Emily H. Cunningham, Sarah Lambart, Pengyuan Guo
et al.
Abstract The mid‐Norwegian Margin, part of the North Atlantic Igneous Province (NAIP), is a well‐studied volcanic rifted margin formed during the breakup between Greenland and Eurasia ∼56 Ma, with the largest accumulation of magmatic material hosted by the Vøring Margin section. Despite extensive study in the area, the main controls on magmatic productivity during continental breakup remain debated. To constrain the drivers of breakup magmatism, we developed an inverse Monte Carlo statistical melting model that infers source mineralogy from basalt chemistry. When applied to basalts recently recovered on the Vøring Margin, our results reveal a clear shift in source mineralogy during rifting, with peak magmatism coinciding with clinopyroxene enrichment, despite mantle potential temperatures likely being capped below 1500°C. We also establish that, while the proto‐Iceland mantle plume played a role during the emplacement of the NAIP, the main driver for the continental breakup magmatism is lithospheric thinning as a consequence of continent breakup. This study provides new insights into the magmatic and geodynamic evolution of the mid‐Norwegian Margin, emphasizing the role of lithospheric refertilization in driving breakup magmatism.
Abstract Wax deposition is a major flow assurance issue arises during pipeline transportation and wax gelation phenomenon, a fundamental characteristic of this deposition process, necessitates detailed investigation to elucidate the underlying mechanisms. The modelling approach helps in understanding the phenomenon of wax deposition and help in deciding appropriate mitigation technique during pipeline transportation of crude oil. Current study however aims to utilize Analysis of Systems (ANSYS) fluent software to model wax deposition phenomena using field data. The crude oil utilized for the study contains 38% wax and has pour point of 36 °C. The fluid flow was 1 GPM and the inlet temperature was 333.15 K which decreases up to 298.15 K. A Computational Fluid Dynamics (CFD) model was created to predict the wax gelation as a function of time, temperature and pipeline length for Indian crude oil using field data. It includes heat and mass transfer calculations, and the molecular diffusion process is considered as the mechanism for wax deposition. The CFD model in this work uses enthalpy porosity method where waxy oil is treated as the solid-liquid region with a porosity which equal to the liquid fraction. Moreover, the efficacy of the chemical additive was also evaluated in terms of liquid fraction by modelling approach in crude oil during pipeline transportation to evaluate its effect during field implementation. The results indicate that the wax deposition process is time dependent as it subsequently decreases with time. Furthermore, the temperature gradient between wall temperature and bulk fluid temperature also has a significant impact on wax deposition. Increase in the temperature gradient between wall and ambient temperature leads to increase the wax deposition and gelling formation. The use of Nanohybrid polymer (NHP) as an additive significantly improves the flow properties by reducing the wax deposition and increases the liquid fraction up to 75%. The study of CFD to model the wax-gelling process, with the wax gelation being monitored by analysing the variations in the liquid fractions of the crude oil aims to offer a thorough understanding of wax deposition and gelation phenomena in waxy oils, thereby facilitating the design of pipelines for waxy oils with suitable interventions, particularly under subsea conditions.
Abstract Soft rock has the properties of low strength, poor integrity, and difficulty in core extraction. In order to study the deformation and failure of soft rock, this study used fine river sand as aggregate, cement and gypsum as bonding materials, and borax as a retarder to produce cylindrical rock-like samples (RLS) with a sand cement ratio of 1:1. Uniaxial compression tests were conducted on RLS under DIT (different immersion times) (0, 4, 8, 12, 24, and 48 h) in the laboratory. The mechanical and energy properties of RLS under water-stress coupling were analyzed. The results showed that the longer the IT of the RLS, the higher their water content (WC). As the moisture time increases, the uniaxial compressive strength, elastic modulus (EM), and softening coefficient (SC) of the sample gradually decrease, while the rate of change of EM is the opposite. The fitted sample SC exhibits a good logarithmic function relationship with WC. During the loading process of the sample, more than 60% of the U (total energy absorbed) during the loading process of the sample is accumulated in the form of U e (releasable elastic energy), while less than 40% of U is dissipated by the newly formed micro cracks during the compaction, sliding, and yield stages of the internal pores and cracks of the sample. The U before the peak and the U e of the RLS decrease exponentially with the moisture content; the relationship curves of U e/U (released elastic energy ratio) and U d/U (dissipated energy ratio) of RLS during uniaxial compression with the σ 1/σ max (axial stress ratio) can be divided into three stages of change, namely the stage of primary fissure compaction and closure (σ 1/σ max < 0.25), continuously absorbing energy stage (0.25 < σ 1/σ max < 0.8), and energy dissipation stage (σ 1/σ max > 0.8); the D (damage variable) was defined by the ratio of U d (dissipated energy) to the U dmax (maximum dissipated energy) at failure time of RLS, the fitting of the relationship between the damage variable and axial strain conforms to the logistic equation.
The present study is a review of publications regarding special aspects of the mineralogy of the Kaba meteorite, clay minerals, hydrous phases, and organic matter. In Section 1, the history of fall and finding of the meteorite and the first classical mineralogical description in the Year 1961 are mentioned. The most frequent alteration product of primary silicates and the glassy matrix is Fe-bearing saponite. By modelling of hydrothermal alteration of Allende-type meteorites, artificial saponite could be produced. The thermodynamic study proved the possibility of hydrous neoformation of silicates and magnetite at low temperatures, mostly below 100°C. The formation of Fe-rich external rims in forsterite grains by hydrothermal action was demonstrated by electron probe microanalysis and scanning electron microscopy-cathodo-luminescence methods. Foliation in CV3 carbonaceous chondrites indicates that the Kaba meteorite is derived from the external, shallow zone of the parent body. A combination of X-ray power diffraction (XRD) and Mössbauer spectroscopy made the exact modal analysis of CV3 chondrites possible, including Kaba. The study of alteration by in situ determination of stable oxygen isotope contents may provide constraints regarding the oxygen isotopic composition of the aqueous fluid on the CV parent asteroid. The degree of thermal metamorphism of the organic matter was determined by using Raman spectroscopy. The presence of aromatic and aliphatic, saturated and unsaturated hydrocarbons, and various amino acids was demonstrated. The non-biogenic origin is more probable; however, there are textural and mineralogical observations that may indicate also the biogenic origin of organic matter. In addition to the review of the literature above, as an appendix, shortly new XRD investigations of the authors are reported that indicated smectite-like phases in a thin section made of the meteorite.
Nadezhda G. Razjigaeva, Larisa A. Ganzey, Tatiana A. Grebennikova
et al.
The distribution of tsunami deposits in the lacustrine-swamp sections on the Kasatka Bay coast is
analyzed. The main objects were a swamp formed on the place of overgrown lagoon-type lake located behind
dune ridge, and a low swampy isthmus between Oktyabrskoe and Srednee lakes. Five major events have been
identified, run-up parameters and age have been determined on the base of radiocarbon dating and
tephrostratigraphy. Diatom analysis data were used to confirm the marine origin of the sand. Established events
are correlated with data on adjacent islands and the Eastern Hokkaido coast. A trace of only one strong historical
tsunami was found, its deposits lie above marking volcanic ash Ta-a (1739) of the Tarumai Volcano, Hokkaido.
The tsunami took place in the second half of the 18th century. Perhaps this is a trace of 1780 AD tsunami, the
source was located near Urup Island. Four paleotsunamis are well compared in age with the megatsunamis of
the region (17th, 13th centuries, 1.5; 2.3–2.4 ka), which most clearly manifested on the Eastern Hokkaido coasts
and left sea sands and silts sheets in marshes of the Lesser Kuril Ridge and Kunashir Island. On Iturup, the
thickness of tsunami deposits and wide of sand cover is much less. It has been suggested that the peat section
of Iturup recorded the run-up values in the distal zone of the Late Holocene megatsunami, which had sources in
the southernmost of the Kuril-Kamchatka Trench. Regional strong tsunamis occurred in the period of instrumental
observations did not leave geological evidence in the studied sections.
The Qorveh batholith, in the N-Sanandaj-Sirjan Zone, comprises several gabbroic, dioritic and granitic masses intruded the Jurassic metamorphic assemblage (i.e., schist, amphibolite and marble). In spite of a number of studies which have been carried out on the various aspects of these rocks, but none of them has been studied the Mixing/Mingling model. Thus, the purpose of present study is to examine the development of the magmatic mixing process in the rocks under study based on geochemical data obtained from the enclaves and their host rocks as well as their field relationship.Analytical MethodIn order to study the geochemical properties of intrusive rocks, 10 samples of enclaves and their host rocks. The rock composition with the least amount of alteration was selected and sent to the Pennsylvania State University of (USA) to determine the amounts of major elements by ICP-AES method, and rare and rare earth elements by ICP-MS method.Field observationsThe enclaves, in the intrusive masses under study, are finer than that of their host rock. Therefore, they belong to the group of mafic fine-grained enclaves or microgranular mafic enclaves. (MMEs). The (MMEs) are in rounded and elliptical shapes in the host rocks and generally they have a sharp contact with their host and are composed of igneous minerals.PetrographyThe host rocks include granite, granodiorite and monzonite, and the enclaves are dioritic and gabbroic in composition. There are similar minerals in the enclaves and their host rocks, but they often differ in the amount of minerals. They are mainly composed of mafic mineral and plagioclase. While their host rocks are characterized by smaller amounts of these minerals, the host rocks instead have higher amounts of quartz alkali feldspar. The transfer of plagioclase crystals at the common boundary of the enclave and the host rock is evidence of the magmatic mixing process in the nature of the intrusive masses studied. A number of enclaves contain megacrystals of feldspar potassium and quartz taken from the host rocks. This supports the formation of enclaves by mixing.GeochemistryGeochemical studies indicate that these rocks are metaluminous, belonging to calc-alkaline magma series, having I-type characteristics. In Harker diagrams, mafic enclaves have higher MgO, TiO2, P2O5, Na2O, FeO(t), Al2O3, MnO and CaO contents than that of the host rocks, and lower K2O and SiO2 contents. The higher contents of CaO, MgO and FeO(t) in the enclaves, compared to their host, confirms their more mafic nature, which is usually proportional to the higher contents of mafic minerals in the modal of the enclaves than that of the host. The enrichment of the studied enclaves in Co, Cr, Ni display that these rocks are globules of mafic magmas mingling to felsic type.DiscussionAccording to field observations as well as petrographic studies, the effective factor in the evolution of magma forming intrusive masses has been mentioned as magmatic mixing. The presence of mafic fine-grained enclaves with evidence of disequilibrium textures such as feldspar with poikilitic texture, the presence of mafic masses and needle apatite, small blades-shaped plagioclase within large plagioclase or two types of plagioclases, and zoning all confirm magmatic mingling/ mixing processes. Considering that the magnesium number (Mg#) in the mantle is about 0.7 and the studied enclaves with a high magnesium number of 0.52-0.62 are evidence of the involvement of mantle-derived mafic magma. High values of Mg# in enclaves compared to their host rock (0.34-0.48) shows the mixing of magmas from the mantle with the crustal magmas. Magma mixing model has also been considered by geochemical differentiation diagrams. The trend of the samples is a curve and indicates that the effective process in magma evolution is most likely magmatic fusion. Numerous studies have shown that mafic microgranular enclaves are globules of a mantle derived mafic magma that crystallize rapidly in the injected felsic magma from the crust and, as a result, become more viscous, forming separated magmatic bubbles. In addition to the mentioned geochemical features, the enclaves are poor in LREE and LILE and enriched in Ti compared to the host rocks. Therefore, they seem to have originated from two different magmas and are placed together due to magmatic mixing.ConclusionThe host rock units in the studied intrusions include granite, granodiorite, monzonite and gabbroic, dioritic enclaves. The constituent magma of this complex is in I- type, metaluminous and is in the calc-alkaline series. Based on the studies, the dominant process in the evolution of magmatic mixing. Some new findings include the presence of reversals in submerged slabs and the penetration of fleshy compounds. Which naturally have different temperatures and compositions compared to higher crustal horizon magmas, provides conditions for the occurrence and the development of the magmatic mixing process.AcknowledgementsThis paper is a part of the dissertation of the first author and therefore the authors acknowledge the financial support of the research assistant, Bu Ali Sina University.
Abstract CO2-EOR is one of the principal techniques for enhanced oil recovery (EOR). The CO2 injection not only promotes oil recovery but also leads to greenhouse gas discharge reduction. Nonetheless, a key challenge in the CO2 flooding process is a premature CO2 breakthrough from highly permeable zones. In recent years, Inflow Control Devices, ICDs, have been used as a potential solution to mitigate an early gas breakthrough. The key and important parameter in ICDs installation is obtaining its opening flow area. The common ways to obtain the ICD flow area such as utilizing optimization algorithms are very complicated and time-consuming, and further these methods are not analytical. The aim of this work is to solve the mentioned challenges—postpone the breakthrough time in gas injection and present an easy, fast, and analytical technique for obtaining ICDs flow area. This paper presents a new analytical method for obtaining inflow control devices flow area for injection wells in an oil reservoir under CO2-EOR in order to balance the injected CO2 front movement in all layers. Then, in order to compare the advantages and disadvantages of the presented technique with other methods such as optimization algorithms, a case study has been done on a real reservoir model under CO2 injection. Later, the results of studied scenarios in the case studied are given and compared. The results show that by utilizing the proposed method recovery factor is raised by improving sweep efficiency, and the breakthrough time is more postponed compared to the other methods about 400 days. Further, the ICD flow area calculation takes 2 min by presented analytical techniques, but the optimization algorithm takes 4040 min to run the simulation model to find the ICD flow area. In the end, the findings of the presented analytical formula can help to set the ICD flow area very fast without the simulation and help researchers for a better quantitative understanding of parameters affecting the ICD flow area by the given formula such as reservoir permeability.
A generalization of the results on the stress drop and the specific seismic energy for the earthquakes in Northern Eurasia has been made. The relationship of these parameters with the seismic moment and the magnitude has been analyzed. Detailed studies for the Northern Tien Shan (Bishkek geodynamic polygon) were carried out, the values of the dynamic parameters of the sources for 183 earthquakes of various energy classes (K = 8.7–14.8) were obtained: angular frequency, spectral density parameter, scalar seismic moment, source radius, stress drop level, seismic energy and specific seismic energy. Two models have been used to compute the source radius and the stress drop – the Brune approach and the improved Madariaga–Kaneko–Shearer model. For relatively weak events, a power-law dependence (regression) of the stress drop on the scalar seismic moment M0 has been identified, that complies with the results on the power-law dependence of the specific seismic energy on M0 in a number of other regions of Northern Eurasia. The relationship between the type of source movement and the stress drop level has been noted as well.
B. Kanimozhi, Jaya Prakash, R. Venkat Pranesh
et al.
Abstract Retrograde vaporization effects on oil production are nearly unprecedented to reservoir engineering community, and its relation to formation damage should be explored. For this purpose, this paper elucidates the importance and role of this phenomenon and its phase change heat transfer (PCHT) on fines migration and subsequent, permeability damage in porous rocks bearing oil and gas. Initially, a fine particle energy conversion equation was successfully acquired by combining fine particle mass balance and general energy equations. Moreover, the computational fluid dynamic model (CFD) was adopted for performing numerical modeling. A 2D CFD model using FEA-Comsol 5.0 version was used to simulate the retrograde vaporization of reservoir fluids. Pore walls are designed as non-adiabatic, and therefore, a modified Dittus-Boelter mass transfer model is provided for a fine particle detachment under PCHT. Hence, from the simulation results it was observed that there is a high degree of heat release during reservoir fluid phase change that is from oil to gas for decreasing pressure and increasing saturation time. This heat transfer from the oil and gas influxes contributes in the expulsion and migration of in situ fines in porous media. Also, an increasing rate of enthalpy was achieved that produces a non-isentropic flow, which is required to mobilize the fines in porous medium, and a satisfactory phase transition simulation outputs were obtained and presented as well. Altogether, these factors play a significant role in the fine particle eviction from the pore chamber, thereby plugging in the pore throat and consequently, decreasing the well productivity during transient flow.
Abstract The distribution of remaining oil is controlled by internal sand body heterogeneity in the middle and late stages of oil field development. Reservoir architecture analysis has been conducted in the third sand group in the Guantao Formation of the Gudao Oil field. Different scales of reservoir architecture units have been identified, including complex meandering river belt, single meandering river belt, single point bar and inner point bar. Four different single channel signatures have been found in the research area to identify the single channel belt. The single point bar has been distinguished based on point bar development characteristics. The architecture of the inner point bar has been analyzed based on subsurface well data and empirical formulas. The lateral accretion angle of the muddy layer ranges from 5° to 8°, the interspace between lateral accretion muddy layers ranges from 20 to 35 m, and the horizontal width of a single lateral accretion sand body is 55–120 m. Based on the above-mentioned reservoir architecture analysis, a reservoir architecture model has been established using the hierarchical modeling method. A three-dimensional porosity and permeability model has been developed within architecture model constraints and could provide a reliable geological template for oil field development and production.
Abstract This study proposes a method of interactive plant simulation modeling which delivers the online simulated results to the field operators and induces them to take proper actions in the case of pre-identified accident scenarios in a chemical plant. The developed model integrates the real-time process dynamic simulation with 3D-CFD accident simulation in a designed interface using object linking and embedding technology so that it can convey to trainees the online information of the accident which is not available in existing operator training systems. The model encompasses the whole process of data transfer till the end of the training at which a trainee operates an emergency shutdown system in a programmed model. In this work, an overall scenario is simulated which is from an abnormal increase in the main valve discharge (second) pressure due to valve malfunction to accidental gas release through the crack of a pressure recorder, and the magnitude of the accident with respect to the lead time of each trainee’s emergency response is analyzed. The model can improve the effectiveness of the operator training system through interactively linking the trainee actions with the simulation model resulting in different accident scenarios with respect to each trainee’s competence when facing an accident.
Abstract A sizable oil reserves are held in a thick oil/water capillary transition zones in the carbonate reservoirs, but it is an ongoing challenge to accurately describe the relationship between capillary pressure, relative permeability and oil/water saturation due to the complex wettability variation, pore geometry and heterogeneity throughout the reservoir column. It has been shown that a proper interpretation of relative permeability and capillary pressure including hysteresis has a substantial influence on the prediction and optimization of field production, especially for a heterogeneous carbonate reservoir with a thick transition zone. The conventional models, such as Corey method and Leverett J-function, cannot precisely present the behaviors of capillary pressure and relative permeability of transition zones in carbonate reservoirs. In the present work, a study has been conducted to provide an improved understanding of capillary pressure and relative permeability of the transition zones in carbonate reservoirs by implementing and optimizing recently developed models considering mixed-wet property and geological heterogeneity. For single core plug and each reservoir rock typing classified on the basis of petrophysical properties, the applicability to generate bounding drainage and imbibition curves of the models was tested with fitting parameters by comparing with experimental data. Also, a comprehensive assessment was provided about the feasibility and efficiency of the models along with an evaluation of the hysteresis between bounding drainage and imbibition curves. The results showed excellent matches in the case of Masalmeh model (SPE Reserv Eval Eng 10(02):191–204, 2007) with a correlation coefficient value of 0.95, in which mixed-wet and pore size distribution are taken into account. Therefore, it can be stated that the work conducted in this study could be used as a guide for further investigation and understanding of transition zones in carbonate reservoirs.
Prenekatere jame v karbonatnih sekvencah (in morda tudi drugod) izkazujejo opazno prostorsko organizacijo, pri čemer je poudarjeno kopičenje rovov v prostoru (drugega nad drugim). Mnoge starejše razlage tega zgoščevanja vključujejo “recentno” dogajanje in medsebojne vplive. Nove ideje, ki temeljijo na proučevanju “denudiranih” ali ”brezstropih” jam, pripisujejo velik pomen pojavom in odnosom, ki so sicer znani že dolgo, a so jih raziskovalci puščali ob strani kot “neznačilne”, “nepomembne” ali celo “nemogoče”, ob enem pa jih interpretirajo na novo. Tako je potrebno nekatere uveljavljene razlage trodimenzionalnega kopičenja rovov popolnoma prevetriti. Opazovanja ne podpirajo privzetka, da vsaka stratigrafska (lezika) ali tektonska (razpoka) nezveznost že sama po sebi odpira vodi pot in in je zato samodejno žarišče nastajanja kraških kanalov. V svojem prvotnem, “pred-jamskem” stanju - ko so posamezne votline v kamnini zgolj možne - karbonatne gmote niso nujno hidrološko aktivne, niti niso geološko homogene. Nova opazovanja in prevrednotenje starejšega znanja nakazujejo, da se “začetje” bodočih rovov odvije samo na majhni podmnožici vseh lezik, ki so priviligirane že v začetku in že od kraja odrejajo smernice bodočemu razvoju kanalov. Spoznanje te temeljne vloge kaže možno pot k razumevanju organizacije jamskih sistemov in kliče po podaljšanju spelogenetske časovne lestvice prav v čas diageneze.
Many caves within carbonate (and perhaps other) rock sequences display marked spatial organization, particularly a tendency to group within vertical clusters. Most past explanations of clustering involve “recent” effects and interactions. New ideas, based on study of “denuded” or “unroofed” caves, acknowledge but reinterpret features and relationships that were observed long ago and commonly dismissed as “atypical”, “irrelevant” or “impossible”. Some traditional explanations of vertical clustering must now be re-assessed. Assumptions that any stratigraphical (bedding plane) or joint/fault fissure in carbonate rock provides (or provided) a de facto route for fluid transfer, and hence a focus for void development, are not confirmed by observation. Primitive pre-cave, but potentially cavernous, carbonate masses are not inevitably active hydrologically; nor are they geologically homogeneous. New evidence, and re-evaluation of earlier observations, implies that dissolutional void “inception” is related to a minor subset of all stratigraphical partings, which dominate initially, imprinting incipient guidance for later cave development. Recognition of this fundamental role provides a possible key to understanding the organization of cave systems and necessitates acceptance of an expansion of speleogenetic timescales back to the time of diagenesis.
Kras pokriva okrog 300.000 km2 (50 %) ozemlja Srednje Amerike in Karibov. Jam je verjetno več desettisoč. V celotni Srednji Ameriki in Karibih je monitoring v jamah zelo redek in agencije za urejanje in varstvo okolja ga nizko cenijo. Izjeme se pojavljajo le v nekaterih zaščitenih področjih in v redkih turističnih jamah. Z mnenjem, da je monitoring res potreben, se v splošnem ne strinjajo. Poleg tega je monitoring omejen zaradi nezadostnega financiranja in opreme in zaradi pomanjkanja ustrezno usposobljenega osebja. Vendar je monitoring v jamah nedvomno potreben, kajti jamsko okolje je izrazito občutljivo in kraška pokrajina doživlja naraščajoč pritisk zaradi razvoja. V tej zvezi je nujna inventarizacija in program monitoringa vsaj v bolj pomembnih jamah. Tak monitoring se lahko usmeri na fizično okolje, zgodovinske ali predzgodovinske ostanke, favno, izkoriščanje surovin, kakovost vode in turistični obisk. Enako pomembno je izvajanje monitoringa na kraškem površju, kajti degradacija površja se nujno odraža tudi v slabšanju podzemeljskega okolja
Karstlands cover about 300,000 km2 (50%) of the land area of Central America and the Caribbean. The number of caves is probably tens of thousands. Cave monitoring is uncommon throughout Central America and the Caribbean, and is generally accorded a low priority by agencies responsible for environmental managementand conservation. Exceptions occur only in some protected areas and in a few commercial caves. Fundamentally, it is not recognized generally that there is a need to monitor caves. Beyond that, monitoring is limited severely by paucity of funding, equipment and qualified personnel. Cave monitoring clearly is warranted, however, because cave environments are inherently fragile and because the karstlands are under increasing developmental pressures. In these contexts, selected inventorying and monitoring programs seem advisable in at least some of the more significant caves. Such monitoring programs might focus on physical environments, historic and prehistoric remains, faunal populations, resource extraction, water quality and human visitation. Equally importantly, surface karst environments need to be monitored too, because degradation at the surface will almost inevitably be mirrored by deterioration in underground conditions.
Speleogenesis is the development of well-organized cave systems by fluids moving through fissures of a soluble rock. Epigenic caves induced by biogenic CO2 soil production are dominant, whereas hypogenic caves resulting from uprising deep flow not directly connected to adjacent recharge areas appear to be more frequent than previously considered. The conceptual models of epigenic cave development moved from early models, through the “four-states model” involving fracture influence to explain deep loops, to the digital models demonstrating the adjustment of the main flow to the water table. The relationships with base level are complex and cave levels must be determined from the elevation of the vadose-phreatic transitions. Since flooding in the epiphreatic zone may be important, the top of the loops in the epiphreatic zone can be found significantly high above the base level. The term Paragenesis is used to describe the upward development of conduits as their lower parts fill with sediments. This process often records a general baselevel rise. Sediment influx is responsible for the regulation of long profiles by paragenesis and contributes to the evolution of profiles from looping to water table caves. Dating methods allow identification of the timing of cave level evolution. The term Ghost-rock karstification is used to describe a 2-phase process of speleogenesis, with a first phase of partial solution of rock along fractures in low gradient conditions leaving a porous matrix, the ghost-rock, then a second phase of mechanical removing of the ghost-rock mainly by turbulent flow in high gradient conditions opening the passages and forming maze caves. The first weathering phase can be related either to epigenic infiltration or to hypogenic upflow, especially in marginal areas of sedimentary basins. The vertical pattern of epigenic caves is mainly controlled by timing, geological structure, types of flow and base-level changes. We define several cave types as (1) juvenile, where they are perched above underlying aquicludes; (2) looping, where recharge varies greatly with time, to produce epiphreatic loops; (3) water-table caves where flow is regulated by a semi-pervious cover; and (4) caves in the equilibrium stage where flow is transmitted without significant flooding. Successive base-level drops caused by valley entrenchment make cave levels, whereas baselevel rise is defined in the frame of the Per ascensum Model of Speleogenesis (PAMS), where deep passages are flooded and drain through vauclusian springs. The PAMS can be active after any type of baselevel rise (transgression, fluvial aggradation, tectonic subsidence) and explains most of the deep phreatic cave systems except for hypogenic.
The term Hypogenic speleogenesis is used to describe cave development by deep upflow independent of adjacent recharge areas. Due to its deep origin, water frequently has a high CO2-H2S concentration and a thermal anomaly, but not systematically. Numerous dissolution processes can be involved in hypogenic speleogenesis, which often include deep-seated acidic sources of CO2 and H2S, “hydrothermal” cooling, mixing corrosion, Sulfuric Acid Speleogenesis (SAS), etc. SAS particularly involves the condensation-corrosion processes, resulting in the fast expansion of caves above the water table, i.e. in an atmospheric environment. The hydrogeological setting of hypogenic speleogenesis is based on the Regional Gravity Flow concept, which shows at the basin scales the sites of convergences and upflows where dissolution focuses. Each part of a basin (marginal, internal, deep zone) has specific conditions. The coastal basin is a sub-type. In deformed strata, flow is more complex according to the geological structure. However, upflow and hypogenic speleogenesis concentrate in structural highs (buried anticlines) and zones of major disruption (faults, overthrusts). In disrupted basins, the geothermal gradient “pumps” the meteoric water at depth, making loops of different depths and characteristics. Volcanism and magmatism also produce deep hypogenic loops with “hyperkarst” characteristics due to a combination of deep-seated CO2, H2S, thermalism, and microbial activity. In phreatic conditions, the resulting cave patterns
can include geodes, 2–3D caves, and giant ascending shafts. Along the water table, SAS with thermal air convection induces powerful condensation-corrosion and the development of upwardly dendritic caves, isolated chambers, water table sulfuricacid caves. In the vadose zone, “smoking” shafts evolve under the influence of geothermal gradients producing air convectionand condensation-corrosion.
Likely future directions for research will probably involve analytical and modeling methods, especially using isotopes, dating, chemical simulations, and field investigations focused on the relationships between processes and resulting morphologies.
Nova področja speleogenetskih raziskav: Povezava med hidrogeološkimi razmerami, prevladujočimi procesi in tipi jam
Speleogeneza je razvoj dobro (samo)organiziranih jamskih sistemov, ko podzemna voda vzdolž toka raztaplja stene razpok. Najbolj poznane so epigene jame v karbonatih, kjer je poglavitni vir kemične agresivnosti pedogeni CO2. Bolj pogoste, kot se je v preteklosti domnevalo, so hipogene jame, ki nastanejo z dviganjem globokega toka in niso neposredno povezane z lokalnim napajalnim območjem. Prvotni konceptualni modeli razvoja epigenih jam so se preko modela štirih stanj, ki speleogenezo pojasnjuje s frekvenco prevodnih razpok, razvili do računalniških modelov, ki pojasnijo prilagoditev glavnega toka freatični površini. Povezava jamskih sistemov s položajem erozijske baze ni enostavna, saj moramo pri interpretaciji upoštevati višino prehoda iz freatične v vadozno cono. Zaradi visokih poplav v epifreatični coni so lahko temena jamskih zavojev visoko nad erozijsko bazo. Termin parageneza se uporablja za opis razvoja kanalov od spodaj navzgor, ko se spodnji deli zapolnijo s sedimenti. Ta proces pogosto beleži splošen dvig erozijske baze. Vdor sedimentov je tudi razlog za uravnavanje dolgih profilov s paragenezo in prispeva k prehodu jam z zavoji v navpični ravnini v jame uravnane z vodnim nivojem. Različne datacijske metode omogočajo določanje časovnega razvoja jamskih nivojev. Speleogeneza lahko poteka tudi v dveh fazah; v prvi fazi voda ob nizkem gradientu raztopi topen del kamninske matrice (angleško Ghost rock weathering), v drugi fazi pa ob visokem gradientu turbulentni tok mehansko odnese preostali del matrice, pri čemer praviloma nastane labirintni tip jam. Prva faza je lahko povezana z epigeno infiltracijo ali s hipogenim dotokom predvsem na mejnih območjih sedimentnih bazenov. Vertikalna geometrija epigenih jam je pogojena s časovnim okvirom, geološko strukturo, vrsto toka in spremembo erozijske baze. Razvoj mladih (juvenilnih) geometrijskih vzorcev nad nivojem neprepustnih plasti, je povezan s hitrimi tektonskimi dvigi in vrezovanji erozijske baze. V pogojih omejenega odtoka ob spremenljivem napajanju zaradi poplavljanja epifreatične cone nastajajo zavoji v navpični ravnini (angl. loops). Jame vodnega nivoja nastajajo na področjih, kjer je kras pokrit z delno prepustnimi plastmi oz. kjer je speleogeneza uravnotežena z največjimi poplavami. Spreminjanje erozijske baze ob vrezovanju dolin se odraža v jamskih nivojih, medtem ko dviganje erozijske baze diktira razvoj jam od spodaj navzgor (Speleogeneza Per ecensum, PAMS) in nastanek izvirov vokluškega tipa. PAMS se lahko aktivira ob različnih vrstah dviga erozijske baze (zaradi transgresije, rečnega naplavljanja, tektonskega ugrezanja) in pojasnjuje nastanek večine globokih freatičnih jamskih sistemov, razen hipogenih. Izraz hipogena speleogeneza se uporablja za opis razvoja jam zaradi dviganja globokega regionalnega toka. Zaradi izvora iz globin ima voda pogosto visoko koncentracijo CO2–H2S in temperaturno anomalijo. Pri hipogeni speleogenezi lahko sodelujejo številni procesi raztapljanja, ki so povezani z globokimi viri CO2 in H2S, "hidrotermalnim" ohlajanjem, korozijo mešanice, speleogenezo žveplene kisline (Sulphuric Acid Speleogenesis, SAS), itd. Zlasti SAS vključuje kondenzacijsko-korozijske procese, zaradi česar prihaja do hitrega nastanka jam nad vodno gladino v atmosferskem okolju. Hidrogeološke razmere pri hipogeni speleogenezi so povezane z regionalnim gravitacijskim tokom, kjer je korozija najmočnejša na območju stekanja in dvigovanja vodnih tokov. Vsak del porečja (obrobni, notranji, globoka cona) ima posebne pogoje. Eden od podtipov je tudi obalno območje. V deformiranih slojih je tok bolj zapleten in strukturno pogojen, pri čemer sta vodni tok in hipogena speleogeneza praviloma vezana na strukturne vrhove (prekrite antiklinale) in na območja večjih strukturnih prekinitev (prelomi, narivi). V prekinjenih bazenih geotermalni gradient "črpa" meteorske vode v globine, kar povzroča zanke na različnih globinah in z različnimi značilnostmi. Vulkanizem in magmatizem tudi povzročata globoke hipogene zanke s "hiperkraškimi" značilnostmi, ki nastajajo zaradi kombinacije globokih virov CO2, H2S, termalnih procesov in mikrobiološke aktivnosti. Geometrijski vzorci jam v freatičnih pogojih lahko vključujejo geode, 2–3D jame in navzgor razvijajoča se brezna izjemnih razsežnosti. Nad vodno gladino se zaradi termalne konvekcije in kondenzacijske korozije ob prisotnosti žveplove kisline razvijajo različni geometrijski vzorci jam; dvigajoče se razvejane jame, izolirane dvorane in jame vodnega nivoja nastale z delovanjem žveplene kisline. V vadozni coni nastajajo tudi »parna« brezna, ko se na območjih termalnih vodonosnikov topel vlažen zrak dviga, ohlaja in kondenzira vzdolž razpok in jih na ta način širi v brezna. V prihodnosti bodo raziskave speleogeneze verjetno temeljile na analitičnih in modelskih pristopih, izotopskih, datacijskih in geokemičnih metodah ter terenskih raziskavah, ki se bodo osredotočala na odnose med procesi in posledično morfologijo.
The Dinarides are the largest continuous karst region in Europe. With regard to a geotectonic view, they are divided into the Outer, Central and Inner Dinarides occupying the territories of Slovenia, Croatia, Bosnia and Herzegovina, Serbia and Montenegro. Numerous occurrences of thermomineral water have been recorded in the Inner Dinarides area. The majority of them are genetically related to carbonate sediments of Mesozoic age. This paper deals with occurrences of thermomineral waters of the Inner Dinarides karst, their quantitative and qualitative characteristics, basic genetic types, the age of karst thermomineral waters of the Inner Dinarides, the available quantities of hydrogeothermalmineral energy, balneological potential and the possibility of rational multi-purpose utilisation. Hydrochemical and isotope methods have been used for the analysis of basic genetic types and age of karst thermomineral waters, while a geothermometer method has been used for the calculation of primary temperatures in water-bearing horizons(geothermal reservoirs) themselves. The carried out research has pointed out that karst thermomineral waters formed in carbonate sediments of Mesozoic age are characterized by temperatures ranging from 15.5oC (Knežina Ilidža) to 75oC (Bogatić), being most frequently of a HCO3-Ca, Mg type with neutral to poor alkaline reaction and mineralization below 1 g/l. Karst thermomineral waters of the Inner Dinarides are most frequently related to geothermal systems formed in carbonate sediments covered by rocks of poor water permeability. In case of some thermomineral water occurrences, the mixing of the karst thermomineral waters with those formed in sedimentary basins occurs due to their hydraulic relation, thus it is not possible to determine only one geothermal system in which they are formed. The overall geothermal potential of the thermomineral waters of the Inner Dinarides karst is about 160 MW. In addition to the geothermal aspect, these waters have been widely utilised in balneology, wellness programmes, as well as for the needs of bottling. The level of research activity and with that the way of the utilisation of these waters are various. With regard to the number of occurrences known so far and their potential, it can be claimed with certainty, that the utilisation of thermomineral water occurring in the karst of the Inner Dinarides will increase significantly in future. An example of the multi-purpose utilisation of the Pribojska Banja Spa thermomineral waters illustrates a possible way of doing it.
Franci Gabrovšek, Janja Kogovšek, Gregor Kovačič
et al.
In the catchment area of the Unica River two combined tracer tests with fluorescent dyes have been performed aiming to characterize the properties of groundwater flow and transport of contaminants through the vadose zone and well developed system of karst channels in the epiphreatic and phreatic zone in different hydrologic conditions. Tracers were injected directly into the ponors and to the oil collector outlet on the karst surface. Prior to tracing monitoring network has been set up, including precipitation, physical and chemical parameters of the springs and cave streams. Field fluorimeters were used to detect tracers in the underground river and conventional sampling techniques and laboratory analyses were used at the springs. Some of the results were quantitatively evaluated by QTRACER2 Program. During the first tracer test, when injection was followed by rain event, flow through the well conductive cave system was characterized by apparent dominant flow velocities of 88–640 m/h. Breakthrough curves were continuous, uniform and single peaked, and almost complete recoveries were observed. During the second tracer test, when water level was in constant recession, the transport velocities through the well developed karst conduits were significantly slower (apparent maximal flow velocities being 2–4 times lower). Results also show lower dispersivity during the second tracer test, which corresponds to lower flow velocities. The tracer injected at the karst surface arrived with the expected delay (vdom around 9 m/h) and showed irregular and elongated breakthrough curves with secondary peaks. In this paper only tracer test results are presented, which are a part of a comprehensive study of groundwater flow through the complex karst aquifers aiming at improving karst water resources understanding, protection and management. The presented assessment will beyond be utilized for further detailed analysis, studies and modelling.