Thread compound for oil casing based on superabsorbent polymer SAP, method for its production and use thereof

Abstract

The application discloses a high water-absorbing resin SAP-based oil casing thread grease, which is composed of the following components: base oil 20-40%, thickening agent 10-20%, solid lubricant 20-45%, tin-phosphor bronze 5-10%, high polymer water-absorbing resin SAP powder 5-15%, and antioxidant and preservative 1-5%, and the sum of the above mass percentages is 100%. The application further discloses a preparation method of the high water-absorbing resin SAP-based oil casing thread grease. The application further discloses application of the high water-absorbing resin SAP-based oil casing thread grease in oil and natural gas drilling oil pipes and casings. The high water-absorbing resin SAP-based oil casing thread grease, the preparation method and the application thereof disclosed by the application solve the problem that the existing thread grease has limited friction resistance and pressure resistance, and the contained grease volatilizes at high temperature to form a leakage channel, thereby resulting in poor sealing performance.

Description

Technical Field

[0001] This invention belongs to the field of tubing and casing technology for oil and gas drilling, specifically relating to tubing and casing thread grease based on superabsorbent polymer (SAP). This invention also relates to the preparation and application of tubing and casing thread grease based on superabsorbent polymer (SAP). Background Technology

[0002] The oil and gas drilling and production sector consumes a large amount of tubing and casing annually. These tubing and casing are connected by threads to form a string. According to statistics, over 70% of tubing string failures occur at the threaded connection. The threaded connection of the tubing and casing is one of the areas subjected to the greatest stress during oil and gas well production. In actual use, external loads (such as tension, compression, bending, and torsion) can increase the thread clearance, and thread grease may not be able to completely fill these gaps, leading to sealing failure and leakage. Existing thread greases still have shortcomings in terms of gap-filling capacity and dynamic sealing performance, especially under high pressure, high temperature, vibration, or corrosive environments, where sealing performance is prone to decline.

[0003] Currently, commonly used thread-locking greases contain graphite powder, a large amount of metal powder, and petroleum-based base greases and oils. However, their anti-wear and pressure-resistant properties are limited, and the greases evaporate at high temperatures, creating leakage channels and resulting in poor sealing performance. Superabsorbent polymers (SAPs), due to their excellent water absorption, swelling, and resilience, exhibit significant advantages in gap-filling sealing. However, there are currently no reports on the use of SAP powder as a thread-locking grease for oil casings. Summary of the Invention

[0004] The first objective of this invention is to provide a thread grease for oil casing based on superabsorbent polymer (SAP), which solves the problems of limited anti-friction and pressure resistance of existing thread greases and the formation of leakage channels due to the volatilization of the grease at high temperatures, resulting in poor sealing performance.

[0005] A second objective of this invention is to provide a method for preparing a casing thread grease based on superabsorbent polymer (SAP).

[0006] A third objective of this invention is to provide the application of a superabsorbent polymer (SAP) based tubing and casing thread grease in oil and gas drilling tubing and casing.

[0007] The first technical solution adopted in this invention is a thread grease for oil casing based on superabsorbent polymer (SAP), which is composed of the following components: 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative, the sum of the above mass percentages being 100%.

[0008] The invention is further characterized by: The base oil is one of mineral oil, synthetic ester oil, or polyalphaolefin oil.

[0009] The thickener is one or more of lithium soap base, calcium sulfonate compound soap, magnetic fluid and liquid silica gel, and the consistency grade of the thickener is 3.

[0010] The solid lubricant is made of molybdenum disulfide, graphite, or a mixture of molybdenum disulfide and graphite. The solid lubricant is in powder form and the particle size of the solid lubricant is not less than 325 mesh.

[0011] The second technical solution adopted in this invention is a method for preparing oil casing thread grease based on superabsorbent polymer (SAP), specifically including the following steps: Step 1: Select 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative; Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at low speed until homogeneous. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; Step 6: Add antioxidants and preservatives, stir, and obtain oil casing thread grease based on water-absorbing resin powder.

[0012] The invention is further characterized by: The target temperature in step 2 is 70-90℃.

[0013] The standard temperature in step 3 is 50-60℃.

[0014] In step 4, the stirring speed is 60-80 r / min.

[0015] The stirring time in step 5 shall be no less than 30 minutes, and the stirring time in step 6 shall be no less than 2 hours.

[0016] The third technical solution adopted in this invention is the application of oil casing thread grease based on superabsorbent polymer (SAP) in oil tubing and casing in oil and gas drilling.

[0017] The beneficial effects of this invention are: This invention relates to a thread grease for casing and tubing based on superabsorbent polymer (SAP), its preparation method, and its application. By introducing SAP powder into the thread grease formulation, and combining its expansion properties and resilience, it can effectively compensate for thread gaps and improve the sealing reliability of threaded connections. Existing thread grease technology has no problem sealing the casing and tubing threaded joints under pressure, but under tension, gaps appear in the metal-to-metal sealed threaded joints, affecting the sealing effect. Leakage is prone to occur under high pressure, vibration, and bending forces. However, superabsorbent polymer (SAP) powder has excellent water absorption, expansion, and resilience, exhibiting strong sealing performance under tensile forces in complex downhole casing and tubing conditions. Detailed Implementation

[0018] The present invention will now be described in detail with reference to specific embodiments.

[0019] The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) provided by this invention specifically includes the following steps: Step 1: Select 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative; Base oils are used to provide a basic level of lubrication; Thickeners are used to improve consistency and temperature stability; Solid lubricants are used to reduce the coefficient of friction and enhance load-bearing capacity; Tin-phosphor bronze is used to increase compressive strength and wear resistance; Superabsorbent polymer (SAP) powder is used to absorb moisture from the air or working fluids and then expand to form a gel to fill thread gaps. Antioxidants and preservatives are used to enhance antioxidant and corrosion resistance, enabling the product to withstand harsh environments; Superabsorbent polymer (SAP) powder exhibits excellent water absorption and swelling properties. Its hydrophilic groups rapidly absorb moisture from the air or downhole fluids upon contact, forming a transparent gel that simultaneously fills thread gaps and counteracts gap widening caused by external loads. The SAP gel also possesses good resilience, with a rebound rate of approximately 25%, maintaining its sealing effect even under pressure fluctuations or dynamic operating conditions. Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. The target temperature is 70-90℃. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; the standard temperature is 50-60℃. Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at low speed until homogeneous; the stirring speed should be 60-80 r / min. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; stirring time should be no less than 30 minutes. Step 6: Add antioxidants and preservatives, stir to obtain oil casing thread grease based on water-absorbing resin powder; the stirring time shall not be less than 2 hours.

[0020] Example 1 The oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment is composed of the following components: 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative, with the sum of the above mass percentages being 100%.

[0021] Example 2 The oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment is composed of the following components: 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and corrosion inhibitor, with the sum of the above mass percentages being 100%. The base oil is one of mineral oil, synthetic ester oil, or polyalphaolefin oil; The thickener is one or more of lithium soap base, calcium sulfonate compound soap, magnetic fluid and liquid silica gel, and the consistency grade of the thickener is 3.

[0022] Example 3 The oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment is composed of the following components: 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and corrosion inhibitor, with the sum of the above mass percentages being 100%. The base oil is one of mineral oil, synthetic ester oil, or polyalphaolefin oil; The thickener is one or more of lithium soap base, calcium sulfonate compound soap, magnetic fluid and liquid silica gel, and the consistency grade of the thickener is 3. The solid lubricant is made of molybdenum disulfide, graphite, or a mixture of molybdenum disulfide and graphite. The solid lubricant is in powder form and the particle size of the solid lubricant is not less than 325 mesh.

[0023] Example 4 The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment specifically includes the following steps: Step 1: Select 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative; Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at low speed until homogeneous. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; Step 6: Add antioxidants and preservatives, stir, and obtain oil casing thread grease based on water-absorbing resin powder.

[0024] Example 5 The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment specifically includes the following steps: Step 1: Select 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative; Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. The target temperature is 70-90℃. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; the standard temperature is 50-60℃. Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at low speed until homogeneous. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; Step 6: Add antioxidants and preservatives, stir, and obtain oil casing thread grease based on water-absorbing resin powder.

[0025] Example 6 The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment specifically includes the following steps: Step 1: Select 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative; Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. The target temperature is 70-90℃. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; the standard temperature is 50-60℃. Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at low speed until homogeneous; the stirring speed should be 60-80 r / min. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; stirring time should be no less than 30 minutes. Step 6: Add antioxidants and preservatives, stir to obtain oil casing thread grease based on water-absorbing resin powder; the stirring time shall not be less than 2 hours.

[0026] Example 7 The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) provided in this embodiment specifically includes the following steps: Step 1: Select 35% base oil, 20% thickener, 25% solid lubricant, 7% tin-phosphor bronze, 10% superabsorbent polymer (SAP) powder, and 3% antioxidant and preservative; The base oil is a synthetic ester oil made from trimethylolpropane oleate; The thickener is a mixture of lithium soap base, magnetic fluid and liquid silica gel, with the addition ratio of lithium soap base, magnetic fluid and liquid silica gel being 2:1:1; The solid lubricant uses a mixture of molybdenum disulfide and graphite, with a molybdenum disulfide to graphite addition ratio of 1:1; The oxidant and preservative are a mixture of diarylamine and passivator, with the ratio of diarylamine to passivator being 1:1. Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. The target temperature is 80℃. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; the standard temperature is 60℃. Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at a low speed until homogeneous; the stirring speed is 70 r / min. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; stirring time should be no less than 30 minutes. Step 6: Add antioxidants and preservatives, stir to obtain oil casing thread grease based on water-absorbing resin powder; the stirring time is 2 hours.

[0027] The anti-sticking performance test was conducted on the oil casing thread grease based on the above-prepared water-absorbing resin powder, specifically as follows: Taking a Φ139.7×9.17mm P110 casing as an example, the threading torque is controlled as shown in Table 1. In order to verify the anti-sticking performance of the oil casing thread grease based on water-absorbing resin powder involved in this invention, the oil pipe is threaded with the maximum torque.

[0028] Table 1 Results of the upper and lower shackle test

[0029] A high interference fit was selected, and the thread was turned on at maximum torque to verify its anti-sticking performance. Table 1 shows that after the fourth uncoupling, neither the external nor internal threads of the bushing exhibited sticking. After field testing, the external thread surface was smooth and undamaged. Therefore, it can be demonstrated that the oil-based bushing thread grease prepared in this application, based on water-absorbing resin powder, has excellent lubrication and anti-sticking properties.

[0030] (2) Sealing performance test A sealing pressure test was conducted using a Φ139.7×9.17mm P110 sleeve. At room temperature, the test medium was water. The pressure was calculated based on 90% VME stress of the material, and the pressure was increased to 15500psi and held for 5 minutes. No leakage was observed.

[0031] Enhanced Dynamic Sealing Performance: The expanding gel filling capacity of SAP powder effectively fills thread gaps, enhancing the sealing effect. Strong Adaptability: The SAP gel can dynamically adjust its shape according to changes in operating conditions, maintaining stable sealing performance under complex conditions such as high temperature, high pressure, and vibration. Increased Resilience Enhances Sealing Life: The resilience of the SAP gel allows it to maintain an effective seal even under multiple cyclic loads.

[0032] Excellent overall lubrication performance: Combining the lubrication capabilities of traditional thread grease with the sealing properties of SAP, it provides more comprehensive protection.

[0033] Example 8 This embodiment provides the application of SAP-based oil casing thread grease in oil and gas drilling tubing and casing.

Claims

1. A threadlocker grease based on superabsorbent polymer (SAP), characterized in that, It is composed of the following components: 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative, with the sum of the above percentages being 100%.

2. The oil casing thread grease based on superabsorbent polymer (SAP) according to claim 1, characterized in that, The base oil is one of mineral oil, synthetic ester oil, and polyalphaolefin oil.

3. The oil casing thread grease based on superabsorbent polymer (SAP) according to claim 1, characterized in that, The thickener is one or more of lithium soap base, calcium sulfonate compound soap, magnetic fluid and liquid silica gel, and the consistency grade of the thickener is 3.

4. The oil casing thread grease based on superabsorbent polymer (SAP) according to claim 1, characterized in that, The solid lubricant is made of molybdenum disulfide, graphite, or a mixture of molybdenum disulfide and graphite. The solid lubricant is in powder form and has a particle size of not less than 325 mesh.

5. The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) according to any one of claims 1-4, characterized in that, Specifically, the following steps are included: Step 1: Select 20%-40% base oil, 10%-20% thickener, 20%-45% solid lubricant, 5%-10% tin-phosphor bronze, 5%-15% superabsorbent polymer (SAP) powder, and 1%-5% antioxidant and preservative; Step 2: Heat the base oil to the target temperature. After heating, add the thickener and stir. Step 3: Add solid lubricant while stirring, mix well, and then cool to the standard temperature; Step 4: After cooling, add superabsorbent polymer (SAP) powder and stir at low speed until homogeneous. Step 5: Add tin phosphor bronze, stir, and cool to room temperature; Step 6: Add antioxidants and preservatives, stir, and obtain oil casing thread grease based on water-absorbing resin powder.

6. The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) according to claim 5, characterized in that, The target temperature mentioned in step 2 is 70-90℃.

7. The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) according to claim 5, characterized in that, The standard temperature mentioned in step 3 is 50-60℃.

8. The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) according to claim 5, characterized in that, The stirring speed in step 4 is 60-80 r / min.

9. The method for preparing oil casing thread grease based on superabsorbent polymer (SAP) according to claim 5, characterized in that, The stirring time in step 5 shall be no less than 30 minutes, and the stirring time in step 6 shall be no less than 2 hours.

10. The application of the superabsorbent polymer (SAP) based oil casing thread grease according to claim 1 in oil tubing and casing for oil and gas drilling.

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