Digital rocks physics

Digital rock physics complements the laboratory and field work that geologists, petroleum engineers, hydrologists, environmental scientists, and others traditionally rely on to characterize subsurface formations. Comprehensive reviews on the state-of-the-art and its use in different fields of geosciences are available in the literature , including a recent textbook . In specific cases, it provides important insights into the interaction of porous rocks and the fluids that flow through them that would be impossible to glean in the lab. Digital rocks physicists typically perform imaging (such as computed tomography (CT)) of rock samples and then reconstruct the material's internal structure using image analysis. Computed tomography (CT), micro-computed tomography (µCT), magnetic resonance imaging (MRI) and focused ion-beam scanning electron microscopy (FIB-SEM,) are now applied routinely to acquire 3D images that reveal the rock structure, and scanning electronic microscopy provides 2D textural information. Each approach is capable of extracting information for a particular range of length scales. FIB-SEM and µCT can be applied to digitally reconstruct objects that range from nanometers to millimeters in size . At larger length scales, CT can be applied to reconstruct spatial variations within a material without resolving details in microstructure. Alternatively, a branch of the field creates model porous materials such as packings of spheres or polyhedra and analyzes their structure in order to test theories of how porous rock structure impacts fluid flow or rock mechanical behavior (though such structures have applications well beyond subsurface).

Using high-resolution representations of the complex pore geometry, digital rock physics has rapidly emerged as a potential source of valuable rock property relations (e.g., elastic, transport, and electrical properties) and fundamental understanding of pore-scale processes governing these properties. Its main principle is “image-and-compute” aimed at imaging 3D geometry of the mineral phase and the pore space of a rock and then computationally simulating physical processes in this digital object: fluid flow to quantify permeability, electrical current flow to quantify resistivity, and elastic deformation to quantify elastic moduli and the elastic-wave velocity.

A key advantage of digital rock techniques is the ability to produce detailed 3D rock models, providing access to the pore space topology and mineral spatial distribution affecting properties on lab to field scale. They also enable the simulation of several physical processes for which a fundamental understanding is essential when constructing robust interpretation methods for formation evaluation in well logging. In this context, whole-core CT data and associated measurements can provide aid in well log interpretation, as well as determine where microstructure images at higher resolution should be taken.

Research imaging centers

• Advanced Photon Source: provides ultra-bright, high-energy storage ring-generated x-ray beams for research in almost all scientific disciplines.
• Advanced Light Source: a department of Energy-funded synchrotron facility that provides users from around the world access to the brightest beams of soft x-rays, together with hard x-ray and infrared light.
• The High-Resolution X-ray Computed Tomography Facility at The University of Texas at Austin (UTCT): a national shared multi-user facility supported by the Instrumentation and Facilities Program of NSF’s Earth Sciences (EAR) directorate
• The "Centre for X-ray Tomography" of the Ghent University (UGCT): an interdisciplinary research facility which performs research on the X-ray micro/nanotomography technique and its applications in a scientific context
• National Synchrotron Light Source II (NSLS-II): one of the world's most advanced synchrotron, providing capabilities for X-ray imaging and high-resolution energy analysis.
• ETH Zurich X-Ray Imaging and Microscopy: dedicated to the development of X-ray imaging technology and methods
• National Energy Research Laboratory CT Scanner Lab

The list above provides some examples of larger imaging centers and is not exhaustive.

Imaged data management

Whether imaged or artificial models, the three-dimensional datasets that are created in digital rocks portal workflow can be gigabytes in size. This leads to significant challenges when researchers seek to store, share and analyze their data. Even when data sets are made available, they typically only live online for a matter of months before they are erased due to space issues. This impedes scientific cross-validation. Furthermore, scientists often want to conduct studies that span multiple length scales — connecting what occurs at the micrometer scale (a millionth of a meter: the size of individual pores and grains making up a rock) to the kilometer scale (the level of a petroleum reservoir, geological basin or aquifer), but cannot do so without available data.

Here is a selection of data management and storage sources:

• Digital Rocks Portal: a data portal for fast storage and retrieval, sharing, organization and analysis of images of varied porous micro-structures. This is the only portal dedicated solely to the curation of 2D and 3D imaged and model porous materials datasets.
• Energy Data Exchange allows allows archiving any energy/subsurface data, code, documents etc. without attempt to ingest and interpret the data.
• Imperial College Pore Scale Modeling Webpage: static webpage with a number of posted images.

Companies

• INGRAIN: specializes in the analysis of complex rock types in a short time-frame.
• Thermo Fisher Scientific Material Science; formerly Digital Rock FEI: a digital rock services company
• GeoDict: provides a software solution for multi-scale 3D image processing, visualization, simulation-driven property characterization, material development, and process optimization.
• iRock Technologies: digital rock software
• Exa Digital Rock: provide a simulation solution for executing the simulation-based design process.

Academic research groups

• Australian National University: Mark Knackstedt, Adrian Sheppard
• The University of Texas at Austin: Maša Prodanović, Richard Ketcham
• University of New South Wales: Christoph Arns, Ryan Armstrong
• Oregon State University: Dorthe Wildenschild
• University of Wyoming: Mohammad Piri
• Imperial College London: Martin Blunt
• Louisiana State University: Karsten Thompson
• Stanford University: Sally Benson, Anthony Kovscek
• University of Oklahoma: Carl Sondergeld
• Ghent University: Veerle Cnudde

The list above is not exhaustive and is somewhat partial to CT imaging.

References

This article "Digital rocks physics" is from Wikipedia. The list of its authors can be seen in its historical and/or the page Edithistory:Digital rocks physics. Articles copied from Draft Namespace on Wikipedia could be seen on the Draft Namespace of Wikipedia and not main one.

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