Matrix stimulation/Hydraulic fracturing pre-flush additive: An efficient "pioneer" in oil and gas development
1. What is a pre-flush additive for acid fracturing?
A pre-flush additive for acid fracturing is a crucial chemical additive in the development of oil and gas fields. It is mainly used to pre-treat the formation before fracturing construction to optimize the formation conditions and create a more favorable environment for subsequent fracturing operations. This pre-flush additive can effectively remove blocking substances in the formation, such as mud, wax, asphaltene and other impurities, through a series of complex chemical and physical effects, thereby significantly improving the permeability of the formation. At the same time, it can also reduce the tension on the surface of the formation, improve the permeability of the fracturing fluid and the conductivity of the fracture, thereby significantly improving the efficiency of oil and gas production. In the process of oil and gas development, the application of pre-flush additives can not only improve the fracturing effect, but also reduce construction costs and extend the service life of oil and gas wells. Therefore, it has been widely used in modern oil and gas field development.
2. Characteristics of pre-flushing additive for acid fracturing
Pre-flushing additive for acid fracturing has the following significant characteristics:
High-efficiency cleaning ability: pre-flushing additive can quickly dissolve and disperse impurities and pollutants in the formation, and effectively remove blocking materials in the formation through its surface activity and chemical action, thereby significantly improving the permeability of the formation. This cleaning ability is particularly important for high-oil formations and formations that are severely blocked after long-term exploitation, and can provide a smoother channel for subsequent fracturing operations.
Good compatibility: pre-flushing additive has good compatibility with fracturing fluid, proppant and other additives, and will not have a negative impact on the fracturing system. This compatibility ensures that the pre-flushing additive can play a stable role in the complex fracturing fluid system without adverse reactions with other components, thereby ensuring the smooth progress of the fracturing operation.
Low toxicity and low corrosion: During use, the pre-flushing additive has low corrosion to equipment and formations and is environmentally friendly. This is particularly important for the long-term development of oil and gas fields, because it can not only protect expensive mining equipment, but also reduce potential damage to the formation, thereby reducing subsequent repair costs.
Adjustable performance: The formula and dosage of the pre-flush additive can be flexibly adjusted according to different formation conditions and fracturing requirements to optimize its performance. This adjustability enables the pre-flush additive to adapt to various complex geological conditions and provide customized solutions for oil and gas field development.
Rapid degradability: The pre-flush additive can be quickly degraded under formation conditions and will not cause long-term pollution to the formation. This is crucial for environmental protection and long-term stability of the formation, because it ensures that the pre-flush additive will not have a negative impact on the formation ecosystem after completing its mission.
3. Classification of pre-flush additives for acid fracturing
Pre-flush additives for acid fracturing can be divided into the following categories according to their chemical composition and mechanism of action:
Alcohol ethoxylate
Molecular formula: This type of compound usually has the general formula R−O−(CH2CH2O)n−H, where R is an alkyl group and n is the number of ethoxy groups. The number of ethoxy groups (n) determines the balance between the hydrophilicity and lipophilicity of the alcohol ether, thereby affecting its performance under different formation conditions.
Characteristics: Alcohol ether pre-flushing additives have good surface activity and can significantly reduce the surface tension of the liquid, thereby improving its penetration ability in the formation. This characteristic enables alcohol ether pre-flushing additives to quickly penetrate into the tiny pores of the formation and effectively remove oil pollutants in the formation. In addition, they also have good emulsification and dispersibility, which can disperse solid impurities in the formation into fine particles, preventing these particles from redepositing and clogging the cracks during the fracturing process.
Application: Alcohol ether pre-flushing additives are widely used in pre-flushing treatment of high-oil formations, especially in oil shale, shale oil and heavy oil formations. They can quickly remove the oil film in the formation and improve the wettability of the formation, thereby significantly improving the penetration effect of the fracturing fluid. In practical applications, alcohol ether pre-flushing additives are usually used in combination with other additives to further improve their performance.
Surfactant
Characteristics: Surfactant pre-flushing additives improve the permeability of the fracturing fluid and the conductivity of the fracture by reducing the interfacial tension between the liquid and the formation. This characteristic of reducing interfacial tension allows the fracturing fluid to be more evenly distributed in the formation, thereby improving the fracturing effect. In addition, surfactants also have good wettability and can change the wettability of the formation, changing the formation from lipophilic to hydrophilic, thereby further improving the flow efficiency of oil and gas.
Application: Surfactant pre-flushing additives are suitable for various types of formations, especially low-permeability formations. In low-permeability formations, the formation pores are small and fracturing fluids are difficult to penetrate. Surfactant pre-flushing additives can significantly improve this situation and increase the permeability of the formation, thereby creating favorable conditions for the efficient exploitation of oil and gas. In addition, surfactant pre-flushing additives are also often used to improve the recovery rate of old wells. By improving the wettability of the formation, the residual oil and gas can be more easily exploited.
Acidic liquid
Characteristics: Acidic liquid pre-flushing additives can react chemically with minerals such as carbonate rocks and sulfate rocks in the formation to dissolve blockages and improve the pore structure of the formation. This chemical reaction can not only remove carbonate scale and other mineral blockages in the formation, but also generate new pores, thereby improving the permeability of the formation. In addition, acid pre-flushing additives also have a certain bactericidal effect, which can reduce microbial contamination in the formation.
Application: Acid pre-flushing additives are often used in carbonate formations and formations containing minerals such as calcium and magnesium. In these formations, carbonate scale and mineral blockages are the main reasons for the decrease in formation permeability, and acid pre-flushing additives can effectively remove these blockages and restore the permeability of the formation. In practical applications, acid pre-flushing additives usually need to be formulated according to the specific composition of the formation to ensure that they can effectively react chemically with the minerals in the formation while avoiding excessive corrosion to the formation.
Polymer
Features: Polymer pre-flushing additives have good thickening and suspension properties, and can carry proppants into cracks to improve the conductivity of cracks. This thickening property enables polymer pre-flushing additives to form a stable support structure in the cracks, preventing the cracks from closing, thereby improving the flow efficiency of oil and gas. In addition, polymer pre-flushing additives also have good shear thinning properties, which can reduce viscosity under high-pressure shear, thereby improving their injection efficiency during fracturing.
Application: Polymer pre-flushing additives are suitable for fracturing operations that require high proppant concentrations, especially in deep formations and high permeability formations, and can effectively support cracks and prevent crack closure. In practical applications, polymer pre-flushing additives are usually used in combination with other additives to further improve their performance. For example, by adding a cross-linking additive, the degree of cross-linking of the polymer can be increased, thereby further improving its supporting capacity.
4. Application of pre-flushing additives for acid fracturing
Pre-flushing additives for acid fracturing have a wide range of applications in oil and gas field development, and their importance has become increasingly prominent with the continuous advancement of oil and gas development technology:
Improve fracturing efficiency: Through pre-flushing treatment, pre-flushing additives can effectively remove impurities and contaminants in the formation, reduce the degree of formation blockage, and thus significantly improve the injection efficiency of fracturing fluid. Under complex formation conditions, the application of pre-flushing additives can ensure that the fracturing fluid can smoothly enter the formation and form an effective fracture network, thereby improving the fracturing effect.
Improve formation permeability: Pre-flushing additives can significantly improve the permeability of the formation by reducing the tension on the formation surface and changing the wettability of the formation. This improvement is particularly important for low-permeability formations, which can make oil and gas flow more easily into the wellbore, thereby improving the efficiency of oil and gas extraction.
Reduce construction pressure: During the fracturing process, the pre-flush additive can reduce the friction resistance between the fracturing fluid and the formation, thereby reducing the construction pressure. This is particularly important for high-pressure formations and deep well fracturing operations, which can significantly reduce construction costs and improve construction safety.
Increase oil and gas production: By improving the permeability of the formation and the conductivity of the fracture, the pre-flush additive can significantly improve the efficiency of oil and gas extraction and increase oil and gas production. In practical applications, the application of pre-flush additives can increase the production of oil and gas wells by several times or even dozens of times, thereby significantly improving the economic benefits of oil and gas fields.
Extend the life of oil and gas wells: Pre-flush additives can reduce the corrosion of impurities and pollutants in the formation on oil and gas well equipment, thereby extending the service life of oil and gas wells. In the long-term oil and gas extraction process, the application of pre-flush additives can effectively protect the production equipment of oil and gas wells, reduce maintenance costs, and increase the service life of oil and gas wells.
In short, as an important auxiliary material for oil and gas development, the pre-flushing additive for acid fracturing provides strong support for the efficient development of oil and gas fields through its efficient cleaning and improved performance. In the development of modern oil and gas fields, the application of pre-flushing additive can not only improve the fracturing effect and reduce the construction cost, but also extend the service life of oil and gas wells, so it has broad application prospects.
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