A kind of non-flowback acidification working fluid and its preparation method and construction process

Abstract

The present application discloses a non-flowback acidizing working fluid and its preparation method and construction process, which belongs to the field of oilfield chemical technology. The non-flowback acidizing working fluid includes a pretreatment fluid and a composite acid fluid, and the volume ratio of the pretreatment fluid to the composite acid fluid is 1: (2~10); the composite acid fluid includes an organic acid, hydrochloric acid and a cationic gemini surfactant; in terms of weight percentage, the composite acid fluid includes 15~25% of an organic acid, 1%~3% of hydrochloric acid, 0.2%~1% of a cationic gemini surfactant, and the remainder is water. The pretreatment fluid cleans and protects the casing of the oil well, dissolves the crude oil and organic scale on the surface of the reservoir; the organic acid, hydrochloric acid and the cationic gemini surfactant are compounded to obtain the composite acid fluid, and the organic acid is combined with the hydrochloric acid to improve the retarding performance, and the cationic gemini surfactant is combined, so that it has stronger surface activity and interfacial activity, is easier to form micelles, and has a good production increase effect.

Description

Technical Field

[0001] The present application relates to a non-flowback acidizing working fluid and a preparation method and construction process thereof, belonging to the technical field of oilfield chemistry. Background Art

[0002] Acidizing is one of the main measures to increase the production and injection of oil and water wells. Acid is injected into the reservoir to cause dissolution reaction between the acid and the reservoir minerals and clay, thereby removing reservoir damage, restoring reservoir permeability, and improving injection capacity and liquid production capacity. Conventional soil acid system is a mixed acid of hydrochloric acid and hydrofluoric acid. The acid reacts with sandstone too quickly, resulting in poor acidizing effect. Conventional acidizing also has the problem of getting worse year by year. Residual acid is prone to form secondary precipitation, which seriously damages the reservoir and greatly limits the acidizing effect.

[0003] In order to obtain acid with superior performance, slow acid systems such as fluoride salt autogenous acid, fluoroboric acid, organic soil acid, phosphoric acid, and polyhydrogen acid have been developed from the perspective of reducing the reaction rate of acid; chelated acid systems have been developed from the perspective of reducing the precipitation damage of reaction products. However, in acidification construction, the residual acid of these acids is not environmentally friendly and cannot be degraded.

[0004] Chinese patent CN 112143479 A discloses a low permeability oil reservoir water injection well non-flowback punching acidizing system and preparation method, which uses a metal ion complexing agent and can avoid flowback after acidification. However, its main acid solution still uses traditional hydrochloric acid and hydrofluoric acid, which are not environmentally friendly and have the problem of too fast reaction rate. The acid solution cannot maintain acid activity for a long time. Summary of the invention

[0005] In order to solve the above problems, a non-flowback acidizing working fluid and a preparation method and construction process thereof are provided. A pretreatment fluid and a composite acid fluid are provided. The pretreatment fluid cleans and protects the casing of the oil well and dissolves the crude oil and organic scale on the reservoir surface. The organic acid, hydrochloric acid and cationic gemini surfactant are compounded to obtain the composite acid fluid, and the reaction rate is further regulated to improve the retarding performance. The cationic gemini surfactant has stronger surface activity and interfacial activity and is more likely to form micelles. The composite acid fluid first enters the hyperpermeable zone or crack. As the reaction proceeds, the cationic gemini surfactant becomes viscous and prevents the acid fluid from continuing to enter the hyperpermeable pores, while the fresh acid continues to penetrate deep and turn to the low permeability layer for production increase treatment.

[0006] According to one aspect of the present application, a flowback-free acidizing working fluid is provided, comprising a pretreatment fluid and a composite acid fluid, wherein the volume ratio of the pretreatment fluid to the composite acid fluid is 1:(2-10); the composite acid fluid comprises an organic acid, hydrochloric acid and a cationic gemini surfactant; in terms of weight percentage, the composite acid fluid comprises 15-25% of an organic acid, 1%-3% of hydrochloric acid, 0.2%-1% of a cationic gemini surfactant, and the remainder is water.

[0007] Optionally, in terms of weight percentage, the organic acid includes a mixture of lactic acid and gluconic acid and an organic phosphoric acid polymer, the mixture of lactic acid and gluconic acid accounts for 10-15% of the composite acid solution; the organic phosphoric acid polymer accounts for 5%-10% of the composite acid solution; the pretreatment solution includes 5%-12% octylphenol polyoxyethylene ether, 2%-7% sodium gluconate, and the remainder is water.

[0008] Optionally, the volume ratio of the pretreatment liquid to the composite acid liquid is 1:2-4.

[0009] Optionally, the molar ratio of lactic acid to gluconic acid is 1-2:1-1.5.

[0010] Optionally, the organic phosphoric acid polymer is polymerized from isopropylphosphonic acid monomer and acrylic acid.

[0011] Optionally, the preparation process of the organophosphoric acid polymer comprises the following steps:

[0012] (1) Dilute the isopropylene phosphonic acid monomer with water to a 50% aqueous solution and heat to 70-80°C;

[0013] (2) A mixture of ammonium persulfate and acrylic acid is dropped into an aqueous solution and the reaction is continued to obtain an organophosphoric acid polymer.

[0014] Optionally, the molar ratio of isopropylene phosphonic acid monomer to acrylic acid is 1-1.2:1, and the amount of ammonium persulfate used is 15-20% of the isopropylene phosphonic acid monomer to acrylic acid.

[0015] Optionally, the cationic gemini surfactant has a molecular formula as shown in formula (1): Formula (1).

[0016] According to another aspect of the present application, the present application also discloses a method for preparing the above-mentioned non-flowback acidification working fluid, comprising the following steps:

[0017] (1) Preparation of pretreatment solution: sodium gluconate was added to water, stirred at room temperature for 5-10 minutes, octylphenol polyoxyethylene ether was added, the temperature was raised to 35-40° C., stirred for 20-25 minutes, and the temperature was naturally lowered to room temperature to obtain a pretreatment solution;

[0018] (2) Preparation of composite acid solution: lactic acid, gluconic acid, organic phosphate polymer and hydrochloric acid are added to water in sequence, stirred at 35-40°C for 20-25 minutes, cooled naturally to room temperature, and cationic gemini surfactant is added, stirred for 10-20 minutes to obtain composite acid solution.

[0019] According to another aspect of the present application, the present application also discloses a construction process of the above-mentioned non-flowback acidizing working fluid, comprising the following steps:

[0020] (1) Inject the pretreatment fluid into the casing annulus of the test oil well;

[0021] (2) Inject the composite acid 3-5 hours after injection, and then shut down the well for 24-72 hours.

[0022] The beneficial effects of this application include but are not limited to:

[0023] 1. According to the non-flowback acidizing working fluid of the present application, octylphenol polyoxyethylene ether, sodium gluconate and water are compounded to obtain a pretreatment fluid, which acts together to clean and protect the casing of the oil well and dissolve the crude oil and organic scale on the surface of the reservoir; lactic acid, gluconic acid, organic phosphoric acid polymer, hydrochloric acid and cationic gemini surfactant are compounded to obtain a composite acid solution, and the four components of lactic acid, gluconic acid, organic phosphoric acid polymer and hydrochloric acid are combined to further regulate the reaction rate and improve the retarding performance. The cationic gemini surfactant has stronger surface activity and interfacial activity and is more likely to form micelles. The composite acid solution first enters the hyperpermeable zone or crack. As the reaction proceeds, the cationic gemini surfactant becomes viscous and prevents the acid solution from continuing to enter the hyperpermeable pores, while the fresh acid continues to penetrate deep and turn to the low permeability layer for production increase treatment.

[0024] 2. According to the non-flowback acidification working fluid of the present application, the components of the composite acid fluid are compounded according to a specific ratio, lactic acid and gluconic acid are used as the main acids, and the protons of the carboxylic acid groups in lactic acid and gluconic acid are replaced by cations to generate carboxylates, and in the acidification process, lactic acid gluconate calcium with high solubility and degradability is generated, and no secondary precipitation will be generated, and lactic acid and gluconic acid are green and environmentally friendly; hydrochloric acid and organic phosphoric acid polymer are compounded with lactic acid gluconic acid to improve the acidification effect and the retarding performance at the same time, hydrochloric acid is a monobasic strong acid, and the hydrogen ions are in a fully ionized state; and the hydrogen ions in the organic phosphoric acid polymer are slowly released, and have the characteristics of multi-stage ionization, so the four acids are compounded and act synergistically, taking into account the acidification effect, retarding performance and green environmental protection.

[0025] 3. According to the non-flowback acidification working fluid of the present application, a specific cationic Gemini surfactant is used. The surfactant contains a hydroxyl C3 and a single-chain oleyl amide group. The introduction of a hydroxyl functional group can reduce the electrostatic repulsion between the two cations and enhance the water solubility of the molecule through the hydrogen bonding of the hydroxyl group, thereby having better interfacial activity and being easier to form a compact micelle structure; the amide-containing Gemini surfactant has excellent biodegradability and can be enzymatically hydrolyzed into non-toxic fatty acids and choline under the action of environmental microbial enzymes without the need for recovery.

[0026] 4. The preparation method and construction process of the non-flowback acidification working fluid according to the present application are simple, easy to operate, green and environmentally friendly, and conducive to large-scale promotion. DETAILED DESCRIPTION

[0027] The present application is described in detail below with reference to embodiments, but the present application is not limited to these embodiments.

[0028] Unless otherwise defined, all professional and scientific terms used herein have the same meanings as those familiar to those skilled in the art. The reagents or raw materials used in the present invention can be purchased through conventional channels. Unless otherwise specified, the reagents or raw materials used in the present invention are used in a conventional manner in the art or in accordance with the product instructions. In addition, any method and material similar or equivalent to the described content can be applied to the method of the present invention. The preferred implementation methods and materials described in this patent are for demonstration purposes only.

[0029] In the following examples and comparative examples, the cationic gemini surfactants involved are prepared by referring to the prior art document Huang Feifei. Study on non-flowback fracturing fluid system and its imbibition oil recovery mechanism in tight oil reservoirs [D]. China University of Petroleum (East China). The specific preparation method includes the following steps:

[0030] (1) Dissolve 20 g of lauryl amine and 3 g of sodium carbonate in a three-necked flask containing 300 ml of DMF;

[0031] (2) Dilute 21 g of 3-bromopropionyl chloride with 100 mL of DMF;

[0032] (3) While stirring at 150 rpm, slowly drip (2) into (1), controlling the dripping rate so that the system temperature does not exceed 45 °C;

[0033] (4) After the addition of 3-bromopropionyl chloride solution is completed, the reaction is continued with stirring for 1 hour. After the reaction, the solution is transferred to a rotary evaporator and evaporated in vacuo at 90°C to remove the solvent and the remaining bromopropionyl chloride, and the intermediate product 3-bromo-N-dodecylpropanamide is isolated;

[0034] (5) Add 300 ml of isopropanol to a three-necked flask fixed in a water bath, add the product of (4) and 6.5 g of 1,3-bis(dimethylamino)propylene glycol to the three-necked flask, and stir under reflux at 30 rpm and 60°C for 15 h;

[0035] (6) The reaction solution in (5) was evaporated to remove the solvent in a rotary evaporator at 90°C, and the product was recrystallized twice with a mixed solvent of ethyl acetate and ethanol (20:1), and dried at 60°C for 24 h.

[0036] Example 1 No-flowback acidification working fluid 1#

[0037] (1) Preparation of organophosphoric acid polymers:

[0038] The isopropylene phosphonic acid monomer is diluted with water to a 50% aqueous solution and heated to 70°C; a mixture of ammonium persulfate and acrylic acid is dripped into the aqueous solution, the molar ratio of the isopropylene phosphonic acid monomer to the acrylic acid is 1:1, and the amount of ammonium persulfate is 15% of the isopropylene phosphonic acid monomer and the acrylic acid, and the reaction is continued to obtain an organic phosphoric acid polymer.

[0039] (2) Raw material preparation: prepare 5% octylphenol polyoxyethylene ether, 2% sodium gluconate, 10% lactic acid and gluconic acid mixture according to weight percentage, and the balance is water; the molar ratio of lactic acid to gluconic acid is 1:1, 5% organic phosphoric acid polymer, 1% hydrochloric acid, 0.2% cationic gemini surfactant, and the balance is water;

[0040] (3) Preparation of pretreatment solution:

[0041] Sodium gluconate was added into water, stirred at room temperature for 5 minutes, octylphenol polyoxyethylene ether was added, the temperature was raised to 35°C, stirred for 20 minutes, and the temperature was naturally lowered to room temperature to obtain a pretreatment solution;

[0042] (4) Preparation of composite acid solution:

[0043] Add lactic acid, gluconic acid, organic phosphate polymer and hydrochloric acid into water in turn, stir at 35°C for 20 minutes, cool naturally to room temperature, add cationic gemini surfactant, and stir for 10 minutes to obtain a composite acid solution. The volume ratio of the pretreatment solution to the composite acid solution is 1:1, and the non-flowback acidification working solution 1# is obtained.

[0044] Example 2 No-flowback acidification working fluid 2#

[0045] (1) Preparation of organophosphoric acid polymers:

[0046] The isopropylene phosphonic acid monomer is diluted with water to a 50% aqueous solution and heated to 80°C; a mixture of ammonium persulfate and acrylic acid is dripped into the aqueous solution, the molar ratio of the isopropylene phosphonic acid monomer to the acrylic acid is 1.2:1, and the amount of ammonium persulfate is 20% of the isopropylene phosphonic acid monomer and the acrylic acid, and the reaction is continued to obtain an organic phosphoric acid polymer.

[0047] (2) Raw material preparation: prepare, by weight percentage, 12% octylphenol polyoxyethylene ether, 7% sodium gluconate, 15% a mixture of lactic acid and gluconic acid, the remainder being water; the molar ratio of lactic acid to gluconic acid is 2:1, 10% organic phosphate polymer, 3% hydrochloric acid, 1% cationic gemini surfactant, the remainder being water;

[0048] (3) Preparation of pretreatment solution:

[0049] Sodium gluconate was added into water, stirred at room temperature for 10 min, octylphenol polyoxyethylene ether was added, the temperature was raised to 40°C, stirred for 25 min, and the temperature was naturally lowered to room temperature to obtain a pretreatment solution;

[0050] (4) Preparation of composite acid solution:

[0051] Lactic acid, gluconic acid, organic phosphoric acid polymer and hydrochloric acid were added to water in sequence, stirred at 40°C for 25 minutes, cooled naturally to room temperature, and cationic gemini surfactant was added, stirred for 20 minutes to obtain a composite acid solution. The volume ratio of the pretreatment solution to the composite acid solution was 1:4, and the non-flowback acidification working solution 2# was obtained.

[0052] Example 3 No-flowback acidification working fluid 3#

[0053] (1) Preparation of organophosphoric acid polymers:

[0054] The isopropylene phosphonic acid monomer is diluted with water to a 50% aqueous solution and heated to 75°C; a mixture of ammonium persulfate and acrylic acid is dripped into the aqueous solution, the molar ratio of the isopropylene phosphonic acid monomer to the acrylic acid is 1.1:1, and the amount of ammonium persulfate is 18% of the isopropylene phosphonic acid monomer and the acrylic acid, and the reaction is continued to obtain an organic phosphoric acid polymer.

[0055] (2) Raw material preparation: prepare 8% octylphenol polyoxyethylene ether, 5% sodium gluconate, 12% lactic acid and gluconic acid mixture according to weight percentage, and the balance is water; the molar ratio of lactic acid to gluconic acid is 1:1.5, 8% organic phosphoric acid polymer, 2% hydrochloric acid, 0.5% cationic gemini surfactant, and the balance is water;

[0056] (3) Preparation of pretreatment solution:

[0057] Sodium gluconate was added into water, stirred at room temperature for 8 minutes, octylphenol polyoxyethylene ether was added, the temperature was raised to 37°C, stirred for 25 minutes, and the temperature was naturally lowered to room temperature to obtain a pretreatment solution;

[0058] (4) Preparation of composite acid solution:

[0059] Add lactic acid, gluconic acid, organic phosphoric acid polymer and hydrochloric acid into water in turn, stir at 35°C for 20 minutes, cool naturally to room temperature, add cationic gemini surfactant, and stir for 15 minutes to obtain a composite acid solution. The volume ratio of the pretreatment solution to the composite acid solution is 1:2 to obtain a non-flowback acidification working solution 3#.

[0060] Example 4 No-flowback acidification working fluid 4#

[0061] (1) Preparation of organophosphoric acid polymers:

[0062] The isopropylene phosphonic acid monomer is diluted with water to a 50% aqueous solution and heated to 70°C; a mixture of ammonium persulfate and acrylic acid is dripped into the aqueous solution, the molar ratio of the isopropylene phosphonic acid monomer to the acrylic acid is 1:1, and the amount of ammonium persulfate is 15% of the isopropylene phosphonic acid monomer and the acrylic acid, and the reaction is continued to obtain an organic phosphoric acid polymer.

[0063] (2) Raw material preparation: prepare, by weight percentage, 12% octylphenol polyoxyethylene ether, 7% sodium gluconate, 15% a mixture of lactic acid and gluconic acid, the remainder being water; the molar ratio of lactic acid to gluconic acid is 1:1, 8% organic phosphate polymer, 1% hydrochloric acid, 0.5% cationic gemini surfactant, the remainder being water;

[0064] (3) Preparation of pretreatment solution:

[0065] Sodium gluconate was added into water, stirred at room temperature for 10 min, octylphenol polyoxyethylene ether was added, the temperature was raised to 35°C, stirred for 20 min, and the temperature was naturally lowered to room temperature to obtain a pretreatment solution;

[0066] (4) Preparation of composite acid solution:

[0067] Add lactic acid, gluconic acid, organic phosphoric acid polymer and hydrochloric acid into water in turn, stir at 35°C for 20 minutes, cool naturally to room temperature, add cationic gemini surfactant, and stir for 15 minutes to obtain a composite acid solution. The volume ratio of the pretreatment solution to the composite acid solution is 1:1, and the non-flowback acidification working solution 4# is obtained.

[0068] Example 5 No-flowback acidification working fluid 5#

[0069] Compared with Example 4, Example 5 differs in that the molar ratio of lactic acid to gluconic acid is 3:1, and the rest are the same.

[0070] Example 6 No-flowback acidification working fluid 6#

[0071] Compared with Example 4, Example 6 differs in that the volume ratio of the pretreatment liquid to the composite acid liquid is 1:10, and the rest are the same.

[0072] Comparative Example 1: No-flowback acidification working fluid D1#

[0073] The difference between Comparative Example 1 and Example 4 is that 8% of the organic phosphoric acid polymer is not included and the weight percentage of hydrochloric acid is 9%.

[0074] Comparative Example 2: No-flowback acidification working fluid D2#

[0075] The difference between Comparative Example 2 and Example 4 is that the surfactant is sodium dodecyl sulfate, and the rest are the same.

[0076] Comparative Example 3: No-flowback acidification working fluid D3#

[0077] The difference between Comparative Example 3 and Example 4 is that the pretreatment liquid is not included, and the rest are the same.

[0078] Experimental Example 1 Evaluation of Dissolution Performance

[0079] First, a disodium EDTA standard solution with a concentration of 0.01 mol / L was prepared; then 100 mL of the composite acid solution in Examples 1 to 5 and Comparative Examples 1 to 2 were prepared respectively; then 6 g of carbonate rock particles were added to the composite acid solution, and after a certain reaction time, the solution was titrated with the disodium EDTA standard solution to determine the calcium ion concentration after a certain reaction time, and the dissolution rate of the composite acid solution on the carbonate rock particles was calculated. The calculation results are shown in Table 1.

[0080] Table 1 Evaluation results of dissolution performance

[0081]

[0082] Experimental Example 2 Evaluation of retarding performance

[0083] The polished and dried carbonate core column (φ 2.5×1 cm) was fixed on the rotating shaft handle in the reactor of the ZDJ-1 acid-rock reaction rotating rock plate instrument, and the dissolution rate of the core was tested in the composite acid solution of Examples 1 to 5 and Comparative Example 1 for 1h, 3h, 8h, and 16h at 80°C and 7 MPa. The results are shown in Table 2.

[0084] Table 2 Evaluation results of retarding performance

[0085]

[0086] Experimental Example 3: Yield Increase Experiment

[0087] The non-flowback acidizing working fluids in Examples 4 to 6 and Comparative Examples 1 to 3 were applied to the wells, and the production increase effects were shown in Table 3.

[0088] Table 3 Results of yield increase experiment

[0089]

[0090] The above is only the embodiment of the present application, and the protection scope of the present application is not limited by these specific embodiments, but is determined by the claims of the present application. For those skilled in the art, the present application can have various changes and variations. Any modification, equivalent replacement, improvement, etc. made within the technical ideas and principles of the present application should be included in the protection scope of the present application.

Claims

1. A non-flowback acidification working fluid, characterized in that: The invention comprises a pretreatment liquid and a composite acid liquid, wherein the volume ratio of the pretreatment liquid to the composite acid liquid is 1:(2-10); the composite acid liquid comprises an organic acid, hydrochloric acid and a cationic gemini surfactant; in terms of weight percentage, the composite acid liquid comprises 15-25% of an organic acid, 1%-3% of hydrochloric acid, 0.2%-1% of a cationic gemini surfactant, and the remainder is water; in terms of weight percentage, the organic acid comprises a mixture of lactic acid and gluconic acid and an organic phosphate polymer, wherein the mixture of lactic acid and gluconic acid accounts for 10-15% of the composite acid liquid; the organic phosphate polymer accounts for 5%-10% of the composite acid liquid; the pretreatment liquid comprises 5-12% of octylphenol polyoxyethylene ether, 2%-7% of sodium gluconate, and the remainder is water; the molar ratio of lactic acid to gluconic acid is (1-2):(1-1.5); the organic phosphate polymer is polymerized from isopropylene phosphonic acid monomer and acrylic acid; the molecular formula of the cationic gemini surfactant is as follows (1): Formula (1).

2. The non-flowback acidification working fluid according to claim 1, characterized in that: The volume ratio of the pretreatment liquid to the composite acid liquid is 1:(2~4).

3. The non-flowback acidification working fluid according to claim 1, characterized in that: The preparation process of the organophosphoric acid polymer comprises the following steps: (1) Dilute the isopropylene phosphonic acid monomer with water to a 50% aqueous solution and heat to 70-80°C; (2) A mixture of ammonium persulfate and acrylic acid is dropped into an aqueous solution and the reaction is continued to obtain an organophosphoric acid polymer.

4. The non-flowback acidification working fluid according to claim 3, characterized in that: The molar ratio of isopropylene phosphonic acid monomer to acrylic acid is 1-1.2:1, and the amount of ammonium persulfate used is 15-20% of the isopropylene phosphonic acid monomer to acrylic acid.

5. The method for preparing the non-flowback acidification working fluid according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Preparation of pretreatment solution: sodium gluconate was added to water, stirred at room temperature for 5-10 minutes, octylphenol polyoxyethylene ether was added, the temperature was raised to 35-40° C., stirred for 20-25 minutes, and the temperature was naturally lowered to room temperature to obtain a pretreatment solution; (2) Preparation of composite acid solution: Add lactic acid, gluconic acid, organic phosphate polymer and hydrochloric acid into water in sequence, stir at 35-40°C for 20-25 minutes, cool naturally to room temperature, add cationic gemini surfactant, stir for 10-20 minutes to obtain composite acid solution.

6. The construction process of the non-flowback acidification working fluid according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) Inject the pretreatment fluid into the casing annulus of the test oil well; (2) Inject the composite acid 3-5 hours after injection, and then shut down the well for 24-72 hours.

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