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A conceptual and numerical model of fluid flow and heat transport in the Topusko hydrothermal system
No full textComprehensive understanding of hydrothermal systems is often obtained through the integration of conceptual and numerical modelling. This integrated approach provides a structured framework for the reconstruction and quantification of fluid dynamics in the reservoir, thereby facilitating informed decision-making for sustainable utilisation and environmental protection of the hydrothermal system. In this study, an updated conceptual model of the Topusko hydrothermal system (THS; central Croatia) is proposed based on structural, geochemical, and hydrogeological analyses. The stratigraphic sequence and the structural framework of the THS were defined based on geological maps and field investigations. As depicted by hydrochemical and isotope analyses, thermal waters in Topusko (temperatures of up to 65 °C) are of meteoric origin and circulate in a carbonate aquifer. The THS receives diffuse recharge approximately 13 km S from Topusko, where Triassic carbonates crop out. Gravity-driven regional groundwater circulation is favoured by regional thrusts that tectonically uplifted Palaeozoic low permeable rocks. These structures confine the fluid flow in the permeable, fractured and karstified, Triassic carbonates favouring the northward circulation of the water. A regional anticline lifts the aquifer closer to the surface in Topusko. Open fractures in the anticline hinge zone increase the fracturing and permeability field of the aquifer promoting the quick upwelling of the thermal water resulting in the Topusko thermal springs. Numerical simulations of fluid flow and heat transport corroborate the proposed conceptual model. In particular, a thermal anomaly was modelled in the Topusko subsurface with temperature values of 31.3 °C and 59.5 °C at the surface and at the base of the thermal aquifer, respectively, approaching the field observations. These findings showed that the circulation of Topusko thermal water is influenced by regional and local geological structures suggesting that the enhanced permeability field in the discharge area enables the formation of the natural thermal springs
Carbonation study of new calcium aluminate cement-based CO2 injection well sealants
No full textIn injection-well carbon storage projects, the degradation of Portland cement under harsh CO2 conditions is a primary concern. This study introduces novel CO2-resistant calcium aluminate cement (CAC) systems with addition of rubber latex and hollow glass microspheres which are added to the system to enhance the set cement resistance to CO2 corrosion and in the same time to optimize it for the application in a wide variety of well conditions. After exposure to near supercritical CO2 conditions (100 ◦C, 7 MPa) these systems exhibited enhanced compressive strength and reduced porosity compared with conventional Portland cement (PC) system, especially the one without latex. By subjecting degradation depth-resolved samples to thermogravimetry (TG) and X-ray diffraction (XRD) techniques, coupled with scanning electron microscopy (SEM), the study scrutinized alterations in microstructural properties. This methodological approach unveiled a profound grasp of carbonation mechanisms. Confirmed through TG and XRD analyses, the considerable reduction in carbonation establishes CAC as a compelling choice for CO2-resistant sealing within injection-well CO2 storage endeavors
Assessment of near-surface geophysical methods used to discover karst bauxite deposits in the Dinarides using the example of Posušje area, Bosnia and Herzegovina
No full textGeophysical exploration of bauxite deposits has been carried out in the area of Posušje in Bosnia and Herzegovina, which were formed on an Upper Cretaceous carbonate substrate, whereas the hanging wall rocks can be Paleogene limestones and sedimentary clastic rocks. Karst terrains are demanding for geophysical exploration due to the relatively complex geological relationships and exceptional near-surface inhomogeneities that generate large noises and challenging conditions for taking field measurements. The fundamental question is whether geophysical research can detect exceptionally irregular karst bauxite deposits with relatively small dimensions. The basic idea is to combine several geophysical methods and a joint interpretation of several data sets to increase the efficiency of geophysical surveying in detecting complex bauxite deposits in karst terrains. Therefore, fundamental near-surface research methods, electrical tomography and seismic refraction are used. In addition, magnetometry was used to examine whether bauxite deposits yield potential magnetic anomalies that could help in detecting them. Research undertaken in the area of Posušje was carried out in the first step on already discovered and known bauxite deposits to determine whether geophysical responses correlate with the occurrence of bauxite deposits and to evaluate the effectiveness of each of the applied surface geophysical methods. Measurements were taken at several locations, and results for two micro-locations, Krstače and Mratnjača, are shown. Geophysical measurements were firstly performed on discovered bauxite deposits in order to reliably determine the possibility of identifying deposits in geophysical inverse models. Bauxite deposits were clearly recognised as characteristic geophysical responses in inversion models using both methods, electrical tomography and seismic refraction. Although the response of bauxite deposits is expressed in both models, resistivity and velocity, it is much more evident in resistivity models. The characteristic resistivity response was confirmed by the discovery of a new deposit. Therefore, the conclusion is that electrical resistivity tomography should be considered a basic method for exploring karst bauxite deposits. Seismic refraction provides a better characterisation of deposits and reduces the interpretation ambiguity. This solution can generally be applied to the problem of researching bauxite deposits in the Dinarides and similar geological models in the Mediterranean. Magnetometric measurements have shown that no magnetic anomalies could be associated with bauxite deposits, and only magnetometry was not successful in discovering bauxite deposits
Impact of coal depository and slag disposal from the Plomin thermal power plant on soil composition: insights from geochemical, mineralogical, and organic petrological analyses, Istria, Croatia
No full textThe potential impact of the open coal depository and the slag disposal of the Plomin thermal power plant (PTPP) on the composition of the surrounding soils was investigated. A comprehensive approach taken included analyses of mineral composition, potentially toxic element content, their bonding properties, distribution to specific geochemical fractions in the soil and investigation of the soil organic petrology and geochemistry. The Cambisols at two sampling sites exhibited a coal dust-covered upper horizon, which led us to consider these soil profiles as Technosol over Cambisol. For practical reasons, we have used the terms Technosol and Cambisol for the upper and lower parts of these profiles respectively. These formations were developed by the long-term deposition of coal dust and slag particles originating from the open coal depository and slag disposal of the PTPP, and widespread wind dispersion. The Technosols, characterized by higher concentrations of lignite and lignite-subbituminous coal, showed elevated levels of C and S. Analysis of the slag sample revealed a mineral composition of mullite, tridymite, graphite, haematite and an amorphous phase, indicating material formation by high temperature coal combustion. The PTPP was identified as the main contributor to the elevated concentrations of Hg, Mo, Se, Sb, U and Cd. The Technosols showed a significant enrichment in Hg, Sb, Se, Mo and U compared to the Cambisols. In the Technosols, elements such as As, Cr, Cu, Fe, Ni and Zn were primarily associated with the organic and Fe-Mn fractions, whereas in the Cambisols these elements, (with the exception of Cu), are mainly associated with the organic and residual fractions. Cadmium, Mn and Pb were predominantly bound to the carbonate and Fe-Mn fractions in all the analyzed samples. The non-residual fraction has been proven to be the predominant repository for As, Zn and Ni in the Technosols and slag, and for Mn, Zn and Cd in the Cambisols. The total content of C and S in the soils and their ratio (C/S) confirmed the higher contamination of soils in the vicinity of the PTPP with coal material. Detection of the coke and soot in the slag sample substantiated its composition as bottom coal ash. In addition, the presence of the bottom coal ash particles in the Cambisol underlined the airborne dispersal of the slag and its integration into the soil composition
Applicability of magnetic susceptibility measurements on cave sediments in karst areas: insight from Dinaric Karst (Velebit Mt., Croatia)
No full textMagnetism in Croatian caves has been significantly underexplored, despite the well-documented preservation of cave sediments. This study investigates whether magnetic susceptibility can be effectively recorded in Croatian caves and, if so, whether there are differences between in situ and laboratory measurements, as well as the extent of these differences. The focus is on two prominent sites within the Velebit Mountain range of the Dinaric Karst: the deep Slovačka Cave and the extensive Crnopac Cave System (ex. Kita Gaćešina Cave). Magnetic susceptibility was measured in soft sediments using the Kappameter KM-7 for in situ assessments and the Bartington MS2B System for laboratory analyses. The comparison of the two devices aimed to evaluate the feasibility of detecting magnetic susceptibility variations within carbonate sediments. Sampling locations were selected based on preliminary assessments of magnetic susceptibility variations and accessibility for sampling. Characteristic samples from each profile underwent X-ray powder diffraction analysis. Results revealed significant variations in magnetic susceptibility across each profile under both in situ and laboratory conditions. In situ measurements ranged from −45 × 10−5 SI to 120 × 10−5 SI, while laboratory measurements ranged from 4.00 × 10−5 SI to 99.40 × 10−5 SI. The portable Kappameter KM-7 provided satisfactory results for preliminary investigations, while the Bartington MS2B System demonstrated high precision in analyzing these variations in detail. These findings support the potential for further investigations into magnetic susceptibility in karst cave environments, with an emphasis on understanding depositional history and the timeline of climate and tectonic changes
Numerical simulation study of cavity formation in soil under blast load
No full textThe main applications of civil explosives in soils are soil compaction, mass excavation, and in situ pile creation. The suitability of explosives for each of these applications strongly depends upon the explosive properties and the soil properties. For those reasons, a reliable estimation or process simulation regarding cost efficiency and explosive work ability in the soil with known soil parameters is relevant. This paper presents a numerical simulation study of different types of soil (different amounts of gravel, sand, silt, and clay) under a blast load modeled using Ansys 2020 R1 Autodyn 2D hydrocode, with different types of explosives. The calculated results from the Ansys 2020 R1 Autodyn 2D and the experimental results obtained from the in situ cavity formation caused by blasting are presented. The Jones–Wilkins–Lee (JWL) equation of state parameters was calculated using EXPLO5 V7.01.01 supported by experimental data, while the soil and explosive properties were measured in laboratory and in situ
Revisiting the theoretical prediction of the explosive performance found by the Trauzl test
No full textThe Trauzl lead block test allows the determination of the approximate performance of explosives in blasting applications by measuring the volume increase (expansion) that is produced by the detonation of an explosive charge in the cavity of a lead block. In this paper, we reconsider the possibility of interpreting the Trauzl test results in terms of detonation parameters or quantities. The detonation parameters used in the analysis are calculated using the thermochemical code EXPLO5, while the hydrocode AUTODYN is used to simulate the effect of explosive charge density and reaction rate on the results of the Trauzl test. The increase in the volume of the lead block cavity was found to correlate best with the product of the detonation heat and the root of the volume of detonation products. Hydrocode simulation showed that the density of explosive charge and the rate of explosive decomposition affect the dynamics of the interaction of the detonation product and the lead block, and consequently the lead block cavity volume increase
Determination of the critical diameter for low density emulsion explosives : master's thesis
No full textZbog sve veće urbanizacije javlja se potreba za izvođenjem opreznih miniranja kako bi se što manje oštetila okolna stjenska masa te da se očuva njena fizikalno-mehanička svojstva van zone miniranja i da se smanji potencijalno štetni utjecaj miniranja na okolne objekte. Tipični eksplozivi koji se koriste u rudarstvu ne zadovoljavaju tražene zahtjeve za izvođenjem opreznih miniranja stoga je potrebno odrediti minersko-tehničke karakteristike emulzijskih eksploziva smanjene gustoće. Ispitivanjem na poligonu određen je kritični promjer i brzina detonacije za ispitivani emulzijski eksploziv smanjene gustoće iniciran trenutnim električnim detonatorom i trenutnim električnim detonatorom s pojačnikom.Due to increasing urbanization, there is a need to carry out careful blasting in order to damage the surrounding rock mass as little as possible and to preserve its physical and mechanical properties outside the blasting zone and to reduce the potentially harmful impact of blasting on surrounding objects. Typical explosives that are used in mining do not meet the requirements for careful blasting, so it is necessary to determine the miningtechnical characteristics of low-density emulsion explosives. The critical diameter and detonation velocity of the tested low-density emulsion explosive, that was initiated by an instantaneous electric detonator and an instantaneous electric detonator with booster, were determined by field tests
Influence of the mandarin peel powder particle size on the filtration properties of a water-based mud : master's thesis
No full textIsplaka predstavlja jedan od ključnih elemenata bušaćih operacija te je vrlo bitno ispravno ju dizajnirati kako bi ispunjavala sve potrebne zadatke. Najčešće se koristi isplaka na bazi vode zbog smanjenog utjecaja na okoliš te dostupnosti vode kao baznog fluida za njenu pripremu. Mnogi aditivi koji se dodaju u isplaku kategoriziraju se kao štetni za okoliš te je stoga potrebno razviti nove vrste aditiva. Brojna istraživanja su provedena u tu svrhu koristeći biorazgradivi otpad kao potencijalne aditive. U ovom radu korišten je prah kore mandarine podijeljen u četiri frakcije raspona veličina čestica od 0,063 mm do 0,10 mm, od 0,05 mm do 0,063 mm, od 0,045 mm do 0,05 mm i od 0 mm do 0,045 mm. Također, prah se dodavao u četiri koncentracije: 0,5%, 1%, 1,5% i 2% na volumen vode. Dobiveni rezultati pokazali su da povećanjem koncentracije praha kore mandarine dolazi do smanjenja API filtracija i do 55% dok veličina čestica nije previše utjecala na rezultat. PPT filtracija se dodavanjem praha smanjivala do 39%. Na temelju rezultata može se zaključiti da prah kore mandarine može služiti kao aditiv za smanjenje filtracije na temperaturama do 140°C.The mud represents one of the key elements of drilling operations, and it is very important to design it correctly in order to fulfill all the necessary tasks. Water-based mud is most often used due to the reduced impact on the environment and the availability of water as based fluid. Many additives that are added to the mud are categorized as harmful to the environment and therefore it is necessary to develop new types of additives. Numerous studies have been conducted for this purpose using biodegradable waste as potential additives. In this work mandarin peel powder was used and divided into four fractions with particle sizes ranging from 0.063 mm to 0.10 mm, from 0.05 mm to 0.063 mm, from 0.045 mm to 0.05 mm and from 0 mm to 0.045 mm. The powder was also added in four concentrations: 0.5%, 1%, 1.5% and 2% by volume of water. The obtained results showed that, by increasing the concentration of mandarin peel powder, the API filtration was reduced by up to 55%, while the particle size did not affect the results too much. PPT filtration was reduced by up to 39% by adding powder. Based on the results, it can be concluded that the mandarin peel powder can be used as an additive to reduce filtration at temperatures up to 140°C
Revitalization of the Savica-1 exploratory well by installing a coaxial heat exchanger : master's thesis
No full textKontinuirani porast broja stanovnika i razvoj industrije u zemljama trećeg svijeta rezultiraju većom potražnjom za energijom. S obzirom da mnoge države nemaju vlastite resurse fosilnih goriva ili provode ''zelenu politiku'' postepeno se razvijaju tehnologije iskorištavanja obnovljivih izvora energije. Geotermalna energija ističe se mogućnošću kontinuirane opskrbe krajnjih korisnika. Ipak, mogućnost proizvodnje vruće slojne vode ovisi o hidrogeološkim svojstvima sloja. Bušotinski izmjenjivač topline jedna je od tehnologija koja omogućava toplinsko iskorištavanje niskih do srednje visokih temperatura suhih bušotina. Veliki broj napuštenih bušotina posjeduje takve toplinske karakteristike. S obzirom na varijabilnost cijena fosilnih goriva, revitalizacija takvih bušotina sve je češća praksa. Ovisno o karakteristikama bušotine i sloja, pridobivena toplina koristi se direktno ili u kombinaciji s drugim izvorima energije. Zbog jednostavnosti ugradnje i visoke učinkovitosti, česta je kombinacija bušotinskog izmjenjivača topline s dizalicom topline na površini. Napuštena bušotina Savica-1 ima potencijal za grijanje objekata srednje veličine. Stoga, cilj ovog diplomskog rada je odabir optimalnog sustava bušotinskog izmjenjivača topline kako bi ekstrakcija toplinske energije bila što učinkovitija.Continuous population growth and industrial development in third-world countries result in an increased demand for energy. Given that many countries lack their own fossil fuel resources or implement "green policies," technologies for harnessing renewable energy sources are gradually developing. Geothermal energy stands out because of its ability to continuously supply end-users. However, the possibility of producing hot layer water depends on the hydrogeological properties of the layer. A borehole heat exchanger is one of the technologies that enable thermal utilization of low to medium-high temperatures of dry boreholes. A large number of abandoned boreholes possess such thermal characteristics. Considering the variability of fossil fuel prices, the revitalization of such boreholes is becoming increasingly common. Depending on the characteristics of the borehole and the layer, the obtained heat can be used directly or in combination with other energy sources. Due to the simplicity of installation and high efficiency, the combination of a borehole heat exchanger with a surface heat pump is frequent. The abandoned borehole Savica-1 has the potential to heat medium-sized buildings. Therefore, the aim of this master's thesis is to determine the optimal system of a borehole heat exchanger in order to make the extraction of thermal energy from as efficient as possible