Bactericide for fracturing fluid as well as preparation method and application of bactericide

Abstract

The invention relates to a bactericide for fracturing fluid as well as a preparation method and application of the bactericide. The bactericide for the fracturing fluid is prepared from the following raw materials: 5-10% of a cationic surfactant, 8-12% of aldehyde, 3-5% of alcohol, 3-5% of sodium salt and the balance of water. The preparation method of the bactericide for the fracturing fluid comprises the following steps: (1) dividing the water into two parts according to the formula ratio; (2) adding a formula amount of alcohol into one part of water, and uniformly stirring to obtain an alcohol solution; (3) continuously adding the cationic surfactant with the formula amount into the alcoholic solution, uniformly stirring, heating to 50-60 DEG C, slowly adding the aldehyde with the formula amount, and uniformly stirring to obtain a mixed solution; and (4) adding the other part of water into the mixed solution, gradually cooling to room temperature, finally adding the sodium salt according to the formula ratio, and uniformly stirring to obtain the bactericide for the fracturing fluid. The bactericide is applied as a fracturing fluid bactericide in oil exploitation.

Description

Technical Field

[0001] The invention belongs to the field of oil and gas field fracturing technology, and specifically relates to a bactericide for fracturing fluid and a preparation method and application thereof. Background Art

[0002] Plant gum belongs to the class of polysaccharide macromolecular compounds and is widely used as a thickener for fracturing fluid. For example, Chinese invention patent application CN 103555297A discloses a method for preparing an environmentally friendly oilfield thickener from citrus peels, wherein naturally air-dried citrus peels are crushed, ethanol is added to citrus peel particles in a reactor, and the peel particles are filtered under reduced pressure until no solution flows out, and dried to a constant weight, and a modified cellulose product is mixed with the citrus peels, stirred evenly, crushed, and sieved to obtain an environmentally friendly oilfield thickener.

[0003] Plant gum contains a large number of saprophytes, molds, yeasts and other microorganisms, especially saprophytes are the most harmful to plant gum, and plant gum is easily degraded by microorganisms. At present, hydroxypropyl guar gum fracturing fluid is widely used because of its good temperature and salt resistance. For example, Chinese invention patent CN 105368437A discloses a hydroxypropyl guar gum fracturing fluid containing potassium monopersulfate and a preparation method thereof. The purpose is to provide a hydroxypropyl guar gum fracturing fluid containing potassium monopersulfate with rapid gel breaking and good residue degradation effect. The hydroxypropyl guar gum fracturing fluid is composed of a raw gum liquid and a cross-linking agent, and the amount of potassium monopersulfate added to the hydroxypropyl guar gum fracturing fluid is 5-20ppm.

[0004] Bacteria reproduce by binary fission, and the group grows at an exponential rate. The damage to plant gum is mainly to hydrolyze the galactomannan molecules in the plant gum under the action of enzymes, causing the glycosidic bond to break and the molecular chain to degrade. If the degradation reaction continues, galactose and mannose can be generated in the end, and the degraded plant gum loses its thickening ability.

[0005] Saprophytes and yeasts are bacteria that use inanimate organic matter as a carbon source for growth. At the same time, the water content of guar gum fracturing fluid is over 99%, which provides a good living environment for various bacteria and microorganisms. Therefore, the fracturing fluid is easily degraded by microorganisms and becomes corrupt and deteriorated, which is manifested as a decrease in the pH value of the gel, slow cross-linking, weak cross-linking or even no cross-linking. This can easily cause gel waste or affect the progress of fracturing construction and increase the risk of sand plugging. Therefore, in order to prevent the corruption and deterioration of guar gum plant gum fracturing fluid, it is often necessary to add fungicides to the guar gum fracturing fluid base fluid to inhibit the degradation of plant gum by microorganisms, so that the plant gum fracturing fluid has a good cross-linking effect during preparation and on-site use, thereby ensuring the construction quality.

[0006] In the past few years, formaldehyde was often used as a fungicide in the preparation of guar gum fracturing fluid. However, due to its strong pungent odor and environmental pollution, various industries are currently restricting the use of formaldehyde. In addition, long-term use of the same type of traditional fungicide can easily cause bacteria to develop drug resistance, and the bactericidal effect will deteriorate. Summary of the invention

[0007] Purpose of the invention: In view of the deficiencies of the above-mentioned prior art, the present invention discloses a bactericide for fracturing fluid and its preparation method and application. The purpose of the present invention is to solve the problem that the viscosity of the current oilfield fracturing fluid is reduced due to the degradation of microorganisms and cannot meet the construction requirements, and the conventional bactericide formaldehyde cannot be used due to its harmfulness to the environment. The bactericide for fracturing fluid of the present invention has good bactericidal performance, a wide sterilization range, and has a strong bactericidal and antibacterial ability against saprophytes, and can effectively reduce the viscosity loss rate of plant gum-based fluid. It has low toxicity to the human body and is non-corrosive to equipment. It can be widely used in the preparation of plant gum fracturing fluid in fracturing construction and has good compatibility with fracturing fluid.

[0008] Technical solution: A fungicide for fracturing fluid, which is composed of the following raw materials in terms of mass percentage:

[0009] Cationic surfactant 5-10%, aldehyde 8-12%, alcohol 3-5%, sodium salt 3-5%, and the balance is water.

[0010] Furthermore, the structural formula of the cationic surfactant is:

[0011] in:

[0012] R 1 is a C10-C12 alkyl group, R 2 is a C1-C12 alkyl group, and X is one of F, Cl, Br and I.

[0013] Furthermore, the cationic surfactant is one of didodecyldimethylammonium chloride, didodecyldimethylammonium bromide, dodecyltrimethylammonium chloride and didecyldimethylammonium chloride.

[0014] Furthermore, the aldehyde is one of acetaldehyde, glutaraldehyde, succinaldehyde and glyoxal.

[0015] Furthermore, the alcohol is one of ethanol, ethylene glycol, glycerol and isopropanol.

[0016] Furthermore, the sodium salt is one of sodium phenolate, sodium xylene sulfonate, sodium acetate, sodium benzoate and sodium chloride.

[0017] The preparation method of the above-mentioned bactericide for fracturing fluid comprises the following steps:

[0018] (1) Divide the amount of water in the formula into two parts;

[0019] (2) Add the formulated amount of alcohol to one portion of the water and stir evenly (stirring time at least 5 minutes) to obtain an alcohol solution;

[0020] (3) Continue to add the cationic surfactant in the formula amount to the alcohol solution, stir evenly, and then heat to 50-60° C., then slowly add the aldehyde in the formula amount, stir evenly (stirring time at least 30 minutes) to obtain a mixed solution;

[0021] (4) Add another portion of water to the mixed solution and gradually cool it to room temperature. Finally, add a formulated amount of sodium salt and stir evenly to obtain a fungicide for fracturing fluid.

[0022] A bactericide for fracturing fluid is prepared by the above preparation method.

[0023] The above-mentioned fungicide is used as a fracturing fluid fungicide in oil production.

[0024] Furthermore, when used, 0.1 wt% to 0.2 wt% of the above-mentioned fungicide for fracturing fluid is directly added to the fracturing fluid based on the total mass of the fracturing fluid, and then directly injected into the target layer.

[0025] Beneficial effects: The present invention discloses a fungicide for fracturing fluid and its preparation method and application have the following advantages:

[0026] Beneficial effects:

[0027] 1. This product is a composite fracturing fluid fungicide, with the appearance of colorless or light yellow liquid, easily soluble in water and good stability;

[0028] 2. It is effective in killing saprophytes, sulfate-reducing bacteria and iron bacteria, and is a green and environmentally friendly composite high-efficiency fracturing fluid fungicide;

[0029] 3. The sterilization efficiency is extremely high, effectively extending the shelf life of the fracturing fluid;

[0030] 4. It has good compatibility with other fracturing fluids and can be used at low concentration. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention discloses a flow chart of a method for preparing a bactericide for fracturing fluid.

[0032] Figure 2 Schematic diagram of the results of the temperature and shear resistance test of the fracturing fluid gel to which the fracturing fluid bactericide was added in Test Example 5.

[0033] Figure 3Schematic diagram of the comparative experimental results of the temperature and shear resistance of the fracturing fluid gel without adding the fracturing fluid bactericide in Experimental Example 5. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with specific embodiments. Specific embodiment 1

[0036] A fungicide for fracturing fluid, composed of the following raw materials in terms of mass percentage:

[0037] Cationic surfactant 8%, aldehyde 6%, alcohol 4%, sodium salt 4%, and the balance is water.

[0038] Furthermore, the structural formula of the cationic surfactant is:

[0039] in:

[0040] R 1 is a C12 alkyl group, R 2 is a C12 alkyl group, X is Cl

[0041] That is to say, the cationic surfactant is didodecyl dimethyl ammonium chloride.

[0042] Furthermore, the aldehyde is acetaldehyde.

[0043] Furthermore, the alcohol is ethanol.

[0044] Furthermore, the sodium salt is sodium phenolate.

[0045] The preparation method of the above-mentioned bactericide for fracturing fluid comprises the following steps:

[0046] (1) Divide the amount of water in the formula into two parts;

[0047] (2) Add the formulated amount of alcohol to one portion of the water and stir for 8 minutes to obtain an alcohol solution;

[0048] (3) Continue to add the cationic surfactant in the formula amount to the alcohol solution, stir evenly, then heat to 55°C, then slowly add the aldehyde in the formula amount, stir for 45 minutes to obtain a mixed solution;

[0049] (4) Add another portion of water to the mixed solution and gradually cool it to room temperature. Finally, add a formulated amount of sodium salt and stir evenly to obtain a fungicide for fracturing fluid.

[0050] The above-mentioned fungicide is used as a fracturing fluid fungicide in oil production.

[0051] Furthermore, when used, 0.15 wt % of the above-mentioned fungicide for fracturing fluid is directly added to the fracturing fluid based on the total mass of the fracturing fluid, and then directly injected into the target layer. Specific embodiment 2

[0053] A fungicide for fracturing fluid, composed of the following raw materials in terms of mass percentage:

[0054] Cationic surfactant 5%, aldehyde 8%, alcohol 3%, sodium salt 3%, and the balance is water.

[0055] Furthermore, the structural formula of the cationic surfactant is:

[0056] in:

[0057] R 1 is a C12 alkyl group, R 2 is a C12 alkyl group, and X is Br.

[0058] That is to say, the cationic surfactant is didodecyl dimethyl ammonium bromide.

[0059] Furthermore, the aldehyde is glutaraldehyde.

[0060] Furthermore, the alcohol is ethylene glycol.

[0061] Furthermore, the sodium salt is sodium xylene sulfonate.

[0062] The preparation method of the above-mentioned bactericide for fracturing fluid comprises the following steps:

[0063] (1) Divide the amount of water in the formula into two parts;

[0064] (2) Add the formulated amount of alcohol to one portion of the water and stir for 5 minutes to obtain an alcohol solution;

[0065] (3) Continue to add the cationic surfactant in the formula amount to the alcohol solution, stir evenly, then heat to 50°C, then slowly add the aldehyde in the formula amount, stir for 60 minutes to obtain a mixed solution;

[0066] (4) Add another portion of water to the mixed solution and gradually cool it to room temperature. Finally, add a formulated amount of sodium salt and stir evenly to obtain a fungicide for fracturing fluid.

[0067] The above-mentioned fungicide is used as a fracturing fluid fungicide in oil production.

[0068] Furthermore, when used, 0.1 wt % of the above-mentioned fracturing fluid bactericide is directly added to the fracturing fluid based on the total mass of the fracturing fluid, and then directly injected into the target layer. Specific embodiment 3

[0070] A fungicide for fracturing fluid is composed of the following raw materials, measured by mass percentage: 10% cationic surfactant, 12% aldehyde, 5% alcohol, 5% sodium salt, and the balance is water. Furthermore, the structural formula of the cationic surfactant is:

[0071] in:

[0072] R 1 is a C10 alkyl group, R 2 is a C10 alkyl group, and X is Cl.

[0073] That is to say, the cationic surfactant is didecyl dimethyl ammonium chloride. In another embodiment, the structural formula of the cationic surfactant is:

[0074] in:

[0075] R 1 is a C11 alkyl group, R 2 is methyl, and X is F.

[0076] In another embodiment: the structural formula of the cationic surfactant is:

[0077] in:

[0078] R 1 is a C11 alkyl group, R 2 is ethyl, and X is I.

[0079] Furthermore, the aldehyde is glyoxal.

[0080] Furthermore, the alcohol is isopropanol.

[0081] Furthermore, the sodium salt is sodium chloride.

[0082] The preparation method of the above-mentioned bactericide for fracturing fluid comprises the following steps:

[0083] (1) Divide the amount of water in the formula into two parts;

[0084] (2) Add the formulated amount of alcohol to one portion of the water and stir for 20 minutes to obtain an alcohol solution;

[0085] (3) Continue to add the cationic surfactant in the formula amount to the alcohol solution, stir evenly, then heat to 60°C, then slowly add the aldehyde in the formula amount, stir for 30 minutes to obtain a mixed solution;

[0086] (4) Add another portion of water to the mixed solution and gradually cool it to room temperature. Finally, add a formulated amount of sodium salt and stir evenly to obtain a fungicide for fracturing fluid.

[0087] The above-mentioned fungicide is used as a fracturing fluid fungicide in oil production.

[0088] Furthermore, when used, 0.2 wt % of the above-mentioned fungicide for fracturing fluid is directly added to the fracturing fluid based on the total mass of the fracturing fluid, and then directly injected into the target layer. Specific embodiment 4

[0090] It is substantially the same as the specific embodiment 1, except that the cationic surfactant is dodecyltrimethylammonium chloride. Specific embodiment 5

[0092] It is substantially the same as Specific Example 1, except that the aldehyde is succinaldehyde. Specific embodiment 6

[0094] It is substantially the same as the specific embodiment 1, except that the alcohol is propylene glycol. Specific embodiment 7

[0096] It is substantially the same as Specific Example 1, except that the sodium salt is sodium acetate. Specific embodiment 8

[0098] It is substantially the same as Specific Example 1, except that the sodium salt is sodium benzoate.

[0099] Verification test:

[0100] Test Example 1

[0101] The fungicide for fracturing fluid provided in Example 1 with a concentration of 0.1% by mass is dissolved in a suitable amount of water to form a uniform liquid, which has no precipitation, turbidity or flocculation after standing.

[0102] Test Example 2

[0103] 400 mL of 0.6% hydroxypropyl guar fracturing fluid was prepared, 0.5 g of soda ash was added, and after complete swelling, 0.2 wt % of the fracturing fluid bactericide prepared in Example 2 was added based on the total mass of the hydroxypropyl guar fracturing fluid. No precipitation or stratification occurred, and no obvious viscosity change was found when stirring with a glass rod, indicating that the bactericide for the fracturing fluid of the present invention has good compatibility with the fracturing fluid base fluid.

[0104] Test Example 3

[0105] Hydroxypropyl guar gum fracturing fluids with different powder ratios were prepared, and a certain concentration of the bactericide for fracturing fluid prepared in Example 3 was added to test the initial viscosity μ 0 , heat to 40℃ in a constant temperature water bath, keep it warm for 7 days, and test the final viscosity μ 1 , calculate the viscosity loss rate C, the results are shown in Table 1, the viscosity loss rate C is calculated according to the following formula:

[0106]

[0107] Table 1

[0108]

[0109] Through a large number of tests in Table 1, it is found that compared with the blank sample without adding the bactericide for fracturing fluid, the bactericide for fracturing fluid prepared in Example 3 has a very strong bactericidal and antibacterial effect in the range of 20 to 40°C.

[0110] Test Example 4

[0111] A certain concentration of the fracturing fluid bactericide prepared in Example 4 was added to the hydroxypropyl guar gum fracturing fluid, and a 1% borax solution was used as a cross-linking agent to observe the hanging performance. The specific results are shown in Table 2:

[0112] Table 2

[0113]

[0114]

[0115] From the test results in Table 2, it can be seen that the fungicide used in fracturing fluid has no effect on the hanging performance.

[0116] Test Example 5

[0117] Two parts of fracturing fluid base fluid were formulated into fracturing fluid jelly according to the cross-linking ratio required by the test (0.3% cross-linking ratio, HTC-160 high temperature cross-linking agent was selected as the cross-linking agent), and 0.2 wt % of the fracturing fluid fungicide prepared in Example 1 was added to one part of the fracturing fluid jelly based on the total mass of the fracturing fluid jelly.

[0118] The heat and shear resistance at 120°C were tested respectively. The results are as follows Figure 2 and Figure 3 As shown, the viscosity of the fracturing fluid added with the bactericide prepared in Example 1 was stable at about 400 mPa.s during the 120-min experimental time, which was much larger than the qualified standard of 50 mPa.s, and the same was true for the blank sample, indicating that the bactericide for fracturing fluid had no negative impact on the rheological properties of the fracturing fluid.

[0119] Test Example 6

[0120] Two parts of fracturing fluid base fluid were formulated into fracturing fluid jelly according to the cross-linking ratio required by the test (0.3% cross-linking ratio, HTC-160 high temperature cross-linking agent was selected as the cross-linking agent), and one part of the fracturing fluid jelly was added with 0.2 wt % of the fracturing fluid fungicide prepared in Example 1 based on the total mass of the fracturing fluid jelly.

[0121] Then the gel breaking experiment was carried out to measure the gel breaking time and gel breaking fluid viscosity. The test results showed that the gel breaking time and gel breaking fluid viscosity of the two fracturing fluid gels were not significantly different, indicating that the fungicide used in the fracturing fluid has no negative impact on the cross-linking of the fracturing fluid.

[0122] The above describes the embodiments of the present invention in detail. However, the present invention is not limited to the above embodiments, and various changes can be made within the knowledge of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A fungicide for fracturing fluid, It is characterized in that In terms of mass percentage, it is composed of the following raw materials: Cationic surfactant 5-10%, aldehyde 8-12%, alcohol 3-5%, sodium salt 3-5%, and the balance is water.

2. A fungicide for fracturing fluid according to claim 1, It is characterized in that The structural formula of the cationic surfactant is: in: R 1 is a C10-C12 alkyl group, R 2 is a C1-C12 alkyl group, and X is one of F, Cl, Br and I.

3. A fungicide for fracturing fluid according to claim 1, It is characterized in that The cationic surfactant is one of didodecyl dimethyl ammonium chloride, didodecyl dimethyl ammonium bromide, dodecyl trimethyl ammonium chloride and didecyl dimethyl ammonium chloride.

4. A fungicide for fracturing fluid according to claim 1, It is characterized in that The aldehyde is one of acetaldehyde, glutaraldehyde, succinaldehyde and glyoxal.

5. A fungicide for fracturing fluid according to claim 1, It is characterized in that The alcohol is one of ethanol, ethylene glycol, glycerol and isopropanol.

6. A fungicide for fracturing fluid according to claim 1, It is characterized in that The sodium salt is one of sodium phenolate, sodium xylene sulfonate, sodium acetate, sodium benzoate and sodium chloride.

7. A method for preparing a fungicide for fracturing fluid according to any one of claims 1 to 6, It is characterized in that Here are the steps: (1) Divide the amount of water in the formula into two parts; (2) adding a prescribed amount of alcohol to one portion of the water and stirring to obtain an alcohol solution; (3) Continue to add the cationic surfactant in the formula amount to the alcohol solution, stir evenly, and then heat to 50-60° C., then slowly add the aldehyde in the formula amount, stir evenly to obtain a mixed solution; (4) Add another portion of water to the mixed solution and gradually cool it to room temperature. Finally, add a formulated amount of sodium salt and stir evenly to obtain a fungicide for fracturing fluid.

8. A fungicide for fracturing fluid, It is characterized in that Prepared by the preparation method described in claim 7.

9. Use of the bactericide according to any one of claims 1 to 6 and claim 8 as a bactericide for fracturing fluid in petroleum production.

10. The use according to claim 9, wherein the specific steps are: when in use, based on the total mass of the fracturing fluid, 0.1 wt% to 0.2 wt% of the above-mentioned fracturing fluid bactericide is directly added to the fracturing fluid, and then directly injected into the target layer.

Images