CN113526730A - Fracturing flow-back fluid treatment method and treatment device - Google Patents
Fracturing flow-back fluid treatment method and treatment device Download PDFInfo
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- 229910052938 sodium sulfate Inorganic materials 0.000 claims abstract description 19
- 235000011152 sodium sulphate Nutrition 0.000 claims abstract description 19
- 239000000126 substance Substances 0.000 claims abstract description 18
- BHPQYMZQTOCNFJ-UHFFFAOYSA-N Calcium cation Chemical compound [Ca+2] BHPQYMZQTOCNFJ-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910001424 calcium ion Inorganic materials 0.000 claims abstract description 15
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- 239000003921 oil Substances 0.000 claims description 54
- 238000001556 precipitation Methods 0.000 claims description 43
- 239000010802 sludge Substances 0.000 claims description 28
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- 238000005345 coagulation Methods 0.000 claims description 16
- 230000015271 coagulation Effects 0.000 claims description 16
- 238000000926 separation method Methods 0.000 claims description 14
- 239000003153 chemical reaction reagent Substances 0.000 claims description 12
- 239000007787 solid Substances 0.000 claims description 12
- 238000005352 clarification Methods 0.000 claims description 10
- 238000005188 flotation Methods 0.000 claims description 10
- 238000006386 neutralization reaction Methods 0.000 claims description 10
- 238000007254 oxidation reaction Methods 0.000 claims description 10
- 238000005191 phase separation Methods 0.000 claims description 10
- 239000006228 supernatant Substances 0.000 claims description 8
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- 230000001376 precipitating effect Effects 0.000 claims description 4
- CBENFWSGALASAD-UHFFFAOYSA-N Ozone Chemical compound [O-][O+]=O CBENFWSGALASAD-UHFFFAOYSA-N 0.000 claims description 3
- 230000002378 acidificating effect Effects 0.000 claims description 3
- 230000001590 oxidative effect Effects 0.000 claims description 3
- 239000000463 material Substances 0.000 claims 2
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 abstract description 20
- 229910000029 sodium carbonate Inorganic materials 0.000 abstract description 13
- 239000012535 impurity Substances 0.000 abstract description 11
- 229910021645 metal ion Inorganic materials 0.000 abstract description 10
- JLVVSXFLKOJNIY-UHFFFAOYSA-N Magnesium ion Chemical compound [Mg+2] JLVVSXFLKOJNIY-UHFFFAOYSA-N 0.000 abstract description 6
- 238000004065 wastewater treatment Methods 0.000 abstract description 2
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- FAPWRFPIFSIZLT-UHFFFAOYSA-M Sodium chloride Chemical compound [Na+].[Cl-] FAPWRFPIFSIZLT-UHFFFAOYSA-M 0.000 description 2
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- 239000011575 calcium Substances 0.000 description 2
- 229910052791 calcium Inorganic materials 0.000 description 2
- OSGAYBCDTDRGGQ-UHFFFAOYSA-L calcium sulfate Chemical compound [Ca+2].[O-]S([O-])(=O)=O OSGAYBCDTDRGGQ-UHFFFAOYSA-L 0.000 description 2
- 239000000701 coagulant Substances 0.000 description 2
- 230000001112 coagulating effect Effects 0.000 description 2
- 239000003814 drug Substances 0.000 description 2
- 239000003344 environmental pollutant Substances 0.000 description 2
- 229910052749 magnesium Inorganic materials 0.000 description 2
- 230000003472 neutralizing effect Effects 0.000 description 2
- 231100000719 pollutant Toxicity 0.000 description 2
- 238000004064 recycling Methods 0.000 description 2
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- 159000000000 sodium salts Chemical class 0.000 description 2
- 239000002699 waste material Substances 0.000 description 2
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 1
- BFNBIHQBYMNNAN-UHFFFAOYSA-N ammonium sulfate Chemical compound N.N.OS(O)(=O)=O BFNBIHQBYMNNAN-UHFFFAOYSA-N 0.000 description 1
- 229910052921 ammonium sulfate Inorganic materials 0.000 description 1
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- 239000003129 oil well Substances 0.000 description 1
- 239000007800 oxidant agent Substances 0.000 description 1
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- 239000011780 sodium chloride Substances 0.000 description 1
- UKLNMMHNWFDKNT-UHFFFAOYSA-M sodium chlorite Chemical compound [Na+].[O-]Cl=O UKLNMMHNWFDKNT-UHFFFAOYSA-M 0.000 description 1
- 229960002218 sodium chlorite Drugs 0.000 description 1
- PFUVRDFDKPNGAV-UHFFFAOYSA-N sodium peroxide Chemical compound [Na+].[Na+].[O-][O-] PFUVRDFDKPNGAV-UHFFFAOYSA-N 0.000 description 1
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F9/00—Multistage treatment of water, waste water or sewage
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/24—Treatment of water, waste water, or sewage by flotation
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/40—Devices for separating or removing fatty or oily substances or similar floating material
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/5236—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents
- C02F1/5245—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using inorganic agents using basic salts, e.g. of aluminium and iron
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/52—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities
- C02F1/54—Treatment of water, waste water, or sewage by flocculation or precipitation of suspended impurities using organic material
- C02F1/56—Macromolecular compounds
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/66—Treatment of water, waste water, or sewage by neutralisation; pH adjustment
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/722—Oxidation by peroxides
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/76—Treatment of water, waste water, or sewage by oxidation with halogens or compounds of halogens
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F1/72—Treatment of water, waste water, or sewage by oxidation
- C02F1/78—Treatment of water, waste water, or sewage by oxidation with ozone
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F1/00—Treatment of water, waste water, or sewage
- C02F2001/007—Processes including a sedimentation step
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
- C02F2103/10—Nature of the water, waste water, sewage or sludge to be treated from quarries or from mining activities
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- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F2301/00—General aspects of water treatment
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- Life Sciences & Earth Sciences (AREA)
- Hydrology & Water Resources (AREA)
- Engineering & Computer Science (AREA)
- Environmental & Geological Engineering (AREA)
- Water Supply & Treatment (AREA)
- Chemical & Material Sciences (AREA)
- Organic Chemistry (AREA)
- Separation Of Suspended Particles By Flocculating Agents (AREA)
- Physical Water Treatments (AREA)
Abstract
The invention discloses a fracturing flow-back fluid treatment method and a treatment device, belonging to the technical field of oilfield wastewater treatment and comprising the following steps: and carrying out suspended matter removal treatment and hardness removal treatment for removing magnesium and calcium ions on the fracturing flow-back fluid, wherein the hardness removal treatment comprises adding a hardness removal substance into the liquid, and the hardness removal substance comprises sodium sulfate. According to the treatment method, various suspended matters and metal ions such as magnesium ions, calcium ions and the like in the liquid are removed through the suspension removal unit and the hardness removal unit, various impurities are effectively removed, the water quality is purified, and the environment is prevented from being polluted; meanwhile, the calcium ions are removed by using the sodium sulfate, and compared with the method using the sodium carbonate, the cost of the hardness removing link can be obviously reduced.
Description
Technical Field
The invention relates to the technical field of oil and gas field wastewater treatment, in particular to a fracturing flow-back fluid treatment method and a treatment device.
Background
The fracturing waste liquid generated in the fracturing process of an oil well and a gas well contains harmful substances which are difficult to biodegrade, such as gelling substances, calcium ions, magnesium ions and the like, has complex components, high concentration, high viscosity and great treatment difficulty, and is one of the sewage which is difficult to treat in an oil-gas field. The fracturing fluid is discharged or recovered after being discharged or recovered or being injected back into the stratum in the well, water quality pretreatment is needed, or the surrounding environment is seriously polluted. In the prior art, sodium carbonate is generally used when calcium ions in the fracturing flow-back fluid are removed, so that the cost is high.
Disclosure of Invention
The invention aims to provide a fracturing flow-back fluid treatment method, which is characterized in that various suspended matters and metal ions such as magnesium ions, calcium ions and the like in liquid are removed through suspended matter removal treatment and hardness removal treatment, so that various impurities are effectively removed, and the water quality is purified; meanwhile, the calcium ions are removed by using the sodium sulfate, and compared with the method using the sodium carbonate, the cost of the hardness removing link can be obviously reduced. The invention also aims to provide a fracturing flow-back fluid treatment device suitable for the treatment method.
In order to achieve the above object, the present invention provides a method for treating a fracturing flow-back fluid, comprising: and carrying out suspended matter removal treatment and hardness removal treatment for removing magnesium and calcium ions on the fracturing flow-back fluid, wherein the hardness removal substances comprise sodium sulfate.
Preferably, the suspended matter removing treatment comprises gel breaking and oil removing treatment for separating jelly and oil slick in the fracturing flowback fluid, alkaline neutralization treatment for separating acid molecules, salt molecules and the like, flocculation precipitation treatment for precipitating suspended matters and secondary oil removing treatment for separating residual oil slick again.
Preferably, the gel breaking and oil removing treatment comprises adding a gel breaker and an alkaline substance into the fracturing flowback fluid, performing gel breaking and oil removing treatment and alkaline neutralization treatment, and performing primary precipitation; the flocculation precipitation treatment comprises the steps of adding a coagulation flocculation reagent into the liquid after the first precipitation, and carrying out the second precipitation; the secondary oil removal treatment comprises the steps of adding a gel breaker into the liquid after the secondary precipitation and carrying out three-phase separation of solid, liquid and oil; and adding the sodium sulfate and the coagulation flocculation reagent into the liquid after the three-phase separation, performing fourth precipitation, clarifying the liquid and separating supernatant.
Preferably, the method also comprises the step of carrying out solid-liquid separation treatment for concentrating the sludge precipitated in each link.
Preferably, the method further comprises dewatering the sludge separated after the solid-liquid separation treatment, and making the sludge after the dewatering treatment into a solid.
Preferably, the method further comprises the step of carrying out oxidation treatment on the liquid after the fourth precipitation treatment.
Preferably, the three-phase separation is performed on the liquid after the second precipitation treatment using an air flotation device.
Preferably, the coagulating and flocculating agent comprises polyacrylamide and polyaluminium chloride.
Preferably, the oxidation treatment comprises injecting ozone into the liquid after the fourth precipitation treatment.
The invention also provides a fracturing flow-back fluid treatment device suitable for the fracturing flow-back fluid treatment method, which is characterized by comprising a primary pre-settling tank, a secondary pre-settling tank, an air floatation device, a hardness removal clarification tank, an oxidation reaction tank, a sludge concentration tank and a filter press which are sequentially connected, wherein the bottom of the secondary pre-settling tank, the solid outer discharge port of the air floatation device and the bottom of the hardness removal clarification tank are connected with the sludge concentration tank through pipelines, and the sludge concentration tank is connected with the feed port of the filter press through a pipeline.
In the technical scheme provided by the invention, the fracturing flow-back fluid treatment method comprises suspended matter removal treatment and hardness removal treatment, wherein the suspended matter removal treatment is used for removing various suspended matters, hardness removal treatment is used for removing metal ions such as magnesium ions and calcium ions in liquid by adding hardness removal substances into the liquid, and the two types of operation are combined, so that various impurities in the liquid are effectively removed, and the water quality is purified; compared with the prior art in which sodium carbonate is used, the cost of the sodium sulfate is far lower than that of the sodium carbonate, and the cost of the hard removing link can be obviously reduced by using the sodium sulfate to replace the sodium carbonate; on the other hand, the flowback liquid stock solution contains sulfate radicals but no carbonate radicals, and the sodium sulfate is used for removing calcium ions, so that excessive carbonate radicals in the liquid can be prevented, and the subsequent removal of the carbonate radicals is avoided.
In the preferred technical scheme provided by the invention, the suspended matter removal treatment comprises gel breaking and oil removing treatment for separating jelly and floating oil in the fracturing flow-back fluid, alkaline neutralization treatment for separating acidic molecules, salt molecules and the like, flocculation precipitation treatment for precipitating suspended matters and secondary oil removing treatment for separating residual floating oil again, various objects to be removed are removed in a targeted manner, and all operation links are combined for use, so that the jelly, the floating oil, the salt molecules, metal ions, the suspended matters and the like in the flow-back fluid are precipitated and effectively separated and removed, and the floating oil is removed twice through the gel breaking and oil removing treatment and the secondary oil removing treatment, so that a good oil removing effect can be achieved, and the purification degree of the fracturing flow-back fluid is improved.
The technical effects that can be produced by the preferred technical scheme in the technical schemes provided by the application are described in detail in the following.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic diagram of a process flow of a fracturing flow-back fluid in an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the technical solutions of the present invention will be described in detail below. It is to be understood that the described embodiments are merely exemplary of the invention, and not restrictive of the full scope of the invention. All other embodiments, which can be derived by a person skilled in the art from the examples given herein without any inventive step, are within the scope of the present invention.
The purpose of this specific embodiment is to provide a method for treating a fracturing flow-back fluid, which combines the steps of gel breaking, oil removal, alkaline neutralization, flocculation precipitation, secondary oil removal and hardness removal, effectively precipitates and separates pollutants in water and effectively removes floating oil, thereby improving the purification degree, reducing the cost of chemicals in the hardness removal treatment, and greatly reducing the cost of waste liquid treatment. The present embodiment also aims to provide a frac flowback fluid treatment apparatus suitable for the treatment method.
Hereinafter, embodiments will be described in detail with reference to the accompanying drawings. The embodiments described below do not limit the contents of the invention recited in the claims. The entire contents of the configurations shown in the following embodiments are not limited to those required as solutions of the inventions described in the claims.
Referring to fig. 1, the method for treating a fracturing flow-back fluid provided by this embodiment includes suspended matter removal treatment and hardness removal treatment, where the suspended matter removal treatment is used to remove various suspended matters, and the hardness removal treatment is used to remove metal ions such as magnesium ions and calcium ions in the fluid by adding a hardness removal substance into the fluid, and the two types of operations are combined to effectively remove various impurities in the fluid and purify the water; compared with the prior art in which sodium carbonate is used, on one hand, the market price of the sodium sulfate is lower than that of the sodium carbonate (the market price of the current sodium carbonate is about 2200 yuan/ton; even the market price of the first-grade sodium sulfate salt is about 400 yuan/ton), and the cost of the hard removing link can be obviously reduced by using the sodium sulfate instead of the sodium carbonate; on the other hand, the stock solution of the flowback liquid contains sulfate radicals without carbonate radicals, and calcium ions are removed by using sodium sulfate, so that excessive carbonate radicals in the stock solution can be prevented; after the sodium sulfate is used for removing calcium ions, only the sulfate radicals need to be blended again if redundant sulfate radicals exist in the liquid, carbonate radicals and sulfate radicals are contained in the liquid if the sodium carbonate is used, the subsequent sulfate radicals need to be removed, the carbonate radicals also need to be removed, the operation links are more, and the cost is saved by using the sodium sulfate compared with the use of the sodium carbonate from the aspect.
Specifically, the suspended matter removal treatment comprises gel breaking and oil removal treatment for separating jelly and floating oil in the fracturing flow-back fluid, alkaline neutralization treatment for separating acidic molecules, salt molecules and the like, flocculation precipitation treatment for removing and separating suspended matters and secondary oil removal treatment for separating residual floating oil again; the method comprises the steps of performing gel breaking and oil removing treatment, breaking viscous substances such as jelly and floating oil, precipitating suspended matters such as the jelly, the floating oil and sticky tapes, reducing the viscosity of liquid, obviously reducing impurities in return liquid, removing the viscous substances such as the jelly and the floating oil in the liquid, and reducing the difficulty of subsequent impurity precipitation, wherein the gel breaking and oil removing treatment can be performed firstly; the alkaline neutralization treatment for separating acid molecules, salt molecules and the like can be synchronously carried out with the gel breaking and oil removing treatment, and the precipitation generated by acid-base neutralization is precipitated along with viscous substances, so that the precipitation degree can be enhanced, the precipitation rate is improved, and the impurities in the liquid are effectively removed; then, flocculation precipitation treatment can be carried out, particles, colloid and solid matters which are not removed, unseparated precipitable matters and the like in the liquid are precipitated and separated again, and impurities in the fracturing flow-back fluid are effectively purified; compared with the treatment method in the prior art in which only one gel breaking and oil removing is performed, the method has the advantages that the thoroughness of removing the floating oil and the floating objects is improved, the floating oil removal rate is improved, the viscosity of the liquid is reduced to the maximum extent, and the removal rate of other impurities can be enhanced during subsequent treatment operation; and thirdly, carrying out hardness removal treatment, wherein the hardness removal treatment comprises adding hardness removal substances into the liquid, the hardness removal substances comprise lime, a coagulation flocculation reagent and sodium sulfate, metal ions such as magnesium, calcium and the like in the liquid can be precipitated and separated through the lime and the sodium sulfate, and the coagulation flocculation reagent is added in the process, so that the precipitation and separation of precipitates can be enhanced, and the removal rate of the metal ions is enhanced.
Therefore, the treatment method of the fracturing flow-back fluid provided by the embodiment carries out targeted removal operation according to the characteristics of various substances to be removed in the fluid, and each operation link is combined for use, at least fourth precipitation and secondary oil removal separation are carried out, through adding the flocculating agent for multiple times and carrying out fourth precipitation, jelly, salt molecules, metal ions and suspended matters in the flow-back fluid can be more thoroughly precipitated and effectively separated and removed, and through gel breaking oil removal treatment and secondary oil removal treatment, gel breaking and oil removal are carried out for two times, so that a good oil removal effect is achieved, the fluid is thoroughly clarified and purified, and effective standard reaching treatment of the fracturing flow-back fluid is realized.
Specifically, first, the fracturing flow-back fluid stock solution to be treated can be physically settled, and a solid-liquid pre-separation is performed, and as shown in fig. 1, the fracturing flow-back fluid stock solution to be treated can be stored in a graded manner according to different impurity concentrations, so as to achieve a good settling effect. Then, in the first step, adding a gel breaker and an alkaline substance such as NAOH into the fracturing flowback fluid, performing gel breaking and oil removing treatment and alkaline neutralization treatment, and performing primary precipitation; the precipitate was separated from the liquid.
Secondly, adding a coagulation flocculation reagent into the liquid subjected to the first precipitation, performing flocculation precipitation treatment, and performing second precipitation; after settling solids such as flocs, the precipitate and the liquid are separated again.
Thirdly, adding a demulsifier and a coagulation flocculation reagent into the liquid after the second precipitation, performing three-phase separation of solid, liquid and oil, further separating residual floating oil and emulsion in the liquid, equivalently performing third precipitation, finishing secondary oil removal treatment, and purifying water quality to a great extent; in the preferred scheme, the air floatation device is used for carrying out three-phase separation on the liquid, the purification effect is better, and the residual floating oil in the liquid can be more thoroughly separated and removed. And the air flotation devices can be two, namely a first-stage air flotation device and a second-stage air flotation device, so that the liquid after the second precipitation is subjected to air flotation separation twice, the residual floating oil is effectively and thoroughly removed, and the water quality is clarified.
Fourthly, adding a hardness removing substance into the liquid after the three-phase separation, carrying out fourth precipitation and clarification on the liquid, and finally separating supernatant; the hardness removing substances comprise lime, sodium sulfate and a coagulation flocculation reagent, wherein the lime and the sodium sulfate are chemically reacted with metal ions in the liquid to generate precipitates, and the metal ions are separated out; a small amount of sodium carbonate can be added, the types of the medicaments are increased, and a plurality of medicaments are combined to enhance the reaction degree and absorb calcium, magnesium and other ions in the liquid to a great extent; most of the generated precipitate can be separated out and precipitated, and the coagulation flocculation reagent is added to strengthen the precipitation, so that calcium sulfate and other parts which are not separated out in the liquid and residual micro particles and the like in the liquid are flocculated into clusters, the liquid is purified powerfully again, and the water quality is clarified. The coagulating and flocculating agent comprises polyacrylamide and polyaluminium chloride. Polyacrylamide and polyaluminium chloride are coagulation and flocculation reagents with good effect.
As shown in fig. 1, when the hardness removal treatment is performed, the treatment may be performed in two steps, in which lime and a coagulation flocculation reagent are first added to the liquid after the three-phase separation, magnesium ions are precipitated, the liquid is clarified, and the supernatant is separated, then sodium sulfate and a coagulation flocculation reagent are added to the separated supernatant, calcium ions are precipitated and separated, and then the liquid is clarified, and the supernatant is separated for use.
Through the treatment of the four aspects, acid-base neutralizing agents, twice gel breaking demulsifiers, lime, ammonium sulfate and other hardness removing agents and four-time coagulation and flocculation agents are added before and after the fracturing flow-back fluid, removal of sticky suspended matters such as jelly and floating oil is carried out at least twice, at least four-time precipitation separation is carried out, various impurities in the fluid can be effectively removed, the water body is effectively purified, and the fracturing flow-back fluid can reach the national specified reinjection standard or can reach the clear water standard required by desalination and recycling.
After the fracturing flow-back fluid is treated, the water quality is clarified, and the treated liquid can be recycled by sodium salt separation because the water contains a large amount of sodium chloride. Therefore, in this embodiment, the method further includes performing an oxidation treatment on the liquid after the fourth precipitation treatment. The oxidation treatment comprises injecting strong oxidant such as ozone, sodium peroxide or sodium chlorite into the liquid after the fourth precipitation treatment. Strong oxidizers can gradually degrade organic matters in water into simple inorganic matters, and can also oxidize pollutants dissolved in water into precipitates which are insoluble in water and easy to separate from the water. After the liquid is further treated by oxidation treatment, the liquid is further purified, the COD and the chromaticity index of the effluent can be greatly reduced, and the requirement of the subsequent sodium salt separation recycling on water quality is further met.
Further, in order to prevent secondary pollution to the surrounding environment, in this embodiment, the method for treating the fracturing flow-back fluid further includes treating the sediment, i.e., sludge, separated by precipitation in each treatment link. Specifically, the method comprises the steps of carrying out solid-liquid separation treatment of concentration on the sludge precipitated in each link, and compressing water in the sludge through evaporation concentration or dehydration treatment; further, the method may further comprise subjecting the sludge separated after the solid-liquid separation treatment to a re-dehydration treatment to drastically reduce the water content of the sludge. The first dehydration treatment can be carried out by an evaporation form or equipment such as a filter press, a centrifugal dehydrator and the like, and then the second dehydration treatment can be carried out by equipment such as a filter press and the like, so that not only can the second dehydration be carried out, but also the sludge can be made into solid matters such as mud cakes. So set up, do not directly discharge mud, but make solid matters such as mud cake into with mud and can transport to cement plant or hollow brick factory and recycle, carried out the resource and recycled, also prevented the secondary pollution to the surrounding environment.
In the sludge treatment link, sewage separated from sludge can be injected into the fracturing flow-back fluid stock solution to be treated for secondary purification treatment instead of direct discharge, so that secondary pollution to the environment is avoided.
The embodiment also provides a fracturing flow-back fluid treatment device suitable for the fracturing flow-back fluid treatment method, which comprises a first-stage pre-settling tank, a second-stage pre-settling tank, an air floatation device, a hardness removal clarification tank and an oxidation reaction tank which are sequentially connected, and further comprises a sludge concentration tank and a pressure filter, wherein the bottom of the second-stage pre-settling tank, the solid outer discharge port of the air floatation device and the bottom of the hardness removal clarification tank are connected with the sludge concentration tank through pipelines, and the sludge concentration tank is connected with the feed inlet of the pressure filter through a pipeline. The air floatation devices are divided into a first-stage air floatation device and a second-stage air floatation device.
Placing a stock solution of the fracturing flow-back fluid to be treated in a storage tank, injecting the stock solution into a primary pre-settling tank through a pipeline, adding a gel breaker and an acid-base neutralizing agent in the injection process, and performing primary sedimentation on the liquid in the primary pre-settling tank; the liquid in the primary pre-settling tank, namely supernatant separated from the precipitate, is injected into the secondary pre-settling tank through a pipeline, and is added with a coagulation and flocculation agent to carry out secondary precipitation in the secondary pre-settling tank; liquid in the secondary pre-settling tank, namely supernatant separated from the sediment enters a primary air flotation device through a pipeline, a coagulation and flocculation agent is added, the coagulation and flocculation agent is added into the liquid separated from the primary air flotation device again and enters a secondary air flotation device for solid-liquid separation, which is equivalent to carrying out third sedimentation; adding the liquid separated from the secondary air flotation device into a hardness removal clarifying tank through a pipeline, injecting a hardness removal substance, and performing fourth precipitation; and injecting the liquid in the hardness-removing clarification tank into an oxidation reaction tank for oxidation reaction. The sludge precipitated in the secondary pre-settling tank, the primary air floating device, the secondary air floating device and the hard removing clarification tank is conveyed to a sludge concentration tank through pipelines, concentration treatment can be carried out in the forms of a centrifugal dehydrator, a filter press or evaporation, the sludge subjected to concentration treatment is conveyed to a filter press to output sludge cakes, and the sludge cakes can be conveyed to a centralized treatment point. The treatment process of the whole device is coherent and smooth, the arrangement is reasonable, and effective clarification and purification treatment can be carried out on the fracturing flow-back fluid.
It is understood that the same or similar parts in the above embodiments may be mutually referred to, and the same or similar parts in other embodiments may be referred to for the content which is not described in detail in some embodiments. The multiple schemes provided by the invention comprise basic schemes, are independent from each other and are not restricted with each other, but can be combined with each other under the condition of no conflict, so that multiple effects are realized together.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.
Claims (10)
1. A method for treating a fracturing flow-back fluid is characterized by comprising the following steps:
the fracturing flow-back fluid is subjected to suspended matter removal treatment and hardness removal treatment for removing magnesium and calcium ions,
the hardness removal treatment comprises adding a hardness removal material to the liquid, wherein the hardness removal material comprises sodium sulfate.
2. The method according to claim 1, wherein the suspended matter removing treatment comprises a gel breaking and oil removing treatment for separating gel and oil slick in the fracturing flowback fluid, an alkaline neutralization treatment for separating acidic molecules and salt molecules, a flocculation precipitation treatment for precipitating suspended matters, and a secondary oil removing treatment for separating residual oil slick again.
3. The method of claim 2, wherein the gel breaking and oil removing treatment comprises adding a gel breaker and an alkaline substance to the frac flowback fluid, performing the gel breaking and oil removing treatment and the alkaline neutralization treatment, and performing a first precipitation; the flocculation precipitation treatment comprises the steps of adding a coagulation flocculation reagent into the liquid after the first precipitation, and carrying out the second precipitation; the secondary oil removal treatment comprises the steps of adding a gel breaker into the liquid after the secondary precipitation and carrying out three-phase separation of solid, liquid and oil; adding the hardness-removing substance into the liquid after three-phase separation, performing fourth precipitation, clarifying the liquid, and separating supernatant.
4. The method of treating a frac flowback fluid of claim 3, further comprising a solid-liquid separation step of concentrating the sludge precipitated in each step.
5. The method of treating a fracturing flow-back fluid according to claim 4, further comprising dehydrating the sludge separated after the solid-liquid separation treatment, and making the sludge after the dehydration treatment into a solid.
6. The method of treating a frac flowback fluid of claim 5, further comprising oxidizing the fluid after the fourth settling treatment.
7. The method of treating flowback fluid of claim 2, wherein the three-phase separation is performed on the liquid after the second settling treatment using an air flotation device.
8. The method of treating a frac flowback fluid of claim 2, wherein the flocculating agent comprises polyacrylamide and polyaluminum chloride.
9. The method of treating a frac flowback fluid of claim 6, further comprising, wherein the oxidizing comprises injecting ozone into the fluid after the fourth settling.
10. The fracturing flow-back fluid treatment device suitable for the fracturing flow-back fluid treatment method according to any one of claims 1 to 9, comprising a primary pre-settling tank, a secondary pre-settling tank, an air floatation device, a hardness removal clarification tank and an oxidation reaction tank which are connected in sequence, and further comprising a sludge concentration tank and a filter press, wherein the bottom of the secondary pre-settling tank, the solid outer discharge port of the air floatation device and the bottom of the hardness removal clarification tank are connected with the sludge concentration tank through pipelines, and the sludge concentration tank is connected with the feed port of the filter press through a pipeline.
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