Brett J. Valentine

Utilization of integrated correlative light and electron microscopy (iCLEM) for imaging sedimentary organic matter

We report here a new microscopic technique for imaging and identifying sedimentary organic matter in geologic materials that combines inverted fluorescence microscopy with scanning electron microscopy and allows for sequential imaging of the same region of interest without transferring the sample between instruments. This integrated correlative light and electron microscopy technique is demonstrated with observations from an immature lacustrine oil shale from the Eocene Green River Mahogany Zone and mid‐oil window paralic shale from the Upper Cretaceous Tuscaloosa Group. This technique has the potential to allow for identification and characterization of organic matter in shale hydrocarbon reservoirs that is not possible using either light or electron microscopy alone, and may be applied to understanding the organic matter type and thermal regime in which organic nanoporosity forms, thereby reducing uncertainty in the estimation of undiscovered hydrocarbon resources.

New Technique for Imaging Geologic Materials via Integrated Correlative Light and Electron Microscopy (iCLEM)

We describe an integrated correlative light and electron microscopy (iCLEM) approach for sequential imaging of geologic materials (shale and mudstone) utilizing both microscope techniques without sample transfer. By avoiding sample transfer this technique identifies low maturity organic matter at micron-scale (1,000x magnifications) and can be followed by characterization at nano-scale (25,000-100,000x magnifications), potentially benefiting studies of organic nano-porosity, which is thought to control hydrocarbon storage and migration in shale petroleum systems [1]. Organic matter in shale, e.g., kerogen vs. solid bitumen, is easily identified by standard optical microscopy techniques such as epifluorescence and incident white light microscopy under oil immersion [2]. However, optical microscopy is diffraction-limited to resolutions of about 1 micron in practice, prohibiting nano-scale observation. Scanning electron microscopy (SEM) allows resolution of features <10 nm, thereby enabling study of organic nano-porosity [3]. Although organic matter is easily identified in SEM by its characteristic low backscatter electron (BSE) intensity, SEM is poorly suited to identify individual organic matter types. Therefore, correlative microscopy [4] or iCLEM studies are necessary to identify organic matter types in which organic nano-porosity develops and the thermal regime of formation.