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

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

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

Cutting-edge tools for spring monitoring and groundwater system characterization in mountain environments

Mountain aquifers represent one of the largest and most valuable water sources, necessary to meet the population's water needs. Over time, they have been threatened by huge anthropogenic exploitation activities, which are currently leading to the depletion of aquifers in many regions worldwide. Furthermore, the vulnerability of groundwater resources is rapidly increasing due to climate change, urbanization, massive industry production, intensive agriculture, and breeding. Knowledge and forecasting about groundwater flow systems are required to guarantee proper management and territorial planning strategies, according to the mountain environmental evolution taking place. Besides, examining how groundwater storage mechanisms in different regions have changed in response to both climate-driven and anthropogenic effects is becoming increasingly crucial. In remote alpine areas, continuous monitoring and data collection of springs’ hydrogeological parameters is still often hampered by technical and logistical problems. In these contexts, new automated techniques and tools need to be applied to monitor springs’ hydrogeological parameters, punctually understanding the dynamics of exhausting of the available groundwater resources. The instrumentation and sensors complex, installed in correspondence with the Mascognaz spring basin (Aosta Valley, Italy) allows detailed analyses of the surface and underground groundwater system, recording continuously hydrogeological variables entering and leaving the spring recharge system. A cutting-edge weather station was here combined with a spring monitoring system through snowpack-hydrometeorological sensors installation. This setup, composed of a snow scale, ultrasonic and laser sensors for snow weight and snow depth reading, provides the possibility of a detailed study of the snow layer evolution during each season. Besides, a multiparametric probe allows water discharge, temperature and electric conductivity values detection. The high quality of the data provided and the small-size basin features have permitted highlighting the variables affecting the system and standing out those are evolving in time. Besides, the relationship between changes in weather conditions and water availability can be defined by performing correlations between different hydrogeological and meteorological available data series. The Mascognaz spring’s pilot site could be helpful as an example for other researchers and authorities who need to identify suitable instruments, sensors and methods to reconstruct the groundwater flow system and hydrogeological structure of a mountain basin

Reliability of spring recession curve analysis as a function of the temporal resolution of the monitoring dataset

AbstractMountain springs represent one of the largest and most precious sources of potable water in Italy, necessary to meet the water needs of the population. Optimizing the present and future management strategies of mountain groundwater resources has become increasingly necessary. The accuracy and frequency of the flow rate (Q) measurements determine and restrict the processes that can be studied using spring hydrograph and recession curve analysis. Therefore, to properly define mountain aquifers' hydrogeological properties, it turns out important to highlight the variation of the error in the estimation of the hydrogeological parameters as the time interval of sampling varies. In this paper, recession curve analysis was performed on two different mountain springs (Spring 1 and Spring 2) of north-western Italy, firstly considering available 4-h resolution measuring data and subsequently by resampling data to simulate longer sampling intervals of 1, 3, 7, 15, and 30 days.The resulting distribution of errors introduced by longer acquisition intervals underlined how the percentage error increases with increasing acquisition interval. For obtaining an adequate estimation of mountain aquifer hydrodynamic parameters, in place of continuous hourly data, 1-day and 3-day sampling intervals with associated errors respectively lower than 5% and 10% were found to be valid

Thermally Affected Zone (TAZ) Assessment in Open-Loop Low-Enthalpy Groundwater Heat Pump Systems (GWHPs): Potential of Analytical Solutions

Thermal perturbation produced in the subsurface by open-loop groundwater heat pump systems (GWHPs) must be predicted and constantly controlled, especially in the shallow aquifers of more densely urbanized areas, in order to guarantee plants' long-term sustainable use and to avoid adverse effects on adjacent geothermal systems. Transient conditions in the flow dynamic can be successfully modelled by means of numerical modelling tools. However, for small plants in suitable hydrogeological systems, an alternative tool for predicting the thermally affected zone (TAZ) around the injection well can be found in analytical solutions for steady advective transport in a shallow aquifer. The validity of using steady analytical solutions to predict the TAZ development at the end of two different cooling seasons (2010 and 2016) was tested in the Politecnico di Torino GWHP system (NW Italy). When fixing the constant thermal difference (ΔT) between the injection and abstraction wells at 5°C, results revealed that a rather reliable assessment of the TAZ of Politecnico di Torino GWHPs, in Turin shallow aquifer, can be performed by plotting the cumulative distribution function of the injected discharge rate (Q) and setting 63% as a steady value

Aosta Valley Mountain Springs: A Preliminary Analysis for Understanding Variations in Water Resource Availability under Climate Change

The availability of freshwater resources in mountain areas has been affected by climate change impacts on groundwater storage mechanisms. As a web of complex interactions characterizes climate systems, understanding how water storage conditions have changed in response to climatedriven factors in different Italian contexts is becoming increasingly crucial. In order to comprehend the relationship between changes in weather conditions and water availability in the Aosta Valley region and how their trends have changed over the last decade, a 7-year discharge series of different Aosta Valley springs (Promise, Alpe Perrot, Promiod, Cheserod) and precipitation data are analysed. Precipitation and flow rate trends using the Mann–Kendall and Sen’s slope trend detection tests were also performed. Not all of the Aosta Valley mountain springs detected seem to respond to the climate variation with a decrease in their stored water resources. Unlike Promiod, Alpe Perrot, Cheserod, and Promise springs have experienced an increase in water discharged amount during the detected 7-year period. This behavior occurs despite the available precipitation data for the associated Sant Vincent, Aymaville-Viayes, La Thuile-Villaret, Champdepraz meteorological stations revealing an overall decreasing trend in annual rainfall (mm), with a slight increase in intensity (mm/day) as a result of the reduction in rainfall events (number of rainy days)

Reliability of spring recession curve analysis considering different time range monitoring datasets

The continuous expansion of urban areas has caused an increase interest in finding new potable water sources and led to consider the exploitation not only of alluvial aquifer but also of mountain aquifers as an increasingly strategic resource. In Italy, 84,3% of the national clean water derives from groundwater where 48,0% results from well, 36,3% from spring, 15,6% from surface waters and the remaining 0,1% from marine water: springs represents therefore one of the largest and precious source of water, necessary to meet the water needs of the population (Istat, 2017). As mountain aquifers can be particularly vulnerable from qualitative and quantitative point of view, they need a high degree of protection: it is important to understand their recharging system, from both geological and hydrogeological perspective, in order to protect and optimize its present and future management. Hydrograph analysis is one of the most common and effective ways to evaluate the properties of an aquifer supplying a spring, such as the type and quantity of its groundwater reserves. Over the decades, many studies were made on recession curve: generally, such curves are still nowadays quantitatively analysed through methods derived from the work of Maillet (1905), who showed that the recession of a spring can be represented by an exponential formula and Boussinesq (1904), who reported that the discharge of aquifer systems is characterised by a non-linear behaviour. Continuous (hourly value) flow rate (Q) dataset are nevertheless needful for the application of these depletion curves analysis. However, in remote settings, continuous monitoring of springs in wilderness is hampered by logistical problems for instrumentation and data collection, and monitoring all springs is both cost and labor prohibitive (Tobin and Schwartz, 2016). To understand if these equations can be valid also using a less dense monitoring dataset, starting from real complete hourly measuring recession curves, we simulated different weekly or biweekly monitoring datasets. Each monitoring series, obtained by this selective measuring range, have been analysed by Boussinesq and Maillet depletion curves methods. These values have then been compared with the ones obtained by hourly value monitoring set in order to understand the validity of these equations even in a realistic and common case characterised by a non-continuous monitoring