A high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid and its preparation method

Abstract

The present invention provides a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid and a preparation method thereof. The preparation method of the foam stabilizer comprises the following steps: using nanocellulose fibrils or nanocellulose crystals as the core and an organic resin material as the shell to prepare a cellulose material with a core-shell structure; adding catalyst A to a sodium hydroxide solution, stirring evenly, and then adding an aqueous dispersion of the cellulose material with the core-shell structure to obtain a mixed solution I; adding catalyst B and a silane coupling agent to water to obtain a mixed solution II; adding the mixed solution II to the mixed solution I, and then adding a grafting monomer to react to obtain. Compared with conventional foam stabilizers, the foam stabilizer in the present invention has a higher foam stabilizing ability, can have a longer half-life under complex geological conditions, and has excellent temperature and salt resistance.

Description

Technical Field

[0001] The invention relates to a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid and a preparation method thereof, belonging to the technical field of drilling industry. Background Art

[0002] Geothermal energy is heat 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 rock fractures 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. Depending on the heat storage medium, geothermal energy can be divided into karst fissure, fracture, and pore geothermal resources. Based on the temperature range, geothermal resources can be divided into low-temperature geothermal resources (<90°C), medium-temperature geothermal resources (90-150°C), and high-temperature geothermal resources (150-650°C). In recent years, with the decline of conventional energy reserves and the improvement of people's environmental awareness, my country has entered the fast lane of developing geothermal resources. my country's geothermal resources are very rich, among which the reserves of medium and low temperature geothermal resources are very large and almost all over the country, with great potential for development.

[0003] The key technology for geothermal development is geothermal drilling. High-temperature geothermal drilling is costly, risky, and involves a great deal of uncertainty. Compared to traditional oil and gas wells, geothermal wells have the following characteristics:

[0004] 1) The bottom hole geological conditions are complex and the reservoir temperature is high (ranging from 150°C to 200°C, and locally reaching over 300°C);

[0005] 2) High-temperature geothermal resources are mostly formed in igneous and metamorphic rocks. The hardness of the reservoir rocks is greater than that of conventional oil drilling and they are highly abrasive (quartz content is greater than 50%).

[0006] 3) Highly developed fractures (fracture width exceeds 1 cm), often with abnormally low-pressure formations;

[0007] 4) The formation fluid has a high mineralization degree, which places high demands on the anti-pollution ability of the drilling fluid system.

[0008] These complex geological conditions 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 is susceptible to thermal cracking when exposed to water, causing wellbore collapse, stuck drill bits, and other accidents.

[0009] To address the problems existing in geothermal drilling, researchers at home and abroad have introduced foam drilling fluid technology into geothermal drilling. Compared with water-based / oil-based drilling fluids, foam drilling fluids have several advantages: foam fluids have low density and low hydrostatic column pressure. Due to the Jamin effect, foam fluids exhibit strong blocking ability when flowing through the borehole. In addition, foam drilling fluids have very low water loss, thus effectively reducing drilling fluid loss. Foam drilling fluid is a mixed system of gas and liquid, composed of a series of dense and fine bubbles. Compared with water-based / oil-based drilling fluids, foam fluids have higher dynamic shear force and higher viscosity, and have good rock carrying capacity. Due to their low density, they have better buoyancy during drilling. At the same flow rate, the solid particle carrying capacity of foam is more than ten times that of liquid medium, which improves rock carrying efficiency. Foam drilling fluid system components are simple, generally only containing foaming agents and foam stabilizers. During drilling, the foam is adsorbed on the drill bit and well wall, providing good lubrication, reducing frictional resistance, lowering circulating pressure drop, and minimizing damage to the reservoir. Therefore, foam drilling fluid has become the preferred drilling fluid for drilling geothermal wells.

[0010] 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. In the high-temperature environment of geothermal wells, the foaming agent and foam stabilizer in the foam drilling fluid are susceptible to thermal degradation and failure due to temperature influences. To address these issues, Chinese invention patent CN113403044A has developed a microfoaming system for drilling fluids. The system primarily comprises a primary polymer foaming agent, an anionic nonionic polymer surfactant containing a rigid benzene ring structure, and an auxiliary foaming agent, an amino acid-based zwitterionic surfactant, capable of maintaining good foam performance in formations. Chinese invention patent CN113122193A improves the surface viscosity of the foam liquid film and prepares a readily soluble, low-molecular-weight, high-temperature-resistant foam stabilizer with a nonionic cellulose ether skeleton, a hydrophobic structure, and sulfonate groups. The stabilizer can be applied to low-pressure oil and gas resources. Chinese invention patent CN107523278A relates to a method for preparing a foaming and foam stabilizing agent. Using the catalytic effect of BF3-ethyl ether, isododecyl alcohol reacts with epoxy ether to form an alcohol ether. The reactants are then reacted with chlorosulfonic acid and sodium hydroxide to form a foaming agent. A small amount of foaming and foam stabilizing agent can produce a large amount of foam, providing a new method for developing high-performance foam drilling fluids.

[0011] In addition, a variety of foam stabilizing substances have been developed at home and abroad to address the problem of foam stabilization, such as polyacrylamide, hydroxyethyl cellulose, hydroxymethyl cellulose, and nonionic surfactants. However, there are a large number of high-valent cations in geothermal wells, such as Ca 2+ The structure and surface activity of the foam stabilizer will be destroyed by the heat, and when the temperature reaches a certain level, the foam stabilizer will completely degrade. Therefore, to address the instability of foam in high-temperature and high-pressure formations, there is an urgent need to develop high-temperature and high-salt resistant foam stabilizers suitable for geothermal wells. Summary of the Invention

[0012] In view of the shortcomings of the existing technology, especially the problem that foam stabilizers are easily degraded and ineffective in high-temperature and high-salinity geothermal formations, the present invention provides a high-temperature and high-salinity resistant Pickering foam stabilizer for geothermal well drilling fluid and a preparation method thereof. The present invention first extracts a biomass-based nanocellulose material with a high specific surface area and high mechanical strength from plants; secondly, an organic resin material is coated on the biomass-based nanocellulose material to increase the heat resistance of the biomass-based nanocellulose material; finally, a compound containing a perfluorocarbon chain and a thiol group is grafted onto the nanocellulose-based Pickering particles. These carbon chains can effectively resist high temperatures and corrosive environments such as strong acids and strong alkalis, and the thiol group has good surface activity and corrosion resistance in high-temperature and high-salinity environments. Compared with conventional foam stabilizers, the foam stabilizer in the present invention has a higher foam stabilizing ability, can have a longer half-life under complex geological conditions, and has excellent heat and salt resistance.

[0013] Explanation of terms:

[0014] Room temperature has the commonly known meaning in the art, which refers to 25±5°C.

[0015] The technical solutions of the present invention are as follows:

[0016] A method for preparing a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid comprises the following steps:

[0017] (1) Using cellulose nanofibrils (CNF) or cellulose nanocrystals (CNC) as the core and organic resin materials as the shell to prepare core-shell structured cellulose materials;

[0018] (2) Adding catalyst A to a sodium hydroxide solution, stirring evenly, and then adding a core-shell structured cellulose material aqueous dispersion to obtain a mixed solution I; adding catalyst B and a silane coupling agent to water to obtain a mixed solution II; adding the mixed solution II to the mixed solution I, and then adding a grafting monomer to react to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid.

[0019] According to the present invention, the organic resin material in step (1) is a chloromethyl-modified phenolic resin or polyphenylmethylsiloxane; the viscosity of the polyphenylmethylsiloxane at 25° C. is 50-500 mPa·s; the chloromethyl-modified phenolic resin is prepared by referring to the Chinese patent document CN108102290A or is commercially available.

[0020] According to the preferred embodiment of the present invention, the mass ratio of the nanocellulose fibrils (CNF) or nanocellulose crystals (CNC) to the organic resin material in step (1) is 1:5-15.

[0021] Preferably, according to the present invention, the cellulose nanofibrils (CNF) in step (1) are prepared according to the following method: weighing Na2CO3 and NaHCO3 and dissolving them in deionized water to obtain a Na2CO3-NaHCO3 buffer solution; dissolving the sodium salt and the oxidant in the buffer solution, and then dispersing the cellulose in the above solution, and then adding NaClO under stirring conditions, stirring and reacting at room temperature, and adjusting the pH value of the system to maintain between 10-10.5 during the reaction; after the reaction is completed, adding anhydrous ethanol to terminate the reaction; removing the supernatant, and washing the obtained solid with deionized water by centrifugation until the supernatant is neutral, removing the supernatant, adding water to the obtained solid for ultrasonic treatment, and then centrifuging to obtain the supernatant, and freeze-drying the obtained supernatant to obtain cellulose nanofibrils (CNF);

[0022] Further preferably, in the preparation of the cellulose nanofibrils (CNF), the mass ratio of Na2CO3 to NaHCO3 is 5-10:3; the concentration of Na2CO3 in the Na2CO3-NaHCO3 buffer solution is 0.1-0.2 mol / L;

[0023] Further preferably, in the preparation of cellulose nanofibrils (CNF), the sodium salt is sodium bromide, sodium nitrate or sodium fluoride; the mass ratio of the sodium salt to cellulose is 0.2-0.5:1;

[0024] Further preferably, in the preparation of cellulose nanofibrils (CNF), the oxidant is 2,2,6,6-tetramethylpiperidinyl oxide or 4-isopropoxy-piperidine; the mass ratio of the oxidant to cellulose is 0.01-0.05:1;

[0025] Further preferably, in the preparation of cellulose nanofibrils (CNF), the ratio of the mass of cellulose to the volume of Na2CO3-NaHCO3 buffer solution is 0.01-0.1 g:1 mL;

[0026] Further preferably, in the preparation of cellulose nanofibrils (CNF), the mass of NaClO is 30-70% of the mass of cellulose;

[0027] Further preferably, in the preparation of cellulose nanofibrils (CNF), a dilute hydrochloric acid solution and a NaOH solution are used to adjust the pH of the system to maintain at 10-10.5, the concentration of the dilute hydrochloric acid solution is 0.1-0.5 mol / L, and the concentration of the NaOH solution is 0.1-1 mol / L;

[0028] Further preferably, the reaction time in the preparation of cellulose nanofibrils (CNF) is 2-8 hours;

[0029] Further preferably, in the preparation of the cellulose nanofibrils (CNF), the ratio of the added volume of anhydrous ethanol to the mass of cellulose is 10-30 mL: 1 g;

[0030] Further preferably, during the ultrasonic treatment in the preparation of cellulose nanofibrils (CNF), the ratio of the volume of water added to the mass of cellulose is 10-50 mL:1 g; and the ultrasonic treatment time is 30-60 min;

[0031] More preferably, the freeze-drying temperature in the preparation of cellulose nanofibrils (CNF) is -26 to -16°C, and the freeze-drying time is 10 to 24 hours.

[0032] According to a preferred embodiment of the present invention, the nanocellulose crystals (CNC) in step (1) are prepared according to the following method: cellulose is added to a sulfuric acid solution for reaction; the suspension obtained by the reaction is then centrifuged, and the obtained solid is centrifuged and washed with water until the pH value of the supernatant is neutral; water is then added to the obtained solid for ultrasonic treatment, and the obtained supernatant is centrifuged and freeze-dried to obtain nanocellulose crystals (CNC);

[0033] Further preferably, in the preparation of nanocellulose crystals (CNC), the mass fraction of the sulfuric acid solution is 50-64%; the mass ratio of the cellulose to the sulfuric acid solution is 1:10-20;

[0034] Further preferably, the reaction temperature in the preparation of nanocellulose crystals (CNC) is 40-80° C. and the reaction time is 1-3 h;

[0035] Further preferably, during the ultrasonic treatment in the preparation of nanocellulose crystals (CNC), the ratio of the volume of water added to the mass of cellulose is 10-50 mL:1 g; the ultrasonic treatment time is 2-4 h;

[0036] Further preferably, the freeze-drying temperature in the preparation of nanocellulose crystals (CNC) is -26 to -16°C, and the freeze-drying time is 10 to 24 hours.

[0037] According to the present invention, in the preparation of nanocellulose fibrils (CNF) or nanocellulose crystals (CNC), the cellulose used is cellulose extracted from plants, the plants are corn stalks or wood, and the extraction method is the existing technology; preferably, the cellulose is extracted according to the following method: first, the corn stalks or wood are crushed into 20-100 mesh plant powder, washed with water, and then dried at 30-80°C for 36-72h; the dried plant powder is added to an alkaline solution for treatment, and then filtered, and the obtained solid is washed with water until the filtrate is neutral, and dried at 30-80°C for 36-72h to obtain an alkali-treated raw material; the alkali-treated raw material is dispersed in water to obtain a dispersion with a concentration of 0.05-0.3g / mL, heated to 60-100°C, and then added with an acid solution and a bleaching agent every 1-2h for extraction. The method comprises the steps of: collecting the cellulose powder, filtering the cellulose powder, washing the obtained solid with deionized water until the filtrate is neutral, washing the solid with acetone, and drying the solid at 40-80° C. to constant weight to obtain cellulose; the alkaline solution is a sodium hydroxide solution with a mass fraction of 5-20%; the volume of the alkaline solution is to the mass ratio of the dried plant powder is 10-50 mL:1 g; the temperature for treating the plant powder with the alkaline solution is 60-100° C., and the treatment time is 1-3 hours; the acid solution is one of glacial acetic acid, a hydrochloric acid solution with a mass fraction of 37%, and a nitric acid solution with a mass fraction of 68%, and the mass ratio of the acid solution added each time to the raw material treated with the alkaline solution is 0.1-1:1; the bleaching agent is one of sulfur dioxide, sodium chlorite, and sulfur, and the mass ratio of the bleaching agent added each time to the raw material treated with the alkaline solution is 0.1-1:1; and the extraction time is 3-6 hours.

[0038] According to the present invention, preferably, the cellulose material with a core-shell structure having cellulose nanofibrils (CNF) as the core in step (1) is a single-core structure, which is prepared according to the following method:

[0039] The pH value of the nanocellulose fibril (CNF) aqueous dispersion is adjusted to 5-8, and then a xylene dispersion of an organic resin material is added, and then an initiator I is added and stirred to react; after the reaction is completed, the cellulose material having a core-shell structure with the nanocellulose fibril (CNF) as the core is obtained by filtering, washing, ultrasonic dispersion, and freeze drying; the concentration of the nanocellulose fibril (CNF) aqueous dispersion is 0.05-0.5 g / mL; the pH value of the nanocellulose fibril (CNF) aqueous dispersion is adjusted using a 0.05 mol / L sodium hydroxide solution; the concentration of the xylene dispersion of the organic resin material is 0.05-0.25 g / mL; the initiator I is benzoyl peroxide or dicumyl peroxide; the mass of the initiator I is 0.5-3% of the mass of the nanocellulose fibrils (CNF); the stirring speed is 2000-5000r / min, and the stirring reaction time is 12-36h; the washing is performed by washing with ethanol 3-5 times; the ultrasonic dispersion is performed by adding the solid obtained by washing to water, ultrasonically dispersing it uniformly to obtain a suspension, and the ratio of the added mass of the water to the mass of the nanocellulose fibrils (CNF) is 40-60:1; the freeze-drying temperature is -26 to -16°C, and the freeze-drying time is 10-24h.

[0040] According to the present invention, preferably, the cellulose material with a core-shell structure having nanocellulose crystals (CNC) as the core in step (1) is a single-core structure or a multi-core structure.

[0041] More preferably, the cellulose material with a single core-shell structure having nanocellulose crystals (CNC) as the core is prepared according to the following method:

[0042] After adjusting the pH value of the nanocellulose crystal (CNC) aqueous dispersion to 5-8, a xylene dispersion of an organic resin material is added, and then an initiator II is added. After stirring evenly, the mixture is allowed to stand for reaction. After the reaction is completed, the mixture is filtered, washed, ultrasonically dispersed, and freeze-dried to obtain a cellulose material with a single core-shell structure having nanocellulose crystals (CNC) as the core. Preferably, the concentration of the nanocellulose crystal (CNC) aqueous dispersion is 0.01-0.1 g / mL. The pH value of the nanocellulose crystal (CNC) aqueous dispersion is adjusted using a 0.05 mol / L sodium hydroxide solution. The organic resin material The concentration of the xylene dispersion is 0.05-0.25 g / mL; the initiator II is benzoyl peroxide or dicumyl peroxide, and the mass of the initiator II is 0.5-3% of the mass of the nanocellulose crystals (CNC); the standing reaction time is 12-36 hours; the washing is washing with ethanol 3-5 times; the ultrasonic dispersion is adding the solid obtained by washing into water, ultrasonically dispersing it uniformly to obtain a suspension, and the ratio of the added mass of the water to the mass of the nanocellulose crystals (CNC) is 40-60:1; the freeze drying is freeze drying at -26 to -16°C for 12-36 hours.

[0043] Further preferably, the multi-core core-shell structure cellulose material with nanocellulose crystals (CNC) as the core is prepared according to the following method:

[0044] (a) After adjusting the pH value of the nanocellulose crystal (CNC) aqueous dispersion to 5-8, a xylene dispersion of an organic resin material is added, and then an initiator III is added, and the mixture is stirred evenly, and then allowed to stand for reaction; after the reaction is completed, the mixture is filtered, washed, ultrasonically dispersed, and freeze-dried to obtain a single-core core-shell structure cellulose material; preferably, the concentration of the nanocellulose crystal (CNC) aqueous dispersion is 0.01-0.1 g / mL; the pH value of the nanocellulose crystal (CNC) aqueous dispersion is adjusted using a 0.05 mol / L sodium hydroxide solution; the xylene dispersion of the organic resin material The concentration of the initiator III is 0.05-0.25 g / mL; the initiator III is benzoyl peroxide or dicumyl peroxide, and the mass of the initiator III is 0.5-3% of the mass of the nanocellulose crystals (CNC); the static reaction time is 12-36 hours; the washing is performed by washing with ethanol 3-5 times; the ultrasonic dispersion is performed by adding the washed solid to water and uniformly dispersing it by ultrasonication to obtain a suspension, and the ratio of the added mass of the water to the mass of the nanocellulose crystals (CNC) is 40-60:1; the freeze drying is performed at -26 to -16°C for 12-36 hours;

[0045] (b) adding the mononuclear core-shell structure cellulose material obtained in step (a) to an ionic liquid, adding a dispersant and an initiator IV, stirring to react, and obtaining a reaction solution; and then vacuum drying the reaction solution to obtain a multinuclear core-shell structure cellulose material with nanocellulose crystals (CNC) as the core; preferably, the ionic liquid is one of 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4), and 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TfO]), and the ionic liquid is 1-butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6), 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4), and 1-butyl-3-methylimidazolium trifluoromethanesulfonate ([BMIM][TfO]). The mass ratio of the liquid to the mononuclear core-shell structure cellulose material is 3-8:1; the dispersant is sodium lauryl sulfate, polyethylene glycol 200 or polyethylene glycol 400, and the mass of the dispersant is 2-5% of the mass of the mononuclear core-shell structure cellulose material; the initiator IV is benzoyl peroxide or dicumyl peroxide, and the initiator IV is 0.5-3% of the mass of the mononuclear core-shell structure cellulose material; the reaction temperature is 60-90°C, and the reaction time is 10-15 hours; the vacuum drying temperature is 40-60°C, and the vacuum drying time is 12-36 hours.

[0046] According to the present invention, the diameter of the cellulose nanofibrils (CNF) in step (1) is 1-100 nm and the length is 500-2000 nm; the diameter of the cellulose nanocrystals (CNC) is 2-20 nm and the length is 100-500 nm.

[0047] According to the present invention, preferably, the catalyst A in step (2) is 2,2,6,6-tetramethylpiperidine-N-oxide (TEMPO), ammonia water or potassium hydroxide; and the mass ratio of the catalyst A to the core-shell structured cellulose material is 0.05-0.5:1.

[0048] Preferably, according to the present invention, the mass fraction of the sodium hydroxide solution in step (2) is 5-15%; the ratio of the volume of the sodium hydroxide solution to the mass of the core-shell structured cellulose material is 1-5 mL:1 g.

[0049] According to the present invention, preferably, the concentration of the core-shell structured cellulose material aqueous dispersion in step (2) is 0.01-0.2 g / mL, more preferably 0.1-0.15 g / mL.

[0050] According to the preferred embodiment of the present invention, the catalyst B in step (2) is one of triethylamine, nickel oxide, and sodium molybdate; the mass ratio of the catalyst B to the core-shell structured cellulose material is 0.3-0.8:1; and the concentration of the catalyst B in the mixed solution II is 0.05-0.15 g / mL.

[0051] According to the present invention, preferably, the silane coupling agent in step (2) is γ-methacryloxypropyltrimethoxysilane (KH570), γ-aminopropyltriethoxysilane (KH550), γ-(2,3-epoxypropoxy)propyltrimethoxysilane (KH560) or vinyltriethoxysilane (A151); the mass ratio of the silane coupling agent to the core-shell structure cellulose material is 0.05-0.3:1.

[0052] According to the present invention, preferably, the grafting monomer in step (2) is 1H,1H,2H,2H-perfluorododecyl mercaptan or 1H,1H,2H,2H-perfluorodecyl mercaptan; and the mass ratio of the grafting monomer to the core-shell structured cellulose material is 5-20:1.

[0053] According to the preferred embodiment of the present invention, the reaction temperature in step (2) is 70-90° C.; and the reaction time is 12-36 h.

[0054] Preferably, according to the present invention, after the reaction in step (2) is completed, a post-treatment step is further included, specifically as follows: the obtained reaction liquid is filtered, the solid obtained by filtration is washed with anhydrous ethanol, and then freeze-dried at -26 to -16°C for 12 to 36 hours to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid.

[0055] The present invention also provides a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid, which is prepared by the above-mentioned preparation method.

[0056] According to the present invention, the high temperature and high salt resistant Pickering foam stabilizer for geothermal well drilling fluid is used to stabilize foam during geothermal well drilling.

[0057] The technical features and beneficial effects of the present invention are as follows:

[0058] 1. The high-temperature and high-salt resistant Pickering foam stabilizer of the present invention is based on plant-extracted nanocellulose material. The nanocellulose material has a high specific surface area and high mechanical strength. Compared with surfactant foam stabilizers, the melting point and temperature resistance of the nanocellulose material are significantly improved.

[0059] 2. The high-temperature and high-salt resistant foam stabilizer of the present invention uses a homemade nanocellulose material as the core and an organic resin material as the shell to form an inorganic-organic core-shell nanoparticle foam stabilizer. The nanocellulose is wrapped by the organic resin material to increase the temperature resistance of the solid particles, providing a strong guarantee for the foam stabilization ability of high-temperature formations.

[0060] 3. The high-temperature, high-salinity foam stabilizer of the present invention, based on molecular structure and the interaction between various intermolecular groups, introduces multiple compounds containing perfluorocarbon chains and thiol groups and grafts them onto nanocellulose-based solid particles. These carbon chains can effectively withstand high temperatures and complex environments such as strong acids and strong bases, while the thiol groups can maintain good surface activity and corrosion resistance in high-temperature, high-salinity environments. This nanocellulose-based foam stabilizer improves its foam stabilization ability under complex conditions (high temperature and high salinity), providing a new approach for geothermal well development and exploitation.

[0061] 4. The high temperature and high salt resistant foam stabilizer 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. BRIEF DESCRIPTION OF THE DRAWINGS

[0062] Figure 1 This is the SEM image of the nanocellulose fibrils prepared in Example 3. DETAILED DESCRIPTION

[0063] The technical solutions of the present invention are described clearly and completely below with reference to specific embodiments. Obviously, the embodiments described are only a portion of the embodiments of the present invention, and not all of them. The raw materials used in the examples are conventional and commercially available; the methods described are based on prior art unless otherwise specified. All other examples improved or modified by persons of ordinary skill in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0064] The chloromethyl modified phenolic resin was prepared according to Example 1 of Chinese patent document CN108102290A.

[0065] Example 1

[0066] A method for preparing a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid comprises the following steps:

[0067] (1) Extraction of cellulose

[0068] First, the corn straw was crushed into 80 mesh powder using a plant crusher, washed with deionized water, and dried in a 40°C oven for 48 hours to obtain corn straw powder; 20g of the dried corn straw powder was weighed and added to 300mL of a 20% sodium hydroxide aqueous solution, stirred at 70°C for 2 hours, and then filtered. The obtained solid was washed with deionized water until the filtrate was neutral, and dried in a 40°C oven for 40 hours to obtain an alkali-treated powder; 10g of the alkali-treated powder was placed in 100mL of deionized water, dispersed evenly, heated to 80°C, and extracted with 2.1g of glacial acetic acid and 3g of sodium chlorite. Subsequently, 2.1g of glacial acetic acid and 3g of sodium chlorite were added every 1 hour for extraction. Glacial acetic acid and sodium chlorite were added three times for a total of 3 hours to obtain a pure white solid. The solid was filtered and washed with deionized water until the filtrate was neutral. The solid was then washed with acetone and dried at 40°C to constant weight to obtain cellulose.

[0069] (2) Preparation of cellulose nanocrystals (CNC)

[0070] The cellulose prepared in step (1) is mixed with a sulfuric acid solution with a mass fraction of 60% in a mass ratio of 1:10, and reacted at 60°C for 2 hours to obtain a suspension; the obtained suspension is centrifuged at a speed of 10,000 r / min for 15 minutes, the supernatant is removed, and the obtained solid is centrifuged and washed with water until the pH value of the supernatant is neutral; then water is added to the obtained solid, and the ratio of the volume of the added water to the mass of the cellulose is 20 mL:1 g; after ultrasonic treatment for 2 hours, the supernatant is centrifuged and taken out, and the obtained supernatant is freeze-dried at -26°C for 12 hours to obtain nanocellulose crystals (CNC) for further use.

[0071] (3) Preparation of CNC-based single-core core-shell cellulose materials

[0072] 5 g of nanocellulose crystals (CNC) were dispersed in 100 mL of water, and the pH value of the obtained nanocellulose crystal dispersion was adjusted to 7 using a 0.05 mol / L sodium hydroxide solution; 50 g of chloromethyl-modified phenolic resin was dispersed in 500 mL of xylene, stirred evenly, and added to the nanocellulose crystal dispersion; 0.05 g of diisopropylbenzene peroxide was added, stirred evenly at a speed of 3000 r / min, and allowed to react at room temperature for 24 h; after the reaction was completed, it was filtered, and the filtered solid product was washed with ethanol three times; the washed solid product was redispersed in 250 g of water, ultrasonically dispersed evenly, and then freeze-dried (temperature of -20°C, time of 24 h) to obtain a single-core core-shell structured cellulose material with nanocellulose crystals (CNC) as the core for further use.

[0073] (4) Nanomaterial surface grafting

[0074] First, 2 g of a single-core core-shell structured cellulose material with nanocellulose crystals (CNC) as the core was weighed and added to 20 mL of deionized water and stirred evenly to obtain a core-shell structured cellulose material dispersion; secondly, 0.2 g of TEMPO (2,2,6,6-tetramethylpiperidine-N-oxide) was weighed and added to 5 mL of a 10% sodium hydroxide aqueous solution, stirred at a speed of 1000 r / min for 2 h, and then the obtained solution was added to the core-shell structured cellulose material dispersion to obtain a mixed solution I; 1 g of triethylamine and 0.2 g of silane coupling agent KH570 were added to 10 mL of deionized water and stirred evenly to obtain a mixed solution II, which was then added to the mixed solution I; finally, 20 g of 1H,1H,2H,2H-perfluorododecanethiol was added, and the mixture was stirred at 80° C. and a speed of 3000 r / min for 24 hours; the obtained reaction solution was then filtered, and the solid obtained by filtration was washed with anhydrous ethanol and freeze-dried at -26° C. for 12 hours to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid.

[0075] The foam stabilizer prepared in this example was tested for foaming volume and half-life. The specific tests are as follows:

[0076] The concentration of the foaming agent in the test sample aqueous solution is 5 g / L, the foaming agent is sodium lauryl sulfate, and the concentration of the foam stabilizer is 1 g / L.

[0077] Foaming volume and half-life of foam stabilizer solution: The foam stabilizer is evaluated based on the Waring Blender method, an industry standard for foam stabilizer evaluation. The specific steps are as follows: Use a slurry cup to hold 200 mL of water, add 1 g of foaming agent sodium lauryl sulfate and 0.2 g of foam stabilizer, and stir continuously for 5 minutes on a high-frequency high-speed stirrer at a stirring speed of 11,000 r / min. After 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.

[0078] The foaming volume and half-life of the solution at different temperatures: The foam stabilizer solution was measured at room temperature (25°C). In addition, four aqueous solutions containing 5g / L foaming agent and 1g / L foam stabilizer sample were placed in a rolling heating furnace at 50°C, 100°C, 150°C, and 200°C, respectively. After 6 hours, they were taken out and stirred continuously for 5 minutes on a high-frequency high-speed stirrer at a stirring speed of 11000r / min. After the stirring stopped, the foam was immediately poured into a glass measuring cylinder. The reading was the foaming volume, and the timer was started. The time taken for 100mL of liquid to be precipitated was the half-life.

[0079] The foaming volume and half-life of the 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, in which Na + , Ca 2+ , Mg 2+ The proportion of plasma is equal. For example, one liter of water contains 1000 mg of salt, of which Na + , Ca 2+ , Mg 2+ The plasma accounts for 333.3 mg. ) is 1×10 4 , 3×10 4 , 5×10 4 , 7×10 4 and 9×10 4 1 g of sodium lauryl sulfate, a foaming agent, and 0.2 g of a foam stabilizer were added to 200 mL of each simulated formation water with a concentration of ppm. The mixture was stirred continuously for 5 min at a stirring speed of 11,000 r / min on a high-frequency high-speed stirrer. After the stirring stopped, the foam was immediately poured into a glass measuring cylinder. The reading was the foaming volume, and the timer was started. The time taken to precipitate 100 mL of liquid was the half-life.

[0080] At the same time, the foaming volume and half-life of the foaming agent aqueous solution (5g / L) without adding a foam stabilizer were tested for comparison.

[0081] The specific test results of the foaming agent solution to which the foam stabilizer of this embodiment was added are shown in Tables 1 and 2, and the test results of the foaming agent aqueous solution to which no foam stabilizer was added are shown in Tables 3 and 4.

[0082] Table 1 Foaming volume and half-life of foaming agent solution with foam stabilizer at different temperatures

[0083] Temperature / ℃ Foaming volume / mL Half-life / min 25 401 156 50 396 154 100 378 150 150 353 148 200 321 140

[0084] Table 2 Foaming volume and half-life of foaming agent solution with different salinity added with foam stabilizer

[0085] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 394 152 <![CDATA[3×10 4 ]]> 385 150 <![CDATA[5×10 4 ]]> 361 147 <![CDATA[7×10 4 ]]> 338 143 <![CDATA[9×10 4 ]]> 305 135

[0086] Table 3 Foaming volume and half-life of solutions without foam stabilizer at different temperatures

[0087] Temperature / ℃ Foaming volume / mL Half-life / min 25 457 20 50 426 17 100 212 14 150 153 2 200 0 0

[0088] Table 4 Foaming volume and half-life of solutions without foam stabilizer at different salinities

[0089] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 437 20 <![CDATA[3×10 4 ]]> 419 17 <![CDATA[5×10 4 ]]> 187 13 <![CDATA[7×10 4 ]]> 129 5 <![CDATA[9×10 4 ]]> 58 1

[0090] Example 1 First, a biomass-based nanocellulose material with high specific surface area and high mechanical strength was extracted from plants. Secondly, an organic resin material was coated on the biomass-based nanocellulose material to increase the heat resistance of the biomass-based nanocellulose material. Finally, a compound containing several perfluorocarbon chains and thiol groups was grafted onto the nanocellulose-based Pickering particles. These carbon chains can effectively resist high temperatures and corrosive environments such as strong acids and strong alkalis. The thiol groups have good surface activity and corrosion resistance in high temperature and high salinity environments. The half-life of the foaming agent solution at room temperature (25°C) is 156 minutes, and the half-life at high temperature (200°C) is 140 minutes; the mineralization degree is 9×10 4 ppm, the half-life of the foam is 135min, and the obtained foam stabilizer has excellent temperature and salt resistance. The half-life of the foaming agent solution without adding foam stabilizer is 20min at room temperature (25℃) and 0min at high temperature (200℃); the mineralization degree is 9×10 4 When the concentration of surfactant is less than 1 ppm, the half-life of the foam is 1 min, and its ability to stabilize the foam is greatly reduced. The main reason for this phenomenon is that when only surfactants are present, at high temperatures, the surfactants are easily affected by high temperatures and lose their activity, and their ability to stabilize the foam is sharply reduced; under high salt conditions, they are easily affected by high salt and lose their ability to stabilize the foam.

[0091] Example 2

[0092] A method for preparing a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid comprises the following steps:

[0093] (1) Extraction of cellulose

[0094] Same as step (1) in Example 1.

[0095] (2) Preparation of cellulose nanocrystals (CNC)

[0096] Same as step (2) in Example 1.

[0097] (3) Preparation of CNC-based single-core core-shell cellulose materials

[0098] Same as step (3) in Example 1.

[0099] (4) Preparation of multi-core core-shell cellulose materials with CNC as the core:

[0100] 5 g of a mononuclear core-shell structured cellulose material with nanocellulose crystals (CNC) as the core was added to 20 g of ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate, 0.15 g of dispersant sodium dodecyl sulfate was added, and 0.05 g of initiator diisopropylbenzene peroxide was added. The mixture was stirred and reacted at 60 ° C for 12 h, and then the resulting reaction solution was vacuum dried at 40 ° C for 24 h to obtain a multinuclear core-shell structured cellulose material with nanocellulose crystals (CNC) as the core.

[0101] (5) Nanomaterial surface grafting

[0102] First, 2 g of a multi-core core-shell structured cellulose material with nanocellulose crystals (CNC) as the core was weighed and added to 20 mL of deionized water and stirred evenly to obtain a core-shell structured cellulose material dispersion; secondly, 0.2 g of TEMPO (2,2,6,6-tetramethylpiperidine-N-oxide) was weighed and added to 5 mL of a 10% sodium hydroxide aqueous solution, stirred at a speed of 1000 r / min for 2 h, and then the obtained solution was added to the core-shell structured cellulose material dispersion to obtain a mixed solution I; 1 g of triethylamine and 0.2 g of silane coupling agent KH570 were added to 10 mL of deionized water and stirred evenly to obtain a mixed solution II, which was then added to the mixed solution I; finally, 20 g of 1H,1H,2H,2H-perfluorododecanethiol was added, and the mixture was stirred at 80° C. and a speed of 3000 r / min for 24 hours; the obtained reaction solution was then filtered, and the solid obtained by filtration was washed with anhydrous ethanol and freeze-dried at -26° C. for 12 hours to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid.

[0103] The foam stabilizer prepared in this example was tested for foam volume and half-life. The specific test method is as shown in Example 1, and the specific test results are shown in Tables 5 and 6.

[0104] Table 5 Foaming volume and half-life of solutions at different temperatures

[0105] Temperature / ℃ Foaming volume / mL Half-life / min 25 397 169 50 375 163 100 354 157 150 335 156 200 304 154

[0106] Table 6 Foaming volume and half-life of solutions at different salinities

[0107] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 381 167 <![CDATA[3×10 4 ]]> 376 163 <![CDATA[5×10 4 ]]> 352 159 <![CDATA[7×10 4 ]]> 321 154 <![CDATA[9×10 4 ]]> 301 151

[0108] The foaming volume of the foaming agent solution added with the foam stabilizer of this embodiment is 397 mL and the half-life is 169 min at room temperature (25 ° C). The foaming volume is 304 mL and the half-life is 154 min at high temperature (200 ° C). The mineralization is 9×10 4At ppm, the foam volume was 301 mL and the foam half-life was 151 min. Compared to the foam volume in Example 1, the foam volume in this example decreased, primarily due to the stronger interfacial bonding ability of the multi-core-shell structure, which slightly reduced the foaming capacity. Compared to a single-core-shell structure, a multi-core-shell structure has multiple cores that can interact, thereby increasing structural stability. Therefore, the foam stabilizer has excellent temperature and salt resistance, and its ability to stabilize foam is enhanced.

[0109] Example 3

[0110] A method for preparing a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid comprises the following steps:

[0111] (1) Extraction of cellulose

[0112] Same as step (1) in Example 1.

[0113] (2) Preparation of cellulose nanofibrils (CNF)

[0114] First, 7 g of sodium carbonate and 3 g of sodium bicarbonate were weighed and dissolved in 500 mL of deionized water to obtain a Na2CO3-NaHCO3 buffer solution; secondly, 4 g of sodium bromide and 0.2 g of 2,2,6,6-tetramethylpiperidinium oxide were weighed and dissolved in the Na2CO3-NaHCO3 buffer solution, and then 10 g of cellulose was dispersed in the above Na2CO3-NaHCO3 buffer solution, 5 g of NaClO was added under stirring, and the reaction was stirred at room temperature for 5 h. During the reaction, 0.1 mol / L dilute hydrochloric acid solution and 0.1 mol / L NaOH solution were used to adjust the pH of the system to maintain between 10-10.5; after the reaction was completed, 200 mL of anhydrous ethanol was added to terminate the reaction, and then the mixture was allowed to stand for 12 h. The supernatant was removed, and the obtained solid was centrifuged and washed with deionized water until the supernatant was neutral. The supernatant was removed, 100 mL of water was added to the obtained solid and ultrasonically treated for 30 min. After centrifugation, the obtained supernatant was freeze-dried at -26°C for 12 h to obtain nanocellulose fibrils (CNF).

[0115] (3) Preparation of cellulose materials with a single core-shell structure using CNF as the core

[0116] 5 g of nanocellulose fibrils (CNF) were dispersed in 50 mL of water, and the pH value of the obtained nanocellulose fibril dispersion was adjusted to 7 using 0.05 mol / L sodium hydroxide solution; 50 g of chloromethyl-modified phenolic resin was dispersed in 500 mL of xylene, stirred evenly, and then added to the nanocellulose fibril dispersion; 0.05 g of diisopropylbenzene peroxide was added, and the reaction was stirred at a speed of 3000 r / min for 24 hours; the solid product obtained by filtration was washed and filtered three times with ethanol; the washed solid product was redispersed in 250 g of water, ultrasonically dispersed evenly, and then freeze-dried (temperature of -20°C, time of 12 hours) to obtain a single-core core-shell structured cellulose material with nanocellulose fibrils (CNF) as the core for further use.

[0117] (4) Nanomaterial surface grafting

[0118] First, 2 g of a single-core core-shell structured cellulose material with cellulose nanofibrils (CNF) as the core was weighed and added to 20 mL of deionized water, and stirred until uniform to obtain a core-shell structured cellulose material dispersion; secondly, 0.2 g of TEMPO (2,2,6,6-tetramethylpiperidine-N-oxide) was weighed and added to 5 mL of a 10% sodium hydroxide aqueous solution, and stirred at a speed of 1000 r / min for 2 h, and then the obtained solution was added to the core-shell structured cellulose material dispersion to obtain a mixed solution I; 1 g of triethylamine and 0.2 g of silane coupling agent KH570 were added to 10 mL of deionized water and stirred evenly to obtain a mixed solution II, which was then added to the mixed solution I; finally, 20 g of 1H,1H,2H,2H-perfluorododecanethiol was added, and the mixture was stirred at 80° C. and a speed of 3000 r / min for 24 hours; the obtained reaction solution was then filtered, and the solid obtained by filtration was washed with anhydrous ethanol and freeze-dried at -26° C. for 12 hours to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid.

[0119] The foam stabilizer prepared in this example was tested for foam volume and half-life. The specific test method is as shown in Example 1, and the specific test results are shown in Tables 7 and 8.

[0120] Table 7 Foaming volume and half-life of solutions at different temperatures

[0121] Temperature / ℃ Foaming volume / mL Half-life / min 25 381 187 50 362 177 100 346 174 150 324 169 200 295 163

[0122] Table 8 Foaming volume and half-life of solutions at different salinities

[0123] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 372 185 <![CDATA[3×10 4 ]]> 365 176 <![CDATA[5×10 4 ]]> 334 171 <![CDATA[7×10 4 ]]> 314 168 <![CDATA[9×10 4 ]]> 292 161

[0124] The foaming agent solution to which the foam stabilizer of this embodiment is added has a half-life of 187 min at room temperature (25°C) and a half-life of 163 min at high temperature (200°C); the mineralization degree is 9×10 4 At ppm, the foam half-life is 161 minutes. Compared with the multi-core shell CNC spherical structure, the CNF core-shell structure is fibrous in shape, which can provide more surface area at the gas / liquid interface, increase the strength of the interfacial film, and thus increase the stability of the foam. Therefore, the foam stabilizer has excellent temperature and salt resistance and stronger ability to stabilize foam.

[0125] Comparative Example 1

[0126] A method for preparing a Pickering foam stabilizer is as described in Example 1, except that the organic resin material in step (3) is replaced by a chloromethyl-modified polystyrene resin.

[0127] The foam stabilizer prepared in this comparative example was tested for foaming volume and half-life. The specific test method is as shown in Example 1, and the specific test results are shown in Tables 9 and 10.

[0128] Table 9 Foaming volume and half-life of solutions at different temperatures

[0129] Temperature / ℃ Foaming volume / mL Half-life / min 25 378 142 50 371 139 100 352 138 150 331 132 200 315 127

[0130] Table 10 Foaming volume and half-life of solutions at different salinities

[0131] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 372 136 <![CDATA[3×10 4 ]]> 363 133 <![CDATA[5×10 4 ]]> 345 130 <![CDATA[7×10 4 ]]> 321 123 <![CDATA[9×10 4 ]]> 307 120

[0132] Compared with Example 1, the organic resin material of this comparative example is adjusted to chloromethyl modified polystyrene resin. The half-life of the solution at room temperature (25°C) is 142 minutes, and the half-life at high temperature (200°C) is 127 minutes. The mineralization degree is 9×10 4 When the content of PEG-100 in the comparative example 1 is less than 1%, the half-life of the foam is 120 min. Compared with the half-life in Example 1, the ability of stabilizing the foam in the comparative example 1 is reduced.

[0133] Comparative Example 2

[0134] A method for preparing a Pickering foam stabilizer is as described in Example 1, except that the grafting monomer in step (4) is changed to 2-acrylamide-2-methylpropanesulfonic acid.

[0135] The foam stabilizer prepared in this comparative example was tested for foam volume and half-life. The specific test method is as shown in Example 1, and the specific test results are shown in Tables 11 and 12.

[0136] Table 11 Foaming volume and half-life of solutions at different temperatures

[0137] Temperature / ℃ Foaming volume / mL Half-life / min 25 425 117 50 413 94 100 386 82 150 321 76 200 234 64

[0138] Table 12 Foaming volume and half-life of solutions at different salinities

[0139] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 413 78 <![CDATA[3×10 4 ]]> 394 75 <![CDATA[5×10 4 ]]> 313 69 <![CDATA[7×10 4 ]]> 301 64 <![CDATA[9×10 4 ]]> 275 46

[0140] Compared with Example 1, the grafting monomer in Comparative Example 2 was replaced with 2-acrylamide-2-methylpropanesulfonic acid. The half-life of the solution was 117 min at room temperature (25 ° C) and 64 min at high temperature (200 ° C); the mineralization was 9×10 4 At 100 ppm, the foam half-life was 46 minutes. Compared to the half-life in Example 1, the foam stabilization ability of Comparative Example 1 was reduced. This was mainly due to the replacement of the grafting monomer with 2-acrylamide-2-methylpropanesulfonic acid, which lacks perfluorocarbon chains and thiols, resulting in reduced foam stabilization ability. Furthermore, it lacks high temperature and salt resistance, resulting in a significant decrease in the foam half-life under high temperature and high salt conditions.

[0141] Comparative Example 3

[0142] A method for preparing a Pickering foam stabilizer is as described in Example 1, except that the concentration of the alkali treatment in the cellulose extraction in step (1) is changed to 40% sodium hydroxide solution.

[0143] The foam stabilizer prepared in this comparative example was tested for foam volume and half-life. The specific test method is as shown in Example 1, and the specific test results are shown in Tables 13 and 14.

[0144] Table 13 Foaming volume and half-life of solutions at different temperatures

[0145] Temperature / ℃ Foaming volume / mL Half-life / min 25 385 142 50 381 140 100 361 138 150 349 136 200 311 130

[0146] Table 14 Foaming volume and half-life of solutions at different salinities

[0147]

[0148]

[0149] Compared with Example 1, the sodium hydroxide concentration in Comparative Example 3 was adjusted to 40%, and the half-life of the solution was 142 min at room temperature (25 ° C) and 130 min at high temperature (200 ° C); the mineralization was 9×10 4 When the concentration of sodium hydroxide was 100 ppm, the half-life of the foam was 128 min. Compared with the half-life in Example 1, the foam stabilization ability of Comparative Example 3 was slightly reduced. The main reason for this phenomenon was that the concentration of sodium hydroxide was too high, which changed the crystal structure of cellulose, resulting in a decrease in strength and temperature resistance, and thus a decrease in its foam stabilization ability.

[0150] Comparative Example 4

[0151] A method for preparing a Pickering foam stabilizer is as described in steps (3)-(4) of Example 1, except that cellulose is replaced by nano-silicon dioxide (commercially available, with a diameter between 2-20 nm).

[0152] The foam stabilizer prepared in this comparative example was tested for foam volume and half-life. The specific test method is as shown in Example 1, and the specific results are shown in Tables 15 and 16.

[0153] Table 15 Foaming volume and half-life of solutions at different temperatures

[0154] Temperature / ℃ Foaming volume / mL Half-life / min 25 405 79 50 401 76 100 381 73 150 369 70 200 331 63

[0155] Table 16 Foaming volume and half-life of solutions at different salinities

[0156] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 402 76 <![CDATA[3×10 4 ]]> 391 75 <![CDATA[5×10 4 ]]> 377 67 <![CDATA[7×10 4 ]]> 349 64 <![CDATA[9×10 4 ]]> 323 60

[0157] Compared with Example 1, the homemade nanocellulose in Comparative Example 4 was replaced with nanosilica. The half-life of the solution was 79 min at room temperature (25 ° C) and 63 min at high temperature (200 ° C); the mineralization was 9×10 4 When the concentration of cellulose nitride was 100 ppm, the half-life of the foam was 60 min. Compared with the half-life in Example 1, the ability of stabilizing the foam in Comparative Example 4 was greatly reduced. The main reason for this phenomenon is that compared with nano-silica, nano-cellulose has a larger aspect ratio, which is more conducive to the stability of the foam.

[0158] Comparative Example 5

[0159] A method for preparing a Pickering foam stabilizer is as described in Example 1, except that no grafting modifier 1H,1H,2H,2H-perfluorododecanethiol is added to the nanomaterial in step 4).

[0160] The foam stabilizer prepared in this comparative example was tested for foam volume and half-life. The specific test method is as shown in Example 1, and the specific results are shown in Tables 17 and 18.

[0161] Table 17 Foaming volume and half-life of solutions at different temperatures

[0162] Temperature / ℃ Foaming volume / mL Half-life / min 25 356 58 50 336 51 100 324 40 150 298 35 200 257 31

[0163] Table 18 Foaming volume and half-life of solutions at different salinities

[0164] Mineralization / ppm Foaming volume / mL Half-life / min <![CDATA[1×10 4 ]]> 304 57 <![CDATA[3×10 4 ]]> 278 54 <![CDATA[5×10 4 ]]> 247 43 <![CDATA[7×10 4 ]]> 214 28 <![CDATA[9×10 4 ]]> 196 20

[0165] Compared with Example 1, in Comparative Example 5, no grafting modifier was added. The half-life of the solution at room temperature (25°C) was 58 min, and the half-life at high temperature (200°C) was 31 min. The mineralization was 9×10 4 ppm, the half-life of the foam is 20min. Compared with the half-life in Example 1, the ability to stabilize the foam in Comparative Example 5 is significantly reduced. The main reason for this phenomenon is that the nanoparticles have not been grafted and modified. The particles do not contain temperature-resistant and salt-resistant perfluorocarbon chains and thiol groups, which reduces the ability to stabilize the foam. This is because the hydrophobicity of the perfluorocarbon chain can effectively inhibit the rupture and fusion of the foam, prevent the instability and degradation of the foam, and the thiol group can serve as a surfactant component to effectively improve the interfacial properties and surface tension of the solution, form a stable gas / liquid interface, and enhance the stability of the foam. When nanocellulose lacks these two groups, the interfacial particle stability is insufficient and the foam stability is reduced. At the same time, it does not have a good ability to stabilize the foam in a high temperature and high salinity environment.

Claims

1. A method for preparing a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid, comprising the following steps: (1) A cellulose material with a core-shell structure is prepared using nanocellulose fibrils or nanocellulose crystals as the core and an organic resin material as the shell; the organic resin material is a chloromethyl-modified phenolic resin; (2) Adding catalyst A to sodium hydroxide solution, stirring evenly, and then adding a core-shell structured cellulose material aqueous dispersion to obtain a mixed solution I; adding catalyst B and a silane coupling agent to water to obtain a mixed solution II; adding the mixed solution II to the mixed solution I, and then adding a grafting monomer to react to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid; the catalyst A is 2,2,6,6-tetramethylpiperidine-N-oxide, ammonia water or potassium hydroxide; the catalyst B is one of triethylamine, nickel oxide and sodium molybdate; the silane coupling agent is γ-methacryloyloxypropyltrimethoxysilane, γ-(2,3-epoxypropoxy)propyltrimethoxysilane or vinyltriethoxysilane; the grafting monomer is 1H,1H,2H,2H-perfluorododecanethiol or 1H,1H,2H,2H-perfluorodecylthiol; Nanocellulose fibrils and nanocellulose crystals are prepared from cellulose, wherein the cellulose used is cellulose extracted from plants, wherein the plants are corn stalks or wood. The cellulose is extracted according to the following method: first, the corn stalks or wood are crushed into plant powder with a mesh size of 20-100, washed with water, and then dried at 30-80°C for 36-72 hours. The dried plant powder is added to an alkaline solution for treatment, and then filtered. The obtained solid is washed with water until the filtrate is neutral, and dried at 30-80°C for 36-72 hours to obtain an alkaline-treated raw material. The alkaline-treated raw material is dispersed in water to obtain a dispersion with a concentration of 0.05-0.3 g / mL, heated to 60-100°C, and then extracted by adding an acid solution and a bleaching agent every 1-2 hours, filtered, and the obtained solid is washed with deionized water until the filtrate is neutral. The solid is then washed with acetone and dried at 40-80°C to a constant weight to obtain cellulose. The alkaline solution is a sodium hydroxide solution with a mass fraction of 5-20%.

2. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: The mass ratio of the nanocellulose fibrils or nanocellulose crystals to the organic resin material in step (1) is 1:5-15.

3. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: The nanocellulose fibrils in step (1) are prepared according to the following method: Na2CO3 and NaHCO3 are weighed and dissolved in deionized water to obtain a Na2CO3-NaHCO3 buffer solution; sodium salt and an oxidant are dissolved in the buffer solution, cellulose is dispersed in the above solution, and then NaClO is added under stirring conditions, and the reaction is stirred at room temperature. During the reaction, the pH value of the system is adjusted to be maintained between 10 and 10.5; after the reaction is completed, anhydrous ethanol is added to terminate the reaction; the supernatant is removed, and the obtained solid is centrifuged and washed with deionized water until the supernatant is neutral, the supernatant is removed, water is added to the obtained solid for ultrasonic treatment, and then the supernatant is centrifuged and taken out, and the obtained supernatant is freeze-dried to obtain nanocellulose fibrils.

4. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 3, characterized in that: The mass ratio of Na2CO3 and NaHCO3 is 5-10:3; the concentration of Na2CO3 in the Na2CO3-NaHCO3 buffer solution is 0.1-0.2 mol / L; the sodium salt is sodium bromide, sodium nitrate or sodium fluoride, and the mass ratio of the sodium salt to cellulose is 0.2-0.5:1; the oxidant is 2,2,6,6-tetramethylpiperidinyl oxide or 4-isopropoxy-piperidine, and the mass ratio of the oxidant to cellulose is 0.01-0.05:1; the ratio of the mass of the cellulose to the volume of the Na2CO3-NaHCO3 buffer solution is 0.01-0.1 g:1 mL; the NaClO The mass of the cellulose is 30-70% of the mass of the cellulose; the pH of the system is adjusted to 10-10.5 using a dilute hydrochloric acid solution and a NaOH solution, the concentration of the dilute hydrochloric acid solution is 0.1-0.5 mol / L, and the concentration of the NaOH solution is 0.1-1 mol / L; the reaction time is 2-8 hours; the ratio of the added volume of the anhydrous ethanol to the mass of the cellulose is 10-30 mL:1 g; during the ultrasonic treatment, the ratio of the added volume of water to the mass of the cellulose is 10-50 mL:1 g; the ultrasonic treatment time is 30-60 minutes; the freeze-drying temperature is -26~-16°C, and the freeze-drying time is 10-24 hours.

5. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: The nanocellulose crystals in step (1) are prepared according to the following method: cellulose is added to a sulfuric acid solution for reaction; the suspension obtained by the reaction is then centrifuged, and the obtained solid is centrifugally washed with water until the pH value of the supernatant is neutral; water is then added to the obtained solid for ultrasonic treatment, and the obtained supernatant is freeze-dried after centrifugation to obtain nanocellulose crystals; the mass fraction of the sulfuric acid solution is 50-64%; the mass ratio of the cellulose to the sulfuric acid solution is 1:10-20; the reaction temperature is 40-80°C, and the reaction time is 1-3h; during the ultrasonic treatment, the ratio of the volume of water added to the mass of cellulose is 10-50mL:1g; the ultrasonic treatment time is 2-4h; the freeze-drying temperature is -26~-16°C, and the freeze-drying time is 10-24h.

6. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: In the cellulose extraction, the volume ratio of the alkaline solution to the mass ratio of the plant powder is 10-50 mL:1 g; the temperature for treatment with the alkaline solution is 60-100° C., and the treatment time is 1-3 hours; the acid solution is one of glacial acetic acid, a hydrochloric acid solution with a mass fraction of 37%, and a nitric acid solution with a mass fraction of 68%, and the mass ratio of the acid solution added each time to the alkali-treated raw material is 0.1-1:1; the bleaching agent is one of sulfur dioxide, sodium chlorite, and sulfur; the mass ratio of the bleaching agent added each time to the alkali-treated raw material is 0.1-1:1; and the extraction time is 3-6 hours.

7. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: The cellulose material with a core-shell structure using nanocellulose fibrils as the core in step (1) is a single-core structure, which is prepared according to the following method: After the pH value of the nanocellulose fibril aqueous dispersion is adjusted to 5-8, a xylene dispersion of the organic resin material is added, and then initiator I is added and stirred to react; after the reaction is completed, the mixture is filtered, washed, ultrasonically dispersed, and freeze-dried to obtain a cellulose material with a core-shell structure with the nanocellulose fibrils as the core.

8. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 7, characterized in that: The concentration of the nanocellulose fibril aqueous dispersion is 0.05-0.5 g / mL; the pH of the nanocellulose fibril aqueous dispersion is adjusted using a 0.05 mol / L sodium hydroxide solution; the concentration of the xylene dispersion of the organic resin material is 0.05-0.25 g / mL; the initiator I is benzoyl peroxide or dicumyl peroxide; the mass of the initiator I is 0.5-3% of the mass of the nanocellulose fibrils; the stirring speed is 2000-5000 r / min, and the stirring reaction time is 12-36 hours; the washing is performed by washing with ethanol 3-5 times; the ultrasonic dispersion is performed by adding the solid obtained by washing into water, ultrasonically dispersing it uniformly, and obtaining a suspension, and the ratio of the added mass of the water to the mass of the nanocellulose fibrils is 40-60:1; the freeze-drying temperature is -26~-16°C, and the freeze-drying time is 10-24 hours.

9. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: In step (1), the cellulose material with a core-shell structure having nanocellulose crystals as the core is a single-core structure or a multi-core structure; The mononuclear core-shell structured cellulose material with nanocellulose crystals as the core was prepared according to the following method: After adjusting the pH value of the nanocellulose crystal aqueous dispersion to 5-8, a xylene dispersion of an organic resin material is added, and then an initiator II is added. After stirring evenly, the mixture is allowed to stand for reaction. After the reaction is completed, the mixture is filtered, washed, ultrasonically dispersed, and freeze-dried to obtain a single-core core-shell structured cellulose material with the nanocellulose crystal as the core.

10. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 9, characterized in that: The concentration of the nanocellulose crystal aqueous dispersion is 0.01-0.1 g / mL; the pH of the nanocellulose crystal aqueous dispersion is adjusted using a 0.05 mol / L sodium hydroxide solution; the concentration of the xylene dispersion of the organic resin material is 0.05-0.25 g / mL; the initiator II is benzoyl peroxide or dicumyl peroxide, and the mass of the initiator II is 0.5-3% of the mass of the nanocellulose crystals; the stirring speed is 2000-5000 r / min, and the static reaction time is 12-36 hours; the washing is performed by washing with ethanol 3-5 times; the ultrasonic dispersion is performed by adding the solid obtained by washing into water and uniformly dispersing it by ultrasonication to obtain a suspension, and the ratio of the added mass of the water to the mass of the nanocellulose crystals is 40-60:1; and the freeze-drying is performed by freeze-drying at -26~-16°C for 12-36 hours.

11. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 9, characterized in that: The multi-core core-shell structured cellulose material with nanocellulose crystals as the core is prepared according to the following method: (a) After adjusting the pH value of the nanocellulose crystal aqueous dispersion to 5-8, a xylene dispersion of an organic resin material is added, and then an initiator III is added, and the mixture is stirred evenly, and then allowed to stand for reaction; after the reaction is completed, the mixture is filtered, washed, ultrasonically dispersed, and freeze-dried to obtain a single-core core-shell structure cellulose material; the concentration of the nanocellulose crystal aqueous dispersion is 0.01-0.1 g / mL; the pH value of the nanocellulose crystal aqueous dispersion is adjusted using a 0.05 mol / L sodium hydroxide solution; the concentration of the xylene dispersion of the organic resin material is 0.05-0.25 g / mL L; the initiator III is benzoyl peroxide or dicumyl peroxide, and the mass of the initiator III is 0.5-3% of the mass of the nanocellulose crystals; the stirring speed is 2000-5000 r / min, and the static reaction time is 12-36 hours; the washing is performed by washing with ethanol 3-5 times; the ultrasonic dispersion is performed by adding the washed solid to water and ultrasonically dispersing it uniformly to obtain a suspension, and the ratio of the added mass of the water to the mass of the nanocellulose crystals is 40-60:1; the freeze-drying is performed at -26~-16°C for 12-36 hours; (b) adding the mononuclear core-shell structure cellulose material obtained in step (a) to an ionic liquid, adding a dispersant and an initiator IV, stirring and reacting to obtain a reaction solution; then vacuum drying the reaction solution to obtain a multinuclear core-shell structure cellulose material with nanocellulose crystals as cores; the ionic liquid is one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-butyl-3-methylimidazolium tetrafluoroborate, and 1-butyl-3-methylimidazolium trifluoromethanesulfonate, and the mass of the ionic liquid is similar to that of the mononuclear core-shell structure cellulose material. The molar ratio is 3-8:1; the dispersant is sodium lauryl sulfate, polyethylene glycol 200 or polyethylene glycol 400, and the mass of the dispersant is 2-5% of the mass of the mononuclear core-shell structure cellulose material; the initiator IV is benzoyl peroxide or dicumyl peroxide, and the initiator IV is 0.5-3% of the mass of the mononuclear core-shell structure cellulose material; the reaction temperature is 60-90°C, and the reaction time is 10-15h; the vacuum drying temperature is 40-60°C, and the vacuum drying time is 12-36h.

12. The method for preparing the high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid according to claim 1, characterized in that: In step (2), the mass ratio of the catalyst A to the core-shell structure cellulose material is 0.05-0.5:1; the mass fraction of the sodium hydroxide solution is 5-15%; the volume ratio of the sodium hydroxide solution to the mass ratio of the core-shell structure cellulose material is 1-5mL:1g; the concentration of the core-shell structure cellulose material aqueous dispersion is 0.01-0.2g / mL; the mass ratio of the catalyst B to the core-shell structure cellulose material is 0.3-0.8:1; the concentration of the catalyst B in the mixed solution II is 0.05-0.15g / mL; the mass ratio of the silane coupling agent to the core-shell structure cellulose material is 0.05-0.3:1; the mass ratio of the grafting monomer to the core-shell structure cellulose material is 5-20:1; The reaction temperature is 70-90°C; the reaction time is 12-36 hours; and after the reaction, a post-processing step is further included, specifically as follows: filtering the obtained reaction liquid, washing the filtered solid with anhydrous ethanol, and then freeze-drying it at -26~-16°C for 12-36 hours to obtain a high-temperature and high-salt resistant Pickering foam stabilizer for geothermal well drilling fluid.

13. A high temperature and high salt resistant Pickering foam stabilizer for geothermal well drilling fluid, characterized in that: The preparation method according to claim 1 is used for preparation.

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