Thickener, fracturing fluid and its preparation and application

Abstract

The invention discloses a thickener, a fracturing fluid and preparation and application thereof, wherein the thickener is a modified plant gum containing a thioether group and its derivatives, and the fracturing fluid contains the thickener. The fracturing fluid provided by the invention has a relatively fast gel breaking rate at low temperature, a more thorough gel breaking, and a low residue content in the gel breaking fluid.

Description

Technical Field

[0001] The invention relates to a thickener, a fracturing fluid and the preparation and application thereof. Background Art

[0002] The water-based fracturing fluid commonly used in reservoir reconstruction mainly uses guar gum and its derivatives as thickeners, which have good fracture-making and sand-carrying functions. The conventional fracturing fluid system with hydroxypropyl guar gum as the thickener has a high content of gel-breaking residue, all above 350 mg / L, which affects the fracturing effect to a certain extent; while the fracturing fluid system with carboxymethyl (hydroxypropyl) guar gum as the thickener is under acidic conditions. Due to the shielding of charges, the molecular chains cannot be fully relaxed and highly aggregated, which affects the gel-breaking efficiency, the gel-breaking is not thorough, and the gel-breaking residue content of the system is also high, above 200 mg / L.

[0003] Conventional methods of breaking gels include enzyme breaking and oxidative breaking. Enzymatic breaking is modified to cultivate biological breaking enzymes that are resistant to high or low temperatures. In production practice, there are problems such as high cost, stringent pH conditions, difficulty in storage, and short shelf life, which affect the construction process and cost, and are difficult to promote and use on a large scale. Oxidative breaking agents often use persulfates such as ammonium persulfate, potassium persulfate, and sodium persulfate. The breaking principle of persulfate is that the persulfate decomposes to produce free radicals, which oxidizes and breaks the acetal bonds of plant gums and their derivatives. The higher the temperature in the breaking process, the stronger the reaction activity of the persulfate, and the more thorough the breaking. However, when the temperature is below 50°C, the lack of sufficient energy to cause the persulfate to decompose and produce free radicals will lead to a slow reaction rate, resulting in a significant reduction in the breaking performance. Summary of the invention

[0004] In view of the defects in the prior art, the present invention provides a thickener and a fracturing fluid containing the thickener to at least partially solve the problems existing in the prior art.

[0005] In a first aspect, the present invention provides a thickener, which is a modified plant gum containing thioether groups and its derivatives.

[0006] In one or some optional embodiments, the plant gum is selected from guar gum and its derivatives.

[0007] In one or some optional embodiments, the sulfur-containing etherification group is selected from episulfide compounds.

[0008] In one or some optional embodiments, the episulfide compound has the following structural formula:

[0009]

[0010] Here, R is H or an alkyl group having 1 to 3 carbon atoms.

[0011] In a second aspect, the present invention provides a fracturing fluid, wherein the fracturing fluid contains the above-mentioned thickener.

[0012] In one or some optional embodiments, the mass of the thickener is 0.35-0.60% of the mass of water, preferably 0.4-0.55%, and more preferably 0.45-0.5%.

[0013] In one or some optional embodiments, the fracturing fluid includes: a thickener, a breaker and an additive; the breaker is selected from ammonium persulfate, potassium persulfate, and sodium persulfate; the additive is selected from one or more of an anti-swelling agent, a drainage agent, an antibacterial agent, and a cross-linking accelerator.

[0014] In one or some optional embodiments, the mass of the breaker is 0.02% of the mass of water.

[0015] In one or some optional embodiments, the anti-swelling agent is a quaternary ammonium salt, preferably dimethylbenzyl ammonium chloride; the mass of the anti-swelling agent is 0.3-0.8% of the mass of water, preferably 0.4-0.7%, and more preferably 0.45-0.55%.

[0016] In one or some optional embodiments, the drainage aid is a surfactant, preferably alkylphenol polyoxyethylene ether; the mass of the drainage aid is 0.15-0.45% of the mass of water, preferably 0.2-0.4%, and more preferably 0.3%.

[0017] In one or some optional embodiments, the antibacterial agent is glyoxal and / or glutaraldehyde; the mass of the antibacterial agent is 0.05-0.25% of the mass of water, preferably 0.1-0.2%, and more preferably 0.15%.

[0018] In one or some optional embodiments, the cross-linking accelerator is selected from one of tetramethylammonium hydroxide, an organic base or acetic acid; the organic base is selected from one or more of triethanolamine, ethanolamine, and sodium alkoxide; the sodium alkoxide is selected from one or more of sodium methoxide, sodium ethoxide, and sodium triethoxide; the mass of the cross-linking accelerator is 0.35-0.65% of the mass of water, preferably 0.4-0.6%, and further preferably 0.5%.

[0019] In one or some optional embodiments, the fracturing fluid also includes a crosslinking agent; the crosslinking agent is selected from one or two of an organic boron crosslinking agent, an organic zirconium crosslinking agent, an organic titanium crosslinking agent, and an organic aluminum crosslinking agent; the mass of the crosslinking agent is 0.2 to 0.8% of the mass of water, preferably 0.3 to 0.7%, and further preferably 0.4 to 0.5%.

[0020] In a third aspect, the present invention provides a method for preparing the above-mentioned fracturing fluid, the method comprising:

[0021] Mix the raw materials of fracturing fluid evenly according to the proportion.

[0022] In a fourth aspect, the present invention provides a use of the above-mentioned fracturing fluid in oil production.

[0023] The thickener provided by the present invention is obtained by modifying plant gum and its derivatives with thioether groups. Since sulfide has reducing properties, it can activate oxidants to generate more oxygen free radicals. The fracturing fluid provided by the present invention contains the thickener. The plant gum and its derivatives modified with thioether groups can promote the activation of persulfate as a breaker, thereby promoting the decomposition of the breaker, accelerating the breaking rate of the fracturing fluid at low temperatures, breaking the gel more thoroughly, and thus achieving low residue. DETAILED DESCRIPTION

[0024] The following is a detailed description of the embodiments of the present invention: The embodiments of the present invention are implemented on the premise of the technical solution of the present invention, and detailed implementation methods and processes are given, but the protection scope of the present invention is not limited to the following embodiments. The process parameters for which specific conditions are not specified in the following embodiments are generally based on conventional conditions.

[0025] The endpoints and any values ​​of the ranges disclosed in the present invention 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 regarded as specifically disclosed in the present invention.

[0026] Example 1

[0027] Preparation of a thickener: 2.0 g of guar gum is dispersed in 15 g of dioxane, and after passing N2 for 30 minutes, 5 mL of a 15 wt% sodium hydroxide solution is added to carry out an alkalization reaction for 30 minutes; 0.8 g of an epoxide etherification agent 2-methyl ethylene sulfide and 9 g of dioxane are added for stirring, and then heated at 65° C. for 4 hours in a reactor equipped with a condensation reflux tube device to obtain a reaction product; the obtained reaction product is filtered, washed twice with an 80 vol% acetone aqueous solution, dried, washed twice with water, and then dried to obtain mercaptopropyl guar gum.

[0028] The fracturing fluid formula components: the dosage of the thickener mercaptopropyl guar gum is 0.5% of the water mass, the dosage of the composite organic boron and organic zirconium cross-linking agent is 0.4% of the water mass, the dosage of the breaker ammonium persulfate is 0.02% of the water mass, the dosage of the anti-swelling agent dimethylbenzyl ammonium chloride is 0.45% of the water mass, the dosage of the drainage aid alkylphenol polyoxyethylene ether is 0.3% of the water mass, the dosage of the antibacterial agent glyoxal is 0.15% of the water mass, the dosage of the cross-linking accelerator tetramethylammonium hydroxide is 0.5% of the water mass, and the pH value is adjusted to 10.5.

[0029] Preparation of fracturing fluid: Weigh 5.0g of mercaptopropyl guar gum, slowly add it to 1000mL of water while stirring, stir for 15 minutes until it is evenly dissolved, swell at room temperature for 4 hours, add other components in the base fluid formula (except the cross-linking agent) in sequence according to the fracturing fluid formula, stir evenly, add the cross-linking agent composite organic boron and organic zirconium, and stir rapidly for 60 seconds to cross-link the fracturing fluid to a hanging state.

[0030] Comparative Example 1

[0031] The thickener was replaced with carboxymethyl hydroxypropyl guar gum, and the rest was the same as in Example 1.

[0032] Test Example 1

[0033] Gel breaking viscosity test: put the sample gel into a hydrothermal kettle and place it in a 120℃ drying oven. Take it out after 2 hours and cool it down. Observe the gel breaking state in the kettle and measure the viscosity of the gel breaking liquid. The viscosity of the gel breaking liquid is measured by a Pinsler capillary viscometer and the average value of three times is taken.

[0034] It was determined that the viscosity of the fracturing fluid system in Comparative Example 1 was reduced from 600 mPa·s to below 5 mPa·s, while the viscosity of the fracturing fluid system in Example 1 of the present invention was reduced from 600 mPa·s to below 2 mPa·s, indicating that the fracturing fluid prepared by using the sulfur-containing thickener has more thorough gel breaking.

[0035] Test Example 2

[0036] Determination of the amount of residue in the degelling liquid: The degelling liquids prepared by Example 1 and Comparative Example 1 in Test Example 1 were mixed uniformly, 50 mL was accurately measured and transferred to a pre-weighed centrifuge tube, and centrifuged at 3000 rpm for 30 min, the supernatant was poured out, 50 mL of distilled water was added to wash the residue, and the mixture was centrifuged for another 20 min, the supernatant was poured out, the centrifuge tube was placed in an electric constant temperature drying oven and dried to constant weight, and then weighed, and the residue content was calculated.

[0037] It is calculated that the residue amount of the degelling liquid prepared by Comparative Example 1 is 357 mg / L, while the residue amount of the degelling liquid prepared by Example 1 is 155 mg / L. Although both Example 1 and Comparative Example 1 are lower than the specified value (500 mg / L) in the industry standard SY / T 6380-2008 "Test method for performance of degelling agents for fracturing", the residue in the degelling liquid prepared by using the sulfur-containing thickener in Example 1 is lower.

[0038] Example 2

[0039] Preparation of thickener: the same as in Example 1.

[0040] The fracturing fluid formula components: the thickener mercaptopropyl guar gum is used in an amount of 0.5% of the water mass, the composite organic titanium zirconium cross-linking agent is used in an amount of 0.4% of the water mass, the breaker ammonium persulfate is used in an amount of 0.02% of the water mass, the anti-swelling agent dimethylbenzyl ammonium chloride is used in an amount of 0.45% of the water mass, the drainage aid alkylphenol polyoxyethylene ether is used in an amount of 0.3% of the water mass, the antibacterial agent glyoxal is used in an amount of 0.15% of the water mass, the cross-linking accelerator acetic acid is used in an amount of 0.4% of the water mass, and the pH is adjusted to 4.5.

[0041] Preparation of fracturing fluid: Weigh 5.0g of mercaptopropyl guar gum, slowly add it to 1000mL of water while stirring, stir for 15 minutes until it is evenly dissolved, swell at room temperature for 4 hours, add other components in the base fluid formula (except the cross-linking agent) in sequence according to the fracturing fluid formula, stir evenly, add the cross-linking agent composite organic titanium zirconium cross-linking agent, and stir rapidly for 60 seconds to cross-link the fracturing fluid to a hanging state.

[0042] Comparative Example 2

[0043] The thickener was replaced with carboxymethyl hydroxypropyl guar gum, and the rest was the same as in Example 2.

[0044] Test Example 3

[0045] Breaking viscosity test: The test method is the same as that of test example 1.

[0046] It was determined that the viscosity of the fracturing fluid system in Comparative Example 2 was reduced from 400 mPa·s to below 5 mPa·s, and the viscosity of the fracturing fluid system in Example 2 was reduced from 500 mPa·s to below 2 mPa·s, indicating that the fracturing fluid prepared by using the sulfur-containing thickener has more thorough gel breaking.

[0047] Test Example 4

[0048] Determination of the amount of residue in the degelling liquid: The test method is consistent with that in Test Example 2.

[0049] After calculation, the residue amount of the degelling liquid prepared by comparative example 2 is 236 mg / L, while the residue amount of the degelling liquid prepared by example 2 is 138 mg / L. Although both example 1 and comparative example 1 are lower than the specified value (500 mg / L) in the industry standard SY / T 6380-2008 "Test method for performance of degelling agents for fracturing", the residue in the degelling liquid prepared by using the sulfur-containing thickener in example 2 is lower.

[0050] Although the specific embodiments of the present invention have been described in detail, it will be understood by those skilled in the art. According to all the teachings disclosed, various modifications and replacements can be made to those details, and these changes are all within the protection scope of the present invention. The full scope of the present invention is given by the attached claims and any equivalents thereof.

Claims

1. A fracturing fluid, characterized in that: The fracturing fluid comprises: a thickener, a breaker, an additive and water; The thickener is a modified plant gum containing sulfur-etherified groups and its derivatives, the plant gum is selected from guar gum and its derivatives, the sulfur-containing etherified groups are selected from episulfide compounds, and the episulfide compounds have the following structural formula: Wherein, R is H or an alkyl group having 1 to 3 carbon atoms; The degumming agent is selected from ammonium persulfate, potassium persulfate, and sodium persulfate; The auxiliary agent is selected from one or more of an anti-swelling agent, a drainage agent, an antibacterial agent, and a cross-linking accelerator; The mass of the thickener is 0.35-0.60% of the mass of water; The mass of the breaker is 0.02% of the mass of water; The anti-swelling agent is a quaternary ammonium salt, the mass of which is 0.3-0.8% of the mass of water; The drainage aid is a surfactant, the mass of which is 0.15-0.45% of the mass of water; The antibacterial agent is glyoxal and / or glutaraldehyde, and the mass thereof is 0.05-0.25% of the mass of water; The cross-linking accelerator is selected from one of tetramethylammonium hydroxide, organic base or acetic acid; the organic base is selected from one or more of triethanolamine, ethanolamine and sodium alcoholate; the sodium alcoholate is selected from one or more of sodium methoxide, sodium ethoxide and sodium triethoxide; the mass of the cross-linking accelerator is 0.35-0.65% of the mass of water.

2. The fracturing fluid according to claim 1, characterized in that: The mass of the thickener is 0.4-0.55% of the mass of water; the anti-swelling agent is dimethylbenzyl ammonium chloride, and the mass is 0.3-0.8% of the mass of water; the drainage agent is alkylphenol polyoxyethylene ether, and the mass is 0.15-0.45% of the mass of water; the antibacterial agent is glyoxal and / or glutaraldehyde, and the mass is 0.1-0.2% of the mass of water; the mass of the cross-linking accelerator is 0.4-0.6% of the mass of water.

3. The fracturing fluid according to claim 2, characterized in that: The mass of the thickener is 0.45-0.5% of the mass of water; the anti-swelling agent is dimethylbenzyl ammonium chloride, the mass of which is 0.4-0.7% of the mass of water; the drainage aid is alkylphenol polyoxyethylene ether, the mass of which is 0.2-0.4% of the mass of water.

4. The fracturing fluid according to claim 3, characterized in that: The anti-swelling agent is dimethylbenzyl ammonium chloride, and its mass is 0.45-0.55% of the mass of water.

5. The fracturing fluid according to any one of claims 1 to 4, characterized in that: The fracturing fluid also includes a crosslinking agent; the crosslinking agent is selected from one or two of an organic boron crosslinking agent, an organic zirconium crosslinking agent, an organic titanium crosslinking agent, and an organic aluminum crosslinking agent; the mass of the crosslinking agent is 0.2-0.8% of the mass of water.

6. The fracturing fluid according to claim 5, characterized in that The mass of the cross-linking agent is 0.3-0.7% of the mass of water.

7. The fracturing fluid according to claim 6, characterized in that: The mass of the cross-linking agent is 0.4-0.5% of the mass of water.

8. A method for preparing the fracturing fluid according to any one of claims 1 to 7, characterized in that: The method comprises: Mix the raw materials of fracturing fluid evenly according to the proportion.

9. Use of the fracturing fluid according to any one of claims 1 to 7 in oil production.

Images