Oil-based defoamer for oil and gas fields and preparation method thereof

Abstract

The application discloses an oil-based defoaming agent for oil and gas fields and a preparation method thereof, and relates to the technical field of defoaming agents, which comprises an intelligent response type polymer, a carrier oil, nano silicon dioxide and a dispersing agent; the preparation method comprises the following steps: 1) preparing a polysiloxane main chain containing a furan functional group; 2) synthesizing a maleimide-terminated fluorine-containing compound; 3) constructing an intelligent response type polymer; and 4) post-treatment. The core innovation of the application is that the active ingredients of the defoaming agent can break the dynamic covalent bond and self-assemble into Janus nanoparticles in a high-temperature and high-shear environment downhole, the nanoparticles have an asymmetric structure, the fluorocarbon surface breaks the foam liquid film first due to the ultra-low surface tension, and then the siloxane surface rapidly spreads, thereby achieving instantaneous and efficient defoaming in cooperation; the process is intelligent and controllable, and the reversibility of the bond endows the active ingredients with self-repairing and reactivating capabilities, thereby significantly improving the service life and temperature resistance, and the application is especially suitable for extreme working conditions such as deep wells and ultra-deep wells.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of defoaming agents, in particular to an oil-based defoaming agent for oil and gas fields and a preparation method thereof. BACKGROUND

[0002] In the drilling operation of oil and gas fields, oil-based drilling fluid is widely used in deep wells, ultra-deep wells and complex formations due to its excellent well stability, lubricity and anti-pollution ability. However, during the circulation of the drilling fluid, a large amount of stable and fine foam is easily generated due to the combined action of surfactants, solid particles and formation invasion gas. These foams can significantly reduce the density of the drilling fluid, causing well kick, blowout and other well control risks; at the same time, the pump efficiency is reduced, the mechanical drilling speed is affected, and the liquid level measurement of the mud tank is inaccurate, which seriously threatens the safety and efficiency of the drilling operation.

[0003] At present, the commonly used defoaming agents on site are mainly polysiloxane, polyether and their modified products. These traditional defoaming agents can still meet the demand at room temperature or low temperature, but their molecular structure is static and single, which has inherent defects: first, their temperature resistance is generally insufficient, and the molecular chain is easily broken or oxidized at high temperature exceeding 150℃, resulting in rapid attenuation of the defoaming performance; second, they lack intelligent responsiveness and cannot adapt to the complex and variable high-temperature and high-shear environment downhole, so the defoaming efficiency and durability are limited; in addition, the components of traditional physical mixed defoaming agents cannot work well together, and the active ingredients are easily inactivated due to adsorption and wrapping, so it is difficult to balance the instantaneous defoaming and long-term foam suppression.

[0004] With the continuous exploration and development of oil and gas into deeper and more complex formations, it has become a key technical problem to be solved in the field to develop an oil-based defoaming agent that can withstand extreme high temperature and intelligently respond, efficiently and durably act in the harsh downhole conditions. SUMMARY

[0005] The present application relates to the technical field of defoaming agents, in particular to an oil-based defoaming agent for oil and gas fields and a preparation method thereof.

[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:

[0007] The present application first proposes an oil-based defoaming agent for oil and gas fields, which comprises the following raw materials by weight:

[0008] Intelligent response type polymer: 5-20 parts;

[0009] Carrier oil: 70-90 parts;

[0010] Hydrophobic fumed silica: 1-5 parts;

[0011] Polyisobutylene succinimide: 0.1-2 parts;

[0012] wherein the intelligent responsive polymer is a polysiloxane-based polymer, comprising a polysiloxane backbone and fluorine-containing segments bonded through DA bonds, and the specific structural formula is as follows:

[0013] .

[0014] Preferably, the preparation process of the intelligent responsive polymer comprises the following steps:

[0015] a. Add polymethylhydrogen siloxane and anhydrous toluene into a reaction kettle, bubble nitrogen for 30 min to remove oxygen under stirring at 300 rpm, add platinum-tetramethyl divinyl disiloxane catalyst, and drop allyl furan; heat to 85°C, reflux for 12 h; after the reaction is completed, cool to room temperature, remove the toluene solvent by distillation under reduced pressure, to obtain a synthesized polysiloxane backbone containing furan functional groups, i.e. PSi-Fu, for standby use;

[0016]

[0017] This reaction is a classic catalytic hydrosilylation reaction. The platinum catalyst activates the Si-H bond, allowing it to add to the carbon-carbon double bond at the end of the allyl furan, forming a stable Si-C bond. In this way, the furan ring, as a strong dienophile, is successfully grafted onto the polysiloxane backbone, providing a reaction site for the subsequent key Diels-Alder reaction.

[0018] b. Dissolve the amino-terminated perfluoropolyether in dichloromethane, continuously stir under 0-5°C ice water bath, add N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine in sequence, after 2 h of reaction, remove the ice bath, slowly raise to room temperature and continue to react for 10 h, after the reaction is completed, filter out the white precipitate N,N'-dicyclohexyl urea generated in the reaction, concentrate the filtrate at 35°C by rotary evaporation, to obtain an amber viscous liquid, i.e. maleimide-terminated perfluoropolyether, PFPE-MI;

[0019]

[0020] Under the catalysis of DCC / DMAP system, the primary amino group of the amino-terminated perfluoropolyether dehydrates and condenses with the carboxyl group of N-maleimide propionic acid, forming an amide bond. In this way, the highly reactive maleimide group is introduced to the end of the fluorine-containing segment.

[0021] c. The PSi-Fu, PFPE-MI, toluene and hydroquinone were added into a reaction kettle, heated to 75°C under nitrogen protection, and stirred for 36 h. After the reaction was completed, it was cooled to room temperature, the reaction solution was precipitated with cold methanol, the solid polymer was collected by filtration, washed with cold methanol, and vacuum dried to obtain a light yellow solid powder, i.e. the intelligent responsive polymer PSi-DA-PFPE.

[0022]

[0023] This is a typical Diels-Alder cycloaddition reaction. The furan ring and the maleimide form a six-membered ring bridge structure through a [4+2] cycloaddition reaction.

[0024] At medium temperature (about 75°C), the reaction proceeds in the forward direction, forming a stable covalent bond connection. At higher temperatures (> 110-130°C, downhole high temperature) or under mechanical force (high-speed shear force during drilling fluid circulation), the adduct will undergo a reversible reaction, breaking down to regenerate furan and maleimide.

[0025] When encountering high temperature and high shear in the downhole, the DA bond connecting fluorocarbon and siloxane breaks, releasing independent fluorine-containing segments and siloxane chains. Subsequently, they self-assemble into Janus nanoparticles with two faces through supramolecular forces such as hydrophobic interaction and fluorine-fluorine interaction. Among them, the fluorocarbon face pierces the foam film first due to its extremely low surface tension, and the siloxane face then performs large-scale spreading, and the two cooperate to achieve instantaneous and efficient foam breaking.

[0026] Hydroquinone acts as a free radical scavenger in the system. Once there are free radicals, such as those generated from the maleimide double bond, the hydroquinone molecules will immediately react with them to form a stable free radical (hydroquinone oxygen radical) that no longer has the ability to initiate chain growth. By being consumed itself, it effectively quenches the initiation point of the chain reaction, preventing the chain growth step of free radical polymerization and terminating the reaction in the embryonic state.

[0027] Preferably, in the preparation process a of the intelligent responsive polymer, the mass ratio of polymethylhydrogen siloxane, platinum-tetramethyldivinylsiloxane, and allyl furan is 100:0.1-0.15:12-13.

[0028] Preferably, in the preparation process b of the intelligent responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide, and 4-dimethylamino pyridine is 80:8-9:10-11:0.7-1.0.

[0029] Preferably, in the preparation process c of the intelligent responsive polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:40-50:0.05.

[0030] The application further provides a preparation method of the oil-based defoamer for oil and gas fields.

[0031] (1) mixing PSi-DA-PFPE with carrier oil, stirring at a speed of 500 rpm for 1 h to form a preliminary dispersion;

[0032] (2) sequentially adding hydrophobic fumed silica and polyisobutylene succinimide, and using a high-pressure homogenizer to treat the mixture under a pressure of 50-150 MPa for 3-8 cycles to form a stable and uniform preparation, i.e., the oil-based defoamer for oil and gas fields;

[0033] (3) filling the homogenized product into a light-tight plastic bucket or a plastic-lined iron bucket and sealing for storage.

[0034] PSi-DA-PFPE serves as an active core, providing the source of intelligent response and high-efficiency defoaming capacity; the carrier oil serves as a dispersion medium and a delivery carrier, uniformly carrying and delivering the active ingredients to the entire drilling fluid system; the hydrophobic fumed silica serves as a synergist and a stabilizer, and the rigid nanoparticles thereof can serve as physical defoaming points, cooperating with the self-assembled Janus particles to further destroy the stability of the foam film; during storage, it helps to thicken and prevent the sedimentation and stratification of other components; the polyisobutylene succinimide has an amphiphilic structure, which can be adsorbed on the surfaces of the nanosilica and the polymer, preventing them from agglomerating through steric hindrance effect, ensuring that the product remains uniform and stable during the storage period, and enabling rapid dispersion during use.

[0035] Preferably, in step (1), the carrier oil is at least one selected from white oil, mineral oil and synthetic oil, and has a kinematic viscosity of 10-50 cSt at 40℃.

[0036] Preferably, in step (2), the nanosilica has a particle size of 10-50 nm and a specific surface area of 100-300 m 2 / g and is subjected to hydrophobic treatment.

[0037] Compared with the prior art, the application has the following beneficial effects:

[0038] The most innovative part of the application is that the active ingredients of the defoamer can self-assemble into Janus particles in situ and in real time after reaching the working area, which is fundamentally different from the conventional method of pre-synthesizing Janus particles and then adding them.

[0039] When the defoamer enters the downhole high temperature environment (such as > 60℃), or when the drilling fluid flows through the drill bit, pump and other high-speed shear area, the huge mechanical force acts on the polymer molecules, and the relatively fragile Diels-Alder dynamic covalent bond is preferentially broken.

[0040] The breaking of the DA bond causes the "siloxane main chain-temperature sensitive segment" assembly originally connected by covalent bonds to dissociate with the "fluorine-containing segment" and become an independent component. At this time, since the temperature-sensitive segment has become hydrophobic, it will drive the siloxane main chain to approach and aggregate with each other, forming a siloxane-rich region. At the same time, the released fluorocarbon segment, due to its extremely strong oleophobicity and strong "fluorine-fluorine interaction" between each other, also begins to spontaneously aggregate, forming a fluorocarbon-rich region.

[0041] In the common environment of the oil phase (drilling fluid), the oleophobic siloxane-rich region and the extremely oleophobic fluorocarbon-rich region cannot be completely miscible; in order to achieve the lowest interface energy of the entire system, the two micro-regions will undergo macroscopic phase separation confined within nanometer scale, but they will not separate into two layers, but will spontaneously organize into a thermodynamically stable structure, i.e. Janus nanoparticles, just like micelles formed by amphiphilic molecules. In this particle, the fluorine-containing segment constitutes one side, and the siloxane main chain and the temperature-sensitive segment constitute the other side, forming a clear, chemically distinct interface between the two.

[0042] The two sides of the Janus particle have different surface tensions and affinities for the oil / gas interface. This asymmetry makes it in a state of "instability" in terms of energy at the interface, with a strong tendency to align and escape from the interface, which translates into a huge defoaming power. When the Janus particle approaches the foam film, its fluorocarbon side with extremely low surface tension will first insert and pierce the oily surface layer of the foam liquid, followed by the siloxane side with lower surface tension but still higher than that of the fluorocarbon, which will rapidly spread at the breach. Due to its flexible molecular chain and large spreading coefficient, it can effectively prop open the breach and expel the oil phase in the liquid film, causing the liquid film to rapidly thin and tear.

[0043] This continuous, physicochemically driven attack makes the foam film unable to effectively self-repair. In addition, the rigid Janus particles themselves can also bridge in the liquid film, further destabilizing the liquid film and accelerating the drainage and coalescence of bubbles.

[0044] In addition, the active molecules of the prior art are fixed or inactivated after spreading at the interface and cannot be reused, and their performance decays with the number of additions. The reversibility of the DA bond of the present application means that after breaking and completing defoaming at a certain location downhole, when the conditions change, such as temperature fluctuations, some of the bonds may re-form and generate Janus particles again in a new high shear zone.

[0045] This shows that the present application has certain self-repairing and reactivation ability, and the utilization rate of active ingredients is extremely high. This makes the single addition of the defoaming agent circulate in the drilling fluid for a longer time, has a longer service life, significantly reduces the frequency of replenishment and the total amount, and reduces the comprehensive cost. At the same time, the present application does not resist high temperature, but utilizes high temperature, and the activity is not attenuated but enhanced at high temperature, and is suitable for extreme high temperature environments such as deep wells and ultra-deep wells.

[0046] In summary, the core innovation of the present application is that the active ingredient of the defoaming agent can break the dynamic covalent bond and self-assemble into Janus nanoparticles in situ under the high temperature and high shear environment in the well. The particle has an asymmetric structure: the fluorocarbon surface pierces the foam film first due to the ultra-low surface tension, and the siloxane surface spreads quickly subsequently, thereby achieving instantaneous and efficient defoaming in cooperation; this process is intelligent and controllable, and the reversibility of the bond endows the active ingredient with self-repairing and reactivation ability, thereby significantly improving the service life and temperature resistance, and being particularly suitable for extreme working conditions such as deep wells and ultra-deep wells. BRIEF DESCRIPTION OF DRAWINGS

[0047] Figure 1 The figure is a diagram of the mechanism of the present application. DETAILED DESCRIPTION

[0048] The technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application and related drawings. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments.

[0049] Preparation Example 1: the preparation process of the intelligent response type polymer, including the following steps:

[0050] a. A reaction kettle is charged with polymethylhydrogen siloxane and anhydrous toluene, oxygen is removed by bubbling nitrogen for 30 min under stirring at 300 rpm, a platinum-tetramethyldivinylsiloxane catalyst is added, and allyl furan is added dropwise; the temperature is raised to 85℃, and reflux reaction is performed for 12 h; after the reaction is completed, the temperature is cooled to room temperature, and the toluene solvent is removed by distillation under reduced pressure to obtain a synthesized polysiloxane main chain containing a furan functional group, i.e. PSi-Fu, which is ready for use;

[0051] b. Amino-terminated perfluoropolyether is dissolved in dichloromethane, and stirring is continuously performed under ice water bath at 0-5℃, N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine are sequentially added, the ice bath is removed after reaction for 2 h, and the temperature is slowly raised to room temperature for continuous reaction for 10 h; after the reaction is completed, the white precipitate N,N'-dicyclohexyl urea generated in the reaction is removed by filtration, and the filtrate is concentrated by rotary evaporation at 35℃ to obtain an amber viscous liquid, i.e. maleimide-terminated perfluoropolyether, i.e. PFPE-MI;

[0052] c.The reactor was charged with PSi-Fu, PFPE-MI, toluene and hydroquinone, heated to 75℃ under nitrogen protection, and stirred for 36h; after the reaction was completed, it was cooled to room temperature, the reaction solution was precipitated with cold methanol, the solid polymer was collected by filtration, washed with cold methanol, and vacuum dried to obtain a light yellow solid powder, an intelligent responsive polymer, namely PSi-DA-PFPE.

[0053] In the preparation process a of the intelligent responsive polymer, the mass ratio of polymethylhydrogen siloxane, platinum-tetramethyldivinylsiloxane, and allyl furan was 100:0.1:13.

[0054] In the preparation process b of the intelligent responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide, and 4-dimethylamino pyridine was 80:8:11:0.7.

[0055] In the preparation process c of the intelligent responsive polymer, the mass ratio of PSi-Fu, PFPE-MI, and hydroquinone was 50:50:0.05.

[0056] Preparation Example 2: The preparation method was the same as that in Preparation Example 1, but in the preparation process a of the intelligent responsive polymer, the mass ratio of polymethylhydrogen siloxane, platinum-tetramethyldivinylsiloxane, and allyl furan was 100:0.125:12.5.

[0057] In the preparation process b of the intelligent responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide, and 4-dimethylamino pyridine was 80:8.5:10.5:0.85.

[0058] In the preparation process c of the intelligent responsive polymer, the mass ratio of PSi-Fu, PFPE-MI, and hydroquinone was 50:45:0.05.

[0059] Preparation Example 3: The preparation method was the same as that in Preparation Example 1, but in the preparation process a of the intelligent responsive polymer, the mass ratio of polymethylhydrogen siloxane, platinum-tetramethyldivinylsiloxane, and allyl furan was 100:0.15:12.

[0060] In the preparation process b of the intelligent responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide, and 4-dimethylamino pyridine was 80:9:10:1.0.

[0061] In the preparation process c of the intelligent responsive polymer, the mass ratio of PSi-Fu, PFPE-MI, and hydroquinone was 50:40:0.05.

[0062] Example 1

[0063] A preparation method of oil-based defoamer for oil and gas field, comprising the following steps:

[0064] (1) 20 kg of PSi-DA-PFPE obtained in Preparation Example 3 is mixed with 70 kg of carrier oil, stirred at a speed of 500 rpm for 1 h to form a preliminary dispersion;

[0065] (2) 5 kg of hydrophobic fumed silica and 0.1 kg of polyisobutylene succinimide are sequentially added, and a high-pressure homogenizer is used to process the mixture at a pressure of 50-150 MPa for 5 cycles to form a stable and uniform preparation, i.e., an oil-based defoamer for oil and gas field;

[0066] (3) The homogenized product is filled into light-tight plastic buckets or plastic-lined iron buckets and stored in a sealed manner.

[0067] In step (1), the carrier oil is selected to be white oil, which has a kinematic viscosity of 10-50 cSt at 40°C.

[0068] In step (2), the nano-silica has a particle size of 10-50 nm and a specific surface area of 100-300 m 2 / g and is subjected to hydrophobic treatment.

[0069] Example 2

[0070] The preparation method is the same as that in Example 1, but 13 kg of the raw material obtained in Preparation Example 2 is used, and in step (1), the carrier oil is selected to be 80 kg of mineral oil, which has a kinematic viscosity of 10-50 cSt at 40°C.

[0071] In step (2), 3 kg of nano-silica having a particle size of 10-50 nm and a specific surface area of 100-300 m 2 / g and subjected to hydrophobic treatment is used, and 1 kg of polyisobutylene succinimide is used.

[0072] Example 3

[0073] The preparation method is the same as that in Example 1, but 5 kg of the raw material obtained in Preparation Example 1 is used, and in step (1), the carrier oil is selected to be 90 kg of synthetic oil, which has a kinematic viscosity of 10-50 cSt at 40°C.

[0074] In step (2), 1 kg of nano-silica having a particle size of 10-50 nm and a specific surface area of 100-300 m 2 / g and subjected to hydrophobic treatment is used, and 2 kg of polyisobutylene succinimide is used.

[0075] Also designed accordingly:

[0076] Comparative Example 1: Same as Preparation Example 2 in formulation and experimental method, but in PSi-DA-PFPE, no hydroquinone was added;

[0077] Comparative Example 2: Same as Preparation Example 2 in formulation and experimental method, but in PFPE-MI, no DA reaction was performed, and the fluorine side chain was directly linked to the silane main chain;

[0078] Comparative Example 3: Same as Preparation Example 2 in formulation and experimental method, only using non-temperature-sensitive segments such as allyl glycidyl ether instead of allyl furan, and reacting with hydrogen-containing silicone oil, and then performing D-A reaction with PFPE-MI;

[0079] Comparative Example 4: Emulsified asphalt type defoamer was used.

[0080] For each example and comparative example, the density (25℃), flash point, room temperature defoaming performance, high temperature and high pressure defoaming performance, foam inhibition durability, and high temperature stability of the present application were detected according to GB / T 13377 "Determination of density of petroleum and liquid petroleum products", GB / T 261 "Determination of flash point - Pensky-Martens closed cup method", and SY / T 5799 "Evaluation procedure for defoamers for drilling fluids", and the corresponding results are shown in Table 1:

[0081] Table 1. Performance test data of defoamer

[0082]

[0083] Data analysis:

[0084] The mechanism of the present application is shown in Figure 1 All examples exhibit excellent instantaneous defoaming rate (>96%) at room temperature (25℃), far exceeding the comparative examples. Even at room temperature, without complete triggering, the intelligent polymer PSi-DA-PFPE described in the present application itself is an amphiphilic molecule, which contains a lipophilic polysiloxane main chain, a temperature-sensitive segment (PNIPAM, hydrophilic below LCST) with a certain polarity, and a strongly oil-repellent fluorine-containing segment. This structure enables it to spontaneously tend to the oil-gas interface in the oil phase and form a certain ordered arrangement in advance, laying the foundation for rapid defoaming.

[0085] The hydrophobic fumed silica in the formulation acts as a rigid nanoparticle, which has a synergistic effect with the polymer molecules that have been pre-aggregated on the interface. The silica physically punctures the foam through the bridging-oil-repellent mechanism, while the polymer expands the puncture by reducing the local surface tension and rapidly spreading. This preliminary combination of physical puncture and chemical spreading has already shown great power at room temperature.

[0086] Comparative Example 1 has a performance decline due to the lack of hydroquinone, which leads to cross-linking of the polymer, hindering the movement of the molecular chain and making it difficult to effectively migrate and spread at the interface.

[0087] Comparative Examples 2 and 3 have relatively simple molecular structures and lack the complex multi-level structure and interface self-adaptive ability of smart polymers, so their room temperature efficiency is insufficient.

[0088] Comparative Example 4 has limited molecular interface activity and the lowest efficiency.

[0089] Under the conditions of 150°C and 3.5MPa, the foam removal rates of Examples 1 and 2 are still as high as 97.9% and 97.5%, and there is almost no performance degradation. However, the performance of all comparative examples, especially Comparative Examples 2, 3 and 4, has a sharp decline.

[0090] When the ambient temperature exceeds the LCST of PNIPAM (about 32°C) and reaches the high temperature downhole, the temperature-sensitive segment undergoes a dramatic hydrophilic-hydrophobic transition, changing from an extended state to a curled hydrophobic ball. This change provides an initial and powerful aggregation driving force for the entire smart polymer, driving the molecular chains to approach each other and form the prototype of the "silicone-rich region". Comparative Example 3 lacks this key "temperature sensor", which cannot start this step, resulting in a lack of effective aggregation power at high temperatures and a significant decline in performance.

[0091] Drilling fluid experiences strong shear force at the drill bit, pump, etc. in circulation. This mechanical force precisely acts on the relatively fragile Diels-Alder dynamic covalent bond in the polymer. The breaking of the DA bond is a mechanochemical process that releases the fluorine-containing segment with ultra-low surface tension from the main chain. Comparative Example 2 uses stable covalent bonds and cannot achieve this "on-demand release" function. Its fluorine-containing segment is permanently locked and cannot function at critical moments, which is the fundamental reason for its sharp degradation in high-temperature performance.

[0092] The released fluorine-containing segment aggregates due to strong "fluorine-fluorine interaction"; at the same time, the silicone main chain driven by the temperature-sensitive segment also forms aggregates. In the oil phase, these two substances undergo nanoscale phase separation due to extreme incompatibility and eventually spontaneously assemble into thermodynamically stable Janus nanoparticles. One side of the particle is fluorocarbon (ultra-low surface tension), and the other side is silicone (low surface tension and easy to spread).

[0093] The fluorocarbon side, with the lowest surface tension among all organic substances, first penetrates the solid foam liquid film and completes the most difficult initial breakthrough.

[0094] The silicone side follows and quickly and massively spreads at the breach, effectively pushing away the oil phase in the liquid film, causing the breach to rapidly expand and leading to the collapse of the bubble.

[0095] This kind of time-space coordination of puncture and spread is the ultimate mechanism of the invention to achieve instant and efficient bubble breaking. All the comparative examples cannot form this kind of efficient asymmetric structure, so they are helpless in dealing with foam that is more stable at high temperature.

[0096] The foam height of the embodiment is still much lower than that of the comparative examples after 2 hours at 150℃, and the performance retention rate is >95% after high-temperature storage.

[0097] Traditional defoamers (such as comparative example 4) are fixed or chemically decomposed after interfacial spreading, and are disposable consumables. The DA bond of the invention has reversibility. In the complex environment downhole, the temperature field and shear field are dynamically changing. This means that after defoaming is completed at a certain place, when the conditions temporarily ease, part of the broken bond may recombine; when it flows to a new high-shear zone, the bond breaks again, generating new Janus particles. This cycle of breaking-acting-partial regeneration-acting again gives the defoamer amazing durability and long-acting foam inhibition ability.

[0098] The performance of the embodiment is almost unchanged after aging at 80℃ for 7 days, which benefits from the intrinsic stability of its chemical structure. The polysiloxane main chain and fluorine-containing segment are extremely heat-resistant, and the alkoxyl-terminated polyether segment avoids oxidative degradation initiated by terminal hydroxyl groups. The whole system is a stable covalently bonded structure in the storage state and cannot spontaneously decompose. Comparative example 1 precipitates due to crosslinking, and comparative example 4 is severely ineffective (retention rate of only 50.3%) due to thermal oxidative decomposition of the traditional polyether or asphalt components.

[0099] The above is only the preferred specific embodiment of the invention, but the protection scope of the invention is not limited thereto. Any skilled person in the art, according to the technical solution and inventive concept of the invention, makes equivalent replacement or changes within the technical scope disclosed by the invention, should be covered within the protection scope of the invention.

Claims

1. An oil-based antifoam agent for use in oil and gas fields, characterized by, The raw materials include the following weight parts: Intelligent response polymer: 5-20 parts; Carrier oil: 70-90 parts; Hydrophobic fumed silica: 1-5 parts; Polyisobutylene succinimide: 0.1-2 parts; The intelligent response polymer is a polysiloxane-based polymer, which comprises a polysiloxane main chain and a fluorine-containing segment bonded by a DA bond, and the specific structural formula is as follows: 。 2. The oil-based defoamer for use in oil and gas fields according to claim 1, characterized in that, The preparation process of the intelligent response polymer comprises the following steps: a. Add polymethylhydrogenosiloxane and anhydrous toluene into a reaction kettle, bubble nitrogen for 30 min to remove oxygen under stirring at 300 rpm, add platinum-tetramethyldivinylsiloxane catalyst, and drop allyl furan; heat to 85 DEG C, reflux for 12 h; after the reaction is completed, cool to room temperature, remove the toluene solvent by distillation under reduced pressure, and obtain a synthesized polysiloxane main chain containing furan functional groups, i.e. PSi-Fu, for standby; b. Dissolve amino-terminated perfluoropolyether in dichloromethane, continuously stir under 0-5 DEG C ice water bath, add N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine in sequence, remove the ice bath after 2 h of reaction, slowly increase to room temperature and continue to react for 10 h, after the reaction is completed, filter to remove the white precipitate N,N'-dicyclohexyl urea generated in the reaction, concentrate the filtrate at 35 DEG C by rotary evaporation, and obtain amber viscous liquid, i.e. maleimide-terminated perfluoropolyether, PFPE-MI; c. Add PSi-Fu, PFPE-MI, toluene and hydroquinone into a reaction kettle, heat to 75 DEG C under nitrogen protection, and stir for 36 h; after the reaction is completed, cool to room temperature, precipitate the reaction liquid with cold methanol, collect the solid polymer by filtration, wash with cold methanol, and vacuum dry to obtain light yellow solid powder, i.e. intelligent response polymer, PSi-DA-PFPE.

3. The oil-based defoamer for oil and gas fields according to claim 1, characterized by, In the preparation process a of the intelligent response polymer, the mass ratio of polymethylhydrogenosiloxane, platinum-tetramethyldivinylsiloxane and allyl furan is 100:0.1-0.15:12-13.

4. The oil-based defoamer for use in oil and gas fields according to claim 1, characterized by, In the preparation process b of the intelligent response polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine is 80:8-9:10-11:0.7-1.

0.

5. The oil-based defoamer for use in oil and gas fields according to claim 1, characterized by, In the preparation process c of the intelligent response polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:40-50:0.

05.

6. A process for the preparation of an oil-based defoamer for use in oil and gas fields as claimed in any one of claims 1 to 5, characterized in that, The preparation process comprises the following steps: (1) Mix PSi-DA-PFPE with carrier oil, stir at a speed of 500 rpm for 1 h to form a preliminary dispersion; (2) Add hydrophobic fumed silica and polyisobutylene succinimide in sequence, use a high-pressure homogenizer to process under a pressure of 50-150 MPa for 3-8 cycles to form a stable and uniform preparation, i.e. oil-based defoamer for oil and gas fields; (3) Fill the homogenized product into light-proof plastic barrels or plastic-lined iron barrels, and seal for storage.

7. A process for the preparation of an oil-based defoamer for use in oil and gas fields as claimed in claim 6, wherein, In step (1), the carrier oil is selected from at least one of white oil, mineral oil, synthetic oil, which has a kinematic viscosity at 40°C of 10-50 cSt.

8. A process for the preparation of an oil-based defoamer for use in oil and gas fields as claimed in claim 6, wherein, In step (2), the hydrophobic fumed silica has a particle size of 10-50 nm, a specific surface area of 100-300 m 2 / g, and is subjected to a hydrophobization treatment.

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