Multiple-scale wettability and imbibition in engineered and natural nanoporous media
Date
2021-06
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Wettability is an important parameter influencing imbibition into nanoporous media, and therefore, affects many processes in the fields of engineering and science. However, there are many challenges in quantifying wettability and imbibition in natural and heterogeneous nanoporous media. In order to provide fundamental understanding of wettability and imbibition in nanoporous media, in this dissertation, an engineered nanoporous carbon scaffold (NCS) with controllable wettability and pore geometry was used to investigate multi-scale wettability and imbibition (including spontaneous and electrocapillary) dynamics. The learnings obtained from studying this engineered material were subsequently applied to the evaluation of multi-scale wettability and spontaneous imbibition in unconventional hydrocarbon reservoirs. For spontaneous imbibition of nanoliter droplets in NCS and tight rocks, it was found that 1) spontaneous imbibition can take place in hydrophobic nanoporous media; 2) contact line remains pinned during the entire droplet lifetime; and 3) the estimated pore- contact angle (from new theoretical models) is larger than the measured macro- and micro- contact angles. For spontaneous imbibition of bulk liquid in NCS and shale/tight rocks, the following results were obtained: 1) a larger pore size leads to faster imbibition; 2) imbibition volume is linear with square root of time until front breakthrough; 3) a small amount of evaporation causes a deviation from this linear relationship; and 4) pore- contact angle is required for upscaling spontaneous imbibition data from laboratory to reservoir scales. Further, two theoretical models were developed to characterize these dynamics in the presence and absence of evaporation, respectively. Additionally, two new methods were developed to examine impacts of osmotic pressure and surfactant on fracturing fluid loss, respectively, which mitigated the effects of capillary pressure and rock heterogeneity. For electrocapillary imbibition of 1 M KCl electrolyte in hydrophobic NCS, two phenomena were observed: a dependence of electrocapillary imbibition on voltage polarity, and an appearance of electro-dewetting at negative voltages. Fundamentally, this dissertation advances the understanding of multi-scale wettability and imbibition physics in nanoporous media, and fracturing fluid loss mechanisms in unconventional reservoirs. Practically, this thesis provides useful guidance on fracturing fluid loss control and prediction in unconventional reservoirs, and on fluid manipulation at nanoscales.
Description
Keywords
Multi-scale wettability, spontaneous imbibition, electrocapillary imbibition, nanoporous media
Citation
Pan, B. (2021). Multiple-scale wettability and imbibition in engineered and natural nanoporous media (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.