An antifoaming agent for the liquid-carrying end of a loose sandstone gas field and its preparation method

Abstract

The present invention belongs to the technical field of natural gas exploitation, and particularly relates to an antifoaming agent for the liquid-carrying end of a loose sandstone gas field and a preparation method thereof. The antifoaming agent for the liquid-carrying end of the loose sandstone gas field comprises the following components in parts by weight: 10-50 parts by weight of a modified silicone intermediate, 0.1-0.5 parts by weight of a sandstone swelling inhibitor, 0.1-0.5 parts by weight of a sandstone wetting agent, 0.1-5 parts by weight of a stabilizer, 1-15 parts by weight of an antifreezing agent, and 29-89 parts by weight of deionized water. The antifoaming agent of the present invention is used for the defoaming work of the sand-containing foam returned to the ground before entering the separator in the back end of the foam drainage gas production process of the water-producing gas well in the loose sandstone gas field, so as to ensure that the sand-containing foam returned from the wellbore is completely eliminated before the separator, and does not cause damage to the subsequent processes and equipment. The preparation process of the method of the present invention is simple, non-toxic and environmentally friendly, and is suitable for industrial production.

Description

Technical Field

[0001] The present invention belongs to the technical field of natural gas exploitation, and particularly relates to an antifoaming agent for the liquid-carrying end of a loose sandstone gas field and a preparation method thereof. Background Technique

[0002] The reservoir of the loose sandstone gas field is a set of strata developed under the control of structure and with a small amount of lithologic control. This reservoir is a clastic salt reservoir with high shale content, poor diagenesis, good physical properties and strong heterogeneity. The lithology is mainly siltstone, argillaceous siltstone with high shale content and a small amount of fine sandstone. During the process of natural gas exploitation, as the gas well produces, the reservoir pressure continuously decreases, the production volume decreases, and liquid accumulation is inevitable. In the initial stage, the gas flow rate is high, and part of the liquid is carried out of the wellbore. However, as the gas well produces, the reservoir energy decreases, the gas flow rate slows down, and the amount of carried liquid becomes less and less until it can no longer carry liquid. Over time, water accumulates continuously, the liquid level increases, and drainage measures must be taken in time. Otherwise, the gas well will not be able to produce, and even be flooded. Therefore, when bottom-hole liquid accumulation occurs, drainage should be carried out in time. In the middle and late stages of exploitation, the foam drainage gas production process has become an essential conventional production process to ensure continuous and stable production. An important link at the end of the foam drainage process is to eliminate foam and ensure gas-liquid separation. If the foam is not eliminated thoroughly, many adverse effects will occur, such as affecting the metering instrument, increasing the pipeline pressure, the foam entering the supercharger will cause flameout, and the foam entering the dehydration skid will cause salt formation, etc.

[0003] During the process of natural gas exploitation in the reservoir of the loose sandstone gas field, sand production in gas wells is very common. Currently, the antifoaming agents used are mainly emulsion-type antifoaming agents based on dimethyl silicone oil, which are continuously injected into the set pipeline at the gas gathering station through an antifoaming tank, an antifoaming skid, etc. Since the produced water contains a large amount of sediment, many problems exist in the actual use process:

[0004] (1) The salinity of the gas reservoir water in sand-containing gas wells is very high, and the dilution stability of conventional dimethyl silicone oil emulsion-type antifoaming agents in high-salinity gas reservoir water is poor;

[0005] (2) Under the disturbance condition of the gas flow, the foam generated by the foam drainage operation is dense due to sediment, resulting in poor defoaming effect of conventional dimethyl silicone oil emulsion-type antifoaming agents on sand-containing foam;

[0006] (3) A large amount of sediment adheres to the surface of the foam during the liquid-carrying process. When the foam breaks, the sediment particles will adhere together in a colloidal mass due to hydration and hydrophobic interaction between particles, forming an "armor"-like solid sediment foam. In severe cases, it will accumulate in the separator, resulting in the failure of gas-liquid separation and causing great difficulties to the subsequent water treatment. Summary of the Invention

[0007] The purpose of the present invention is to provide an antifoaming agent for the liquid-carrying end of a loose sandstone gas field and a preparation method thereof, so as to solve the problems proposed in the above background technique.

[0008] The implementation process of the present invention is as follows:

[0009] An antifoaming agent for the liquid-carrying end of a loose sandstone gas field, comprising the following components by weight:

[0010]

[0011] Furthermore, the modified silicone intermediate is a polyether-modified silicone oil synthesized by using a monoallyl polyether with a mixture of allyl alcohol and sodium α-olefin sulfonate as the initiator and low-hydrogen silicone oil under the conditions of high temperature, negative pressure, and high-speed stirring. Then, the polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles are dehydrated and de-low-boiling components under reduced pressure and heating to obtain the modified silicone intermediate.

[0012] Furthermore, the specific preparation process of the modified silicone intermediate is as follows:

[0013] (1) Add the initiator and catalyst into a high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyl trimethyl ammonium chloride. Under the conditions of a pressure of 0.2 - 0.3 Mpa and the reactor temperature rising to 60 - 100 °C, ring-opening polymerization reaction occurs, and keep warm for 2 - 5 h to obtain monoallyl polyether;

[0014] (2) Add low-hydrogen silicone oil and monoallyl polyether into the synthesis reactor according to the mass ratio of 1:1 - 1.6, stir for 5 - 30 min to ensure uniform mixing of raw materials, heat up to 60 - 80 °C, evacuate under a vacuum degree of 700 - 900 Pa for 1 h, heat up to 80 - 90 °C and then add a noble metal catalyst. After the induction period reaction generates heat, heat up to 95 - 115 °C, keep the temperature at 95 - 115 °C for 4 h, take a sample and measure the residual amount of Si-H groups to determine the reaction end point. After reducing to normal pressure and room temperature, obtain polyether-modified silicone oil;

[0015] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles into the synthesis reactor according to the mass ratio of 1:(0.5 - 1):(0.1 - 0.3):(0.01 - 0.03), stir for 30 - 60 min to ensure uniform mixing of raw materials, heat up to 100 - 120 °C, evacuate under a vacuum degree of 700 - 900 Pa for 1 h, and after reducing to normal pressure and room temperature, obtain the modified silicone intermediate.

[0016] Furthermore, in step (1), the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyl trimethyl ammonium chloride is 1:(3 - 10):(5 - 15):(0.01 - 0.05), the initiator is a mixture of allyl alcohol and sodium α-olefin sulfonate with a mass ratio of 1:(0.1 - 1), and the catalyst is sodium hydroxide or potassium hydroxide.

[0017] Further, in step (2), the hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:(1 - 10).

[0018] Further, in step (3), the salt-resistant emulsifier is a composite emulsifier prepared from Span emulsifier and Tween emulsifier with a mass ratio of 1:(0.1 - 1), where the Span emulsifier is a mixture composed of one or any several of sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, and sorbitan trioleate in any proportion; the Tween emulsifier is a mixture composed of one or any several of polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate in any proportion; the fumed nano-silica particles are nano-silica powdery solids containing partial hydroxyl structures, with a specific surface area of 200 - 300 m 2 / g and a hydrophobicity of 40 - 60.

[0019] Further, the sandstone swelling inhibitor is a mixture composed of one or any several of allyltrimethylammonium chloride, allylbenzyldimethylammonium chloride, and (2-hydroxyethyl)trimethylammonium chloride in any proportion.

[0020] Further, the sandstone wetting agent is a mixture composed of one or any several of alkyl polyglycoside, alkylphenol polyoxyethylene ether, and sodium lauryl polyoxyethylene ether sulfate in any proportion.

[0021] Further, the stabilizer is a mixture composed of one or any several of anionic hydrophobically modified polyacrylic acid, sodium carboxymethyl cellulose, and starch graft modified polyacrylamide in any proportion; the antifreeze is a mixture composed of one or any several of methanol, ethanol, ethylene glycol, glycerol, ethylene glycol monobutyl ether, and glycerol monomethyl ether in any proportion.

[0022] A preparation method of an antifoaming agent for the liquid-carrying end of a loose sandstone gas field includes the following steps:

[0023] (1) Weigh 10 - 50 parts by weight of a modified organosilicon intermediate, 0.1 - 0.5 parts by weight of a sandstone swelling inhibitor, 0.1 - 0.5 parts by weight of a sandstone wetting agent, 0.1 - 5 parts by weight of a stabilizer, 1 - 15 parts by weight of an antifreeze, and 29 - 89 parts by weight of deionized water;

[0024] (2) Add the modified silicone intermediate, sandstone swelling inhibitor, rock wetting agent, stabilizer, antifreeze agent and deionized water into the reactor, and carry out stirring and emulsification reaction at normal temperature and pressure for 30 - 60 min to obtain the defoaming agent for the liquid-carrying end of loose sandstone gas fields.

[0025] Compared with the prior art, the present invention has the following beneficial effects:

[0026] (1) For the defoaming agent for the liquid-carrying end of loose sandstone gas fields prepared by the present invention, the foam suppression component in the main agent silicone intermediate is a polyether-modified silicone oil synthesized by using a monoallyl polyether with a hydrophilic allyl alcohol and sodium α-olefin sulfonate mixture as the initiator and low-hydrogen silicone oil under the conditions of high temperature, negative pressure and high-speed stirring. By strictly controlling the residual amount of Si-H groups, it is ensured that the low-hydrogen silicone oil in the foam suppression component reacts completely, so that there is no precipitation of low-hydrogen silicone oil during the dissolution and dispersion of the defoaming agent product in water, greatly increasing the dilution stability of the defoaming agent product in mineralized gas reservoir water.

[0027] (2) For the defoaming agent for the liquid-carrying end of loose sandstone gas fields prepared by the present invention, the foam suppression component polyether-modified silicone oil in the main agent silicone intermediate has allyltrimethylammonium chloride incorporated into the molecular chain segment of the monoallyl polyether. When the defoaming agent intermediate is dispersed in water in the form of emulsion droplets, the droplets are positively charged on the surface, so that the droplets repel each other through electrostatic interaction. This can not only improve the dilution stability of the product in water, but also reduce the cloud point of the polyether-modified silicone oil in the foam aqueous solution, making the defoaming agent micelle droplets with hydrophilic exterior and lipophilic interior smaller in particle size and larger in specific surface area, thus improving the foam suppression performance of the product in high-mineralization gas reservoir water.

[0028] (3) For the defoaming agent for the liquid-carrying end of loose sandstone gas fields prepared by the present invention, the foam-breaking component polydimethylsiloxane in the main agent silicone intermediate, polyether-modified silicone oil, salt-tolerant emulsifier and fumed nano-silica particles are first emulsified and then diluted under the conditions of high temperature, negative pressure and high-speed stirring. Under the action of the salt-tolerant surfactant, the polydimethylsiloxane and nano-silica particles can be uniformly and stably dispersed in the silicone intermediate; the uniformly dispersed nano-silica particles in the product system can not only form a stable Pickering emulsion of hydrophobic polydimethylsiloxane in the aqueous phase, increasing the dilution stability of polydimethylsiloxane in water, but also the silica particles help the silicone compound to diffuse in water as a carrier, improving the foam-breaking performance of the product in high-mineralization gas reservoir water.

[0029] (4) Due to the hydration effect and the hydrophobic effect on the surface of some particles, the underground argillaceous siltstone will cause the sediment to adhere together, forming a "coat" - like solid sediment foam. The hydration effect makes the volume of sediment particles expand and the surface become virtual, and it is easy for particles to adhere to each other; the surface of some underground argillaceous siltstone is strongly hydrophobic. In the aqueous solution, sediment particles are not only easy to agglomerate, but also will wrap the droplets of modified silicone intermediate liquid, forming sediment micelles. The sandstone swelling inhibitor can effectively prevent the expansion of sediment particles through ion distribution coupling, cause the hydrated and expanded sediment minerals to shrink, and effectively disperse the sediment particles adhered together due to the hydration effect in water; the sandstone wetting agent can effectively improve the hydrophilicity of the surface of sediment particles through the reversal of the wettability of the sandstone surface, preventing the formation of "coat" - like solid sediment foam. The defoamer prepared in the present invention for the liquid - carrying end of loose sandstone gas fields improves the dispersibility of argillaceous sandstone in water by using the sandstone swelling inhibitor and the sandstone wetting agent, effectively solves the problem of agglomeration of argillaceous sandstone in high - salinity brine, and ensures the continuous normal operation of the separator equipment. Brief Description of the Drawings

[0030] Figure 1 It is the infrared spectrogram for determining the reaction end point by measuring the residual amount of Si - H groups in the polyether - modified silicone oil in Example 1;

[0031] Figure 2 It is the laboratory effect photos before defoaming - after defoaming - foam - suppressing when Example 1 is used as a defoamer;

[0032] Figure 3 It is the experimental photos before and after adding defoamers when Example 1 and Comparative Examples 1 - 2 are used as defoamers in the defoaming rate test;

[0033] Figure 4 It is the dilution stability experiment of Examples 1 - 6 and Comparative Examples 1 - 2 as defoamers in high - salinity field gas reservoir water in the dilution stability experiment;

[0034] Figure 5 It is the appearance photos of the products of Examples 1 - 6 and Comparative Examples 1 - 2;

[0035] Figure 6 It is the photos of the defoaming process in the sewage pool at the end of the gas reservoir water when Example 1 is used as a defoamer in the on - site use at the liquid - carrying end of the loose sandstone gas field. Detailed Embodiments

[0036] The present invention will be further described below in conjunction with examples.

[0037] The defoamer of the present invention is used for defoaming the sand-containing foam returned to the ground before it enters the separator in the foam drainage gas production process at the back end of the water-producing gas well in the unconsolidated sandstone gas field, so as to ensure that the sand-containing foam returned from the wellbore is completely defoamed before entering the separator, and does not cause damage to the subsequent processes and equipment. The preparation process of the method of the present invention is simple, non-toxic and environmentally friendly, and is suitable for industrial production.

[0038] Example 1

[0039] A defoamer for the liquid-carrying end of an unconsolidated sandstone gas field comprises the following components by weight:

[0040]

[0041] Among them, the specific preparation process of the modified silicone intermediate is as follows:

[0042] (1) Add the initiator and catalyst into a high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyltrimethylammonium chloride. Under the condition of a pressure of 0.2 Mpa and the reactor temperature rising to 80 °C, ring-opening polymerization reaction occurs, and keep the temperature for 3 h to obtain a single-end allyl polyether;

[0043] Among them, the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyltrimethylammonium chloride is 1:6:10:0.03. The initiator is a mixture of allyl alcohol and α-olefin sulfonate with a mass ratio of 1:0.5, and the catalyst is sodium hydroxide, and the dosage is 0.3% of the total mass of all materials;

[0044] (2) Add low-hydrogen silicone oil and single-end allyl polyether into the synthesis reactor according to a mass ratio of 1:1.3, stir at a stirring speed of 70 r / min for 20 min to ensure uniform mixing of the raw materials, heat up to 70 °C, and evacuate under a vacuum degree of 800 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture, unreacted ethylene oxide and epichlorohydrin in the single-end allyl polyether, and light hydrocarbon components in the silicone oil, etc.), heat up to 85 °C and then add the noble metal catalyst. After the induction period reaction generates heat, heat up to 105 °C, keep the reaction at 105 °C for 4 h, take samples and determine the reaction end point by measuring the residual amount of Si-H groups through infrared spectroscopy (the end infrared spectrum is shown in Figure 1 ), after reducing to normal pressure and room temperature, obtain polyether-modified silicone oil. It can be seen from Figure 1 that there is no Si-H characteristic absorption peak at about 2130 cm -1 position, indicating that the low-hydrogen silicone oil has completely reacted and does not precipitate;

[0045] Among them, the hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:5, and the dosage of the noble metal catalyst is 0.1% of the total mass of all materials;

[0046] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-tolerant emulsifier, and fumed nano-silica particles into a synthesis reactor according to a mass ratio of 1:0.7:0.2:0.02, stir for 40 min at a stirring speed of 70 r / min to ensure uniform mixing of raw materials, heat up to 110 °C, and evacuate under a vacuum of 800 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture and light hydrocarbon components in polydimethylsiloxane). After returning to normal pressure and room temperature, a modified silicone intermediate is obtained.

[0047] Among them, the salt-tolerant emulsifier is a composite emulsifier prepared from sorbitan monolaurate (Span20) and polyoxyethylene sorbitan monooleate (Tween80) with a mass ratio of 1:0.5. The fumed nano-silica particles are nano-silica powdery solids containing partial hydroxyl structures, with a specific surface area of 200 - 300 m 2 / g, a hydrophobicity of 40 - 60, manufactured by Wacker Chemie, model: N23. The sandstone swelling inhibitor is allyltrimethylammonium chloride. The sandstone wetting agent is alkyl glycoside. The stabilizer is anionic hydrophobically modified polyacrylic acid. The antifreeze is methanol.

[0048] The preparation method of the defoamer for the liquid-carrying end of a loose sandstone gas field includes the following steps:

[0049] (1) Weigh 30 parts by weight of the modified silicone intermediate, 0.3 parts by weight of the sandstone swelling inhibitor, 0.3 parts by weight of the sandstone wetting agent, 3 parts by weight of the stabilizer, 8 parts by weight of the antifreeze, and 60 parts by weight of deionized water;

[0050] (2) Add the modified silicone intermediate, sandstone swelling inhibitor, rock wetting agent, stabilizer, antifreeze, and deionized water into a reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 50 min to obtain a defoamer for the liquid-carrying end of a loose sandstone gas field. It should be noted that the modified silicone intermediate has strong emulsifying ability and dilution stability, so no secondary addition of emulsifier is required during this process.

[0051] Example 2

[0052] A defoamer for the liquid-carrying end of a loose sandstone gas field, comprising the following components in parts by weight:

[0053]

[0054] Among them, the specific preparation process of the modified silicone intermediate is as follows:

[0055] (1) Add the initiator and catalyst into the high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyltrimethylammonium chloride. Under the conditions of a pressure of 0.2 Mpa and the reactor temperature rising to 100 °C, ring-opening polymerization reaction occurs, and keep the temperature for 2 h to obtain allyl-terminated polyether;

[0056] Among them, the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyltrimethylammonium chloride is 1:3:5:0.01. The initiator is a mixture of allyl alcohol and α-olefin sulfonate with a mass ratio of 1:1. The catalyst is sodium hydroxide, and the dosage is 0.1% of the total mass of all materials;

[0057] (2) Add low-hydrogen silicone oil and allyl-terminated polyether into the synthesis reactor according to the mass ratio of 1:1, stir at a stirring speed of 50 r / min for 30 min to ensure uniform mixing of the raw materials, heat up to 80 °C, evacuate under a vacuum degree of 900 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture, unreacted ethylene oxide and epichlorohydrin in allyl-terminated polyether, and light hydrocarbon components in silicone oil, etc.), heat up to 90 °C and then add the noble metal catalyst. After the induction period, the reaction generates heat, heat up to 115 °C, keep the temperature at 115 °C for 4 h, take samples and determine the reaction end point by measuring the residual amount of Si-H groups through infrared spectroscopy. After reducing to normal pressure and room temperature, polyether-modified silicone oil is obtained, and the low-hydrogen silicone oil reacts completely without precipitation;

[0058] Among them, the hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:10, and the dosage of the noble metal catalyst is 0.5% of the total mass of all materials;

[0059] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles into the synthesis reactor according to the mass ratio of 1:1:0.3:0.03, stir at a stirring speed of 50 r / min for 60 min to ensure uniform mixing of the raw materials, heat up to 120 °C, evacuate under a vacuum degree of 700 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture and light hydrocarbon components in polydimethylsiloxane), and after reducing to normal pressure and room temperature, a modified silicone intermediate is obtained.

[0060] Among them, the salt-resistant emulsifier is a composite emulsifier prepared from sorbitan monopalmitate (Span40), polyoxyethylene sorbitan monolaurate (Tween20), and polyoxyethylene sorbitan monopalmitate (Tween40) with a mass ratio of 1:0.5:0.5. The fumed nano-silica particles are nano-silica powder-like solids containing partial hydroxyl structures, and the specific surface area is 200 - 300 m 2 / g, with a hydrophobicity of 40 - 60, manufactured by Wacker Chemie, model: N23. The sandstone swelling inhibitor is allylbenzyl dimethyl ammonium chloride. The sandstone wetting agent is a mixed sandstone wetting agent composed of alkylphenol polyoxyethylene ether and sodium lauryl polyoxyethylene ether sulfate with a mass ratio of 1:1. The stabilizer is starch grafted modified polyacrylamide. The antifreeze is a mixed antifreeze composed of ethanol, ethylene glycol, and glycerol with a mass ratio of 1:0.3:1.

[0061] The preparation method of the defoamer for the liquid-carrying end of the loose sandstone gas field is as follows:

[0062] (1) Weigh 10 parts by weight of the modified silicone intermediate, 0.5 parts by weight of the sandstone swelling inhibitor, 0.3 parts by weight of the sandstone wetting agent, 5 parts by weight of the stabilizer, 1 part by weight of the antifreeze, and 89 parts by weight of deionized water;

[0063] (2) Add the modified silicone intermediate, sandstone swelling inhibitor, rock wetting agent, stabilizer, antifreeze, and deionized water into a reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 60 min to obtain the defoamer for the liquid-carrying end of the loose sandstone gas field. It should be noted that the modified silicone intermediate has strong emulsifying ability and dilution stability, so no secondary emulsifier needs to be added during this process.

[0064] Example 3

[0065] A defoamer for the liquid-carrying end of a loose sandstone gas field, comprising the following components in parts by weight:

[0066]

[0067]

[0068] Among them, the specific preparation process of the modified silicone intermediate is as follows:

[0069] (1) Add the initiator and catalyst into a high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyltrimethyl ammonium chloride. Under the condition of a pressure of 0.2 Mpa and the reactor temperature rising to 60 °C, a ring-opening polymerization reaction occurs, and keep the temperature for 4 h to obtain a single-terminal allyl polyether;

[0070] Among them, the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyltrimethyl ammonium chloride is 1:10:15:0.05. The initiator is a mixture of allyl alcohol and α-olefin sulfonate with a mass ratio of 1:0.1, and the catalyst is sodium hydroxide, with a dosage of 0.5% of the total mass of all materials;

[0071] (2) Add low-hydrogen silicone oil and monoallyl polyether to the synthesis reactor according to a mass ratio of 1:1.6, stir at a stirring speed of 100 r / min for 5 min to ensure uniform mixing of the raw materials, heat up to 60 °C, and evacuate under a vacuum of 700 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture, unreacted ethylene oxide, epichlorohydrin in monoallyl polyether, and light hydrocarbon components in silicone oil, etc.). Heat up to 80 °C and then add the noble metal catalyst. After the induction period, the reaction generates heat, heat up to 95 °C, and maintain the reaction at 95 °C for 4 h. Take samples and determine the reaction end point by measuring the residual amount of Si-H groups through infrared spectroscopy. After cooling to normal pressure and room temperature, polyether-modified silicone oil is obtained, and the low-hydrogen silicone oil reacts completely without precipitation;

[0072] Among them, the hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:1, and the dosage of the noble metal catalyst is 0.2% of the total mass of all materials;

[0073] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles to the synthesis reactor according to a mass ratio of 1:0.5:0.1:0.01, stir at a stirring speed of 100 r / min for 30 min to ensure uniform mixing of the raw materials, heat up to 100 °C, and evacuate under a vacuum of 700 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture and light hydrocarbon components in polydimethylsiloxane). After cooling to normal pressure and room temperature, a modified silicone intermediate is obtained.

[0074] Among them, the salt-resistant emulsifier is a composite emulsifier prepared from sorbitan trioleate (Span85), sorbitan monostearate (Span60), and polyoxyethylene sorbitan monostearate (Tween60) with a mass ratio of 0.2:0.8:0.1. The fumed nano-silica particles are nano-silica powder-like solids containing partial hydroxyl structures, with a specific surface area of 200 - 300 m 2 / g, a hydrophobicity of 40 - 60, the manufacturer is Wacker Chemical, model: N23. The sandstone swelling inhibitor is a mixed sandstone swelling inhibitor composed of allyltrimethylammonium chloride and (2-hydroxyethyl)trimethylammonium chloride with a mass ratio of 1:2. The sandstone wetting agent is alkylphenol polyoxyethylene ether. The stabilizer is sodium carboxymethylcellulose. The antifreeze agent is ethanol.

[0075] The preparation method of the defoamer for the liquid-carrying end of a loose sandstone gas field includes the following steps:

[0076] (1) Weigh 50 parts by weight of the modified organosilicon intermediate, 0.1 part by weight of the sandstone swelling inhibitor, 0.5 part by weight of the sandstone wetting agent, 4 parts by weight of the stabilizer, 15 parts by weight of the antifreeze, and 29 parts by weight of deionized water;

[0077] (2) Add the modified organosilicon intermediate, the sandstone swelling inhibitor, the rock wetting agent, the stabilizer, the antifreeze, and the deionized water into a reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 30 min to obtain an antifoaming agent for the liquid-carrying end of a loose sandstone gas field. It should be noted that the modified organosilicon intermediate has strong emulsifying ability and dilution stability, so there is no need to add an emulsifier twice during this process.

[0078] Example 4

[0079] An antifoaming agent for the liquid-carrying end of a loose sandstone gas field, comprising the following components by weight:

[0080]

[0081] Among them, the specific preparation process of the modified organosilicon intermediate is as follows:

[0082] (1) Add the initiator and the catalyst into a high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyltrimethylammonium chloride. Under the condition of a pressure of 0.3 Mpa and the reactor temperature rising to 70 °C, a ring-opening polymerization reaction occurs, and keep the temperature for 3.5 h to obtain a mono-end allyl polyether;

[0083] Among them, the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyltrimethylammonium chloride is 1:5:8:0.04. The initiator is a mixture of allyl alcohol and α-olefin sulfonate with a mass ratio of 1:0.7, and the catalyst is sodium hydroxide, and the dosage is 0.4% of the total mass of all materials;

[0084] (2) Add the low-hydrogen silicone oil and the mono-end allyl polyether into the synthesis reactor according to a mass ratio of 1:1.2, stir at a stirring speed of 90 r / min for 15 min to ensure uniform mixing of the raw materials, heat up to 75 °C, and evacuate under a vacuum degree of 850 Pa for 1 h to remove low-boiling substances (the low-boiling substances mainly include moisture, unreacted ethylene oxide and epichlorohydrin in the mono-end allyl polyether, and light hydrocarbon components in the silicone oil, etc.). Then heat up to 85 °C and add the noble metal catalyst. After the induction period, the reaction generates heat, heat up to 100 °C, and keep the reaction at 100 °C for 4 h. Take a sample and determine the reaction end point by measuring the residual amount of Si-H groups through infrared spectroscopy. After cooling to normal pressure and room temperature, obtain a polyether-modified silicone oil, and the low-hydrogen silicone oil completely reacts without precipitation;

[0085] Among them, the hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:3, and the dosage of the noble metal catalyst is 0.2% of the total mass of all materials.

[0086] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles into the synthesis reactor according to the mass ratio of 1:0.8:0.15:0.015, stir at a stirring speed of 90 r / min for 45 min to ensure uniform mixing of raw materials, heat up to 105 °C, and evacuate under a vacuum of 850 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture and light hydrocarbon components in polydimethylsiloxane). After returning to normal pressure and room temperature, a modified silicone intermediate is obtained.

[0087] Among them, the salt-resistant emulsifier is a composite emulsifier prepared from sorbitan monooleate (Span80) and polyoxyethylene sorbitan trioleate (Tween85) with a mass ratio of 1:0.7. The fumed nano-silica particles are nano-silica powder solid containing partial hydroxyl structures, with a specific surface area of 200 - 300 m 2 / g, a hydrophobicity of 40 - 60, the manufacturer is Wacker Chemie, model: N23. The sandstone swelling inhibitor is (2-hydroxyethyl) trimethyl ammonium chloride. The sandstone wetting agent is a mixed sandstone wetting agent composed of alkyl polyglycoside and sodium lauryl polyoxyethylene ether sulfate with a mass ratio of 1:5. The stabilizer is a mixed stabilizer composed of sodium carboxymethyl cellulose and starch grafted modified polyacrylamide with a mass ratio of 1:1. The antifreeze agent is glycerol monomethyl ether.

[0088] The preparation method of the defoamer for the liquid-carrying end of a loose sandstone gas field includes the following steps:

[0089] (1) Weigh 35 parts by weight of the modified silicone intermediate, 0.3 parts by weight of the sandstone swelling inhibitor, 0.1 parts by weight of the sandstone wetting agent, 0.1 parts by weight of the stabilizer, 10 parts by weight of the antifreeze agent, and 55 parts by weight of deionized water;

[0090] (2) Add the modified silicone intermediate, sandstone swelling inhibitor, rock wetting agent, stabilizer, antifreeze agent, and deionized water into the reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 45 min to obtain a defoamer for the liquid-carrying end of a loose sandstone gas field. It should be noted that the modified silicone intermediate has strong emulsifying ability and dilution stability, so no secondary emulsifier needs to be added during this process.

[0091] Example 5

[0092] A defoamer for the liquid-carrying end of a loose sandstone gas field, comprising the following components in parts by weight:

[0093]

[0094]

[0095] Among them, the specific preparation process of the modified silicone intermediate is as follows:

[0096] (1) Add an initiator and a catalyst into a high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyltrimethylammonium chloride. Under the conditions of a pressure of 0.2 Mpa and the reactor temperature rising to 95 °C, ring-opening polymerization reaction occurs, and keep the temperature for 2 h to obtain a mono-terminal allyl polyether;

[0097] Among them, the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyltrimethylammonium chloride is 1:4:13:0.01. The initiator is a mixture of allyl alcohol and α-olefin sulfonate with a mass ratio of 1:0.7. The catalyst is sodium hydroxide, and the dosage is 0.4% of the total mass of all materials;

[0098] (2) Add low-hydrogen silicone oil and mono-terminal allyl polyether into a synthesis reactor according to a mass ratio of 1:1.1, stir at a stirring speed of 100 r / min for 10 min to ensure uniform mixing of the raw materials, heat up to 80 °C, and evacuate under a vacuum degree of 900 Pa for 1 h to remove low-boiling substances (the low-boiling substances mainly include moisture, unreacted ethylene oxide and epichlorohydrin in the mono-terminal allyl polyether, and light hydrocarbon components in the silicone oil, etc.). Then heat up to 90 °C and add a noble metal catalyst. After the induction period, the reaction generates heat, heat up to 105 °C, and keep the reaction at 105 °C for 4 h. Take a sample and determine the reaction end point by measuring the residual amount of Si-H groups through infrared spectroscopy. After cooling to normal pressure and room temperature, polyether-modified silicone oil is obtained, and the low-hydrogen silicone oil reacts completely without precipitation;

[0099] The hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:4, and the dosage of the noble metal catalyst is 0.1% of the total mass of all materials;

[0100] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles into a synthesis reactor according to a mass ratio of 1:0.7:0.25:0.02, stir at a stirring speed of 100 r / min for 35 min to ensure uniform mixing of the raw materials, heat up to 120 °C, and evacuate under a vacuum degree of 900 Pa for 1 h to remove low-boiling substances (the low-boiling substances mainly include moisture and light hydrocarbon components in the polydimethylsiloxane). After cooling to normal pressure and room temperature, a modified silicone intermediate is obtained.

[0101] The salt-tolerant emulsifier is a composite emulsifier prepared from sorbitan monostearate (Span60) and polyoxyethylene sorbitan monolaurate (Tween20) with a mass ratio of 1:0.5. The fumed nano-silica particles are nano-silica powdery solids containing partial hydroxyl structures, with a specific surface area of 200 - 300 m 2 / g, a hydrophobicity of 40 - 60, manufactured by Wacker Chemie, model: N23. The sandstone swelling inhibitor is (2-hydroxyethyl) trimethyl ammonium chloride. The sandstone wetting agent is sodium lauryl polyoxyethylene ether sulfate. The stabilizer is anionic hydrophobically modified polyacrylic acid. The antifreeze is ethylene glycol monobutyl ether.

[0102] The preparation method of the defoamer for the liquid-carrying end of a loose sandstone gas field is as follows:

[0103] (1) Weigh 45 parts by weight of the modified silicone intermediate, 0.2 parts by weight of the sandstone swelling inhibitor, 0.4 parts by weight of the sandstone wetting agent, 0.8 parts by weight of the stabilizer, 4 parts by weight of the antifreeze, and 51 parts by weight of deionized water;

[0104] (2) Add the modified silicone intermediate, the sandstone swelling inhibitor, the rock wetting agent, the stabilizer, the antifreeze, and deionized water into a reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 50 min to obtain the defoamer for the liquid-carrying end of a loose sandstone gas field. It should be noted that the modified silicone intermediate has strong emulsifying ability and dilution stability, so no secondary addition of emulsifier is required during this process.

[0105] Example 6

[0106] A defoamer for the liquid-carrying end of a loose sandstone gas field, comprising the following components in parts by weight:

[0107]

[0108] Among them, the specific preparation process of the modified silicone intermediate is as follows:

[0109] (1) Add the initiator and catalyst into a high-pressure reactor, and then sequentially add propylene oxide, ethylene oxide, and allyl trimethyl ammonium chloride. Under the condition of a pressure of 0.3 Mpa and the reactor temperature rising to 90 °C, an ring-opening polymerization reaction occurs, and keep the temperature for 5 h to obtain a mono-terminal allyl polyether;

[0110] Among them, the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyl trimethyl ammonium chloride is 1:6:8:0.04. The initiator is a mixture of allyl alcohol and α-olefin sulfonate with a mass ratio of 1:0.5. The catalyst is potassium hydroxide, and the dosage is 0.3% of the total mass of all materials;

[0111] (2) Add low-hydrogen silicone oil and allyl-terminated polyether to the synthesis reactor according to a mass ratio of 1:1.5, stir for 20 min at a stirring speed of 100 r / min to ensure uniform mixing of the raw materials, heat up to 75 °C, and evacuate under a vacuum of 900 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture, unreacted ethylene oxide, epichlorohydrin in allyl-terminated polyether, and light hydrocarbon components in silicone oil, etc.), heat up to 90 °C and then add the noble metal catalyst. After the induction period, the reaction generates heat, heat up to 100 °C, and keep reacting at 100 °C for 4 h. Take a sample and determine the reaction end point by measuring the residual amount of Si-H groups through infrared spectroscopy. After cooling to normal pressure and room temperature, polyether-modified silicone oil is obtained, and the low-hydrogen silicone oil reacts completely without precipitation;

[0112] The hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:9, and the dosage of the noble metal catalyst is 0.25% of the total mass of all materials;

[0113] (3) Add polyether-modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles to the synthesis reactor according to a mass ratio of 1:0.7:0.3:0.03, stir for 45 min at a stirring speed of 100 r / min to ensure uniform mixing of the raw materials, heat up to 110 °C, and evacuate under a vacuum of 900 Pa for 1 h to remove low-boiling substances (low-boiling substances mainly include moisture and light hydrocarbon components in polydimethylsiloxane). After cooling to normal pressure and room temperature, a modified silicone intermediate is obtained.

[0114] The salt-resistant emulsifier is a composite emulsifier prepared from sorbitan trioleate (Span85) and polyoxyethylene sorbitan monopalmitate (Tween40) with a mass ratio of 1:1. The fumed nano-silica particles are nano-silica powder-like solids containing partial hydroxyl structures, with a specific surface area of 200 - 300 m 2 / g, a hydrophobicity of 40 - 60, the manufacturer is Wacker Chemie, model: N23. The sandstone swelling inhibitor is (2-hydroxyethyl) trimethyl ammonium chloride. The sandstone wetting agent is alkylphenol polyoxyethylene ether. The stabilizer is an anionic hydrophobically modified polyacrylic acid. The antifreeze agent is ethylene glycol.

[0115] The preparation method of the defoamer for the liquid-carrying end of loose sandstone gas fields includes the following steps:

[0116] (1) Weigh 40 parts by weight of the modified silicone intermediate, 0.2 parts by weight of the sandstone swelling inhibitor, 0.3 parts by weight of the sandstone wetting agent, 3 parts by weight of the stabilizer, 10 parts by weight of the antifreeze agent, and 50 parts by weight of deionized water;

[0117] (2) Add the modified silicone intermediate, sand swelling inhibitor, rock wetting agent, stabilizer, antifreeze agent and deionized water into a reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 55 min to obtain an antifoaming agent for the liquid-carrying end of a loose sandstone gas field. It should be noted that the modified silicone intermediate has strong emulsifying ability and dilution stability, so there is no need to add an emulsifier twice during this process.

[0118] Performance test method for the antifoaming agent for the liquid-carrying end of a loose sandstone gas field:

[0119] Preparation of the foaming liquid: Use the betaine-type foaming agent used on site, and prepare 0.4 wt% with the high salinity brine of the on-site gas reservoir as the foaming liquid for standby.

[0120] Preparation of 10 wt% antifoaming agent dilution: Dilute the antifoaming agent to 10 wt% with deionized water.

[0121] (1) Foam-breaking time

[0122] Measure 100 ml of the prepared foaming agent solution with a measuring cylinder and pour it into a 500 ml measuring cylinder. Use a syringe with a needle to suck 3 ml of the 10 wt% antifoaming agent dilution for standby; connect the elbow quartz sand dispersion head, put the dispersion head into the measuring cylinder, and pass in 0.1 m 3 / h of gas until the fine foam reaches the 500 ml scale, then stop passing in the gas, quickly take out the quartz sand dispersion head, immediately spray the 3 ml of antifoaming agent in the syringe quickly and evenly (spray it out within 3 seconds) on the 500 ml of foam, and at the same time press the stopwatch to observe the time required for the foam to completely break (looking down from the mouth of the measuring cylinder, the liquid surface can be seen), which is the foam-breaking time.

[0123] (2) Foam suppression time

[0124] Measure 100 ml of the prepared foaming agent solution with a measuring cylinder and pour it into a 500 ml measuring cylinder. Use a syringe to suck 3 ml of the prepared antifoaming agent dilution and add it to the measuring cylinder. Connect the straight quartz sand dispersion head, insert the dispersion head into the porous rubber stopper, put it into the measuring cylinder, and pass in 0.3 m 3 / h of gas and press the stopwatch at the same time to observe the time required for the foam to reach the 500 ml scale, which is the foam suppression time. If the foam has not reached 500 ml after 60 min, the experiment can be terminated and it is determined that the foam suppression performance of the antifoaming agent meets the standard.

[0125] (3) Defoaming rate

[0126] Weigh 3 g of on-site argillaceous sandstone into a stirring cup, and then weigh 100 mL of the prepared foaming liquid into the stirring cup to obtain a foaming liquid sample with a sand content of 3%. Fix the stirring cup on a high-speed stirrer and stir at a speed of 12,000 r / min for 3 min. Immediately pour it into a 500 mL measuring cylinder after taking it down, and record the foam volume V1 in the measuring cylinder.

[0127] Configure the foaming liquid sample with a sand content of 3% in the same way, stir it at a speed of 12,000 r / min for 3 min, remove the stirring cup, add 0.4 mL of the undiluted defoaming agent to the stirred foam, fix the stirring cup on the high-speed stirrer, and stir it at a speed of 12,000 r / min for 1 min. Immediately pour it into a 500 mL graduated cylinder after removing, press the stopwatch, and record the volume V2 of the foam in the graduated cylinder when it stands still for 1 min.

[0128] Calculation of defoaming rate: D = (V1 - V2) × 100 / V1

[0129] In the formula: D - defoaming rate, %

[0130] V1 - volume of the foaming liquid foam, mL

[0131] V2 - volume of the foam after standing still for 1 min after adding the defoaming agent and stirring, mL (4) Dilution stability in gas reservoir water

[0132] Measure 10 mL of the defoaming agent into a 100 mL stoppered test tube, add 90 mL of the high salinity brine from the on-site gas reservoir, cover the bottle cap, invert the test tube up and down 20 times, shake well, let it stand at room temperature for 24 h, and record the volume of the supernatant liquid separated out.

[0133]

[0134]

[0135] Figure 2 For Example 1 as the defoaming agent, the laboratory effect photos before defoaming - after defoaming - foam suppression. As can be seen from the pictures, Example 1 has good defoaming and foam suppression performance for the betaine-based foaming agent used on-site in high salinity brine, with a fast defoaming time and a long foam suppression time.

[0136] Figure 3 For Example 1 and Comparative Examples 1 - 2 as defoaming agents in the defoaming rate test, the experimental photos before and after adding the defoaming agent. For the dense foam containing sediment formed under high-speed conditions, at a concentration of 0.4 wt%, the defoaming rate of Example 1 reaches 100%, and there is no residual foam on the liquid surface after defoaming. While under the same conditions, the defoaming rates of the foreign samples in Comparative Examples 1 and 2 are only 88.26% and 92.18%, respectively, and there are more residual foams on the liquid surface after defoaming.

[0137] Figure 4For the dilution stability experiments of Examples 1 to 6 and Comparative Examples 1 to 2 as defoamers in high salinity field gas reservoir water in the dilution stability experiment. Examples 1 to 6 have good dilution stability in the field high salinity gas reservoir water. The 10% diluted aqueous solution is left standing at room temperature and normal pressure for 24 hours without stratification, precipitation, or floating substances, and the solution remains a homogeneous emulsion. The 10% diluted aqueous solutions of Comparative Examples 1 to 2 have poor emulsion stability under the same conditions. Stratification occurs in the solution after 0.5 hours, and the stratification reaches equilibrium after 24 hours. It can be seen that the concentration of the oil phase defoaming component in the lower layer solution becomes significantly smaller, and the stratification phenomenon will greatly affect the on-site use effect of the defoamer.

[0138] Figure 5 They are the appearance photos of the products of Examples 1 to 6 and Comparative Examples 1 to 2.

[0139] Figure 6 They are the photos of the defoaming process in the sewage pool at the end of the gas reservoir water when Example 1 is used as a defoamer in the field of the liquid-carrying end of a loose sandstone gas field. As can be seen from the figure, when the defoamer is continuously added at a concentration of 0.4% of the gathering and transportation liquid volume, after 6 hours of defoaming, at the end of the gas reservoir water, 5000 m 3 The area of dry foam containing sediment on the sewage pool liquid surface is significantly reduced. After 24 hours of defoaming, all the dry foam containing sediment on the sewage pool liquid surface disappears.

[0140] In summary, the defoamer prepared for the liquid-carrying end of the loose sandstone gas field of the present invention has good defoaming and foam inhibition performance; under the harsh conditions of high-speed stirring with sand-containing liquid, the defoaming performance remains stable; the dilution stability of the product evaluated with field gas reservoir high salinity brine is good, and it can achieve the purpose of quickly defoaming at the liquid-carrying end of the foam drainage operation in the loose sandstone gas field.

[0141] The above content is a further detailed description of the present invention in combination with specific preferred embodiments, and it cannot be determined that the specific implementation of the present invention is limited to these descriptions. For those of ordinary skill in the art to which the present invention pertains, without departing from the concept of the present invention, several simple deductions or substitutions can be made, and all should be regarded as belonging to the protection scope of the present invention.

Claims

1. An antifoaming agent for the liquid-carrying end of a loose sandstone gas field, characterized in that, Composed of the following components in parts by weight: The modified silicone intermediate is a polyether-modified silicone oil synthesized by using a monoallyl polyether with a mixture of allyl alcohol and sodium α-olefin sulfonate as the initiator and low-hydrogen silicone oil under the conditions of high temperature, negative pressure and high-speed stirring. Then, the polyether-modified silicone oil, polydimethylsiloxane, salt-tolerant emulsifier and fumed nano-silica particles are dehydrated and low-boiling components are removed under reduced pressure and heating to obtain the modified silicone intermediate.

2. The defoamer for the liquid-carrying end of a loose sandstone gas field according to claim 1, wherein The specific preparation process of the modified silicone intermediate is as follows: (1) Add the initiator and catalyst into a high-pressure reaction kettle, and then sequentially add propylene oxide, ethylene oxide, and allyl trimethyl ammonium chloride. Under the conditions of a pressure of 0.2 - 0.3 Mpa and the reaction kettle being heated to 60 - 100 °C, ring-opening polymerization reaction occurs, and keep warm for 2 - 5 h to obtain monoallyl polyether. (2) Add low-hydrogen silicone oil and monoallyl polyether into the synthesis reaction kettle according to a mass ratio of 1:(1 - 1.6), stir for 5 - 30 min, heat up to 60 - 80 °C, evacuate for 1 h under a vacuum degree of 700 - 900 Pa, then add the noble metal catalyst when heating up to 80 - 90 °C. After the induction period reaction generates heat, heat up to 95 - 115 °C, keep reacting at 95 - 115 °C for 4 h, take a sample and measure the residual amount of Si-H groups to determine the reaction end point. After reducing to normal pressure and room temperature, obtain the polyether-modified silicone oil. (3) Add the polyether-modified silicone oil, polydimethylsiloxane, salt-tolerant emulsifier and fumed nano-silica particles into the synthesis reaction kettle according to a mass ratio of 1:(0.5 - 1):(0.1 - 0.3):(0.01 - 0.03), stir for 30 - 60 min to ensure uniform mixing of raw materials, heat up to 100 - 120 °C, evacuate for 1 h under a vacuum degree of 700 - 900 Pa, and after reducing to normal pressure and room temperature, obtain the modified silicone intermediate.

3. The defoamer for the liquid-carrying end of a loose sandstone gas field according to claim 2, wherein: In step (1), the mass ratio of the initiator, propylene oxide, ethylene oxide, and allyl trimethyl ammonium chloride is 1:(3 - 10):(5 - 15):(0.01 - 0.05), the initiator is a mixture of allyl alcohol and sodium α-olefin sulfonate with a mass ratio of 1:(0.1 - 1), and the catalyst is sodium hydroxide or potassium hydroxide.

4. The defoamer for the liquid-carrying end of a loose sandstone gas field according to claim 2, wherein: In step (2), the hydrogen content of the low-hydrogen silicone oil is 0.1% - 0.2%, and the viscosity is 150 - 300 cst; the noble metal catalyst is a mixed solution prepared from chloroplatinic acid and isopropanol with a mass ratio of 1:(1 - 10).

5. The defoamer for the liquid-carrying end of a loose sandstone gas field according to claim 2, wherein: In step (3), the salt-tolerant emulsifier is a composite emulsifier prepared from Span emulsifier and Tween emulsifier with a mass ratio of 1:(0.1 - 1). The Span emulsifier is a mixture composed of one or any several of sorbitan monolaurate, sorbitan monopalmitate, sorbitan monostearate, sorbitan monooleate, and sorbitan trioleate in any proportion; the Tween emulsifier is a mixture composed of one or any several of polyoxyethylene sorbitan monolaurate, polyoxyethylene sorbitan monopalmitate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monooleate, and polyoxyethylene sorbitan trioleate in any proportion; the gas-phase nano-silica particles are nano-silica powder-like solids containing partial hydroxyl structures, with a specific surface area of 200 - 300m 2 / g and a hydrophobicity of 40 - 60.

6. The defoamer for the liquid-carrying end of a loose sandstone gas field according to claim 1, wherein: The sandstone swelling inhibitor is a mixture composed of one or any several of allyl trimethyl ammonium chloride, allyl benzyl dimethyl ammonium chloride, and (2-hydroxyethyl) trimethyl ammonium chloride in any proportion.

7. The defoamer for the liquid-carrying end of a loose sandstone gas field according to claim 1, wherein: The sandstone wetting agent is a mixture composed of one or any several of alkyl glycoside, alkylphenol polyoxyethylene ether, and sodium fatty alcohol polyoxyethylene ether sulfate in any proportion.

8. The antifoaming agent for the liquid-carrying end of a loose sandstone gas field according to claim 1, wherein: The stabilizer is a mixture composed of one or any several of anionic hydrophobically modified polyacrylic acid, sodium carboxymethyl cellulose, and starch graft modified polyacrylamide in any proportion; the antifreeze is a mixture composed of one or any several of methanol, ethanol, ethylene glycol, glycerol, ethylene glycol monobutyl ether, and glycerol monomethyl ether in any proportion.

9. A preparation method of an antifoaming agent for the liquid-carrying end of a loose sandstone gas field, characterized in that, It includes the following steps: (1) Weigh 10 - 50 parts by weight of the modified silicone intermediate, 0.1 - 0.5 parts by weight of the sandstone swelling inhibitor, 0.1 - 0.5 parts by weight of the sandstone wetting agent, 0.1 - 5 parts by weight of the stabilizer, 1 - 15 parts by weight of the antifreeze, and 29 - 89 parts by weight of deionized water; The modified silicone intermediate is a polyether modified silicone oil synthesized by using a monoallyl polyether with a mixture of allyl alcohol and sodium α-olefin sulfonate as the initiator and low hydrogen silicone oil under the conditions of high temperature, negative pressure, and high-speed stirring. Then, the polyether modified silicone oil, polydimethylsiloxane, salt-resistant emulsifier, and fumed nano-silica particles are dehydrated and de-low-boiling components under reduced pressure and heating to obtain the modified silicone intermediate; (2) Add the modified silicone intermediate, sandstone swelling inhibitor, rock wetting agent, stabilizer, antifreeze, and deionized water into a reactor, and carry out a stirring and emulsifying reaction at normal temperature and pressure for 30 - 60 min to obtain an antifoaming agent for the liquid-carrying end of a loose sandstone gas field.

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