Blocking remover for dissolving trithiane blockages as well as preparation method and application of blocking remover

Abstract

The invention provides a blocking remover for dissolving trithiane blockages and a preparation method and application of the blocking remover, and belongs to the technical field of oilfield chemical blocking removal, the blocking remover is obtained by mixing the following raw materials: concentrated nitric acid, a sodium hypochlorite solution, a cleanup additive, a corrosion inhibitor and a clay stabilizer, the blocking remover has a good dissolving effect on trithiane of the blocking remover, the dissolution rate is high, and the blocking remover can be recycled. The blocking remover is low in corrosion rate, low in reservoir damage and low in secondary damage, can adapt to dissolution of special trithiane blockages existing in part of gas wells, provides a brand-new blocking remover for recovery of gas well productivity, and achieves the purposes of removing gas well blockage and recovering gas well productivity.

Description

Technical Field

[0001] The invention belongs to the technical field of oil field chemical plugging removal, and in particular belongs to a plugging remover for dissolving trithiane plugging material, and a preparation method and 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, which seriously affects the production of oil and gas wells. Through component analysis, some oil and gas fields have a relatively rare blockage of 1,3,5-trithiane. The molecular formula of trithiane is C3H6S3, and the structural formula is:

[0003]

[0004] Trithiane plugs are not native materials of the formation, with a molecular weight of 138.27 and a melting point of 215-220°C. They have low solubility in water and relatively low solubility in organic solvents. The formation mechanism of trithiane plugs is mainly due to the fact that some gas wells with high H2S content have a large amount of paraformaldehyde or formaldehyde in the well working fluid during reservoir reconstruction. Under certain conditions, trithiane plugs are easily generated. The formation of trithiane plugs blocks the oil and gas channels, causing great losses to the production of oil and gas fields, resulting in a sharp decrease in the production of single wells in gas fields. Conventional hydrochloric acid and soil acid plugging fluids cannot destroy the cyclic molecular structure of trithiane, so trithiane plugs in the wellbore cannot be removed. 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 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 the production capacity of gas wells, thereby achieving the purpose of removing gas well blockage and restoring gas well production capacity.

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

[0007] Furthermore, the raw materials include, 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.

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

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

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

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

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

[0013] Furthermore, in terms of weight, the added amounts of the raw materials are: 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 use of the above-mentioned unblocking agent for dissolving trithiane blockage or the unblocking agent prepared by the above-mentioned preparation method in unblocking trithiane blockage in oil field gas wells, wherein the dissolution rate of the unblocking agent is ≥95%, and the corrosion rate is less than ≤15g / (m 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 plugging remover 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 and interfacial tension of 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 the 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 corrosion inhibitors, drainage aids, clay stabilizers and the like as main auxiliary agents. The dissolution rate of trithiane blockages can reach more than 95%, and the use is safe, and the corrosion rate is 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, and 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 the plugging remover was dissolved. DETAILED DESCRIPTION

[0023] The present invention is further described in detail below in conjunction with specific embodiments. The embodiments 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 plugging. The raw materials include, 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.

[0025] The method for preparing the above-mentioned blocking remover for dissolving trithiane blockage comprises the following steps:

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

[0027] 2) According to the weight proportions, 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 plugging.

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

[0029] Furthermore, the mass percentage 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] Embodiment 1:

[0034] 80 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 3 parts of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 5 parts of a corrosion inhibitor (Mannich bases) 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 blockages.

[0035] Embodiment 2:

[0036] 90 parts of concentrated nitric acid (68% by mass) and 5 parts of sodium hypochlorite solution (12% by mass) are mixed uniformly to obtain 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 for dissolving trithiane blockage.

[0037] Embodiment 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 blockages.

[0039] Embodiment 4:

[0040] 85 parts of concentrated nitric acid (mass percentage concentration 68%) and 5 parts of sodium hypochlorite solution (mass percentage concentration 12%) 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 bases) 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 blockages.

[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 uniformly to obtain a mixed solution, and then 2 parts of a drainage aid (fatty alcohol polyoxyethylene ether sulfonate), 4 parts of a corrosion inhibitor (Mannich bases) and 1.5 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 for dissolving trithiane blockage.

[0043] The performance evaluation of the trithiane blockage remover is mainly to determine the dissolution rate of the trithiane blockage, and the dissolution rate is determined by the weight loss method. The steps are as follows:

[0044] (1) drying the trithiane plugging material in an oven at 102°C, and drying the filter paper in an oven at 102°C, and weighing them as 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 plugging remover under experimental conditions (certain temperature, plugging remover 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, put the filter paper into a 102°C oven and dry it to 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 dissolution rate for trithiane. The dissolution rate of trithiane is shown in Table 1:

[0050] Table 1 Dissolution rate of blockage by trithiane blockage remover

[0051]

[0052] It can be seen from Table 1 that the examples all have good dissolution efficiency for trithiane blockages, and the average dissolution rate is above 95%.

[0053] The trithiane blockage remover prepared by the present invention utilizes concentrated nitric acid (mass percentage concentration 68%) and sodium hypochlorite solution with very strong oxidizing ability to oxidize and degrade trithiane and then dissolve it. In order to make the blockage remover system have better applicability on site and realize on-site application, the introduced drainage aid is fatty alcohol polyoxyethylene ether sulfonate, which has good ability to reduce the surface and interfacial tension of residual liquid and is conducive to backflow; the introduced corrosion inhibitor stomach Mannich base corrosion inhibitor has excellent corrosion inhibition effect and can prevent the blockage remover system from corroding the oil pipe during the injection process; the introduced clay stabilizer is 2-chloroethyltrimethylammonium chloride organic small cation, which has good 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 high dissolution rate of trithiane blockages in gas wells, low corrosion rate, low damage to reservoirs, and low secondary damage, thereby achieving the effect of restoring production capacity. It provides a brand-new method for unblocking trithiane blockages in oil field gas wells and restoring production capacity; it solves the problem that trithiane blockages in some oil and gas fields block reservoirs and lead to 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 production capacity restoration. It provides a brand-new method for unblocking trithiane blockages in oil field gas wells and restoring production capacity.

[0055] After the trithiane blockage was oxidized by the unblocking agent, the structure of the ablation product was analyzed by nuclear magnetic resonance hydrogen spectrum (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 peak of the H NMR spectrum of the 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 soluble mixture after dissolution. The blockage remover has an excellent effect in dissolving trithiane.

[0057] In order to make the plugging remover more applicable on site, it can be applied on site, drainage aid, corrosion inhibitor, clay stabilizer and other additives, and the evaluation results of other properties of the plugging remover are shown in Table 2.

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

[0059]

[0060] It can be seen from Table 2 that the blockage remover prepared by the present invention for dissolving trithiane blockage is mainly composed of strong oxidants 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 blockage remover 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 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 production capacity.

Claims

1. A plugging remover for dissolving trithiane plugging, characterized in that: The method is obtained by mixing the following raw materials, wherein the raw materials include concentrated nitric acid, sodium hypochlorite solution, a drainage aid, a corrosion inhibitor and a clay stabilizer.

2. A plugging remover for dissolving trithiane plugging according to claim 1, characterized in that: Calculated by weight, the raw materials include: 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.

3. A plugging remover for dissolving trithiane plugging according to claim 1 or 2, characterized in that: The mass percentage concentration of concentrated nitric acid is 68%.

4. A plugging remover for dissolving trithiane plugging according to claim 1 or 2, characterized in that: The mass percentage concentration of sodium hypochlorite solution is 12%.

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

6. The method for preparing a blocking remover for dissolving trithiane blockage according to claim 5, characterized in that: Calculated by weight, the added amounts of raw materials are: 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.

7. The method for preparing a blocking remover for dissolving trithiane blockage according to claim 5, characterized in that: The drainage aid is fatty alcohol polyoxyethylene ether sulfonate.

8. The method for preparing a blocking remover for dissolving trithiane blockage according to claim 5, characterized in that: The corrosion inhibitor is a Mannich base corrosion inhibitor.

9. The method for preparing a blocking remover for dissolving trithiane blockage according to claim 5, characterized in that: The clay stabilizer is 2-chloroethyltrimethylammonium chloride.

10. Use of the blocking remover for dissolving trithiane blockages according to claim 1 or the blocking remover prepared by the preparation method according to claims 5 to 9 in unblocking trithiane blockages 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.

Images