Sandstone Intercalations Research Articles

THE LITHOSTRATIGRAPHY OF THE NEAR-SURFACE IN PART OF SEDIMENTARY KOLMANI FIELD IN NORTHERN BENUE TROUGH, NIGERIA, USING SOIL CORE AND SEISMIC REFRACTION DATA

Soil samples from 31 shallow boreholes were acquired at depths 0m, 1m, 2m, 3m, 4m, 5m, 7m, 10m, 15m, 20m, 25m, 30m, 35m, 40m, 45m, 50m, 55m, and 60m in Pingida (Kolmani Field) in Ako LGA, Gombe State, Nigeria. Using the same boreholes, seismic refraction data was also acquired. The aim of the survey was to delineate the near-surface lithology and velocity layering. The boreholes were drilled using rotary drilling rig and the core samples acquired and described using Wentworth Scale. Seismic refraction data acquired using a single trace Stratavisor NZXP portable digital recorder. The recording spread consisted of a single SM4- 10Hz geophone positioned at depths where the soil samples were taken. A hammer was used as the energy source and placed 3m away from the hole to obtain the first breaks. The refraction data was interpreted using UDISYS Version 1.0.0.0 software. The soil layers in the Kolmani Field have three distinct layers specified as follows, namely, top weathered and sub-consolidated layers made up of intercalation of sandstone, gravel ash clay and muddy coal shale. The lithologic strata do not correlate throughout the field resulting from the highly variable elevation which ranged from 317m and 524m with average of 389.16m. The top weathered layer of laterite intercalated with cobblestones with compressional wave velocity ranging from 342 ms-1 to 517 ms-1 with an average of 405.03 ms-1. Beneath the weathered layer is the sub-consolidated Clay layer intercalated with silt and laterite of compressional wave velocity ranging from 440 ms-1 to 1854 ms-1 of average of 826 ms-1. The underlying consolidated layer is the shale and coal layer having compressional wave velocity ranging from 1518 ms-1 to 4201 ms-1 with an average of 2162.65 ms-1. The dominant lithologic sequences encountered are laterite, clay, silt, sand, gravel, coal and shale. The results of this work can be used for static corrections in seismic reflection processing, planning and assessing risk for engineering structures, and for groundwater exploration. The laterite, clay, silt, sand, gravel, coal and shale can be utilized in agriculture, construction, process industries, and environmental remediation.

Tectono-sedimentary evolution and petroleum systems of the Mundaú subbasin: A new deep-water exploration frontier in equatorial Brazil

The Brazilian equatorial margin (BEM) evolved in response to transform motion between Brazil and Africa. In 2012, Petrobras drilled the Pecem well in the Mundau subbasin (Ceara Basin) of the BEM to record the first deep-water oil discovery in the region. This work investigates the deep-water evolution of the Mundau subbasin focusing on its structural and sedimentary evolution, and characterizes the petroleum systems in this new exploration frontier. For such purposes, poststack seismic reflection, borehole, and geochemical data were used. Three tectono-stratigraphic sequences representing synrift (Mundau Formation), transitional (Paracuru Formation), and drift strata (Ubarana Formation) were divided into seven seismic units. Different tectonic domains were interpreted: proximal, distal, and Romanche Fracture Zone. Typical structures of transform margins, such as marginal ridges and marginal plateaus, were not identified in the Mundau subbasin. Instead, the subbasin was predominantly deformed by transtensional movements. The Mundau and Paracuru Formations are mature within the oil window, whereas the Ubarana Formation is immature. Main reservoir intervals consist of approximately 1-m (∼3.28-ft)-thick intercalations of sandstone between shales, siltstones, and marls. The seal rocks comprise shales in the Ubarana Formation, whereas the hydrocarbon trap is related to an unconformity and a normal fault. This work concludes that the Paracuru Formation is the main source and reservoir in the deep-water Mundau subbasin, effectively comprising a Paracuru–Paracuru petroleum system. The results have significant implications for petroleum exploration in the BEM by proposing a developed transitional petroleum system in the distal parts of northeastern Brazil.

Sedimentology, Structure and Depositional Environments of the Subsurface Cretaceous, North Sinai, Egypt Using Well Logs

A complete set of well logs was used to study the sedimentology, structural and depositional environments of the subsurface Cretaceous rocks of northern Sinai, as a promising hydrocarbon province in Egypt. The sedimentological interpretations of well logs show sedimentary sequence of the Early Cretaceous, represented by the Neocomian, Aptian and Albian, which is composed mainly of shales and marls with minor carbonate and sandstone intercalations. Based on the Th/K ratios, the argillaceous sediments are composed of illite, montmorillonite and micas with little amounts of glauconite and chlorite. The environmental interpretations revealed sedimentological environments vary from estuarine to lagoonal and backreef of the Barremian-Aptian rocks, and from continental to estuarine in the Aptian-Albian. By contrast, the Late Cretaceous rocks, represented by the Cenomanian, Turonian, Santonian and Maastrichtian, are mainly composed of carbonates with few shale and marl intercalations. This sequence was accumulated under lagoonal to neritic and bathyal environments. The structural interpretations of well logs show that the Cretaceous section attains a wide range of dip magnitudes and dispersed azimuths all over the study area, which is probably attributed to tectonic and sedimentological processes. The inherited structural complexities indicate possible rejuvenations along old fault planes and rotation of the faulted blocks.

Geoelectrical analysis for evaluating the groundwater characteristics of wadi El Madamud Area, Southeast Luxor, Egypt

In this work, the totally 31 Vertical Electric Soundings (VESes) were carried out at wadi El Madamud, Southeastern Luxor city. These are processed and interpreted the forms of geologic models composed of five geoelectric layers of varying resistivities, lithologies, depths and thicknesses. They are surfacial unconsolidated dry silts, sands and gravels, consolidated silts, sandy gravels, sandstone and clay saturated with water, clay with unsaturated sand intercalations and chalky limestone with chert bands. The surficial layer, dry silts, sands and gravels layer (Quaternary) is cropped out on the surface of the whole area with a very small thickness range (0.5-2.2 meter (m.)) and average thickness 1.1 meters. The surficial layer, Unconsolidated wadi deposits composed of silts, sands and gravels which show the highest resistivity range (3073-90,581 Ω.m.) with average value 27,968 Ω.m. throughout the whole study area. The consolidated silt, sandy and gravels is the second geoelectric layer, which has decreasing resistivity values than the first layer. Thickness of the second geoelectric layer ranges from 1–14 meter. The third geoelectric layer is sandstone and clay saturated with groundwater, which has resistivity range from 4 to1887 Ω.m. and average value 234 Ω.m. and thickness range from 18 to 41 meters with average 21.3 meters. The main target is the shallow aquifer which represented in third geoelectric layer. The clay with unsaturated sandstone intercalation is forth geoelectric layer and has resistivity range from 11 to 10,700 Ω.m. and thickness ranges from 44 to 83 m. The last geoelectric layer is the chalky limestone with chert band, having a wide resistivity range (264–37,045 Ω.m.) with non-defined thickness. The thickness and true resistivity maps of the different layers and 2D geoelectric cross sections are generated for the represented layers to delineate their spatial distribution. The aquifer hydraulic characteristics; such as hydraulic conductivity and transmissivity within the salty aquifer, as well as the groundwater quality (salinity) are estimated, utilizing the true resistivity values acquired on the surface through the geoelectric resistivity survey.

Case Study of College Veng Road Section Landslide, Aizawl, Mizoram, India

Landslide is a very common feature along highways, roads and inhabited areas, in and around Mizoram. It is one of the most problematic hazards in the region. The present case of landslide, is in the ‘College Veng’ road section. It lies in the south eastern parts of the Aizawl town. This section is situated along the Sikulpuikawn-Bethlehem Veng road. The Coordinates of the “College Veng” slide are between 23°43՛28.56՛՛/92°43՛28.28՛՛ to 23°43՛28.56՛՛/92°43՛28.34՛՛. The slide took place on 17th September, 2017, at mid night. The section had a relatively high amount of dip (48°-50°), and has a lithology comprising of Shale and Sandstone intercalation. The total length of the slide section along the road was 75 feet, with a height of 25 feet. After the critical observation of the incidence, the major aggravating factors were found to be that the heavy rainfall induced the top most shale bed to move down the dip slope. Improper sewage and subsequent mud erosion at the bottom of the shale layer, further accelerated the down slope movement of the slided block.

The architecture of the Buem Structural Unit: Implications for the tectonic evolution of the Pan-African Dahomeyide Orogen, West Africa

The Buem Structural Unit (BSU) occurs about 50 km west of the high-pressure (HP) rocks of the Pharusian suture zone (PSZ) of the Dahomeyide Orogen, West Africa. Shale and sandstone intercalations form the base of the BSU, followed by serpentinised peridotite, gabbro, massive and pillow basalts (fragment of oceanic crust), jasper/chert, and limestone/dolostone, with sandstone and diamictite forming the top of the BSU. The package was deformed at lower greenschist-facies conditions during the Pan-African orogeny. The N-S-trending BSU has been affected by three deformational events. The main deformation event D2, which transposed bedding-parallel D1 fabrics, produced a steeply ENE-dipping S2 tectonic foliation. S2 is axial planar to upright or west-verging isoclinal and chevron F2 folds. Top-to-the-west D2 shear zones in the sandstone, shale and serpentinised peridotite are associated with a down-dip ENE-plunging L2 stretching lineation. The mafic-ultramafic rocks occur as D2 tectonic slices, marking the boundaries between thrust sheets within the BSU. The D2-related N-S trending structural and short-wavelength (<1 km) magnetic grain of the BSU is superimposed on ENE-trending long-wavelength (>1 km) magnetic anomalies that are continuous along trend with the regional structures of the West African Craton (WAC) and are interpreted as signals from the basement rocks of the BSU. D2 deformation is interpreted to result from overthrusting of the BSU onto the southeastern margin of the WAC during collision of the WAC and Benino-Nigerian Shield (BNS). Meter-scale, steep and open F3 kink and crenulation folds with steeply SE-dipping axial planes are sporadically observed throughout the entire BSU. D3 deformation is inferred to reflect a period of NW-SE-shortening. Deformation history of the BSU shares structural similarities with the one of the PSZ. We, therefore, interpret the BSU as an allochthonous fold and thrust belt with a geodynamic evolution involving subduction of the WAC beneath the BNS and the ensuing collision between the two terranes. The tectonic framework of the BSU suggests a geodynamic evolution of the Dahomeyide Orogen evolving from initial accretion of oceanic crust and deposition of passive margin sedimentary sequences, and their inversion due to continent-continent collision during the Pan-African orogeny.

Hydrogeological Features of Geothermal Waters in Havran (Balıkesir), Turkey

In this study, geothermal waters of Havran were studied in detail. In the area, Karakaya formation in Early Triassic age is the basement consisting volcanic and sedimentary rocks such as of basalts, mudstones, and radiolarites in which there are intercalations of limestone, sandstones and conglomerates. Granodiorite intrusions in Oligocene to Miocene age occur in association with intense volcanic events in the area. From Upper Oligocene to Early Miocene, andesitic and dacitic pyroclastics occur due to intensively volcanism in the area. Later, lacustrine sediments consisting of conglomerates, sandstones, claystones, marls and limestones form from Middle to Upper Miocene. Geothermal waters in the area of Havran are of Na-Ca-(SO4)-HCO3, Na-(SO4)-HCO3 and Na-SO4 type. The geothermal waters display immature waters and were represented within this study as a hydrogeological model.

PERMEABILITY-POROSITY TRENDS IN CAWC RESERVOIR SANDS IN THE NIGER DELTA NIGERIA, USING WELL-LOG DATA

Reservoir characteristics analysis in the onshore Cawthorne Channel (CAWC) oil field, Niger Delta is here presented. The aim of the research was to assess reservoir properties and their relationships. A suite of geophysical logs comprising gamma ray, resistivity, neutron and density logs from eight wells were used in the analysis. Three reservoirs sands were delineated and linked across all eight wells. The litho-stratigraphy correlation section revealed that each of the sand units spreads over the field are differs in thickness with some units occurring at greater depth than their adjacent unit, that is possibly an evidence of faulting. The results show volume of shale values range from 11% to 17% indicating that the fraction of shale in the reservoirs is quite low. The total porosity of the reservoirs ranges from 0.22 to 0.39 indicating a very good reservoir quality and reflecting probably well sorted coarse-grained sandstone reservoirs. The permeability of the reservoirs ranges from 288 mD to 1250mD and this suggests good reservoir horizons. The hydrocarbon saturation of the reservoirs ranges from 0.59 to 0.71 indicating that the proportion of void spaces occupied by water is low consequently high hydrocarbon production. Sand-shale lithology was calculated, with sandstone volume decreasing with increasing depth, while shale volume increases with depth. Porosity and permeability showed decreasing trend with depth for both sandstone and shale units in all wells with few exceptions. This could be as a result of low compaction by overburden pressure from overlying rocks. Plot of lithology versus depth reveals that shale lithology increases with depth, while sandstone decreases. Lithology versus porosity plots show an inverse relationship between permeability and shale volume and direct relationship between permeability and volume of sand. Lithology versus permeability shows that permeability and shale volume have an inverse relationship whereas permeability and volume of sand have a direct relationship. Permeability decreases exponentially with decrease in porosity in rock matrix made up of intercalation of sandstone and shale. The modelled equation of permeability and porosity is given by K = 0.053e32.934Ф. This implies that in the absence of core and well-log data, permeability can be estimated using only porosity data. The results of this work can be used as an exploration tool for the identification of prospective areas and also for feasibility studies during an appraisal activity.

Hydrogeological Modelling of Geothermal Waters in Cesme and Environs, Western Anatolia, Turkey

The geothermal fields of Çeşme are located in the western part of province capital of Izmir and can be considered as important tourist resorts with a great number of thermal hot springs which are used for thermal bathing since several years. Nowadays, the geothermal waters in the fields are used for district heating and greenhouses. In the area of Çeşme, there are sedimentary and volcanic rocks predominantly. The basement rocks are of Devonian age and consists of intercalations of sandstones, greywackes and limestones overline by Upper to Middle Triassic carbonate rocks with intercalations of sandstones and claystones. These rocks are overlain by Neogene volcanic and terrestrial sedimentary rocks. In 1995, we have measured in-situ parameters in many locations of groundwaters and geothermal waters with collection of a great number of samples for these waters. The geothermal waters are of Na-Cl, Na-(Cl)-HCO3, Na-Ca-Cl, Na-Mg-(Cl)-HCO3, Na-Mg-Ca-(Cl)-HCO3 and Ca-Na-Mg-(Cl)-HCO3 type waters during the groundwaters display Na-Cl, Na-HCO3, Na-Mg-(Cl)-HCO3, Na-Mg-HCO3, Na-Mg-Ca-(Cl)-HCO3, Mg-Ca-Na-(Cl)-HCO3 and Mg-Ca-Na-(Cl)-HCO3 type waters. The Na-Cl type waters are originated from deep reservoir during the others can be considered as diluted Cl-HCO3 water type. The plot of δ18O versus δD shows that the geothermal waters are enriched in δ18O and δD and located on the mixing trend between groundwaters and seawaters indicating mixing of these both different waters. The proportion of seawaters in geothermal waters seems to be very higher than groundwaters. The shift in the δ18O values are related to δ18O exchange between the deeply circulating meteoric waters and reservoir rocks in the area. The increase of δD is related to the contribution of seawaters. The geothermal waters in the area fall into fields of immature to partially equilibrated waters. In general, the reservoir temperature of the area of Çeşme is estimated to be 80 to 120 °C.

Estratigrafia da transição entre os grupos Bambuí e Paranoá no Distrito Federal

O norte do Distrito Federal (DF) inclui uma expressiva sucessão de rochas carbonáticas de posicionamento estratigráfico divergente, tendo sido incluídos tanto no Grupo Bambuí como no Grupo Paranoá. Neste trabalho, os carbonatos do Grupo Paranoá foram individualizados e separados daqueles da Formação Sete Lagoas do Grupo Bambuí. O primeiro é composto de uma unidade siliciclástica formada predominantemente por intercalações rítmicas de siltitos e arenitos sobreposta por rochas pelito-carbonáticas, com lentes de calcários dolomíticos, onde é possível observar o estromatólito Conophyton metulum Kirichenko. A Formação Sete Lagoas do Grupo Bambuí recobre de forma discordante as rochas do Grupo Paranoá e foi subdividida em duas sucessões estratigráficas distintas. A Sucessão 1 da Formação Sete Lagoas inclui três unidades litoestratigráficas distintas: (i) a unidade basal começa por um dolarenito cinza, sobreposto por uma sucessão rítmica de calcilutitos/calcarenitos arroxeados com argilas não carbonáticas, (ii) na unidade intermediária, predominam calcarenitos puros sucedidos pela (iii) unidade de dolomitos. Uma superfície erosiva marcada por níveis de brecha limita a Sucessão 2, que começa com 1–2 metros de siltitos seguidos por calcarenitos com camadas de argilosas crescentes em direção ao topo. O norte do DF está na zona externa da Faixa Brasília, onde foram identificadas duas fases de deformações, perpendiculares entre si, orientadas com direções grosseiramente NS e EW.

Facies characterisation of a shallow-water deltaic succession: the Upper Jurassic Wagad Sandstone Formation of Kachchh, western India

AbstractAncient deltaic facies are difficult to differentiate from tidally influenced shallow-marine facies. The Wagad Sandstone Formation of the Wagad Highland (eastern Kachchh Basin) is typified by offshore and deltaic facies with sedimentary characteristics that represent different conditions of hydrodynamics and related depositional processes. The study area, the Adhoi Anticline, constitutes a ~154-m-thick, shale-dominated sequence with progressive upward intercalations of bioturbated micritic sandstone and quartz arenite. Two thickAstartebeds (sandy allochemic limestone), with an erosional base and gravel blanketing, illustrate tidal amplification and high-energy stochastic events such as storms. Sedimentological characteristics document three depositional facies: an offshore, shale-dominated sequence prograding to proximal prodeltaic micritic sandstone and quartz arenite with sandy allochemic limestones, further prograding to mouth bars and abandoned channel deposits. The Wagad Sandstone Formation displays depositional environmental conditions that are dissimilar from those of coeval deposits in Kachchh sub-basins as well as on regional and global scales. This is attributed to a reactivation of the Kachchh Mainland and South Wagad faults which resulted in detachment and uplift of the Wagad block which then experienced prograding deltaic conditions.

Depositional environmental evolution of Kalibiuk formation based on paleontological molluscan Study, Cisaat River section, Bumiayu, Central Java, Indonesia

This paper presents new finding from the sedimentary sequences, overlooked by previous researchers, which provide insights to the sea level changes during the deposition of the Middle to Late Pliocene Kalibiuk Formation. Data were acquired from fieldwork via detailed measured section of each sedimentary sequence from the bottom to the upper part of the formation followed by molluscan fossil association analyses. Lithologically, the Cisaat River stratigraphic section is dominated by greenish grey claystone with some light grey fine-grained sandstone intercalation. Based on about 50 m stratigraphic section, 10 molluscan fossils associations were successfully determined. The sequence from bottom to top are: Corbula – Natica association, Nassa sp. association, Olividae – Turricula association, Pecten – Telina association, Telina – Placuna association, Corbula – Marginella association, Placuna – Natica association, Turritella association, Turritella – Marginella association and Dentalina – Architectonica association. Changes in vertical succession of the molluscan association indicates a development from shallow marine to terrestrial depositional environment before gradually overlain by terrestrial sediments of the Kaliglagah Formation. At least there are 2 deepening - shallowing sea level cycles during the deposition of Kalibiuk Formation observed from this section.

A Late Cretaceous epeiric carbonate platform: the Haftoman Formation of Central Iran

An integrated study of the litho-, bio-, and microfacies of several sections has greatly improved the knowledge on the stratigraphy and depositional setting of the Coniacian to Campanian Haftoman Formation in the Khur area of the northern Yazd Block, Central Iran. Generally, the Haftoman Formation rests on a major tectonic unconformity and commences with a basal conglomerate followed by up to 900 m of shallow-water carbonates with local red sandstone intercalations. Five different depositional environments (from distal to proximal) characterize the facies associations (FA) of the Haftoman Formation: silty, spiculitic wackestone (proximal basin, FA I), bio-/intraclastic wacke-, pack-, and grainstone (marginal shoals, FA II), bioclastic rud-/float-/boundstone (outer platform, FA III), silty mud-/wackestone (lagoonal inner platform, FA IV), and sandstone/sandy limestone (areas close to the mouth of ephemeral streams, FA V). The litho-, micro-, and biofacies of the Haftoman Formation are typical for an epeiric carbonate platform characterized by an arid climate and lagoonal circulation, resulting in nutrient-poor waters, warm temperatures, and high salinities. The Haftoman Platform was attached to an emergent arid hinterland formed by the Anarak Metamorphic Complex to the west and southwest of the study area. Unconformity-bounded depositional units indicate sea-level changes that may correspond to 400-kyr high-frequency sequences but further studies are needed to fully exploit the potential of sequence stratigraphy for regional and inter-regional correlation of the Haftoman Formation.

Hydrogeological Modelling of Some Geothermal Waters of Ivrindi, Havran and Gönen in the Province Capital of Balikesir, Western Anatolia, Turkey

In this study, hydrogeological, hydrogeochemical and isotope geochemical features of Havran, Gönen and Ivrindi within the province capital of Balıkesir, Turkey were investigated in detail. The Early Triassic Karakaya formation in the study area of Havran forms the oldest rocks consisting of spilitic basalts, diabases, gabbros, mudstones, cherts and radiolarites. There are limestone blocks in this formation with intercalations with sandstones and with feldspar contents, quartzite, conglomerates and siltstones. Oligocene to Miocene granodiorite intrusions were generated in association with intensively volcanic events in the area. Between Upper Oligocene and Early Miocene, andesitic and dacitic pyroclastic rocks cropped out due to intensively volcanism. Later, conglomerates, sandstones, claystones, marls and limestones as lacustrine sediments formed from Middle to Upper Miocene in the study area. In the study area of Gönen, the Lower Triassic Karakaya formation consists of basalts, diabases, gabbros, mudstones, cherts and radiolarites and forms the basement rocks overlain by Upper Jurassic to Lower Cretaceous sandy limestones. Upper and Middle Miocene volcanics which can be considered intensive Biga Peninsula volcanos outcrop in the area. These andesitic lava flows are of black, gray and red color with intensive fissures. Neogene lacustrine sediments consist of conglomerates, sandstones, marl, claystone and clayey limestones. Upper Miocene to Pliocene rhyolitic pyroclastics and dacitic lava flows are the volcanic rocks which are overlain by Pliocene conglomerates, sandstones and claystones. In the study area of Ivrindi, the Çaldağ limestones are the oldest formation in Permian age. Çavdartepe metamorphic rocks are of Lower Triassic in which can be observed marbles sporadically. The Kınık formation consisting of conglomerates, sandstones, siltstones and limestones are of Lower Triassic age and display a lateral Stratigraphic progress with volcanic rocks. Upper Miocene to Pliocene Yürekli formation consists of dacites and rhyodacites. Upper Miocene to Pliocene Soma formation is composed of clayey limestone, marl, siltstone, intercalations of sandstone, agglomerate and andesitic gravels and blocks cemented by tuffs. Quaternary alluvium is the youngest formation. The samples of geothermal waters in the area of Havran can be considered as Na-Ca-(SO4)-HCO3, Na-(SO4)-HCO3 and Na-SO4 type waters. In comparison, the geothermal waters in Gönen are of Na-(SO4)-HCO3 and Na-HCO3 type waters. The geothermal waters of Ivrindi are considered as Na-Ca-HCO3 type waters. In the area, a groundwater sample is of Ca-Mg-HCO3 type water.The geothermal waters belong to the cations of Na+K>Ca>Mg in Havran, Gönen and Ivrindi and to the anions of SO4>HCO3>Cl in Havran, HCO3>SO4>Cl in Gönen and SO4>HCO3>Cl in Ivrindi. In the diagram of Na-K-Mg1/2, the geothermal waters in Havran, Gönen and Ivrindi of the province capital of Balıkesir can be classified as immature waters.

Reservoir interpretation of Rotliegend seismic reflections in the central part of the Mid-Polish Trough

The search for gas reservoirs in the deep central parts of the Mid-Polish Trough remains an open question because of fragmentary knowledge of the area caused by the small amount of available borehole data and poor seismic imaging of sub-Zechstein formations on vintage seismic data.2D seismic data acquired in 2011 reveals seismic events related to strongly indurated sandstone intercalation found within fine-grained playa-lake deposits in the axial part of the Mid-Polish Trough. Seismic full-wave modelling has been carried out along recorded seismic 2D line in order to analyse seismic signatures from potential reservoir layers of variable porosity and gas saturation. This has allowed to evaluate the possibility of use of seismic methods to detect potential reservoir sandstones located in the deep parts of the basin below a thick Zechstein-Mesozoic cover, in which the actual spatial distribution of Rotliegend formations is only hypothetical.The analyses were focused on impact of porosity changes and variations in content of minerals with high bulk modulus on the P-wave velocity and seismic response. 2D seismic modelling have revealed that under specific geological conditions, playa formation may contain a sandstone layer – with a porosity of approx. 5% and acoustic impedance values not distinctly different from those observed for the surrounding rocks. As the result sandstone reflections will be undetectable through seismic methods.Promising results have been obtained by comparison of synthetic sections against a seismic profile recorded in the other deep part of the Mid-Polish Trough. The similarity of seismic signatures on synthetic section calculated for layer with porosity of 9% and observed on actual section implies that these events are related to a porous sandstone layer. This interpretation is confirmed by borehole data showing a thin layer of aeolian sandstone with 11% porosity.

Research on the Presence Greyic Phaeozems in Romania

Areas under greyic phaeozems of Romania corresponding geographical areas as compared lithostratigraphic are made of clay and marly clay with frequent intercalations of sands and sandstones in a thick package, belonging Sarmatian, respectively, Volhinian and Basarabian, which directly influences the characteristics of the parent material of the soil.In this way, due to differences in altitude, these soils were formed and evolved deposits vary in granulometric composition, it is represented by loess, loess-like deposit, loam and loess, marly clay.Thus, we believe that the presence greyic phaeozems of our country in eastern, the genesis and evolution of the important role they have parental materials rich in fine sand fraction (31-41%). Specific these soils is the formation of humic acids and precipitate in place, under the influence of calcium ions, contributing to the development and the individualization of the horizon Am.Fulvic acids from the breakdown of litter cvercinee does not precipitate in the upper horizon, but migrate to the base, they favoring the migration is known as the iron and aluminum hydroxides and enriching the waste in the lower part of the quartz diagnostic horizon for greyic phaeozems, and a clay horizon B argic migrated upper horizon.

GEOLOGICAL AND GEOPHYSICAL DATA OF “EPSILON” FIELD IN PRINOS OIL BASIN

The Epsilon field, is located at the centre of Prinos oil basin (N. Aegean, Greece), 11 km NW of the island of Thassos and 4 km NW of the Prinos field, the first productive oil field in the Aegean Sea. The taphrogenetic basin of Prinos has been widely studied, due to its hydrocarbon reservoirs. Extensive geophysical survey, started at early 1970 ‘s, led to a number of drilling jobs, which confirmed the existence of hydrocarbons in the area. The combined geological information, derived from the analysis of lithological, stratigraphic and geochemical data of the basin, suggested a structural and depositional model, strongly related to the Miocene tectonics and sedimentation. The new geophysical and drilling data from Epsilon oil field, are correlated to that already known, completing the model of the basin. Pay zone is found to be below an evaporitic sequence, consisting predominantly of salt, with anhydrite, clay and sandstone intercalations. These upper Miocene aged evaporites extend, varying in thickness, throughout Prinos basin. Reservoir consists mainly of sandstone with intercalations of claystone and trace of siltstone. The geology of the structure and the initial productivity, were positive for further drilling operations in Epsilon field.

Stratigraphy, sedimentology, and geochemistry of the Upper Mississippian Pride Shale in the Appalachian Basin

Tide-dominated or tide-influenced coastal marine deposits form some of the most complicated and largest hydrocarbon fields in the world (Wood, 2004 and references cited therein). Good outcrop analogs can provide significant insight to geologists for recognizing tidal influence in core and interpreting petrophysical log data, thus reducing uncertainty and risk when developing depositional models and planning for field development. Despite the observation that 8 of the 12 largest deltas in the modern world are either tide dominated or strongly tidally influenced (Middleton, 1991), many geologists fail to recognize tidal influence in the rock record, perhaps, in part, because of the influence of preexisting paradigms. This seems to be particularly so for many geologists prospecting for hydrocarbons within Pennsylvanian sediments in the Arkoma and Anadarko Basin of the southcentral United States. Although good ancient analogs of tide-dominated deltas exist (see summary table in Feldman et al., 2014), many of these studies inferred tidal influence from the intercalation of sandstone and mudstone, an abundance of fluidized mud deposits, a dominance of structures formed from currents, and the shoreline-perpendicular orientation of elongate sandstone bodies. Few studies have identified sedimentary structures in delta-front and prodelta settings that can be directly related to semidiurnal, semimonthly, and longer-term tidal deposition. This may reflect background interference from storms or variable fluvial discharge that disrupted tidal deposition and thus obscures evidence of fortnightly or longer tidal signals, or it may reflect …

Experience with the TBM drive through clay rocks with low strength in the Boßler Tunnel

AbstractThe Tunnel Albaufstieg consortium won the contract with an alternative proposal to drive a section about 2.8 km long of the 8.8 km long Boßler Tunnel with a tunnel boring machine (TBM). The next section, where squeezing conditions were forecast, was to be tunnelled by the shotcrete method according to the tender documents. Manifold and extensive additional investigations delivered the basis for the extension of the TBM drive along the entire length of the Boßler Tunnels. The driving of the section through the Aalenian 1 geology was problem free due to the low strengths and good cuttability of the rock mass combined with its impermeability. The next section in the intercalation of claystone and sandstone of the Aalenian 2 was much more differentiated but managable. The breakthrough of the east bore of the Boßler Tunnel confirms to the responsible people for the client and contractor that the decision to follow the aim of consistent mechanised tunnelling had been correct.

Stratigraphic architecture of the Knarr Field, Norwegian North Sea: sedimentology and biostratigraphy of an evolving tide- to wave-dominated shoreline system

Abstract The Knarr Field is located on the Tampen Spur, Norwegian continental shelf and was discovered in 2008 by the Jordbær well (34/3-1S), with additional resources later added to the field by the Jordbær Vest well (34/3-3S) in 2011. Within the Knarr Field, the Cook Formation is informally divided into the Lower Cook and Upper Cook successions and appears to have prograded from east to west. The Lower Cook consists of Sands 1, 2 and 3 and the Upper Cook consists of Sands 4 and 5, with the sands separated by intraformational mudstones that are commonly chronostratigraphically constrained; the J15 maximum flooding surface separates the Lower and Upper Cook. The tide-dominated Lower Cook is notably heterolithic, with intricate intercalations of sandstone and mudrock lithologies representing tidal channel, tidal bar and intertidal bar facies. The Upper Cook represents a series of coarsening-upwards cycles that displays the systematic changes in facies and ichnology expected for a shoreface succession, consisting of offshore, offshore transition zone and shoreface facies. Palynomorphs confirm these observations and suggest that the Lower Cook was deposited in brackish-water conditions, whereas the presence of more marine fossils in the Upper Cook suggests an increase in marine influence. The integration of the sedimentology and biostratigraphy described herein enabled the establishment of a robust reservoir zonation that has been utilized during the development and ongoing exploitation of the Knarr Field.