Preparation method of high-temperature-resistant emulsified acid for acidification

Abstract

The invention relates to a preparation method of high-temperature-resistant emulsified acid for acidification, and belongs to the technical field of oilfield chemistry. Acidic compounds such as concentrated hydrochloric acid and sulfamic acid are dissolved in water to form acid liquor; a silicon-containing polymer with a plurality of silicate ester groups in molecules is prepared through copolymerization of a silicon-containing monomer, a hydrophilic monomer and an oleophylic monomer in an organic solvent, and then the silicon-containing polymer, a silicon-containing surfactant and a conventional surfactant are dissolved in an oil solvent to form an oil phase. On the basis, acid liquid and an oil phase are mixed and stirred to form emulsified acid. The emulsified acid prepared in the invention has good stability at high temperature, and has good application prospects in oilfield acidification operation.

Description

Technical Field

[0001] This invention relates to a method for preparing a high-temperature resistant emulsifying acid for acidification, belonging to the field of oilfield chemical technology. Background Technology

[0002] Carbonate reservoirs are among the most common types of oil and gas reservoirs in my country, characterized by large reserves, wide distribution, low permeability, and high exploration and development difficulty. For carbonate reservoirs, the most widely used well enhancement technology in China is acid fracturing. This involves pumping acid into the reservoir to create fractures in the formation. The acid then enters the fractures and, through an acid-rock reaction, creates non-uniform etching channels. After the fractures close, these channels allow oil and gas to flow. Currently, conventional acid systems generally use hydrochloric acid due to its low cost, high solubility, and high hydrochloric acid salt solubility. However, because carbonate reservoirs are buried at great depths and have high formation temperatures, conventional acid systems react too quickly in the near-wellbore zone, sometimes even being completely depleted, preventing them from penetrating deeper into the fractures and resulting in poor acidizing effects. Furthermore, direct contact between the acid and the tubing at high temperatures can lead to pipeline corrosion, posing safety hazards to field operations. Therefore, researching a high-temperature resistant acid system with a slow-release effect is of great significance for improving acid fracturing operations.

[0003] Commonly used slow-release acids include thickened acids (gelling acids), emulsified acids, and self-generating acids. Thickened acids are produced by adding a thickener, usually a linear polymer, to a conventional acid solution. After the thickener dissolves fully in the acid, its molecular chains fully extend and intertwine to form random polymer coils, thereby increasing the viscosity of the acid. This increase in viscosity leads to increased H₂O. + The diffusion rate in acid is reduced, thus achieving a slowing effect. Under high-temperature conditions, thickened acid can also severely corrode the tubing, and the polymeric thickener may react with metal ions in the formation to form insoluble substances, blocking oil and gas channels. Autogenous acid refers to the generation of HCl to dissolve fractures under formation conditions using one or more substances, without initially producing acid, greatly reducing corrosion to the pipeline. However, autogenous acid generation is usually insufficient and difficult to control, resulting in poor dissolution effects. To solve the problems encountered by thickened acid and autogenous acid, emulsified acid has emerged. Emulsified acid refers to the formation of a water-in-oil emulsion by adding an emulsifier, with the oil phase as the external phase and the acid as the internal phase. The oil phase fully encapsulates the acid, preventing H2 from spreading. +The diffusion of emulsified acid has a good slowing effect, allowing the acid to penetrate deep into the formation. Under high temperature or high salinity conditions, the emulsion breaks down, releasing the acid and dissolving fractures to achieve deep acidification. Furthermore, because the acid and tubing are isolated through the oil phase, the emulsified acid can more effectively protect the tubing. However, due to the insufficient strength of the adsorption film formed by conventional emulsifiers at the oil-water interface and the harsh environment created by acidic substances in the aqueous phase, conventional emulsified acids have poor high-temperature stability, significantly reducing their performance in deep acidification and reducing tubing corrosion.

[0004] Chinese invention patent CN 116836695A discloses a W / O / W type multi-structure emulsified acid, its preparation method, and its application. The method involves mixing a synthesized first polymer synergist with an oil solvent, a first hydrochloric acid solution, and a first emulsifier for a first emulsification to obtain a W / O type initial phase. This initial phase is then mixed with a second hydrochloric acid solution, a second emulsifier, and a synthesized second polymer synergist for a second emulsification to obtain the W / O / W type multi-structure emulsified acid. While the W / O / W type emulsified acid can be used as an acidizing working fluid in oilfields, the acid solution it uses contains only 10% HCl by mass, and the proportion of the internal acid phase is relatively low. This makes it difficult to avoid corrosion of the tubing during injection, and the insufficient acid content after penetrating deep into the formation results in poor dissolution effects.

[0005] Chinese invention patent CN 108285784A discloses a gelled emulsified acid and its preparation method, which integrates the properties of gelled and emulsified acids. A thickener is added to the inner phase of the emulsified acid to form an oil-in-gelled acid emulsion, which exhibits better sustained-release performance and stability than conventional acids, and provides acidizing effects after injection into the formation. The gelled emulsified acid preparation process is simple, its performance is reliable, it is safe to transport, and it is convenient to use, making it suitable as an oilfield acidizing material. However, this gelled emulsified acid is only suitable for acidizing at 80℃; at higher temperatures, demulsification occurs more rapidly. Summary of the Invention

[0006] To address the shortcomings of existing technologies, this invention provides a method for preparing a high-temperature resistant emulsifying acid for acidification. Invention Overview

[0008] This invention dissolves acidic compounds such as concentrated hydrochloric acid and aminosulfonic acid in water to form an acid solution. A silicon-containing polymer with multiple silicate ester groups is prepared by copolymerizing silicon-containing monomers, hydrophilic monomers, and lipophilic monomers in an organic solvent. Then, the silicon-containing polymer, a silicon-containing surfactant, and a conventional surfactant are dissolved in an oil solvent to form an oil phase. The acid solution and oil phase are then mixed and stirred to form an emulsified acid. The silicon-containing polymer and surfactant are used to hydrolyze and condense at the oil-water interface to form siloxane structures, thereby enhancing the strength of the adsorption film formed at the oil-water interface and improving the stability of the emulsified acid at high temperatures. Test results show that the emulsified acid exhibits excellent stability at high temperatures and has promising application prospects in deep acid fracturing operations in carbonate reservoirs. Invention Details

[0010] The technical solution of the present invention is as follows.

[0011] A method for preparing a high-temperature resistant emulsifying acid for acidification includes the following steps:

[0012] (1) Preparation of silicon-containing polymers

[0013] Silicon-containing monomers, hydrophilic monomers, lipophilic monomers, initiators, and organic solvents are added to a flask equipped with a stirrer, a nitrogen inlet tube, and a thermometer. After stirring until all raw materials are dissolved, nitrogen gas is introduced for 30 minutes. The polymerization temperature is controlled at 40–80℃, and the polymerization reaction is carried out for 1–24 hours to obtain the product. The mass ratio of silicon-containing monomers, hydrophilic monomers, and lipophilic monomers is 1:(0.02–0.2):(0.05–1), the ratio of the total mass of silicon-containing monomers, hydrophilic monomers, and lipophilic monomers to the mass of organic solvent is 1:(0.8–9), and the mass ratio of organic solvent to initiator is 1:(0.001–0.02).

[0014] (2) Preparation of acid solution

[0015] Concentrated hydrochloric acid and an acidic compound are added to water and stirred to dissolve, thus obtaining the product. The mass fraction of HCl in the concentrated hydrochloric acid is 30% to 38%, the mass ratio of concentrated hydrochloric acid to the acidic compound is 1:(0.001 to 0.2), and the ratio of the total mass of concentrated hydrochloric acid and the acidic compound to the mass of water is 1:(0.1 to 3).

[0016] (3) Preparation of emulsified acid

[0017] Add the oil solvent, emulsifier-1, emulsifier-2, and silicone polymer to a flask equipped with a stirrer and thermometer, stir to dissolve, and add acid solution dropwise to the flask using a dropping funnel over a period of 10–30 min at a stirring speed of 1000–2000 r / min. After the addition is complete, raise the temperature to 35–65 °C and continue stirring for 1–6 h to obtain the final product. The mass ratio of emulsifier-1 to emulsifier-2 is 1:(0.25–1.5), the mass ratio of emulsifier-2 to silicone polymer is 1:(0.8–6.5), the ratio of the total mass of emulsifier-1, emulsifier-2, and silicone polymer to the mass of oil solvent is 1:(10–50), and the mass ratio of oil solvent to acid solution is 1:(0.3–3).

[0018] According to the present invention, preferably, the silicon-containing monomer in step (1) is one or a mixture of two or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane.

[0019] Preferably, the hydrophilic monomer is

[0020]

[0021] Where n is 10 to 20, and R1 is a hydrogen atom, methyl or ethyl;

[0022] Preferably, the lipophilic monomer is one or a mixture of two or more of 1-octadecene, 1-hexadecene, 1-tetradecene, and 1-dodecene;

[0023] Preferably, the initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine hydrochloride;

[0024] Preferably, the organic solvent is one or a mixture of two or more of formamide, N,N-dimethylformamide, tetrahydrofuran, dioxane, ethanol, and tert-butanol;

[0025] Preferably, the mass ratio of the silicon-containing monomer, hydrophilic monomer, and lipophilic monomer is 1:(0.05~0.15):(0.25~1);

[0026] Preferably, the ratio of the total mass of the silicon-containing monomer, hydrophilic monomer, and lipophilic monomer to the mass of the organic solvent is 1:(1.5-5);

[0027] Preferably, the mass ratio of organic solvent to initiator is 1:(0.005~0.02);

[0028] Preferably, the polymerization temperature is 50–70℃ and the polymerization time is 3–15 h.

[0029] According to the present invention, preferably, the acidic compound in step (2) is one or a mixture of two or more of aminosulfonic acid, formic acid, acetic acid, lactic acid, and glycolic acid;

[0030] Preferably, the ratio of the total mass of concentrated hydrochloric acid and acidic compounds to the mass of water is 1:(0.25-2).

[0031] According to the present invention, preferably, the oil solvent mentioned in step (3) is one or a mixture of two or more of diesel oil, kerosene, and white oil;

[0032] Preferably, the emulsifier-1 is one or a mixture of two or more of propylene glycol monostearate, glyceryl monostearate, propylene glycol monolaurate, sorbitan monooleate, sorbitan tristearate, and sorbitan monostearate.

[0033] Preferably, the emulsifier-2 is

[0034]

[0035] Where R2 and R3 are methyl or ethyl, R4 is dodecyl, tetradecyl, hexadecyl or octadecyl, R5 is methyl, ethyl, n-propyl or n-butyl, and R6 is an oxygen atom or methylene.

[0036] Preferably, the mass ratio of emulsifier-1 to emulsifier-2 is 1:(0.25~0.75);

[0037] Preferably, the mass ratio of emulsifier-2 to the silicone-containing polymer is 1:(1-4.5);

[0038] Preferably, the ratio of the total mass of emulsifier-1, emulsifier-2, and silicone-containing polymer to the mass of oil solvent is 1:(10-30);

[0039] Preferably, the mass ratio of oil solvent to acid is 1:(1-3).

[0040] The superior effects of this invention are as follows:

[0041] 1. The raw materials of this invention are readily available, the reaction conditions are mild, the process is simple and safe, and it can be used for large-scale industrial production.

[0042] 2. This invention utilizes the fact that silicates can only hydrolyze and condense when they come into contact with water, and that the selected silicon-containing components are all amphiphilic substances with strong lipophilicity, ensuring that the silicon-containing components mainly react at the oil-water interface, avoiding problems such as emulsion thickening and precipitation that may be caused by the condensation of silicon-containing components in the aqueous or oil phase.

[0043] 3. This invention uses a silicon-containing polymer as a backbone, and through its reaction with a silicon-containing surfactant, a condensation product is formed in which the molecules of the two components are connected by covalent chains, thereby giving the oil-water interface film good strength and improving the dispersion stability of emulsified acids at high temperatures.

[0044] 4. This invention can efficiently slow down the acid-rock reaction rate of the working fluid, has deep penetration, and can achieve deep formation acidification.

[0045] 5. The product of this invention avoids direct contact between acid and tubing, which can reduce the corrosion of tubing at high temperatures.

[0046] 6. The product prepared by this invention is convenient to store, transport and use, and is suitable for on-site online mixing operations in acid fracturing. Detailed Implementation

[0047] In the following examples and comparative examples, the iron ion stabilizer is TW-3 iron ion stabilizer for acidification produced by Shaanxi Lanxin Chemical Co., Ltd., the corrosion inhibitor is THIF-117 corrosion inhibitor produced by Yantai Hengxin Chemical Technology Co., Ltd., and the high-temperature emulsifier is Degussa EM90 emulsifier supplied by Guangzhou Bolu Chemical Co., Ltd.

[0048] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0049] The present invention will be further described below with reference to specific embodiments, but the scope of protection of the present invention is not limited thereto.

[0050] Example 1:

[0051] (1) Preparation of silicon-containing polymers

[0052] 20g vinyltriethoxysilane, 1g allyl polyoxyethylene ethyl ether (n=10), 5g 1-octadecene, 1.5g azobisisobutyronitrile, and 100g formamide were added to a flask equipped with a stirrer, a nitrogen purging tube, and a thermometer. After stirring until all raw materials were dissolved, nitrogen gas was introduced for 30 minutes. The polymerization temperature was controlled at 55℃, and the polymerization reaction was carried out for 8 hours to obtain a silicon-containing polymer.

[0053] (2) Preparation of acid solution

[0054] Add 40g of concentrated hydrochloric acid (HCl mass fraction of 37%) and 2g of aminosulfonic acid to 11g of water, stir to dissolve, and obtain acid solution;

[0055] (3) Preparation of emulsified acid

[0056] 20g of diesel oil, 0.6g of sorbitan monooleate, 0.2g of dodecyltrimethoxysilane, and 0.3g of silicon-containing polymer were added to a flask equipped with a stirrer and a thermometer. The mixture was stirred until dissolved. 30g of acid solution was added dropwise to the flask using a dropping funnel over a period of 10 minutes. The stirring speed was 1200 r / min. After the addition was complete, the temperature was raised to 40℃ and stirring was continued for 1 hour to obtain emulsified acid.

[0057] While stirring, add 1.5% THIF-117 and 1% TW-3 by mass of the total system to the above emulsified acid, and set aside.

[0058] Example 2:

[0059] As described in Example 1, except that the amount of allyl polyoxyethylene ethyl ether (n is 10) added in step (1) is 3g.

[0060] Example 3:

[0061] As described in Example 1, except that the amount of 1-octadecene added in step (1) is 8g.

[0062] Example 4:

[0063] As described in Example 1, the difference is that in step (1), the hydrophilic monomer is allyl polyoxyethylene ethyl ether (n is 20), and the amount added is 2g.

[0064] Example 5:

[0065] As described in Example 1, except that the initiator in step (1) is 0.5g of azobisisobutyronitrile and 1.0g of azobisisobutyramidine hydrochloride.

[0066] Example 6:

[0067] As described in Example 1, except that the organic solvent in step (1) is 50g tetrahydrofuran and 50g N,N-dimethylformamide.

[0068] Example 7:

[0069] As described in Example 1, except that the organic solvent in step (1) is 40g of formamide.

[0070] Example 8:

[0071] As described in Example 1, except that the mass fraction of HCl in the concentrated hydrochloric acid in step (2) is 30%.

[0072] Example 9:

[0073] As described in Example 1, except that the amount of aminosulfonic acid added in step (2) is 8g.

[0074] Example 10:

[0075] As described in Example 1, except that in step (3), emulsifier-1 is sorbitan tristearate, and the amount added is 0.6g.

[0076] Example 11:

[0077] As described in Example 1, except that in step (3), emulsifier-2 is octadecyltrimethoxysilane, and the amount added is 0.3g.

[0078] Example 12:

[0079] As described in Example 1, except that in step (3) there are 0.4g of dehydrated sorbitan monooleate, 0.3g of dodecyltrimethoxysilane, and 0.4g of silicon-containing polymer.

[0080] Example 13:

[0081] As described in Example 1, except that in step (3) there are 0.3g of dehydrated sorbitan monooleate, 0.2g of dodecyltrimethoxysilane, and 0.6g of silicon-containing polymer.

[0082] Example 14:

[0083] As described in Example 1, except that the amount of acid added in step (3) is 70g.

[0084] Comparative Example 1:

[0085] (1) Preparation of acid solution

[0086] Add 40g of concentrated hydrochloric acid (HCl mass fraction of 37%) and 2g of aminosulfonic acid to 11g of water, stir and dissolve to obtain the product;

[0087] (2) Preparation of emulsified acid

[0088] Add 20g of diesel oil and 0.6g of sorbitan monooleate to a flask equipped with a stirrer and a thermometer, stir to dissolve, and then add 30g of acid solution dropwise to the flask using a dropping funnel over a period of 10 minutes while stirring at 1200 rpm. After the addition is complete, raise the temperature to 40°C and continue stirring for 1 hour to obtain the final product.

[0089] While stirring, add 1.5% THIF-117 and 1% TW-3 by mass of the total system to the above emulsified acid, and set aside.

[0090] Comparative Example 2:

[0091] (1) Preparation of acid solution

[0092] Add 40g of concentrated hydrochloric acid (HCl mass fraction of 37%) and 2g of aminosulfonic acid to 11g of water, stir and dissolve to obtain the product;

[0093] (2) Preparation of emulsified acid

[0094] Add 20g of diesel oil and 0.6g of EM90 to a flask equipped with a stirrer and a thermometer, stir to dissolve, and then add 30g of acid solution dropwise to the flask using a dropping funnel over a period of 10 minutes while stirring at 1200 rpm. After the addition is complete, raise the temperature to 40°C and continue stirring for 1 hour to obtain the final product.

[0095] While stirring, add 1.5% THIF-117 and 1% TW-3 by mass of the total system to the above emulsified acid, and set aside.

[0096] Performance Evaluation

[0097] Evaluation method:

[0098] The demulsification rate of different emulsified acid systems was determined using the bottle test method. The prepared emulsified acid system was added to a graduated pressure-resistant tube, which was then placed in a 150°C oil bath. The volume of water separated from the emulsified acid system was observed at 10-minute intervals. The demulsification rate was calculated using the demulsification rate calculation formula; a lower demulsification rate indicates stronger stability of the emulsified acid system. The demulsification rate calculation formula is shown below.

[0099]

[0100] In the formula:

[0101] f—the demulsification rate of the emulsion;

[0102] V1—Volume of water separated, mL;

[0103] V2 — Total volume of water in the emulsion system, mL.

[0104] The stability of the emulsified acid systems prepared in Examples 1-14 at 150°C was tested and compared with that of the emulsified acid systems prepared in Comparative Examples 1-2. The results are shown in Table 1. The emulsified acid systems prepared in Examples 1-14 had a lower demulsification rate at 150°C than those prepared in Comparative Examples 1-2, showing good temperature stability.

[0105] Table 1. Relationship between demulsification rate and time for different samples

[0106]

Claims

1. A method for preparing a high-temperature resistant emulsifying acid for acidification, comprising the following steps: (1) Preparation of silicon-containing polymers Silicon-containing monomers, hydrophilic monomers, lipophilic monomers, initiators, and organic solvents are added to a flask equipped with a stirrer, a nitrogen inlet tube, and a thermometer. After stirring until all raw materials are dissolved, nitrogen gas is introduced for 30 minutes. The polymerization temperature is controlled at 40–80℃, and the polymerization reaction is carried out for 1–24 hours to obtain the product. The mass ratio of silicon-containing monomers, hydrophilic monomers, and lipophilic monomers is 1:(0.02–0.2):(0.05–1), the ratio of the total mass of silicon-containing monomers, hydrophilic monomers, and lipophilic monomers to the mass of organic solvent is 1:(0.8–9), and the mass ratio of organic solvent to initiator is 1:(0.001–0.02). (2) Preparation of acid solution Concentrated hydrochloric acid and an acidic compound are added to water and stirred to dissolve, thus obtaining the product. The mass fraction of HCl in the concentrated hydrochloric acid is 30% to 38%, the mass ratio of concentrated hydrochloric acid to the acidic compound is 1:(0.001 to 0.2), and the ratio of the total mass of concentrated hydrochloric acid and the acidic compound to the mass of water is 1:(0.1 to 3). (3) Preparation of emulsified acid Add the oil solvent, emulsifier-1, emulsifier-2, and silicone polymer to a flask equipped with a stirrer and thermometer, stir to dissolve, and then add acid solution dropwise to the flask using a dropping funnel over a period of 10–30 min at a stirring speed of 1000–2000 r / min. After the addition is complete, raise the temperature to 35–65 °C and continue stirring for 1–6 h to obtain the final product. The mass ratio of emulsifier-1 to emulsifier-2 is 1:(0.25–1.5), the mass ratio of emulsifier-2 to silicone polymer is 1:(0.8–6.5), the ratio of the total mass of emulsifier-1, emulsifier-2, and silicone polymer to the mass of oil solvent is 1:(10–50), and the mass ratio of oil solvent to acid solution is 1:(0.3–3). The silicon-containing monomer is one or a mixture of two or more of vinyltrimethoxysilane, vinyltriethoxysilane, allyltrimethoxysilane, and allyltriethoxysilane; The hydrophilic monomer is Where n is 10 to 30, and R1 is a hydrogen atom, methyl or ethyl; The lipophilic monomer is one or a mixture of two or more of 1-octadecene, 1-hexadecene, 1-tetradecene, and 1-dodecene; The initiator is one of azobisisobutyronitrile, azobisisoheptanenitrile, dimethyl azobisisobutyrate, azobisisobutyramidine hydrochloride, and azobisisobutyramidine hydrochloride; The organic solvent is one or a mixture of two or more of formamide, N,N-dimethylformamide, tetrahydrofuran, dioxane, ethanol, and tert-butanol; The acidic compound is one or a mixture of two or more of aminosulfonic acid, formic acid, acetic acid, lactic acid, and glycolic acid; The oil solvent is one or a mixture of two or more of diesel oil, kerosene, and white oil; The emulsifier-1 is one or a mixture of two or more of the following: propylene glycol monostearate, glyceryl monostearate, propylene glycol monolaurate, sorbitan monooleate, sorbitan tristearate, and sorbitan monostearate. The emulsifier-2 is R2 and R3 are methyl or ethyl, R4 is dodecyl, tetradecyl, hexadecyl or octadecyl, R5 is methyl, ethyl, n-propyl or n-butyl, and R6 is an oxygen atom or methylene.

2. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (1), the mass ratio of silicon monomer, hydrophilic monomer, and lipophilic monomer is 1:(0.05~0.15):(0.25~1).

3. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (1), the ratio of the total mass of silicon monomers, hydrophilic monomers, and lipophilic monomers to the mass of organic solvent is 1:(1.5-5).

4. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (1), the mass ratio of organic solvent to initiator is 1:(0.005~0.02).

5. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (1), the polymerization temperature is 50-70℃ and the polymerization time is 3-15h.

6. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (2), the ratio of the total mass of concentrated hydrochloric acid and acidic compounds to the mass of water is 1:(0.25~2).

7. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (3), the mass ratio of emulsifier-1 to emulsifier-2 is 1:(0.25~0.75).

8. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (3), the mass ratio of emulsifier-2 to silicone polymer is 1:(1-4.5).

9. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (3), the ratio of the total mass of emulsifier-1, emulsifier-2, and silicone polymer to the mass of oil solvent is 1:(10-30).

10. The method for preparing high-temperature resistant emulsifying acid for acidification according to claim 1, characterized in that, In step (3), the mass ratio of oil solvent to acid solution is 1:(1-3).

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