| dc.description.abstract | As the global population increases with science and technology advancements, the energy demand continues to grow, which presents a generational challenge between energy production and climate change. Understanding capillary trapping in porous media and its implications would aid in meeting the increasing energy demands through enhanced oil recovery and reducing the carbon dioxide concentration in the atmosphere through CO_2 sequestration. Capillary trapping is a phenomenon caused by the displacement of the non-wetting phase by the wetting phase in the reservoir. Capillary trapping dictates the efficiency of enhanced oil recovery (EOR) and CCS.
The objective of this work was to study the relationship between the pore structure – in terms of the average coordination number and the average aspect ratio – and capillary trapping.
It was found that the average aspect ratio and average coordination number of a system directly influence capillary trapping. The higher the average aspect ratio, the higher the capillary trapping due to the difference in size between the pore and the surrounding throats. When the pore is significantly bigger in size than the throats, the non-wetting phase gets trapped in the pore due to the snap-off effect. On the contrary, capillary trapping decreases with the increase in coordination number value due to more throats connected to each pore, making mobility easier. The aspect ratio has more effect on the capillary trapping when compared to the coordination number. Additionally, this study shows that the higher the pore structure parameter, the higher the capillary trapping at higher initial gas (non-wetting phase) saturations. Based on the results of this work, the pore structure parameter is recommended to be extracted using an extraction model that utilizes the maximal axis ball algorithm when compared to the medial axis algorithm. Moreover, an empirical equation, including the effect of pore structure, was formulated to estimate the trapping capacity of any water-wet system. The formulated equation was tested using one extraction method and showed significant agreement to two widely used capillary trapping estimation models. | |
