Non-acid type composite blocking remover as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of yield increase and plug removal in oilfield development, and particularly relates to a non-acid type composite plug remover as well as a preparation method and application thereof. The non-acid type composite blocking remover is prepared from the following components in percentage by weight: 1 to 4 weight percent of a nonionic surfactant, 0.5 to 3 weight percent of an anionic surfactant, 0.5 to 3 weight percent of a metal chelating agent, 0.5 to 2 weight percent of caustic soda flakes, 2 to 6 weight percent of sodium carbonate and the balance of water. The non-acid composite blocking remover disclosed by the invention has the advantages of high descaling speed and low-concentration scale dissolving capacity, and the descaling rate of an oil well can reach 100%; under the synergistic effect of a proper proportion of a nonionic surfactant, an anionic surfactant, a metal chelating agent, caustic soda flakes, sodium carbonate and water, the compound scale in a stratum is dissolved, and a reservoir blocked by the inorganic and organic compound scale is broken through, so that the water injection quantity of a water injection well or the acidification yield of an oil-water well is increased.

Description

Technical Field

[0001] This invention belongs to the field of oilfield development, production enhancement, and unblocking technology, specifically relating to a non-acidic composite unblocking agent, its preparation method, and its application. Background Technology

[0002] Currently, many oilfields in China have entered the high water-cut development stage, and some oilfields have gradually implemented measures to enhance oil recovery, such as water shut-off and profile control, alkaline flooding, ternary composite flooding, carbon dioxide flooding, air foam flooding, and surfactant flooding. These measures often require the addition of organic or inorganic reagents or alteration of the physicochemical state of the oil wells, which may lead to scaling in the oil wells. The high salinity of formation water exacerbates the scaling in oil wells.

[0003] Currently, declogging technologies mainly include physical declogging and chemical declogging, with chemical declogging being more commonly used. Chemical declogging utilizes the chemical properties of agents to degrade and dissolve components such as oil, polymers, and inorganic substances in the blockage, thus achieving the purpose of unclogging. Examples include oxidation declogging systems, surfactant viscosity-reducing systems, acid declogging systems, thermochemical declogging systems, and composite declogging systems. Chemical declogging technologies are highly targeted; the prerequisite for chemical descaling is to clearly understand the composition, location, and extent of the scale buildup, and then select the type and dosage of chemical agents.

[0004] In chemical descaling technology, acid descaling systems are commonly used. These systems use acid-based descaling agents to remove scale. However, acid-based descaling agents have the following problems: slow descaling speed, low scale dissolution rate, and the violent reactions of inorganic or organic acids such as hydrochloric acid, nitric acid, and hydrofluoric acid during the descaling process can cause scale to flake off and block pipes. Furthermore, the acid washing process can also cause corrosion damage to the equipment materials.

[0005] In view of this, the present invention is hereby proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a non-acid composite unblocking agent, its preparation method, and its application. This non-acid composite unblocking agent can replace acidizing and descaling measures for increasing production in water injection wells. It has the advantages of fast descaling speed, low concentration scale dissolution ability, and a descaling rate of over 98% for oil wells.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A non-acidic composite unblocking agent comprises, by weight percentage: 1-4 wt% nonionic surfactant, 0.5-3 wt% anionic surfactant, 0.5-3 wt% metal chelating agent, 0.5-2 wt% caustic soda flakes, 2-6 wt% soda ash, and the remainder being water.

[0009] Furthermore, the nonionic surfactant includes one or more of laurylamine polyoxyethylene ether, octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, glycerol ester, and sorbitol ester.

[0010] Furthermore, the anionic surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, fatty alcohol polyoxyethylene ether sulfate, and alkyl alcohol polyoxyethylene ether phosphate.

[0011] Furthermore, the metal chelating agent includes one or more of the following: sodium ethylenediaminetetraacetate, ammonium citrate, sodium diethylenetriaminepentaacetate, and sodium ethylenediaminetetraacetate.

[0012] Furthermore, the pH range of the non-acidic composite unblocking agent is 10 to 12.5.

[0013] In addition, the present invention also provides a method for preparing the above-mentioned non-acidic composite unblocking agent, comprising the following steps:

[0014] After mixing nonionic surfactant and water in a certain proportion and stirring evenly, anionic surfactant is added in a certain proportion and stirred evenly. Then, metal chelating agent is added in a certain proportion and stirred evenly. Then, caustic soda flakes are added in a certain proportion and stirred evenly. Finally, soda ash is added in a certain proportion and stirred until completely dissolved to obtain the non-acidic composite unblocking agent.

[0015] Furthermore, the stirring rate after mixing nonionic surfactant and water is 30–60 rpm, and the stirring time is 20–60 minutes; and / or, the stirring rate after adding anionic surfactant is 40–60 rpm, and the stirring time is 20–30 minutes; and / or, the stirring rate after adding metal chelating agent is 10–60 rpm, and the stirring time is 30–120 minutes; and / or, the stirring rate after adding caustic soda flakes is 30–60 rpm, and the stirring time is 5–20 minutes.

[0016] Further, a metal chelating agent is added, and after stirring evenly, the temperature is raised to 40-50°C, and then caustic soda flakes are added in proportion.

[0017] In addition, the present invention also provides the application of the non-acid composite unblocking agent as described above and the non-acid composite unblocking agent prepared by the above preparation method in oilfield reservoir unblocking.

[0018] Furthermore, the non-acidic composite unblocking agent is diluted with water to a mass concentration of 20% before use.

[0019] Compared with the prior art, the technical solution of the present invention has at least the following technical effects:

[0020] (1) The non-acid composite unblocking agent of the present invention has a fast descaling speed and low concentration scale dissolution ability, and the descaling rate of oil wells can reach more than 98%. Under the synergistic effect of nonionic surfactant, anionic surfactant, metal chelating agent, caustic soda, soda ash and water in appropriate proportion, it dissolves the composite scale in the formation and opens up the reservoir blocked by inorganic and organic composite scale, thereby increasing the injection volume of water injection wells or increasing the acidizing production of oil and water wells.

[0021] (2) The non-acidic composite unblocking agent of the present invention can replace the acidizing and descaling measures for increasing production in water injection wells. When reacting with scale, it does not react violently like hydrochloric acid or nitric acid, but is dissolved through a loose, dispersed and penetrating process. It avoids the pipe blockage caused by scale flakes falling off in traditional acid washing, and also avoids the corrosive damage to equipment materials caused by acid washing. It is non-toxic, odorless, non-flammable and non-explosive. The effect is better at higher operating temperatures.

[0022] (3) The preparation process of the non-acid composite unblocking agent of the present invention is simple and the preparation conditions are mild, making it suitable for large-scale production. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions in the embodiments of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Those skilled in the art should understand that the embodiments described are merely illustrative of the invention and should not be considered as specific limitations thereof. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention. Process parameters not specifically specified in the following embodiments are generally performed under conventional conditions.

[0024] The endpoints and any values ​​of the ranges disclosed in this invention 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 in this invention.

[0025] According to a first aspect of the present invention, a non-acidic composite unblocking agent is provided, comprising, by weight percentage, the following components: 1-4 wt% (e.g., 1 wt%, 2 wt%, 3 wt%, 4 wt%) of nonionic surfactant, 0.5-3 wt% (e.g., 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%) of anionic surfactant, 0.5-3 wt% (e.g., 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 2.5 wt%, 3 wt%) of metal chelating agent, 0.5-2 wt% (e.g., 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%) of caustic soda flakes, 2-6 wt% (e.g., 2 wt%, 3 wt%, 4 wt%, 5 wt%, 6 wt%) of soda ash, with the remainder being water.

[0026] Among the scale deposits in oilfield wells, the most common are insoluble salts such as calcium carbonate, calcium sulfate, strontium sulfate, and barium sulfate, which are inorganic scale. Additionally, heavy oil mainly consists of various hydrocarbons, gums, and asphaltenes. Gums and asphaltenes, with their large molecular weight and high viscosity, are prone to aggregation and scale formation, classifying them as organic scale. Therefore, the scale blockages that typically require treatment are complex scales composed of both inorganic and organic components. This invention utilizes the active groups in the unblocking agent to achieve a synergistic effect with asphalt and polymer scale in the oilfield formation, exhibiting low-concentration scale-dissolving capabilities. It reacts with scale and rust to form water-soluble complexes. Furthermore, a metal chelating agent encapsulates and dissolves the inorganic scale, reacting to form water-soluble complexes that dissolve the complex scale in the formation, clearing the reservoir blocked by the inorganic-organic complex scale. This allows for an increase in the water injection volume of injection wells or an increase in the acidizing production of oil-water wells.

[0027] In the components of the non-acidic composite unblocking agent of this invention, the nonionic surfactant plays a role in dispersion and wetting, and its addition also contributes to the stability of the product. By controlling its proportion, it can carry the metal chelating agent into the rock and the blocked pore throat, achieving a similar intelligent scale-finding operation. The anionic surfactant can reduce the oil-water interfacial tension, thereby extracting the portion of oil that is not easily flowable and adheres to the rock surface and adsorbed in the core pore throat. The metal chelating agent forms a stable complex with metal scale ions, especially with divalent metal ions, and can also combine with metal ions in water to form an even more stable complex, achieving the effect of scale removal and unblocking. The addition of caustic soda utilizes its adsorption properties to remove and dissolve inorganic scale, achieving the purpose of working in conjunction with the metal chelating agent. It can also adjust the pH value, which can be neutral or alkaline. The inventors found in their research that the unblocking agent under alkaline conditions is more effective than that under neutral conditions, and the non-acidic composite unblocking agent is more effective when the pH range is 10-12.5. Adding soda ash utilizes its descaling and cleaning properties to remove iron and limescale from complex scale. The effect is even better when used in conjunction with metal chelating agents.

[0028] In the above-mentioned non-acidic composite unblocking agent, as a preferred embodiment, the nonionic surfactant includes one or more of laurylamine polyoxyethylene ether, octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, glycerol ester, and sorbitol ester.

[0029] In the above-mentioned non-acidic composite unblocking agent, as a preferred embodiment, the anionic surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, fatty alcohol polyoxyethylene ether sulfate, and alkyl alcohol polyoxyethylene ether phosphate.

[0030] In the above-mentioned non-acidic composite unblocking agent, as a preferred embodiment, the metal chelating agent includes one or more of the following: ethylenediaminetetraacetic acid tetrasodium salt, ammonium citrate salt, diethylenetriaminepentaacetic acid pentasodium salt, and ethylenediaminetetraacetic acid sodium salt.

[0031] According to a second aspect of the present invention, a method for preparing the above-mentioned non-acidic composite unblocking agent is provided, comprising the following steps:

[0032] After mixing nonionic surfactant and water in a certain proportion and stirring evenly, anionic surfactant is added in a certain proportion and stirred evenly. Then, metal chelating agent is added in a certain proportion and stirred evenly. Then, caustic soda flakes are added in a certain proportion and stirred evenly. Finally, soda ash is added in a certain proportion and stirred until completely dissolved to obtain the non-acidic composite unblocking agent.

[0033] In the preparation method of the present invention, the addition steps of each component need to be strictly defined. If the components are added in different steps, the solution is easy to separate into layers or be incompletely dissolved. In addition, the synergistic effect between the surfactant and the chelating agent, and the synergistic effect between the chelating agent and the alkali, cannot be systematically achieved. Therefore, it is necessary to first dissolve the surfactant, then dissolve the chelating agent, and finally adjust the pH value with alkali.

[0034] In the above preparation method, as a preferred embodiment, the stirring rate after mixing the nonionic surfactant and water is 30-60 rpm, and the stirring time is 20-60 minutes; optionally, the stirring rate after adding the anionic surfactant is 40-60 rpm, and the stirring time is 20-30 minutes; optionally, the stirring rate after adding the metal chelating agent is 10-60 rpm, and the stirring time is 30-120 minutes; optionally, the stirring rate after adding caustic soda flakes is 30-60 rpm, and the stirring time is 5-20 minutes.

[0035] In the above preparation method, as a preferred embodiment, a metal chelating agent is added, and after stirring evenly, the solution is heated to 40-50°C, and then caustic soda flakes are added in proportion.

[0036] According to a third aspect of the present invention, the application of the above-described non-acid composite unblocking agent and the non-acid composite unblocking agent prepared by the above-described preparation method in oilfield reservoir unblocking is provided.

[0037] In the above applications, as a preferred embodiment, the non-acidic composite unblocking agent can be diluted with water to a 20% (w / w) solution before use. The longer the application time, the better the descaling effect.

[0038] The present invention will now be described in detail with reference to embodiments thereof. These examples are provided by way of explanation and not by way of limitation. In fact, those skilled in the art will recognize that modifications and variations can be made to the present invention without departing from its scope or spirit. For example, a feature shown or described as part of one embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desirable that the present invention encompass such modifications and variations that fall within the scope of the appended claims and their equivalents.

[0039] In the embodiments of the present invention, unless otherwise specified, the experimental methods used are conventional methods, and the materials and reagents used are commercially available unless otherwise specified.

[0040] Example 1

[0041] This embodiment provides a non-acidic composite unblocking agent with the following component contents: 2% laurylamine polyoxyethylene ether, 1% sodium dodecylbenzene sulfonate, 2% tetrasodium ethylenediaminetetraacetate, 1% caustic soda flakes, 4% soda ash, and 90% water;

[0042] The preparation method is as follows:

[0043] Dissolve 2% laurylamine polyoxyethylene ether in 90% water and stir until homogeneous. Add 1% sodium dodecylbenzenesulfonate and stir until homogeneous. Continue to add 2% tetrasodium ethylenediaminetetraacetate and stir until homogeneous. Raise the solution temperature to 45°C, add 1% caustic soda flakes and stir until homogeneous. Continue to add 4% soda ash and stir until completely dissolved to obtain the non-acidic composite unblocking agent of this embodiment, with a pH value of 12.4.

[0044] The scale dissolution rate of the non-acid composite unblocking agent prepared in this embodiment was determined. The specific method was as follows: 10g of scale sample from an oilfield injection well was dissolved in 100ml of the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%). The mixture was stirred for 24 hours at 85℃ (reservoir temperature), then soaked for another 24 hours. The undissolved scale sample was dried and the moisture evaporated. The sample was filtered through paper, and the remaining weight was found to be 0.48g. The dissolved scale sample was 9.52g. The scale dissolution rate was calculated as (original scale sample weight - remaining weight) ÷ original scale sample weight × 100%, resulting in a scale dissolution rate of 95.2%. The longer the time, the better the scale dissolution effect. After more than 66 hours of testing, the scale dissolution rate of the 20% concentration non-acid composite unblocking agent in this embodiment was 100%. The scale dissolution rate of the 10% concentration non-acid composite unblocking agent was 98.01%.

[0045] Example 2

[0046] This embodiment provides a non-acidic composite unblocking agent with the following component contents: 3% nonylphenol polyoxyethylene ether, 0.5% alkyl alcohol polyoxyethylene ether phosphate salt, 1% sodium ethylenediaminetetraacetate, 1% caustic soda flakes, 3% soda ash and 91.5% water;

[0047] The preparation method is as follows:

[0048] Dissolve 3% nonylphenol polyoxyethylene ether in 91.5% water and stir until homogeneous. Add 0.5% alkyl alcohol polyoxyethylene ether phosphate salt and stir until homogeneous. Continue to add 1% sodium ethylenediaminetetraacetate and stir until homogeneous. Raise the solution temperature to 40°C, add 1% caustic soda flakes and stir until homogeneous. Continue to add 3% soda ash and stir until completely dissolved to obtain the non-acidic composite unblocking agent of this embodiment, with a pH value of 11.5.

[0049] The scale dissolution rate of the non-acid composite unblocking agent prepared in this embodiment was determined. The specific determination method was as follows: a scale sample from an oilfield injection well was dissolved in the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%). 10g of scale sample was dissolved in 100ml of unblocking agent. The mixture was stirred for 24h at 80℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 1.28g. The dissolved scale sample was 8.72g, and the scale dissolution rate was 87.2%.

[0050] Example 3

[0051] This embodiment provides a non-acidic composite unblocking agent with the following component contents: 1% sorbitol ester, 2% sodium lauryl sulfate, 2.5% diethylenetriaminepentaacetic acid pentasodium salt, 1.5% caustic soda flakes, 2% soda ash, and 91% water;

[0052] The preparation method is as follows:

[0053] Dissolve 1.0% sorbitol ester in 91% water and stir until homogeneous. Add 2% sodium lauryl sulfate and stir until homogeneous. Continue to add 2.5% diethylenetriaminepentaacetic acid pentasodium salt and stir until homogeneous. Raise the solution temperature to 50°C, add 1.5% caustic soda flakes and stir until homogeneous. Continue to add 2% soda ash and stir until completely dissolved to obtain the non-acidic composite unblocking agent of this embodiment, with a pH value of 10.7.

[0054] The scale dissolution rate of the non-acid composite unblocking agent prepared in this embodiment was determined. The specific determination method was as follows: the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%) was used to dissolve the scale sample from an oilfield injection well. 10g of scale sample was dissolved in 100ml of unblocking agent. The mixture was stirred for 24h at 90℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 0.82g. The dissolved scale sample was 9.18g, and the scale dissolution rate was 91.8%.

[0055] Example 4

[0056] This embodiment provides a non-acidic composite unblocking agent with the following component contents: 4% octylphenol polyoxyethylene ether, 1.5% alkyl alcohol polyoxyethylene ether phosphate salt, 1% citrate ammonium salt, 1.5% caustic soda flakes, 3% soda ash and 89% water;

[0057] The preparation method is as follows:

[0058] 4% octylphenol polyoxyethylene ether was dissolved in 89% water and stirred until homogeneous. 1.5% alkyl alcohol polyoxyethylene ether phosphate salt was added and stirred until homogeneous. 1% citrate ammonium salt was then added and stirred until homogeneous. The solution temperature was raised to 40°C, and 1.5% caustic soda flakes were added and stirred until homogeneous. 3% soda ash was then added and stirred until completely dissolved to obtain the non-acidic composite unblocking agent of this embodiment, with a pH value of 12.0.

[0059] The scale dissolution rate of the non-acid composite unblocking agent prepared in this embodiment was determined. The specific determination method was as follows: the scale sample from a water injection well in an oilfield was dissolved with the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%). 10g of scale sample was dissolved in 100ml of unblocking agent. The mixture was stirred for 24h at 85℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was 1.40g. The dissolved scale sample was 8.60g, and the scale dissolution rate was 86%.

[0060] Comparative Example 1

[0061] This comparative example provides a non-acidic composite unblocking agent with the following component contents: 2% laurylamine polyoxyethylene ether, 1% sodium dodecylbenzenesulfonate, 2% tetrasodium ethylenediaminetetraacetate, 1% caustic soda flakes, and 94% water.

[0062] The preparation method is as follows: Dissolve 2% laurylamine polyoxyethylene ether in 90% water, stir evenly, add 1% sodium dodecylbenzenesulfonate, stir evenly, continue to add 2% tetrasodium ethylenediaminetetraacetate, stir evenly, raise the solution temperature to 45°C, add 1% caustic soda flakes, stir evenly, and obtain the non-acidic composite unblocking agent of this embodiment with a pH value of 8.2.

[0063] The scale dissolution rate of the non-acid composite unblocking agent prepared in this embodiment was determined. The specific determination method was as follows: 10g of scale sample from an oilfield injection well was dissolved in 100ml of the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%). The mixture was stirred for 24 hours at 85℃ (reservoir temperature) and then soaked for another 24 hours. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 3.18g. The dissolved scale sample was 6.82g. The scale dissolution rate was calculated as (original scale sample weight - remaining weight) ÷ original scale sample weight × 100%, which was 68.2%.

[0064] Comparative Example 2

[0065] This comparative example provides a non-acidic composite unblocking agent with the following component contents: 3% nonylphenol polyoxyethylene ether, 0.5% alkyl alcohol polyoxyethylene ether phosphate salt, 1% sodium ethylenediaminetetraacetate, 3% soda ash and 92.5% water;

[0066] The preparation method is as follows: Dissolve 3% nonylphenol polyoxyethylene ether in 91.5% water and stir evenly. Add 0.5% alkyl alcohol polyoxyethylene ether phosphate salt and stir evenly. Continue to add 1% sodium ethylenediaminetetraacetate and stir evenly. Raise the solution temperature to 40°C and add 3% soda ash. Stir until completely dissolved to obtain the non-acidic composite unblocking agent of this embodiment with a pH value of 10.9.

[0067] The scale dissolution rate of the non-acid composite unblocking agent prepared in this embodiment was determined. The specific determination method was as follows: the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%) was used to dissolve the scale sample from a water injection well in an oilfield. 10g of scale sample was dissolved in 100ml of unblocking agent. The mixture was stirred for 24h at 80℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 1.95g. The dissolved scale sample was 8.05g, and the scale dissolution rate was 80.5%.

[0068] Comparative Example 3

[0069] This comparative example provides a non-acidic composite unblocking agent with the following component contents: 1% sorbitol ester, 2% fluorocarbon surfactant, 2.5% diethylenetriaminepentaacetic acid pentasodium salt, 1.5% caustic soda flakes, 2% soda ash, and 91% water;

[0070] The preparation method is as follows:

[0071] Dissolve 1% sorbitol ester in 91% water and stir until homogeneous. Add 2% fluorocarbon surfactant and stir until homogeneous. Continue to add 2.5% diethylenetriaminepentaacetic acid pentasodium salt and stir until homogeneous. Raise the solution temperature to 50°C, add 1.5% caustic soda flakes and stir until homogeneous. Continue to add 2% soda ash and stir until completely dissolved to obtain the non-acidic composite unblocking agent of this comparative example with a pH value of 10.4.

[0072] The scale dissolution rate of the non-acid composite unblocking agent prepared in this comparative example was determined. The specific determination method was as follows: 10g of scale sample from an oilfield injection well was dissolved in 100ml of the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%). The mixture was stirred for 24h at 90℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 2.22g. The dissolved scale sample was 7.78g, and the scale dissolution rate was 77.8%.

[0073] Comparative Example 4

[0074] This comparative example provides a non-acidic composite unblocking agent with the following component contents: 4% octylphenol polyoxyethylene ether, 1.5% alkyl alcohol polyoxyethylene ether phosphate salt, 1% citrate ammonium salt, 1.5% caustic soda flakes, 3% soda ash and 89% water;

[0075] The preparation method is as follows:

[0076] 4% octylphenol polyoxyethylene ether and 1.5% alkyl alcohol polyoxyethylene ether phosphate salt were dissolved in 89% water and stirred until homogeneous. The solution temperature was raised to 40°C, and 1% citrate ammonium salt, 1.5% caustic soda flakes, and 3% soda ash were added. The mixture was stirred until completely dissolved to obtain the non-acidic composite unblocking agent of this embodiment, with a pH value of 11.8.

[0077] The scale dissolution rate of the non-acid composite unblocking agent prepared in this comparative example was determined. The specific determination method was as follows: the non-acid composite unblocking agent (diluted with water to a mass concentration of 20%) was used to dissolve the scale sample from a water injection well in an oilfield. 10g of scale sample was dissolved in 100ml of unblocking agent. The mixture was stirred for 24h at 85℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 2.40g. The dissolved scale sample was 7.60g, and the scale dissolution rate was 76%.

[0078] Comparative Example 5

[0079] This comparative example provides a composite acid unblocking agent with the following component contents: 12% hydrochloric acid, 3% hydrofluoric acid, 3% citric acid and 92% water; its preparation method is as follows: mix the components and stir evenly.

[0080] The scale dissolution rate of the composite acid unblocking agent prepared in this comparative example was determined. The specific determination method was as follows: 10g of scale sample from an oilfield water injection well was dissolved in 100ml of the unblocking agent. The solution was stirred for 24h at 85℃ (reservoir temperature) and then soaked for another 24h. The undissolved scale sample was dried and the water was evaporated. The sample was filtered through paper, and the remaining weight was found to be 4.16g. The dissolved scale sample was 5.84g, and the scale dissolution rate was 58.4%.

[0081] The foregoing has described and evaluated some embodiments of the present invention. It should be understood that the present invention is not limited to the specific embodiments described above. Any person skilled in the art can make many possible variations and modifications to the technical solutions of the present invention, or modify them into equivalent embodiments, without departing from the scope of the present invention. This does not affect the essential content of the present invention. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention, without departing from the content of the present invention, still fall within the protection scope of the present invention.

Claims

1. A non-acidic composite unblocking agent, characterized in that, By weight percentage, it comprises the following components: 1-4 wt% nonionic surfactant, 0.5-3 wt% anionic surfactant, 0.5-3 wt% metal chelating agent, 0.5-2 wt% caustic soda flakes, 2-6 wt% soda ash, and the remainder being water.

2. The non-acidic composite unblocking agent according to claim 1, characterized in that, The nonionic surfactant includes one or more of laurylamine polyoxyethylene ether, octylphenol polyoxyethylene ether, nonylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, glycerol ester, and sorbitol ester.

3. The non-acidic composite unblocking agent according to claim 1, characterized in that, The anionic surfactant includes one or more of sodium dodecylbenzenesulfonate, sodium lauryl sulfate, fatty alcohol polyoxyethylene ether sulfate, and alkyl alcohol polyoxyethylene ether phosphate.

4. The non-acidic composite unblocking agent according to claim 1, characterized in that, The metal chelating agent includes one or more of the following: sodium ethylenediaminetetraacetate, ammonium citrate, sodium diethylenetriaminepentaacetate, and sodium ethylenediaminetetraacetate.

5. The non-acidic composite unblocking agent according to any one of claims 1-4, characterized in that, The pH range of the non-acidic composite unblocking agent is 10 to 12.

5.

6. A method for preparing a non-acidic composite unblocking agent as described in any one of claims 1-5, characterized in that, Includes the following steps: After mixing nonionic surfactant and water in a certain proportion and stirring evenly, anionic surfactant is added in a certain proportion and stirred evenly. Then, metal chelating agent is added in a certain proportion and stirred evenly. Then, caustic soda flakes are added in a certain proportion and stirred evenly. Finally, soda ash is added in a certain proportion and stirred until completely dissolved to obtain the non-acidic composite unblocking agent.

7. The preparation method according to claim 6, characterized in that, The stirring rate after mixing nonionic surfactant and water is 30–60 rpm, and the stirring time is 20–60 minutes; and / or, the stirring rate after adding anionic surfactant is 40–60 rpm, and the stirring time is 20–30 minutes; and / or, the stirring rate after adding metal chelating agent is 10–60 rpm, and the stirring time is 30–120 minutes; and / or, the stirring rate after adding caustic soda flakes is 30–60 rpm, and the stirring time is 5–20 minutes.

8. The preparation method according to claim 6, characterized in that, Add a metal chelating agent, stir well, heat to 40-50℃, and then add caustic soda flakes in proportion.

9. The application of the non-acid composite unblocking agent according to any one of claims 1-5 and the non-acid composite unblocking agent prepared by the preparation method according to any one of claims 6-8 in oilfield reservoir unblocking.

10. The application according to claim 9, characterized in that, The non-acidic composite unblocking agent is diluted with water to a mass concentration of 20% before use.