The necessity of reducing the need for high horsepower to fracture the formation led to the use of friction reducers intensively; however, the consequences of pumping friction reducers could lead to poor fracturing fluid flow-back. The unrecovered fluid creates a water blockage at the matrix-fracture interface in the reservoir, which could impact the oil recovery factor eventually. Therefore, adding surfactants is believed to improve oil recovery during fracture treatment by reducing the oil-water Inter-Facial Tension (IFT) and altering the matrix-fracture interface wettability. Although many studies have shown the benefit of adding surfactants, there is a quite lack of experimental studies about the impact of surfactants and friction reducers on oil recovery factor. Thus, this study emphasizes studying the effects of surfactants and friction reducers on oil recovery factor during fracture treatment.
Core samples from the Wolfcamp were utilized to conduct the study as core samples were cut to small chips and aged in dead crude oil for two months under reservoir temperature 155 F. Then, the chip wettability was measured and immersed in a solution mixture of water and surfactants (nonionic surfactant, anionic surfactant, and zwitterionic surfactant). The wettability was measured again to identify the best surfactant candidates. Additionally, the IFT was measured between crude oil and the fracture solution mixtures. Moreover, two types of Friction Reducers (FR), an anionic friction reducer and a cationic friction reducer, were added to the surfactant mixtures to investigate any impact of the friction reducers on the oil recovery.
The results of the study demonstrate that adding surfactants will potentially improve the oil recovery factor significantly. The results also reveal that using a cationic friction reducer in fracturing fluid can help in recovering more oil as a higher oil recovery factor was observed compared to when an anionic friction reducer was utilized. Non-ionic surfactants showed a good capability in reducing the IFT between oil and water, unlike anionic and zwitterionic surfactants. Including non-ionic surfactants in fracture fluid systems can mitigate water blockage damage and increase the ultimate oil recovery factor.