A method of manufacturing a well logging transducer cable head

Abstract

The application discloses a kind of preparation methods of well logging transducer cable head;Including surface treatment to polytetrafluoroethylene lead-out wire;Give polytetrafluoroethylene lead-out wire activation group;Coupling treatment polytetrafluoroethylene lead-out wire using gradient coupling agent;Using preforming technology controls the quality, shape of fluorine rubber raw material;The treated polytetrafluoroethylene lead-out wire and preformed fluorine rubber are vulcanized process.This application solves the existing fluorine rubber and polytetrafluoroethylene lead-out wire bonding difficult problem, better realizes well logging transducer downhole water tight, provides reference for long distance, long time while drilling exploration work.

Description

Technical Field

[0001] This invention relates to the field of well logging transducer manufacturing, and particularly to a method for preparing a watertight cable head, especially a method for preparing a watertight cable head for well logging transducers using special cables and rubber. Background Technology

[0002] As a vital energy source in the 21st century, oil's significant economic and strategic value makes it an indispensable foundation for economic development and modernization in all countries. However, oil is typically found in the fissures of rock layers, where high temperatures and pressures make it difficult to extract using conventional exploration techniques. Considering oil's outstanding economic and strategic value, long-distance exploration of oil wells is of paramount importance.

[0003] Sonic logging is a crucial means of downhole exploration and signal transmission, and the logging transducer is the core technology of sonic logging. To meet the requirements of long-term downhole operation of sonic logging equipment, the logging transducer must possess excellent oil-tightness and water-tightness capabilities. Generally, the cable head, being the connection point between the sheathing material and the cable, is more prone to water-tightness or oil-tightness failure; therefore, the preparation of the cable head is particularly important, encompassing the selection of sheathing materials and cables, as well as their bonding processes. The downhole operating environment is complex, requiring the sheathing material to withstand not only high temperatures and pressures but also corrosion from drilling fluids and other oils. Prolonged exposure to high temperatures, high pressures, and corrosive media can alter the properties of ordinary sheathing materials. Therefore, conventional sheathing materials used in transducers, such as polyurethane, chlorinated butyl rubber, and neoprene rubber, no longer meet the requirements.

[0004] Generally, high-temperature resistant cable head sheathing materials mainly include fluororubber and silicone rubber, with temperature resistance exceeding 200℃. Given the abundance of oil in downhole environments, fluororubber has greater versatility, while polytetrafluoroethylene (PTFE) cables are commonly used for lead-out wires. However, untreated PTFE cables are chemically inert and cannot form effective chemical bonds with most materials, making effective adhesion to the sheathing material difficult during the vulcanization of logging transducers. Furthermore, PTFE cables are flexible, making positioning difficult during vulcanization and prone to friction with the vulcanization mold, leading to outer sheath damage. Therefore, to adapt to the high-temperature, high-pressure, and corrosive downhole operating environment, in-depth research on the vulcanization bonding process of PTFE cable heads is necessary. Summary of the Invention

[0005] To address the shortcomings of existing technologies and solve the problem of difficult bonding between fluororubber and polytetrafluoroethylene (PTFE) lead wires, thereby achieving better downhole watertightness of logging transducers and providing a reference for long-distance, long-duration drilling exploration, this invention provides a method for preparing a watertight cable head for logging transducers. However, the preparation of watertight cable heads using fluororubber and PTFE lead wires may be affected by five factors. To address these five factors, this invention proposes a method to reduce their impact:

[0006] (1) To reduce the impact of the smooth, stable, and non-adhesive outer surface of the PTFE lead wire, this invention employs a chemical method to treat the outer sheath of the PTFE lead wire, thereby improving its adhesive properties. Since PTFE material possesses strong chemical stability and cannot react with other materials, its stability as a lead wire in a watertight cable head may reduce its watertightness. Therefore, by using a chemical grafting reaction, the number of activating groups on the surface of the PTFE lead wire is increased, enhancing its potential to react with other materials and reducing damage to the cable sheath.

[0007] (2) In order to avoid the influence of chemical treatment agents on other polytetrafluoroethylene leads, the invention designed a treatment tank according to the size of the cable head and used an immersion method to treat the leads, avoiding surface damage to excess leads caused by the container being too large or coating methods; however, if only the necessary leads are coated, the coating effect is poor and uneven treatment is likely to occur.

[0008] (3) To reduce the impact of weak adhesion of fluororubber, this invention employs coupling agent technology to achieve adhesion between fluororubber and polytetrafluoroethylene (PTFE) wires. As a crucial medium for adhesion and achieving watertightness, the selection and use of coupling agents must be targeted. The vulcanization process of fluororubber differs from that of conventional rubber, involving secondary vulcanization at higher temperatures. Generally, coupling agents compatible with the vulcanization process of fluororubber should be selected. Due to the small diameter of the PTFE lead wires, a strong medium is needed to achieve adhesion with fluororubber. Unlike traditional vulcanization processes, this invention utilizes the gradient method principle to construct a gradient coupling agent system. Through a multi-layer coupling system, the influence of the materials of the fluororubber and PTFE lead wires is reduced, thereby improving adhesion strength.

[0009] (4) To avoid the impact of vulcanization on the outer sheath of the PTFE lead wire, this invention avoids damage to the lead wire outer sheath caused by excessive fluororubber raw material and excessive pressure. It applies preforming technology to control the amount of fluororubber raw material and avoids the impact of outer sheath damage on the watertight performance of the cable head. At the same time, the preforming technology solves the problem of PTFE cables being unable to be fixed due to their soft nature.

[0010] (5) To address the problem of quantitatively measuring the bonding performance of cable sheaths, this invention designs a watertightness test piece for cable heads. Conventional bonding tests involve preparing two materials into sheet or tension pin shapes, but cable sheaths have fixed shapes and are usually not obtainable individually, making testing difficult. This invention cleverly utilizes the easily moldable nature of rubber to embed the PTFE lead wire. A water pressure test is performed to measure the continuity between the lead wire and water, determining the bonding between the PTFE lead wire and the fluororubber, thus verifying the watertightness of the watertight cable head.

[0011] Specifically, the objective of this invention is achieved through the following technical solutions:

[0012] This invention relates to a method for preparing a logging transducer cable head, the method comprising the following steps:

[0013] S1. Surface treatment of polytetrafluoroethylene lead wires;

[0014] S2, imparts activating groups to the polytetrafluoroethylene lead wires;

[0015] S3. Polytetrafluoroethylene leads are coupled using a gradient coupling agent.

[0016] S4. Use preforming technology to control the quality and shape of fluororubber raw materials;

[0017] S5. Perform a vulcanization process on the polytetrafluoroethylene lead wire and the pre-formed fluororubber processed in step S3.

[0018] As described in the method for preparing a logging transducer cable head, all the steps of the cable head are not limited to the type and form of the lead wire and rubber.

[0019] As described in the method for preparing a logging transducer cable head, the basic surface treatment work in step S1 is not limited to sandpaper, sandblasting, or other similar methods.

[0020] As described in the method for preparing a logging transducer cable head, step S2, which involves imparting activating groups to the polytetrafluoroethylene lead wire, is not limited to chemical treatment, high-temperature melting, plasma treatment, or other similar methods.

[0021] As one embodiment, the chemical treatment involves immersing the polytetrafluoroethylene (PTFE) lead wire in a chemical treatment solution formulated with 125-130g naphthalene, 1000ml tetrahydrofuran, and 20-25g metallic sodium. The immersion time is 5-20 minutes.

[0022] As described in the method for preparing a logging transducer cable head, in step S3, the gradient coupling agent technology is not limited to coupling agents, adhesives, or other forms.

[0023] As one implementation, the gradient coupling agent is first treated with Chemlock 5150 at room temperature for 12 hours; then Chemlock 607 is added at 80°C for 30 minutes.

[0024] As described in the method for preparing a logging transducer cable head, step S4, the preforming technology is not limited to other cutting processes.

[0025] As described in the method for preparing a logging transducer cable head, step S5, the vulcanization process is not limited to vulcanization, potting, and injection molding.

[0026] The method for preparing a logging transducer cable head, as described above, further includes the steps of making a watertight cable head water pressure model, conducting water pressure tests, and verifying the watertight performance of the fluororubber and polytetrafluoroethylene lead wires.

[0027] As described in the method for preparing a logging transducer cable head, the water pressure model is not limited to other forms such as sheet clamps or metal pins that are conducive to testing watertightness.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] (1) The present invention designs a watertight cable head, which, compared with the traditional integral vulcanized cable head, extends the watertight path inside the cable head and reduces the impact of vulcanization defects on the insulation and acoustic performance of the logging transducer.

[0030] (2) The coupling agent technology used in this invention is gradient coupling agent technology. Compared with the traditional coupling agent method, multiple coupling platforms are built on the surface of polytetrafluoroethylene lead wire and fluororubber, which effectively improves the bonding strength between fluororubber and polytetrafluoroethylene lead wire.

[0031] (3) The present invention, through preforming technology, not only effectively avoids the squeezing damage to the outer sheath of the polytetrafluoroethylene lead wire caused by excessive fluororubber raw material, but also determines the fixed position of the polytetrafluoroethylene lead wire, avoiding the problem of threading friction caused by softness.

[0032] (4) The cable head water pressure model designed in this invention solves the problem that the bonding strength of the cable sheath cannot be quantitatively measured; by conducting water pressure tests at different pressures and measuring the insulation resistance of the cable head after water pressure, the bonding strength of the cable sheath with other materials can be effectively determined. Attached Figure Description

[0033] Other features, objects, and advantages of the invention will become more apparent from the following detailed description of non-limiting embodiments with reference to the accompanying drawings:

[0034] Figure 1This is a schematic diagram of the overall structure of the watertight cable head of the present invention;

[0035] Figure 2 This is a model diagram of the hydraulic cable head of the present invention;

[0036] Figure 3 This is a diagram illustrating the specific implementation steps of the present invention. Detailed Implementation

[0037] The present invention will now be described in detail with reference to specific embodiments. These embodiments will help those skilled in the art to further understand the present invention, but do not limit the invention in any way. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention. These all fall within the scope of protection of the present invention.

[0038] Example 1

[0039] This embodiment provides a method for preparing a logging transducer cable head; a schematic diagram of the overall logging transducer cable head is shown below. Figure 1 The two lines are polytetrafluoroethylene (PTFE) leads, with the middle part hidden in fluororubber.

[0040] Its preparation method is as follows Figure 3 As shown, it includes the following steps:

[0041] Step 1: Roughen the part of the PTFE lead wire to be bonded with sandpaper of appropriate grit until the surface is rough and undamaged, wipe the lead wire with alcohol and let it dry.

[0042] Step 2: Place the lead wire into a treatment tank containing 10ml of chemical treatment solution, let it stand for 10 minutes, observe the surface of the lead wire, wipe off the excess chemical treatment solution on the surface and let it dry. The chemical treatment solution consists of 123g naphthalene, 1000ml tetrahydrofuran and 23g sodium.

[0043] Step 3: Apply a layer of Chemlock 5150 evenly to the surface of the treated lead wire, with a thickness of 0.1mm, and let it air dry overnight.

[0044] Step 4: Continue to evenly coat the surface of the PTFE lead wire with a layer of Chemlock 607, with a thickness of 0.1mm. After air drying at room temperature, place it in an 80℃ oven and let it stand for 30 minutes.

[0045] Step 5: Place the fluororubber raw material into a preforming mold and press it overnight to obtain fluororubber raw material of the corresponding shape and size;

[0046] Step 6: Place the vulcanizing mold on the flat vulcanizing press and preheat for 30 minutes until the mold and the vulcanizing press are at the same temperature;

[0047] Step 7: Embed the treated PTFE lead wire in the fluororubber preform and perform vulcanization assembly. After fixing the position of the PTFE lead wire with the mold, vulcanize at 175°C for 10 minutes.

[0048] Step 8: After vulcanization, remove the watertight cable head and allow it to cool to room temperature;

[0049] Step 9: Place the watertight cable head in a 200℃ oven for secondary vulcanization;

[0050] Step 10: Construct a watertight cable head hydraulic model. Test it for 30 minutes under 20MPa water pressure and 140MPa oil pressure respectively. Use an insulation meter to measure the continuity with water, verifying the adhesion performance and watertightness of the PTFE lead wire and fluororubber. The watertight cable head hydraulic model is shown below. Figure 2 As shown, the two ends of a PTFE (polytetrafluoroethylene) wire are pre-embedded in fluororubber raw material and then vulcanized. A water pressure model is placed in water or oil pressure for testing. After the test, the PTFE lead wire is cut in the middle, and part of the model is submerged in water. One end of an insulation tester is clamped to the wire, and the other end is submerged in water to measure the insulation resistance and determine the watertightness.

[0051] The test results are shown in the table below:

[0052] Pressure conditions (MPa) 0 20 140 Insulation resistance (GΩ) ＞11 ＞3.3 ＞3.3

[0053] Test conditions: Insulation resistance test for 1 minute at 1000V.

[0054] Comparative Example 1

[0055] Other implementation conditions are the same as in Example 1, except that the coupling agent coating conditions are changed to verify the constructiveness of the gradient coupling agent technology.

[0056]

[0057] Comparative Example 2

[0058] Other implementation conditions are the same as in Example 1, except that preforming technology is used, and the impact on the polytetrafluoroethylene lead wire is compared.

[0059] This comparative example did not employ pre-forming technology: damage appeared on the surface of the PTFE lead wire, affecting the watertight insulation performance of the cable head. Analysis of the causes: 1. Operators need extensive vulcanization experience to cut rubber sheets appropriately to the mold size, and strict control over the rubber materials used. 2. Because the PTFE lead wire is flexible, and the mold has a fixing function at both ends, uneven thickness of the rubber sheets at the upper and lower ends under 10MPa pressure can easily cause damage.

[0060] Example 1 uses pre-forming technology: the surface of the polytetrafluoroethylene lead wire is intact and has good watertight insulation performance.

[0061] The specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art can make various modifications or variations within the scope of the claims, which do not affect the essence of the present invention.

Claims

1. A method for preparing a logging transducer cable head, characterized in that, The method includes the following steps: S1. Surface treatment of polytetrafluoroethylene lead wires; S2. Immerse the polytetrafluoroethylene (PTFE) lead wire in a chemical treatment solution to impart activating groups to the PTFE lead wire; the chemical treatment solution is formulated with 125-130 g of naphthalene, 1000 ml of tetrahydrofuran, and 20-25 g of metallic sodium. S3. The polytetrafluoroethylene lead wire is coupled with a gradient coupling agent. The gradient coupling agent is first Chemlock 5150, the temperature is room temperature and the treatment time is 12h; then Chemlock 607 is added, the temperature is 80℃ and the treatment time is 30min. S4. Use preforming technology to control the quality and shape of fluororubber raw materials; S5. Embed the polytetrafluoroethylene lead wire processed in step S3 into the fluororubber preform, perform vulcanization assembly, and after fixing the position of the polytetrafluoroethylene lead wire with the mold, perform the vulcanization process.

2. The method for preparing the logging transducer cable head according to claim 1, characterized in that, In step S1, the surface treatment includes sandpaper and sandblasting.

3. The method for preparing the logging transducer cable head according to claim 1, characterized in that, The preforming includes cutting and shaping.

4. The method for preparing the logging transducer cable head according to claim 1, characterized in that, The vulcanization process includes vulcanization, potting, and injection molding.

5. The method for preparing the logging transducer cable head according to claim 1, characterized in that, The method also includes steps such as making a watertight cable head water pressure model, conducting water pressure tests, and verifying the watertight performance of fluororubber and polytetrafluoroethylene leads.

6. The method for preparing the logging transducer cable head according to claim 5, characterized in that, The watertight cable head water pressure model includes a sheet-like clamp or metal pin to facilitate testing watertight performance.

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