Development and performance evaluation of multi-functional slickwater fracturing fluid system for shale reservoirs.

The rapid decline in energy and production following the primary fracturing development of shale oil reservoirs, and the low production of single wells are the problems facing the development of Cangdong shale oil in the Bohai Bay Basin. A multi-functional fracturing fluid system with emulsification, viscosity reduction, oil washing, and wettability improvement was developed by introducing a mixed-charge surfactant (PSG) to environmentally friendly and low-cost slickwater fracturing fluid (SWFF). The evaluation focused on several key properties including temperature and shear resistance, interfacial activity, viscosity reduction, wettability, and oil washing, all of which were assessed through laboratory experiments. The results showed that the 0.2% PSG and SWFF have high compatibility, forming a functional fracturing fluid system that exhibits exceptional temperature and shear resistance, as well as high interfacial activity. The rate of emulsification and viscosity reduction between the system and GY734H shale oil exceeds 93.45%. Moreover, the system is completely demulsified after being left to stand at 70 °C for 2 h. Furthermore, the static oil washing efficiency of the functional fracturing fluid system at 80 °C is 20.99%, while the SWFF is only 11.65%, which confirms the indoor effectiveness of the system. With the further optimization and application of the multifunctional slickwater fracturing fluid system (SWFF + PSG), it is expected to play an important role in the efficient development of shale reservoirs in the Bohai Bay Basin.