A rapid pretreatment agent for guar gum fracturing flowback fluid, its preparation method and application

Abstract

This invention proposes a rapid pretreatment agent for guar gum fracturing flowback fluid, its preparation method, and its application. The agent is prepared according to the following mass fractions: acid 0.025%–3.0%, kaolin 66.6%–85%, and polyaluminum chloride 12.0%–33.3%. The rapid pretreatment agent, preparation method, and application of this invention for guar gum fracturing flowback fluid have advantages such as being non-toxic and harmless, easy to store, convenient to add, fast flocculation speed, easy floc separation, and low cost. It is suitable for use in wastewater treatment plants or tanker transport, minimizing the damage to subsequent wastewater treatment equipment and the impact on the treatment system caused by guar gum fragments. The treatment method optimizes the agent usage, reduces operating costs, and lowers the load on subsequent treatment processes.

Description

Technical Field

[0001] This invention belongs to the field of fracturing flowback fluid treatment technology, and specifically relates to a rapid pretreatment agent for guar gum fracturing flowback fluid, its preparation method, and its application. Background Technology

[0002] Hydraulic fracturing is one of the main measures for enhancing oil and gas production. The fracturing process involves injecting fracturing fluid into the formation using a high-pressure pump unit to create fractures and introduce proppant. After fracturing, the fracturing fluid breaks down under formation conditions and the action of a breaker, reducing its viscosity. It then flows back to the surface through the tubing or casing, becoming the fracturing flowback fluid. Currently, guar gum fracturing systems are widely used in the field. However, due to incomplete breaking down of the fracturing fluid in the formation, the flowback fluid contains a large amount of dissolved guar gum, broken guar gum fragments, and various additives (flowback aids, demulsifiers, bactericides, etc.), resulting in high viscosity and stability. This leads to problems such as difficulty in solid-liquid separation and caking of the filtration system during processing. Therefore, high-viscosity guar gum fracturing flowback fluid must be pretreated before entering the subsequent processing system.

[0003] The invention patent "A Harmless Pretreatment Agent for Fracturing Flowback Fluid and Its Treatment Method" (patent application number: 201610556236.2) discloses a harmless pretreatment agent for fracturing flowback fluid and its treatment method. The pretreatment agent is a compound breaker and a compound flocculant. The compound breaker is potassium persulfate, calcium oxide and enzyme breaker. The compound flocculant is aluminum sulfate, ferrous sulfate, polyacrylamide and activated clay. In the pretreatment of fracturing flowback fluid, 10 g / L of breaker solution is added first and reacted for 10 min. Then 6 g / L of flocculant is added and reacted for 100 min. Existing pretreatment methods for guar gum fracturing flowback fluid mainly use chemical agents to remove colloids and suspended solids. However, the viscosity of guar gum fracturing flowback fluid is mainly contributed by guar gum. Although oxidants can effectively destroy the molecular structure of guar gum and reduce viscosity, a large amount of oxidizable substances in the flowback fluid will consume a large amount of oxidant, resulting in a large amount of oxidant added, a long reaction time, and the hazardous chemicals used are not easy to store. Summary of the Invention

[0004] To address the above problems, this invention proposes a rapid pretreatment agent for guar gum fracturing flowback fluid, wherein the agent is prepared in the following mass fraction ratios: acid 0.025%–3.0%, kaolin 66.6%–85%, and polyaluminum chloride 12.0%–33.3%.

[0005] Furthermore, the acids include hydrochloric acid, sulfuric acid, and nitric acid.

[0006] This invention also provides a method for preparing a rapid pretreatment agent for guar gum fracturing flowback fluid, the method comprising:

[0007] Prepare an acid solution containing 0.025%–3.0% acid, 66.6%–85% kaolin, and 12.0%–33.3% polyaluminum chloride by mass fraction.

[0008] The kaolin and the acid solution are mixed evenly to form a mixture, and the mixture is stirred until it becomes gel-like;

[0009] The gel-like liquid, after being left to stand for a predetermined time, is dried to obtain a premix;

[0010] The premixed material is uniformly mixed with the polyaluminum chloride, then pulverized and sieved to obtain the desired reagent.

[0011] Furthermore, the concentration of the acid solution is 1 mmol / L to 10 mmol / L.

[0012] Furthermore, the mixing speed of the mixture is 200-500 rpm.

[0013] Furthermore, the drying temperature of the gel-like liquid is 105℃~120℃.

[0014] Furthermore, the mass ratio of the premix to the polyaluminum chloride is 3 to 7:1.

[0015] Furthermore, the predetermined time is 1 hour to 5 hours.

[0016] This invention also provides an application of a rapid pretreatment agent for guar gum fracturing flowback fluid in the treatment of guar gum fracturing flowback fluid.

[0017] Furthermore, the mass ratio of the agent to the effluent is 1:250-500.

[0018] The rapid pretreatment agent, preparation method, and application of guar gum fracturing flowback fluid of the present invention have advantages such as being non-toxic and harmless, easy to store, convenient to add, fast flocculation speed, easy floc separation, and low cost. It is suitable for use in wastewater treatment plants or tanker transport, minimizing the damage to subsequent wastewater treatment equipment and the impact on the treatment system caused by guar gum fragments. The treatment method optimizes the dosage of the agent, reduces operating costs, and lowers the load on subsequent treatment processes.

[0019] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures pointed out in the description, claims and drawings. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 The diagram illustrates the turbidity changes of the backflow liquid with and without the addition of the reagent in an embodiment of the present invention. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0023] In this embodiment of the invention, a rapid pretreatment agent for guar gum fracturing flowback fluid is provided, comprising acid (calculated as hydrochloric acid), kaolin, and polyaluminum chloride, formulated in proportions of 0.025%–3.0%, 66.6%–85%, and 12.0%–33.3% by mass, respectively.

[0024] For example, in the pretreatment agents described in this disclosure, the acid covers hydrochloric acid, sulfuric acid, and nitric acid, and is prepared into a solution by molar quantity.

[0025] This invention also provides a method for preparing a rapid pretreatment agent for guar gum fracturing flowback fluid, comprising the following steps:

[0026] Prepare an acid solution containing 0.025%–3.0% acid, 66.6%–85% kaolin, and 12.0%–33.3% polyaluminum chloride by mass fraction.

[0027] The kaolin and the acid solution are uniformly mixed to form a mixture, and the mixture is stirred until it becomes gel-like. The concentration of the acid solution is 1 mmol / L to 10 mmol / L, and the stirring speed of the mixture is 200 to 500 rpm.

[0028] The gel-like liquid, after being left to stand for a predetermined time, is dried to obtain a premix; the drying temperature of the gel-like liquid is 105℃~120℃, and the predetermined time is 1h~5h;

[0029] The premix and the polyaluminum chloride are mixed evenly and then pulverized and sieved to obtain the desired reagent; the mass ratio of the premix to the polyaluminum chloride is 3 to 7:1.

[0030] This disclosure also provides a method for rapid pretreatment of guar gum fracturing flowback fluid. The required dosage of the pretreatment agent is calculated based on the volume of guar gum fracturing flowback fluid per liter. The dosage is added at a ratio of agent to flowback fluid mass of 1:250-500. After the agent reacts in the water for 1-2 minutes, it is allowed to stand for 5-30 minutes. In the pretreatment agent, polyaluminum chloride aggregates large polymer molecules such as guar gum or surfactants in the wastewater into larger flocs through charge neutralization and netting / sweeping action. Kaolin rapidly separates and settles the flocs through surface adsorption. The acid-modified kaolin has increased pores, which enhances its adsorption performance. Because this pretreatment agent is non-toxic and harmless, has a fast flocculation speed, and is easy to separate and settle, it is suitable not only for wastewater treatment plants but also for tanker transportation. This method can shorten the treatment process and reduce the floor space required.

[0031] The technical solution of the present invention will be further described below with reference to specific embodiments:

[0032] The pretreatment agents used in this invention are for use in guar gum fracturing flowback fluid after field fracturing of oil and gas wells and for preparing simulated guar gum fracturing flowback fluid in the laboratory. The agents used in the laboratory preparation of the simulated guar gum fracturing flowback fluid are all provided from the oilfield. The preparation process simulates the field fracturing process: 4.0g of hydroxypropyl guar gum powder is dispersed in 1L of water under high-speed stirring to prepare a 0.3% guar gum solution. 0.01% alkali is added to adjust the pH. After complete dissolution, 0.1% flowback aid, 0.1% bactericide, 0.3% clay stabilizer, and 0.3% demulsifier (based on the total mass of the solution) are added and stirred until dissolved to obtain the guar gum fracturing fluid base. 0.02% demulsifier (based on the total mass of the solution) is added to the guar gum fracturing fluid base and dissolved completely. Under stirring conditions, a crosslinking agent solution is added to the guar gum fracturing fluid base, controlling the base fluid to crosslinking agent ratio at 100:0.4. The mixture is stirred thoroughly until complete gel formation to obtain the guar gum fracturing fluid. The cross-linked fracturing fluid colloid was broken up at 90℃ for 2 hours, then removed and cooled to a constant temperature. Ions dissolved from the fracturing fluid during the flowback process with rocks, quartz sand, clay, etc. were added: FeCl3 (30mg / L), MgSO4 (400mg / L), CaCl2 (300mg / L), NaHCO3 (1700mg / L), KCl (70mg / L), and NaCl 4000mg / L. Finally, a simulated guar gum fracturing flowback fluid was obtained.

[0033] Example 1:

[0034] Preparation process of pretreatment agent: 10g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 10 mmol / L hydrochloric acid solution and stirred continuously at 500rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is then mixed evenly with 3.3g of polyaluminum chloride at a mass ratio of 3:1 and then pulverized and sieved for later use.

[0035] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.1 g of pretreatment agent, and use the sample without pretreatment agent as a control. Mix and react for 1 min, then let stand for 30 min. The turbidity removal rate of the flowback fluid without agent is 41.7%, while the turbidity removal rate of the flowback fluid with pretreatment agent #1 reaches 73.9% (see Table 1 for the effect of agent #1). The precipitate after adding the pretreatment agent is dense and compact, while the precipitate after natural settling is flocculent and easily floats.

[0036] Example 2:

[0037] Preparation process of pretreatment agent: 10g of kaolin after grinding and sieving is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 500rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is mixed evenly with 3.3g of polyaluminum chloride at a mass ratio of 3:1 and then crushed and sieved by a pulverizer for later use.

[0038] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.1 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 69.4%, see the effect of agent #2 in Table 1, the precipitate is dense and compact, and forms irregular agglomerates.

[0039] Example 3:

[0040] Preparation process of pretreatment agent: 1g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 200rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is mixed evenly with 0.33g of polyaluminum chloride at a mass ratio of 3:1 and then crushed and sieved for later use.

[0041] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.15 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 73.9%, see the effect of agent #3 in Table 1, the precipitate is dense and compact, and it is an irregular agglomerate.

[0042] Example 4:

[0043] Preparation process of pretreatment agent: 1g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 200rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is mixed evenly with 0.33g of polyaluminum chloride at a mass ratio of 3:1 and then crushed and sieved for later use.

[0044] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.2 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 75.6%, see the effect of agent #4 in Table 1. The precipitate is dense and compact, and forms irregular agglomerates.

[0045] Example 5:

[0046] Preparation process of pretreatment agent: 1g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 200rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is then mixed evenly with 0.2g of polyaluminum chloride at a mass ratio of 5:1 and then pulverized and sieved for later use.

[0047] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.15 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 73.6%, see the effect of agent #5 in Table 1, the precipitate is dense and compact, and it is an irregular agglomerate.

[0048] Example 6:

[0049] Preparation process of pretreatment agent: 1g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 200rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is then mixed evenly with 0.2g of polyaluminum chloride at a mass ratio of 5:1 and then pulverized and sieved for later use.

[0050] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.2 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 75.5%, see the effect of agent #6 in Table 1. The precipitate is dense and compact, and forms irregular aggregates.

[0051] Example 7:

[0052] Preparation process of pretreatment agent: 1g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 200rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is then mixed evenly with 0.15g of polyaluminum chloride at a mass ratio of 7:1, pulverized and sieved by a pulverizer for later use.

[0053] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.15 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 73.5%, see the effect of agent #7 in Table 1. The precipitate is dense and compact, and forms irregular agglomerates.

[0054] Example 8:

[0055] Preparation process of pretreatment agent: 1g of kaolin that has been ground and sieved is mixed evenly with 0.1L of 1 mmol / L hydrochloric acid solution and stirred continuously at 200rpm until it becomes gel-like. After standing for 2 hours, it is dried in a vacuum drying oven at 105℃ and weighed to constant weight. The dried solid is then mixed evenly with 0.15g of polyaluminum chloride at a mass ratio of 7:1, pulverized and sieved by a pulverizer for later use.

[0056] Take 50 mL of simulated guar gum fracturing flowback fluid, add 0.2 g of pretreatment agent, mix and react for 1 min, let stand for 30 min, the turbidity removal rate of the flowback fluid can reach 76.7%, see the effect of agent #8 in Table 1. The precipitate is dense and compact, and forms irregular aggregates.

[0057] Table 1. Preparation conditions and treatment effects of the pharmaceutical preparation of the present invention.

[0058]

[0059]

[0060] Figure 1 This diagram illustrates the turbidity changes of the backflow solution with and without the added reagent in an embodiment of the present invention. Figure 1 In the treatment of the backflow liquid using the agent in this embodiment of the invention, the turbidity of the backflow liquid decreases sharply within 5 minutes of standing, then decreases slowly from 5 to 30 minutes, and finally reaches equilibrium after 30 to 60 minutes. The turbidity of the backflow liquid without the agent exceeds 200 mg / L after 30 minutes of standing, while the turbidity of the backflow liquid treated with the agent in this embodiment of the invention is approximately 100 mg / L less than that of the untreated backflow liquid after 30 minutes of standing. Therefore, the agent in this embodiment of the invention has a significant effect on the treatment of backflow liquid.

[0061] The rapid pretreatment agent, preparation method, and application of guar gum fracturing flowback fluid of the present invention have advantages such as being non-toxic and harmless, easy to store, convenient to add, fast flocculation speed, easy floc separation, and low cost. It is suitable for use in wastewater treatment plants or tanker transport, minimizing the damage to subsequent wastewater treatment equipment and the impact on the treatment system caused by guar gum fragments. The treatment method optimizes the dosage of the agent, reduces operating costs, and lowers the load on subsequent treatment processes.

[0062] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. The use of a guart fracturing flowback fluid rapid pretreatment agent in the treatment of guart fracturing flowback fluid, characterized in that, The preparation method of the medicament comprises: The acid, kaolin and polyaluminum chloride are configured in the proportion of mass fraction 0.025%-3.0%, 66.6-85% and 12.0%-33.3% respectively; The acid comprises hydrochloric acid, sulfuric acid and nitric acid, and the concentration of the acid solution is 1-10 mmol / L; The kaolin and the acid solution are uniformly mixed to form a mixed solution, and the mixed solution is stirred to be gelatinous; The gelatinous solution is dried for a predetermined time to obtain a premix; The premix and the polyaluminum chloride are uniformly mixed, crushed by a crusher and sieved to obtain the required medicament; the mass ratio of the premix to the polyaluminum chloride is 3-7:

1.

2. The application of claim 1, wherein The stirring speed of the mixed solution is 200-500 rpm.

3. The application of claim 1, wherein The drying temperature of the gelatinous solution is 105-120 DEG C.

4. The application of claim 1, wherein The predetermined time is 1-5 h.

5. The use according to claim 1, characterized in that, The mass ratio of the medicament to the flowback fluid is 1:250-500.

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