Title: Pore system characterization of organic-rich shales using nanoscale-resolution 3D imaging

Abstract

The Vaca Muerta Shale in Argentina is the first signifcant commercial shale oil/gas play outside of North America. High-resolution 2D/3D imaging of shale rocks for the purpose of establishing their mineralogy, total, and connected porosities has become more and more sophisticated. In this paper, nanoscale-resolution focused ion beam (FIB)-scanning electron microscopy (SEM) nano-tomography was used to obtain images of pore structures within two organic-rich regions of interest (ROIs), selected based on correlative SEM and automated mineralogy maps. Advanced machine learning classification tools were used to segment the images and assign porosities and other components. Pore size distribution and pore connectivity analyzes revealed that about 95% of all the pores, present within the two ROIs, had a diameter of less than approximately 75 nm, and that most of these pores were poorly connected. In a similar fashion, the flow rate distribution analysis showed that pores with diameters of about 150-330 nm contributed to over 50% of the flow capacity of the connected pore systems. These results suggest that although most of the pores typically found in shales have pore diameter smaller than about 100 nm, most of the hydrocarbon production may be carried by a relatively small number of larger connectedmore » pores with pore diameter greater than about 150 nm. This research implies that a large portion of the organic-hosted pores (with diameter typically smaller than about 100 nm) may not provide permeable flow pathways for the oil and/or gas migration, and hence may have very little contribution to the hydrocarbon production.« less

Authors:

Goral, Jan ^[1]; Walton, Ian ^[1]; Andrew, Matthew ^[2]; Deo, Milind  ^[1]

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• Search DOE PAGES for ORCID "0000-0002-4569-7097"

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+ Show Author Affiliations

1. Univ. of Utah, Salt Lake City, UT (United States)
2. Carl Zeiss X-ray Microscopy, Pleasanton, CA (United States)

Publication Date:

Fri Sep 20 00:00:00 EDT 2019

Research Org.:

Energy Frontier Research Centers (EFRC) (United States). Multi-Scale Fluid-Solid Interactions in Architected and Natural Materials (MUSE); Univ. of Utah, Salt Lake City, UT (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1594054

Grant/Contract Number:  

SC0019285

Resource Type:

Accepted Manuscript

Journal Name:

Fuel

Additional Journal Information:

Journal Volume: 258; Journal Issue: C; Journal ID: ISSN 0016-2361

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

58 GEOSCIENCES; Porosity and permeability of shales; Multi-scale imaging; Correlative microscopy; Machine learning image segmentation; Digital rock; Vaca Muerta Shale