Jana Fridrichová, Peter Bačík, Olena Rybnikova
et al.
Abstract Topaz is frequently subjected to heat treatment and irradiation to enhance colour, particularly to produce the market’s most preferred salmon pink and sky blue varieties. However, an insufficient description of these processes can lead to fraudulent practices. This experimental and forensic mineralogical and gemmological study investigates eighteen heat-treated topaz samples from Ouro Preto (OP) and Caraí (CA), Brazil, using electron microanalysis, LA-ICP-MS, Raman, and optical absorption spectroscopy before and after heat treatment at various temperatures. The most significant optical changes were observed at 300 °C when the CA sample lost its colour from sky blue to colourless, while OP samples retained their imperial orange colour up to 500 °C before transitioning to pink at 700 °C. Chemically, the CA samples are rich in F (> 1.8 apfu) with low trace element concentration (Fe ≤ 125 ppm, Ge ≤ 153 ppm), falling to the pegmatite and greisen field of topaz origin. The OP samples contain less F (1.4–1.5 apfu) but higher trace element contents (Cr up to 204 ppm, Ti up to 115 ppm, Fe, Mn, Ge < 64 ppm), consistent with a hydrothermal origin. Raman spectra show no significant inter-sample variation, but their luminescence spectra feature strong differences: Mn acts as the luminophore in CA samples, while Cr3+ centers dominate in OP samples. The optical absorption spectra reveal distinct thermal responses. The OP samples heated to temperatures ≥ 500 °C developed new absorption bands at 530–532 nm, consequently resulting in a visible pink colour. On the other hand, the CA spectra exhibit strong absorption in the NIR region; the unheated sample has a broad absorption band at 634 nm, responsible for the sky-blue colour of topaz. Heating ≥ 300 °C eliminates the transmission window in the blue to cyan regions, removing blue colouration. These thermal-optical signatures serve as indicators of heat treatment in topaz declared from these two localities. Moreover, the combination of spectroscopic methods, which we successfully applied in recognizing heat treatment on the studied samples, provides a systematic approach for identifying treatment in topaz and potentially other gemstones.
<p>Gas species are widely used as natural or artificial tracers to study fluid dynamics in environmental and geological systems. The recently developed gas equilibrium membrane inlet mass spectrometry (GE-MIMS) method is most useful for accurate and autonomous on-site quantification of dissolved gases in aquatic systems. GE-MIMS works by pumping water through a gas equilibrator module containing a gas headspace, which is separated from the water by a gas-permeable membrane. The partial pressures of the gas species in the headspace equilibrate with the gas concentrations in the water according to Henry's Law and are quantified with a mass spectrometer optimized for low gas consumption (miniRUEDI or similar). However, the fragile membrane structures of the commonly used equilibrator modules break down at water pressures <span class="inline-formula">≳3</span> <span class="inline-formula">bar</span>. These modules are therefore not suitable for use in deep geological systems or other environments with high water pressures. To this end, the SysMoG® MD membrane module (Solexperts AG, Switzerland; “SOMM”) was developed to withstand water pressures of up to 100 <span class="inline-formula">bar</span>. Compared to the conventionally used GE-MIMS equilibrator modules, the mechanically robust construction of the SOMM module entails slow and potentially incomplete gas–water equilibration. We tested the gas equilibration efficiency of the SOMM and developed an adapted protocol that allows correct operation of the SOMM for GE-MIMS analysis at high water pressures. This adapted SOMM GE-MIMS technique exhibits a very low gas consumption from the SOMM to maintain the gas–water equilibrium according to Henry's Law and provides the same analytical accuracy and precision as the conventional GE-MIMS technique. The analytical potential of the adapted SOMM GE-MIMS technique was demonstrated in a high-pressure fluid migration experiment in an underground rock laboratory. The new technique overcomes the pressure limitations of conventional gas equilibrators and thereby opens new opportunities for efficient and autonomous on-site quantification of dissolved gases in high-pressure environments, such as in research and monitoring of underground storage of <span class="inline-formula">CO<sub>2</sub></span> and waste deposits or in the exploration of natural resources.</p>
Marko Bermanec, Noa Vidović, Liubomyr Gavryliv
et al.
Abstract Crystal structures of minerals are defined by a specific atomic arrangement within the unit‐cell, which follows the laws of symmetry specific to each crystal system. The causes for a mineral to crystallize in a given crystal system have been the subject of many studies showing their dependency on different formation conditions, such as the presence of aqueous fluids, biotic activity and many others. Different attempts have been made to quantify and interpret the information that we can gather from studying crystal symmetry and its distribution in the mineral kingdom. However, these methods are mostly outdated or at least not compatible for use on large datasets available today. Therefore, a revision of symmetry index calculation has been made in accordance with the growing understanding of mineral species and their characteristics. In the gathered data, we observe a gradual but significant decrease in crystal symmetry through the stages of mineral evolution, from the formation of the solar system to modern day. However, this decrease is neither uniform nor linear, which provides further implications for mineral evolution from the viewpoint of crystal symmetry. The temporal distribution of minerals based on the number of essential elements in their chemical formulae and their symmetry index has been calculated and compared to explore their behaviour. Minerals with four to eight essential elements have the lowest average symmetry index, while being the most abundant throughout all stages of mineral evolution. There are many open questions, including those pertaining to whether or not biological activity on Earth has influenced the observed decrease in mineral symmetry through time and whether or not the trajectory of planetary evolution of a geologically active body is one of decreasing mineral symmetry/increasing complexity.
Abstract During the development of a field, many fluid samples are taken from wells. Selecting a robust fluid sample as the reservoir representative helps to have a better field characterization, reliable reservoir simulation, valid production forecast, efficient well placement and finally achieving optimized ultimate recovery. First, this paper aims to detect and separate the samples that have been collected under poor conditions or analyzed in a non-standard way. Moreover, it introduces a novel ranking method to score the samples based on the amount of coordination with other fluid samples in the region. The dataset includes 136 fluid samples from five reservoirs in Iranian fields, each of them consisting of 21 key parameters. Five acknowledged machine learning based anomaly detection techniques are implemented to compare fluid samples and detect those whose results deviate from others, indicating non-standard samples. To ensure the proper detection of outlier data, the results are compared with the traditional validation method of gas-oil ratio estimation. All five outlier detection methods demonstrate acceptable performance with average accuracy of 79% compared to traditional validation. Furthermore, the fluid samples with the highest scores in scoring-based algorithms are introduced as the best reservoir’s representative fluid. Finally, fuzzy logic is used to obtain a final score for each sample, taking the results of the six methods as input and ranking the samples based on their output score. The study confirms the robustness of the novel approach for fluid validation using outlier detection techniques and the value of machine learning and fuzzy logic for sample ranking, excelling in considering all critical fluid parameters simultaneously over traditional methods.
Cyril Mayaud, Blaž Kogovšek, Franci Gabrovšek
et al.
Poljes are flat closed karst depressions prone to regular flooding. The floods can be several meters high, last for months and damage significantly human infrastructures. To predict the maximum level reached, the polje water balance needs to be implemented. This technique encounters the difficulty that important part of the inflow and outflow flowing through many poljes is ungauged, as it is challenging to measure accurately the numerous springs and ponors activating temporarily with the rise of water level. This work aims to see whether this problem can be handled and the polje water balance reconstituted. To do so, a typical Dinaric polje is equipped with several water level stations installed over its surface and in the nearby water active caves. Combining a 1*1m digital elevation model of the polje surface with water levels and inflow records of the main two springs allowed assessing the variation of flooded volume and reconstructing the water balance. The highest total inflow values reached during the observed period were of about 140-150 m3/s, with up to a third of it being ungauged. In addition, the effect of a large estavelles group on the polje inflow and outflow could be identified, and helped to characterize the outflow, with values comprised between 65 and 75 m3/s. Finally, intense rainfall over the polje flooded surface showed to be a temporary important source of inflow. The values found by the water balance analysis have been used as input and calibration data in a numerical model reproducing the flood dynamics in the polje and its surrounding aquifer. Results validated both polje water balance and conceptual hydrogeological model. They justify the significance of combining water level measurements with a digital elevation model to monitor the floods. The method can be applied to other poljes flooding in a complex way of superposed input and output signals. Finally, the places to be equipped in priority if the polje has no measurement network or if available funding is limited are discussed.
Ankita Kukshal, Ravi Sharma, Hirak Jyoti Kalita
et al.
Abstract One of the main challenges for healthy hydrocarbon yields from the production wells is the sand production, and its control assumes significant importance for successful production operations. The prime objective remains to control the sand production without compromising on the fluid flow rates. Sand production is conventionally associated with diverse heterogeneous formations, especially poorly consolidated formations. Scrutinizing fluid flow rates at different orientations of perforations is a valuable analysis in controlling the sand production. This study was conducted to examine the case of sand production in a few development wells from Malleshwaram field of the Krishna Godavari (KG) basin in south India and provide alternatives to arrest this sand production. The influence of oriented perforations on fluid flow rates to minimize sanding tendencies was examined. Sand grain diameter was estimated using the distribution plots of the grain sizes obtained from the photomicrographs, and the average value of the grain size was estimated around 100 μm. The fluid flow model was simulated for actual scenario in the hydrocarbon bearing Nandigama formation using finite element modeling (FEM). Sanding tendencies in these formations were studied at varying depletion rates. Critical draw down pressure (CDDP), which is a function of both critical bottom hole pressure and reservoir pore pressure, for well 1 and well 2 is estimated as 4650 Psi and 3400 Psi, respectively, at 0% depletion. CDDP was used to estimate the onset of sanding, and the flow rate for horizontal perforation was calculated as 0.024548 $${\mathrm{m}}^{3}$$ m 3 /sec. Strength parameters, namely the unconfined compressive strength (UCS) and cohesion, were also investigated in all the wells to decipher the formation strength and a possible linkage to sanding. These results present a completely fresh analysis of the sanding potential and the related parameters responsible for it in these formations. Fluid flow rates for the producing reservoir are studied at different set of oriented and sized perforations. It was observed that a hiked flow rate in horizontal perforations maintains the production in a safe and no-sanding zone. This study provides vital information and a workflow for similar heterogeneous complex formations for designing the well completions, augmenting economic production and reinforcing future reservoir management.
Couzinié Simon, Bouilhol Pierre, Laurent Oscar
et al.
It is well-acknowledged that the northern margin of the Gondwana supercontinent was affected by a major magmatic event at late Cambrian (Furongian) to early Ordovician (Tremadocian–Floian) times. However, an accurate assessment of its extent, origin, and significance is partly hampered by the incomplete characterization of the numerous gneiss massifs exposed in the inner part of the Variscan belt, as some of them possibly represent dismembered and deformed Furongian–Lower Ordovician igneous bodies. In this study, we document the case of the “Cézarenque–Joyeuse” gneiss complex in the Cévennes parautochthon domain of the French Massif Central. The gneisses form decametre- to kilometre-thick concordant massifs interlayered within a pluri-kilometric sequence of mica- and quartz schists. They encompass two main petrological types: augen gneisses and albite gneisses, both typified by their blue and engulfed quartz grains with the augen facies differing by the presence of centimetre-sized pseudomorphs after K-feldspar and the local preservation of igneous textures. Whole-rock geochemistry highlights that many gneisses have magmatic ferrosilicic (acidic with anomalously high FeOt and low CaO) compositions while others are akin to greywackes. Collectively, it is inferred that the bulk of the Cézarenque–Joyeuse gneisses represents former rhyodacite lava flows or ignimbrites and associated epiclastic tuffs. Volumetrically subordinate, finer grained, and strongly silicic leucogneisses are interpreted as microgranite dykes originally intrusive within the volcanic edifices. LA–ICP–MS U–Pb dating of magmatic zircon grains extracted from an augen gneiss and a leucogneiss brackets the crystallization age of the silicic magmas between 486.1 ± 5.5 Ma and 483.0 ± 5.5 Ma which unambiguously ties the Cézarenque–Joyeuse gneisses to the Furongian–Lower Ordovician volcanic belt of SW Europe. Inherited zircon date distributions, Ti-in-zircon and zircon saturation thermometry demonstrate that they formed by melting at 750–820 °C of Ediacaran sediments. Zircon Eu/Eu* and Ce/Ce* systematics indicate that the melts were strongly reduced (fO2 probably close to the values expected for the iron–wüstite buffer), possibly because they interacted during ascent with Lower Cambrian black shales. This would have enhanced Fe solubility in the melt phase and may explain the peculiar ferrosilicic signature displayed by many Furongian–Lower Ordovician igneous rocks in the northern Gondwana realm. We infer that crustal melting resulted from a combination of mantle-derived magma underplating in an intracontinental rift setting and anomalously elevated radiogenic heat production within the Ediacaran sedimentary sequences.
payam tarighi, Omid Kheyri Namin, Mohammad Ali Kafi
One of the effective parts in providing the hard rigid connections of the beam to the column is continuity plates in the connections panel zone. The continuity plates in providing the connection hardness and its suitable operation play key role. Using continuity plates in the H columns is performable easily but in the box columns since of closing the cross section, its connection had problem. For this reason some times the flows of the steel structures prevented of using them. Installing internal continuity plates is a difficult fabrication task and also a costly procedure, and therefore researchers have tried to improve this type of connection not only by improving the connection details in the presence of internal continuity plates, but also by avoiding internal continuity plates and providing new load paths via external features. In this study to evaluate the performance of the U plates as external continuity plates of box column under cyclic loading. The results showed that in proposed connection with small dimention the plastic hing location is in the beam and stress of the column remains in the elastic limit, but proposed connection with medium and large dimention the plastic hing location is in the column. Therefor the medium and large connection strengthend whit rib plates. The rib plates in the proposed connection caused the plastic hing location is in the beam and the hysteresis curve is regular and stable.
Abstract Compartmentalization of reservoirs and technical failures experienced in data acquisition, processing and interpretation, without doubt, hinder the effective characterization of reservoirs. In this research, to ensure accuracy, three methods were integrated to characterize reservoirs in SOKAB field. Petrophysical analysis, seismic interpretation, and modeling, and rock physics analysis were utilized. Its objectives were: to develop a template to facilitate improvements in future reservoir characterization research works and producibility determination; to utilize rock physics models to quality check the seismic results and to properly define the pore connectivity of the reservoirs, and to locate the best productive zones for future wells in the field. Forty-three faults were mapped and this included five major faults. Two hydrocarbon bearing sand units (A & B) were correlated across five wells. Structural maps were generated for both reservoirs from which majorly fault assisted and dependent closures were observed. The petrophysical analysis indicated that the reservoirs have good pore interconnectivity (Average Ф effective = 23% & 22% and K average = 1754md & 2295md). The seismic interpretation and modeling alongside the petrophysical analysis were then quality checked via qualitative rock physics analysis. From the K dry/Porosity plot, the sands were generally observed to lie within the lower Reuss and upper Voigt bound which indicates a low level of compaction. From the velocity–porosity cross plot, it was revealed that the lower portions of the reservoirs were poorly cemented and this could hinder their producibility.
Abstract The Middle Jurassic Shaximiao Formation encompasses tens of meters of thick lowstand meandering valley (LMV) strata in the western Sichuan foreland basin. Ancient LMVs newly discovered in this area were further studied based on sequence stratigraphy and seismic sedimentology. The aim of the present study was to investigate the sedimentary characteristics, sequence architecture, and the controls on LMV deposition in this tectonically active basin using field survey data, seismic sections, seismic amplitude imaging, core description, and comprehensive application of drilling data. The results show the following: (1) Three regional sequence boundaries and two flooding surfaces were recognized, and the Shaximiao Formation was divided into two-third-order sequences and four systems tracts. (2) Three sedimentary facies associations were identified: incised valley-fill, tributary channel, and overbank facies. Incised valleys are 5–17 km wide, 20–60 m deep and traceable for 120 km along their axes. (3) In the downstream segment, the role of tectonism gradually diminishes, and periodic base-level changes control the form and evolution of the incised valleys. Three types of LMVs—A1, A2, and A3—developed with changes in base level (lake level); of these types, the base level of the A3 LMV was likely the lowest.
Joshua H. F. L. Davies, Tom E. Sheldrake, Jesse R. Reimink
et al.
Abstract The isochron technique for dating geological events is widely used in many fields of isotope geochemistry. However, data sets can be complex, and many samples may not behave as closed systems, resulting in excess scatter around a regression line. In certain data sets, however, excess scatter may result when geological samples are partially reset or when samples are comprised of multiple components recording different geological processes separated in time and/or initial isotope composition. Here we introduce a new approach for investigating evidence of such multicomponent mixtures within isochron space. We provide a mathematical framework to resolve the number of mixture components, without requiring any prior knowledge of this number. Crucially, the model reports the proportion of each individual sample that belongs to each mixture component, allowing the user to return to the samples and independently test model outputs with other techniques. It is important to distinguish accurate and meaningful ages and initial daughter isotope compositions from the meaningless values that are caused by mismatch between geological processes and the models that we use to describe them. First, we demonstrate our new model on a synthetic data set to show that it can successfully separate distinct isochrons in a complex mixture. We further validate our approach with a previously published data set using the 187Re‐187Os system in bitumen and 147Sm/144Nd system in magmatic rocks. We identify discrete components in these data sets and using complementary geological observations discuss the implications of treating these scattered data as recording multiple geological processes.
Abstract One of the most valuable wastes of the oil industry is oil sludge, found at oil wells, oil pipelines and refineries, and stored in storage units. Oil sludge has many similarities with heavy oil components. This study evaluates the use of oil sludge from the Iranian Oil Pipelines and Telecommunication Company for the manufacture of asphalt. The approximate structure of the oil sludge was analyzed and compared with the structure of conventional bitumen for road construction. Marshall asphalt samples were analyzed according to the American Society for Testing and Materials D1559 0–5–7.5–10–12.5 standard using 15% oil sludge with bitumen and aggregate. To study the physical characteristics of samples of Marshall asphalt, two important tests were performed (1) to determine the pressure resistance, and (2) the relative deformation of examples of all samples. The results showed that asphalt resistance is increased using 25–50% sulfur and 2–7% butadiene styrene polymer. Therefore, Marshall asphalt samples with 30% sulfur were prepared with bitumen and oil sludge. Fifty percent oil sludge in bitumen and a 2% polymer and 15% oil sludge mix with bitumen gave the best results. These mixtures are economically viable.
Jama leži v Matarskem podolju, v SZ delu Slovenije. Okolico sestavljajo apnenci ter apnenčaste breče kredne starosti. Njen vhodni del je udornega nastanka in leži v večji vrtači, jama pa se konča s podorom pod drugo vrtačo. Nad osrednjim delom jame je tudi manjša vrtača; posledica je, da je v tem delu obilnejša siga. Očitne so poškodbe zaradi zmrzali, ki segajo globoko v jamo; v vhodnem delu so značilni pojavi plazenja krioklastičnega grušča. Jama je sprva nastajala v freatčnih, nato pa v epifreatičnih pogojih. Izračunan nekdanji pretok kaže na veliko količino vode.
Cave lies in Matarsko podolje, in southwestern part of Slovenia. Surrounding beds are composed of limestones and limestone breccias of Cretaceous age. In the vicinity there are many dolines and collapse dolines. The entrance and final part of the cave are situated directly under the big dolines. Because of the small doline, which can be found above the middle part of the cave, there are many flowstone features. Obvious damages due to the freezing and thawing are found along the most part of the cave, at the entrance there is a lot of cryoclastic gravel. Cave began to form in phreatic and later in epiphreatic conditions. Palaeoflow discharge indicates great amount of water.
Abstract Authigenic grain-coating chlorite is widely distributed in the clastic rocks of many sedimentary basins around the world. These iron minerals were mainly derived from flocculent precipitates formed when rivers flow into the ocean, especially in deltaic environments with high hydrodynamic conditions. At the same time, sandstone sequences with grain-coating chlorites also tend to have relatively high glauconite and pyrite content. EPMA composition analysis shows that glauconites with “high Al and low Fe” content indicate slightly to semi-saline marine environments with weak alkaline and weakly reducing conditions. By analyzing the chlorite-containing sandstone bodies of the southern Sichuan Xujiahe Formation, this study found that chlorite was mainly distributed in sedimentary microfacies, including underwater distributary channels, distributary channels, shallow lake sandstone dams, and mouth bars. Chlorite had a tendency to form in the upper parts of sandstone bodies with signs of increased base level, representing the influence of marine (lacustrine) transgression. This is believed to be influenced by megamonsoons in the Middle and Upper Yangtze Region during the Late Triassic Epoch. During periods of abundant precipitation, river discharges increased and more Fe particulates flowed into the ocean (lake). In the meantime, increases or decreases in lake level were only affected by precipitation for short periods of time. The sedimentary environment shifted from weakly oxidizing to weak alkaline, weakly reducing conditions as sea level increased, and Fe-rich minerals as authigenic chlorite and glauconite began to form and deposit.
Prispevek obravnava značilnosti 17 kraških presihajočih jezer Zgornje Pivke. V času dolgotrajnega deževja v novembru 2000, ko je izmerjena količina dežja več kot trikrat presegala povprečno mesečno količino padavin, se je voda, po več desetletjih, pojavila v vseh jezerih. Izjemoma so bile poplavljene tudi številne druge manjše kraške globeli, kjer ojezeritve še niso bile dokumentirane. S pomočjo terenskih meritev in interpretacijo letalskih posnetkov so bili izmerjeni vodostaji in površine jezer ter prostornina vode v njih.
The article presents the characteristics of the 17 intermittent karst lakes of Upper Pivka. During the extended precipitation in November 2000, when the amount of precipitation was more than three times the average, all the lakes were flooded for the first time in several decades. Also several additional small karst depressions were flooded, where overflowing had never been recorded before. By combining field observations with the interpretation of aerial photographs the water level, the extent of the lakes and the volumes of containing water were calculated.