Low-viscosity nano drag reducer applicable to tight oil reservoir'fracturing-three production 'integrated process as well as preparation method and application of low-viscosity nano drag reducer

Abstract

The invention relates to a low-viscosity nano drag reducer applicable to a tight oil reservoir'fracturing-three-production 'integrated process as well as a preparation method and application of the low-viscosity nano drag reducer. The low-viscosity nano drag reducer comprises the following components in percentage by weight: 10-40% of a water-soluble monomer, 10-30% of a nonionic vinyl monomer and 10-50% of a cosolvent, 5-25% of inorganic salt; 0.01%-0.3% of an initiator; and the balance of water. The low-viscosity nano drag reducer suitable for the tight oil reservoir fracturing-three-production integrated process has a nanoscale molecular beam size, so that fracturing fluid can penetrate into a micro-nanoscale pore throat in a tight oil reservoir, and effective utilization of oil and gas resources is realized; the fracturing fluid prepared from the low-viscosity nano drag reducer has the characteristic of low viscosity, so that the fracturing fluid has small damage to a reservoir after gel breaking and flowback, and continuous production of oil and gas resources is facilitated.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil and gas exploration and development, in particular to a low-viscosity nano drag-reducing agent suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, a preparation method and application. BACKGROUND

[0002] The reservoir matrix of a tight oil reservoir is generally low in porosity (<10%) and permeability (<0.1 mD), and micro-nano pore throats are developed in the reservoir, so it is difficult to produce oil and gas, and the natural production capacity is low. Therefore, the reservoir must be reformed to increase production, so as to realize efficient development of the tight oil reservoir. At present, the mainstream technology is a "fracturing-three extraction" integrated process of volume fracturing and tertiary oil recovery. On the basis of generating artificial fractures and connecting natural fractures by fracturing fluid, the oil displacement agent continuously penetrates into the far well zone and the micro-pore channel of the reservoir matrix, increases the swept volume, improves the formation energy, and finally improves the recovery efficiency.

[0003] The fracturing fluid commonly used in the "fracturing-three extraction" integrated process is high-viscosity fracturing fluid, which realizes the functions of filtration loss reduction, pressure building for fracture creation, sand carrying, etc. by using its high viscosity. However, the high viscosity also causes the fracturing fluid to have a large molecular beam diameter, resulting in a large flow resistance in the formation, and it is difficult to enter the micro-nano pore throat and matrix. Therefore, there are problems of high initial production, rapid decline, and low recovery efficiency. The high-viscosity fracturing fluid is not completely broken, and residues are left in the formation, which reduces the permeability of the reservoir and causes damage to the reservoir. Therefore, a suitable fracturing fluid system should be selected to improve the fracturing effect while avoiding secondary damage to the formation.

[0004] In the prior art, a nano thickening agent is synthesized by using 2-acrylamide-2-methylpropane sulfonic acid. Although the synthesized thickening agent has a nano-level molecular beam size, practical application shows that the resistance of the fracturing fluid entering the nano-level pore throat is much greater than that of the main fracture, and the fracturing fluid flows a lot to the main fracture, so it is difficult to form a complex fracture network. SUMMARY

[0005] The purpose of the present application is to provide a low-viscosity nano drag-reducing agent suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, which solves the problem that the low-viscosity nano slick water fracturing fluid developed in the prior art has a much greater resistance to entering the nano-level pore throat than the main fracture, and the fracturing fluid flows a lot to the main fracture, so it is difficult to form a complex fracture network.

[0006] To solve the above technical problems, the present application adopts the following technical solutions: A low-viscosity nano drag-reducing agent suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, the weight percentage of each component is as follows: water-soluble monomer: 10-40%; non-ionic vinyl monomer: 10-30%; co-solvent: 10-50%; inorganic salt: 5-25%; initiator: 0.01-0.3%; the balance is water.

[0007] Further, the water-soluble monomer is at least one of acrylic acid, acrylic acid salt, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid sodium, styrene sulfonic acid sodium, vinyl sulfonic acid sodium, and N-vinyl pyrrolidone.

[0008] Further, the non-ionic vinyl monomer is at least one of N,N-dimethyl acrylamide, N-phenyl maleimide, and N-hydroxymethyl acrylamide.

[0009] Further, the co-solvent is at least one of isopropyl alcohol, ethylene glycol monomethyl ether, dimethylformamide, and methyl isobutyl ketone.

[0010] Further, the inorganic salt is at least one of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, ammonium carbonate, potassium sulfate, sodium sulfate, and ammonium sulfate.

[0011] Further, the initiator is at least one of an azo initiator, a peroxide initiator, or a persulfate initiator.

[0012] Another object of the present application is to provide a preparation method of the low-viscosity nano drag reducer, comprising the following steps: S1. Under an inert gas atmosphere and stirring, sequentially adding water-soluble vinyl monomers and inorganic salts into water to obtain solution A; S2. Continuously adding non-ionic vinyl monomers and co-solvents into solution A to obtain solution B; S3. After solution B is heated, adding an initiator solution to perform a reaction; S4. When the solution becomes viscous, stopping stirring, removing the inert gas atmosphere, and sealing the reaction to obtain the low-viscosity nano drag reducer.

[0013] Further, in S1, the stirring rate of the stirring state is 100-600 rpm, and the time of the inert gas atmosphere is 15-60 min.

[0014] Further, in S3, the initiator solution comprises a potassium persulfate solution and a sodium bisulfite solution, the mass ratio is 1:1, the two are added with an interval of 5-15 min, the reaction temperature is 30-50℃, and the reaction time is 4-6 h.

[0015] The present application also provides an application of the low-viscosity nano drag reducer in a "fracturing-three extraction" integrated process of a compact oil reservoir.

[0016] Compared with the prior art, the present application has the following beneficial effects: (1) The low viscosity nanometer drag reduction agent provided by the application has a nanometer molecular beam size, which ensures that the fracturing fluid can enter the micro-nanometer pore throat in the tight oil reservoir, and realizes effective use of oil and gas resources. (2) The fracturing fluid prepared by the low viscosity nanometer drag reduction agent has low viscosity, which causes less damage to the reservoir after the fracturing fluid is broken and returned, and is beneficial to the continuous production of oil and gas resources. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 A graph showing the change of the drag reduction rate of the drag reduction agent with time. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the application clearer and more apparent, the following examples are used to further illustrate the application. It should be understood that the specific examples described herein are only used to explain the application, and are not used to limit the application.

[0019] The application provides a low viscosity nanometer drag reduction agent suitable for a "fracturing-three mining" integrated process of a tight oil reservoir, a preparation method and application, which has the following advantages: The application provides a low viscosity nanometer drag reduction agent suitable for a "fracturing-three mining" integrated process of a tight oil reservoir, a preparation method and application, which has a nanometer molecular beam size, ensures that the fracturing fluid can enter the micro-nanometer pore throat in the tight oil reservoir, has low viscosity, causes less damage to the reservoir after the fracturing fluid is broken and returned, and is suitable for the "fracturing-three mining" integrated process of the tight oil reservoir.

[0020] According to one aspect of the application, the application provides the following technical scheme: A low viscosity nanometer drag reduction agent suitable for a "fracturing-three mining" integrated process of a tight oil reservoir, raw materials including the following components (weight percentage): Water-soluble monomer: 10-40%; Non-ionic vinyl monomer: 10-30%; Cosolvent: 10-50%; Inorganic salt: 5-25%; Initiator: 0.01-0.3%; The balance is water; Preferably, the water-soluble monomer is at least one of acrylic acid, acrylic acid salt, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid sodium, styrene sulfonic acid sodium, vinyl sulfonic acid sodium, and N-vinyl pyrrolidone.

[0021] The non-ionic vinyl monomer is at least one of N,N-dimethyl acrylamide, N-phenyl maleimide, and N-hydroxymethyl acrylamide.

[0022] The cosolvent is at least one of isopropyl alcohol, ethylene glycol monomethyl ether, dimethylformamide, and methyl isobutyl ketone.

[0023] The inorganic salt is at least one of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, ammonium carbonate, potassium sulfate, sodium sulfate, and ammonium sulfate.

[0024] The initiator is at least one of an azo initiator, a peroxide initiator, or a persulfate initiator, and when the initiator is a redox system, the mass ratio of the oxidant to the reducing agent is 1:1.

[0025] According to another aspect of the present application, the present application provides the following technical solutions: A preparation method of a low-viscosity nano drag-reducing agent suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, comprising the following steps: S1. In an inert gas atmosphere and under stirring, water-soluble vinyl monomers and inorganic salts are sequentially added to water to obtain solution A; S2. Non-ionic vinyl monomers and a cosolvent are continuously added to solution A, and the mixture is uniformly mixed to obtain solution B; S3. After solution B is warmed, an initiator solution is added, and a reaction is performed; S4. When the solution becomes viscous, stirring is stopped, the inert gas atmosphere is removed, and a sealed reaction is obtained.

[0026] Preferably, the inert gas atmosphere in step S1 is nitrogen, the stirring rate is 100-600 rpm, and further preferably 250 rpm, and the time of the inert gas atmosphere is 15-60 min.

[0027] Preferably, the initiator in step S3 is potassium persulfate and sodium bisulfite, the mass ratio of the two is 1:1, and the two are added with an interval of 5-15 min, and further preferably 10 min.

[0028] Preferably, in step S3, the reaction is performed at a reaction temperature of 30-50℃.

[0029] Preferably, in step S3, the reaction time of the sealed reaction is 4-6 h.

[0030] Preferably, in step S4, the time for removing the inert gas atmosphere is 15-60 min, and further preferably 30 min.

[0031] The present application is further described below in conjunction with specific embodiments.

[0032] Example 1: A preparation method of a low-viscosity nano drag-reducing agent suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, comprising the following steps: (1) Under the inert gas atmosphere and stirring state, 5 g of acrylamide, 5 g of sodium vinyl sulfonate and 10 g of sodium chloride were sequentially added into 30.1 g of water to obtain solution A; (2) 10 g of N,N-dimethyl acrylamide and 20 g of ethylene glycol monomethyl ether were continuously added into solution A to obtain solution B; (3) Solution B was heated to 40℃, 0.15 g of potassium persulfate and 0.15 g of sodium bisulfite were respectively dissolved in 9.8 g of water, the potassium persulfate solution was first added into solution B, and the dropping was completed within 3 min, 10 min later, the sodium bisulfite solution was added dropwise, and the dropping was completed within 3 min, and the reaction was carried out; (4) When the solution became viscous, the stirring was stopped, the inert gas atmosphere was removed, and the low-viscosity nano drag reducer was obtained after sealing for 4 h.

[0033] Then the obtained low-viscosity nano drag reducer was used in the subsequent JHJZ-I high temperature and high pressure dynamic drag reduction evaluation system, a 2.5 m long and 10 mm inner diameter stainless steel pipe was used, the change of the drag reduction rate of 0.1% drag reducer with time under the displacement of 30 L / min was tested and analyzed, and the results were shown in Figure 1 .

[0034] Example 2: A preparation method of a low-viscosity nano drag reducer suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, the steps were as follows: (1) Under the inert gas atmosphere and stirring state, 5 g of acrylamide, 5 g of 2-acrylamide-2-methylpropanesulfonic acid sodium and 5 g of potassium chloride were sequentially added into 40.1 g of water to obtain solution A; (2) 10 g of N-phenylmaleimide and 5 g of dimethylformamide were continuously added into solution A to obtain solution B; (3) Solution B was heated to 30℃, 0.05 g of potassium persulfate and 0.05 g of sodium bisulfite were respectively dissolved in 14.9 g of water, the potassium persulfate solution was first added into solution B, and the dropping was completed within 3 min, 15 min later, the sodium bisulfite solution was added dropwise, and the dropping was completed within 3 min, and the reaction was carried out; (4) When the solution became viscous, the stirring was stopped, the inert gas atmosphere was removed, and the low-viscosity nano drag reducer was obtained after sealing for 5 h.

[0035] Then the obtained low-viscosity nano drag reducer was used in the subsequent JHJZ-I high temperature and high pressure dynamic drag reduction evaluation system, a 2.5 m long and 10 mm inner diameter stainless steel pipe was used, the change of the drag reduction rate of 0.1% drag reducer with time under the displacement of 30 L / min was tested and analyzed, and the results were shown in Figure 1 .

[0036] Example 3: A preparation method of a low-viscosity nano drag-reducing agent suitable for a "fracturing-three extraction" integrated process of a tight oil reservoir, steps as follows: (1) under the inert gas atmosphere and stirring state, 15g acrylamide, 5g N-vinyl pyrrolidone and 5g sodium sulfate are sequentially added into 30g water to obtain solution A; (2) 10g N-methylol acrylamide and 5g methyl isobutyl ketone are continuously added into solution A, and mixed uniformly to obtain solution B; (3) solution B is heated to 50 DEG C, 0.1g potassium persulfate and 0.1g sodium bisulfite are respectively dissolved in 14.9g water, the potassium persulfate solution is first added into solution B, and the addition is completed within 3min, 5min later, the sodium bisulfite solution is added, and the addition is completed within 3min, and the reaction is carried out; (4) when the solution becomes viscous, the stirring is stopped, the inert gas atmosphere is removed, and the low-viscosity nano drag-reducing agent is obtained after sealing for 6h.

[0037] Then the obtained low-viscosity nano drag-reducing agent is used in the subsequent JHJZ-I high-temperature and high-pressure dynamic drag-reducing evaluation system, a 2.5m long and 10mm inner diameter stainless steel pipe is adopted, the drag-reducing rate of 0.1% drag-reducing agent under 30L / min displacement is analyzed with time, and the results are shown in Figure 1 .

[0038] In summary, referring to Figure 1 It is shown that the drag-reducing agents prepared by example 1 to example 3 are respectively used in the JHJZ-I high-temperature and high-pressure dynamic drag-reducing evaluation system, the drag-reducing rates are all 75.8% at 70s, and are all above 83.4% at 90s, and the drag-reducing rates are stable until the experiment is finished after 5min, that is, the system has the abilities of instant dissolution and high-efficiency drag reduction, does not need to be prepared in advance, can be directly pumped into a sand mixing vehicle, meets the requirements of continuous mixing and preparation on site, and further, the low-viscosity nano drag-reducing agent has the nano molecular beam size, guarantees that the fracturing fluid can enter the micro-nano pore throat in the tight oil reservoir, and realizes the effective use of oil and gas resources; meanwhile, the fracturing fluid prepared by the low-viscosity nano drag-reducing agent has the low-viscosity characteristics, so that the reservoir damage is small after the fracturing fluid is broken and flowed back, and the continuous production of oil and gas resources is facilitated.

[0039] Although the present application has been described with reference to explanatory examples thereof, it is to be understood that many other modifications can be made by those skilled in the art which fall within the principles and spirit of the disclosure. More specifically, many changes can be made in the composition of matter and / or methods employed in carrying out the subject combination layout within the scope of the disclosure and the claims attached hereto. In addition, still other purposes, as well as much of the general or specific details of the examples can be readily apparent to those skilled in the art, while the like make no contribution to the spirit and scope of the examples.

Claims

1. A low viscosity nano-drag reducer suitable for "fracturing-triple production" integrated process of tight oil reservoirs, characterized in that: The weight percentage of each component is: water-soluble monomer: 10-40%; Non-ionic vinyl monomer: 10-30%; Co-solvent: 10-50%; Inorganic salt: 5-25%; Initiator: 0.01-0.3%; The balance is water.

2. The low viscosity nano-drag reducer suitable for the "fracturing-three production" integrated process of tight oil reservoirs according to claim 1, characterized in that: The water-soluble monomer is at least one of acrylic acid, acrylic acid salt, acrylamide, 2-acrylamide-2-methylpropane sulfonic acid sodium, styrene sulfonic acid sodium, vinyl sulfonic acid sodium, and N-vinyl pyrrolidone. 3.The low viscosity nano-drag reducer suitable for the "fracturing-three production” integrated process of tight oil reservoirs according to claim 1, characterized in that: The non-ionic vinyl monomer is at least one of N,N-dimethyl acrylamide, N-phenyl maleimide, and N-hydroxymethyl acrylamide.

4. The low viscosity nano-drag reducer suitable for the "fracturing-three production" integrated process of tight oil reservoirs according to claim 1, characterized in that: The co-solvent is at least one of isopropyl alcohol, ethylene glycol monomethyl ether, dimethyl formamide, and methyl isobutyl ketone.

5. The low viscosity nano-drag reducer suitable for "fracturing-three production" integrated process of tight oil reservoirs according to claim 1, characterized in that: The inorganic salt is at least one of sodium chloride, potassium chloride, sodium carbonate, potassium carbonate, ammonium carbonate, potassium sulfate, sodium sulfate, and ammonium sulfate.

6. The low viscosity nano drag reducer suitable for "fracturing-triple recovery" integrated process of tight oil reservoirs according to claim 1, characterized in that: The initiator is at least one of azo, peroxide, or persulfate initiator.

7. A method for preparing a low viscosity nano-drag reducer suitable for "fracking- EOR" integrated process in tight oil reservoirs according to any one of claims 1-6, characterized in that: The method comprises the following steps: S1. Under an inert gas atmosphere and stirring, water-soluble vinyl monomer and inorganic salt are sequentially added to water to obtain solution A; S2. Non-ionic vinyl monomer and co-solvent are continuously added to solution A, and mixed uniformly to obtain solution B; S3. After solution B is warmed, initiator solution is added, and reaction is performed; S4. When the solution becomes viscous, stirring is stopped, the inert gas atmosphere is removed, and the reaction is sealed to obtain the product.

8. The method according to claim 7, wherein the method is characterized in that: In S1, the stirring rate of the stirring state is 100-600 rpm; the time of the inert gas atmosphere is 15-60 min.

9. The method for preparing a low-viscosity nano drag reducer suitable for the integrated process of "fracturing-three-recovery" in tight oil reservoirs according to claim 7, characterized in that: In S3, the initiator solution comprises potassium persulfate solution and sodium bisulfite solution, with a mass ratio of 1:1, and the two are added with an interval of 5-15 min; the reaction temperature is 30-50°C, and the reaction time is 4-6 h.

10. The application of the low-viscosity nano-drag-reducing agent prepared by the method of any one of claims 1-6 or any one of claims 8-9 in the "fracturing-three extraction" integrated process of compact oil reservoirs.

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