<p>Large-scale creeping landslides are widespread in alpine areas. Associated long-term, slow deformations threaten urban settlement, railways, main roads and hydropower facilities, on which our society is strictly dependent. Over the next decades, the continuous growing of the global population, the resulting increase in the urbanization (also closer to hazard-prone areas), and the climate change (e.g. melting of alpine glaciers) will increase these interactions and the related risk. Nevertheless, assessing the vulnerability of different types of elements at risk to this kind of hazard is not obvious, especially when hydropower structures (including dams, tunnels, penstocks, etc.) are involved. Large rockslides complexity often results in a variety of different evolutionary trends, making their forecasting and risk reduction a challenge. While catastrophic collapse can cause huge instantaneous damages, slow movements along long periods may lead to progressive damage of structures and infrastructures.<br>In the alpine and pre-alpine areas of Lombardia (Central Italian Alps), slow rock-slope deformations affect an area of 750 km2, threatening more than 10 km2 of urban areas and about 100 km of penstocks or tunnels related to hydropower facilities. Here we focus on the Mt. Palino slope (Valmalenco, Italian Central Alps), that is affected by a complex, apparently long-lived DSGSD (Deep seated Gravitational Slope Deformation) with a relief exceeding 1000 m. The slope hosts hydropower facilities and a tourist resort. In order to recognize dominant processes and their possible evolution (internal deformation, low-rate steady activity, progressive behaviour, seasonal effects) for better risk assessment and mitigation, we investigated the volume and depth of displaced rock mass and the possible localization of deformations along a basal shear zone.&#160;<br>Geomechanical and geomorphological surveys, seismic tomography, deep borehole logs and monitoring data (borehole instrumentation, precise levelling, topographic and GB-InSAR) allowed recognizing different sectors with different evolutionary stage and activity degree. The DSGSD which affect the entire Mt. Palino was probably active before the last LGM (Last Glacial Maximum), while only the northern slope sector is now considered as active. We recognized multiple nested phenomena faster than the main mass, identified as large rockslides. They are suspended over the valley floor and may evolve into fast rock avalanches. One of them is located in correspondence with the hydropower penstock, causing differential deformation to the structure. Borehole evidence of localization along cataclastic shear zones was found, motivating a petrographic geomechanical characterization of both rock masses and shear zone samples. Integrated 3D analysis of different information permitted to reconstruct displacement patterns, long-term mechanisms and the controlling factors of possible future evolution.&#160;</p>
Description of the material. In this paper a novel methodology for the estimation of the formation permeability, based on the integration of resistivity modeling and near wellbore modeling, is presented. Results obtained from the application to a real case is shown and discussed.The well log interpretation process provides a reliable estimation of the main petrophysical parameters such as porosity, fluid saturations and shale content, but the formation permeability is traditionally obtained through laboratory tests on plugs, at the scale of centimeters, and through well test interpretation, at the scale of tens or hundreds of meters.However, log measurements, and in particular resistivity logs, are strongly affected by the presence of the near wellbore zone invaded by mud filtrate. In turn, the extension of the invaded zone depends on formation properties and, in particular, on permeability.As a consequence, the resistivity measured by the tools (the apparent resistivity) has to be properly corrected through a resistivity modeling process to obtain the true formation resistivity and the geometry and resistivity of the invaded zone.Resistivity profiles within the invaded zone are function of fluid properties, petrophysical properties and rock-fluid interaction properties. The novelty of the approach is to numerically simulate the mud invasion phenomenon and match the resistivity profile provided by resistivity modeling to estimate the formation permeability. In the proposed methodology the match of the resistivity profile is obtained by integrating the near wellbore simulator with an optimization algorithm.Application. This novel approach was applied to a heterogeneous shaly-sand oil-bearing reservoir in the Norwegian offshore area. The analyzed sequence was characterized by a high degree of variations in the layers' thickness, from meters down to below tools' vertical resolution. A complete set of wireline logs were acquired in the considered well; several cores were cut and routine and special core analyses performed.Results, Observations, and Conclusions. First, a conventional petrophysical characterization was achieved and the appropriate resistivity corrections were calculated. Then, the modeled resistivity was used as the input for the optimization algorithm so as to obtain a continuous quantitative estimation of permeability in the entire logged interval. The results were satisfactorily compared to core measurements: in both thick, conventional layers and thinner beds the match was very accurate.Significance of subject matter. The new approach provided a robust permeability estimate also in un-cored intervals and, more generally, can be used to predict permeability in un-cored and un-tested wells.
Carbonate reservoirs are often characterized by karst features occurrence, usually related to a significant permeability enhancement in presence of low porosity and low permeability matrix type sediments. The distribution of such karst features is generally highly heterogeneous and difficult to predict, making the reservoir management challenging. In Zubair Field (Iraq), there are numerous evidences of karst events within the Upper interval of Mishrif Formation. The production behavior of Upper Mishrif is therefore very heterogeneous, moving from wells with relatively low flow capacity, as expected from petrophysical interpretation, to wells with a very high flow capacity, hence related to karst enhanced permeability. The integration of petrophysical interpretation, well test and multi-rate production logging allowed to preliminary highlight the improved permeability intervals associated to karst. In addition, accurate image log analysis on the same wells investigated a possible relationship between vug densities and production data, to be extended also to wells lacking the latter data. This process allowed to define a karst flag in more than 60 wells. Then, correlations between karst features and different seismic and geological attributes were identified. The most meaningful parameters were used as input data for a Neural Net Process, leading to the definition of a probability 3D Volume of karst occurrence. The final outcomes of the workflow are karst probability maps, used as a driver for the definition of new wells targets and associated trajectories. The recent drilled wells, with optimized paths according to these prediction-maps, have demonstrated the reliability of this approach intercepting the desired karst intervals. This study represents a valuable opportunity in terms of understanding of the reservoir behavior and impact on the ongoing intensive drilling campaign and related field performance.
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