No abstract

Spontaneous imbibition (SI) during the extended shut-in period effectively enhances the production performance of shale gas wells. This study presents an experimental work to evaluate the relationship between SI and microscopic pore structures and assess the dynamics of fluid distributions during imbibition for Longmaxi shale. We conducted imbibition tests on six samples collected from the Longmaxi Shale in Southern Sichuan Basin. Also, we conducted a series of experiments on these six samples to characterize microscopic pore-structure parameters. Correlation analysis indicates that porosity, reservoir quality index, permeability, and average pore radius are among the key pore-structure parameters impacting imbibition recovery of our shale samples. In this study, we also conducted nuclear magnetic resonance (NMR) tests to investigate the dynamics of water distribution during imbibition. The NMR results indicate that the micropores and microfractures in the samples are filled with water earlier compared with macropores and macrofractures. The findings may thus provide new insights into the SI after fracturing operations in shales.