Acid liquid for acid treatment of oil layers and method for preparing the same

Abstract

The application belongs to the technical field of oil exploitation, and particularly relates to an acid liquid for acid treatment of an oil layer and a preparation method thereof. The preparation method is as follows: the specific steps of the preparation method are as follows: in a reactor, piperazine-1,4-diethyl sulfonate monosodium salt, ethanol and bromoalkane are added, heated to reflux, and during the reaction, sodium hydroxide solution is used to maintain pH 7-8; 1-bromo-6-(trimethylammonium) hexyl bromide is added, heated to reflux, and during the reaction, sodium hydroxide solution is used to maintain pH 8-9; vacuum distillation is performed to obtain a viscous solid, cyclohexane recrystallization is performed to obtain a solid, and the solid is dried at 90 DEG C overnight to obtain corrosion-inhibiting acid; hydrochloric acid, hydrofluoric acid, hydroxyethylidene diphosphonic acid, corrosion-inhibiting acid and water are added to the reactor, stirred uniformly, and the acid liquid is obtained. The acid liquid has the advantages of low corrosion rate and long acidification time.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to an acid solution for oil reservoir acid treatment and its preparation method. Background Technology

[0002] Acidizing is an important technical measure for enhancing oilfield production and injection. Its core principle is to inject acid into the formation to dissolve mineral components (such as carbonate rocks and clay minerals) or blockages (such as drilling fluid, completion fluid residue, and scale) in the near-wellbore reservoir rocks. This expands or opens up oil and gas flow channels, restores or increases formation permeability, and ultimately improves reservoir permeability and oil and gas production.

[0003] Traditional acid systems have significant limitations in reservoir acid treatment: First, the reaction rate is too fast under high temperature conditions, causing the acid to be rapidly consumed in the near-wellbore zone, making it difficult to penetrate deep into the reservoir to form effective acid-etched fractures, especially in ultra-deep carbonate reservoirs where deep penetration performance is severely limited; Second, the acid is highly corrosive to metal equipment, and the precipitates such as calcium fluoride and iron hydroxide generated by the reaction with the rock can easily block pore channels, causing secondary damage to the reservoir; Third, although existing slow-reaction technologies (such as thickened acid and cross-linked acid) can prolong the reaction time, they have problems such as excessively high viscosity leading to pumping difficulties and poor backflow, or weak erosion resistance of the isolation film formed by surfactants.

[0004] Therefore, there is an urgent need in this field to develop a novel acid solution for oil reservoir acid treatment. This acid solution should possess comprehensive properties such as good slowing effect, long penetration distance, minimal secondary precipitation damage, low corrosivity to tubing, good compatibility with formation fluids and additives, strong adaptability, environmental friendliness, and controllable cost. Simultaneously, its preparation method should be as simple, controllable, and easy to prepare and apply on-site. Summary of the Invention

[0005] This invention addresses the shortcomings of the prior art by providing an acid solution for oil layer acid treatment and its preparation method. The acid solution of this invention has the advantages of low corrosion rate and long acidification time.

[0006] One objective of this invention is to disclose an acid solution for treating oil layers, the composition and mass fraction of which are as follows: Hydrochloric acid (30wt%) 15-20 parts; Hydrofluoric acid (30wt%) 5-10 parts; 2-5 parts of hydroxyethylidene diphosphonic acid; 10-20 parts of corrosion-inhibiting acid; The remaining portion is water, totaling 100 portions; The molecular structural formula of the corrosion-inhibiting acid is as follows:

[0007] Where R is C8-C 18 Straight-chain alkyl groups.

[0008] Another objective of this invention is to disclose a method for preparing the aforementioned acid solution, the specific steps of which are as follows: (1) Add piperazine-1,4-diethanesulfonic acid monosodium salt, ethanol, and bromoalkane to the reactor, heat and reflux the reaction, and maintain the pH at 7-8 with sodium hydroxide solution during the process; (2) Add 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux and maintain pH 8-9 with sodium hydroxide solution during the process; (3) Vacuum distillation was performed to obtain a viscous solid. Cyclohexane was recrystallized to obtain a solid. The solid was dried at 90-95℃ overnight to obtain a corrosion-inhibiting acid. (4) Add hydrochloric acid (30wt%), hydrofluoric acid (30wt%), hydroxyethylidene diphosphonic acid, corrosion inhibitory acid and water to a container and stir until the acid solution is obtained.

[0009] Preferably, based on 1 mole of piperazine-1,4-diethanesulfonic acid monosodium salt, the amounts of the bromoalkane and 1-bromo-6-(trimethylammonium)hexyl bromide are 0.8-1.2 moles and 0.8-1.2 moles, respectively; more preferably, based on 1 mole of piperazine-1,4-diethanesulfonic acid monosodium salt, the amounts of the bromoalkane and 1-bromo-6-(trimethylammonium)hexyl bromide are 0.9-1.1 moles and 0.9-1.1 moles, respectively.

[0010] Preferably, in step (1), the mass ratio of ethanol to piperazine-1,4-diethanesulfonic acid monosodium salt is 15-20:1.

[0011] Preferably, in step (1), the reflux reaction time is 4-8 hours.

[0012] Preferably, in step (2), the reflux reaction time is 8-24 hours.

[0013] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The acid solution for oil layer acid treatment of the present invention is an acidifying solution with multiple functions. Among them, hydrochloric acid and hydrofluoric acid are the main acidifying agents, which dissolve carbonates and silicates to achieve the purpose of creating fractures in the rock formation; hydroxyethylidene diphosphonic acid is the scale inhibitor, which inhibits the formation of common inorganic scale and prevents these scales from clogging formation pores or tubing, thereby maintaining the smooth flow of wellbore and pipeline; corrosion inhibitor is the corrosion inhibitor, which forms an adsorption film on the surface of metal pipes, significantly reducing the corrosion rate of the acid solution on steel; auxiliary acid solution can reduce the acidification rate to achieve the purpose of creating fractures deep in the rock formation; drainage aid reduces the surface tension of the liquid and promotes drainage.

[0014] (2) The acid solution used for oil layer acid treatment in this invention has a strong corrosion inhibition effect, and the lowest corrosion rate at room temperature can reach 0.18 g / (m³). 2 The corrosion rate at 120℃ can reach as low as 0.72 g / (m³). 2 (·h); The acid solution used for oil layer acid treatment in this invention can significantly extend the acidification time and dissolve deep rock layers. Detailed Implementation

[0015] The endpoints and any values ​​of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0016] The technical solution of the present invention will be further described below with reference to specific embodiments: Example 1 Preparation of corrosion-inhibiting acid S1 (1) Add 50 mmol piperazine-1,4-diethanesulfonic acid monosodium salt, 243 g ethanol and 40 mmol n-octadecane to the reactor, heat and reflux for 4 h, and maintain pH 7-8 with sodium hydroxide solution during the process; (2) Add 40 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux for 8 h, and maintain pH 8-9 with sodium hydroxide solution during the process; (3) Distilled under reduced pressure to obtain a viscous solid, recrystallized from cyclohexane to obtain a solid, dried at 90°C overnight to obtain corrosion-inhibiting acid S1.

[0017] Example 2 Preparation of corrosion-inhibiting acid S2 (1) Add 50 mmol piperazine-1,4-diethanesulfonic acid monosodium salt, 324 g ethanol and 60 mmol n-octane to the reactor and heat under reflux for 8 h. During this period, use sodium hydroxide solution to maintain pH 7-8. (2) Add 60 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux for 24 h, and maintain pH 8-9 with sodium hydroxide solution during the process; (3) Distilled under reduced pressure to obtain a viscous solid, recrystallized from cyclohexane to obtain a solid, dried at 95°C overnight to obtain corrosion-inhibiting acid S2.

[0018] Example 3 Preparation of corrosion-inhibiting acid S3 (1) Add 50 mmol piperazine-1,4-diethanesulfonic acid monosodium salt, 286 g ethanol and 45 mmol n-hexadecane to the reactor, heat and reflux for 5 h, and maintain pH 7-8 with sodium hydroxide solution during the process; (2) Add 55 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux for 12 h, and maintain pH 8-9 with sodium hydroxide solution during the process; (3) Distilled under reduced pressure to obtain a viscous solid, recrystallized from cyclohexane to obtain a solid, dried at 92°C overnight to obtain corrosion-inhibiting acid S3.

[0019] Example 4 Preparation of corrosion-inhibiting acid S4 (1) Add 50 mmol piperazine-1,4-diethanesulfonic acid monosodium salt, 273 g ethanol and 55 mmol n-dodecane to the reactor and heat under reflux for 6 h. During this period, use sodium hydroxide solution to maintain pH 7-8. (2) Add 45 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux for 16 h, and maintain pH 8-9 with sodium hydroxide solution during the process; (3) Distillation under reduced pressure to obtain a viscous solid, recrystallize cyclohexane to obtain a solid, dry at 93°C overnight to obtain corrosion inhibitor acid S4.

[0020] Example 5 Preparation of corrosion-inhibiting acid S5 (1) Add 50 mmol piperazine-1,4-diethanesulfonic acid monosodium salt, 300 g ethanol and 50 mmol n-dodecane to the reactor and heat under reflux for 6 h. During this period, use sodium hydroxide solution to maintain pH 7-8. (2) Add 52 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux for 24 h, and maintain pH 8-9 with sodium hydroxide solution during the process; (3) Distilled under reduced pressure to obtain a viscous solid, recrystallized from cyclohexane to obtain a solid, dried at 91°C overnight to obtain corrosion-inhibiting acid S5.

[0021] Example 6 Preparation of acid solution Add 15g hydrochloric acid (30wt%), 10g hydrofluoric acid (30wt%), 2g hydroxyethylidene diphosphonic acid, 10g S1, and 63g water to the reactor and stir until homogeneous to obtain the acid solution.

[0022] Example 7 Preparation of acid solution Add 16g hydrochloric acid (30wt%), 9g hydrofluoric acid (30wt%), 3g hydroxyethylidene diphosphonic acid, 12g S2, and 60g water to a container and stir until well mixed to obtain the acid solution.

[0023] Example 8 Preparation of acid solution Add 18g hydrochloric acid (30wt%), 8g hydrofluoric acid (30wt%), 4g hydroxyethylidene diphosphonic acid, 15g S3, and 55g water to a container and stir until well mixed to obtain the acid solution.

[0024] Example 9 Preparation of acid solution Add 19g hydrochloric acid (30wt%), 7g hydrofluoric acid (30wt%), 4g hydroxyethylidene diphosphonic acid, 18g S4, and 52g water to a container and stir until well mixed to obtain the acid solution.

[0025] Example 10 Preparation of acid solution Add 20g hydrochloric acid (30wt%), 5g hydrofluoric acid (30wt%), 5g hydroxyethylidene diphosphonic acid, 20g S5, and 50g water to a container and stir until well mixed to obtain the acid solution.

[0026] Comparative Example 1 The preparation process is the same as in Example 6, except that 10g of S1 is not added.

[0027] Comparative Example 2 Add 15g hydrochloric acid (30wt%), 10g hydrofluoric acid (30wt%), and 63g water to the reactor and stir until homogeneous.

[0028] Test Example 1: Testing of Corrosion Rate at Room Temperature According to SY / T 5405-2019 "Test Methods and Evaluation Methods for Performance of Corrosion Inhibitors for Acidification" 4.1, the coating was prepared and placed in Examples 6-10, Comparative Example 1, and Comparative Example 2. After being placed at room temperature for 4 hours, the corrosion rate at room temperature was measured. The test results are shown in Table 1.

[0029] Test Example 2 Similar to Test Example 1, except that the 4-hour placement at room temperature was changed to 4 hours at 120℃, and the high-temperature corrosion rate was measured. The test results are shown in Table 1.

[0030] Table 1 Corrosion rate test results

[0031] Test Example 3 Natural rock cores from a low-permeability block in the Shengli Oilfield were immersed in Examples 6-10, Comparative Example 1, and Comparative Example 2 to test the change in dissolution rate over time. The test results are shown in Table 2.

[0032] Table 2. Change in solubility over time (%)

[0033] As can be seen from Examples 6-10 and Comparative Example 2, the acidizing time of the present invention can be longer, enabling acidification and dissolution of deep rock strata and achieving deep fracture formation in oil layers. As can be seen from Example 6 and Comparative Example 1, the corrosion-inhibiting acid of the present invention has the functions of corrosion inhibition and extending acidizing time.

[0034] In summary, the acid solution used for oil layer acid treatment in this invention has a strong corrosion inhibition effect, and the lowest corrosion rate at room temperature can reach 0.18 g / (m³). 2 The corrosion rate at 120℃ can reach as low as 0.72 g / (m³). 2 (h); The acid solution used for oil layer acid treatment in this invention can significantly extend the acidification time and dissolve deep rock layers. Therefore, this product has broad market application prospects.

[0035] The preferred embodiments of the present invention have been described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the scope of the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the protection scope of the present invention.

[0036] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not describe the various possible combinations separately.

[0037] Furthermore, various different embodiments of the present invention can be combined in any way, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed by the present invention.

Claims

1. An acid solution for treating oil layers, characterized in that, The composition and mass components of the acid solution used for oil layer acid treatment are as follows: Hydrochloric acid (30wt%) 15-20 parts; Hydrofluoric acid (30wt%) 5-10 parts; 2-5 parts of hydroxyethylidene diphosphonic acid; 10-20 parts of corrosion-inhibiting acid; The remaining portion is water, totaling 100 portions; The molecular structural formula of the corrosion-inhibiting acid is as follows: ， Where R is C8-C 18 Straight-chain alkyl groups.

2. The method for preparing the acid solution for oil layer acid treatment according to claim 1, characterized in that, The specific steps of the preparation method are as follows: (1) Add piperazine-1,4-diethanesulfonic acid monosodium salt, ethanol, and bromoalkane to the reactor, heat and reflux the reaction, and maintain the pH at 7-8 with sodium hydroxide solution during the process; (2) Add 1-bromo-6-(trimethylammonium)hexyl bromide, heat under reflux and maintain pH 8-9 with sodium hydroxide solution during the reaction; (3) Vacuum distillation was performed to obtain a viscous solid. Cyclohexane was recrystallized to obtain a solid. The solid was dried at 90-95℃ overnight to obtain a corrosion-inhibiting acid. (4) Add hydrochloric acid (30wt%), hydrofluoric acid (30wt%), hydroxyethylidene diphosphonic acid, corrosion inhibitory acid and water to a container and stir until the acid solution is obtained.

3. The preparation method according to claim 2, characterized in that, Based on 1 mole of piperazine-1,4-diethanesulfonic acid monosodium salt, the amounts of the bromoalkane and 1-bromo-6-(trimethylammonium)hexyl bromide are 0.8-1.2 moles and 0.8-1.2 moles, respectively.

4. The preparation method according to claim 3, characterized in that, Based on 1 mole of piperazine-1,4-diethanesulfonic acid monosodium salt, the amounts of the bromoalkane and 1-bromo-6-(trimethylammonium)hexyl bromide are 0.9-1.1 moles and 0.9-1.1 moles, respectively.

5. The preparation method according to claim 2, characterized in that, In step (1), the mass ratio of ethanol to piperazine-1,4-diethanesulfonic acid monosodium salt is 15-20:

1.

6. The preparation method according to claim 2, characterized in that, In step (1), the reflux reaction time is 4-8 hours.

7. The preparation method according to claim 2, characterized in that, In step (2), the reflux reaction time is 8-24h.

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