Preparation method and application of solid-free wellhead squeezing resin

Abstract

The invention relates to the technical field of oil and gas field chemicals, and discloses a preparation method and application of solid-free wellhead squeezing resin, the preparation method comprises the following steps: S1, hydrogenated bisphenol A epoxy resin as main resin and at least one low-viscosity liquid auxiliary resin are uniformly mixed to obtain composite resin; s2, uniformly mixing at least two amine curing agents with different reaction activities to obtain a composite curing agent; s3, mixing the composite resin with the composite curing agent when the composite resin needs to be used, so as to obtain the solid-free wellhead squeezing resin. Through full-liquid and solid-phase-free component design, the obtained resin system is low in initial viscosity and good in pourability; through compounding of the curing agent, the pot life is precisely adjustable, and different construction requirements are met; all the components are reactive components, a compact sealing body with high strength and high toughness is formed after curing, and the plugging effect is lasting and reliable.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas field chemicals, in particular to a preparation method and application of a solid-phase-free wellhead squeeze resin. BACKGROUND

[0002] Oil and gas wellhead annulus pressure is a common safety hazard in the production process of oil and gas fields, which indicates that at least one sealing barrier (such as a cement sheath or a casing) in the well has failed, causing the formation fluid (oil, gas, water) to channel and leak. If not treated in time, the annulus pressure may continue to rise, which may seriously threaten the safety of wellhead equipment, damage oil and gas layers, pollute the environment, and even cause blowouts and other major accidents. Therefore, effective management of annulus pressure is a key link to ensure the safe production of oil and gas wells.

[0003] At present, the common technical means for treating wellhead annulus pressure include squeezing cement and squeezing chemical plugging agents. As a traditional method, cement squeezing has a low material cost, but its technical defects are also very obvious. The cement slurry system contains a large amount of solid particles, which are prone to particle bridging when squeezed into a small leakage channel, resulting in incomplete plugging effect because the cement slurry cannot reach the leakage source. At the same time, the hardened cement stone is brittle, and under the complex temperature and stress environment in the well, it is easy to crack or fail to adhere to the interface of the casing wall, forming a new leakage channel and resulting in poor long-term reliability of the plugging.

[0004] In order to overcome the shortcomings of cement-based materials, polymer-based chemical plugging agents such as epoxy resin have been increasingly applied. However, the existing conventional resin plugging systems also have some technical bottlenecks. In order to improve the strength or reduce the cost, inorganic fillers such as quartz powder are still added in many resin systems, which makes them also face the problem of solid particle plugging in small channels. A part of resin systems without fillers have high viscosity, poor flowability and permeability, and are difficult to enter micron-sized cracks. Non-reactive diluents added to reduce viscosity will volatilize or separate out during the curing process, causing volume shrinkage of the cured product, and significantly reducing the density and adhesion strength of the sealing body. In addition, the reaction speed of the resin and the curing agent is difficult to accurately control, and when the temperature is high in the well, the resin often gels too early in the squeezing process due to the short pot life, resulting in construction failure. These factors jointly restrict the application effect and long-term effectiveness of the existing resin plugging technology in complex well conditions. SUMMARY

[0005] The technical problem to be solved by the present application is to provide a preparation method and application of a solid-phase-free wellhead squeeze resin, which has low initial viscosity, does not contain solid particles, has adjustable pot life, and can form a sealing body with high strength and high toughness after curing, so as to effectively manage the wellhead annulus pressure of oil and gas wells.

[0006] To solve the above technical problems, the application adopts the following technical solutions: In a first aspect, the application provides a preparation method of a solid-phase-free wellhead squeeze resin, which adopts the following technical solutions: A preparation method of a solid-phase-free wellhead squeeze resin, comprising the following steps: S1, uniformly mixing hydrogenated bisphenol A epoxy resin as a main resin and at least one auxiliary resin at room temperature to obtain a composite resin; S2, uniformly mixing at least two different amine curing agents at room temperature to obtain a composite curing agent; S3, mixing the composite resin obtained in step S1 and the composite curing agent obtained in step S2 when needed to obtain the solid-phase-free wellhead squeeze resin.

[0007] By adopting the above technical solutions, first, in step S1, hydrogenated bisphenol A epoxy resin is selected as the main resin. The saturated alicyclic structure in the molecular structure of the resin has smaller molecular chain segment rotation resistance and weaker intermolecular force than the rigid benzene ring structure of conventional bisphenol A epoxy resin, so that the resin body has lower viscosity. At the same time, compounding with a low molecular weight auxiliary resin further reduces the viscosity of the resin component. Secondly, in step S2, at least two amine curing agents with different reaction activities are mixed in advance to prepare a composite curing agent. This design realizes effective regulation of the final curing reaction process through the difference in reaction rate of different amine molecules, avoids the sharp heat release and rapid gelation caused by a single high-activity curing agent, and prolongs the workable time of the system. Finally, the entire system does not contain any solid-phase particle fillers, and is a uniform liquid-phase system, which fundamentally avoids the viscosity increase caused by solid-phase particles and the bridging effect in micro cracks. Therefore, the resin obtained by the preparation method has the characteristics of low initial viscosity, long workable time and mild heat release, and can be effectively squeezed into the micro cracks of the wellhead cement sheath.

[0008] Preferably, the solid-phase-free wellhead squeeze resin is prepared from the following components by weight: The composite resin: 100 parts by weight; The composite curing agent: 20-50 parts by weight.

[0009] By adopting the above technical solutions, the amount of the composite curing agent is limited to 20-50 parts by weight, which ensures that the active hydrogen equivalent in the curing agent matches the epoxy group equivalent in the composite resin, so that the curing reaction can be fully carried out, thereby forming a cured body with a stable three-dimensional network structure and excellent mechanical properties.

[0010] Preferably, the composite resin is composed of the following components by weight: 100 parts by weight of the hydrogenated bisphenol A epoxy resin and 10-50 parts by weight of the auxiliary resin.

[0011] By adopting the technical scheme, the amount of the auxiliary resin is limited to 10-50 parts by weight. The amount range can effectively reduce the viscosity of the composite resin while forming a cured network with the main resin that has both strength and toughness. If the amount is too low, the viscosity reduction and toughness improvement effects are not obvious; if the amount is too high, the overall strength and heat resistance of the cured system may be affected.

[0012] Preferably, the auxiliary resin is at least one of tetrahydrophthalic acid diglycidyl ester, bis((3,4-epoxycyclohexyl)methyl) adipate, N,N-diglycidyl aniline, and 4,5-epoxyhexane-1,2-diglycidyl ester.

[0013] By adopting the technical scheme, the selected auxiliary resin is a low-viscosity epoxy resin, which is compatible with the main resin, and its molecular structure (such as an alicyclic or flexible segment) can be introduced into the crosslinked network after curing, playing an internal toughening role and improving the maximum compression ratio and impact resistance of the cured body.

[0014] Preferably, the epoxy equivalent weight of the hydrogenated bisphenol A epoxy resin is 180-220 g / eq.

[0015] By adopting the technical scheme, the epoxy equivalent weight of the hydrogenated bisphenol A epoxy resin is limited to the range of 180-220 g / eq. The epoxy equivalent weight in this range means that the resin has a moderate molecular weight, which can ensure low viscosity while providing sufficient chain length for the crosslinked network formed after curing, thereby achieving a balance between mechanical strength and toughness.

[0016] Preferably, the composite curing agent is composed of at least two of diethyltoluene diamine, diethyldiaminodicyclohexyl methane, cardanol-modified phenolic amine curing agent, polyamide 400, dimethyl diaminodicyclohexyl methane, methylcyclohexyl diamine, and polyamide 230.

[0017] Preferably, the composite curing agent is any one of (a), (b), or (c): (a) a composition composed of diethyltoluene diamine and diethyldiaminodicyclohexyl methane, and the weight ratio of the two is 1:1; or (b) a composition composed of diethyltoluene diamine, cardanol-modified phenolic amine curing agent, and polyamide 400, and the weight ratio of the three is 30:40:30; or (c) a composition composed of dimethyl diaminodicyclohexyl methane, methylcyclohexyl diamine, and polyamide 230, and the weight ratio of the three is 40:30:30.

[0018] By adopting the technical scheme, the combination of the curing agent utilizes the characteristics of different amine curing agents. For example, methylcyclohexyl diamine has fast reaction speed and good rigidity of the cured product; and dimethyl diamino dicyclohexyl methane, cashew phenol modified phenolic amine curing agent and polyamide curing agent have long molecular chains or flexible structures, which can endow the cured body with excellent toughness. By compounding them in a specific ratio, the curing rate, exothermic peak and mechanical properties of the final cured body can be accurately controlled to realize the synergy of rigidity and toughness.

[0019] Preferably, in step S3, before mixing the composite resin with the composite curing agent, a step of adding an active diluent to the composite resin is further included; the amount of the active diluent is 5-10 parts by weight relative to 100 parts by weight of the composite resin, and the active diluent is at least one of phenyl glycidyl ether, propylene oxide butyl ether and butanediol diglycidyl ether.

[0020] By adopting the technical scheme, the addition of the active diluent can further reduce the mixing viscosity of the whole system and improve its flowability in a low-temperature environment. The active diluent all contains an epoxy group, which can participate in the curing reaction and become part of the crosslinked network, avoiding the performance decline or late migration problem caused by the non-active diluent. In particular, when phenyl glycidyl ether is selected, the benzene ring structure in the molecule has high thermal stability, which can improve the long-term performance stability of the final cured body in a high-temperature environment downhole.

[0021] Preferably, the mixing in the S3 step is carried out at a temperature of 10-25℃, and the stirring time is 5-10 minutes.

[0022] By adopting the technical scheme, the mixing temperature is limited to 10-25℃, which covers the common temperature range of field construction, and the mixing and construction can still be smoothly carried out under the low-temperature condition of 10℃. The stirring time of 5-10 minutes is sufficient to uniformly mix the components with low viscosity, ensuring the uniformity of the curing reaction.

[0023] In a second aspect, the application provides an application of a solid-phase-free wellhead squeeze resin, which adopts the following technical scheme: The squeeze resin prepared according to any one of the preparation methods is applied in the treatment of pressure in the annulus of the wellhead of an oil and gas well.

[0024] By adopting the technical scheme, since the resin prepared by the method has the comprehensive properties of low viscosity, long squeeze time, low-temperature curability, high-strength and high-toughness of the cured body, it can be successfully pumped into the micro-cracks in the cement sheath of the wellhead and cured to form a performance-stable plugging body in the downhole environment, effectively isolating the oil and gas channeling channel, thereby solving the technical problem of pressure in the annulus of the wellhead.

[0025] The application provides a preparation method and application of a solid-phase-free wellhead squeeze resin. 1、The application uses liquid hydrogenated bisphenol A epoxy resin as the main resin, and one or more low-viscosity liquid auxiliary resins are compounded, so that a pure liquid resin system without any solid filler is obtained.

[0026] 2、The application mixes two or more amine curing agents with different chemical structures and reaction activities to prepare a composite curing agent, so that the curing reaction speed of the whole resin system is accurately controlled.

[0027] 3、The auxiliary resin and active viscosity reducer used in the application are reactive components containing epoxy groups, which can participate in the curing crosslinking reaction and become part of the crosslinked network of the final curing product while reducing the viscosity of the system, avoiding the volume shrinkage and performance loss caused by non-reactive solvents. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 The thickening curve of the embodiment S-2 of the application. DETAILED DESCRIPTION

[0029] The technical solutions in the embodiments of the application will be described in detail below with reference to the preparation examples, comparative examples and test examples of the application. Obviously, the described embodiments are only part of the embodiments of the application, rather than all the embodiments. Based on the embodiments in the application, all other embodiments obtained by those skilled in the art without creative labor fall within the protection scope of the application.

[0030] Preparation Example 1-2: Preparation Example 1: Preparation of a composite resin Composite resin A-1 : 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent weight 180 g / eq) and 10 parts by weight of tetrahydrophthalic acid diglycidyl ester were weighed into a container with mechanical stirring, stirred at room temperature 25 °C for 30 minutes until the system was mixed uniformly to form a clear transparent liquid, which was composite resin A-1. It was sealed and stored for later use.

[0031] Composite resin A-2: 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent weight 200 g / eq), 15 parts by weight of tetrahydrophthalic acid diglycidyl ester and 15 parts by weight of bis((3,4-epoxycyclohexyl)methyl) adipate were weighed into a container with mechanical stirring, stirred at room temperature 25 °C for 30 minutes until the system was mixed uniformly to form a clear transparent liquid, which was composite resin A-2. It was sealed and stored for later use.

[0032] Composite resin A-3: 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent weight 200 g / eq) and 50 parts by weight of N,N-diglycidyl aniline were weighed into a container with mechanical stirring, stirred at room temperature 25 °C for 30 minutes until the system was mixed uniformly to form a clear transparent liquid, which was composite resin A-3. It was sealed and stored for later use.

[0033] Composite resin A-4: 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent weight 220 g / eq) and 20 parts by weight of 4,5-epoxyhexane-1,2-diglycidyl oxymethylate were weighed into a container with mechanical stirring, stirred at room temperature 25 °C for 30 minutes until the system was mixed uniformly to form a clear transparent liquid, which was composite resin A-4. It was sealed and stored for later use.

[0034] Preparation example 2: Preparation of composite curing agent Composite curing agent B-1 : 50 parts by weight of diethyltoluene diamine (DETDA) and 50 parts by weight of diethyl diamino dicyclohexyl methane were weighed into a stirring container, stirred at room temperature 25 °C for 20 minutes until mixed uniformly, which was composite curing agent B-1. It was sealed and stored for later use.

[0035] Composite curing agent B-2: 30 parts by weight of diethyltoluene diamine (DETDA), 40 parts by weight of cardanol modified phenalkamine curing agent and 30 parts by weight of polyamide 400 were weighed into a stirring container, stirred at room temperature 25 °C for 30 minutes until mixed uniformly, which was composite curing agent B-2. It was sealed and stored for later use.

[0036] Composite curing agent B-3: 40 parts by weight of dimethyl diamino dicyclohexyl methane, 30 parts by weight of methyl cyclohexyl diamine and 30 parts by weight of polyamide 230 were weighed into a stirring vessel and stirred at room temperature 25°C for 30 minutes until well mixed, to give composite curing agent B-3. It was stored in a sealed container.

[0037] Example 1-8:

[0038] Example 1

[0039] Example 1

[0040] Example 2

[0041] Example 2

[0042] Example 3

[0043] Example 3

[0044] Example 4

[0045] Example 4

[0046] Example 5

[0047] Example 5

[0048] Example 6

[0049] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1, first add 8 parts by weight of butanediol diglycidyl ether, and stir at room temperature 25°C for 5 minutes to mix uniformly. Then, add 40 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2, and continue to stir for 5 minutes until the mixture is a uniform transparent liquid, to obtain a sealant S-6.

[0050] Example 7

[0051] Take 100 parts by weight of the composite resin A-4 prepared in Preparation Example 1, and add 30 parts by weight of the composite curing agent B-3 prepared in Preparation Example 2. Place the above components in a container, and stir at room temperature 25°C for 5 minutes using a mechanical stirrer until the mixture is a uniform transparent liquid, to obtain a sealant S-7.

[0052] Example 8

[0053] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1, first add 10 parts by weight of phenyl glycidyl ether, and stir at an ambient temperature of 10°C for 5 minutes to mix uniformly. Then, add 40 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2, and continue to stir at 10°C for 5 minutes until the mixture is a uniform transparent liquid, to obtain a sealant S-8. This sealant still has good flowability at low temperature, and is easy to mix and to inject.

[0054] Comparative Examples 1-5: Comparative Example 1: The difference from Example 2 is that 100 parts by weight of the hydrogenated bisphenol A epoxy resin in its composite resin A-2 is replaced by an equal weight of a conventional liquid bisphenol A epoxy resin (E-51, epoxy equivalent weight 190 g / eq), and the rest of the components and the preparation method are the same.

[0055] Comparative Example 2: The difference from Example 2 is that no auxiliary resin is added in its composite resin system, i.e. only 100 parts by weight of the hydrogenated bisphenol A epoxy resin is used as the resin component, and the curing agent amount is adjusted accordingly to match the epoxy equivalent weight, and the rest of the preparation method is the same.

[0056] Comparative Example 3: The difference from Example 2 is that its composite curing agent B-2 is replaced by a single curing agent, i.e. only diethyltoluene diamine (DETDA) with an equivalent amount of total active hydrogen in the composite curing agent B-2 is used, and the rest of the components and the preparation method are the same.

[0057] Comparative Example 4: The difference between Example 4 and the present example is that 5 parts by weight of phenyl glycidyl ether (active diluent) in Example 4 is replaced by equal weight of dodecyl and tetradecyl glycidyl ether (a conventional non-temperature resistant aliphatic active diluent), and the other components and preparation methods are the same.

[0058] Comparative Example 5: The difference between Example 1 and the present example is that 30 parts by weight of oil well cement (particle size 400 mesh) is additionally added as a solid-phase thickening and reinforcing material after the components of the sealant S-1 are uniformly mixed, and the mixture is vigorously stirred to disperse the oil well cement uniformly.

[0059] Test Examples 1-4: Test Example 1: To verify the basic properties and cured properties of the sealant compositions prepared in Examples S-1 to S-8, the present test is performed. The test content includes initial mixing viscosity, maximum temperature rise, pumpable time, setting time, compressive strength after curing, and toughness.

[0060] Experimental procedure: Initial physical property determination: Initial mixing viscosity: According to GB / T10247-2008 standard, using a Brookfield viscometer, at the specified test temperature (25℃ for Examples S-1 to S-7, and 10℃ for Example S-8), using a No. 3 rotor at a speed of 60 revolutions per minute, the viscosity value of the sample within 5 minutes after mixing is determined.

[0061] Maximum temperature rise: Take 500 mL of freshly prepared sample and place it in an adiabatic container. Place a thermocouple sensor at the geometric center of the sample. Record the temperature change of the system after mixing at the specified test temperature. Record the difference between the highest temperature and the initial temperature.

[0062] Construction-related property determination: Pumpable time: According to GB / T19139-2012, using a high temperature and high pressure thickener, at the specified test temperature, the time required for the sample consistency to reach 100 BC from the initial value is determined.

[0063] Setting time: The sample is cured at the specified test temperature, and the surface hardness is measured using a Vicat hardness tester type D timer. Record the time elapsed when the hardness value first reaches 20.

[0064] Cured body mechanical property determination: Test block preparation and curing: Each sample is poured into a 50mm x 50mm x 50mm cubic test block, and cured at the specified test temperature for 48 hours.

[0065] Compressive strength and flexibility: According to GB10238-2005, the YAW-300 type electro-hydraulic compression testing machine was used to compress the cured test block axially at a loading rate of 0.2 MPa / s, and the maximum compressive strength was recorded. At the same time, the ratio of the compression displacement to the original height when the visible cracks appeared on the surface of the test block was recorded as the maximum compression ratio, which was used to represent the flexibility.

[0066] Experimental data: The samples of Examples S-1 to S-8 were tested according to the above steps, and the results are recorded in Table 1.

[0067] Table 1. Test results of comprehensive performance of Examples S-1 to S-8

[0068] Summary: The test results in Table 1 show that the sealant compositions of all examples exhibit low viscosity liquid after mixing, with an initial mixing viscosity at 25°C ranging from 31.5 to 93.4 mPa·s. This property is due to the lower intermolecular force of the saturated cyclohexane structure in the hydrogenated bisphenol A epoxy resin compared to the benzene ring structure of the conventional bisphenol A epoxy resin, and the synergistic viscosity reduction effect of the low viscosity auxiliary resin. At the same time, each example shows a mild exothermic peak below 15°C and a pumpable time of more than 4 hours, which is due to the use of amine curing agents with different reactivities to achieve effective control of the curing reaction rate, avoiding rapid crosslinking and concentrated exothermic at the initial stage of the reaction.

[0069] The test data show that the cured bodies of each example form a solid with high mechanical strength after 48 hours of curing. Under the curing condition of 25°C, the compressive strength is more than 50 MPa, and the maximum compression ratio is more than 15%, indicating that the material has both load bearing capacity and deformation capacity. This performance is due to the high rigidity of the cured network provided by the aliphatic ring structure formed by the hydrogenated epoxy resin, and the flexible segment introduced by a specific component (such as polyamide or diethyl diaminodicyclohexyl methane) in the composite curing agent, which plays a role in internal toughening in the crosslinked network, so that the final cured body has high strength and high toughness.

[0070] As can be seen from the data of Example S-8, this technical solution is still applicable at a low temperature of 10°C. Its initial viscosity (66.5 mPa·s) is still within the pumpable range, the pumpable time is extended to 10.6 hours, and the curing can be completed within 48 hours to form a cured body with a compressive strength of 29.5 MPa. This shows that by selecting a composite curing agent containing a high-activity component, the technical solution ensures that the ring-opening polymerization reaction of the epoxy groups can still be effectively initiated at low temperatures, solving the technical problem of slow or no curing of conventional epoxy systems at low temperatures, and widening the construction temperature window of the material.

[0071] Test Example 2 To illustrate the technical effects corresponding to the selection of specific components and the composition of the system in the technical solution, performance comparison tests are conducted on Example S-1, S-2 and Comparative Examples D-1 to D-3, D-5. The tests aim to reveal the influence of each technical feature on the performance of the final product through single variable comparison.

[0072] Experimental steps: Comparison Group 1 (Main Resin System): Performance Comparison of Example S-2 and Comparative Example D-1 Initial Mixing Viscosity Measurement: Prepare samples of Example S-2 and Comparative Example D-1 respectively. According to GB / T10247-2008 standard, use a Brookfield viscometer at 25°C constant temperature, with a No. 3 rotor at a speed of 60 revolutions per minute, to measure the viscosity value within 5 minutes after the sample is mixed evenly.

[0073] Elasticity and Toughness Measurement: Pour the above two samples into 50mm x 50mm x 50mm cubic test blocks, and cure them at 25°C for 48 hours. According to GB10238-2005, use a YAW-300 type electro-hydraulic compression testing machine with a loading rate of 2.0MPa / s to compress the cured test blocks axially, and record the ratio of the compression displacement to the original height when visible cracks appear on the surface of the test block as the maximum compression ratio.

[0074] Comparison Group 2 (Auxiliary Resin System): Performance Comparison of Example S-2 and Comparative Example D-2 Initial Mixing Viscosity Measurement: Prepare samples of Example S-2 and Comparative Example D-2 respectively. Use the same steps as in Comparison Group 1, and measure the initial mixing viscosity of each sample at 25°C according to GB / T10247-2008 standard.

[0075] Comparison Group 3 (Curing Agent System): Performance Comparison of Example S-2 and Comparative Example D-3 Maximum Temperature Rise Measurement: Take 500mL of freshly prepared Example S-2 and Comparative Example D-3 samples respectively, place them in an adiabatic container, and place a thermocouple sensor at the geometric center of the sample. Record the temperature change of the system after mixing begins at 25°C ambient temperature, and record the difference between the highest temperature and the initial temperature.

[0076] Extrudable Time Measurement: According to GB / T19139-2012, use a high temperature and high pressure thickening instrument to measure the time required for the consistency of the two samples to reach 100 BC from the initial value at 25°C.

[0077] Flexibility test: The two samples above were cast into cubic blocks with the size of 50mm x 50mm x 50mm, and cured at 25℃ for 48 hours. The maximum compression ratio was determined according to GB10238-2005, using the same procedure as in Comparative Group 1.

[0078] Comparative Group 4 (effect of solid phase particles): Performance comparison between Example S-1 and Comparative Example D-5 Initial mixing viscosity test: Samples of Example S-1 and Comparative Example D-5 were prepared respectively. The initial mixing viscosity of each sample at 25℃ was determined according to GB / T10247-2008, using the same procedure as in Comparative Group 1.

[0079] Experimental data: The samples in each group above were tested according to the corresponding procedure, and the results are recorded in Table 2. The symbol “-” in Table 2 means that the technical index was not determined. In each comparative group, the technical index that was not determined is because the value of the index is determined by the same components of the samples in the group, and is not affected by the comparative variable in the group. Taking Comparative Group 3 as an example, the resin components of Example S-2 and Comparative Example D-3 are set to be the same in the formulation, so the initial mixing viscosity values of the two samples before the curing reaction occurs are the same, and this index does not reflect the influence caused by the difference in the curing agent system.

[0080] Table 2. Test results of key performance comparison between examples and comparative examples

[0081] Summary: The test results in Table 2 show that when the main resin is replaced by a conventional bisphenol A epoxy resin (Comparative Example D-1), the initial viscosity of the system increases significantly to 285.4 mPa·s, and the flexibility of the cured body decreases to 9.3%. The mechanism of this phenomenon is that the saturated aliphatic ring structure in the hydrogenated bisphenol A epoxy resin molecule is more easily rotated than the rigid benzene ring structure in the conventional bisphenol A epoxy resin, and the intermolecular force is smaller, thereby giving the liquid resin a lower viscosity; after curing, the flexible aliphatic ring structure units are introduced into the crosslinked network, improving the ability of the cured body to withstand deformation. In addition, not adding auxiliary resin (Comparative Example D-2) also leads to an increase in viscosity, indicating that the low molecular weight auxiliary resin plays an effective role in reducing the intermolecular distance and internal friction in the system, and is an essential part to achieve low viscosity.

[0082] The results of Comparative Example S-2 and Comparative Example D-3 show that the selection of the curing agent system has a decisive influence on the workability and final mechanical properties of the product. The use of a single high-activity curing agent (Comparative Example D-3) results in a violent reaction, with a maximum temperature rise of 42.7°C, a pumpable time of only 0.8 hours, and a solidified body with a toughness of only 8.7%. The reason for this is that the polymerization reaction initiated by a single curing agent is too fast, and a large amount of heat is released in a short time and a crosslinked network is formed, resulting in a very short workable time window, and the dense network structure formed quickly has high internal stress, which is manifested as macroscopic brittleness. The composite curing agent used in the technical solution is combined by amine compounds with different reactivity, which controls the progress of the curing reaction, so that the reaction proceeds smoothly, thereby prolonging the pumpable time, reducing the heat release, and forming a cured network with both strength and toughness.

[0083] Comparative Example S-2, refer to the attached Figure 1 As can be seen from the thickening curve, the temperature of the mixed components after preheating (500ml volume) is 31°C, and the temperature only rises to 37°C in the thickening instrument under the condition of no oil and only air medium. The consistency only rises obviously at 5:30h under the simulated summer environment temperature of 50°C (wellhead device temperature). This shows that the control of the curing reaction avoids the rapid rise in temperature caused by the rise in consistency, which leads to a rapid rise in squeeze pressure under microfractures, meeting the requirements of low displacement long-time squeezing into microfracture deep to block gas at the wellhead.

[0084] The data of Comparative Group 4 directly show the influence of the physical form of the system on the flowability. The introduction of solid particles into the pure liquid sealant S-1 (Comparative Example D-5) causes the initial mixing viscosity of the system to increase sharply from 31.5mPa·s to 1350mPa·s. This is because the addition of solid particles introduces additional flow resistance into the liquid and destroys the original laminar flow state of the fluid. The solid-free, all-liquid component design used in the technical solution fundamentally avoids the sharp increase in viscosity caused by solid particles and the bridging effect in small cracks, which is the structural basis for ensuring that it can be effectively squeezed into the cement sheath microfracture.

[0085] Test Example 3: To verify the influence of the active diluent selected in the technical solution on the long-term high-temperature resistance of the curing system, Comparative Example S-4 and Comparative Example D-4 were selected for thermal aging performance comparison testing.

[0086] Experimental steps: Preparation of test blocks: Samples of Example S-4 and Comparative Example D-4 were prepared, and poured into 50mm x 50mm x 50mm cubic test blocks.

[0087] Initial strength measurement: After curing the test blocks at 25°C for 48 hours, the compressive strength was measured according to GB10238-2005 standard using a YAW-300 type electro-hydraulic compression testing machine at a loading rate of 2.0 MPa / s, and recorded as the initial compressive strength value.

[0088] Thermal aging treatment: The remaining test blocks were placed in a constant temperature oven at 80°C ± 1°C for thermal aging treatment, with a duration of 30 days.

[0089] Post-aging strength measurement: After the aging period, the test blocks were removed and cooled to room temperature. The same procedure as the initial strength measurement was used to measure the post-aging compressive strength.

[0090] Strength retention rate calculation: The compressive strength retention rate of each sample was calculated according to the following formula: Strength retention rate (%) = (post-aging compressive strength / initial compressive strength) x 100% Experimental data: The samples of Example S-4 and Comparative Example D-4 were tested according to the above procedure, and the results are recorded in Table 3.

[0091] Table 3. Comparison of thermal aging performance of Example S-4 and Comparative Example D-4

[0092] Summary: The test results in Table 3 show that the compressive strength retention rate of the cured body of Example S-4 after undergoing thermal aging treatment at 80°C for 30 days is 93.5%. In contrast, the compressive strength retention rate of Comparative Example D-4, which uses a conventional aliphatic active diluent, is only 45.5% under the same aging conditions, indicating that its mechanical properties have deteriorated significantly.

[0093] The difference in performance is due to the difference in the molecular structure of the active diluent. The phenyl glycidyl ether used in Example S-4 contains a benzene ring in its molecular structure. The benzene ring structure has high bond energy and conjugate stability, and this structure is not prone to chain breaking or degradation under high temperature conditions. Therefore, when it reacts through the epoxy group and becomes part of the crosslinked network, it can maintain the structural integrity and thermal stability of the entire cured system.

[0094] The aliphatic active diluent used in Comparative Example D-4 has a molecular backbone composed of carbon-carbon single bonds. These types of chemical bonds have relatively low bond energies and are prone to thermal oxidative degradation under sustained high temperature conditions, leading to molecular chain breaking and thus destroying the topological structure of the cured network, which macroscopically manifests as a significant decrease in mechanical strength. In summary, by selecting an active diluent containing a thermally stable structural unit (such as a benzene ring), the present technical solution solves the problem of performance degradation of conventional epoxy systems due to insufficient thermal stability of the diluent when serving in high temperature environments for a long time, ensuring that the plugging body can maintain long-term structural stability and load-bearing capacity under high temperature conditions downhole.

[0095] Test Example 4: To verify the curing ability and mechanical properties of the sealant described in the technical solution under the simulated oil-water mixed working condition in the well, Example S-2 was selected for comparative curing environment test.

[0096] Experimental procedure: Sample preparation and grouping: The sealant sample of Example S-2 was prepared and cast into two groups of 50mm x 50mm x 50mm cubic test blocks. One group was the control group and the other group was the experimental group.

[0097] Curing environment setting: Control group: The test block mold was completely immersed in a container containing 25°C clean water.

[0098] Experimental group: The test block mold was completely immersed in a container containing 25°C oil-water mixture, which was composed of 1:1 by volume of crude oil and simulated formation brine.

[0099] Sample curing: The samples of the control group and the experimental group were simultaneously cured at 25°C for 72 hours in the respective set environment.

[0100] Performance determination: After the curing period, the test blocks were removed from the respective containers, and the oil stains on the surface of the test blocks in the experimental group were cleaned with solvent. According to the GB10238-2005 standard, a YAW-300 type electro-hydraulic compression testing machine was used to determine the compressive strength of the test blocks in the two groups at a loading rate of 2.0MPa / s.

[0101] Strength retention rate calculation: The compressive strength retention rate of the sample in the experimental group was calculated according to the following formula: Strength retention rate (%) = (Experimental group compressive strength / Control group compressive strength) x 100% Experimental data: The sample of Example S-2 was tested according to the above steps, and the results are recorded in Table 4.

[0102] Table 4. Performance test results of Example S-2 under different curing environments

[0103] Summary: The test results in Table 4 show that the compressive strength of the cured body of the sample of Example S-2 after curing in the oil-water mixture for 72 hours reaches 54.7MPa, and the strength retention rate relative to the sample cured in clean water reaches 89.2%. The data shows that the curing reaction process and the final mechanical properties of the sealant composition in the environment where oil and water coexist are not significantly negatively affected.

[0104] The realization mechanism of this performance lies in the selection of the composite curing agent B-2 component. The curing agent contains cashew phenol modified phenolic amine curing agent, which has both hydrophilic amine group function and lipophilic long carbon chain alkyl side chain in its molecular structure. This amphiphilic structure makes it have surface activity at the oil-water interface, can migrate to the reaction interface, and expel the oil and water phase from the surface to be bonded or the reactant interface, thereby creating conditions for the contact and reaction of amine groups and epoxy groups.

[0105] Therefore, the composite curing agent solves the technical problems that the conventional epoxy amine curing agent is difficult to effectively contact with the epoxy resin in the presence of the oil phase due to the hydrophilicity, or the curing reaction is incomplete due to the physical barrier of the oil phase. Through the interface action of the curing agent molecules, it is ensured that even in the oil-water emulsion or multi-phase interface environment, the epoxy resin and the curing agent can still undergo sufficient ring-opening polymerization and crosslinking reaction, and finally form a continuous, homogeneous and high mechanical strength three-dimensional network structure cured body, thereby ensuring the plugging reliability in the complex downhole fluid environment.

Claims

1. A method for preparing a solids-free wellhead extrusion resin, characterized in that, Includes the following steps: S1. Hydrogenated bisphenol A epoxy resin, which is the main resin, is mixed with at least one auxiliary resin at room temperature to obtain a composite resin. S2. Mix at least two different amine curing agents evenly at room temperature to obtain a composite curing agent; S3. When needed, the composite resin obtained in step S1 is mixed with the composite curing agent obtained in step S2 to obtain the solid-free wellhead injection resin.

2. The method for preparing a solid-free wellhead extrusion resin according to claim 1, characterized in that, The solid-free wellhead extrusion resin is prepared from the following components in parts by weight: The composite resin: 100 parts by weight; The composite curing agent: 20-50 parts by weight.

3. The method for preparing a solid-free wellhead extrusion resin according to claim 1, characterized in that, The composite resin is composed of the following components in parts by weight: It consists of 100 parts by weight of the hydrogenated bisphenol A epoxy resin and 10-50 parts by weight of the auxiliary resin.

4. The method for preparing a solid-free wellhead extrusion resin according to claim 3, characterized in that, The auxiliary resin may be selected from at least one of diglycidyl tetrahydrophthalate, bis((3,4-epoxycyclohexyl)methyl)adipic acid, N,N-diglycidyl aniline, and diglycidyl 4,5-epoxyhexane-1,2-carboxylic acid.

5. The method for preparing a solid-free wellhead extrusion resin according to claim 3, characterized in that, The epoxy equivalent of the hydrogenated bisphenol A epoxy resin is 180-220 g / eq.

6. The method for preparing a solid-free wellhead extrusion resin according to claim 1, characterized in that, The composite curing agent is composed of at least two of the following: diethyltoluene diamine, diethyldiaminodicyclohexylmethane, cashew phenol-modified phenolic amine curing agent, polyamide 400, dimethyldiaminodicyclohexylmethane, methylcyclohexyldiamine, and polyamide 230.

7. The method for preparing a solid-free wellhead extrusion resin according to claim 6, characterized in that, The composite curing agent is any one of the following (a), (b), or (c): (a) A composition consisting of diethyltoluenediamine and diethyldiaminodicyclohexylmethane in a weight ratio of 1:1; Or (b) a composition consisting of diethyltoluenediamine, cashew phenol-modified phenolic amine curing agent and polyamide 400, wherein the weight ratio of the three is 30:40:30; Or (c) a composition consisting of dimethyldiaminodicyclohexylmethane, methylcyclohexyldiamine and polyamide 230, wherein the weight ratio of the three is 40:30:

30.

8. The method for preparing a solid-free wellhead extrusion resin according to claim 1, characterized in that, In step S3, before mixing the composite resin with the composite curing agent, the step of adding an active diluent to the composite resin is further included. The amount of the active viscosity reducer is 5-10 parts by weight relative to 100 parts by weight of the composite resin, and the active diluent is selected from at least one of phenyl glycidyl ether, propylene oxide butyl ether, and butanediol diglycidyl ether.

9. The method for preparing a solid-free wellhead extrusion resin according to claim 1, characterized in that, The mixing in step S3 is carried out at a temperature of 10-25°C for 5-10 minutes.

10. An application of a solids-free wellhead extrusion resin, characterized in that, The extrusion resin obtained by the preparation method according to any one of claims 1-9 is used to treat the annular pressure zone at the wellhead of oil and gas wells.

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