Preparation method of water-in-oil emulsion type defoaming agent for shale gas exploitation

Abstract

The application discloses a preparation method of a water-in-oil emulsion type defoaming agent for shale gas exploitation, which comprises the following steps: adding 32# industrial grade white oil into a beaker, adding yellow block-shaped microcrystalline wax, heating to 70 DEG C to dissolve the microcrystalline wax, adding Span 80 after uniform mixing and stirring, keeping constant temperature magnetic stirring for 10 min, keeping stirring at 70 DEG C for 30 min, adding tertiary distilled water, continuing stirring for 60 min, and finally adding 2g of 5% PVA water solution to obtain the water-in-oil emulsion type defoaming agent for shale gas exploitation. The surface active agent generated after starch modification is used to treat the surface groups, so that the silane groups are attached to the wax surface with low surface energy, are wrapped on the outer surface of the raw material through hydrogen bond or electrostatic force, the hydrophobicity is increased, the surface tension is reduced, and the defoaming purpose is achieved at the gas-liquid interface. The silicon grease material is compounded in the later stage, the silicon-containing groups can be better adsorbed on the outermost layer of the raw material, so that the defoaming is more helpful, and the defoaming rate and defoaming speed are improved.

Description

A method for preparing a water-in-oil emulsion defoamer for shale gas development. Technical Field

[0001] This invention relates to the field of oilfield chemical additives technology, specifically to a method for preparing an oil-in-water emulsion defoamer for shale gas development. Background Technology

[0002] Shale oil and gas are mainly found in shale oil-bearing formations, which are composed of shale. Shale is a rock mixture of mud and sand with extremely small pores, invisible to the naked eye. Shale oil and gas are contained within these pores. Rocks containing shale oil and gas are called oil shale. Oil shale is light brown or dark black, with a dull surface, and emits black smoke and a bitumen smell when burned. By mechanically crushing oil shale and heating it to about 500 degrees Celsius, shale oil can be extracted, along with shale gas.

[0003] Currently, widely used defoamers can be classified into organosilicon, fatty acid, amide, phosphate, alcohol, and polyether types. Among them, the most widely used is the broad-spectrum organosilicon defoamer, which comes in five types: oil-based, paste-based, solid, emulsion-based, and self-emulsifying. It has the characteristics of low dosage, high efficiency, convenient use, good resistance to high and low temperatures, stable physicochemical properties, physiological inertness, and non-toxicity and non-polluting properties, and has attracted the attention of various industries. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing a defoamer that can improve the defoaming rate and defoaming efficiency.

[0005] To achieve the above objectives, the present invention provides a method for preparing a water-in-oil emulsion defoamer for shale gas development, which employs the following technical solution:

[0006] A method for preparing an oil-in-water emulsion defoamer for shale gas development involves taking 32# industrial-grade white oil and adding it to a beaker. Yellow lumps of microcrystalline wax are added, and the mixture is heated to 70°C to dissolve the microcrystalline wax. After thorough mixing, Span 80 is added, and the mixture is magnetically stirred at a constant temperature for 10 minutes. Then, it is stirred at 70°C for 30 minutes. Third-grade distilled water is added, and stirring continues for 60 minutes. Finally, 2g of a 5% PVA aqueous solution is added to obtain the oil-in-water emulsion defoamer for shale gas development.

[0007] A further improvement of the preparation method of the oil-in-water emulsion defoamer for shale gas development in this invention is that the yellow lumpy microcrystalline wax is replaced by white paraffin wax.

[0008] A further improvement of the preparation method of the oil-in-water emulsion defoamer for shale gas development of the present invention is that p-toluenesulfonic acid starch ester is added simultaneously when adding Span 80.

[0009] A further improvement of the preparation method of the oil-in-water emulsion defoamer for shale gas development in this invention is that silicone grease is added after constant temperature magnetic stirring for 10 minutes.

[0010] A further improvement of the preparation method of the water-in-oil emulsion defoamer for shale gas development in this invention is that the preparation steps of p-toluenesulfonic acid starch ester include: mixing starch, ethanol, and water and heating to 70°C; adding concentrated hydrochloric acid and stirring for 1 hour for acid hydrolysis; then cooling the reaction solution to room temperature with ice water; neutralizing with sodium bicarbonate; centrifuging the neutralized reaction solution and filtering under reduced pressure; drying under reduced pressure at 90°C to constant weight to obtain acid-hydrolyzed waxy corn starch; dispersing the acid-hydrolyzed waxy corn starch in DMF; heating to 120°C and continuing magnetic stirring for 1 hour; then cooling to 100°C; adding LiCl; after the dispersion is completely transparent; cooling to room temperature in an ice water bath; adding triethylamine and p-toluenesulfonyl chloride; reacting overnight to obtain an orange-yellow turbid liquid; precipitating with a large amount of deionized water; filtering; washing repeatedly with water and ethanol; and drying under vacuum at 50°C to obtain p-toluenesulfonic acid starch ester.

[0011] Compared with the prior art, the beneficial effects of the present invention are:

[0012] This invention utilizes a surfactant derived from starch modification to treat the surface groups, resulting in the attachment of silane groups to the low-surface-energy wax surface. These groups are then wrapped around the outer surface of the raw material via hydrogen bonding or electrostatic forces, increasing its hydrophobicity and reducing surface tension, thus achieving defoaming at the gas-liquid interface. Subsequently, a silicone grease material is formulated to better adsorb the silicon-containing groups onto the outermost layer of the raw material, further aiding in defoaming and improving both the defoaming rate and defoaming speed. Attached Figure Description

[0013] Figure 1A is a schematic diagram of the contact angle between particles, water, and ethyl acetate;

[0014] Figure 1B is a schematic diagram of emulsion droplets;

[0015] Figure 2A is a schematic diagram of the formation of starch-based nanoparticles after complete removal of dichloromethane;

[0016] Figure 2B is a schematic diagram of the average size of starch-based nanoparticles. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] A method for preparing a water-in-oil emulsion defoamer for shale gas development includes first preparing p-toluenesulfonic acid starch ester. Specifically, 80g of starch is added to a 500mL three-necked flask equipped with a reflux condenser, a stirrer, and a thermometer. 288mL of ethanol and 32mL of water are added, and the mixture is stirred until homogeneous. The mixture is then heated to 70°C. 14mL of concentrated hydrochloric acid is added, and the mixture is acid-hydrolyzed at 70°C and a stirring rate of 250rpm for 1 hour. The reaction solution is then rapidly cooled to room temperature with ice water and neutralized with 180mL of 1mol / L sodium bicarbonate. After centrifugation, the product is filtered under reduced pressure and dried under reduced pressure at 90°C to constant weight to obtain acid-hydrolyzed waxy corn starch. 10g of the acid-hydrolyzed waxy corn starch is dispersed in 80mL of LDM, heated to 120°C, and magnetically stirred for 1 hour. Then, the temperature was lowered to 100℃, 2g of LiCl was added, and after the dispersion became completely transparent, it was cooled to room temperature in an ice-water bath. 20ml of triethylamine and 6g of p-toluenesulfonyl chloride were added, and the reaction was carried out overnight to obtain an orange-yellow turbid liquid. The liquid was precipitated with a large amount of deionized water, filtered, washed repeatedly with water and ethanol, and dried under vacuum at 50℃ to obtain p-toluenesulfonic acid starch ester.

[0019] Example 1

[0020] Take 30g of 32# industrial grade white oil and add it to a 250ml beaker. Add 10g of yellow lumps of microcrystalline wax and heat to 70℃ to dissolve the microcrystalline wax. After mixing and stirring evenly, add 7g of Span 80 and stir magnetically at a constant temperature for 10 minutes. Then add 51g of third-grade distilled water and continue stirring for 60 minutes. Finally, add 2g of 5% PVA aqueous solution to obtain the oil-in-water emulsion defoamer type I for shale gas development.

[0021] Example 2

[0022] Take 30g of 32# industrial grade white oil and add it to a 250ml beaker. Add 10g of yellow lumps of microcrystalline wax and heat to 70℃ to dissolve the microcrystalline wax. After mixing and stirring evenly, add 5g of p-toluenesulfonic acid starch ester and 2g of Span 80. Stir magnetically at a constant temperature for 10 minutes, then add 51g of third-grade distilled water and continue stirring for 60 minutes. Finally, add 2g of 5% PVA aqueous solution to obtain the water-in-oil emulsion defoamer type II for shale gas development.

[0023] Example 3

[0024] Take 30g of 32# industrial grade white oil and add it to a 250ml beaker. Add 10g of yellow lumps of microcrystalline wax and heat to 70℃ to dissolve the microcrystalline wax. After mixing and stirring evenly, add 5g of p-toluenesulfonic acid starch ester and 2g of Span 80. Stir magnetically at a constant temperature for 10 minutes, then add 6g of silicone grease and stir at 70℃ for 30 minutes. Add 45g of third-grade distilled water and continue stirring for 60 minutes. Finally, add 2g of 5% PVA aqueous solution to obtain the oil-in-water emulsion defoamer type III for shale gas development.

[0025] Example 4

[0026] Take 30g of 32# industrial grade white oil and add it to a 250ml beaker. Add 10g of 10# white paraffin wax and heat to 70℃ to dissolve the white paraffin wax. After mixing and stirring evenly, add 5g of p-toluenesulfonic acid starch ester and 2g of Span 80. Stir magnetically at a constant temperature for 10 minutes, then add 6g of silicone grease. Stir at 70℃ for 30 minutes, then add 45g of third-grade distilled water and continue stirring for 60 minutes. Finally, add 2g of 5% PVA aqueous solution to obtain the oil-in-water emulsion defoamer type IV for shale gas development.

[0027] In Examples 1-4 of this invention, the surface groups of the surfactant generated after starch modification were treated, resulting in the attachment of silane groups to the low surface energy wax surface. These groups are then wrapped around the outer surface of the raw material through hydrogen bonding or electrostatic forces, increasing its hydrophobicity and reducing surface tension, thus achieving defoaming at the gas-liquid interface. Later, a silicone grease material was formulated, allowing the silicon-containing groups to be better adsorbed onto the outermost layer of the raw material, further aiding in defoaming and improving the defoaming rate and defoaming speed.

[0028] The wettability of p-toluenesulfonic acid starch nanoparticles was studied by measuring the contact angle (θow) between the particles, water, and ethyl acetate. As shown in Figure 1A, the three-phase contact angle was approximately 104°, greater than 90°. This indicates that the hydrophobicity of the starch modified with p-toluenesulfonyl chloride was significantly enhanced, tending to stabilize water-in-oil emulsions. The morphology of the stable water-ethyl acetate emulsion droplets of p-toluenesulfonic acid starch was observed using CLSM, with a particle content of 1 wt%. Figure 1B shows that the droplet size was approximately 27 μm, with most of the fluorescence concentrated at the droplet interface, forming a dense and relatively uniformly sized fluorescent ring, indicating that the starch-based particles were distributed at the oil-water interface. Based on the laser confocal microscopy image of the droplets, it is shown that the prepared hydrophobic starch-based particles are amphiphilic, capable of stabilizing the emulsion droplets and preventing droplet aggregation.

[0029] p-Toluenesulfonic acid starch nanoparticles were prepared via a nano-coprecipitation method. A dichloromethane solution of p-toluenesulfonic acid starch was added dropwise to ethyl acetate under stirring. Starch was deposited at the interface between the two liquid phases, forming starch-based nanoparticles. SEM characterization confirmed the formation of starch-based nanoparticles after complete removal of dichloromethane (Figure 2A). The particle morphology was not a regular sphere, possibly due to collapse and deformation caused by moisture loss during the drying process. Furthermore, DLS results showed that the average size of the obtained starch-based nanoparticles was approximately 150 nm, with a particle size distribution (PDI) of 0.144 (Figure 2B).

[0030] The evaluation of organosilicon defoamers in shale gas development was conducted according to Item 5 of the Southwest Oil and Gas Branch Company's enterprise standard Q / SH 15000028—2019 "Technical Specifications for Chemical Agents Used in Gas Production". Water-in-oil emulsion defoamers of types I-IV were used.

[0031] Evaluation data on the use of water-in-oil emulsion defoamers in shale gas development.

[0032]

[0033]

[0034] Defoamers spread easily on the solution surface, carrying away a layer of foaming agent solution from adjacent surfaces during the spreading process, thus thinning the liquid film. When the foam film thickness is less than the critical film thickness, the foam will break. Generally speaking, the faster the defoamer spreads on the solution surface, the thinner the liquid film becomes, and the more obvious the defoaming effect. Analysis of the above evaluation data shows that Defoamer Type III, after emulsification with p-toluenesulfonic acid starch ester, disperses more evenly in the foaming liquid than Defoamers Types I, II, and IV, reducing surface tension and spreading easily on the foaming liquid solution surface, effectively shortening the defoaming time and improving its defoaming ability. Because defoamer type III uses microcrystalline wax, and waxes are natural substances that can reduce surface tension, similar to the surface of a lotus leaf, after emulsification with p-toluenesulfonic acid starch ester particles, wax microspheres can be effectively formed, arranged in an orderly manner on their surface. The gaps between the microspheres are smaller than the diameter of water molecules, enhancing their hydrophobicity. When industrial-grade 32# white oil is added, under the action of surfactant Span 80, it is grafted onto the CH side chains of the wax under the action of van der Waals forces, further enhancing its lipophilicity, thus improving its defoaming performance. Regarding foam suppression, because microcrystalline wax has strong adhesion, it accelerates the rate of water repulsion on the surface of bubbles, forming a very thin wax film, thus improving foam suppression.

[0035] After a 6-month trial of water-in-oil emulsion defoamer type III in shale gas development wells, scale samples were analyzed and XRD patterns were created. The results showed that water-in-oil emulsion defoamer type III effectively reduced silica deposits. This is because it contains p-toluenesulfonic acid starch ester nanoparticles, whose particle size is smaller than that of silicon atoms. These nanoparticles form a temporary oil film on the inner surface of the pipe. Additionally, the 32# white oil has a certain degree of adhesion, making it difficult for silicon atoms to adhere and form scale. However, due to long-term formation water erosion, the reliability of the formed hydrophobic oil film decreases. Therefore, water-in-oil emulsion defoamer type III can only be used as a short-term scale inhibitor and cannot prevent the formation of lead-barium sulfate scale over a long period.

[0036] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

Claims

1. A method for preparing a water-in-oil emulsion defoamer for shale gas development, characterized in that: Take 32# industrial grade white oil and add it to a beaker. Add yellow lumps of microcrystalline wax and heat to 70°C to dissolve the microcrystalline wax. After mixing and stirring evenly, add Span 80 and p-toluenesulfonic acid starch ester. Stir magnetically at a constant temperature for 10 minutes, then add silicone grease and stir at 70°C for 30 minutes. Add third-grade distilled water and continue stirring for 60 minutes. Finally, add 2g of 5% PVA aqueous solution to obtain an oil-in-water emulsion defoamer for shale gas development. The preparation steps of the p-toluenesulfonic acid starch ester include mixing corn starch, ethanol, and water, heating to 70°C, adding concentrated hydrochloric acid, and stirring for 1 hour for acid hydrolysis. The reaction solution was cooled to room temperature with ice water, then neutralized with sodium bicarbonate. After centrifugation, the neutralized reaction solution was filtered under reduced pressure and dried under reduced pressure at 90°C to constant weight to obtain acid-hydrolyzed waxy corn starch. The acid-hydrolyzed waxy corn starch was dispersed in DMF, heated to 120°C and stirred magnetically for 1 hour, then cooled to 100°C and LiCl was added. After the dispersion became completely transparent, it was cooled to room temperature in an ice-water bath, and triethylamine and p-toluenesulfonyl chloride were added. The reaction was carried out overnight to obtain an orange-yellow turbid liquid. The liquid was precipitated with a large amount of deionized water, filtered, washed repeatedly with water and ethanol, and dried under vacuum at 50°C to obtain p-toluenesulfonic acid starch ester.

2. The preparation method of a water-in-oil emulsion defoamer for shale gas development according to claim 1, characterized in that: The yellow lumps of microcrystalline wax were replaced with white paraffin wax.

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