A plug remover for dissolving trithiane plug and its preparation method and application

Abstract

The application provides a kind of dissolving trithiane plug and its preparation method and application, belong to oil field chemical plugging removal technical field, the following raw materials are mixed to obtain, the raw materials include: concentrated nitric acid, sodium hypochlorite solution, cleanup agent, corrosion inhibitor and clay stabilizer, the dissolution effect of the plugging removal agent trithiane is good, the corrosion rate is high, and the plugging removal agent corrosion rate is small, the reservoir damage is low, the secondary damage is low, can be adapted to the dissolution of some gas well special trithiane plug, provides a kind of new plugging removal agent for restoring gas well productivity, achieves the purpose of removing gas well plugging and restoring gas well productivity.

Description

Technical Field

[0001] The invention belongs to the technical field of oil field chemical blockage removal, and in particular relates to a blockage remover for dissolving trithiane blockages, a preparation method and an application thereof. Background Art

[0002] During the production process of oil and gas fields, high-temperature and high-pressure oil and gas wells often produce sludge-like blockages in the wellbore, seriously affecting the oil and gas well production. Through component analysis, some oil and gas fields have found that the relatively rare blockage is 1,3,5-trithiane. The molecular formula of trithiane is C3H6S3, and the structural formula is:

[0003]

[0004] Trithiane plugs are not native to the formation. They have a molecular weight of 138.27, a melting point of 215-220°C, and low solubility in water and organic solvents. The formation mechanism of trithiane plugs is primarily due to the presence of large amounts of paraformaldehyde or formaldehyde in the wellbore fluid used in reservoir stimulation in some gas wells with high H2S content. Under certain conditions, trithiane plugs are easily formed. The formation of trithiane plugs blocks oil and gas pathways, causing significant losses to oil and gas field production and leading to a sharp drop in single-well production. Conventional hydrochloric acid and earth acid declogging fluids are unable to destroy the trithiane cyclic molecular structure, making it impossible to remove trithiane plugs from the wellbore. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a plugging remover for dissolving trithiane blockages, a preparation method thereof, and an application thereof. The plugging remover has a good dissolving effect on trithiane, a high dissolution rate, a low corrosion rate, low damage to the reservoir, and low secondary damage. The plugging remover can be adapted to the dissolution of special trithiane blockages in some gas wells, and provides a new plugging remover for restoring gas well productivity, thereby achieving the purpose of removing gas well blockage and restoring gas well productivity.

[0006] To achieve the above object, the present invention provides the following technical solution: a plugging remover for dissolving trithiane blockage, which is obtained by mixing the following raw materials: concentrated nitric acid, sodium hypochlorite solution, a drainage aid, a corrosion inhibitor and a clay stabilizer.

[0007] Furthermore, the raw materials include, by weight, 80 to 90 parts of concentrated nitric acid, 5 to 10 parts of sodium hypochlorite solution, 1 to 3 parts of drainage aid, 3 to 5 parts of corrosion inhibitor, and 1 to 2 parts of clay stabilizer.

[0008] Furthermore, the mass percentage concentration of concentrated nitric acid is 68%.

[0009] Furthermore, the mass percent concentration of the sodium hypochlorite solution is 12%.

[0010] Furthermore, the present invention also provides a method for preparing a blocking agent for dissolving trithiane blockage, the specific steps of which are as follows:

[0011] S1: Mixing concentrated nitric acid and sodium hypochlorite solution uniformly to prepare a mixed solution;

[0012] S2: adding a drainage aid, a corrosion inhibitor, and a clay stabilizer to the mixed solution and mixing them evenly to obtain a plugging remover that dissolves trithiane plugging.

[0013] Furthermore, the addition amount of the raw materials is, by weight, 80-90 parts of concentrated nitric acid, 5-10 parts of sodium hypochlorite solution, 1-3 parts of drainage aid, 3-5 parts of corrosion inhibitor, and 1-2 parts of clay stabilizer.

[0014] Furthermore, the drainage aid is fatty alcohol polyoxyethylene ether sulfonate.

[0015] Furthermore, the corrosion inhibitor is a Mannich base corrosion inhibitor.

[0016] Furthermore, the clay stabilizer is 2-chloroethyltrimethylammonium chloride.

[0017] The present invention also provides a method for dissolving trithiane blockages or a method for dissolving trithiane blockages in oil and gas wells. The method comprises the following steps: 2 .h), anti-swelling rate ≥85%, surface tension ≤30mN / m.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] The invention provides a plugging remover for dissolving trithiane blockages. The invention adopts concentrated nitric acid and sodium hypochlorite solution as main raw materials, utilizes the very strong oxidizing ability of the two to oxidize and degrade trithiane and then dissolve it. Furthermore, in order to make the plugging remover have better applicability on site and realize on-site application, a drainage aid, a corrosion inhibitor and a clay stabilizer are introduced. The drainage aid has a good ability to reduce the surface tension of the residual liquid, which is beneficial to flowback; the corrosion inhibitor can prevent the plugging remover from corroding the oil pipe during the injection process; the clay stabilizer can prevent secondary damage to the reservoir during the injection of the plugging remover, and has a good reservoir protection function. The plugging remover of the invention mainly uses concentrated nitric acid and sodium hypochlorite as strong oxidants, and uses the corrosion inhibitor, the drainage aid, the clay stabilizer and the like as main auxiliary agents. The dissolution rate of trithiane blockages can reach more than 95%, and the invention is safe to use, with a corrosion rate of less than or equal to 15g / (m 2 .h), low core damage rate to reservoir, anti-swelling rate ≥85%, good flowback performance, surface tension ≤30mN / m, with good effect of relieving gas well blockage and restoring gas well productivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 Comparative Example for the dissolution of trithiane blockage.

[0021] Figure 2 Original H NMR spectrum of the blockage.

[0022] Figure 3 H NMR spectrum after dissolution of the plugging remover. DETAILED DESCRIPTION

[0023] The present invention will be further described in detail below with reference to specific examples. The examples are only used to illustrate the present invention and are not intended to limit the scope of protection of the present invention.

[0024] The invention provides a plugging remover for dissolving trithiane blockages. The raw materials include, by weight, 80-90 parts of concentrated nitric acid, 5-10 parts of sodium hypochlorite solution, 1-3 parts of a drainage aid, 3-5 parts of a corrosion inhibitor, and 1-2 parts of a clay stabilizer.

[0025] The preparation method of the above-mentioned blocking agent for dissolving trithiane blockage comprises the following steps:

[0026] 1) Mix 80-90 parts by weight of concentrated nitric acid and 5-10 parts of sodium hypochlorite solution to obtain a mixed solution;

[0027] 2) According to parts by weight, 1 to 3 parts of drainage aid, 3 to 5 parts of corrosion inhibitor, and 1 to 2 parts of clay stabilizer are added to the mixed solution in proportion, and stirred and mixed evenly to obtain a plugging remover for dissolving trithiane blockage.

[0028] Furthermore, the mass percentage concentration of concentrated nitric acid is 68%.

[0029] Furthermore, the mass percent concentration of the sodium hypochlorite solution is 12%.

[0030] Furthermore, the drainage aid is fatty alcohol polyoxyethylene ether sulfonate.

[0031] Furthermore, the corrosion inhibitor is a Mannich base corrosion inhibitor.

[0032] Furthermore, the clay stabilizer is 2-chloroethyltrimethylammonium chloride.

[0033] Example 1:

[0034] 80 parts of concentrated nitric acid (68% by mass) and 10 parts of sodium hypochlorite solution (12% by mass) are mixed evenly to prepare a mixed solution, and then 3 parts of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 5 parts of a corrosion inhibitor (Mannich base), and 2 parts of a clay stabilizer (2-chloroethyltrimethylammonium chloride) are added to the mixed solution in proportion, and the mixture is stirred and mixed evenly to obtain a plugging remover that dissolves trithiane blockage.

[0035] Example 2:

[0036] 90 parts of concentrated nitric acid (68% by mass) and 5 parts of sodium hypochlorite solution (12% by mass) are mixed evenly to prepare a mixed solution, and then 1 part of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 3 parts of a corrosion inhibitor (Mannich base), and 1 part of a clay stabilizer (2-chloroethyltrimethylammonium chloride) are added to the mixed solution in proportion, and the mixture is stirred and mixed evenly to obtain a plugging remover that dissolves trithiane blockage.

[0037] Example 3:

[0038] 85 parts of concentrated nitric acid (68% by mass) and 10 parts of sodium hypochlorite solution (12% by mass) are mixed uniformly to prepare a mixed solution, and then 1 part of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 3 parts of a corrosion inhibitor (Mannich base), and 1 part of a clay stabilizer (2-chloroethyltrimethylammonium chloride) are added to the mixed solution in proportion, and the mixture is stirred and mixed uniformly to obtain a plugging remover that dissolves trithiane blockage.

[0039] Example 4:

[0040] 85 parts of concentrated nitric acid (68% by mass) and 5 parts of sodium hypochlorite solution (12% by mass) are mixed uniformly to prepare a mixed solution, and then 3 parts of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 5 parts of a corrosion inhibitor (Mannich base) and 2 parts of a clay stabilizer (2-chloroethyltrimethylammonium chloride) are added to the mixed solution in proportion, and the mixture is stirred and mixed uniformly to obtain a plugging remover that dissolves trithiane blockage.

[0041] Example 5

[0042] 88 parts of concentrated nitric acid (68% by mass) and 7 parts of sodium hypochlorite solution (12% by mass) are mixed evenly to prepare a mixed solution, and then 2 parts of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 4 parts of a corrosion inhibitor (Mannich base) and 1.5 parts of a clay stabilizer (2-chloroethyltrimethylammonium chloride) are added to the mixed solution in proportion and stirred to mix evenly to obtain a plugging remover that dissolves trithiane blockage.

[0043] The performance evaluation of the trithiane blockage remover is mainly carried out by measuring the dissolution rate of the trithiane blockage. The dissolution rate is determined by the weight loss method. The steps are as follows:

[0044] (1) Dry the trithiane plug in an oven at 102°C, and dry the filter paper in an oven at 102°C, weighing M1;

[0045] (2) Use an electronic balance to accurately weigh a certain mass of trithiane powder M, put it into a wide-mouth bottle containing a certain amount of blocking agent under experimental conditions (certain temperature, blocking agent concentration, reaction time), and keep it at a constant temperature for a certain period of time;

[0046] (3) Filter the liquid in the wide-mouth bottle with dried and weighed filter paper. After filtration, place the filter paper in a 102°C oven and dry it to a constant weight. Weigh it as M2 and calculate the scale dissolution rate.

[0047] (4) Dissolution rate calculation formula:

[0048] The above experimental conditions are as follows: temperature of 50°C, concentration of unblocking agent of 20%, and reaction time of 4h.

[0049] The trithiane blockage remover prepared by the present invention has a good solubility rate for trithiane. The solubility rate of trithiane is shown in Table 1:

[0050] Table 1 Dissolution rate of blockage by trithiane as a blocking agent

[0051]

[0052] As can be seen from Table 1, the examples all have good dissolution efficiency for trithiane blockages, with an average dissolution rate of more than 95%.

[0053] The trithiane blockage remover prepared by the present invention utilizes the very strong oxidizing power of concentrated nitric acid (68% by mass) and sodium hypochlorite solution to oxidatively degrade trithiane and dissolve it. To ensure better applicability of the blockage remover system in the field, a drainage aid of fatty alcohol polyoxyethylene ether sulfonate is introduced, which has excellent ability to reduce the surface tension of the residual liquid, facilitating flowback. A Mannich base corrosion inhibitor is introduced, which has excellent corrosion inhibition effect and can prevent corrosion of the oil pipe during the injection process of the blockage remover system. The clay stabilizer introduced is 2-chloroethyltrimethylammonium chloride, an organic small cation, which has excellent clay stabilization function, prevents secondary damage to the reservoir during the injection of the blockage remover, and has good reservoir protection function.

[0054] The unblocking agent for dissolving trithiane blockages of the present invention has the advantages of a high dissolution rate of trithiane blockages in gas wells, a low corrosion rate, low damage to the reservoir, and low secondary damage, thereby achieving the effect of restoring production capacity. A new method is provided for unblocking trithiane blockages in oilfield gas wells and restoring production capacity; it solves the problem of trithiane blockages in some oil and gas fields clogging the reservoir and causing reduced gas well production. After a large number of experiments and studies, the unblocking agent for dissolving trithiane blockages prepared by the present invention has a good effect of removing gas well blockages and achieving the effect of restoring production capacity. A new method is provided for unblocking trithiane blockages in oilfield gas wells and restoring production capacity.

[0055] After the trithiane blockage was oxidized by the deblocking agent, the structure of the ablation product was analyzed by nuclear magnetic resonance spectroscopy (deuterated DMSO) and compared with the original spectrum of trithiane. The experimental results are as follows: Figure 2 、 3 Show.

[0056] Depend on Figure 2 It can be seen that the H NMR spectrum peak of trithiane blockage is located at 4.70. Figure 3 It can be seen that after dissolution, the ablation product has no spectral peak at the displacement of 4.70, and becomes a complex mixture of other soluble substances. The blocking agent has an excellent effect in dissolving trithiane.

[0057] In order to make the plugging agent more applicable on site, it can be used on site, and auxiliary agents such as drainage aid, corrosion inhibitor, clay stabilizer, etc. The evaluation results of other properties of the plugging agent are shown in Table 2.

[0058] Table 2 Comprehensive performance test of trithiane plugging remover

[0059]

[0060] As can be seen from Table 2, the anti-blocking agent prepared by the present invention for dissolving trithiane blockage is mainly composed of strong oxidizing agents concentrated nitric acid and sodium hypochlorite, and corrosion inhibitors, drainage agents, clay stabilizers, etc. are used as main auxiliary agents. The dissolution rate of trithiane blockage is high, and the dissolution rate of the anti-blocking agent of the present invention is ≥95%. According to SYT5405-2019 "Test Method and Evaluation Index of Corrosion Inhibitor Performance for Acidification", the corrosion rate is less than ≤15g / (m 2 .h), safe to use, low damage rate to reservoir core; anti-swelling rate ≥85%, good flowback performance; surface tension ≤30mN / m, with good effect of relieving gas well blockage and restoring production capacity.

Claims

1. A plugging remover for dissolving trithiane blockage, characterized in that: The following raw materials are mixed to obtain a soil slurry, wherein the raw materials include: concentrated nitric acid, sodium hypochlorite solution, a drainage aid, a corrosion inhibitor, and a clay stabilizer; in parts by weight, the raw materials include: 80-90 parts of concentrated nitric acid, 5-10 parts of sodium hypochlorite solution, 1-3 parts of the drainage aid, 3-5 parts of the corrosion inhibitor, and 1-2 parts of the clay stabilizer; The drainage agent is fatty alcohol polyoxyethylene ether sulfonate; The corrosion inhibitor is a Mannich base corrosion inhibitor; The clay stabilizer is 2-chloroethyltrimethylammonium chloride.

2. A blocking agent for dissolving trithiane blockage according to claim 1, characterized in that: The mass percentage concentration of concentrated nitric acid is 68%.

3. The blocking agent for dissolving trithiane blockage according to claim 1, characterized in that: The mass percentage concentration of sodium hypochlorite solution is 12%.

4. The method for preparing a blocking agent for dissolving trithiane blockage according to claim 1, characterized in that: The specific steps are as follows: S1: Mixing concentrated nitric acid and sodium hypochlorite solution uniformly to prepare a mixed solution; S2: adding a drainage aid, a corrosion inhibitor, and a clay stabilizer to the mixed solution and mixing them evenly to obtain a plugging remover that dissolves trithiane plugging.

5. Use of the blocking remover for dissolving trithiane blockage according to claim 1 or the blocking remover prepared by the preparation method according to claim 4 in unblocking trithiane blockage in oil and gas wells, characterized in that: The dissolution rate of the blocking agent is ≥95%, and the corrosion rate is less than ≤15g / (m 2 .h), anti-swelling rate ≥85%, surface tension ≤30mN / m.

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