Combined sealing structure for oil field production and telescopic pipe column system

Abstract

The invention relates to the field of petroleum and natural gas exploration and development, in particular to a combined sealing structure and a telescopic pipe column system for oil field production, which comprise a combined sealing ring, and the combined sealing ring comprises a V-PAC sealing ring and a pre-cooling expansion sealing ring which are arranged in parallel; the outer circumferential face of the V-PAC sealing ring and the outer circumferential face of the pre-cooling expansion sealing ring are both coated with hydrogel. A cavity is formed in the precooling expansion sealing ring, and the cavity is filled with gallium-based liquid metal; the inner pipe is used for transmitting media, and the outer pipe plays a role in protection and supporting. The inner pipe is sleeved with the outer pipe, sliding fit is formed, stretching is achieved through sliding, and the effect of compensating for the length change of the pipe column is achieved. The inner pipe and the outer pipe are connected into a whole through the connected flanges and the connecting rods, and meanwhile the connecting rods play a sliding guiding and limiting role. The sealing ring combination is arranged between the inner pipe and the outer pipe, so that the sealing performance of the telescopic pipe column system is ensured.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of oil and gas exploration and development, and particularly relates to a combined sealing structure for oilfield production and a telescopic pipe string system. BACKGROUND

[0002] The existing pipe string system is prone to deformation and vibration under the influence of temperature changes, water pressure shocks, etc., which can lead to pipe string damage, affecting the service life and safety of the pipe string system. It can also cause packer unsealing or upper and lower friction to damage the packer rubber barrel sealing. To solve this problem, some telescopic pipe string designs have appeared in the prior art, but these designs often have insufficient telescopic performance, poor stability, and other problems, which cannot meet the complex and variable pipe string system requirements. In particular, in the CCUS engineering water-gas alternating injection pipe string repeated telescopic working environment, affected by high and low temperature (-50℃-70℃) cycles, the sealing structure is prone to failure, and a telescopic pipe string structure that can be used for a long time is urgently needed. SUMMARY

[0003] The present application aims to provide a combined sealing structure for oilfield production and a telescopic pipe string system that adopts a new telescopic mechanism to achieve superior telescopic performance, stability, and durability to meet various complex and variable pipe string system requirements.

[0004] The present application provides a combined sealing structure for oilfield production, which comprises a combined sealing ring, the combined sealing ring comprising a V-PAC sealing ring and a pre-cooled expansion sealing ring arranged side by side; the outer circumferential surface of the V-PAC sealing ring and the pre-cooled expansion sealing ring is coated with a hydrogel. The pre-cooled expansion sealing ring is internally provided with a cavity, and the cavity is filled with gallium-based liquid metal.

[0005] Preferably, the V-PAC sealing ring is internally provided with a cavity, and the cavity is filled with gallium-based liquid metal.

[0006] Preferably, the gallium-based liquid metal is of LGM-1 type specified in GB / T 39859-2021 "Gallium-based Liquid Metal".

[0007] Preferably, the pre-cooled expansion sealing ring is made of perfluorinated ether rubber or low-acrylonitrile butadiene rubber low-temperature resistant rubber.

[0008] Preferably, the hydrogel is prepared by the following method: Dissolve 1 part of carboxyl-modified nanocellulose in 20 parts of deionized water by weight ratio, and ultrasonicate in a 55°C water bath until transparent to obtain a first solution; Dissolve 3 parts acrylamide, 0.003 parts methylenebisacrylamide, and 0.09 parts ammonium persulfate in 30 parts deionized water and stir magnetically to obtain a second solution. The first and second solutions were mixed at a mass ratio of 1:2 and heated to 40°C for 40 minutes under nitrogen protection to obtain the hydrogel.

[0009] Preferably, there are 6-8 V-PAC sealing rings and pre-cooling expansion sealing rings in the combined sealing ring, and the V-PAC sealing rings and pre-cooling expansion sealing rings are arranged alternately.

[0010] A telescopic tubing system includes an inner tube and an outer tube sleeved outside the inner tube and a connecting rod, wherein the inner tube and the outer tube are slidably connected. The system is characterized in that an inner tube flange is fixedly connected to one end of the inner tube, and an outer tube flange is fixedly connected to the end of the outer tube away from the inner tube flange. A sealing ring groove is provided on the end of the inner tube near the outer tube flange, and a combined sealing structure for oilfield production is provided within the sealing ring groove. A movable flange is fixedly installed on the outer circumferential surface of the outer tube at the end away from the outer tube flange; The outer pipe flange, inner pipe flange and movable flange are each provided with a number of guide through holes, and the guide through holes on the outer pipe flange, inner pipe flange and movable flange are provided correspondingly. One end of the connecting rod extends from the guide hole on the inner tube flange, passes through the guide hole correspondingly provided on the movable flange, and then extends out from the guide hole on the outer tube flange. Limit nuts are provided at both ends of the connecting rod; The distance between the two limit nuts is less than the sum of the lengths of the inner and outer tubes.

[0011] Preferably, the inner pipe flange and the inner pipe are connected by welding, and the outer pipe flange and the outer pipe are connected by welding.

[0012] Preferably, the outer circumferential surface of the inner tube is coated with a coating, which is a laser cladding coating of an iron-based alloy with added lubricant.

[0013] Preferably, the iron-based alloy laser cladding coating with added lubricant has the following composition by weight: 90-95 parts iron-based alloy powder, 2-6 parts tungsten disulfide powder, 0-2 parts hexagonal boron nitride, 0-5 parts calcium fluoride, 0.2-1 parts talc, and 0.1-0.6 parts tungsten hexafluoride.

[0014] In this invention, the inner tube is responsible for transmitting the medium, while the outer tube provides protection and support. The outer tube is fitted over the inner tube, forming a sliding fit. Expansion and contraction are achieved through this sliding mechanism, compensating for changes in the length of the tube string. The inner and outer tubes are connected as a whole by a flange and a connecting rod, which also serves as a sliding guide and limiter. A sealing ring assembly is placed between the inner and outer tubes to ensure the airtightness of the telescopic tube string system.

[0015] When thermal expansion and contraction or longitudinal vibration occurs in this invention, the outer tube can slide relative to the inner tube column under the guidance of the connecting rod, thereby achieving expansion and contraction compensation. This design not only simplifies the structure of the expansion compensator, but also improves its expansion and contraction performance and stability.

[0016] The inner tube, outer tube, and connecting rod of this invention are all made of corrosion-resistant and wear-resistant materials to improve the durability of the telescopic string. Meanwhile, the sealing element is made of elastic material, providing excellent sealing performance and preventing media leakage.

[0017] This invention utilizes the property of liquid metal rubber rings to expand upon solidification, cleverly offsetting the shrinkage of rubber rings at low temperatures. After being heated to a liquid state, the liquid metal rubber ring can be compressed or deformed to fit the shape of the sealing surface. When the liquid metal solidifies, its volume expands, and this expansion effect compensates for the shrinkage of the rubber ring caused by low temperatures, thus ensuring the durability and stability of the seal. This characteristic allows the liquid metal rubber ring to maintain excellent sealing performance even under extreme temperature conditions, especially in low-temperature environments.

[0018] Meanwhile, the application of cryogenic gel further enhances the stability and reliability of the sealing system. Cryogenic gel maintains its flexibility at extremely low temperatures, preventing ice crystal formation and thus avoiding seal failure due to low temperatures. Combined with liquid metal rubber rings, cryogenic gel not only provides additional sealing protection but also enhances the freeze resistance and chemical corrosion resistance of the entire sealing system.

[0019] In summary, the combined application of liquid metal rubber rings and cryogenic gels significantly improves the performance of the sealing system by utilizing the volume expansion property of liquid metal upon solidification to offset the low-temperature shrinkage of the rubber ring. This innovative technology not only enhances the durability and stability of the seal but also strengthens the reliability and safety of the sealing system under extreme temperature conditions. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the contracted state of the present invention.

[0021] Figure 2 This is a schematic diagram of the elongated state of the present invention.

[0022] Reference numerals: 1-Inner pipe flange, 2-Moving flange, 3-Connecting rod, 4-Outer pipe, 5-Inner pipe, 6-Outer pipe connecting ring, 7-Combined sealing structure, 8-Outer pipe flange. Detailed Implementation

[0023] The present invention provides a combined sealing structure 7 for oilfield production, comprising a combined sealing ring, wherein the combined sealing ring comprises a V-PAC sealing ring and a pre-cooling expansion sealing ring arranged side by side; the outer peripheral surfaces of the V-PAC sealing ring and the pre-cooling expansion sealing ring are coated with hydrogel. The pre-cooled expansion sealing ring has an internal cavity filled with gallium-based liquid metal.

[0024] The V-PAC sealing ring has an internal cavity filled with gallium-based liquid metal.

[0025] In one embodiment, the gallium-based liquid metal adopts the LGM-1 model specified in GB / T 39859-2021 "Galanium-based Liquid Metals".

[0026] In one embodiment, the pre-cooling expansion sealing ring is made of polyvinylidene fluoride rubber or low-acrylonitrile butadiene rubber, which is resistant to low temperatures.

[0027] The hydrogel was prepared using the following method: By weight, 1 part of carboxylated modified nanocellulose was dissolved in 20 parts of deionized water and sonicated in a 55°C water bath until transparent to obtain the first solution; Dissolve 3 parts acrylamide, 0.003 parts methylenebisacrylamide, and 0.09 parts ammonium persulfate in 30 parts deionized water and stir magnetically to obtain a second solution. The first solution and the second solution were mixed at a mass ratio of 1:2 and heated to 40°C for 40 minutes under nitrogen protection to obtain the hydrogel. In practical applications, the hydrogel is prepared as follows: 1g of carboxylated modified nanocellulose produced by Nanjing Tianlu Nanotechnology Co., Ltd. is dissolved in 20g of deionized water and sonicated in a 55°C water bath for 30 minutes until transparent; 3g of acrylamide, 0.003g of methylenebisacrylamide, and 0.09g of ammonium persulfate are added to 30g of deionized water and dissolved, and magnetically stirred for 20 minutes to obtain a second solution. The two solutions are mixed and heated to 40°C under nitrogen protection for 40 minutes to obtain the hydrogel.

[0028] In one embodiment, the V-PAC sealing ring and the pre-cooling expansion sealing ring in the combined sealing ring are both set to 6-8, and the V-PAC sealing ring and the pre-cooling expansion sealing ring are alternately arranged.

[0029] A telescopic tubing system includes an inner tube 5, an outer tube 4 sleeved outside the inner tube 5, and a connecting rod 3. The inner tube 5 and the outer tube 4 are slidably connected. The system is characterized in that an inner tube flange 1 is fixedly connected to one end of the inner tube 5, and an outer tube flange 8 is fixedly connected to the end of the outer tube 4 away from the inner tube flange 1. A sealing ring groove is provided on the end of the inner tube 5 near the outer tube flange 8 between the inner tube 5 and the outer tube 4. A combined sealing structure 7 for oilfield production is provided in the sealing ring groove. A movable flange 2 is fixedly installed on the outer circumferential surface of the outer tube 4 at the end away from the outer tube flange 8; The outer pipe flange 8, the inner pipe flange 1, and the movable flange 2 are each provided with a number of guide through holes, and the guide through holes on the outer pipe flange 8, the inner pipe flange 1, and the movable flange 2 are provided accordingly. One end of the connecting rod 3 extends into the guide hole on the inner tube flange 1, passes through the guide hole correspondingly provided on the movable flange 2, and then extends out from the guide hole on the outer tube flange 8. Limit nuts are provided at both ends of the connecting rod 3; The distance between the two limit nuts is less than the sum of the lengths of the inner tube 5 and the outer tube 4.

[0030] Inner flange 1 and inner pipe 5 are connected by welding, and outer flange 8 and outer pipe 4 are connected by welding.

[0031] The outer circumferential surface of the inner tube 5 is coated with a coating, which is a laser cladding coating of an iron-based alloy with added lubricant.

[0032] In one embodiment, the composition of the iron-based alloy laser cladding coating with added lubricant is as follows by weight: 90-95 parts iron-based alloy powder, 2-6 parts tungsten disulfide powder, 0-2 parts hexagonal boron nitride, 0-5 parts calcium fluoride, 0.2-1 parts talc, and 0.1-0.6 parts tungsten hexafluoride.

[0033] In implementing this invention, firstly, based on the specific requirements of the tubular system, appropriate materials and dimensions are selected to manufacture the inner tube 5, outer tube 4, and the connecting flanges. The inner tube 5 is responsible for transmitting the medium, while the outer tube 4 serves as protection and support.

[0034] The inner pipe flange 1, the movable flange 2, the connecting rod 3, the outer pipe 4, the inner pipe 5, and the outer pipe connecting ring 6 can all be made of low-expansion alloy grade 4J335. The outer pipe connecting ring 6 is fixedly connected to the outer pipe flange 8 through the external thread set at the end of the outer pipe connecting ring 6 and the internal thread set on the protruding ring platform at one end of the outer pipe flange 8. The function of the outer pipe connecting ring 6 is to realize the fixed connection between the outer pipe 4 and the outer pipe flange 8. The outer pipe connecting ring 6 is sleeved on one end of the outer pipe 4 and abuts against the ring platform at the end of the outer pipe 4.

[0035] During installation, the inner pipe flange 1 and the outer pipe flange 8 are connected to the pipe column system respectively and fixed by connecting flanges. The outer pipe 4 can slide relative to the inner pipe 5 under the guidance of the connecting rod 3, thereby realizing expansion and contraction compensation.

[0036] The improved telescopic tubing system described in this invention provides effective protection for the tubing system, enhancing its stability and safety. Furthermore, its simple structure and convenient installation make this telescopic tubing system promising for a wide range of applications.

[0037] This invention combines the advantages of elastic expansion and contraction with a tubular structure, enabling it to adapt to various changes in the tubular system. During operation, this invention plays a crucial role when the tubular system undergoes length changes due to factors such as temperature variations, pressure fluctuations, or mechanical vibrations. It absorbs these changes and compensates for the expansion and contraction of the tubular system through length expansion and contraction, thereby ensuring the reliability of the tubular system's connection and sealing. Another beneficial effect is that the expandable tubular system can adjust for stress changes caused by temperature and pressure variations through its own expansion and contraction, thus mitigating corrosion and maintaining the long-term stability and safety of the tubular system.

[0038] Low-temperature long-life sealing technology has demonstrated significant benefits at the technical level. Firstly, it employs special sealing materials and designs that maintain excellent elasticity and sealing performance under extreme low-temperature conditions, effectively preventing deformation and leakage of the sealing material caused by temperature changes. This technology not only improves the reliability and stability of the seal but also significantly extends the service life of the sealing components, reducing maintenance and replacement costs due to seal failure. An indirect effect is the reduction of corrosion caused by leakage.

[0039] At the application level, cryogenic long-life sealing technology ensures normal operation of equipment under low-temperature conditions, avoiding tubing maintenance time due to seal failure, thereby improving production efficiency and reducing production costs. This is particularly important for CCUS projects, which require continuous operation and high-efficiency production. Secondly, cryogenic long-life sealing technology prevents injected fluids such as CO2 and water from entering the annulus due to leakage, thus ensuring the annulus does not corrode. In addition, cryogenic long-life sealing technology can also reduce safety risks and minimize potential hazards such as formation contamination caused by leakage. These application-level advantages make cryogenic long-life sealing technology significantly beneficial in improving oilfield production efficiency, ensuring wellbore tubing safety, and reducing safety risks.

Claims

1. A combined sealing structure for oilfield production, comprising a combined sealing ring, characterized in that, The combined sealing ring includes a V-PAC sealing ring and a pre-cooling expansion sealing ring arranged side by side; both the outer peripheral surfaces of the V-PAC sealing ring and the pre-cooling expansion sealing ring are coated with hydrogel. The pre-cooled expansion sealing ring has an internal cavity filled with gallium-based liquid metal.

2. The combined sealing structure for oilfield production as described in claim 1, characterized in that, The V-PAC sealing ring has an internal cavity filled with gallium-based liquid metal.

3. The combined sealing structure for oilfield production as described in claim 1, characterized in that, The pre-cooling expansion sealing ring is made of polyvinylidene fluoride rubber or low-acrylonitrile butadiene rubber, which is resistant to low temperatures.

4. The combined sealing structure for oilfield production as described in claim 1, characterized in that, The hydrogel was prepared using the following method: By weight, 1 part of carboxylated modified nanocellulose was dissolved in 20 parts of deionized water and sonicated in a 55°C water bath until transparent to obtain the first solution; Dissolve 3 parts acrylamide, 0.003 parts methylenebisacrylamide, and 0.09 parts ammonium persulfate in 30 parts deionized water and stir magnetically to obtain a second solution. The first and second solutions were mixed at a mass ratio of 1:2 and heated to 40°C for 40 minutes under nitrogen protection to obtain the hydrogel.

5. The combined sealing structure for oilfield production as described in claim 1, characterized in that, The combined sealing ring contains 6-8 V-PAC sealing rings and pre-cooling expansion sealing rings, which are arranged alternately.

6. A telescopic tube system, comprising an inner tube and an outer tube sleeved outside the inner tube, and a connecting rod, wherein the inner tube and the outer tube are slidably connected, characterized in that, An inner pipe flange is fixedly connected to one end of the inner pipe, and an outer pipe flange is fixedly connected to the end of the outer pipe away from the inner pipe flange. A sealing ring groove is provided on the end of the inner pipe near the outer pipe flange between the inner pipe and the outer pipe. A combined sealing structure for oilfield production as described in any one of claims 1-5 is provided in the sealing ring groove. A movable flange is fixedly installed on the outer circumferential surface of the outer tube at the end away from the outer tube flange; The outer pipe flange, inner pipe flange and movable flange are each provided with a number of guide through holes, and the guide through holes on the outer pipe flange, inner pipe flange and movable flange are provided correspondingly. One end of the connecting rod extends from the guide hole on the inner tube flange, passes through the guide hole correspondingly provided on the movable flange, and then extends out from the guide hole on the outer tube flange. Limit nuts are provided at both ends of the connecting rod; The distance between the two limit nuts is less than the sum of the lengths of the inner and outer tubes.

7. The telescopic tubing system as described in claim 6, characterized in that, The inner pipe flange and the inner pipe are connected by welding, and the outer pipe flange and the outer pipe are connected by welding.

8. The telescopic tubing system as described in claim 6, characterized in that, The outer circumferential surface of the inner tube is coated with a coating, which is a laser cladding coating of an iron-based alloy with added lubricant.

9. The telescopic tubing system as described in claim 8, characterized in that, The iron-based alloy laser cladding coating with added lubricant has the following composition by weight: 90-95 parts iron-based alloy powder, 2-6 parts tungsten disulfide powder, 0-2 parts hexagonal boron nitride, 0-5 parts calcium fluoride, 0.2-1 parts talc, and 0.1-0.6 parts tungsten hexafluoride.

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