Reuse of Decommissioned Hydrocarbon Wells in Italian Oilfields by Means of a Closed-Loop Geothermal System

Geological and geophysical exploration campaigns have ascertained the coexistence of low to medium-temperature geothermal energy resources in the deepest regions of Italian sedimentary basins. As such, energy production based on the exploitation of available geothermal resources associated with disused deep oil and gas wells in Italian oilfields could represent a considerable source of renewable energy. This study used information available on Italian hydrocarbon wells and on-field temperatures to apply a simplified closed-loop coaxialWellbore Heat Exchanger (WBHE) model to three different hydrocarbon wells located in different Italian oilfields (Villafortuna-Trecate, Val d’Agri field, Gela fields). From this study, the authors have highlighted the differences in the quantity of potentially extracted thermal energy from different analysed wells. Considering the maximum extracted working fluid temperature of 100 °C and imagining a cascading exploitation mode of the heat accumulated, for Villafortuna 1 WBHE was it possible to hypothesise a multi-variant and comprehensive use of the resource. This could be done using existing infrastructure, available technologies, and current knowledge

Neural Network approach to assess the thermal affected zone around the injection well in a groundwater heat pump system

The common use of well doublets for groundwater-sourced heating or cooling results in a thermal plume of colder or warmer re-injected groundwater known as the Thermal Affected Zone(TAZ). The plumes may be regarded either as a potential anthropogenic geothermal resource or as pollution, depending on downstream aquifer usage. A fundamental aspect in groundwater heat pump (GWHP) plant design is the correct evaluation of the thermally affected zone that develops around the injection well. Temperature anomalies are detected through numerical methods. Crucial elements in the process of thermal impact assessment are the sizes of installations, their position, the heating/cooling load of the building, and the temperature drop/increase imposed on the re-injected water flow. For multiple-well schemes, heterogeneous aquifers, or variable heating and cooling loads, numerical models that simulate groundwater and heat transport are needed. These tools should consider numerous scenarios obtained considering different heating/cooling loads, positions, and operating modes. Computational fluid dynamic (CFD) models are widely used in this field because they offer the opportunity to calculate the time evolution of the thermal plume produced by a heat pump, depending on the characteristics of the subsurface and the heat pump. Nevertheless, these models require large computational efforts, and therefore their use may be limited to a reasonable number of scenarios. Neural networks could represent an alternative to CFD for assessing the TAZ under different scenarios referring to a specific site. The use of neural networks is proposed to determine the time evolution of the groundwater temperature downstream of an installation as a function of the possible utilization profiles of the heat pump. The main advantage of neural network modeling is the possibility of evaluating a large number of scenarios in a very short time, which is very useful for the preliminary analysis of future multiple installations. The neural network is trained using the results from a CFD model (FEFLOW) applied to the installation at Politecnico di Torino (Italy) under several operating conditions

Abandoned oil and gas wells exploitation by means of closed-loop geothermal systems: a review

In mature oilfields, decommissioned oil and gas wells with depths reaching approximately 5000-6000 metres represent good candidate structures for geothermal heat exploitation, as they can provide useful access to subsurface geothermal energy resources. Comprehending the possibility to economically harness geothermal energy by means of co-axial WBHEs is bound to the main features of the physical model, applied to estimate the amount of heat that can be gained from the borehole. Simultaneously, due to the continuous spatial variability of geological formations in oilfields, accurate and realistic estimates of the heat exchanger performances cannot be separated from a proper consideration of the thermophysical parameters of geological strata surrounding the hydrocarbon wells

Groundwater thermal-effective injection systems in shallow aquifers: possible alternatives to vertical water wells

Urbanized areas have environmental features that may influence the development of low-enthalpy geothermal systems and the choice of the most suitable among the available (roughly earth coupled closed-loop and groundwater open-loop type). In particular, if compared to less anthropized areas, some characteristic urban elements require particular attention: underground extensive use, contamination of groundwater, interference between the systems, authorization procedures and planning restrictions, the competition with cogeneration systems and the impact on emissions of pollutants. In this general context, the increasing implementation in several areas of the world of the open-loop groundwater heat pumps technology which discharge into the aquifer for cooling and heating buildings, could potentially cause, even in the short term, a significant environmental impact associated with thermal interference with groundwater, particularly in the shallow aquifers. The discharge of water at different temperatures compared to baseline (warmer in summer and colder in winter) poses a number of problems in relation to the potential functionality of many existing situations of use of the groundwater (drinking water wells, agricultural, industrial, etc.). In addition, there may be cases of interference between systems, especially in the more densely urbanized areas. Appropriate hydrogeological investigations should be performed for the characterization of the main hydrogeological parameters of the subsoil at the considered site in order to minimize the environmental impact of discharges into aquifers. The current Italian legislation related to withdrawals and discharges into aquifers designs a framework suitable for the protection of groundwater and induce deciding the best configuration of the plant with a case by case approach. An increased contact area between the dispersant system and the ground makes it possible to affect a greater volume of aquifer and, consequently, reduce the areal extent of the thermal plume that develops around the area of injection minimizing the time and the space needed for the disappearance of the thermal plume and the restoration of undisturbed temperature conditions. The reduction in plan and temporal extension of the thermal plume would have several benefits, minimizing the use of large areas around the buildings involved by the thermal perturbation, with direct implementation benefits. In order to investigate alternatives to traditional drilled water well for the re-injection and dispersion of water in aquifer downstream of the heat pump, we modeled with FEFLOWthe possible reverse use of commercial draining gabions in various types of ground configuration, geometry and interconnection with systems of pre-fabricated vertical drains on a possible reliable test-site. The results highlighted that they can represent a good and efficient alternative for the groundwater dispersion in the aquifers

Tunnelling and groundwater interaction: the role of the hydrogeological monitoring

The interaction between tunnelling and groundwater is an important factor to be considered in any underground work. Groundwater can represent a major constraint for many technical decisions related to the tunnel construction and, at the same time, a fundamental valuable natural resource to be preserved quantitatively and qualitatively during and after the tunnel completion. The knowledge of the geological subsurface conditions, the hydrogeological mechanisms of groundwater infiltration and circulation, the degree of the aquifers connection with the river network as well as the chemical composition of the circulating groundwater are some of the more important topics that should be analysed in the early phase of the tunnel design. Moreover the numerical modelling of the tunnel-groundwater system requires a large amount of suitable data derived by field investigation. The hydrogeological monitoring represents a fundamental tool for the tunnel design, construction and functioning and has to be developed in a program which includes surface and subsurface data in an integrated geo-referred way. The system needs the continuous uploading of the environmental data coming form the tunnel and the surface environment in order to check the short and long-term interactions, verify the modelling hypothesis and monitor the dynamic behaviour of the whole system and the compliance with the local environmental regulations

SOURCE: a semi-automatic tool for spring-monitoring data analysis and aquifer characterisation

It has become increasingly necessary to optimise mountain groundwater resource management and comprehend resourcerecharging systems from a hydrogeological perspective to formulate adequate resource protection strategies. Analysing mountain spring behaviour and aquifer characteristics can be time-consuming, so new automated techniques and software tools are needed to estimate hydrogeological parameters and understand the exhaustion dynamics of groundwater resources. This paper introduces SOURCE, a new semi-automatic tool that automates the hydrogeological characterisation of water springs and provides proper estimations of the vulnerability index, as well as autocorrelation and cross-correlation statistical coefficients. SOURCE rapidly processed input data from the Mascognaz 1 spring (Aosta Valley) water probes and meteorological station to provide graphical outputs and values for the main hydrodynamic parameters. Having a single software package that contains all the main methods of water spring analysis could potentially reduce analysis times from a few days to a few hours

Engineering geology challenges at the Politecnico di Torino

The Engineering Geology area studies the physical geography and geomorphology of the “Environment system”. In particular, Engineering Geology deals with the defense of the soil, territory and civil protection, with attention to landslides, hydrogeology, the study of underground water circulation, the geological-technical survey, geological exploration of the subsoil and thematic cartography, geological and hydrogeological risk; interpretation of aerial photos and satellite images, topographical analysis on digital models of the survey, study of climate changes and their influence on erosion, sedimentation and pedogenesis processes, the study of geothermal systems, the analysis of geological systems related to hydrocarbons and minerals. Research methods include field and laboratory experiments and appropriate numerical modeling software is often used. In conclusion, the aim of this paper should be a review of all engineering geology tematics analysed and studied by Applied Geology Group in Politecnico di Torino