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Title: Permeability evolution of shale during spontaneous imbibition

Shales have small pore and throat sizes ranging from nano to micron scales, low porosity and limited permeability. The poor permeability and complex pore connectivity of shales pose technical challenges to (a) understanding flow and transport mechanisms in such systems and, (b) in predicting permeability changes under dynamic saturation conditions. This paper presents quantitative experimental evidence of the migration of water through a generic shale core plug using micro CT imaging. In addition, in-situ measurements of gas permeability were performed during counter-current spontaneous imbibition of water in nano-darcy permeability Marcellus and Haynesville core plugs. It was seen that water blocks severely reduced the effective permeability of the core plugs, leading to losses of up to 99.5% of the initial permeability in experiments lasting 30 days. There was also evidence of clay swelling which further hindered gas flow. When results from this study were compared with similar counter-current gas permeability experiments reported in the literature, the initial (base) permeability of the rock was found to be a key factor in determining the time evolution of effective gas permeability during spontaneous imbibition. With time, a recovery of effective permeability was seen in the higher permeability rocks, while becoming progressively detrimental and irreversiblemore » in tighter rocks. Finally, these results suggest that matrix permeability of ultra-tight rocks is susceptible to water damage following hydraulic fracturing stimulation and, while shut-in/soaking time helps clearing-up fractures from resident fluid, its effect on the adjacent matrix permeability could be detrimental.« less
 [1] ;  [1] ;  [1] ;  [2]
  1. Pennsylvania State Univ., University Park, PA (United States). Dept. of Energy and Mineral Engineering. EMS Energy Inst.
  2. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States). Geoscience Research and Applications
Publication Date:
Report Number(s):
Journal ID: ISSN 1875-5100; 647644
Grant/Contract Number:
AC04-94AL85000; SC0006883
Accepted Manuscript
Journal Name:
Journal of Natural Gas Science and Engineering
Additional Journal Information:
Journal Volume: 38; Journal ID: ISSN 1875-5100
Research Org:
Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1398130