Study on a reusable surfactant fracturing fluid and its application in Chang-6 oil reservoir

Abstract

In order to improve the utilization of fracturing fluid and reduce the environmental pollution risk in large-scale fracturing of oil reservoirs in Ordos Basin, a type of reusable surfactant fracturing fluid is developed. Its formula composition is 15 × 10⁻³ g/mL of the synthesized surfactant and 6 × 10⁻³ g/mL of composite acid. The synthesized surfactant is formed by using 13-docosaenoic acid, 3-dimethylaminopropylamine, sodium chloroacetate, and other raw materials. The dissolution time of the fracturing fluid is less than 1 min. Due to the reversible entanglement interactions between the surfactant micelles, it is a viscosity-elastic fracturing fluid with good sand carrying capacity. It can remain basically unchanged after shearing. The surfactant fracturing fluid can be automatically broken to contact with the crude oil in the oil reservoir. The breaking time can be controlled within 100 min by adjusting the concentration of crude oil. After gel breaking, the viscosity is less than 2.9 mPa ∙ s and the residue content is less than 1.25 mg/L. The interfacial tension of oil and the breaking liquid is below 0.1 mN/m. Subsequently, the field application of the fracturing fluid in N190 oil well has been carried out successfully. The backflow fluid of the surfactant fracturing fluid is successfully reused three times, and the performance of the fracturing fluid prepared in the field is basically consistent with the results of laboratory experiments. The fracturing construction by using the developed surfactant fracturing fluid can achieve a good fracturing stimulation effect and save a large amount of water resources.