Understanding reservoir quality is essential for subsurface use and exploration as it determines economic viability and reduces uncertainty, risk, and cost. In part I reservoir quality for e.g., geothermal brines, CO2 storage, and hydrocarbons are assessed for three different areas. In part II the impact of the Russia-Ukraine conflict on global raw material supply chains is evaluated and furthermore the role of selected African countries in raw material supply is assessed. This study contributes with case studies on reservoir rocks and global supply chains, to the optimal utilization of the subsurface for fluid and solid raw materials.
The Campanian lithologies in Beckum are studied as outcrop analog to understand petrophysical and petrographic heterogeneity and the presence on possible fluid migration pathways from underlying Upper Carboniferous strata. He-pycnometry, Klinkenberg-corrected air permeabilities, p-wave velocities, transmitted and reflected light analyses, point-counting, and cathodoluminescence were used. Results show low matrix porosity (1.0–18.7%) and permeability (<0.0001–0.2 mD), due to compaction, early (ferroan) calcite cementation, and formation of compaction bands in the vicinity to ductile clay mineral laminae. ... mehrP-wave velocities range from 2089 to 5843 m/s. The introduced “Compactable Depositional Volume” (CDV) helps evaluate the timing of cementation relative to compaction, and the effect of compactional volume loss on reservoir properties can be obtained. NW-SE oriented, partially sealed veins with (ferroan) calcite and strontianite likely formed during Late Cretaceous inversion and fault reactivation. Due to poor reservoir quality, these lithologies may act as barriers to rising mine water from abandoned coal mines, unless disrupted by faults or fault-related damage zones.
An outcrop analog study evaluates diagenesis, fractures, and vein cementation in tight, fractured limestones of the Upper Muschelkalk-Lower Keuper transition on the eastern Upper Rhine Graben shoulder (SW Germany). Fracture occurrence, spacing, and clustering are critical for reservoir performance, especially in tight formations. Early and burial diagenetic cementation with (ferroan) calcite and dolomite reduces matrix porosity (0.16–10.58%) and permeability (<0.0001–9.7 mD). Samples with stylolites and partially sealed fractures show highest permeability (up to 9.7 mD at 1.2 MPa) and retain up to 41% of the initial permeability measured at 30 MPa. Fracture orientations were recorded manually and analyzed using the normalized correlation count method. Clustering around a breached kink band fault plane is not symmetrically arranged and contains fracture sets of different strike. Fracture clusters are also recorded away from the fault. Slip and dilation tendencies reveal, that fracture sets striking NNE-SSW, WNW-ESE, and NW-SE are more likely to contribute to fluid flow as they are suitably oriented in the present-day stress field. The (breached) reverse kink bands are the first reported in this region (~180–200 km N-NE of the Alpine front) and are likely related to compression by far field stresses induced by the Alpine orogeny during the Eocene.
The Flysch play in the Vienna Basin is composed of several nappes, forming complex reservoir compartments and hosts several sandstone-mudrock interbeds. This study focuses on reservoir assessment using drill cuttings from two wells covering ~ 400 m of stratigraphy targeting the Paleocene-Eocene Greifenstein Fm. (Glauconite Sandstone, 1.–3. GLS). The samples are analyzed for petrographic properties using transmitted light microscopy and cathodoluminescence, and compared to well sections with known production data. The sandstones are cemented by mostly ferroan calcite, resulting in low optical porosity (<5%). Individually elevated porosity is related to partially dissolved K-feldspar. The highest glauconite content is observed in the 3. GLS. The paragenetic sequence indicate that reservoir quality is independent of compaction. Depth accuracy of cuttings is improved using handheld X-ray fluorescence (pXRF) based on Si/Al ratio, and gamma ray logs to distinguish sandstone- and mudrock-rich intervals. Diagenetic variations and the geochemical fingerprint are linked to reservoir quality and known production performance of individual well sections. The reservoir quality is restricted to fractures and partially sealed veins, and areas of known production are related to lower optical porosity in finer-grained sandstones, higher carbonate vein cement contents, and lower Fe+Mg contents. While fracture orientations cannot be derived from cuttings, vein presence and internal textures can be identified. Drill cuttings are the first sample obtained while drilling a well and thus the first opportunity to analyze the subsurface on-site. However, cuttings are often underutilized.
The Russia-Ukraine conflict disrupted global supply chains for oil, gas, metals, and other raw materials. Both countries are resource-rich and had strong economic ties to the EU and Germany. The EU27 lists currently 34 critical and 17 strategic raw materials. Individual raw materials show a high market concentration in individual countries, often over 90%. Russia plays a major role in mining and refining, using available and inexpensive energy. Ukraine was a key alumina producer, and supplied ~50% of the global neon market before production came to halt. The conflict’s impact on bauxite, alumina, titanium, lithium, noble gases, nickel, palladium, platinum, and vanadium is assessed. Responses from countries like South Korea and China show how infrastructure and affordable energy help offset shortages. South Korea’s steelworks mitigated neon shortages, while China increased titanium sponge production by ~1.6 in three years due to existing capacity and energy availability.
The mining potential of Botswana, Morocco, Namibia, and Zimbabwe in mining, processing of mining products and participation in smelters, are highlighted which are to date barely recognized by German investors. China e.g., directly invests in mining projects in Africa, and Russia, and is also actively involved in the mining sector, some of which are accompanied by a military presence. Botswana shows comparatively good WGI indicators and emphasizes the need for investment, which is to date not perceived from e.g., German companies. For many African nations, mining and raw material exports are vital for economic growth.
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