A method for recycling waste diatomite after filtering fracturing flowback fluid

Abstract

The invention belongs to the technical field of diatomite recycling, and specifically provides a method for recycling waste diatomite after filtering fracturing return fluid, comprising the following steps: uniformly mixing the waste diatomite with clean water, adding a cleaning and repairing agent to the uniformly mixed mixture, stirring the mixture with the cleaning and repairing agent added until complete reaction, performing solid-liquid separation on the mixture after complete reaction, directly using the separated solid for filtration, or drying and screening for reuse, and using the separated liquid for compounding fracturing fluid; the invention solves the problem that there is currently no treatment plan for the waste diatomite generated after filtering fracturing return fluid, and the waste diatomite can only be classified as oily sludge for outsourcing treatment, which is costly and cannot be reused, causing waste; the invention has the advantages of simple treatment process, good treatment effect, low cost and reuse, and strong economic practicality.

Description

Technical Field

[0001] The invention belongs to the technical field of diatomite recycling, and in particular relates to a method for recycling waste diatomite after filtering fracturing flowback fluid. Background Art

[0002] In the process of oil and gas field development, fracturing is an important measure to increase production, but the fracturing process will produce flowback fluid, which contains a variety of difficult-to-degrade substances such as guar gum, crude oil and other organic additives, and has the characteristics of high concentration, high stability and high viscosity, which poses a severe test to the ecological environment of the oil field. At present, most domestic oil fields use the "natural sedimentation-coagulation-filtration" method to treat fracturing flowback fluid. Although a variety of new treatment methods such as ozone oxidation, electrochemistry, and microbial treatment have also been tested, most process flows ultimately require filtration treatment to meet water quality requirements. Traditional media filters mostly use filter materials such as walnut shells, quartz sand, and fiber balls, but this type of filtration method requires frequent backwashing and is not easy to backwash clean. In addition, replacing the filter material is time-consuming and labor-intensive.

[0003] Diatomaceous earth is a porous biological siliceous rock, the main component of which is SiO2. It is widely distributed in the earth's crust. Its unique microporous structure has excellent permeability and adsorption. It is widely used as a filter material and is more suitable for filtering sewage with high viscosity. It is efficient and does not damage the original water quality system. At present, there are many patents showing the use of diatomaceous earth as a filtration aid for fracturing return fluid, such as CN110270309A, CN110981040A, etc. Among them, CN110981040A uses a coated filter material to filter the fracturing return fluid, which has the advantages of good effluent water quality and no need for backwashing. It is believed that with the further development of this technology, diatomaceous earth as a filter material will be widely used in the filtration unit of fracturing return fluid.

[0004] According to statistics, after the fracturing operation is completed, about 15-90% of the construction fluid is discharged back to the ground. The massive consumption of water resources and the increasing amount of wastewater are posing an increasingly serious threat to the environment. Although diatomaceous earth has excellent filtration properties, there is currently no treatment solution for the waste diatomaceous earth generated after filtering the fracturing return fluid. It can only be classified as oily sludge and outsourced for treatment, which is costly and cannot be reused, resulting in waste. Summary of the invention

[0005] The present invention provides a method for recycling waste diatomaceous earth after filtering fracturing return fluid, aiming to overcome the problem that in the prior art, there is currently no treatment plan for waste diatomaceous earth generated after filtering fracturing return fluid, and the waste diatomaceous earth can only be classified as oily sludge for outsourcing treatment, which is costly and cannot be reused, resulting in waste.

[0006] To this end, the present invention provides a method for recycling waste diatomite after filtering fracturing flowback fluid, comprising the following steps:

[0007] 1) Mix the waste diatomaceous earth and clean water evenly;

[0008] 2) adding a cleaning and repairing agent to the uniformly mixed mixture;

[0009] 3) Stirring the mixture with the cleaning and repairing agent until the reaction is complete;

[0010] 4) The mixture after the complete reaction is separated into solid and liquid, the separated solid is used for filtration or drying and screening before reuse, and the separated liquid is used for compounding of fracturing fluid.

[0011] Preferably, in step 1), the mass ratio of the waste diatomaceous earth to clean water is 1:3 to 1:20.

[0012] Preferably, the mass ratio of the mixture in step 1) to the cleaning and repairing agent is 1:0.005 to 1:0.03.

[0013] Preferably, the active ingredients of the cleaning and repairing agent are sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid, and the mass ratio of sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid is 1-3:0.6-1:0.6-1:1-2.

[0014] Preferably, the stirring speed in step 3) is 0.1 to 120 rpm.

[0015] Preferably, the mixture to which the cleaning and repairing agent is added is stirred after being heated.

[0016] Preferably, the temperature after heating is 70-90°C.

[0017] Preferably, the constant temperature stirring time after heating is 0.5 to 2.0 hours.

[0018] Preferably, the surface floating oil after stirring in step 3) is collected by overflow and centrally processed.

[0019] Preferably, the stirring in step 3) is carried out using a stirring tank with overflow.

[0020] Beneficial effects of the present invention:

[0021] 1. The method for recycling and reusing waste diatomaceous earth after filtering fracturing flowback fluid provided by the present invention adopts "mixing waste diatomaceous earth and clean water evenly, adding a cleaning and repairing agent to the evenly mixed mixture, stirring the mixture with the cleaning and repairing agent until complete reaction, and separating the mixture into solid and liquid after complete reaction. Further drying, roasting, grinding and screening" as the main process flow of the waste diatomaceous earth regeneration treatment method, which is mainly aimed at the treatment of waste diatomaceous earth generated after filtering fracturing flowback fluid, and can also be used as a supporting process for filtering fracturing flowback fluid. The separated solid diatomaceous earth is used for filtration or reuse after drying and screening, and the separated liquid is used for compounding fracturing fluid; the process has simple treatment process, good treatment effect, low cost and can be reused, and has strong economic practicality.

[0022] 2. The method for recycling and reusing the waste diatomite after filtering the fracturing flowback fluid provided by the present invention can be used as the treatment of the waste diatomite after filtering the fracturing flowback fluid. The treated diatomite can be continuously used for filtering the fracturing flowback fluid to achieve resource utilization; it can also be used as a supporting process for filtering the fracturing flowback fluid, for online treatment of the waste diatomite, and recycling the treated diatomite and the filtrate. The waste generated during the treatment process is relatively small, far less than the amount of waste diatomite outsourced as solid waste, there is no secondary pollution of diatomite, and the operability is strong. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The present invention will be further described in detail below with reference to the accompanying drawings.

[0024] Figure 1 It is a flow chart of a method for recycling waste diatomaceous earth after filtering fracturing flowback fluid. DETAILED DESCRIPTION

[0025] The principles and features of the present invention are described below in conjunction with the accompanying drawings. The examples are only used to explain the present invention and are not used to limit the scope of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0026] like Figure 1 As shown, a method for recycling waste diatomite after filtering fracturing flowback fluid comprises the following steps:

[0027] 1) Mix the waste diatomaceous earth and clean water evenly;

[0028] 2) adding a cleaning and repairing agent to the uniformly mixed mixture;

[0029] 3) Stirring the mixture with the cleaning and repairing agent until the reaction is complete;

[0030] 4) The mixture after the complete reaction is separated into solid and liquid. The separated solid is used for filtration or drying, sieving and then recycling, and the separated liquid is used for compounding of fracturing fluid.

[0031] 5) Further, the solid after solid-liquid separation is dried and roasted.

[0032] 6) Grinding the roasted diatomaceous earth solid into powder, sieving the ground solid, and then classifying and storing it for reuse.

[0033] The method for recycling waste diatomite after filtering fracturing flowback fluid provided by the present invention can be used as a waste diatomite treatment after filtering fracturing flowback fluid. The treated diatomite can be continuously used for filtering fracturing flowback fluid to achieve resource utilization; it can also be used as a supporting process for filtering fracturing flowback fluid, for online treatment of waste diatomite, and recycling the treated diatomite and filtrate; the waste generated during the treatment process is relatively small, far less than the amount of waste diatomite outsourced as solid waste, there is no secondary pollution of diatomite, and the operability is strong. The process has simple treatment process, good treatment effect, low cost and can be reused, and has strong economic practicality.

[0034] Preferably, the mass ratio of the waste diatomaceous earth to clean water in step 1) is 1:3 to 1:20, so that the waste diatomaceous earth can be cleaned conveniently with a cleaning and repairing agent.

[0035] Preferably, the mass ratio of the mixture in step 1) to the cleaning and repairing agent is 1:0.005 to 1:0.03, so as to ensure that the cleaning and repairing agent can completely react with the mixture in step 1) within a reasonable dosage range, reduce waste and improve utilization.

[0036] Preferably, the active ingredients of the cleaning and repairing agent are sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid, and the mass ratio of sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid is 1-3:0.6-1:0.6-1:1-2.

[0037] The main ingredients of the cleaning and repairing agent are sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid; its principle is to use redox reaction to oxidize FeS adsorbed in diatomaceous earth.

[0038] The reaction process is ClO - +FeS+2H + =Cl - +S↓+H2O+Fe 2+

[0039] EDTA is an organic acid. It uses its own acidity or active groups to wet, solubilize and disperse FeS scale to achieve the purpose of cleaning and descaling. In addition, the lone pair of electrons of -NH2 in EDTA can react with Fe2+ Ion coordination chelation solubilization; sodium pyrophosphate, used as a chelating agent and surfactant; hydrochloric acid, a small amount of hydrochloric acid is used here to adjust the pH value of the washing liquid to prevent Fe 2+ hydrolysis.

[0040] Preferably, hydrochloric acid adjusts the pH value of the washing liquid to pH 3-5. 2+ hydrolysis.

[0041] Preferably, the stirring speed in step 3) is 0.1 to 120 rpm. This speed increases the reaction speed of the mixture to which the cleaning and repairing agent is added.

[0042] Preferably, the mixture with the cleaning and repairing agent added is stirred after heating. Stirring after heating can increase the reaction speed of the mixture with the cleaning and repairing agent added, shorten the cleaning time, and improve work efficiency.

[0043] Preferably, the temperature after heating is 70-90° C. This temperature range can shorten the original reaction time by half at the same stirring speed.

[0044] Preferably, the temperature after heating is 80° C. This temperature can shorten the original reaction time by more than half at the same stirring speed.

[0045] Preferably, the constant temperature stirring time after heating is 0.5 to 2.0 hours to ensure that the mixture with the cleaning and repairing agent is completely reacted.

[0046] Preferably, the surface oil after stirring in step 3) is collected by overflow and centrally processed. The advantage of stirring is to make the reaction more complete and uniform, and to increase the reaction rate; the advantage of overflow collection is that the operation is simple and does not require complicated supporting equipment.

[0047] Preferably, the stirring in step 3) is carried out in a stirring tank with overflow, so that while the mixture with the cleaning and repairing agent is stirred, the surface floating oil is collected and centrally processed through the overflow.

[0048] Preferably, a rotary drum vacuum filter is used for solid-liquid separation of the mixture after the complete reaction.

[0049] Preferably, the drying step 4) is performed by drying and roasting.

[0050] Preferably, the drying and roasting temperature is 400-600°C.

[0051] Preferably, the drying and roasting time is 20 to 60 minutes.

[0052] Within this temperature and time range, some organic matter that is difficult to remove with cleaning and repairing agents can be completely volatilized, thereby forming a better pore structure.

[0053] Preferably, the specific step of the step 4) of screening is to grind the dried and roasted solid into powder, and then screen the powder and store it in different categories for easy storage and reuse.

[0054] Preferably, the sieve mesh number is 50-300.

[0055] Diatomaceous earth that is classified and stored after screening can be selected with different mesh sizes according to specific needs and applications. It is highly practical and has a high degree of recycling and reuse.

[0056] During the separation process of the rotary drum vacuum filter, the treated diatomite can be peeled off by adjusting the scraper height. The peeled diatomite can be dried and sieved for reuse. The diatomite can also be retained on the drum surface for fracturing fluid treatment. Since even new diatomite needs to be mixed with water, the treated diatomite stock liquid can be directly sucked out to form a diatomite filter cake for use or mixed with a certain proportion of new diatomite for use. For those that are not used temporarily, they can be dried and sieved for storage. The treated liquid can be stored in a liquid tank for fracturing fluid reuse.

[0057] Preferably, a filter press is used for solid-liquid separation of the mixture after the complete reaction because it has a simple structure, is easy to operate, runs stably, is convenient to maintain, has strong adaptability to materials, and has excellent separation effect and solid content.

[0058] Embodiment 1:

[0059] A method for recycling waste diatomaceous earth after filtering fracturing flowback fluid comprises the following steps:

[0060] 1) Mix 100 g of waste diatomaceous earth and 1000 g of clean water evenly;

[0061] 2) adding a cleaning and repairing agent to the uniformly mixed mixture; the active ingredients of the cleaning and repairing agent are 10 mL 10% sodium hypochlorite, 6 g ethylenediaminetetraacetic acid, 6 g sodium pyrophosphate and 10 mL 37% hydrochloric acid, specifically: dissolving the active ingredients of the cleaning and repairing agent in 1000 g water, and adding the dissolved cleaning and repairing agent to the uniformly mixed mixture in step 1);

[0062] 3) stirring the mixture with the cleaning and repairing agent until the reaction is complete; specifically, heating the mixture with the cleaning and repairing agent to 80° C. and keeping the temperature, stirring and washing at 120 rpm for 60 minutes at a constant temperature of 80° C., collecting the surface floating oil through overflow during stirring and centrally treating it until the reaction is complete;

[0063] 4) separating the solid from the liquid in the mixture after the complete reaction, filtering or drying and screening the separated solid for reuse, and using the separated liquid for compounding the fracturing fluid; specifically, using a rotary drum vacuum filter to separate the solid from the liquid in the mixture after the complete reaction, the separated solid is the treated diatomaceous earth, and the treated diatomaceous earth is peeled off by adjusting the scraper height during the separation process of the rotary drum vacuum filter, and the peeled diatomaceous earth is dried and reused, or the treated diatomaceous earth can be retained on the surface of the drum for fracturing fluid treatment, and the treated liquid can be stored in a liquid tank for fracturing fluid reuse.

[0064] Embodiment 2:

[0065] A method for recycling waste diatomaceous earth after filtering fracturing flowback fluid comprises the following steps:

[0066] 1) Mix 100 g of waste diatomaceous earth and 1000 g of clean water evenly;

[0067] 2) adding a cleaning and repairing agent to the uniformly mixed mixture; the active ingredients of the cleaning and repairing agent are 20 mL 10% sodium hypochlorite, 6 g ethylenediaminetetraacetic acid, 6 g sodium pyrophosphate and 10 mL 37% hydrochloric acid, specifically: dissolving the active ingredients of the cleaning and repairing agent in 1000 g water, and adding the dissolved cleaning and repairing agent to the uniformly mixed mixture in step 1);

[0068] 3) stirring the mixture with the cleaning and repairing agent until the reaction is complete; specifically, heating the mixture with the cleaning and repairing agent to 80° C. and keeping the temperature, stirring and washing at 110 rpm for 60 minutes at a constant temperature of 80° C., collecting the surface floating oil through overflow during stirring and centrally treating it until the reaction is complete;

[0069] 4) separating the solid from the liquid in the mixture after the complete reaction, filtering or drying and screening the separated solid for reuse, and using the separated liquid for compounding the fracturing fluid; specifically, using a rotary drum vacuum filter to separate the solid from the liquid in the mixture after the complete reaction, the separated solid is the treated diatomaceous earth, and the treated diatomaceous earth is peeled off by adjusting the scraper height during the separation process of the rotary drum vacuum filter, and the peeled diatomaceous earth is dried and reused, or the treated diatomaceous earth can be retained on the surface of the drum for fracturing fluid treatment, and the treated liquid can be stored in a liquid tank for fracturing fluid reuse.

[0070] Embodiment 3:

[0071] A method for recycling waste diatomaceous earth after filtering fracturing flowback fluid comprises the following steps:

[0072] 1) Mix 100 g of waste diatomaceous earth and 1000 g of clean water evenly;

[0073] 2) adding a cleaning and repairing agent to the uniformly mixed mixture; the active ingredients of the cleaning and repairing agent are 10 mL 10% sodium hypochlorite, 12 g ethylenediaminetetraacetic acid, 6 g sodium pyrophosphate and 10 mL 37% hydrochloric acid, specifically: dissolving the active ingredients of the cleaning and repairing agent in 1000 g water, and adding the dissolved cleaning and repairing agent to the uniformly mixed mixture in step 1);

[0074] 3) stirring the mixture with the cleaning and repairing agent until the reaction is complete; specifically, heating the mixture with the cleaning and repairing agent to 80° C. and keeping the temperature, stirring and washing at 100 rpm for 60 minutes at a constant temperature of 80° C., collecting the floating oil on the surface through overflow during stirring and centrally treating it until the reaction is complete;

[0075] 4) separating the solid from the liquid in the mixture after the complete reaction, filtering or drying and screening the separated solid for reuse, and using the separated liquid for compounding the fracturing fluid; specifically, using a rotary drum vacuum filter to separate the solid from the liquid in the mixture after the complete reaction, the separated solid is the treated diatomaceous earth, and the treated diatomaceous earth is peeled off by adjusting the scraper height during the separation process of the rotary drum vacuum filter, and the peeled diatomaceous earth is dried and reused, or the treated diatomaceous earth can be retained on the surface of the drum for fracturing fluid treatment, and the treated liquid can be stored in a liquid tank for fracturing fluid reuse.

[0076] Embodiment 4:

[0077] A method for recycling waste diatomaceous earth after filtering fracturing flowback fluid comprises the following steps:

[0078] 1) Mix 340 g of waste diatomaceous earth and 1000 g of clean water;

[0079] 2) adding a cleaning and repairing agent to the uniformly mixed mixture; the active ingredients of the cleaning and repairing agent are 250 mL 10% sodium hypochlorite, 9 g ethylenediaminetetraacetic acid, 10 g sodium pyrophosphate and 45 mL 37% hydrochloric acid, specifically: dissolving the active ingredients of the cleaning and repairing agent in 3000 g water, and adding the dissolved cleaning and repairing agent to the uniformly mixed mixture in step 1);

[0080] 3) stirring the mixture with the cleaning and repairing agent until the reaction is complete; specifically, heating the mixture with the cleaning and repairing agent to 90° C. and keeping the temperature, stirring and washing at 90 rpm for 30 minutes at a constant temperature of 90° C., collecting the surface floating oil through overflow during stirring and centrally treating it until the reaction is complete;

[0081] 4) separating the solid from the liquid in the mixture after the complete reaction, filtering or drying and screening the separated solid for reuse, and using the separated liquid for compounding the fracturing fluid; specifically, using a rotary drum vacuum filter to separate the solid from the liquid in the mixture after the complete reaction, the separated solid is the treated diatomaceous earth, and the treated diatomaceous earth is peeled off by adjusting the scraper height during the separation process of the rotary drum vacuum filter, and the peeled diatomaceous earth is dried and reused, or the treated diatomaceous earth can be retained on the surface of the drum for fracturing fluid treatment, and the treated liquid can be stored in a liquid tank for fracturing fluid reuse.

[0082] Embodiment 5:

[0083] A method for recycling waste diatomaceous earth after filtering fracturing flowback fluid comprises the following steps:

[0084] 1) Mix 100 g of waste diatomaceous earth and 2000 g of clean water;

[0085] 2) adding a cleaning and repairing agent to the uniformly mixed mixture; the active ingredients of the cleaning and repairing agent are 120 mL 10% sodium hypochlorite, 6 g ethylenediaminetetraacetic acid, 8 g sodium pyrophosphate and 25 mL 37% hydrochloric acid, specifically: dissolving the active ingredients of the cleaning and repairing agent in 1000 g water, and adding the dissolved cleaning and repairing agent to the uniformly mixed mixture in step 1);

[0086] 3) stirring the mixture with the cleaning and repairing agent until the reaction is complete; specifically, heating the mixture with the cleaning and repairing agent to 70° C. and keeping the temperature, stirring and washing at 70 rpm for 120 min at a constant temperature of 70° C., collecting the surface floating oil through overflow and centrally treating it during stirring until the reaction is complete;

[0087] 4) separating the solid from the liquid in the mixture after the complete reaction, filtering or drying and screening the separated solid for reuse, and using the separated liquid for compounding the fracturing fluid; specifically, using a rotary drum vacuum filter to separate the solid from the liquid in the mixture after the complete reaction, the separated solid is the treated diatomaceous earth, and the treated diatomaceous earth is peeled off by adjusting the scraper height during the separation process of the rotary drum vacuum filter, and the peeled diatomaceous earth is dried and reused, or the treated diatomaceous earth can be retained on the surface of the drum for fracturing fluid treatment, and the treated liquid can be stored in a liquid tank for fracturing fluid reuse.

[0088] Experimental results:

[0089] Example Performance evaluation of regenerated diatomaceous earth (treated diatomaceous earth) and comparison of its permeability with fresh diatomaceous earth (see Table 1). The permeability is mainly calculated by the following formula:

[0090]

[0091] Where:

[0092] k—permeability, in darcy;

[0093] A—filtration area, in square centimeters (cm 2 );

[0094] Q—filtrate flow rate (the average of three test results), Q=V / t, in milliliters per second (mL / s);

[0095] t—filtering time, in seconds (s);

[0096] V—filtrate area within filtration time t, in milliliters (mL);

[0097] η—viscosity coefficient, in centipoise (cP);

[0098] h—filter cake thickness, in centimeters (cm);

[0099] P—vacuum degree, unit is Pa (Pa).

[0100] Table 1 Performance evaluation of regenerated diatomite and comparison of its permeability with fresh diatomite

[0101]

[0102]

[0103] According to the above formula, it can be seen from Table 1 that the permeability of the waste diatomite recycled by Example 1 is 1.17 Darcy, the permeability of the fresh diatomite is 1.46 Darcy, and the permeability of the untreated waste diatomite is 1.37 Darcy. It can be seen that the permeability of the recycled diatomite is lower than 20.21%, but it is also within the reasonable range of 0.8 to 1.5 Darcy of the permeability of 200 mesh diatomite.

[0104] The filtration time of the untreated waste diatomaceous earth is shorter than that of Examples 1 to 5 and fresh diatomaceous earth. The reason is that the particles and pores of the untreated waste diatomaceous earth are larger than those of the treated diatomaceous earth and fresh diatomaceous earth. Therefore, the water quality of the untreated waste diatomaceous earth after filtration is worse than that of the treated diatomaceous earth, and the filtration speed of the untreated waste diatomaceous earth is fast.

[0105] Further comparison shows that the use of the cleaning and repairing agent in Examples 1 to 5 makes the permeability of the regenerated diatomite within a reasonable range, but within the component range of the cleaning and repairing agent, changes in the component content of the cleaning and repairing agent have little effect on the permeability of the regenerated diatomite.

[0106] Analysis of the filtration performance of fracturing flowback fluid by regenerated diatomite (treated diatomite) (see Table 2)

[0107] Take 50g of regenerated diatomaceous earth, add 500ml of water, stir to form a suspension, form a filter cake in a filtration device, then add 100ml of fracturing flowback fluid to filter, and analyze the filtered liquid.

[0108] Table 2 Analysis of the filtration performance of regenerated diatomite on fracturing flowback fluid

[0109]

[0110]

[0111] From the analysis in Table 2, it can be seen that the filtrate after filtration with regenerated diatomaceous earth has lower chromaticity and is better for treating fracturing flowback fluid.

[0112] The above examples are merely illustrative of the present invention and do not constitute a limitation on the protection scope of the present invention. All designs that are the same or similar to the present invention fall within the protection scope of the present invention.

Claims

1. A method for recycling waste diatomite after filtering fracturing flowback fluid, characterized in that: The steps include: 1) Mix the waste diatomaceous earth and clean water evenly; 2) adding a cleaning and repairing agent to the uniformly mixed mixture; the active ingredients of the cleaning and repairing agent are sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid; 3) Stirring the mixture with the cleaning and repairing agent until the reaction is complete; 4) The mixture after the complete reaction is separated into solid and liquid, the separated solid is used for filtration or drying and screening and then reused, and the separated liquid is used for compounding the fracturing fluid; the drying is carried out by drying and roasting, the drying and roasting temperature is 400-600° C., and the drying and roasting time is 20-60 minutes.

2. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 1, characterized in that: In the step 1), the mass ratio of the waste diatomaceous earth to the clean water is 1:3 to 1:

20.

3. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 1, characterized in that: The mass ratio of the mixture in step 1) to the cleaning and repairing agent is 1:0.005 to 1:0.

03.

4. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 3, characterized in that: The mass ratio of the sodium hypochlorite, ethylenediaminetetraacetic acid, sodium pyrophosphate and hydrochloric acid is 1-3:0.6-1:0.6-1:1-2.

5. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 1, characterized in that: The stirring speed in step 3) is 0.1 to 120 rpm.

6. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 1, characterized in that: The mixture with the cleaning and repairing agent added thereto is heated and then stirred.

7. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 6, characterized in that: The temperature after heating is 70-90°C.

8. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 7, characterized in that: The constant temperature stirring time after the heating is 0.5 to 2.0 hours.

9. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 1, characterized in that: The surface oil floating after stirring in step 3) is collected by overflow and processed centrally.

10. The method for recycling waste diatomaceous earth after filtering fracturing flowback fluid according to claim 9, characterized in that: The stirring in step 3) is carried out using a stirring tank with overflow.

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