Abstract
The evolution of the pore space of mudrocks induced by drying shrinkage and effective stresses is of importance to several areas of research. Drying is a prerequisite for most mudrock characterization methods, while effective stresses have a direct impact on mudrocks properties such as permeability, compressibility, and strength. Mercury porosimetry intrusion has been widely utilized to show that drying shrinkage and effective stresses lead to the collapse of large pores only (~ > 50 nm), while small pores (~ < 50 nm) remain unaffected. However, the validity of mercury porosimetry intrusion-derived pore size distributions is greatly doubted in the literature due to the fact that most pores in mudrocks are not directly accessible to the surrounding mercury. This study follows a different approach by utilizing a suite of methods including imaging by transmission electron microscopy and scanning electron microscopy at cryogenic temperature after high-pressure freezing (cryoSEM), and gravimetric porosity measurements to investigate the influence of volumetric changes on the pore space of mudrocks. Contrary to previously published results, we show that volumetric changes induced by drying and effective stresses lead to the collapse of pores of all sizes. Furthermore, we show that porosity measured from SEM images is dependent on SEM resolution and reveals only a fraction of the actual porosity. These results provide valuable insights used to interpret the results of characterization methods requiring drying and modeling of effective stress influence on the properties of mudrocks.
Original language | English (US) |
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Pages (from-to) | 4290-4304 |
Number of pages | 15 |
Journal | Journal of Geophysical Research: Solid Earth |
Volume | 124 |
Issue number | 5 |
DOIs | |
State | Published - May 2019 |
Funding
Shell, the UT GeoFluids consortium at the University of Texas at Austin, the NSF (MRI-1229693), the Northwestern University Materials Research Center (NSF DMR-1121262), and the International Institute for Nanotechnology (IIN) in part supported this work. TEM and oven-dried SEM imaging were performed at the Center for Nanoscale Systems (CNS) at Harvard University, a member of the National Nanotechnology Infrastructure Network (NNIN) supported by the National Science Foundation (ECS-0335765). CryoSEM imaging and preparation was performed at NUANCE-EPIC and OMM, Northwestern University core facilities that are supported by the MRSEC program (NSF DMR-1121262) at the Materials Research Center. EPIC (NUANCECenter-Northwestern University) further received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI-1542205), the International Institute for Nanotechnology (IIN), and the State of Illinois, through the IIN. Data supporting our conclusions are included in the tables and figures of this paper. Shell, the UT GeoFluids consortium at the University of Texas at Austin, the NSF (MRI‐1229693), the Northwestern University Materials Research Center (NSF DMR‐1121262), and the International Institute for Nanotechnology (IIN) in part supported this work. TEM and oven‐dried SEM imaging were performed at the Center for Nanoscale Systems (CNS) at Harvard University, a member of the National Nanotechnology Infrastructure Network (NNIN) supported by the National Science Foundation (ECS‐0335765). CryoSEM imaging and preparation was performed at NUANCE‐EPIC and OMM, Northwestern University core facilities that are supported by the MRSEC program (NSF DMR‐1121262) at the Materials Research Center. EPIC (NUANCECenter‐Northwestern University) further received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF NNCI‐ 1542205), the International Institute for Nanotechnology (IIN), and the State of Illinois, through the IIN. Data supporting our conclusions are included in the tables and figures of this paper.
Keywords
- CryoSEM
- Gulf of Mexico mudrocks
- drying shrinkage
- effective stress application
- mudrock porosity
- pore space evolution
ASJC Scopus subject areas
- Geophysics
- Geochemistry and Petrology
- Space and Planetary Science
- Earth and Planetary Sciences (miscellaneous)