Multifunctional temperature-control slow-release solid acid and application thereof

Abstract

The invention discloses a multifunctional temperature-control slow-release solid acid and application thereof. According to the high-temperature slow-release solid acid, phosphonitrilic chloride trimer powder with the particle size smaller than 500 micrometers is dispersed in water or seawater at the room temperature to form 15-25 wt% of solid acid dispersion liquid, and the high-temperature slow-release solid acid can be used for deep stratum acidification and is simple in preparation process, free of acid generation under the normal-temperature condition, convenient to construct on site and capable of being applied to deep stratum acidification. After the phosphonitrilic chloride trimer is injected into a stratum, phosphonitrilic chloride trimer is promoted to be hydrolyzed by utilizing an underground high-temperature environment to release phosphonitrilic acid with a corrosion inhibition function and hydrochloric acid capable of etching a carbonate reservoir, so that controllable generation and release of hydrochloric acid at underground characteristic temperature are realized, and deep stratum acidification can be realized. According to the high-temperature slow-release solid acid, the transportation and storage safety of an acid system can be effectively improved, the dosage of a corrosion inhibitor is reduced, and far-end deep acidification is realized.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and particularly relates to a high-temperature slow-release solid acid integrating corrosion inhibition and acidification functions and its application. Background Art

[0002] Acidizing and plugging removal is an oilfield stimulation measure that has been widely adopted to restore or increase the permeability of formation pores and fractures and improve the production capacity of oil and gas wells by using the dissolution or etching effect of acid solution. The commonly used acid solution in the acidification process is hydrochloric acid or an acidification system mainly composed of hydrochloric acid. However, the traditional hydrochloric acid-based acidification system reacts very fast with formation rocks, the effective action distance of the acid solution is short, in addition, the corrosion of the pipe string is very serious, and the filtration loss during the injection process is large and it is difficult to reach the deep part of the fracture or pore. Moreover, especially for seawater platforms with limited working space and working time, the storage and transportation of the traditional hydrochloric acid-based liquid acidification system have huge safety hazards and high costs, and its use has been severely restricted. Therefore, it is of great scientific significance and application value to develop an acidification system with stronger dissolution ability, less corrosion, and safe and convenient storage and transportation.

[0003] Solid acids convert traditional liquid acidification systems into solid particle or powder forms. Compared with current conventional liquid acidification systems, the main advantages of solid acid acidification are as follows: (1) Solid acids can be injected deeper into fractures with carrier fluids and then release acids, significantly reducing near-wellbore acid consumption and increasing the reservoir penetration distance for stimulation. (2) Natural fractures can be effectively temporarily plugged in solid acid systems, reducing the filtration loss of the acidification system. (3) Solid acids can exist in the form of solid powders, microcapsules, or polymers in surface pipelines and downhole tubular strings, with basically no acidity or weak acidity in surface pipelines and downhole tubular strings. Therefore, the corrosion of pipelines and equipment is low, and the dosage of corrosion inhibitors is also reduced. (4) Solid acids are stored in solid form, are convenient for transportation, and have high safety, especially suitable for storage and use on offshore platforms with limited space and time. These advantages of solid acids have attracted extensive attention at home and abroad. Solid acid systems represented by sulfamic acid have been practically applied in some oilfields, achieving good acidification effects. Nevertheless, these solid acids dissolve and release acids too quickly in water, the acidity of the acid solution is strong, the reaction is fast, and the reaction consumption in the near-wellbore area is serious. It is difficult to carry them to the deep part of oil and gas wells by water or seawater, and the advantages of solid acids in reducing acid filtrate loss and pipeline corrosion cannot be effectively exerted. In addition, there are also research reports on solid acid systems hydrolyzed by compounds or polymers containing ester bonds and acid anhydrides. However, these solid acids not only have high raw material costs, but also the acids generated by hydrolysis are all organic weak acids, with low acid etching ability for calcium carbonate and prone to forming organic calcium salt precipitates. Therefore, developing a solid acid system with low cost, low corrosion, convenient for preparation, injection, storage, and transportation safety, and capable of controllably releasing hydrochloric acid at a wide range of formation temperatures is a common technical problem and important challenge at home and abroad, and has important significance and application value for the exploration and development of oil and gas resources on offshore platforms with limited operation space and time. Summary of the Invention

[0004] In order to solve the above technical problems, the present invention provides a multifunctional temperature-controlled slow-release solid acid and its application.

[0005] In the first aspect, the present invention provides a multifunctional temperature-controlled slow-release solid acid, which is achieved by the following technical solutions.

[0006] A multifunctional temperature-controlled slow-release solid acid, the solid acid is hexachlorocyclotriphosphazene, and has the following molecular structure:

[0007]

[0008] By adopting the above technical solution, the present invention utilizes the catalytic and hydrolysis-promoting effects in the high-temperature environment underground to promote the high-temperature hydrolysis of hexachlorocyclotriphosphazene to release hydrochloric acid. It not only realizes the controllable generation and release of hydrochloric acid in the high-temperature environment underground, but also the phosphonitrile acid generated by hydrolysis can achieve the corrosion inhibition effect, and can reduce the corrosion degree of pipelines or tubing strings. The high-temperature slow-release solid acid of the present invention can ensure that no or a small amount of acidic substances are released during the ground pumping process and the initial stage of acidification, increase the acid etching distance while reducing the corrosion of pipelines and equipment, and significantly improve the acidification performance in the high-temperature environment of the reservoir formation.

[0009] Further, the hexachlorocyclotriphosphazene is a white or off-white solid powder that is stable at room temperature and insoluble in water, with a particle size less than 500 μm. Preferably, the particle size of hexachlorocyclotriphosphazene is 200 - 300 μm.

[0010] In the second aspect, the present invention provides the use of a multifunctional temperature-controlled slow-release solid acid, which is achieved by adopting the following technical solution.

[0011] The application of the above multifunctional temperature-controlled slow-release solid acid in acidizing and removing blockages.

[0012] Further, the solid acid is dispersed in water or seawater at room temperature to form a 15 - 25 wt% solid acid dispersion, which is injected into the formation under high-speed stirring. Through the high temperature of the formation, a hydrolysis reaction is triggered to release phosphonitrile acid with a corrosion inhibition function and hydrochloric acid that can etch carbonate reservoirs, and a large amount of hydrochloric acid generated deeply acid-etches carbonate rocks.

[0013] Furthermore, the formation is a carbonate rock formation with a depth of 2000 - 6000 m and a temperature of 60 - 120 °C.

[0014] In the present application, hexachlorocyclotriphosphazene can be stably dispersed in water at room temperature, and the rate of acid release by hydrolysis is slow. However, when the temperature rises to above 60 °C, a rapid hydrolysis reaction as shown in the following formula occurs, releasing phosphonitrile acid with a corrosion inhibition function and hydrochloric acid that can etch carbonate reservoirs. In addition, the rate of acid generation by hydrolysis of the solid acid in the present application can be regulated by the formation temperature and the particle size of the solid acid.

[0015]

[0016] The present application has the following beneficial effects.

[0017] (1) The high-temperature slow-release solid acid of the present invention is hexachlorocyclotriphosphazene, which is a common monomer for synthesizing polyphosphazenes. It has been widely used in fields such as high-efficiency flame retardants, special rubbers, and electronic materials. It is an industrial product with relatively low price, stable physical and chemical properties, high safety in storage and transportation, and low cost;

[0018] (2) The high-temperature slow-release solid acid of the present invention can be directly dispersed in water or seawater at room temperature and can be injected in a one-time manner, which greatly facilitates on-site oilfield construction and can effectively solve the filtration loss problem faced by traditional liquid acidizing systems. It can also achieve remote deep acidizing and solve the problem of deep penetration and uniform transformation of highly heterogeneous high-temperature reservoirs.

[0019] (3) The high-temperature slow-release solid acid of the present invention undergoes hydrolysis reaction to produce hydrochloric acid at a relatively slow rate below 60°C. As the temperature rises, the rate of hydrolysis reaction to produce hydrochloric acid accelerates, making it possible to control the acid generation rate by the formation temperature. At high formation temperatures (≥120°C), hexachlorocyclotriphosphazene will melt and cause extremely rapid hydrolysis to produce acid and generate ammonium chloride as a side reaction, affecting the etching ability of carbonates. Therefore, the solid acid is suitable for etching carbonates in formations with a depth of 2000 to 6000 m and a temperature of 60 to 120°C.

[0020] (4) The high-temperature slow-release solid acid of the present invention is stable at room temperature and hydrolyzes at high temperatures to generate phosphazene acid with corrosion inhibition function. Therefore, the system has low corrosion to pipelines and requires no or only a small amount of corrosion inhibitors or other additives.

[0021] (5) The high-temperature slow-release solid acid of the present invention is dispersed in water to form a 15-25 wt% acidizing working solution, and the solution is placed in a high-pressure closed hydrothermal reactor with an excess of calcium carbonate core. The dissolution rate of the calcium carbonate core is measured at 60-120°C to investigate the rate and concentration of hydrochloric acid produced by the high-temperature slow-release solid acid at different temperatures. The experimental results show that the high-temperature slow-release solid acid has an equivalent capacity of 7-12% hydrochloric acid when reacted at 60-120°C for 1-4 hours.

[0022] (6) The high-temperature slow-release solid acid of the present invention is dispersed in water to form a 15-25wt% acidizing working solution. N80 steel sheet (50mm*10mm*3mm) is selected as the metal substrate. The corrosion inhibition efficiency is tested and evaluated by SY / T 5886-2018 "Performance Evaluation Method of Acidizing Working Solution". The results show that the solid acid basically does not produce acidity at room temperature and has almost no obvious corrosive effect on the N80 steel sheet, showing an excellent corrosion inhibition effect. However, it begins to hydrolyze and generate acid at 60°C, but at the same time, phosphazene acid with excellent corrosion inhibition function is generated, which can reduce the corrosive effect of hydrochloric acid generated by the hydrolysis of the solid acid on the N80 steel sheet. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a curve diagram of the dissolution rate of calcium carbonate core by the high-temperature slow-release solid acid of the present invention and 10% hydrochloric acid. DETAILED DESCRIPTION

[0024] The present patent application is further described below with reference to the embodiments.

[0025] In the following examples, the materials used in the preparation process were not further processed without special instructions and were all purchased through commercial channels.

[0026] In the following examples of this application, the hexachlorocyclotriphosphazene used has a CAS number of 940-71-6 and was purchased from Jinan Quansheng Chemical Co., Ltd.

[0027] Example 1

[0028] Hexachlorocyclotriphosphazene was selected, pulverized using a pulverizer, and then sieved through a sieve with a mesh size of 35 to obtain hexachlorocyclotriphosphazene powder with a particle size less than 500 μm. Subsequently, 15 g of the hexachlorocyclotriphosphazene powder was weighed and dispersed in 85 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0029] Example 2

[0030] Hexachlorocyclotriphosphazene was selected, pulverized using a pulverizer, and then sieved through a sieve with a mesh size of 50 to obtain hexachlorocyclotriphosphazene powder with a particle size less than 300 μm. Subsequently, 15 g of the hexachlorocyclotriphosphazene powder was weighed and dispersed in 85 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0031] Example 3

[0032] Hexachlorocyclotriphosphazene was selected, pulverized using a pulverizer, and then sieved through a sieve with a mesh size of 75 to obtain hexachlorocyclotriphosphazene powder with a particle size less than 200 μm. Subsequently, 15 g of the hexachlorocyclotriphosphazene powder was weighed and dispersed in 85 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0033] Example 4

[0034] Hexachlorocyclotriphosphazene was selected, pulverized using a pulverizer, and then sieved through a sieve with a mesh size of 150 to obtain hexachlorocyclotriphosphazene powder with a particle size less than 100 μm. Subsequently, 15 g of the hexachlorocyclotriphosphazene powder was weighed and dispersed in 85 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0035] Example 5

[0036] Hexachlorocyclotriphosphazene was selected, pulverized using a pulverizer, and then sieved through a sieve with a mesh size of 50 to obtain hexachlorocyclotriphosphazene powder with a particle size less than 300 μm. Subsequently, 18 g of the hexachlorocyclotriphosphazene powder was weighed and dispersed in 82 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0037] Example 6

[0038] Select hexachlorocyclotriphosphazene, crush it with a crusher, and sieve it through a sieve with a mesh size of 50 meshes to obtain hexachlorocyclotriphosphazene powder with a particle size less than 300 μm. Subsequently, weigh 20 g of hexachlorocyclotriphosphazene powder and disperse it in 80 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0039] Example 7

[0040] Select hexachlorocyclotriphosphazene, crush it with a crusher, and sieve it through a sieve with a mesh size of 50 meshes to obtain hexachlorocyclotriphosphazene powder with a particle size less than 300 μm. Subsequently, weigh 25 g of hexachlorocyclotriphosphazene powder and disperse it in 75 g of water under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0041] Example 8

[0042] Select hexachlorocyclotriphosphazene, crush it with a crusher, and sieve it through a sieve with a mesh size of 50 meshes to obtain hexachlorocyclotriphosphazene powder with a particle size less than 300 μm. Subsequently, weigh 20 g of hexachlorocyclotriphosphazene powder and disperse it in 80 g of seawater under stirring at room temperature to obtain a high-temperature slow-release solid acid sample.

[0043] Performance Test 1

[0044] Hexachlorocyclotriphosphazene can be stably dispersed in water at room temperature for a certain period of time, but heating can accelerate its hydrolysis, and phosphazene acid with a corrosion inhibition function and salts that can etch carbonate reservoirs are released during hydrolysis. To investigate the concentration of hydrochloric acid generated by the high-temperature slow-release solid acid prepared from hexachlorocyclotriphosphazene according to the present invention at different temperatures, take 25 mL of the high-temperature slow-release solid acid samples prepared in Examples 1 to 4 and place them in a high-pressure hydrothermal reaction kettle. Subsequently, add a columnar calcium carbonate core to the kettle. Place the sealed hydrothermal reaction kettle in an oil bath pot set at a certain temperature and react for 2 h. By studying the dissolution of the calcium carbonate core at different reaction temperatures, measure the equivalent hydrochloric acid concentration generated by the self-generated acid reaction for 2 h. The experimental results are shown in Table 1.

[0045] Table 1

[0046]

[0047] As can be seen from Table 1, the high-temperature slow-release solid acid of the present invention basically does not produce acidity at room temperature and has almost no obvious corrosion effect on the calcium carbonate core. However, it begins to produce obvious acidity above 60 °C and can significantly corrode the calcium carbonate core. Moreover, the higher the temperature, the greater the concentration of hydrochloric acid produced. A solid content of 15% can achieve an equivalent hydrochloric acid concentration of about 7%. However, when the temperature is greater than 120 °C, the corrosion performance on the calcium carbonate core significantly decreases. This is because when the temperature is greater than 120 °C, hexachlorocyclotriphosphazene will melt, its hydrolysis rate is very fast, and the phosphonitrile acid generated by its hydrolysis will further hydrolyze and react with the generated hydrochloric acid to form phosphoric acid and ammonium chloride, consuming a large amount of hydrochloric acid, resulting in a decrease in its corrosion performance on calcium carbonate. In addition, as can be seen from Table 1, the particle size of the high-temperature slow-release solid acid has a significant impact on its temperature-controlled hydrolysis. The smaller the particle size, the faster the temperature-controlled hydrolysis. Therefore, the hydrolysis acid generation rate of the high-temperature slow-release solid acid of the present invention can be regulated by the formation temperature and the particle size of the solid acid.

[0048] Performance Detection 2

[0049] To investigate the concentration of hydrochloric acid generated by the high-temperature slow-release solid acid prepared from hexachlorocyclotriphosphazene of the present invention at different temperatures, 25 mL of the prepared high-temperature slow-release solid acid samples of Examples 5 to 8 were taken and placed in a high-pressure hydrothermal reaction kettle, and then a columnar calcium carbonate core was added to the kettle. The sealed hydrothermal reaction kettle was placed in an oil bath at a set temperature and reacted for 4 h. By studying the corrosion of the calcium carbonate core at different reaction temperatures, the equivalent hydrochloric acid concentration generated by the self-generated acid reaction for 4 h was measured. The experimental results are shown in Table 2.

[0050] Table 2

[0051]

[0052] As can be seen from Table 2, the high-temperature slow-release solid acid of the present invention basically does not produce acidity at room temperature and has almost no obvious corrosion effect on the calcium carbonate core. However, it begins to produce obvious acidity above 60 °C and can significantly corrode the calcium carbonate core. Moreover, the higher the temperature, the greater the concentration of hydrochloric acid produced, and the greater the concentration of the solid acid dispersion, the greater the concentration of hydrochloric acid produced. Among them, a solid content of 25% can achieve an equivalent hydrochloric acid concentration of about 12%. In addition, as can be seen from Table 2, the equivalent hydrochloric acid concentration of the solid acid prepared with seawater and the equivalent hydrochloric acid concentration of the solid acid prepared with fresh water have similar corrosion performance on calcium carbonate under the same conditions, indicating that the calcium solid acid can be directly prepared with seawater, which is convenient for preparation and use on offshore platforms.

[0053] Performance Detection 3

[0054] Investigate the slow corrosion performance of the acid generated by the high-temperature sustained-release solid acid of the present invention on calcium carbonate cores at 100°C. Take 25 mL of the high-temperature sustained-release solid acid sample prepared in Example 6 and place it in a hydrothermal reaction kettle. Subsequently, add columnar calcium carbonate cores to the kettle. Place the sealed hydrothermal reaction kettle in an oil bath at 100°C and react for different times and then take it out to study the corrosion of calcium carbonate cores at different reaction times. As a comparison, the corrosion of calcium carbonate cores by a 10% hydrochloric acid solution at room temperature was also measured. The experimental results are shown in Figure 1 .

[0055] It can be seen from Figure 1 that the high-temperature sustained-release solid acid of the present invention generates obvious acidity at 100°C, and with the extension of the reaction time, more hydrochloric acid is generated, and the corrosion of calcium carbonate cores is greater. The corrosion of calcium carbonate cores is a slow and controllable process, which is beneficial for deep formation acidification and extending the acidification distance.

[0056] Performance Detection 4

[0057] While the high-temperature sustained-release solid acid of the present invention hydrolyzes to generate acid, it can generate phosphonitrile acid with corrosion inhibition function, which has corrosion inhibition function. Select N80 steel sheets (50 mm * 10 mm * 3 mm) as the metal substrate, and test and evaluate its corrosion inhibition efficiency at room temperature of 25°C and 60°C through SY / T 5886-2018 "Evaluation Method for Acidizing Working Fluid Performance". The corrosion inhibition efficiency is equal to the percentage of the ratio of the difference obtained by subtracting the corrosion rate of the high-temperature sustained-release solid acid system from the corrosion rate of the hydrochloric acid solution without corrosion inhibitor at equivalent concentration to the corrosion rate of the hydrochloric acid solution without corrosion inhibitor at equivalent concentration. The experimental results are shown in Table 3.

[0058] Table 3

[0059]

[0060] It can be seen from Table 3 that the high-temperature sustained-release solid acid of the present invention basically does not generate acidity in a room-temperature environment and has almost no obvious corrosion effect on N80 steel sheets. Compared with hydrochloric acid of the same concentration, it has excellent corrosion inhibition effect. It starts to hydrolyze and generate acid at 60°C, but at the same time generates phosphonitrile acid with excellent corrosion inhibition function, which can reduce the corrosion of hydrochloric acid generated by the hydrolysis of solid acid on N80 steel sheets. Therefore, the dosage of corrosion inhibitor can be significantly reduced, and the chemical agent cost of acidification operation can be reduced.

[0061] The embodiments of this specific implementation manner are all preferred embodiments of the present invention, and do not limit the protection scope of the present invention accordingly. Therefore, all equivalent changes made according to the structure, shape, and principle of the present invention should be covered within the protection scope of the present invention.

Claims

1. A multifunctional temperature-controlled slow-release solid acid, characterized in that: The solid acid is hexachlorocyclotriphosphazene, which has the following molecular structure:

2. The multifunctional temperature-controlled sustained-release solid acid according to claim 1, characterized in that: The hexachlorocyclotriphosphazene is a white or off-white solid powder that is stable at room temperature and insoluble in water, with a particle size less than 500 μm.

3. The multifunctional temperature-controlled slow-release solid acid according to claim 2, wherein: The particle size of the hexachlorocyclotriphosphazene is 200 - 300 μm.

4. Application of the multifunctional temperature-controlled slow-release solid acid according to any one of claims 1 - 3 in acidizing and plugging removal.

5. The application according to claim 4, characterized in that: The solid acid is dispersed in water or seawater at room temperature to form a 15 - 25 wt% solid acid dispersion, which is injected into the formation under high-speed stirring. Through the hydrolysis reaction initiated by the high temperature of the formation, phosphazene acid with a corrosion inhibition function and hydrochloric acid capable of etching carbonate reservoirs are released, and a large amount of the generated hydrochloric acid deeply acid-etches the carbonate rock.

6. The application according to claim 5, wherein: The formation is a carbonate rock formation with a depth of 2000 - 6000 m and a temperature of 60 - 120 °C.

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