Gel breaker for oilfield fracturing as well as preparation method and application of gel breaker

Abstract

The invention belongs to the technical field of oil exploitation fracturing, and particularly relates to a gel breaker for oil field fracturing and a preparation method and application thereof. The preparation method comprises the following steps: adding 1, 3, 5-tribenzoyl chloride and tetrahydrofuran into a reactor, dropwise adding a tetrahydrofuran solution of tert-butyl hydroperoxide and sodium ethoxide, and reacting for 3-5 minutes; cyclohexanone peroxide and tetrahydrofuran are uniformly mixed, a tetrahydrofuran solution of sodium ethoxide is dropwise added, and a reaction is performed for 8-10 min; the preparation method comprises the following steps: uniformly mixing 2-naphthylamine-3, 6, 8-trisulfonic acid and tetrahydrofuran, dropwise adding a tetrahydrofuran solution of sodium ethoxide, and reacting for 30-60 minutes; and carrying out reduced pressure distillation, recrystallization and drying to obtain the product gel breaker. The gel breaker is good in gel breaking effect, and the apparent viscosity of the gel breaker with the concentration of 0.02 wt% can reach 1.2 mPa.s at the minimum 30 min under the condition of 95 DEG C.

Description

Technical Field

[0001] The invention belongs to the technical field of oil extraction fracturing, and in particular relates to a gel breaker for oil field fracturing and a preparation method and application thereof. Background Art

[0002] Most of the domestic oil fields have entered the middle and late stages of water injection development. Due to the heterogeneity of the reservoir, the injected water easily breaks through and flushes along the high permeability layer, further increasing the permeability of the high permeability layer, further expanding the heterogeneity of the reservoir, causing a large amount of water to flow out of the oil well, reducing production capacity and worsening economic benefits. In order to make the injected water advance evenly, reduce the water flow out of the oil well, and improve the oil recovery rate, the most effective method is to inject chemical profile control agents from the water injection well to plug the high permeability layer and adjust the water absorption profile of the water well, that is, to perform fracturing operations.

[0003] The process of oil layer fracturing is to use a fracturing truck to squeeze a high-pressure, high-volume liquid with a certain viscosity into the oil layer. After many cracks are formed in the oil layer, proppants are added to fill the cracks to improve the permeability of the oil layer, so as to increase the water injection volume or oil production. The quality of fracturing directly affects the production increase effect after fracturing measures. How to minimize the damage of foreign substances to the formation and propping cracks during the construction process through effective process technology and reduce the displacement pressure gradient from the reservoir to the bottom of the well is the key to increase production. Among them, the degree of gel breaking of fracturing fluid is one of the key links. Its principle is to accelerate the return and removal of fracturing fluid by decomposing the polymer in the fracturing fluid, which can partially destroy the structure of the polymer and form a mixed state of large molecules and small molecules in the colloid. This mixed state reduces the viscosity of the colloid and improves the drainage capacity.

[0004] After the fracturing operation is completed, it is crucial to choose the right breaker.

[0005] Potassium persulfate is a commonly used degumming agent, but its ability to release oxygen at low temperatures is poor, and it cannot completely degumming the guar fracturing fluid, which will cause residue damage to the formation. In addition, the sulfate ions produced after oxidation will react with the barium and strontium in the formation to produce precipitation and block the formation. Potassium persulfate will also cause corrosion problems for equipment pipelines. Summary of the invention

[0006] The present invention aims at the deficiencies of the current prior art and provides a debonding agent for oilfield fracturing and a preparation method and application thereof. The debonding agent of the present invention has the advantage of good debonding effect.

[0007] One of the purposes of the present invention is to disclose a method for preparing a breaker for oilfield fracturing, and the specific steps of the preparation method are as follows:

[0008] (1) Add 1,3,5-tribenzoyl chloride and tetrahydrofuran into a reactor, cool to below 5°C in an ice bath, slowly drop tert-butyl hydroperoxide and a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 20°C and pH 6-7, and continue the reaction for 3-5 minutes after the dropwise addition is completed;

[0009] (2) mixing cyclohexanone peroxide and tetrahydrofuran evenly, slowly dripping into the reactor of step (1), and simultaneously dripping a tetrahydrofuran solution of sodium ethoxide, maintaining the temperature below 20° C. and the pH 6-7, and continuing the reaction for 8-10 minutes after the dripping is completed;

[0010] (3) 2-naphthylamine-3,6,8-trisulfonic acid and tetrahydrofuran are mixed evenly, and slowly dripped into the reactor of step (1), and a tetrahydrofuran solution of sodium ethoxide is dripped at the same time, while maintaining the temperature below 40° C. and the pH value at 6-7. After the dripping is completed, the reaction is continued for 30-60 minutes;

[0011] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain a product breaker.

[0012] In the present invention, preferably, based on 1 mol part of 1,3,5-tribenzoyl chloride, the tert-butyl hydroperoxide, cyclohexanone peroxide and 2-naphthylamine-3,6,8-trisulfonic acid are 0.8-1.2 mol parts, 0.8-1.2 mol parts and 0.8-1.2 mol parts respectively.

[0013] In the present invention, preferably, based on 1 part by mass of 1,3,5-tribenzoyl chloride, the amount of tetrahydrofuran in step (1), step (2) and step (3) is 4-5 parts by mass, 2-3 parts by mass and 3-4 parts by mass respectively.

[0014] The synthesis equation of the oilfield fracturing breaker of the present invention is as follows:

[0015]

[0016] Another object of the present invention is to disclose a breaker for oilfield fracturing, wherein the molecular structure of the breaker is as follows:

[0017]

[0018] The third object of the present invention is to disclose the application of the above-mentioned breaker in oil field fracturing.

[0019] The molecule of the breaker for oilfield fracturing of the present invention contains a peroxide bond and two peroxy ester bonds, both of which have strong oxidizing ability, and react with the glycosidic bonds in the guar gum molecules to break them, thereby greatly reducing the viscosity of the fracturing fluid and discharging it from the formation. 2-Naphthylamine-3,6,8-trisulfonic acid has strong hydrophilicity, which allows the present invention to fully contact with the water-based fracturing fluid, thereby improving the breaking effect and reducing the breaking time. The breaker of the present invention has a good breaking effect. At a concentration of 0.02wt%, the apparent viscosity of the 30-minute breaking fluid can reach a minimum of 1.2mPa at 95°C. · s. DETAILED DESCRIPTION

[0020] The endpoints and any values ​​of the ranges disclosed in this article 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 each range, the endpoint values ​​of each range and the individual point values, and the 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 article.

[0021] The present invention will be further described below in conjunction with specific embodiments:

[0022] Example 1

[0023] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 21.2 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 16 mmol tert-butyl hydroperoxide and 40 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 3 min after the dropwise addition is completed;

[0024] (2) 20 mmol of cyclohexanone peroxide and 11.7 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 40 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, maintaining the temperature below 20° C. and pH 6-7, and continuing the reaction for 8 min after the dripping was completed;

[0025] (3) 24 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 21.2 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 40 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, while maintaining the temperature below 40° C. and pH 6-7. After the dripping was completed, the reaction was continued for 30 min;

[0026] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A1.

[0027] Example 2

[0028] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 25.2 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 24 mmol tert-butyl hydroperoxide and 35 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 4 min after the dropwise addition is completed;

[0029] (2) 16 mmol of cyclohexanone peroxide and 10.6 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 40 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, maintaining the temperature below 20° C. and pH 6-7, and continuing the reaction for 10 min after the dripping was completed;

[0030] (3) 22 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 20 g of tetrahydrofuran were mixed evenly, and the mixture was slowly dripped into the reactor of step (1), and a 40 wt % solution of sodium ethoxide in tetrahydrofuran was simultaneously dripped, while maintaining the temperature below 40° C. and the pH value at 6-7. After the dripping was completed, the reaction was continued for 60 min;

[0031] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A2.

[0032] Example 3

[0033] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 24.5 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 18 mmol tert-butyl hydroperoxide and 40 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 5 min after the dropwise addition is completed;

[0034] (2) 21 mmol of cyclohexanone peroxide and 13.8 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 40 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, maintaining the temperature below 20° C. and pH 6-7, and continuing the reaction for 8 min after the dripping was completed;

[0035] (3) 21 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 18.4 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 30 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, while maintaining the temperature below 40° C. and pH 6-7. After the dripping was completed, the reaction was continued for 35 min;

[0036] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A3.

[0037] Example 4

[0038] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 26.5 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 22 mmol tert-butyl hydroperoxide and 30 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 5 min after the dropwise addition is completed;

[0039] (2) 19 mmol of cyclohexanone peroxide and 12.3 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 35 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, maintaining the temperature below 20° C. and pH 6-7. After the dripping was completed, the reaction was continued for 9 minutes;

[0040] (3) 20 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 18 g of tetrahydrofuran were mixed evenly, and the mixture was slowly dripped into the reactor of step (1), and a 40 wt % solution of sodium ethoxide in tetrahydrofuran was simultaneously dripped, while maintaining the temperature below 40° C. and the pH value at 6-7. After the dripping was completed, the reaction was continued for 40 min;

[0041] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A4.

[0042] Example 5

[0043] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 23.8 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 19 mmol tert-butyl hydroperoxide and 40 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 3.5 min after the dropwise addition is completed;

[0044] (2) 24 mmol of cyclohexanone peroxide and 15 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 40 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, maintaining the temperature below 20° C. and pH 6-7. After the dripping was completed, the reaction was continued for 9.5 min;

[0045] (3) 18 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 17.1 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 30 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, while maintaining the temperature below 40° C. and pH 6-7. After the dripping was completed, the reaction was continued for 60 min;

[0046] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A5.

[0047] Example 6

[0048] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 24.2 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 21 mmol tert-butyl hydroperoxide and 40 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 5 min after the dropwise addition is completed;

[0049] (2) 23 mmol of cyclohexanone peroxide and 14.8 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 30 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, while maintaining the temperature below 20° C. and pH 6-7. After the dripping was completed, the reaction was continued for 10 min;

[0050] (3) 17 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 16.2 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 35 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, while maintaining the temperature below 40° C. and pH 6-7. After the dripping was completed, the reaction was continued for 60 min;

[0051] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A6.

[0052] Example 7

[0053] (1) Add 20 mmol 1,3,5-tribenzoyl chloride and 25.8 g tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 20 mmol tert-butyl hydroperoxide and 40 wt % sodium ethoxide solution in tetrahydrofuran, maintain the temperature below 20° C. and pH 6-7, and continue the reaction for 3 min after the dropwise addition is completed;

[0054] (2) 24 mmol of cyclohexanone peroxide and 15.9 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 30 wt % of sodium ethoxide tetrahydrofuran solution was dripped at the same time, while maintaining the temperature below 20° C. and pH 6-7. After the dripping was completed, the reaction was continued for 8 min;

[0055] (3) 16 mmol of 2-naphthylamine-3,6,8-trisulfonic acid and 15.9 g of tetrahydrofuran were mixed evenly, and slowly dripped into the reactor of step (1), and 40 wt % of sodium ethoxide solution in tetrahydrofuran was added dropwise at the same time, while maintaining the temperature below 40° C. and pH 6-7. After the addition was completed, the reaction was continued for 50 min;

[0056] (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain the product breaker A7.

[0057] Example 8 Gel breaking performance test

[0058] The fracturing fluid was prepared with reference to SY / T 5107-2005 "Method for evaluating performance of water-based fracturing fluids", with commercially available guar gum being used as the thickener at a concentration of 0.6 wt%, and DRKJ-04 organic boron crosslinker produced by Zhengzhou Derong Technology Co., Ltd. being used as the crosslinker at a concentration of 0.4 wt%.

[0059] The apparent viscosity after breaking was tested with reference to SY / T 6380-2008 "Test method for performance of breakers for fracturing", wherein the amount of the breakers (A1-A7) of the present invention was 200 mg / L, the breaking temperature was 95° C., and the breaking time was 30 min.

[0060] The breaking time was tested with reference to SY / T 6380-2008 “Test method for performance of breakers for fracturing”, wherein the amount of the breakers (A1-A7) of the present invention was 200 mg / L and the breaking temperature was 90°C.

[0061] Potassium persulfate was used for comparative experiments, and the test results are shown in Table 1.

[0062] Table 1 Apparent viscosity and gel breaking time test after gel breaking

[0063]

[0064]

[0065] From Table 1 we can see that:

[0066] (1) The apparent viscosity of the 30-min breaker solution of the breaker (A1-A7) of the present invention at a concentration of 0.02 wt% at 95°C was lower than 1.6 mPa·s, with the lowest reaching 1.2 mPa·s; while the apparent viscosity of the comparative experiment was 4.5 mPa·s, which was significantly higher than that of the present invention;

[0067] (2) When the debonding agent (A1-A7) of the present invention is used at a concentration of 0.02wt% and a debonding temperature of 90°C, the debonding time does not exceed 5min, and the minimum is 4min; while the debonding time of the comparative experiment is 8min, which is significantly higher than that of the present invention.

[0068] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a gel breaker for oilfield fracturing, characterized in that: The specific steps of the preparation method are as follows: (1) Add 1,3,5-tribenzoyl chloride and tetrahydrofuran into a reactor, cool to below 5°C in an ice bath, slowly drop tert-butyl hydroperoxide and a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 20°C and pH 6-7, and continue the reaction for 3-5 minutes after the dropwise addition is completed; (2) mixing cyclohexanone peroxide and tetrahydrofuran evenly, slowly dripping into the reactor of step (1), and simultaneously dripping a tetrahydrofuran solution of sodium ethoxide, maintaining the temperature below 20° C. and the pH 6-7, and continuing the reaction for 8-10 minutes after the dripping is completed; (3) 2-naphthylamine-3,6,8-trisulfonic acid and tetrahydrofuran are mixed evenly, and slowly dripped into the reactor of step (1), and a tetrahydrofuran solution of sodium ethoxide is dripped at the same time, while maintaining the temperature below 40° C. and the pH value at 6-7. After the dripping is completed, the reaction is continued for 30-60 minutes; (4) The mixed solution was distilled under reduced pressure at 60° C. until there was no solvent, recrystallized with cyclohexane, and dried to obtain a product breaker.

2. The preparation method according to claim 1, characterized in that: Based on 1 mol part of 1,3,5-tribenzoyl chloride, the amounts of tert-butyl hydroperoxide, cyclohexanone peroxide and 2-naphthylamine-3,6,8-trisulfonic acid are 0.8-1.2 mol parts, 0.8-1.2 mol parts and 0.8-1.2 mol parts respectively.

3. The preparation method according to claim 1, characterized in that: Based on 1 part by mass of 1,3,5-tribenzoyl chloride, the amount of tetrahydrofuran in step (1) is 4-5 parts by mass.

4. The preparation method according to claim 1, characterized in that: Based on 1 part by mass of 1,3,5-tribenzoyl chloride, the amount of tetrahydrofuran in step (2) is 2-3 parts by mass.

5. The preparation method according to claim 1, characterized in that: Based on 1 part by mass of 1,3,5-tribenzoyl chloride, the amount of tetrahydrofuran in step (3) is 3-4 parts by mass.

6. A gel breaker prepared by the preparation method according to any one of claims 1 to 5, characterized in that: The molecular structure of the breaker is as follows:

7. Use of the gel breaker according to claim 6 in oil field fracturing.

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