A clean water fracturing gas suspended proppant and a preparation method thereof

Abstract

The present disclosure provides a clean water fracturing gas suspended proppant and a preparation method thereof, and belongs to the technical field of proppant preparation. The preparation method comprises the following steps: mixing polyethylene oxide, polyacrylamide, a surfactant and potassium chloride, and then grinding them into powder to obtain a mixed powder; mixing quartz sand and an ethanol solution of perfluorosilane coupling agent, and stirring them uniformly, and then drying them in an oven, and then heating them to a preset temperature, and then stirring while adding the mixed powder to coat the mixed powder on the surface of the quartz sand to obtain the clean water fracturing gas suspended proppant. The proppant can be stably suspended in clean water and fracturing flowback water, so that the requirement for the viscosity of fracturing fluid is not too high, and the preparation of fracturing fluid and the configuration of equipment are simplified; while the suspension stability is improved, the fracturing construction efficiency is improved, the operation cost is reduced, and the secondary damage to the reservoir is reduced.

Description

Technical Field

[0001] This disclosure belongs to the field of proppant preparation technology, specifically relating to a water fracturing gas suspension proppant and its preparation method. Background Technology

[0002] Hydraulic fracturing, as an important production enhancement measure to improve the productivity of oil and gas wells and the injection capacity of water wells, has been widely used in the large-scale development of low-permeability oil and gas reservoirs. Its basic principle is to create artificial fractures in the formation using a pumping pressure higher than the formation fracturing pressure, and then fill these fractures with proppant, thereby significantly improving the fracture conductivity and ultimately increasing productivity or injection capacity. In this process, the core role of the proppant is to maintain effective fracture connectivity. Typically, the fracturing fluid relies on a high-viscosity thickener to carry the proppant and deliver it to the artificial fractures. Even after the fracturing is completed, if the bottomhole pressure drops below the formation closure pressure, the fractures can still maintain conductivity under the support of the proppant.

[0003] Currently, commonly used proppants include quartz sand, ceramsite, and film-coated proppants. Quartz sand is widely used due to its abundant resources and low price, but its insufficient strength and brittleness limit its application in high-pressure closed reservoirs. Ceramsite proppants have higher strength and are suitable for deep and ultra-deep high-temperature and high-pressure formations, but their high density places extremely high demands on the viscosity and proppant-carrying capacity of the fracturing fluid. To ensure smooth operation, various additives such as thickeners, drag reducers, and anti-swelling agents are often added to the fracturing fluid, along with corresponding preparation and construction equipment. This not only complicates the construction process and increases costs but also causes reservoir damage due to incomplete fracturing fluid flowback, reducing the effectiveness of the fracturing. While existing self-suspended proppants can improve proppant-carrying performance to some extent, their suspension stability is insufficient and their function is limited, making it difficult to meet the fracturing requirements under deep and complex reservoir conditions. Summary of the Invention

[0004] This disclosure aims to at least solve one of the technical problems existing in the prior art, namely, the high density and fast settling speed of the proppant, which requires high viscosity fracturing fluid to achieve effective carrying, and to provide a water fracturing air suspension proppant and its preparation method.

[0005] One aspect of this disclosure provides a method for preparing a water fracturing gas suspension proppant, the method comprising: Polyethylene oxide, polyacrylamide, surfactant, and potassium chloride are mixed and then ground into powder to obtain a mixed powder. Quartz sand and an ethanol solution of perfluorosilane coupling agent are mixed and stirred evenly, then dried in an oven. After heating to a preset temperature, the mixed powder is added while stirring to coat the surface of the quartz sand, thus obtaining a water fracturing gas suspension proppant.

[0006] Optionally, the content ratio of the polyethylene oxide, the polyacrylamide, the surfactant and the potassium chloride is (1-3):(0.5-1.5):(0.05-0.15):(18-22).

[0007] Optionally, the polyethylene oxide has a molecular weight of 5-10 million.

[0008] Optionally, the polyacrylamide has a molecular weight of 5-10 million.

[0009] Optionally, the surfactant includes any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, fatty acid salts, alkylphenol polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers, and hexadecyltrimethylammonium bromide.

[0010] Optionally, the content ratio of the quartz sand, the ethanol solution of the perfluorosilane coupling agent, and the mixed powder is 1000:(10-80):(13-15).

[0011] Optionally, the perfluorosilane coupling agent is any one of perfluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, and heptadecafluorodecyltriethoxysilane.

[0012] Optionally, in the ethanol solution of the perfluorosilane coupling agent, the mass of the perfluorosilane coupling agent accounts for 0.5-5% of the total mass of the ethanol solution of the perfluorosilane coupling agent.

[0013] Optionally, the preset temperature is 130-150℃.

[0014] Optionally, the proppant has a suspension rate of over 95%, a liquid drag reduction rate of 78%, a swelling prevention rate of 85%, and a core permeability reduction of 5%.

[0015] In another aspect of this disclosure, a water fracturing gas suspension proppant is provided, which is prepared by the preparation method described above.

[0016] This disclosure presents a water-based fracturing gas-suspended proppant and its preparation method. The preparation method includes: mixing polyethylene oxide, polyacrylamide, a surfactant, and potassium chloride, then grinding the mixture into powder to obtain a mixed powder; mixing quartz sand with an ethanol solution of a perfluorosilane coupling agent and stirring until homogeneous, drying the mixture in an oven, then heating it to a preset temperature, and adding the mixed powder while stirring to coat the surface of the quartz sand, thus obtaining the water-based fracturing gas-suspended proppant. This disclosure provides a proppant that can achieve stable suspension in water, thereby avoiding excessively high requirements on fracturing fluid viscosity, simplifying fracturing fluid preparation and equipment configuration; while improving suspension stability, it also increases fracturing operation efficiency, reduces operating costs, and minimizes secondary damage to the reservoir, thus solving the problems of existing proppants such as high density, fast settling speed, and reliance on high-viscosity fracturing fluid for effective proppant carrying. Attached Figure Description

[0017] Figure 1 This is a flowchart illustrating the preparation method of the water fracturing air suspension proppant according to a specific embodiment of this disclosure. Detailed Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of this disclosure, the disclosure will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain this disclosure and represent a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without creative effort are within the protection scope of this disclosure.

[0019] As shown in Figure 1, one aspect of this disclosure provides a method S100 for preparing a water fracturing gas suspension proppant, specifically including the following steps S110~S120: S110, after mixing, is ground into powder to obtain mixed powder.

[0020] In step S110, the content ratio of polyethylene oxide, polyacrylamide, surfactant, and potassium chloride is (1-3):(0.5-1.5):(0.05-0.15):(18-22). For example, a ratio of 2:1:0.1:20 is preferred.

[0021] In step S110, the preferred molecular weight of polyethylene oxide is 5-10 million, and the preferred molecular weight of polyacrylamide is 5-10 million. This component acts as a drag reducer, which reduces the energy loss during fracturing fluid pumping by reducing the turbulent frictional resistance of the fluid. It also works synergistically with polyethylene oxide to enhance suspension stability and optimize the flow performance of the fracturing fluid.

[0022] In step S110, the surfactant includes any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, fatty acid salt, alkylphenol polyoxyethylene ether, fatty alcohol polyoxyethylene ether, and hexadecyltrimethylammonium bromide. The surfactant can form stable bubble units in water, assisting the proppant particles to achieve air suspension and increasing suspension stability.

[0023] In step S110, potassium chloride acts as an anti-swelling agent, inhibiting the swelling of clay minerals upon contact with water through ion exchange, protecting the reservoir pore structure, and reducing permeability damage.

[0024] S120. Mix quartz sand with an ethanol solution of perfluorosilane coupling agent and stir evenly. Place the mixture in an oven to dry, then heat it to a preset temperature. While stirring, add the mixed powder to coat the surface of the quartz sand to obtain a water fracturing gas suspension proppant.

[0025] In step S120, the content ratio of quartz sand, ethanol solution of perfluorosilane coupling agent and mixed powder is 1000:(10-80):(13-15), for example, preferably 1000:50:14. In step S120, the perfluorosilane coupling agent is any one of perfluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, and heptadecafluorodecyltriethoxysilane. This component acts as a hydrophobic agent, forming a hydrophobic layer on the surface of the quartz sand through chemical bonding. When the proppant is added to water, the gas film on the surface of the proppant is not replaced by the liquid. During stirring, it combines with the bubbles formed by the particles and surfactants, reducing the effective density and enhancing the suspension capacity, thereby achieving the "air suspension" effect.

[0026] In step S120, the mass of the perfluorosilane coupling agent in the ethanol solution accounts for 0.5-5% of the total mass of the perfluorosilane coupling agent in the ethanol solution.

[0027] In step S120, the preset processing temperature is 130–150 °C. Within this temperature range, after pre-hydrolysis, the silanol groups of the perfluorosilane coupling agent (such as perfluorodecyltrimethoxysilane) undergo a condensation reaction with the hydroxyl groups (-OH) on the surface of the quartz sand, forming stable Si-O-Si covalent bonds, thereby constructing a low surface energy hydrophobic modified layer on the sand grain surface. When the temperature is too low, the condensation reaction is insufficient, the anchoring efficiency of the coupling agent decreases, and the hydrophobic modification effect is limited, thus affecting the suspension performance of the proppant; while too high a temperature may cause thermal degradation of the organic functional groups of the coupling agent or lead to thermal degradation of the functional powder, thereby weakening the stability of the functional layer. In addition, the above temperature range allows thermoplastic components such as polyethylene oxide to melt, thereby tightly bonding with the hydrophobically modified quartz sand surface to form a relatively stable functional coating layer.

[0028] In step S120, the proppant suspension rate is above 95%, the liquid drag reduction rate is 78%, the swelling prevention rate is 85%, the core permeability damage is 5%, and the recovery rate is increased by 20% compared with conventional proppant.

[0029] The proppant disclosed herein has the ability to be stably suspended in clear water, thus achieving effective proppant carrying without relying on high-viscosity fracturing fluid. This type of proppant can simplify the fracturing fluid system, reduce construction equipment and operation steps, lower costs, and improve flowback effect. It is worth noting that the proppant disclosed herein not only provides suspension function, but also further takes into account reservoir protection and fracturing stimulation efficiency improvement.

[0030] In another aspect of this disclosure, a water fracturing gas suspension proppant is proposed, which is prepared by the preparation method described above. For details of the preparation process, please refer to the above description and will not be repeated here.

[0031] The proppant disclosed herein, when mixed with water, can self-release drag-reducing agents, anti-swelling agents, suspending agents in surfactants, and permeation displacement agents, reducing the need for liquid additive transportation and liquid preparation equipment, simplifying the fracturing process, and synergistically improving oil recovery through multiple functions.

[0032] The following will further illustrate the air suspension proppant for water fracturing and its preparation method with specific embodiments: Example 1 The preparation method of the air suspension proppant for water fracturing in this example includes the following steps: 1. Mix 2g of polyethylene oxide (molecular weight 8 million), 1g of polyacrylamide (molecular weight 10 million), 0.1g of sodium dodecyl sulfate, and 20g of potassium chloride, and then grind them into powder to obtain a mixed powder.

[0033] 2. Mix 1 kg of quartz sand with 50 g of a 1% ethanol solution of perfluorosilane coupling agent (perfluorodecyltrimethoxysilane) and stir evenly. Place the mixture in an oven to dry, then heat it to 140°C. While stirring, add 14 g of the mixed powder obtained in step 1 to coat the surface of the quartz sand to obtain a proppant.

[0034] The proppant performance of Example 1 is shown in Table 1. The proppant has a suspension rate of over 95%, a liquid drag reduction rate of 78%, and an anti-swelling performance of 85% as per SY / T 5971-2016 Evaluation Method for Clay Stabilizers for Fracturing, Acidizing and Water Injection in Oil and Gas Fields, with a core permeability reduction of 5% and a migration distance of 900 mm. Compared to Comparative Example 1, this migration distance has increased by 100%, and the recovery rate is 45%, which is 50% higher than that of conventional proppant.

[0035] Comparative Example 1 The proppant used in this comparative example was conventional quartz sand, which was untreated. Its suspension rate, liquid drag reduction rate, swelling prevention rate, and core permeability damage were all 0, the recovery rate was 30%, and the migration distance was 450 mm.

[0036] As can be seen from Comparative Example 1 and Example 1, the proppant formed by the above-described method of this disclosure can achieve stable suspension in clear water, with high anti-swelling rate and recovery rate, which can improve the flowback effect of fracturing fluid and reduce secondary damage to the reservoir.

[0037] Table 1. Propionette performance results for Example 1 and Comparative Example 1

[0038] This disclosure presents a water fracturing gas suspension proppant and its preparation method, which has the following advantages compared to the prior art: First, the proppant disclosed herein can achieve stable suspension under clear water conditions and has a good sand-carrying effect, thereby avoiding the dependence on various additives such as thickeners, drag reducers, and anti-swelling agents in traditional fracturing processes, avoiding excessive requirements on the viscosity of fracturing fluid, simplifying fracturing fluid preparation and equipment configuration, and reducing operating costs. Secondly, the proppant disclosed herein can improve suspension stability, increase fracturing efficiency, improve fracturing fluid flowback, and reduce secondary damage to the reservoir.

[0039] It is understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of this disclosure, and this disclosure is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of this disclosure, and these modifications and improvements are also considered to be within the scope of protection of this disclosure.

Claims

1. A method for preparing a water fracturing gas suspension proppant, characterized in that, The preparation method includes: Polyethylene oxide, polyacrylamide, surfactant, and potassium chloride are mixed and then ground into powder to obtain a mixed powder. Quartz sand and an ethanol solution of perfluorosilane coupling agent are mixed and stirred evenly, then dried in an oven. After heating to a preset temperature, the mixed powder is added while stirring to coat the surface of the quartz sand, thus obtaining a water fracturing gas suspension proppant.

2. The preparation method according to claim 1, characterized in that, The content ratio of the polyethylene oxide, the polyacrylamide, the surfactant and the potassium chloride is (1-3):(0.5-1.5):(0.05-0.15):(18-22).

3. The preparation method according to claim 1, characterized in that, The molecular weight of the polyethylene oxide is 5-10 million; The polyacrylamide has a molecular weight of 5-10 million.

4. The preparation method according to claim 1, characterized in that, The surfactant includes any one of sodium dodecyl sulfate, sodium dodecylbenzene sulfonate, fatty acid salts, alkylphenol polyoxyethylene ethers, fatty alcohol polyoxyethylene ethers, and hexadecyltrimethylammonium bromide.

5. The preparation method according to claim 1, characterized in that, The content ratio of the quartz sand, the ethanol solution of the perfluorosilane coupling agent, and the mixed powder is 1000:(10-80):(13-15).

6. The preparation method according to claim 1, characterized in that, The perfluorosilane coupling agent is any one of perfluorodecyltrimethoxysilane, tridecafluorooctyltrimethoxysilane, heptadecafluorodecyltrimethoxysilane, perfluorodecyltriethoxysilane, and heptadecafluorodecyltriethoxysilane.

7. The preparation method according to claim 1, characterized in that, In the ethanol solution of the perfluorosilane coupling agent, the mass of the perfluorosilane coupling agent accounts for 0.5-5% of the total mass of the ethanol solution of the perfluorosilane coupling agent.

8. The preparation method according to claim 1, characterized in that, The preset temperature is 130-150℃.

9. The preparation method according to claim 1, characterized in that, The proppant has a suspension rate of over 95%, a liquid drag reduction rate of 78%, an anti-swelling rate of 85%, and a core permeability reduction of 5%.

10. A water fracturing gas suspension proppant, characterized in that, The water fracturing air suspension proppant is prepared by the preparation method described in any one of claims 1-9.

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