Method and device for treating oil field fracturing flow-back fluid by using floating island green plants

Abstract

The invention relates to the technical field of oil field sewage treatment, in particular to a method and device for treating oil field fracturing flow-back fluid through floating island green plants, and the method comprises the following steps: selecting floating island aquatic plants suitable for being planted in a fracturing flow-back fluid storage pool; the method comprises the following steps: planting floating island aquatic plants in a water inlet area of a storage pool in a gradient and row manner at intervals, carrying out gel breaking flocculation, flotation and filtration on wellhead fracturing flow-back fluid wastewater, conveying pretreated water into the storage pool, filtering harmful substances in the pretreated water by the floating island aquatic plants through root systems, and absorbing nutrient substances required by growth to obtain purified water. The artificial floating island is used for planting aquatic plants in the fracturing flow-back fluid storage pool, the concentration of pollutants such as COD, suspended solids, total nitrogen and ammonia nitrogen remaining in water and the salinity of the water are effectively reduced, the ecological system in the storage pool after pretreatment of the fracturing flow-back fluid is optimized, the water quality stability in the storage pool is improved, and the quality guarantee time of the water quality is prolonged.

Description

Technical Field

[0001] The invention relates to the technical field of oilfield sewage treatment, in particular to a method and a device for treating oilfield fracturing return fluid by utilizing floating island green plants. Background Art

[0002] The composition of fracturing flowback wastewater is complex and difficult to treat. The characteristic components are mainly petroleum, guar gum, polyacrylamide, surfactants, cross-linking agents, bacteria, metal ions, nitrides, sulfides, salts, etc.; organic components are alkanes, aromatic hydrocarbons, chlorinated hydrocarbons, alcohols, esters, ketones, phenols, quinones, etc., which have certain biological toxicity. The impact of organic components is mainly reflected in water quality indicators such as COD, suspended solids, and chromaticity. Nitrogen compounds are mainly reflected in ammonia nitrogen and total nitrogen indicators. Sulfides, bacteria, etc. are mainly reflected in water odor.

[0003] On the one hand, in recent years, with the promotion and development of fracturing mining technology in the process of oil and gas development, there are many studies and related literature reports on the treatment of fracturing flowback wastewater. Fracturing flowback wastewater also belongs to the category of oil and gas field produced wastewater. The reported literature is still mainly based on conventional oilfield wastewater treatment technology or derivative technology, and the types of technology are still dominated by physical, chemical, and biochemical treatment methods. On the other hand, there are many studies on the use of aquatic plants or artificial floating island green plants for eutrophic water purification (mainly in the treatment of black and smelly water bodies in rivers and lakes).

[0004] However, there are few reports on the intersection of the above two aspects, namely, the use of aquatic plants to treat oilfield wastewater. There are only a few reports on the use of natural or artificial wetlands to treat oilfield produced water. At the same time, there are no reports or literature on the use of artificial floating island aquatic plants to purify and treat oilfield fracturing return fluid wastewater. Summary of the invention

[0005] The present invention provides a method and device for treating oilfield fracturing return fluid by using floating island green plants, which overcomes the shortcomings of the above-mentioned prior art and can effectively solve the problems of poor water stability, easy corruption and deterioration, increased chroma and aggravated odor during the long-term open-air storage of pretreated water in the treatment of fracturing return wastewater.

[0006] One of the technical solutions of the present invention is achieved through the following measures: a method for treating oilfield fracturing return fluid using floating island green plants, which is carried out according to the following steps: the first step is to select floating island aquatic plants suitable for planting in a fracturing return fluid storage pool; the second step is to plant floating island aquatic plants in the water inlet area of ​​the storage pool in stages and rows; the third step is to obtain pretreated water by subjecting the wellhead fracturing return fluid wastewater to gel breaking flocculation, flotation and filtration; the fourth step is to send the pretreated water to the storage pool, and the floating island aquatic plants filter harmful substances in the pretreated water through their roots in the water, and absorb the nutrients required for growth to obtain purified water.

[0007] The following is a further optimization and / or improvement of one of the above-mentioned technical solutions: The above-mentioned floating island aquatic plants are salt-tolerant and have well-developed root systems.

[0008] The above-mentioned floating island aquatic plants include one or more of canna, water plantain, pickerel grass, yellow iris, loosestrife, water hyacinth, reed, red polygonum, iris, cattail, wild rice stem, Vallisneria, foxtail, and arrowhead.

[0009] In the fourth step above, the nutrients absorbed by the roots of the floating island aquatic plants in the water are pollutants enriched in COD, suspended solids, total nitrogen, and ammonia nitrogen.

[0010] The second technical solution of the present invention is achieved through the following measures: a device for implementing the method of using floating island green plants to treat oil field fracturing return fluid, including a sedimentation tank, a pretreatment device and a deep treatment device, the sedimentation tank inlet is fixedly connected to a wastewater discharge pipeline, the sedimentation tank outlet and the pretreatment device inlet are fixedly connected with a pretreated water inlet pipeline, the pretreatment device outlet and the deep treatment device inlet are fixedly connected with a pretreated water discharge pipeline, and the deep treatment device outlet is fixedly connected with a purified water discharge pipeline.

[0011] The following is a further optimization and / or improvement of the second technical solution of the above invention: The above-mentioned deep treatment device includes a plurality of storage pools, on which partitions are arranged, between which artificial green plant floating islands are arranged in sequence, and the outlets of the storage pools are fixedly connected to purified water discharge pipelines. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Attached Figure 1 It is a schematic diagram of the front view and half-section structure of the present invention.

[0013] The codes in the attached drawings are: 1 is a sedimentation tank, 2 is a pretreatment device, 3 is a wastewater discharge pipeline, 4 is a pretreated water inlet pipeline, 5 is a pretreated water discharge pipeline, 6 is a water storage tank, 7 is a partition, 8 is an artificial green plant floating island, and 9 is a purified water discharge pipeline. DETAILED DESCRIPTION

[0014] The present invention is not limited by the following embodiments, and specific implementation methods can be determined based on the technical solution of the present invention and actual conditions.

[0015] The present invention will be further described below in conjunction with embodiments: Embodiment 1: As attached Figure 1As shown, the method of using floating island green plants to treat oilfield fracturing return fluid is carried out according to the following steps: the first step is to select floating island aquatic plants suitable for planting in the fracturing return fluid storage pool; the second step is to plant the floating island aquatic plants in the water inlet area of ​​the storage pool in stages and rows; the third step is to obtain pre-treated water after the wellhead fracturing return fluid wastewater is subjected to gel breaking flocculation, flotation and filtration; the fourth step is to send the pre-treated water to the storage pool, and the floating island aquatic plants filter the harmful substances in the pre-treated water through the root system in the water, and absorb the nutrients required for growth to obtain purified water.

[0016] The present invention utilizes artificial floating islands to plant preferred aquatic plants in a fracturing return fluid storage pool, and in the water inlet area of ​​the storage pool, the floating island aquatic plants are planted in stages and rows. The roots of aquatic plants absorb and enrich pollutants such as COD, suspended matter, total nitrogen, and ammonia nitrogen in the water, and the aquatic plants are optimized to screen aquatic plants that are salt-tolerant and have developed root systems. The organic pollutants and ammonia nitrogen and other substances remaining after pretreatment in the water are used as nutrients for aquatic green plants. At the same time, the roots of aquatic plants also filter and fix harmful substances in the water to a certain extent, gradually purify the water body, reduce the content of COD, suspended matter, ammonia nitrogen, and total nitrogen, and cultivate beneficial bacteria. At the same time, the water temperature rise caused by direct sunlight on the water surface in Xinjiang in summer is reduced, the breeding of harmful bacteria is reduced, the stability of water quality is improved, and the water quality is prevented from being corrupted, deteriorated, discolored, and smelly.

[0017] Embodiment 2: As an optimization of the above embodiment, the floating island aquatic plants are salt-tolerant floating island aquatic plants with well-developed root systems.

[0018] Embodiment 3: As an optimization of the above embodiment, the floating island aquatic plants include one or more of canna, water plantain, pickerel grass, yellow iris, loosestrife, water hyacinth, reed, red polygonum, iris, cattail, wild rice stem, Vallisneria, foxtail, and arrowhead.

[0019] Example 4: As an optimization of the above example, in the fourth step, the nutrients absorbed by the roots of the floating island aquatic plants in the water are pollutants enriched in COD, BOD, total nitrogen, and ammonia nitrogen.

[0020] Embodiment 5: As attached Figure 1 As shown, the device for implementing the method of using floating island green plants to treat oilfield fracturing return fluid includes a sedimentation tank 1, a pretreatment device 2 and a deep treatment device. The inlet of the sedimentation tank 1 is fixedly connected to a wastewater discharge pipeline 3, the outlet of the sedimentation tank 1 and the inlet of the pretreatment device 2 are fixedly connected to a pretreated water inlet pipeline 4, the outlet of the pretreatment device 2 and the inlet of the deep treatment device are fixedly connected to a pretreated water discharge pipeline 5, and the outlet of the deep treatment device is fixedly connected to a purified water discharge pipeline 9.

[0021] Embodiment 6: As an optimization of the above embodiment, as shown in the attached Figure 1As shown, the deep treatment device includes a plurality of storage pools 6, on which partitions 7 are arranged, and between which artificial green floating islands 8 are arranged in sequence, and the outlets of the storage pools are fixedly connected to a purified water discharge pipeline 9, and a variety of green plants are planted in the artificial green floating islands 8.

[0022] In the present invention, unless otherwise specified, the equipment and devices used are all the equipment and devices known and used in the art.

[0023] As needed, conventional valves, thermometers, pressure gauges, etc. known and used in the art may be installed on the pipelines and equipment of the apparatus for implementing the method of treating oilfield fracturing flowback fluid using floating island green plants according to production needs.

[0024] Example 7: The present invention is applied to the fracturing flowback fluid treatment site in the shale oil area of ​​Jiqing operating area.

[0025] After the original gel breaking, flocculation, flotation and filtration, the oil content of the fracturing return fluid is less than 5mg / L, and the suspended solids are 10mg / L. After the pretreatment is completed, the purified water enters the 150,000 cubic meter open-air storage pool. Because the water quality still contains organic components such as COD and suspended solids, the water quality of the storage pool often changes over time before the water volume can be immediately re-injected or reused. The significant phenomenon is that the water color becomes dark brown, bacteria breed seriously, the odor is obvious, and the visual effect is poor. In the water inlet direction of the 150,000 cubic meter open-air storage pool, multiple rows of artificial green plant floating islands 8 are vertically installed, and a variety of green plants such as canna, water onion, pickerel grass, yellow iris, loosestrife, water hyacinth, reed bamboo, red polygonum, iris, cattail, wild rice, Vallisneria, foxtail, and arrowhead mushrooms are selected. After field tests, the test results are good, the green plants grow well, the water color improves, and the odor gradually dissipates. Among them, the water quality monitoring data before and after the artificial green plant floating island is used are shown in Table 1. As shown in Table 1, the water quality stability in the pool is significantly improved, and the contents of COD, suspended solids, ammonia nitrogen and total nitrogen are effectively reduced.

[0026] In summary, the present invention utilizes artificial floating islands to plant aquatic plants in the fracturing return fluid storage pool, which effectively reduces the concentration of pollutants such as COD, suspended matter, total nitrogen, ammonia nitrogen and the salinity of the water, optimizes the ecological system in the storage pool after fracturing return water pretreatment, improves the water quality stability in the storage pool, and extends the shelf life of the water quality.

[0027] The above technical features constitute the embodiments of the present invention, which have strong adaptability and implementation effect. Non-essential technical features can be added or reduced according to actual needs to meet the requirements of different situations.

Claims

1. A method for treating oilfield fracturing flowback fluid using floating island green plants, characterized in that The following steps are followed: first, select floating island aquatic plants suitable for planting in the fracturing flowback fluid storage pool; second, plant the floating island aquatic plants in the water inlet area of ​​the storage pool in stages and rows; In the third step, the wellhead fracturing flowback wastewater is subjected to gel breaking flocculation, flotation and filtration to obtain pre-treated water; The fourth step is to send the pretreated water to a storage tank, where the floating island aquatic plants filter harmful substances in the pretreated water through their roots and absorb the nutrients needed for growth to obtain purified water.

2. The method for treating oilfield fracturing flowback fluid using floating island green plants according to claim 1, characterized in that Floating island aquatic plants are salt-tolerant and have well-developed root systems.

3. The method for treating oilfield fracturing flowback fluid using floating island green plants according to claim 2, characterized in that The floating island aquatic plants include one or more of canna, water plantain, pickerel grass, yellow iris, loosestrife, water hyacinth, reed, red polygonum, iris, cattail, wild rice stem, Vallisneria, foxtail, and arrowhead.

4. The method for treating oilfield fracturing flowback fluid using floating island green plants according to claim 1, characterized in that In the fourth step, the nutrients absorbed by the roots of the floating island aquatic plants in the water are pollutants enriched in COD, suspended solids, total nitrogen, and ammonia nitrogen.

5. A device for implementing the method for treating oilfield fracturing flowback fluid using floating island green plants according to any one of claims 1 to 4, characterized in that It includes a sedimentation tank, a pretreatment device and a deep treatment device. The inlet of the sedimentation tank is fixedly connected to a wastewater discharge pipeline, the outlet of the sedimentation tank and the inlet of the pretreatment device are fixedly connected to a pretreated water inlet pipeline, the outlet of the pretreatment device and the inlet of the deep treatment device are fixedly connected to a pretreated water discharge pipeline, and the outlet of the deep treatment device is fixedly connected to a purified water discharge pipeline.

6. The device according to claim 5, characterized in that The deep treatment device includes a plurality of storage pools, on which partitions are arranged, between which artificial green plant floating islands are arranged in sequence, and the outlets of the storage pools are fixedly connected with purified water discharge pipelines.

Images