A method for in-situ treatment of oily waste in oilfields

Abstract

The present invention belongs to the technical field of waste treatment, and relates to a method for in-situ treatment of oil-containing waste in oil fields. A cement plug is injected into the annulus formed by the tubing and casing of the abandoned oil well; then the oil-containing sludge is collected and injected into the annulus; then a packer is injected into the top of the oil-containing sludge, and the packer is locked on the inner side of the casing to form a sealed space for the downhole oil-containing sludge section; then water and EATD are added, and carbon dioxide is injected into the oil-containing sludge through the tubing. The carbon dioxide carries the hydrocarbon components and heavy metals extracted from the oil-containing sludge and flows out of the wellhead, and the oil components and heavy metals are recovered through an oil-containing sludge collection device and a heavy metal collection device respectively; finally, the carbon dioxide is recycled through a carbon dioxide generation and recovery device to realize the harmless treatment of the oil-containing sludge; avoid the risk of secondary pollution, efficiently recover the oil components and heavy metals in the oil-containing sludge, reduce the adverse impact on the surrounding environment, and improve the comprehensive utilization efficiency of oil well resources.

Description

Technical Field

[0001] The present invention belongs to the technical field of waste treatment, and relates to a method for in-situ treatment of oily waste in oilfields. Background Art

[0002] Currently, the methods for treating oily waste in abandoned oil wells mainly include chemical, mechanical and incineration treatments. Among them, the chemical treatment method mainly uses various chemical agents to treat oily waste in oilfields. The characteristics of these methods are complex structures, requiring a large amount of chemical agents, resulting in high costs, and there may be a risk of secondary pollution due to the treatment of chemical residues; mechanical treatment involves separating the components of oily waste by physical means, which requires a large amount of energy and usually it is difficult to achieve complete separation of oil and heavy metals; the incineration treatment method burns oily waste at high temperatures. However, these processes have high energy consumption, may cause air pollution, and release harmful gases into the environment. CN111410981A discloses a method for extracting oil from drilling waste by supercritical CO2 assisted by entrainer. The method includes the following steps: S1, putting the drilling waste into a blast drying oven for drying, and then crushing it with a crusher; S2, mixing the entrainer with the drilling waste obtained in S1, stirring evenly, and loading it into a supercritical extraction kettle; S3, performing supercritical carbon dioxide extraction on the mixture obtained in S2 to generate a solid product and a liquid mixture of the drilling waste; S4, discharging the liquid mixture obtained in S3 into a separation tank I and a separation tank II in sequence for separation to separate the oil; S5, after the extraction is completed, collecting the oil obtained in S4 from the bottom of the separation tank; however, this method still has the following disadvantages: one is the low treatment efficiency. When the supercritical CO2 extraction method assisted by entrainer is used to treat oily waste in oilfields, it needs to go through multiple steps, including drying, crushing, mixing, stirring, loading into a supercritical extraction kettle, supercritical carbon dioxide extraction, etc., and the treatment efficiency is low; the second is the high cost. This method requires the use of a large amount of entrainer and supercritical extraction equipment, increasing the treatment cost; the third is the greater impact on the environment. The entrainer may cause pollution to the environment during use, and at the same time, a large amount of energy and resources are consumed during the supercritical extraction process, having a greater impact on the environment; the fourth is the limited scope of application. This method is mainly applicable to the treatment of drilling waste and may not be applicable to other types of oily waste in oilfields. Summary of the Invention

[0003] In order to overcome the above problems, the present invention is designed to provide a method for in-situ treatment of oily waste in oilfields, which realizes the secondary utilization of abandoned oil wells and recovers useful components in the waste by using supercritical carbon dioxide extraction technology.

[0004] To achieve the above object, the specific process of the in-situ treatment of oily waste in oilfields by the present invention is as follows:

[0005] (1) Select abandoned oil wells near the centralized location of oily sludge, and select the target formation range that meets the supercritical carbon dioxide extraction and recovery effect, that is, the ambient temperature needs to be greater than 31.4 °C and the pressure needs to be greater than 7.38 MPa. Inject a cement plug into the annulus formed by the tubing and casing of the abandoned oil well.

[0006] (2) Collect the oily sludge centrally, transport it to the oilfield site and inject it into the annulus.

[0007] (3) Inject a packer into the top of the oily sludge injected in (2). The packer is locked inside the casing of the abandoned oil well to form a closed space for the downhole oily sludge section.

[0008] (4) Through the carbon dioxide generation and recovery device on the ground, add entrainer water and chelating agent ethylenediaminetetraacetic acid (EATD), and inject carbon dioxide into the oily sludge through the tubing. Through the wellhead temperature control device, adjust the downhole temperature and pressure so that carbon dioxide always remains in the supercritical state during the downhole flow extraction process. The flow rate of carbon dioxide injection is 10 L / m, the downhole temperature is controlled at 50 - 120 °C, and the downhole pressure is controlled at 15 - 50 MPa.

[0009] (5) Close the wellhead for 2 - 2.5 hours to allow carbon dioxide to fully contact and extract the oily sludge.

[0010] (6) Through the wellhead temperature control device, reduce the wellhead pressure to below 10 MPa, so that the supercritical carbon dioxide carries the hydrocarbon components and heavy metals extracted from the oily sludge out of the wellhead, and recover the oil components and heavy metals through the oily sludge collection device and heavy metal collection device respectively.

[0011] (7) Carbon dioxide is recycled through the carbon dioxide generation and recovery device, and after 2 - 3 cycles of extraction, the harmless treatment of the oily sludge is realized. The harmless sludge after treatment is then buried in the abandoned oil well.

[0012] As a further technical solution of the present invention, the packer includes a collar, a central pipe, a retaining ring, an anti - retraction snap ring, a snap - ring sleeve, a plug, a rubber barrel assembly, an anti - protrusion mechanism and a casing nipple. The two ends of the central pipe are respectively connected to one end of the collar and the anti - retraction snap ring. A retaining ring is provided at the connection between the central pipe and the anti - retraction snap ring. The other end of the anti - retraction snap ring is connected to the rubber barrel assembly. The rubber barrel assembly, the anti - protrusion mechanism and the casing nipple are connected in sequence. The snap - ring sleeve is sleeved outside the packer, and a plug is provided on the snap - ring sleeve. When in use, place the packer on the top of the oily sludge injected into the abandoned oil well, mechanically press down to lock the annulus formed by the tubing and casing of the abandoned oil well, expand and seal the rubber barrel assembly, thereby sealing the outer surface of the annulus to prevent annular gas channeling. The anti - protrusion mechanism expands and seals together with the rubber barrel assembly to improve the pressure - bearing capacity of the rubber barrel assembly. The anti - retraction snap ring ensures that the seated rubber barrel assembly will not retract and fail.

[0013] As a further technical solution of the present invention, the wellhead temperature control and adjustment device includes an air inlet heat exchange device, an air return heat exchange device and a circulation pump. The circulation pump is arranged between the air inlet heat exchange device and the air return heat exchange device. The air inlet heat exchange device introduces external cold air into the device. Through contact with an internal heat exchanger or other heat conduction materials, the cold air is heated, thereby increasing the temperature of the air. The heated air is transported to the air return heat exchange device for further temperature adjustment. The air return heat exchange device cools the air heated by the air inlet heat exchange device to maintain the stability of the wellhead temperature. The air return heat exchange device achieves cooling through contact with external cold air or cooling water, reducing the temperature of the heated air. The air processed by the air return heat exchange device is transported to the air inlet heat exchange device for reheating, forming a cycle. The circulation pump circulates the air between the air inlet heat exchange device and the air return heat exchange device. The air flows between the two heat exchange devices through the circulation pump, thereby realizing the adjustment and control of the temperature. The circulation pump adjusts the flow rate and speed of the air as needed to adapt to different temperature adjustment requirements.

[0014] As a further technical solution of the present invention, the oily sludge collection device includes a cooling storage tank, a separation storage tank and an oil recovery device. After cooling, pressure reduction, separation and purification in sequence, the oil recovery device separates the oil from the supercritical carbon dioxide carrying the oil component from the carbon dioxide for further utilization or treatment.

[0015] As a further technical solution of the present invention, the product model of the carbon dioxide generation and recovery device is the commercially available QT120-ZFC-12.

[0016] Compared with the prior art, the present invention avoids the risk of secondary pollution that may be brought by traditional treatment methods, realizes harmless and environmental protection treatment; efficiently recovers the oil components and heavy metals in the oily sludge, realizing the comprehensive recovery and utilization of resources; treats in-situ in abandoned oil wells, reducing the adverse impact on the surrounding environment and improving the comprehensive utilization efficiency of oil well resources. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the working process for in-situ treatment of oily waste in oil fields of the present invention.

[0018] Figure 2 It is a schematic diagram of the structure of the packer of the present invention.

[0019] Figure 3 It is a schematic diagram of the structure of the wellhead temperature control and adjustment device of the present invention.

[0020] Figure 4 It is a schematic diagram of the structure of the oily sludge collection device of the present invention.

[0021] Figure 5 This is the treatment effect diagram of supercritical carbon dioxide for oil-based drilling fluid waste in the embodiments of the present invention. Specific Embodiments

[0022] The present invention will be further described below through embodiments in conjunction with the accompanying drawings.

[0023] Embodiment 1:

[0024] The specific process of in-situ treatment of oil-containing waste in oilfields by the present invention is as follows:

[0025] (1) Select an abandoned oil well near the oil sludge concentration area, and select the target formation range that meets the supercritical carbon dioxide extraction and recovery effect, that is, the ambient temperature needs to be greater than 31.4 °C, and the pressure needs to be greater than 7.38 MPa. Drive a cement plug into the annulus formed by the tubing and casing of the abandoned oil well.

[0026] (2) Collect the oil sludge centrally, transport it to the oilfield site and inject it into the annulus.

[0027] (3) Drive a packer into the top of the oil sludge injected in (2). The packer is locked on the inner side of the casing of the abandoned oil well (i.e., the outer surface of the annulus), forming a closed space for the downhole oil sludge section; the packer includes a collar 1, a central tube 2, a retaining ring 3, an anti-retreat snap ring 4, a snap ring sleeve 5, a plug 6, a rubber barrel assembly 7, an anti-burst mechanism 8 and a casing nipple 9. The two ends of the central tube 2 are respectively connected to one end of the collar 1 and the anti-retreat snap ring 4. A retaining ring 3 is provided at the connection between the central tube 2 and the anti-retreat snap ring 4. The other end of the anti-retreat snap ring 4 is connected to the rubber barrel assembly 7. The rubber barrel assembly 7, the anti-burst mechanism 8 and the casing nipple 9 are connected in sequence. The snap ring sleeve 6 is sleeved on the outside of the packer, and a plug 6 is provided on the snap ring sleeve 5. During use, place the packer on the top of the oil sludge injected into the abandoned oil well, mechanically press down to lock the annulus formed by the tubing and casing of the abandoned oil well, expand the rubber barrel assembly 7, so as to seal the outer surface of the annulus and prevent annular gas channeling. The anti-burst mechanism 8 expands together with the rubber barrel assembly 7 to improve the pressure-bearing capacity of the rubber barrel assembly 7; the anti-retreat snap ring 4 ensures that the seated rubber barrel assembly 7 will not retreat and fail.

[0028] (4) Through the carbon dioxide generation and recovery device on the ground, entraining agent water and chelating agent ethylenediaminetetraacetic acid (EATD) are added, and carbon dioxide is injected into the oil-containing sludge through the oil pipe; through the wellhead temperature control and regulation device, the downhole temperature and pressure are adjusted to keep carbon dioxide in a supercritical state throughout the downhole flow extraction process; the injection flow rate of carbon dioxide is 10 L / m, the downhole temperature is controlled at 50 - 120 °C, and the downhole pressure is controlled at 15 - 50 MPa; the product model of the carbon dioxide generation and recovery device is the commercially available QT120-ZFC-12; the wellhead temperature control and regulation device includes an air inlet heat exchange device, an air return heat exchange device, and a circulation pump. The circulation pump is arranged between the air inlet heat exchange device and the air return heat exchange device. The air inlet heat exchange device introduces external cold air into the device. Through contact with the internal heat exchanger or other heat conduction materials, the cold air is heated, thereby increasing the air temperature. The heated air is transported to the air return heat exchange device for further temperature regulation; the air return heat exchange device cools the air heated by the air inlet heat exchange device to maintain the stability of the wellhead temperature. The air return heat exchange device achieves cooling by contacting with external cold air or cooling water, reducing the temperature of the heated air; the air processed by the air return heat exchange device is transported to the air inlet heat exchange device for reheating, forming a cycle process; the circulation pump circulates the air between the air inlet heat exchange device and the air return heat exchange device, and the air flows between the two heat exchange devices through the circulation pump, thereby achieving temperature regulation and control. The circulation pump adjusts the flow rate and speed of the air as needed to adapt to different temperature regulation requirements;

[0029] (5) Close the wellhead for 2 - 2.5 hours to allow carbon dioxide to fully contact and extract the oil-containing sludge;

[0030] (6) Through the wellhead temperature control and regulation device, lower the wellhead pressure below 10 MPa, so that supercritical carbon dioxide carrying the hydrocarbon components and heavy metals extracted from the oil-containing sludge flows out of the wellhead, and the oil components and heavy metals are recovered through the oil-containing sludge collection device and the heavy metal collection device respectively; the oil-containing sludge collection device includes a cooling storage tank, a separation storage tank, and an oil recovery device. After cooling, pressure reduction, separation, and purification in sequence, the oil recovery device separates the oil from the supercritical carbon dioxide carrying the oil components for further utilization or treatment;

[0031] (7) Carbon dioxide is recycled through the carbon dioxide generation and recovery device, and after 2 - 3 cycles of extraction, the harmless treatment of the oil-containing sludge is achieved; the treated harmless sludge is then buried in abandoned oil wells.

[0032] Example 2:

[0033] This embodiment adopts the steps described in Embodiment 1 to treat the oil-containing sludge in a certain abandoned oil well. During the treatment of the oil-containing sludge in the abandoned oil well, the supercritical carbon dioxide extraction technology is used for recovery and treatment. The specific implementation steps are as follows:

[0034] S1. Determine the target formation range:

[0035] First, conduct a detailed survey and calculation of the formation of a certain abandoned oil well. By comprehensively analyzing factors such as the formation temperature, pressure, and the properties of the oil-containing sludge, determine the target formation range that meets the supercritical carbon dioxide extraction and recovery effect. The ambient temperature in this range is greater than 31.4 degrees Celsius, and the pressure is greater than 7.38 MPa.

[0036] S2. Collection and transportation of oil-containing sludge:

[0037] Near the abandoned oil well, set up a centralized collection point for oil-containing sludge, and transport the oil-containing sludge to the oilfield site through professional transportation equipment; during the transportation process, strictly control the temperature and pressure of the oil-containing sludge to ensure that there is no leakage and pollution.

[0038] S3. Installation of packer and injection of oil-containing sludge:

[0039] At the oilfield site, according to the design requirements, inject the oil-containing sludge into the annulus formed by the tubing and casing of the abandoned oil well. At the same time, seal the target formation by injecting a cement plug to ensure the enclosed space of the oil-containing sludge underground. Then, inject a packer into this enclosed space to form an enclosed space for the oil-containing sludge section underground.

[0040] S4. Injection and extraction of carbon dioxide:

[0041] Inject carbon dioxide into the oil-containing sludge through a carbon dioxide generation and recovery device, and at the same time add an appropriate amount of entrainer water and chelating agent ethylenediaminetetraacetic acid (EATD) to promote the full contact and extraction of carbon dioxide and the oil-containing sludge; during the carbon dioxide injection process, adjust the underground temperature and pressure through the wellhead temperature control device to keep carbon dioxide in a supercritical state all the time. The flow rate of carbon dioxide injection is 10 L / m, the underground temperature is controlled at about 100 °C, and the underground pressure is controlled at about 45 MPa.

[0042] S5. Monitoring and data collection during the extraction process:

[0043] During the carbon dioxide injection and extraction process, conduct real-time monitoring and data collection on the whole process, record key parameters such as the injection volume, temperature, and pressure of carbon dioxide, and regularly take samples to analyze the composition and content of the extract. Through these data, the efficiency and effect of the extraction process can be understood in a timely manner, providing important references for subsequent treatment.

[0044] S6. Recovery and treatment of the extract:

[0045] After a period of extraction, the wellhead pressure is reduced by the wellhead temperature control device, so that the supercritical carbon dioxide carries the hydrocarbon components and heavy metals extracted from the oil-containing sludge and flows out of the wellhead; then the extract is recovered and treated through the oil-containing sludge collection device and the heavy metal collection device respectively; for the hydrocarbon components, professional separation and purification technologies are used for treatment; for the heavy metals, harmless treatment methods such as precipitation method and adsorption method are used for collection.

[0046] S7. Recycling of carbon dioxide and harmless treatment after treatment:

[0047] During the extraction process, carbon dioxide is recycled. The recycled carbon dioxide is treated and then injected into the next round of extraction process again. At the same time, the treated harmless sludge is safely buried in the abandoned oil well to avoid the risk of secondary pollution.

[0048] After the above treatment process, the oil-containing sludge of a certain abandoned oil well was effectively treated. Through the supercritical carbon dioxide extraction technology, the hydrocarbon components and heavy metals in the oil-containing sludge were successfully recovered. At the same time, the treated harmless sludge was properly treated through harmless treatment methods. The specific data are as follows:

[0049] Recovery rate of hydrocarbon components: After being treated by the supercritical carbon dioxide extraction technology, the recovery rate of hydrocarbon components reached more than 90%, which means that a large amount of hydrocarbon components were successfully extracted from the oil-containing sludge, realizing the effective recovery and utilization of resources.

[0050] Removal rate of heavy metals: Through the harmless treatment method, the heavy metals in the oil-containing sludge were successfully removed. After treatment, the content of heavy metals was lower than the relevant national standards, ensuring that the treated harmless sludge would not cause secondary pollution to the environment.

[0051] Recycling rate of carbon dioxide: During the treatment process, the recycling of carbon dioxide was realized. After multiple rounds of extraction, the recycling rate of carbon dioxide reached more than 95%, which not only reduced the treatment cost, but also reduced the carbon dioxide emissions, contributing to slowing down global climate change.

[0052] In this embodiment, through experiments, it is found that under the laboratory conditions of 14 MPa, 45 °C, 60 min and 10 mL / min, the extraction efficiency for the oil-containing components can reach more than 98%. Supercritical carbon dioxide has an obvious treatment effect on oil-based drilling fluid waste, such as Figure 5 shown, the waste changes from sludge-like to granular, the cuttings are in a dispersed state, the color returns to the normal state, and the extracted oil is a light yellow liquid with an obvious oily texture.

[0053] Obviously, the above embodiments are merely examples given for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or alterations can be made based on the above description. It is not necessary and impossible to enumerate all implementation manners here. And the obvious changes or alterations derived therefrom still fall within the protection scope of the present invention.

Claims

1. A method for in-situ treatment of oily waste in oilfields, characterized in that, The specific process is as follows: S1. Determine the target formation range: First, conduct a detailed survey and calculation on the formation of a certain abandoned oil well. By comprehensively analyzing the temperature, pressure, and properties of the oily sludge in the formation, determine the target formation range that meets the supercritical carbon dioxide extraction and recovery effect. The ambient temperature in this range is greater than 31.4 °C, and the pressure is greater than 7.38 MPa; S2. Collection and transportation of oily sludge: Near the abandoned oil well, set up a centralized collection point for oily sludge, and transport the oily sludge to the oilfield site through professional transportation equipment. During the transportation process, strictly control the temperature and pressure of the oily sludge to ensure that there is no leakage and pollution; S3. Installation of packer and injection of oily sludge: At the oilfield site, according to the design requirements, inject the oily sludge into the annulus formed by the tubing and casing of the abandoned oil well. At the same time, seal the target formation by driving in a cement plug to ensure the confined space of the oily sludge in the well. Then, inject a packer into this confined space to form a confined space for the downhole oily sludge section; The packer includes a collar, a central pipe, a retaining ring, an anti-backoff circlip, a circlip sleeve, a plug, a rubber barrel assembly, an anti-bulging mechanism, and a casing nipple. The two ends of the central pipe are respectively connected to the collar and one end of the anti-backoff circlip. A retaining ring is provided at the connection between the central pipe and the anti-backoff circlip. The other end of the anti-backoff circlip is connected to the rubber barrel assembly. The rubber barrel assembly, the anti-bulging mechanism, and the casing nipple are connected in sequence. The circlip sleeve is sleeved on the outside of the packer, and a plug is provided on the circlip sleeve. During use, place the packer on the top of the oily sludge injected into the abandoned oil well, mechanically press down to lock the annulus formed by the tubing and casing of the abandoned oil well, and expand and seal the rubber barrel assembly, thereby sealing the outer surface of the annulus. The anti-bulging mechanism expands and seals together with the rubber barrel assembly; S4. Injection and extraction of carbon dioxide: Inject carbon dioxide into the oily sludge through a carbon dioxide generation and recovery device, and at the same time add an appropriate amount of entrainer water and chelating agent ethylenediaminetetraacetic acid to promote the full contact and extraction of carbon dioxide and oily sludge; During the carbon dioxide injection process, adjust the downhole temperature and pressure through the wellhead temperature control device to keep carbon dioxide in a supercritical state all the time. The flow rate of carbon dioxide injection is 10 L / m, the downhole temperature is controlled at 100 °C; the downhole pressure is controlled at 45 MPa; S5. Monitoring and data collection during the extraction process: During the carbon dioxide injection and extraction process, conduct real-time monitoring and data collection on the whole process, record the carbon dioxide injection volume, temperature, and pressure parameters, and regularly take samples to analyze the composition and content of the extract; S6. Recovery and treatment of the extract: After a period of extraction, reduce the wellhead pressure through the wellhead temperature control device, so that the supercritical carbon dioxide carries the hydrocarbon components and heavy metals extracted from the oily sludge and flows out of the wellhead; The extract is then recovered and processed through an oily sludge collection device and a heavy metal collection device respectively; for hydrocarbon components, professional separation and purification technologies are used for treatment; for heavy metals, harmless treatment methods such as precipitation and adsorption methods are used for collection; the wellhead temperature control and regulation device includes an air inlet heat exchange device, an air return heat exchange device and a circulation pump. The circulation pump is arranged between the air inlet heat exchange device and the air return heat exchange device. The air inlet heat exchange device introduces external cold air into the device. Through contact with an internal heat exchanger or other heat conduction materials, the cold air is heated, thereby increasing the temperature of the air. The heated air is transported to the air return heat exchange device for further temperature regulation; the air return heat exchange device cools the air heated by the air inlet heat exchange device to maintain the stability of the wellhead temperature. The air return heat exchange device achieves cooling through contact with external cold air or cooling water, reducing the temperature of the heated air; the air processed by the air return heat exchange device is transported to the air inlet heat exchange device for reheating, forming a cycle process; the circulation pump circulates the air between the air inlet heat exchange device and the air return heat exchange device. The air flows between the two heat exchange devices through the circulation pump, thereby achieving temperature regulation and control. The circulation pump adjusts the flow rate and speed of the air as needed to adapt to different temperature regulation requirements; S7. Recycling and harmless treatment of carbon dioxide after treatment: During the extraction process, carbon dioxide is recycled. The recovered carbon dioxide is processed and then injected into the next round of extraction process again. At the same time, the harmless sludge after treatment is safely buried in abandoned oil wells to avoid the risk of secondary pollution; After treatment by the supercritical carbon dioxide extraction technology, the recovery rate of hydrocarbon components reaches over 90%; during the treatment process, the recycling rate of carbon dioxide reaches over 95%.

2. The method for in-situ treatment of oily waste in oilfields according to claim 1, characterized in that, The oily sludge collection device includes a cooling storage tank, a separation storage tank and an oil recovery device. After cooling, pressure reduction, separation and purification in sequence, the oil recovery device separates the oil from the supercritical carbon dioxide carrying the oil component for further utilization or treatment.

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