Sviluppo di una metodologia per la modellazione geologica-geomeccanica ed il monitoraggio di reservoir adibiti a siti di stoccaggio di gas naturale

La valutazione dei rischi associati all’operatività dei sistemi di stoccaggio, quali la sismicità indotta e la subsidenza, è requisito basilare per una loro corretta gestione e progettazione, e passa attraverso la definizione dell’influenza sullo stato tensionale delle variazioni di pressione di poro nel sottosuolo. Principale scopo di questo progetto è lo sviluppo di una metodologia in grado di quantificare le deformazioni dei reservoir in funzione della pressione di poro, di tarare i modelli utilizzati con casi studio che presentino dati di monitoraggio reali, tali da consentire un confronto con le previsioni di modello. In questa tesi, la teoria delle inomogeneità è stata utilizzata, tramite un approccio semianalitico, per definire le variazioni dei campi elastici derivanti dalle operazioni di prelievo e immissione di fluidi in serbatoi geologici. Estensione, forma e magnitudo delle variazioni di stress indotte sono state valutate tramite il concetto di variazione dello sforzo critico secondo il criterio di rottura di Coulomb, tramite un’analisi numerica agli elementi finiti. La metodologia sviluppata è stata applicata e tarata su due reservoir sfruttati e riconvertiti a sistemi di stoccaggio che presentano dataset, geologia, petrofisica, e condizioni operative differenti. Sono state calcolate le variazioni dei campi elastici e la subsidenza; è stata mappata la variazione di sforzo critico di Coulomb per entrambi i casi. I risultati ottenuti mostrano buon accordo con le osservazioni dei monitoraggi, suggerendo la bontà della metodologia e indicando la scarsa probabilità di sismicità indotta. Questo progetto ha consentito la creazione di una piattaforma metodologica di rapido ed efficace utilizzo, per stimare l’influenza dei sistemi di stoccaggio di gas sullo stato tensionale della crosta terrestre; in fase di stoccaggio, permette di monitorare le deformazioni e gli sforzi indotti; in fase di progettazione, consente di valutare le strategie operative per monitorare e mitigare i rischi geologici associati a questi sistemi.

Evaluation of alkali flooding combined with intermittent flow in carbonate reservoir

The majority of carbonate reservoir is oil-wet, which is an unfavorable condition for oil production. Generally, the total oil recovery after both primary and secondary recovery in an oil-wet reservoir is low. The amount of producible oil by enhanced oil recovery techniques is still large. Alkali substances are proven to be able to reverse rock wettability from oil-wet to water-wet, which is a favorable condition for oil production. However, the wettability reversal mechanism would require a noneconomical aging period to reach the maximum reversal condition. An intermittent flow with the optimum pausing period is then combined with alkali flooding (combination technique) to increase the wettability reversal mechanism and as a consequence, oil recovery is improved. The aims of this study are to evaluate the efficiency of the combination technique and to study the parameters that affect this method. In order to implement alkali flooding, reservoir rock and fluid properties were gathered, e.g. interfacial tension of fluids, rock wettability, etc. The flooding efficiency curves are obtained from core flooding and used as a major criterion for evaluation the performance of technique. The combination technique improves oil recovery when the alkali concentration is lower than 1% wt. (where the wettability reversal mechanism is dominant). The soap plug (that appears when high alkali concentration is used) is absent in this combination as seen from no drop of production rate. Moreover, the use of low alkali concentration limits alkali loss. This combination probably improves oil recovery also in the fractured carbonate reservoirs in which oil is uneconomically produced. The results from the current study indicate that the combination technique is an option that can improve the production of carbonate reservoirs. And a less quantity of alkali is consumed in the process.

Dimensionamento di invasi per il controllo dei deflussi nei bacini urbanizzati

Urbanization is a continuing phenomenon in all the world. Grasslands, forests, etc. are being continually changed to residential, commercial and industrial complexes, roads and streets, and so on. One of the side effects of urbanization with which engineers and planners must deal with, is the increase of peak flows and volumes of runoff from rainfall events. As a result, the urban drainage and flood control systems must be designed to accommodate the peak flows from a variety of storms that may occur. Usually the peak flow, after development, is required not to exceed what would have occurred from the same storm under conditions existing prior to development. In order to do this it is necessary to design detention storage to hold back runoff and to release it downstream at controlled rates. In the first part of the work have been developed various simplified formulations that can be adopted for the design of stormwater detention facilities. In order to obtain a simplified hydrograph were adopted two approaches: the kinematic routing technique and the linear reservoir schematization. For the two approaches have been also obtained other two formulations depending if the IDF (intensity-duration-frequency) curve is described with two or three parameters. Other formulations have been developed taking into account if the outlet have a constant discharge or it depends on the water level in the pond. All these formulations can be easily applied when are known the characteristics of the drainage system and maximum discharge that these is in the outlet and has been defined a Return Period which characterize the IDF curve. In this way the volume of the detention pond can be calculated. In the second part of the work have been analyzed the design of detention ponds adopting continuous simulation models. The drainage systems adopted for the simulations, performed with SWMM5, are fictitious systems characterized by different sizes, and different shapes of the catchments and with a rainfall historical time series of 16 years recorded in Bologna. This approach suffers from the fact that continuous record of rainfall is often not available and when it is, the cost of such modelling can be very expensive, and that the majority of design practitioners are not prepared to use continuous long term modelling in the design of stormwater detention facilities. In the third part of the work have been analyzed statistical and stochastic methodologies in order to define the volume of the detention pond. In particular have been adopted the results of the long term simulation, performed with SWMM, to obtain the data to apply statistic and stochastic formulation. All these methodologies have been compared and correction coefficient have been proposed on the basis of the statistic and stochastic form. In this way engineers which have to design a detention pond can apply a simplified procedure appropriately corrected with the proposed coefficient.

Mg for hydrogen storage: synthesis, nanostructure and thermodynamics properties

Nowadays alternative energies are an extremely important topic and the possibility of using hydrogen as an energy carrier must be explored. Many problems infer the technological application of this abundant and powerful resource, one of them the possibility of storage. In the framework of suitable materials for hydrogen storage, magnesium has been the center of this study because it is cheap and the amount of stored hydrogen that it achieves (7.6 wt%) is extremely appealing. Nanostructure helps to overcome the slow hydrogen diffusion and the functionalization of surfaces with transition metals or oxides favors the hydrogen molecule dissociation/recombination. The aim of this research is the investigation of the metal-hydride transformation in magnesium nanoparticles synthesized by inert-gas condensation, exploiting the fact that they are a simple model system. The so produced nanostructured powder has been analyzed in response to nanoparticles surface functionalization by transition metal clusters, specifically palladium, nickel and titanium, chosen on the basis of their completely different Mg-related phase diagrams. The role of the intermetallic phases formed upon heating and hydrogenation treatments will be presented to provide a comprehensive picture of hydrogen sorption in this class of nanostructured storage materials.

Characterization of geothermal reservoirs’ parameters by inverse problem resolution and geostatistical simulations

BTES (borehole thermal energy storage)systems exchange thermal energy by conduction with the surrounding ground through borehole materials. The spatial variability of the geological properties and the space-time variability of hydrogeological conditions affect the real power rate of heat exchangers and, consequently, the amount of energy extracted from / injected into the ground. For this reason, it is not an easy task to identify the underground thermal properties to use when designing. At the current state of technology, Thermal Response Test (TRT) is the in situ test for the characterization of ground thermal properties with the higher degree of accuracy, but it doesn’t fully solve the problem of characterizing the thermal properties of a shallow geothermal reservoir, simply because it characterizes only the neighborhood of the heat exchanger at hand and only for the test duration. Different analytical and numerical models exist for the characterization of shallow geothermal reservoir, but they are still inadequate and not exhaustive: more sophisticated models must be taken into account and a geostatistical approach is needed to tackle natural variability and estimates uncertainty. The approach adopted for reservoir characterization is the “inverse problem”, typical of oil&gas field analysis. Similarly, we create different realizations of thermal properties by direct sequential simulation and we find the best one fitting real production data (fluid temperature along time). The software used to develop heat production simulation is FEFLOW 5.4 (Finite Element subsurface FLOW system). A geostatistical reservoir model has been set up based on literature thermal properties data and spatial variability hypotheses, and a real TRT has been tested. Then we analyzed and used as well two other codes (SA-Geotherm and FV-Geotherm) which are two implementation of the same numerical model of FEFLOW (Al-Khoury model).

Development of a microgrid with renewable energy sources and electrochemical storage system integration

Beside the traditional paradigm of "centralized" power generation, a new concept of "distributed" generation is emerging, in which the same user becomes pro-sumer. During this transition, the Energy Storage Systems (ESS) can provide multiple services and features, which are necessary for a higher quality of the electrical system and for the optimization of non-programmable Renewable Energy Source (RES) power plants. A ESS prototype was designed, developed and integrated into a renewable energy production system in order to create a smart microgrid and consequently manage in an efficient and intelligent way the energy flow as a function of the power demand. The produced energy can be introduced into the grid, supplied to the load directly or stored in batteries. The microgrid is composed by a 7 kW wind turbine (WT) and a 17 kW photovoltaic (PV) plant are part of. The load is given by electrical utilities of a cheese factory. The ESS is composed by the following two subsystems, a Battery Energy Storage System (BESS) and a Power Control System (PCS). With the aim of sizing the ESS, a Remote Grid Analyzer (RGA) was designed, realized and connected to the wind turbine, photovoltaic plant and the switchboard. Afterwards, different electrochemical storage technologies were studied, and taking into account the load requirements present in the cheese factory, the most suitable solution was identified in the high temperatures salt Na-NiCl2 battery technology. The data acquisition from all electrical utilities provided a detailed load analysis, indicating the optimal storage size equal to a 30 kW battery system. Moreover a container was designed and realized to locate the BESS and PCS, meeting all the requirements and safety conditions. Furthermore, a smart control system was implemented in order to handle the different applications of the ESS, such as peak shaving or load levelling.

Effect of antioxidant supplementation on pig and horse gamete storage

According to recent studies, antioxidant supplementation on gamete processing and/or storage solutions improvesgamete quality parameters, after cooling or storage at sub zero temperature. The aim of the present study was to investigate the effects of antioxidant supplementation on pig and horse gamete storage. The first study aimed to determine the effects of resveratrol (RESV) on the apoptotic status of porcine oocytes vitrified by Cryotop method, evaluating phosphatidylserine (PS) exteriorization and caspases activation. RESV(2µM) was added during: IVM (A); 2 h post-warming incubation (B); vitrification/warming and 2 h post-warming incubation (C); all previous phases (D). The obtained data demonstrate that RESV supplementation in the various steps of IVM and vitrification/warming procedure can modulate the apoptotic process, improving the resistance of porcine oocytes to cryopreservation-induced damage. In the second work different concentrations of RESV (10, 20, 40, and 80µM) were added during liquid storage of stallion sperm for 24 hours at either 10°C or 4°C, under anaerobic conditions. Our findings demonstrate that RESV supplementation does not enhance sperm quality of stallion semen after 24 hours of storage. Moreover, the highest RESV concentrations tested (40 and 80µM) could damage sperm functional status, probably acting as pro-oxidant. Finally, in the third work other two antioxidants, ascorbic acid (AA) (100 µM) and glutathione (GSH) (5mM) were added on boar freezing and/or thawing solutions. In our study different sperm parameters were evaluated before freezing and at 30 and 240 minutes after thawing. Our results showed that GSH and AA significantly improved boar sperm cryotolerance, especially when supplemented together to both freezing and thawing media. This improvement was observed in sperm viability and acrosome integrity, sperm motility, and nucleoprotein structure. Although ROS levels were not much increased by freeze-thawing procedures, the addition of GSH and AA to both freezing and thawing extenders significantly decreased intracellular peroxide levels.

Quality control of virgin olive oils with regard to different storage and shipment conditions

Virgin olive oil(VOO) is a product characterized by high economic and nutritional values, because of its superior sensory characteristics and minor compounds (phenols and tocopherols) contents. Since the original quality of VOO may change during its storage, this study aimed to investigate the influence of different storage and shipment conditions on the quality of VOO, by studying different solutions such as filtration, dark storage and shipment inside insulated containers to protect it. Different analytical techniques were used to follow-up the quality changes during virgin olive oil storage and simulated shipments, in terms of basic quality parameters, sensory analysis and evaluation of minor components (phenolic compounds, diglycerides, volatile compounds). Four main research streams were presented in this PhD thesis: The results obtained from the first experimental section revealed that the application of filtration and/or clarification can decrease the unavoidable quality loss of the oil samples during storage, in comparison with unfiltered oil samples. The second section indicated that the virgin olive oil freshness, evaluated by diglycerides content, was mainly affected by the storage time and temperature. The third section revealed that fluctuation in temperature during storage may adversely affect the virgin olive oil quality, in terms of hydrolytic rancidity and oxidation quality. The fourth section showed that virgin olive oil shipped inside insulated containers showed lower hydrolytic and oxidation degradation than those without insulation cover. Overall, this PhD thesis highlighted that application of adequate treatment, such as filtration or clarification, in addition to a good protection against other external variables, such as temperature and light, will improve the stability of virgin olive oil during storage.