Conference Agenda

Cost-effective and environmentally sensitive shale gas production requires detailed knowledge of the petrophysical characteristics of the shale from which the gas is extracted. Parameters such as the kerogen fraction, pore size distributions, porosity, permeability, the frackability of the rock and the degree to which natural fracturing already occurs are required in order to be able to estimate potential gas reserves and how easily it can be extracted. Innovative imaging techniques, including Focused Ion Beam Scanning Electron Microscopy (FIB-SEM) and Nanoscale X-Ray Tomography (nano-CT), can be used to characterise the microstructural properties of shale. Here we report using FIB-SEM serial sectioning and nano-CT on approximately cubic samples of side length about 25 µm. The resolution of the FIB-SEM scanning is approximately 20 nm, while that of the nano-CT is about 50 nm, providing between 125 and 1953 million voxels per scan. These ultra-high resolution techniques have been shown to be effective methods for the analysis and imaging of shale microstructure. Each technique can provide data over a different and separate range of scales, and with different resolutions. Results analysed so far indicate that pores which seem to be unconnected when imaged on a micrometre scale by micro-CT scanning, are connected by thin pathways when imaged at these higher resolutions. This nano-scale connectivity is responsible for the small but non-zero permeability of gas shales to gas flow, which is typically measured in the range 5 nD – 200 nD. The volume, size, aspect ratios, surface area to volume ratio and orientations have all been calculated from the scanned data as a function of scale. These data indicate an extremely complex, heterogeneous, anisotropic and multimodal pore nanostructure and microstructure for the shales, with structure at all scales contributing to both gas storage and gas flow. Further work analysing the connectivity of the microscale and nanoscale pore spaces within the rock is underway. We believe that the combination of nano-CT with FIB-SEM on the same sample has the potential for providing an enhanced understanding of shale microstructure, which is necessary for modelling elastic behaviour, gas storage, gas desorption and gas flow in gas shales.

Material samples are a basic element for reference, study, and experimentation in the Earth sciences. Observations made on samples collected in the field and in the laboratory constitute a critical data resource for research that addresses grand challenges of our planet’s future sustainability, from environmental change; to food, energy, and water resources; to natural hazards. These samples need to be openly accessible, easily discoverable online, and documented with sufficient information to make them reusable. They need to be linked to the data derived from them (interoperable) and to the interpretations of these data published in the literature, which is also essential to making sample-based data reproducible. In order to achieve this, material samples need globally unique, persistent identifiers (PID), which link to persistent landing pages with metadata that describe the sample and its provenance and which allow unambiguously linking samples with data and publications.

This presentation will provide an update on existing and emerging data infrastructures for Earth science samples, including the IGSN Global Sample Number and the Internet of Samples (iSamples) project. The IGSN is increasingly adopted in the Earth sciences with now > 7.2 million samples registered, and is currently revising its technical and organizational architecture via the IGSN 2040 project to ensure reliable and sustainable PID services. iSamples is a US-based multi-disciplinary project to develop a distributed cyberinfrastructure with services for consistent, and convenient unique identification of samples, metadata about them, and linking them to other samples, derived data, and research results published in the literature.

Formal publication of data articles, involving standards, expert review and permanent identification, emerged during the International Polar Year 2007-2008 with the inauguration of Earth System Science Data (ESSD) as a new Copernicus journal. Several other ‘data journals’ subsequently joined ESSD in facilitating free access to a wide variety of well-described data products. After a decade of operation, the editorial staff of ESSD lists several unexpected benefits while confronting new data challenges. On the positive side, we note adoption of data sharing ideals across many geoscience disciplines, expansion of products and definitions beyond ‘geoscience’ to the more generic ‘earth system’, a clear evolution of data standards and data services, and a surprising variety of shareable data products from many providers. We also note positive feedback among data quality, user interest and journal impact. At the same time we recognize additional challenging workloads for the geoscience reviewer community, our increasing dependence on very large data products, continuing tension between observations and models (with global re-analyses as a useful example), the need to stay current with changing formats, permanent identifiers and data practices, and the continuing growth in expectations for disciplinary as well as generic data repository services. Overall, we commend authors and managers of new databases for positive contributions to standards and access. These newly-constructed databases offer innovative organisation tools while establishing new sharing expectations and opportunities within their communities.