Capsule gel breaker as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a capsule gel breaker and a preparation method and application thereof. The preparation method of the capsule gel breaker comprises the following four steps: (1) preparing the main agent of the gel breaker; (2) preparing a gel breaker capsule core; (3) preparing a gel breaker capsule dressing solution; and (4) preparing the capsule gel breaker. The capsule gel breaker has the advantages that the gel breaking effect is good, and the maximum viscosity retention rate reaches 99%; the gel breaking time and temperature are controllable, the gel breaking time can be controlled to be 3-5 h under the condition of 110 DEG C, and the gel breaking time can be controlled to be 1.2-2.5 h under the condition of 130 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of petroleum extraction technology, specifically relating to a capsule de-icing agent, its preparation method, and its application. Background Technology

[0002] In the extraction of energy resources such as oil and natural gas, hydraulic fracturing is a key technology for improving reservoir permeability and oil and gas production. Fracturing fluid (usually a polymer-thickened aqueous solution, such as guar gum fracturing fluid) is pumped into the formation under high pressure, forming fractures and carrying proppant into them. After the operation, the fracturing fluid needs to be broken up, its viscosity reduced, and it flowed back in a timely and thorough manner to create highly conductive oil and gas channels.

[0003] However, the application of conventional breaker agents faces a key contradiction: the timing of breaker breaking is difficult to control precisely. If the breaker is added at the initial stage of fluid preparation or pumping, it may prematurely begin to degrade the fracturing fluid before reaching the target fracture location, causing the fracturing fluid viscosity to drop prematurely, resulting in proppant settling, sand blockage, or even failure of the operation. If the amount of breaker used is reduced or a low-activity breaker is used to delay breaker breaking, it may lead to incomplete breaker breaking, leaving residual breaker and filtrate trapped in the formation, severely damaging the fracture conductivity and reservoir permeability.

[0004] To resolve the contradiction between "instantaneous breaking" and "delayed breaking," capsule breaking technology was developed. Its core idea is to encapsulate the active ingredient of the breaking agent within a special capsule wall material, forming a microcapsule. During fracturing operations, the capsule wall protects the internal breaking agent, isolating it from the fracturing fluid and preventing premature reaction. When fracturing is complete and breaking is necessary, a specific triggering mechanism (such as changes in formation temperature, pressure, pH, release of the breaking agent from the fracturing fluid, or mechanical breakage during flowback) causes the capsule wall to rupture or permeate, releasing the breaking agent and achieving timed, targeted, and controllable breaking.

[0005] CN111394087A discloses a method for preparing a non-oxidizing fracturing breaker. The breaker is composed of the following components by weight: 15-18 parts of guanidine glycoside specific hydrolase, 1-5 parts of chain scission agent, 3-8 parts of synergist, 5-10 parts of salt, and 50-100 parts of water. The preparation method includes: mixing the synergist, salt, and water evenly according to the above-mentioned weight proportions; adding the guanidine glycoside specific hydrolase to the mixture from step (1), heating to 40-45°C at a rate of 4-8°C / min with stirring, stirring at a constant temperature for 1-2 hours, then heating to 50-65°C at a rate of 1-3°C / min, stirring at a constant temperature for 2-3 hours, and cooling to room temperature; adding the chain scission agent to the mixture from step (2) to obtain the breaker. The breaker described in this invention exhibits good breaker performance against guar gum-based fracturing fluids at temperatures ranging from 25°C to 85°C, and features safe and convenient on-site operation with no corrosive effects on equipment. However, the breaker completes breaker formation within approximately 40 minutes, which is significantly short. In practical applications, coating modification is necessary to achieve a delayed breaker effect.

[0006] CN112322271B relates to a low-temperature gel breaking activator and its application method. The gel breaking activator comprises ferrous acetylacetone (0.2-0.5%), ferrous sulfate (0.3-0.8%), glucose (0.5-3%), and the remainder being water. In a system using hydroxypropyl guar gum and carboxymethyl guar gum, with ammonium persulfate or hydrogen peroxide as the gel breaking agent, adding 0.1%-0.4% of the gel breaking activator at low temperatures of 30°C and 40°C can achieve gel breaking in 3-4 hours, with the fracturing fluid viscosity after gel breaking ≤5 mPa·s. This invention reduces the dosage, enhances the applicability of the gel breaking activator, ensures thorough gel breaking, reduces the environmental impact of peroxides, and meets the requirements of oilfield fracturing operations. However, this low-temperature gel breaking activator contains Fe. 2+ After the gel breaks, Fe(OH)3 precipitate will be generated, which may cause some damage to the formation and affect the construction quality. Summary of the Invention

[0007] This invention addresses the shortcomings of the prior art by providing a capsule de-icing agent, its preparation method, and its application. The capsule de-icing agent of this invention has excellent de-icing effect, with a viscosity retention rate reaching up to 99%; the de-icing time and temperature are controllable; at 110℃, the de-icing time can be controlled within 3-5 hours, and at 130℃, the de-icing time can be controlled within 1.2-2.5 hours.

[0008] One objective of this invention is to disclose a method for preparing a capsule breaker, the method being as follows: (1) Preparation of the main component of the de-colloiding agent Sodium 3-chloro-2-phenylpropanesulfonate, chloroform, and dodecylamine were added to the first reactor and heated to reflux. During the reaction, the pH was adjusted to 7-8. The temperature was lowered to 0-10℃ in an ice bath, and malonyl chloride was slowly added dropwise, controlling the reaction temperature not to exceed 10℃. After the addition was completed, the reaction continued for 20 minutes or more. A viscous solid was obtained by vacuum distillation. Dichloromethane was added, and the mixture was stirred. Tert-butyl hydroperoxide was slowly added dropwise, controlling the reaction temperature not to exceed 20℃. After the addition was completed, the reaction continued for 30 minutes or more. Distilled water was added, and the mixture was washed, separated, and vacuum distilled to obtain a viscous solid, which is the main agent of the de-gelling agent.

[0009] In a preferred embodiment, in step (1), based on 1 mole of sodium 3-chloro-2-phenylpropanesulfonate, the dodecylamine, malonyl chloride, and tert-butyl hydroperoxide are 0.8-1.2 moles, 0.8-1.2 moles, and 0.8-1.2 moles, respectively.

[0010] More preferably, in step (1), based on 1 mole of sodium 3-chloro-2-phenylpropanesulfonate, the dodecylamine, malonyl chloride, and tert-butyl hydroperoxide are 0.9-1.1 moles, 0.9-1.1 moles, and 0.9-1.1 moles, respectively.

[0011] In a preferred embodiment, in step (1), the mass ratio of chloroform to sodium 3-chloro-2-phenylpropanesulfonate is 10-15:1.

[0012] In a preferred embodiment, the heating reflux time in step (1) is 1-4 hours.

[0013] In a preferred embodiment, in step (1), the mass ratio of dichloromethane to sodium 3-chloro-2-phenylpropanesulfonate is 8-12:1.

[0014] (2) Preparation of the core of the de-gelling agent Add water and the main degreasing agent to the second reactor, stir thoroughly, add HB-620 type fumed silica, stir ultrasonically, let stand for 12-24 hours, filter, vacuum dry, and grind.

[0015] In a preferred embodiment, in step (2), the weight ratio of water, desiccant, and fumed silica is 5-10:0.5-1:1.

[0016] (3) Preparation of capsule-coating solution for breaking the gelling agent Ethyl acetate, butanone, acrylic resin, and polystyrene are added to the third reactor and heated to 70-75°C while stirring to dissolve. In a preferred embodiment, in step (3), the weight ratio of ethyl acetate, butanone, acrylic resin and polystyrene is 10-50:10-50:0.2-5:1.

[0017] (4) Preparation of capsule de-icing agent Add the capsule core of step (2) to the capsule coating solution of step (3) and mix. Keep warm at 70-75℃ for 1-4 hours while stirring. Filter, cool to 30℃ or below, vacuum dry, grind, and obtain capsule breaker.

[0018] Preferably, in step (4), the mass ratio of the de-icing agent core in step (2) to the de-icing agent coating solution in step (3) is 0.2-0.3:1.

[0019] The second objective of this invention discloses a capsule breaker prepared by the above-described method, wherein the molecular structural formula of the main breaker in the capsule breaker is as follows: .

[0020] The third objective of this invention is to disclose the application of the above-mentioned capsule breaker in hydraulic fracturing of oil and gas wells.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects: The breaker agent of this invention contains peroxide bonds in its main molecule, giving it strong oxidizing power. This oxidizes the residual fluid after fracturing, significantly reducing its viscosity and facilitating its removal from the formation. It also contains long-chain alkanes and sulfonates, acting as surfactants to effectively remove residual fracturing fluid from the formation during flowback. The breaker capsule gradually melts under high temperature and pressure, releasing the breaker agent from its core. The significant difference in glass transition temperatures between acrylic resin and polystyrene allows for adjustment of the breaker's breaking temperature and time as needed.

[0022] This invention exhibits a high viscosity retention rate for fracturing fluid, reaching up to 99%. It also allows for better control of the breaking time; at 110°C, the breaking time can be controlled within 3-5 hours, and at 130°C, it can be controlled within 1.2-2.5 hours. Detailed Implementation

[0023] The endpoints and any values ​​of the ranges disclosed herein 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 the various ranges, the endpoint values ​​of the various ranges and individual point values, and individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.

[0024] The present invention will be further described below with reference to specific embodiments.

[0025] Example 1: Preparation of Debonding Agent Main Component A (1) Add 0.05 mol of sodium 3-chloro-2-phenylpropanesulfonate, 128.5 g of chloroform and 0.04 mol of dodecylamine to the first reactor, heat under reflux for 1 h, and control the pH value to 7-8 with sodium hydroxide solution during the reaction; (2) Cool the temperature to 10°C in an ice bath, slowly add 0.04 mol malonyl chloride, control the reaction temperature at 10°C, and continue the reaction for 20 min after the addition is complete; (3) A viscous solid was obtained by vacuum distillation. 102.8 g of dichloromethane was added, and the mixture was stirred. 0.06 mol of tert-butyl hydrogen peroxide was slowly added dropwise, and the reaction temperature was controlled at 10 °C. After the addition was completed, the reaction continued for 30 min. (4) Add distilled water, mix and wash, separate the liquid, and distill under reduced pressure to obtain a viscous solid, namely the desiccant A.

[0026] Example 2 Preparation of Debonding Agent Main Component B (1) Add 0.05 mol of sodium 3-chloro-2-phenylpropanesulfonate, 192 g of chloroform and 0.06 mol of dodecylamine to the first reactor, heat and reflux for 4 h, and control the pH value to 7-8 with sodium hydroxide solution during the reaction; (2) Cool the temperature to 5°C in an ice bath, slowly add 0.055 mol malonyl chloride, control the reaction temperature at 5°C, and continue the reaction for 30 min after the addition is complete; (3) A viscous solid was obtained by vacuum distillation. 154 g of dichloromethane was added, and the mixture was stirred. 0.04 mol of tert-butyl hydrogen peroxide was slowly added dropwise, and the reaction temperature was controlled at 20 °C. After the addition was completed, the reaction continued for 60 min. (4) Add distilled water, mix and wash, separate the liquid, and distill under reduced pressure to obtain a viscous solid, namely the desiccant B.

[0027] Example 3 Preparation of Debonding Agent Main Component C (1) Add 0.05 mol of sodium 3-chloro-2-phenylpropanesulfonate, 155 g of chloroform and 0.055 mol of dodecylamine to the first reactor, heat under reflux for 2 h, and control the pH value to 7-8 with sodium hydroxide solution during the reaction; (2) Cool the temperature to 2°C in an ice bath, slowly add 0.06 mol malonyl chloride, control the reaction temperature at 5°C, and continue the reaction for 30 min after the addition is complete; (3) A viscous solid was obtained by vacuum distillation. 133 g of dichloromethane was added, and the mixture was stirred. 0.045 mol of tert-butyl hydrogen peroxide was slowly added dropwise, and the reaction temperature was controlled at 10 °C. After the addition was completed, the reaction continued for 30 min. (4) Add distilled water, mix and wash, separate the liquid, and distill under reduced pressure to obtain a viscous solid, namely the desiccant main agent C.

[0028] Example 4 Preparation of De-icing Agent Main Component D (1) Add 0.05 mol of sodium 3-chloro-2-phenylpropanesulfonate, 180 g of chloroform and 0.045 mol of dodecylamine to the first reactor, heat under reflux for 3 h, and control the pH value to 7-8 with sodium hydroxide solution during the reaction; (2) Cool the temperature to 5°C in an ice bath, slowly add 0.045 mol malonyl chloride, control the reaction temperature at 3°C, and continue the reaction for 40 min after the addition is complete; (3) A viscous solid was obtained by vacuum distillation. 128 g of dichloromethane was added, and the mixture was stirred. 0.055 mol of tert-butyl hydrogen peroxide was slowly added dropwise, and the reaction temperature was controlled at 15 °C. After the addition was completed, the reaction continued for 30 min. (4) Add distilled water, mix and wash, separate the liquid, and distill under reduced pressure to obtain a viscous solid, namely the desiccant D.

[0029] Example 5 Preparation of Debonding Agent Main Component E (1) Add 0.05 mol of sodium 3-chloro-2-phenylpropanesulfonate, 170 g of chloroform and 0.05 mol of dodecylamine to the first reactor, heat under reflux for 3 h, and control the pH value to 7-8 with sodium hydroxide solution during the reaction; (2) Cool the temperature to 3°C in an ice bath, slowly add 0.05 mol malonyl chloride, control the reaction temperature at 2°C, and continue the reaction for 40 min after the addition is complete; (3) A viscous solid was obtained by vacuum distillation. 132 g of dichloromethane was added, and the mixture was stirred. 0.06 mol of tert-butyl hydrogen peroxide was slowly added dropwise, and the reaction temperature was controlled at 10 °C. After the addition was completed, the reaction continued for 40 min. (4) Add distilled water, mix and wash, separate the liquid, and distill under reduced pressure to obtain a viscous solid, namely the desiccant E.

[0030] Example 6 Preparation of capsule breaker P1 (1) Preparation of the core of the de-gelling agent Add 20g of water and 2g of desiccant A to the second reactor, stir thoroughly, add 4g of HB-620 fumed silica, stir ultrasonically, let stand for 24 hours, filter, vacuum dry, and grind.

[0031] (2) Preparation of capsule-coating solution for breaking the gelling agent Add 100g ethyl acetate, 200g butanone, 2g acrylic resin, and 10g polystyrene to the third reactor, heat to 70℃ and stir to dissolve; (3) Preparation of capsule de-icing agent Add 4g of capsule core from step (1) to 20g of solution from step (2) and mix. Keep warm at 70°C for 1 hour while stirring. Filter, cool to 30°C, vacuum dry, grind, and obtain capsule decomposing agent P1.

[0032] Example 7 Preparation of capsule breaker P2 (1) Preparation of the core of the de-gelling agent Add 24g of water and 2.4g of desiccant B to the second reactor, stir thoroughly, add 4g of HB-620 fumed silica, stir ultrasonically, let stand for 12 hours, filter, vacuum dry, and grind.

[0033] (2) Preparation of capsule-coating solution for breaking the gelling agent Add 200g ethyl acetate, 100g butanone, 7g acrylic resin, and 10g polystyrene to the third reactor, and heat to 73°C while stirring to dissolve. (3) Preparation of capsule de-icing agent Add 4.5g of capsule core from step (1) to 20g of solution from step (2) and mix. Keep warm at 74℃ for 2 hours while stirring. Filter, cool to 25℃, vacuum dry, grind, and obtain capsule de-icing agent P2.

[0034] Example 8 Preparation of capsule breaker P3 (1) Preparation of the core of the de-gelling agent Add 28g of water and 2.8g of desiccant C to the second reactor, stir thoroughly, add 4g of HB-620 fumed silica, stir ultrasonically, let stand for 18 hours, filter, vacuum dry, and grind.

[0035] (2) Preparation of capsule-coating solution for breaking the gelling agent Add 300g ethyl acetate, 300g butanone, 10g acrylic resin, and 10g polystyrene to the third reactor, and heat to 72°C while stirring to dissolve. (3) Preparation of capsule de-icing agent Add 5g of capsule core from step (1) to 20g of solution from step (2) and mix. Keep warm at 75°C for 3 hours while stirring. Filter, cool to 28°C, vacuum dry, grind, and obtain capsule decomposing agent P3.

[0036] Example 9 Preparation of capsule breaker P4 (1) Preparation of the core of the de-gelling agent Add 32g of water and 3.2g of desiccant D to the second reactor, stir thoroughly, add 4g of HB-620 fumed silica, stir ultrasonically, let stand for 20h, filter, vacuum dry, and grind.

[0037] (2) Preparation of capsule-coating solution for breaking the gelling agent Add 400g ethyl acetate, 400g butanone, 30g acrylic resin, and 10g polystyrene to the third reactor, and heat to 73°C while stirring to dissolve. (3) Preparation of capsule de-icing agent Add 4g of capsule core from step (1) to 20g of solution from step (2) and mix. Keep warm at 72℃ for 4 hours with stirring. Filter, cool to 30℃, vacuum dry, grind, and obtain capsule decomposing agent P4.

[0038] Example 10 Preparation of capsule breaker P5 (1) Preparation of the core of the de-gelling agent Add 40g of water and 4g of desiccant E to the second reactor, stir thoroughly, add 4g of HB-620 fumed silica, stir ultrasonically, let stand for 16 hours, filter, vacuum dry, and grind.

[0039] (2) Preparation of capsule-coating solution for breaking the gelling agent Add 500g ethyl acetate, 500g butanone, 50g acrylic resin, and 10g polystyrene to the third reactor, heat to 75°C and stir to dissolve. (3) Preparation of capsule de-icing agent Add 6g of capsule core from step (1) to 20g of solution from step (2) and mix. Keep warm at 70°C for 4 hours while stirring. Filter, cool to 30°C, vacuum dry, grind, and obtain capsule decomposing agent P5.

[0040] Example 11: Fracturing fluid viscosity retention test The viscosity retention rate of the fracturing fluid of the capsule breaker (P1-P5) of this invention was tested according to SY / T 6380-2008 "Test Method for Performance of Fracturing Breaker". The test results are shown in Table 1.

[0041] As shown in Table 1, the capsule breaker (P1-P5) of the present invention maintains a viscosity retention rate of greater than or equal to 98.5% for fracturing fluid at 60°C. This indicates that during fracturing operations, the viscosity of the fracturing fluid will not be affected by the addition of the capsule breaker of the present invention during the preparation process and before entering the reservoir, thus ensuring the fracturing effect.

[0042] Example 12: Debonding Time Test Referencing SY / T 6380-2008 "Test Methods for Performance of Fracturing Breakers" 6.5, the breaking time was tested at 110℃ and 130℃. The test results are shown in Table 1.

[0043] Preparation of fracturing fluid: Measure 500 mL of 70°C water and pour it into a sterile mixer. Stir the mixer at 3000 rpm, add 3.0 g of commercially available hydroxypropyl guar gum, stir evenly, let stand for 1 hour, adjust the speed to 500 rpm, quickly add 2 g of organoboron crosslinking agent, and after 30 seconds, add 0.5 g of the capsule breaker of this invention (P1-P5).

[0044] Take 100ml of fracturing fluid and test the breaking time according to SY / T 6380-2008 "Test Method for Performance of Fracturing Breaker" 6.5. The test temperature is 110℃ and 130℃. The test results are shown in Table 1.

[0045] Table 1. Tests for viscosity retention and breakage time

[0046] As can be seen from Table 1, the capsule breaking agent (P1-P5) of the present invention can effectively control the breaking time. Under the condition of 110℃, the breaking time can be controlled within 3-5 hours, and under the condition of 130℃, the breaking time can be controlled within 1.2-2.5 hours.

[0047] Therefore, the capsule breaker of the present invention can release the breaker through the melting of the capsule at a higher temperature to break the fracturing fluid, thereby controlling the breaking time as needed, so that the fracturing fluid can be more easily discharged from the formation after the operation is completed.

[0048] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A method for preparing a capsule breaker, characterized in that, The preparation method is as follows: (1) Preparation of the main component of the de-colloiding agent Sodium 3-chloro-2-phenylpropanesulfonate, chloroform, and dodecylamine were added to the first reactor and heated to reflux. During the reaction, the pH was adjusted to 7-8. The temperature was lowered to 0-10℃ in an ice bath, and malonyl chloride was slowly added dropwise, controlling the reaction temperature not to exceed 10℃. After the addition was completed, the reaction continued for 20 minutes or more. A viscous solid was obtained by vacuum distillation. Dichloromethane was added, and the mixture was stirred. Tert-butyl hydroperoxide was slowly added dropwise, controlling the reaction temperature not to exceed 20℃. After the addition was completed, the reaction continued for 30 minutes or more. Distilled water was added, the mixture was washed, and the layers were separated. Vacuum distillation was then carried out to obtain a viscous solid, which is the main component of the de-gelling agent. Based on 1 mole of sodium 3-chloro-2-phenylpropanesulfonate, the dodecylamine, malonyl chloride, and tert-butyl hydroperoxide are in the amounts of 0.8-1.2 moles, 0.8-1.2 moles, and 0.8-1.2 moles, respectively. (2) Preparation of the core of the de-gelling agent Add water and desiccant to the second reactor, stir thoroughly, add HB-620 fumed silica, stir ultrasonically, let stand for 12-24 hours, filter, vacuum dry, and grind. (3) Preparation of capsule-coating solution for breaking the gelling agent Ethyl acetate, butanone, acrylic resin, and polystyrene are added to the third reactor and heated to 70-75°C while stirring to dissolve. (4) Preparation of capsule de-icing agent Add the capsule core of step (2) to the capsule coating solution of step (3) and mix. Keep warm at 70-75℃ for 1-4 hours while stirring. Filter, cool to 30℃ or below, vacuum dry, grind, and obtain capsule breaker.

2. The preparation method according to claim 1, characterized in that, In step (1), based on 1 mole of sodium 3-chloro-2-phenylpropanesulfonate, the dodecylamine, malonyl chloride, and tert-butyl hydroperoxide are 0.9-1.1 moles, 0.9-1.1 moles, and 0.9-1.1 moles, respectively.

3. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of chloroform to sodium 3-chloro-2-phenylpropanesulfonate is 10-15:

1.

4. The preparation method according to claim 1, characterized in that, In step (1), the heating reflux time is 1-4 hours.

5. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of dichloromethane to sodium 3-chloro-2-phenylpropanesulfonate is 8-12:

1.

6. The preparation method according to claim 1, characterized in that, In step (2), the weight ratio of water, de-gumming agent, and fumed silica is 5-10:0.5-1:

1.

7. The preparation method according to claim 1, characterized in that, In step (3), the weight ratio of ethyl acetate, butanone, acrylic resin and polystyrene is 10-50:10-50:0.2-5:

1.

8. The preparation method according to claim 1, characterized in that, In step (4), the mass ratio of the core of the breaker in step (2) to the shell solution of the breaker in step (3) is 0.2-0.3:

1.

9. The capsule breaker prepared by the preparation method according to any one of claims 1-8.

10. The application of the capsule breaker according to claim 9 in hydraulic fracturing of oil and gas wells.

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