Sequential coupled simulation of a dual source heat pump and shallow geothermal reservoir

The numerical simulation is an important tool for the assessment of exploiting geothermal energy. It can be used in shallow geothermal applications to evaluate the different production scenarios and the sustainability of the system (geothermal reservoir and heat pump) on long term. Moreover, in shallow geothermal projects, to simulate the real behaviour of the system, the load profiles of the end user and variations of the working mode of the heat pump should be taken into account. The present work introduces and describes a coupled numerical model, in which a dedicated Matlab\uae script has been realized to allow a sequential coupled simulation of a shallow geothermal reservoir exploited with a dual source heat pump. A mathematical model of a dual source heat pump that can work with the ground or the air as source/sink has been developed in Matlab\uae environment. Each component of the heat pump has been modelled considering the equations that govern the physical phenomena. The dynamic numerical simulator FEFLOW\uae has been used to simulate the behaviour of the geothermal reservoir, subjected to heat extraction/reinjection by a closed loop vertical heat exchangers field. This methodological approach is useful to evaluate the performance of the coupled system on the long term, and it is important for understanding the advantages and limits of the dual source heat pump in assuring the sustainability over time when heat is exchanged with the ground, avoiding the depletion of geothermal resources. The mathematical models have been validated with experimental data from a geothermal plant located in Tribano (Padova, IT). This is one of the four pilot sites realized within the framework of the H2020 GEOTeCH Project. It consists of eight coaxial borehole heat exchangers 30 m deep, connected to the 16 kW dual source heat pump prototype realized by HIREF S.p.A. The geothermal heat pump system has been working, and monitored, since October 2017 and it provides heating and air conditioning to an office area. Experimental results have been used to verify the new coupled model, and although the preliminary results are encouraging, further study and work are necessary to make it robust and stable for future routine work

Three dimensional fractures detection by geo-radar for sustainable production of ornamental stones

Fractures in rock mass threaten exploitability and productivity of ornamental stones quarries. Since propagation of fractures inside the rock mass is a random phenomenon, a non-destructive detection method of fractures shall be used. Between several fractures detection methods, Ground Penetrating Radar (GPR) was selected as data acquisition tool. GPR is fast, accurate and reliable method of fractures detection in rock masses. The in-situ survey, in a case study in a sandstone quarry in Firenzuola, Italy, was planned for achieving two main targets. The first one was focused on accurately modeling fractures as 3D surfaces from data obtained by a high frequency GPR antenna. The second main target was focused on surveying the rock mass to detect large aperture fractures surfaces as deep as possible by a low frequency GPR antenna. The proposed method was applied to two different benches using 400 MHz and 70 MHz antennas. A visualized 3D semi-deterministic model (as close as possible to reality) of sub-horizontal and sub-vertical fractures in a rock mass of 25 m length x 6m width x 2.5m depth was obtained from the high frequency GPR antenna survey. Whilst the low GPR frequency antenna survey allowed characterizing the extension, shape and orientation of the detected fractures surfaces in a rock mass of 12m length x 7m width x 14m depth. Moving from these results to further sustainable objectives, suggested exploitation and planning scenarios based on the presented fracture models are described in this paper in objectives to short term production optimization and long term production planning

Joints representation strategy: Performance evaluation by a Finite Element code. A feasibility analysis of a tunnel infrastructure in the Carnian Alps

This study is part of a wider feasibility analysis of a new forestry road in the Dolomitic region. The investigated area is located in northeastern Italy, in the Carnic Alps complex geological context. The rock mass which would be crossed by the tunnel is a highly tectonized limestone characterized by a relatively high strength of the intact rock. The project focuses on the rock mass characterization and the modelling of its behavior by means of numerical simulations with a Finite Elements (FE) code. The generalized Hoek-Brown criterion is used, normal and shear stiffness of the joints are evaluated and different strategies for the representation of the rock mass discontinuities are adopted. The effects of two support systems, preliminary designed by a diffused simplified method, are evaluated focusing on the space around the tunnel, where the joints reach the critical state

Application of low frequency georadar antenna to fractures detection and 3D visualization in a new quarry bench

Quarrying of ornamental stone deposits produces huge amount of wastes due to rock mass fractures that entail economic losses. Fractures in rockmass affect the quality and the required commercial size of stones blocks or may lead to difficulty of exploitation. There are several fracture detection and characterization methods and choice of a method is controlled by the application objective. After a review of fractures detection methods, we introduced a classification based on destructive and non-destructive methods. Among these methods, the authors investigated ground penetrating radar (GPR) as a data acquisition tool. The objective of this research is to image large aperture fractures (2-3 cm) as deep as possible, in a case study in a sandstone quarry in Firenzuola, Italy. The data acquisition was carried out by low frequency GPR antenna (70 MHz) in a 3D survey grid (7 m x 12 m) over the bench surface. Due to the wet and fractured condition of the rock mass, a penetration depth of just 14 m was obtained. Wise data processing led to enhancing the signal. A processing software allowed visualizing the data in 3D GPR cuboid. Interpretation of the main fractures was performed through the entire body of the cuboid. Extension, shape and orientation of the main fracture surfaces could be explored to be then an aid for the quarrying decision makers of this bench

3D modeling of discontinuities using GPR in a commercial size ornamental limestone block

Discontinuities can be hidden or out-cropping with variable aperture sizes in rock media. Obtaining deterministic geo-spatial features of discontinuities inside quarried ornamental stone blocks is a decision-making tool for the post processing phase of cutting slabs. In a case study of a limestone block, discontinuities were detected by the Ground Penetrating Radar (GPR) through a high frequency antenna (700\u202fMHz) and deterministically modeled in three dimensions following the method presented in Elkarmoty et al. (2017). The use of the 700\u202fMHz GPR antenna in this kind of rock allowed to detect tiny-size apertures of discontinuities. The results showed that it is possible to detect and model not only the outcropping discontinuities, but also the hidden ones. Hidden three-dimensional voids or defects were detected and modeled as well. The resulting model was visualized in different orientations, using a 3D data visualization software package, for a better perception of the results

Deliverable D7.2. GEOTeCH Project. Mapping and Risk Assessment

This document presents Deliverable 7.2 \u201cMapping and Risk Assessment\u201d (UNIBO, M30) and provides consortium partners with a general overview of the qualitative and quantitative potential of GEOTeCH technologies (a combination of auger drilling technology, spiral geoexchangers, and dual source heat pump) in Europe. The key indicators used for mapping are the results of the activity performed in Task 7.1 (M1-M30). A specific procedure tailored on GEOTeCH technologies and combining different information sources was adopted to define the indicators. Relevant inputs were provided by Work Package 2 (drilling), WP3 (geoexchange) and WP4 (heat pump). The purpose of this document is to present the three final maps of the activity at European level: 1 the map of sustainable drilling conditions (up to 50 m depth); a drillability index was realised to identify the potential of the GEOTeCH drilling machine in different geological and hydrogeological conditions; 2 the map of thermal parameters at appropriate depths (up to 50 m depth); estimations of ground temperature and depth and thickness of neutral zone, where the weather ambient becomes negligible, were performed, to identify the optimum depth of installation of GEOTeCH heat exchanger; 3 the map of areas suitable for the installation of innovative GEOTeCH technologies; a suitability index was realised to provide a qualitative evaluation of the potential of market introduction and practical application of integrated GEOTeCH technology (drilling + heat exchanger + dual source heat pump). Together with the Market Assessment (D7.1, M18), the maps provided in the present Deliverable will be used by Project Consortium Members to develop the Business Models (D7.3, M36), the Business Plans (D7.4, M48) and the Final Plan for the Exploitation of Results (D7.6, M48) of the GEOTeCH Project technological outputs

3D Voronoi Pre- and Post- Processing Tools for Using the Tough2 Family of Numerical Simulator for Hydrocarbon Gas Migration

The TOUGH family of multi-component, multiphase numerical reservoir simulators have a well know and a long history of applications in different fields of mass and heat transport in porous media. The use a full three-dimensional (3D) unstructured grid permits a great degree of flexibility to reproduce the geometry of complex geological formations and performs accurate reservoir numerical simulations. The full 3D Voronoi tessellation approach also allows reproducing the geometry of geological formations (useful, for example, in directional drilling). In this work, we present some applications of the 3D Voronoi pre- and post-processing software tools dedicated to the TOUGH family of codes (developed at the DICAM Department of the University of Bologna by the Geothermal research group), to study problems of gas migration in hydrocarbon reservoirs. In particular, a small set of 3D grids of a deep sedimentary formation has been created with VORO2MESH, and the simulation results analysed with TOUGH2Viewer. VORO2MESH is a software coded in C++ able to rapidly compute the 3D Voronoi tessellation for a given domain and to create a ready-to-use TOUGH2 MESH file, up to million blocks. It is based on the well-known and powerful open source voro++ library. The new extended version of the TOUGH2Viewer post-processor was used to easily inspect the 3D Voronoi discretization and to better manage the numerical simulation results. The software, written in Java, handles the visualization of both 3D grids (structured and unstructured) and simulation results. This study shows the effectiveness of these tools, and that the use of unstructured grids, instead of structured grids, substantially improve both the reproduction of the geological model and the TOUGH simulation results

Partial Grade method to improve estimation of multi-unit deposits with soft boundaries: application to an iron mine deposit

In multi-unit deposits, the risk of facing uncertainties in estimating geological domains is generally high. The uncertainties increase when there is no exact boundary among geological domains, which is called \u201csoft boundaries\u201d. The geostatistical method of Partial Grade (PG) is an estimation technique developed for multi-unit deposits in the presence of \u201csoft boundaries\u201d when the spatial variability of the grades varies between different geological formations. A partial grade is the product of the indicators of the geological domains with the ore grade, so the partial grade cokriging of different geological formations can be performed in the case of multi-unit deposits. However, the partial grade cokriging is relevant only in the presence of a \u201cborder effect\u201d, evidencing the evolution rate of average grade when moving from one geological domain to another. Additional geostatistical tools with respect to standard geostatistics, such as variogram ratio and preferential relationship schemes allows to identify the grade relation among different geological domains. In this work, we present an application of partial grade cokriging to an iron multi-unit deposit with soft boundaries located in Iran. Up to the knowledge of authors, although the PG method has been applied to several case studies in literature, this application is the first case study where the border effect is present. The three main geological domains are defined: Poor mineralization: (low grade of iron, 20 < Fe% < 45), Rich mineralization: (high grade of iron, Fe% 65 45) and Metasomatite mineralization (strongly altered rock, Fe% < 45). The partial grade cokriging results have shown to reduce uncertainties in grade estimation of geological domains with respect to the classical geostatistical estimation methods (Ordinary Kriging and Co-Kriging). Results were validated with the blast hole data used as reference

INTERPRETATION OF PRODUCTION TESTS IN GEOTHERMAL WELLS WITH T2WELL-EWASG

A crucial aspect of geothermal reservoir engineering is the performance and interpretation of field tests, such as production tests, flowing temperature and pressure logs - both during injection and production, and down-hole pressure transient recording. Such tests are of great importance in order to evaluate the reservoir properties and to predict wells production capacity. However, production tests duration is often limited by environmental constraints related to the disposal of brines, and the running of downhole measurements is constrained by safety and cost considerations related to the use of expensive tools in high temperature high productive wells. From this point of view, the capability to simulate the whole production tests can be extremely useful to improve the data interpretation and reduce the impact of lacking field data. In particular, the coupled simulation of transient fluid flow within the wellbore and the reservoir with the matching of output production curve, flowing logs, and downhole pressure transients, should result in a more reliable evaluation of reservoir properties. This can be done using T2Well, a coupled wellbore-reservoir numerical simulator, with proper equation of state (EOS) modules. EWASG is an EOS module for high enthalpy geothermal fluids consisting of mixtures of water, salts and a non-condensable gas (NCG). We have recently plugged it into T2Well and also improved the analytical computation of heat exchange between the well and the surrounding formations at early time, which may be important for reproducing the transient results of production tests. The resulted wellbore-reservoir simulator, T2Well-EWASG, is capable to simulate high enthalpy geothermal wells. We validated T2Well-EWASG against flowing pressure and temperature logs taken from published literature