Abstract
Horizontal well and hydraulic fracturing have been proven to be effective technologies for increasing the recovery of shale gas reservoirs. During a fracturing treatment, a pair of main fractures is first generated perpendicular to the wellbore direction. As fluids continue to be pumped, more microsized fractures are generated near the main fractures and form a fracture network. This micrometer-sized fracture network has much more contact area with the matrix than a traditional single pair of fractures and holds the majority of the productivity potential of shale gas. Friction reducer (FR) is one of the primary components of this fracturing fluid. It is used to decrease the flowing friction in pipeline. Flow loop tests in lab and field applications have addressed this issue thoroughly. However, the flow characteristics of friction reducer solutions in microfractures are not clear. This study used capillary tubes to represent microchannels, and the flow behavior of FR solutions in these microchannels was systematically studied. With FR solution flowing in the microchannels at various velocities, the impact of different FR concentrations, microchannel sizes, and microchannel surface wettability on the FR flow behavior was investigated in detail. It is found that the friction reducer is a slight shear-thinning fluid with properties that can be expressed by a power-law equation. Its residual resistance factor to water was also specified, which is closely related with the fluid flowback. Finally, the experimental results were compared with the data in a flow loop experiment. Its flow resistance was found to be increased in microchannels rather than decreased as was observed in the centimeter-sized tubing.