A downhole swivel sub employing bellows type pressure equalization and dynamic seal

Abstract

The application discloses a downhole rotating nipple with bellows type pressure balance and dynamic sealing device, which comprises a mandrel, the upper end of the mandrel is connected with a protective shell, the upper end of the protective shell is connected with an upper connector, the upper end of the upper connector is connected with an upper joint assembly, the lower end of the mandrel is connected with a slip ring, the lower end of the slip ring is connected with a lower connector, a bearing is arranged between the lower connector and the mandrel, and a bellows assembly is sleeved on the mandrel. The downhole rotating nipple disclosed by the application adopts the bellows assembly as a pressure balance device, when the volume of silicone oil changes under the high-temperature and high-pressure working condition in the well, the bellows assembly can stretch and contract along the mandrel in the axial direction, so that pressure compensation is effectively carried out, and the balance of internal and external pressure is ensured.

Description

Technical Field

[0001] This invention belongs to the field of oil well logging, and specifically relates to a downhole rotary sub with a bellows-type pressure balancing and dynamic sealing device. Background Technology

[0002] A downhole rotating sub is generally divided into two parts: an upper part and a lower part. The upper part connects to the logging cable, and the lower part connects to other downhole instrument strings. The upper and lower parts can rotate relative to each other. When other downhole instrument strings rotate, the lower part of the downhole rotating sub can rotate along with them, while the upper part and the logging cable remain stationary. This relieves the rotational torque on the logging cable and prevents torsional damage to the logging cable.

[0003] To ensure the normal rotation of the downhole rotary sub, a pressure balancing mechanism is generally installed to maintain the pressure balance between the internal and external well fluids of the downhole rotary sub. Currently, the pressure balancing mechanism of the downhole rotary sub generally adopts a bladder structure or a piston structure. The pressure balancing mechanism is filled with silicone oil. When the external well fluid pressure or temperature changes, the volume of silicone oil changes, and through the deformation of the bladder or the movement of the piston, the pressure inside and outside the downhole rotary sub is balanced.

[0004] Under the high temperature and high pressure conditions downhole, rubber-made bladders age after a period of use, leading to a decrease in elasticity and affecting their pressure balancing performance. In oil wells with high sulfur content, the bladders react with sulfides in the well fluid, rendering the pressure balancing mechanism of the bladder structure unusable and limiting the application range of this type of downhole rotary sub.

[0005] Because the upper and lower ends of the downhole rotary sub rotate relative to each other, it must contain a rotating dynamic seal. Downhole instrument strings frequently sway during operation and sometimes collide with the wellbore. The resulting impact vibrations alter the fit between the moving and stationary components, typically causing radial or axial misalignment, and sometimes even bending deformation. Changes in the fit also accelerate the wear of flexible sealing elements, affecting the service life of the dynamic seal. In some cases, the moving and stationary components may even interfere with each other, leading to friction. In severe cases, this can cause the moving and stationary components to seize up, rendering the downhole rotary sub unable to rotate and potentially causing the logging cable to break. Summary of the Invention

[0006] The technical problem to be solved by the present invention is to provide a downhole rotary sub with a bellows-type pressure balancing and dynamic sealing device.

[0007] The present invention adopts the following technical solution:

[0008] An improvement of a downhole rotary sub with a bellows-type pressure balancing and dynamic sealing device is as follows: It includes a mandrel, the upper end of which is connected to a protective housing, the upper end of which is connected to an upper connector, the upper end of which is connected to an upper joint assembly, the lower end of which is connected to a slip ring, the lower end of which is connected to a lower connector, and a bearing is provided between the lower connector and the mandrel. A bellows assembly is fitted onto the mandrel, one end of which is sealed to the mandrel by a dynamic sealing element, and the other end is connected to the lower connector. Silicone oil is filled between the upper and lower connectors. The lower end of the lower connector is connected to a lower adapter, the lower end of which is connected to a lower steel cylinder, and the lower end of the lower steel cylinder is connected to the lower joint assembly.

[0009] Furthermore, the upper end of the upper connector assembly is connected to the upper protective cap via a threaded ring and sealed by a sealing ring; the lower end of the lower connector assembly is connected to the lower protective cap via a thread and sealed by a sealing ring.

[0010] Furthermore, after the upper connector assembly and the upper connector head are circumferentially positioned by the positioning key, they are connected by a threaded ring and sealed by a sealing ring; the upper connector head and the protective housing are connected by threads and sealed by a sealing ring.

[0011] Furthermore, after the mandrel is connected to the protective housing through a hexagonal or square rotating surface to prevent rotation, it is sealed by a sealing ring, and a support is added at the sealing surface. The mandrel and the protective housing are locked together by a tension nut and a set screw. There are two or more tension nuts, and each tension nut is equipped with two or more set screws.

[0012] Furthermore, the slip ring is connected to the mandrel via a set screw; a waist-shaped flushing groove is provided on the protective housing.

[0013] Furthermore, the bearings located between the lower connector and the spindle include two deep groove ball bearings, two thrust ball bearings, and two bearing connecting rings.

[0014] Furthermore, the bellows assembly is connected by screws and a lower connector, and sealed by a sealing ring. The dynamic sealing element uses a star-shaped sealing ring.

[0015] Furthermore, the lower connector and the lower adapter are connected by threads and sealed by a sealing ring, with added support at the sealing surface; the lower adapter is connected to the lower steel cylinder by threads and sealed by a sealing ring; the lower steel cylinder and the lower connector assembly are connected by a positioning block assembly and sealed by a sealing ring.

[0016] Furthermore, a one-way oil filling port, an overflow valve, two vent screws, and four oil passage ports are provided, and an oil passage groove is added to the inner hole of the lower connector.

[0017] The beneficial effects of this invention are:

[0018] The downhole rotary sub disclosed in this invention uses a bellows assembly as a pressure balancing device. Under high-temperature and high-pressure conditions downhole, when the volume of silicone oil changes, the bellows assembly can expand and contract along the mandrel axially, effectively compensating for pressure and ensuring the balance of internal and external pressures. The bellows assembly is made of highly corrosion-resistant metal, adaptable to various corrosive well fluids, and can operate safely and reliably in high-temperature, high-pressure, and highly corrosive downhole environments. Simultaneously, the bellows assembly also acts as the moving part of the rotary dynamic seal device, floatingly supporting the stationary part (mandrel). When the downhole rotary sub is subjected to impact vibration, the displacement or deformation of the bellows assembly maintains the fit between the moving and stationary parts of the rotary dynamic seal device, effectively improving the service life of the rotary dynamic seal device and enhancing the safety, reliability, and adaptability of the downhole rotary sub in logging operations, providing effective protection for logging operations. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the downhole rotating sub disclosed in Embodiment 1 of the present invention;

[0020] Figure 2 This is a schematic diagram of the rotating assembly in the downhole rotating sub disclosed in Embodiment 1 of the present invention;

[0021] Figure 3 This is a schematic diagram of the mandrel structure in the downhole rotating sub disclosed in Embodiment 1 of the present invention;

[0022] Figure 4 This is a schematic diagram of the protective outer shell in the downhole rotating sub disclosed in Embodiment 1 of the present invention;

[0023] Figure 5 This is a schematic diagram of the oil circuit of the pressure balancing device in the downhole rotating sub disclosed in Embodiment 1 of the present invention;

[0024] Figure 6 This is a schematic diagram of the structure of the lower connector in the downhole rotating sub disclosed in Embodiment 1 of the present invention. Detailed Implementation

[0025] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0026] Example 1, as Figure 1As shown, this embodiment discloses a downhole rotary sub with a bellows-type pressure balancing and dynamic sealing device, including a mandrel 83. The upper end of the mandrel 83 is connected to a protective housing 4, the upper end of the protective housing 4 is connected to an upper connector 3, the upper end of the upper connector 3 is connected to an upper connector assembly 2, the lower end of the mandrel 83 is connected to a slip ring 9, and the lower end of the slip ring 9 is connected to a lower connector 6. A bearing is provided between the lower connector 6 and the mandrel 83. The bearing includes two deep groove ball bearings, two thrust ball bearings, and two bearing connecting rings. A bellows assembly 5 is fitted onto the mandrel 83, with one end sealed to the mandrel 83 by a dynamic sealing element 92, and the other end connected to the lower connector 6. Silicone oil is filled between the upper connector 3 and the lower connector 6. The lower end of the lower connector 6 is connected to a lower adapter 7, pressing and fixing the lower end of the mandrel 83 inside the lower adapter 7 through the lower connector 6. The lower end of the lower adapter 7 is connected to the lower steel cylinder 10, and the lower end of the lower steel cylinder 10 is connected to the lower connector assembly 11.

[0027] like Figure 2 As shown, the rotating assembly 8 consists of a tension nut 81, a set screw 82, a spindle 83, a deep groove ball bearing 84, a deep groove ball bearing 89, a thrust ball bearing 86, a thrust ball bearing 87, a bearing connecting ring 85, a bearing connecting ring 88, and a sealing ring 91.

[0028] In this embodiment, the upper end of the upper connector assembly 2 is connected to the upper protective cap 1 via a threaded ring 13 and sealed by a sealing ring 14; the lower end of the lower connector assembly 11 is connected to the lower protective cap 12 via a thread and sealed by a sealing ring 26.

[0029] After the upper connector assembly 2 and the upper connector 3 are circumferentially positioned by the positioning key 17, they are connected by the threaded ring 15 and sealed by the sealing ring 16; the upper connector 3 and the protective shell 4 are connected by threads and sealed by the sealing ring 18.

[0030] like Figure 3 As shown, after the spindle 83 is connected to the protective housing 4 through a hexagonal or square rotating surface to prevent rotation, it is sealed by a sealing ring 91, and a support is added at the sealing surface to reduce the radial offset of the spindle and the angular deflection caused by bending deformation. The spindle 83 and the protective housing 4 are locked together by a tension nut 81 and a set screw 82. In order to better withstand the tensile force, there are more than two tension nuts 81. In order to prevent loosening, each tension nut 81 is provided with more than two set screws 82.

[0031] Slip ring 9 is connected to mandrel 83 via set screw 22; as Figure 4 As shown, in order to allow well fluid to flow freely and avoid mud deposition, and to ensure the flexible movement of the bellows assembly 5, and to facilitate flushing during subsequent downhole rotary sub maintenance, multiple waist-shaped flushing grooves are provided on the protective shell.

[0032] The bellows assembly 5 is connected to the lower connector 6 by screws 20 and sealed by sealing ring 21. In order to make the bellows assembly 5 flexible in axial extension and retraction along the spindle 83, the dynamic sealing element 92 adopts a star-shaped sealing ring or other elements with low frictional resistance.

[0033] The lower connector 6 and the lower adapter 7 are connected by threads and sealed by a sealing ring 19. Supports are added at the sealing surface to reduce the radial offset of the spindle and the angular deflection caused by bending deformation. The lower adapter 7 is connected to the lower steel cylinder 10 by threads and sealed by a sealing ring 23. The lower steel cylinder 10 and the lower connector assembly 11 are connected by a positioning block assembly 24 and sealed by a sealing ring 25.

[0034] like Figure 5 As shown, to prevent well fluid from entering the downhole rotating sub and contaminating the silicone oil, a one-way injection port 32 and an overflow valve 31 are also provided to ensure that the internal pressure of the downhole rotating sub is slightly greater than the external pressure. Two vent screws 30 and 33, and four oil passages 34, 35, 36, and 37 are also provided. Figure 6 As shown, an oil groove is added to the inner hole of the lower connector. These structures ensure better expulsion of internal gas and filling with silicone oil during oil injection.

[0035] In this embodiment, when the downhole rotary sub is in operation, the upper cap 1 and the lower cap 12 are removed, the upper connector assembly 2 is connected to the logging cable, and the lower connector assembly 11 is connected in series with other downhole instruments.

[0036] The upper connector assembly 2, upper connector 3, protective housing 4, and mandrel 83 follow the logging cable and do not rotate. The bellows assembly 5, lower connector 6, lower adapter 7, lower steel cylinder 10, and lower connector assembly 11 rotate with other downhole instruments. The slip ring 9 is divided into two parts: one part is fixed with the mandrel 83, and the other part rotates with the lower connector 6. The two deep groove ball bearings, two thrust ball bearings, and two bearing connecting rings in the rotating assembly 8 rotate, while the rest do not rotate.

[0037] As a pressure balancing device, the bellows assembly 5 can expand and contract axially along the mandrel 83 when the volume of silicone oil changes under high temperature and high pressure conditions downhole, thereby effectively compensating for pressure and ensuring the balance of internal and external pressure.

[0038] Furthermore, the bellows assembly 5 rotates around the mandrel 83, and a rotary dynamic seal exists at their connection. The mandrel 83 is the stationary component of the rotary dynamic seal, and the bellows assembly 5 is the moving component. Since the stiffness of the bellows assembly 5 is much smaller than that of the mandrel 83, it can be approximated as a flexible element, so the stationary and moving components are in a floating support fit. When the downhole rotary sub is subjected to impact vibration downhole, the mandrel 83 will experience radial displacement or angular deflection due to bending deformation. At this time, because the bellows assembly 5 is a flexible component, it will follow the displacement or deflection of the mandrel 83, thus keeping their fit unchanged and ensuring that the rotary dynamic seal remains in an effective state.

Claims

1. A downhole swivel sub employing bellows type pressure equalization and dynamic sealing means, characterized by: The device includes a mandrel, the upper end of which is connected to a protective housing, the upper end of which is connected to an upper connector, the upper end of which is connected to an upper connector assembly, the lower end of which is connected to a slip ring, the lower end of which is connected to a lower connector, and a bearing is provided between the lower connector and the mandrel. A bellows assembly is fitted onto the mandrel, with one end sealed to the mandrel by a dynamic sealing element and the other end connected to the lower connector. Silicone oil is filled between the upper and lower connectors. The lower end of the lower connector is connected to a lower adapter, the lower end of which is connected to a lower steel cylinder, and the lower end of the lower steel cylinder is connected to the lower connector assembly. After the spindle is connected to the protective housing through a hexagonal or square rotating surface to prevent rotation, it is sealed by a sealing ring and a support is added at the sealing surface. The spindle and the protective housing are locked together by a tension nut and a set screw. There are two or more tension nuts, and each tension nut is equipped with two or more set screws. The slip ring is connected to the mandrel via a set screw; a waist-shaped rinsing groove is provided on the protective housing; The bellows assembly is connected by screws and a lower connector, and sealed by a sealing ring. The dynamic sealing element uses a star-shaped sealing ring.

2. The downhole rotary sub with bellows-type pressure balancing and dynamic sealing device as described in claim 1, characterized in that: The upper end of the upper connector assembly is connected to the upper protective cap via a threaded ring and sealed by a sealing ring; the lower end of the lower connector assembly is connected to the lower protective cap via a threaded connection and sealed by a sealing ring.

3. The downhole rotary sub with bellows-type pressure balancing and dynamic sealing device as described in claim 1, characterized in that: After the upper connector assembly and the upper connector head are circumferentially positioned by the positioning key, they are connected by a threaded ring and sealed by a sealing ring; the upper connector head and the protective housing are connected by threads and sealed by a sealing ring.

4. The downhole rotary sub with bellows-type pressure balancing and dynamic sealing device as described in claim 1, characterized in that: The bearings located between the lower connector and the spindle include two deep groove ball bearings, two thrust ball bearings, and two bearing connecting rings.

5. The downhole rotary sub with bellows-type pressure balancing and dynamic sealing device as described in claim 1, characterized in that: The lower connector and the lower adapter are connected by threads and sealed by a sealing ring, with added support at the sealing surface; the lower adapter is connected to the lower steel cylinder by threads and sealed by a sealing ring; the lower steel cylinder and the lower connector assembly are connected by a positioning block assembly and sealed by a sealing ring.

6. The downhole rotary sub with bellows-type pressure balancing and dynamic sealing device as described in claim 1, characterized in that: It is also equipped with a one-way oil filling port, an overflow valve, two vent screws and four oil passage ports, and an oil passage groove is added to the inner hole of the lower connector.

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