ABSTRACT
Bubble nucleation and bubble growth during pressure depletion in porous media is an important problem encountered in solution gas-drive. The problem was recently analyzed by Yortsos and Parlar (1989) who proposed a theoretical model valid at low decline rates. In this paper we continue their work using both experimental and numerical methods.A numerical pore network model is developed to simulate the process under various conditions. The model includes gas expansion, concentration gradients and finite size effects, previously neglected. Emphasis is placed on the determination of the critical gas saturation, Sgc, and on effects of the rate of pressure decline. Experiments similar to Yousfi et al. (1990) are also carried out in glass micromodels and Hele-Shaw cells. The nucleation of bubbles in various places and their subsequent growth are recorded. As previously predicted, bubble growth occurs from various nucleation sites, which are activated at different stages of the process. In the micromodel, bubbles grow as ramified clusters, which have the general features of a percolation process (e.g., similar to drainage). This is in contrast to Hele-Shaw cells, where growth of compact clusters is observed. Numerical simulation with the use of the pore network model gives results in good agreement with the experiments.
