174,789 research outputs found
-Lettera di riconoscimento per l'attività scientifica del Presidente Argentino Nèstor Kirchner(21.12.2006) a Adolfo Perez Esquivel (Premio Nobel per la Pace) e al Prof Marcelo Conti per l'informe: 'Scientific Report - Consultancy Report on Pulp Mills'in merito al contenzioso giuridico internazionale tra Argentina e Uruguay, per l'impatto ambientale della mega-fabbrica di pasta di cellulosa Botnia-UPM sul fiume Uruguay.
No full textL'informe scientifico, scritto a richiesta del Premio Nobel della Pace Perez Esquivel al Dr M.E. Conti, che ha coordinato il gruppo di esperti e coautori del lavoro (C. Botrè, F. Botrè, A. Alimonti), è depositato presso il Tribunale della Corte Internazionale di Giustizia(L'Aia)nel memoriale difensivo presentato dalla Repubblica Argentina; ed è stato consegnato ai Presidenti di Argentina e Uruguay
Reliability analysis for preliminary forecasts of hydrogeological unit productivity
No full textThe aim of this work is to find a probabilistic characterization of the productive capacity of a well in a geological formation hosting an aquifer. Such characterization in terms of productive capacity may allow a preliminary assessment to be made of the probability of success for a required productivity (i.e. target point). This evaluation is usually carried out by statistical analysis of a geological dataset, which is likely to be influenced by many parameters. Such datasets are often incomplete or unreliable. Therefore, a method for evaluating potential productivity, using probabilistic hydraulic conductivity data, is proposed. The hydraulic characterization of hydrogeologic units is based on the collection of information obtained mainly through pumping tests and their interpretation. The results, expressed in terms of hydraulic conductivity, are summarized in a range of variability that is strictly dependent on the number of performed tests and their spatial distribution in the unit itself. If this range is known, an estimate of well’s yield can be made on a deterministic basis, through Thiem’s relationship for steady state conditions, by setting a value of hydraulic conductivity that corresponds to the average value of the range. The proposed reliability analysis enables to overcome the limitations of the deterministic approach by correlating each calculated flow rate, which is taken to be a design flow rate exceeding the critical flow rate of the hydrogeologic unit, to its probability of failure. Therefore, this approach aims to evaluate the probability of failure of the water system. The preliminary result is to associate the values of aquifer exploitation with a probability failure function. This outcome can then be used to define the potential solutions in the optimal allocation of the withdrawal by means of reliability analysis that takes into account the uncertainty of the system
Hydrocarbon wells potentially suitable for geothermal repurposing in Italy. A first assessment
No full textGlobal changes urge a radical transformation and improvement of the energy production systems to meet the very ambitious and challenging decarbonisation targets of the European economy by 2050. In this context, the possible repurposing of depleted hydrocarbon wells for geothermal heat production represents a promising contribution, with an approach inspired by the circular economy, to the decarbonisation of energy production systems.
The mature stage of oil and gas wells is often characterized by the production of hydrocarbons and associated formation waters, which must be treated continuously being often reinjected into the reservoir. Usually, the volume of produced water increases with the maturity of the fields until the production of hydrocarbons becomes uneconomic and the wells are cemented and closed. However, according to their depth and the local geothermal gradient, these oil and gas wells could have bottom-hole temperatures high enough to sustain the geothermal exploitation of the reservoirs fluids. Therefore, when the hydrocarbon wells are going to be depleted and where a geothermal potential exists, the conversion into geothermal wells could be a reasonable alternative to the mining closure, which will compromise the possibility to repurpose the existing wells for geothermal applications.
Many existing Italian oil and gas (O&G) wells are approaching the end of their economic lifespan. This irreversible process necessarily requires an in-depth and systematic assessment of their conversion potential for heat production.
To identify the most promising hydrocarbon wells suitable for geothermal repurposing we have combined information on onshore wells and fields made available by the Italian National Mining Office for Hydrocarbons and Georesources, which have been integrated with data retrieved in the scientific literature, with the estimated temperatures at depth derived from the Italian National Geothermal Database. According to the latest available data, there are 892 active wells in Italy located onshore in the existing mining licenses with different operational status (i.e., productive wells, potentially productive wells, reinjection, monitoring or other purposes),
With this simplified approach, we have selected wells, associated with 42 hydrocarbons fields with depths deeper than 2000-3000 m and with temperatures higher than 60-70 °C, which have the potential to be repurposed for geothermal application. For five of these oil & gas fields, the geothermal potential has been evaluated, by applying the volume method. An estimation of the geothermal energy that could be recovered by repurposing the exiting hydrocarbons fields has been obtained.
Finally, we discuss how the use of a screening matrix, based on a review of the approach already proposed by Soldo and Alimonti (2015), can allow an analysis of the existing wells to define the more appropriate technology for their geothermal repurposing
Back analysis of a horizontal geothermal plant implemented in a wine production process
No full textThe Salcheto winery has undertaken a process of reduction of its primary energy consumption and the implementation of green energy technologies. They adopted solar photovoltaic, wood biomass, and geothermal energy sources. A horizontal ground source heat exchanger (GSHE) plant is used to cool a part of the pressed grapes and control the wine production temperature. The goal of this work was to investigate some technical issues of the plant and to increase the efficiency of the whole system. The first step was the evaluation of the actual operating conditions of the GSHE plant, by performing a thermal response test. The results allowed us to find the thermal diffusivity of 3.5 × 10−7 m2 /s, and the calculation with the IGSHPA standard indicated a cooling performance of about 6 kW. A survey during the harvest highlighted a peak power of 6 kW. Therefore, to improve the plant, some modifications were proposed and analyzed. In the new layout, the geothermal plant serves the condenser of the refrigeration unit, allowing cooling of the all production lines, instead of only one. The peak power was evaluated as 32 kW, and the GSHE can fulfil this, up to 18 kW. For higher power, the evaporative tower will supply the remainder, covering a maximum of 45%. Furthermore, the refrigeration unit may cover the cooling requirements of the entire residential and office building, without other plant improvements
Producing geothermal energy with a deep borehole heat exchanger. Exergy optimization of different applications and preliminary design criteria
No full textThis paper aims at proposing fast and plain design tools to evaluate the best energy application for deep borehole heat exchangers, exploiting geothermal resources. Exergy efficiency has been chosen as a performance index. Five possible utilization solutions have been analyzed: district heating, adsorption cooling, ORC power production, a thermal cascade system, and combined heat and power configuration. An extensive sensitivity analysis on source characteristics and well geometry has been performed to find the design criteria that ensure the maximum exergy performance. Results show that configurations involving district heating are recommended for exclusive power production. If optimized, district heating exergy efficiency can reach values in the range 40%–50% when a geothermal source at the well bottom is lower than 300 °C. For higher values, the combined heat and power production is a preferable choice, reaching an exergy efficiency of up to 60%. Design charts are also provided to read first-attempt values of the well operative temperatures and flow rate to maximize exergy efficiency for each utilization layouts
Producing geothermal energy with a deep borehole heat exchanger: Exergy optimization of different applications and preliminary design criteria
No full textThis paper aims at proposing fast and plain design tools to evaluate the best energy application for deep borehole heat exchangers, exploiting geothermal resources. Exergy efficiency has been chosen as a performance index. Five possible utilization solutions have been analyzed: district heating, adsorption cooling, ORC power production, a thermal cascade system, and combined heat and power configuration. An extensive sensitivity analysis on source characteristics and well geometry has been performed to find the design criteria that ensure the maximum exergy performance. Results show that configurations involving district heating are recommended for exclusive power production. If optimized, district heating exergy efficiency can reach values in the range 40%–50% when a geothermal source at the well bottom is lower than 300 °C. For higher values, the combined heat and power production is a preferable choice, reaching an exergy efficiency of up to 60%. Design charts are also provided to read first-attempt values of the well operative temperatures and flow rate to maximize exergy efficiency for each utilization layouts
Evaluating the Available Regional Groundwater Resources using the Distributed Hydrogeological Budget
No full textIn this study, several hydrogeological catchments of Central Italy have been characterized focusing the attention on the presence of areas in which, over the last two decades,the hydrological equilibrium between recharge and discharge (phenomena of marked reduction of spring discharge and progressive drawdown of groundwater levels) has been compromised
by overexploitation of groundwater resources. A GIS system has been used in order to develop the study and the homogenous distribution of the hydrological knowledge and of the existing imbalances has been performed. Characterizing elements of the research are: a) the definition
of the hydrogeological units; b) the hydrogeological survey of around a thousand water-points;
c) the monthly analysis of climatic data of numerous survey stations; d) the census and the recording of water concessions; e) the evaluation of agriculture hydro-exigency derived from
the analysis of the use of soil; f) the withdrawals defined by a statistic analysis of data. These
elements have allowed to define the Distributed Hydrogeological Budget which is a useful instrument to evaluate critical areas
A comprehensive exergy evaluation of a deep borehole heat exchanger coupled with a ORC plant. The case study of Campi Flegrei
No full textThe paper presents a comprehensive energy and exergy analysis of a possible geothermal power plant located in the geothermal district of Campi Flegrei (Italy), made of a coaxial WellBore Heat eXchanger coupled to an Organic Rankine Cycle. We have accounted for all system components: the ground source, the WellBore Heat eXchanger, the Organic Rankine Cycle cycle, and cooling system. The energy and exergy performance indexes of each subsystems and overall system have been evaluated, thus calculating the net power, the First-Law efficiency, the Second-Law efficiency, the irreversibilities. The results indicate a good potential of the WellBore Heat eXchanger – Organic Rankine Cycle technology in the area, as the estimated performances have similar values to those of classical binary geothermal power plants: a First-Law efficiency of 11.67% and a Second-Law efficiency of about 43.80%. The overall system performances decrease respectively to 10.62% due to the fans energy requirements in the cooling tower and to 23.15% due to the large exergy destruction occurring in the WellBore Heat eXchanger. A deep exergy analysis of the WellBore Heat eXchanger has highlighted that the overall irreversibility is strongly affected by the insulation performance between the two coaxial pipes and by the temperature deviation between the ground and the fluid. The latter one is mainly due to the continuous heat extraction from the geothermal source, therefore proposed improvement strategies consist of both the increasing of thermal resistance of the material insulating the upward pipe and the reduction of the equivalent thermal radius of the well optimizing the heat extraction profiles over the plant lifetime
Knowledge Discovery in Databases and Multiphase Flow Metering: The Integration of Statistics, Data Mining, Neural Networks, Fuzzy Logic, and Ad Hoc Flow Measurements Towards Well Monitoring and Diagnosis
No full textThe usual approach to the interpretation of producing wells is based on mechanistic models for the simulation of steady state and transient flow regimes. However, there are significant reservations about convergence problems, computational limits, the need for extensive tuning on field data, the instability of boundary conditions, the limited applicability of existing multiphase flow models, and the uncertainties associated with choke valve models. The current industry standards are critically reviewed within this framework. The real-time monitoring of producing wells is recognised as the best way of optimising field performance. Monitoring a producing well implies the ability to track, in real-time, any changes in fluid composition, flow rates, or pressure and temperature profiles. Multiphase Flow Metering (MFM) plays a key role in this scenario. Such information, combined with the critical analysis of historical data from the well itself or from analogue wells, allows diagnosis of the system and prediction of future trends. However, field data per se' do not necessarily generate knowledge. This is particularly true for large databases, which are difficult to manipulate to provide suitable inputs for wellbore simulators. This paper suggests how MFM, Knowledge Discovery in Databases (KDD) and Fuzzy Logic (FL) can offer an alternative approach to the analysis of producing wells. KDD is the automated extraction of patterns representing knowledge implicitly stored in large information repositories. Distributed, ad-hoc field measurements (including MFM and downhole measurements) can be processed via data cleaning, data integration, data mining, artificial intelligence, and pattern evaluation. FL can then manage the resulting information in terms of flow assurance and production optimisation. The same techniques can also be extended to the reservoir and the production network, for an integrated approach to production system analysis
INTEGRATION OF MULTIPHASE FLOW METERING, NEURAL NETWORKS AND FUZZY LOGIC IN FIELD PERFORMANCE MONITORING
No full textThe usual approach to the interpretation of producing wells is based on mechanistic models for the simulation of steady state and transient flow regimes. However, there are significant reservations about convergence problems, computational limits, the need for extensive tuning on field data, the instability of boundary conditions, the limited applicability of existing multiphase flow models, and the uncertainties associated with choke valve models. The current industry standards are critically reviewed within this framework. The real-time monitoring of producing wells is recognised as the best way of optimising field performance. Monitoring a producing well implies the ability to track, in real-time, any changes in fluid composition, flow rates, or pressure and temperature profiles. Multiphase Flow Metering (MFM) plays a key role in this scenario. Such information, combined with the critical analysis of historical data from the well itself or from analogue wells, allows diagnosis of the system and prediction of future trends. However, field data per se’ do not necessarily generate knowledge. This is particularly true for large databases, which are difficult to manipulate to provide suitable inputs for wellbore simulators. This paper suggests how MFM, Knowledge Discovery in Databases (KDD) and Fuzzy Logic (FL) can offer an alternative approach to the analysis of producing wells. KDD is the automated extraction of patterns representing knowledge implicitly stored in large information repositories. Distributed, ad-hoc field measurements (including MFM and downhole measurements) can be processed via data cleaning, data integration, data mining, artificial intelligence, and pattern evaluation. FL can then manage the resulting information in terms of flow assurance and production optimisation. The same techniques can also be extended to the reservoir and the production network, for an integrated approach to production system analysis
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