@article {630, title = {Mesoscale structure, mechanics, and transport properties of source rocks{\textquoteright} organic pore networks}, journal = {Proceedings of the National Academy of Sciences}, volume = {115}, year = {2018}, month = {Dec-04-2018}, pages = {12365-12370}, abstract = {

Organic matter is responsible for the generation of hydrocarbons during the thermal maturation of source rock formation. This geochemical process engenders a network of organic hosted pores that governs the flow of hydrocarbons from the organic matter to fractures created during the stimulation of production wells. Therefore, it can be reasonably assumed that predictions of potentially recoverable confined hydrocarbons depend on the geometry of this pore network. Here, we analyze mesoscale structures of three organic porous networks at different thermal maturities. We use electron tomography with subnanometric resolution to characterize their morphology and topology. Our 3D reconstructions confirm the formation of nanopores and reveal increasingly tortuous and connected pore networks in the process of thermal maturation. We then turn the binarized reconstructions into lattice models including information from atomistic simulations to derive mechanical and confined fluid transport properties. Specifically, we highlight the influence of adsorbed fluids on the elastic response. The resulting elastic energy concentrations are localized at the vicinity of macropores at low maturity whereas these concentrations present more homogeneous distributions at higher thermal maturities, due to pores\&$\#$39; topology. The lattice models finally allow us to capture the effect of sorption on diffusion mechanisms with a sole input of network geometry. Eventually, we corroborate the dominant impact of diffusion occurring within the connected nanopores, which constitute the limiting factor of confined hydrocarbon transport in source rocks.

}, keywords = {porous media; electron tomography; mechanics; fluid transport; mesoscale}, issn = {0027-8424}, doi = {10.1073/pnas.1808402115}, url = {http://www.pnas.org/lookup/doi/10.1073/pnas.1808402115}, author = {Berthonneau, Jeremie and Ama{\"e}l Obliger and Valdenaire, Pierre-Louis and Grauby, Olivier and Ferry, Daniel and Chaudanson, Damien and Pierre E. Levitz and Kim, Jae Jin and Franz-Josef Ulm and Roland Jean-Marc Pellenq} } @article {625, title = {Native Morphology of Hydrated Spheroidal Halloysite Observed by Environmental Transmission Electron Microscopy}, journal = {Clays and Clay Minerals}, volume = {63}, year = {2015}, month = {Oct-2015}, pages = {368 - 377}, abstract = {

Natural mineral materials such as tabular and spheroidal halloysites have recently been suggested as candidates for intercalating metal ions or organic molecules. Their potential use as nano-adsorbents is related to their porous structure and water content. Although the two morphologies can coexist in natural deposits, spheroidal halloysites remain poorly characterized whereas much literature exists on tubular halloysites. The present study investigates the native morphology, internal porous structure, and behavior upon dehydration of spheroidal halloysite from Opotiki (New Zealand). This mineral was characterized in its natural hydrated state using a transmission electron microscope equipped with an environmental cell (EC-TEM). The sample was placed in a sealed block in which water vapor-saturated air circulated at a pressure of 30 Torr. The observed particles consisted of almost complete spheroids displaying polyhedral external surfaces. 1:1 layers stack concentrically as a pore-free, onion-like structure. The dynamic processes of dehydration created by slow depressurization of the cell resulted in a decrease in the layer-to-layer distance (d001) from ~10 \Å to ~7 \Å due to the loss of interlayer water molecules. Irreversible formation of spurious \‘internal pores\’ was recorded during this process. These pores were not indigenous to the hydrated 10 \Å halloysite and resulted from the collapse of the native layers. They cannot account for the physical chemical properties of spheroidal halloysite. Spheroidal halloysites would have a lower propensity for intercalating ions or molecules than tubular halloysites. Isolated facets were also observed in high-resolution-TEM and displayed a pseudo-hexagonal morphology. The three-dimensional microstructure of the spheroid appeared bent along the three pseudo equivalent yi directions of the kaolinite-like single layers. An analogy with polyhedral serpentine has allowed the proposal of a formation process of hydrated spheroidal halloysite triggered by enrichment in divalent ions in the growth system.

}, issn = {00098604}, doi = {10.1346/CCMN.2015.0630503}, url = {http://openurl.ingenta.com/content/xref?genre=article\&issn=0009-8604\&volume=63\&issue=5\&spage=368}, author = {Berthonneau, Jeremie and Grauby, Olivier and Jeannin, Charlotte and Chaudanson, Damien and Joussein, Emmanuel and Alain Baronnet} }