Acidic low-temperature gel breaking activator and preparation method thereof

Abstract

The invention relates to the technical field of gel breaker preparation, in particular to an acidic low-temperature gel breaking activator and a preparation method thereof.The acidic low-temperature gel breaking activator comprises an organic activator, a pH buffering agent and water, and the acidic low-temperature gel breaking activator is obtained according to the following method that at the room temperature, the organic activator and the pH buffering agent with the required amount are added into the water with the required amount, and the mixture is evenly stirred to obtain the acidic low-temperature gel breaking activator. The acidic low-temperature gel breaking activator can realize thorough gel breaking of the polymer fracturing fluid at the temperature of 10-50 DEG C, the gel breaking time is 4 h, the viscosity of the gel breaking fluid is smaller than 5 mPa.s, the standard requirements are met, and the acidic low-temperature gel breaking activator has good low-temperature gel breaking performance for the polymer fracturing fluid.

Description

Technical Field

[0001] The invention relates to the technical field of breaker preparation, in particular to an acidic low-temperature breaker activator and a preparation method thereof. Background Art

[0002] Hydraulic fracturing is one of the main means of increasing the production of oil and gas wells. During the fracturing construction process, timely and thorough debonding of the fracturing fluid is a key factor in determining the success of fracturing. At present, conventional fracturing fluid debonding technology is used for low-temperature (15℃ to 50℃) and shallow (300m to 1500m) reservoirs at home and abroad. There are problems such as long debonding time, incomplete debonding, long flowback time, and incomplete flowback, which cause great damage to the reservoir. Especially for polymer emulsions, low-temperature debonding is more difficult due to the presence of emulsifiers.

[0003] Water-based fracturing fluid breakers mainly use peroxides, such as ammonium persulfate, sodium persulfate, etc., and their breaking rate depends on the decomposition rate of persulfate, which in turn depends on the temperature of the reservoir. When the temperature is 50°C, the half-life of persulfate is nearly ten times longer than that of 60°C, and the decomposition rate is greatly reduced, which is prone to incomplete breaking or high residue content. In order to improve the low-temperature breaking effect, it is often used to increase the concentration of peroxide and match it with an activator, but the effect is not obvious, and there are also outstanding problems such as increasing construction risks and inducing an increase in the hydrogen sulfide content in the formation. In addition, the activator usually contains iron ions or ferrous ions. The iron ions generated by the redox reaction will greatly affect the performance of the fracturing fluid, and at the same time, iron hydroxide precipitation will be generated, causing reservoir damage.

[0004] Therefore, it is urgent to develop a suitable low-temperature degelling activator to ensure timely and thorough degelling of the polymer emulsion, reduce the viscosity and residue content of the degelling liquid, which has significant practical significance for the promotion and application of polymer emulsion in low-temperature reservoir fracturing transformation and can greatly reduce the cost of fracturing construction. Summary of the invention

[0005] The present invention provides an acidic low-temperature debonding activator and a preparation method thereof, which overcomes the above-mentioned deficiencies of the prior art and can effectively solve the problem that the prior debonding activator cannot ensure timely and thorough debonding of the polymer emulsion.

[0006] One of the technical solutions of the present invention is achieved through the following measures: an acidic low-temperature degelling activator, the raw materials of which include 2% to 5% of an organic activator and 0% to 20% of a pH buffer by weight, and the rest is water.

[0007] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The organic activator is one or more of formic acid, oxalic acid, ascorbic acid, hydroxylamine hydrochloride, hydroxylamine sulfate, diethylhydroxylamine hydrochloride, hydrazine hydrochloride, hydrazine sulfate, hydrazine acetate, ammonium sulfate hydrochloride and ammonium sulfate nitrate.

[0008] The pH buffer is one or more of ammonium chloride, ammonium sulfate, ammonium acetate, ammonium formate and ammonium oxalate.

[0009] The acidic low-temperature gel-breaking activator is obtained by the following method: adding a required amount of organic activator and pH buffer to a required amount of water at room temperature and stirring evenly to obtain the acidic low-temperature gel-breaking activator.

[0010] The above stirring time is 0.5h to 1.0h.

[0011] The second technical solution of the present invention is achieved by the following measures: a method for preparing an acidic low-temperature gel-breaking activator is carried out as follows: at room temperature, a required amount of an organic activator and a pH buffer are added to a required amount of water and stirred evenly to obtain an acidic low-temperature gel-breaking activator.

[0012] The following is a further optimization and / or improvement of the second technical solution of the above invention: The above stirring time is 0.5h to 1.0h.

[0013] The acidic low-temperature degelling activator of the present invention can achieve complete degelling of polymer fracturing fluid at 10°C to 50°C, the degelling time is 4h, and the viscosity of the degelling fluid is less than 5mPa·s, which meets the standard requirements and has good low-temperature degelling performance for polymer fracturing fluid. DETAILED DESCRIPTION

[0014] The present invention is not limited by the following embodiments, and the specific implementation method can be determined according to the technical scheme of the present invention and the actual situation. Unless otherwise specified, the various chemical reagents and chemicals mentioned in the present invention are all known and commonly used chemical reagents and chemicals in the prior art. Unless otherwise specified, the percentages in the present invention are all mass percentages; unless otherwise specified, the solutions in the present invention are all aqueous solutions with water as the solvent, for example, hydrochloric acid solution is a hydrochloric acid aqueous solution; the normal temperature and room temperature in the present invention generally refer to a temperature of 15°C to 25°C, and are generally defined as 25°C.

[0015] The present invention will be further described below in conjunction with embodiments: Embodiment 1: The acidic low-temperature debonding activator comprises, by weight percentage, 2% to 5% of an organic activator and 0% to 20% of a pH buffer, and the remainder is water.

[0016] Example 2: As an optimization of the above example, the organic activator is one or more of formic acid, oxalic acid, ascorbic acid, hydroxylamine hydrochloride, hydroxylamine sulfate, diethylhydroxylamine hydrochloride, hydrazine hydrochloride, hydrazine sulfate, hydrazine acetate, ammonium sulfate hydrochloride and ammonium sulfate nitrate.

[0017] Example 3: As an optimization of the above example, the pH buffer is one or more of ammonium chloride, ammonium sulfate, ammonium acetate, ammonium formate and ammonium oxalate.

[0018] Example 4: As an optimization of the above example, the acidic low-temperature gel-breaking activator is obtained by the following method: at room temperature, a required amount of organic activator and pH buffer are added to a required amount of water and stirred for 0.5h to 1.0h to obtain an acidic low-temperature gel-breaking activator.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) The acidic low-temperature debonding activator of the present invention can enable the polymer emulsion to be completely debonded at a low temperature of 10°C to 50°C, and has the advantages of low cost, small dosage, controllable debonding time and stable performance; (2) The low-temperature gel-breaking activator of the present invention does not contain metal ions, and the solution is acidic, so no precipitation will be produced in the formation, thus avoiding reservoir damage and greatly expanding the application scope of the activator; (3) The acidic low-temperature debonding activator of the present invention has a safe and reliable preparation method, simple operation, low equipment requirements, is suitable for industrial production, and has the conditions for large-scale application.

[0020] Embodiment 5: The acidic low-temperature gel-breaking activator comprises raw materials, by weight percentage, of 5% organic activator (4% hydrazine sulfate + 1% ascorbic acid) and 20% pH buffer (5% ammonium formate + 15% ammonium oxalate), and the remainder is water, and is obtained by the following method: at room temperature (25°C), 75 parts of water are added into a reaction kettle, stirring is started, and organic activator (4 parts of hydrazine sulfate + 1 part of ascorbic acid) and pH buffer (5 parts of ammonium formate + 15 parts of ammonium oxalate) are slowly added, and stirring is performed for 0.5h to obtain the acidic low-temperature gel-breaking activator.

[0021] Embodiment 6: The acidic low-temperature gel-breaking activator comprises, by weight percentage, 5% of an organic activator (3% hydrazine hydrochloride + 1% hydroxylamine hydrochloride + 1% formic acid) and 10% of a pH buffer (5% ammonium oxalate + 4% ammonium chloride + 1% ammonium oxalate), and the remainder is water, and is obtained by the following method: at room temperature (25°C), 75 parts of water are added into a reaction kettle, stirring is started, and an organic activator (3 parts of hydrazine hydrochloride + 1 part of hydroxylamine hydrochloride + 1 part of formic acid) and a pH buffer (5 parts of ammonium oxalate + 4 parts of ammonium chloride + 1 part of ammonium oxalate) are slowly added, and stirring is performed for 1.0h to obtain the acidic low-temperature gel-breaking activator.

[0022] Embodiment 7: The acidic low-temperature gel-breaking activator comprises, by weight percentage, 4% of an organic activator (2% hydroxylamine sulfate + 2% dimethylhydroxylamine hydrochloride) and 5% of a pH buffer (2% ammonium oxalate + 2% ammonium formate + 1% ammonium acetate), and the remainder is water. The acidic low-temperature gel-breaking activator is obtained by the following method: at room temperature (25°C), 75 parts of water are added into a reaction kettle, stirring is started, and an organic activator (2 parts of hydroxylamine sulfate + 2 parts of dimethylhydroxylamine hydrochloride) and a pH buffer (2 parts of ammonium oxalate + 2 parts of ammonium formate + 1 part of ammonium acetate) are slowly added, and stirring is performed for 0.8 hours to obtain the acidic low-temperature gel-breaking activator.

[0023] Embodiment 8: The acidic low-temperature gel-breaking activator comprises, by weight percentage, 4% of an organic activator (2% hydroxylamine hydrochloride + 2% dimethylhydroxylamine hydrochloride) and 5% of a pH buffer (2% ammonium oxalate + 2% ammonium formate + 1% ammonium acetate), and the remainder is water. The acidic low-temperature gel-breaking activator is obtained by the following method: at room temperature (25°C), 75 parts of water are added into a reaction kettle, stirring is started, and an organic activator (2 parts of hydroxylamine sulfate + 2 parts of dimethylhydroxylamine hydrochloride) and a pH buffer (2 parts of ammonium oxalate + 2 parts of ammonium formate + 1 part of ammonium acetate) are slowly added, and stirring is performed for 1.0 hour to obtain the acidic low-temperature gel-breaking activator.

[0024] Embodiment 9: The acidic low-temperature gel-breaking activators prepared in Examples 5 to 8 of the present invention were formulated into gel-breaking liquids, and the gel-breaking liquids were subjected to viscosity tests.

[0025] A 0.6% concentration of clean fracturing fluid thickener for fracturing (GDQC, a clean fracturing fluid thickener for fracturing provided by Karamay Zhongke Hengxin Technology Co., Ltd.) was preheated for 20 minutes, placed at different temperatures (10°C, 20°C, 30°C, 40°C and 50°C), and different amounts of ammonium persulfate (1.0‰ (10°C), 0.9‰ (20°C), 0.8‰ (30°C), 0.7‰ (40°C), 0.6‰ (50°C)) were added and stirred evenly, and then different amounts of acidic low-temperature degelling activator (0.03% (10°C), 0.025% (20°C), 0.02% (30°C), 0.015% (40°C), 0.01% (50°C)) were added and stirred evenly again to obtain a fracturing fluid. Each fracturing fluid was placed in a constant temperature water bath, and the degelling was considered to be complete when the viscosity was less than or equal to 5mPa·s.

[0026] The test results are shown in Tables 1 to 4, wherein Table 1 is the breaking test results of Example 5 of the present invention at different temperatures, Table 2 is the breaking test results of Example 6 of the present invention at different temperatures, Table 3 is the breaking test results of Example 7 of the present invention at different temperatures, and Table 4 is the breaking test results of Example 8 of the present invention at different temperatures. It can be seen from Tables 1 to 4 that Examples 1 to 4 of the present invention can achieve complete breaking of the polymer fracturing fluid at 10°C to 50°C, the breaking time is 4h, and the viscosity of the broken fluid is less than 5mPa·s, which meets the standard requirements.

[0027] In summary, the acidic low-temperature degelling activator of the present invention can achieve complete degelling of the polymer fracturing fluid at 10°C to 50°C, the degelling time is 4h, and the viscosity of the degelling fluid is <5mPa·s, which meets the standard requirements and has good low-temperature degelling performance for the polymer fracturing fluid.

[0028] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. An acidic low temperature debonding activator, characterized in that The raw materials include 2% to 5% of an organic activator and 0% to 20% of a pH buffer by weight, and the rest is water.

2. The acidic low temperature degelling activator according to claim 1, characterized in that The organic activator is one or more of formic acid, oxalic acid, ascorbic acid, hydroxylamine hydrochloride, hydroxylamine sulfate, diethylhydroxylamine hydrochloride, hydrazine hydrochloride, hydrazine sulfate, hydrazine acetate, ammonium sulfate hydrochloride and ammonium sulfate nitrate.

3. The acidic low temperature degelling activator according to claim 1 or 2, characterized in that The pH buffer is one or more of ammonium chloride, ammonium sulfate, ammonium acetate, ammonium formate and ammonium oxalate.

4. The acidic low-temperature debonding activator according to any one of claims 1 to 3, characterized in that The method is as follows: at room temperature, a required amount of organic activator and pH buffer are added to a required amount of water and stirred evenly to obtain an acidic low-temperature degelling activator.

5. The acidic low-temperature debonding activator according to claim 4, wherein the stirring time is 0.5 h to 1.0 h.

6. An acidic low-temperature gel-breaking activator according to any one of claims 1 or 2 or 3 or 5, characterized in that The method is as follows: at room temperature, add a required amount of organic activator and pH buffer to a required amount of water and stir evenly to obtain an acidic low-temperature degelling activator.

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