Preparation method and application of solid-phase-free wellhead squeeze resin

Abstract

The application relates to the technical field of oil and gas field chemicals, and discloses a preparation method and application of a solid-phase-free wellhead squeeze resin, which comprises the following steps: S1, uniformly mixing hydrogenated bisphenol A epoxy resin as a main resin and at least one low-viscosity liquid auxiliary resin to obtain a composite resin; S2, uniformly mixing at least two amine curing agents with different reaction activities to obtain a composite curing agent; and S3, mixing the composite resin and the composite curing agent to obtain the solid-phase-free wellhead squeeze resin when the solid-phase-free wellhead squeeze resin needs to be used. Through the design of all-liquid and solid-phase-free components, the resin system obtained by the application has low initial viscosity and good pourability; through the compounding of the curing agents, the pot life can be accurately adjusted, and different construction requirements can be met; all the components are reactive components, and a dense sealing body with high strength and high toughness is formed after curing, so that the plugging effect is durable and reliable.

Description

Technical Field

[0001] This invention relates to the field of oil and gas field chemicals technology, specifically to a method for preparing and applying a solids-free wellhead injection resin. Background Technology

[0002] Annular pressure at the wellhead is a common safety hazard in oil and gas field production. It indicates that at least one downhole sealing barrier (such as a cement sheath or casing) has failed, leading to leakage of formation fluids (oil, gas, and water). If not addressed promptly, the annular pressure may continue to rise, potentially threatening wellhead equipment safety, damaging the oil and gas reservoir, polluting the environment, and even triggering major accidents such as well blowouts. Therefore, effectively managing annular pressure is a crucial step in ensuring safe production in oil and gas wells.

[0003] Currently, common techniques for dealing with pressurized annulus at the wellhead include cement injection and chemical plugging agents. While cement injection, as a traditional method, has relatively low material costs, its technical drawbacks are also significant. The cement slurry system contains a large number of solid particles, which easily cause particle bridging when injected into tiny leakage channels, preventing the cement slurry from reaching the source of the leakage and resulting in incomplete sealing. Furthermore, the cured cement stone is brittle and prone to cracking under the complex temperature and stress conditions downhole, or to failure of the bonding interface with the casing wall, forming new leakage channels and leading to poor long-term reliability of the seal.

[0004] To overcome the shortcomings of cement-based materials, polymer-based chemical plugging agents such as epoxy resins are increasingly being used. However, existing conventional resin plugging systems also face several technical bottlenecks. To improve strength or reduce costs, many resin systems still incorporate inorganic fillers such as quartz powder, which leads to the same problem of solid particles clogging microchannels. Some filler-free resin systems typically have high viscosity, poor flowability and permeability, making it difficult to penetrate micron-sized cracks. Non-reactive diluents added to reduce viscosity can volatilize or precipitate during curing, causing volume shrinkage of the cured product and significantly reducing the tightness and bond strength of the seal. Furthermore, the reaction rate between the resin and the curing agent is difficult to control precisely. At high downhole temperatures, the resin often gels prematurely during injection due to a short pot life, leading to construction failure. These factors collectively limit the effectiveness of existing resin plugging technologies in complex well conditions and their long-term sealing efficacy. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a method for preparing a solid-free wellhead extrusion resin and its application. The resin system has low initial viscosity, does not contain solid particles, has an adjustable pot life, and can form a seal with both high strength and high toughness after curing, so as to effectively solve the problem of annular pressure at the wellhead of oil and gas wells.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] In a first aspect, this application provides a method for preparing solids-free wellhead extrusion resin, employing the following technical solution:

[0008] A method for preparing a solids-free wellhead extrusion resin includes the following steps:

[0009] 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.

[0010] S2. Mix at least two different amine curing agents evenly at room temperature to obtain a composite curing agent;

[0011] 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.

[0012] By adopting the above technical solution, firstly, in step S1, hydrogenated bisphenol A epoxy resin is selected as the main resin. Compared with the rigid benzene ring structure of conventional bisphenol A epoxy resin, the saturated alicyclic structure in the resin molecular structure has less steric hindrance of molecular chain segments and correspondingly weaker intermolecular forces, thus giving the resin body a lower viscosity. Simultaneously, compounding with low molecular weight auxiliary resins further reduces the viscosity of the resin components. Secondly, in step S2, at least two amine curing agents with different reactivity are pre-mixed to prepare a composite curing agent. This design, through the difference in reaction rates of different amine molecules, effectively controls the final curing reaction process, avoiding the rapid exothermic reaction and rapid gelation caused by a single highly active curing agent, thus extending the system's workability time. Finally, the entire system contains no solid phase fillers and is a homogeneous liquid phase system, fundamentally avoiding the dramatic increase in viscosity caused by solid phase particles and the bridging effect in micro-cracks. Therefore, the resin obtained by this preparation method has the characteristics of low initial viscosity, long workability time, and mild exothermic reaction, and can be effectively squeezed into the micro-cracks of the wellhead cement sheath.

[0013] Preferably, the solid-free wellhead injection resin is prepared from the following components in parts by weight:

[0014] The composite resin: 100 parts by weight;

[0015] The composite curing agent: 20-50 parts by weight.

[0016] By adopting the above technical solution, the amount of composite curing agent is limited to 20-50 parts by weight, ensuring that the active hydrogen equivalent in the curing agent matches the epoxy group equivalent in the composite resin, so that the curing reaction can proceed fully, thereby forming a cured body with a stable three-dimensional network structure and excellent mechanical properties.

[0017] Preferably, the composite resin is composed of the following components in parts by weight:

[0018] It consists of 100 parts by weight of the hydrogenated bisphenol A epoxy resin and 10-50 parts by weight of the auxiliary resin.

[0019] By adopting the above technical solution, the amount of auxiliary resin is limited to 10-50 parts by weight. This dosage range effectively reduces the viscosity of the composite resin while synergistically forming a cured network with both strength and toughness with the main resin. If the dosage is too low, the viscosity reduction and toughening effects will be insignificant; if the dosage is too high, it may affect the overall strength and heat resistance of the cured system.

[0020] Preferably, the auxiliary resin is 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.

[0021] By adopting the above technical solution, the selected auxiliary resins are all low-viscosity epoxy resins, which have good compatibility with the main resin. Moreover, their molecular structure (such as alicyclic or flexible segments) can be introduced into the cross-linking network after curing, playing an internal toughening role and improving the maximum compression ratio and impact resistance of the cured body.

[0022] Preferably, the epoxy equivalent of the hydrogenated bisphenol A epoxy resin is 180-220 g / eq.

[0023] By adopting the above technical solution, the epoxy equivalent of hydrogenated bisphenol A epoxy resin is limited to the range of 180-220 g / eq. This range of epoxy equivalent means that the resin has a suitable 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.

[0024] Preferably, 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.

[0025] Preferably, the composite curing agent is any one of the following (a), (b), or (c):

[0026] (a) A composition consisting of diethyltoluenediamine and diethyldiaminodicyclohexylmethane in a weight ratio of 1:1;

[0027] 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;

[0028] Or (c) a composition consisting of dimethyldiaminodicyclohexylmethane, methylcyclohexyldiamine and polyamide 230, wherein the weight ratio of the three is 40:30:30.

[0029] By employing the above technical solutions, the combination of curing agents utilizes the characteristics of different amine curing agents. For example, methylcyclohexyldiamine has a fast reaction rate and produces a rigid cured product; while dimethyldiaminodicyclohexylmethane, cashew phenol-modified phenolic amine curing agents, and polyamide curing agents have longer molecular chains or contain flexible structures, which can impart excellent toughness to the cured body. By compounding them in specific proportions, the curing rate, exothermic peak, and the mechanical properties of the final cured body can be precisely controlled, achieving a synergistic effect of rigidity and toughness.

[0030] Preferably, in step S3, before mixing the composite resin with the composite curing agent, the step further includes adding an active diluent to the composite resin; 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 optionally at least one of phenyl glycidyl ether, propylene oxide butyl ether, and butanediol diglycidyl ether.

[0031] By adopting the above technical solution, the addition of reactive diluents can further reduce the mixing viscosity of the entire system and improve its fluidity at low temperatures. The reactive diluents all contain epoxy groups, enabling them to participate in the curing reaction and become part of the cross-linking network, thus avoiding performance degradation or subsequent migration problems that may be caused by inactive diluents. In particular, when phenyl glycidyl ether is used, its benzene ring structure exhibits high thermal stability, which can improve the long-term performance stability of the final cured body in high-temperature downhole environments.

[0032] Preferably, the mixing in step S3 is carried out at a temperature of 10-25°C and the stirring time is 5-10 minutes.

[0033] By adopting the above technical solution, the mixing temperature is limited to 10-25℃, covering the common temperature range for on-site construction. It is particularly effective at low temperatures of 10℃, ensuring smooth mixing and construction. A stirring time of 5-10 minutes is sufficient to ensure the low-viscosity components are mixed evenly, guaranteeing the uniformity of the curing reaction.

[0034] Secondly, this application provides an application of solid-free wellhead resin injection, employing the following technical solution:

[0035] The extrusion resin obtained according to any of the aforementioned preparation methods is used to treat the annular pressure zone at the wellhead of oil and gas wells.

[0036] By adopting the above technical solution, the resin prepared by this method has comprehensive properties such as low viscosity, long extrusion time, low temperature curing, and high strength and toughness of the cured body. It can be successfully pumped into the micro-cracks of the wellhead cement sheath and cured in the downhole environment to form a stable sealing body, effectively sealing the channel for oil and gas to rise, thereby solving the technical problem of pressurized wellhead annulus.

[0037] This invention provides a method for preparing and applying a solids-free wellhead extrusion resin. It offers the following advantages:

[0038] 1. This invention utilizes liquid hydrogenated bisphenol A epoxy resin as the main resin, and combines it with one or more low-viscosity liquid auxiliary resins to obtain a pure liquid resin system free of any solid fillers. This system has a low initial mixing viscosity and good fluidity, effectively penetrating and sealing micro-channels in the wellhead annulus during injection, avoiding sealing failures caused by solid particles blocking these channels, and improving the success rate of the operation.

[0039] 2. This invention achieves precise control over the curing reaction rate of the entire resin system by pre-mixing two or more amine curing agents with different chemical structures and reactivity to form a composite curing agent. By adjusting the components and ratios of the composite curing agent, a suitable application period can be obtained to meet the requirements of different downhole temperatures and construction time windows, ensuring that the resin does not gel before being fully injected into the target location, thus guaranteeing the safety and controllability of the construction process.

[0040] 3. The auxiliary resin and active viscosity reducer used in this invention are both reactive components containing epoxy groups. While reducing the viscosity of the system, they can fully participate in the curing and crosslinking reaction, becoming part of the crosslinking network of the final cured product, thus avoiding the volume shrinkage and performance loss caused by non-reactive solvents. The resulting cured seal has a dense structure, and through the combination of the main resin and different curing agents, it achieves a balance between high mechanical strength and high toughness, enabling it to withstand downhole pressure shocks and temperature changes stably over a long period, ensuring the durability and reliability of annular sealing. Attached Figure Description

[0041] Figure 1 This is a thickening curve diagram of embodiment S-2 of the present invention. Detailed Implementation

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0043] Preparation Examples 1-2:

[0044] Preparation Example 1: Preparation of Composite Resin

[0045] Composite Resin A-1: ​​Weigh 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent 180 g / eq) and 10 parts by weight of tetrahydrophthalic acid diglycidyl ester, place them in a container equipped with a mechanical stirrer, and stir at room temperature (25°C) for 30 minutes until the system is uniformly mixed and forms a clear and transparent liquid, which is Composite Resin A-1. Seal and store for later use.

[0046] Composite Resin A-2: Weigh 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent 200 g / eq), 15 parts by weight of tetrahydrophthalic acid diglycidyl ester, and 15 parts by weight of bis((3,4-epoxycyclohexyl)methyl)adipate, place them in a container equipped with a mechanical stirrer, and stir at room temperature (25°C) for 30 minutes until the system is uniformly mixed and forms a clear and transparent liquid, which is Composite Resin A-2. Store in a sealed container for later use.

[0047] Composite Resin A-3: Weigh 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent 200 g / eq) and 50 parts by weight of N,N-diglycidylaniline, place them in a container equipped with a mechanical stirrer, and stir at room temperature (25°C) for 30 minutes until the system is uniformly mixed and forms a clear and transparent liquid, which is Composite Resin A-3. Store in a sealed container for later use.

[0048] Composite Resin A-4: Weigh 100 parts by weight of hydrogenated bisphenol A epoxy resin (epoxy equivalent 220 g / eq) and 20 parts by weight of 4,5-epoxyhexane-1,2-carboxylic acid diglycidyl ester, place them in a container equipped with a mechanical stirrer, and stir at room temperature (25°C) for 30 minutes until the system is uniformly mixed and forms a clear and transparent liquid, which is Composite Resin A-4. Store in a sealed container for later use.

[0049] Preparation Example 2: Preparation of Composite Curing Agent

[0050] Composite curing agent B-1: Weigh 50 parts by weight of diethyltoluene diamine (DETDA) and 50 parts by weight of diethyldiaminodicyclohexylmethane, place them in a stirring container, and stir at room temperature (25°C) for 20 minutes until they are evenly mixed. This is composite curing agent B-1. Store in a sealed container for later use.

[0051] Composite curing agent B-2: Weigh 30 parts by weight of diethyltoluenediamine (DETDA), 40 parts by weight of cashew phenol-modified phenolic amine curing agent, and 30 parts by weight of polyamide 400, place them in a mixing container, and stir at room temperature (25°C) for 30 minutes until uniformly mixed. This is composite curing agent B-2. Seal and store for later use.

[0052] Composite curing agent B-3: Weigh 40 parts by weight of dimethyldiaminodicyclohexylmethane, 30 parts by weight of methylcyclohexyldiamine, and 30 parts by weight of polyamide 230, place them in a mixing container, and stir at room temperature (25°C) for 30 minutes until uniformly mixed. This is composite curing agent B-3. Store in a sealed container for later use.

[0053] Examples 1-8:

[0054] Example 1

[0055] Take 100 parts by weight of the composite resin A-1 prepared in Preparation Example 1 and add 20 parts by weight of the composite curing agent B-1 prepared in Preparation Example 2. Place the above components in a container and stir with a mechanical stirrer at room temperature (25°C) for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-1.

[0056] Example 2

[0057] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1 and add 35 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2. Place the above components in a container and stir with a mechanical stirrer at room temperature (25°C) for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-2.

[0058] Example 3

[0059] Take 100 parts by weight of the composite resin A-3 prepared in Preparation Example 1 and add 50 parts by weight of the composite curing agent B-1 prepared in Preparation Example 2. Place the above components in a container and stir with a mechanical stirrer at room temperature (25°C) for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-3.

[0060] Example 4

[0061] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1, add 5 parts by weight of phenyl glycidyl ether, and stir at room temperature (25°C) for 5 minutes to mix evenly. Then, add 40 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2, and continue stirring for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-4.

[0062] Example 5

[0063] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1, add 8 parts by weight of propylene oxide butyl ether, and stir at room temperature (25°C) for 5 minutes to mix evenly. Then, add 40 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2, and continue stirring for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-5.

[0064] Example 6

[0065] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1, add 8 parts by weight of butylene glycol diglycidyl ether, and stir at room temperature (25°C) for 5 minutes to mix evenly. Then, add 40 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2, and continue stirring for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-6.

[0066] Example 7

[0067] 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 with a mechanical stirrer at room temperature (25°C) for 5 minutes until the mixture is a homogeneous and transparent liquid to obtain sealant S-7.

[0068] Example 8

[0069] Take 100 parts by weight of the composite resin A-2 prepared in Preparation Example 1, add 10 parts by weight of phenyl glycidyl ether, and stir at 10°C for 5 minutes to mix evenly. Then, add 40 parts by weight of the composite curing agent B-2 prepared in Preparation Example 2, and continue stirring at 10°C for 5 minutes until the mixture is a homogeneous and transparent liquid, obtaining sealant S-8. This sealant still has good fluidity at low temperatures and is easy to mix and extrude.

[0070] Comparative Examples 1-5:

[0071] Comparative Example 1:

[0072] Compared with Example 2, the difference is that 100 parts by weight of hydrogenated bisphenol A epoxy resin in its composite resin A-2 were replaced with an equal weight of conventional liquid bisphenol A epoxy resin (E-51, epoxy equivalent 190g / eq), while the remaining components and preparation methods are the same.

[0073] Comparative Example 2:

[0074] Compared with Example 2, the difference is that no auxiliary resin is added to its composite resin system, that is, only 100 parts by weight of hydrogenated bisphenol A epoxy resin is used as the resin component, and the amount of curing agent is adjusted accordingly to match the epoxy equivalent. The rest of the preparation methods are the same.

[0075] Comparative Example 3:

[0076] Compared with Example 2, the difference is that the composite curing agent B-2 is replaced with a single curing agent, that is, only diethyltoluene diamine (DETDA) with an equivalent amount of active hydrogen in the composite curing agent B-2 is used, while the other components and preparation methods are the same.

[0077] Comparative Example 4:

[0078] Compared with Example 4, the difference is that 5 parts by weight of phenyl glycidyl ether (active diluent) are replaced with equal weights of dodecyl and tetradecyl glycidyl ether (a conventional non-temperature-resistant aliphatic active diluent), while the remaining components and preparation methods are the same.

[0079] Comparative Example 5:

[0080] Compared with Example 1, the difference is that after the components of sealant S-1 are mixed evenly, an additional 30 parts by weight of oil well cement (particle size 400 mesh) is added as a solid phase thickener and reinforcing material, and it is vigorously stirred to disperse it evenly.

[0081] Test Examples 1-4:

[0082] Test Example 1:

[0083] This test was conducted to verify the basic and post-cured properties of the sealant compositions prepared in Examples S-1 to S-8. The test included initial mixing viscosity, maximum temperature rise, extrudable time, setting time, compressive strength and elasticity after curing.

[0084] Experimental steps:

[0085] Initial physical property determination:

[0086] 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), a No. 3 rotor was used at a speed of 60 rpm to measure the viscosity value of each sample within 5 minutes after they were mixed evenly.

[0087] Maximum temperature rise: Take 500 mL of freshly prepared sample and place it in an insulated container. Place the thermocouple sensor at the geometric center of the sample and record the temperature change of the system after mixing begins at the specified test temperature. Record the difference between the highest temperature and the initial temperature.

[0088] Construction-related performance testing:

[0089] Squeezable pouring time: According to GB / T19139-2012, using a high temperature and high pressure thickener, the time required for the sample consistency to reach 100 BC from the initial value is determined at the specified test temperature.

[0090] Setting time: The sample is cured at a specified test temperature, and its surface hardness is measured at regular intervals using a Vickers Type D hardness tester. The time elapsed when the hardness value first reaches 20 is recorded.

[0091] Mechanical property testing of cured body:

[0092] Specimen preparation and curing: Each sample was cast into a 50mm×50mm×50mm cubic specimen and cured at the specified test temperature for 48 hours.

[0093] Compressive strength and elastic toughness: According to GB10238-2005, a YAW-300 electro-hydraulic compression testing machine was used to axially compress the cured specimens at a loading rate of 0.2 MPa / s, and the maximum compressive strength was recorded. Simultaneously, the ratio of the compressive displacement to the original height when visible cracks appeared on the specimen surface was recorded as the maximum compression ratio, used to characterize the elastic toughness.

[0094] 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.

[0095] Table 1. Comprehensive performance test results of Examples S-1 to S-8

[0096]

[0097] Summary: The test results in Table 1 show that the sealant compositions of all embodiments exhibit low-viscosity liquids after mixing, with initial mixed viscosities ranging from 31.5 to 93.4 mPa·s at 25°C. This characteristic stems from the lower intermolecular forces of the hydrogenated bisphenol A epoxy resin saturated cyclohexane structure compared to the benzene ring structure of conventional bisphenol A epoxy resin, as well as the synergistic viscosity-reducing effect of the low-viscosity auxiliary resin. Simultaneously, all embodiments exhibit a mild exothermic peak below 15°C and an extrudable time exceeding 4 hours. This phenomenon is attributed to the use of amine curing agents with different reactivity, which effectively controls the curing reaction rate and avoids rapid crosslinking and concentrated exothermic reactions in the initial stages of the reaction.

[0098] Test data shows that the cured bodies of each embodiment formed solids with high mechanical strength after 48 hours of curing. Under curing conditions of 25°C, the compressive strength exceeded 50 MPa, and the maximum compression ratio exceeded 15%, indicating that the material possesses both load-bearing and deformation capabilities. This performance is achieved because the alicyclic structure formed after the hydrogenated epoxy resin cures provides high rigidity to the cured network, while the flexible segments introduced by specific components in the composite curing agent (such as polyamide or diethyldiaminodicyclohexylmethane) act as internal toughening agents in the crosslinked network, thus enabling the final cured body to simultaneously achieve high strength and high toughness.

[0099] As can be seen from the data in Examples S-8, this technical solution remains applicable even at a low temperature of 10°C. Its initial viscosity (66.5 mPa·s) remains within the pumpable range, the extrusion time is extended to 10.6 hours, and curing is completed within 48 hours, forming a cured body with a compressive strength of 29.5 MPa. This indicates that this technical solution, by selecting a composite curing agent containing highly active components, ensures that the ring-opening polymerization reaction of epoxy groups can still be effectively initiated at low temperatures, solving the technical problem of slow or non-curing of conventional epoxy systems at low temperatures, and broadening the material's application temperature window.

[0100] Test Example 2:

[0101] To illustrate the technical effects of specific component selection and system composition in this technical solution, performance comparison tests were conducted between Examples S-1 and S-2 and Comparative Examples D-1 to D-3 and D-5. The tests aimed to reveal the impact of each technical feature on the performance of the final product through single-variable comparison.

[0102] Experimental steps:

[0103] Comparative Group 1 (Main Resin System): Performance Comparison of Example S-2 and Comparative Example D-1

[0104] Initial mixed viscosity determination: Samples of Example S-2 and Comparative Example D-1 were prepared respectively. According to GB / T10247-2008 standard, using a Brookfield viscometer, under constant temperature of 25℃, a No. 3 rotor was used at a rotation speed of 60 rpm to measure the viscosity value of each sample within 5 minutes after uniform mixing.

[0105] Elasticity and toughness determination: The two types of samples were cast into 50mm×50mm×50mm cubic blocks and cured at 25℃ for 48 hours. According to GB10238-2005, a YAW-300 electro-hydraulic compression testing machine was used to axially compress the cured blocks at a loading rate of 2.0MPa / s. The ratio of the compression displacement to the original height when visible cracks appeared on the surface of the block was recorded as the maximum compression ratio.

[0106] Comparative Group 2 (Auxiliary Resin System): Performance Comparison of Example S-2 and Comparative Example D-2

[0107] Initial mixed viscosity determination: Samples of Example S-2 and Comparative Example D-2 were prepared respectively. Using the same procedure as in Comparative Group 1, the initial mixed viscosity of each sample was determined at 25°C according to GB / T10247-2008 standard.

[0108] Comparative Group 3 (Curing Agent System): Performance Comparison of Example S-2 and Comparative Example D-3

[0109] Maximum temperature rise determination: Take 500 mL of freshly prepared sample S-2 and sample D-3 respectively, place them in an insulated container, place the thermocouple sensor at the geometric center of the sample, record the temperature change of the system after mixing at an ambient temperature of 25°C, and record the difference between the highest temperature and the initial temperature.

[0110] Determination of extrusion time: According to GB / T19139-2012, the time required for the consistency of the two samples to reach 100 BC from the initial value was determined using a high temperature and high pressure thickener at 25℃.

[0111] Elasticity and toughness test: The two samples were cast into 50mm×50mm×50mm cubes and cured at 25℃ for 48 hours. Using the same procedure as control group 1, the maximum compression ratio was determined according to GB10238-2005.

[0112] Comparison Group 4 (Influence of Solid Particles): Performance Comparison of Example S-1 and Comparative Example D-5

[0113] Initial mixed viscosity determination: Samples of Example S-1 and Comparative Example D-5 were prepared respectively. Using the same procedure as in Comparative Group 1, the initial mixed viscosity of each sample at 25°C was determined according to GB / T10247-2008 standard.

[0114] Experimental data:

[0115] The samples in each group were tested according to the corresponding steps, and the results are recorded in Table 2. The symbol "-" in Table 2 indicates that the technical indicator was not measured. In each comparative group, the technical indicators that were not measured are because their values ​​are determined by the same components in the samples within the group and are not affected by the comparative variables of that group. Taking comparative group 3 as an example, the resin components of Example S-2 and Comparative Example D-3 were set to be the same in the formulation, therefore the initial mixed viscosity values ​​of the two samples before the curing reaction were the same, and this indicator does not reflect the influence caused by differences in the curing agent system.

[0116] Table 2. Key performance comparison test results between the examples and comparative examples

[0117]

[0118] Summary: The test results in Table 2 show that replacing the main resin from hydrogenated bisphenol A epoxy resin to conventional bisphenol A epoxy resin (Comparative Example D-1) significantly increased the initial viscosity of the system to 285.4 mPa·s, and decreased the elasticity and toughness of the cured body to 9.3%. The mechanism of this phenomenon lies in the fact that the saturated alicyclic structure in the hydrogenated bisphenol A epoxy resin molecule, compared to the rigid benzene ring structure of conventional bisphenol A epoxy resin, allows for easier molecular chain rotation and weaker intermolecular forces, thus imparting a lower viscosity to the liquid resin. After curing, this flexible alicyclic structural unit is introduced into the crosslinking network, improving the cured body's ability to withstand deformation. Furthermore, the absence of auxiliary resin (Comparative Example D-2) also resulted in an increase in viscosity, indicating that the low molecular weight auxiliary resin effectively reduces intermolecular distance and internal friction in the system, and is an essential component for achieving low viscosity.

[0119] Comparing the results of Example S-2 and Comparative Example D-3, it is evident that the choice of curing agent system has a decisive impact on the workability and final mechanical properties of the product. Using a single highly reactive curing agent (Comparative Example D-3) resulted in a violent reaction, with a maximum temperature rise of 42.7°C, a shortened extrusion time to 0.8 hours, and a cured body elasticity and toughness of only 8.7%. This is because the polymerization reaction rate initiated by the single curing agent is too fast, releasing a large amount of heat and forming a cross-linked network in a short period, resulting in an extremely short workable time window. Simultaneously, the rapidly formed dense network structure exhibits high internal stress, manifesting as macroscopic brittleness. The composite curing agent used in this technical solution, through the combination of amine compounds with different reactivity, achieves control over the curing reaction process, allowing the reaction to proceed gradually, thereby extending the extrusion time, reducing exothermic reactions, and forming a cured network that combines strength and toughness.

[0120] Compare with Case S-2, see Appendix Figure 1 The thickening curve shows that the preheated mixture (500ml volume) of each component reaches a temperature of 31℃. In the thickener, with only air as the medium and no oil, the temperature only rises to 37℃. Only after 5 hours and 30 hours under simulated summer ambient temperature of 50℃ (wellhead equipment temperature) does the consistency show a significant increase. This demonstrates effective control over the solidification reaction, preventing a rapid increase in temperature that would lead to a rapid increase in consistency and consequently a sharp rise in injection pressure under microfracture conditions. This satisfies the requirement for low-volume, long-term injection of sealing gas into the deep microfractures at the wellhead.

[0121] The data from Comparative Group 4 clearly demonstrate the influence of the system's physical state on its flowability. Introducing solid particles (Comparative Example D-5) into the pure liquid sealant S-1 caused a sharp increase in the initial mixing viscosity from 31.5 mPa·s to 1350 mPa·s. This is because the addition of solid particles introduces additional flow resistance into the liquid and disrupts the original laminar flow state. The solid-free, all-liquid component design employed in this technical solution fundamentally avoids the dramatic increase in viscosity caused by solid particles and the bridging effect in micro-cracks, providing the structural basis for ensuring its effective insertion into the micro-cracks of the cement ring.

[0122] Test Example 3:

[0123] To verify the effect of the active diluent selected in this technical solution on the long-term high-temperature resistance of the curing system, Example S-4 and Comparative Example D-4 were selected for thermal aging performance comparison test.

[0124] Experimental steps:

[0125] Specimen preparation: Samples of Example S-4 and Comparative Example D-4 were prepared respectively, and cast into cubic specimens of 50mm×50mm×50mm.

[0126] Initial strength determination: After curing some specimens at 25℃ for 48 hours, the compressive strength was determined using a YAW-300 electro-hydraulic compressive strength testing machine with a loading rate of 2.0MPa / s, in accordance with GB10238-2005 standard, and recorded as the initial compressive strength value.

[0127] Heat aging treatment: The remaining test blocks were placed in a constant temperature oven at 80℃±1℃ for heat aging treatment for 30 days.

[0128] Strength determination after aging: After the aging period, the specimen is removed and cooled to room temperature. The compressive strength after aging is determined using the same procedure as the initial strength determination.

[0129] Strength retention rate calculation: The compressive strength retention rate of each sample is calculated according to the following formula: Strength retention rate (%) = (Compressive strength after aging / Initial compressive strength) × 100%

[0130] Experimental data: The samples of Example S-4 and Comparative Example D-4 were tested according to the above steps, and the results are recorded in Table 3.

[0131] Table 3. Comparison of thermal aging performance between Example S-4 and Comparative Example D-4

[0132]

[0133] Summary: The test results in Table 3 show that the cured body of Example S-4 retained 93.5% of its compressive strength after undergoing thermal aging treatment at 80°C for 30 days. In contrast, Comparative Example D-4, which used a conventional aliphatic reactive diluent, only retained 45.5% of its compressive strength under the same aging conditions, indicating a significant deterioration in its mechanical properties.

[0134] This performance difference stems from the different molecular structures of the reactive diluents. The phenyl glycidyl ether used in Example S-4 contains a benzene ring in its molecular structure. The benzene ring structure has high chemical bond energy and conjugation stability, and this structure is not prone to chain breaking or degradation under high temperature conditions. Therefore, when it reacts through epoxy groups and becomes part of the cross-linking network, it can maintain the structural integrity and thermal stability of the entire cured system.

[0135] The aliphatic reactive diluent used in Comparative Example D-4 has a molecular backbone composed of carbon-carbon single bonds. These chemical bonds have relatively low bond energies and are prone to thermal oxidative degradation under sustained high temperatures, leading to molecular chain breakage and thus disrupting the topological structure of the solidified network. Macroscopically, this manifests as a significant decrease in mechanical strength. In summary, by selecting a reactive diluent containing thermally stable structural units (such as benzene rings), this technical solution solves the problem of performance degradation in conventional epoxy systems due to insufficient thermal stability of the diluent during long-term service in high-temperature environments, ensuring that the plugging body maintains long-term structural stability and load-bearing capacity under high-temperature downhole conditions.

[0136] Test Example 4:

[0137] To verify the curing ability and mechanical properties of the sealant described in this technical solution under simulated downhole oil-water mixing conditions, Example S-2 was selected for comparative curing environment testing.

[0138] Experimental steps:

[0139] Sample preparation and grouping: Prepare the sealant sample of Example S-2 and cast it into two groups of 50mm×50mm×50mm cubic test blocks, one group as the control group and the other group as the experimental group.

[0140] Maintenance environment setup:

[0141] Control group: The test block mold was completely immersed in a container filled with 25°C water.

[0142] Experimental group: The test block mold was completely immersed in a container containing an oil-water mixture at 25°C, which consisted of crude oil and simulated formation brine in a 1:1 volume ratio.

[0143] Sample curing: The samples of the control group and the experimental group were simultaneously cured at 25°C for 72 hours in their respective set environments.

[0144] Performance testing: After the curing period, the test blocks were removed from their respective containers, and the oil stains on the surface of the test blocks in the experimental group were cleaned with solvent. According to GB10238-2005 standard, the compressive strength of the two groups of test blocks was determined using a YAW-300 electro-hydraulic compressive strength testing machine at a loading rate of 2.0 MPa / s.

[0145] Strength retention rate calculation: The compressive strength retention rate of the experimental group samples is calculated according to the following formula: Strength retention rate (%) = (Experimental group compressive strength / Control group compressive strength) × 100%

[0146] Experimental data: The samples of Example S-2 were tested according to the above steps, and the results are recorded in Table 4.

[0147] Table 4. Performance test results of Example S-2 under different maintenance environments

[0148]

[0149] Summary: The test results in Table 4 show that after curing in an oil-water mixture for 72 hours, the compressive strength of the cured sample of Example S-2 reached 54.7 MPa, and the strength retention rate was 89.2% compared to the sample cured in water. This data indicates that the curing process and final mechanical properties of this sealant composition were not significantly negatively affected in an oil-water coexisting environment.

[0150] The mechanism behind this performance lies in the selection of component B-2 in the composite curing agent. This curing agent contains a cashew phenol-modified phenolic amine curing agent, whose molecular structure possesses both hydrophilic amine functional groups and lipophilic long-chain alkyl side chains. This amphiphilic structure gives it surface activity at the oil-water interface, enabling it to migrate to the reaction interface and repel the oil and water phases from the surfaces to be bonded or the interfaces of the reactants, thereby creating conditions for the contact and reaction between the amine and epoxy groups.

[0151] Therefore, this composite curing agent solves the technical problem that conventional epoxy amine curing agents, due to their hydrophilicity, are difficult to effectively contact with epoxy resin in the presence of an oil phase, or that the curing reaction is incomplete due to the physical barrier of the oil phase. Through the interfacial interaction of the curing agent molecules, it ensures that even in oil-water emulsions or multiphase interface environments, the epoxy resin and curing agent can still undergo sufficient ring-opening polymerization and cross-linking reactions, ultimately forming a continuous, homogeneous, and high-mechanical-strength three-dimensional network structure, thus guaranteeing the reliability of plugging in complex downhole fluid environments.

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 extrusion resin. The auxiliary resin is selected from at least one of tetrahydrophthalic acid diglycidyl ester, bis((3,4-epoxycyclohexyl)methyl) adipate, N,N-diglycidyl aniline, and 4,5-epoxyhexane-1,2-carboxylic acid diglycidyl ester. 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.

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 epoxy equivalent of the hydrogenated bisphenol A epoxy resin is 180-220 g / eq.

5. The method for preparing a solid-free wellhead extrusion resin according to claim 1, 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.

6. 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 reactive diluent is 5-10 parts by weight relative to 100 parts by weight of the composite resin, and the reactive diluent is selected from at least one of phenyl glycidyl ether, propylene oxide butyl ether, and butanediol diglycidyl ether.

7. 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.

8. An application of a solids-free wellhead extrusion resin, characterized in that, The solid-free wellhead extrusion resin obtained by the preparation method according to any one of claims 1-7 is used to treat the annular pressure zone at the wellhead of oil and gas wells.

Images