Qualitative Endoscopic Observation of Hydraulic Fractures to Investigate the Effect of Fluid Viscosity

The control of induced fracture network generated by hydraulic fracturing treatment plays an important role in predicting the productivity of hydrocarbon resources. In particular, both nature of pressurized injection fluid and in-situ stress condition significantly affect the formation of fracture network. The previous studies have mostly reported qualitative tendency of fracturing mechanism and its manifestation that are partially understood by numerical and experimental results. To better understand the effect of fluid viscosity, a series of experimental tests are systematically performed with cylindrical specimen under axisymmetric condition. The artificially made specimens with cement paste and mortar ensure the homogeneity and isotropy for experimental consistency. Water and oil are served as fracturing fluids at constant pumping rate. The monitoring of stress evolution with increasing pressurization and high-resolution optical endoscopy imaging together allow assessing the morphological characteristics of generated fracture.