A short-process high-salinity fracturing flowback fluid treatment process

Abstract

The present application relates to fracturing flowback fluid treatment technical field, and disclose a kind of short process's high salinity fracturing flowback fluid treatment process, comprising the following steps: S1, high salinity fracturing flowback fluid is conveyed from stock solution water tank to ceramic ultrafiltration system by water inlet pump, before entering ceramic membrane, filtration is carried out through self-cleaning filter, and large particle suspended solids are removed;The present application uses the process of "ceramic ultrafiltration+immersed combustion evaporation" to treat high salinity fracturing flowback fluid, can keep the stable treatment efficiency, and the final water can reach discharge standard;The process reagent addition amount is less, and the solid product produced is also less, and its solid product disposal cost is low;The process can be continuously operated, and the system does not need to be frequently started and stopped;The process is short, and the land occupation is small, and the operation personnel are less, and the operation cost is reduced, finally realizes the treatment of high salinity fracturing flowback fluid wastewater treatment efficiency, process is short, and the treatment cost is low and so on goal.

Description

Technical Field

[0001] This invention relates to the field of fracturing flowback fluid treatment technology, specifically a short-process high-mineralization fracturing flowback fluid treatment process. Background Technology

[0002] Shale gas is an important strategic resource, generally stored in difficult-to-extract sedimentary rocks, requiring specialized processes to obtain economically viable hydrocarbon gases. Traditional oil and gas field extraction methods cannot unlock the potential of low-permeability fields, making hydraulic fracturing a crucial means of increasing production. Hydraulic fracturing utilizes water power to inject fracturing fluid, applying pressure to the oil-bearing reservoir, causing it to fracture, thus improving fracturing efficiency and achieving the goals of increased permeability and oil and gas field production. This fracturing fluid will flow back during oilfield production and transportation, and is known as "fracturing flowback fluid."

[0003] To improve fracturing efficiency and fluid properties, fracturing fluids typically contain various chemical additives such as thickeners, pH adjusters, surfactants, crosslinking agents, clay stabilizers, and breaker agents, increasing the difficulty of treating fracturing flowback fluids. Furthermore, after entering the formation, the fracturing fluid mixes with formation water, and during flowback, it carries out large amounts of clay minerals, heavy metal ions, and bacteria from deep within the formation. Therefore, the water quality characteristics of fracturing flowback fluids are mainly characterized by high mineralization, high viscosity, high suspended solids content, and high COD values. Direct discharge to the surface would cause serious pollution to the surrounding environment. Moreover, shale gas extraction is often carried out in remote, arid, and water-scarce areas, and the fracturing process requires large amounts of freshwater, further exacerbating the uneven distribution of water resources. Therefore, effectively treating fracturing flowback fluids, recycling and reusing them, or subjecting them to harmless treatment to reduce pollutant emissions into the environment is not only a requirement for environmental protection in the development area but also a key technical aspect of clean and sustainable shale gas development.

[0004] Currently, the disposal methods for fracturing flowback fluids both domestically and internationally are mainly divided into three categories: First, discharge the fluids according to the Class I standard in the National Integrated Wastewater Discharge Standard (GB8978~1996); second, reinject the fluids into the formation after treatment to meet the standards according to the Recommended Indicators and Analysis Methods for Water Quality in Clastic Rock Reservoirs; and third, prepare the fluids into drilling fluids or fracturing fluids for reuse, referring to energy industry standards (NB / T14002.3~2022). Deep well reinjection is limited by regional geology and external environmental conditions, and carries certain geological and environmental risks, thus its application scenarios are limited. The requirements for reuse fluid preparation are extremely high, requiring stable water quality, no scaling tendency, and good compatibility with chemical additives. Currently, the main disposal method for fracturing flowback fluids is discharge after meeting the standards.

[0005] Considering the characteristics of fracturing flowback fluid, treatment to meet discharge standards requires removal of suspended solids, reduction of hardness, mineralization, and COD. Traditional treatment processes consist of "turbidity removal and softening pretreatment (air flotation, high-density tanks, softening membranes, etc.) + organic matter treatment (mostly advanced oxidation or combined advanced oxidation processes) + concentration treatment (depending on the influent quality, often high-pressure reverse osmosis and electrodialysis) + indirect evaporation (MVC, MVR)." This conventional process is suitable for treating fracturing flowback fluid with low mineralization. However, when the flowback fluid has high mineralization, this process suffers from problems such as easy equipment scaling, frequent shutdowns for cleaning, inability to operate continuously, high reagent consumption, high sludge production, high operating costs, cumbersome process flow, large equipment footprint, and high investment costs. Therefore, a short-process high-mineralization fracturing flowback fluid treatment technology is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide a short-process high-mineralization fracturing flowback fluid treatment process to solve the problems mentioned in the background art.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a short-process high-mineralization fracturing flowback fluid treatment process, comprising the following steps:

[0008] S1. High-mineralization fracturing flowback fluid is pumped from the raw fluid tank to the ceramic ultrafiltration system via the feed pump. Before entering the ceramic membrane, it is filtered by a self-cleaning filter to remove large suspended particles.

[0009] S2. The pretreated return liquid enters the ceramic ultrafiltration system. Under the retention of the ceramic membrane, the permeate is discharged into the permeate tank through the permeate outlet, and the concentrate is returned to the original liquid tank for recycling.

[0010] S3. Backwashing and chemical cleaning: Use the product water in the product water tank to backwash the ceramic membrane;

[0011] S4. The permeate water of the ceramic ultrafiltration system is transported to the submerged combustion evaporation system via an evaporation feed pump. Landfill gas, anaerobic biogas or natural gas are used as energy sources to heat, evaporate, concentrate and crystallize the permeate water. The steam and non-condensable gas generated by evaporation are separated by a separation tower to remove the liquid droplets entrained in the mist. The steam enters the condensation system and is condensed to meet the emission standards. The non-condensable gas enters the non-condensable gas treatment system.

[0012] S5. Non-condensable gas passes through the acid spray tower and the alkali spray tower in sequence. The alkaline substances in the gas phase react with the acidic substances in the liquid phase to form soluble salts. The treated non-condensable gas is discharged in compliance with regulations through the exhaust stack. The soluble salts at the bottom of the tower are returned to the submerged combustion evaporation system.

[0013] S6. The saturated residual liquid generated by evaporation is transported to the salt mud dewatering system by a booster pump. The dewatered salt mud is packaged and sealed and centrally processed. The supernatant is returned to the submerged combustion evaporation system.

[0014] Preferably, in S1, the filtration accuracy is 50–500 μm.

[0015] Preferably, in S2, the ceramic ultrafiltration system comprises a ceramic membrane;

[0016] The area of ​​a single ceramic membrane is 10–25 m². 2 The operating throughput is 20–150 LMH, the operating pH range is 1–13.5, the operating temperature range is 15–40℃, and the operating pressure range is 0.1–0.6 MPa.

[0017] Preferably, in S3, the ceramic ultrafiltration system is backwashed once every 30 to 60 minutes using the product water. The backwash time is 30 to 120 seconds, the backwash flux is 40 to 240 LMH, the backwash pH range is 1 to 13.5, and the backwash water enters the raw water tank.

[0018] Preferably, the ceramic ultrafiltration system described above is chemically cleaned every 3 to 4 months, using sodium hydroxide, citric acid, and hydrochloric acid to remove residual organic matter, colloids, and microorganisms.

[0019] The concentration of sodium hydroxide is 0.1-1.0%, the concentration of citric acid is 5-20%, and the concentration of hydrochloric acid is 0.1-0.4%. The cleaning agents enter the ceramic ultrafiltration system through the chemical cleaning system, and the wastewater after cleaning is returned to the chemical cleaning system.

[0020] Preferably, in step S6, the dehydrated salt mud has a moisture content of 40-70%.

[0021] This invention also provides a short-process high-mineralization fracturing flowback fluid treatment system, including a raw fluid tank, a ceramic ultrafiltration system, a product water tank, a backwashing system, a chemical cleaning system, an immersion combustion evaporation system, a steam condensation system, a non-condensable gas system, a salt mud dewatering system, a condensate tank, and a chemical dosing system;

[0022] The raw material tank is used to temporarily store high-mineralization fracturing flowback fluid to be processed;

[0023] The ceramic ultrafiltration system is used to pretreat fracturing flowback fluid, remove silica, suspended solids and organic matter from the water, and reduce the viscosity and turbidity of the water.

[0024] The water production tank is used to store the water produced by the ceramic ultrafiltration system, providing a stable water source for the subsequent immersion combustion evaporation system;

[0025] The backwashing system is used to periodically backwash the ceramic membrane with the produced water to prevent the membrane surface from becoming clogged.

[0026] The chemical cleaning system is used to periodically chemically clean the ceramic membrane;

[0027] The immersion combustion evaporation system is used for deep treatment of the water produced by the ceramic ultrafiltration system. Through heating, evaporation, concentration and crystallization, it removes TDS, COD, ammonia nitrogen, calcium, magnesium ions and salt ions from the water.

[0028] The steam condensation system is used to condense the steam generated by evaporation into liquid water;

[0029] The non-condensable gas system is used to purify the non-condensable gas generated during the evaporation process;

[0030] The salt mud dewatering system is used to dewater the saturated evaporation residue generated by evaporation, thereby reducing the volume of waste residue.

[0031] The condensate tank is used to store the condensate generated by the steam condensation system as a treated clean water resource.

[0032] The dosing system is used to add reagents to the submerged combustion evaporation system.

[0033] Preferably, the following configuration is used: the outlet of the raw liquid tank is connected to the inlet of the ceramic ultrafiltration system; the outlet of the ceramic ultrafiltration system is connected to the inlet of the product water tank; the inlet of the ceramic ultrafiltration system is connected to the outlet of the backwashing system; the inlet of the ceramic ultrafiltration system is connected to the outlet of the chemical cleaning system; the outlet of the product water tank is connected to the inlet of the submerged combustion evaporation system; the dosing system is connected to the inlet pipe of the submerged combustion evaporation system; the steam and non-condensable gas outlet of the submerged combustion evaporation system is connected to the inlet of the steam condensation system; the outlet of the steam condensation system is connected to the inlet of the condensate tank; the non-condensable gas outlet of the steam condensation system is connected to the inlet of the non-condensable gas system; and the residual liquid outlet of the submerged combustion evaporation system is connected to the inlet of the salt mud dewatering system.

[0034] Compared with the prior art, the present invention, employing the above technical solution, has the following technical effects:

[0035] I. This invention discloses a short-process high-mineralization fracturing flowback fluid treatment technology and system. It treats high-mineralization fracturing flowback fluid through a combination of ceramic ultrafiltration and submerged combustion evaporation. First, the ceramic ultrafiltration system pre-treats the high-mineralization fracturing flowback fluid, primarily removing silica, viscosity, and suspended solids. Then, the submerged combustion evaporation system evaporates and crystallizes the fracturing flowback fluid containing high concentrations of pollutants such as TDS, COD, ammonia nitrogen, calcium, and magnesium ions, ultimately producing condensate, non-condensable gases, and salt sludge. Since over 90% of the salt is removed as crystalline salt, the condensate meets the Class I standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996). After deep treatment by acid and alkali spraying, the non-condensable gases also meet all standards.

[0036] II. The invention utilizes a ceramic ultrafiltration system to pretreat high-mineralization fracturing flowback fluid, removing silica, viscosity, and suspended solids, thereby improving the processing efficiency of the subsequent immersion combustion evaporation system. This system requires only a small amount of membrane cleaning agent and does not generate additional sludge.

[0037] Third, this invention utilizes a submerged combustion evaporation system to pressurize and immerse gaseous fuel on the subsurface of a liquid, and forms microbubbles through a special structure. The microbubbles directly contact the high-mineralization fracturing flowback fluid for heat exchange, resulting in high mass and heat transfer efficiency. Furthermore, because there is no wall between the two sides, the evaporation system does not accumulate scale or coke. While maintaining high processing capacity, the evaporation system can operate continuously and stably without the need for frequent shutdowns to clean the equipment and remove coke.

[0038] Fourth, this invention combines ceramic ultrafiltration and submerged combustion evaporation systems to treat high-mineralization fracturing flowback fluid. The process is short, reducing costs and energy consumption, minimizing floor space, simplifying operation and maintenance, and enhancing adaptability and flexibility to suit situations with limited land resources, cost sensitivity, and high environmental requirements. Attached Figure Description

[0039] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0040] Figure 1 This is a process flow diagram of the present invention;

[0041] Figure 2 This diagram illustrates the effect of direct evaporation of fracturing flowback fluid on contaminant removal according to the present invention.

[0042] Figure 3This is a diagram illustrating the effect of ceramic ultrafiltration on contaminant removal from the fracturing flowback fluid of the present invention.

[0043] Figure 4 This diagram illustrates the pollutant removal effect of the ceramic ultrafiltration + immersion combustion evaporation process of the present invention.

[0044] Figure 5 This is a membrane flux diagram illustrating the effect of temperature on silica rejection rate according to the present invention.

[0045] Figure 6 This is a graph showing the effect of temperature on silica retention rate in this invention, representing the viscosity removal rate.

[0046] Figure 7 This is a membrane flux diagram showing the effect of operating pressure on silica rejection rate according to the present invention.

[0047] Figure 8 This is a viscosity removal rate graph showing the effect of operating pressure on silica retention rate according to the present invention.

[0048] Figure 9 This is a comparison chart of the treatment effects of immersion combustion evaporation and ceramic ultrafiltration + immersion combustion evaporation according to the present invention. Detailed Implementation

[0049] 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. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0050] It should be noted that the structures, proportions, sizes, etc., shown in the accompanying drawings of this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed in the specification, and are not intended to limit the conditions under which this application can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size should still fall within the scope of the technical content disclosed in this application, provided that they do not affect the effects and purposes that this application can produce.

[0051] Example

[0052] Please see Figure 1 This invention provides a technical solution: a short-process high-mineralization fracturing flowback fluid treatment process, comprising the following steps:

[0053] S1. High-mineralization fracturing flowback fluid is pumped from the raw fluid tank to the ceramic ultrafiltration system via a feed pump. Before entering the ceramic membrane, it is filtered by a self-cleaning filter to remove large suspended particles; the filtration accuracy is 50-500μm.

[0054] S2. The pretreated return liquid enters the ceramic ultrafiltration system. Under the retention of the ceramic membrane, the permeate is discharged into the permeate tank through the permeate outlet, and the concentrate is returned to the original liquid tank for recycling.

[0055] The ceramic ultrafiltration system includes a ceramic membrane; the ceramic membrane can be made of TiN, and the area of ​​a single ceramic membrane is 10–25 m². 2 The operating throughput is 20–150 LMH, the operating pH range is 1–13.5, the operating temperature range is 15–40℃, and the operating pressure range is 0.1–0.6 MPa.

[0056] The optimal operating conditions for a ceramic ultrafiltration system are: operating temperature 25–30℃ and operating pressure 0.1–0.4 MPa.

[0057] S3. Backwashing and chemical cleaning: Use the product water in the product water tank to backwash the ceramic membrane;

[0058] The ceramic ultrafiltration system is backwashed every 30-60 minutes using the product water. The backwash time is 30-120 seconds, the backwash flux is 40-240 LMH, and the backwash pH range is 1-13.5. The backwash water enters the raw water tank.

[0059] The ceramic ultrafiltration system should be chemically cleaned every 3 to 4 months, using sodium hydroxide, citric acid and hydrochloric acid to remove residual organic matter, colloids and microorganisms;

[0060] The concentration of sodium hydroxide is 0.1-1.0%, the concentration of citric acid is 5-20%, and the concentration of hydrochloric acid is 0.1-0.4%. The cleaning agents enter the ceramic ultrafiltration system through the chemical cleaning system. The wastewater after cleaning is returned to the chemical cleaning system, and the residual pollutants on the surface of the ceramic membrane are removed by impact and friction.

[0061] S4. The permeate water of the ceramic ultrafiltration system is transported to the submerged combustion evaporation system via an evaporation feed pump. Landfill gas, anaerobic biogas or natural gas are used as energy sources to heat, evaporate, concentrate and crystallize the permeate water. The steam and non-condensable gas generated by evaporation are separated by a separation tower to remove the liquid droplets entrained in the mist. The steam enters the condensation system and is condensed to meet the emission standards. The non-condensable gas enters the non-condensable gas treatment system.

[0062] S5. Non-condensable gas passes through the acid spray tower and the alkali spray tower in sequence. The alkaline substances in the gas phase react with the acidic substances in the liquid phase to form soluble salts. The treated non-condensable gas is discharged in compliance with regulations through the exhaust stack. The soluble salts at the bottom of the tower are returned to the submerged combustion evaporation system.

[0063] S6. The saturated residual liquid generated by evaporation is transported to the salt mud dewatering system by a booster pump. The dewatered salt mud is packaged and sealed and centrally processed. The supernatant is returned to the immersion combustion evaporation system. The water content of the dewatered salt mud is 40-70%.

[0064] This invention also provides a short-process high-mineralization fracturing flowback fluid treatment system, including a raw fluid tank, a ceramic ultrafiltration system, a product water tank, a backwashing system, a chemical cleaning system, an immersion combustion evaporation system, a steam condensation system, a non-condensable gas system, a salt mud dewatering system, a condensate tank, and a chemical dosing system;

[0065] The outlet of the raw liquid tank is connected to the inlet of the ceramic ultrafiltration system; the outlet of the ceramic ultrafiltration system is connected to the inlet of the product water tank; the inlet of the ceramic ultrafiltration system is connected to the outlet of the backwash system; the inlet of the ceramic ultrafiltration system is connected to the outlet of the chemical cleaning system; the outlet of the product water tank is connected to the inlet of the submerged combustion evaporation system; the dosing system is connected to the inlet pipe of the submerged combustion evaporation system; the steam and non-condensable gas outlet of the submerged combustion evaporation system is connected to the inlet of the steam condensation system; the outlet of the steam condensation system is connected to the inlet of the condensate tank; the non-condensable gas outlet of the steam condensation system is connected to the inlet of the non-condensable gas system; and the residual liquid outlet of the submerged combustion evaporation system is connected to the inlet of the salt mud dewatering system.

[0066] The raw material tank is used to temporarily store high-mineralization fracturing flowback fluid awaiting treatment.

[0067] Ceramic ultrafiltration systems are used to pretreat fracturing flowback fluids, removing silica, suspended solids, and organic matter from the water, and reducing the viscosity and turbidity of the water.

[0068] The product water tank is used to store the product water treated by the ceramic ultrafiltration system, providing a stable water source for the subsequent submerged combustion evaporation system;

[0069] The backwashing system is used to periodically backwash the ceramic membrane with product water to prevent membrane surface clogging.

[0070] A chemical cleaning system is used for periodic chemical cleaning of ceramic membranes;

[0071] The submerged combustion evaporation system is used for the advanced treatment of water produced by the ceramic ultrafiltration system. It removes TDS, COD, ammonia nitrogen, calcium, magnesium ions and salt ions from the water through heating, evaporation, concentration and crystallization.

[0072] A steam condensation system is used to condense the steam generated by evaporation into liquid water;

[0073] The non-condensable gas system is used to purify the non-condensable gases generated during the evaporation process.

[0074] The salt mud dewatering system is used to dewater the saturated evaporation residue produced by evaporation, thereby reducing the volume of waste residue.

[0075] Condensate tanks are used to store condensate produced by steam condensation systems as treated clean water resources.

[0076] A dosing system is used to add chemicals to a submerged combustion evaporation system.

[0077] Water produced by the ceramic ultrafiltration system enters the submerged combustion evaporation system to remove TDS, COD, ammonia nitrogen, calcium, magnesium ions, and other salt ions. The water is then pumped to the submerged combustion evaporation system via an evaporation feed pump. Using landfill gas, anaerobic biogas, or natural gas as an energy source, the water undergoes heating, evaporation, concentration, and crystallization. The steam and non-condensable gases generated during evaporation are separated by a separation tower to remove entrained droplets before entering the steam condensation system via pipeline. The condensate produced after condensation meets discharge standards. The non-condensable gases that cannot be condensed enter the non-condensable gas system for treatment. The non-condensable gases are first introduced into the acid spray tower by an induced draft fan, where they rapidly fill the inlet section under negative pressure and then rise evenly through the flow equalization section. In the packed absorption section, alkaline substances in the gas phase react chemically with acidic substances in the liquid phase to form soluble salts, which are discharged to the bottom of the tower. The non-condensable gas then enters the alkaline spray tower, where acidic substances in the gas phase react chemically with alkaline substances in the liquid phase to form soluble salts, which are also discharged to the bottom of the tower. After dual purification treatment by acid and alkaline spraying, all indicators of the non-condensable gas meet the standards, and it is finally discharged in compliance with regulations through the exhaust stack. The soluble salts at the bottom of the tower are returned to the submerged combustion evaporation system. The saturated residual liquid produced during the evaporation process is transported to the salt mud dewatering system by a booster pump for dewatering treatment. The water content of the dewatered salt mud is about 40-70%. The final salt mud is packaged and sealed for periodic centralized treatment. The supernatant continues to flow back to the submerged combustion evaporation system for treatment.

[0078] Application examples

[0079] The process of this invention was used to treat the fracturing flowback fluid in a well in the Fuling oil and gas field.

[0080] As shown in Data 1 below, this fracturing flowback fluid has a very high degree of mineralization, with TDS ≥ 50000 mg / L; high organic matter concentration and poor biodegradability; high silica content; high viscosity; and high foaming ability with strong foam stability. It is difficult to treat using conventional processes.

[0081] Data 1: Water quality of fracturing flowback fluid

[0082] Serial Number Pollutant Indicators Pressure backflow fluid unit 1 Total dissolved solids (TDS) 112000.00 mg / L 2 Total organic carbon (TOC) 60.00 mg / L 3 Chemical oxygen demand (COD) 4180.00 mg / L 4 Total alkalinity 187.00 mg / L 5 calcium 3360.00 mg / L 6 magnesium 270.00 mg / L 7 Total Hardness 13200.00 mg / L 8 silicon dioxide 824.00 mg / L 9 Viscosity 0.84 <![CDATA[mm 2 / s]]>

[0083] Direct evaporation of the fracturing flowback fluid produces condensate and a small amount of salt mud. The condensate is collected and tested; its quality is shown in Data 2. The condensate and raw water data are compared to calculate the removal rate; the results are as follows. Figure 2 As shown:

[0084] Data 2: Water quality indicators of condensate from raw liquid evaporation

[0085] Serial Number detection indicators Pressure backflow fluid Evaporation condensate 1 COD (mg / L) 4000.00 95.74 2 Ammonia nitrogen (mg / L) 114.00 12.45 3 Calcium (mg / L) 13011.70 1801.62 4 Magnesium (mg / L) 3160.30 291.72 5 TDS (mg / L) 112000.00 451.00 6 Silica (mg / L) 824.00 554.00 7 <![CDATA[Viscosity (mm 2 / s)]]> 0.84 0.82

[0086] Depend on Figure 2 It can be seen that when the fracturing flowback fluid is directly treated by immersion combustion evaporation, the COD, ammonia nitrogen, calcium, magnesium and TDS can meet the first-level discharge standard in the "Integrated Wastewater Discharge Standard" (GB8978~1996), but the removal effect on silica and viscosity is poor and does not meet the discharge standard.

[0087] Because fracturing flowback fluid exhibits significant foaming during evaporation, characterized by large foam volume, high stability, and resistance to breakage, this foam can lead to mist entrainment. This causes contaminants attached to the foam to enter the condensate with the steam. While a small amount of mist entrainment is difficult to avoid, excessive mist entrainment can result in liquid carryover, increasing the concentration of contaminants in the condensate and affecting water quality standards. Furthermore, fracturing fluids typically contain guar gum, thickeners, pH adjusters, surfactants, and clay stabilizers to increase viscosity and stability. Therefore, fracturing flowback fluids contain colloidal silica, resulting in a relatively high viscosity.

[0088] A certain amount of fracturing flowback fluid is injected into the feed tank. The concentrate-side pressure regulating valve is fully open. The feed pump is started, and the concentrate-side pressure valve is adjusted slowly from fully open, while simultaneously observing the pressure gauge reading at the inlet of the ceramic ultrafiltration system. The feed pressure is set according to actual conditions, typically not exceeding 0.3 MPa. By measuring the permeate flow rate and production time, the ceramic membrane flux can be calculated. Testing the feed and permeate water quality of the ceramic ultrafiltration system reveals its contaminant rejection rate.

[0089] This patent describes the testing of ceramic ultrafiltration permeate water; detailed test results are shown in data 3. Figure 3 It can be seen that the ceramic ultrafiltration system has a significant removal effect on COD, silica, and viscosity, while TDS, calcium, and magnesium ions remain basically unchanged before and after entering the membrane.

[0090] Data 3: Water quality indicators of ceramic ultrafiltration permeate

[0091] Serial Number detection indicators Pressure backflow fluid Ceramic ultrafiltration water production 1 COD (mg / L) 4107.00 752.50 2 Ammonia nitrogen (mg / L) 123.00 88.91 3 Calcium (mg / L) 12471.70 12412.06 4 Magnesium (mg / L) 3287.40 3086.84 5 TDS (mg / L) 135000.00 113570.00 6 Silica (mg / L) 905.00 70.00 7 <![CDATA[Viscosity (mm 2 / s)]]> 0.85 0.32

[0092] An evaporation experiment was conducted on ceramic ultrafiltration permeate using this invention. Compared with direct evaporation, it exhibited virtually no mist entrainment. The condensate produced by evaporation was analyzed, and the removal efficiency of each pollutant is detailed in Data 4. Figure 5 and Figure 6 After ceramic ultrafiltration pretreatment, the fracturing flowback fluid is evaporated, resulting in a significant reduction in viscosity.

[0093] Data 4: Condensate Water Quality Indicators for "Ceramic Ultrafiltration + Submerged Combustion Evaporation"

[0094] Serial Number detection indicators Pressure backflow fluid Evaporation condensate 1 COD (mg / L) 4107.00 50.24 2 Ammonia nitrogen (mg / L) 123.00 10.75 3 Calcium (mg / L) 12471.70 715.00 4 Magnesium (mg / L) 3287.40 194.00 5 TDS (mg / L) 135000.00 354.00 6 Silica (mg / L) 905.00 0.06 7 <![CDATA[Viscosity (mm 2 / s)]]> 0.85 0.21

[0095] This invention selects an operating pressure of 0.3 MPa and a pH of 6–8, controls the temperature of the fracturing flowback fluid entering the membrane to be 15–40°C using a circulating cooling pump, and conducts a treatment time of 60 min to investigate the retention rate of silica in the fracturing flowback fluid by the ceramic membrane under different temperature conditions. Figure 5 As shown, as the temperature of the fracturing flowback fluid entering the membrane increases from 15℃ to 40℃, the flux of the ceramic membrane increases from 23.57 L / m³. 2 h increased to 98.74 L / m 2 The silica retention rate decreased from 94.61% to 61.78%. Therefore, considering the actual application of the project, the temperature of the feed solution can be controlled at 25-30℃.

[0096] Operating pressure is also a crucial operating factor affecting ceramic ultrafiltration systems. It drives the ceramic membrane filtration process and has a vital impact on the ceramic membrane flux. Too low an operating pressure hinders the achievement of high permeate flux, while too high an operating pressure not only increases energy consumption and operating costs but also accelerates the rate of ceramic membrane fouling, shortening the operating cycle of the ceramic ultrafiltration system. Therefore, it is necessary to find the optimal operating pressure.

[0097] This patent describes a ceramic ultrafiltration system used to treat fracturing flowback fluid under the following conditions: operating temperature 25℃, single run time 60 min, pH 6–8. The operating pressure is adjusted via valves. The relationship between pressure and membrane flux and viscosity removal rate is shown in [reference needed]. Figure 7 and Figure 8 .

[0098] Depend on Figure 7 and Figure 8 As shown, as the operating pressure increases from 0.1 MPa to 0.4 MPa, the ceramic membrane flux increases from 25.78 L / m³. 2 h increased to 50.12 L / m 2As the operating pressure increases, the silica retention rate also increases. However, when the operating pressure continues to increase to 0.6 MPa, the membrane flux decreases due to the adsorption of colloidal substances in the fracturing flowback fluid, pore blockage, or gelation, which affects the stability of the membrane flux and thus the silica retention effect. Therefore, the operating pressure of the ceramic ultrafiltration system in this patent is 0.2–0.4 MPa.

[0099] like Figure 9 As shown, a comparison of the pollutant removal rates of fracturing flowback fluid after direct "immersion combustion evaporation" and "ceramic ultrafiltration + immersion combustion evaporation" treatments revealed that the effluent quality after ceramic ultrafiltration pretreatment followed by immersion combustion evaporation was superior to that after direct immersion combustion evaporation treatment, especially in terms of silica and viscosity.

[0100] This invention utilizes a "ceramic ultrafiltration + immersion combustion evaporation" process to treat high-mineralization fracturing flowback fluid. This process maintains stable treatment efficiency under high-mineralization conditions, and the final produced water meets discharge standards. The process requires low reagent dosage and generates minimal solid waste, resulting in low solid waste disposal costs. The process can operate continuously without frequent system start-ups and shutdowns. It also features a short process flow, small footprint, fewer personnel, and reduced operating costs, ultimately achieving the goals of high treatment efficiency, short process flow, and low treatment costs for high-mineralization fracturing flowback fluid wastewater.

[0101] In summary, this invention provides a short-process high-mineralization fracturing flowback fluid treatment technology and system. It treats high-mineralization fracturing flowback fluid through a combination of ceramic ultrafiltration and submerged combustion evaporation. First, the ceramic ultrafiltration system pre-treats the high-mineralization fracturing flowback fluid, primarily removing silica, viscosity, and suspended solids. Then, the submerged combustion evaporation system evaporates and crystallizes the fracturing flowback fluid containing high concentrations of pollutants such as TDS, COD, ammonia nitrogen, calcium, and magnesium ions, ultimately producing condensate, non-condensable gases, and salt sludge. Since over 90% of the salt is removed as crystalline salt, the condensate meets the Class I standard of the "Integrated Wastewater Discharge Standard" (GB8978-1996). After deep treatment by acid and alkali spraying, the non-condensable gases also meet all relevant standards.

[0102] This invention utilizes a ceramic ultrafiltration system to pretreat high-mineralization fracturing flowback fluid, removing silica, viscosity, and suspended solids, thereby improving the processing efficiency of the subsequent immersion combustion evaporation system. This system requires only a small amount of membrane cleaning agent and does not generate additional sludge.

[0103] This invention utilizes a submerged combustion evaporation system to pressurize and immerse gaseous fuel on the subsurface of a liquid, forming microbubbles through a special structure. These microbubbles directly contact and exchange heat with the high-mineralization fracturing flowback fluid, resulting in high mass and heat transfer efficiency. Furthermore, because there is no partition wall for heat exchange, the evaporation system does not accumulate scale or coke. While maintaining high processing capacity, the evaporation system can operate continuously and stably without the need for frequent shutdowns to clean the equipment and remove coke.

[0104] This invention combines ceramic ultrafiltration and submerged combustion evaporation systems to treat high-mineralization fracturing flowback fluid. The process is short, reduces costs and energy consumption, minimizes land area, simplifies operation and maintenance, and enhances adaptability and flexibility to suit situations with limited land resources, cost sensitivity, and high environmental requirements.

[0105] Those skilled in the art will understand that the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways, even if such combinations or combinations are not explicitly described in the present invention. In particular, the features described in the various embodiments and / or claims of the present invention can be combined or combined in various ways without departing from the spirit and teachings of the present invention. All such combinations and / or combinations fall within the scope of the present invention.

Claims

1. A short-process, high-mineralization fracturing flowback fluid treatment technology, characterized in that, Includes the following steps: S1. High-mineralization fracturing flowback fluid is pumped from the raw fluid tank to the ceramic ultrafiltration system via the feed pump. Before entering the ceramic membrane, it is filtered by a self-cleaning filter to remove large suspended particles. S2. The pretreated return liquid enters the ceramic ultrafiltration system. Under the retention of the ceramic membrane, the permeate is discharged into the permeate tank through the permeate outlet, and the concentrate is returned to the original liquid tank for recycling. S3. Backwashing and chemical cleaning: Use the product water in the product water tank to backwash the ceramic membrane; S4. The permeate water of the ceramic ultrafiltration system is transported to the submerged combustion evaporation system through the evaporation feed pump. Landfill gas, anaerobic biogas or natural gas are used as energy to heat, evaporate, concentrate and crystallize the permeate water. The steam and non-condensable gas generated by evaporation are separated by a separation tower to remove the liquid droplets entrained in the mist. The steam enters the condensation system and is condensed to meet the emission standards. The non-condensable gas enters the non-condensable gas treatment system. S5. Non-condensable gas passes through the acid spray tower and the alkali spray tower in sequence. The alkaline substances in the gas phase react with the acidic substances in the liquid phase to form soluble salts. The treated non-condensable gas is discharged in compliance with regulations through the exhaust stack. The soluble salts at the bottom of the tower are returned to the submerged combustion evaporation system. S6. The saturated residual liquid generated by evaporation is transported to the salt mud dewatering system by a booster pump. The dewatered salt mud is packaged and sealed and centrally processed. The supernatant is returned to the submerged combustion evaporation system.

2. The short-process, high-mineralization fracturing flowback fluid treatment process according to claim 1, characterized in that: In S1, the filtration accuracy is 50–500 μm.

3. The short-process, high-mineralization fracturing flowback fluid treatment process according to claim 1, characterized in that: In S2, the ceramic ultrafiltration system includes a ceramic membrane; The area of ​​a single ceramic membrane is 10–25 m². 2 The operating throughput is 20–150 LMH, the operating pH range is 1–13.5, the operating temperature range is 15–40℃, and the operating pressure range is 0.1–0.6 MPa.

4. The short-process, high-mineralization fracturing flowback fluid treatment process according to claim 1, characterized in that: In S3, the ceramic ultrafiltration system is backwashed once every 30 to 60 minutes using the product water. The backwash time is 30 to 120 seconds, the backwash flux is 40 to 240 LMH, and the backwash pH range is 1 to 13.

5. The backwash water enters the raw water tank.

5. The short-process, high-mineralization fracturing flowback fluid treatment process according to claim 4, characterized in that: The ceramic ultrafiltration system is chemically cleaned every 3 to 4 months, using sodium hydroxide, citric acid and hydrochloric acid to remove residual organic matter, colloids and microorganisms; The concentration of sodium hydroxide is 0.1-1.0%, the concentration of citric acid is 5-20%, and the concentration of hydrochloric acid is 0.1-0.4%. The cleaning agents enter the ceramic ultrafiltration system through the chemical cleaning system, and the wastewater after cleaning is returned to the chemical cleaning system.

6. The short-process, high-mineralization fracturing flowback fluid treatment process according to claim 1, characterized in that: In S6, the dehydrated salt mud has a moisture content of 40-70%.

7. A short-process, high-salinity fracturing flowback fluid treatment system, characterized in that: It includes a raw liquid tank, a ceramic ultrafiltration system, a product water tank, a backwashing system, a chemical cleaning system, an immersion combustion evaporation system, a steam condensation system, a non-condensable gas system, a salt mud dewatering system, a condensate tank, and a dosing system; The raw material tank is used to temporarily store high-mineralization fracturing flowback fluid to be processed; The ceramic ultrafiltration system is used to pretreat fracturing flowback fluid, remove silica, suspended solids and organic matter from the water, and reduce the viscosity and turbidity of the water. The water production tank is used to store the water produced by the ceramic ultrafiltration system, providing a stable water source for the subsequent immersion combustion evaporation system; The backwashing system is used to periodically backwash the ceramic membrane with the produced water to prevent the membrane surface from becoming clogged. The chemical cleaning system is used to periodically chemically clean the ceramic membrane; The immersion combustion evaporation system is used for deep treatment of the water produced by the ceramic ultrafiltration system. Through heating, evaporation, concentration and crystallization, it removes TDS, COD, ammonia nitrogen, calcium, magnesium ions and salt ions from the water. The steam condensation system is used to condense the steam generated by evaporation into liquid water; The non-condensable gas system is used to purify the non-condensable gas generated during the evaporation process; The salt mud dewatering system is used to dewater the saturated evaporation residue generated by evaporation, thereby reducing the volume of waste residue. The condensate tank is used to store the condensate generated by the steam condensation system as a treated clean water resource. The dosing system is used to add reagents to the submerged combustion evaporation system; The outlet of the raw liquid tank is connected to the inlet of the ceramic ultrafiltration system; the outlet of the ceramic ultrafiltration system is connected to the inlet of the product water tank; the inlet of the ceramic ultrafiltration system is connected to the outlet of the backwashing system; the inlet of the ceramic ultrafiltration system is connected to the outlet of the chemical cleaning system; the outlet of the product water tank is connected to the inlet of the submerged combustion evaporation system; the dosing system is connected to the inlet pipe of the submerged combustion evaporation system; the steam and non-condensable gas outlet of the submerged combustion evaporation system is connected to the inlet of the steam condensation system; the outlet of the steam condensation system is connected to the inlet of the condensate tank; the non-condensable gas outlet of the steam condensation system is connected to the inlet of the non-condensable gas system; and the residual liquid outlet of the submerged combustion evaporation system is connected to the inlet of the salt mud dewatering system.

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