Capsule breaker for oilfield fracturing and its preparation method and application

Abstract

The present invention belongs to the technical field of oil production fracturing, and specifically relates to a capsule breaker for oilfield fracturing and its preparation method and application. The preparation method is as follows: add cyclohexanone peroxide and the first tetrahydrofuran in a reactor, stir evenly, add isonicotinic acid chloride and the second tetrahydrofuran in another container, add the tetrahydrofuran solution of isonicotinic acid chloride dropwise to the tetrahydrofuran solution of cyclohexanone oxide, and control pH 6-7; add HB-620 type fumed silica to the above-mentioned mixed solution, soak for 12-24h, and distill off the tetrahydrofuran under reduced pressure; add German Roma acrylic resin to toluene, heat and dissolve to obtain a toluene solution; add the toluene solution to the above-mentioned reactor, stir evenly, distill under reduced pressure to no solvent, dry, and grind to obtain a capsule breaker. The breaker of the present invention has the advantages of good breaking effect and controllable breaking time.

Description

Technical Field

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

[0002] After the fracturing operation is completed, it is required to add a debonding agent to break the gel. The main function of the fracturing fluid debonding agent is to quickly reduce the viscosity of the fracturing fluid after the fracturing operation and enhance its fluidity. The principle is to accelerate the return and removal of the 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. If the degree of debonding of the fracturing fluid is not enough and there is still a certain viscosity, it is bound to be difficult to return. The liquid will remain in the formation for a long time, making the viscous fracturing fluid and residue firmly wrapped on the surface of the proppant and blocking the cracks, causing the permeability of the cracks and proppant pores to decrease, causing temporary or even permanent damage to the reservoir.

[0003] 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.

[0004] CN112322271B discloses a low-temperature gel-breaking activator and a method of using the same. The gel-breaking activator includes ferrous acetylacetonate, 0.2-0.5%; ferrous sulfate, 0.3-0.8%; glucose, 0.5-3%; 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.

[0005] CN103980874B discloses a guar gum fracturing fluid breaker and its preparation method and application, which belongs to the field of oilfield fracturing fluid. The preparation method comprises the following steps: adding a solvent to a reactor or a mixer; turning on the agitator, adding amylase, reacting for 1-30 minutes; adding oxidase, reacting for 1-30 minutes; adding mannanase, reacting for 1-30 minutes; adding an activator, reacting for 10-60 minutes; adding cellulase, reacting for 10-60 minutes. The guar gum fracturing fluid breaker of the invention is mainly used in oilfield fracturing, and the usage amount is 0.01-3% of the total amount of fracturing fluid. The invention is beneficial in that the guar gum fracturing fluid breaker can overcome the incomplete breaking of ammonium persulfate, the large amount of residue, and the generation of sulfate ions that are easy to precipitate barium and strontium in the formation and cause formation damage, and can also solve the problem of ammonium persulfate corrosion to pipeline equipment. However, the guar gum fracturing fluid breaker of the invention can only be used for a single guar gum fracturing fluid, and is relatively demanding on formation conditions, temperature, and pH. The breaker is easily deactivated, and the preparation method is relatively complicated. Summary of the invention

[0006] The present invention aims at the deficiencies of the above-mentioned prior art and provides a capsule breaker for oilfield fracturing and a preparation method and application thereof. The breaker of the present invention has the advantages of good breaking effect and controllable breaking time.

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

[0008] (1) Add cyclohexanone peroxide and the first tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add isonicotinic acid chloride and the second tetrahydrofuran into another container, stir and cool to below 5°C; dropwise add the tetrahydrofuran solution of isonicotinic acid chloride into the tetrahydrofuran solution of cyclohexanone oxide, control the temperature below 30°C during the dropwise addition process, and control the pH to 6-7 with a sodium hydroxide solution;

[0009] (2) Add HB-620 fumed silica to the above mixed solution, soak for 12-24 hours, and distill off tetrahydrofuran under reduced pressure;

[0010] (3) Add German Rohm acrylic resin DEGALAN 66 / 02N to toluene, heat and dissolve to obtain a toluene solution;

[0011] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 60-65°C until there is no solvent, dry at 80-85°C, and grind to obtain a capsule breaker.

[0012] In the present invention, preferably, based on 1 mole of cyclohexanone peroxide, the isonicotinic acid chloride is 0.8-1.2 mole parts.

[0013] In the present invention, preferably, in step (1), the mass ratio of the first tetrahydrofuran, the second tetrahydrofuran and cyclohexanone peroxide is 4-5:4-5:1.

[0014] In the present invention, preferably, the mass ratio of the HB-620 fumed silica to the cyclohexanone peroxide in step (2) is 1-1.5:1.

[0015] In the present invention, preferably, the mass ratio of the German Rohm acrylic resin DEGALAN 66 / 02N to cyclohexanone peroxide in step (3) is 0.1-0.15:1.

[0016] The synthesis formula of the capsule breaker of the present invention is as follows:

[0017]

[0018] Another object of the present invention is to disclose a capsule breaker for oilfield fracturing, wherein the molecular structure of the capsule breaker is as follows:

[0019] .

[0020] The third object of the present invention is to disclose the application of the above-mentioned capsule breaker in oil field fracturing.

[0021] The molecule of the capsule breaker of the present invention contains a peroxide bond and a peroxy ester bond, both of which have strong oxidizing ability and act on the glycosidic bond in the guar gum molecule to break it, thereby greatly reducing the viscosity of the fracturing fluid and discharging it from the formation; HB-620 type fumed silica can play the role of a carrier and a dispersant; acrylic resin has thermoplasticity and can play the role of capsule coating, which can delay the release of the main components of the breaker and thus control the fracturing fluid breaking time, and can achieve complete breaking within 90-240 minutes (viscosity is less than 5mPa•s). DETAILED DESCRIPTION

[0022] 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.

[0023] The present invention will be further described below with reference to specific embodiments.

[0024] Example 1

[0025] (1) Add 50 mmol of cyclohexanone peroxide and 49.2 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 40 mmol of isonicotinoyl chloride and 49.2 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone oxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0026] (2) Add 18.45 g of HB-620 fumed silica to the above mixed solution, soak for 12 hours, and distill off tetrahydrofuran under reduced pressure;

[0027] (3) Add 1.84 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0028] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 60° C. until there is no solvent, dry at 80° C., grind, and obtain a capsule breaker for fracturing.

[0029] Example 2

[0030] (1) Add 50 mmol of cyclohexanone peroxide and 58.8 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 60 mmol of isonicotinoyl chloride and 61.5 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone oxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0031] (2) Add 16.13 g of HB-620 fumed silica to the above mixed solution, soak for 12 hours, and distill off tetrahydrofuran under reduced pressure;

[0032] (3) Add 1.64 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0033] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 65° C. until there is no solvent, dry at 82° C., grind, and obtain a capsule breaker for fracturing.

[0034] Example 3

[0035] (1) Add 50 mmol of cyclohexanone peroxide and 53.3 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 43 mmol of isonicotinoyl chloride and 54.5 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone oxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0036] (2) Add 14.98 g of HB-620 fumed silica to the above mixed solution, soak for 20 hours, and distill off tetrahydrofuran under reduced pressure;

[0037] (3) Add 1.54 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0038] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 62° C. until there is no solvent, dry at 81° C., grind, and obtain a capsule breaker for fracturing.

[0039] Example 4

[0040] (1) Add 50 mmol of cyclohexanone peroxide and 61.5 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 56 mmol of isonicotinoyl chloride and 56.2 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone peroxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0041] (2) Add 14.14 g of HB-620 fumed silica to the above mixed solution, soak for 16 h, and distill off tetrahydrofuran under reduced pressure;

[0042] (3) Add 1.44 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0043] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 63° C. until there is no solvent, dry at 80° C., grind, and obtain a capsule breaker for fracturing.

[0044] Example 5

[0045] (1) Add 50 mmol of cyclohexanone peroxide and 55.3 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 47 mmol of isonicotinoyl chloride and 60 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone peroxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0046] (2) Add 13.45 g of HB-620 fumed silica to the above mixed solution, soak for 18 hours, and distill off tetrahydrofuran under reduced pressure;

[0047] (3) Add 1.35 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0048] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 61° C. until there is no solvent, dry at 83° C., grind, and obtain a capsule breaker for fracturing.

[0049] Example 6

[0050] (1) Add 50 mmol of cyclohexanone peroxide and 54.7 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 52 mmol of isonicotinoyl chloride and 52 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone oxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0051] (2) Add 12.98 g of HB-620 fumed silica to the above mixed solution, soak for 18 hours, and distill off tetrahydrofuran under reduced pressure;

[0052] (3) Add 1.28 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0053] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 64°C until there is no solvent, dry at 82°C, and grind to obtain a capsule breaker for fracturing.

[0054] Example 7

[0055] (1) Add 50 mmol of cyclohexanone peroxide and 59.2 g of tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add 50 mmol of isonicotinoyl chloride and 51.2 g of tetrahydrofuran into another container, stir and cool to below 5°C; add the tetrahydrofuran solution of isonicotinoyl chloride dropwise to the tetrahydrofuran solution of cyclohexanone peroxide, control the temperature below 30°C during the addition process, and control the pH to 6-7 with a 30 wt% sodium hydroxide solution;

[0056] (2) Add 12.3 g of HB-620 fumed silica to the above mixed solution, soak for 24 hours, and distill off tetrahydrofuran under reduced pressure;

[0057] (3) Add 1.23 g of German Rohm acrylic resin DEGALAN 66 / 02N to toluene and heat to dissolve to obtain a toluene solution;

[0058] (4) Add the toluene solution of step (3) into the reactor of step (2), stir evenly, distill under reduced pressure at 60° C. until there is no solvent, dry at 85° C., grind, and obtain a capsule breaker for fracturing.

[0059] Example 8 Gel breaking performance test

[0060] The evaluation method refers to Q / SH1020 2381-2020 "Technical Requirements for Capsule Breakers for Fracturing Fluids" and tests the viscosity of the breaking fluid at different times.

[0061] 500 mL of 80°C water was measured and poured into a sterile mixer. The mixer was stirred at a speed of 3000 rpm. 3.0 g of commercially available hydroxypropyl guar gum was added and stirred evenly. The mixture was allowed to stand for 1 h. The speed was adjusted to 500 rpm. 2 g of boron crosslinking agent from Shaanxi Yanchang Petroleum Energy Technology Co., Ltd. was quickly added. After 30 s, 0.1 g of the capsule breaker of the present invention (Example 1-7) was added and stirred evenly. The mixture was placed in an oven at 80°C and the viscosity was measured from time to time using a Fann-35 type rotational viscometer at a shear rate of 170 s -1 The viscosity was tested under the conditions of

[0062] Potassium persulfate was used for comparative experiments, and the test results are shown in Table 1.

[0063] Table 1 Viscosity of degelling liquid at different times (mPa•s)

[0064] 0 min 20 min 40 min 60 min 90 min 120 min Example 1 680 680 680 675 640 450 Example 2 680 680 670 665 580 380 Example 3 680 675 650 580 380 248 Example 4 680 665 610 480 245 110 Example 5 680 660 550 285 115 5 Example 6 680 655 475 120 6.8 3.3 Example 7 680 650 295 15 4 2.5 Comparative Example 680 18 5.3 4.5 4 4

[0065] Table 2 Viscosity of degelling liquid at different times (mPa•s)

[0066] 150 min 180 min 210 min 240 min 300min 360 min Example 1 270 154 60 4.8 2.4 1.8 Example 2 218 125 49 4.2 2.3 1.8 Example 3 148 45 20 10 2.3 2 Example 4 4 3.5 2.8 2.5 2 1.8 Example 5 3.6 3 2.5 2 1.8 1.7 Example 6 3 2.3 1.9 1.7 1.7 1.5 Example 7 2 1.8 1.6 1.5 1.5 1.4 Comparative Example 4 3.9 3.9 3.9 3.9 3.9

[0067] From Tables 1 and 2 we can see that:

[0068] The breaking time of the breaker of the present invention is controllable, and complete breaking can be achieved within 90-240 minutes (viscosity is less than 5 mPa•s); while the comparative example completely breaks the gel within 60 minutes, and the breaking speed is too fast and cannot be controlled.

[0069] 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 capsule breaker for oilfield fracturing, characterized in that: The specific steps of the preparation method are as follows: (1) Add cyclohexanone peroxide and the first tetrahydrofuran into a reactor, stir evenly, and cool to below 5°C in an ice bath; add isonicotinic acid chloride and the second tetrahydrofuran into another container, stir and cool to below 5°C; dropwise add the tetrahydrofuran solution of isonicotinic acid chloride into the tetrahydrofuran solution of cyclohexanone oxide, control the temperature below 30°C during the dropwise addition process, and control the pH to 6-7 with a sodium hydroxide solution; (2) Add HB-620 fumed silica to the above mixed solution, soak for 12-24 hours, and distill off tetrahydrofuran under reduced pressure; (3) Add German Rohm acrylic resin DEGALAN 66 / 02N to toluene, heat and dissolve to obtain a toluene solution; (4) adding the toluene solution of step (3) into the reactor of step (2), stirring evenly, distilling under reduced pressure at 60-65° C. until there is no solvent, drying at 80-85° C., and grinding to obtain a capsule breaker; Based on 1 mole of cyclohexanone peroxide, the isonicotinic acid chloride is 0.8-1.2 mole parts; In step (1), the mass ratio of the first tetrahydrofuran, the second tetrahydrofuran and cyclohexanone peroxide is 4-5:4-5:1; The mass ratio of HB-620 fumed silica to cyclohexanone peroxide in step (2) is 1-1.5:1; The mass ratio of the German Rohm acrylic resin DEGALAN 66 / 02N to cyclohexanone peroxide in step (3) is 0.1-0.15:

1.

2. Application of the capsule breaker prepared by the preparation method according to claim 1 in oil field fracturing.

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