ABSTRACT
The cavity volume and growth in all the directions at corresponding operating conditions and the effect of various design and operating parameters, such as the distance between the wells, flow rates, vertical injection, and operating time, on the cavity evolution has been reported by Daggupati and team. This chapter discusses the effect of different parameters on cavity evolution and the gas quality. It presents a laboratory-scale experimental technique to approximately measure the spalling rate under the underground coal gasification (UCG)-like conditions and throws a light on the possible mechanism and its role in UCG. One of the challenges in modeling a UCG cavity is its irregular geometry and the nonideal flow patterns of the gas flowing through it. As a part of their analysis of cavity evolution, they developed empirical correlations for cavity growth parameters like cavity forward length, backward length, width, height, and volume.
