Experimental and Numerical Studies of CO2 Injection into Water-Saturated Porous Medium: Drainage Process

Abstract

Injection of anthropogenic CO2 into depleted oil and gas reservoirs or deep saline geological formations is seen as a possible way of mitigating carbon dioxide and removing it from the environment. The early injection of CO2 into saline aquifer can be considered as the immiscible displacement of an aqueous phase by a less dense and less viscous gas phase. This process causes unstable fingers to extend into the saturated rock pores. In this work, the crossover from capillary pressure fingering to viscous fingering and/or fracturing is studied experimentally and numerically. In the experimental part, a Hele-Shaw cell with micro-beads was set up to study the vertical gas invasion of saturated porous medium. The simplified experiments were done under room temperature and pressure conditions. Air was injected into a single point at the bottom part of the water-saturated Hele-Shaw cell. Experimental work enabled us to conduct an analysis of the invasion pattern as well as suitable studies for different injection rates and bead sizes. The crossover from capillary to viscous regime was observed visually and through the computation of the fractal number. The fractal dimension number computed was 1.6 for capillary invasion, 1.4 for viscous fingering and 1.03 for fracture. The transition between capillary invasion and viscous fingering happened at a capillary number of 3.6 x 10-4. Comparison made between numerical simulation results using the code STOMP (Subsurface Transport Over Multiple Phases) showed that even though the amount of air injected and the conditions of injection were the same between experiments and simulations, STOMP is unable to capture the exact invasion pattern of this phenomenon accurately, and this calls for better modeling of the phenomenon at pore-scale so that the invasion can be better predicted using simulations.

Date of Award	2012
Original language	American English
Supervisor	Mohamed Sassi (Supervisor)