Lattice numerical modeling of the effects of synthetic gas flow rate and pre-existing cleat dimensions on the crack propagation and cavity growth in UCG process

In this study, the effects of synthetic gas flow rates and its viscosity on the crack propagation and cavity growth of the UCG process have been numerically investigated. Numerical modeling is performed using the discrete element method and lattice model, and the effects of flow rate and pre-existing cleat dimensions on the cavity growth have been studied. For this purpose, the fracture fluid pressure, the aperture (primary cleat or secondary cracks aperture), and the number of formed microcracks have been analyzed to evaluate the cavity growth rate. The numerical modeling results show that by increasing the value of syngas flow rate by 2, 5, and 10 times, the fracture fluid pressure and crack aperture increase in the samples. On the other hand, fracture fluid pressure and number of formed microcracks in the UCG process decrease as the pre-existing cleat dimensions increase by 2, 3 and 4 times. As a result, the probability of growth of the cavity decreases. Additionally, the results of numerical models have shown that simultaneous increase of the syngas flow rate and pre-existing cleat dimensions has less effect on crack growth rate in cases that the rate of synthetic gas injection is equal.