Dolomitic Limestone Research Articles

Optimal control and nonlinear numerical simulation analysis of tunnel rock deformation parameters

Abstract In order to study the influence of nonlinear numerical simulation on the optimal control of the tunnel rock deformation parameters, the author proposes a numerical simulation study of the deformation characteristics of the layered rock tunnel, and determines the calculation model according to the thickness of the rock mass. The estimated thicknesses of the dolomite limestone surrounding the tunnel are 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, and 0.9 m. Select the vertical displacement to analyze as a result of the calculation. In order to study the influence of the structural slope on the tunnel stability, the thickness of the rock layer was 0.6 m, and the structural slopes of 5°, 15°, 30°, 45°, 60°, 75°, and 85° were used for simulation calculations. During on-site construction, focus on monitoring the tunnel section deformation before the construction of the secondary lining. Every 10–20 m and at the change of the surrounding rock, the observation section of the surrounding convergence and vault settlement shall be arranged, according to the observed deformation, the peripheral displacement rate and the vault subsidence rate are calculated. The results show that the vertical displacement of the top of the tunnel is generally in a “V” shape, that is, the maximum settlement in the tunnel; when the layer thickness is 0.3 m, the maximum vertical displacement of the rock layer is 7.2 mm, and the total settlement in the lining support tunnel is 8.23 mm. When the layer thickness is 0.9 m, the vertical displacement of the rock layer is 5.14 mm, and the total settlement in the lining support tunnel is 5.22 mm. When the layer thickness is from 0.9 to 0.3 m, the maximum vertical displacement of the rock layer increases by 140%, and the settlement at the vault increases by 158%. The focus of tunnel support at this time is the two sides of the lining structure and the vault with large vertical settlement. For the YK51 + 032 section, the phenomenon of first decreasing and then increasing is due to the sudden mud on the surrounding YK51 + 040, which causes the short-term deformation to increase. Only the ZK49 + 356 sections at the entrance of the spider has very good deformation due to the thin overlying stratum, and other sections are similar, which shows the reliability of the calculation results.

Characterizations and potential recovery pathways of phosphate mines waste rocks

The phosphate ore production is steadily increasing due to its high demand for agriculture, medicine, and others. Ore extraction generates a considerable quantity of waste rocks that are generally stocked in piles. The current research aims to investigate the characterization of phosphate mine waste rocks (PMWR) generated in Benguerir, Morocco mine site. As a part of a wide project aiming to recycle those stockpiles, sensor-based ore sorting will be employed to separate the different lithologies. As a prior investigation before implementing this technology, two samples of 25 tons from the destoning and screening PMWR piles were sampled and submitted to manual sorting. The latter operation revealed the presence of different lithologies including indured phosphate, different types of siliceous, carbonate, phosphorus, and marly rock types. Those waste rocks were characterized physically, chemically, and mineralogically. Their potential uses for recycling or upcycling was investigated and addressed. About 25% of indured phosphate was found, which can be first recovered by ore sorting. This reserve of residual phosphate could be recovered using beneficiation methods. The flintstone, phosphated flintstone, and dolomitic limestone exhibit good physical and mechanical properties that meet the requirements to produce concrete. The silexite and siliceous marls have a low density and could be used as lightweight aggregate for non-structural concrete blocks production. The investigation on tender marls corroborates the literature and their suitability as alternative binders or as supplementary cementitious materials. Those marls could be used as well as lime binder for repairing historical buildings or as hydraulic lime binder for road construction. PMWR valorization as road construction materials was already proved. However, studying this remediation pathway after the recovery of phosphate and other lithologies by ore sorting is highly recommended. The recycling of those by-products will decrease the natural resources consumption in the civil engineering field alongside with resolving their environmental problems.

Geothermal reservoir characterisation of Devonian carbonates in North Rhine-Westphalia (W. Germany): Mineralogy- and depofacies-related extrapolation of petrophysical parameters

Across Germany, coal-fired power plants will be shut down not later than 2038. In the Rhine-Ruhr area of western Germany, their waste heat is the main supply for one of Europe’s largest district heating networks. Because of the projected shutdown of coal-fired power plants, sustainable alternatives must be implemented. This paper evaluates the hydrothermal potential of Devonian carbonates. A depofacies and mineralogy model is proposed and discussed. Tentative conclusions are drawn based on petrophysical laboratory tests. Extrapolating the thermal and hydraulic rock properties into geothermal reservoir depths offers constraints for associated reservoir simulations. This task applies existing and derived extrapolation equations taking local pressure and temperature gradients into consideration. The change from a non-linear to a linear development at the critical crack-closure pressure provides evidence regarding the petrophysical in-situ reservoir conditions. Results show a positive effect of increased dolomite volumes on reservoir properties. The spatial distribution of fracture networks significantly affects the geothermal reservoir potential, whereas the impact of regionally distributed depofacies variations is moderate. The critical crack-closure pressure equals 40MPa for limestones and 60MPa for dolomitic limestones, as well as dolostones, representing depths of approx. 3.6 and 5.4km, respectively. At depths of 6km, non-linear and linear extrapolation principles must be applied accordingly. At that depth, the thermal conductivity decreases by 14 to 20% compared to the outcrop values, depending on the sample category. The equivalent decrease in porosity amounts to one to two orders of magnitude. The permeability decrease equals three to four orders of magnitude. The petrophysical values of outcrop samples discussed here plot, within the error range, in the same domain as those of the Malm carbonates in the Munich area. Results are considered encouraging for those concerned with the sustainable transition of the district heating network in the Rhine-Ruhr area. Side-strands of regionally important fault systems, often characterised by hydrothermal dolomitisation, combine tectonic and petrophysical aspects that are advantageous and highly relevant for hydrothermal operations.

Interaction of Rutba-Dhabaa Groundwater with the Mulussa Aquifer Host Rocks, Western Iraq

Mulussa aquifer extended the area of Rutba-Dhabaa, Western Iraq, has been studied in order to determine the most important chemical functions and interaction between rocks and groundwater (Groundwater–rocks interaction). The results of wet and dry periods indicated that Ca2+ and SO4 2- in the groundwater are the dominant ions. Average of Hydrogen Number (pH), Total Dissolved Solids (TDS), calcium (Ca2+), magnesium (Mg2+), sodium (Na+), potassium (K+), chlorine (Cl-), sulfate (SO4 2-), bicarbonate (HCO3 -) and nitrate (NO3 -) are 7.43, 718.25 mg/l, 120.8 mg/l, 40.875 mg/l, 32.865 mg/l, 2.93 mg/l, 103.527 mg/l, 195.9 mg/l, 214.85 mg/l and 4.275 mg/l respectively in the dry period, while its averages 7.33, 664.2375 mg/l, 114.25 mg/l, 35.8 mg/l, 29.28 mg/l, 2.33 mg/l, 90.3 mg/l, 181.1 mg/l, 203.85 mg/l, and 3.6 mg/l respectively in the wet period. The groundwater is characterized by low alkalinity hard to very hard water, between moderately and excessively mineralized water, and fresh to slightly water in both periods. Rock–water interaction processes are indicating that there is a possible contribution of the seawater in Mulussa aquifer, the dominant process is limestone–dolomite weathering, where the source of calcium is rather than gypsum or silicates rocks, and contribution of calcite more than dolomite in the Mulussa aquifer.

A Digital Assessment Method for Multisource Influence Factors on Corrosion Characteristics in the Karst Areas

Taking dolomite and limestone in Guilin and Liuzhou regions in the north of Guangxi Province as research objects, this paper analyzed their mineral composition and chemical composition and proposed a digital assessment method for multi-source factors on corrosion characteristics in the Karst areas. Specifically, the chemical corrosion test, the corrosion test under the chemical-temperature actions, and the corrosion test under the action of vibration load are carried out from the digital view, respectively. Four aspects can be found in digital assessment results. Firstly, the dolomite in northern Guangxi mainly has a fine crystalline texture and a massive structure with low content of acid-insoluble matters, while limestone mainly has a powder crystalline texture and a massive structure with high content of acid-insoluble matters, and the purity of both dolomite and limestone are very high. Secondly, the difference of corrosion between dolomite and limestone mainly depends on the ratio of CaO/MgO in their chemical composition and the content of silica and acid insoluble matters. Thirdly, the corrosion rates of pure dolomite and pure limestone are basically the same under the same external conditions. Finally, temperature and vibration load have a relatively large influence on the corrosion rates of dolomite and limestone, and the corrosion rates of dolomite and limestone increase with the increase of temperature, but the influence of vibration load on the corrosion rate is more significant than temperature. This research can provide theoretical basis and technical support for large-scale engineering construction and prevention of karst geologic disasters in karst stone mountainous areas in northern Guangxi.

Circumfusicillium cavernae gen. et sp. nov. (Bionectriaceae, Hypocreales) Isolated from a Hypogean Roman Cryptoporticus.

Stone monuments and relics are prone to biodeterioration processes prompted by microbial proliferation and activity. Among the distinct microbes capable of stone colonization, fungi are known to strongly contribute to stone biodeterioration. During the ongoing efforts aiming to study fungi thriving in dolomitic limestone walls of the Coimbra’s hypogean Roman cryptoporticus (Portugal), two unknown Bionectriaceae isolates were retrieved. The aim of this work was to depict the molecular and phenotypic characteristics of these microorganisms. The phylogenetic analyses revealed that the studied strains could not be assigned to any of the currently known Bionectriaceae genera. Moreover, the isolates exhibited distinctive and peculiar characteristics, such as the packing of conidia by surrounding hyphal segments and the formation of rope-like microsclerotia with a textura globose. Taking into account all the data obtained, a novel genus and species, Circumfusicillium cavernae gen. et sp. nov. in Bionectriaceae (Hypocreales), is proposed here.

Reservoir Characterization of Lower Qamchuqa (Shu'aiba) Formation from the Well BH-86, Bai- Hassan Oil field, Northern Iraq

The reservoir characterization of Lower Qamchuqa (Shu'aiba) Formation (Aptian) is studied at the well BH-86 of Bai- Hassan Oilfield in Kirkuk area, Northern Iraq. The lithological study (of 91 thin sections) revealed that the formation consists of shaly limestone, a thin bed of marl within the limestone, and dolomitic limestone. Four petrographic microfacies were noticed Lime mudstone microfacies, Dolomudstone microfacies, Lime wackestone microfacies, subdivided into benthonic foraminifera lime wackestone submicrofacies and bioclasts lime wackestone submicrofacies, and the last microfacies is the Lime packstone microfacies, which is subdivided into pelloidal lime packstone submicrofacies and Orbitolina lime packstone microfacies. Shale content is calculated from the gamma-ry log, showing that the formation is mainly of low shale content (less than 35%). The porosity determined from sonic, density, and neutron logs reflect that the range between <1 and 15% and in some intervals about 6% is secondary porosity type. The estimated permeability ranges between <0.01 and 2.0mD, reflecting low permeability. The formation is subdivided into six reservoir units according to the shale content, average porosity, and permeability. The unit RU-5 has the best reservoir properties among the identified units with an average shale content of about 3.15%, about 6.2% porosity, and about 1.75mD average permeability. On the other hand, the least reservoir property is noticed in the unit RU-1 with average 9.48% shale content, 3.64% porosity, and 0.5mD average permeability. The research indicates that the fractures contribute to the flow within the Lower Qamchuqa Formation. Fluids flow through the formation in four unique Hydraulic Flow Units (HFU). Only about 8% of the gross 146m of the formation is expected to have the required reservoir properties for oil production and about 68% for gas production. The actual productive thickness for oil is only about 2.8% of the gross thickness of the studied section, and it’s more than 50% of the gross thickness for gas.

Unconformity and Paleokarst in the Lower Part of the Qamchuqa Formation; An Example from the Arabian Carbonate Platform in the Zagros Belt NE Iraq

Northeastern Arabian Plate Margin is now part of the Zagros Collisional belt and extends nearly parallel to the Iraq-Iran border. The margin comprised, during the Early Cretaceous, of the Arabian Carbonate Platform which is poorly explored. This margin consists of thick carbonate succession and separates the Neo-Tethys Ocean (present Sanandaj-Sirjan Zone) from the Arabian Plate interior. The carbonate succession, as the Qamchuqa and Balambo formations, consists of more than 600 m of dolomite and reefal limestone. The present study focused on records and discussions of evidence of unconformity and paleokarst (UaPK) inside the Arabian platform in northeast Iraq. The study recorded this evidence inside the lower part of the Qamchuqa Formation and the pieces of evidence include limestone conglomerate, plaeo-solution cavities, erosional surfaces, widespread coarse and fine grain detrital limestones, hardground, extensive burrows of Thalassiniodes, and mineralization. The solution cavities shaped a complex network, developed inside fine-grain limestone and filled with yellow to brown ooid and detrital limestones. Most of these features are observable over more than 500 km2 in the Sulaymaniyah and traceable inside gorges and valley sides. Toward the north and northeast of the studied area, the unconformity changes to correlative conformity in the Neo-Tethys basin of the studied area where the sediments consist of laminated and graded detrital limestone (packstone-wackstone) and are deposited as a thick succession of calciturbidite that stratigraphically designated as the Balambo Formation. The result of the present study debates the previously claimed unconformities and uncovers many processes and features of the Northeastern Arabian Carbonate Platform Margin. Additionally, it reveals tectonic and paleogeographic settings of the Arabian Plate Margin that have application in searches for oil and better reconsideration of the geologic setting of the Zagros Belt in the future.

Seasonal Differences in the Hydrochemical Characteristics of Karst Wetlands and the Associated Mechanisms in Huixian, China

The present study aimed to identify the seasonal changes in the hydrochemical characteristics of the Huixian karst wetland and the underlying mechanism. Conventional ions and isotopes of 130 groundwater samples collected during the wet and dry seasons were analyzed. The hydrochemical characteristics of groundwater in the Huixian karst wetland were clarified using mathematical statistics and hydrochemical methods, including Durov diagrams, ionic ratios, Gibbs diagrams, and H and O isotopes. The hydrochemical evolution and sources of major ions in the Huixian karst wetland were also investigated. The results showed that cations and anions in groundwater in the study area were dominated by Ca2+ and HCO3−, respectively, sourced mainly from calcite weathering. The ions of some groundwater samples were regulated by weathering of dolomite, dolomitic limestone, and pyrite, resulting in relatively high concentrations of Mg2+ and SO42−. K+, Na+, SO42−, NO3−, and Cl− in groundwater originated from precipitation, Na+ and Cl− originated from domestic sewage, K+ was related to the application of potassium fertilizer in agriculture, and NO3− mainly originated from chemical fertilizer. Groundwater ions were primarily controlled by rock weathering, followed by evaporative concentration. The sources of major ions were dependent on the dissolution and precipitation of carbonate rock, as well as the chemical weathering of silicate rock and evaporite. Samples from the various water sources were scattered on both sides of the local meteoric water line (δD = 3.13δ18O − 13.9), which indicated isotopic composition was affected by evaporation and precipitation.

Stable isotope geochemistry and microfossil assemblages of carbonate rocks in the ophiolite mélange zone of the Indo–Myanmar orogenic Belt, NE India: Implications on age and depositional environment

A comprehensive data of whole‐rock and stable isotopic geochemistry along with microfossil assemblages of the carbonate rocks of the ophiolite mélange zone of the Indo–Myanmar orogenic Belt (IMOB), north‐east India are discussed, to determine the influence of terrigenous contamination during the formation of these carbonate rocks and also to understand their depositional environment and ages. These carbonate rocks contain a diverse fauna with the dominance of foraminiferal assemblages of planktonic foraminifera (Globotruncana sp. and Heterohelix sp., etc.) which indicates they were formed during the Santonian to Maastrichtian age. Based on chemical compositions, these carbonate rocks have been identified as limestone (CaO/MgO > 50.1) to slightly dolomitic limestone (9.1 < CaO/MgO < 50.1). Total rare earth element (REE) contents in these carbonates are variable (22.39–146.05 ppm). The Post‐Archean Australian Shale (PAAS)‐normalized REE + Y patterns of these carbonates exhibit seawater‐like REE patterns with LREE depletion and relative HREE enrichment with negative Ce anomalies (Ce/Ce* = 0.32–0.79) and positive Y (4.42–27.81 ppm) and Eu anomalies (Eu/Eu* = 1.11–1.86), suggesting that they were deposited under an oxygenated environment with contamination by hydrothermal activity. They are also depleted in δ13C 0/00 (PDB) (1.02–1.570/00) and δ18O 0/00 (PDB) (−6.37 to −9.00%) values which characterize marine precipitates. Eu anomalies and spread in negative δ18O 0/00 (PDB) values to a lesser extent of δ13C 0/00 (PDB) values of these carbonates suggest their formation was altered by diagenesis in the shallow marine environment. Our new whole‐rock and stable isotope geochemical characteristics, in conjunction with microfacies, suggest that the investigated carbonate rocks might have been formed in low‐energy environments, and deposited in neritic to bathyal palaeoenvironments during the Santonian to Maastrichtian interval.

Microfacies analysis and depositional environment of the Upper Devonian Dankovo-Lebedyansky sediments, Tatarstan, Volga-Ural Basin, Russia

The Upper Devonian, Middle Famennian Dankovo-Lebedyansky sediments in Southeast Tatarstan territory are a carbonate sequence composed of limestone and dolomite, which is important hydrocarbon reservoir units, therefore, it is necessary to conduct in-depth study on its microfacies and depositional environment. In this study, a multidisciplinary approach that combines core observation with thin section examination is used. The limestone contains abundant skeletal grains (echinoderms, foraminifera, algae, gastropods, and calcispheres), as well as non-skeletal grains (intraclasts and peloids). On the basis of detailed petrographic investigations, six sedimentary microfacies can be identified, including (i) peloidal grainstone (MF 1), (ii) cemented bioclastic peloidal grainstone (MF 2), (iii) echinoderm-concentrated packstone (MF 3), (iv) algae packstone (MF 4), (v) bioclastic wackestone (MF 5), (vi) whole-fossil wackestone (MF 6), as well as dolomite or dolostone as diagenetic facies (MF 7). Based on microfacies analysis, the Dankovo-Lebedyansky sediments were deposited in three distinct sedimentary facies belts (shoal, lagoon and open marine environment). In order to reflect dispositional energy condition, the microfacies were grouped into facies associations: (i) low-energy microfacies associations including MF 5 and MF 6, (ii) moderate energy microfacies associations including MF 1, MF 2, MF 3, and MF 4. The dolomite, or diagenetic facies (MF 7), is the result of slightly to extensively dolomitization of limestone in the Dankovo-Lebedyansky sediments. Most of frequent dolostone types are euhedral planar-e and subhedral planar-s. According to petrographic characteristic of the dolostone, a seepage reflux model can be used to explain the dolomitization process of Dankovo-Lebedyansky sediments.

Porosity estimation of a geothermal carbonate reservoir in the German Molasse Basin based on seismic amplitude inversion

The Molasse Basin is one of the most promising areas for deep geothermal exploitation in Germany and the target horizon is the aquifer in the Upper Jurassic carbonates. Carbonate deposits can be very heterogeneous even over a small area due to diagenetic processes and varying depositional environments. The preferential targets for geothermal exploitation in carbonate deposits are fault zones, reef facies and karstified areas, since they are expected to act as hydraulically permeable zones due to high porosity and high permeability. Therefore, identifying these structures and characterizing, e.g., their internal porosity distribution are of high importance. This can be accomplished using 3D reflection seismic data. Besides structural information, 3D seismic surveys provide important reservoir properties, such as acoustic impedance, from which a porosity model can be derived. In our study area in Munich we carried out a seismic amplitude inversion to get an acoustic impedance model of the Upper Jurassic carbonate reservoir using a 3D seismic data set, a corresponding structural geological model, and logging data from six wells at the ‘Schäftlarnstraße’ geothermal site. The impedance model and porosity logs were than used to calculate a porosity model. The model shows a wide porosity range from 0 to 20% for the entire reservoir zone and the lithology along the wells reveals that dolomitic limestone has the highest porosities and calcareous dolomite has the lowest porosities. The study area is cut by a large W–E striking fault, the Munich Fault, and the footwall north of it shows higher porosities and more intense karstification than the hanging wall to the south. Considering the entire study area, an increase in porosity from east to west is observed. Furthermore, we identified a complex porosity distribution in reef buildups and pinnacle reefs. The reef cores have mostly low porosities of, e.g., < 3% and the highest porosities of up to 7 to 14% are observed at the reef caps and on the reef slopes. The reef slopes show a characteristic interfingering of the reef facies with the surrounding bedded facies, which indicates a syn-sedimentary reef development with slightly varying build up growth rates. We also assessed the reservoir quality with regard to porosity distribution and determined areas with moderate to good quality for geothermal exploitation by defining porosity evaluation levels. The porosity evaluation maps show that the carbonate rocks of Berriasian to Malm zeta1 are preferential targets for exploitation, especially in the footwall of the Munich Fault and to the west of the hanging wall, because these areas are characterized by high porosities due to intense karstification of bedded and massive facies, although the latter is mainly restricted to reef caps and reef slopes.

Relationship between stylolite morphology and the sealing potential of stylolite-bearing carbonate cap rocks

AbstractWe analyzed the sealing effectiveness of cap rocks bearing different types of stylolites using a combination of petrographic, petrophysical, pore structure, and sealing capacity characterization techniques. This study was based on examples of carbonate cap rocks that seal ultradeep hydrocarbon reservoirs of the Tarim Basin (China). Samples from both drill cores and their outcrop analogues were investigated to quantify how morphology influences the sealing capacity of different types of stylolite-bearing rocks. The study cap rocks consisted of mudstone, wackestone to packstone, grainstone, and dolomitic limestone. Four types of stylolites were identified: rectangular layer, seismogram pinning, suture and sharp peak, and simple wave-like types. The difference in the sealing capacity of carbonate cap rocks is attributed to their pore structure connections and the types of stylolites they develop. Samples bearing simple wave-like stylolites showed the best sealing capacity, followed by those with rectangular layer and suture and sharp peak types, whereas carbonates hosting seismogram pinning types had the lowest sealing capacity. The impact of stylolite segments on the rock sealing properties, however, differed from one segment to another. Rectangular layer–type stylolites could be divided into three distinct segments (with good, moderate, and poor sealing, respectively). Both the seismogram pinning and suture and sharp peak stylolite types were divided in two parts, with the former one having moderate and poor sealing and the latter exhibiting good and moderate sealing. The simple wavelike type had a good sealing capacity all along the pressure-solution seam. The most effective sealing barriers for vertical fluid flow form when (1) calcite and siliceous cements are pervasively distributed in the vicinity of stylolites, forming highly cemented zones with lower porosity and permeability than their surrounding host rocks; (2) stylolites are enriched in insoluble residues; and (3) rare microfractures and dissolution vugs are found along the stylolites. This work provides useful examples for the prediction of the sealing potential of stylolite-bearing carbonate rocks according to stylolite morphology in other geologic settings.

Depositional Setting of Khurmala Formation (Paleocene-Early Eocene) in Nerwa section, Berat Anticline, Kurdistan Region, Northern Iraq

The depositional environment of the Khurmala Formation (Paleocene-Early Eocene) has been investigated in the Nerwa section, the southern limb of the Berat anticline in the High Folded Zone of Iraq. The thickness of the formation in the studied section was about 113m and can be divided into three units; fossiliferous bedded limestone unit (Unit A), massive dolomitic limestone unit (Unit B) and bedded marly dolomitic limestone unit (Unit C). The petrographic study of the 81 thin sections of the Khurmala carbonates revealed that the majority of skeletal grains are shallow marine derivative faunas and non-skeletal grains include peloids, cortoids and intraclasts. Depending on detailed field observations and petrographic study of the carbonate rocks, five main microfacies were recorded, these are; lime mudstone, lime wackestone, lime packstone, grainstone and boundstone in addition to one lithofacies which is an intraformational conglomerate. Based on the integration of the recognized microfacies and the field criteria of the Khurmala Formation, two facies associations were identified which elucidate deposition in a lagoonal environment including reef patches. Accompanying facies indicate that the formation's sedimentary model is a ramp carbonate platform.

Three new Achnanthidium (Bacillariophyceae) species from Lake Salda (Anatolia, Turkey), a deep soda lake

Background and aims – Kützing separated the genus Achnanthidium from the genus Achnanthes based on two species: Achnanthes minutissima and Achnanthidium microcephalum. These two genera were distinguished by the presence of stalks in the Achnanthes genus and their absence in Achnanthidium. Before electron microscopy, the difference between Achnanthes and Achnanthidium was not clear, especially in Achnanthidium minustissimum sensu lato. The aim of the study is to describe three new species of Achnanthidium from Lake Salda. Material and methods – Lake Salda is located in southwestern Anatolia, in Turkey. The diatoms were collected seasonally from four stations in the lake between 2016 and 2020, from different substrata (epipelic, epiphytic, and epilithic). Key results – Three new species belonging to the genus Achnanthidium have been found in Lake Salda, Turkey. Based on the morphological observations, all new taxa are part of the Achnanthidium minutissimum complex. Achnanthidium barlasii sp. nov. and A. dumlupinarii sp. nov. show a high degree of similarity to each other, but can be separated based on valve outline and a denser areolation, especially in striae close to the apices of the raphe valve. Both species can be distinguished from A. minutissimum based on more separate apices and less elliptic valves. In the case of A. dumlupinarii sp. nov., large specimens show slight undulations of the valve, which is a unique feature. Achnanthidium anatolicum sp. nov. is the most characteristic based on its valve width, broadly rounded valve apices, and almost straight valves in girdle view. All newly described Achnanthidium species can be found in lentic environments, with alkaline water and high calcium ion content. Conclusion – The newly described taxa occurred in the unique habitat of a soda lake. The environment of the lake is highly alkaline, rich in magnesium and calcium, and derived from limestone and dolomitic limestone rocks.

Petrophysical analysis of well logs and core samples for reservoir evaluation: a case study of southern Issaran Field, Gulf of Suez province, Egypt

Understanding basic petrophysical properties may enhance the recovery of residual oil saturation and help in reservoir management. Reservoir oil saturation is the fraction of the porosity of a zone occupied by oil. The trapping may increase with the increase of porosity. Oil reservoirs represent a significant fraction of the reservoirs in the world-wide. We try to make a reservoir evaluation using petrophysical analysis of well logs and core samples at Issaran Field, South Gharib Formation, West of the Gulf of Suez, southeast Egypt. This area was heavily influenced by the structural setting of the Gulf of Suez’s central province, which is characterized by major SW dipping faults with a regional stratigraphic dip toward the NE. The high structural blocks are located in the center of the research area, and the low structural region is located in the southwest. South Gharib Formation is primarily composed of carbonates with few sulfates that grade upwards into sulfate-rich beds in the upper part. Laminated dolomitic limestone, with evaporites grades, changes downward into laminated dolomitic limestone and marly limestone, in the lower part. The anhydrite and dolomite units near the bottom have spotty oil stains. The structural setup is continued by the spread and deposition of this formation. We try to make analytical examination, of some reservoirs, accomplished by analyzing both well log data and core rock samples, vertically and laterally. According to the study of the horizontal permeability to vertical permeability ratio (Permeability anisotropy; lambda_{k}), the reservoir is laminated rock (lambda_{k} = 1.1 - 5), with a few data samples nearly isotropic (lambda_{k} = {1 mathord{left/ {vphantom {1 {1.1}}} right. kern-nulldelimiterspace} {1.1}}–1.1) and fractured (lambda_{k} = {1 mathord{left/ {vphantom {1 {2.5}}} right. kern-nulldelimiterspace} {2.5}}–1/1.1). Reservoir data histograms show that the most typical values of the data are 20–30% oil saturation and 7–10% porosity. The net-pay zone varies from four to 71 feet at different depths (897–1414 feet). Due to low shale content, water saturation, high effective porosity values, hydrocarbon saturation, may show higher net-pay thickness. These results may help to enhance the oil recovery. The area in the middle of the research area is suggested for future hydrocarbon development and using more petrophysical analysis.

Microfossils (Foraminifera and Calcareous Algae) of the Yamama Formation, Southern Iraq

The Yamama Formation is one of the important reservoirs, in southern Iraq. This formation in all studied wells consists of limestone and dolomitic limestone. Microfacies analysis clarified that the formation represented a ramp, inner, middle and outer environments, seventy-one species are recorded, the main fossils are composed of many genera and species related to main groups such as foraminifera, calcareous algae, and stromatoporids with few occurrences of gastropods, bivalves, bryozoa, spiculites and Echinoderms. The study has recorded 6 genera of foraminifera and 11 genera (green algae), 3 species related to Salpingoporella sp., 2 genera related to red algae, 1genera related to Charophytes (nonmarine plants) for the first time in the Yamama Formation.

Microfacies Analysis And Depositional Environment Of Pila Spi Formation (Middle - Late Eocene) In The Nerwa Section, Berat Anticline, High Folded Zone, Kurdistan Region, Northern Iraq

Microfacies analysis and depositional environment of the Pila Spi Formation (Middle-Late Eocene) were studied in the Nerwa outcrop, Berat anticline, High Folded Zone in Iraqi Kurdistan Region. The total thickness of the formation is 13.5 m composed of medium to thick bedded yellow to white limestone and thick bedded grey to white dolomitic limestone. It is interbedded with thin beds of yellow marl in the lower part and have chert nodules in the upper part. The petrographic study of 17 thin sections of the Pila Spi carbonate showed that the majority of the carbonates are micritic mixed with some microspar. The skeletal grains involve benthonic foraminifera, ostracods, mollusca, dasycladacean green algae, pelecypods, gastropods, rare planktonic foraminifera and bioclasts. Non skeletal grain included peloids, intraclasts and extraclasts which is mainly monocrystalline quartz grain. Based on field observations and petrographic analysis, three different lithological units were distinguished in the Pila Spi Formation in the studied section. They are in ascending order: medium to thick bedded limestone interbedded with marl unit, thick bedded dolomitic limestone unit and, cherty limestone unit. Depending on detailed microfacies analysis of carbonate rocks, three main microfacies and twelve submicrofacies were recognized in the studied section of the Pila Spi Formation. From the sum of all petrographic, facies and textural analyses, it is here concluded that Pila Spi Formation in the Nerwa section was deposited at subtidal semi-restricted lagoon, in lower part gradually changed to open lagoon environment toward the upper part.

Geoconservation in Sicily (Italy): the Example of the Isola delle Femmine (Palermo)

The Regional Administration of Sicily recently erected Isola delle Femmine—a small island of the Tyrrhenian Sea, close to Palermo—as a geosite. A detailed geological survey has been carried out in order to define the most important geological features of the island together with the development of a new geological map based on topographic data and a digital model at 1:2.000 scale specially processed. Finally, a geological pathway through the island has been traced and illustrated. The geological substrate of Isola delle Femmine consists of a Mesozoic carbonate succession belonging to the Panormide Carbonate Platform. Two lithostratigraphic units have been differentiated. The lowest one consists of dolomitic limestones cropping out in the intermediate and northern part of the island. Despite the absence of biostratigraphic constrains, analogies with comparable deposits from the Palermo Mountains suggested to ascribe this unit to the Upper Triassic. The overlying unit consists of well-bedded rudist and stromatolitic limestones organized in peritidal cycles. The macro- and micro-facies analysis of these Cretaceous limestones allows to attribute this unit to the Lower Cretaceous (i.e., Aptian). Patches of upper Pleistocene skeletal calcarenites rich in benthic foraminifers and calcareous algae overlap the Mesozoic units. Spectacular speleothems such as stalagmites, ray crystals (“raggioni”) of calcite, and mammillary calcite suggest a relative long-lasting exposure of the Mesozoic carbonate substrate to groundwater. This is not surprising since glacio-eustatic oscillations caused sea-level to fall up to 125 m during the Pleistocene thus exposing and linking to the mainland (Sicily) Isola delle Femmine and the surrounding area.

Inhibition of Alkali-Carbonate Reaction by Fly Ash and Metakaolin on Dolomitic Limestones.

In this paper, the dolomitic limestone determined as alkali–carbonate-reactive by various methods is used as an aggregate. Inhibition experiments were carried out on the basis of the concrete microbar method (RILEM AAR-5 standard), in which 10%, 30%, and 50% fly ash and metakaolin were used to replace cement. Thermogravimetric–differential scanning calorimetry (TG-DSC), X-ray diffractometry (XRD), mercury intrusion porosimetry (MIP), and scanning electron microscopy–energy dispersive X-ray spectrometry (SEM-EDS) were used to analyze the inhibition mechanism of fly ash and metakaolin on ACR. The results show that the expansion of samples at the age of 28 days are less than 0.10% when the fly ash contents exceed 30% and the metakaolin contents exceed 10%, which proves that the ACR is inhibited effectively. Meanwhile, the Ca(OH)2 content of the samples was reduced and the pore structure of the samples was optimized after adding fly ash and metakaolin. The dolomite crystals in the samples containing 50% fly ash and metakaolin are relatively complete.