Demonstrating the effect of hydraulic continuity of the wetting phase on the performance of pore network micromodels during gas assisted gravity drainage

Abstract

The flow of fluids during oil recovery processes can be visualized in pore network micromodels that represent the porous nature of reservoir rocks. In a permeable rock, pores are formed in spaces between connected solid grains with various sizes and shapes. The surface roughness and irregularities of solid grains create networks of fine capillaries in conjunction with coarse pores. These fine capillaries can maintain films of a wetting phase in regions occupied by a non-wetting phase. In two-dimensional micromodels, the pore network is formed between separated solid grains, and the hydraulic communication of the wetting phase between regions separated by the non-wetting phase is terminated. In this paper, we present a simple procedure for the fabrication of oil-wet and water-wet micromodels that provide the wetting phase with strong hydraulic continuity. The new micromodel contains a pattern of coarse pores covered by fine capillaries without affecting its visualization capabilities. The performance of micromodels with and without fine capillaries was evaluated with the gas assisted gravity drainage (GAGD) experiments under oil-wet and water-wet conditions. The experimental results show that the presence of fine capillaries improved of the hydraulic continuity of a residual wetting phase. The new micromodel effectively demonstrated the interaction between capillary and gravitational forces in gravity drainage processes.