A drainage aid for oil and gas well fracturing and preparation method thereof

Abstract

The present invention belongs to the technical field of oil extraction, and specifically relates to a drainage aid for oil and gas well fracturing and a preparation method thereof. The preparation method is as follows: N-hydroxyethylpiperazine, isopropanol, and dodecane bromide are added to a reactor, the pH value is adjusted, heated, and the reaction is kept warm; dimethyl sulfate is added dropwise, the reaction is kept warm, and the pH value is adjusted; vacuum distillation is performed, transferred to a high-pressure reactor, solid sodium hydroxide is added, vacuumized, stirred and heated, propylene oxide is added, the temperature is increased, ethylene oxide is passed through, and after the passage is completed, the temperature is increased, cooled, filtered, and vacuum distillation is performed to obtain a drainage aid for product fracturing. The drainage aid for fracturing of the present invention has the advantages of low synthesis cost, low surface interfacial tension, low critical micelle concentration, and good drainage effect.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a drainage aid for oil and gas well fracturing and a preparation method thereof. Background Art

[0002] Tight oil and gas resources are important replacement resources for increasing reserves and production in the future. Due to their narrow pore throats, the effect of exploitation by natural energy is not good. Hydraulic fracturing is an important means to improve the fracture network of tight sandstone gas reservoirs. This method can effectively improve the seepage capacity of tight gas to achieve efficient development of tight gas. However, when hydraulic fracturing is implemented, a large amount of fracturing fluid entering the formation is likely to cause water lock damage, resulting in the "Jiamin effect", reducing the relative permeability of the gas phase and affecting the development effect.

[0003] However, the formation pressure is generally not enough to overcome the capillary resistance and cannot discharge the operating fluid from the pore channels. Therefore, it is necessary to use a drainage agent to reduce the surface and interfacial tension of the operating fluid and increase the contact angle, which is beneficial to weaken the adsorption of the reservoir, reduce the pore capillary force, and promote the discharge of the fracturing fluid from the dense core. It can solve the water lock and backflow problems of fracturing fluids and formation fluids in low-permeability and ultra-low-permeability reservoirs.

[0004] Fracturing aid is a chemical additive specially designed for fracturing operation of oil and gas wells. Fracturing aid can improve the viscosity, fluidity and uniformity of fracturing fluid, making it have better rheological properties. Fracturing aid also plays a role in reducing capillary pressure in fracturing operation of oil and gas wells. The addition of fracturing aid can improve the fluidity and uniformity of fracturing fluid, making the formation fractures more stable and uniform. Fracturing aid can increase the production capacity and collection efficiency of oil and gas wells.

[0005] CN109575903A discloses a formula of a drainage aid for fracturing containing fluorocarbon compounds and a preparation method thereof, and relates to the technical field of oil and gas field exploitation. The formula comprises the following components by mass: 50-80 parts of perfluoroalkyl butanamide, 50-70 parts of cationic surfactant, and 5-10 parts of fluorocarbon surfactant. The formula of the drainage aid for fracturing containing fluorocarbon compounds of the invention and its preparation method are compounded by the setting of perfluoroalkyl butanamide, cationic surfactant, fluorocarbon surfactant, alkylphenol polyoxyethylene ether, fatty alcohol and sodium sulfonate, and have good salt resistance, acid resistance and temperature resistance, can significantly reduce the oil, gas and water surface and interfacial tension, achieve fast and efficient drainage, backflow effect, widely used in the exploitation of oil and gas wells, can effectively reduce the surface and interfacial tension of the operating fluid, reduce capillary pressure and change the wetting condition of the formation, so that the operating fluid can easily enter the formation. However, the content of fluorocarbon surfactant in the formula of the invention is relatively high, resulting in high cost. In addition, fluorocarbon surfactant is difficult to degrade and will cause persistent biological accumulation.

[0006] CN109135718A discloses a method for preparing a fracturing acidification foaming and drainage agent. The foam-stabilizing surfactant prepared by the invention is mainly composed of zwitterionic surfactants, which have a large relative molecular weight and a larger surface area. After sacrificing part of the foaming ability, it can form a denser and more solid interface film on the surface of the solid and liquid phases, so that the bubbles are not easy to break; the dodecyl sulfobetaine molecules have a higher positive charge and are easy to associate with the negatively charged sodium dodecyl sulfate molecules. The hydrophobic force and electrostatic force between the two molecules work together to enhance the compounding effect and make up for the insufficient foaming ability of the foam-stabilizing surfactant; the fracturing acidification foaming and drainage agent prepared by the invention has two uses in one dose, avoiding the trouble of compounding the foaming agent and the drainage agent during construction, and at the same time, the foaming is fast, the bubble strength is high, the use is simpler, and the cost is reduced. However, the invention uses sodium hydride as the raw material. Sodium hydride has high chemical reactivity and can spontaneously combust in humid air. When heated or in contact with moisture or acids, it releases heat and hydrogen, causing combustion and explosion. Therefore, it is difficult to achieve industrial synthesis. Summary of the invention

[0007] The present invention aims to provide a drainage aid for oil and gas well fracturing and a preparation method thereof in view of the above-mentioned deficiencies in the prior art. The drainage aid for fracturing of the present invention has the advantages of low synthesis cost, low surface interfacial tension, low critical micelle concentration and good drainage effect.

[0008] One of the purposes of the present invention is to disclose a drainage aid for oil and gas well fracturing, the molecular structure of the drainage aid for fracturing is as follows:

[0009]

[0010] Among them: m=5-20, n=2-10.

[0011] Another object of the present invention is to provide a method for preparing a drainage agent for oil and gas well fracturing, the preparation method specifically comprising the following steps:

[0012] (1) Add N-hydroxyethylpiperazine, isopropanol, and dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 80-90° C., and keep the temperature for 2-6 hours;

[0013] (2) adjusting the pH to 3-4 with sulfuric acid, slowly adding dimethyl sulfate, and after the addition is complete, keeping the reaction at 80-90° C. for 2-6 hours, and adjusting the pH to 8-9 with sodium hydroxide solution;

[0014] (3) The viscous solid is obtained by distillation under reduced pressure, dissolved with DMF and transferred to a high-pressure reactor, solid sodium hydroxide is added, the reactor is purged with nitrogen for 5-8 minutes, and vacuum is applied, followed by stirring and heating to 80-85°C, the vacuum is stopped, propylene oxide is added, the temperature is raised to 130-160°C, the reaction pressure gradually decreases, and when the pressure no longer decreases, ethylene oxide is introduced. After the introduction is completed, the temperature is raised to 150-180°C, the reaction pressure gradually decreases, and when the pressure no longer decreases, the reaction is stopped, the system is cooled to below 60°C, filtered, and distilled under reduced pressure to obtain the product fracturing drainage agent.

[0015] In the present invention, preferably, based on 1 mole part of N-hydroxyethylpiperazine, the amounts of dodecane bromide, dimethyl sulfate, propylene oxide and ethylene oxide are 0.8-1.2 mole parts, 1.6-2.4 mole parts, 2-10 mole parts and 5-20 mole parts respectively; more preferably, based on 1 mole part of N-hydroxyethylpiperazine, the amounts of dodecane bromide, dimethyl sulfate, propylene oxide and ethylene oxide are 0.9-1.1 mole parts, 1.8-2.2 mole parts, 5-10 mole parts and 10-20 mole parts respectively.

[0016] In the present invention, preferably, the mass ratio of isopropanol to N-hydroxyethylpiperazine in step (1) is 10-12:1.

[0017] In the present invention, preferably, the mass ratio of DMF to N-hydroxyethylpiperazine in step (3) is 10-20:1.

[0018] In the present invention, preferably, the mass ratio of the sodium hydroxide solid to N-hydroxyethylpiperazine in step (3) is 0.2-0.5:1.

[0019] The reaction equation for the synthesis of the drainage agent for oil and gas well fracturing of the present invention is as follows:

[0020]

[0021]

[0022] The molecule of the drainage aid for oil and gas well fracturing of the present invention is a composite surfactant, in which the lipophilic group is provided by dodecyl and polyoxypropylene ether, and the hydrophilic group is two quaternary ammonium salts and polyoxyethylene ether. The present invention can reduce the oil-water interfacial tension, increase the wetting angle of the rock surface or increase the capillary radius, reduce the capillary pressure, and strongly remove the formation blockage, thereby facilitating the return of the fracturing residual fluid.

[0023] Compared with the prior art, the present invention has the following beneficial effects and advantages:

[0024] (1) The raw material source of the oil and gas well fracturing agent of the present invention is wide, the synthesis process is simple, and it is easy to industrialize and produce;

[0025] (2) The oil and gas well fracturing agent of the present invention has the characteristics of low surface tension and interfacial tension, and the lowest surface tension and interfacial tension are 27.2mN / m and 0.015mN / m respectively;

[0026] (3) The drainage agent for oil and gas well fracturing of the present invention has the characteristic of low critical micelle concentration, which is as low as 32 mg / L;

[0027] (4) The drainage aid for oil and gas well fracturing of the present invention has the characteristics of low dosage and high drainage rate, and the drainage rate reaches more than 90%. DETAILED DESCRIPTION

[0028] The endpoints and any values ​​of the ranges disclosed in this article 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 considered as specifically disclosed in this article.

[0029] Example 1

[0030] (1) Add 0.1 mol N-hydroxyethylpiperazine, 130 g isopropanol, and 0.08 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 80° C., and keep the temperature for 2 hours;

[0031] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.16 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 80°C for 2 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0032] (3) The viscous solid was obtained by vacuum distillation, which was dissolved in 130 g of DMF and transferred to a high-pressure reactor. 2.6 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 5 min, and then vacuumed. Then, the reactor was stirred and heated to 80° C., and the vacuuming was stopped. 0.2 mol of propylene oxide was added, and the temperature was raised to 130° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 0.5 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 150° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and vacuum distilled to obtain the product fracturing drainage agent.

[0033] Example 2

[0034] (1) Add 0.1 mol N-hydroxyethylpiperazine, 156 g isopropanol, and 0.12 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 90° C., and keep the temperature for 6 hours;

[0035] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.24 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 90°C for 2.5 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0036] (3) The viscous solid was obtained by vacuum distillation, which was dissolved in 150 g of DMF and transferred to a high-pressure reactor. 3.3 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 6 min, and then vacuumed. Then, the reactor was stirred and heated to 81° C., and the vacuuming was stopped. 0.3 mol of propylene oxide was added, and the temperature was raised to 130° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 0.8 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 160° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and vacuum distilled to obtain the product fracturing drainage agent.

[0037] Example 3

[0038] (1) Add 0.1 mol N-hydroxyethylpiperazine, 135 g isopropanol, and 0.085 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 82° C., and keep the temperature for 6 hours;

[0039] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.18 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 80°C for 6 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0040] (3) The viscous solid was obtained by vacuum distillation, which was dissolved in 180 g of DMF and transferred to a high-pressure reactor. 3.8 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 7 min, and then vacuumed. Then, the reactor was stirred and heated to 82° C., and the vacuuming was stopped. 0.4 mol of propylene oxide was added, and the temperature was raised to 140° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 1.4 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 160° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and vacuum distilled to obtain the product fracturing drainage agent.

[0041] Example 4

[0042] (1) Add 0.1 mol N-hydroxyethylpiperazine, 150 g isopropanol, and 0.115 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 85° C., and keep the temperature for 3 hours;

[0043] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.22 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 90°C for 3 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0044] (3) A viscous solid was obtained by vacuum distillation, which was dissolved in 214 g of DMF and transferred to a high-pressure reactor. 4.9 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 8 min, and then vacuumed. Then, the reactor was stirred and heated to 83° C., and the vacuuming was stopped. 0.5 mol of propylene oxide was added, and the temperature was raised to 140° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 1 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 156° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and vacuum distilled to obtain a product fracturing drainage agent.

[0045] Example 5

[0046] (1) Add 0.1 mol N-hydroxyethylpiperazine, 140 g isopropanol, and 0.09 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 85° C., and keep the temperature for 6 hours;

[0047] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.19 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 88°C for 2 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0048] (3) A viscous solid was obtained by distillation under reduced pressure, which was dissolved in 246 g of DMF and transferred to a high-pressure reactor. 5.2 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 5 min and evacuated. Then, the reactor was stirred and heated to 84° C., and the evacuation was stopped. 0.7 mol of propylene oxide was added, and the temperature was raised to 145° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 1.2 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 170° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and distilled under reduced pressure to obtain a product fracturing drainage agent.

[0049] Example 6

[0050] (1) Add 0.1 mol N-hydroxyethylpiperazine, 148 g isopropanol, and 0.11 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 88° C., and keep the temperature for 5 hours;

[0051] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.21 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 90°C for 4 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0052] (3) The viscous solid was obtained by vacuum distillation, which was dissolved in 252 g of DMF and transferred to a high-pressure reactor. 5.8 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 6 min, and then vacuumed. Then, the reactor was stirred and heated to 85° C., and the vacuuming was stopped. 0.8 mol of propylene oxide was added, and the temperature was raised to 160° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 1.8 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 170° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and vacuum distilled to obtain the product fracturing drainage agent.

[0053] Example 7

[0054] (1) Add 0.1 mol N-hydroxyethylpiperazine, 146 g isopropanol, and 0.1 mol dodecane bromide into a reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 90° C., and keep the temperature for 6 hours;

[0055] (2) Adjust the pH to 3-4 with sulfuric acid, slowly add 0.2 mol of dimethyl sulfate, and after the addition is complete, keep the reaction at 90°C for 2 hours, and adjust the pH to 8-9 with sodium hydroxide solution;

[0056] (3) The viscous solid was obtained by vacuum distillation, which was dissolved in 260 g of DMF and transferred to a high-pressure reactor. 6.5 g of solid sodium hydroxide was added, and the reactor was purged with nitrogen for 8 min, and then vacuumed. Then, the reactor was stirred and heated to 80° C., and the vacuuming was stopped. 1 mol of propylene oxide was added, and the temperature was raised to 160° C. The reaction pressure gradually decreased. When the pressure no longer decreased, 2 mol of ethylene oxide was introduced. After the introduction was completed, the temperature was raised to 180° C., and the reaction pressure gradually decreased. When the pressure no longer decreased, the reaction was stopped, and the system was cooled to below 60° C., filtered, and vacuum distilled to obtain the product fracturing drainage agent.

[0057] Example 8 Testing of surface tension and interfacial tension

[0058] The fracturing drainage agent of the present invention (Examples 1-7) was diluted to a concentration of 1000 mg / L, and the surface tension and interfacial tension were measured according to the method in SY / T 5370-2018 "Surface and interfacial tension determination method", and the results are shown in Table 1. A comparative experiment was conducted using the acidified fracturing drainage agent of Jinan Beiyate Chemical Technology Co., Ltd.

[0059] From Table 1 we can see that:

[0060] (1) The surface tension of the fracturing drainage agent of the present invention (Examples 1-7) is less than 28 mN / m when the concentration is 1000 mg / L, and the lowest is 27.2 mN / m; while the surface tension of the acid fracturing drainage agent of Jinan Beiyate Chemical Technology Co., Ltd. in the comparative example is 42.8 mN / m, which is significantly higher than that of the present invention;

[0061] (2) The interfacial tension of the fracturing drainage agent of the present invention (Examples 1-7) is less than 0.1 mN / m when used at a concentration of 1000 mg / L, with the lowest reaching 0.015 mN / m; while the interfacial tension of the acid fracturing drainage agent of the comparative example Jinan Beiyate Chemical Technology Co., Ltd. is 0.63 mN / m, which is significantly higher than that of the present invention.

[0062] Example 9 Test of critical micelle concentration

[0063] The critical micelle concentration was determined according to the method in GB / T 11276-2007 “Determination of critical micelle concentration of surfactants”. The results are shown in Table 1.

[0064] It can be seen from Table 1 that the critical micelle concentrations of the fracturing drainage agents of the present invention (Examples 1-7) are all less than 70 mg / L, with the lowest reaching 32 mg / L; while the critical micelle concentration of the acidified fracturing drainage agent of the comparative example Jinan Beiyate Chemical Technology Co., Ltd. is 250 mg / L, which is significantly higher than that of the present invention.

[0065] Example 10 Test of drainage aid rate

[0066] The drainage rate was determined according to Method 1 in SY / T 5755-2016 "Performance Evaluation Method of Discharge Aids for Fracturing Acidification", and the results are shown in Table 1. The test concentration was 5000 mg / L, and the acid fracturing discharge aid of Jinan Beiyate Chemical Technology Co., Ltd. was used for comparative experiments.

[0067] Table 1 Test results of surface tension, interfacial tension, critical micelle concentration and drainage rate

[0068]

[0069] It can be seen from Table 1 that the drainage rate of the fracturing drainage agent of the present invention (Examples 1-7) is greater than 90% when the use concentration is 5000 mg / L, and the highest is 96%; while the drainage rate of the acid fracturing drainage agent of Jinan Beiyate Chemical Technology Co., Ltd. in the comparative example is 82%, which is significantly lower than that of the present invention.

[0070] The above is only a preferred embodiment of the present invention, and is not any formal or substantial limitation of the present invention. It should be pointed out that ordinary technicians in this technical field can make several improvements and supplements without departing from the method of the present invention, and these improvements and supplements are also considered as the protection scope of the present invention. Any technician familiar with this profession, without departing from the spirit and scope of the present invention, can make some changes, modifications and equivalent changes made by using the technical content disclosed above, which are equivalent embodiments of the present invention; at the same time, any changes, modifications and evolutions of any equivalent changes made to the above embodiments based on the essential technology of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a drainage agent for oil and gas well fracturing, characterized in that: The preparation method specifically comprises the following steps: (1) Add N-hydroxyethylpiperazine, isopropanol and dodecane bromide into the reactor, adjust the pH to 9-10 with sodium hydroxide solution, heat to 80-90°C, and keep the temperature for 2-6 hours; (2) Adjust the pH to 3-4 with sulfuric acid, slowly add dimethyl sulfate, and after the addition is complete, keep the reaction at 80-90°C for 2-6 hours, and adjust the pH to 8-9 with sodium hydroxide solution; (3) The viscous solid is obtained by vacuum distillation, dissolved with DMF and transferred to a high-pressure reactor, solid sodium hydroxide is added, the reactor is purged with nitrogen for 5-8 minutes, vacuumed, then stirred and heated to 80-85°C, vacuumed, propylene oxide is added, the temperature is raised to 130-160°C, the reaction pressure gradually decreases, and when the pressure no longer decreases, ethylene oxide is introduced. After the introduction is completed, the temperature is raised to 150-180°C, the reaction pressure gradually decreases, and when the pressure no longer decreases, the reaction is stopped, the system is cooled to below 60°C, filtered, and vacuum distilled to obtain the product fracturing drainage agent; Based on 1 molar part of N-hydroxyethylpiperazine, the usage amounts of dodecane bromide, dimethyl sulfate, propylene oxide and ethylene oxide are 0.8-1.2 molar parts, 1.6-2.4 molar parts, 2-10 molar parts and 5-20 molar parts respectively.

2. The method for preparing a drainage agent for oil and gas well fracturing according to claim 1, characterized in that: Based on 1 molar part of N-hydroxyethylpiperazine, the usage amounts of dodecane bromide, dimethyl sulfate, propylene oxide and ethylene oxide are 0.9-1.1 molar parts, 1.8-2.2 molar parts, 5-10 molar parts and 10-20 molar parts respectively.

3. The method for preparing a drainage agent for oil and gas well fracturing according to claim 1, characterized in that: The mass ratio of isopropanol to N-hydroxyethylpiperazine in step (1) is 10-12:

1.

4. The method for preparing a drainage agent for oil and gas well fracturing according to claim 1, characterized in that: The mass ratio of DMF to N-hydroxyethylpiperazine in step (3) is 10-20:

1.

5. The method for preparing a drainage agent for oil and gas well fracturing according to claim 1, characterized in that: The mass ratio of sodium hydroxide solid to N-hydroxyethylpiperazine in step (3) is 0.2-0.5:1.

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