Low-adsorption strong flowback treatment agent and fracturing fluid containing same

Abstract

The invention provides a low-adsorption strong flowback treatment agent and fracturing fluid containing the same. The low-adsorption strong-flowback treating agent comprises triethanolamine, ethylene glycol, urea, a fluorocarbon surfactant and water. The low-adsorption strong-flowback fracturing fluid comprises a thickening agent, a clay stabilizer, a discharge aiding agent, a cross-linking agent, water and the low-adsorption strong-flowback treating agent.

Description

Technical Field

[0001] The present invention relates to the field of fracturing fluids, and particularly to a fracturing fluid containing a low-adsorption and strong-backflow treatment agent. Background Art

[0002] Domestic tight gas reservoirs are characterized by small porosity, low permeability, and strong heterogeneity. Polymer fracturing fluids are mainly used in large-scale volume fracturing treatments. Polymer fracturing fluids cause relatively serious core matrix damage to the reservoir, with a damage rate exceeding 50%, and the gas-measured core permeability recovery rate not exceeding 30%. The main factors causing matrix damage include polymer residues in the fracturing fluid, adsorption and retention damage of thickeners, water locking and water sensitivity effects. Conventional polymer fracturing fluid thickeners have a high density of hydrophilic groups, and their core adsorption and retention damage is greater than that of plant gums such as guar gum, which will directly reduce the oil and gas seepage channels; after water intrusion, it will cause core water locking and water sensitivity effects, the water saturation of the core increases, clay minerals absorb water and swell, the capillary resistance at the oil-water interface in the pores increases, and it is more difficult for oil and gas to flow through the matrix pore throats.

[0003] According to data research, under the condition that polymer fracturing fluids are basically polyacrylamide products, generally at home and abroad, measures such as reducing polymer residues and adding water-blocking agents to the fracturing fluid are taken to reduce the damage to the reservoir. Therefore, there is an urgent need to develop a product that can reduce the adsorption and retention damage of polymer fracturing fluids, and at the same time improve its backflow ability, significantly reduce the damage of polymers, so as to meet the technical requirements of fracturing treatments for more low-permeability tight gas reservoirs. Summary of the Invention

[0004] One aspect of the present invention provides a low-adsorption and strong-backflow treatment agent, which includes triethanolamine, ethylene glycol, urea, fluorocarbon surfactant, and water.

[0005] In a specific embodiment, based on the total mass of the low-adsorption and strong-backflow treatment agent being 100%, the content of triethanolamine is 40% to 50%, the content of ethylene glycol is 30% to 40%, the content of urea is 5% to 20%, and the content of fluorocarbon surfactant is 1% to 2%.

[0006] In a specific embodiment, the fluorocarbon surfactant is sodium perfluorononenyloxybenzenesulfonate.

[0007] Another aspect of the present invention provides a low-adsorption and strong-backflow fracturing fluid, which includes a thickener, a clay stabilizer, a backflow aid, a crosslinking agent, water, and the low-adsorption and strong-backflow treatment agent according to any one of the first aspect of the present invention.

[0008] In a specific embodiment, based on 100% by mass of water, the content of the thickening agent is 0.01% to 0.5%, the content of the clay stabilizer is 0.1% to 1%, the content of the flowback aid is 0.1% to 1%, the content of the crosslinking agent is 0.1% to 1%, and the content of the low adsorption and strong flowback treatment agent is 0.1% to 0.2%.

[0009] In a specific embodiment, the thickening agent is polyacrylamide and / or polyacrylamide copolymer.

[0010] In a specific embodiment, the molecular weight of the polyacrylamide is more than 18 million.

[0011] In a specific embodiment, the polyacrylamide copolymer is at least one of acrylamide-acryloyloxyethyl trimethyl ammonium chloride copolymer, acrylamide-sodium acrylate-acrylic acid copolymer, and acrylamide-acryloyloxyethyl trimethyl ammonium chloride-sodium acrylate-acrylic acid copolymer.

[0012] In a specific embodiment, the molecular weight of the polyacrylamide copolymer is more than 18 million.

[0013] In a specific embodiment, the flowback aid is polyoxyethylene amine ether and / or polyoxyethylene fatty alcohol ether.

[0014] In a specific embodiment, the polyoxyethylene amine ether is oleylamine polyoxyethylene ether and / or rosin amine polyoxyethylene ether.

[0015] In a specific embodiment, the polyoxyethylene fatty alcohol ether is at least one of polyoxyethylene dodecyl ether, polyoxyethylene tetradecyl ether, polyoxyethylene hexadecyl ether, and polyoxyethylene octadecyl ether.

[0016] In a specific embodiment, the clay stabilizer is dimethylamine quaternary ammonium salt and / or polyquaternary ammonium salt.

[0017] In a specific embodiment, the polyquaternary ammonium salt is polyquaternary ammonium salt-126.

[0018] In a specific embodiment, the crosslinking agent is an organic zirconium crosslinking agent.

[0019] In a specific embodiment, the organic zirconium crosslinking agent is zirconium lactate.

[0020] In a specific embodiment, the pH value of the low adsorption and strong flowback fracturing fluid is 6 to 8.

[0021] Advantages of the present invention:

[0022] The fracturing fluid of the present invention is a low-adsorption and strong-backflow fracturing fluid. The low-adsorption and strong-backflow high-efficiency treatment agent contained therein can reduce the adsorption and retention of the polymer fracturing fluid during construction, and at the same time improve the backflow efficiency of the liquid.

[0023] Compared with the comparative example and the prior art, the matrix damage of the low-adsorption and strong-backflow fracturing fluid to the tight sandstone reservoir is significantly reduced, the damage rate is less than 30%, and the core permeability recovery rate of the tight gas reservoir is ≥70%. Detailed implementation manners

[0024] The present invention will be further described below in conjunction with embodiments. However, the embodiments of the present invention are only exemplary descriptions, and this implementation manner does not constitute a limitation to the present invention under any circumstances.

[0025] Preparation of the low-adsorption and strong-backflow high-efficiency treatment agent

[0026] Example 1

[0027] The total system is 100 g.

[0028] 1) Add 40 g of triethanolamine and 30 g of ethylene glycol to a container, mix evenly to obtain a first mixture;

[0029] 2) Add 20 g of urea to the first mixture at the natural ambient temperature, mix evenly to obtain a second mixture;

[0030] 3) Add 9 g of distilled water to the second mixture at the natural ambient temperature, mix evenly, and stir until the urea is completely dissolved to obtain a third mixture;

[0031] 4) Add 1 g of perfluorononenyloxybenzenesulfonate (Shanghai Futian Technology Co., Ltd.) to the third mixture at the natural ambient temperature, mix evenly, thereby preparing the low-adsorption and strong-backflow high-efficiency treatment agent 1#, which is a homogeneous milky liquid product.

[0032] Take 0.1 g of the prepared low-adsorption and strong-backflow high-efficiency treatment agent 1# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the standard of SY / T 5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0033] Example 2

[0034] The total system is 100 g.

[0035] 1) Add 45 g of triethanolamine and 35 g of ethylene glycol to a container, mix evenly to obtain a first mixture;

[0036] 2) Add 15 g of urea to the first mixture at the natural ambient temperature, mix evenly to obtain a second mixture;

[0037] 3) Add 3 g of distilled water to the second mixture at natural ambient temperature, mix evenly, and stir until the urea is completely dissolved to obtain a third mixture;

[0038] 4) Add 2 g of sodium perfluorononenyloxybenzenesulfonate (Shanghai Futian Technology Co., Ltd.) to the third mixture at natural ambient temperature, mix evenly, thereby obtaining the low adsorption and strong backflow high-efficiency treatment agent 2#, which is a homogeneous milky liquid product.

[0039] Take 0.1 g of the above-prepared low adsorption and strong backflow high-efficiency treatment agent 2# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the SY / T 5107-2016 "Evaluation Method for the Performance of Water-Based Fracturing Fluids" standard, measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0040] Example 3

[0041] The total system is 100 g.

[0042] 1) Add 50 g of triethanolamine and 40 g of ethylene glycol to a container, mix evenly, to obtain a first mixture;

[0043] 2) Add 5 g of urea to the first mixture at natural ambient temperature, mix evenly, to obtain a second mixture;

[0044] 3) Add 3.5 g of distilled water to the second mixture at natural ambient temperature, mix evenly, and stir until the urea is completely dissolved to obtain a third mixture;

[0045] 4) Add 1.5 g of sodium perfluorononenyloxybenzenesulfonate (Shanghai Futian Technology Co., Ltd.) to the third mixture at natural ambient temperature, mix evenly, thereby obtaining the low adsorption and strong backflow high-efficiency treatment agent 3#, which is a homogeneous milky liquid product.

[0046] Take 0.1 g of the above-prepared low adsorption and strong backflow high-efficiency treatment agent 3# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the SY / T 5107-2016 "Evaluation Method for the Performance of Water-Based Fracturing Fluids" standard, measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0047] Comparative Example 1

[0048] The total system is 100 g.

[0049] 1) Add 30 g of triethanolamine and 20 g of ethylene glycol to a container, mix evenly, to obtain a first mixture;

[0050] 2) Add 2.5 g of urea to the first mixture at the natural ambient temperature, and mix evenly to obtain a second mixture;

[0051] 3) Add 47 g of distilled water to the second mixture at the natural ambient temperature, mix evenly, and stir until the urea is completely dissolved to obtain a third mixture;

[0052] 4) Add 0.5 g of sodium perfluorononenyloxybenzenesulfonate (Shanghai Futian Technology Co., Ltd.) to the third mixture at the natural ambient temperature, and mix evenly to prepare the low-adsorption and strong-backflow high-efficiency treatment agent 3#, which is a homogeneous milky liquid product.

[0053] Take 0.1 g of the prepared low-adsorption and strong-backflow high-efficiency treatment agent 4# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the standard of SY / T 5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0054] Comparative Example 2

[0055] The total system is 100 g.

[0056] 1) Add 55 g of triethanolamine and 42 g of ethylene glycol to a container, and mix evenly to obtain a first mixture;

[0057] 2) Add 1 g of urea to the first mixture at the natural ambient temperature, and mix evenly to obtain a second mixture;

[0058] 3) Add 1.9 g of distilled water to the second mixture at the natural ambient temperature, mix evenly, and stir until the urea is completely dissolved to obtain a third mixture;

[0059] 4) Add 0.1 g of sodium perfluorononenyloxybenzenesulfonate (Shanghai Futian Technology Co., Ltd.) to the third mixture at the natural ambient temperature, and mix evenly to prepare the low-adsorption and strong-backflow high-efficiency treatment agent 5#, which is a homogeneous milky liquid product.

[0060] Take 0.1 g of the prepared low-adsorption and strong-backflow high-efficiency treatment agent 5# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the standard of SY / T 5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0061] Comparative Example 3

[0062] The total system is 100 g.

[0063] 1) Add 35 g of triethanolamine and 25 g of ethylene glycol to a container, and mix evenly to obtain a first mixture;

[0064] 2) Add 2 g of urea to the first mixture at natural ambient temperature, mix evenly to obtain a second mixture;

[0065] 3) Add 38 g of distilled water to the second mixture at natural ambient temperature, mix evenly, and stir until the urea is completely dissolved, thereby preparing the low adsorption and strong backflow high-efficiency treatment agent No. 6#, which is a homogeneous milky liquid product.

[0066] Take 0.1 g of the prepared low adsorption and strong backflow high-efficiency treatment agent No. 6# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the standard SY / T 5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0067] Comparative Example 4

[0068] The total system is 100 g.

[0069] Add 58 g of triethanolamine and 42 g of ethylene glycol to a container, mix evenly, thereby preparing the low adsorption and strong backflow high-efficiency treatment agent No. 7#, which is a homogeneous colorless liquid product.

[0070] Take 0.1 g of the prepared low adsorption and strong backflow high-efficiency treatment agent No. 7# and add it to 99.9 g of distilled water to prepare an aqueous solution with a mass concentration of 0.1%. According to the standard SY / T 5107-2016 "Evaluation Method for Performance of Water-Based Fracturing Fluids", measure the surface tension of the aqueous solution, and the results are shown in Table 1.

[0071] Table 1

[0072] Example Surface tension (mN / m) Example 1 23.04 Example 2 21.87 Example 3 22.93 Comparative Example 1 27.96 Comparative Example 2 28.15 Comparative Example 3 35.26 Comparative Example 4 32.07

[0073] It can be seen from the results in Table 1 that the surface tension of the low adsorption and strong backflow high-efficiency treatment agents prepared in the above examples of the present invention is lower than 25 mN / m, and compared with Comparative Examples 1 to 4, the surface tension of the solution can be significantly reduced after being added to water, playing a role of strong backflow.

[0074] Preparation of Fracturing Fluid

[0075] Example 4

[0076] Step 1. Add 0.01 g of thickening agent polyacrylamide with a relative molecular weight of 18 million (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and adjust the rotation speed at all times to ensure a vortex state until it is fully dissolved to form a uniform solution, thereby preparing the first base fluid;

[0077] Step 2. While maintaining the stirring state, add 0.1 g of dimethylamine quaternary ammonium salt (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base liquid, and stir evenly to obtain the second base liquid;

[0078] Step 3. Lower the stirring speed, add 0.1 g of oleylamine polyoxyethylene ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base liquid, and stir evenly to obtain the third base liquid;

[0079] Step 4. Add 0.1 g of low adsorption and strong backflow high-efficiency treatment agent 1# and 0.1 g of zirconium lactate crosslinking agent to the third base liquid, and stir to obtain the fracturing fluid.

[0080] Example 5

[0081] Step 1. Add 0.02 g of polyacrylamide with a relative molecular weight of 18 million (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, obtaining the first base liquid;

[0082] Step 2. While maintaining the stirring state, add 0.3 g of dimethylamine quaternary ammonium salt (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base liquid, and stir evenly to obtain the second base liquid;

[0083] Step 3. Lower the stirring speed, add 0.3 g of rosin amine polyoxyethylene ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base liquid, and stir evenly to obtain the third base liquid;

[0084] Step 4. Add 0.15 g of low adsorption and strong backflow high-efficiency treatment agent 1# and 0.2 g of zirconium lactate crosslinking agent to the third base liquid, and stir to obtain the fracturing fluid.

[0085] Example 6

[0086] Step 1. Add 0.1 g of polyacrylamide with a relative molecular weight of 18 million (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, obtaining the first base liquid;

[0087] Step 2. While maintaining the stirring state, add 0.5 g of polyquaternium-126 (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base liquid, and stir evenly to obtain the second base liquid;

[0088] Step 3. Lower the stirring speed, add 0.5 g of polyoxyethylene dodecyl alcohol ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base liquid, and stir evenly to obtain the third base liquid;

[0089] Step 4. Add 0.2 g of low adsorption and strong flowback high-efficiency treatment agent 1# and 0.3 g of zirconium lactate crosslinking agent to the third base fluid, and stir to obtain the fracturing fluid.

[0090] Example 7

[0091] Step 1. Add 0.2 g of polyacrylamide with a relative molecular weight of 18 million (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base fluid;

[0092] Step 2. While maintaining the stirring state, add 0.8 g of polyquaternium-126 (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base fluid and stir evenly to obtain the second base fluid;

[0093] Step 3. Lower the stirring speed, add 0.5 g of polyoxyethylene cetyl alcohol ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base fluid, and stir evenly to obtain the third base fluid;

[0094] Step 4. Add 0.1 g of low adsorption and strong flowback high-efficiency treatment agent 2# and 0.4 g of zirconium lactate crosslinking agent to the third base fluid, and stir evenly to obtain the fracturing fluid.

[0095] Example 8

[0096] Step 1. Add 0.3 g of polyacrylamide with a relative molecular weight of 18 million (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base fluid;

[0097] Step 2. While maintaining the stirring state, add 0.8 g of polyquaternium-126 (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base fluid and stir evenly to obtain the second base fluid;

[0098] Step 3. Lower the stirring speed, add 0.8 g of polyoxyethylene octadecyl alcohol ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base fluid, and stir evenly to obtain the third base fluid;

[0099] Step 4. Add 0.15 g of low adsorption and strong flowback high-efficiency treatment agent 2# and 0.5 g of zirconium lactate crosslinking agent to the third base fluid, and stir evenly to obtain the fracturing fluid.

[0100] Example 9

[0101] Step 1. Add 0.4 g of acrylamide-acryloyloxyethyltrimethylammonium chloride copolymer with a relative molecular weight of 18 million (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base liquid;

[0102] Step 2. While maintaining the stirring state, add 1.0 g of dimethylamine quaternary ammonium salt (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the first base liquid and stir evenly to obtain the second base liquid;

[0103] Step 3. Lower the stirring speed, add 1.0 g of polyoxyethylene cetyl ether (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the second base liquid and stir evenly to obtain the third base liquid;

[0104] Step 4. Add 0.2 g of low adsorption and strong backflow high-efficiency treatment agent No. 2 and 0.6 g of zirconium lactate crosslinking agent to the third base liquid and stir evenly to obtain the fracturing fluid.

[0105] Example 10

[0106] Step 1. Add 0.5 g of acrylamide-sodium acrylate-acrylic acid copolymer with a relative molecular weight of 18 million (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base liquid;

[0107] Step 2. While maintaining the stirring state, add 0.25 g of dimethylamine quaternary ammonium salt (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) and 0.25 g of polyquaternium-126 (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the first base liquid and stir evenly to obtain the second base liquid;

[0108] Step 3. Lower the stirring speed, add 0.25 g of oleamine polyoxyethylene ether (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) and 0.25 g of polyoxyethylene cetyl ether (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the second base liquid and stir evenly to obtain the third base liquid;

[0109] Step 4. Add 0.15 g of low adsorption and strong backflow high-efficiency treatment agent No. 3 and 0.8 g of zirconium lactate crosslinking agent to the third base liquid and stir evenly to obtain the fracturing fluid.

[0110] Example 11

[0111] Step 1. Add 0.5 g of acrylamide-acryloyloxyethyltrimethylammonium chloride-sodium acrylate-acrylic acid copolymer (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) with a relative molecular weight of 18 million to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base liquid;

[0112] Step 2. While maintaining the stirring state, add 0.5 g of dimethylamine quaternary ammonium salt (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) and 0.5 g of polyquaternium-126 (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base liquid, and stir evenly to obtain the second base liquid;

[0113] Step 3. Lower the stirring speed, add 0.5 g of oleamine polyoxyethylene ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) and 0.5 g of polyoxyethylene cetyl ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base liquid, and stir evenly to obtain the third base liquid;

[0114] Step 4. Add 0.2 g of low adsorption and strong backflow high-efficiency treatment agent No. 3 and 1.0 g of zirconium lactate crosslinking agent to the third base liquid, and stir evenly to obtain the fracturing fluid.

[0115] Comparative Example 5

[0116] Step 1. Add 0.005 g of polyacrylamide (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) with a relative molecular weight of 18 million to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base liquid;

[0117] Step 2. While maintaining the stirring state, add 0.02 g of dimethylamine quaternary ammonium salt (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the first base liquid, and stir evenly to obtain the second base liquid;

[0118] Step 3. Lower the stirring speed, add 0.02 g of polyoxyethylene cetyl ether (Dongying Shiprui Petroleum Engineering Technology Co., Ltd.) to the second base liquid, and stir evenly to obtain the third base liquid;

[0119] Step 4. Add 0.05 g of zirconium lactate crosslinking agent to the third base liquid and stir to obtain the fracturing fluid.

[0120] Comparative Example 6

[0121] Step 1. Add 1.0 g of polyacrylamide with a relative molecular weight of 18 million (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fisheyes, and constantly adjust the rotation speed to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base liquid;

[0122] Step 2. While maintaining the stirring state, add 2.0 g of dimethylamine quaternary ammonium salt (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the first base liquid and stir evenly to obtain the second base liquid;

[0123] Step 3. Lower the stirring speed, add 2.0 g of polyoxyethylene cetyl ether (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the second base liquid and stir evenly to obtain the third base liquid;

[0124] Step 4. Add 0.05 g of low adsorption and strong backflow high-efficiency treatment agent No. 1 and 1.5 g of zirconium lactate cross-linking agent to the third base liquid and stir to obtain the fracturing fluid.

[0125] Comparative Example 7

[0126] The low adsorption and strong backflow high-efficiency treatment agent used was prepared from Comparative Example 1, and the others were the same as in Example 9.

[0127] Comparative Example 8

[0128] The low adsorption and strong backflow high-efficiency treatment agent used was prepared from Comparative Example 2, and the others were the same as in Example 9.

[0129] Comparative Example 9

[0130] The low adsorption and strong backflow high-efficiency treatment agent used was prepared from Comparative Example 3, and the others were the same as in Example 9.

[0131] Comparative Example 10

[0132] The low adsorption and strong backflow high-efficiency treatment agent used was prepared from Comparative Example 4, and the others were the same as in Example 9.

[0133] Comparative Example 11

[0134] Step 1. Add 1.0 g of N-carboxymethylacrylamide, 0.1 g of anthranilic acid, 0.1 g of urea, 0.01 g of Span-40 and 17.5 g of ethanol aqueous solution with a mass fraction of 92% to 13.5 g of sodium hydroxide aqueous solution with a mass fraction of 50 wt%. Mix evenly (heat will be released), cool to 15 °C, add 10 g of refined cotton with a degree of polymerization of 3400, carry out an alkalization reaction at 25 °C for 1 h, then add 11.8 g of chloroacetic acid aqueous solution with a mass fraction of 70%, continue the reaction for 2 h, and then carry out drying and crushing to obtain a polyacrylamide copolymer containing urea and ethanol.

[0135] Step 2. Add 0.01 g of polyacrylamide copolymer containing urea and ethanol into 100 g of clear water. During the addition process, control the addition speed to prevent the formation of fish eyes, and adjust the rotation speed at all times to ensure a vortex state until it is fully dissolved to form a uniform solution, thus obtaining the first base liquid;

[0136] Step 3. While maintaining the stirring state, add 0.1 g of dimethylamine quaternary ammonium salt (Dongying Shipurui Petroleum Engineering Technology Co., Ltd.) to the first base liquid and stir evenly to obtain the second base liquid;

[0137] Step 4. Lower the stirring speed, add 0.02 g of polyoxyethylene cetyl ether and 0.1 g of perfluorononenyloxybenzenesulfonic acid sodium salt (Shanghai Futian Technology Co., Ltd.) to the second base liquid, and stir evenly to obtain the third base liquid;

[0138] Step 5. Add 4 g of ethylene glycol and 0.1 g of zirconium lactate crosslinking agent to the third base liquid and stir evenly to obtain the fracturing fluid.

[0139] Performance determination of the fracturing fluid

[0140] Use a six-speed rotary viscometer to measure the viscosity of the fracturing fluids prepared in Examples 4 to 11 and Comparative Examples 5 to 11. The results are shown in Table 2.

[0141] Use a pH meter to measure the viscosity of the fracturing fluids prepared in Examples 4 to 11 and Comparative Examples 5 to 11. The results are shown in Table 2.

[0142] Respectively use the core displacement device for the fracturing fluids prepared in Examples 4 to 11 and Comparative Examples 5 to 11 to conduct a tight sandstone core damage performance evaluation experiment according to the standard SY / T5107-2016 water-based fracturing fluid performance evaluation method. The specific steps are as follows: Add the fracturing fluid of each example or comparative example into a high-temperature and high-pressure filtration loss instrument, set the temperature to 80 °C and the pressure to 3.5 MPa to obtain 300 mL of filtrate. Select tight sandstone natural cores with the same order of magnitude of permeability, measure the core permeability before and after being damaged by the filtrate, and calculate the reduction rate of the core permeability after being damaged by the filtrate compared to the core permeability before damage (i.e., the core damage rate). The results are shown in Table 2.

[0143] Conduct a permeability recovery rate (flowback efficiency) evaluation experiment on the fracturing fluids prepared in Examples 4 to 11 and Comparative Examples 5 to 11. The specific steps are as follows: Select tight sandstone natural cores with the same order of magnitude of permeability, and use 20000 mg / L standard brine (2 wt% KCl + 5.5 wt% NaCl + 0.45 wt% MgCl 2 + 0.55 wt% CaCl 2Establish an initial water saturation of 40 wt% and an initial gas-measured core permeability based on the mass ratio; add 0.08 wt% of ammonium persulfate to the fracturing fluid to break the gel for 180 min to obtain a gel-breaking fluid. After heating the gel-breaking fluid to 80 °C, add it to an intermediate container, pressurize it to 3.5 MPa through a pressure source, and reverse-squeeze it into the core from the other end inlet of the core holder. After 180 min of displacing the damage with the gel-breaking fluid, measure the gas-measured core permeability 24 hours after 180 min of damage by the gel-breaking fluid, calculate the ratio of the gas-measured core permeability 24 hours after damage to the initial permeability before damage, and obtain the permeability recovery rate (24-hour flowback efficiency) of the fracturing fluid. The results are shown in Table 2.

[0144] It can be clearly seen from the experimental results in Table 2 that adding a low-adsorption and high-flowback efficient treatment agent in the above embodiments of the present invention does not affect the viscosity and pH value of the fracturing fluid, and the damage rate of the prepared low-adsorption and high-flowback fracturing fluid to the tight sandstone core is less than 30%. Compared with Comparative Examples 5 to 11, the damage reduction rate reaches more than 50%, and at the same time, the permeability recovery rate (flowback efficiency) is greater than 70%. Thus, it can be seen that the low-adsorption and high-flowback fracturing fluid of the present invention can be widely suitable for the fracturing transformation of various tight sandstone gas reservoirs.

[0145] Table 2

[0146]

[0147] Although the present invention has been described with reference to specific embodiments, those skilled in the art should understand that various changes can be made without departing from the true spirit and scope of the present invention. In addition, various changes can be made to the subject matter, spirit, and scope of the present invention to adapt to specific situations, materials, material compositions, and methods. All such changes are included within the scope of the claims of the present invention.

Claims

1. A low-adsorption strong flowback treatment agent, which comprises triethanolamine, ethylene glycol, urea, a fluorocarbon surfactant and water.

2. The low adsorption strong flowback treatment agent according to claim 1, It is characterized in that Taking the total mass of the low-adsorption strong flowback treatment agent as 100%, the content of triethanolamine is 40% to 50%, the content of ethylene glycol is 30% to 40%, the content of urea is 5% to 20%, and the content of fluorocarbon surfactant is 1% to 2%.

3. The low adsorption strong flowback treatment agent according to claim 1, It is characterized in that The fluorocarbon surfactant is sodium perfluorononenyloxybenzenesulfonate.

4. A low-adsorption strong flowback fracturing fluid, comprising a thickener, a clay stabilizer, a drainage aid, a cross-linking agent, water and the low-adsorption strong flowback treating agent according to any one of claims 1 to 3.

5. The low-adsorption strong flowback fracturing fluid according to claim 4, It is characterized in that Taking the mass of water as 100%, the content of the thickener is 0.01% to 0.5%, the content of the clay stabilizer is 0.1% to 1%, the content of the drainage aid is 0.1% to 1%, the content of the cross-linking agent is 0.1% to 1%, and the content of the low-adsorption strong backflow treatment agent is 0.1% to 0.2%.

6. The low-adsorption strong flowback fracturing fluid according to claim 4, It is characterized in that The thickener is polyacrylamide and / or polyacrylamide copolymer; Preferably, the molecular weight of the polyacrylamide is greater than 18 million; Preferably, the polyacrylamide copolymer is at least one of acrylamide-acryloyloxyethyltrimethylammonium chloride copolymer, acrylamide-sodium acrylate-acrylic acid copolymer and acrylamide-acryloyloxyethyltrimethylammonium chloride-sodium acrylate-acrylic acid copolymer; Preferably, the molecular weight of the polyacrylamide copolymer is greater than 18 million.

7. The low-adsorption strong flowback fracturing fluid according to claim 4, It is characterized in that The drainage aid is polyoxyethylene amine ether and / or polyoxyethylene fatty alcohol ether; Preferably, the polyoxyethylene amine ether is oleylamine polyoxyethylene ether and / or rosin amine polyoxyethylene ether; Preferably, the polyoxyethylene fatty alcohol ether is at least one of polyoxyethylene lauryl alcohol ether, polyoxyethylene tetradecanol ether, polyoxyethylene cetyl alcohol ether and polyoxyethylene octadecyl alcohol ether.

8. The low-adsorption strong flowback fracturing fluid according to claim 4, It is characterized in that The clay stabilizer is dimethylamine quaternary ammonium salt and / or polyquaternary ammonium salt; Preferably, the polyquaternium salt is polyquaternium-126.

9. The low-adsorption strong flowback fracturing fluid according to claim 4, It is characterized in that The cross-linking agent is an organic zirconium cross-linking agent; Preferably, the organic zirconium cross-linking agent is zirconium lactate.

10. The low-adsorption, strong flowback fracturing fluid according to any one of claims 4 to 9, It is characterized in that The pH value of the low-adsorption and strong flowback fracturing fluid is 6 to 8.

Images