Emulsified acid and preparation method thereof

Abstract

The invention relates to emulsified acid and a preparation method thereof. The emulsified acid is prepared from the following components in percentage by weight: 140-160 parts of diesel oil or kerosene, 15-25 parts of an emulsifier and 340-360 parts of hydrochloric acid. The calcium carbonate retarder has the advantages of excellent normal temperature stability, low corrosivity, high corrosion rate on calcium carbonate and remarkable retarding performance.

Description

Technical Field

[0001] This invention relates to the field of chemical engineering, and more particularly to an emulsified acid and its preparation method. Background Technology

[0002] Emulsified acid is an emulsion formulated with acid, oil, and emulsifier, and is a primary form of acid used in oilfield acidizing processes. Existing emulsified acid is typically an oil-in-acid emulsion, with its core components including hydrochloric acid (containing corrosion inhibitors and other additives) as the internal phase, diesel or crude oil as the external phase, and most importantly, an emulsifier that forms and stabilizes the oil-acid interface. While this technology aims to achieve slow and deep acidizing, it has several inherent drawbacks. The primary challenge lies in balancing stability and demulsification: the robust interfacial film designed to ensure pumping stability often lacks an intelligent demulsification mechanism, preventing the acid from being released promptly and completely after entering the formation, potentially clogging pores and affecting acidizing efficiency. Secondly, the inherent high viscosity of the emulsion results in extremely high pump friction, which not only places stricter demands on equipment but also significantly increases construction energy consumption and risk. Furthermore, this system is sensitive to formation conditions (such as temperature and crude oil properties), and the introduction of foreign oil phases and chemicals carries the potential risk of formation wettability reversal and secondary damage such as the formation of organic scale. The root of these defects lies in the fact that emulsified acid is a "passively stable" thermodynamically unstable system. Its performance is highly dependent on the rigidity of the emulsifier interface film, and this film structure cannot adapt to the complex and ever-changing underground environment, thus exhibiting limitations in terms of controllability, efficiency and compatibility. Summary of the Invention

[0003] To address the technical problems existing in the background art, the present invention provides an emulsified acid and its preparation method. The present invention has excellent room temperature stability, low corrosivity, high solubility for calcium carbonate, and significant retardation properties.

[0004] The technical solution of the present invention is as follows: The present invention is an emulsified acid, which is special in that the emulsified acid is prepared by weight percentage components including 140-160 parts of diesel or kerosene, 15-25 parts of emulsifier and 340-360 parts of hydrochloric acid.

[0005] Furthermore, the emulsified acid is prepared from components comprising, by weight percentage, 150 parts diesel or kerosene, 20 parts emulsifier, and 350 parts hydrochloric acid.

[0006] Furthermore, the hydrochloric acid is a 10% hydrochloric acid solution.

[0007] Furthermore, the emulsifier is specifically a sorbitan ester or a fatty amine polyoxyethylene ether.

[0008] This invention also provides a method for preparing the above-mentioned emulsified acid, characterized in that the method includes the following steps:

[0009] 1) Weigh the kerosene according to the mixing ratio and place it in a three-necked bottle;

[0010] 2) Add the emulsifier according to the ratio, stir evenly, and ensure that the emulsifier is fully dispersed in the kerosene;

[0011] 3) Under high-speed stirring conditions, slowly add hydrochloric acid using a dropper according to the mixing ratio;

[0012] 4) After all the liquid has been added, seal the opening with plastic wrap and then stir at high speed to fully emulsify the emulsified acid and form a stable system.

[0013] Furthermore, in step 3), the conditions for high-speed stirring are: at room temperature, the speed is 2000-2500 rpm.

[0014] Furthermore, in step 4), the high-speed stirring temperature is room temperature, the speed is 2000-2500 rpm, and the stirring time is 20-40 min.

[0015] Furthermore, in step 3), the hydrochloric acid is a 10% hydrochloric acid solution.

[0016] This invention provides an emulsified acid and its preparation method. The emulsified acid is a nonionic emulsified acid, comprising an external oil phase and an internal acid phase. The internal acid phase is a 10% hydrochloric acid solution. The external oil phase consists of a measured volume of diesel or kerosene with the addition of a certain amount of emulsifier. Compared with the prior art, this invention has the following advantages:

[0017] 1) The emulsified acid of the present invention has excellent stability at room temperature, which can meet the storage and transportation requirements in practical applications.

[0018] 2) The emulsified acid of the present invention has low corrosivity, which can effectively reduce corrosion of oil and gas well equipment, extend equipment service life, and reduce equipment maintenance costs.

[0019] 3) The oil-in-acid structure of the emulsified acid of this invention can slow down the reaction rate between the acid and calcium carbonate, allowing the acid to react with calcium carbonate over a longer period of time, thereby improving the dissolution efficiency. This characteristic gives it a significant advantage in deep acidizing operations, effectively improving reservoir permeability and increasing oil and gas production in oil and gas wells.

[0020] 4) In this invention, the acid phase of the emulsified acid is encapsulated by the oil phase, and the release rate of the acid is limited by the oil phase, thereby slowing down the reaction rate between the acid and the formation. This characteristic gives it a significant advantage in deep acidizing operations, effectively increasing the effective range of the acid and improving the reservoir permeability of oil and gas wells. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the room temperature stability test of the emulsified acid of the present invention;

[0022] Figure 2 This is a schematic diagram of the emulsified acid slow-release performance test of the present invention. Detailed Implementation

[0023] This invention provides an emulsified acid, which is prepared from 140-160 parts by weight of diesel or kerosene, 15-25 parts by weight of emulsifier and 340-360 parts by weight of hydrochloric acid.

[0024] The diesel fuel is No. 0 diesel fuel, and the hydrochloric acid is a 10% hydrochloric acid solution. The emulsifier is specifically a sorbitan ester such as Span 80, or a fatty amine polyoxyethylene ether, such as cocoa butter amine polyoxyethylene ether or tallow amine polyoxyethylene ether.

[0025] The present invention also provides a method for preparing the emulsified acid according to the above, the method comprising the following steps:

[0026] 1) Weigh the kerosene according to the mixing ratio and place it in a three-necked bottle;

[0027] 2) Add the emulsifier according to the ratio, stir evenly, and ensure that the emulsifier is fully dispersed in the kerosene;

[0028] 3) Under high-speed stirring conditions, slowly add hydrochloric acid using a dropper according to the ratio; the high-speed stirring conditions are room temperature and a speed of 2000-2500 rpm.

[0029] The hydrochloric acid is a 10% hydrochloric acid solution.

[0030] 4) After all the liquid has been added, seal the container with plastic wrap and then stir at high speed for 20-40 minutes to fully emulsify the emulsified acid and form a stable system. The stirring temperature should be room temperature, the speed should be 2000-2500 rpm, and the stirring time should be 20-40 minutes.

[0031] The present invention will be further described in detail below with reference to specific embodiments:

[0032] The emulsified acid in a specific embodiment of the present invention is prepared by weight percentage components including 150 parts of kerosene, 20 parts of emulsifier and 350 parts of hydrochloric acid.

[0033] The emulsified acid in the second specific embodiment of the present invention is prepared by weight percentage components including 142 parts of diesel oil, 16 parts of emulsifier and 343 parts of hydrochloric acid.

[0034] The emulsified acid in the third specific embodiment of the present invention is prepared by weight percentage components including 158 parts of kerosene, 24 parts of emulsifier and 355 parts of hydrochloric acid.

[0035] The emulsified acid in the preferred embodiment of the present invention is prepared by weight percentage components including 150g of diesel or kerosene, 20g of emulsifier and 350g of 10% hydrochloric acid solution.

[0036] The specific preparation method is as follows:

[0037] 1) Weigh 150g of kerosene and place it in a three-necked bottle;

[0038] 2) Add 20g of emulsifier and stir well to ensure the emulsifier is fully dispersed in the kerosene; hydrochloric acid is...

[0039] 3) Under high-speed stirring conditions, slowly add 350g of 10% hydrochloric acid solution using a dropper according to the specified ratio. The high-speed stirring conditions are room temperature and a stirring speed of 2500 rpm.

[0040] 4) After all the liquid has been added, seal the container with plastic wrap and then stir at high speed to fully emulsify the emulsified acid and form a stable system. The high-speed stirring conditions are: at room temperature, stirring continuously at 2500 rpm for 40 minutes.

[0041] The test results of the emulsified acid in this preferred embodiment four are shown in Table 1:

[0042] Table 1. Basic Performance Test Table of Emulsified Acids

[0043]

[0044] The emulsifying acid performance test results in this preferred embodiment four are as follows:

[0045] I. Stability at room temperature

[0046] The prepared emulsified acid was left to stand at room temperature for 24 hours to observe whether it separated into layers. The experimental results are as follows: Figure 1 As shown, the emulsified acid did not exhibit stratification within 24 hours, indicating that the prepared emulsified acid has good room temperature stability. This result demonstrates that optimizing the emulsifier and stirring process can effectively improve the stability of the emulsified acid, enabling it to maintain a stable emulsified state for a longer period in practical applications. Room temperature stability is an important performance indicator for emulsified acids during storage and transportation. Good room temperature stability ensures that the emulsified acid will not stratify or deteriorate during storage, thus guaranteeing its performance and effectiveness during use. Experimental results show that the emulsified acid of this invention has excellent stability at room temperature, meeting the storage and transportation requirements of practical applications.

[0047] II. Static Corrosion Rate

[0048] 1. Experimental Objective

[0049] Based on SY / T5405 "Evaluation Method for the Performance of Slow-Moving Acids for Acidizing Oil and Gas Wells", the experimental conditions simulated actual working conditions, and the corrosion rates of emulsified acid and hydrochloric acid on N80 steel sheets were compared and tested to verify the corrosion inhibition performance of emulsified acid and its application advantages in acidizing operations of oil and gas wells.

[0050] 2. Experimental Materials

[0051] N80 steel sheet; emulsified acid; hydrochloric acid (10% concentration); petroleum ether; anhydrous ethanol; filter paper.

[0052] 3. Experimental equipment

[0053] Constant temperature water bath (temperature control accuracy ±0.5℃); desiccator; electronic analytical balance (accuracy 0.1mg); vernier caliper (accuracy 0.02mm); glass container (with hanging plate bracket).

[0054] 4. Experimental Procedure

[0055] 1) Pretreatment of the hanging strips: Measure the surface area of ​​the hanging strips with vernier calipers; degrease with petroleum ether, then wash the hanging strips with anhydrous ethanol, wipe them dry with filter paper, place them in a desiccator to constant weight for 4 hours, and then weigh the initial mass.

[0056] 2) Experimental conditions

[0057] Experimental group: emulsified acid; control group: 10% hydrochloric acid.

[0058] Solution volume: 400 mL, temperature: 45℃ (constant temperature water bath), reaction time: 4 h.

[0059] 3) Operating Procedures

[0060] The tablets were suspended in emulsified acid and hydrochloric acid solutions respectively. After the reaction was completed, the tablets were removed, rinsed with deionized water, dehydrated with anhydrous ethanol, and the oil was gently wiped off with filter paper. After drying, the final mass was weighed.

[0061] 5. Data Processing and Results

[0062] Formula for calculating static corrosion rate:

[0063] In the formula:

[0064] Δm: mass loss (g);

[0065] A: Surface area of ​​the hanging plate (m²) 2 );

[0066] t: Reaction time (h).

[0067] The experimental results are shown in Table 2. Calculations show that the corrosion rate of emulsified acid on N80 steel sheets is significantly lower than that of hydrochloric acid. This is because the oil phase of the emulsified acid forms a separating film between the steel sheet and the acid solution, isolating them and preventing H+ from corroding the steel sheet. This greatly reduces corrosion of pipelines and equipment during field operations, avoiding unnecessary losses and saving money and resources. The experimental results demonstrate that the emulsified acid of this invention has low corrosivity, effectively reducing corrosion of oil and gas well equipment, extending equipment service life, and lowering equipment maintenance costs.

[0068] Table 2 Results of Emulsified Acid Corrosion Test

[0069]

[0070] III. Corrosiveness

[0071] 1. Experimental Objective

[0072] According to the "SY / T 5886-2012 Evaluation Method for Slow-Rate Acids", the dissolution performance of emulsified acid on calcium carbonate was tested to provide a basis for its effectiveness in oil and gas well acidizing applications. Calcium carbonate dissolution testing is an important indicator for evaluating the ability of emulsified acid to dissolve formation plugging materials in oil and gas well acidizing operations.

[0073] 2. Experimental materials:

[0074] Calcium carbonate (CaCO3, analytical grade, particle size ≤0.075mm, dried at 105℃ to constant weight); emulsified acid; deionized water.

[0075] 3. Experimental equipment

[0076] Constant temperature water bath (temperature control accuracy ±0.5℃); analytical balance (accuracy 0.1mg); drying oven; centrifuge tubes (50mL); quantitative filter paper (slow speed, pore size ≤2μm); weighing bottle.

[0077] 4. Experimental steps:

[0078] 1) Dry the CaCO3 powder in an oven at 105℃ for 4 hours, cool it to room temperature, and weigh 1.000g for later use (recorded as m1). Weigh the pre-dried quantitative filter paper (recorded as m2).

[0079] 2) Transfer 1,000g of dried CaCO3 to a 50mL centrifuge tube, add 20mL of emulsified acid, and seal the tube.

[0080] 3) Place the centrifuge tubes in a 45°C constant temperature water bath and let them react for 2 hours.

[0081] 4) After the reaction is complete, immediately filter the mixture using pre-dried quantitative filter paper to separate the unreacted CaCO3. Wash the filter residue three times (10 mL each time) with deionized water to ensure complete removal of residual acid.

[0082] 5) Transfer the filter paper and unreacted CaCO3 to a weighing bottle and dry it in an oven at 105°C for 4 hours until constant weight.

[0083] 6) After cooling to room temperature, weigh the mass of the unreacted CaCO3 and the total mass of the filter paper (denoted as m3).

[0084] 5. Formula for calculating the dissolution rate (η):

[0085] η = (m1 + m2 - m3) / m3 × 100%

[0086] Table 3. Experimental data on the corrosive properties of emulsified acids.

[0087]

[0088] Experimental Results: Calculations showed that the emulsified acid of this invention achieved a dissolution rate of 89% for calcium carbonate powder. As shown in Table 3, the experimental results demonstrate that the emulsified acid of this invention exhibits a high dissolution rate for calcium carbonate, primarily due to its slowing properties and the stability of the emulsion system. The oil-in-acid structure of the emulsified acid can slow down the reaction rate between the acid and calcium carbonate, allowing the acid to react with calcium carbonate over a longer period, thereby improving dissolution efficiency. This characteristic gives it a significant advantage in deep acidizing operations, effectively improving reservoir permeability and increasing oil and gas production in oil and gas wells.

[0089] IV. Slowing down

[0090] 1. Experimental Objective

[0091] Neutralization reaction rate testing is an important method for evaluating the slow-release properties of emulsified acids. By measuring the neutralization reaction rate of emulsified acids with 1 mol / L NaOH at different times, the acid release characteristics of emulsified acids over a long period of time can be investigated.

[0092] 2. Experimental Principle

[0093] Emulsified acid is a slow-release acid system formed by emulsifying an acidic phase and an oil phase. In an acidic environment, phenolphthalein indicator is colorless, but turns pink when reacting with NaOH to a neutral or weakly alkaline state. The slow-release capability of the emulsified acid can be reflected by recording the volume of NaOH consumed at different time points through titration.

[0094] 3. Experimental Materials

[0095] Emulsified acid, 10% hydrochloric acid, phenolphthalein indicator, 1 mol / L NaOH standard solution.

[0096] 4. Experimental apparatus

[0097] Alkaline burette; conical flask (100ml); graduated cylinder (10ml, 50ml); timer.

[0098] 5. Experimental Procedure

[0099] 1) Sample pretreatment: Measure 15 ml of emulsified acid, transfer it to an Erlenmeyer flask, add 1-2 drops of phenolphthalein indicator, and gently shake to mix.

[0100] 2) Immediately titrate with 1 mol / L NaOH until the solution changes from colorless to pink (endpoint), and record the amount of NaOH solution consumed.

[0101] 3) Take 15ml samples at 1h, 2h, 3h, 5h, and 9h respectively, and repeat steps 1-2), recording the amount of NaOH solution consumed at each time point. The hydrochloric acid control test procedure is the same as steps 1 and 2 above.

[0102] 6. Experimental Data Processing

[0103] Table 4. Experimental data on the retardation properties of emulsified acids

[0104]

[0105] See Figure 2 As shown in Table 4, the emulsified acid of this invention exhibits a significant slowing effect, with NaOH consumption gradually increasing over 9 hours. This is primarily attributed to its unique oil-in-acid structure. In this structure, the acid phase is encapsulated by the oil phase, limiting the acid release rate and thus slowing down the reaction rate between the acid and the formation. This characteristic provides a significant advantage in deep acidizing operations, effectively increasing the acid's effective range and improving reservoir permeability in oil and gas wells.

[0106] VI. Wax Dissolution Rate

[0107] 1. Experimental Objective

[0108] To investigate the dissolving ability of emulsified acid on paraffin under simulated working conditions and to evaluate its potential application value as a paraffin remover (such as oil well paraffin remover).

[0109] 2. Experimental Materials

[0110] Paraffin blocks (purity ≥ 99%), emulsified acid.

[0111] 3. Experimental equipment

[0112] Constant temperature water bath (temperature control accuracy ±0.5℃); analytical balance (accuracy 0.0001g); quantitative filter paper; centrifuge tubes (50mL).

[0113] 4. Experimental Procedure

[0114] 1) Initial mass determination: Weigh the whole paraffin block and record it as m1.

[0115] 2) Place the paraffin block in a centrifuge tube and add 20 ml of emulsified acid to ensure complete immersion.

[0116] 3) Let it stand in a 45℃ water bath for 2 hours, avoiding stirring or disturbance.

[0117] 4) After 2 hours, remove the wax block, gently wipe the surface with filter paper to remove any residual acid, let it air dry at room temperature for 10 minutes, weigh the wax block after the reaction, and record it as m2.

[0118] 5. Experimental Results

[0119] The data on quality changes are shown in Table 5:

[0120] Table 5 Quality Change Data

[0121]

[0122] Wax dissolution rate calculation:

[0123] Experimental results show that the emulsified acid of this invention has an extremely low solubility of paraffin wax at 45°C for 2 hours, only 0.769%. This indicates that the emulsified acid has a weak ability to directly dissolve paraffin wax and cannot be used as a single wax-removing agent.

[0124] This result is mainly attributed to the fact that paraffin is a nonpolar hydrocarbon with poor affinity for acidic aqueous solutions, making it difficult for emulsified acids to dissolve paraffin directly. Therefore, emulsified acids cannot be used as a single wax-removing agent, but their effectiveness can be improved through synergistic effects with other wax-removing agents.

[0125] The technical contents of this invention and those not specifically described in the above embodiments are the same as those in the prior art.

[0126] The present invention is not limited to the above embodiments; all embodiments described herein can be implemented and have the aforementioned good effects.

[0127] The above are merely specific embodiments disclosed in this invention, but the scope of protection disclosed in this invention is not limited thereto. The scope of protection disclosed in this invention should be determined by the scope of the claims.

Claims

1. An emulsified acid, characterized in that: The emulsified acid is prepared by weight percentage of 140-160 parts diesel or kerosene, 15-25 parts emulsifier and 340-360 parts hydrochloric acid.

2. The emulsified acid according to claim 1, characterized in that: The emulsified acid is prepared by weight percentage of 150 parts diesel or kerosene, 20 parts emulsifier and 350 parts hydrochloric acid.

3. The emulsified acid according to claim 1 or 2, characterized in that: The hydrochloric acid is a 10% hydrochloric acid solution.

4. The emulsified acid according to claim 3, characterized in that: The emulsifier is specifically a sorbitan ester or a fatty amine polyoxyethylene ether.

5. A method for preparing the emulsified acid according to claim 1, characterized in that: The method includes the following steps: 1) Weigh the kerosene according to the mixing ratio and place it in a three-necked bottle; 2) Add the emulsifier according to the ratio, stir evenly, and ensure that the emulsifier is fully dispersed in the kerosene; 3) Under high-speed stirring conditions, slowly add hydrochloric acid using a dropper according to the mixing ratio; 4) After all the liquid has been added, seal the opening with plastic wrap and then stir at high speed to fully emulsify the emulsified acid and form a stable system.

6. The method for preparing emulsified acid according to claim 5, characterized in that: In step 3), the high-speed stirring conditions are room temperature and a speed of 2000-2500 rpm.

7. The method for preparing emulsified acid according to claim 6, characterized in that: In step 4), the high-speed stirring conditions are: at room temperature, stirring continuously at a speed of 2000-2500 rpm for 20-40 minutes.

8. The method for preparing emulsified acid according to any one of claims 5 to 7, characterized in that: In step 3), the hydrochloric acid is a 10% hydrochloric acid solution.

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