Study On Clean Fracturing Fluid System With Low Adsorption Surfactant

Fracturing,as an effective way to improve oil and gas recovery,is widely used in oil and gas field extraction operations.As the core of fracturing technology,the performance of fracturing fluid plays a crucial role in fracturing construction.Against the backdrop of low permeability development challenges faced by major oil fields in China,weak cationic surfactant clean fracturing fluids have broad application prospects in the extraction of low permeability oil and gas reservoirs due to their advantages of low adsorption and easy flowback.This article uses the method of primary amine methylation to prepare a novel tertiary amine（OADA）,using synthetic products and several commercially available weak cationic surfactants as thickening agents.The single factor variable method is used to screen additives and their dosage,and a low adsorption surfactant fracturing system is constructed.The system is evaluated for temperature resistance,shear resistance,sand suspension,viscoelasticity,and core damage in the laboratory.The experimental results show that the synthesized OADA+acetic acid+5%potassium chloride system has the best comprehensive performance,and the systems with 1%,2%,and 3%main agent concentrations can withstand temperatures of 80℃,90℃,and 100℃,respectively;The sedimentation rate of the system with 1%main agent concentration is less than 0.5 cm/min at 50℃ and 80℃,which can effectively suspend sand;Fresh water,kerosene,and ether can completely break the system.At 65℃,the damage rate of the breaking fluid to the rock core is only 5.82%,which is significantly lower than that of the guanidine gel and cationic systems under the same conditions.The breaking fluid is well compatible with formation water and does not produce precipitation or flocculation;The system was mixed with fresh water in a 1:3 volume to simulate a gel breaker.By adding the main agent and adjusting the pH,the viscosity of the system reached its peak.After continuous shear at 170 s^-1 and 65℃for 30 minutes,there was still a viscosity greater than 30 mPa·s,achieving the reuse of the gel breaker;Perform frequency and stress scans on the system to obtain G’>G".When the room temperature rises to 50℃,both the elastic modulus G’ and the viscous modulus G" of the system decrease,but there are still G’>G",indicating good viscoelasticity,indicating that the contribution of elasticity to suspended sand is greater than that of viscosity.On the basis of determining the optimal system,the microscopic appearance and particle size of the system were characterized using fluorescence microscopy and particle size analyzer,respectively.It was found that sodium ions are more conducive to promoting aggregation between micelles than potassium ions.The modified formula obtained by replacing potassium chloride with sodium chloride is OADA+acetic acid+5%sodium chloride.The system with 1%,2%,and 3%main agent concentrations can withstand temperatures of 90℃,100℃,and 110℃,respectively.The modification not only further improves the temperature resistance and shear resistance of the system,but also reduces the cost of use under the same conditions.