A through casing resistivity logging instrument downhole probe

Abstract

The application provides a downhole probe of a through casing resistivity logging instrument, which comprises at least two transmitting electrode units, a plurality of measuring electrode units and flexible connecting components, the at least two transmitting electrode units are arranged at intervals, and each of the transmitting electrode units is provided with a transmitting part, the transmitting part can be elastically deformed to abut against the inner wall of a casing, and a transmitting large current provided by a current source is applied to the casing; the plurality of measuring electrode units are arranged in sequence between the two opposite transmitting electrode units, and each of the measuring electrode units is provided with a plurality of receiving parts, the plurality of receiving parts can reciprocate along the radial direction of the casing, the receiving parts knock the casing to make the dirt layer fall off, and are used for receiving the current returned from the formation; and the flexible connecting components are arranged between the adjacent two measuring electrode units respectively, and are used for deflecting the angle between the plurality of measuring electrode units, so that the through casing measurement can be applied to different pipe diameters, and the accuracy of the measurement data is effectively ensured.

Description

Technical Field

[0001] This invention relates to the field of oil drilling technology, and in particular to a downhole probe for a casing resistivity logging tool. Background Technology

[0002] Exploring oil and gas and evaluating oil and gas saturation in casing wells has always been a focus of attention. Formation resistivity is an essential factor for evaluating reservoir oil content. Formation resistivity mainly depends on the fluids contained within it. Traditional resistivity measurements are performed in open-hole wells. However, if a metal casing is run through the well, it is difficult to measure the formation resistivity because the resistivity of the metal casing is extremely small compared to the formation resistivity. Through-casing resistivity logging technology is a new technology developed in recent years for resistivity logging in casing wells. This technology has unique advantages in monitoring remaining oil, tapping the potential of old wells, determining the water flooding status of oil reservoirs, and monitoring oil reservoir production dynamics, and therefore has received increasing attention.

[0003] Publication No. CN102141636A discloses a piston-type through-sleeve resistivity push electrode. This piston-type through-sleeve resistivity push electrode includes an electrode support, a piston cylinder fixed to the electrode support, a probe seat equipped with an electrode probe, a slip ring, and a probe straightening arm. The two ends of the probe straightening arm are respectively axially connected to the probe seat and the slip ring. The slip ring is slidably sleeved with the end of the electrode support. A retractable spring is sleeved inside the slip ring at the end of the electrode support. The top end of the secondary piston of the piston cylinder is fixedly fitted to the probe seat. An insulating pad is fixedly fitted to the top end of the secondary piston. A probe insulating sleeve is sleeved outside the electrode probe.

[0004] In the actual logging process, the electrodes of the instrument described above undergo multi-stage piston movement. The multi-stage pistons are dynamically sealed with O-rings. Due to the influence of various impurities in the well fluid, the pistons are prone to jamming and cannot move flexibly. This can also lead to wear and failure of the O-rings, allowing well fluid to enter the instrument and damage it. Furthermore, the electrode probe of this instrument is set at a 90-degree angle. When the casing is deformed, there may be a situation where the probe cannot make contact with the casing, resulting in the inability to log normally and thus low reliability. Summary of the Invention

[0005] In view of this, the present invention proposes a downhole probe for a casing resistivity logging tool, which is applicable to different casing diameters and environments, and can keep the instrument stably in the centered position, thereby effectively improving the accuracy of casing resistivity measurement.

[0006] The technical solution of this invention is implemented as follows: This invention provides a downhole probe for an over-casing resistivity logging tool, comprising at least two transmitting electrode units, multiple measuring electrode units, and a flexible connection assembly, wherein, At least two emitting electrode units are arranged at intervals, and each emitting electrode unit is provided with an emitting part. The emitting part can undergo elastic deformation and abut against the inner wall of the sleeve, so as to apply the large emitting current provided by the current source to the sleeve. Multiple measuring electrode units are arranged sequentially between two opposite transmitting electrode units, and each measuring electrode unit is provided with multiple receiving parts. Multiple receiving parts can reciprocate along the radial direction of the sleeve. The receiving parts knock the sleeve to make the dirt layer fall off and abut against the inner wall of the sleeve to receive the current returning from the formation. Several flexible connection components are respectively disposed between two adjacent measuring electrode units to cause the angle between multiple measuring electrode units to deflect.

[0007] Based on the above technical solutions, preferably, the transmitting electrode unit includes a first housing, an insulating layer, a first ring assembly, a second ring assembly, multiple first elastic elements, and multiple transmitting electrode elements, wherein, An insulating layer is fitted onto the outside of the first housing, and the inner wall of the insulating layer abuts against the outer wall of the first housing. The first ring assembly is fixed to the outside of the insulating layer and is positioned on the side close to the measuring electrode unit; The second ring assembly is fitted on the outside of the insulating layer, and the second ring assembly can slide linearly along the axial direction of the first housing. The second ring assembly and the first ring assembly are arranged opposite to each other. Multiple first elastic elements are arc-shaped and are all disposed between the first ring assembly and the second ring assembly. The two ends of the first elastic elements are respectively hinged to the first ring assembly and the second ring assembly. The multiple first elastic elements are evenly arranged along the circumferential direction of the first housing. Multiple transmitting electrodes are respectively disposed on the side of each first elastic member away from the first housing and located in the middle of the first elastic member, and the transmitting electrodes serve as the transmitting part of the transmitting electrode unit.

[0008] Based on the above technical solutions, preferably, the transmitting electrode unit further includes an insulator and fasteners, wherein, The outer side of the first ring assembly has a mounting hole that penetrates the insulation layer; the insulator is disposed inside the mounting hole; Both the insulator and the first housing have corresponding threaded holes. The fastener passes through the threaded hole and extends into the first housing, and is threadedly connected to the threaded hole to fix the first ring assembly to the outside of the first housing.

[0009] Based on the above technical solutions, preferably, the insulating layer is made of fiberglass.

[0010] Based on the above technical solutions, preferably, the measuring electrode unit includes a second housing, a fixing component, a movable component, several first connecting components, several probe wheels, and a hydraulic actuation mechanism, wherein, The second housing is cylindrical and hollow inside. Several windows and guide openings are provided on the outer side of the second housing along the axial direction of the sleeve. The number of windows is equal to the number of guide openings. The fastener is fixed inside the second housing, and the position of the fastener corresponds to the position of the window; The movable part is located inside the second housing and is slidably connected between several guide ports, and is arranged at relative intervals with the fixed part; Several first connecting members are respectively hinged to the fixed member and the movable member, and two first connecting members with corresponding positions are hinged to each other at one end, and the position of the first connecting members corresponds to the position of the window; Several probe wheels are respectively set at the hinged ends of two first connectors that are close to each other at each position. The probe wheels serve as the receiving part of the measuring electrode unit. The hydraulic actuation mechanism is disposed in the second housing along the axial direction of the sleeve, and the hydraulic actuation mechanism has a telescopic end that can move along the axial direction of the second housing. The telescopic end of the hydraulic actuation mechanism is fixedly connected to the movable part. The telescopic end of the hydraulic push mechanism pushes the movable part to move linearly back and forth, causing the first connecting part to change angle and move the probe wheel toward the inner wall of the sleeve.

[0011] Based on the above technical solutions, preferably, the plurality of probe wheels are evenly distributed in a ring around the center of the second housing, and the probe wheels are in the shape of wheel teeth.

[0012] Based on the above technical solutions, preferably, the hydraulic actuation mechanism includes a cylinder, a piston block, a piston rod, and a second elastic element, wherein, The cylinder is fixed inside the second shell, and the inside of the cylinder is hollow, with an opening on the side near the moving part; The piston block slides and is sealed within the cylinder. The piston rod is fixed on the side of the piston block facing the opening of the cylinder, and one end of the piston rod passes through the opening of the cylinder and is fixed to the moving part; The second elastic element is sleeved on the outside of the piston rod, and the two sides of the second elastic element abut against the inner wall of the cylinder and the piston block, respectively. The cylinder has an inlet hole for connecting to the hydraulic system on the side away from the moving part, and an outlet hole for connecting to the hydraulic system is opened on the side wall of the cylinder.

[0013] Based on the above technical solutions, preferably, the flexible connection assembly includes a cross-shaped connecting block, multiple connecting pins, and two second connecting members, wherein... The cross-shaped connecting block has four mounting slots, which are located on each side of the cross-shaped connecting block. Multiple connecting pins are inserted into each mounting slot and secured with screws; The two second connectors are arranged in a cross shape and are fixed to the ends of the two adjacent second housings that are close to each other. Each second connector is provided with symmetrically distributed ears, and the ears of the second connectors are rotatably connected to the corresponding connecting pins.

[0014] Based on the above technical solutions, preferably, the axis of the cross connecting block is in the same straight line position as the axis of the two adjacent second housings.

[0015] Based on the above technical solution, preferably, the number of the measuring electrode units is four, the distance between the second and fourth measuring electrode units and the third measuring electrode unit is 500mm, and the distance between the second and fourth measuring electrode units and the adjacent transmitting electrode units is 1300mm.

[0016] The downhole probe of the through-casing resistivity logging tool of the present invention has the following advantages over the prior art: By incorporating an elastically deformable transmitting part on the transmitting electrode unit, reliable contact with the inner wall of the casing can be achieved during current transmission. The two transmitting electrode units, arranged vertically, can also be used for vertical alignment of the downhole probe, ensuring the instrument is centered. The measuring electrode unit features multiple receiving parts that can reciprocate along the radial direction of the casing, striking it and dislodging dirt layers. This ensures a contact resistance of less than 0.1Ω between the receiving parts and the casing, guaranteeing measurements can be completed even when the inner wall of the casing is not clean. Furthermore, adjacent measuring electrode units are connected by a flexible connection assembly, allowing for angular deflection. This enables the downhole probe of the logging tool to bend to a certain extent, ensuring close contact with the casing even in irregular casing conditions, thus effectively improving the accuracy of through-casing resistivity measurements. By setting up an insulating layer and insulator, the transmitting electrode can be insulated from the first housing, preventing the large current emitted from flowing away along the housing, effectively ensuring measurement stability, and facilitating the reception of small signals returned from the ground surface, thus improving measurement accuracy. The extension and retraction of the hydraulic push mechanism allows multiple probe wheels to retract from the window into the second housing, making the mechanical structure more compact, reducing the instrument's outer diameter, and facilitating maintenance. At the same time, the synchronous extension and retraction of the three sets of hinged first connecting parts allows the probe wheels to abut against the tube wall, improving the stability of the support structure, keeping the instrument in a centered position, and effectively improving measurement stability. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a schematic diagram of the downhole probe of the through-casing resistivity logging tool of the present invention; Figure 2 This is a cross-sectional view of the transmitting electrode unit structure of the downhole probe of the through-casing resistivity logging tool of the present invention; Figure 3 The downhole probe of the through-casing resistivity logging tool of the present invention Figure 2 Enlarged view of a portion of point A in the middle; Figure 4 This is a cross-sectional view of the measuring electrode unit structure of the downhole probe of the through-casing resistivity logging tool of the present invention. Figure 5 This is a diagram showing the probe wheel of the downhole probe of the through-casing resistivity logging tool of the present invention extending out of the second housing; Figure 6 This is a schematic diagram of the probe wheel structure of the downhole probe of the through-casing resistivity logging tool of the present invention; Figure 7 This is a schematic diagram of the flexible connection assembly structure of the downhole probe of the through-casing resistivity logging tool of the present invention; Figure 8 The downhole probe of the through-casing resistivity logging tool of the present invention Figure 7 Cross-sectional view at point BB. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] like Figure 1-7As shown, a downhole probe for a casing resistivity logging tool according to the present invention includes at least two transmitting electrode units 1, multiple measuring electrode units 2, and flexible connection components 3. The at least two transmitting electrode units 1 are spaced apart, and each transmitting electrode unit 1 is provided with a transmitting part. The transmitting part can undergo elastic deformation to abut against the inner wall of the casing, applying a large transmitting current provided by a current source to the casing. Multiple measuring electrode units 2 are arranged sequentially between two opposing transmitting electrode units 1, and each measuring electrode unit 2 is provided with multiple receiving parts. These receiving parts can reciprocate along the radial direction of the casing, striking the casing to dislodge the fouling layer and abut against the inner wall of the casing to receive the current returning from the formation. Several flexible connection components 3 are respectively disposed between two adjacent measuring electrode units 2, used to deflect the angle between the multiple measuring electrode units 2.

[0021] It should be noted that by setting an elastically deformable emitting part on the emitting electrode unit 1, it can reliably contact the inner wall of the casing when emitting current. Furthermore, the two emitting electrode units 1 are arranged vertically, which can also be used for vertical alignment of the downhole probe. At the same time, multiple receiving parts are set on multiple measuring electrode units 2 between the two emitting electrode units 1. These receiving parts can reciprocate along the radial direction of the casing to knock off the dirt layer, making the contact resistance between the receiving part and the casing less than 0.1Ω. This ensures that the measurement can be completed even when the inner wall of the casing is not clean. Moreover, two adjacent measuring electrode units 2 are connected by a flexible connecting component 3. Both adjacent measuring electrode units 2 can be deflected at an angle, which allows the downhole probe of the logging tool to bend to a certain extent. This allows the electrode to fit tightly against the casing even in irregular casing. The downhole probe of the logging tool can bend to adapt to slight deformation of the casing, increasing the measurement success rate and thus effectively improving the accuracy of the through-casing resistivity measurement.

[0022] To accommodate stable measurements with different sleeves, the transmitting electrode unit 1 in this embodiment includes a first housing 11, an insulating layer 12, a first ring assembly 13, a second ring assembly 14, multiple first elastic members 15, and multiple transmitting electrode members 16. The insulating layer 12 is sleeved on the outside of the first housing 11, and its inner wall abuts against the outer wall of the first housing 11. The first ring assembly 13 is fixed to the outside of the insulating layer 12 and positioned near the measuring electrode unit 2. The second ring assembly 14 is sleeved on the outside of the insulating layer 12 and can move along the first housing 11. The second ring assembly 14 and the first ring assembly 13 are arranged opposite each other in a linear sliding direction in the axial direction; multiple first elastic members 15 are arc-shaped and are all arranged between the first ring assembly 13 and the second ring assembly 14, and the two ends of the first elastic members 15 are respectively hinged to the first ring assembly 13 and the second ring assembly 14; multiple emitting electrode members 16 are evenly arranged along the circumferential direction of the first housing 11; multiple emitting electrode members 16 are respectively arranged on the side of each first elastic member 15 away from the first housing 11 and are located in the middle position of the first elastic member 15, and the emitting electrode members 16 serve as the emitting part of the emitting electrode unit 1.

[0023] It should be noted that, since the first elastic element 15 is arc-shaped and has elastic deformation capability, when the well logging tool downhole probe is placed inside the casing, it can be adjusted according to the diameter of the casing so that the transmitting electrode 16 is always in contact with the inner wall of the casing. At the same time, the two transmitting electrode units 1 distributed vertically can be used to straighten the downhole probe vertically, ensuring the instrument is centered and effectively improving measurement stability.

[0024] Specifically, in this embodiment, the first elastic element 15 is a leaf spring.

[0025] To prevent the large current emitted by the transmitting electrode unit 1 from flowing away along the housing and causing the inability to perform normal logging measurements, the transmitting electrode unit 1 in this embodiment also includes an insulator 17 and a fastener 18. The first ring assembly 13 has a mounting hole 100 that penetrates the insulating layer 12 on its outer side. The insulator 17 is disposed in the mounting hole 100. The insulator 17 and the first housing 11 both have threaded holes 110 that are correspondingly positioned. The fastener 18 penetrates the threaded hole 110 and extends into the first housing 11, and is threadedly connected to the threaded hole 110 to fix the first ring assembly 13 to the outside of the first housing 11.

[0026] It should be noted that by providing an insulating layer 12 on the outside of the first housing 11 and by providing an insulator 17 at the connection between the first ring assembly 13 and the first housing 11, the transmitting electrode 16 can be insulated from the first housing 11, preventing the large current emitted from flowing away along the housing, effectively ensuring measurement stability, and facilitating the reception of small signals returned from the ground surface, thus providing measurement accuracy.

[0027] Since the depth of the well measurement may reach hundreds or thousands of meters, the bottom environment at this depth is relatively harsh and highly corrosive. Therefore, the insulation layer 12 in this embodiment is made of fiberglass. This structure is wear-resistant, highly corrosion-resistant and has good insulation, and can withstand the harsh environment of the well.

[0028] In a preferred embodiment, the measuring electrode unit 2 includes a second housing 21, a fixing member 22, a movable member 23, several first connecting members 24, several probe wheels 25, and a hydraulic actuation mechanism 26. The second housing 21 is cylindrical and hollow. Several windows 200 and guide openings 210 are provided on the outer side of the second housing 21 along the axial direction of the sleeve, with the number of windows 200 equal to the number of guide openings 210. The fixing member 22 is fixed inside the second housing 21, and its position corresponds to the position of the windows 200. The movable member 23 is located inside the second housing 21 and is slidably connected between the several guide openings 210, and is spaced apart from the fixing member 22. Several first connecting members 24 are respectively hinged to the fixing member 22. Two first connecting members 24, which are on the movable part 23 and are in corresponding positions, are hinged at their close ends, and the positions of the first connecting members 24 correspond to the positions of the window 200. Several probe wheels 25 are respectively set at the hinged ends of the two first connecting members 24 in corresponding positions, and the probe wheels 25 serve as the receiving part of the measuring electrode unit 2. A hydraulic pushing mechanism 26 is set inside the second housing 21 along the axial direction of the sleeve, and the hydraulic pushing mechanism 26 has a telescopic end that can move along the axial direction of the second housing 21. The telescopic end of the hydraulic pushing mechanism 26 is fixedly connected to the movable part 23. The telescopic end of the hydraulic pushing mechanism 26 pushes the movable part 23 to move linearly back and forth, causing the first connecting members 24 to change angle and move the probe wheels 25 toward the inner wall of the sleeve.

[0029] It should be noted that the telescopic end of the hydraulic push mechanism 26 pushes the movable part 23 to move linearly back and forth, causing the angle between the two hinged first connecting parts 24 to change, thus changing the radial position of the probe wheel 25. Furthermore, the length of the probe wheel 25 is adjusted according to the diameter of the sleeve, making it suitable for use with sleeves of different diameters. When the movable part 23 moves towards the fixed part 22, the included angle between the two hinged first connecting parts 24 decreases, causing the probe wheel 25 to extend outward from the window 200 and move towards the sleeve wall. Before measurement, the telescopic end of the hydraulic push mechanism 26 pushes the movable part 23 to move linearly back and forth, striking the sleeve to remove dirt from the sleeve wall. Then, the telescopic end of the hydraulic push mechanism 26 pushes the movable part 23 to ensure that the contact resistance between the receiving part and the sleeve is less than 0.1Ω, ensuring that the measurement is completed even when the inner wall of the sleeve is not clean, effectively guaranteeing the stability and accuracy of the measurement.

[0030] Furthermore, after the measurement is completed, the telescopic end of the hydraulic push mechanism 26 pushes the movable part 23 to retract multiple probe wheels 25 from the window 200 into the second housing 21, thereby making the mechanical structure more compact, reducing the outer diameter of the instrument, and facilitating maintenance.

[0031] The existing probes are designed at 90°. When the casing is deformed, there is a possibility that the probes may not make contact with the casing, resulting in the inability to log normally.

[0032] In this embodiment, a number of probe wheels 25 are evenly distributed in a ring around the center of the second housing 21, and the probe wheels 25 are in the shape of wheel teeth.

[0033] Specifically, in this embodiment, each of the second housings 21 has three windows 200. The three windows 200 are evenly distributed in a ring around the axis of the second housing 21. The synchronous extension and retraction of the three sets of first connecting members 24 that are hinged to each other can improve the stability of the support structure and keep the instrument in a central position, which effectively improves the measurement stability. The probe wheel 25 is in the shape of a wheel tooth and can make point contact or surface contact with the casing to adapt to casing deformation and effectively ensure the stability of logging.

[0034] In a preferred embodiment, the hydraulic actuation mechanism 26 includes a cylinder 261, a piston block 262, a piston rod 263, and a second elastic member 264. The cylinder 261 is fixed inside the second housing 21 and is hollow inside, with an opening on the side near the movable member 23. The piston block 262 is slidably and sealingly connected inside the cylinder 261. The piston rod 263 is fixed to the side of the piston block 262 facing the opening of the cylinder 261, and one end of the piston rod 263 passes through the opening of the cylinder 261 and is fixed to the movable member 23. The second elastic member 264 is sleeved on the outside of the piston rod 263, and both sides of the second elastic member 264 abut against the inner wall of the cylinder 261 and the piston block 262, respectively. The side of the cylinder 261 away from the movable member 23 has an inlet hole 220 for connecting to the hydraulic system, and the side wall of the cylinder 261 has an outlet hole 230 for connecting to the hydraulic system.

[0035] It should be noted that hydraulic oil is input into the inlet hole 220 through the external hydraulic system. The hydraulic oil pushes the piston rod 263 connected to the piston block 262 to move linearly towards the opening side. At this time, the piston block 262 moves and pushes the second elastic element 264 to put it in a compressed state, thereby pushing the movable part 23. When the hydraulic system is depressurized, the input hydraulic oil returns to the hydraulic system from the outlet hole 230. The second elastic element 264 elastically resets and pushes the piston block 262 to move into the cylinder 261, so that the first connecting part 24, which is hinged to each other, is retracted, and the probe wheel 25 is retracted into the window 200.

[0036] Specifically, the second elastic element 264 is a threaded spring.

[0037] Due to the complexity of downhole conditions, the well may have curved sections and is not a straight well. Therefore, the flexible connection component 3 in this embodiment includes a cross-shaped connecting block 31, multiple connecting pins 32, and two second connecting members 33. The cross-shaped connecting block 31 has four mounting slots 300, which are located on each side of the cross-shaped connecting block 31. The multiple connecting pins 32 are inserted into each mounting slot 300 and fixed with screws. The two second connecting members 33 are arranged in a relatively cross shape and are fixed to the adjacent ends of the two second housings 21. Each second connecting member 33 has symmetrically distributed ears, and the ears of the second connecting members 33 are rotatably connected to the corresponding connecting pins 32.

[0038] It should be noted that the two ears of the second connector 33 are rotatably connected to the two connecting pins 32 respectively, so that the second connector 33 can be deflected at an angle along the axis of the connecting pins 32. The downhole probe of the logging tool can bend to a certain extent so that the electrode can be in close contact with the casing even in the irregular casing, thereby effectively improving the accuracy of the through-casing resistivity measurement.

[0039] Meanwhile, the axis of the cross connecting block 31 is in the same straight line position as the axes of the two adjacent second housings 21.

[0040] It should be noted that this allows for positioning of two adjacent measuring electrode units 2, centered instrument placement, ensuring measurement stability and effectively improving measurement accuracy.

[0041] In this embodiment, there are four measuring electrode units 2. The distance between the second measuring electrode unit 2 and the fourth measuring electrode unit 2 and the third measuring electrode unit 2 is 500mm. The distance between the second measuring electrode unit 2 and the fourth measuring electrode unit 2 and the adjacent transmitting electrode unit 1 is 1300mm. The transmitting electrode units 1 on both sides are symmetrically arranged with respect to the third measuring electrode unit 2.

[0042] Working principle: During measurement, the instrument is placed inside the downhole casing. The first elastic element 15, which has elastic deformation capability, ensures that the transmitting electrode 16 is always in contact with the inner wall of the casing. The upper and lower transmitting electrode units 1 are in contact with the casing wall at the same time, so that the instrument reaches the center position. After being placed in the designated position, hydraulic oil is injected into the inlet 220 through the external hydraulic system. The hydraulic oil pushes the piston rod 263 connected to the piston block 262 to move linearly towards the opening side. The piston rod 263 pushes the movable part 23 to move linearly, causing the two hinged first connecting parts 24 to extend out of the window, bringing the probe wheel 25 close to the inner wall of the casing. After the hydraulic system is hydraulically activated, the second elastic element 264 elastically resets, causing the probe wheel 25 to retract into the window 200. This reciprocating motion can be used to tap the casing, causing the dirt layer on the casing wall to fall off. After the dirt falls off, the probe wheel 25 is brought into contact with the inner wall of the casing for measurement. During measurement, large currents are continuously emitted in a crisscross pattern through the two upper and lower emitting electrodes 16. The probe wheel 25, located in the middle, receives the magnitude of the current returning from the formation. This data is packaged and sent to the backend system for calculation to obtain the formation resistivity.

[0043] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A downhole probe for a casing resistivity logging tool, characterized in that, It includes at least two transmitting electrode units (1), multiple measuring electrode units (2), and a flexible connection assembly (3), wherein, At least two emitting electrode units (1) are arranged at intervals, and each emitting electrode unit (1) is provided with an emitting part. The emitting part undergoes elastic deformation and abuts against the inner wall of the sleeve, applying the large emitting current provided by the current source to the sleeve. The transmitting electrode unit (1) includes a first housing (11), an insulating layer (12), a first ring assembly (13), a second ring assembly (14), a plurality of first elastic elements (15), and a plurality of transmitting electrode elements (16). The insulating layer (12) is sleeved on the outside of the first housing (11), and the inner wall of the insulating layer (12) abuts against the outer wall of the first housing (11). The first ring assembly (13) is fixed on the outside of the insulating layer (12) and is disposed on the side close to the measuring electrode unit (2). The second ring assembly (14) is sleeved on the outside of the insulating layer (12), and the second ring assembly (14) slides linearly along the axial direction of the first housing (11). The second ring assembly (14) is arranged opposite to the first ring assembly (13); multiple first elastic members (15) are arc-shaped and are all arranged between the first ring assembly (13) and the second ring assembly (14), and the two ends of the first elastic members (15) are respectively hinged to the first ring assembly (13) and the second ring assembly (14), and the multiple first elastic members (15) are evenly arranged along the circumferential direction of the first housing (11); multiple emitting electrode members (16) are respectively arranged on the side of each first elastic member (15) away from the first housing (11) and located in the middle position of the first elastic member (15), and the emitting electrode members (16) serve as the emitting part of the emitting electrode unit (1); The transmitting electrode unit (1) further includes an insulator (17) and a fastener (18), wherein the outer side of the first ring assembly (13) is provided with a mounting hole (100) that penetrates the insulating layer (12); the insulator (17) is disposed in the mounting hole (100); the insulator (17) and the first housing (11) are both provided with threaded holes (110) that are corresponding to each other; the fastener (18) penetrates the threaded hole (110) and extends into the first housing (11), and is threadedly connected to the threaded hole (110) to fix the first ring assembly (13) on the outer side of the first housing (11); Multiple measuring electrode units (2) are arranged sequentially between two opposite transmitting electrode units (1), and each measuring electrode unit (2) is provided with multiple receiving parts. The multiple receiving parts reciprocate along the radial direction of the sleeve. The receiving parts knock the sleeve to make the dirt layer fall off and abut against the inner wall of the sleeve, which is used to receive the current returning from the formation. The measuring electrode unit (2) includes a second housing (21), a fixing member (22), a movable member (23), several first connecting members (24), several probe wheels (25), and a hydraulic pushing mechanism (26). The second housing (21) is cylindrical and hollow inside. Several windows (200) and guide ports (210) are opened on the outer side of the second housing (21) along the axial direction of the sleeve. The number of windows (200) is equal to the number of guide ports (210). The fixing member (22) is fixed inside the second housing (21), and the position of the fixing member (22) corresponds to the position of the window (200). The movable member (23) is located inside the second housing (21) and is slidably connected between several guide ports (210), and is arranged at relative intervals with the fixing member (22). Several first connecting members (24) are respectively hinged to the fixing member (22) and the movable member. (23) and two first connecting pieces (24) with corresponding positions are hinged at their close ends, and the position of the first connecting piece (24) corresponds to the position of the window (200); a number of probe wheels (25) are respectively set at the hinged ends of the two first connecting pieces (24) with corresponding positions, and the probe wheels (25) serve as the receiving part of the measuring electrode unit (2); the hydraulic push mechanism (26) is set in the second housing (21) along the axial direction of the sleeve, and the hydraulic push mechanism (26) has a telescopic end that moves along the axial direction of the second housing (21), and the telescopic end of the hydraulic push mechanism (26) is fixedly connected to the movable part (23); the telescopic end of the hydraulic push mechanism (26) pushes the movable part (23) to move linearly back and forth, so that the first connecting piece (24) changes angle and moves the probe wheel (25) toward the inner wall of the sleeve; Several flexible connection components (3) are respectively disposed between two adjacent measuring electrode units (2) to cause the angle between multiple measuring electrode units (2) to deflect; The flexible connection assembly (3) includes a cross-shaped connecting block (31), multiple connecting pins (32) and two second connecting pieces (33). The cross-shaped connecting block (31) has four mounting slots (300) located on each side of the cross-shaped connecting block (31). The multiple connecting pins (32) are inserted into each mounting slot (300) and fixed by screws. The two second connecting pieces (33) are arranged in a relatively cross shape and are fixed to the adjacent ends of the two second housings (21). Each second connecting piece (33) has symmetrically distributed ears, and the ears of the second connecting piece (33) are rotatably connected to the corresponding connecting pins (32).

2. The downhole probe of the through-casing resistivity logging tool as described in claim 1, characterized in that: The insulating layer (12) is made of fiberglass.

3. The downhole probe of the through-casing resistivity logging tool as described in claim 1, characterized in that: The plurality of probe wheels (25) are evenly distributed in a ring around the center of the second housing (21), and the probe wheels (25) are in the shape of wheel teeth.

4. The downhole probe of the through-casing resistivity logging tool as described in claim 1, characterized in that: The hydraulic actuation mechanism (26) includes a cylinder (261), a piston block (262), a piston rod (263), and a second elastic element (264), wherein, The cylinder (261) is fixed inside the second housing (21), and the inside of the cylinder (261) is hollow, with an opening on the side near the movable part (23); The piston block (262) is slidably and sealingly connected inside the cylinder (261); The piston rod (263) is fixed on the side of the piston block (262) facing the opening of the cylinder (261), and one end of the piston rod (263) passes through the opening of the cylinder (261) and is fixed to the movable part (23); The second elastic element (264) is sleeved on the outside of the piston rod (263), and the two sides of the second elastic element (264) abut against the inner wall of the cylinder (261) and the piston block (262) respectively. The cylinder (261) has an inlet hole (220) for connecting the hydraulic system on the side away from the movable part (23), and an outlet hole (230) for connecting the hydraulic system is provided on the side wall of the cylinder (261).

5. The downhole probe of the through-casing resistivity logging tool as described in claim 1, characterized in that: The axis of the cross connecting block (31) is in the same straight line position as the axes of the two adjacent second housings (21).

6. The downhole probe of the through-casing resistivity logging tool as described in claim 1, characterized in that: The number of the measuring electrode units (2) is four. The distance between the second measuring electrode unit (2) and the fourth measuring electrode unit (2) and the third measuring electrode unit (2) is 500 mm. The distance between the second measuring electrode unit (2) and the fourth measuring electrode unit (2) and the adjacent transmitting electrode unit (1) is 1300 mm.

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