Downhole steering mechanism, testing device, and testing method

Abstract

The present application relates to the technical field of geophysical well logging, and provides a downhole guiding mechanism, a testing device and a testing method, wherein the downhole guiding mechanism is arranged below a well mouth and comprises a first shell, a counterweight part, a universal joint and a first connecting rod; the first shell is formed with a first cavity; the counterweight part is arranged in the first cavity; the universal joint is connected to one end of the first shell close to the well mouth; and the first connecting rod is arranged at one end of the universal joint away from the first shell and is adapted to connect a testing mechanism. The counterweight part is arranged in the first cavity in the first shell, which can effectively guarantee the weight and prevent external force from being damaged; the universal joint is arranged between the first shell and the testing mechanism, thereby realizing flexible connection therebetween; and through the combination of the flexible connection of the universal joint and the counterweight, the adjustment angle and the passing capacity of the testing mechanism in the downhole are greatly increased, so as to realize active obstacle winding and posture self-adaptive adjustment of the testing mechanism in a complex wellbore.

Description

Technical Field

[0001] This invention relates to the field of geophysical logging technology, and in particular to a downhole guiding mechanism, testing device, and testing method. Background Technology

[0002] During well logging operations, logging instruments are lowered to the bottom of the well via drill pipe or casing to collect formation geophysical parameters. However, in actual operations, due to factors such as dogleg deviation in the wellbore trajectory, variations in well diameter, stepped well walls, fractured formations, and unstable drilling fluid properties, the instrument string often encounters sticking problems. Statistics show that in wells with complex structures, the probability of logging instruments encountering sticking is high, severely impacting operational efficiency and data quality.

[0003] Existing technologies mainly employ two solutions: one is to rigidly connect a weight rod to the bottom of the instrument to overcome resistance by increasing the instrument's weight; the other is to use a hinged structure with a limited angle. However, the former results in insufficient flexibility and maneuverability of the instrument string due to the rigid connection; while the latter can achieve a certain angle of deflection, its single-point hinged structure has a limited deflection range and cannot adapt to complex and ever-changing wellbore trajectories. Summary of the Invention

[0004] This invention provides a downhole guiding mechanism, a testing device, and a testing method to solve the technical problems in well logging operations, such as the poor flexibility and maneuverability of existing guiding mechanisms, which cannot adapt to complex and ever-changing wellbore trajectories, resulting in a high probability of obstruction when lowering logging instruments.

[0005] This invention provides a downhole guiding mechanism, disposed below the wellhead, comprising: The first shell has a first chamber; The counterweight is located in the first chamber; A universal joint is connected to the end of the first housing near the wellhead. The first connecting rod is located at the end of the universal joint away from the first housing and is suitable for connecting the testing mechanism.

[0006] According to the present invention, a downhole guiding mechanism is provided. The end of the first housing away from the test mechanism is configured in a blunt cone shape.

[0007] According to the present invention, a downhole guiding mechanism is provided. The first housing is a separate unit that can be detachably connected.

[0008] According to the present invention, a downhole guiding mechanism is provided. The counterweight is made of lead. The lead material is one or a combination of two of metallic lead and lead-based alloys.

[0009] According to the present invention, a downhole guiding mechanism is provided, wherein the universal joint comprises: A star-shaped sleeve, the center of which is connected to the first connecting rod, and a plurality of first tracks are formed around the circumference of the star-shaped sleeve; A sphere is positioned on the first track and rolls in conjunction with the first track. A retainer is disposed on the outer periphery of the star-shaped sleeve. The retainer has a plurality of limiting holes formed in its circumference. The limiting holes are arranged one-to-one with the first track and are suitable for limiting the position of the ball. The second housing is disposed around the periphery of the cage, and the inner wall of the second housing is circumferentially formed with a second track, which is suitable for rolling engagement with the ball.

[0010] According to the present invention, a downhole guiding mechanism is provided. The outer wall of the second housing is connected to the outer wall of the first housing and encloses it to form a second chamber, providing space for the rotation of the star-shaped sleeve.

[0011] A downhole guiding mechanism according to the present invention further includes: A flexible protective sleeve is fitted onto the outer wall of the second housing; The flexible protective sleeve has an opening that allows the first connecting rod to pass through.

[0012] The present invention also provides a testing device, including the above-mentioned downhole guiding mechanism, and further comprising: The testing mechanism is connected to the end of the first connecting rod furthest from the universal joint; A traction rope is connected to the testing mechanism.

[0013] A testing device provided by the present invention, The number of test mechanisms is multiple, and the universal joint is provided between adjacent test mechanisms; One end of the second housing is open for mounting the star-shaped sleeve, the sphere and the cage, while the other end of the second housing is closed. Also includes: The second connecting rod has one end connected to the test mechanism and the other end connected to the closed end of the second housing.

[0014] The present invention also provides a testing method using the above-described testing apparatus, comprising at least the following steps: The number of testing mechanisms and the counterweight are determined based on the well conditions; Assemble the test apparatus; Lubricant was applied to the surfaces of both the testing mechanism and the first housing. Lower the test device; The resistance changes of the test device during descent are observed in real time through a ground monitoring system, and the number of the first housing and / or the weight of the counterweight are adjusted according to the resistance value.

[0015] The above-mentioned one or more technical solutions provided by the present invention have at least the following beneficial technical effects: the counterweight is set in the first chamber of the first housing, which can effectively ensure the weight while preventing damage from external forces; a universal joint is set between the first housing and the testing mechanism to realize the flexible connection between the two; through the combination of the flexible connection of the universal joint and the counterweight, the adjustment angle and passage capability of the testing mechanism downhole are greatly increased, so as to realize the active obstacle avoidance and attitude adaptive adjustment of the testing mechanism in complex wells. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in this 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 some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0017] Figure 1 This is a schematic diagram of the downhole guiding mechanism provided in an embodiment of the present invention; Figure 2 This is a schematic diagram of a universal joint provided in an embodiment of the present invention; Figure 3 This is one of the schematic diagrams of the testing device provided in the embodiments of the present invention; Figure 4 This is a second schematic diagram of the testing device provided in the embodiments of the present invention.

[0018] Figure label: 1. First shell; 11. First chamber; 2. Counterweight; 3. Universal joint; 31. Star sleeve; 311. First track; 32. Sphere; 33. Cage; 34. Second housing; 341. Second track; 35. Second chamber; 4. First connecting rod; 5. Flexible protective sleeve; 6. Testing mechanism; 7. Traction rope; 8. Second connecting rod. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this invention. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0020] The following is combined with Figures 1-4 This invention describes a downhole guiding mechanism, a testing device, and a testing method according to embodiments of the present invention.

[0021] like Figure 1 As shown, an embodiment of the present invention provides a downhole guiding mechanism, disposed below the wellhead, comprising: a first housing 1, a counterweight 2, a universal joint 3, and a first connecting rod 4; the first housing 1 forms a first chamber 11; the counterweight 2 is disposed in the first chamber 11; the universal joint 3 is connected to the end of the first housing 1 near the wellhead; the first connecting rod 4 is disposed at the end of the universal joint 3 away from the first housing 1, and is suitable for connecting a testing mechanism 6.

[0022] It should be understood that the counterweight 2 in this embodiment is located in the first chamber 11 of the first housing 1, which can effectively ensure the weight while preventing damage from external forces; a universal joint 3 is provided between the first housing 1 and the testing mechanism 6 to realize a flexible connection between the two; through the combination of the flexible connection of the universal joint 3 and the counterweight, the adjustment angle and passage capability of the logging instrument downhole are greatly increased, so as to realize the active obstacle avoidance and attitude adaptive adjustment of the logging instrument in complex wells.

[0023] In some possible implementations, the first housing 1 may be made of high-strength alloy steel or corrosion-resistant stainless steel to withstand the high temperature, high pressure, and corrosive environment downhole. It should be understood that the shape of the counterweight 2 matches the inner contour of the first chamber 11 to achieve stable installation.

[0024] In a preferred embodiment, the counterweight 2 is fixed to the bottom of the first chamber 11 (i.e., the end furthest from the wellhead) by screws or a snap-fit ​​structure, thereby tilting the center of gravity of the entire guiding mechanism downwards. During downhole operations, the mechanism automatically adjusts its attitude by gravity, ensuring that the testing mechanism 6 always faces the well wall or the target direction. Furthermore, the mass of the counterweight 2 can be optimized based on factors such as well inclination angle, well depth, and fluid resistance.

[0025] In a preferred embodiment, the first connecting rod 4 may be a cylindrical solid or hollow rod with a standard API thread, quick-connect fitting, or flange at its top for quick and reliable docking with the testing mechanism 6. The axis of the first connecting rod 4 is aligned with the rotation center of the universal joint 3 to ensure uniform force distribution during load transfer and avoid structural failure caused by uneven loading.

[0026] In practical use, this downhole guiding mechanism is integrated into the lower part of the logging tool string. After the tool string is lowered into the wellbore, due to the counterweight 2, the first housing 1 naturally tilts vertically towards the bottom of the well under gravity, maintaining the predetermined orientation of the testing mechanism 6. Simultaneously, the universal joint 3 allows the upper testing mechanism 6 to flexibly adjust its posture in curved sections of the wellbore, avoiding jamming or measurement deviations caused by rigid connections. This structure significantly improves the stability and data accuracy of downhole testing.

[0027] like Figure 1 As shown, in a downhole guiding mechanism provided by an embodiment of the present invention, the end of the first housing 1 away from the test mechanism 6 is provided in a blunt cone shape.

[0028] In some possible implementations, the angle (i.e., cone angle) between the generatrix of the blunt conical structure and the axis of the first housing 1 is preferably 30° to 60°, more preferably 45°, so as to avoid the risk of well wall scratches or jamming caused by sharp edges while ensuring good guiding performance.

[0029] Specifically, the blunt conical end is integrally formed to the bottom of the first housing 1 by forging or machining. Its surface is polished or coated with a wear-resistant coating (such as tungsten carbide or diamond-like carbon coating) to improve wear resistance and maneuverability under complex well conditions. This blunt conical structure does not have a sharp apex; its cone tip has a rounded transition, thus creating a "blunt head" effect, effectively reducing impact damage to the wellbore, casing couplings, or other downhole obstacles during the lowering of deviated, horizontal, or casing sections.

[0030] In addition, the blunt conical end can play a preliminary guiding and reaming buffer role during the descent of the tool string: when there is slight diameter reduction, sediment accumulation or slight bending in the wellbore, the blunt conical structure can smoothly push away obstacles or guide the entire guiding mechanism to move along the central axis of the wellbore, preventing the tool string from deflecting, getting stuck or being obstructed in rotation.

[0031] According to an embodiment of the present invention, a downhole guiding mechanism is provided, wherein the first housing 1 is separately disposed and detachably connected.

[0032] In some possible implementations, the first housing 1 adopts a split structure, including at least two housing segments, such as an upper housing segment and a lower housing segment. The upper housing segment and the lower housing segment are axially connected and fixedly connected by a detachable connection structure, thereby forming a complete hollow cylindrical first housing 1, which together encloses a first chamber 11 for accommodating the counterweight 2.

[0033] Furthermore, the detachable connection structure can employ various mechanical connection methods. In one specific embodiment, the lower end of the upper housing section is provided with an external thread, and the upper end of the lower housing section is provided with a matching internal thread; the two are connected by thread engagement. To prevent downhole vibration from causing the threads to loosen, a locking pin, a stop screw, or thread-locking adhesive can be applied to the threaded connection.

[0034] Furthermore, to ensure the sealing of the first chamber 11, especially in high-pressure mud environments, the mating surfaces between the shell sections can be designed as conical fits, stepped stops, or dovetail groove structures to improve alignment accuracy and limit radial misalignment. Simultaneously, at least one annular sealing ring is provided at the mating interface to effectively prevent downhole fluid from entering the chamber, protecting the counterweight 2 and its internal structure.

[0035] It should be understood that the use of a split and detachable first housing 1 has significant advantages: on the one hand, it facilitates the installation of the counterweight 2, sensors, or other internal components into the chamber from the open end during the manufacturing stage before completing the housing assembly; on the other hand, when maintaining or replacing the counterweight, there is no need to scrap the entire housing; only the connecting structure needs to be disassembled to remove the internal components, significantly reducing usage costs and maintenance time. Furthermore, counterweights 2 of different masses or materials can be replaced for different operating conditions while sharing the same housing platform, improving the equipment's versatility and modularity.

[0036] According to an embodiment of the present invention, a downhole guiding mechanism is provided, wherein the counterweight 2 is made of lead material; wherein the lead material is one or a combination of two of metallic lead and lead-based alloys.

[0037] It should be understood that the counterweight 2 is made of lead material to achieve high-density counterweight in a limited space, thereby effectively adjusting the overall center of gravity of the downhole guiding mechanism and ensuring that it automatically achieves attitude stability and directional guidance in the wellbore by relying on gravity.

[0038] Specifically, lead materials can be selected from one of the following: (1) Pure metallic lead has good ductility and processing properties, and is easy to be formed into the required shape by casting, cutting or pressing; (2) Lead-based alloys, such as lead-antimony alloys, lead-tin alloys, lead-calcium alloys, or lead-antimony-tin multi-element alloys. Among them, lead-antimony alloys can significantly improve the hardness and creep resistance of materials, and are suitable for downhole working conditions with vibration or impact loads; lead-tin alloys have a lower melting point and good fluidity, which makes it easy to precision cast counterweights with complex geometries.

[0039] In some possible implementations, the counterweight 2 may adopt a composite structure, in which pure lead is used in some areas to maximize local density, and lead-based alloys are used in other areas to enhance structural strength or wear resistance. The two can be combined into one unit by means of inlay casting, welding or mechanical fixing.

[0040] Furthermore, the counterweight 2 is shaped to fit the first chamber 11, typically as a cylindrical, stepped shaft, or irregularly shaped block with a narrowed bottom. Its outer surface may be provided with positioning bosses, threaded holes, or slots to engage with corresponding structures on the inner wall of the housing, preventing axial movement or circumferential rotation during the lowering or rotation of the tool string. To prevent the lead material from deteriorating due to oxidation or corrosive downhole media during long-term use, an anti-corrosion layer can be applied to the surface of the counterweight 2, such as an epoxy resin coating, a stainless steel thin-shell encapsulation, or a heat-shrink tubing seal.

[0041] Furthermore, the choice of lead materials also takes into account cost-effectiveness and recyclability. Compared to high-density materials such as tungsten alloys, lead materials are significantly cheaper and easier to recycle after disposal, meeting the economic requirements for large-scale application of downhole tools.

[0042] like Figure 2 As shown, a downhole guiding mechanism according to an embodiment of the present invention includes a universal joint 3 comprising: a star-shaped sleeve 31, the center of which is connected to a first connecting rod 4, and a plurality of first tracks 311 formed circumferentially on the star-shaped sleeve 31; a ball 32 disposed on the first tracks 311 and in rolling engagement with the first tracks 311; a retainer 33 disposed on the outer periphery of the star-shaped sleeve 31, and a plurality of limiting holes formed circumferentially on the retainer 33, the limiting holes corresponding one-to-one with the first tracks 311, suitable for limiting the ball 32; and a second housing 34 disposed on the periphery of the retainer 33, and a second track 341 formed circumferentially on the inner wall of the second housing 34, suitable for rolling engagement with the ball 32.

[0043] In some possible implementations, the universal joint 3 adopts a ball cage type constant velocity universal joint 3 structure to achieve multi-degree-of-freedom angular deflection between the first housing 1 and the upper test mechanism 6, while ensuring stable transmission of torque or axial force and adapting to the dynamic working conditions of complex curved wellbores downhole.

[0044] On the outer circumferential surface of the star-shaped sleeve 31, six arc-shaped first tracks 311 are evenly distributed along the circumference. Each first track 311 is concave spherical, and its center of curvature is located on the rotation axis of the star-shaped sleeve 31, which is used to accommodate and guide the sphere 32 to roll.

[0045] The ball 32 is a high-precision steel ball with a hardened and polished surface to improve wear resistance and fatigue life. Each ball 32 is embedded in a first track 311 and forms a rolling fit pair with it in point contact or small-area line contact, thereby allowing the star sleeve 31 to deflect at an angle relative to the external structure while transmitting load.

[0046] The retainer 33 is fitted around the outer periphery of the star-shaped sleeve 31, forming an overall annular cage structure made of high-strength engineering plastic or alloy steel. The retainer 33 has circumferentially spaced limiting holes, the same number as the first track 311, that correspond one-to-one. Each limiting hole is a through hole, its inner contour conforming to the shape of the ball 32. This allows the ball 32 to roll moderately radially and tangentially within the track while also constraining its axial position, preventing the ball 32 from dislodging or colliding with each other during the deflection of the universal joint 3, ensuring smooth movement and structural reliability.

[0047] The second housing 34 is a cylindrical outer shell, fitted around the cage 33, and fixedly connected to the end of the first housing 1 near the wellhead (e.g., via flange, thread, or welding). The inner wall of the second housing 34 has second tracks 341 circumferentially formed, the number, position, and curvature of which strictly correspond to the first tracks 311. The second tracks 341 are also concave spherical structures, with their center of curvature located at the overall geometric center of the universal joint 3. When the star-shaped sleeve 31 deflects, the sphere 32 simultaneously maintains rolling contact with both the first and second tracks 311, forming a "hyperboloid conjugate rolling pair," thereby achieving constant velocity transmission and large-angle deflection capability (typical deflection angles can reach ±20° or more).

[0048] like Figure 1 As shown, according to an embodiment of the present invention, a downhole guiding mechanism is provided in which the outer wall of the second housing 34 is connected to the outer wall of the first housing 1 and encloses it to form a second chamber 35, providing space for the rotation of the star-shaped sleeve 31.

[0049] It should be understood that the second housing 34 not only serves as the external load-bearing component of the universal joint 3, but also works with the first housing 1 to form a closed or semi-closed second chamber 35, which is used to accommodate the internal moving parts of the universal joint 3 (especially the star sleeve 31 and the root of the first connecting rod 4 connected to it), and to provide sufficient rotation and swing space for it during multi-angle deflection.

[0050] Furthermore, the radial dimensions and axial length of the second chamber 35 are precisely designed to ensure that moving parts such as the star sleeve 31, cage 33, and ball 32 will not interfere with the inner wall of the chamber when the universal joint 3 reaches its maximum permissible deflection angle. At the same time, the volume of the second chamber 35 is sufficient to hold grease or lubricating oil, providing continuous lubrication for the rolling pairs and buffering downhole vibration and shock.

[0051] like Figure 1 As shown, a downhole guiding mechanism provided according to an embodiment of the present invention further includes: a flexible protective sleeve 5, which is sleeved on the outer wall of the second housing 34; wherein the flexible protective sleeve 5 has an clearance opening, which is suitable for the first connecting rod 4 to pass through.

[0052] It should be understood that the flexible protective sleeve 5 is used to provide physical protection and sealing isolation for the external connection parts of the universal joint 3 area and the second housing 34, so as to improve the reliability and durability of the whole machine in complex downhole environments.

[0053] In some possible implementations, the flexible protective sleeve 5 is cylindrical or corrugated, made of a highly elastic, oil-resistant, high-temperature-resistant, and aging-resistant flexible material, such as neoprene rubber, hydrogenated nitrile rubber, thermoplastic polyurethane, or fluororubber. Under certain high-wear conditions, an aramid fiber or stainless steel wire braided layer may be embedded in the rubber matrix to enhance its tear and puncture resistance. The flexible protective sleeve 5 is tightly fitted onto the outer wall of the second housing 34, with its inner diameter slightly smaller than the outer diameter of the second housing 34. Axial positioning is achieved through interference fit or clamp fastening to prevent slippage or detachment during tool string lowering or rotation.

[0054] Furthermore, to ensure smooth connection of the upper testing mechanism 6, the flexible protective sleeve 5 has a clearance opening at its end near the wellhead. This clearance opening is a circular through hole with a diameter slightly larger than the outer diameter of the first connecting rod 4, allowing the first connecting rod 4 to pass through freely without interference. Simultaneously, the edge of the clearance opening can be designed as a flanged structure or covered with a metal pressure ring, which on the one hand enhances the strength of the orifice and prevents tearing due to repeated friction, and on the other hand facilitates docking with the sealing interface of the upper testing mechanism 6, forming a continuous external protective barrier.

[0055] like Figure 3 As shown, this embodiment of the invention also provides a testing device, including the above-mentioned downhole guiding mechanism, and further including: a testing mechanism 6, connected to the end of the first connecting rod 4 away from the universal joint 3; and a traction rope 7, connected to the testing mechanism 6.

[0056] It should be understood that the testing unit 6 is a logging instrument module used to obtain downhole physical parameters (such as formation resistivity, natural gamma, sonic velocity, wellbore, well inclination angle, etc.).

[0057] In some possible implementations, the housing of the testing mechanism 6 is typically made of a high-strength non-magnetic material (such as titanium alloy or stainless steel) to avoid interference with the measurement signal. The lower end of the testing mechanism 6 is equipped with a standard connection interface (e.g., API external thread, quick-connect fitting, or flange) to be fixedly connected to the end of the first connecting rod 4 in the downhole guiding mechanism away from the universal joint 3. The connection method can employ a threaded engagement with a locking pin to prevent loosening, or a keyway + lock nut structure to achieve high torque transmission and tensile reliability. This connection ensures that the testing mechanism 6 remains flexibly coupled to the guiding mechanism during downhole operations, allowing it to deflect flexibly with the wellbore direction while maintaining a predetermined orientation under the action of the counterweight 2.

[0058] Furthermore, the traction rope 7 is a high-strength, flexible force transmission element used to lower the entire testing device to the target well depth and achieve retrieval. The traction rope 7 can be an armored cable, steel wire rope, or composite fiber cable, with one end securely connected to the upper end of the testing mechanism 6 via a dedicated lifting ring, crimp sleeve, or threaded joint. In the embodiment using an armored cable, the cable not only undertakes the traction function but also integrates power transmission lines and signal communication lines, enabling real-time power supply to the testing mechanism 6 and transmission of logging data back; while in the storage-type logging mode, the traction rope 7 can be simply a passive steel wire rope, with test data recorded by the internal memory of the testing mechanism 6 and played back after the operation is completed.

[0059] Furthermore, to enhance overall operational safety, stress-relief structures, such as universal joints or flexible transition joints, are typically installed at the connection between the traction rope 7 and the testing mechanism 6 to prevent stress concentration at the connection point due to wellbore bending or tool string torsion. Additionally, centralizers or vibration-damping short sections can be installed on the section of the traction rope 7 near the testing mechanism 6 to reduce the impact of vortex-induced vibrations on precision sensors.

[0060] like Figure 4 As shown, a testing device according to an embodiment of the present invention includes multiple testing mechanisms 6, with universal joints 3 provided between adjacent testing mechanisms 6; one end of the second housing 34 is open for mounting a star-shaped sleeve 31, a ball 32, and a retainer 33, and the other end of the second housing 34 is closed; it also includes a second connecting rod 8, one end of which is connected to the testing mechanism 6, and the other end of which is connected to the closed end of the second housing 34.

[0061] It should be understood that, to ensure that adjacent test mechanisms 6 can deflect independently without interfering with each other in the curved section of the wellbore, a universal joint 3 is installed between every two adjacent test mechanisms 6. This forms a series flexible structure of "test mechanism 6 - universal joint 3 - test mechanism 6 - universal joint 3...", which enables the entire tool string to have multi-degree-of-freedom spatial attitude adjustment capability, effectively follow the wellbore direction, and avoid problems such as stuck drill bit, wall adhesion, or sensor detachment from the target measurement surface caused by rigid connections.

[0062] In some possible implementations, if the dogleg height of the wellbore is too high, additional counterweights can be added between adjacent test units 6 to increase the guiding capability of the instrument string; in other embodiments, flexible connectors (such as flexible ropes) can be used to connect multiple test units 6 in series to enhance the flexibility of the instrument string.

[0063] It should be noted that whether to add universal joints and / or additional counterweights between adjacent test mechanisms 6 depends on the actual working conditions. If the length or flexibility of multiple test mechanisms 6 is still sufficient for successful well deployment after connection, then it is not necessary to add universal joints and / or additional counterweights between adjacent test mechanisms 6.

[0064] In some possible implementations, the second connecting rod 8 is a high-strength solid or hollow rod made of alloy steel or stainless steel. One end of it is fixedly connected to the lower end of the upper test mechanism 6, and the other end is connected to the closed end of the second housing 34 of the lower universal joint 3. This connection not only transmits axial tensile force but also ensures that the universal joint 3 is securely integrated between the two test mechanisms 6, while providing a stable external support frame for the deflection movement of the star sleeve 31.

[0065] It should be understood that the length of the second connecting rod 8 can be customized according to the wellbore dogleg and the required flexibility. Its outer diameter is smaller than that of the testing mechanism 6 to ensure a smooth overall outline of the tool string and reduce downhole resistance. In addition, the second connecting rod 8 can be provided with through holes for passing power supply lines or signal lines to achieve electrical interconnection between multiple sections of the testing mechanism 6.

[0066] This invention also provides a testing method using the above-described testing apparatus, comprising at least the following steps: S1, Determine the number of test units 6 and calculate the counterweight according to the well conditions; S2, Assemble the testing device; S3, apply lubricant to both the test mechanism 6 and the first housing 1; S4, Deploy the testing equipment; S5, observe the changes in resistance as the test device descends in real time through the ground monitoring system, and adjust the number of first housings 1 and / or the weight of counterweights 2 according to the resistance value.

[0067] In step S1: First, acquire wellbore structure data for the target well, including well depth, inclination angle variation curve (dogleg), wellbore diameter, casing specifications, mud properties, and historical sticking records. Based on these parameters, and combined with the logging mission requirements (such as the types of physical parameters to be measured and spatial resolution), determine the required number of testing units 6. For example, in shale gas wells with long horizontal sections, 3-5 testing units 6 can be configured to cover multiple functions such as resistivity imaging, acoustic logging, natural gamma ray logging, and wellbore measurement; while in vertical wells, only 1-2 testing units 6 may be needed.

[0068] Subsequently, based on the total length of the entire tool string, the center of gravity distribution, and the expected wall-adhering force requirements, the total mass and distribution scheme of the counterweight unit 2 are calculated. Specifically, the minimum vertical force required to maintain the sensor window against the well wall at the maximum well inclination angle is estimated using a mechanical model, and then the required counterweight mass is calculated in reverse. Considering the high density of lead material, lead or lead-antimony alloy counterweights are preferred, and they can be concentrated in the first housing 1 at the bottom, or arranged in sections in multiple guide units to optimize the overall center of gravity.

[0069] In step S2: The testing equipment is assembled sequentially from bottom to top: The counterweight 2 is installed into the cavity of the first housing 1. If the first housing 1 is a split structure, the counterweight 2 is first placed into the lower housing section, and then the upper housing section is screwed together and locked and sealed. Insert the star-shaped sleeve 31, ball 32 and cage 33 of the universal joint 3 into the open end of the second housing 34, and after confirming that the rolling fit is smooth, install the end cover for sealing. The upper test mechanism 6 is connected to the closed end of the second housing 34 of the lower universal joint 3 via the second connecting rod 8; Repeat the above process until all test mechanisms 6 and universal joints 3 are connected in series according to the design quantity; Finally, the traction rope 7 is connected to the upper end of the top test mechanism 6, and the reliability of each electrical interface and mechanical fastener is checked.

[0070] In step S3: The lubricant can be selected from: lithium-based grease containing molybdenum disulfide, fluorosilicone-based anti-sticking agent, or water-based drag-reducing coating specifically for logging tools; key application areas include: the blunt conical end of the first housing 1, the periphery of the centralizer or sensor window of the test mechanism 6, and the outer surface of the flexible protective sleeve 5.

[0071] In step S4: The assembled test device is slowly lowered down the wellbore using a winch system; the lowering speed is dynamically adjusted based on wellbore cleanliness and dogleg severity; in open-hole wells or sections with high risk of narrowing, a "lower-pause-gentle lift" cycle is used to monitor changes in well conditions. The traction rope 7 synchronously powers the test mechanism 6 and transmits preliminary attitude and environmental parameters back in real time.

[0072] In step S5: The ground monitoring system collects the tension signal of the traction rope 7 in real time and calculates the descent resistance by combining it with the depth encoder data. When the resistance value continues to be higher than the preset threshold, it indicates that the tool string may have problems such as getting stuck, mud clogging, or being too tightly attached to the wall; at this time, the following measures can be taken: If the excessive resistance is due to excessive wall-adhering force, the weight of counterweight 2 can be reduced (e.g., by replacing it with a counterweight block of lower density, or by removing part of the counterweight unit). If the tool string is not rigid enough and causes bending and jamming, the number of first housings 1 can be increased (i.e., the number of guide mechanisms can be increased) to improve the overall rigidity of the test device. In extreme cases, the tool string can be temporarily raised, the wellbore conditions reassessed, and the configuration adjusted before being lowered again.

[0073] Through the aforementioned closed-loop feedback mechanism, dynamic optimization of the testing equipment configuration is achieved, ensuring safe and efficient completion of measurements throughout the entire well section.

[0074] The device embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate, and the components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without any creative effort.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; 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 downhole guiding mechanism, disposed below the wellhead, characterized in that, include: The first shell (1) has a first chamber (11). A counterweight (2) is disposed in the first chamber (11); Universal joint (3) is connected to the end of the first housing (1) near the wellhead; The first connecting rod (4) is located at the end of the universal joint (3) away from the first housing (1) and is suitable for connecting the test mechanism (6).

2. The downhole guiding mechanism according to claim 1, characterized in that, The first housing (1) is set in a blunt cone shape at the end away from the test mechanism (6).

3. The downhole guiding mechanism according to claim 1, characterized in that, The first housing (1) is a separate unit that can be detachably connected.

4. The downhole guiding mechanism according to any one of claims 1-3, characterized in that, The counterweight (2) is made of lead material; The lead material is one or a combination of two of metallic lead and lead-based alloys.

5. The downhole guiding mechanism according to claim 1, characterized in that, The universal joint (3) includes: Star-shaped sleeve (31), the center of which is connected to the first connecting rod (4), and the star-shaped sleeve (31) has a plurality of first tracks (311) formed in the circumference. A sphere (32) is disposed on the first track (311) and rolls in cooperation with the first track (311); A retainer (33) is disposed on the outer periphery of the star-shaped sleeve (31). The retainer (33) has a plurality of limiting holes in its circumferential direction. The limiting holes are disposed one-to-one with the first track (311) and are suitable for limiting the ball (32). The second housing (34) is disposed on the periphery of the retainer (33), and the inner wall of the second housing (34) is circumferentially formed with a second track (341) suitable for rolling engagement with the ball (32).

6. The downhole guiding mechanism according to claim 5, characterized in that, The outer wall of the second housing (34) is connected to the outer wall of the first housing (1) and encloses it to form a second chamber (35), providing space for the rotation of the star-shaped sleeve (31).

7. The downhole guiding mechanism according to claim 5 or 6, characterized in that, Also includes: A flexible protective sleeve (5) is fitted onto the outer wall of the second housing (34); The flexible protective sleeve (5) has an opening for the first connecting rod (4) to pass through.

8. A testing device, characterized in that, The downhole guiding mechanism, including any one of claims 1-7, further includes: The testing mechanism (6) is connected to the end of the first connecting rod (4) away from the universal joint (3); The traction rope (7) is connected to the test mechanism (6).

9. The testing apparatus according to claim 8, characterized in that, The number of the test mechanism (6) is multiple, and the universal joint (3) is provided between adjacent test mechanisms (6). One end of the second housing (34) is open for mounting the star-shaped sleeve (31), the ball (32) and the cage (33), and the other end of the second housing (34) is closed; Also includes: The second connecting rod (8) has one end connected to the test mechanism (6) and the other end connected to the closed end of the second housing (34).

10. A testing method, characterized in that, Using the testing apparatus according to claim 8 or 9, the process includes at least the following steps: The number of the test mechanism (6) is determined according to the well conditions and the counterweight is calculated; Assemble the test apparatus; Lubricant was applied to the surfaces of both the test mechanism (6) and the first housing (1); Lower the test device; The resistance change of the test device during descent is observed in real time by the ground monitoring system, and the number of the first housing (1) and / or the weight of the counterweight (2) are adjusted according to the resistance value.

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