Instant high-temperature-resistant two-water-phase drag reduction agent, preparation method and application thereof

Abstract

The application discloses a kind of instant high-temperature-resistant double-water-phase drag reduction agent and its preparation method and application, by weight fraction, including the following components: inorganic salt 5~25 parts, water-soluble polymer 10~20 parts, water-soluble vinyl monomer containing sulfonic acid group or cyclic structure 10~20 parts, non-ionic water-soluble vinyl monomer 30~65 parts, initiator 0.01~0.5 parts and water 150~190 parts.The application adopts double dispersant system, which is beneficial to form polymer with high molecular weight and good stability, and all solvents used in the preparation method are clean water, which is environmentally friendly and low in cost;By controlling the content of suitable temperature-resistant groups, the application ensures the drag reduction effect of the synthesized polymer at high temperature, and the temperature resistance reaches 100 DEG C.

Description

Technical Field

[0001] This invention belongs to the field of drag-reducing agents for fracturing in shale oil and gas reservoir stimulation, specifically relating to a fast-dissolving, high-temperature resistant, two-phase aqueous drag-reducing agent, its preparation method, and its application. Background Technology

[0002] Unconventional oil and gas reservoirs are characterized by poor storage properties, low porosity, and low permeability. They generally lack natural industrial production and require reservoir stimulation techniques to connect natural fractures, forming complex fracture networks to create oil and gas channels and thus increase production. Therefore, permeability-enhancing stimulation is an essential step in the development of shale oil and gas resources.

[0003] Slickwater fracturing is a primary technology for the efficient development of shale reservoirs, and polymer drag reducers are its core additives. During injection, fracturing fluid generates significant turbulence, losing a large amount of kinetic energy that should have reached the reservoir, preventing the fracturing fluid from achieving its intended goals. The addition of polymer drag reducers can suppress turbulence and significantly reduce friction generated in long wellbores during hydraulic fracturing. Polyacrylamide is a primary drag reducer type for slickwater fracturing fluids due to its low cost and excellent drag-reducing effect. However, the high temperatures of deep shale reservoirs place higher demands on the temperature resistance of fracturing fluids, making the temperature resistance of drag reducers a crucial performance indicator for fracturing fluids. Existing drag-reducing agents are mainly powder drag-reducing agents, but their slow dissolution rate increases the pumping cost of fracturing fluid. Oil-in-water emulsion drag-reducing agents are suitable for continuous mixing fracturing operations, but they have disadvantages such as high production costs and significant environmental pollution. Moreover, drag-reducing agents are mostly used in aqueous solution form, and the introduction of dissolved oxygen from the air during solution preparation is unavoidable, leading to the oxidative degradation of polyacrylamide. High temperatures will exacerbate this process, causing damage and breakage of the polyacrylamide molecular chain structure, resulting in a significant decrease in the drag-reducing performance of polyacrylamide.

[0004] Therefore, it is necessary to develop a drag-reducing agent for slickwater fracturing fluid with good high-temperature resistance. Summary of the Invention

[0005] The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, its preparation method, and its application, thereby solving the technical problem of poor temperature resistance of drag-reducing agents in the prior art.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent:

[0007] By weight, it includes the following components:

[0008] The mixture contains 5-25 parts of inorganic salt, 10-20 parts of water-soluble polymer, 10-20 parts of water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures, 30-65 parts of nonionic water-soluble vinyl monomer, 0.01-0.5 parts of initiator, and 150-190 parts of water.

[0009] Furthermore, by weight, it includes the following components:

[0010] The mixture contains 8-20 parts of inorganic salt, 15-16 parts of water-soluble polymer, 13-15 parts of water-soluble vinyl monomers containing sulfonic acid groups or cyclic structures, 45-65 parts of nonionic water-soluble vinyl monomers, 0.03-0.2 parts of water-soluble initiator, and 160-185 parts of water.

[0011] Furthermore, the inorganic salt is at least one selected from sodium chloride, potassium chloride, potassium sulfate, ammonium sulfate, and sodium sulfate.

[0012] Furthermore, the water-soluble polymer is one of PEG6000, PEG8000, PEG10000 and PEG20000.

[0013] Further, the water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures is at least one of sodium 2-acrylamido-2-methylpropanesulfonate, sodium styrene sulfonate, sodium vinyl sulfonate, N-vinylpyrrolidone, and N-vinylimidazole;

[0014] The nonionic water-soluble vinyl monomer is a mixture of dimethylallylamide and acrylamide.

[0015] Furthermore, the initiator is a mixture of ammonium persulfate and sodium bisulfite.

[0016] This invention also provides a technical solution for preparing a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, comprising the following steps:

[0017] Under stirring, inorganic salts and water-soluble polymers are added to water to obtain solution A;

[0018] Then, water-soluble vinyl monomers containing sulfonic acid groups or cyclic structures and non-ionic water-soluble vinyl monomers are added to solution A and mixed evenly to obtain solution B;

[0019] After deoxygenating solution B, an initiator solution is added to initiate the reaction;

[0020] After the reaction is complete, cooling yields a fast-dissolving, high-temperature resistant aqueous drag-reducing agent.

[0021] Furthermore, the stirring speed is 100-500 r / min; deoxygenation is achieved by introducing nitrogen gas into solution B.

[0022] Furthermore, the initiator solution includes ammonium persulfate solution and sodium bisulfite solution, which are added to the deoxygenated solution B at intervals of 5–15 min; the reaction is carried out at 20–30 °C for 4–6 h.

[0023] The present invention also provides an application of the above-mentioned fast-dissolving, high-temperature resistant, two-phase drag-reducing agent in the preparation of water-based fracturing fluid.

[0024] Compared with the prior art, the beneficial effects of the present invention include:

[0025] (1) The present invention adopts a dual dispersant system—inorganic salt and water-soluble polymer. Inorganic salt has low cost and water-soluble polymer has good biocompatibility. The combination of the two dispersants makes the phase separation and dispersion effect of the reaction substrate better during the polymerization reaction, which is conducive to the preparation of high molecular weight and good stability aqueous two-phase emulsion drag reducing agent. The fast-dissolving and high-temperature resistant aqueous two-phase drag reducing agent obtained by the present invention is a milky white viscous liquid. It is fast-dissolving and fast-acting. No pre-mixed solution is required, and direct mixing fracturing operation can be realized without preparation.

[0026] (2) The method for preparing the two-phase drag reducer used in this invention removes the oil phase continuous phase in the synthesis of commonly used reverse emulsion drag reducers, and all solvents are water, which not only achieves the purpose of environmental protection but also reduces the material cost of drag reducer synthesis.

[0027] (3) This invention uses nonionic water-soluble vinyl monomers as the main body of the polymerization reaction to increase the polymer chain length and form a polymer with a certain molecular weight. On this basis, various water-soluble vinyl monomers containing sulfonic acid groups or cyclic structures are used as heat-resistant monomers. These heat-resistant monomers increase the resistance to molecular chain segment movement, weaken the thermal motion within and between molecules, and improve the rigidity of the molecular chain, thereby improving the heat resistance of the polymer. The contradiction between the rigidity of the polymer molecular chain and efficient drag reduction requires the selection of suitable heat-resistant monomers and the optimization of the side group ratio. This invention ensures the drag reduction effect of the synthesized polymer at high temperatures by controlling the content of suitable heat-resistant groups, with a temperature resistance of up to 100℃; the drag reduction rate can reach more than 70%. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0029] To address the shortcomings of existing powder drag reducers, such as slow dissolution rate and high production cost and significant environmental pollution of water-in-oil emulsion drag reducers, this invention provides a fast-dissolving, high-temperature resistant aqueous two-phase drag reducer. This fast-dissolving, high-temperature resistant aqueous two-phase drag reducer features high temperature resistance, low production cost, fast dissolution rate, and environmentally friendly synthesis process, making it suitable for deep shale oil and gas fracturing operations.

[0030] A fast-dissolving, high-temperature resistant aqueous drag-reducing agent comprises the following components in parts by weight: 5-25 parts of a water-soluble inorganic salt, 10-20 parts of a water-soluble polymer, 10-20 parts of a water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures, 30-65 parts of a nonionic water-soluble vinyl monomer, 0.01-0.5 parts of a water-soluble redox initiator, and 150-190 parts of water.

[0031] Preferably, the aqueous drag-reducing agent comprises the following components in parts by weight: 8-20 parts of a water-soluble inorganic salt, 15-16 parts of a polyethylene glycol dispersant, 13-15 parts of a water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures, 45-65 parts of a nonionic water-soluble vinyl monomer, 0.03-0.2 parts of a water-soluble redox initiator, and 160-185 parts of water.

[0032] Preferably, the water-soluble inorganic salt is at least one selected from sodium chloride, potassium chloride, potassium sulfate, ammonium sulfate, and sodium sulfate.

[0033] Preferably, the polyethylene glycol dispersant is one of polyethylene glycol 6000 (PEG6000), polyethylene glycol 8000 (PEG8000), polyethylene glycol 10000 (PEG10000), and polyethylene glycol 20000 (PEG20000).

[0034] Preferably, the water-soluble vinyl monomer containing a sulfonic acid group or a cyclic structure is at least one selected from sodium 2-acrylamido-2-methylpropanesulfonate (AMPS-Na), sodium styrene sulfonate (SSS-Na), sodium vinyl sulfonate (VS-Na), N-vinylpyrrolidone (NVP), and N-vinylimidazole (NVL). It is understood that when there are two or more water-soluble vinyl monomers containing a sulfonic acid group or a cyclic structure, they can be a mixture in any proportion.

[0035] Preferably, the nonionic water-soluble vinyl monomer is a mixture of dimethylallylamide (i.e., dimethylacrylamide) and acrylamide, wherein the mass ratio of dimethylallylamide to acrylamide is 1:4 to 6.

[0036] Preferably, the initiator of the water-soluble redox initiation system is a mixture of ammonium persulfate and sodium bisulfite in a mass ratio of 1:1.

[0037] The preparation method of the fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent includes the following steps:

[0038] (1) Under stirring, inorganic salt and water-soluble polymer are added to water to obtain dispersant solution A;

[0039] (2) Under stirring, water-soluble vinyl monomers containing sulfonic acid groups or cyclic structures and non-ionic water-soluble vinyl monomers are added sequentially to solution A obtained in step (1) and mixed evenly to obtain solution B.

[0040] (3) Deoxygenate the solution B obtained in step (2) with nitrogen, then heat it to 20-30°C, add an initiator, and carry out the reaction;

[0041] (4) After the reaction is complete, the mixture is naturally cooled to room temperature to obtain the aqueous drag reducer.

[0042] Preferably, the stirring speed in step (1) is 100-500 r / min, and more preferably 300 r / min.

[0043] Preferably, the stirring speed in step (2) is 100-500 r / min, and more preferably 300 r / min.

[0044] Preferably, the nitrogen deoxygenation time in step (3) is 30 minutes.

[0045] Preferably, the initiator in step (3) is ammonium persulfate and sodium bisulfite, which are added to the reaction system in two portions in aqueous solutions of 0.005 to 0.01 g / mL, with an interval of 5 to 15 min between the two additions, more preferably 5 min.

[0046] Preferably, the reaction time in step (3) is 4 to 6 hours.

[0047] The fast-dissolving, high-temperature resistant, aqueous drag-reducing agent of this invention is a milky white, viscous, homogeneous liquid.

[0048] The fast-dissolving, high-temperature resistant, aqueous two-phase drag-reducing agent is used as a drag-reducing agent for water-based fracturing fluids.

[0049] The present invention will be further described in detail below through specific embodiments.

[0050] Example 1

[0051] A method for preparing a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, comprising the following steps:

[0052] (1) Add 15g sodium chloride and 15g PEG 6000 to 180g water under stirring, and stir for 30min to obtain a dispersant solution;

[0053] (2) Under stirring, 15g AMPS-Na, 30g acrylamide and 7.5g dimethylallylamide are added to the solution obtained in step (1) in sequence and mixed evenly to obtain a solution;

[0054] (3) Deoxygenate the solution obtained in step (2) with nitrogen for 30 min, then heat it to 25°C. Dissolve 0.015 g of ammonium persulfate and 0.015 g of sodium bisulfite in 1.5 g of water respectively. First, add the ammonium persulfate solution dropwise to the reaction solution, completing the addition within 1 min, and then proceed with the reaction after 5 min. Next, add the sodium bisulfite solution dropwise to the reaction solution, completing the addition within 1 min, and then proceed with the reaction.

[0055] (4) After the solution in step (3) reacts for 6 hours, it is naturally cooled to room temperature to obtain the aqueous drag-reducing agent.

[0056] Example 2

[0057] A method for preparing a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, comprising the following steps:

[0058] (1) Add 10g potassium chloride, 10g sodium sulfate and 15g PEG 8000 to 140g water under stirring, and stir for 30min to obtain a dispersant solution;

[0059] (2) Under stirring, 14g SSS-Na, 51g acrylamide and 8.5g dimethylallylamide were added to the solution obtained in step (1) in sequence and mixed evenly to obtain a solution;

[0060] (3) Deoxygenate the solution obtained in step (2) with nitrogen for 30 min, then heat it to 30°C. Dissolve 0.1 g of ammonium persulfate and 0.1 g of sodium bisulfite in 20 g of water respectively. First, add the ammonium persulfate solution dropwise to the reaction solution, completing the addition within 3 min, and then proceed with the reaction after 5 min. Then, add the sodium bisulfite solution dropwise to the reaction solution, completing the addition within 3 min, and then proceed with the reaction.

[0061] (4) After the solution in step (3) reacts for 4 hours, it is naturally cooled to room temperature to obtain the aqueous drag-reducing agent.

[0062] Example 3

[0063] A method for preparing a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, comprising the following steps:

[0064] (1) Add 8g sodium sulfate and 15g PEG 10000 to 140g water under stirring, and stir for 30min to obtain a dispersant solution;

[0065] (2) Under stirring, 13g NVP, 42g acrylamide and 7g dimethylallylamide were added to the solution obtained in step (1) in sequence and mixed evenly to obtain a solution.

[0066] (3) Deoxygenate the solution obtained in step (2) with nitrogen for 30 min, then heat it to 25°C. Dissolve 0.05 g of ammonium persulfate and 0.05 g of sodium bisulfite in 10 g of water respectively. First, add the ammonium persulfate solution dropwise to the reaction solution, completing the addition within 3 min, and then proceed with the reaction after 5 min. Then, add the sodium bisulfite solution dropwise to the reaction solution, completing the addition within 3 min, and then proceed with the reaction.

[0067] (4) After the solution in step (3) reacts for 5 hours, it is naturally cooled to room temperature to obtain the aqueous drag-reducing agent.

[0068] Example 4

[0069] A method for preparing a fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, comprising the following steps:

[0070] (1) Add 10g of ammonium sulfate and 16g of PEG 20000 to 140g of water under stirring, and stir for 30min to obtain a dispersant solution;

[0071] (2) Under stirring, 5g NVL, 8g VS-Na, 42g acrylamide and 7g dimethylallylamide were added to the solution obtained in step (1) in sequence and mixed evenly to obtain a solution;

[0072] (3) Deoxygenate the solution obtained in step (2) with nitrogen for 30 min, then heat it to 25°C. Dissolve 0.05 g of ammonium persulfate and 0.05 g of sodium bisulfite in 10 g of water respectively. First, add the ammonium persulfate solution dropwise to the reaction solution, completing the addition within 3 min, and then proceed with the reaction after 5 min. Then, add the sodium bisulfite solution dropwise to the reaction solution, completing the addition within 3 min, and then proceed with the reaction.

[0073] (4) After the solution in step (3) reacts for 5 hours, it is naturally cooled to room temperature to obtain the aqueous drag-reducing agent.

[0074] Comparative Example 1

[0075] Comparative Example 1 is basically the same as Example 1, except that the dispersant added in step (1) is PEG2000, and the amount added is 15g.

[0076] Comparative Example 2

[0077] Comparative Example 2 is basically the same as Example 2, except that only water-soluble polymer PEG 8000 is added in step (1), and inorganic salts are removed.

[0078] Comparative Example 3

[0079] Comparative Example 3 is basically the same as Example 3, except that no water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures was added in step (2).

[0080] Comparative Example 4

[0081] Comparative Example 4 is basically the same as Example 1, except that the amount of AMPS-Na in step (2) is adjusted to 25g.

[0082] The results showed that excessive use of AMPS-Na increased the number of anions in the polymer side chains, enhanced the electrostatic compatibilization effect, improved the solubility of the polymer in the continuous phase (polyethylene glycol + inorganic salt + water), made it difficult to precipitate and separate the phases, resulting in the inability to form an aqueous two-phase emulsion or a decrease in emulsion stability, and a decrease in the drag reduction performance of the product.

[0083] Performance testing:

[0084] The drag-reducing agents prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to performance testing, and the specific methods are as follows:

[0085] Referring to Chapter 7.8 of the Chinese energy industry standard "NB / T 14003.1-2015 Shale Gas Fracturing Fluid Part 1: Slickwater Performance Indicators and Evaluation Methods", the drag reduction rate of a 0.1 wt% sample added online was tested.

[0086] Table 1 Performance tests of drag-reducing agents prepared in Examples 1-4 and Comparative Examples 1-3 of the present invention

[0087]

[0088] As shown in Table 1, the drag-reducing agents prepared in the embodiments of the present invention can achieve drag reduction rates of over 70% at room temperature, 50°C, 75°C, and 95°C. However, in the comparative examples, changing the type of water-soluble polymer, removing inorganic salts, and removing water-soluble vinyl monomers containing sulfonic acid groups or cyclic structures all significantly affect the performance of the drag-reducing agents. For example, the molecular weight of the dispersant added in Comparative Example 1 is too low, resulting in poor phase separation and the inability to form a high molecular weight, stable polymer emulsion, thus deteriorating the drag reduction effect of the polymer. In Comparative Example 2, the removal of inorganic salts weakens the electrostatic shielding effect on the polymer molecular chains, resulting in a low molecular weight product that cannot form a stable polymer emulsion, thereby deteriorating the drag reduction effect. The drag reduction rate of Comparative Example 3 at room temperature is the same as or even slightly better than that of the embodiments, but the drag reduction rate drops sharply after heating, indicating poor temperature resistance. Compared with the comparative examples, the drag-reducing agent in the present invention has a significant temperature resistance effect and can meet the requirements of fracturing operations in deep shale oil and gas.

[0089] Meanwhile, the Chinese energy industry standard "NB / T 14003.1-2015 Shale Gas Fracturing Fluid Part 1: Slickwater Performance Indicators and Evaluation Methods" requires that when the operating temperature is above 100℃, the test temperature should be selected at 95℃. According to the test results in Table 1, the drag reduction rate of Examples 1-4 of the present invention can reach more than 70%, and the drag reduction rate decreases only slightly with increasing temperature. Therefore, the drag reduction agent obtained by the present invention can withstand temperatures up to 100℃.

[0090] The above description is merely a preferred embodiment of the present invention. The above examples do not limit the substantive content of the present invention in any way. Any simple modifications or variations made by those skilled in the art to the above specific embodiments based on the technical essence of the present invention after reading this specification, as well as equivalent embodiments that may be changed or modified using the disclosed technical content, shall still fall within the scope of the technical solution of the present invention and shall not depart from the essence and scope of the present invention.

Claims

1. A fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent, characterized in that, By weight, it consists of the following components: The mixture contains 8-20 parts of inorganic salt, 15-16 parts of water-soluble polymer, 13-15 parts of water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures, 45-65 parts of nonionic water-soluble vinyl monomer, 0.03-0.2 parts of water-soluble initiator, and 160-185 parts of water. The inorganic salt is at least one of sodium chloride, potassium chloride, potassium sulfate, ammonium sulfate, and sodium sulfate; The water-soluble polymer is one of PEG6000, PEG8000, and PEG10000; The water-soluble vinyl monomer containing sulfonic acid groups or cyclic structures is at least one of sodium 2-acrylamido-2-methylpropanesulfonate, sodium styrene sulfonate, sodium vinyl sulfonate, N-vinylpyrrolidone, and N-vinylimidazolium. The nonionic water-soluble vinyl monomer is a mixture of dimethylallylamide and acrylamide, wherein the mass ratio of dimethylallylamide to acrylamide is 1:4 to 6. The initiator is a mixture of ammonium persulfate and sodium bisulfite; The preparation method of the fast-dissolving, high-temperature resistant aqueous two-phase drag-reducing agent includes the following steps: Under stirring, inorganic salts and water-soluble polymers are added to water to obtain solution A; Then, water-soluble vinyl monomers containing sulfonic acid groups or cyclic structures and non-ionic water-soluble vinyl monomers are added to solution A and mixed evenly to obtain solution B; After deoxygenating solution B, an initiator solution is added to initiate the reaction; After the reaction is complete, cooling yields a fast-dissolving, high-temperature resistant aqueous drag-reducing agent. The stirring speed is 100-500 r / min; deoxygenation is achieved by introducing nitrogen gas into solution B. The initiator solution includes ammonium persulfate solution and sodium bisulfite solution. The ammonium persulfate solution and sodium bisulfite solution are added to the deoxygenated solution B at intervals of 5 to 15 minutes. The reaction is carried out at 20 to 30°C for 4 to 6 hours.

2. The application of the fast-dissolving, high-temperature resistant, two-phase drag-reducing agent as described in claim 1 in the preparation of water-based fracturing fluid.

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