Pore structure characterization of North American shale gas reservoirs using USANS/SANS, gas adsorption, and mercury intrusion
► SANS/USANS is used to characterize pore structure of shale gas reservoirs. ► SANS/USANS results are compared to gas adsorption and mercury intrusion. ► There are substantial differences in surface areas and pore size distributions between samples. ► Pore size distributions from gas adsorption and...
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| Published in: | Fuel (Guildford) Vol. 103; pp. 606 - 616 |
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| Main Authors: | , , , , , , , , |
| Format: | Journal Article |
| Language: | English |
| Published: |
Kidlington
Elsevier Ltd
01-01-2013
Elsevier |
| Subjects: | |
| Online Access: | Get full text |
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| Summary: | ► SANS/USANS is used to characterize pore structure of shale gas reservoirs. ► SANS/USANS results are compared to gas adsorption and mercury intrusion. ► There are substantial differences in surface areas and pore size distributions between samples. ► Pore size distributions from gas adsorption and SANS/USANS are in reasonable agreement. ► Accessible porosity estimates were obtained for a Barnett shale sample.
Small-angle and ultra-small-angle neutron scattering (SANS and USANS), low-pressure adsorption (N2 and CO2), and high-pressure mercury intrusion measurements were performed on a suite of North American shale reservoir samples providing the first ever comparison of all these techniques for characterizing the complex pore structure of shales. The techniques were used to gain insight into the nature of the pore structure including pore geometry, pore size distribution and accessible versus inaccessible porosity. Reservoir samples for analysis were taken from currently-active shale gas plays including the Barnett, Marcellus, Haynesville, Eagle Ford, Woodford, Muskwa, and Duvernay shales.
Low-pressure adsorption revealed strong differences in BET surface area and pore volumes for the sample suite, consistent with variability in composition of the samples. The combination of CO2 and N2 adsorption data allowed pore size distributions to be created for micro–meso–macroporosity up to a limit of ∼1000Å. Pore size distributions are either uni- or multi-modal. The adsorption-derived pore size distributions for some samples are inconsistent with mercury intrusion data, likely owing to a combination of grain compression during high-pressure intrusion, and the fact that mercury intrusion yields information about pore throat rather than pore body distributions.
SANS/USANS scattering data indicate a fractal geometry (power-law scattering) for a wide range of pore sizes and provide evidence that nanometer-scale spatial ordering occurs in lower mesopore–micropore range for some samples, which may be associated with inter-layer spacing in clay minerals. SANS/USANS pore radius distributions were converted to pore volume distributions for direct comparison with adsorption data. For the overlap region between the two methods, the agreement is quite good. Accessible porosity in the pore size (radius) range 5nm–10μm was determined for a Barnett shale sample using the contrast matching method with pressurized deuterated methane fluid. The results demonstrate that accessible porosity is pore-size dependent. |
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| Bibliography: | ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 USDOE Office of Science (SC) AC05-00OR22725 |
| ISSN: | 0016-2361 1873-7153 |
| DOI: | 10.1016/j.fuel.2012.06.119 |