Experimental study on the characteristics of foam flow in fractures

Foam is widely used in well treatment or enhanced oil recovery (EOR). In EOR, foam is an effective agent for mobility control to improve sweep efficiency. Foam's flow characteristic is the foundation of its application. In this work, we systematically investigated the effects of the surfactant concentration, the liquid flow rate, and the fracture width on the flow resistance and the bubble shape characteristics of foam in a fracture by using a visualized fracture model. The results showed that the pressure drop increased with the concentration of the surfactant. When the concentration of surfactant was 0.03%, the pressure drop reached a maximum value at a foam quality of 60%, and this value increased to 92% for a surfactant concentration of 0.3%. The pressure drop reached a maximum with the surfactant solution flow rate and decreased thereafter, and the pressure drop reached a maximum for a foam quality of 92% at the gas flow velocity of 2.0 m/min. The foam bubbles were small in diameter and high in number with the increase of surfactant concentration. The number of polygonal foam bubbles raised with the foam quality, and the bubble shape shifting took place at a foam quality of 90%. The flow resistance of the foam in the fracture dropped with the fracture width, and the fracture width hardly affected the shape and size of the foam.