Matthias Halisch

Alteration of a Submarine Basaltic Glass under Environmental Conditions Conducive for Microorganisms: Growth Patterns of the Microbial Community and Mechanism of Palagonite Formation

In basaltic glass from the southern Mid-Atlantic-Ridge conducive environmental conditions for biogenic weathering resulted in excellent preserved microbial morphologies on glass surfaces. The distinct glass interface and open spaces between palagonite sheet and glass indicate a dissolution-reprecipitation mechanism of glass alteration potentially supported by microorganisms. On internal fracture surfaces, branching channels with widths at 20–30 μm containing longish structures with targeted dissolution of the glass by growing tips were observed. Alteration resulted in enrichment of Fe, Ti, P, and K in palagonite in amorphous mineral forms.

Analysis of Wellbore Skin Samples—Typology, Composition, and Hydraulic Properties

The presence of a wellbore skin layer, formed during the drilling process, is a major impediment for the energy-efficient use of water wells. Many models exist that predict its potential impacts on well hydraulics, but so far its relevant hydraulic parameters were only estimates or, at best, model results. Here, we present data on the typology, thickness, composition, and hydraulic properties obtained from the sampling of excavated dewatering wells in lignite surface mines and from inclined core drilling into the annulus of an abandoned water well. Despite the limited number of samples, several types of skin were identified. Both surface cake filtration and particle straining in the aquifer occur. The presence of microcracks may be a determining feature for the hydraulic conductivity of skin layers. In the case of the well-developed water supply well, no skin layer was detected. The observed types and properties of wellbore skin samples can be used to test the many mathematical skin models.

Evaluation of Rock Properties and Rock Structures in the µ-range with sub-µ X-ray Computed Tomography

In recent years high resolution X-ray Computed Tomography (CT) for geological purposes contribute increasing value to the quantitative analysis of rock properties. Especially spatial distribution of minerals, pores and fractures are extremely important in the evaluation of reservoir properties. The possibility to visualize a whole plug volume in a non-destructive way and to use the same plug for further analysis is undoubtedly currently the most valuable feature of this new type of rock analysis and will be a new area for routine application of high resolution X-ray CT in the near future. The paper outlines new developments in hard- and software requirements for high resolution CT. It showcases several geological applications which were performed with the phoenix nanotom and recently phoenix nanotom m, the first 180 kV nanofocus CT system tailored specifically for extremely high-resolution scans of samples up to 240 mm in diameter and weighing up to 3 kg with voxel-resolutions down to <300 nm.