Speaker
Description
Radial flow of shear-thinning fluids in rock fractures is ubiquitous in subsurface engineering practices, including drilling, hydraulic fracturing and rock grouting. It is hence of practical significance to investigate the flow dynamics of shear-thinning fluids in radial injection scenario. Here, by conducting a series of visualization experiments of xanthan gum solutions displacing silicone oil in a radial Hele-Shaw cell, we obtain a phase diagram of radial displacement patterns for shear-thinning fluids. We observe a novel mixed displacement pattern where the invasion front gradually changes from unstable (viscous fingering) to stable (compact displacement) as the injection proceeds. We demonstrate that the combined effect of shear-thinning property and radial flow geometry plays a controlling role in the evolution of the patterns. Further, we propose a theoretical criterion to predict the transition of interfacial stability, which agrees well with the experimental observations. At high flow rates, we observe reverse fingers caused by dilation of the flow cell under high fluid pressure. We propose a theoretical model to quantify the uneven dilation by taking into account the rheological properties of the fluids and the mechanical properties of the confining plates. We find that the normal deformation tends to reduce the radial displacement efficiency of the invading phase, especially in the early and final stages of injection. This research underpins the importance of solid phase deformation on two-phase flow dynamics in rock fractures.
| Country | China |
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