Carolina Cardell, Maja Urosevic, Danielle Dias Martins
et al.
This work presents the first systematic archaeometric data of 13th–14th century AD Nasrid glazed architectural ceramics from the Alhambra and Generalife, focusing on colour-specific glazing technologies. Findings provide new insights into Nasrid glazing technology, ceramic typologies, and conservation implications, contributing to discussions on Islamic material culture and technical traditions in al-Andalus. Analysed typologies include mosaic, inlay, relief tiles, roof lights, and steles with glazes in white, blue, green-turquoise, black, and honey tones. Microstructural and chemical results reveal decorative chromophores and techniques to be a reference for future studies. Most glazes are inglaze on lead tin-opacified bases, fired in oxidising conditions at ∼950 °C. Phosphorus was found in weathered glazes (associated with a burial environment) and unweathered white and blue glazes, suggesting deliberate addition of bones (fragments/ashes). Identified phases in most glazes were unmelted quartz and feldspars grains, and relatively abundant Cr-bearing wollastonite crystals precipitated during firing. Furthermore, one of the fragments with a black surface was determined not to be a glaze, but rather a polished section of a metamorphic rock. Resumen: Este trabajo presenta datos del primer análisis arqueométrico sistemático de cerámicas vidriadas arquitectónicas de los siglos XIII y XIV n.e. de la Alhambra y Generalife, centrándose en la tecnología de esmaltado de diversos colores. Los resultados ofrecen nuevas perspectivas sobre la tecnología del vidriado nazarí, las tipologías cerámicas y su estado de conservación. Estos hallazgos permiten abordar una discusión más amplia de la cultura material islámica y de las tradiciones técnicas de al-Andalus. Las tipologías cerámicas estudiadas incluyen alicatados, incrustados, sebkas, lucernarios y bordillos funerarios coloreados en blanco, azul, verde-turquesa, negro y melado. Los resultados microestructurales y químicos revelan que los cromóforos y técnicas decorativas en determinados tipos cerámicos pueden servir como marcadores en estudios futuros. Los esmaltes son de plomo opacificados con estaño, y cocidos en atmósfera oxidante a unos 950 °C. Se detectó fósforo en muestras alteradas (relacionado con condiciones de enterramiento), y en esmaltes blancos y azules no alterados, lo que sugiere la adición deliberada de huesos o cenizas óseas al vidriado. Asimismo, se identificaron en la mayoría de los esmaltes granos de cuarzo y feldespatos no fundidos, y abundantes precipitados de wollastonita con trazas de cromo. Además, se determinó que uno de los fragmentos con decoración negra no era un vidriado, sino una sección pulida de una roca metamórfica.
Mehdi Razavifar, Timur Yunusov, Aliya Mukhametdinova
et al.
Abstract In the last two decades, ultrasonic wave irradiation has gained increased attention from both environmental and economic perspectives in the oil industry. This study investigates the effects of ultrasonic wave irradiation on the components of crude oil and asphaltene deposition in porous media. A series of various experimental methods, including gas chromatography, microscopic imaging, viscosity and average molecular weight measurements, and core flooding, were conducted before and after ultrasonic treatment. The results showed that ultrasonic treatment reduced the number of asphaltene clusters. Additionally, ultrasonic irradiation reduced the average molecular weight of crude oil by 7%. Ultrasonic treatment also decreased core damage by restoring rock permeability. The permeability of the core decreased dramatically from 131 to 27 mD (about 79%) after the injection of crude oil due to asphaltene deposition. However, after ultrasonic treatment, the permeability of the damaged core improved to 82 mD. The findings of this study are valuable for improved oil recovery projects aimed at reducing formation damage near production wells. Graphical abstract
Abstract Carbon dioxide (CO2) flooding is an effective method for enhanced oil recovery. However, its application in complex, small-block reservoirs presents significant challenges owing to their limited size and intricate oil–water systems. This study investigates the potential and effectiveness of CO2 huff-and-puff technology for improving oil recovery in such reservoirs, with a focus on identifying key influencing factors. A “toothbrush-shaped” reservoir in the Shulu Sag was selected for a case study. Its geological framework, sand body types, and pore types were characterized, and a three-dimensional geological model was constructed. Based on the CO2 flooding theory, a mathematical model tailored to the study area was developed to simulate CO2 huff-and-puff processes. Numerical simulations were conducted to investigate the impact of various parameters and influencing factors on oil recovery. The predicted oil recovery from CO2 huff-and-puff in the toothbrush-shaped reservoir was then calibrated against production data from existing CO2 huff-and-puff wells. The study found that heterogeneous reservoirs with moderate heterogeneity and oil saturation greater than 0.5 are suitable candidates for CO2 huff-and-puff. Furthermore, a soaking period of 20 days yielded favorable development outcomes. These findings provide valuable insights for enhancing oil recovery in similar reservoirs.
Lutfi Mulyadi Surachman, Abdulazeez Abdulraheem, Abdullatif Al-Shuhail
et al.
Abstract Acoustic impedance is the product of the density of a material and the speed at which an acoustic wave travels through it. Understanding this relationship is essential because low acoustic impedance values are closely associated with high porosity, facilitating the accumulation of more hydrocarbons. In this study, we estimate the acoustic impedance based on nine different inputs of seismic attributes in addition to depth and two-way travel time using three supervised machine learning models, namely extra tree regression (ETR), random forest regression, and a multilayer perceptron regression algorithm using the scikit-learn library. Our results show that the R 2 of multilayer perceptron regression is 0.85, which is close to what has been reported in recent studies. However, the ETR method outperformed those reported in the literature in terms of the mean absolute error, mean squared error, and root-mean-squared error. The novelty of this study lies in achieving more accurate predictions of acoustic impedance for exploration.
To further reveal the development characteristics of Jurassic source rocks in the southwest depression of the Tarim Basin and their paleoenvironments, with the aim of guiding future shale oil exploration and development, the study integrated rock pyrolysis, maceral analysis, inorganic geochemistry, biomarker compounds, and carbon isotope analyzes.It explored the development characteristics and organic matter enrichment patterns of coal-bearing mudstones from the Lower Jurassic Kangsu Formation and mudstones and silty mudstones from the Middle Jurassic Yangye Formation in the Kekeya area of the southwest depression, Tarim Basin. The results showed that the total organic carbon (TOC) content in the source rocks of the Kangsu and Yangye formations was relatively higher, ranging from 1.7% to 63.5% (with an average of 24.4%), and 0.6% to 6.9% (with an average of 2.1%), respectively, indicating source rocks of good to excellent quality. Source rocks from both formations exhibited low maturity, being in the low-maturity to mature stage.In addition, carbon isotope analysis of kerogen, thin section observations, and biomarker compound analysis indicated that the parent material of the organic matter in the coal-bearing mudstones of the Kangsu Formation and the lower section of the Yangye Formation mainly derived from higher terrestrial plants, while the silty mudstones of the upper section of the Yangye Formation contained abundant planktonic algae. During the depositional period of the Kangsu Formation, the paleoclimate was warm and humid, and the water environment was freshwater, with suboxic and slightly oxidizing conditions. In the early depositional stages of the Yangye Formation, the paleoclimate was also hot and humid, and the depositional environment was similar to that of the Kangsu Formation, characterized by freshwater and suboxic conditions. With the gradual rise in lake level in the late depositional period of the Yangye Formation, the paleoenvironment transitioned to a brackish and suboxic environment. The hot and humid climate, coupled with increased salinity, was conducive to the reproduction of planktonic algae and other aquatic organisms, thereby affecting the organic matter supply in silty mudstones of the upper section of the Yangye Formation. Furthermore, the enhancement of water reducibility during this period was also beneficial for the preservation of organic matter. In summary, paleoclimate, paleosalinity, and depositional environment are important factors influencing the organic matter enrichment in the Jurassic lacustrine source rocks of the Kekeya area.
Yury N. Poltev, Tatyana G. Koreneva, Vsevolod E. Maryzhikhin
et al.
The content of Fe, As, Cu, Mn, Cr, Ni, Pb and Cd in the muscles of some aquatic organism species from the Sea of Okhotsk waters of Northeastern Sakhalin was estimated: walleye pollack (Gadus chalcogrammus Pallas, 1814), longhead dab (Limanda proboscidea Gilbert, 1896) and Bering flounder (Hippoglossoides robustus Gill & Townsend, 1897), snow crab (Chionoecetes opilio (O.Fabricius, 1788)). The concentrations of Fe and Cu are reliably higher in the snow crab, in contrast to fish, and Pb concentration is higher in fish relative to the snow crab. There was no difference in the content of trace elements between the flounders and snow crab, and in relation to the walleye pollock, the snow crab has reliably higher concentrations of Fe, Cu, and Hg and lower ones of Pb. The content of Fe is higher in the flounders compared to the walleye pollack. The concentrations of Pb, Cd, As and Hg are safe according to the hygienic requirements for food products and may indirectly indicate a favorable environmental situation in terms of the content of regulated toxic elements in the waters of Northeastern Sakhalin.
Abstract Amplitude variation with offset (AVO) analysis is an important tool for identifying natural gas-bearing reservoirs. The changes in seismic amplitudes based on the variation of density and velocity of the rock matrix are captured through the AVO analysis. The current work was performed in the Ghotaru region of the Jaisalmer Sub-basin area, where limited and discrete hydrocarbon discoveries were observed from the Lower Goru Formation during the earlier various exploration campaigns. The discrete nature of the reservoir lithofacies developed challenging scenarios for the successful exploratory campaign. The campaign encountered more difficulties because of limited advanced datasets, which affected the study to capture the extension of hydrocarbon-bearing reservoir lithofacies and its characterization towards a successful exploration campaign. This study shows the way to overcome these challenges using an existing conventional dataset. The study shows the possibility of AVO analysis using a post-stack seismic dataset. A unique conversion method from post-stack to pre-stack seismic is introduced in this study based on the uses of the integrated velocity model. An integrated, robust velocity model was developed with consideration of anisotropy factors. Introducing a machine learning-based algorithm in the petrophysical study, including the conventional approach, provides a robust validation of this work. Intercept (A) and gradient (B) are the basic outcome of AVO analysis. The well-based study and AVO analysis based on intercept (A) and gradient (B) complement each other for finding hydrocarbon-bearing reservoir rock. Cross-plots and AVO analysis show the reservoir's lithofacies extension and fluids. The study reveals the potential of natural gas retained in the Lower Goru Formation, which is composed of patchy sandstone. Two AVO classes (Class I and Class III) of gas-bearing sandstone have been identified in this study. This study presents a unique method for identifying natural gas reservoirs with limited old conventional data.
Ehsan Khamehchi, Mohammad Zolfagharroshan, Mohammad Reza Mahdiani
Abstract Flow rate prediction of multiphase flow in the oil and gas wellbores is more complicated than single-phase flow avoiding direct measurements such as using flowmeters or well logging. This study offers an approach to find the accurate two-phase flow rates, applicable in extensive cases of two-phase wells/pipelines. When in a production well, the wellhead data are accessible except for flow rate, and bottom hole conditions, computing the pressure and temperature profiles through the wellbore can be brought about by replacing different values for flow rates, and lead us to probable accurate answers. This aim can be achieved by hiring a heuristic solver to find the most accurate answers as quickly as possible. This approach is flexible and practical depending on the statement of the problem. So, in this study, it has been applied to some vertical two-phase flow wells, which their well survey data was available to avoid future loggings, the wells modeled. Two models were developed, where each one predicted the flow rate by an error of less than 2%. Considering the final results for vertical wells, in this study, the model in which a mechanistic method for predicting pressure gradient applied in proposed compared with experiment-based methods.
Muhammad Akram Qureshi, Shahid Ghazi, Muhammad Riaz
et al.
Abstract Seismic as well as structural techniques were exploited to elucidate the subsurface structure of the Zamzama area that directly led to petroleum system. Zamzama gas field is located in the Kirthar Foredeep, southern Indus Basin, Pakistan. The current research is based on data scrutinized systematically through eight seismic lines (796-JH-01, 02, 03, 07, 10, GHPK-98A-32, 34 and 40) and three wells (Zamzama-02, 03 and 05) drilled in the Zamzama field. Seismic interpretation reveals that Tertiary and Cretaceous sequence is deformed by transpressive tectonics, and a reverse fault is located from 400 to 3400 ms deep on the vertical seismic section. The hanging wall moves up along the fault plane under the action of eastward directed stress as a result an extensive North–South oriented and eastward verging thrusted anticline is formed. Stratigraphically, area encompasses well-developed Mesozoic–Cenozoic sequence. The Late Cretaceous Pab Formation is well-known primary hydrocarbon reservoir capped by the shale of the Paleocene Ranikot Formation that acts as a regional seal rock. The Jurassic and Cretaceous shales of the Sember and Goru formations are substantiated as main source rocks. The execution and portrayal of seismic and subsurface geological data provide the clues that area contains appropriate petroleum play potential. Present study suggests a worthwhile regional geo-seismic model that might be significant for future exploration in the Kirther Foredeep and adjacent areas.
Abo Taleb T. Al-Hameedi, Husam H. Alkinani, Mohammed M. Alkhamis
et al.
Abstract The cost of the drilling operation is very high. Drilling fluid presents 15 to 30% of the entire expense of the drilling process. Ordinarily, the major drilling fluids additives are viscosity modifiers, filtration control agents, and partial loss treatments. In this experimental work, full-set measurements under fresh and aged conditions, as well as high-temperature and high-pressure (HTHP) API filtration, were conducted to study the impacts of adding 0.5%, 1.5%, 2.5%, and 3.5% of black sunflower seeds’ shell powder (BSSSP) to spud mud. BSSSP of various grain sizes showed their ability to be invested for viscosity modifying, seepage loss controlling, and partial loss remediation. In addition to BSSSP eminent efficiency to be used as a multifunctional additive, the BSSSP is cheap, locally obtainable in commercial quantities, environmentally friendly additive and easy to grind into various desired grain sizes. Besides its outstanding strength to behave under conditions up to 30 h aged time and under 50 °C (122 °F) temperature, the utilization of powdered waste black sunflower shells in the drilling process and other industrial applications can reduce the effects of food waste on the environment and the personnel safety. To sum it up, experimental findings revealed that BSSSP can be used for multiple applications as a novel fibrous and particulate additive. The results elucidated BSSSP suitability in substituting or at least minimizing some of the traditional chemical materials utilized in the petroleum industry such as salt clay, polymers, and lost circulation materials (LCM).
Caves reaching the (epi)phreatic zone may provide the only access to groundwater in the internal parts of karst aquifers. Modern instruments enable unattended high frequency measurements of groundwater parameters in such caves. A network of distributed observation points may give new information on temporal and spatial pattern of groundwater flow. Such network, recording water level, temperature and specific electrical conductivity was established in all major ponors and active water caves of the karst aquifer between Planinsko Polje and springs of the Ljubljanica River, Slovenia. Up to three and a half years long records were analysed in view of available and relevant geological, speleological, meteorological and hydrological information, and basic hydraulic principles of the epiphreatic flow. The result of the interpretation were models of possible conduit networks of the three main flow subsystems draining Planinsko Polje. For each subsystem a hydraulic model comprising the main features of the inferred conduit network and inputs was made. The models were adjusted until their response to the typical flood situations gave a good qualitative fit to the response of the observation network. The results provide new insights into the mechanism of flood propagation through the system and its relation to the known conduit geometry. The hydraulic role of known cave passages is assessed and new flow pathways are proposed. Back-flooding within the aquifer causes an increase of head in the polje, followed by the activation of higher located ponor zones and flow pathways related to them. Hydrographs recorded in two caves located northwest from Planinsko Polje revealed pos sible high transmissivity zone of the Idrija Fault Zone and the mechanism of estavelles located at the polje’s north-western border. The approach taken in this work offers new insights into the relation between the conduit network geometry and flood mechanism. It can be used elsewhere in conduit-dominated systems with multiple accesses to groundwater flow and well constrained recharge.
Key words: karst aquifer, epiphreatic zone, groundwater monitoring, hydraulic models, Planinsko Polje, Ljubljanica River.
Dinamika podzemne vode med Planinskim poljem in izviri Ljubljanice, Slovenija
Jame v epifratični coni običajno predstavljajo edini dostop do podzemne vode znotraj kraškega vodonosnika. Sodobni merilniki omogočajo kakovostne zvezne meritve različnih parametrov tudi v takšnih jamah. Merilna mreža z več lokacijami znotraj izbranega vodonosnika lahko ponudi nove podatke o časovni in prostorski dinamiki toka podzemne vode. Takšna merilna mreža, z meritvami višine, temperature in elektroprevodnosti vode, je bila vzpostavljena v vseh pomembnejših ponorih in vodnih jamah na območju med Planinskim poljem in izviri Ljubljanice. Do tri in pol leta dolgi nizi podatkov so bili analizirani z vidika razpoložljivih geoloških, speleoloških, meteoroloških in hidroloških podatkov ter osnovnih hidravličnih načel o epifreatičnem toku vode. Rezultat interpretacij so poenostavljeni modeli z domnevno razporeditvijo podzemnih kanalov v treh glavnih podsistemih, ki odvajajo Planisko polje. Za vsak podsistem je bil napravljen hidravličen model z dotokom in mrežo kanalov, ki najbolje ponazarja resnično stanje. Tekom raziskave so se hidravlični modeli nadgrajevali do takšne mere, da je simulacija vodnega toka zadovoljivo ponazarjala dogajanje, izmerjeno v resničnem okolju. Rezultati so prinesli nove ugotovitve o širjenju in dinamiki poplavljanja skozi sistem ter njihovo povezavo s poznano geometrijo proučevanega vodonosnika. Ocenjena je bila hidravlična vloga poznanih jamskih rovov, na podlagi njih pa interpretirane nove smeri pretakanja vode. Ugotovljeno je bilo tudi zajezitveno poplavljanje znotraj vodonosnika, ki vpliva tudi na vodostaj na polju in nadalje na aktivacijo višje ležečih požiralnikov ter njim sledečih kanalov. V dveh jamah severozahodno od Planinskega polja so višinski hidrogrami nakazali na obstoj bolj prepustnega območja Idrijske prelomne cone ter delovanje estavel na severozahodnem obrobju polja. Postopek, ki je bil uporabljen v pričujočem delu, omogoča nova dognanja o razporeditvi podzemnih kanalov in s tem povezano dinamiko poplavljanja v kraškem vodonosniku. Predstavljeno metodo je mogoče uporabiti tudi v drugih kraških sistemih z dobro razvitimi kanali, z več dostopi do toka podzemne toka vode in dobro poznanem dotoku v sistem.
Ključne besede: kraški vodonosnik, epifreatična cona, spremljanje podzemne vode, hidravlični modeli, Planinsko polje, Ljubljanica.
Mehdi Mazarei, Afshin Davarpanah, Amirhossein Ebadati
et al.
Abstract Due to the increasing demand for gas consumption during cold seasons, it is a sense of urgency to provide a reliable resource for gas supply during these periods. The objectives of this comprehensive research entail reservoir core analysis, reservoir fluid study, investigation and optimization of improved condensate recovery during gas storage processes in one of Iranian-depleted fractured gas condensate reservoir. We have attempted to make a balance among reservoir petrophysical and operational characteristics such as production rate, ultimate reservoir pressure after production, cumulative condensate production, number of wells and the required time periods for the reservoir depletion, to obtain an optimum condition for the gas storage process. It’s a foregone conclusion that the quality of management decision-making regarding reservoir depletion, maximum gas recovery and natural gas condensate production subsequently optimize at the minimum pressure drop. Furthermore, according to the simulation analysis, pipeline gas injection may lead to condensate recovery improvement.
Arezoo Moradi, Nahid Shabanian Boroujeni , Ali Reza Davoudian Dehkordy
Introduction
Studied mylonitic granite-gneiss body is located in the Northwest of the Azna region in the Lorestan province close to the June dimension stone mine. It is a part of the metamorphic- magmatic complex including granite-gneiss, amphibolite, marble and schist. The crystalline basement is attributed to late-Neoproterozoic and it indicates a Panafrican basement, which yields a laser-ablation ICP–MS U–Pb zircon ages of 608 ± 18 Ma and 588 ± 41 Ma (Shakerardakani et al., 2015). There are two granite-gneiss plutons in the complex that are Galeh– Dezh (Shabanian et al., 2009), and June plutons. The Galeh-Doz pluton are previously proposed as syn-deformation pluton with a major S-shaped bend which has been imparted during dextral shearing with a Late Cretaceous (Mohajjel and Fergusson, 2000). However, new age dating on the pluton using U–Pb in the magmatic zircon produced the late-Neoproterozoic dates (Nutman et al., 2014; Shakerardakani et al., 2015). The granite-gneiss plutons show mylonitic fabrics and microstructures (Shabanian et al., 2010). The geochemical characteristics of mylonitic granite-gneiss body near June mine in NW Azna, is in the focus of our research.
Materials and methods
Petrographic investigations of 30 thin sections were made. Then eight samples were selected and analyzed for whole rock major, trace and REE compositions by ICP-emission spectrometry and ICP-mass spectrometry using natural rock standards as reference samples for calibration at the ACME Analytical Laboratories in Vancouver, British Columbia, Canada.
Results
The studied gneiss- granitic body has lepido-granoblastic texture as its major texture. It variably shows evidence of dynamic deformation from ultramylonite to protomylonite. The gneiss- granite consists of quartz, alkali feldspar (mostly as perthite), plagioclase, biotite, white mica (muscovite and phengitic muscovite). Accessory phases in the granitoid include, tourmaline, zircon, magmatic epidote, allanite, apatite, and magnetite. The mylonitic gneiss-granite has a mantled porphyroclast texture that may be characterized by large asymmetrical porphyroclasts of K-feldspar and plagioclase with a mantle which includes white-mica, biotite, quartz and feldspar aggregates. Some of the petrographic evidence show dynamic deformation during the crystallization such as grain boundary migration (GBM) or sub-grain rotation (SGR), patchy perthite. Evidence of strain, such as deformation twins, bent or curved twins, undulatory extinction occur characteristically in plagioclase and display dynamic deformation in solid state. The rocks exhibit identical compositional ranges with 71.24–78.35 wt.% SiO2; high levels of alkalies (Na2O ranges from 3.07 to 4.02 %, K2O varies from 4.18 to 5.53 %); low levels of Fe2O3tot (0.80 to 2.60 %). Also, the trace element compositions display significant variations, such as Zr (157.7-330.5 ppm), Eu (0.07-0.28 ppm), Nb (40.9-77.3 ppm), Ga (19.7-25.97 ppm). The studied rocks are strongly enriched in LREE and HFSE and show a strong depletion in Ba, Sr, Eu and Ti and enrichment in Rb and Zr. The element contents are also similar to typical A-type granite (Whalen et al., 1987). The rocks are alkali to alkali-calcic, metaluminous to mildly peraluminous granite and ferroan in new geochemical classification scheme for granitoids (proposed by Frost et al., 2001).
Discussion
The chondrite-normalized rare-earth element patterns of the mylonitic gneiss- granitic rocks indicate the LREE over HREE fractionation with significant negative Eu anomalies. Primitive-mantle-normalized spidergrams (Sun and McDonough, 1989) normalized trace element patterns with negative Ba and Nb anomalies, and positive Rb, Th and Ce anomalies, simulate the collisional and post-collisional granitoids of Pearce et al (Pearce et al., 1984). All of the samples fall in the A2 group in Eby classification (Eby, 1992). On the tectonic discrimination plots, the granites show a within-plate granite (WPG) character (Pearce et al., 1984).
Acknowledgements
The study was completed at the Shahrekord University and it was supported by the office of graduate studies. The authors are grateful to the office for their support.
References
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Nutman, A.P., Mohajjel, M., Bennett, V.C. and Fergusson, C.L., 2014. Gondwanan Eoarchean Neoproterozoic ancient crustal material in Iran and Turkey: zircon U–Pb–Hf isotopic evidence1. Canadian Journal of Earth Sciences, 51(3): 272–285.
Pearce, J.A., Harris, N.W. and Tindle, A.G., 1984. Trace element discrimination diagrams for the tectonic interpretation of granitic rocks. Journal of Petrology, 25(4): 956–983.
Shabanian, N., Davoudian, A.R., Khalili, M. and Khodami, M., 2010. Texture evidences imply on dynamic conditions in late-stage to post magmatic crystallization from dynamo-magmatic gnessies of Ghaleh-Dezh, Azna. Iranian Society of Crystallography and Mineralogy, 18(3): 463-472. (in Persian with English abstract)
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Ehsan Khamehchi, Mahmood Shakiba, Mohammad Shaker Ardakani
Abstract Nowadays, the significance of hydrocarbon reservoirs as the main supply of world energy is being increased more than before. Hence, a safe and continuous production process of oil and gas wells is one of the most important criteria in the oil industry. In this regard, some issues such as deposition of heavy organic materials, especially asphaltene in the tubing, and surface pipelines can cause considerable damages to the production unit. Asphaltene precipitation occurs due to change in thermodynamic conditions, such as the composition of crude oil, temperature and pressure, which can disturb the thermodynamic equilibrium and result in asphaltene deposition. These particles would result in obstruction of the tubing and surface pipelines. In this study, the distribution profile of asphaltene precipitation in a well of one of the Iranian south oil reservoirs has been developed using an integrated thermodynamic modeling. The impacts of hydrodynamic parameters on asphaltene precipitation have also been investigated, and some sensitivity analyses have been made on them in order to optimize well completion and production conditions. Optimization operation can obviate shortcomings associated with the asphaltene deposition, and as a result, it would decrease costs and subsequently lead to more benefit. If there is an optimized integrated model for tubing and surface facilities, it can not only be used for investigating the fluid flow behavior but also it can prolong the lifetime of the entire production unit. In this case study, one of the most important intelligent optimization algorithms (i.e., the particle swarm optimization algorithm) has been used to solve the problem. The results showed that cumulative oil production and thickness of asphaltene deposition under optimum conditions are 5.6 million barrels and 0.33 inches, respectively. According to the outcomes of optimization operation, tubing size and surface choke bean size are 4.25 and 47.9 inches, respectively. In addition, the oil production rate has been determined as 5972 STB/day. At these conditions, well head pressure and temperature should be considered as 1336 psi and 160 °F, respectively.
Gavdel intrusive body, situated in NW Iran and NE of Uromieh-Dokhtar zone, is a part of Garehdagh, South-Arminian Zone (Arasbaran). The major outcrops of intrusive include of granodiorite, monzonite accompanied with granodioritic dyke. The studied samples display granular texture with essential minerals of, plagioclase, K-feldspar, amphibole ± quartz ± clinopyroxene. Geochemically, the studied rocks characterized by SiO2 in the range of (59.1-67.8%), Al2O3 (14.09-18.3%), high Sr (507.18-1150 ppm) content , high ratios of Sr/Y (32.93-83.54), La/Yb and low Y (12.05-16.13) contents, which can indicate the adakitic characters of studied rocks. These features of Gavdel intrusive display geochemical similarity with high SiO2 adakites (HAS) that comprise enriched LREE, LILE and depleted HFS elements such as Ta, Nb, and Ti. The fractionated REE pattern and low HREE and Y amount can be related to the occurrence of garnet or amphibole in residual source of adakitic magmas. High content of Sr and depletion of Ta, Nb and Ti can be ascribed either to the absence of plagioclase and the presence of Fe-Ti oxides in melt residue or fractionation of titanomagnetite and amphibole minerals with respect to petrograhic indications. Subducted slab breaking off followed by its partial melting and the overlying sediments accompanied by crustal assimilation through magma rising generated the magma in the studied area and the NW of Iran.
Tisova jama (-235 m) je na gori Beljanici (Karpato-Balkanidi) v Vzhodni Srbiji. Vhod vanjo se odpira v dnu udornice (180 × 160 m), pod katero je podzemeljska dvorana z do sedaj največjo znano površino (11 374 m2 ) in prostornino (približno 170 000 m3 ) med jamami v Srbiji. Tako velikost si je mogoče razložiti s prisotnostjo močnega podzemeljskega toka v nedostopnih delih jame. Odnašanje gradiva je porušilo stabilnost kamnine pod vrtačo, kar je povzročilo podiranje in poglabljanje vrtače.
The cave Tisova Jama (-235 m) is located on Beljanica Mountain (Carpatho-Balkanides, Eastern Serbia). Its entrance pit is situated at the bottom of a great collapse doline (dimensions 180 x 160 m), below which there is a chamber with the greatest surface (11 374 m2) and volume (approx. 170 000 m3) so far known among Serbian caves. Such dimensions can be explained by the presence of a strong underground stream in the unreachable part of the cave. Removal of the material disrupts the stability of the rock below the doline, which leads to breakdown and deepening of the doline.
Introduction<br>
The study area is a small part of the Urumieh-Dokhtar structural zone in the Markazi province, located in the northeastern part of the Farmahin, north of Arak (Hajian, 1970). The volcanic rocks studied from the area include andesite, dacite, rhyodacite, ignimbrite and tuff of Middle to Late Eocene age (middle Lutetian to upper Lutetian) (Ameri et al., 2009). It seems that folding and faulting is caused in sedimentary basin and volcanic activities. On the other hand, except of orogeny maybe rifting had rule in eruption so that this case has seen in the other area such as Taft and Khezrabad in central Iran (Zarei Sahamieh et al., 2008). The oldest formation in the studied area is Triassic limestones. The dominant textures of these rocks are porphyritic, microlite porphyritic, microlitic and rarely sieve-texture. Sieve texture and dusty texture (dusty plagioclases) indicates magma mixing. Mineralogically, they contain plagioclases, clinopyroxenes, amphiboles, quartz and biotite as the main constituents and zircon, apatite, and opaque minerals as accessories. Plagioclases in the andesitic and basaltic- andesite rocks are labradorite, bytownite and anorthite (based on electron microprobe) .Moreover, plagioclases in andesitic rocks show that H2O is lesser than 2.5 precent. Amphibole is found in both plagioclases and groundmass. <br><br>
Materials and methods<br>
In this article are used different analyses methods such as XRF, ICP-MS and EPMA.
Whole-rock major and trace element analyses were determined with ICP-MS method. <br>
The major and trace element composition of some rock was determined by electron probe micro-analysis (EPMA) using a Cameca SX100 instrument in Iran Mineral Processing Research Center (IMPRC). Moreover, whole-rock major and some trace element analyses for some samples were obtained by X-ray fluorescence (XRF), using an ARL Advant-XP automated X-ray spectrometer. <br><br>
Results<br>
Chemical data based on electron micro probe studies of minerals indicate the presence of labradorite, bytownite, anorthite as the plagioclases in volcanic rocks, as well as augite, pigeonite and clinoenstatite among the pyroxenes are abundant. Microscopic study of these lavas and pyroclastic rocks show evidences of magmatic contamination in the form of oscillatory zoning, resorption rims in plagioclase and presence of basic inclusions. The presence of oxidized amphibole rims (in hornblende) indicates the high temperature of the magma at the time of eruption. <br>
Based on geochemistry especially the ratio of Eu/Eu* is variable between liquid and solid phases. The calculated of this ratio in studied rocks show negative anomaly (Eu<1) (Tabatabai Manesh et al., 2010). <br>
According to classification diagrams is used of different diagrams for example TAS/SiO2, R1-R2 and Zr/TiO2-Nb/Y. TAS/SiO2 diagram show that the rocks are of basaltic-andesite, andesite and dacite. R1-R2 diagram show these rocks are andesite, andesi-basalt, dacite and rhyodacite. Finally, based on Zr/TiO2-Nb/Y the rocks in area under study are andesite, basalt, dacite and rhyodacite type. <br>
The geochemical diagrams (such as AFM) for identify of mama series show that the rocks studied are calc-alkaline and A/NK-A/CNK show magma is peraluminous to metaluminous in nature. Enrichment of incompatible and LILE elements such as Ba, K and Rb show that contamination of magma with continental crust have been occurred in this area. Similarity between REE patterns in all samples is related to common source for all volcanic rocks in the studied area. <br><br>
Discussion<br>
The tectonic setting diagrams show that these rocks belong to the continental margin which have been involved in a subduction zone and belong to the orogenic andesite belt. <br>
The position of the samples on the major elements-SiO2 diagrams indicate that magma differentiation has been occurred. Spider diagrams show depletion and enrichment that the type of rocks in studied area have positive anomalous of Rb and negative anomalous of Nb and Ti, this phenomenon shows contamination between magma and crustal rocks (Ghasemi and Talbot, 2006; Rollinson, 1993). Comparison of spider diagrams normalized to chondrite or MORB also show that the parent magma has been contaminated. It appears that assimilation and fractional crystallization (AFC) were the dominant processes in the genesis of the studied volcanic rocks (Roozbehani and Arvin, 2010). As a conclusion and regarding to what we said in this article ,the area under study are included both lava and pyroclastic rocks such as andesite, dacite, rhyodacite, ignimbrite ,tuff and tuffits that cut by younger dykes and belong to Middle to Late Eocene age(middle Lutetian to upper Lutetian).There is no rocks older than Triassic age. Volcanic rocks have been occurred in two environments, dry and water together. From volumetric point of view, Aciditic and intermediate rocks such as dacite, rhyodacite and andesite are the most in the area under study (Ahmadian et al., 2010). Basitic rocks are a lesser amount than the others. <br>
Regarding to all evidences such as field works, structurally, texturally, mineralogically, geochemically and petrologically show that rocks in studied area belong to subduction zone and magma that created of these rocks have been originated from mantle and contaminated with continental crust during eruption and rising. <br><br>
Acknowledgments<br>
The authors wish to thank Journal Manager and reviewers who critically reviewed the manuscript and made valuable suggestions for its improvement. <br><br>
References<br>
Ahmadian, J., Bahadoran, N., Torabi, G. and Morata, M., 2010. Geochemistry and petrogenesis of volcanic rocks in Aroosan Kabood (north-east of Anarak). Journal of Petrology, 1(1): 103-120. (in Persian) <br>
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Roozbehani, L. and Arvin, M., 2010. Petrography, geochemistry and petrogenesis of ryolitic and andesitic rocks in Nasir Abad, south-west, Kerman .Journal of Petrology, 1(2): 1-16. (in Persian). <br>
Tabatabai Manesh, M., Sayed Safai, H. and Mirlohi, A.S., 2010. Study of mineralogy and effective process on volcanic rocks in Jahaq anticlinal (south of Kashan). Journal of Petrology, 1(2): 61-76. (in Persian) <br>
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Benjamin F. Schwartz, Susanne Schwinning, Brett Gerrard
et al.
The epikarst is a permeable boundary between surface and subsurface environments and can be conceptualized as the vadose critical zone of epigenic karst systems which have not developed under insoluble cover. From a hydrologic perspective, this boundary is often thought of as being permeable in one direction only (down), but connectivity between the flow paths of water through the epikarst and the root systems of woody plants means that water moves both up and down across the epikarst. However, the dynamics of these flows are complex and highly dependent on variability in the spatial structure of the epikarst, vegetation characteristics, as well as temporal variability in precipitation and evaporative demand. Here we summarize insights gained from working at several sites on the Edwards Plateau of Central Texas, combining isotopic, hydrogeochemical, and ecophysiological methodologies. 1) Dense woodland vegetation at sites with thin to absent soils (0-30 cm) is in part supported by water uptake from the epikarst. 2) However, tree transpiration typically becomes water-limited in dry summers, suggesting that the plant-available fraction of stored water in the epikarst depletes quickly, even when sustained cave drip rates indicate that water is still present in the epikarst. 3) Flow paths for water that feeds cave drips become rapidly disconnected from the evaporation zone of the epikarst and out of reach for plant roots. 4) Deep infiltration and recharge does not occur in these systems without heavy or continuous precipitation that exceeds some threshold value. Thresholds are strongly correlated with antecedent potential evapotranspiration and rainfall, suggesting control by the moisture status of the epikarst evapotranspiration zone. The epikarst and unsaturated zone in this region can be conceptualized as a variably saturated system with storage in fractures, matrix porosity, and in shallow perched aquifers, most of which is inaccessible to the root systems of trees, although woody vegetation may control recharge thresholds.
Keywords: hydraulic disconnection, precipitation thresholds, root zone, plant water use, recharge, epikarst storage, barometric pressure.
DOI: 10.3986/ac.v42i2-3.670