Non-oxidized weakly acidic polyacrylamide degradation agent and preparation and use methods thereof

Abstract

The invention discloses a non-oxidized weakly acidic polyacrylamide degradation agent as well as a preparation method and a use method thereof. The degradation agent comprises the following components: a reducing agent, a regulator, a mutual solvent and water, the reducing agent is one of 3-O-ethyl ascorbic acid ether and L-ascorbic acid-2, 6-dibutyrate; the conditioning agent is ammonium chloride; the mutual solvent is one of ethylene glycol monobutyl ether and isopropanol; the problems that an isolation slug is needed in the oxidation-reduction reaction of an existing degradation agent or the oxidation-reduction reaction of the existing degradation agent and subsequently injected mud acid, or secondary precipitation is produced due to the fact that the existing degradation agent contains metal ions such as Na < + >, K < + > and Fe < 2 + > and the subsequently injected mud acid are effectively solved.

Description

Technical Field

[0001] The present invention relates to the technical field of oil production engineering, and to a non-oxidative weakly acidic degradation agent for removing polyacrylamide blockage and a preparation method thereof. Background Art

[0002] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0003] With the continuous development of oil fields, some oil fields have gradually entered the high water content development stage, with a water content of more than 90%. For this reason, tertiary oil recovery technologies such as polymer flooding and ASP flooding have been applied on site, and the recovery rate of oil fields has been greatly improved compared with water flooding. However, since the displacement media of polymer flooding and ASP flooding and the reinjected chemical flooding wastewater contain polyacrylamide, the reservoir pores become smaller due to the adsorption and retention of polyacrylamide. At the same time, the viscous polyacrylamide solution will also carry inorganic particles to migrate and block the pores between mineral particles. Under the joint action of polyacrylamide and inorganic particles, the reservoir permeability is greatly reduced and the injection capacity is reduced.

[0004] For the injection wells whose injection capacity decreased due to the above reasons, chemical unblocking measures were adopted on site to remove the blockage caused by polyacrylamide and inorganic particles, which achieved good results, but there were the following problems:

[0005] First, most of the conventional degradation agents used to remove polyacrylamide blockages are oxidants, which will undergo redox reactions with the subsequently injected acid system such as soil acid used to remove inorganic blockages. For example, the oxidant ammonium persulfate will react with the hydrochloric acid in the soil acid system, resulting in a significant decrease in the degradation performance of polyacrylamide. At the same time, the reaction in the confined space of the wellbore produces a large amount of gas, which poses a safety hazard. Therefore, they need to be injected separately on site, and an isolation plug is injected in the middle to avoid contact between the oxidant and the soil acid system, resulting in complicated construction procedures and a long construction period.

[0006] Second, some polyacrylamide degradation agents contain Na + , K + , Fe 2+ Metal ions such as Na and N have good degradation performance on polyacrylamide, but the introduction of a large amount of Na + , K + , Fe 2+ The metal ions will react with the residual mud acid solution injected later after removing the inorganic blockage to generate secondary precipitation of sodium fluorosilicate and potassium fluorosilicate. At the same time, as the pH value of the formation fluid gradually increases during the subsequent water injection process, Fe 2+ Precipitation will also be generated, affecting the effectiveness of the measures. The soil acid after removing the inorganic blockage can be replaced with an acid system such as an organic acid on site to avoid the formation of secondary precipitation, but the cost of the agent will increase.

[0007] It should be noted that the information disclosed in the above background technology section is only used to enhance the understanding of the background of the present disclosure, and therefore may contain information that does not constitute prior art. Summary of the invention

[0008] In view of this, the present invention provides a non-oxidizing weakly acidic polyacrylamide degradation agent, which solves the problem that the existing degradation agent may undergo redox reaction with the subsequently injected soil acid and require an isolation slug, or may contain Na + , K + , Fe 2+ The problem of secondary precipitation produced by metal ions and subsequent injected soil acid.

[0009] In addition, the present disclosure also provides a preparation method and a use method of the degradation agent.

[0010] In a first aspect, the non-oxidative weakly acidic polyacrylamide degradation agent comprises:

[0011] Reducing agent, regulating agent, mutual solvent and water;

[0012] The reducing agent is one of 3-O-ethyl ascorbic acid ether and L-ascorbic acid-2,6-dibutyrate.

[0013] In the present disclosure and possible embodiments, the regulator is ammonium chloride.

[0014] In the present disclosure and possible embodiments, the mutual solvent is one of ethylene glycol monobutyl ether and isopropyl alcohol.

[0015] In the present disclosure and possible embodiments, the amounts of the components are as follows, calculated by mass percentage:

[0016] Reducing agent 0.5-1.0%, regulating agent 1.0-3.0%, mutual solvent 0.1-0.3%, and the balance is water.

[0017] In a second aspect, a method for preparing the non-oxidative degradation agent described in the first aspect comprises:

[0018] The mutual solvent, reducing agent and regulating agent are added into the water in proportion and mixed evenly.

[0019] In a second aspect, a method for using the non-oxidative degradation agent described in the first aspect comprises:

[0020] The non-oxidative degradation agent is prepared into a solution with a mass concentration of 1% and injected into the well to be unblocked, followed by the injection of acid solution.

[0021] The present disclosure has the following beneficial effects:

[0022] The non-oxidizing weakly acidic polyacrylamide degradation agent disclosed in the present invention has good compatibility with acidic liquid systems such as mud acid, and does not react after mixing. The non-oxidizing weakly acidic degradation agent for removing polyacrylamide blockage and the acidic liquid system such as mud acid for removing inorganic blockage can be continuously injected on site, without the need for isolation of clear water slugs, thereby simplifying the construction process and shortening the construction period. In addition, the degradation agent will not react with the mud acid residual liquid after removing the inorganic blockage to generate secondary precipitation, and will not cause secondary damage to the reservoir, further ensuring the effect of the blockage removal measures; effectively solving the problem that the existing degradation agent may undergo redox reaction with the subsequently injected mud acid and need to isolate the slug, or because it contains Na + , K + , Fe 2+ The problem of secondary precipitation produced by metal ions and subsequent injected soil acid. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of the present disclosure will become more apparent through the following description of the embodiments of the present disclosure with reference to the accompanying drawings, in which:

[0024] Figure 1 This is the viscosity change curve of the polyacrylamide solution after the reaction with the degradation agent at 45°C in the embodiment of the present disclosure. DETAILED DESCRIPTION

[0025] The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the detailed description of the present disclosure below, some specific details are described in detail. However, for the parts that are not described in detail, those skilled in the art can also fully understand the present disclosure.

[0026] In addition, those skilled in the art should understand that the drawings are provided only to illustrate the purpose, features and advantages of the present disclosure, and the drawings are not actually drawn to scale. At the same time, unless the context clearly requires, the words "include", "comprise" and the like in the entire specification and claims should be interpreted as inclusive rather than exclusive or exhaustive; that is, "including but not limited to" meaning.

[0027] Embodiment 1:

[0028] Weigh 3.0 g of 3-O-ethyl ascorbic acid ether, 7.5 g of ammonium chloride, 1.0 g of ethylene glycol monobutyl ether, and 488.5 g of water, mix the above components evenly, and prepare degradation agent I.

[0029] Embodiment 2:

[0030] Weigh 3.0 g of L-ascorbic acid-2,6-dibutyrate, 7.5 g of ammonium chloride, 1.0 g of ethylene glycol monobutyl ether, and 488.5 g of water, mix the above components evenly, and prepare degradation agent II.

[0031] Embodiment 3:

[0032] Weigh 3.0 g of 3-O-ethyl ascorbic acid ether, 7.5 g of ammonium chloride, 1.0 g of isopropanol, and 488.5 g of water, mix the above components evenly, and prepare degradation agent III.

[0033] Embodiment 4:

[0034] Weigh 3.0 g of L-ascorbic acid-2,6-dibutyrate, 7.5 g of ammonium chloride, 1.0 g of isopropanol, and 488.5 g of water, mix the above components evenly, and prepare degradation agent IV.

[0035] Embodiment 5:

[0036] Weigh 5.0 g of 3-O-ethyl ascorbic acid ether, 10 g of ammonium chloride, 1.5 g of ethylene glycol monobutyl ether, and 483.5 g of water, mix the above components evenly, and prepare degradation agent V.

[0037] Embodiment 6:

[0038] Weigh 4.0 g of L-ascorbic acid-2,6-dibutyrate, 8 g of ammonium chloride, 1.2 g of ethylene glycol monobutyl ether, and 486.8 g of water, mix the above components evenly, and prepare degradation agent VI.

[0039] The performance evaluation of the degradation agents I-IV prepared in each embodiment of the present disclosure and the oxidative degradation agent (5% ammonium persulfate, 10% hydrogen peroxide) commonly used in the art was carried out, as follows:

[0040] 1. Compatibility evaluation:

[0041] Weigh 100 ml each of degradation agent I, degradation agent II, degradation agent III, degradation agent IV, 5% ammonium persulfate, and 10% hydrogen peroxide, add them to 100 ml of conventional earth acid (i.e., a mixed acid of hydrochloric acid and hydrofluoric acid in a ratio of 12:3) solution, mix them evenly, observe whether the solution has gas, flocculation, and precipitation, and after placing it at 45°C for 24 hours, observe whether the solution has gas, flocculation, and precipitation; the specific evaluation results are shown in Table 1:

[0042] Table 1 Compatibility evaluation results

[0043]

[0044] As can be seen from Table 1, degraders I, II, III and IV have good compatibility with mud acid, and no gas, flocculation or precipitation is generated after mixing. However, ammonium persulfate and hydrogen peroxide solution have poor compatibility with mud acid, and a large amount of gas is generated after mixing, which cannot meet the requirements of on-site application.

[0045] 2. Evaluation of degradation performance:

[0046] Polyacrylamide with a molecular weight of 16-19 million was prepared into a solution with a mass fraction of 300 mg / L and placed at room temperature for 24 hours; 10 ml of degradation agent I, degradation agent II, degradation agent III and degradation agent IV were weighed and added to 100 ml of polyacrylamide solution respectively, mixed evenly and placed in a 45°C water bath, and the solution viscosity was tested every 30 minutes; the specific evaluation results are shown in Table 2 and Figure 1 :

[0047] Table 2 Evaluation results of degradation performance of degradation agents Ⅰ-Ⅳ

[0048]

[0049] It can be seen from Table 2 that after 120 minutes of reaction between degradation agents Ⅰ, Ⅱ, Ⅲ and Ⅳ and polyacrylamide solution, its viscosity can be reduced to below 3 MPa.s. The viscosity of the degraded polyacrylamide solution is close to that of water, which can relieve its blockage to the reservoir.

[0050] from Figure 1 It can be seen that the four non-oxidative weakly acidic polyacrylamide degradation agents in the examples have a good effect of degrading polymers and a fast degradation rate.

[0051] 3. Corrosion performance evaluation:

[0052] The treated N80 test piece was suspended in the solutions of degradation agent I, degradation agent II, degradation agent III and degradation agent IV, sealed and placed in a 45°C water bath, taken out after 4 hours, and its corrosion rate was measured; the specific evaluation results are shown in Table 3:

[0053] Table 3 Evaluation results of corrosion performance of degradation agents Ⅰ-Ⅳ

[0054]

[0055] It can be seen from Table 3 that the corrosion rates of degradation agents Ⅰ, Ⅱ, Ⅲ and Ⅳ on N80 specimens are all within 1 g / m 2 h or less, meeting the requirements of field application.

[0056] 4. Evaluation of natural core plugging removal performance:

[0057] First, core displacement was carried out using polymer-containing wastewater containing polyacrylamide, suspended solids and other blockages, and then the blocked cores were unblocked using degradation agents I-IV and soil acid, and the permeability of the cores after sewage displacement, degradation agent displacement and soil acid displacement was measured respectively; the specific evaluation results are shown in Table 4:

[0058] Table 4 Evaluation results of core plugging removal performance of degradation agents Ⅰ-Ⅳ

[0059]

[0060] As can be seen from Table 4, degradation agents I, II, III and IV have obvious effects on declogging the core after sewage blockage, and the permeability improvement rate is all above 100%; the subsequent injection of mud acid can further declogging the core after sewage blockage, and the core permeability is increased by more than 75% again; the degradation agent has a better effect when used in combination with mud acid solution, which can restore the permeability of the core after polymer-containing sewage blockage to more than 130% of the initial permeability.

[0061] Through the above examples and evaluation test results, the degradation agent of the present invention has the following advantages compared with conventional oxidative degradation agents:

[0062] ① Using the reducing agent 3-O-ethyl ascorbic acid ether or L-ascorbic acid-2,6-dibutyrate to degrade polyacrylamide, the viscosity of the polyacrylamide solution with a molecular weight of 16 million to 19 million and a mass fraction of 300 mg / L can be quickly degraded to below 3 mpa.s within 2 hours;

[0063] ② Both 3-O-ethyl ascorbic acid ether and L-ascorbic acid-2,6-dibutyrate are non-oxidizing agents, and their aqueous solutions are weakly acidic. They are compatible with soil acid and other acid systems, and do not react after mixing. Non-oxidizing weakly acidic degradation agents for removing polyacrylamide blockages and soil acid and other acid systems for removing inorganic blockages can be continuously injected on site. There is no need for water plugs for isolation, and there will be no problems of agent failure and ineffective measures. At the same time, the construction process can be simplified and the construction period can be shortened;

[0064] ③ Use regulators to replace free Na in reservoir minerals + , K + Metal ions such as Na + , K + The metal ions are driven to the deep oil layer to prevent the secondary precipitation caused by the subsequent mud acid residual liquid, thus ensuring the effectiveness of the plugging removal measures;

[0065] ④The degradation agent itself does not contain Na + , K + , Fe 2+ Metal ions such as ions will not react with the residual mud acid after the inorganic blockage is removed to generate secondary precipitation, and will not cause secondary damage to the reservoir, further ensuring the effectiveness of the blockage removal measures.

[0066] The above-described embodiments are only embodiments of the present disclosure, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the present disclosure. It should be noted that, for a person of ordinary skill in the art, without departing from the concept of the present disclosure, several variations, equivalent substitutions, improvements, etc. may be made, all of which fall within the scope of protection of the present disclosure. Therefore, the scope of protection of the present disclosure shall be subject to the attached claims.

Claims

1. A non-oxidative weakly acidic polyacrylamide degradation agent, characterized in that: include: Reducing agent, regulating agent, mutual solvent and water; The reducing agent is one of 3-O-ethyl ascorbic acid ether and L-ascorbic acid-2,6-dibutyrate.

2. The non-oxidative weakly acidic polyacrylamide degradation agent according to claim 1, characterized in that: The regulator is ammonium chloride.

3. The non-oxidative weakly acidic polyacrylamide degradation agent according to claim 2, characterized in that: The mutual solvent is one of ethylene glycol monobutyl ether and isopropanol.

4. The non-oxidative weakly acidic polyacrylamide degradation agent according to claim 3, characterized in that: In terms of mass percentage, the amounts of each component are: Reducing agent 0.5~1.0%, regulating agent 1.0~3.0%, mutual solvent 0.1~0.3%, and the balance is water.

5. The method for preparing the non-oxidative degradation agent according to any one of claims 1 to 4, characterized in that: include: The mutual solvent, reducing agent and regulating agent are added into the water in proportion and mixed evenly.

6. The method for using the non-oxidative degradation agent according to any one of claims 1 to 4, characterized in that: include: The non-oxidizing degradation agent is prepared into a solution with a mass concentration of 1% and injected into the well to be unblocked, and then the acid solution is injected.

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