Method for recycling water-based fracturing flowback fluid and application thereof

Abstract

The application discloses a water-based fracturing flowback fluid recycling method and a method for preparing integrated multifunctional fracturing fluid by using the flowback fluid treatment fluid obtained by the recycling method. The water-based fracturing flowback fluid recycling method provided by the application fully utilizes the performance effects of treatment material functionalization and fracturing fluid functionalization, fully utilizes the existing hardware conditions of fracturing equipment on site, and only by using two kinds of treatment materials, namely, a degrading agent and a synergist, and in combination with the fracturing equipment on site, the water-based fracturring flowback fluid can be treated, and the obtained flowback fluid treatment fluid can be used to prepare integrated multifunctional fracturing fluid. The method for preparing the integrated multifunctional fracturing fluid has the unique effects of "two functionalizations" of treatment material functionalization and fracturing fluid functionalization, and the unique advantages of "four integrations" of material and equipment integration, treatment and fluid preparation integration, reservoir protection and environmental protection integration, and low treatment cost and high oil and gas production integration.

Description

Technical Field

[0001] This invention belongs to the field of fracturing production enhancement technology, specifically relating to a method for reusing water-based fracturing flowback fluid, and a method for preparing an integrated multifunctional fracturing fluid using the flowback fluid treatment fluid obtained by the reuse method. Background Technology

[0002] Fracturing is one of the important measures for enhancing oil and gas well production. Currently used fracturing fluids include water-based fracturing fluids, oil-based fracturing fluids, foam fracturing fluids, energy-enhancing fracturing fluids, and dry fracturing fluids. Among them, water-based fracturing fluids have the advantages of low cost and high safety, and are currently the most widely used. In China, water-based fracturing fluids account for more than 90% of the entire fracturing fluid system. The basic components of water-based fracturing fluids are: natural high-molecular-weight guar gum, low-molecular-weight polymers, pH adjusters, anti-swelling agents, demulsifiers, drainage aids, clay stabilizers, bactericides, defoamers, high-temperature crosslinking agents, organoboron crosslinking agents, and breaker agents, etc.

[0003] After fracturing operations in oil and gas wells are completed, 30-60% of the fracturing flowback fluid will be discharged from the formation. This flowback fluid has a complex composition, with high levels of low-molecular-weight polymers, a certain COD concentration, and a significant amount of inorganic salts. It is a difficult-to-treat wastewater characterized by low viscosity, high salinity, and relatively low levels of organic matter and reducing agents. Direct discharge would cause serious pollution and has become a major source of pollution for oilfield water bodies. Therefore, fracturing flowback fluid generally requires multi-stage treatment processes to completely decompose organic pollutants. This typically involves a combination of methods such as de-gelling, flocculation, oxidation, and membrane separation. This results in long, costly, and complex existing treatment processes with unsatisfactory treatment effects.

[0004] The multi-stage treatment processes commonly used for fracturing flowback fluid are no longer adequate for the needs of fracturing flowback fluid treatment. This is mainly due to the complexity of the process, higher treatment costs, increased wastewater settling and separation time, increased dosage of purifying agents, increased sludge production after flocculation and sedimentation, and unstable post-treatment water quality. Therefore, oilfields urgently need new wastewater treatment technologies with higher treatment efficiency, effluent that can meet the requirements for repeated preparation and recycling, and investment and operating costs that are within the economic capacity of the oilfields. Summary of the Invention

[0005] In view of this, the main objective of the present invention is to provide a method for reusing water-based fracturing flowback fluid, and a method for preparing an integrated multifunctional fracturing fluid using the flowback fluid treatment fluid obtained by the reuse method, in order to at least partially solve at least some of the technical problems existing in the above-mentioned prior art.

[0006] To achieve the above objectives, as a first aspect of the present invention, a method for reusing water-based fracturing flowback fluid is provided. This method performs multifunctional treatment on the water-based fracturing flowback fluid to obtain a flowback fluid treatment solution, comprising:

[0007] The outlet of the water-based fracturing flowback fluid storage tank is connected to the inlet of the sand mixing truck through a pipeline, and the outlet of the sand mixing truck is connected to the inlet of the water-based fracturing flowback fluid storage tank through a pipeline to form a complete one-way liquid circulation pipeline.

[0008] Turn on the inlet and outlet pumps of the sand mixing truck and adjust them to a suitable flow rate so that the water-based fracturing flowback fluid circulates between the storage tank and the sand mixing truck.

[0009] The dosage of degradation agent and synergist is calculated based on the volume of water-based fracturing flowback fluid in the storage tank. Then, the calculated dosage of degradation agent and synergist is added through the solids-addition pump and liquid-addition pump inlet of the sand mixing truck, respectively.

[0010] After the degradation agent and synergist are added, the system is circulated for 30-60 minutes to obtain the backflow treatment solution.

[0011] In the above scheme, the water-based fracturing flowback fluid is the fracturing fluid used in single-well or multi-well fracturing operations on an oil and gas well platform. After well shut-in and pressure reduction, it is flowed back to the surface and collected and stored in a storage tank. The suitable flow rate of the mixing truck's inlet and outlet pumps is 2~5 m³ / h. 3 / min; the amount of the degrading agent added is 0.05~0.2wt% of the volume of the water-based fracturing flowback fluid; the amount of the synergist added is 0.5~2.0wt% of the volume of the water-based fracturing flowback fluid.

[0012] In the above scheme, the degradation agent is a solid, which is a mixture formed by any one of potassium persulfate compound salt and potassium monopersulfate compound salt with any one of manganese sulfate and manganese chloride at a mass ratio of 100:(0.5~5).

[0013] In the above scheme, the degrading agent is prepared by the following method:

[0014] Maintain the temperature inside the mixing container at 10~30℃, add either the potassium persulfate compound salt or the potassium monopersulfate compound salt of the formula to the mixing container, and start stirring;

[0015] While stirring, add either manganese sulfate or manganese chloride (the amount specified in the formula) to the mixing container, and stir for 1-2 hours to ensure thorough mixing; and

[0016] Stop stirring; the resulting white powder is the degradation agent.

[0017] In the above scheme, the synergist is a liquid, and its raw material composition comprises the following raw material components by mass percentage:

[0018] Deionized water 35-58.5%;

[0019] Anhydrous ethanol 10-15%;

[0020] pH buffer 1-3%;

[0021] Chelating agent 0.5~2%;

[0022] Fluorocarbon surfactants 5-10%;

[0023] Inorganic anti-swelling agent 10-15%; and

[0024] Organic anti-swelling agent 15-20%.

[0025] In the above scheme, the pH buffer is any one or a combination of two or more of sodium bicarbonate, potassium bicarbonate and ammonium bicarbonate;

[0026] The chelating agent is a composition formed by any one or more of sodium diethyltriaminepentaacetate, sodium ethylenediaminetetramethylenephosphonate and sodium diethylenetriaminepentamethylenephosphonate with sodium ethylenediamine diophenylacetate in a mass ratio of (2~4):1.

[0027] Fluorocarbon surfactants are ultra-concentrated emission aids;

[0028] Inorganic anti-swelling agents are any one or a combination of two of potassium chloride and ammonium chloride;

[0029] The organic anti-swelling agent is any one or a combination of two or more of trimethylbenzylammonium chloride, tetramethylammonium chloride, and choline chloride.

[0030] In the above scheme, the synergist is prepared by the following method:

[0031] Maintain the temperature inside the stirring container at 10~30℃, add the prescribed amount of deionized water and anhydrous ethanol to the stirring container, turn on the stirring, and stir for 0.5~1h to make the two completely miscible.

[0032] While stirring, add the inorganic and organic anti-swelling agents in the formula to the mixing container in sequence, and stir for 1-2 hours to ensure they are fully dissolved;

[0033] While stirring, add the pH buffer and chelating agent to the mixing container in sequence, and stir for 1-2 hours to ensure they are fully dissolved;

[0034] While stirring, add the fluorocarbon surfactant to the mixing container and stir for 1-2 hours until fully dissolved;

[0035] Stop stirring and wait for the foam to completely disappear. The resulting colorless to pale yellow transparent liquid is the synergist.

[0036] To achieve the above objectives, as a second aspect of the present invention, the present invention also provides a method for preparing an integrated multifunctional fracturing fluid using a flowback fluid treatment fluid, the method comprising:

[0037] Connect the outlet of the backflow treatment liquid storage tank to the inlet of the sand mixing truck via a pipeline, and then connect the outlet of the sand mixing truck normally to the high-pressure manifold inlet; and

[0038] By adding emulsion-type fracturing fluid thickener and breaker to the flowback fluid treatment fluid in proportion through the feed ports of the sand mixing truck fluid addition pump and the solid addition pump, an integrated fracturing fluid for drag reduction and sand-carrying fracturing operations is obtained.

[0039] In the above scheme, the emulsion-type fracturing fluid thickener is one of an oil-in-water emulsion salt-resistant fracturing fluid thickener and a suspension emulsion salt-resistant fracturing fluid thickener; the breaker is one of ammonium persulfate and a capsule breaker.

[0040] In the above scheme, an emulsion-type fracturing fluid thickener and a breaker are added to the flowback fluid treatment fluid in proportion. The amount of emulsion-type fracturing fluid thickener added is 0.05~1.5wt% of the flowback fluid treatment fluid volume, and the amount of the breaker added is 0.01~0.2%wt% of the flowback fluid treatment fluid volume.

[0041] When used to reduce drag in slickwater, the amount of thickener added to the emulsion-type fracturing fluid is 0.05~0.3%wt of the volume of the flowback fluid, and the amount of breaker added is 0.01~0.05%wt of the volume of the flowback fluid.

[0042] When used as a sand-carrying fluid, the thickener of the emulsion-type fracturing fluid is added at 0.3~1.5%wt of the volume of the flowback fluid, and the breaker is added at 0.05~0.2%wt of the volume of the flowback fluid.

[0043] As can be seen from the above technical solution, the technical solution provided by the present invention can achieve at least the following beneficial effects compared with the prior art:

[0044] (1) Multifunctional treatment materials: When the water-based fracturing flowback fluid is treated in a multifunctional way to obtain the flowback fluid treatment fluid, only two treatment materials, a degrading agent and an synergist, need to be added to obtain the flowback fluid treatment fluid. The multifunctional application integrates the rapid, efficient and environmentally friendly degradation function of the degrading agent and the chelation, anti-swelling, drainage assistance and waterproof locking functions of the synergist.

[0045] (2) Multifunctional fracturing fluid: When the flowback fluid treatment fluid obtained in this invention is used to prepare an integrated multifunctional fracturing fluid, the prepared integrated multifunctional fracturing fluid integrates functions such as anti-swelling, flow aid, water-locking and cleanliness with low damage. By adding synergists, the anhydrous ethanol, fluorocarbon surfactant and various anti-swelling agents contained therein enable the fracturing fluid to have anti-swelling, flow aid and water-locking functions. By using emulsion-type fracturing fluid thickener, the fracturing fluid has a cleanliness with low damage function.

[0046] (3) Integration of reservoir protection and environmental protection: When the flowback fluid treatment fluid obtained by the present invention is used to prepare an integrated multifunctional fracturing fluid, the prepared integrated multifunctional fracturing fluid has functions such as anti-swelling, assisting flowback, water-locking and cleaning with low damage, which can fully protect the reservoir. At the same time, the degradation agent degrades quickly, efficiently and environmentally, without generating additional solid and liquid waste that causes environmental pollution. It is environmentally friendly and integrates reservoir protection and environmental protection.

[0047] (4) Integration of materials and equipment: The water-based fracturing flowback fluid reuse method and its application provided by the present invention achieves the integrated application of materials and field fracturing equipment through degradation agents and synergists, emulsion fracturing fluid thickeners and breaker agents, thus integrating materials and field fracturing equipment into one;

[0048] (5) Integrated treatment and liquid preparation: The water-based fracturing flowback fluid reuse method and its application provided by the present invention are both achieved through storage tanks and sand mixing trucks. The addition of treatment materials and liquid preparation materials are both achieved through liquid addition equipment and solid addition equipment. Both treatment and liquid preparation are simple, convenient and easy to operate.

[0049] (6) Low processing cost and high oil and gas production enhancement: The water-based fracturing flowback fluid reuse method and its application provided by this invention do not require the use of special treatment agents such as flocculants, precipitants and adsorbents, nor do they require special treatment methods and special treatment equipment such as electrochemical, flotation and ozone. At the same time, the amount of treatment materials used is small and the overall reuse cost is low. The full protection of the reservoir can greatly improve the oil and gas production enhancement effect, thus integrating low processing cost and high oil and gas production enhancement. Attached Figure Description

[0050] Figure 1 This is a flowchart of a method for reusing water-based fracturing flowback fluid according to an embodiment of the present invention.

[0051] Figure 2 This is a flowchart of a method for preparing a degradation agent according to an embodiment of the present invention.

[0052] Figure 3 This is a flowchart of a method for preparing a synergist according to an embodiment of the present invention.

[0053] Figure 4A flowchart illustrating a method for preparing an integrated multifunctional fracturing fluid using flowback fluid treatment fluid according to an embodiment of the present invention. Detailed Implementation

[0054] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments.

[0055] During the research and development process, the engineers of this invention gradually realized that the currently used fracturing fluid systems are numerous and the composition and components of water-based fracturing fluids are also quite complex. This results in complex compositions of the fracturing flowback fluid after fracturing operations, making the wastewater difficult to treat and unable to be directly reused. Currently used treatment methods, such as gel breaking, flocculation, oxidation, and membrane separation, have long processing flows, high costs, large investments, and complex processes, and the treatment effects are not ideal. Through in-depth understanding of the actual conditions of fracturing field equipment and in-depth research on the fluid preparation process, the engineers of this invention abandoned conventional treatment methods and, through persistent experimentation, boldly innovated a method for reusing flowback fluid. Simultaneously, they continuously optimized the types and formulations of treatment materials, achieving "two functionalizations"—functionalized treatment materials and multifunctionalized fracturing fluid—and implemented "four integrations": integration of materials and equipment, integration of treatment and fluid preparation, integration of reservoir protection and environmental protection, and integration of low treatment costs and high oil and gas production enhancement. Ultimately, this invention formed an integrated reuse method for water-based fracturing flowback fluid and successfully prepared an integrated multifunctional fracturing fluid.

[0056] like Figure 1 As shown, Figure 1 This is a flowchart of a method for reusing water-based fracturing flowback fluid according to an embodiment of the present invention. The method involves multifunctionalizing the water-based fracturing flowback fluid to obtain a treated flowback fluid, specifically including:

[0057] Step S1: Connect the outlet of the water-based fracturing flowback fluid storage tank to the inlet of the sand mixing truck through a pipeline, and at the same time connect the outlet of the sand mixing truck to the inlet of the water-based fracturing flowback fluid storage tank through a pipeline to form a complete one-way liquid circulation pipeline.

[0058] Step S2: Turn on the inlet and outlet pumps of the sand mixing truck and adjust them to a suitable flow rate so that the water-based fracturing flowback fluid circulates between the storage tank and the sand mixing truck.

[0059] Step S3: Calculate the dosage of degradation agent and synergist based on the volume of water-based fracturing flowback fluid in the storage tank, and then add the degradation agent and synergist according to the calculated dosage through the feed ports of the solid addition pump and liquid addition pump of the sand mixing truck respectively.

[0060] Step S4: After the degradation agent and synergist are added, circulate for 30-60 minutes to obtain the backflow liquid treatment solution.

[0061] In this embodiment of the invention, the water-based fracturing flowback fluid mentioned in steps S1 to S3 is the fracturing fluid used in single-well or multi-well fracturing operations on an oil and gas well platform. After the well is shut in and pressure is closed, the flowback fluid is flowed back to the surface and collected and stored in a storage tank.

[0062] In this embodiment of the invention, the suitable flow rates of the inlet and outlet pumps of the sand mixing truck in step S2 are 2~5 m³ / h. 3 / min.

[0063] In this embodiment of the invention, the amount of the degradation agent added in step S3 is 0.05~0.2wt% of the volume of the water-based fracturing flowback fluid, and the amount of the synergist added is 0.5~2.0wt% of the volume of the water-based fracturing flowback fluid.

[0064] In this embodiment of the invention, the degradation agent is a solid, which is a mixture formed by any one of potassium persulfate complex salt and potassium monopersulfate complex salt with any one of manganese sulfate and manganese chloride at a mass ratio of 100:(0.5~5).

[0065] In this embodiment of the invention, the ozone released from the decomposition of potassium peroxymonosulfate complex salt and potassium peroxymonosulfate complex salt upon contact with water has a highly efficient bactericidal and water purification effect. At the same time, its strong oxidizing properties react efficiently and rapidly with organic matter and reducing substances such as oligomers, organic matter, ammonia nitrogen and nitrite, thereby effectively reducing COD concentration. Meanwhile, the addition of manganese sulfate and manganese chloride for low-temperature catalysis significantly reduces the activation energy of potassium peroxymonosulfate complex salt and potassium peroxymonosulfate complex salt, thus fully exerting its rapid, efficient and environmentally friendly degradation performance in the temperature range of 0-40℃.

[0066] In this embodiment of the invention, the method for preparing the degrading agent is as follows: Figure 2 As shown, it includes the following steps:

[0067] Step 21: Keep the temperature inside the mixing container at 10~30℃, add either potassium persulfate compound salt or potassium monopersulfate compound salt to the mixing container according to the formula amount, and start stirring;

[0068] Step 22: While stirring, add either manganese sulfate or manganese chloride to the mixing container in the prescribed amount, and stir for 1-2 hours to ensure that the two are fully mixed.

[0069] Step 23: Stop stirring. The resulting white powder is the degradation agent.

[0070] In this embodiment of the invention, the synergist is a liquid, and its raw material composition comprises the following raw material components by mass percentage:

[0071] Deionized water 35-58.5%;

[0072] Anhydrous ethanol 10-15%;

[0073] pH buffer 1-3%;

[0074] Chelating agent 0.5~2%;

[0075] Fluorocarbon surfactants 5-10%;

[0076] Inorganic anti-swelling agent 10-15%; and

[0077] Organic anti-swelling agent 15-20%.

[0078] In this embodiment of the invention, the pH buffer is any one or a combination of two or more of sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate; the chelating agent is any one or a combination of two or more of sodium diethyltriaminepentaacetate, sodium ethylenediaminetetramethylenephosphonate, and sodium diethylenetriaminepentamethylenephosphonate, and sodium ethylenediamine di-o-phenylacetate in a mass ratio of (2-4):1; the fluorocarbon surfactant is a super-concentrated discharge aid; the inorganic anti-swelling agent is any one or a combination of two of potassium chloride and ammonium chloride; and the organic anti-swelling agent is any one or a combination of two or more of trimethylbenzylammonium chloride, tetramethylammonium chloride, and choline chloride.

[0079] The preparation method of the synergist is as follows: Figure 3 As shown, it includes the following steps:

[0080] Step 31: Keep the temperature inside the stirring container at 10~30℃, add the formula amount of deionized water and anhydrous ethanol to the stirring container, turn on the stirring, and stir for 0.5~1h to make the two completely miscible.

[0081] Step 32: While stirring, add the inorganic anti-swelling agent and organic anti-swelling agent in the formula amount to the stirring container in sequence, and stir for 1-2 hours to fully dissolve them;

[0082] Step 33: While stirring, add the pH buffer and chelating agent to the mixing container in sequence, and stir for 1-2 hours to ensure they are fully dissolved;

[0083] Step 34: While stirring, add the fluorocarbon surfactant to the stirring container and stir for 1-2 hours to ensure it is fully dissolved;

[0084] Step 35: Stop stirring and wait for the foam to completely disappear. The resulting colorless to pale yellow transparent liquid is the synergist.

[0085] based on Figure 1 The flowchart shown is a method for reusing water-based fracturing flowback fluid according to an embodiment of the present invention. Figure 4A flowchart illustrating a method for preparing an integrated multifunctional fracturing fluid using flowback fluid treatment fluid according to an embodiment of the present invention is shown. The integrated multifunctional fracturing fluid prepared according to this embodiment is obtained by adding an emulsion-type fracturing fluid thickener and a breaker to the flowback fluid treatment fluid in proportion using a sand mixing truck fluid addition pump and a solids addition pump, respectively. The method includes the following steps:

[0086] Step 41: Connect the outlet of the backflow treatment liquid storage tank to the inlet of the sand mixing truck through a pipeline, and then connect the outlet of the sand mixing truck to the high-pressure manifold inlet normally.

[0087] Step 42: Add emulsion-type fracturing fluid thickener and breaker to the flowback fluid treatment fluid in proportion through the feed ports of the sand mixing truck fluid addition pump and the solid addition pump, respectively, to obtain an integrated fracturing fluid for drag reduction and sand-carrying fracturing operations.

[0088] In this embodiment of the invention, the emulsion-type fracturing fluid thickener is one of an oil-in-water emulsion salt-resistant fracturing fluid thickener and a suspension emulsion salt-resistant fracturing fluid thickener; the breaker is one of ammonium persulfate and a capsule breaker.

[0089] In this embodiment of the invention, an emulsion-type fracturing fluid thickener and a breaker are added to the flowback fluid treatment fluid in proportion. The amount of emulsion-type fracturing fluid thickener added is 0.05~1.5 wt% of the flowback fluid treatment fluid volume, and the amount of the breaker added is 0.01~0.2% wt% of the flowback fluid treatment fluid volume. Specifically, when used as a slickwater drag reducing agent, the amount of emulsion-type fracturing fluid thickener added is 0.05~0.3% wt% of the flowback fluid treatment fluid volume, and the amount of the breaker added is 0.01~0.05% wt% of the flowback fluid treatment fluid volume. When used as a proppant-carrying fluid, the amount of emulsion-type fracturing fluid thickener added is 0.3~1.5% wt% of the flowback fluid treatment fluid volume, and the amount of the breaker added is 0.05~0.2% wt% of the flowback fluid treatment fluid volume.

[0090] Several specific embodiments are further provided below to illustrate the technical solution of the present invention in more detail. It should be noted that the specific values ​​and amounts in the following embodiments are merely illustrative and can be scaled up according to the proportions in specific applications.

[0091] Example 1

[0092] The method for reusing water-based fracturing flowback fluid and the method for preparing integrated multifunctional fracturing fluid using flowback fluid treatment fluid provided in Embodiment 1 of this invention are as follows:

[0093] 1. Preparation of the degradation agent:

[0094] (1) Keep the temperature inside the mixing container at 20°C, add 1000 kg of potassium persulfate compound salt to the mixing container, and start stirring;

[0095] (2) Keep stirring, add 50 kg of manganese chloride to the mixing container, stir for 1.5 h to make the two fully mixed;

[0096] (3) Stop stirring. The white powder obtained is the degradation agent.

[0097] 2. Preparation of synergists:

[0098] (1) Keep the temperature inside the stirring container at 10°C, add 510 kg of deionized water and 100 kg of anhydrous ethanol to the stirring container, turn on the stirring and stir for 1 h to make the two completely miscible.

[0099] (2) While stirring, add 100 kg of potassium chloride and 200 kg of trimethylbenzylammonium chloride to the stirring container in sequence, and stir for 1.5 h to make them fully dissolved;

[0100] (3) Keep stirring and add 20 kg of sodium bicarbonate, 14 kg of sodium diethyltriaminepentaacetate and 6 kg of sodium ethylenediaminedi-o-phenylacetate to the stirring container in sequence, and stir for 1.5 h to make it fully dissolved;

[0101] (4) Keep stirring, add 50 kg of super-concentrated drainage aid to the stirring container, stir for 1.5 h to make it fully dissolved;

[0102] (5) Stop stirring and wait for the foam to completely disappear. The resulting colorless to pale yellow transparent liquid is the synergist.

[0103] 3. Reuse of fracturing flowback fluid:

[0104] (1) Connect the outlet of the return liquid storage tank to the inlet of the sand mixing truck through a pipeline, and connect the outlet of the sand mixing truck to the inlet of the return liquid storage tank through a pipeline to form a complete one-way liquid circulation pipeline.

[0105] (2) Turn on the inlet and outlet pumps of the sand mixing truck and adjust the flow rate to 2m. 3 / min, allowing the backflow liquid to circulate between the storage tank and the sand mixing truck;

[0106] (3) Based on the backflow volume of 30m³ in a single storage tank 3 Add 15 kg of degradation agent through the solid feed port of the sand mixing truck, and add 150 kg of synergist through the liquid feed port of the sand mixing truck.

[0107] (4) After the degradation agent and synergist are added, the mixture is circulated for 30 minutes to obtain the backflow liquid treatment solution.

[0108] 4. Preparation of integrated multifunctional fracturing fluid:

[0109] (1) Keep the outlet of the backflow liquid storage tank connected to the inlet of the sand mixing truck through a pipeline, and then connect the outlet of the sand mixing truck to the high-pressure manifold inlet according to the fracturing design pipeline;

[0110] (2) Using the flowback fluid treatment fluid, add 0.05% of water-in-oil emulsion salt-resistant fracturing fluid thickener and 0.01% of ammonium persulfate to the flowback fluid treatment fluid through the fluid addition pump and solid addition pump of the sand mixing truck to prepare slickwater, and add 0.5% of water-in-oil emulsion salt-resistant fracturing fluid thickener and 0.1% of ammonium persulfate to prepare sand-carrying fluid to obtain an integrated multi-functional fracturing fluid for drag reduction and sand-carrying fracturing operations.

[0111] The above-prepared integrated multifunctional fracturing fluid, when tested, has the following properties: viscosity 3 mPa·s and drag reduction rate 72% when used as slickwater; viscosity 36 mPa·s and anti-swelling rate 84% when used as proppant-carrying fluid; surface tension 27 mN / m; interfacial tension 1.5 mN / m; contact angle 72°; and core damage rate 14%.

[0112] Example 2

[0113] The method for reusing water-based fracturing flowback fluid and the method for preparing integrated multifunctional fracturing fluid using flowback fluid treatment fluid provided in Embodiment 2 of the present invention are as follows:

[0114] 1. Preparation of the degradation agent:

[0115] (1) Keep the temperature inside the mixing container at 10°C, add 1000 kg of potassium persulfate compound salt to the mixing container, and start stirring;

[0116] (2) Keep stirring, add 5 kg of manganese sulfate to the mixing container, stir for 1 hour to make the two fully mixed;

[0117] (3) Stop stirring. The white powder obtained is the degradation agent.

[0118] 2. Preparation of synergists:

[0119] (1) Keep the temperature inside the stirring container at 30°C, add 510 kg of deionized water and 150 kg of anhydrous ethanol to the stirring container, turn on the stirring and stir for 0.5 h to make the two completely miscible.

[0120] (2) Keep stirring and add 50 kg of ammonium chloride and 150 kg of tetramethylammonium chloride to the stirring container in sequence, and stir for 2 hours to fully dissolve them;

[0121] (3) Keep stirring and add 30 kg of potassium bicarbonate, 7 kg of sodium ethylenediaminetetramethylenephosphonate and 3 kg of sodium ethylenediamine di-o-phenylacetate to the stirring container in sequence. Stir for 1 hour to fully dissolve them.

[0122] (4) Keep stirring, add 100Kg of super-concentrated drainage aid to the stirring container, stir for 1 hour to fully dissolve it;

[0123] (5) Stop stirring and wait for the foam to completely disappear. The resulting colorless to pale yellow transparent liquid is the synergist.

[0124] 3. Reuse of fracturing flowback fluid:

[0125] (1) Connect the outlet of the return liquid storage tank to the inlet of the sand mixing truck through a pipeline, and connect the outlet of the sand mixing truck to the inlet of the return liquid storage tank through a pipeline to form a complete one-way liquid circulation pipeline.

[0126] (2) Turn on the inlet and outlet pumps of the sand mixing truck and adjust the flow rate to 5m³ / h. 3 / min, allowing the backflow liquid to circulate between the storage tank and the sand mixing truck;

[0127] (3) Based on a single storage tank's backflow liquid volume of 40m³ 3 Add 80 kg of degradation agent through the solid feed port of the sand mixing truck, and add 800 kg of synergist through the liquid feed port of the sand mixing truck at the same time.

[0128] (4) After the degradation agent and synergist are added, the mixture is circulated for 60 minutes to obtain the backflow liquid treatment solution.

[0129] 4. Preparation of integrated multifunctional fracturing fluid:

[0130] (1) Keep the outlet of the backflow liquid storage tank connected to the inlet of the sand mixing truck through a pipeline, and then connect the outlet of the sand mixing truck to the high-pressure manifold inlet according to the fracturing design pipeline;

[0131] (2) Using the flowback fluid treatment fluid, 0.3% of oil-in-water emulsion salt-resistant fracturing fluid thickener and 0.05% of ammonium persulfate are added to the flowback fluid treatment fluid through the fluid addition pump and solid addition pump of the sand mixing truck to prepare slickwater. 1.2% of suspension emulsion salt-resistant fracturing fluid thickener and 0.2% of ammonium persulfate are added to prepare sand-carrying fluid to obtain an integrated multi-functional fracturing fluid for drag reduction and sand-carrying fracturing operations.

[0132] The above-prepared integrated multifunctional fracturing fluid, when tested, has the following properties: viscosity 6 mPa·s and drag reduction rate 72% when used as slickwater; viscosity 96 mPa·s and anti-swelling rate 80% when used as proppant-carrying fluid; surface tension 26 mN / m; interfacial tension 1.2 mN / m; contact angle 73°; and core damage rate 16%.

[0133] Example 3

[0134] The method for reusing water-based fracturing flowback fluid and the method for preparing integrated multifunctional fracturing fluid using flowback fluid treatment fluid provided in Embodiment 3 of the present invention are as follows:

[0135] 1. Preparation of the degradation agent:

[0136] (1) Keep the temperature inside the mixing container at 30°C, add 1000 kg of potassium persulfate compound salt to the mixing container, and start stirring;

[0137] (2) Keep stirring, add 25 kg of manganese sulfate to the mixing container, stir for 2 hours to make the two fully mixed;

[0138] (3) Stop stirring. The white powder obtained is the degradation agent.

[0139] 2. Preparation of synergists:

[0140] (1) Keep the temperature inside the stirring container at 20°C, add 500 kg of deionized water and 120 kg of anhydrous ethanol to the stirring container, turn on the stirring and stir for 1 h to make the two completely miscible.

[0141] (2) Keep stirring and add 40 kg of potassium chloride, 40 kg of ammonium chloride, 90 kg of tetramethylammonium chloride and 90 kg of choline chloride to the stirring container in sequence, and stir for 1 hour to make them fully dissolved;

[0142] (3) Keep stirring and add 5 kg of potassium bicarbonate, 5 kg of ammonium bicarbonate, 12 kg of sodium ethylenediaminetetramethylenephosphonate, 12 kg of sodium diethylenetriaminepentamethylenephosphonate and 6 kg of sodium ethylenediaminedi-o-phenylacetate to the stirring container in sequence. Stir for 2 hours to fully dissolve them.

[0143] (4) Keep stirring, add 80 kg of super-concentrated drainage aid to the stirring container, stir for 2 hours to fully dissolve it;

[0144] (5) Stop stirring and wait for the foam to completely disappear. The resulting colorless to pale yellow transparent liquid is the synergist.

[0145] 3. Reuse of fracturing flowback fluid:

[0146] (1) Connect the outlet of the return liquid storage tank to the inlet of the sand mixing truck through a pipeline, and connect the outlet of the sand mixing truck to the inlet of the return liquid storage tank through a pipeline to form a complete one-way liquid circulation pipeline.

[0147] (2) Turn on the inlet and outlet pumps of the sand mixing truck and adjust the flow rate to 4m³ / h. 3 / min, allowing the backflow liquid to circulate between the storage tank and the sand mixing truck;

[0148] (3) Based on a single storage tank with a backflow volume of 50m³ 3 Add 50 kg of degradation agent through the solid feed port of the sand mixing truck, and add 500 kg of synergist through the liquid feed port of the sand mixing truck at the same time.

[0149] (4) After the degradation agent and synergist are added, the mixture is circulated for 45 minutes to obtain the backflow liquid treatment solution.

[0150] 4. Preparation of integrated multifunctional fracturing fluid:

[0151] (1) Keep the outlet of the backflow liquid storage tank connected to the inlet of the sand mixing truck through a pipeline, and then connect the outlet of the sand mixing truck to the high-pressure manifold inlet according to the fracturing design pipeline;

[0152] (2) Using the flowback fluid treatment fluid, 0.2% of oil-in-water emulsion salt-resistant fracturing fluid thickener and 0.02% of ammonium persulfate are added to the flowback fluid treatment fluid through the fluid addition pump and solid addition pump of the sand mixing truck to prepare slickwater. 0.8% of suspension emulsion salt-resistant fracturing fluid thickener and 0.1% of ammonium persulfate are added to prepare sand-carrying fluid to obtain an integrated multi-functional fracturing fluid for drag reduction and sand-carrying fracturing operations.

[0153] The above-prepared integrated multifunctional fracturing fluid, when tested, has the following properties: viscosity 5 mPa·s and drag reduction rate 72% when used as slickwater; viscosity 60 mPa·s and anti-swelling rate 86% when used as proppant-carrying fluid; surface tension 28 mN / m; interfacial tension 1.0 mN / m; contact angle 75°; and core damage rate 12%.

[0154] The fracturing flowback fluid reuse method implemented in the above embodiments and its application in the preparation of integrated multifunctional fracturing fluid have been shown through practical application to have the following significant advantages:

[0155] (1) Connect the outlet of the return liquid storage tank to the inlet of the sand mixing truck through a pipeline, and connect the outlet of the sand mixing truck to the inlet of the return liquid storage tank through a pipeline to form a complete one-way liquid circulation pipeline.

[0156] (2) Turn on the inlet and outlet pumps of the sand mixing truck and adjust the flow rate to a suitable level so that the return liquid circulates between the storage tank and the sand mixing truck.

[0157] (3) Calculate the amount of degradation agent and synergist to be added based on the amount of liquid returned from the storage tank, and then add the degradation agent and synergist in proportion through the solid addition pump and liquid addition pump of the sand mixing truck respectively;

[0158] (4) After the degradation agent and synergist are added, the mixture is circulated for 30-60 minutes to obtain the backflow liquid treatment solution.

[0159] The suitable flow rates for the inlet and outlet pumps of the sand mixing vehicle are 2-5 m³ / h. 3 / min; the amount of the degradation agent added is 0.05~0.2wt% of the backflow liquid volume; the amount of the synergist added is 0.5~2.0wt% of the backflow liquid volume.

[0160] As can be seen from the above technical solution, the technical solution provided by the present invention can achieve at least the following beneficial effects compared with the prior art:

[0161] (1) Multifunctional treatment materials: When the water-based fracturing flowback fluid is treated in a multifunctional way to obtain the flowback fluid treatment fluid, only two treatment materials, a degrading agent and an synergist, need to be added to obtain the flowback fluid treatment fluid. The multifunctional application integrates the rapid, efficient and environmentally friendly degradation function of the degrading agent and the chelation, anti-swelling, drainage assistance and waterproof locking functions of the synergist.

[0162] (2) Multifunctional fracturing fluid: When the flowback fluid treatment fluid obtained in this invention is used to prepare an integrated multifunctional fracturing fluid, the prepared integrated multifunctional fracturing fluid integrates functions such as anti-swelling, flow aid, water-locking and cleanliness with low damage. By adding synergists, the anhydrous ethanol, fluorocarbon surfactant and various anti-swelling agents contained therein enable the fracturing fluid to have anti-swelling, flow aid and water-locking functions. By using emulsion-type fracturing fluid thickener, the fracturing fluid has a cleanliness with low damage function.

[0163] (3) Integration of reservoir protection and environmental protection: When the flowback fluid treatment fluid obtained by the present invention is used to prepare an integrated multifunctional fracturing fluid, the prepared integrated multifunctional fracturing fluid has functions such as anti-swelling, assisting flowback, water-locking and cleaning with low damage, which can fully protect the reservoir. At the same time, the degradation agent degrades quickly, efficiently and environmentally, without generating additional solid and liquid waste that causes environmental pollution. It is environmentally friendly and integrates reservoir protection and environmental protection.

[0164] (4) Integration of materials and equipment: The water-based fracturing flowback fluid reuse method and its application provided by the present invention achieves the integrated application of materials and field fracturing equipment through degradation agents and synergists, emulsion fracturing fluid thickeners and breaker agents, thus integrating materials and field fracturing equipment into one;

[0165] (5) Integrated treatment and liquid preparation: The water-based fracturing flowback fluid reuse method and its application provided by the present invention are both achieved through storage tanks and sand mixing trucks. The addition of treatment materials and liquid preparation materials are both achieved through liquid addition equipment and solid addition equipment. Both treatment and liquid preparation are simple, convenient and easy to operate.

[0166] (6) Low processing cost and high oil and gas production enhancement: The water-based fracturing flowback fluid reuse method and its application provided by this invention do not require the use of special treatment agents such as flocculants, precipitants and adsorbents, nor do they require special treatment methods and special treatment equipment such as electrochemical, flotation and ozone. At the same time, the amount of treatment materials used is small and the overall reuse cost is low. The full protection of the reservoir can greatly improve the oil and gas production enhancement effect, thus integrating low processing cost and high oil and gas production enhancement.

[0167] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for reusing water-based fracturing flowback fluid, wherein the method performs multifunctional treatment on the water-based fracturing flowback fluid to obtain a flowback fluid treatment solution, characterized in that, include: The outlet of the water-based fracturing flowback fluid storage tank is connected to the inlet of the sand mixing truck through a pipeline, and the outlet of the sand mixing truck is connected to the inlet of the water-based fracturing flowback fluid storage tank through a pipeline to form a complete one-way liquid circulation pipeline. Turn on the inlet and outlet pumps of the sand mixing truck and adjust them to a suitable flow rate so that the water-based fracturing flowback fluid circulates between the storage tank and the sand mixing truck. The dosage of degradation agent and synergist is calculated based on the volume of water-based fracturing flowback fluid in the storage tank. Then, the calculated dosage of degradation agent and synergist is added through the solids-addition pump and liquid-addition pump inlet of the sand mixing truck, respectively. After the degradation agent and synergist are added, the system is circulated for 30-60 minutes to obtain the backflow liquid treatment solution. The degradation agent is a solid, and is a mixture formed by mixing any one of potassium persulfate compound salt and potassium persulfate compound salt with any one of manganese sulfate and manganese chloride in a mass ratio of 100:(0.5~5). The synergist is a liquid, and its raw material composition, by mass percentage, comprises the following raw material components: 35-58.5% deionized water; 10-15% anhydrous ethanol; 1-3% pH buffer; 0.5-2% chelating agent; 5-10% fluorocarbon surfactant; 10-15% inorganic anti-swelling agent; and 15-20% organic anti-swelling agent; wherein the pH buffer is any one or a combination of two or more of sodium bicarbonate, potassium bicarbonate, and ammonium bicarbonate; the chelating agent is any one or a combination of two or more of sodium diethyltriaminepentaacetate, sodium ethylenediaminetetramethylenephosphonate, and sodium diethylenetriaminepentamethylenephosphonate, and sodium ethylenediaminedi-o-phenylacetate in a mass ratio of (2-4):1; the fluorocarbon surfactant is a super-concentrated discharge aid; the inorganic anti-swelling agent is any one or a combination of two of potassium chloride and ammonium chloride; and the organic anti-swelling agent is any one or a combination of two or more of trimethylbenzylammonium chloride, tetramethylammonium chloride, and choline chloride.

2. The method for reusing water-based fracturing flowback fluid according to claim 1, characterized in that, The water-based fracturing flowback fluid is the fracturing fluid used in single-well or multi-well fracturing operations on oil and gas well platforms. After the well is shut in and pressure is closed, it is flowed back to the surface and collected and stored in a storage tank. The suitable flow rates for the inlet and outlet pumps of the sand mixing vehicle are 2~5 m³ / h. 3 / min; The amount of the degradation agent added is 0.05~0.2wt% of the volume of the water-based fracturing flowback fluid; The amount of the synergist added is 0.5~2.0 wt% of the volume of the water-based fracturing flowback fluid.

3. The method for reusing water-based fracturing flowback fluid according to claim 1, characterized in that, The degradation agent is prepared by the following method: Maintain the temperature inside the mixing container at 10~30℃, add either the potassium persulfate compound salt or the potassium monopersulfate compound salt of the formula to the mixing container, and start stirring; While stirring, add either manganese sulfate or manganese chloride (the amount specified in the formula) to the mixing container, and stir for 1-2 hours to ensure thorough mixing; and Stop stirring; the resulting white powder is the degradation agent.

4. The method for reusing water-based fracturing flowback fluid according to claim 1, characterized in that, The synergist is prepared using the following method: Maintain the temperature inside the stirring container at 10~30℃, add the prescribed amount of deionized water and anhydrous ethanol to the stirring container, turn on the stirring, and stir for 0.5~1h to make the two completely miscible. While stirring, add the inorganic and organic anti-swelling agents in the formula to the mixing container in sequence, and stir for 1-2 hours to ensure they are fully dissolved; While stirring, add the pH buffer and chelating agent to the mixing container in sequence, and stir for 1-2 hours to ensure they are fully dissolved; While stirring, add the fluorocarbon surfactant to the mixing container and stir for 1-2 hours until fully dissolved; Stop stirring and wait for the foam to completely disappear. The resulting colorless to pale yellow transparent liquid is the synergist.

5. A method for preparing an integrated multifunctional fracturing fluid using the flowback fluid treatment fluid obtained by any one of claims 1 to 4, characterized in that, The method includes: Connect the outlet of the backflow treatment liquid storage tank to the inlet of the sand mixing truck via a pipeline, and then connect the outlet of the sand mixing truck normally to the high-pressure manifold inlet; and By adding emulsion-type fracturing fluid thickener and breaker to the flowback fluid treatment fluid in proportion through the feed ports of the sand mixing truck fluid addition pump and the solid addition pump, an integrated fracturing fluid for drag reduction and sand-carrying fracturing operations is obtained.

6. The method for preparing integrated multifunctional fracturing fluid according to claim 5, characterized in that, The emulsion-type fracturing fluid thickener is one of an oil-in-water emulsion salt-resistant fracturing fluid thickener and a suspension emulsion salt-resistant fracturing fluid thickener; The de-icing agent is one of ammonium persulfate and capsule de-icing agent.

7. The method for preparing integrated multifunctional fracturing fluid according to claim 5, characterized in that, The flowback fluid treatment fluid is to be added in proportion to an emulsion-type fracturing fluid thickener and a breaker, wherein the amount of emulsion-type fracturing fluid thickener added is 0.05~1.5wt% of the flowback fluid treatment fluid volume, and the amount of the breaker added is 0.01~0.2%wt% of the flowback fluid treatment fluid volume. When used to reduce drag in slickwater, the amount of thickener added to the emulsion-type fracturing fluid is 0.05~0.3%wt of the volume of the flowback fluid, and the amount of breaker added is 0.01~0.05%wt of the volume of the flowback fluid. When used as a sand-carrying fluid, the thickener of the emulsion-type fracturing fluid is added at 0.3~1.5%wt of the volume of the flowback fluid, and the breaker is added at 0.05~0.2%wt of the volume of the flowback fluid.

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