Oil-based defoaming agent for oil and gas fields and preparation method of oil-based defoaming agent

Abstract

The invention 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, the oil-based defoaming agent comprises an intelligent response type polymer, 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-processing. The core innovation of the invention lies in that the active components of the defoaming agent can generate dynamic covalent bond breakage and in-situ self-assembly to form Janus nano-particles in an underground high-temperature and high-shear environment, the particles have asymmetric structures: a fluorocarbon surface firstly punctures a foam liquid film by virtue of ultralow surface tension, and a siloxane surface then spreads quickly to synergistically realize instantaneous efficient foam breaking; the process is intelligent and controllable, the bonding reversibility endows active components with self-repairing and reactivation capabilities, the service life is remarkably prolonged, the temperature resistance is remarkably improved, and the method is particularly 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 produced 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 technical scheme adopted by the present application is as follows: The present application first proposes an oil-based defoaming agent for oil and gas fields, which comprises the following raw materials by weight: Intelligent response type 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, comprising a polysiloxane backbone and a fluorine-containing segment bonded by a DA bond, and the specific structural formula is as follows: .

[0007] Preferably, the preparation process of the intelligent response polymer comprises the following steps: 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℃, and reflux for 12 h; after the reaction is completed, cool to room temperature, and remove toluene solvent by distillation under reduced pressure to obtain a synthesized polysiloxane backbone containing furan functional groups, i.e. PSi-Fu, for standby use; This reaction is a classic catalytic hydrosilylation reaction. The platinum catalyst activates the Si-H bond to make it add to the carbon-carbon double bond at the end of the allyl furan to form a stable Si-C bond. In this way, the furan ring is successfully grafted onto the polysiloxane backbone as a strong dienophile, providing a reaction site for the subsequent key Diels-Alder reaction.

[0008] b. Dissolve the amino-terminated perfluoropolyether in dichloromethane, continuously stir under 0-5℃ ice water bath, and sequentially add N-maleimide propionic acid, N,N'-dicyclohexyl carbodiimide and 4-dimethylamino pyridine. 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 to remove the white precipitate N,N'-dicyclohexyl urea generated in the reaction, and concentrate the filtrate at 35℃ by rotary evaporation to obtain an amber viscous liquid, i.e. maleimide-terminated perfluoropolyether, PFPE-MI; Under the DCC / DMAP catalytic system, the primary amino group of the amino-terminated perfluoropolyether dehydrates and condenses with the carboxyl group of the N-maleimide propionic acid to form an amide bond. In this way, the highly reactive maleimide group is introduced to the end of the fluorine-containing segment.

[0009] c. Add PSi-Fu, PFPE-MI, toluene and hydroquinone into a reaction kettle, heat to 75℃ 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 a light yellow solid powder, i.e. the intelligent response polymer, PSi-DA-PFPE.

[0010] This is a typical Diels-Alder cycloaddition reaction, in which the furan ring reacts with maleimide via a [4+2] cycloaddition reaction to form an oxygen-containing six-membered bridged ring structure.

[0011] At moderate temperatures (around 75°C), the reaction proceeds in the forward direction, forming stable covalent bonds. At higher temperatures (>110-130°C, downhole high temperatures) or under mechanical forces (high-speed shear forces during drilling fluid circulation), the adduct undergoes a reversible reaction, breaking down to regenerate furan and maleimide.

[0012] When exposed to high temperatures and shear in the well, the DA bonds connecting the fluorocarbon and siloxane chains break, releasing independent fluorinated segments and siloxane chains. Subsequently, through supramolecular interactions such as hydrophobic interactions and fluorine-fluorine interactions, they self-assemble into Janus nanoparticles with dual properties. Among them, the fluorocarbon side, with its extremely low surface tension, is the first to puncture the foam liquid film, while the siloxane side subsequently spreads on a large scale. The two work together to achieve instantaneous and efficient foam breaking.

[0013] Hydroquinone acts as a free radical scavenger in the system. Once a free radical is present, such as one generated from the maleimide double bond, the hydroquinone molecule will immediately react with it to generate a stable free radical (hydroquinone oxygen radical) that no longer has the ability to initiate chain growth. By being consumed by itself, it effectively quenches the initiation point of the chain reaction, thereby preventing the chain growth step of free radical polymerization and terminating the reaction in its nascent stage.

[0014] Preferably, in the preparation process a of the smart responsive polymer, the mass ratio of polymethylhydrosiloxane, platinum-tetramethyldivinyldisiloxane, and allylfuran is 100:0.1-0.15:12-13.

[0015] Preferably, in the preparation process b of the smart responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 80:8-9:10-11:0.7-1.0.

[0016] Preferably, in the preparation process c of the smart responsive polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:40-50:0.05.

[0017] This invention also proposes a method for preparing an oil-based defoamer for oil and gas fields, comprising the following steps: (1) Mix PSi-DA-PFPE with carrier oil and stir at 500 rpm for 1 hour to form a preliminary dispersion; (2) Add hydrophobic fumed silica and polyisobutylene succinimide in sequence, and use a high-pressure homogenizer at a pressure of 50-150MPa to cycle the process 3-8 times to form a stable and uniform formulation, namely, an oil-based defoamer for oil and gas fields. (3) Fill the homogenized product into an opaque plastic bucket or a plastic-lined iron bucket and seal it for storage.

[0018] PSi-DA-PFPE serves as the active core, providing intelligent response and efficient defoaming capabilities; the carrier oil acts as a dispersion medium and delivery carrier, uniformly carrying and transporting the active ingredients throughout the drilling fluid system; hydrophobic fumed silica, as an synergist and stabilizer, has nanoscale rigid particles that act as physical defoaming points, working synergistically with self-assembled Janus particles to further disrupt the stability of the foam film; during storage, it helps thicken and prevents the sedimentation and stratification of other components; polyisobutylene succinimide, with its amphiphilic structure, can adsorb onto the surface of nano-silica and polymers, preventing their aggregation through steric hindrance, ensuring the product remains uniform and stable during storage, and can be rapidly dispersed during use.

[0019] Preferably, in step (1), the carrier oil is selected from at least one of white oil, mineral oil, and synthetic oil, and its kinematic viscosity at 40°C is 10-50 cSt.

[0020] Preferably, in step (2), the nano-silica has a particle size of 10-50 nm and a specific surface area of ​​100-300 m². 2 / g, and has undergone hydrophobic treatment.

[0021] Compared with the prior art, the beneficial effects of the present invention are: The most innovative part of this invention is that the active ingredient of the defoamer can self-assemble into Janus particles in situ and in real time after arriving at the working area. This process is fundamentally different from the traditional method of pre-synthesizing Janus particles and then adding them.

[0022] When defoamers enter high-temperature environments downhole (e.g., >60°C), or when drilling fluid flows through high-speed shear zones such as drill bits and pumps, enormous mechanical forces act on polymer molecules, preferentially breaking the relatively fragile Diels-Alder dynamic covalent bonds within them.

[0023] The breaking of the DA bond causes the previously covalently linked "siloxane backbone-temperature-sensitive segment" aggregate to dissociate from the "fluorinated segment," becoming independent components. At this point, because the temperature-sensitive segments have become hydrophobic, they drive the siloxane backbone to approach and aggregate, forming a siloxane-rich region. Simultaneously, the released fluorinated segments, due to their strong oleophobicity and intense "fluorine-fluorine interactions," also begin to spontaneously aggregate, forming a fluorocarbon-rich region.

[0024] In the shared environment of the oil phase (drilling fluid), the oleophobic siloxane-rich region and the extremely oleophobic fluorocarbon-rich region are not completely miscible. To achieve the lowest interfacial energy in the entire system, these two micro-regions undergo macroscopic phase separation confined to the nanoscale. However, they do not separate into two layers; instead, they spontaneously organize into a thermodynamically stable structure, namely Janus nanoparticles, much like amphiphilic molecules form micelles. In this particle, the fluorinated segments constitute one side, and the siloxane backbone and temperature-sensitive segments constitute the other side, forming a clear interface with distinctly different chemical properties.

[0025] Janus particles have different surface tensions and affinity for the oil / gas interface on both sides. This asymmetry puts them in an energy-unstable state at the interface, exhibiting a strong tendency to oriented and escape from the interface. This tendency translates into a huge defoaming force. When Janus particles approach the foam liquid film, the fluorocarbon side with extremely low surface tension will first insert and pierce the oily surface of the foam liquid. Immediately afterwards, the siloxane side, with a lower surface tension but still higher than that of fluorocarbon, will follow closely and spread rapidly at the break. Due to its flexible molecular chains and large spreading coefficient, it can effectively open the break, displacing the oil phase in the liquid film, causing the liquid film to rapidly thin and tear.

[0026] This continuous attack, driven by different physicochemical properties, prevents the foam liquid film from effectively self-repairing. Furthermore, the rigid Janus particles themselves can bridge within the liquid film, further disrupting its stability and accelerating drainage and bubble coalescence and rupture.

[0027] Furthermore, in existing technologies, the active molecules are fixed or rendered ineffective after spreading at the interface, making them unusable and causing performance degradation with repeated additions. The reversibility of the DA bond in this invention means that even after breakage and defoaming at a certain point downhole, when conditions change, such as temperature fluctuations, some bonds may reform and break again in a new high-shear region to generate Janus particles.

[0028] This indicates that the invention possesses a certain degree of self-repair and reactivation capabilities, with extremely high utilization of the active ingredients. This allows the defoamer added once to circulate in the drilling fluid for a longer period, resulting in a longer service life, significantly reducing the frequency of replenishment and the total dosage, thus lowering overall costs. Furthermore, the invention does not resist high temperatures but rather utilizes them; its activity is not diminished but rather enhanced at high temperatures, making it suitable for extreme high-temperature environments such as deep wells and ultra-deep wells.

[0029] In summary, the core innovation of this invention lies in the fact that the active ingredient of the defoamer can undergo dynamic covalent bond breakage and in-situ self-assembly into Janus nanoparticles under high temperature and high shear conditions downhole. These particles possess an asymmetric structure: the fluorocarbon surface, with its ultra-low surface tension, first punctures the foam liquid film, while the siloxane surface rapidly spreads out, synergistically achieving instantaneous and efficient foam defoaming. This process is intelligently controllable, and the reversibility of the bonding endows the active ingredient with self-repair and reactivation capabilities, significantly improving its service life and temperature resistance, making it particularly suitable for extreme conditions such as deep and ultra-deep wells. Attached Figure Description

[0030] Figure 1 This is a diagram illustrating the mechanism of action of the present invention. Detailed Implementation

[0031] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the embodiments and related figures. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0032] Preparation Example 1: The preparation process of smart responsive polymers includes the following steps: a. Add polymethylhydrosiloxane and anhydrous toluene to the reactor, stir at 300 rpm, purge with nitrogen, and bubble for 30 min to remove oxygen; add platinum-tetramethyldivinyldisiloxane catalyst, and add allyl furan dropwise; heat to 85℃ and reflux for 12 h; after the reaction is completed, cool to room temperature, remove toluene solvent by vacuum distillation to obtain the synthesized polysiloxane backbone containing furan functional groups, i.e., PSi-Fu, for later use; b. The amino-terminated perfluoropolyether was dissolved in dichloromethane and stirred continuously in an ice-water bath at 0-5°C. N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine were added sequentially. After reacting for 2 hours, the ice bath was removed and the mixture was slowly raised to room temperature and reacted for another 10 hours. After the reaction was completed, the white precipitate N,N'-dicyclohexylurea was removed by filtration. The filtrate was concentrated by rotary evaporation at 35°C to obtain an amber viscous liquid, which is the maleimide-terminated perfluoropolyether, i.e., PFPE-MI. c. Add PSi-Fu, PFPE-MI, toluene and hydroquinone to the reactor, heat to 75°C under nitrogen protection, and stir for 36 hours. After the reaction is complete, cool to room temperature, precipitate the reaction solution with cold methanol, filter to collect the solid polymer, wash with cold methanol, and vacuum dry to obtain a light yellow solid powder, which is a smart responsive polymer, namely PSi-DA-PFPE.

[0033] In the preparation process a of the smart responsive polymer, the mass ratio of polymethylhydrosiloxane, platinum-tetramethyldivinyldisiloxane, and allylfuran is 100:0.1:13.

[0034] In the preparation process b of the smart responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 80:8:11:0.7.

[0035] In the preparation process c of the smart responsive polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:50:0.05.

[0036] Preparation Example 2: The preparation method is the same as that in Preparation Example 1, but in the preparation process a of the smart responsive polymer, the mass ratio of polymethylhydrosiloxane, platinum-tetramethyldivinyldisiloxane, and allylfuran is 100:0.125:12.5.

[0037] In the preparation process b of the smart responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 80:8.5:10.5:0.85.

[0038] In the preparation process c of the smart responsive polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:45:0.05.

[0039] Preparation Example 3: The preparation method is the same as that in Preparation Example 1, but in the preparation process a of the smart responsive polymer, the mass ratio of polymethylhydrosiloxane, platinum-tetramethyldivinyldisiloxane, and allylfuran is 100:0.15:12.

[0040] In the preparation process b of the smart responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 80:9:10:1.0.

[0041] In the preparation process c of the smart responsive polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:40:0.05.

[0042] Example 1: A method for preparing an oil-based defoamer for oil and gas fields includes the following steps: (1) 20 kg of PSi-DA-PFPE obtained in Preparation Example 3 was mixed with 70 kg of carrier oil and stirred at 500 rpm for 1 h to form a preliminary dispersion; (2) Add 5 kg of hydrophobic fumed silica and 0.1 kg of polyisobutylene succinimide in sequence, and use a high-pressure homogenizer at a pressure of 50-150 MPa to cycle the process 5 times to form a stable and uniform formulation, namely, an oil-based defoamer for oil and gas fields. (3) Fill the homogenized product into an opaque plastic bucket or a plastic-lined iron bucket and seal it for storage.

[0043] In step (1), the carrier oil is selected as white oil, which has a kinematic viscosity of 10-50 cSt at 40°C.

[0044] In step (2), the nano-silica has a particle size of 10-50 nm and a specific surface area of ​​100-300 m². 2 / g, and has undergone hydrophobic treatment.

[0045] Example 2: The preparation method is the same as in Example 1, but 13 kg of the raw material obtained in Preparation Example 2 is used. In step (1), the carrier oil is selected as 80 kg of mineral oil with a kinematic viscosity of 10-50 cSt at 40°C.

[0046] In step (2), 3 kg of nano-silica with a particle size of 10-50 nm and a specific surface area of ​​100-300 m² is used. 2 / g, and has undergone hydrophobic treatment; 1kg of polyisobutylene succinimide was used.

[0047] Example 3: The preparation method is the same as in Example 1, but 5 kg of the raw material obtained in Example 1 is used. In step (1), the carrier oil is selected as 90 kg of synthetic oil with a kinematic viscosity of 10-50 cSt at 40°C.

[0048] In step (2), 1 kg of nano-silica with a particle size of 10-50 nm and a specific surface area of ​​100-300 m² is used. 2 / g, and has undergone hydrophobic treatment; 2kg of polyisobutylene succinimide was used.

[0049] Based on this, the following design was also created: Comparative Example 1: The formulation and experimental method were the same as those in Preparation Example 2, but hydroquinone was not added to PSi-DA-PFPE; Comparative Example 2: The formulation and experimental method were the same as those in Preparation Example 2, but in PFPE-MI, the DA reaction was not carried out, and the fluorine side was directly linked into the silane backbone. Comparative Example 3: The formulation and experimental method were the same as those in Preparation Example 2, except that non-thermosensitive segments such as allyl glycidyl ether were used instead of allyl furan. It was reacted with hydrogen-containing silicone oil and then reacted with PFPE-MI in a DA reaction. Comparative Example 4: Using emulsified asphalt-based defoamers.

[0050] For each embodiment and comparative example, the density (25℃), flash point, room temperature defoaming performance, high temperature and high pressure defoaming performance, foam suppression persistence, and high temperature stability of the present invention were tested according to GB / T 13377 "Determination of Density of Petroleum and Liquid Petroleum Products", GB / T261 "Determination of Flash Point - Binsky-Martin Closed Cup Method", and SY / T 5799 "Evaluation Procedure for Defoamers for Drilling Fluids". The corresponding results are shown in Table 1. Table 1. Test data of various performance aspects of defoamer Data Analysis: The mechanism of action of this invention is as follows Figure 1 As shown, all embodiments exhibited superior instantaneous defoaming rates (>96%) at room temperature (25°C), far exceeding the comparative examples. Even at room temperature, without complete triggering, the intelligent polymer PSi-DA-PFPE described in this invention is itself an amphiphilic molecule, its structure simultaneously containing a lipophilic polysiloxane backbone, a temperature-sensitive segment with a certain polarity (PNIPAM, hydrophilic below LCST), and a strongly oleophobic fluorinated segment. This structure allows it to spontaneously tend towards the oil-gas interface in the oil phase and pre-form a certain ordered arrangement, laying the foundation for rapid defoaming.

[0051] The hydrophobic fumed silica in the formulation, acting as rigid nanoparticles, synergistically interacts with the pre-aggregated polymer molecules at the interface. Silica physically punctures the foam through a bridging-oil-draining mechanism, while the polymer expands the breach by reducing local surface tension and spreading rapidly. This initial combination of physical puncture and chemical spreading has already demonstrated powerful efficacy at room temperature.

[0052] Comparative Example 1 showed that the lack of hydroquinone caused polymer cross-linking, which hindered the movement of molecular chains and made it difficult for them to migrate and spread effectively at the interface, thus resulting in a decrease in performance.

[0053] Comparative Examples 2 and 3 have relatively simple molecular structures and lack the complex multi-level structure and interfacial self-adaptation capabilities of smart polymers, thus their room temperature efficiency is already insufficient.

[0054] Comparative Example 4 shows that the traditional molecular interface has limited activity and the lowest efficiency.

[0055] At 150°C and 3.5 MPa, the defoaming rates of Examples 1 and 2 remained as high as 97.9% and 97.5%, respectively, with almost no performance degradation. However, all comparative examples, especially Comparative Examples 2, 3, and 4, showed a precipitous drop in performance.

[0056] When the ambient temperature exceeds the LCST of PNIPAM (approximately 32°C) and reaches the downhole high temperature, the temperature-sensitive segments undergo a dramatic hydrophobic-philic transition, changing from an extended state to a coiled hydrophobic sphere. This change provides the entire smart polymer with an initial and powerful aggregation driving force, driving the molecular chains to approach each other and forming the prototype of a "siloxane-rich region." Comparative Example 3, lacking this crucial "temperature sensor," cannot initiate this step, resulting in a lack of effective aggregation motive force at high temperatures and a significant decline in performance.

[0057] Drilling fluid experiences extremely strong shear forces from the drill bit, pump, and other components during circulation. This mechanical force precisely acts on the relatively fragile Diels-Alder dynamic covalent bonds in the polymer. The breaking of the DA bond is a mechanochemical process that releases fluorinated segments with ultra-low surface tension from the main chain. Comparative Example 2, using stable covalent bonds, cannot achieve this "on-demand release" function; its fluorinated segments are permanently locked and cannot function at critical moments. This is the fundamental reason for its drastic degradation in high-temperature performance.

[0058] The released fluorinated segments aggregate due to strong fluorine-fluorine interactions; simultaneously, the siloxane backbone, driven by temperature-sensitive segments, also forms aggregates. In the oil phase, these two components undergo nanoscale phase separation due to extreme incompatibility, ultimately spontaneously assembling into thermodynamically stable Janus nanoparticles. These particles consist of fluorocarbon (ultra-low surface tension) on one side and siloxane (low surface tension and flexible, easily spreadable) on the other.

[0059] Fluorocarbon surfaces, with their lowest surface tension of all organic materials, were the first to pierce the solid foam liquid film, achieving the most difficult initial breakthrough.

[0060] The siloxane surface follows closely behind, spreading rapidly and on a large scale at the breach, effectively displacing the oil phase in the liquid film, causing the breach to expand rapidly and leading to bubble collapse.

[0061] This spatiotemporal coordination of first puncturing and then spreading is the ultimate mechanism by which this invention achieves instantaneous and efficient bubble breaking. All comparative examples are unable to form this efficient asymmetric structure, and therefore are helpless when dealing with more stable foams at high temperatures.

[0062] The foam height of the example was still much lower than that of the comparative example after 2 hours at 150°C, and the performance retention rate was >95% after high-temperature storage.

[0063] Traditional defoamers (such as Comparative Example 4) are fixed or chemically decomposed after interfacial spreading, making them disposable consumables. In contrast, the DA bond in this invention is reversible. In the complex downhole environment, temperature and shear fields are dynamically changing. This means that after defoaming is completed at one point, when conditions temporarily ease, some broken bonds may recombine; when flowing to a new high-shear zone, the bonds break again, regenerating new Janus particles. This cycle of breakage-action-partial regeneration-reaction endows the defoamer with remarkable durability and long-lasting foam suppression capabilities.

[0064] The performance of the examples remained almost unchanged after aging at 80°C for 7 days, thanks to the intrinsic stability of their chemical structure. The polysiloxane backbone and fluorinated segments themselves have excellent heat resistance, while the alkoxy-terminated polyether segments avoid oxidative degradation initiated by the terminal hydroxyl groups. The entire system maintains a stable covalent bonded structure in storage and does not spontaneously decompose. Comparative Example 1 precipitated due to crosslinking, while Comparative Example 4 suffered severe failure due to the thermal oxidative decomposition of the traditional polyether or asphalt components (retention rate of only 50.3%).

[0065] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. An oil-based defoamer for oil and gas fields, characterized in that, Including the following parts by weight of raw materials: Smart responsive polymer: 5-20 parts; Carrier oil: 70-90 parts; Hydrophobic fumed silica: 1-5 parts; Polyisobutylene succinimide: 0.1-2 parts; The smart responsive polymer is a polysiloxane polymer, comprising: a polysiloxane backbone and fluorinated segments bonded by DA bonds, with the following specific structural formula: 。 2. The oil-based defoamer for oil and gas fields according to claim 1, characterized in that, The preparation process of the smart responsive polymer includes the following steps: a. Add polymethylhydrosiloxane and anhydrous toluene to the reactor, stir at 300 rpm, purge with nitrogen, and bubble for 30 min to remove oxygen; add platinum-tetramethyldivinyldisiloxane catalyst, and add allyl furan dropwise; heat to 85℃ and reflux for 12 h; after the reaction is completed, cool to room temperature, remove toluene solvent by vacuum distillation to obtain the synthesized polysiloxane backbone containing furan functional groups, i.e., PSi-Fu, for later use; b. The amino-terminated perfluoropolyether was dissolved in dichloromethane and stirred continuously in an ice-water bath at 0-5°C. N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine were added sequentially. After reacting for 2 hours, the ice bath was removed and the mixture was slowly raised to room temperature and reacted for another 10 hours. After the reaction was completed, the white precipitate N,N'-dicyclohexylurea was removed by filtration. The filtrate was concentrated by rotary evaporation at 35°C to obtain an amber viscous liquid, which is the maleimide-terminated perfluoropolyether, i.e., PFPE-MI. c. Add PSi-Fu, PFPE-MI, toluene and hydroquinone to the reactor, heat to 75°C under nitrogen protection, and stir for 36 hours. After the reaction is complete, cool to room temperature, precipitate the reaction solution with cold methanol, filter to collect the solid polymer, wash with cold methanol, and vacuum dry to obtain a light yellow solid powder, which is a smart responsive polymer, namely PSi-DA-PFPE.

3. The oil-based defoamer for oil and gas fields according to claim 2, characterized in that, In the preparation process a of the smart responsive polymer, the mass ratio of polymethylhydrosiloxane, platinum-tetramethyldivinyldisiloxane, and allylfuran is 100:0.1-0.15:12-13.

4. The oil-based defoamer for oil and gas fields according to claim 2, characterized in that, In the preparation process b of the smart responsive polymer, the mass ratio of amino-terminated perfluoropolyether, N-maleimide propionic acid, N,N'-dicyclohexylcarbodiimide and 4-dimethylaminopyridine is 80:8-9:10-11:0.7-1.

0.

5. The oil-based defoamer for oil and gas fields according to claim 2, characterized in that, In the preparation process c of the smart responsive polymer, the mass ratio of PSi-Fu, PFPE-MI and hydroquinone is 50:40-50:0.

05.

6. A method for preparing an oil-based defoamer for oil and gas fields according to any one of claims 1-5, characterized in that, Includes the following steps: (1) Mix PSi-DA-PFPE with carrier oil and stir at 500 rpm for 1 hour to form a preliminary dispersion; (2) Add hydrophobic fumed silica and polyisobutylene succinimide in sequence, and use a high-pressure homogenizer at a pressure of 50-150MPa to cycle the process 3-8 times to form a stable and uniform formulation, namely, an oil-based defoamer for oil and gas fields. (3) Fill the homogenized product into an opaque plastic bucket or a plastic-lined iron bucket and seal it for storage.

7. The method for preparing an oil-based defoamer for oil and gas fields according to claim 6, characterized in that, In step (1), the carrier oil is selected from at least one of white oil, mineral oil, and synthetic oil, and its kinematic viscosity at 40°C is 10-50 cSt.

8. The method for preparing an oil-based defoamer for oil and gas fields according to claim 6, characterized in that, In step (2), the hydrophobic fumed silica has a particle size of 10-50 nm and a specific surface area of ​​100-300 m². 2 / g, and has undergone hydrophobic treatment.

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