High-density and high-resistance-reduction type unblocking liquid system

Abstract

The invention relates to the technical field of oilfield chemistry, and provides a high-density and high-resistance-reduction type plug removal liquid system which is prepared from the following raw materials in percentage by mass: 20-30% of a plug removal agent, 1.2-1.8% of a corrosion inhibitor, 1.2-1.8% of an iron ion stabilizer, 0.5-1.5% of a discharge aiding agent, 1-3% of a clay stabilizer and the balance of water, the blocking remover comprises hydrochloric acid, hydrofluoric acid and aniline-2, 4-disulfonic acid. According to the technical scheme, the problem of poor corrosion performance of a high-density unblocking liquid system in related technologies is solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oilfield chemistry, and in particular to a high-density and high-resistance-reducing plugging removal liquid system. Background Art

[0002] As global oil and gas exploration and development continues to advance into deep, ultra-deep, and complex reservoirs, the challenges facing plugging removal technologies are becoming increasingly severe, with the bottleneck of dissolution performance being particularly prominent. Blockages in deep reservoirs are often multi-component and difficult to dissolve. These include carbonate scales, such as calcium carbonate and magnesium carbonate, which are soluble in conventional acids. More common are hard sulfate scales, such as barium sulfate and strontium sulfate, which are difficult to dissolve with conventional acid solutions. These include organic deposits such as asphaltene and colloids that solidify at high temperatures, and even composite scales formed by the reaction of drilling fluid filter cake, clay particles, and formation fluids. These complex blockages intertwine to form a dense barrier, significantly reducing the dissolution efficiency of conventional plugging removal fluids and making it difficult to effectively restore formation permeability.

[0003] Under extreme formation conditions of high temperature and high pressure, the existing deblocking fluids lack the ability to dissolve, making it difficult to sustain the dissolution reaction. For example, some chelating agents are easily decomposed at high temperatures, significantly reducing their ability to chelate calcium, barium, and other ions. Furthermore, the compatibility of acidic solutions with highly mineralized formation water often triggers the precipitation and deposition of inorganic salts, forming new blockages. Furthermore, the dissolution process of traditional deblocking fluids lacks specificity, and their selective dissolution capacity for the rock matrix and blockages is insufficient. While clearing blockages, they may cause over-acidification of the reservoir, destroying the rock structure and, in turn, reducing reservoir permeability. Furthermore, deep operations often require high-density deblocking fluids to balance formation pressure. However, the addition of high-concentration salts will increase the solution viscosity and flow resistance. If the dissolution performance is insufficient, it will be difficult for the high-density deblocking fluid to penetrate deep into the blockage, further exacerbating the problem of incomplete dissolution.

[0004] In summary, it is of vital importance to develop a high-density and high-resistance-reducing plugging removal fluid system that can improve the dissolution performance. Summary of the Invention

[0005] The present invention provides a high-density and high-resistance-reducing plugging removal liquid system, which solves the problem of poor dissolution performance of high-density plugging removal liquid systems in related technologies.

[0006] The technical solutions of the present invention are as follows: The present invention proposes a high-density, high-resistance-reducing plugging removal liquid system, the raw materials of which are composed of the following components in percentage by mass: 20% to 30% of a plugging remover, 1.2% to 1.8% of a corrosion inhibitor, 1.2% to 1.8% of an iron ion stabilizer, 0.5% to 1.5% of a drainage aid, 1% to 3% of a clay stabilizer, and the balance being water; The blocking remover includes hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid.

[0007] When the deplugging fluid comes into contact with metal equipment in the oil well, the corrosion inhibitor protects the equipment from corrosion by the acidic substances in the deplugging fluid. The iron ion stabilizer inhibits the hydrolysis and oxidation reactions of iron ions by forming a stable complex with iron ions, thereby avoiding the formation of precipitation. The drainage aid reduces the oil-water interfacial tension, making the oil droplets easier to disperse in the water, which is conducive to the discharge of the oil phase from the formation pores. The clay stabilizer effectively inhibits the expansion of clay particles and keeps the formation pores unobstructed.

[0008] As a further technical solution, the mass ratio of the hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid is 5:1:0.5~1.

[0009] In the present invention, the mass ratio of hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid can be 5:1:0.5, 5:1:0.52, 5:1:0.54, 5:1:0.56, 5:1:0.58, 5:1:0.6, 5:1:0.62, 5:1:0.64, 5:1:0.66, 5:1:0.68, 5:1:0.7, 5:1:0.8 1:0.72, 5:1:0.74, 5:1:0.76, 5:1:0.78, 5:1:0.8, 5:1:0.82, 5:1:0.84, 5:1:0.86, 5:1:0.88, 5:1:0.9, 5:1:0.92, 5:1:0.94, 5:1:0.96, 5:1:0.98, 5:1:1.

[0010] In the present invention, the dissolution performance of the high-density plugging removal liquid system is further improved by adjusting the mass ratio of hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid to 5:1:0.5~1. When the proportion of aniline-2,4-disulfonic acid is too low, the dissolution performance will be poor. When the proportion of aniline-2,4-disulfonic acid is too high, the reactivity of other components will be affected.

[0011] As a further technical solution, the corrosion inhibitor includes cetylpyridinium chloride.

[0012] In the present invention, hexadecylpyridinium chloride is selected as a corrosion inhibitor. When a high-density, high-resistance-reducing plugging removal fluid system comes into contact with metal equipment in an oil well, the hexadecylpyridinium chloride molecules are oriented, the long-chain alkyl portion thereof is lipophilic, and the positively charged pyridinium cation head is hydrophilic. Since the metal surface usually carries a negative charge in the electrolyte solution, the cation head of the hexadecylpyridinium chloride is adsorbed on the metal surface to form a dense adsorption film. This adsorption film effectively prevents corrosive substances (such as acidic components such as hydrochloric acid and hydrofluoric acid) in the plugging removal fluid from directly contacting the metal surface, suppressing the dissolution of metal ions and the diffusion of corrosive media, thereby ensuring the corrosion inhibition effect.

[0013] As a further technical solution, the corrosion inhibitor further includes 4,4'-methylenebis(2-methylcyclohexylamine).

[0014] In the present invention, 4,4'-methylenebis(2-methylcyclohexylamine) and cetylpyridinium chloride are used together as corrosion inhibitors. When the high-density, high-resistance-reducing plugging removal fluid system comes into contact with oil well metal equipment, the quaternary ammonium cations in the 4,4'-methylenebis(2-methylcyclohexylamine) are adsorbed on the metal surface, and the cetylpyridinium chloride and the 4,4'-methylenebis(2-methylcyclohexylamine) work synergistically to form a dense adsorption film, thereby improving the corrosion inhibition effect of the high-density, high-resistance-reducing plugging removal fluid system and effectively extending the service life of the oil well equipment.

[0015] As a further technical solution, the mass ratio of the hexadecylpyridinium chloride to the 4,4'-methylenebis(2-methylcyclohexylamine) is 5-7:1.

[0016] In the present invention, the mass ratio of hexadecylpyridinium chloride to 4,4'-methylenebis(2-methylcyclohexylamine) can be 5:1, 5.1:1, 5.2:1, 5.3:1, 5.3:1, 5.4:1, 5.5:1, 5.6:1, 5.7:1, 5.8:1, 5.9:1, 6:1, 6.1:1, 6.2:1, 6.3:1, 6.4:1, 6.5:1, 6.6:1, 6.7:1, 6.8:1, 6.9:1, and 7:1.

[0017] In the present invention, by adjusting the mass ratio of hexadecylpyridinium chloride and 4,4'-methylenebis(2-methylcyclohexylamine), the corrosion inhibition effect of the high-density, high-resistance-reduction type plugging removal liquid system is further improved. This mass ratio range is conducive to the uniform dispersion of the two corrosion inhibitors in the plugging removal liquid. The two can better cooperate with each other, preventing the aggregation or precipitation of a certain corrosion inhibitor due to imbalance in the ratio, ensuring the corrosion inhibition performance of the plugging removal liquid, and improving processing efficiency and product quality stability.

[0018] As a further technical solution, the iron ion stabilizer includes one or more of citric acid, acetic acid, and nitrilotriacetic acid.

[0019] In the present invention, the iron ion stabilizer can be any one or more of conventional iron ion stabilizers, and can be one or more of citric acid, acetic acid, nitrilotriacetic acid, ethylenediaminetetraacetic acid, tartaric acid, and gluconic acid, preferably one or more of citric acid, acetic acid, and nitrilotriacetic acid.

[0020] In the present invention, the addition of an iron ion stabilizer greatly enhances the stability and reliability of the plugging removal fluid system. By inhibiting the harmful reactions of iron ions, it not only ensures the unobstructed flow of formation pores, but also avoids the negative impact of iron ion precipitation on other properties of the plugging removal fluid (such as fluidity, plugging removal effect, etc.), thereby improving the overall plugging removal performance and service life of the plugging removal fluid. In practical applications, these iron ion stabilizers can significantly improve the adaptability of the plugging removal fluid under different formation conditions. When the pH value, temperature, and type of iron-containing minerals in the formation change, they can effectively stabilize the iron ions, ensure the smooth progress of the plugging removal operation, avoid secondary blockage caused by iron ion precipitation, and improve the plugging removal efficiency of the oil well. Among them, when the iron ion stabilizer is one or more of citric acid, acetic acid, and nitrilotriacetic acid, since citric acid, acetic acid, and nitrilotriacetic acid all have good water solubility, they can be evenly mixed with other components in the plugging removal fluid and have excellent processability.

[0021] In the present invention, the drainage aid can be any one or more of conventional drainage aids, and can be one or more of octylphenol polyoxyethylene ether, dodecyl betaine, polyoxyethylene fatty alcohol ether, cocamidopropyl betaine, and sodium lauryl polyoxyethylene ether sulfate.

[0022] As a further technical solution, the drainage aid includes one or both of octylphenol polyoxyethylene ether and dodecyl betaine.

[0023] In the present invention, both octylphenol polyoxyethylene ether and dodecyl betaine have good solubility and dispersibility, can be evenly mixed with other components in the unblocking fluid, and will not cause stratification or precipitation. They can significantly improve the drainage effect of the high-density, high-resistance-reducing unblocking fluid system, especially in low-permeability formations or formations containing a large amount of oil-water emulsions. They can effectively reduce the resistance to liquid flow, making it easier to discharge the residual liquid in the formation after unblocking, reducing the impact on the formation permeability, and increasing the oil well production. The use of drainage aids enhances the comprehensive performance of the unblocking fluid system. By reducing the oil-water interfacial tension and improving the wettability, not only the drainage efficiency is improved, but also the secondary blockage caused by the retention of residual liquid can be prevented, thereby improving the adaptability and effectiveness of the unblocking fluid under complex formation conditions.

[0024] As a further technical solution, the clay stabilizer includes polydimethyldiallylammonium chloride.

[0025] In the present invention, the clay stabilizer includes polydimethyldiallyl ammonium chloride. Clay particles in the formation usually have a negative charge. If not stabilized, the clay particles will expand and disperse due to electrostatic repulsion and migrate with the fluid, thereby blocking the formation pores, reducing the formation permeability, and affecting the deblocking effect. Polydimethyldiallyl ammonium chloride is a cationic polymer with a large number of positively charged quaternary ammonium groups distributed on its molecular chain. When polydimethyldiallyl ammonium chloride is added to the deblocking fluid, the positively charged quaternary ammonium groups will interact with the negatively charged surface of the clay particles. Multiple polydimethyldiallyl ammonium chloride molecules form a coating on the surface of the clay particles, neutralizing the negative charge on the surface of the clay particles and reducing the electrostatic repulsion between the clay particles, thereby effectively inhibiting the expansion and dispersion of the clay particles. At the same time, this coating can also connect the clay particles together, further restricting the migration of clay particles and keeping the formation pores unobstructed.

[0026] The present invention also proposes a method for preparing a high-density, high-resistance-reducing plugging removal liquid system, which is used to prepare the high-density, high-resistance-reducing plugging removal liquid system, comprising the following steps: The blocking remover, corrosion inhibitor, iron ion stabilizer, drainage aid, clay stabilizer and water are uniformly mixed to obtain the high-density and high-resistance-reduction blocking remover liquid system.

[0027] In the present invention, the preparation method of the high-density and high-resistance-reduction plugging removal fluid system is simple to operate, and the various components fully interact with each other during the mixing process, which can better exert a synergistic effect. The corrosion inhibitor can be more effectively adsorbed on the metal surface after uniform mixing, the iron ion stabilizer can more comprehensively complex with the iron ions, and the drainage aid can more evenly reduce the oil-water interfacial tension, thereby significantly improving the overall plugging removal, corrosion inhibition, iron stabilization, drainage aid and clay stabilization properties of the plugging removal fluid system, and enhancing its adaptability in complex formation conditions.

[0028] As a further technical solution, during the mixing, the temperature is 25-35°C.

[0029] In the present invention, when the mixing temperature is 25-35°C, the volatilization of hydrochloric acid and hydrofluoric acid at high temperature can be prevented from being aggravated, so that the corrosion inhibitor can maintain good dispersibility and activity, the complexation reaction between the iron ion stabilizer and the iron ion can be stably carried out, and the performance of the drainage agent in reducing the oil-water interfacial tension can be fully exerted within this temperature range. Similarly, the clay stabilizer polydimethyldiallyl ammonium chloride also has a good stabilizing effect on clay particles at this temperature.

[0030] The working principle and beneficial effects of the present invention are: In the present invention, hydrochloric acid can dissolve carbonate blockages in the formation, hydrofluoric acid can dissolve and dredge silicate minerals, and aniline-2,4-disulfonic acid acts on organic blockages. On the basis of hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid act synergistically to improve the dissolution performance of the high-density plugging removal liquid system. In addition, the pH environment adjusted by aniline-2,4-disulfonic acid is conducive to the hydrochloric acid and hydrofluoric acid to better exert their dissolving effects, thereby improving the plugging removal efficiency, so that the overall plugging removal ability far exceeds the effect of each acid when used alone. Compared with some mixed acid systems that lack effective synergy, the acid system of the present invention has more advantages in plugging removal effect. DETAILED DESCRIPTION

[0031] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0032] In the following examples and comparative examples, the model of octylphenol polyoxyethylene ether is DOWFAX X-405, and polydimethyldiallylammonium chloride is purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. with the product number LNB-1642.

[0033] Example 1 A high-density, high-resistance-reducing plugging removal fluid system, the raw materials of which are composed of the following components in percentage by mass: 30% of a plugging remover, 1.8% of cetylpyridinium chloride, 0.6% of citric acid, 0.6% of acetic acid, 0.6% of nitrilotriacetic acid, 0.7% of octylphenol polyoxyethylene ether, 0.8% of dodecyl betaine, 3% of polydimethyldiallylammonium chloride, and the balance being water; The blocking agent includes hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid in a mass ratio of 5:1:1.5; The preparation method of the high-density high-resistance-reducing plugging removal liquid system comprises the following steps: The plugging remover, corrosion inhibitor, iron ion stabilizer, drainage aid, clay stabilizer and water are mixed uniformly at 35° C. to obtain a high-density and high-resistance-reduction plugging remover liquid system.

[0034] Example 2 A high-density, high-resistance-reducing plugging removal fluid system, the raw materials of which are composed of the following components in percentage by mass: 20% of a plugging remover, 1.2% of cetylpyridinium chloride, 1.2% of nitrilotriacetic acid, 0.5% of octylphenol polyoxyethylene ether, 1% of polydimethyldiallylammonium chloride, and the balance being water; The blocking agent includes hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid in a mass ratio of 5:1:0.2; The preparation method of the high-density high-resistance-reducing plugging removal liquid system comprises the following steps: The plugging remover, corrosion inhibitor, iron ion stabilizer, drainage aid, clay stabilizer and water are mixed uniformly at 25° C. to obtain a high-density and high-resistance-reduction plugging remover liquid system.

[0035] Example 3 A high-density, high-resistance-reducing plugging removal fluid system, the raw materials of which are composed of the following components in percentage by mass: 25% of a plugging remover, 1.5% of hexadecylpyridinium chloride, 1.4% of citric acid, 1.0% of dodecyl betaine, 2% of polydimethyldiallylammonium chloride, and the balance being water; The blocking agent includes hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid in a mass ratio of 5:1:1.2; The preparation method of the high-density high-resistance-reducing plugging removal liquid system comprises the following steps: The plugging remover, corrosion inhibitor, iron ion stabilizer, drainage aid, clay stabilizer and water are mixed uniformly at 30° C. to obtain a high-density and high-resistance-reducing plugging remover liquid system.

[0036] Example 4 The only difference between this embodiment and embodiment 3 is that the mass ratio of hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid in this embodiment is 5:1:0.3.

[0037] Example 5 The only difference between this embodiment and embodiment 3 is that the mass ratio of hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid in this embodiment is 5:1:0.5.

[0038] Example 6 The only difference between this embodiment and embodiment 3 is that the mass ratio of hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid in this embodiment is 5:1:1.

[0039] Example 7 The only difference between this embodiment and embodiment 6 is that in this embodiment, cetylpyridinium chloride is replaced by an equal mass of corrosion inhibitor, which includes cetylpyridinium chloride and 4,4'-methylenebis(2-methylcyclohexylamine) in a mass ratio of 7:1.

[0040] Example 8 The only difference between this embodiment and embodiment 6 is that in this embodiment, cetylpyridinium chloride is replaced by an equal mass of corrosion inhibitor, which includes cetylpyridinium chloride and 4,4'-methylenebis(2-methylcyclohexylamine) in a mass ratio of 5:1.

[0041] Example 9 The only difference between this embodiment and embodiment 6 is that in this embodiment, hexadecylpyridinium chloride is replaced by 4,4'-methylenebis(2-methylcyclohexylamine).

[0042] Comparative Example 1 The only difference between this comparative example and Example 3 is that the blocking agent in this comparative example comprises hydrochloric acid and hydrofluoric acid in a mass ratio of 5:2.2.

[0043] Comparative Example 2 The only difference between this comparative example and Example 3 is that the blocking agent in this comparative example comprises hydrochloric acid and aniline-2,4-disulfonic acid in a mass ratio of 5:2.2.

[0044] Experimental Example 1 The high-density, high-resistance-reducing plugging removal fluid systems prepared in Examples 1 to 6 and Comparative Examples 1 to 2 were tested for permeability before treatment and permeability after treatment using the high-density, high-resistance-reducing plugging removal fluid systems according to core flow simulation experiments. The experimental method is as follows: A carbonate reservoir core measuring 2.5 cm x 2.5 cm was drilled from Well Yingdong 101 in the Qaidam Basin. A pre-flush, a high-density, high-resistance-reducing plugging removal fluid system, and a post-flush were sequentially injected. The permeabilities of the pre-flush and post-flush fluids were calculated, with a displacement volume of 5 PV. Both the pre-flush and post-flush fluids were deionized water. The test results are shown in Table 1.

[0045] Table 1 Permeability test results

[0046] As can be seen from Table 1, the change rate of the permeability of Examples 1 to 6 is higher than the change rate of the permeability of Comparative Examples 1 to 2. Therefore, in the present invention, hydrofluoric acid and aniline-2,4-disulfonic acid act synergistically on the basis of hydrochloric acid, thereby improving the dissolution performance of the high-density plugging removal liquid system.

[0047] Experimental Example 2 The high-density, high-resistance-reduction plugging removal fluid systems prepared in Examples 6-9 were tested for corrosion inhibition rates according to the method specified in SY / T 5405-2019, "Test Methods and Evaluation Indicators for Acidizing Corrosion Inhibitors." The test results are shown in Table 2.

[0048] Table 2 Corrosion inhibition rate test results

[0049] As shown in Table 2, the corrosion inhibition rate of the high-density high-resistance-reducing plugging liquid system prepared in Examples 7 to 9 of the present invention reached 39.85 g / (m 2 h) or less. Therefore, in the present invention, cetylpyridinium chloride and 4,4'-methylenebis(2-methylcyclohexylamine) are used together as corrosion inhibitors to improve the corrosion inhibition performance of the high-density and high-resistance-reducing plugging removal liquid system.

[0050] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A high-density, high-resistance-reducing plugging removal liquid system, characterized in that: The raw materials are composed of the following components in percentage by mass: 20% to 30% of a blocking agent, 1.2% to 1.8% of a corrosion inhibitor, 1.2% to 1.8% of an iron ion stabilizer, 0.5% to 1.5% of a drainage aid, 1% to 3% of a clay stabilizer, and the balance being water; The blocking remover includes hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid.

2. A high-density, high-resistance-reducing plugging removal liquid system according to claim 1, characterized in that: The mass ratio of the hydrochloric acid, hydrofluoric acid and aniline-2,4-disulfonic acid is 5:1:0.5~1.

3. A high-density, high-resistance-reducing plugging removal liquid system according to claim 1, characterized in that: The corrosion inhibitor includes cetylpyridinium chloride.

4. A high-density, high-resistance-reducing plugging removal liquid system according to claim 3, characterized in that: The corrosion inhibitor also includes 4,4'-methylenebis(2-methylcyclohexylamine).

5. A high-density, high-resistance-reducing plugging removal liquid system according to claim 4, characterized in that: The mass ratio of the hexadecylpyridinium chloride to the 4,4'-methylenebis(2-methylcyclohexylamine) is 5-7:

1.

6. The high-density, high-resistance-reducing plugging removal liquid system according to claim 1, characterized in that: The iron ion stabilizer includes one or more of citric acid, acetic acid, and nitrilotriacetic acid.

7. The high-density, high-resistance-reducing plugging removal liquid system according to claim 1, characterized in that: The drainage aid includes one or both of octylphenol polyoxyethylene ether and lauryl betaine.

8. The high-density, high-resistance-reducing plugging removal liquid system according to claim 1, characterized in that: The clay stabilizer includes polydimethyldiallylammonium chloride.

9. A method for preparing a high-density, high-resistance-reducing plugging-removing liquid system, for preparing a high-density, high-resistance-reducing plugging-removing liquid system according to any one of claims 1 to 8, characterized in that: The following steps are involved: The blocking remover, corrosion inhibitor, iron ion stabilizer, drainage aid, clay stabilizer and water are uniformly mixed to obtain the high-density and high-resistance-reduction blocking remover liquid system.

10. The method for preparing a high-density, high-resistance-reducing plugging removal liquid system according to claim 9, characterized in that: During the mixing, the temperature is 25-35°C.

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