Reservoir quality controls on Rotliegend fluvio-aeolian wells in Germany and the Netherlands, Southern Permian Basin – Impact of grain coatings and cements

Reservoir quality in sandstones can be a function of temperature, pressure, and chemical alterations over time. Some intrinsic properties of sandstones can additionally impact the evolution of reservoir quality. The detrital composition, depositional environment, and properties controlled thereby, dictate some of the diagenetic changes. Extrinsic processes, like external fluids, e.g. from hydrothermal events or dewatering of clay minerals, can additionally result in changes of reservoir quality. One of these properties are grain coatings on quartz grains, which can strongly affect pore cementation by quartz overgrowths. To predict and infer the quality of undrilled reservoirs, constraints are needed to predict their occurrence. We analyse two reservoir settings in the Southern Permian Basin and delineate the impact of depositional systems, lithologies, detrital and authigenic composition on reservoir quality and with regard to grain coatings. Results highlight the importance of diagenetic alterations and the source area in regards to burial development in different parts of the Southern Permian Basin. Samples from the Rotliegend Bahnsen Sandstone Member from Germany and the Slochteren Sandstone Formation from the Netherlands have been petrographically and petrophysically analysed and linked to depositional environments. Our data shows that the emplacement and presence of grain coating minerals cannot be simply linked to the depositional environment or processes controlled thereby (e.g. grain size and sorting), neither on a reservoir-, nor on a basin scale. The dissolution of alumosilicates additionally has no consistent impact on the authigenesis of chloritic grain coatings on the reservoir- or basin scale in this study. This implies the necessity of sample specific analyses and importance of the assessment of diagenetic alterations when analysing, modelling, or predicting reservoir quality in similar settings worldwide

Reservoir quality and burial model evaluation by kinetic quartz and illite cementation modeling : Case study of Rotliegendes, north Germany

Silicate reaction kinetics provide a complementary means to other established paleothermal indicators such as organic maturation for evaluating thermal reconstructions. In this study we combine the use of an organic maturation model with kinetic models for quartz and illite cementation to evaluate burial history scenarios for five subsalt wells in lithologically and structurally complex Rotliegendes reservoirs. Models for organic maturation are most sensitive to maximum temperature and provide no direct evidence for the time of peak temperature or the overall duration of high temperatures. By contrast, the kinetics of quartz cementation are much more strongly influenced by the duration of exposure to high temperatures compared with organic indicators. Kinetic models for fibrous illite formation similarly are sensitive to time and temperature and provide predictions for the time of illite formation that can be compared with radiometric dates. Used collectively, these organic and inorganic paleothermal indicators provide improved constraints on thermal evolution compared with conventional approaches. In this study we use these indicators to evaluate two alternative burial history scenarios. Scenario 1 incorporates a hypothesized Jurassic heat flow peak together with significant Late Jurassic deposition and subsequent erosion. Scenario 2 omits the Jurassic heat flow peak and omits the deposition and erosion of the Upper Jurassic. Although both of these scenarios are consistent with organic maturation data, scenario 2 leads to a far better match with quartz cement volumes and fibrous illite K-Ar dates

Cementation and structural diagenesis of fluvio-aeolian Rotliegend sandstones, northern England

Quartz cementation in sandstones is closely linked to grain coating phases and diagenetic alteration. Grain coatings consisting of illite–smectite stained with iron oxides and hydroxides are able to preserve large amounts of porosity by preventing the formation of syntaxial quartz overgrowth cement. The Penrith Sandstone Formation was chosen as an analogue for Rotliegend reservoirs to test the impact of grain coatings on quartz cementation. This adds to an existing model of cementation. Differences of grain coating coverage can be linked to grain size. Extensive grain coatings are present in finer grained laminae in some samples. Coarser grained laminae contain less extensive grain coatings. The analysis of grain coatings based on standard petrographic analyses is combined with high-resolution QEMSCAN® analyses. Structural features include deformation bands of different ages. Diagenetic alterations around faults, recorded by grain coatings, allow the delineation of relative temporal relations, revealing at least two generations of deformation band formation associated with normal faulting. In the Vale of Eden succession one normal faulting event postdates burial diagenetic quartz cementation as is evident by fault focused fluid flow and associated bleaching of iron and absence of quartz overgrowth

Reservoir quality and burial model evaluation by kinetic quartz and illite cementation modeling: Case study of Rotliegendes, north Germany

Silicate reaction kinetics provide a complementary means to other established paleothermal indicators such as organic maturation for evaluating thermal reconstructions. In this study we combine the use of an organic maturation model with kinetic models for quartz and illite cementation to evaluate burial history scenarios for five subsalt wells in lithologically and structurally complex Rotliegendes reservoirs. Models for organic maturation are most sensitive to maximum temperature and provide no direct evidence for the time of peak temperature or the overall duration of high temperatures. By contrast, the kinetics of quartz cementation are much more strongly influenced by the duration of exposure to high temperatures compared with organic indicators. Kinetic models for fibrous illite formation similarly are sensitive to time and temperature and provide predictions for the time of illite formation that can be compared with radiometric dates. Used collectively, these organic and inorganic paleothermal indicators provide improved constraints on thermal evolution compared with conventional approaches. In this study we use these indicators to evaluate two alternative burial history scenarios. Scenario 1 incorporates a hypothesized Jurassic heat flow peak together with significant Late Jurassic deposition and subsequent erosion. Scenario 2 omits the Jurassic heat flow peak and omits the deposition and erosion of the Upper Jurassic. Although both of these scenarios are consistent with organic maturation data, scenario 2 leads to a far better match with quartz cement volumes and fibrous illite K-Ar dates

Seed layer and multistack approaches to reduce leakage in SrTiO3-based metal-insulator-metal capacitors using TiN bottom electrode

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Different conformational forms of serum carnosinase detected by a newly developed sandwich ELISA for the measurements of carnosinase concentrations

Serum carnosinase (CN-1) measurements are at present mainly performed by assessing enzyme activity. This method is time-consuming, not well suited for large series of samples and can be discordant to measurements of CN-1 protein concentrations. To overcome these limitations, we developed sandwich ELISA assays using different anti-CN-1 antibodies, i.e., ATLAS (polyclonal IgG) and RYSK173 (monoclonal IgG1). With the ATLAS-based assay, similar amounts of CN-1 were detected in serum and both EDTA and heparin plasma. The RYSKS173-based assay detected CN-1 in serum in all individuals at significantly lower concentrations compared to the ATLAS-based assay (range: 0.1-1.8 vs. 1-50 mu g/ml, RYSK- vs. ATLAS-based, P <0.01). CN-1 detection with the RYSK-based assay was increased in EDTA plasma, albeit at significantly lower concentrations compared to ATLAS. In heparin plasma, CN-1 was also poorly detected with the RYSK-based assay. Addition of DTT to serum increased the detection of CN-1 in the RYSK-based assay almost to the levels found in the ATLAS-based assay. Both ELISA assays were highly reproducible (R: 0.99, P <0.01 and R: 0.93, P <0.01, for the RYSK- and ATLAS-based assays, respectively). Results of the ATLAS-based assay showed a positive correlation with CN-1 activity (R: 0.62, P <0.01), while this was not the case for the RYSK-based assay. However, there was a negative correlation between CN-1 activity and the proportion of CN-1 detected in the RYSK-based assay, i.e., CN-1 detected with the RYSK-based assay/CN-1 detected with the ATLAS-based assay x 100% (Spearman-Rang correlation coefficient: -0.6, P <0.01), suggesting that the RYSK-based assay most likely detects a CN-1 conformation with low CN-1 activity. RYSK173 and ATLAS antibodies reacted similarly in Western blot, irrespective of PNGase treatment. Binding of RYSK173 in serum was not due to differential N-glycosylation as demonstrated by mutant CN-1 cDNA constructs. In conclusion, our study demonstrates a good correlation between enzyme activity and CN-1 protein concentration in ELISA and suggests the presence of different CN-1 conformations in serum. The relevance of these different conformations is still elusive and needs to be addressed in further studies