Non-acid composite active plug-breaking agent and preparation method thereof

Abstract

The application provides a non-acid composite active plug removing agent and a preparation method thereof, and belongs to the technical field of plug removing agents.The non-acid composite active plug removing agent comprises the following raw materials: ethylene-vinyl acetate copolymer, a solvent, a mutual solvent, an organic sulfonate, diethylene triamine pentaacetic acid, sodium gluconate, a pH regulator, benzotriazole, hydroxyethyl ethylenediamine triacetic acid and methanol.The non-acid composite active plug removing agent is composed of an organic sulfonate, various active agents and a penetrating agent and the like.Through the penetration and dispersion of molecules, various types of plugging materials in the rock gap throat are dispersed, the pore throat is increased, and an effective seepage channel is formed.The non-acid composite active plug removing agent prepared by the application does not corrode and damage metal pipes and the dense rock body, is not acid-sensitive, does not cause flowback pollution, has a long plug removing and dredging distance, has a good and long-lasting effect, and is a new method for deep plug removing.

Description

Technical Field

[0001] This invention relates to the field of unblocking agents, and in particular to a non-acid composite active unblocking agent and its preparation method. Background Technology

[0002] At various stages of oilfield development, such as drilling, well workover, and fracturing, the mud cake formed during drilling, the kill fluid during well workover, the residual fluid from fracturing, and the solid particles generated by scaling, waxing, and organic impurities during production can reduce conductivity and damage formation permeability, and even cause formation blockage, leading to a significant decrease in oil well production and an increase in water injection pressure in water wells.

[0003] The main causes of oil and water well blockage include: (1) Poor reservoir properties, resulting in increased crude oil viscosity and decreased permeability; (2) Damage to the oil reservoir caused by the migration of solid particles; (3) Damage caused by incompatibility between external fluids and the original fluids and minerals in the oil reservoir; (4) Damage caused by external fluids to the corrosion and scaling of the tubing.

[0004] Existing technologies employ methods such as physical fracturing, chemical acidizing, and neutral chelation to address the problem of oil and water well blockage. However, these methods have the following advantages and disadvantages: Physical fracturing results in long fractures, good formation connectivity, long stable production time, and good production increase benefits. It can be carried out on a large scale, but it also carries high safety risks and high costs.

[0005] Chemical acidizing has a shorter construction cycle than neutral acidizing, but its treatment radius is limited and rarely exceeds 1.5 meters; complex lithology requires high-quality acid solutions; the reservoir is highly sensitive to acid and prone to secondary precipitation; acid can corrode tubing and equipment, posing a safety hazard; and residual acid cannot enter the process and requires secondary treatment, increasing costs. Furthermore, acid leaks can easily damage the ecological environment.

[0006] Neutral chelation has poor descaling and unclogging capabilities, and is almost ineffective against calcium sulfate scale, silica scale, and rolled scale; it can only remove a limited range of minerals and has poor broad-spectrum properties; the chelate is greatly affected by mineralization and pH, and is prone to secondary clogging. Thorough backflow is required, and prolonged storage can lead to secondary precipitation. Summary of the Invention

[0007] In view of this, the object of the present invention is to provide a non-acid composite active unblocking agent, comprising the following raw materials in weight percentages: Ethylene-vinyl acetate copolymer (EVA) 5-8%, solvent 10-15%, miscible solvent 1-2%, organic sulfonate 2-5%, diethylenetriaminepentaacetic acid (DTPA) 5-10%, sodium gluconate 2-5%, pH adjuster 3-5%, benzotriazole (BTA) 0.1-0.5%, hydroxyethyl ethylenediaminetriacetic acid (HEDTA) 0.3-0.5%, methanol 50-60%.

[0008] Preferably, the non-acid composite active unblocking agent comprises the following raw materials by weight percentage: Ethylene-vinyl acetate copolymer 5.8%, solvent 15%, miscible solvent 1%, organic sulfonate 3%, diethylenetriaminepentaacetic acid 8%, sodium gluconate 3%, pH adjuster 6%, benzotriazole 0.3%, hydroxyethylethylenediaminetriacetic acid 0.4%, methanol 57.5%.

[0009] Preferably, the solvent is tetramethylbenzene.

[0010] Preferably, the mutual solvent is ethylene glycol butyl ether.

[0011] Preferably, the pH adjuster is sodium hydroxide.

[0012] Preferably, the organic sulfonate is sodium dodecylbenzenesulfonate.

[0013] Another object of the present invention is to provide a method for preparing a non-acid composite active unblocking agent, comprising the following steps: At room temperature, the ethylene-vinyl acetate copolymer is completely dissolved in a solvent under low-speed stirring. Then, a mutual solvent and an organic sulfonate are added and stirring is continued for 15-20 minutes. Other raw materials are added and stirring is carried out for 20-30 minutes. After standing for 30 minutes, the non-acid composite active unblocking agent is obtained.

[0014] Preferably, the transmission ratio of the low-speed mixer is 1.45-727, the input power is 0.18-22KW, the output torque is 1.5-22500Nm, and the time is 20min-30min.

[0015] The unblocking agent of the present invention has the following functions: (1) Surfactants can penetrate and disperse, remove various organic mixed impurities and organic oil stains, and reduce the viscosity of crude oil.

[0016] (2) Promote and accelerate the dispersion and dissolution reaction of the plugging material in the oil reservoir crevices, and prevent the formation of precipitates to avoid secondary blockage; (3) It will not cause acid-sensitive damage, thus enabling long-distance deep dredging and unblocking.

[0017] (4) Organic sulfonates are acidic after hydrolysis under the action of initiators. They can be used for formation micro-modification in the near-wellbore area to improve the permeability of the oil layer.

[0018] (5) The penetration of surfactant (sodium dodecylbenzenesulfonate) can disperse large crude oil particles into small particles through oleophilic and hydrophilic groups, which is beneficial to passing through smaller pores and throats and reducing flow resistance in pores. (6) The irregular movement of the surfactant (sodium dodecylbenzenesulfonate) peels off the oil film on the rock surface, changes the wettability of the rock surface, achieves hydrophilicity and oleophobicity, and promotes the release and flow of crude oil.

[0019] (7) The surfactant (sodium dodecylbenzenesulfonate) is easily soluble in water and mixes with water to form active water.

[0020] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a non-acid composite active unblocking agent, which is composed of organic sulfonates, surfactants (sodium dodecylbenzenesulfonate), corrosion inhibitors (benzotriazole), and other components. Through molecular penetration and dispersion, it disperses various blockages in rock fissures and throats, enlarges the pore throat, and forms effective seepage channels. The non-acid composite active unblocking agent prepared by this invention does not corrode or damage metal pipes and dense rock bodies, is not acid-sensitive, does not cause backflow pollution, has a long unblocking distance, and has good and long-lasting effects, making it a new method for deep unblocking. Detailed Implementation

[0021] The present invention will be further described below with reference to the embodiments.

[0022] Example 1 A non-acid composite active unblocking agent, composed of the following raw materials by weight percentage: Ethylene-vinyl acetate copolymer 5.8%, tetramethylbenzene 15%, ethylene glycol butyl ether 1%, sodium dodecylbenzenesulfonate 3%, diethylenetriaminepentaacetic acid 8%, sodium gluconate 3%, sodium hydroxide 6%, benzotriazole 0.3%, hydroxyethyl ethylenediaminetriacetic acid 0.4%, methanol 57.5%.

[0023] The preparation method of the non-acid composite active unblocking agent includes the following steps: At room temperature, ethylene-vinyl acetate copolymer was completely dissolved in a solvent under a gearbox with a transmission ratio of 122, an input power of 20 kW, and an output torque of 300 Nm, and stirred for 20 minutes. Then, the mutual solvents ethylene glycol monobutyl ether and sodium dodecylbenzene sulfonate were added, and stirring continued for another 20 minutes. Other raw materials were then added, and stirring was continued for another 20 minutes. The mixture was then allowed to stand for 30 minutes to obtain the non-acid composite active unblocking agent. The cost of unblocking one well is approximately 250,000 yuan. Comparative Example 1 A non-acid composite active unblocking agent, the raw material composition and preparation method are the same as in Example 1, except that comparative example 1 does not add ethylene glycol butyl ether and sodium dodecylbenzene sulfonate.

[0024] Comparative Example 2 A non-acid composite active unblocking agent, the raw material composition and preparation method are the same as in Example 2, except that benzotriazole is not added in Comparative Example 2.

[0025] Comparative Example 3 A non-acid composite active unblocking agent, the raw material composition and preparation method are the same as in Example 3, except that hydroxyethyl ethylenediamine triacetic acid is not added to Comparative Example 3.

[0026] Comparative Example 4 A physical fracturing method, under a pressure of 70 MPa for 20 minutes, creates artificial fractures in underground rock formations with fluid, opening channels for crude oil outflow and increasing crude oil production. The added fracturing fluid mainly consists of 15% guar gum powder, 30% quartz sand, and the remainder water. It is costly, costing approximately 5 million yuan to fracture one well.

[0027] Comparative Example 5 A neutral chelation method uses a neutral chelating agent consisting of 15% ethylenediaminetetraacetic acid (EDTA), 8% sodium citrate, and the remainder water. The pH is then adjusted to neutral using sodium hydroxide. Neutral chelating agents are a class of substances that can form stable complexes with metal ions; this process is called chelation.

[0028] Comparative Example 6 A chemical acidification method uses an acidification solution made of 25% hydrochloric acid, 3% hydrofluoric acid, and the remainder water. The solution is highly acidic, reacts violently, and has a short acidification distance.

[0029] The following experiments were conducted on the unblocking agents of Examples 1-6; 1. Crude oil viscosity reduction experiment (1) Place 100g of crude oil in a 50℃ constant temperature water bath and heat for 1 hour. Then, measure its viscosity using a No. 4 rotor (diameter 25.4mm) at a speed of 30r / s. After the value stabilizes, record the crude oil viscosity value η0 (mPa*s). (2) Add 5% or 10% of unblocking agent to crude oil, stir evenly and place it in a 50℃ constant temperature water bath. After heating and emulsifying for 1 hour, use a No. 3 rotor (diameter 20.0 mm) at a speed of 30 r / s to measure its viscosity. After the value stabilizes, record the viscosity η1 (mPa*s) of the treated crude oil.

[0030] The formula for calculating the viscosity reduction rate is as follows (1): Viscosity reduction rate = (η0-η1) / η0×100% (1) The viscosity reduction results are shown in Table 1.

[0031] Table 1

[0032] 2. Experiment on the breaking down of mud cake by unblocking fluid Solid mud (made by mixing 55% bentonite and 45% water for 30 minutes, with the bentonite manufactured by Shandong Huwei Bentonite Company, model: sodium-based bentonite for drilling fluid) was used to prepare a filter cake with a thickness of about 1-2 mm using a medium-pressure filtration analyzer. Filter paper and filter cake were cut into approximately 2*2 cm filter cakes for later use. 50 ml of 8% (w / w) unblocking solution was placed in a sealed glass bottle, and a filter cake was placed in the solution. The bottle was then placed in a 90℃ constant temperature water bath and reacted for 1 hour. After that, the unblocking solution was poured out, and then 50 ml of 10% (w / w) unblocking solution was added. The state of the mud cake was observed at different times, and the results are shown in Table 2.

[0033] Table 2

[0034] 3. Corrosion rate experiment of unblocking fluid on N80 steel sheet The static corrosion rate of N80 steel sheets under normal pressure was evaluated by determining the unblocking solution prepared in Example 1 at different concentrations according to method 5.1 of SY / T 5405-2019. The results are shown in Table 3. (Steel sheet surface area 1360 mm²) 2 (Reaction time 4 hours) Table 3

[0035] 4. Dissolution experiment of rock powder by unblocking fluid According to the method in section 7.2 of SY / T 5886-2018, and following the unblocking process requirements, 10g of oil well rock powder from the eastern South China Sea was first placed in a beaker, and 20ml of an 8% (w / w) unblocking solution was poured in. The mixture was then placed in a 90°C constant temperature water bath and reacted for 1 hour. Next, 15ml of a 10% (w / w) unblocking solution was added, and the mixture was reacted at 90°C for 3 hours. The mixture was then filtered using rapid filter paper that had been dried at 105°C (45 minutes) to constant weight. Finally, it was placed in a 105°C oven and dried (45 minutes) to constant weight before being weighed. The dissolution rate of the unblocking solution after 4 hours was determined. Dissolution data are shown in Table 4.

[0036] Table 4

[0037] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A non-acid composite active unblocking agent, characterized in that, The raw materials include the following weight percentages: Ethylene-vinyl acetate copolymer 5-8%, solvent 10-15%, mutual solvent 1-2%, organic sulfonate 2-5%, diethylenetriaminepentaacetic acid 5-10%, sodium gluconate 2-5%, pH adjuster 3-5%, benzotriazole 0.1-0.5%, hydroxyethylethylenediaminetriacetic acid 0.3-0.5%, methanol 50-60%.

2. The non-acid composite active unblocking agent according to claim 1, characterized in that, The non-acid composite active unblocking agent comprises the following raw materials by weight percentage: Ethylene-vinyl acetate copolymer 5.8%, solvent 15%, miscible solvent 1%, organic sulfonate 3%, diethylenetriaminepentaacetic acid 8%, sodium gluconate 3%, pH adjuster 6%, benzotriazole 0.3%, hydroxyethylethylenediaminetriacetic acid 0.4%, methanol 57.5%.

3. The non-acid composite active unblocking agent according to claim 1, characterized in that, The solvent is tetramethylbenzene.

4. The non-acid composite active unblocking agent according to claim 1, characterized in that, The mutual solvent is ethylene glycol butyl ether.

5. The non-acid composite active unblocking agent according to claim 1, characterized in that, The pH adjuster is sodium hydroxide.

6. The non-acid composite active unblocking agent according to claim 1, characterized in that, The organic sulfonate is sodium dodecylbenzenesulfonate.

7. The preparation method of the non-acid composite active unblocking agent according to claim 1, characterized in that, Includes the following steps: At room temperature, the ethylene-vinyl acetate copolymer is completely dissolved in a solvent under low-speed stirring. Then, a mutual solvent and an organic sulfonate are added and stirring is continued for 15-20 minutes. Other raw materials are added and stirring is carried out for 20-30 minutes. After standing for 30 minutes, the non-acid composite active unblocking agent is obtained.

8. The preparation method of the non-acid composite active unblocking agent according to claim 7, characterized in that, The low-speed mixer has a transmission ratio of 1.45-727, an input power of 0.18KW-22KW, an output torque of 1.5Nm-22500Nm, and a mixing time of 20min-30min.

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