Mitigating water blockage using surfactant into completion fluid – An experimental study

The necessity of reducing the need for high horsepower to frack 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 mitigate the water blockage and increase the flow back by reducing the oil–water interfacial 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 water blockage. Thus, this study emphasizes studying the effects of surfactants and friction reducers on the water blockage problems and oil recovery factor. Core samples from 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 68 °C. Then, the chip's 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 surfactants candidate. Moreover, the IFT was measured between crude oil and the fracture solution mixtures. To study the water blockage problems, two types of friction reducers (FR), an anionic friction reducer and a cationic friction reducer, were added to the surfactants mixture to investigate the impact of FR on the water blockage. The results of the study showed adding surfactants will improve the oil recovery factor significantly and mitigate the water blockage problems. The results also reveal that using a cationic friction reducer in fracture fluid can help in reducing water blockage damage 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.