodiment of the present invention.

[0037] Figure 2 This is a schematic diagram of a non-contact through-casing formation resistivity measurement current loop according to an embodiment of the present invention.

[0038] Figure 3 This is a schematic diagram illustrating a non-contact through-casing formation resistivity measurement mode for obtaining formation resistivity according to an embodiment of the present invention.

[0039] Figure 4 This is a schematic diagram of the internal structure of an electronic circuit module according to an embodiment of the present invention;

[0040] Figure 5 This is a schematic diagram of a non-contact through-casing formation resistivity measurement method according to an embodiment of the present invention;

[0041] Figure 6 This is a schematic diagram of the electrode arrangement for a non-contact through-casing formation resistivity measurement according to an embodiment of the present invention.

[0042] The markings in the diagram are: 101-formation, 102-casing, 103-emitting electrode, 104, 105-monitoring electrode, 106-loop electrode, 107-wellbore fluid, 108-specific circuit device, 109-current loop, 201 represents different formations, and 202, 203, 204, 205 and 206 represent a set of current phase difference information. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of the embodiments of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this invention, and not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0044] like Figures 1 to 6 As shown in this embodiment, a through-casing formation resistivity logging instrument is disclosed. The logging instrument is placed inside a metal casing. The through-casing formation resistivity logging instrument includes an electronic circuit module, a transmitting electrode, a loop electrode, and a monitoring electrode. An even number of monitoring electrodes are provided, and every two monitoring electrodes form a pair of monitoring electrodes. The monitoring electrodes are all located between the transmitting electrode and the loop electrode. The transmitting electrode, monitoring electrode, and loop electrode are all electrically connected to the electronic circuit module. The transmitting electrode, monitoring electrode, and loop electrode are all spaced apart on the main structure of the instrument, and each pair of electrodes is insulated from each other.

[0045] In the above technical solution, a transmitting electrode is installed in the well, which generates an alternating current of a certain frequency. This current propagates in the form of a wave and enters the formation through the fluid, casing, cement sheath, and other media in the wellbore. An even number of monitoring electrodes are installed at a certain distance from the transmitting electrode, with each pair of monitoring electrodes forming a monitoring electrode pair. The monitoring electrodes are used to monitor and acquire current signals, and the paired installation of the monitoring electrodes ensures the acquisition of current phase difference information. In addition, a loop electrode is installed at a distance from the well to allow the current to flow back into the well from the formation in the form of a wave. Both the monitoring electrodes and the loop electrode have current signal acquisition capabilities. The monitoring electrodes are positioned between the transmitting electrode and the loop electrode. The main function of the loop electrode is to act as part of the current loop, ensuring that the current can effectively flow through the formation and return to the logging instrument, thereby accurately measuring the formation resistivity and other relevant parameters. In this embodiment, both the monitoring electrode and the loop electrode can acquire current signals. By setting different loads, this embodiment can adjust the amount of current entering the monitoring electrode and the loop electrode, ensuring the accuracy and stability of signal acquisition. In this system, the signal quantity refers to the current flowing into the electrode, which is the current signal that the electrode can acquire. The load mainly refers to the resistive load, the resistance value of which can be changed. By flexibly adjusting the load, this technical solution can precisely control the current signal quantity entering the monitoring electrode and the loop electrode, ensuring the accuracy and stability of signal acquisition. The acquired monitoring electrode current signal and loop electrode current signal will be processed by the electronic circuit module to extract phase information. This phase information can accurately reflect the propagation characteristics of the current in the formation, and then calculate the resistivity of the corresponding formation.

[0046] In some optional embodiments, both the monitoring electrode and the loop electrode are disposed on one side of the transmitting electrode (either above or below), and this is a preferred implementation. In other optional embodiments, the transmitting electrode is disposed in the middle, with loop electrodes disposed on both sides at a relatively far distance from the transmitting electrode, and a monitoring electrode disposed between the transmitting electrode and the loop electrode. In all the above optional embodiments, the monitoring electrode is disposed between the transmitting electrode and the loop electrode.

[0047] Figure 1 A schematic diagram of a non-contact, through-casing formation resistivity measurement mode is presented, taking the setup of one transmitting electrode, one loop electrode, and two monitoring electrodes as an example. Figure 1As shown, 103 is the transmitting electrode, 104 and 105 are monitoring electrodes, and 106 is the loop electrode. The transmitting electrode, monitoring electrode, and loop electrode are all mounted on the main structure of the logging instrument. In this embodiment, 104 and 105 form a pair of monitoring electrodes, which can collect phase information between these two monitoring electrodes, thereby ensuring the acquisition of current phase difference information. In specific implementations, the number of monitoring electrodes can be adjusted according to the actual logging instrument design. The number is at least two, and they are set in pairs. Increasing the number of monitoring electrode pairs can help improve the accuracy of actual measurements. The transmitting electrode 103 is loaded with an alternating current of a specific frequency. The current passes through the wellbore fluid 107 and casing 102 in the form of a wave, entering the formation 101.

[0048] exist Figure 1 In this method, the transmitting electrode generates an alternating current, and the monitoring electrode and the loop electrode are both located on one side of the transmitting electrode (in specific implementations, this can be above or below; in this embodiment, the lower side is used as an example). The alternating current flows through the wellbore, casing, and formation. A portion of the current flows back into the wellbore through the casing, mainly returning to the loop electrode, and secondarily to the monitoring electrode. Taking the transmitting electrode as T, the monitoring electrodes as R1 and R2, and the loop electrode as B, the current signals of T-R1, T-R2, and TB can be measured in this measurement mode, and then the phase and amplitude can be calculated. Assuming that the phase measured by T-R1 is Φ1 and the phase measured by T-R2 is Φ2, then the phase difference obtained by Φ2-Φ1 can reflect the formation resistivity information. The phase Φ3 measured by TB can also participate in the phase difference acquisition, such as Φ3-Φ2 and Φ3-Φ1. Then, the phase differences obtained by Φ2-Φ1, Φ3-Φ2, and Φ3-Φ1 can reflect the formation resistivity information.

[0049] Figure 2 A schematic diagram of a non-contact, through-casing formation resistivity measurement current loop is provided. Taking a single transmitting electrode, a loop electrode, and two monitoring electrodes as an example, in this embodiment, 108 is a specific circuit device for generating alternating current (the aforementioned electronic circuit module). It, along with the transmitting electrode 103, monitoring electrodes 104 and 105, loop electrode 106, wellbore fluid 107, casing 102, and formation 101, constitutes a current loop 109. This current loop 109 is the most advantageous for obtaining current phase difference information in the measurement mode. "Most advantageous" emphasizes that without the loop electrode 106, a large loop would not be formed, and the current would flow elsewhere, resulting in a weaker signal entering 104 and 105. The loop electrode 106 ensures that the current effectively returns to 104 and 105, and of course, also returns to 106, meaning it primarily returns to the loop electrode 106, and secondarily to the monitoring electrodes 104 and 105. The phase information acquired by 104 and 105 is the basis for measuring and calculating the corresponding formation resistivity.

[0050] The aforementioned current loop 109 refers to the path through which the alternating current flows. 103, 104, 105, 106, and 108 are connected internally by electronic circuitry. Specifically, the positive terminal of 108 is connected to 103, and its negative terminal is connected to 104, 105, and 106. Simultaneously, the wellbore fluid, casing, and formation are all good conductors, thus forming a loop. The monitoring electrodes 104 and 105 are insulated from each other and have good contact with the wellbore fluid, thus allowing for the measurement of current signals. The amount of current signal entering the monitoring electrodes and the loop electrode is controlled by setting load resistors for the monitoring electrodes 104 and 105 and the loop electrode 106. The load resistors are connected in series with the monitoring electrodes 104 and 105 and the loop electrode 106, respectively. In this embodiment, the transmitting electrode, monitoring electrode, and loop electrode set on the logging instrument are preferably electrode rings, which are fitted onto the main structure of the instrument. In specific implementations, the electrode form is not limited to electrode rings.

[0051] Figure 3 A schematic diagram of a non-contact, through-casing formation resistivity measurement mode is provided. Taking the setting of one transmitting electrode, one loop electrode and two monitoring electrodes as an example, when the logging instrument is pulled up for measurement, it passes through different formations 201, and the current loop 109 formed above completes the measurement. This measurement mode allows the instrument to complete the measurement without being in close contact with the well wall, thereby reducing the difficulty of operation and improving the measurement efficiency.

[0052] During the measurement process, as the instrument passes through different formations 201, the transmitting electrode generates an alternating current of a certain frequency. This current flows into formation 201 through the wellbore and casing. The transmitting electrode 103, monitoring electrodes 104 and 105, and the loop electrode 106 are synchronized via an electronic circuit module (i.e., the instrument's internal circuitry). After the current flows into formation 201, a portion returns to the loop electrode, and another portion returns to the monitoring electrode. The current phase information acquired by the monitoring electrode reflects the resistivity of the formation. If the two monitoring electrodes are in the same homogeneous formation, the phase difference is zero. If the two monitoring electrodes are in different formations, the acquired current phase information will differ. Therefore, the resistivity information of the formation can be obtained through the current phase difference. In this measurement mode, the current phase difference information is acquired through monitoring electrodes 104 and 105 as the instrument passes through each formation, resulting in a set of current phase difference information 202, 203, 204, 205, and 206. This information is then used to obtain the apparent resistivity of the formation using a conversion chart. The conversion chart used to obtain the apparent resistivity of the formation is based on the relationship between the phase difference and the apparent resistivity calculated by simulation. It is a corresponding relationship. The conversion chart can be further referenced from existing technologies, which will not be elaborated here.

[0053] As a preferred technical solution, the through-casing formation resistivity logging instrument includes at least two pairs of monitoring electrodes. Multiple monitoring electrodes are continuously spaced apart. The two monitoring electrodes located in the middle form the first pair, and the two monitoring electrodes adjacent to the first pair form the second pair, and so on. This increases the number of monitoring electrode pairs, allowing for multiple sets of current phase difference measurements and enabling measurement data compensation and correction, thereby further improving measurement accuracy. When multiple pairs of monitoring electrodes are set, the phase information extracted from the signals collected by each monitoring electrode is different. The extracted phase information can be used for differential calculation to complete compensation and correction. When the number of monitoring electrode pairs in the logging instrument is greater than two pairs, the monitoring electrodes are set in pairs as described above. The following is a simple explanation using three pairs of monitoring electrodes as an example: six monitoring electrodes are continuously spaced apart. The three pairs of monitoring electrodes are set as follows: the two monitoring electrodes located in the middle form the first pair, the two monitoring electrodes adjacent to the first pair form the second pair, and the two monitoring electrodes adjacent to the second pair form the third pair.

[0054] As a preferred technical solution, when at least two pairs of monitoring electrodes are provided, the spacing between the multiple monitoring electrodes arranged in successive intervals is equal. This embodiment provides multiple monitoring electrodes with consistent spacing to monitor and acquire current signals. Maintaining consistent spacing between the monitoring electrodes can improve the actual measurement effect of formation resistivity.

[0055] As a preferred technical solution, such as Figure 4 As shown, the electronic circuit module includes a main control circuit, a transmitting circuit, and a data acquisition circuit. The main control circuit controls signal transmission, the transmitting circuit generates alternating current and transmits it outward through the transmitting electrode, and the data acquisition circuit is divided into a first data acquisition circuit (i.e., data acquisition circuit 1) and a second data acquisition circuit (i.e., data acquisition circuit 2). The first data acquisition circuit receives the data acquisition signal from the monitoring electrode and extracts phase information from it. The second data acquisition circuit receives the data acquisition signal from the loop electrode and extracts phase information from it. In this embodiment, the current signal acquired by the monitoring electrode is processed and its phase information is extracted after being transmitted to the first data acquisition circuit, and the current signal acquired by the loop electrode is processed and its phase information is extracted after being transmitted to the second data acquisition circuit. The extracted phase information can reflect the characteristics of current propagation in the formation, thereby obtaining the resistivity of the corresponding formation. In specific implementations, a mode selection circuit and a programmable amplifier circuit can be used to adapt to different types of signal acquisition. The extraction of the above-mentioned phase information can refer to existing technologies and will not be elaborated here.

[0056] Based on the same inventive concept, this invention also provides a method for measuring formation resistivity through casing, using the aforementioned through-casing formation resistivity logging instrument, the method comprising:

[0057] S1. Emit alternating current to the metal sleeve through the transmitting electrode;

[0058] In this step, the electronic circuit module controls the transmitting electrode to generate an alternating current and emit AC power into the metal bushing. The emission frequency of the transmitting electrode is adjustable, preferably between 10kHz and 100kHz. In actual measurements, a suitable emission frequency can be selected first based on the actual operating conditions. Then, during a single measurement, the selected specific emission frequency can be consistently used to emit AC power for measurement.

[0059] S2. While the transmitting electrode emits AC current, the monitoring electrode and the loop electrode start to collect current signals. The transmission time and the collection time are strictly synchronized and corrected using a shared clock line.

[0060] In this step, the monitoring electrode and the loop electrode are preferably positioned to one side of the transmitting electrode (either above or below it). The transmission time is strictly synchronized with the acquisition time. This strict synchronization ensures that the acquired current phase information occurs at the same moment, guaranteeing that the measured current phase difference and the subsequent formation resistivity information reflect measurements at a specific depth. Using a shared clock line for calibration helps ensure strict synchronization between the transmission and acquisition times.

[0061] S3. The signal acquisition between the monitoring electrodes must be strictly synchronized. The accuracy of the acquired phase information must be less than 1°. If it is greater than 1°, the acquired signal is considered to be erroneous, and the signal acquisition will start to resynchronize until the accuracy of the acquired phase information is stable again less than 1°.

[0062] In this step, the phase information acquired by the two monitoring electrodes that form a pair is related to the information of the strata that flow through. The acquisition circuit associated with the two monitoring electrodes (i.e., the first acquisition circuit) will ensure that the signal acquisition between the two monitoring electrodes is strictly synchronized through signal synchronization, that is, to ensure that the signals acquired by the two monitoring electrodes are at the same time.

[0063] S4. Extract phase information from the signals acquired by the monitoring electrodes, and obtain formation resistivity information from the phase difference generated by the two signals acquired by a pair of monitoring electrodes.

[0064] In this step, phase information is extracted from the signal acquired by the monitoring electrode through the first acquisition circuit in the electronic circuit module. In this embodiment, the formation resistivity information obtained from the phase difference is achieved based on an apparent resistivity conversion chart. According to the apparent resistivity conversion chart, the corresponding apparent resistivity (i.e., formation resistivity information) can be obtained from the phase difference. The apparent resistivity conversion chart is a correspondence between phase difference and apparent resistivity calculated based on simulation.

[0065] Furthermore,

[0066] If the loop electrode is involved in the calculation, the signal acquisition between the monitoring electrode and the loop electrode is also strictly synchronized. The accuracy of the acquired phase information must be less than 1°. If it is greater than 1°, it is considered that the acquired signal is incorrect, and the signal acquisition begins to resynchronize until the accuracy of the acquired phase information is stable at less than 1° again.

[0067] In this step, the participation of the loop electrode in the calculation means that the signal acquired by the loop electrode is also used to calculate the formation resistivity information. When the loop electrode is close to the monitoring electrode (e.g., within 5m), the three-way phase difference information obtained can be used in the calculation and is considered reliable. Only when reliable is the loop electrode included in the calculation. If the loop electrode is far from the monitoring electrode (e.g., more than 5m), the participation of the loop electrode in the calculation is considered unreliable because the large distance between the electrodes will result in significant errors. When the loop electrode participates in the calculation, the accuracy between each pair of phase information acquired by the monitoring electrode and the loop electrode must be less than 1° to ensure strict synchronization. The aforementioned close proximity between the loop electrode and the monitoring electrode refers to the close distance between the loop electrode and the monitoring electrode closest to it. In practice, this close distance needs to be greater than the distance between two adjacent monitoring electrodes.

[0068] Phase information is extracted from the signals acquired by the monitoring electrode and the loop electrode, and formation resistivity information is obtained from the phase difference generated by the three signals acquired by a pair of monitoring electrodes and a loop electrode.

[0069] In this step, the first acquisition circuit extracts phase information from the signal acquired by the monitoring electrode, and the second acquisition circuit extracts phase information from the signal acquired by the loop electrode. In this embodiment, the formation resistivity information obtained from the phase difference is also achieved based on the apparent resistivity conversion chart.

[0070] Taking a method with one transmitting electrode, one loop electrode, and two monitoring electrodes as an example, the above measurement method requires that transmitting electrode 103, monitoring electrode 104, and monitoring electrode 105 be synchronized before measurement to ensure that the phase information of the current signals acquired by monitoring electrode 104 and monitoring electrode 105 is at the same moment. Ensuring this synchronization relies primarily on the electronic circuit module achieving strict synchronization between different acquisition boards through a shared clock line and synchronization signal. If they are not at the same moment, it cannot be concluded that the phase information acquired at that moment reflects the resistivity of the formation. This is related to the logging depth. In specific implementation, the main control circuit controls signal transmission. The main control circuit is electrically connected to the transmitting circuit and the acquisition circuit. Clock synchronization is achieved through the electronic circuit module composed of the main control circuit, transmitting circuit, and acquisition circuit, ensuring signal synchronization. Signal synchronization in specific implementation includes, but is not limited to, calibration methods. The calibration method generates a calibration signal through the transmitting circuit and sends it to each acquisition circuit, thereby achieving synchronization of the monitoring electrode and loop electrode signal acquisition. A linear phase-shift filter circuit is used to filter out noise and facilitate signal calibration; the acquisition circuits can achieve strict synchronization between different acquisition boards through a shared clock line and synchronization signal.

[0071] As a preferred technical solution, when multiple pairs of monitoring electrodes are set, these multiple pairs of monitoring electrodes constitute multiple sets of current phase difference measurements. The phase information extracted from the signals collected by each monitoring electrode is different. By using the extracted phase information to perform differential calculations, measurement data compensation and correction can be completed. The above solution increases the number of monitoring electrode pairs, which can constitute multiple sets of current phase difference measurements and realize measurement data compensation and correction, thereby further improving the accuracy of the measurement.

[0072] The following explanation uses the example of setting up two pairs of monitoring electrodes. Figure 6 A schematic diagram of the electrode arrangement for non-contact through-casing formation resistivity measurement is provided. In this embodiment, the transmitting electrode T is at the top, the monitoring electrodes R3, R1, R2, and R4 are arranged sequentially, and the loop electrode B is at the bottom. This allows for the acquisition of more sets of phase difference information. The differential process involves acquiring the phase information at the same moment on the electrodes through the acquisition circuit. The phase Φ1 measured by T-R1 is Φ1 = ph(I T-R1) Similarly, the phase Φ2 produced by T-R2 is ph(I T-R2 The phase Φ3 generated by T-R3 is ph(I) T - R3 The phase Φ4 = Φ4 = ph(I) generated by T-R4 T-R4 Then, by performing a difference operation, the two phase differences ph can be obtained. R1-R2 =ph(I T-R1 )-ph(I T-R2 ) and ph R3-R4 =ph(I T-R3 )-ph(IT-R4 The compensation correction is determined by the relative positions of R1, R2, R3, and R4, and the phase difference ph obtained between R3 and R4 is... R3-R4 It clearly includes the phase difference ph obtained between R1 and R2. R1-R2 Since the relative spacing of R1, R2, R3, and R4 is constant, the phase difference ph R3-R4 The reflected formation resistivity is greater than pH. R1-R2 The average of the two phase differences in the reflected formation resistivity can reflect the average change in the resistivity of that section of the formation. The aforementioned differential and compensation corrections can be further applied to this measurement mode with reference to existing technologies, which can effectively reflect changes in formation resistivity.

[0073] Therefore, the above measurement method describes the specific measurement mode of the through-casing formation resistivity logging instrument. This measurement mode provides specific principles and steps, as well as a clear electrode arrangement. According to the measurement mode, formation resistivity information can be obtained relatively quickly. In addition, the measurement method adopts a synchronous signal measurement mode, which can effectively improve the measurement accuracy. The phase measurement difference compensation correction achieved by multiple pairs of electrodes can ensure the accuracy of the effective measurement depth range.

[0074] Based on the same inventive concept, the present invention also provides a computer-readable storage medium storing one or more programs, which, when executed, can realize the aforementioned through-casing formation resistivity measurement method.

[0075] This invention employs a non-contact measurement method, cleverly configuring the transmitting electrode, monitoring electrode, and loop electrode to achieve rapid and accurate measurement of the formation resistivity outside the casing. Compared to traditional contact-type measurement methods, this invention eliminates the need for electrodes to be tightly bonded to the inner wall of the casing, thus completely eliminating interference from factors such as casing deformation, inner wall corrosion, and wellbore oil contamination, significantly improving the stability and reliability of the measurement results.

[0076] Furthermore, the present invention offers rapid measurement, significantly reducing logging operation time and improving work efficiency. This not only lowers operating costs but also provides more timely and accurate geological information for oilfield development, helping oil and gas engineers better evaluate reservoir oil content and quantitatively calculate remaining oil saturation, thus providing strong support for developing more scientific extraction plans. In summary, the present invention demonstrates significant advantages and effects in improving logging efficiency and accuracy, reducing operating costs, and promoting oilfield development, possessing broad application prospects and market value.

[0077] The parts not covered in this embodiment are the same as or can be implemented using existing technologies, and will not be further described here.

[0078] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A cross-formation resistivity logging instrument characterized by, The through-casing formation resistivity logging instrument is placed in a metal casing, and comprises an electronic circuit module, a transmitting electrode, a return electrode and supervisory electrodes, the supervisory electrodes are arranged in pairs, each pair of supervisory electrodes is arranged between the transmitting electrode and the return electrode, and the transmitting electrode, the supervisory electrodes and the return electrode are electrically connected to the electronic circuit module.

2. The through-casing resistivity logging instrument of claim 1, wherein, The through-casing formation resistivity logging instrument comprises at least two pairs of supervisory electrodes, and the supervisory electrodes are arranged in succession, and two supervisory electrodes in the middle form a first pair of supervisory electrodes, two supervisory electrodes adjacent to the first pair of supervisory electrodes form a second pair of supervisory electrodes, and each pair of supervisory electrodes is arranged in sequence.

3. The through-casing resistivity logging instrument of claim 1, wherein, When at least two pairs of supervisory electrodes are arranged, the intervals of the supervisory electrodes arranged in succession are equal.

4. A through-casing resistivity logging instrument according to any one of claims 1-3, characterized in that, The electronic circuit module comprises a main control circuit, a transmitting circuit and a collection circuit, the main control circuit controls signal transmission, the transmitting circuit generates alternating current and transmits the alternating current outward through the transmitting electrode, and the collection circuit comprises a first collection circuit and a second collection circuit, the first collection circuit is used for receiving collection signals of the supervisory electrodes and extracting phase information from the collection signals, and the second collection circuit is used for receiving collection signals of the return electrode and extracting phase information from the collection signals.

5. A method of measuring resistivity of a formation through a casing, characterized by, The through-casing formation resistivity logging instrument is used for measurement, and the method comprises the following steps: Alternating current is transmitted to the metal casing through the transmitting electrode; When the transmitting electrode transmits the alternating current, the supervisory electrodes and the return electrode start to collect current signals, and the transmission time is strictly synchronized with the collection time; The signal collection of the supervisory electrodes must be strictly synchronized; Phase information is extracted from the collected signals of the supervisory electrodes, and the phase difference between two signals collected by a pair of supervisory electrodes is used to obtain formation resistivity information.

6. A method of measuring resistivity of a formation across a casing as defined in claim 5 wherein, When the transmission time is strictly synchronized with the collection time, a shared clock line is used for correction.

7. The method of claim 5 wherein, The signal collection of the supervisory electrodes must be strictly synchronized, and the accuracy of the collected phase information is less than 1°, if the accuracy is greater than 1°, it is considered that the collected signals are wrong, and the signal collection is re-synchronized until the accuracy of the collected phase information is less than 1° again.

8. The through-casing formation resistivity measurement method according to claim 5, wherein If the return electrode is involved in the calculation, the signal collection between the supervisory electrodes and the return electrode must also be strictly synchronized, and the accuracy of the collected phase information is less than 1°, if the accuracy is greater than 1°, it is considered that the collected signals are wrong, and the signal collection is re-synchronized until the accuracy of the collected phase information is less than 1° again; Phase information is extracted from the collected signals of the supervisory electrodes and the return electrode, and the phase difference between three signals collected by a pair of supervisory electrodes and a return electrode is used to obtain formation resistivity information.

9. A method of measuring resistivity of a formation across a casing as defined in any of claims 5 to 8, characterised in that, When multiple pairs of monitoring electrodes are set, the multiple pairs of monitoring electrodes form multiple groups of current phase difference measurements, the phase information extracted from the signals collected by each monitoring electrode is different, and the extracted phase information is used for difference, and then the measurement data compensation correction is completed.

10. A computer-readable storage medium storing one or more programs, the one or more programs comprising instructions that cause one or more processors to perform operations comprising: When the one or more programs are executed, the method for measuring the resistivity of a formation through a casing as claimed in any one of claims 5-9 can be implemented.

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