Imaging Unconventional Reservoir Pore Systems
This Memoir covers recent advances in the acquisition and application of high-resolution image data to unconventional reservoirs. The value of integrating multiple techniques is a common theme. Chapters address imaging methods, recognition of artifacts, and case studies that explore nanopore systems within particular depositional settings. The importance of mineralogy, organic matter content, and fabric to reservoir quality issues such as wettability, porosity, and formation damage are addressed. This volume will prove useful to anyone interested in the methods for observing and quantifying the pore systems that control hydrocarbon storage and flow in unconventional reservoirs. Unconventional reservoirs studied include Bakken, Barnett, Bossier, Eagle Ford, Geneseo, Green River, Horn River, Marcellus, Mississippi Lime, Monterey, Niobrara, Wolfcamp, and Woodford formations.
Multiresolution Imaging of Shales Using Electron and Helium Ion Microscopy
Published:January 01, 2016
Timothy Cavanaugh, Joel Walls, 2016. "Multiresolution Imaging of Shales Using Electron and Helium Ion Microscopy", Imaging Unconventional Reservoir Pore Systems, Terri Olson
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Scanning electron microscopy (SEM) has become a common way to estimate porosity and organic matter (OM) content within shale resource rocks. Since quantitative SEM analysis has emerged as a means for assessing the porosity of shale, a common goal has been to image polished samples at the highest possible resolutions. Because nanopores are visible at pixel resolutions ranging from 5 to 10 nm, it is natural to consider the possibility of a pore regime below 5 nm that could contribute a significant amount to the total porosity of the system. When considering that a molecule of methane gas is on the order of 0.4 nm diameter, pores smaller than 5 nm could contribute significant storage volume and transport pathways in a reservoir. These nanopores may be a significant source of porosity within certain OM bodies, where total detectable pores using SEM (i.e., ~10 nm pore body diameter and up) have been observed to be volumetrically equivalent to the OM body volumes themselves. With the potential to examine the population of pores below ~10 nm in diameter using the helium ion microscope (HIM), it is possible to construct a rock model that is more representative of the varied pore size regimes present. The primary goal of this study was to quantify the amount of organic-associated pores below the resolution of conventional field emission scanning electron microscope (FESEM). In this study, 51 individual imaging locations from 12 organic shale samples were selected for systematic imaging using a HIM. These samples and locations were selected because of the presence of porous OM identified from previously completed SEM imaging. After methodical HIM imaging and digital segmentation, it was concluded that most samples had no significant incremental, resolvable, organic pore fraction below the detection threshold of conventional FESEM imaging. The advanced resolution of the helium ion beam provides sharper definition of pore boundaries, but the total porosity fraction of these <10 nm diameter pores within the OM in most samples was negligible. We also notice that FESEM and HIM can be considered complementary techniques, as each provides beneficial information that cannot be obtained from using only one method.
- Bee County Texas
- Bossier Formation
- clastic rocks
- Eagle Ford Formation
- Harrison County Texas
- Harrison County West Virginia
- La Salle County Texas
- Lower Permian
- Marcellus Shale
- Middle Devonian
- mineral composition
- noble gases
- organic compounds
- quantitative analysis
- Reagan County Texas
- scanning electron microscopy
- sedimentary rocks
- shale oil
- Taylor County West Virginia
- United States
- Upper Cretaceous
- Upper Jurassic
- West Virginia
- Zavala County Texas
- ion microscopy
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