Method for preparing micro-nano oil displacement agent by using oil sludge sand and prepared nano oil displacement agent

Abstract

The application discloses a method for preparing micro-nano oil displacement agent by using oil sludge sand and the prepared nano oil displacement agent. The micro-nano oil displacement agent is not prepared by removing crude oil in the oil sludge, but by removing large-diameter oil sand (10 microns or above), and then the oil sludge, the crude oil in the oil sludge, a dispersion assisting substance and water are prepared into a composite micro-nano oil displacement agent. The preparation method comprises the following steps: pretreatment of the oil sludge sand, sulfonation process treatment and micro-nano refining treatment. Finally, the composite micro-nano oil displacement agent is formed by the micro-nano oil sludge, micro-nano oil droplets, the dispersion assisting substance and water. The oil sludge sand of the oil field waste is used as the micro-nano oil displacement agent, the oil sludge sand is deeply utilized, the risk of ground environmental pollution is reduced, the oil sludge treatment cost is saved, the crude oil production is improved, and the waste is turned into treasure.

Description

Technical Field

[0001] This invention relates to the field of comprehensive utilization of oily sludge solid waste and enhanced oil recovery technology, and in particular to a method for preparing micro-nano oil displacement agents using oily sludge sand and the obtained nano oil displacement agents. Background Technology

[0002] Petroleum is hailed as the lifeblood of modern industry. However, the processes of oil extraction, refining, processing, crude oil gathering, transportation, and storage generate large quantities of hazardous waste, oil sludge. Statistics show that my country's annual crude oil production of 210 million tons produces 4.2 million tons of oil sludge. Open-air stockpiling of oil sludge causes serious pollution to soil and groundwater. Furthermore, the volatile hydrocarbons in oil sludge pose a serious threat to the ecological environment. Therefore, relevant Chinese laws explicitly require enterprises to carry out harmless treatment of hazardous waste oil sludge. Given the large reserves of oil sludge in oil fields, the high difficulty of treatment, and the increasing national emphasis on environmental protection, there is an urgent need to develop economical and safe methods for treating oil sludge.

[0003] Oil sludge is a chemically stable, high-viscosity, multiphase suspension system mainly composed of crude oil, solid suspended particles, asphaltene, wax, microorganisms, and heavy metals that are tightly adhered to each other. The most commonly used technologies for treating oil sludge currently include (1) reinjection profile control, which can improve water channeling and expand the swept volume, but its applicability is limited by reservoir conditions, oil sludge particle size, and suspended impurities; (2) thermochemical cleaning, which utilizes the principle of similar compatibility, consumes little energy and produces good oil, but the treatment speed is slow, consumes a large amount of chemicals, and generates a large amount of wastewater; (3) incineration, which can treat various types of oil sludge, has a wide range of applications and a considerable treatment capacity, but it causes air pollution, and crude oil is difficult to recover, resulting in waste. In addition, the equipment is relatively complex and costly; (4) solidification landfill, which is technically mature, easy to operate, and low in cost, and can effectively treat large amounts of oil sludge, but this technology occupies a large amount of land and is not conducive to environmental protection. The above-mentioned existing technologies all have problems to varying degrees, such as high treatment costs, secondary pollution, and low resource utilization. In fact, the main component of oil sludge sand, the solid suspended particles, range in size from micro-nano to millimeter. They originate from loose sand and skeletal sand in the formation, with a stable source and high yield. Micro-nano particles account for 20% to 60% of the total particles, possessing potential for utilization but currently underutilized. To fully utilize oil sludge sand resources and further explore its application potential in enhanced oil recovery, it is necessary to refine and deepen the application of oil sludge sand particles of different size ranges.

[0004] In recent years, the petroleum industry has made significant progress in utilizing nanoparticle-based enhanced oil recovery (EOR) technology, which is expected to boost oil and gas production to new heights during the Fifth Technological Revolution (2020-2035). Nanoparticles are small in size and possess unique physicochemical properties such as a large specific surface area and special oil-water interface effects. They exhibit various EOR mechanisms, including the "wedge compression" mechanism, reduced water-oil mobility ratio, wetting reversal mechanism, reduced interfacial tension, and improved reservoir heterogeneity. Currently, nanoparticle-based EOR technology has not been effectively promoted in oilfields. The main reasons include (1) the extremely high cost of nanoparticle raw materials and manufacturing; (2) the challenging nature of nanoparticle stability studies in the system; and (3) the incompatibility of some nanomaterials with the formation, which can easily damage the reservoir.

[0005] Micro- and nano-sized oil sludge sand has inherent advantages in preparation as micro- and nano-sized oil displacement agents, such as wide availability, low cost, stable particle composition, and good compatibility with the formation. However, it is necessary to solve problems such as large particle removal of oil sludge sand, modification of micro- and nano-sized particles, and uniform dispersion of micro- and nano-sized particles and oil droplets. Summary of the Invention

[0006] The technical problem to be solved by this invention is to provide a method for preparing micro-nano oil displacement agents using oil sludge and sand, and the resulting nano-oil displacement agent. This solves the problems of high treatment cost, secondary pollution, and low resource utilization in existing oil sludge and sand treatment technologies. This invention utilizes oilfield waste oil sludge and sand as a micro-nano oil displacement agent, achieving refined and in-depth utilization of oil sludge and sand, and turning waste into treasure.

[0007] To solve the above-mentioned technical problems, the technical solution adopted by the present invention is: a method for preparing micro-nano oil displacement agents using oil sludge sand, comprising the following steps:

[0008] (1) Pretreatment of oily sludge to remove oil and impurities from the oily sludge;

[0009] (2) The oil sludge sand after the pretreatment in step (1) is subjected to sulfonation process, and then neutralized with alkaline solution to adjust the pH value to 6-8;

[0010] (3) The oil sludge sand after the sulfonation process in step (2) is subjected to micro-nano refinement treatment to remove the sludge sand with a particle size greater than or equal to 50 μm, and a micro-nano oil displacement agent is obtained.

[0011] The oil sludge pretreatment in step (1) involves diluting the oil sludge with water, stirring, allowing it to settle statically, removing oil sludge and impurities with a particle size greater than or equal to 500 μm, and taking the remaining oil sludge portion.

[0012] The oil sludge-to-water ratio is 1:(0.4-19) by mass, and the mineralization value of the water is less than 100,000 mg / L.

[0013] In step (2), the sulfonating agent is concentrated sulfuric acid, and the mass percentage concentration of concentrated sulfuric acid is not less than 90%. According to the mass fraction, the ratio of concentrated sulfuric acid to oil sludge is 1:(4-8).

[0014] The stirring time for the sulfonation reaction is 10–30 min.

[0015] The alkaline solution mentioned in step (2) is one or a combination of sodium hydroxide solution and ammonia water, and the mass percentage concentration of the alkaline solution is 10% to 50%.

[0016] In step (3), a dispersant is added to the sulfonated sludge after step (2), and a first stirring treatment, ultrasonic treatment, centrifugal separation treatment, and a second stirring treatment are performed; the frequency of the ultrasonic device is 16-100kHz; the centrifugal speed is 1500-4000r / min and the centrifugation time is 5-60min; the second stirring speed is greater than 1000r / min and the duration is greater than 30min.

[0017] The dispersant is one or a combination of several of the following: an oil displacement surfactant and a weakly alkaline substance; the oil displacement surfactant is one or a combination of several of the following: petroleum sulfonate, alkylbenzene sulfonate, alkanolamide and betaine; the weakly alkaline substance is sodium carbonate or sodium bicarbonate; the mass percentage concentration of the dispersant solution is 5% to 20%; and the mass ratio of oil sludge to dispersant solution is 1:(1 to 3).

[0018] The micro-nano oil displacement agent prepared by the above method using oil sludge sand is a micro-nano oil displacement agent.

[0019] The concentration range of the micro-nano oil displacement agent in oil fields is 0.3% to 5%, and the percentage concentration is the mass percentage concentration.

[0020] The beneficial effects of this invention are: fully utilizing the characteristics and oil displacement potential of micro- and nano-sized oil sludge sand to prepare a green micro- and nano-sized oil displacement agent, reducing the risk of surface environmental pollution, saving oil sludge treatment costs, partially replacing polymers and surfactants, and adding a novel tertiary oil recovery system technology. Furthermore, since the oil sludge originates from the formation, it has good compatibility with the reservoir, which is beneficial for reservoir protection. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the method for preparing micro / nano oil displacement agents using oil sludge sand according to the present invention. Detailed Implementation

[0022] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art without creative effort are within the protection scope of the present invention.

[0023] like Figure 1 As shown, the method for preparing micro / nano oil displacement agents using oil sludge sand according to the present invention includes the following steps:

[0024] (1) Pretreatment of oily sludge to remove oil and impurities from the oily sludge;

[0025] (2) The oil sludge sand after the pretreatment in step (1) is subjected to sulfonation process, and then neutralized with alkaline solution to adjust the pH value to 6-8;

[0026] (3) The oil sludge sand after the sulfonation process in step (2) is subjected to micro-nano refinement treatment to remove the sludge sand with a particle size greater than or equal to 50 μm, and a micro-nano oil displacement agent is obtained.

[0027] The oil sludge pretreatment in step (1) involves diluting the oil sludge with water, stirring, allowing it to settle statically, removing oil sludge and impurities with a particle size greater than or equal to 500 μm, and taking the remaining oil sludge portion.

[0028] The oil sludge-to-water ratio is 1:(0.4-19) by mass, and the mineralization value of the water is less than 100,000 mg / L.

[0029] In step (2), the sulfonating agent is concentrated sulfuric acid, and the mass percentage concentration of concentrated sulfuric acid is not less than 90%. According to the mass fraction, the ratio of concentrated sulfuric acid to oil sludge is 1:(4-8).

[0030] The stirring time for the sulfonation reaction is 10–30 min.

[0031] The alkaline solution mentioned in step (2) is one or a combination of sodium hydroxide solution and ammonia water, and the mass percentage concentration of the alkaline solution is 10% to 50%.

[0032] In step (3), a dispersant is added to the sulfonated sludge after step (2), and a first stirring treatment, ultrasonic treatment, centrifugal separation treatment, and a second stirring treatment are performed; the frequency of the ultrasonic device is 16-100kHz; the centrifugal speed is 1500-4000r / min and the centrifugation time is 5-60min; the second stirring speed is greater than 1000r / min and the duration is greater than 30min.

[0033] The dispersant is one or a combination of several of the following: an oil displacement surfactant and a weakly alkaline substance; the oil displacement surfactant is one or a combination of several of the following: petroleum sulfonate, alkylbenzene sulfonate, alkanolamide and betaine; the weakly alkaline substance is sodium carbonate or sodium bicarbonate; the mass percentage concentration of the dispersant solution is 5% to 20%; and the mass ratio of oil sludge to dispersant solution is 1:(1 to 3).

[0034] The micro-nano oil displacement agent prepared by the above method using oil sludge sand is a micro-nano oil displacement agent.

[0035] The concentration range of the micro-nano oil displacement agent in oil fields is 0.3% to 5%, and the percentage concentration is the mass percentage concentration.

[0036] The micro-nano oil displacement agent prepared by the above-mentioned method of preparing micro-nano oil displacement agent using oil sludge sand is composed of oil sludge and oil droplets with micro-nano particle size, dispersing agent and water.

[0037] The principle of this invention is as follows:

[0038] (1) This invention utilizes oilfield waste mud sand to prepare micro-nano oil displacement agents. In this system, micro-nano particles can adjust the micropore throat structure of high-permeability layers, reduce the water-oil mobility ratio, and effectively improve the channeling phenomenon of injected fluid. At the same time, this system can also improve the wettability of rock surfaces, which helps residual oil to peel off the core wall and further improve the crude oil recovery rate.

[0039] (2) Oil sludge is a complex multiphase system in which the oil and water phases are deeply emulsified and firmly bound to micro-particles, and each phase exists stably in the system, making it difficult to process. This invention can utilize oil sludge as a micro-nano oil displacement agent, making refined use of oil sludge resources, turning waste into treasure, reducing the risk of ground environmental pollution, saving oil sludge treatment costs, and benefiting the country's green and environmentally friendly development.

[0040] (3) Oily sludge mainly comes from the formation and has good compatibility with the reservoir. It can protect the reservoir during the development process and has a positive effect on the sustainable development of the petroleum and petrochemical industry.

[0041] (4) Commonly used micro and nanoparticle materials are expensive, while oily sludge solid waste is inexpensive and widely available, and can be used in large quantities, with extremely high application value and potential.

[0042] (5) The micro-nano particles prepared by the present invention using oil sludge have good temperature resistance and good adaptability to harsh formation conditions. At the same time, the prepared micro-nano oil displacement agent has good compatibility and can achieve synergistic effect when combined with different types of chemical agents to maximize the recovery rate of crude oil.

[0043] This invention utilizes oil sludge as a micro / nano-based oil displacement agent, turning waste into treasure. This helps alleviate the pressure of solid waste disposal in oilfields and plays a positive role in the sustainable development and energy conservation and environmental protection of the petroleum and petrochemical industry. Simultaneously, the micro / nano particles in this system can adjust the micropore throat structure of high-permeability layers, reduce the water-oil mobility ratio, effectively improve the channeling phenomenon of injected fluids, and increase the sweep efficiency. Commonly used nanomaterials are expensive, while the oily sludge solid waste used in this invention is inexpensive, widely available, and can be used in large quantities, possessing considerable economic development benefits and application potential. Furthermore, the oily sludge mainly originates from the formation and has good compatibility with the reservoir. This invention protects the reservoir during development, facilitating efficient crude oil development.

[0044] The present invention will be further described below with reference to embodiments, but is not limited thereto.

[0045] The working liquid level of the large sedimentation tank at the Gangdong Joint Station of Dagang Oilfield is 1.2-2.3m. Oil sludge suspended in the liquid phase was sampled at a depth of 1.7m in the middle layer. This sample did not contain obvious large particles of sediment. At room temperature, the sample appeared as a black, viscous solid with a water content of 28.6%, an oil content of 12.7%, and a sludge content of 58.7%.

[0046] This invention utilizes the above-mentioned oil sludge sand sample to prepare a micro / nano oil displacement agent, and the specific steps are as follows:

[0047] (1) Pretreatment of oil sludge

[0048] The selected oil sludge was suspended in the middle layer of the large sedimentation basin at the Gangdong Joint Station of Dagang Oilfield. This sample was a black, viscous solid at room temperature, with a water content of 28.6%, an oil content of 12.7%, and a sludge content of 58.7%. One part of the oil sludge was mixed with three parts of oilfield produced fluid reinjection water with a salinity of 3000 mg / L and stirred to remove oil sand and impurities with a particle size greater than or equal to 500 μm. A schematic diagram of the pretreated oil sludge is shown below. Figure 1 As shown in (a), the mud particles are entrained by heavy oil and randomly agglomerated together, resulting in poor dispersion.

[0049] (2) Sulfonation process

[0050] The remaining oil sludge sand after pretreatment was subjected to sulfonation with 95% concentrated sulfuric acid, where the amount of concentrated sulfuric acid used was 1 part by mass and the amount of oil sludge sand was 5 parts by mass. The stirring time for the sulfonation reaction was set to 25 min. After the sulfonation reaction was completed, it was neutralized with 20% alkali and the pH was finally adjusted to 7.

[0051] (3) Micro-nano refinement process

[0052] A compound surfactant solution was added to the sulfonated oil sludge. The water used to prepare the compound surfactant solution was oilfield produced fluid reinjection water with a salinity of 3000 mg / L, comprising 75 parts by mass of reinjection water, 15 parts by mass of the compound surfactant, and 10 parts by mass of the sulfonated oil sludge. The compound surfactant consisted of petroleum sulfonate and alkanolamide, with 3 parts by mass of petroleum sulfonate and 1 part by mass of alkanolamide. A first stirring treatment was then performed to initially disperse the large agglomerated oil sludge into a sludge sample encapsulated in heavy oil.

[0053] Ultrasonic treatment further disperses the sludge: After the first stirring, the suspension is ultrasonically treated with the ultrasonic device at a frequency of 28 kHz for 30 minutes. Ultrasonic treatment gradually disperses the sludge sand; a schematic diagram of the dispersion process is shown below. Figure 1 As shown in (b), the ultrasonic action intensifies the dispersion of mud and sand particles, and the heavy oil is gradually broken down, causing the surfactant to be adsorbed on the surface of the mud and sand particles. The oil phase is gradually peeled off on the surface of the mud and sand particles, and the oil and water phases are separated into layers. The hydrophilic mud and sand particles are uniformly dispersed in the aqueous system.

[0054] Centrifugation: This step removes large-diameter suspended mud and sand from the system. The specific experimental procedures are as follows: the centrifuge speed was set to 3000 r / min, and the centrifugation time was set to 20 min. After the centrifugation experiment, the unstable large-diameter mud and sand in the system separated to the bottom.

[0055] Second stirring treatment: The above suspension is stirred at high speed (4000 r / min) for 35 minutes to further disperse the sludge particles and detached oil droplets, ultimately forming a composite micro-nano oil displacement agent composed of micro-nano sludge, micro-nano oil droplets, oil-displacing surfactant, and water. This is the micro-nano oil displacement agent (e.g., ...). Figure 1 (c)). The micro-nano oil displacement agent prepared in this experiment is uniformly and stably dispersed.

[0056] (4) Particle size analysis of micro / nano oil displacement agents

[0057] The particle size distribution of micro / nano oil displacement agents was measured using a Topsizer laser particle size analyzer. Aqueous phase was selected as the dispersion medium, and the refractive index and absorptivity of the sample material were set to 1.480 and 0.001, respectively. The analysis range was 0.010 μm–3664 μm. The measured data were: D0 = 0.029 μm, D10 = 0.062 μm, D25 = 0.090 μm, D50 = 0.110 μm, D75 = 0.220 μm, D90 = 1.024 μm, and D100 = 4.100 μm.

[0058] Table 1. Particle size distribution of micro / nano oil displacement agents

[0059] Particle size / μm 0-0.062 0.062-0.090 0.090-0.110 0.110-0.220 0.220-1.024 1.024-4.100 Proportion / % 10 15 25 25 15 10

[0060] (5) Interfacial tension

[0061] The interfacial tension of the oil-water two-phase system in the micro-nano oil displacement agent system was measured using a CNG-701 rotating drop tensiometer. First, the micro-nano oil displacement agent was diluted to a solution with a concentration of 3.0 wt%. Then, a capillary sample tube was prepared. Finally, under the condition of a simulated formation temperature of 50℃, the oil-water two-phase interface was measured to be stable at 0.008 mN / m.

[0062] (6) Emulsifying properties

[0063] The first step is to measure 20 mL of the micro-nano oil displacement agent prepared above and add it to a 100 mL volumetric flask. Then, dilute the volume with simulated saline solution with a mineralization of 30000 mg / L and shake well to obtain a micro-nano oil displacement agent with a concentration of 3.0 wt%.

[0064] The second step involves taking 15 mL of the 3.0 wt% micro-nano oil displacement agent solution and adding it to a 25 mL stoppered graduated cylinder. Then, 5 mL of crude oil from the Gangxi Block of Dagang Oilfield is added. Finally, the stoppered graduated cylinder is placed in a constant temperature water bath simulating a formation temperature of 50°C for 1 hour.

[0065] The third step involves using an SHZ-B water bath constant temperature oscillator to uniformly oscillate the removed stoppered measuring cylinder 100 times using a reciprocating oscillation method. Then, the cylinder is left to stand at room temperature, and the time for complete oil-water separation is recorded. The final separation time is greater than 5 minutes.

[0066] In summary, the content of this invention is not limited to the above-described embodiments. Those skilled in the art can easily propose other embodiments within the technical guiding principles of this invention, but such embodiments are all included within the scope of this invention.

Claims

1. A method for preparing micro / nano-sized oil displacement agents using oil sludge sand, characterized in that, Includes the following steps: (1) Pretreatment of oily sludge to remove oil and impurities from the oily sludge; (2) The oil sludge sand after the pretreatment in step (1) is subjected to sulfonation process, and then neutralized with alkaline solution to adjust the pH value to 6-8; (3) The oil sludge sand after the sulfonation process in step (2) is subjected to micro-nano fine treatment to remove the sludge sand with a particle size greater than or equal to 50μm, and a micro-nano oil displacement agent is obtained. In step (3), a dispersant is added to the sulfonated sludge after step (2), and a first stirring treatment, ultrasonic treatment, centrifugal separation treatment, and a second stirring treatment are performed; the frequency of the ultrasonic device is 16-100kHz; the centrifugal speed is 1500-4000r / min and the centrifugation time is 5-60min; the second stirring speed is greater than 1000r / min and the duration is greater than 30min. The dispersant is one or a combination of several of the following: an oil displacement surfactant and a weakly alkaline substance; the oil displacement surfactant is one or a combination of several of the following: petroleum sulfonate, alkylbenzene sulfonate, alkanolamide and betaine; the weakly alkaline substance is sodium carbonate or sodium bicarbonate; the mass percentage concentration of the dispersant solution is 5% to 20%; and the mass ratio of oil sludge to dispersant solution is 1:(1 to 3).

2. The method for preparing micro / nano oil displacement agents using oil sludge sand according to claim 1, characterized in that, The oil sludge pretreatment in step (1) involves diluting the oil sludge with water, stirring, allowing it to settle statically, removing oil sludge and impurities with a particle size greater than or equal to 500 μm, and taking the remaining oil sludge portion.

3. The method for preparing micro / nano oil displacement agents using oil sludge sand according to claim 2, characterized in that, The oil sludge-to-water ratio is 1:(0.4-19) by mass, and the mineralization value of the water is less than 100,000 mg / L.

4. The method for preparing micro / nano oil displacement agents using oil sludge sand according to claim 1, characterized in that, In step (2), the sulfonating agent is concentrated sulfuric acid, and the mass percentage concentration of concentrated sulfuric acid is not less than 90%. According to the mass fraction, the ratio of concentrated sulfuric acid to oil sludge is 1:(4-8).

5. The method for preparing micro / nano oil displacement agents using oil sludge sand according to claim 4, characterized in that, The stirring time for the sulfonation reaction is 10–30 min.

6. The method for preparing micro / nano oil displacement agents using oil sludge sand according to claim 1, characterized in that, The alkaline solution mentioned in step (2) is one or a combination of sodium hydroxide solution and ammonia water, and the mass percentage concentration of the alkaline solution is 10% to 50%.

7. The micro-nano oil displacement agent prepared by the method for preparing micro-nano oil displacement agents using oil sludge as described in any one of claims 1-6.

8. The micro / nano oil displacement agent according to claim 7, characterized in that, The concentration range of the micro-nano oil displacement agent in oil fields is 0.3% to 5%, and the percentage concentration is the mass percentage concentration.

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