A high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations, and its preparation method and application

Abstract

The present invention provides a high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations, as well as its preparation method and application. The preparation method comprises the following steps: mixing an anhydride monomer and an aromatic phenol polyoxyethylene ether compound, stirring until dissolved, heating to the reaction temperature, adding catalyst A under nitrogen protection, and reacting to obtain a monoester polymer; mixing a monoester polymer, a hydroxyl-containing monomer, and a benzene ring-containing vinyl monomer, stirring until dissolved, heating to the reaction temperature, adding catalyst B and an initiator under nitrogen protection, and reacting to obtain a diester polymer; adding the diester polymer to water, adding a sulfonated compound, heating to the reaction temperature, adding catalyst C under nitrogen protection, and reacting to obtain. Compared with conventional foaming agents, the foaming agent of the present invention has better foaming ability, can maintain stable foaming ability under complex formation conditions, and has excellent temperature and salt resistance.

Description

Technical Field

[0001] The invention relates to a high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations, a preparation method and application thereof, and belongs to the field of oilfield additives for drilling. Background Art

[0002] Geothermal energy is thermal energy stored in the Earth's crust. Originating from the Earth's center, geothermal heat is the energy released during the decay and formation of naturally occurring radioactive isotopes (uranium, thorium, and potassium) trapped in magma during Earth's formation. This energy is typically transferred by heating rocks and fluids within their cracks and pores. In recent years, with the rapid growth of global energy demand and the rapid development of new energy industries, the development and utilization of geothermal energy has gradually come into focus, with many countries beginning to use geothermal energy for power generation and heating. Geothermal energy is a clean, pollution-free energy source with abundant reserves. In some countries with abundant geothermal resources, geothermal energy has become an important alternative to conventional energy sources such as coal and oil. Its green, renewable nature meets the requirements of sustainable development and offers significant potential for development. The key technology for geothermal development is geothermal drilling. High-temperature geothermal drilling is costly, risky, and involves significant uncertainty. Furthermore, complex formations make drilling extremely difficult. First, the geothermal reservoirs are characterized by well-developed fractures and low formation pressure, making the use of water-based and oil-based drilling fluids prone to fluid loss. Downhole losses can also lead to serious rock-carrying difficulties, causing a series of complex downhole accidents such as stuck and buried drill bits. This can extend drilling cycles and increase geothermal development costs, with serious consequences that can even result in the abandonment of the wellbore. Second, the hot rock mass of the wellbore wall can be thermally fractured when exposed to water, causing wellbore collapse and stuck drill bits.

[0003] To address the challenges of geothermal drilling, researchers both domestically and internationally have introduced foam drilling fluid technology. Compared to water-based and oil-based drilling fluids, foam drilling fluids offer several advantages: low density and lower hydrostatic pressure. Furthermore, foam drilling fluids are a gas-liquid mixture composed of a series of tightly packed, fine bubbles. Compared to water-based and oil-based drilling fluids, foam fluids exhibit higher dynamic shear force and greater viscosity, resulting in superior rock-carrying capacity. Consequently, foam drilling fluids have become the preferred drilling fluid for geothermal wells.

[0004] While much research has been conducted on foam drilling fluids for drilling, this research primarily focuses on their application in conventional oil and gas drilling. Research on their application in geothermal drilling is limited. Foam is a thermodynamically and kinetically unstable system, and in the high-temperature environment of geothermal wells, the foaming agent in the foam drilling fluid is susceptible to thermal degradation and failure due to temperature fluctuations. To address these issues, Chinese patent document CN104109520A develops a foaming agent suitable for formation temperatures of 95°C and salt contents of 100,000 to 150,000 mg / L. This foaming agent is primarily composed of 50-70 wt% alkyl sulfonate, 10-15 wt% alkylamine oxide, and distilled water. At 95°C, the maximum foaming volume of the foaming agent is 960 mL, but the foaming agent has a short half-life of less than 10 minutes. Chinese patent document CN112707941A develops an improved biodegradable zwitterionic foaming agent based on alkyl glycoside. The foaming agent is prepared using long-chain alkyl glycoside as a raw material through a series of steps including anhydride esterification and diamine salt formation. The maximum foaming volume of the foaming agent is 630 mL and the foam half-life is 132 minutes. However, the foaming agent does not consider the effect of temperature on the foaming ability of the foaming agent, and its temperature resistance is poor.

[0005] Although a variety of foam stabilizing substances have been developed at home and abroad, such as polyacrylamide, hydroxyethyl cellulose, hydroxymethyl cellulose and non-ionic surfactants, there are a large number of high-valent cations in geothermal wells, such as Ca 2+ These factors can destroy the structural viscosity and surface activity of the foaming agent. When a certain temperature is reached, these foaming agents completely thermally degrade. Therefore, to address the instability of foams in high-temperature, high-pressure formations, there is an urgent need to develop high-temperature and high-salt-resistant foaming and foam stabilizers suitable for geothermal wells. Summary of the Invention

[0006] In response to the deficiencies of the prior art, especially the degradation and failure of foaming agents in high-temperature geothermal formations, the present invention provides a high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations, and its preparation method and application. The present invention adopts a free radical polymerization method to obtain a temperature-resistant and salt-resistant amphoteric surfactant foaming agent. The foaming agent molecular chain contains a rigid benzene ring, which enhances the rigidity of the molecular chain and is beneficial to improving the high-temperature stability of the foaming agent. The sulfonic acid group in the molecule is a strong hydrophilic group with a high degree of water solubility, and at the same time, the foaming agent has good salt resistance. Compared with conventional foaming agents, the foaming agent of the present invention has better foaming ability, can maintain stable foaming ability under complex formation conditions, and has excellent temperature and salt resistance.

[0007] The technical solutions of the present invention are as follows:

[0008] A method for preparing a high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations comprises the following steps:

[0009] (1) mixing an anhydride monomer and an aromatic phenol polyoxyethylene ether compound, stirring until dissolved, heating to a reaction temperature, adding a catalyst A under nitrogen protection, and reacting to obtain a monoester polymer;

[0010] (2) mixing the monoester polymer obtained in step (1), the hydroxyl-containing monomer, and the benzene ring-containing vinyl monomer, stirring until dissolved, heating to the reaction temperature, adding catalyst B and initiator under nitrogen protection, and reacting to obtain a diester polymer;

[0011] (3) adding the diester polymer obtained in step (2) into water, adding the sulfonated compound and heating to the reaction temperature, adding the catalyst C under nitrogen protection, and reacting to obtain a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations.

[0012] According to the present invention, preferably, the anhydride monomer in step (1) is cyclobutanetetracarboxylic dianhydride, (±)-1,8,8-trimethyl-3-oxabicyclo[3.2.1]octane-2,4-dione ((±)-camphoric anhydride) or maleic anhydride.

[0013] According to the present invention, preferably, the aromatic phenol polyoxyethylene ether compound in step (1) is 2-naphthol polyoxyethylene ether, tristyrylphenol polyoxyethylene ether or distyrylphenol polyoxyethylene ether; the general formulas of the 2-naphthol polyoxyethylene ether, tristyrylphenol polyoxyethylene ether and distyrylphenol polyoxyethylene ether are shown in Formula I, Formula II and Formula III, respectively.

[0014]

[0015] In Formula I, m is an integer of 1-10; in Formula II, n is an integer of 1-30; and in Formula III, x is an integer of 1-20.

[0016] According to the present invention, preferably, the molar ratio of the anhydride monomer to the aromatic phenol polyoxyethylene ether compound in step (1) is 1-4:1, more preferably 2-3:1.

[0017] According to the preferred embodiment of the present invention, the catalyst A in step (1) is concentrated sulfuric acid, aminosulfonic acid or p-toluenesulfonic acid; the mass fraction of the concentrated sulfuric acid is 98%; the mass of the catalyst A is 1-5% of the total mass of the anhydride monomer and the aromatic phenol polyoxyethylene ether compound.

[0018] According to the preferred embodiment of the present invention, the reaction temperature in step (1) is 80-110° C., more preferably 90-100° C.; and the reaction time is 2-5 h.

[0019] According to a preferred embodiment of the present invention, after the reaction in step (1) is completed, a post-treatment step is further included, specifically as follows: the reaction product is washed with anhydrous ethanol, filtered, and the obtained solid is vacuum-dried at 40-60° C. for 4-12 hours to obtain a monoester polymer.

[0020] According to the present invention, preferably, the hydroxyl-containing monomer in step (2) is lactic acid, glucose or ethylene glycol; the molar ratio of the hydroxyl-containing monomer to the monoester polymer is 1:2-2.5, more preferably 1:2.2.

[0021] According to the present invention, preferably, the benzene ring-containing vinyl monomer in step (2) is p-divinylbenzene, m-divinylbenzene, 1,3-diisopropenylbenzene or 1,4-diisopropenylbenzene; and the molar ratio of the benzene ring-containing vinyl monomer to the hydroxyl-containing monomer is 1-1.2:1, more preferably 1.1:1.

[0022] According to the present invention, preferably, the catalyst B in step (2) is dinonylnaphthalene disulfonic acid, dinonylnaphthalene sulfonic acid or p-toluenesulfonic acid; the mass of the catalyst B is 1-4% of the total mass of the monoester polymer, hydroxyl-containing monomer and benzene ring-containing vinyl monomer.

[0023] According to the preferred embodiment of the present invention, the initiator in step (2) is one of potassium persulfate, sodium persulfate and ammonium persulfate; the mass of the initiator is 0.5-4% of the total mass of the monoester polymer, the hydroxyl-containing monomer and the benzene ring-containing vinyl monomer.

[0024] According to the preferred embodiment of the present invention, the reaction temperature in step (2) is 120-150° C., more preferably 130-140° C.; and the reaction time is 4-6 h.

[0025] According to a preferred embodiment of the present invention, in step (2), after the reaction is completed, a post-treatment step is further included: the reaction product is washed with anhydrous ethanol, filtered, and the obtained solid is vacuum-dried at 40-60° C. for 4-12 hours to obtain a diester polymer.

[0026] According to the preferred embodiment of the present invention, the ratio of the volume of water to the mass of the diester polymer in step (3) is 10-50 mL:1 g.

[0027] According to the present invention, preferably, the sulfonated compound in step (3) is sulfite; further preferably, the sulfonated compound is sodium bisulfite, sodium sulfite or sodium metabisulfite; the mass ratio of the sulfonated compound to the diester polymer is 2-4:1.

[0028] According to the preferred embodiment of the present invention, the catalyst C in step (3) is thionyl chloride, chlorosulfonic acid or sulfuryl chloride; the mass of the catalyst C is 2-6% of the total mass of the diester polymer and the sulfonated compound.

[0029] According to the preferred embodiment of the present invention, the reaction temperature in step (3) is 80-100° C., more preferably 90-95° C.; and the reaction time is 4-6 h.

[0030] Preferably, according to the present invention, in step (3), after the reaction is completed, a post-processing step is further included: the reaction product is washed with anhydrous ethanol, filtered, and the obtained solid is vacuum-dried at 40-60°C for 4-12 hours to obtain a high-temperature and high-salt double-cross-linked foaming agent suitable for geothermal formations.

[0031] The present invention also provides a high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations, which is prepared by the above-mentioned preparation method.

[0032] According to the present invention, the above-mentioned high-temperature and high-salt resistant double cross-linked foaming agent suitable for geothermal formations is used in foam drilling fluid; the concentration of the high-temperature and high-salt resistant double cross-linked foaming agent suitable for geothermal formations in the foam drilling fluid is 0.1-3g / L.

[0033] The technical features and beneficial effects of the present invention are as follows:

[0034] 1. The molecular structure of the high-temperature and high-salt resistant double-cross-linked foaming agent of the present invention contains both hydrophilic groups and hydrophobic groups. The hydrophilic groups are connected by hydrogen bonds and covalent bonds of the linking groups. The water solubility of the hydrophilic groups in the foaming agent is not destroyed. Compared with other traditional surfactants, the foaming agent of the present invention has good surface activity, excellent solubilization ability and unique rheological properties, and can maintain good stability under neutral, acidic, alkaline and high-salt conditions.

[0035] 2. The novel high-temperature-resistant and high-salt double-crosslinked foaming agent of the present invention starts with the molecular structure, studies the interaction between the various groups in the molecules, and introduces heat-resistant functional groups (benzene rings) and salt-resistant groups (sulfonic acid groups). First, the benzene ring group can increase the rigidity of the segment and increase the heat resistance of the reaction product. Secondly, the structure contains multiple double bonds that can be cross-linked to each other, increasing the network structure of the segment. The segment is multiply cross-linked to increase the strength and heat resistance of the molecular segment. In addition, multiple effective groups are added, including long-chain polyoxyethylene and polyvalent benzene ring groups in arylphenol polyoxyethylene ether compounds. Polyoxyethylene can provide good salt resistance, and polyvalent benzene ring groups can provide a good amount of heat resistance for cross-linked polymers, thereby improving the foaming performance of surfactants under complex formation conditions (high temperature, high salt), and providing a new idea for geothermal well development.

[0036] 3. The high temperature and high salt resistance double cross-linking of the present invention does not affect the performance of the drilling fluid, and the preparation process is simple, which is convenient for production operations. DETAILED DESCRIPTION

[0037] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only a portion of the embodiments of the present invention, not all of them. The raw materials used in the embodiments are conventional and commercially available; the methods described are based on existing technologies unless otherwise specified. All other examples based on the embodiments of the present invention, improved or modified by those skilled in the art, are within the scope of protection of the present invention.

[0038] The general formula of tristyrylphenol polyoxyethylene ether used in the examples is shown below.

[0039]

[0040] Example 1

[0041] A method for preparing a high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations comprises the following steps:

[0042] (1) 9.8 g (0.1 mol) of maleic anhydride and 64 g (0.05 mol) of tristyrylphenol polyoxyethylene ether were mixed and magnetically stirred at a speed of 1000 r / min until dissolved to obtain a monomer mixed solution X; the monomer mixed solution X was then heated to 95° C., and 1.48 g (2%) of p-toluenesulfonic acid was added dropwise under nitrogen protection at a drop rate of 1 drop / s; after the addition was completed, the mixture was reacted at 95° C. under nitrogen protection for 4 h; the reaction product was then washed with anhydrous ethanol and filtered, and the obtained solid was vacuum dried at 40° C. for 12 h to obtain a monoester polymer (molecular weight 1379.9);

[0043] (2) 30.7 g (0.022 mol) of the monoester polymer obtained in step (1), 0.62 g (0.01 mol) of ethylene glycol and 1.43 g (0.011 mol) of p-divinylbenzene were mixed and magnetically stirred at a speed of 1500 r / min until dissolved to obtain a mixed solution Y, and then the mixed solution Y was heated to 135° C., and 0.66 g (2%) of dinonylnaphthalene disulfonic acid was added dropwise under nitrogen protection at a drop rate of 1 drop / s; after the dropwise addition was completed, 0.32 g (0.0014 mol) of ammonium persulfate was added, and then the mixture was reacted at 135° C. under nitrogen protection for 6 h. After the reaction was completed, the product was washed with 20 mL of anhydrous ethanol and filtered. The obtained solid was placed in a vacuum drying oven and vacuum dried at 60° C. for 12 h to obtain a diester polymer;

[0044] (3) 10 g of the diester polymer obtained in step (2) was added to a three-necked flask containing 100 mL of water, and then 20 g of sodium bisulfite was added and stirred thoroughly to obtain a mixed solution Z. The mixture was then heated to 90° C. and 0.9 g (3%) of thionyl chloride was added dropwise under nitrogen protection at a drop rate of 1 drop / s. After the addition was completed, the mixture was reacted at 90° C. under nitrogen protection for 5 h. After the reaction was completed, the product was washed with 30 mL of anhydrous ethanol and filtered. The obtained solid was placed in a vacuum drying oven and vacuum dried at 50° C. for 12 h to obtain a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations.

[0045] The foaming agent prepared in this example was tested for foaming volume and half-life, and the specific tests were as follows:

[0046] Foaming volume and half-life of foaming agent solution: The foaming agent is evaluated based on the Waring Blender method, an industry standard for foaming agent evaluation. The specific steps are as follows: Add the foaming agent to water to prepare a foaming agent solution with a concentration of 5 g / L. Use a slurry cup to hold 200 mL of the foaming agent solution. Stir continuously for 5 minutes on a high-frequency high-speed stirrer at a stirring speed of 11,000 r / min. After the stirring stops, immediately pour the foam into a glass measuring cylinder. The reading is the foaming volume, and the timer is started. The time it takes to precipitate 100 mL of liquid is the half-life.

[0047] Foaming volume and half-life of foaming agent solution at different temperatures: Add foaming agent to water to prepare a foaming agent solution with a concentration of 5g / L. The foaming agent solution is measured at room temperature (25℃). In addition, four portions of foaming agent solution are placed in a rolling heating furnace at 50℃, 100℃, 150℃, and 200℃ and heated for 6h, respectively. Then, they are taken out and stirred continuously for 5min on a high-frequency high-speed stirrer at a stirring speed of 11000r / min. After stirring stops, the foam is immediately poured into a glass measuring cylinder. The reading is the foaming volume, and the timing is started. The time taken to precipitate 100mL of liquid is the half-life. The volume of the foaming agent solution used for the test is 200mL.

[0048] The foaming volume and half-life of the foaming agent solution under different salinity: the salinity is respectively configured (the salinity is expressed in mg / L or ppm. For example, if one liter of water contains 1000 mg of salt, its salinity is 1000 mg / L, that is, 1000 ppm. The solution is configured using simulated formation water, which contains Na + , Ca 2+ , Mg 2+ Plasma, here Na + , Ca 2+ , Mg 2+ The mass ratio of plasma is equal. For example, one liter of water contains 1000 mg of salt, of which Na + , Ca2+ , Mg 2+ plasma accounted for 333.3 mg) for 1×10 4 , 3×10 4 , 5×10 4 , 7×10 4 and 9×10 4 Add 1g of foaming agent to 200mL of each solution to prepare a foaming agent solution with a concentration of 5g / L. Stir each solution continuously on a high-frequency high-speed stirrer at a stirring speed of 11000r / min for 5 minutes. Immediately after stirring, pour the foam into a glass measuring cylinder. The reading is the foaming volume, and the timer is started. The time it takes to extract 100mL of liquid is the half-life.

[0049] Table 1 Foaming volume and half-life of foaming agent solution at different temperatures

[0050] Temperature / ℃ Foaming volume / mL Half-life / min 25 547 497 50 524 491 100 472 485 150 453 461 200 415 432

[0051] Table 2 Foaming volume and half-life of foaming agent solution at different salinities

[0052] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 526 486 <![CDATA[3×10 4 ]]> 513 472 <![CDATA[5×10 4 ]]> 489 453 <![CDATA[7×10 4 ]]> 439 426 <![CDATA[9×10 4 ]]> 403 412

[0053] Example 2

[0054] A method for preparing a high-temperature, high-salt, double-crosslinked foaming agent suitable for geothermal formations is as described in Example 2, except that 0.05 mol of maleic anhydride is added in step (1).

[0055] The foaming agent prepared in this example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 3 and 4.

[0056] Table 3 Foaming volume and half-life of foaming agent solution at different temperatures

[0057]

[0058]

[0059] Table 4 Foaming volume and half-life of foaming agent solution at different salinities

[0060] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 503 471 <![CDATA[3×10 4 ]]> 492 453 <![CDATA[5×10 4 ]]> 456 421 <![CDATA[7×10 4 ]]> 413 405 <![CDATA[9×10 4 ]]> 391 382

[0061] Example 3

[0062] A method for preparing a high-temperature, high-salt, double-crosslinked foaming agent suitable for geothermal formations is as described in Example 1, except that 0.2 mol of maleic anhydride is added in step (1).

[0063] The foaming agent prepared in this example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 5 and 6.

[0064] Table 5 Foaming volume and half-life of foaming agent solution at different temperatures

[0065] Temperature / ℃ Foaming volume / mL Half-life / min 25 542 481 50 501 476 100 451 458 150 413 436 200 401 420

[0066] Table 6 Foaming volume and half-life of foaming agent solution at different salinities

[0067] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 512 472 <![CDATA[3×10 4 ]]> 482 458 <![CDATA[5×10 4 ]]> 451 421 <![CDATA[7×10 4 ]]> 410 403 <![CDATA[9×10 4 ]]> 387 386

[0068] Comparative Example 1

[0069] A method for preparing a foaming agent suitable for geothermal formations is as described in Example 1, except that in step (2), p-divinylbenzene is replaced with an equimolar amount of styrene.

[0070] The foaming agent prepared in this comparative example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 7 and 8.

[0071] Table 7 Foaming volume and half-life of foaming agent solution at different temperatures

[0072] Temperature / ℃ Foaming volume / mL Half-life / min 25 412 407 50 386 363 100 362 358 150 356 337 200 321 305

[0073] Table 8 Foaming volume and half-life of foaming agent solution at different salinities

[0074] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 389 391 <![CDATA[3×10 4 ]]> 348 347 <![CDATA[5×10 4 ]]> 336 336 <![CDATA[7×10 4 ]]> 314 332 <![CDATA[9×10 4 ]]> 301 303

[0075] Comparative Example 2

[0076] A method for preparing a foaming agent suitable for geothermal formations is as described in Example 1, except that p-divinylbenzene is not added in step (2).

[0077] The foaming agent prepared in this comparative example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 9 and 10.

[0078] Table 9 Foaming volume and half-life of foaming agent solution at different temperatures

[0079]

[0080]

[0081] Table 10 Foaming volume and half-life of foaming agent solution at different salinities

[0082] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 261 278 <![CDATA[3×10 4 ]]> 235 246 <![CDATA[5×10 4 ]]> 201 212 <![CDATA[7×10 4 ]]> 193 201 <![CDATA[9×10 4 ]]> 167 156

[0083] Comparative Example 3

[0084] A method for preparing a foaming agent suitable for geothermal formations is as described in Example 1, except that in step (2), p-divinylbenzene is replaced by an equimolar amount of sodium p-styrenesulfonate.

[0085] The foaming agent prepared in this comparative example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 11 and 12.

[0086] Table 11 Foaming volume and half-life of foaming agent solution at different temperatures

[0087] Temperature / ℃ Foaming volume / mL Half-life / min 25 357 402 50 326 378 100 323 354 150 317 342 200 286 314

[0088] Table 12 Foaming volume and half-life of foaming agent solution at different salinities

[0089] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 382 395 <![CDATA[3×10 4 ]]> 371 358 <![CDATA[5×10 4 ]]> 362 345 <![CDATA[7×10 4 ]]> 347 337 <![CDATA[9×10 4 ]]> 326 317

[0090] Comparative Example 4

[0091] A method for preparing a foaming agent suitable for geothermal formations is as described in Example 1, except that the sulfonation reaction in step (3) is not performed, and the diester polymer obtained in step (2) is used as the foaming agent.

[0092] The foaming agent prepared in this comparative example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 13 and 14.

[0093] Table 13 Foaming volume and half-life of foaming agent solution at different temperatures

[0094] Temperature / ℃ Foaming volume / mL Half-life / min 25 356 371 50 332 361 100 285 336 150 269 314 200 251 304

[0095] Table 14 Foaming volume and half-life of foaming agent solution at different salinities

[0096] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 295 293 <![CDATA[3×10 4 ]]> 288 281 <![CDATA[5×10 4 ]]> 267 261 <![CDATA[7×10 4 ]]> 217 203 <![CDATA[9×10 4 ]]> 153 135

[0097] Comparative Example 5

[0098] A method for preparing a foaming agent suitable for geothermal formations is as described in Example 1, except that in step (1), tristyrylphenol polyoxyethylene ether is replaced by an equimolar amount of ethylene glycol butyl ether acetate.

[0099] The foaming agent prepared in this comparative example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 15 and 16.

[0100] Table 15 Foaming volume and half-life of foaming agent solution at different temperatures

[0101]

[0102]

[0103] Table 16 Foaming volume and half-life of foaming agent solution at different salinities

[0104] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 303 332 <![CDATA[3×10 4 ]]> 268 325 <![CDATA[5×10 4 ]]> 234 274 <![CDATA[7×10 4 ]]> 168 179 <![CDATA[9×10 4 ]]> 125 151

[0105] Comparative Example 6

[0106] A method for preparing a foaming agent suitable for geothermal formations is as described in Example 1, except that in step (1), tristyrylphenol polyoxyethylene ether is replaced by an equimolar amount of alkylphenol polyoxyethylene ether.

[0107] The foaming agent prepared in this comparative example was tested for foaming volume and half-life. The specific testing method was as described in Example 1. The results are shown in Tables 17 and 18.

[0108] Table 17 Foaming volume and half-life of foaming agent solution at different temperatures

[0109] Temperature / ℃ Foaming volume / mL Half-life / min 25 336 332 50 267 305 100 259 299 150 219 281 200 159 231

[0110] Table 18 Foaming volume and half-life of foaming agent solution at different salinities

[0111] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 321 327 <![CDATA[3×10 4 ]]> 273 324 <![CDATA[5×10 4 ]]> 218 294 <![CDATA[7×10 4 ]]> 153 175 <![CDATA[9×10 4 ]]> 134 157

[0112] The comprehensive analysis is as follows:

[0113] In Example 1, multiple benzene rings are introduced based on the molecular structure design. Since multiple benzene ring groups are introduced into the chain segment, the foaming volume of the foaming agent is 547 mL at room temperature (25°C) and 415 mL at high temperature (200°C), while maintaining excellent foaming performance.

[0114] In Example 2, the content of monomer maleic anhydride in the monoester reaction is reduced, resulting in a decrease in the generation rate of monoester in the system. Therefore, the foaming performance is slightly reduced compared to that in Example 1. At the same time, for the entire reaction system, the content of rigid groups (benzene rings) is too high, which destroys the overall water solubility of the foaming agent. Therefore, the foaming volume is 521 mL at room temperature (25°C) and 389 mL at high temperature (200°C), and the foaming volume is slightly reduced.

[0115] In Example 3, the content of monomer maleic anhydride in the monoester reaction was increased. The content of maleic anhydride was relatively high, which affected the esterification rate. Under the reaction conditions, the foaming volume of the foaming agent was 542 mL at room temperature (25°C) and 401 mL at high temperature (200°C), while maintaining excellent foaming performance, which was slightly lower than that in Example 1.

[0116] In Comparative Example 1, the vinyl monomer containing a benzene ring in the diester cross-linking reaction was replaced with styrene. The foaming volume of the foaming agent at room temperature (25°C) was 412 mL, and the foaming volume at high temperature (200°C) was 321 mL. Compared with Example 1, the foaming performance decreased. The main reason is that although styrene is also a cross-linking agent, compared with the monomer selected in this patent, it lacks cross-linking groups and cannot connect the entire chain segments together, resulting in a decrease in foaming performance.

[0117] Comparative Example 2 removed the benzene-containing vinyl monomer from the diester reaction. Under these reaction conditions, the foaming volume of the foaming agent at room temperature (25°C) was 321 mL, and at high temperature (200°C) it was 121 mL. Under high temperature conditions, the foaming performance of the foaming agent decreased significantly. This is mainly because the benzene-containing monomer in the diester reaction, which contains a benzene ring and a double bond, acts as a dual crosslink in the entire system, increasing the strength and heat resistance of the chain segments, significantly improving the heat resistance of the system. When this component is missing, the heat resistance is insufficient.

[0118] In Comparative Example 3, the vinyl monomer containing a benzene ring in the diester cross-linking reaction was replaced with sodium p-styrene sulfonate. The foaming volume of the foaming agent at room temperature (25°C) was 357 mL, and the foaming volume at high temperature (200°C) was 286 mL. Compared with Comparative Example 1, the foaming performance of the foaming agent under high temperature conditions increased, mainly because the sodium p-styrene sulfonate contains a benzene ring group, which can significantly improve the temperature resistance of the entire system. In addition, since the sodium p-styrene sulfonate structure also contains a sulfonic acid group, the salt resistance is slightly increased. However, compared with the original polymerized monomer in Example 1, it also plays a cross-linking role, achieving a double cross-linking effect, and therefore, its performance is worse than that of Example 1.

[0119] In Comparative Example 4, the sulfonation reaction in step (3) was not carried out, and the diester polymer obtained in step (2) was used as a foaming agent. 4 , 3×10 4 , 5×10 4 , 7×10 4 and 9×10 4 The optimal foaming performance is 295mL at 9×10 4The foaming performance under high salinity conditions was 153 mL, indicating insufficient foaming performance. This is primarily due to the lack of sulfonation, which results in no sulfonate formation in the system, impairing the overall water solubility of the foaming agent. Furthermore, the sulfonic acid group itself exhibits excellent salt tolerance, which is reduced by the sulfonation reaction. Consequently, the surfactant's foaming performance is slightly insufficient under high-salt conditions.

[0120] In Comparative Example 5, tristyrylphenol polyoxyethylene ether was replaced with an equal mass of ethylene glycol butyl ether acetate. The foaming volume of the foaming agent was 314 mL at room temperature (25°C) and 153 mL at high temperature (200°C). Compared to the foaming performance in Example 1, the foaming performance was significantly reduced. This was primarily due to the lack of a temperature-resistant group (benzene ring structure) and a salt-resistant group (polyoxyethylene structure) in the selected monomer, resulting in insufficient foaming performance under both high-temperature and high-mineralization conditions.

[0121] In Comparative Example 6, tristyrylphenol polyoxyethylene ether was replaced with an equal mass of alkylphenol polyoxyethylene ether. The foaming volume of the foaming agent was 336 mL at room temperature (25°C) and 159 mL at high temperature (200°C). Compared to the foaming performance in Example 1, the foaming performance was significantly reduced. This was primarily due to the lack of a heat-resistant group in the selected monomer, resulting in insufficient foaming performance at high temperatures.

Claims

1. A method for preparing a high-temperature, high-salt, double-crosslinked foaming agent suitable for geothermal formations, comprising the following steps: (1) Mixing an anhydride monomer and an aromatic phenol polyoxyethylene ether compound, stirring until dissolved, then heating to the reaction temperature, adding catalyst A under nitrogen protection, and reacting to obtain a monoester polymer; The anhydride monomer is maleic anhydride; The aromatic phenol polyoxyethylene ether compound is tristyrylphenol polyoxyethylene ether or distyrylphenol polyoxyethylene ether; the general formulas of the tristyrylphenol polyoxyethylene ether and distyrylphenol polyoxyethylene ether are shown in Formula II and Formula III, respectively. ； In formula II, n is an integer of 1-30; in formula III, x is an integer of 1-20; (2) The monoester polymer obtained in step (1), the hydroxyl-containing monomer and the benzene ring-containing vinyl monomer are mixed, stirred until dissolved, and then heated to the reaction temperature. Under nitrogen protection, catalyst B and an initiator are added to react to obtain a diester polymer; the hydroxyl-containing monomer is lactic acid, glucose or ethylene glycol; the benzene ring-containing vinyl monomer is p-divinylbenzene, m-divinylbenzene, 1,3-diisopropenylbenzene or 1,4-diisopropenylbenzene; (3) Add the diester polymer obtained in step (2) to water, add the sulfonated compound, and heat to the reaction temperature. Add the catalyst C under nitrogen protection to react to obtain a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations; the sulfonated compound is sulfite.

2. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The molar ratio of the anhydride monomer to the aromatic phenol polyoxyethylene ether compound in step (1) is 1-4:

1.

3. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The molar ratio of the anhydride monomer to the aromatic phenol polyoxyethylene ether compound in step (1) is 2-3:

1.

4. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The catalyst A in step (1) is concentrated sulfuric acid, aminosulfonic acid or p-toluenesulfonic acid; the mass of the catalyst A is 1-5% of the total mass of the acid anhydride monomer and the aromatic phenol polyoxyethylene ether compound; The reaction temperature is 80-110°C; the reaction time is 2-5h; After the reaction in step (1) is completed, a post-treatment step is further included, specifically as follows: the reaction product is washed with anhydrous ethanol, filtered, and the obtained solid is vacuum-dried at 40-60° C. for 4-12 hours to obtain a monoester polymer.

5. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The molar ratio of the hydroxyl-containing monomer to the monoester polymer in step (2) is 1:2-2.

5.

6. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The molar ratio of the hydroxyl-containing monomer to the monoester polymer in step (2) is 1:2.

2.

7. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The molar ratio of the benzene ring-containing vinyl monomer to the hydroxyl-containing monomer in step (2) is 1-1.2:

1.

8. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The molar ratio of the benzene ring-containing vinyl monomer to the hydroxyl-containing monomer in step (2) is 1.1:

1.

9. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The catalyst B in step (2) is dinonylnaphthalene disulfonic acid, dinonylnaphthalene sulfonic acid or p-toluenesulfonic acid; the mass of the catalyst B is 1-4% of the total mass of the monoester polymer, the hydroxyl-containing monomer and the benzene ring-containing vinyl monomer; The initiator is one of potassium persulfate, sodium persulfate, and ammonium persulfate; the mass of the initiator is 0.5-4% of the total mass of the monoester polymer, the hydroxyl-containing monomer, and the benzene ring-containing vinyl monomer; The reaction temperature is 120-150° C.; the reaction time is 4-6 hours; In step (2), after the reaction is completed, a post-treatment step is further included: the reaction product is washed with anhydrous ethanol, filtered, and the obtained solid is vacuum-dried at 40-60° C. for 4-12 hours to obtain a diester polymer.

10. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The ratio of the volume of water to the mass of the diester polymer in step (3) is 10-50 mL:1 g; The sulfite is sodium bisulfite, sodium sulfite or sodium metabisulfite; the mass ratio of the sulfonated compound to the diester polymer is 2-4:

1.

11. The method for preparing a high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations according to claim 1, characterized in that: The catalyst C in step (3) is thionyl chloride, chlorosulfonic acid or sulfuryl chloride; the mass of the catalyst C is 2-6% of the total mass of the diester polymer and the sulfonated compound; The reaction temperature is 80-100°C; the reaction time is 4-6h; In step (3), after the reaction is completed, a post-processing step is also included: the reaction product is washed with anhydrous ethanol, filtered, and the obtained solid is vacuum-dried at 40-60°C for 4-12 hours to obtain a high-temperature and high-salt double-cross-linked foaming agent suitable for geothermal formations.

12. A high-temperature and high-salt double-crosslinked foaming agent suitable for geothermal formations, characterized in that: The preparation method according to claim 1 is used for preparation.

13. Use of the high temperature and high salt resistant double cross-linked foaming agent suitable for geothermal formations according to claim 12 in foam drilling fluid, characterized in that: The concentration of the high-temperature and high-salt resistant double-crosslinked foaming agent suitable for geothermal formations in the foam drilling fluid is 0.1-3 g / L.

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