Shale oil reservoir nitrogen foam fracturing fluid system as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of oil exploitation, and particularly relates to a shale oil reservoir nitrogen foam fracturing fluid system and a preparation method and application thereof. The preparation method comprises the following steps: adding disodium lauroiminodipropionate, a solvent and 1-bromine-6-(trimethyl ammonium) hexyl bromide into a reactor, uniformly stirring, heating and refluxing, and regulating and maintaining the pH value to be 8-9 by using sodium hydroxide; and carrying out reduced pressure distillation to obtain viscous liquid, recrystallizing with ethyl acetate to obtain solid, and drying to obtain the foaming agent. And uniformly stirring the foaming agent, the foam stabilizer and the simulated water in proportion to obtain the product foam fracturing fluid system. The foam fracturing fluid system has the advantages of large foaming volume and long half-life period.

Description

Technical Field

[0001] The invention belongs to the technical field of petroleum extraction, and in particular relates to a shale oil reservoir nitrogen foam fracturing fluid system and a preparation method and application thereof. Background Art

[0002] In the field of shale oil reservoir development, fracturing technology is one of the key measures to increase the production and recovery rate of oil and gas wells. Traditional fracturing fluid systems mainly include water-based fracturing fluids, oil-based fracturing fluids, and alcohol-based fracturing fluids. However, these traditional fracturing fluid systems have certain limitations in practical applications.

[0003] As oil and gas exploration and development expands to deep and unconventional oil and gas reservoirs, the formation conditions become more complex, which places higher demands on fracturing technology. For example, deep oil and gas reservoirs have high temperatures and pressures, dense formation rocks and low porosity, and conventional fracturing fluids are difficult to effectively open the formation and form a complex fracture network, making it impossible to achieve efficient oil and gas production.

[0004] Foam fracturing technology has emerged as a new type of fracturing technology. Foam fracturing fluid is a multiphase system composed of gas phase (usually nitrogen, carbon dioxide and other gases), liquid phase (water or other liquid additives) and additives such as surfactants. Its unique foam structure gives the fracturing fluid many excellent properties. First, the foam fracturing fluid has a low filtration loss, which can reduce the loss of fracturing fluid in the formation, improve the utilization rate of fracturing fluid, and reduce damage to the formation. Secondly, the presence of foam gives it a good sand carrying capacity, which can effectively transport the proppant into the formation cracks and maintain the conductivity of the cracks. In addition, the foam fracturing fluid has a high apparent viscosity, which can better control the expansion of cracks under high pressure conditions, forming a more complex fracture network, which is conducive to improving the production and recovery rate of oil and gas wells.

[0005] However, there are still some problems in the existing foam fracturing technology that need to be further solved. For example, the stability of the foam is difficult to control accurately. Under high temperature and high pressure conditions, the foam is easy to break, resulting in a decrease in the performance of the fracturing fluid; the formula of the foam fracturing fluid is relatively complex, and the synergistic mechanism between the components has not been fully clarified, and the adaptability under different formation conditions needs to be improved; the preparation process and construction equipment of the foam fracturing fluid also need to be further optimized to improve the efficiency and reliability of its industrial application. In summary, the development of a more stable and efficient foam fracturing system has important practical significance and broad application prospects for promoting foam fracturing technology.

[0006] CN104312563B discloses a cationic micro-bubble surfactant for drilling fluid and a preparation method thereof, wherein the surfactant is obtained by mixing vinyl cationic monomer A and vinyl amide compound B in a mass ratio of 10:1-10, adding a relative molecular mass regulator, and copolymerizing the mixture through free radicals, and the average relative molecular mass is between 1000 and 4000. However, the invention has poor foaming performance and foam stabilization performance, and the effect in practical applications is difficult to meet the on-site requirements.

[0007] CN102020981A discloses a heat-resistant, salt-resistant, low-tension foam oil-displacing agent and a preparation method thereof, which is prepared by continuously stirring alkanolamide, a bipolar surfactant and water at 40-60°C until they are completely dissolved. The heat-resistant, salt-resistant, low-tension foam agent of the invention is suitable for tertiary oil recovery under conditions of a temperature of 50-120°C and a mineralization of 0-100,000ppm. However, the main agent of the foam agent is alkanolamide and a bipolar surfactant. Alkanolamide is easily hydrolyzed, has poor high-temperature stability, is easily ineffective in the formation, and its application is limited. Summary of the invention

[0008] The present invention aims to solve the above-mentioned deficiencies in the prior art and provides a shale oil reservoir nitrogen foam fracturing fluid system and its preparation method and application. The foam fracturing fluid system of the present invention has the advantages of large foaming volume and long half-life.

[0009] One of the purposes of the present invention is to disclose a nitrogen foam fracturing fluid system for shale oil reservoirs, wherein the composition and components of the foam fracturing fluid system are as follows: Foaming agent 0.1-0.3 parts by mass; Foam stabilizer 0.05-0.2 parts by mass; 100 parts by mass of simulated water.

[0010] The foam stabilizer is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium lauryl polyoxyethylene ether sulfate.

[0011] The simulated water contains 1 wt % sodium chloride, 0.1 wt % calcium chloride, 0.05 wt % sodium bicarbonate, and the rest is water, and its pH value is 7.5.

[0012] The molecular structural formula of the foaming agent is as follows: .

[0013] Another object of the present invention is to disclose a method for preparing the above-mentioned foam fracturing fluid system, and the specific steps of the preparation method are as follows: (1) Add disodium lauryl iminodipropionate, solvent, and 1-bromo-6-(trimethylammonium)hexyl bromide into a reactor, stir evenly, heat to reflux, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with ethyl acetate to obtain a solid, and drying to obtain a foaming agent; (3) The foaming agent, foam stabilizer and simulated water are mixed evenly in proportion to obtain a foam fracturing fluid system.

[0014] In the present invention, preferably, based on 1 mole part of disodium lauryl iminodipropionate, the amount of 1-bromo-6-(trimethylammonium)hexyl bromide is 0.8-1.2 mole parts; more preferably, based on 1 mole part of disodium lauryl iminodipropionate, the amount of 1-bromo-6-(trimethylammonium)hexyl bromide is 0.9-1.1 mole parts.

[0015] Preferably, in step (1), the solvent is one of methanol, ethanol, propanol, isopropanol, butanol and isobutanol, more preferably one of ethanol and isobutanol, and the weight ratio of the solvent to disodium lauryl iminodipropionate is 20-40:1.

[0016] Preferably, the heating reflux time in step (1) is 24-72 hours.

[0017] Preferably, the foam stabilizer in step (3) is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium lauryl polyoxyethylene ether sulfate.

[0018] The synthetic reaction equation of the blowing agent of the present invention is as follows:

[0019] The third object of the present invention is to disclose the application of the above foam fracturing fluid system in shale oil reservoir fracturing.

[0020] The shale oil reservoir nitrogen foam fracturing fluid system of the present invention is composed of a foaming agent, a foam stabilizer and water. The foaming agent is an amphoteric surfactant. The lipophilic group is a fatty alkyl group, and the hydrophilic group is a dicarboxylic acid or a diquaternary ammonium salt. When the present invention is stirred or bubbled, air will enter the solution to form bubbles. When the bubbles contact and collide, the bubbles are difficult to merge because the hydration layer of the foaming agent molecules and their polar groups acts as a buffer in the middle, so small bubbles are easy to preserve. In addition, the foaming agent can also make the bubble surface elastic, and when the bubble is vibrated or subjected to external force, its shape and stability can be maintained. The foam stabilizer can control the structural stability of the bubble liquid film, so that the surfactant molecules are orderly distributed on the bubble liquid film, thereby giving the foam good elasticity and self-repairing ability.

[0021] Compared with the prior art, the present invention has the following advantages and beneficial effects: (1) The shale oil reservoir nitrogen foam fracturing fluid system of the present invention has the characteristic of large foaming volume, reaching 800 mL or more at room temperature; (2) The nitrogen foam fracturing fluid system for shale oil reservoirs of the present invention has the characteristic of a long half-life, which reaches more than 1300 seconds at room temperature. DETAILED DESCRIPTION

[0022] 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.

[0023] Example 1 (1) Add 20 mmol of disodium lauryl iminodipropionate, 149 g of methanol, and 16 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0024] (3) Mix 0.5 g of foaming agent, 1 g of carboxymethyl cellulose and 500 g of simulated water and stir evenly to obtain a foam fracturing fluid system.

[0025] Example 2 (1) Add 20 mmol of disodium lauryl iminodipropionate, 249 g of ethanol, and 24 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0026] (3) Mix 0.8 g of foaming agent, 0.5 g of carboxymethyl cellulose and 500 g of simulated water and stir evenly to obtain a foam fracturing fluid system.

[0027] Example 3 (1) Add 20 mmol of disodium lauryl iminodipropionate, 200 g of propanol, and 17 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 24 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0028] (3) Mix 1 g of foaming agent, 0.25 g of hydroxyethyl cellulose and 500 g of simulated water and stir evenly to obtain a foam fracturing fluid system.

[0029] Example 4 (1) Add 20 mmol of disodium lauryl iminodipropionate, 298 g of methanol, and 22 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 72 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0030] (3) Mix 1 g of foaming agent, 0.5 g of hydroxyethyl cellulose and 500 g of simulated water and stir evenly to obtain a foam fracturing fluid system.

[0031] Example 5 (1) Add 20 mmol of disodium lauryl iminodipropionate, 250 g of butanol, and 18 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 72 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0032] (3) Mix 1.2 g of foaming agent, 0.7 g of polyvinyl alcohol, and 500 g of simulated water and stir evenly to obtain a foam fracturing fluid system.

[0033] Example 6 (1) Add 20 mmol of disodium lauryl iminodipropionate, 264 g of isopropanol, and 19 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 48 hours, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0034] (3) Mix 1.2 g of foaming agent, 1 g of sodium lauryl polyoxyethylene ether sulfate, and 500 g of simulated water and stir evenly to obtain a foam fracturing fluid system.

[0035] Example 7 (1) Add 20 mmol of disodium lauryl iminodipropionate, 290 g of ethanol, and 20 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 48 h, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0036] (3) 1.3 g of foaming agent, 0.5 g of sodium lauryl polyoxyethylene ether sulfate, 0.5 g of hydroxyethyl cellulose, and 500 g of simulated water were stirred evenly to obtain a foam fracturing fluid system.

[0037] Example 8 (1) Add 20 mmol of disodium lauryl iminodipropionate, 270 g of isobutyl alcohol, and 21 mmol of 1-bromo-6-(trimethylammonium)hexyl bromide into the reactor, stir evenly, heat under reflux for 48 hours, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) Vacuum distillation is performed to obtain a viscous liquid, which is recrystallized from ethyl acetate to obtain a solid, which is then dried to obtain a foaming agent.

[0038] (3) 1.5 g of foaming agent, 0.8 g of sodium lauryl polyoxyethylene ether sulfate, 0.2 g of polyvinyl alcohol, and 500 g of simulated water were stirred evenly to obtain a foam fracturing fluid system.

[0039] Example 9 Foaming agent performance test Take 100 mL of the foam fracturing fluid system of the present invention, pour it into a high-stirring cup, place it on a high-speed stirrer, introduce nitrogen into the upper end to maintain the nitrogen atmosphere, start the high-speed stirrer, and record the time with a stopwatch. Stir for 60 seconds at a speed of (11000±300) r / min, quickly remove the high-stirring cup, pour all the generated foam liquid into a 1000 mL measuring cylinder, and record the time with a stopwatch. Then observe and record the foam volume in the measuring cylinder, which is the foaming volume.

[0040] The time taken for 50 mL of liquid to separate out from the foam is recorded as the half-life.

[0041] The fracturing foaming agent DRKJ-13 produced by Zhengzhou Derong Technology Co., Ltd. was prepared with simulated water to a concentration of 0.3wt% for comparative experiments.

[0042] Table 1 Foaming performance test results

[0043] From Table 1 we can see that: (1) The foam fracturing fluid system of the present invention has the characteristic of large foaming volume. The foaming volume at room temperature reaches 800 mL or more, and the highest reaches 890 mL (Examples 7 and 8). The foaming volume of the comparative example is 390 mL, which is significantly lower than that of the present invention.

[0044] (2) The foam fracturing fluid system of the present invention has the characteristic of a long half-life, which is more than 1300 s at room temperature, and the highest is 1580 s (Example 8), while the half-life of the comparative example is 410 s, which is significantly lower than that of the present invention.

[0045] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, a variety of simple modifications can be made to the technical solution of the present invention, and these simple modifications all belong to the protection scope of the present invention.

[0046] It should also be noted that the various specific technical features described in the above specific embodiments can be combined in any suitable manner without contradiction. In order to avoid unnecessary repetition, the present invention will not further describe various possible combinations.

[0047] In addition, various embodiments of the present invention may be arbitrarily combined, and as long as they do not violate the concept of the present invention, they should also be regarded as the contents disclosed by the present invention.

Claims

1. A shale oil reservoir nitrogen foam fracturing fluid system, characterized in that: The composition and components of the foam fracturing fluid system are as follows: Foaming agent 0.1-0.3 parts by mass; Foam stabilizer 0.05-0.2 parts by mass; 100 parts by mass of simulated water; The foam stabilizer is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium lauryl polyoxyethylene ether sulfate; The simulated water contains 1wt% sodium chloride, 0.1wt% calcium chloride, 0.05wt% sodium bicarbonate, and the rest is water, and its pH value is 7.5; The molecular structural formula of the foaming agent is as follows: 。 2. A method for preparing a nitrogen foam fracturing fluid system for shale oil reservoirs, characterized in that: The specific steps of the preparation method are as follows: (1) Add disodium lauryl iminodipropionate, solvent, and 1-bromo-6-(trimethylammonium)hexyl bromide into a reactor, stir evenly, heat to reflux, and adjust and maintain the pH at 8-9 with sodium hydroxide; (2) distilling under reduced pressure to obtain a viscous liquid, recrystallizing with ethyl acetate to obtain a solid, and drying to obtain a foaming agent; (3) Mix the foaming agent, foam stabilizer and simulated water in proportion to obtain a foam fracturing fluid system; Based on 1 molar part of disodium lauryl iminodipropionate, the amount of 1-bromo-6-(trimethylammonium)hexyl bromide used is 0.8-1.2 molar parts.

3. The method for preparing a shale oil reservoir nitrogen foam fracturing fluid system according to claim 2, characterized in that: Based on 1 molar part of disodium lauryl iminodipropionate, the amount of 1-bromo-6-(trimethylammonium)hexyl bromide used is 0.9-1.1 molar parts.

4. The method for preparing a shale oil reservoir nitrogen foam fracturing fluid system according to claim 2, characterized in that: In step (1), the solvent is one of methanol, ethanol, propanol, isopropanol, butanol and isobutanol, and the weight ratio of the solvent to disodium lauryl iminodipropionate is 20-40:

1.

5. The method for preparing a shale oil reservoir nitrogen foam fracturing fluid system according to claim 2, characterized in that: The heating reflux time in step (1) is 24-72 hours.

6. The method for preparing a shale oil reservoir nitrogen foam fracturing fluid system according to claim 2, characterized in that: The foam stabilizer described in step (3) is one or more of carboxymethyl cellulose, hydroxyethyl cellulose, polyvinyl alcohol, and sodium lauryl polyoxyethylene ether sulfate.

7. The method for preparing a shale oil reservoir nitrogen foam fracturing fluid system according to claim 2, characterized in that: The simulated water in step (3) contains 1 wt% sodium chloride, 0.1 wt% calcium chloride, 0.05 wt% sodium bicarbonate, and the remainder is water, and its pH value is 7.

5.

8. The method for preparing a shale oil reservoir nitrogen foam fracturing fluid system according to claim 2, characterized in that: The mass ratio of the foaming agent, the foam stabilizer and the simulated water in step (3) is 0.1-0.3:0.05-0.2:

100.

9. Use of the fracturing fluid system according to claim 1 in shale oil reservoir fracturing.

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