Device for treating gas field produced water with oil content less than or equal to 30mg / L

Abstract

The utility model relates to a gas field produced water treatment device with the oil content smaller than or equal to 30 mg / L, and relates to the technical field of produced water treatment. Comprising a homogenizing unit connected with a water outlet pipe of the gas field produced water and used for homogenizing the gas field produced water; the mechanical stirring unit is connected with the homogenizing unit and is used for mechanically stirring the gas field produced water so as to reduce calcium and magnesium ions in the gas field produced water; the first filtering unit is connected with the mechanical stirring unit and is used for removing suspended matters with first granularity in the gas field produced water; the electrolysis unit is connected with the first filtering unit and is used for removing oil in the gas field produced water; the COD removal unit is connected with the electrolysis unit and is used for removing organic pollutants in the gas field produced water; the second filtering unit is connected with the COD removing unit and used for removing suspended solids with second granularity in the gas field produced water, and the first granularity is larger than the second granularity; and the reverse osmosis membrane unit is connected with the second filtering unit and is used for removing impurities and salt in the gas field produced water.

Description

Technical Field

[0001] This utility model relates to the technical field of produced water treatment, and in particular to a produced water treatment device for gas fields with an oil content ≤30mg / L. Background Technology

[0002] During gas well production, low acid flowback rates often result in residual acid fracturing fluid remaining in the formation. To increase well production and fully realize capacity, acid fracturing is typically used to modify the well network and develop reservoir fractures. During well production, residual formation fluid is carried to the surface with the gas and undergoes gas-liquid separation before entering subsequent processes. This fluid contains oil and bitumen-like impurities (injected fracturing fluid). To ensure the stable, full-capacity, and efficient operation of natural gas desulfurization units, it is necessary to treat and effectively utilize the produced water from the relevant oil and gas fields.

[0003] The related technology discloses a process and system for the resource-based treatment of produced water from oil and gas fields, including: a stirring and clarification device for removing scale-forming ions from the produced water; an electrochemical oxidation device including an electrolytic cell for electrolyzing the produced water to remove ammonia nitrogen and reduce COD; an iron-carbon filtration device containing iron-carbon packing material for further removing ammonia nitrogen and reducing COD; and a reverse osmosis device for further removing conductive ions and reducing COD, to obtain the treated effluent.

[0004] However, the process systems for resource-based treatment of produced water from oil and gas fields provided by related technologies have problems such as poor treatment effect and high treatment cost for produced water from low-content oil and gas fields, such as oil content ≤30mg / L. Utility Model Content

[0005] This invention provides a treatment device for produced water from gas fields with an oil content of ≤30mg / L. It can at least solve the problems of poor treatment effect and high treatment cost of the process system for resource utilization treatment of produced water from oil and gas fields provided by related technologies for low-content, such as produced water from low-oil-content gas fields with an oil content of ≤30mg / L.

[0006] This utility model provides a treatment device for produced water from gas fields with an oil content ≤30mg / L, wherein the produced water has an oil content ≤30mg / L and is emulsified and transparent. The device includes:

[0007] The homogenization unit is connected to the outlet pipe of the produced water from the gas field and is used to homogenize the produced water from the gas field.

[0008] A mechanical stirring unit, connected to the homogenization unit, is used to mechanically stir the produced water from the gas field to reduce the calcium and magnesium ions in the produced water.

[0009] The first filtration unit, connected to the mechanical stirring unit, is used to remove suspended solids of the first particle size from the produced water of the gas field.

[0010] An electrolysis unit, connected to the first filtration unit, is used to remove oil from the produced water from the gas field.

[0011] The COD removal unit is connected to the electrolysis unit and is used to remove organic pollutants from the produced water of the gas field.

[0012] The second filtration unit is connected to the COD removal unit and is used to remove suspended solids of a second particle size from the gas field produced water, wherein the first particle size is larger than the second particle size.

[0013] The reverse osmosis membrane unit, connected to the second filtration unit, is used to remove impurities and salts from the produced water from the gas field.

[0014] In one embodiment, the COD removal unit includes: a plurality of interconnected reaction units, the inlet of which is connected to the electrolysis unit, and the outlet of which is connected to the second filtration unit;

[0015] The reaction unit contains an oxidant, which is used to react with organic pollutants in the produced water of the gas field to remove the organic pollutants.

[0016] In one embodiment, the reaction unit includes a reaction vessel and a grid. One end of the grid is connected to the inner wall of the reaction vessel, and the other end is spaced apart from the interior of the reaction vessel. The inner wall of the reaction vessel has overnight passage holes, and the spaced distance of the reaction vessel and the overnight passage holes form a liquid passage channel.

[0017] In one embodiment, the reaction unit further includes a stirrer located in the reaction vessel.

[0018] In one embodiment, the reverse osmosis membrane unit includes: a high-pressure membrane reverse osmosis unit and a low-pressure membrane reverse osmosis unit;

[0019] The inlet of the high-pressure membrane reverse osmosis unit is connected to the second filtration unit, and the outlet is connected to the low-pressure membrane reverse osmosis unit.

[0020] In one embodiment, a mechanical vapor recompression unit is also included;

[0021] The inlet of the mechanical vapor recompression unit is connected to the outlet of the high-pressure membrane reverse osmosis unit, the first outlet is connected to the low-pressure membrane reverse osmosis unit, and the second outlet is used to discharge waste liquid.

[0022] In one embodiment, the first filtration unit is a diamond filter and the second filtration unit is a manganese sand filter.

[0023] In one embodiment, a booster pump is also included, which is provided between the mechanical stirring unit and the homogenizing unit, and between the mechanical stirring unit and the first filtering unit.

[0024] In one embodiment, the system further includes a gas field water receiving unit connected to the homogenization unit.

[0025] In one embodiment, a desulfurization unit is also included, which is connected to the gas field water receiving unit and is used to remove sulfur from the produced water of the gas field.

[0026] Compared with existing technologies, the gas field produced water treatment device provided by this utility model embodiment can treat produced water from low-oil-content gas fields with an oil content of ≤30mg / L. Based on the application of electrolysis units and reverse osmosis membrane units, the water quality of the treated gas field produced water meets the requirements for the makeup water quality of the circulating cooling water system in the "Water Conservation and Emission Reduction Assessment Indicators and Reclaimed Water Quality Control Indicators for Refining and Chemical Enterprises" (Q / SH 0104-2007). Moreover, the treatment cost is low, and the economic benefits throughout the entire life cycle are considerable. It not only reduces the amount of wastewater reinjection, but also "turns waste (gas field produced water) into treasure", realizing the full utilization of resources, and has practical significance and promotion value for environmental protection. Attached Figure Description

[0027] The present invention will be described in more detail below based on embodiments and with reference to the accompanying drawings.

[0028] Figure 1 This is a schematic diagram of the structure of a gas field produced water treatment device with an oil content of ≤30mg / L, as described in an embodiment of this utility model.

[0029] Figure 2 This is a schematic diagram of the COD treatment unit in a gas field produced water treatment device with an oil content ≤30mg / L, as described in an embodiment of this utility model.

[0030] Figure label:

[0031] 1-Homogenization unit, 2-Mechanical stirring unit, 3-First filtration unit, 4-Electrolysis unit, 5-COD removal unit, 6-Second filtration unit, 61-Reaction vessel, 62-Grid, 7-High-pressure membrane reverse osmosis unit, 8-Low-pressure membrane reverse osmosis unit, 9-Desulfurization unit, 10-Boost pump, 11-Gas field water receiving unit, 12-Mechanical steam recompression unit. Detailed Implementation

[0032] The present invention will be further described below with reference to the accompanying drawings.

[0033] Please see Figure 1 This utility model provides a gas field produced water treatment device for oil content ≤30mg / L. The oil content of the gas field produced water is ≤30mg / L and the gas field produced water is emulsified and transparent. The device includes: a homogenization unit 1, a mechanical stirring unit 2, a first filtration unit 3, an electrolysis unit 4, a second filtration unit 6 and a reverse osmosis membrane unit. The system comprises the following components: a homogenization unit 1 connected to the outlet pipe of the gas field produced water for homogenizing the produced water; a mechanical stirring unit 2 connected to the homogenization unit 1 for mechanically stirring the produced water to reduce calcium and magnesium ions; a first filtration unit 3 connected to the mechanical stirring unit 2 for removing suspended solids of the first particle size from the produced water; an electrolysis unit 4 connected to the first filtration unit 3 for removing oil from the produced water; a COD removal unit 5 connected to the electrolysis unit 4 for removing organic pollutants from the produced water; a second filtration unit 6 connected to the COD removal unit 5 for removing suspended solids of the second particle size from the produced water, wherein the first particle size is larger than the second particle size; and a reverse osmosis membrane unit connected to the second filtration unit 6 for removing impurities and salts from the produced water.

[0034] The gas field produced water treatment device provided in this embodiment can treat produced water from low-oil-content gas fields with an oil content of ≤30mg / L. Based on the application of electrolysis unit 4 and reverse osmosis membrane unit, the water quality of the treated gas field produced water meets the requirements for the makeup water quality of the circulating cooling water system in the "Water Conservation and Emission Reduction Assessment Indicators and Reclaimed Water Quality Control Indicators for Refining and Chemical Enterprises" (Q / SH 0104-2007). Moreover, the treatment cost is low and the economic benefits throughout the entire life cycle are considerable. It not only reduces the amount of wastewater reinjection, but also "turns waste (gas field produced water) into treasure", realizing the full utilization of resources, and has practical significance and promotion value for environmental protection.

[0035] In this embodiment of the invention, the homogenization unit 1 can be a gas field water receiving tank. Gas field produced water is placed in the receiving tank, and homogenization is achieved through extensive aeration to break up the agglomerates in the system. Microbubbles are used to remove petroleum contaminants and a large amount of suspended solids (SS) from the produced water. Homogenization of gas field water removes suspended solids and colloidal substances, thereby improving water quality and reducing the impact on subsequent treatment processes. Homogenization effectively reduces the suspended solids content in the produced water, improves its transparency and stability, and provides better conditions for subsequent treatment processes.

[0036] In this embodiment of the invention, mechanical stirring of the produced water from the gas field can promote mixing, improve mass transfer efficiency, prevent sedimentation, and promote chemical reactions. The mechanical stirring unit 2 stirs the produced water from the gas field by placing it into a mechanical stirring tank or other stirring container, thereby fully dispersing the gas, liquid, or solid particles in the produced water within the liquid, thus accelerating the heat and mass transfer process and improving processing efficiency.

[0037] In this embodiment of the invention, the gas field produced water is filtered by the first filtration unit 3, which can remove suspended solids of the first particle size from the gas field produced water; in an optional embodiment, the first filtration unit 3 is a diamond filter.

[0038] Filtering produced water from gas fields using a diamond filter removes impurities and suspended solids. Diamond filters effectively remove particles, silt, and other impurities from the water, ensuring pure treated water and preventing equipment clogging and damage. Diamond filters also reduce equipment wear and maintenance needs, extending equipment lifespan. Cleaned produced water improves the efficiency of the entire treatment unit, ensuring the smooth operation of the produced water treatment process.

[0039] Manganese sand filters can remove suspended solids, particulate matter, iron ions, and manganese ions from produced water in gas fields, thereby improving the quality of the treated water and meeting treatment standards. Iron and manganese ions in the produced water are removed by adsorption from the manganese sand after aeration and oxidation. The oxidized iron and manganese ions form insoluble compounds, which are effectively removed by the adsorption and filtration action of the manganese sand filter. Through adsorption and filtration, impurities in the water are effectively removed, ensuring the quality of the treated produced water.

[0040] Electrolysis unit 4 can be an electrolysis device. The role of the electrolysis device in gas field water treatment is to remove pollutants from the produced water of the gas field through the electrolysis process, mainly including heavy metal ions, organic matter and other harmful substances.

[0041] The specific steps involved in using electrolysis units for gas field water treatment include: Electrolytic oxidation: Pollutants in the produced water are removed through oxidation-reduction reactions generated during electrolysis. This step is typically carried out in an electrolytic cell, where the cathode is connected to the negative terminal of the power supply, and the anode is connected to the positive terminal. The anode acts as the oxidant, and the cathode acts as the reducing agent. Membrane system treatment: The produced water after electrolytic oxidation is treated through a membrane system to further remove residual pollutants. Evaporation treatment: Salt and other impurities in the produced water are removed through evaporation. Electron beam irradiation treatment: Finally, electron beam irradiation treatment ensures that the effluent meets discharge standards, achieving "zero discharge."

[0042] The role of COD removal unit 5 in gas field produced water treatment is to reduce the chemical oxygen demand (COD) in the produced water, reduce organic pollution, and ensure that the treated water quality meets the reinjection or discharge standards, thereby protecting the environment and ecosystem.

[0043] The COD removal unit 5 provided in this embodiment of the present invention uses chemical oxidation: chemical oxidants such as ozone, hydrogen peroxide or potassium permanganate are used to oxidize organic matter, which is suitable for treating water from gas fields with high sulfur content.

[0044] For example, ferrous ions (Fe) 2+ A chain reaction occurs between H₂O₂ and hydrogen peroxide (H₂O₂) to generate hydroxyl radicals (·OH) with strong oxidizing power. This reaction proceeds under acidic conditions, where H₂O₂ reacts with Fe. 2+ Under catalysis, it decomposes to produce ·OH, with an oxidation potential as high as 2.80V, second only to fluorine in oxidation ability. Hydroxyl radicals have strong electronegativity and addition reaction characteristics, enabling them to non-selectively oxidize most organic matter in produced water from gas fields and effectively degrade organic wastewater.

[0045] In one optional embodiment, the second filtration unit 6 is a manganese sand filter. The main function of the manganese sand filter in gas field produced water treatment is to remove suspended solids, particulate matter, iron and manganese ions, and other impurities from the water, thereby improving water quality. The manganese sand filter utilizes the adsorption and filtration properties of manganese sand to purify the water by intercepting and adsorbing impurities. The specific working principle of the manganese sand filter is to remove suspended solids, particulate matter, and organic matter from the water through the adsorption of manganese sand. The manganese dioxide in the manganese sand undergoes a redox reaction with the iron and manganese ions in the water, oxidizing ferrous iron and manganese to insoluble ferric iron and manganese tetravalent iron, which are then removed through adsorption.

[0046] In this embodiment of the invention, the reverse osmosis membrane unit includes: a high-pressure membrane reverse osmosis unit 7 and a low-pressure membrane reverse osmosis unit 8; the inlet of the high-pressure membrane reverse osmosis unit 7 is connected to the second filtration unit 6, and the outlet is connected to the low-pressure membrane reverse osmosis unit 8.

[0047] The principle of reverse osmosis technology is to use a semi-permeable membrane that allows only the solvent (such as water) to pass through, but not the solute. By applying pressure higher than the osmotic pressure of the solution, the produced water from the gas field is forced to permeate through the reverse osmosis membrane with extremely small pores, thereby separating the solute from the solvent. This technology can remove not only various ions from the produced water from the gas field, but also larger particles, organic matter, colloids, viruses, bacteria, and suspended solids.

[0048] The role and pathway of high-pressure membrane reverse osmosis in gas field produced water treatment is mainly to remove impurities from the produced water through efficient filtration, including dissolved salts, heavy metals, organic pollutants, bacteria, and viruses, thereby producing pure water that meets high water quality standards. Reverse osmosis technology can remove more than 99% of impurities in water, including dissolved salts, heavy metals, organic pollutants, bacteria, and viruses. Therefore, water treated by reverse osmosis is extremely pure and suitable for various high-standard water quality requirements.

[0049] Low-pressure membrane reverse osmosis plays a crucial role in gas field produced water treatment by removing salts and impurities, reducing chemical oxygen demand (COD), and bringing the water quality up to reuse standards. This method is particularly important in treating produced water from sulfur-containing gas fields, where it can significantly improve the water's "green content," i.e., its environmental performance.

[0050] Low-pressure membrane reverse osmosis technology achieves its function through the following pathways: Electrolytic catalytic oxidation: First, electrolytic catalytic oxidation oxidizes and decomposes organic matter in the produced water from the gas field, reducing the chemical oxygen demand (COD). High and low pressure reverse osmosis technology: Next, high and low pressure reverse osmosis technology is used to remove salt and impurities from the produced water from the gas field. This step involves using ultra-low pressure reverse osmosis membranes, which operate at lower pressures and are suitable for produced water solutions from gas fields with low salinity. Post-biological treatment: Finally, post-biological treatment further removes organic matter and ammonia nitrogen from the produced water from the gas field, ensuring that the water quality meets reuse standards.

[0051] In an optional embodiment, the COD removal unit 5 includes: a plurality of interconnected reaction units, the inlet of which is connected to the electrolysis unit 4 and the outlet of which is connected to the second filtration unit 6; wherein, the reaction unit contains an oxidant, which is used to react with organic pollutants in the gas field produced water to remove the organic pollutants.

[0052] Please see Figure 2 In one optional embodiment, the reaction unit includes a reaction vessel 61 and a grid 62. One end of the grid 62 is connected to the inner wall of the reaction vessel 61, and the other end is spaced apart from the interior of the reaction vessel 61. The inner wall of the reaction vessel 61 has overnight perforations, and the spaced-apartments and overnight perforations form a liquid passage. Figure 2 The arrows in the diagram indicate the flow direction of the produced water from the gas field.

[0053] In an alternative embodiment, the reaction unit further includes a stirrer located in the reaction vessel 61.

[0054] In an optional embodiment, a mechanical vapor recompression unit 12 is further included; the inlet of the mechanical vapor recompression unit 12 is connected to the outlet of the high-pressure membrane reverse osmosis unit 7, the first outlet is connected to the low-pressure membrane reverse osmosis unit 8, and the second outlet is used to discharge waste liquid.

[0055] In an optional embodiment, a booster pump 10 is also included, with booster pumps 10 provided between the mechanical stirring unit 2 and the homogenizing unit 1, and between the mechanical stirring unit 2 and the first filtering unit 3.

[0056] In an optional embodiment, the gas field water receiving unit 11 is also included, which is connected to the homogenization unit 1.

[0057] In an optional embodiment, a desulfurization unit 9 is also included, which is connected to the gas field water receiving unit 11. The desulfurization unit 9 is used to remove sulfur from the produced water of the gas field.

[0058] The role of desulfurization unit 9 in gas field water treatment is to remove sulfides from produced water to prevent them from harming the environment and health. Common desulfurization technologies include biological deodorization and air stripping processes. Specific Implementation

[0060] This embodiment targets produced water from gas fields with low oil content (≤30 mg / L). A treatment process of "electrolytic oxidation (primarily for oil removal) + reverse osmosis membrane treatment (for resource utilization)" is employed. All the resulting treated water is reused, and the oil content of the treated water is ≤1 mg / L. Data for the treated produced water from the gas field are shown in Table 1.

[0061] Table 1

[0062]

[0063] The original data refers to untreated produced water from gas fields, while the actual data refers to treated produced water from gas fields. As can be seen from Table 1, all data for the treated produced water from gas fields are within the regulated range.

[0064] Furthermore, this utility model embodiment involves the reuse of gas field produced water after reinjection treatment to meet standards. Before treatment, reinjection costs 300 yuan per cubic meter. After treatment, each cubic meter of water produces 90% reclaimed water, 5% miscellaneous salt, and 5% mother liquor. Reclaimed water costs 40 yuan per cubic meter, miscellaneous salt costs 145 yuan per cubic meter, mother liquor costs 400 yuan per cubic meter, and purchased circulating water costs 5 yuan per cubic meter. Therefore, each cubic meter reused saves 300 - (40*90% + 145*5% + 400*5% + 5) = 230 yuan, resulting in considerable economic benefits throughout its lifecycle. This not only reduces the amount of wastewater reinjected but also "turns waste into treasure," achieving full resource utilization and possessing practical significance and promotional value for environmental protection. The device provided by this utility model embodiment has broad promotion and application value in the oil and gas field development industry and the field of low-oil-content produced water extraction.

[0065] Although the present invention has been described with reference to preferred embodiments, various modifications can be made thereto and components can be replaced with equivalents without departing from the scope of the invention. In particular, the technical features mentioned in the various embodiments can be combined in any manner, provided there is no structural conflict. The present invention is not limited to the specific embodiments disclosed herein, but includes all technical solutions falling within the scope of the claims.

Claims

1. A treatment device for produced water from gas fields with an oil content ≤30mg / L, characterized in that, The device includes: The homogenization unit is connected to the outlet pipe of the produced water from the gas field and is used to homogenize the produced water from the gas field. A mechanical stirring unit, connected to the homogenization unit, is used to mechanically stir the produced water from the gas field to reduce the calcium and magnesium ions in the produced water. The first filtration unit, connected to the mechanical stirring unit, is used to remove suspended solids of the first particle size from the produced water of the gas field. An electrolysis unit, connected to the first filtration unit, is used to remove oil from the produced water from the gas field. The COD removal unit is connected to the electrolysis unit and is used to remove organic pollutants from the produced water of the gas field. The second filtration unit is connected to the COD removal unit and is used to remove suspended solids of a second particle size from the gas field produced water, wherein the first particle size is larger than the second particle size. The reverse osmosis membrane unit, connected to the second filtration unit, is used to remove impurities and salts from the produced water from the gas field.

2. The gas field produced water treatment device for oil content ≤30mg / L according to claim 1, characterized in that, The COD removal unit includes: multiple interconnected reaction units, the inlet of which is connected to the electrolysis unit, and the outlet of which is connected to the second filtration unit; The reaction unit contains an oxidant, which is used to react with organic pollutants in the produced water of the gas field to remove the organic pollutants.

3. The gas field produced water treatment device for oil content ≤30mg / L according to claim 2, characterized in that, The reaction unit includes a reaction vessel and a grid. One end of the grid is connected to the inner wall of the reaction vessel, and the other end is spaced apart from the interior of the reaction vessel. The inner wall of the reaction vessel has overnight passage holes. The spaced distance between one end of the grid and the reaction vessel and the overnight passage holes form a liquid passage channel.

4. The gas field produced water treatment device for oil content ≤30mg / L according to claim 3, characterized in that, The reaction unit also includes a stirrer located in the reaction vessel.

5. The gas field produced water treatment device for oil content ≤30mg / L according to claim 1, characterized in that, The reverse osmosis membrane unit includes: a high-pressure membrane reverse osmosis unit and a low-pressure membrane reverse osmosis unit; The inlet of the high-pressure membrane reverse osmosis unit is connected to the second filtration unit, and the outlet is connected to the low-pressure membrane reverse osmosis unit.

6. The gas field produced water treatment device for oil content ≤30mg / L according to claim 5, characterized in that, It also includes a mechanical vapor recompression unit; The inlet of the mechanical vapor recompression unit is connected to the outlet of the high-pressure membrane reverse osmosis unit, the first outlet is connected to the low-pressure membrane reverse osmosis unit, and the second outlet is used to discharge waste liquid.

7. The gas field produced water treatment device for oil content ≤30mg / L according to claim 5, characterized in that, The first filtration unit is a diamond filter, and the second filtration unit is a manganese sand filter.

8. The gas field produced water treatment device according to any one of claims 1-7 for oil content ≤30mg / L, characterized in that, It also includes lift pumps, which are installed between the mechanical stirring unit and the homogenizing unit, and between the mechanical stirring unit and the first filtration unit.

9. The gas field produced water treatment device according to any one of claims 1-7 for oil content ≤30mg / L, characterized in that, It also includes a gas field water receiving unit, which is connected to the homogenization unit.

10. The gas field produced water treatment device for oil content ≤30mg / L according to claim 9, characterized in that, It also includes a desulfurization unit, which is connected to the gas field water receiving unit and is used to remove sulfur from the produced water of the gas field.

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