Experimental study on multiphase flow in fracture-vug medium using 3D printing technology and visualization techniques

Abstract

Strong heterogeneity and anisotropy exist in fractured-vuggy reservoirs, resulting in complex flow and relatively low oil recovery. Therefore, the mechanism of water flooding and gas injection displacement in fracture-vug medium constitutes a key issue in oil production. In this study, based on similarity criteria, physical models of fracture-vug medium are designed and constructed through 3D printing technology. Then, by combining the LED (light-emitting diode) backlight visualization method (BVM) and the particle image velocimetry (PIV) technique, experiments of multiphase flow (i.e., oil-water and gas-oil) through the printed fracture-vug medium are carried out. During the experiments, the morphological changes of the fluid interfaces are captured with BVM, and the velocity field and streamlines of the fluid in the system are determined by the PIV technique. In addition, we also investigate various factors affecting the recovery efficiency of fracture-vug medium, such as injection velocity, gravity, outlet position, and shape factors. Results show that oil recovery in fracture-vug medium varies with injection velocity (or Reynolds number), shape of the vug, and fracture-vug structure. Specifically, distribution of the remaining oil is affected by the shape of the vug. Gravity also exerts a great influence on the morphology of bubbles in the case of gas injection. The present study leads to a better understanding of multiphase flow in fracture-vug medium and a valuable experimental dataset.