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Fractal evolution under in situ pressure and sorption conditions for coal and shale

Authors :
Rui Zhang
Shimin Liu
Yang Wang
Source :
Scientific Reports, Vol 7, Iss 1, Pp 1-11 (2017)
Publication Year :
2017
Publisher :
Nature Portfolio, 2017.

Abstract

Abstract Coalbed methane (CBM) and shale gas become two most important unconventional natural gas resources in US. The fractal dimension, known as the degree of self-similarity or irregularity, is an important parameter to quantitatively characterize gas storage capacity and gas transport properties in pores of rock matrix. In this study, two coal and two shale samples were evaluated to estimate fractal dimensions using combined small angle X-ray scattering (SAXS), small angle neutron scattering (SANS) and low-pressure N2 adsorption techniques. The results show that surface fractal dimension D s of inaccessible pores is greater than that for total pores based on SANS results for all four tested samples. D s of accessible pores estimated by N2 desorption is greater than that for N2 adsorption for each linear section of each tested sample. Based on in situ SANS results, D s slightly decreases with increasing argon injecting pressure for San Juan coal. D s decreases with increasing methane and CO2 injecting pressure for samples with high D s . However, D s significantly increases when CO2 became liquid phase for samples with low D s . Furthermore, D s almost didn’t change after methane and argon penetrations for all these samples except Marcellus outcrop shale.

Subjects

Subjects :
Medicine
Science

Details

Language :
English
ISSN :
20452322
Volume :
7
Issue :
1
Database :
Directory of Open Access Journals
Journal :
Scientific Reports
Publication Type :
Academic Journal
Accession number :
edsdoj.9ae07de0d228409a8eeea3548c510144
Document Type :
article
Full Text :
https://doi.org/10.1038/s41598-017-09324-9