Fracturing fluid low-temperature gel breaker as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil exploitation fracturing, and particularly relates to a fracturing fluid low-temperature gel breaker and a preparation method and application thereof. The preparation method comprises the following steps: adding cumyl hydroperoxide and tetrahydrofuran into a reactor, cooling to 5 DEG C or below in an ice bath, slowly dropwise adding a tetrahydrofuran solution of succinyl chloride and sodium ethoxide, maintaining the temperature to be lower than 10 DEG C and the pH to be 6-7, and continuously reacting for 5-10 minutes after dropwise adding; 2, 5-dimethyl n-hexane-2, 5-dimethyl hydroxyl peroxide and tetrahydrofuran are mixed evenly, the temperature is reduced to 5 DEG C or below, the mixture is slowly and dropwise added into the reactor, meanwhile, a tetrahydrofuran solution of sodium ethoxide is dropwise added, the temperature is kept to be lower than 20 DEG C, the pH is kept to be 6-7, and after dropwise adding is completed, the reaction continues to be conducted for 10-20 min; and carrying out reduced pressure distillation on the mixed solution at 60 DEG C until no solvent exists, recrystallizing with cyclohexane, and drying to obtain the product gel breaker. The gel breaker disclosed by the invention has a good gel breaking effect under a low-temperature condition.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum exploitation and fracturing, and in particular relates to a low-temperature gel breaker for fracturing fluid and a preparation method and application thereof. Background Art

[0002] With the rapid increase in demand for oil and gas resources, China's main oil and gas production is gradually shifting from conventional oil and gas resources to unconventional oil and gas resources. As an important reservoir transformation technology, hydraulic fracturing plays an important role in the development of unconventional oil and gas reservoirs.

[0003] The fracturing process is to squeeze a high-pressure, large-volume liquid with a certain viscosity into the oil layer, and after many cracks are created in the oil layer, proppant is added to fill the cracks to improve the permeability of the oil layer, thereby increasing the water injection volume or oil production.

[0004] After the fracturing operation is completed, how to use effective process technology to minimize the damage of foreign substances to the formation and supporting cracks during the construction process and reduce the displacement pressure gradient from the reservoir to the bottom of the well is the key to increasing production. Among them, the degree of fracturing fluid gel breaking 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 high-molecular 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.

[0005] Therefore, after the fracturing operation is completed, choosing the right breaker to break the gel and flow back in a timely and thorough manner is a key link in determining whether the fracturing is successful or not.

[0006] However, some oil wells often have lower temperatures, and conventional breakers are difficult to meet the needs. Research on the breaking of low-temperature oil and gas well fracturing fluids is of great significance and plays an important role in improving the ultimate recovery rate of oil fields.

[0007] CN112322271B discloses a low-temperature gel-breaking activator and a method of using the same. The gel-breaking activator includes 0.2-0.5% ferrous acetylacetonate; 0.3-0.8% ferrous sulfate; 0.5-3% glucose; and the rest is water. In a system of hydroxypropyl guar gum and carboxymethyl guar gum, when ammonium persulfate or hydrogen peroxide is used as a gel-breaking agent, at low temperatures of 30°C and 40°C, adding 0.1%-0.4% of a gel-breaking activator can achieve gel-breaking in 3-4 hours, and the viscosity of the fracturing fluid after gel-breaking is ≤5mPa·s. The gel-breaking activator of the invention reduces the amount of addition, enhances the applicability of the gel-breaking activator, breaks the gel thoroughly, reduces the impact of peroxides on the environment, and meets the requirements of oil field fracturing construction. However, the low-temperature gel-breaking activator of the invention contains Fe 2+ After the gel is broken, Fe(OH)3 precipitation will be generated, which may affect the formation and construction process. Summary of the invention

[0008] The present invention aims to solve the above-mentioned deficiencies in the prior art and provides a low-temperature gel breaker for fracturing fluid and a preparation method and application thereof. The gel breaker of the present invention has a good gel breaking effect under low temperature conditions.

[0009] One of the purposes of the present invention is to disclose a method for preparing a low-temperature breaker for fracturing fluid, the specific steps of which are as follows:

[0010] (1) adding cumene hydroperoxide and tetrahydrofuran into a reactor, cooling the reactor to below 5°C in an ice bath, slowly adding a tetrahydrofuran solution of succinyl chloride and sodium ethoxide dropwise, maintaining the temperature below 10°C and the pH value at 6-7, and continuing the reaction for 5-10 minutes after the addition is complete;

[0011] (2) 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and tetrahydrofuran are mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and a tetrahydrofuran solution of sodium ethoxide is dripped at the same time, maintaining the temperature below 20° C. and the pH value at 6-7. After the dripping is completed, the reaction is continued for 10-20 minutes;

[0012] (3) 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.

[0013] In the present invention, preferably, based on 1 mole of cumene hydroperoxide, the amounts of succinyl chloride and 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide are 0.8-1.2 mole parts and 0.4-0.6 mole parts, respectively.

[0014] In the present invention, preferably, based on 1 part by mass of cumene hydroperoxide, the amount of tetrahydrofuran in step (1) and step (2) is 8-10 parts by mass and 5-6 parts by mass, respectively.

[0015] The synthesis equation of the low-temperature breaker of the fracturing fluid of the present invention is as follows:

[0016]

[0017] Another object of the present invention is to disclose a low-temperature breaker for fracturing fluid, the molecular structure of the breaker is as follows:

[0018]

[0019] The third object of the present invention is to disclose the application of the above-mentioned breaker in fracturing fluid.

[0020] The low-temperature gel breaker for the fracturing fluid of the present invention belongs to the Gemi strong oxidant, and contains two symmetrical peroxide bonds and two peroxyester bonds in the molecule. The effect of Gemi chemical agents is usually multiplied by that of ordinary chemical agents. At a relatively low temperature, the present invention can achieve better gel breaking for the fracturing fluid. The principle is that the peroxide bonds and peroxyester bonds act on the glycosidic bonds in the guar gum molecules in the fracturing fluid to break them, thereby greatly reducing the viscosity of the fracturing fluid and discharging it from the formation. The low-temperature gel breaker for the fracturing fluid of the present invention has a good gel breaking effect. At a concentration of 200 mg / L of the gel breaker at 40°C, the apparent viscosity of the 5-minute broken gel liquid can reach a minimum of 3.3 mPa. · s. The apparent viscosity of the 30-min degelling liquid can reach a minimum of 1.4 mPa · s. DETAILED DESCRIPTION

[0021] 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.

[0022] The present invention will be further described below with reference to specific embodiments.

[0023] Example 1

[0024] (1) Add 50 mmol of cumene hydroperoxide and 60.8 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 40 mmol of succinyl chloride and 30 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 5 min after the dropwise addition is complete;

[0025] (2) 25 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 42.6 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and at the same time, a 40 wt % solution of sodium ethoxide in tetrahydrofuran was dripped, the temperature was maintained below 20° C. and the pH was 6-7, and the reaction was continued for 10 min after the dripping was completed;

[0026] (3) 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.

[0027] Example 2

[0028] (1) Add 50 mmol of cumene hydroperoxide and 73 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 60 mmol of succinyl chloride and 40 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 6 min after the dropwise addition is complete;

[0029] (2) 20 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 38 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and at the same time, a 30 wt % solution of sodium ethoxide in tetrahydrofuran was dripped, the temperature was maintained below 20° C. and the pH was 6-7, and the reaction was continued for 15 min after the dripping was completed;

[0030] (3) 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.

[0031] Example 3

[0032] (1) Add 50 mmol of cumene hydroperoxide and 68.8 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 45 mmol of succinyl chloride and 40 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 8 min after the dropwise addition is complete;

[0033] (2) 30 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 45.6 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and at the same time, a 40 wt % solution of sodium ethoxide in tetrahydrofuran was dripped, the temperature was maintained below 20° C. and the pH was 6-7, and the reaction was continued for 12 min after the dripping was completed;

[0034] (3) 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.

[0035] Example 4

[0036] (1) Add 50 mmol of cumene hydroperoxide and 71.8 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 55 mmol of succinyl chloride and 35 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 10 min after the dropwise addition is complete;

[0037] (2) 22 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 40 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and at the same time, a 35 wt % solution of sodium ethoxide in tetrahydrofuran was dripped, the temperature was maintained below 20° C. and the pH was 6-7, and the reaction was continued for 18 min after the dripping was completed;

[0038] (3) 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.

[0039] Example 5

[0040] (1) Add 50 mmol of cumene hydroperoxide and 73 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 48 mmol of succinyl chloride and 30 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 5 min after the dropwise addition is complete;

[0041] (2) 27 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 39.8 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and at the same time, a 40 wt % solution of sodium ethoxide in tetrahydrofuran was dripped, the temperature was maintained below 20° C. and the pH was 6-7, and the reaction was continued for 10 min after the dripping was completed;

[0042] (3) 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.

[0043] Example 6

[0044] (1) Add 50 mmol of cumene hydroperoxide and 74.6 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 53 mmol of succinyl chloride and 40 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 7 min after the dropwise addition is complete;

[0045] (2) 23 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 42.4 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., 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 18 min;

[0046] (3) 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.

[0047] Example 7

[0048] (1) Add 50 mmol of cumene hydroperoxide and 75 g of tetrahydrofuran into a reactor, cool to below 5° C. in an ice bath, slowly dropwise add 50 mmol of succinyl chloride and 35 wt % of a tetrahydrofuran solution of sodium ethoxide, maintain the temperature below 10° C. and pH 6-7, and continue the reaction for 10 min after the dropwise addition is complete;

[0049] (2) 25 mmol of 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and 44 g of tetrahydrofuran were mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and at the same time, a 30 wt % solution of sodium ethoxide in tetrahydrofuran was dripped, the temperature was maintained below 20° C. and the pH was 6-7, and the reaction was continued for 15 min after the dripping was completed;

[0050] (3) 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.

[0051] Example 8 Gel breaking performance test

[0052] 500 mL of 40° C. deionized water was measured and poured into a sterile mixer. The mixer was stirred at a speed of 3000 rpm. 3.0 g of hydroxypropyl guar gum was slowly added and stirred evenly. After standing for 1 h, the speed was adjusted to 500 rpm. 2 g of DRKJ-04 organic boron crosslinker from Zhengzhou Derong Technology Co., Ltd. was quickly added. After 30 s, 1 g of 10 wt% of the breaker of the present invention (Example 1-7) was added and stirred evenly. The mixture was placed in an oven at 40° C. and samples were taken from time to time. The mixture was measured using a Fann-35 rotational viscometer at a shear rate of 170 s - The viscosity was tested under the conditions of . The viscosity at 0 min was tested without adding the fracturing fluid of the present invention, and a comparative experiment was conducted with potassium persulfate of the same concentration. The test results are shown in Table 1.

[0053] Table 1 Viscosity of degelling liquid at different times (mPa·s)

[0054]

[0055]

[0056] From Table 1 we can see that:

[0057] The debonding agent of the present invention (Examples 1-7) can effectively break the fracturing fluid at 40°C, and the viscosity of the debonding fluid can be less than 5 mPa·s within 5 minutes to achieve rapid debonding. However, the comparative example cannot effectively break the fracturing fluid under this condition.

[0058] 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 low-temperature breaker for fracturing fluid, characterized in that: The specific steps of the preparation method are as follows: (1) adding cumene hydroperoxide and tetrahydrofuran into a reactor, cooling the reactor to below 5°C in an ice bath, slowly adding a tetrahydrofuran solution of succinyl chloride and sodium ethoxide dropwise, maintaining the temperature below 10°C and the pH value at 6-7, and continuing the reaction for 5-10 minutes after the addition is complete; (2) 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide and tetrahydrofuran are mixed evenly, cooled to below 5° C., and slowly dripped into the reactor of step (1), and a tetrahydrofuran solution of sodium ethoxide is dripped at the same time, maintaining the temperature below 20° C. and the pH value at 6-7. After the dripping is completed, the reaction is continued for 10-20 minutes; (3) distilling the mixed solution under reduced pressure at 60° C. until there is no solvent, recrystallizing it with cyclohexane, and drying it to obtain a product breaker; Based on 1 mole of cumene hydroperoxide, the amounts of succinyl chloride and 2,5-dimethyl-n-hexane-2,5-dimethylhydroxyperoxide are 0.8-1.2 mole and 0.4-0.6 mole, respectively.

2. The preparation method according to claim 1, characterized in that: Based on 1 part by mass of cumene hydroperoxide, the amount of tetrahydrofuran in step (1) is 8-10 parts by mass.

3. The preparation method according to claim 1, characterized in that: Based on 1 part by mass of cumene hydroperoxide, the amount of tetrahydrofuran in step (2) is 5-6 parts by mass.

4. The gel breaker prepared by the preparation method according to any one of claims 1 to 3, characterized in that: The molecular structure of the debonding agent is as follows:

5. Use of the gel breaker according to claim 4 in fracturing fluid.

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