Highlights• T2Well-EWASG, a coupled wellbore-reservoir numerical simulator for geothermal systems.• Interpretation of geothermal well-tests.• Application of T2Well-EWASG on a short well-test performed on a well of the Wotten Waven geothermal field (Dominica). AbstractIn the geothermal sector, being able to simulate production tests by combining surface and downhole measurements can be extremely useful, improving data interpretation and reducing the impact of unavailable field data. This is possible with T2Well, a coupled wellbore-reservoir simulator. We plugged the EWASG equation of state for high enthalpy geothermal reservoirs into T2Well and extended the function to analytically compute the heat exchange between wellbore and formation at the short times. Changes to the analytical heat exchange function were verified by comparison with wellbore-formation heat exchange numerically simulated. T2Well-EWASG was validated by reproducing the flowing pressure and temperature logs taken from literature, and by using the software for the interpretation of a short production test. Simulation results indicate that T2Well-EWASG can be effectively used to improve the interpretation of production tests performed in geothermal wells.

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Abstract:The exploitation potential of shallow geothermal energy is usually defined in terms of site-specific ground thermal characteristics. While true, this assumption limits the complexity of the analysis, since feasibility studies involve many other components that must be taken into account when calculating the effective market viability of a geothermal technology or the economic value of a shallow geothermal project. In addition, the results of a feasibility study are not simply the sum of the various factors since some components may be conflicting while others will be of a qualitative nature only. Different approaches are therefore needed to evaluate the suitability of an area for shallow geothermal installation. This paper introduces a new GIS platform-based multicriteria decision analysis method aimed at comparing as many different shallow geothermal relevant factors as possible. Using the Analytic Hierarchic Process Tool, a geolocalized Suitability Index was obtained for a specific technological case: the integrated technologies developed within the GEOTeCH Project. A suitability map for the technologies in question was drawn up for Europe.

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Rock mass is typically characterized by inherent fractures that cause natural blocks of rocks. Unplanned cutting of stone deposits in quarries may lead to over-producing waste (rock debris) or extracting unfi t (fractured) stone blocks. This paper presents two case studies through the use of low and high frequency Ground Penetrating Radar (GPR) antennas to detect fractures in two benches of a quarry. In the fi rst case study, a high frequency GPR antenna was used aiming to: (i) compare the GPR results with a map of the out-cropping fracture intensity in the bench surface, developed using the data of the GPR survey marks and interpolated by the Ordinary Kriging technique, and (ii) present how sub-vertical fractures can be numerically modelled in three dimensions from the GPR results. The second case study was focused on using a low frequency antenna to detect large aperture size of fracture surfaces as deep as possible in order to evaluate a deposit stratum before quarrying. This could be done through studying the refl ections from a 3D cross-sectional GPR model and a 3D transparent GPR model. In the discussion section, an exploitation planning approach, based on modelling fractures as 3D surfaces, is theoretically and graphically proposed to optimize the stone production recovery. The two case studies showed that GPR is a successful tool for the assessment of ornamental stone deposits and a promising tool for recovery optimization.

Rock mass fractures adversely affect the cutting of commercial-size blocks and cause rock material loss in ornamental stone quarries. In order to obtain a reliable evaluation and an optimized production of ornamental stone deposits, it is fundamental to detect fractures in a non-destructive manner identifying them through 3D deterministic modeling. In this study, a recently published fracture modeling strategy, based on Ground Penetrating Radar (GPR) survey was implemented on a large area of bench (27.0 m × 65.0 m) in a limestone quarry in Italy. The survey was done using a dual-frequency GPR system (250 MHz and 700 MHz). The objective of this work was to investigate the large-scale applicability of the mentioned fracture model for future consideration in quarrying optimization studies. Only the 700 MHz radargrams were considered for the fracture modeling, as they provided a higher resolution than the 250 MHz radargrams and a penetration depth of about 4.0 m. The bulk dielectric constant of the rock mass of the bench was estimated by averaging the velocities obtained from fitting the hyperbolic diffractions of fractures at different depths. The model showed that fractures from the same family set can have noticeable spatial variations. The results allowed us to roughly estimate the sizes of the blocks exploitable from the different rock layers of the quarry bench.

TMGAS, an equation of state module of TOUGH2 V.2.0 reservoir simulator, was used to model the migration of CO2, H2S, and CH4 in a deep sedimentary formation. The scope is the improvement of the description of non‐condensable gas (NCG) migration within modeling studies of sedimentary basins’ evolution. Different scenarios have been simulated with NCG migration taking place in a large sedimentary formation discretized with a full 3D Voronoi approach by using specifically improved versions of the pre‐ and post‐processing tools for TOUGH2 developed at the University of Bologna. Simulated reference scenarios are related to the migration of CO2, H2S, and CH4 generated at constant rate for 1 × 106 years in a fresh water aquifer. Additional scenarios are simulated with NCG migration taking place in the same formation but saturated with brine. The effects of pressure‐temperature‐composition (PTX) conditions on thermodynamic equilibria, phase composition, phase thermo‐physical properties and, consequently, on the migration features of different NCGs are modeled and discussed. © 2016 Society of Chemical Industry and John Wiley & Sons, Ltd

In mineral resource estimation, identification of the geological domains to be used for modeling, and the type of boundaries dividing them, is a major concern. Generally, the variables within a domain are estimated with an assumption of the hard boundaries (sharp contact). However, in many cases, the geologic structures that generate a deposit are transitional (overlapping of several geologic domains). Consequently, boundary identification of the geological domains is essential for an accurate estimate of resources. This paper considers a real application to examine whether the addition of geologic information benefits grade estimation in the presence of transitional boundaries. Results proved that the accuracy of the grade estimation can be improved by adding geological information and there is a significant sensitivity in grade estimation results in the existence of transitional boundaries.