Pore and Grain Geometry Analysis of Sandstone Reservoir Rocks from a Well of a Northern German Basin

Pore space and grain geometry are important physical properties distinguished in reservoir rocks, particularly in sandstones, due to their influence on oil and gas reservoir quality. Therefore, a detailed study of pore space morphology and grain surface roughness in sandstone reservoir rocks is a key element in petroleum geology. It is eminent in understanding of the adhesion of hydrocarbons in rocks and coupled fluid flows in pores and along grain surfaces. In this work, sandstone samples taken from a well of a Northern German basin deposit have been analysed by thin section petrography, Confocal Raman Microscopy and Confocal Laser Scanning Microscopy (CLSM). The roughness of grain surfaces is analysed and the pore geometries of sandstone rocks are verified. Roughness and pore geometry have a significant impact on the wetting behaviour and adhesion properties of hydrocarbon fluids, water or carbon dioxide (CO2) to the pore walls. The results show the relationship between the composition of sandstones and their pore geometry and the grain surface roughness. The geometry of the pore morphology and the grain surface shows a range from very rough to flat smooth crystal facets, from few hundreds to sub-micron, depending on the scale of observation. The 50x and 100x magnifications were applied in this study. The findings offer a detailed insight into the relationship of pore space morphology and the grain surface roughness. The results add important parameters to the calculation models for hydrocarbon exploitation and to enhancement of the amount of oil recovery

Skin tribology: Science friction?

The application of tribological knowledge is not just restricted to optimizing mechanical and chemical engineering problems. In fact, effective solutions to friction and wear related questions can be found in our everyday life. An important part is related to skin tribology, as the human skin is frequently one of the interacting surfaces in relative motion. People seem to solve these problems related to skin friction based upon a trial-and-error strategy and based upon on our sense for touch. The question of course rises whether or not a trained tribologist would make different choices based upon a science based strategy? In other words: Is skin friction part of the larger knowledge base that has been generated during the last decades by tribology research groups and which could be referred to as Science Friction? This paper discusses the specific nature of tribological systems that include the human skin and argues that the living nature of skin limits the use of conventional methods. Skin tribology requires in vivo, subject and anatomical location specific test methods. Current predictive friction models can only partially be applied to predict in vivo skin friction. The reason for this is found in limited understanding of the contact mechanics at the asperity level of product-skin interactions. A recently developed model gives the building blocks for enhanced understanding of friction at the micro scale. Only largely simplified power law based equations are currently available as general engineering tools. Finally, the need for friction control is illustrated by elaborating on the role of skin friction on discomfort and comfort. Surface texturing and polymer brush coatings are promising directions as they provide way and means to tailor friction in sliding contacts without the need of major changes to the produc

Chemical Analysis of Spray Pyrolysis Gadolinia-Doped Ceria Electrolyte Thin Films for Solid Oxide Fuel Cells

Current solid oxide fuel cell research aims for the reduction of operating temperatures while maintaining power output to reduce the cost of operation. A promising strategy for achieving this goal is to replace common microcrystalline yttria-stabilized zirconia (YSZ) electrolytes of 10-200 ím thickness with nanocrystalline gadolinia-doped ceria electrolytes (CGO) of 100-500 nm thickness deposited by spray pyrolysis. While decreasing the electrolyte thickness, we expect ohmic losses of the fuel cell to decrease linearly and can realize lower operation temperatures at equal efficiency. In this study, the chemical homogeneity of as-deposited and annealed Ce0.8Gd0.2O1.9-x thin films deposited by spray pyrolysis at 350 °C and annealed at 1000 °C were investigated. The chemical composition of the gadolinia-doped ceria films was studied by X-ray photoelectron spectroscopy and Ar+ sputtering as a function of film depth. After the topmost layer was removed by Ar+ sputtering, the thin films showed a surprisingly homogeneous dopant concentration of 23.4 ( 0.6 at % gadolinia in ceria, independent of the film depth. However, spray-pyrolysis-related residues of the precursors (i.e., chlorine from the precursor salt, carbon from the pyrolysis solvents, and water) could be found at unexpected depths in the film and even after annealing at temperatures as high as 1000 °C. The pyrolytic decomposition of the spray pyrolysis thin films is not completely finished after deposition. Changes in the chemical composition may be present during solid oxide fuel cell operation of CGO electrolytes at 600-1000°C