Composite acid for acidification and preparation method thereof

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to compound acid for acidification and a preparation method thereof. The preparation method comprises the following steps: adding 2-naphthylamine-1, 5-disulfonic acid and water into a reactor, stirring, heating and dissolving, and adjusting the pH value to 8-9 by using a sodium hydroxide solution; simultaneously dropwise adding carbon disulfide and a sodium hydroxide solution into the reactor, maintaining the pH value to be 8-9 in the reaction process, and heating and refluxing after dropwise adding; cooling the mixture to below 5 DEG C, separating out crystals, and centrifugally drying to obtain multifunctional acid; the preparation method comprises the following steps: adding multifunctional acid, hydrochloric acid (30wt%), polymaleic anhydride, formic acid, amino trimethylene phosphonic acid and water into a container, and uniformly stirring to obtain the composite acid. According to the compound acid for acidification, the acidification time can be greatly prolonged, and a deep rock stratum is dissolved; the acidizing requirements of rock stratums at different depths can be met by adjusting the composition of each component of the composite acid and adjusting the acidizing speed.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a composite acid for acidification and its preparation method. Background Technology

[0002] Acidizing is a key production enhancement technology that improves near-wellbore permeability through the chemical dissolution of acid. Its core function is to effectively remove various contaminants and blockages formed during drilling, operations, or production, restoring the original formation permeability. Simultaneously, by etching the rock (especially in carbonate reservoirs), it actively creates highly conductive acid-etched fractures, significantly improving oil and gas flow efficiency and achieving deep stimulation. Furthermore, this technology can also be used to adjust the production or injection profile of heterogeneous reservoirs, optimizing resource utilization.

[0003] Currently, the acid systems commonly used for acidification on-site mainly include: (1) Inorganic acids, such as hydrochloric acid, which have the advantages of low cost, strong reactivity and strong dissolving ability, but also have the disadvantages of strong corrosiveness, excessively fast reaction speed and high risk of secondary damage; (2) Organic acids, such as formic acid and acetic acid, which have the advantages of mild reaction, good slowing effect and lower high-temperature corrosiveness than inorganic acids, but also have the disadvantages of weak dissolving ability, limited solubility and poor dissolving effect on some blockages; (3) Conventional composite acids, such as hydrochloric acid and organic acid are physically mixed to take advantage of each other's strengths and weaknesses, but the synergistic effect is limited, the system stability is poor, the formulation is not targeted enough, and it is difficult to adapt to complex and ever-changing reservoir conditions.

[0004] Therefore, developing a novel composite acid for acidizing, which achieves high synergy among its components through scientific formulation and preparation processes, has controllable performance, and can adapt to complex reservoir conditions, along with its corresponding preparation method, is of significant practical importance and application value for improving acidizing operation efficiency, ensuring operational safety, and reducing overall costs. Summary of the Invention

[0005] This invention addresses the shortcomings of the prior art by providing a composite acid for acidification and its preparation method. The composite acid of this invention has the function of adjusting the acidification rate and dissolving rock strata at different depths.

[0006] One objective of this invention is to disclose a composite acid for acidification, the composition and mass fraction (total 100 parts) of which are as follows: 10-15 parts of multifunctional acid; Hydrochloric acid (30wt%) 15-25 parts; 2-5 parts of polymaleic anhydride; Formic acid 2-5 parts; 3-6 parts of aminotrimethylphosphonic acid; The remaining part is water; The molecular structural formula of the aforementioned multifunctional acid is as follows: .

[0007] Another objective of this invention is to disclose a method for preparing the aforementioned composite acid, the specific steps of which are as follows: (1) Add 2-naphthylamine-1,5-disulfonic acid and water to the reactor, stir and heat to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add carbon disulfide and sodium hydroxide solution dropwise to the above reactor simultaneously, maintain pH 8-9 during the reaction process, and heat and reflux after the addition is complete; (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain a multifunctional acid; (4) Add the multifunctional acid, hydrochloric acid (30wt%), polymaleic anhydride, formic acid, aminotrimethylphosphonic acid and water to a container and stir until homogeneous to obtain the composite acid.

[0008] In this invention, preferably, the molar ratio of carbon disulfide to 2-naphthylamine-1,5-disulfonic acid is 0.4-0.6:1, more preferably 0.45-0.55:1.

[0009] Preferably, in step (1), the mass ratio of water to 2-naphthylamine-1,5-disulfonic acid is 6-10:1.

[0010] Preferably, in step (1), the heating temperature is 50-80℃.

[0011] Preferably, in step (2), the heating reflux time is 1-4 hours.

[0012] The reaction equation for the synthesis of the multifunctional acid of this invention is as follows: Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The composite acid for acidification of the present invention has multiple functions. Among them, the multifunctional acid: reduces the reaction rate of acid-rock and increases the effective action distance of active acid, which is the key to deep etching in acid fracturing technology; it inhibits corrosion and forms an adsorption film on the surface of metal pipes (tubing, casing), significantly reducing the corrosion rate of acid on steel; it aids in drainage, reduces the surface tension of the liquid, reduces capillary resistance, and promotes flowback. Hydrochloric acid: dissolves carbonate rock blockages and removes formation blockages near the bottom of the well. Polymaleic anhydride: inhibits scale formation, suppresses the formation of common inorganic scales such as calcium carbonate and calcium sulfate, and prevents these scales from blocking formation pores or tubing, thereby maintaining the smooth flow of wellbore and pipeline. Formic acid: assists the acid solution and can solve the equipment corrosion risk caused by strong acid operation at low temperatures. Aminotrimethylphosphonic acid: inhibits scale and corrosion, chelates metal ions (such as calcium, magnesium, etc.) in water, and prevents these ions from depositing on the equipment surface to form scale.

[0013] (2) The composite acid for acidification of the present invention can significantly extend the acidification time and dissolve deep rock layers; at the same time, the acidification speed can be adjusted by adjusting the composition of each component of the composite acid of the present invention to meet the needs of acidification of rock layers at different depths. Detailed Implementation

[0014] 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.

[0015] The technical solution of the present invention will be further described below with reference to specific embodiments: Example 1: Preparation of multifunctional acid D1 (1) Add 40 mmol of 2-naphthylamine-1,5-disulfonic acid and 73 g of water to the reactor, stir and heat to 80 °C to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add 16 mmol of carbon disulfide and sodium hydroxide solution to the reactor simultaneously, maintain pH 8-9 during the reaction, and heat under reflux for 1 hour after the addition is complete. (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain multifunctional acid D1.

[0016] Example 2: Preparation of multifunctional acid D2 (1) Add 40 mmol of 2-naphthylamine-1,5-disulfonic acid and 84 g of water to the reactor, stir and heat to 70 °C to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add 24 mmol of carbon disulfide and sodium hydroxide solution to the reactor simultaneously, maintain pH 8-9 during the reaction, and heat under reflux for 4 hours after the addition is complete. (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain multifunctional acid D2.

[0017] Example 3: Preparation of multifunctional acid D3 (1) Add 40 mmol of 2-naphthylamine-1,5-disulfonic acid and 93 g of water to the reactor, stir and heat to 60 °C to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add 18 mmol of carbon disulfide and sodium hydroxide solution to the reactor simultaneously, maintain pH 8-9 during the reaction, and heat under reflux for 2 hours after the addition is complete. (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain multifunctional acid D3.

[0018] Example 4: Preparation of multifunctional acid D4 (1) Add 40 mmol of 2-naphthylamine-1,5-disulfonic acid and 105 g of water to the reactor, stir and heat to 60 °C to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add 22 mmol of carbon disulfide and sodium hydroxide solution to the reactor simultaneously, maintain pH 8-9 during the reaction, and heat under reflux for 3 hours after the addition is complete. (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain multifunctional acid D4.

[0019] Example 5: Preparation of multifunctional acid D5 (1) Add 40 mmol of 2-naphthylamine-1,5-disulfonic acid and 121 g of water to the reactor, stir and heat to 50 °C to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add 20 mmol of carbon disulfide and sodium hydroxide solution to the reactor simultaneously, maintain pH 8-9 during the reaction, and heat under reflux for 3 hours after the addition is complete. (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain multifunctional acid D5.

[0020] Example 6: Preparation of composite acid Add 10g D1, 25g hydrochloric acid (30wt%), 2g polymaleic anhydride, 2g formic acid, 3g aminotrimethylphosphonic acid, and 58g water to a container and stir to dissolve to obtain a composite acid.

[0021] Example 7: Preparation of Composite Acid Add 12g D2, 20g hydrochloric acid (30wt%), 2g polymaleic anhydride, 3g formic acid, 3g aminotrimethylphosphonic acid, and 60g water to a container and stir to dissolve to obtain a composite acid.

[0022] Example 8: Preparation of composite acid Add 12g D3, 20g hydrochloric acid (30wt%), 3g polymaleic anhydride, 3g formic acid, 4g aminotrimethylphosphonic acid, and 58g water to a container and stir to dissolve to obtain a composite acid.

[0023] Example 9: Preparation of Composite Acid Add 14g D4, 15g hydrochloric acid (30wt%), 4g polymaleic anhydride, 4g formic acid, 5g aminotrimethylphosphonic acid, and 58g water to a container and stir to dissolve to obtain a composite acid.

[0024] Example 10: 15g D5, 15g hydrochloric acid (30wt%), 5g polymaleic anhydride, 5g formic acid, 6g aminotrimethylphosphonic acid, and 54g water were added to a container and stirred to dissolve, thus obtaining a composite acid.

[0025] Comparative Example 1 Same as Example 6, except that 10g of D1 is not added.

[0026] Comparative Example 2 Add 25g of hydrochloric acid and 58g of water to a container and stir to dissolve.

[0027] Example 11: Identical natural rock cores, cut from a fracturing block, were placed in the immersion test of Examples 6-10, Comparative Examples 1 and 2 to test the change in dissolution rate over time. The test results are shown in Table 1.

[0028] Table 1. Change in solubility over time (%)

[0029] As can be seen from Examples 6-10 and Comparative Example 1, the initial dissolution rate decreased significantly after the addition of the multifunctional acid, indicating that the multifunctional acid dissolves the rock core at a low rate. Therefore, the acidification time of this invention can be longer, enabling acidification and dissolution of deep rock strata. As can be seen from Examples 6-10, Comparative Example 1, and Comparative Example 2, components such as polymaleic anhydride, formic acid, and aminotrimethylphosphonic acid also play a significant role in reducing the acidification rate and extending the acidification time.

[0030] In summary, the composite acid for acidification of the present invention can significantly extend the acidification time and dissolve deep rock strata; at the same time, the acidification rate can be adjusted by changing the composition of each component of the composite acid to meet the acidification needs of rock strata at different depths. Therefore, it has broad market application prospects.

[0031] 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.

[0032] 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.

[0033] 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. A composite acid for acidification, characterized in that, The composition and mass fraction of the composite acid are as follows. 10-15 parts of multifunctional acid; Hydrochloric acid (30wt%) 15-25 parts; 2-5 parts of polymaleic anhydride; Formic acid 2-5 parts; 3-6 parts of aminotrimethylphosphonic acid; The remaining portion is water, totaling 100 portions; The molecular structural formula of the aforementioned multifunctional acid is as follows: 。 2. The method for preparing the composite acid for acidification according to claim 1, characterized in that, The specific steps of the preparation method are as follows: (1) Add 2-naphthylamine-1,5-disulfonic acid and water to the reactor, stir and heat to dissolve, and adjust the pH to 8-9 with sodium hydroxide solution; (2) Add carbon disulfide and sodium hydroxide solution dropwise to the above reactor simultaneously, maintain pH 8-9 during the reaction process, and heat and reflux after the addition is complete; (3) Cool the above mixture to below 5°C to precipitate crystals, centrifuge and dry to obtain a multifunctional acid; (4) Add the multifunctional acid, hydrochloric acid (30wt%), polymaleic anhydride, formic acid, aminotrimethylphosphonic acid and water to a container and stir until homogeneous to obtain the composite acid.

3. The preparation method according to claim 2, characterized in that, The molar ratio of carbon disulfide to 2-naphthylamine-1,5-disulfonic acid is 0.4-0.6:

1.

4. The preparation method according to claim 3, characterized in that, The molar ratio of carbon disulfide to p-2-naphthylamine-1,5-disulfonic acid is 0.45-0.55:

1.

5. The preparation method according to claim 2, characterized in that, In step (1), the mass ratio of water to 2-naphthylamine-1,5-disulfonic acid is 6-10:

1.

6. The preparation method according to claim 2, characterized in that, In step (1), the heating temperature is 50-80℃.

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

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