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Keywords shale gas

Abstract

Shale gas mining is mainly viewed as an industrial and economic issue. But we can also look at it from the scientific perspective. Why should we?
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Abstract

Describing the gas boiler fuel consumption as a time series gives the opportunity to use tools appropriate for the processing of such data to analyze this phenomenon. One of them are ARIMA models. The article proposes this type of model to be used for predicting monthly gas consumption in a boiler room working for heating and hot water preparation. The boiler supplies heat to a group of residential buildings. Based on the collected data, three specific models were selected for which the forecast accuracy was assessed. Calculations and analyses were carried out in the R environment using “forecast” and “ggplot2” packages. A good quality of the obtained forecasts has been demonstrated, confirming the usefulness of the proposed analytical tools. The article summary also indicates for what purposes the forecasts obtained in this way can be used. They can be useful for diagnosing the correct operation of a heat source. Registering fuel consumption at a level significantly deviating from the forecast should be a signal to immediately diagnose the boiler room and the heat supply system and to explain the reason for this difference. In this way, it is possible to detect irregularities in the operation of the heat supply system before they are detected by traditional methods. The gas consumption forecast is also useful for optimizing the financial management of the property manager responsible for the operation of the boiler room. On this basis, operating fees or financial operations with the use of periodic surplus capital may be planned.
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Abstract

The article discusses the validation process of a certain method of balancing gas contained in the pore space of rocks. The validation was based upon juxtaposition of the examination of rocks’ porosity and the effects of comminution in terms of assessing the possibility of opening the pore space. The tests were carried out for six dolomite samples taken from different areas of the ‘Polkowice-Sieroszowice’ copper mine in Poland. Prior to the grinding process, the rocks’ porosity fell in the range of 0.3-14.8%, while the volume of the open pores was included in the 0.01-0.06 cm3/g range. The grinding process was performed using an original device – the GPR analyzer. The SEM analysis revealed pores of various size and shape on the surface of the rock cores, while at the same time demonstrating lack of pores following the grinding process. The grain size distribution curves were compared with the cumulative pore volume curves of the cores before grinding. In order to confirm the argument put forward in this paper – i.e. that comminution of a rock to grains of a size comparable with the size of the rock’s pores results in the release of gas contained in the pore space – the amount of gas released as a result of the comminution process was studied. The results of gas balancing demonstrated that the pore space of the investigated dolomites was filled with gas in amounts from 3.19 cm3/kg to 45.86 cm3/kg. The obtained results of the rock material comminution to grains comparable – in terms of size – to the size of the pores of investigated rocks, along with asserting the presence of gas in the pore space of the studied dolomites, were regarded as a proof that the method of balancing gas in rocks via rock comminution is correct.
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Abstract

The article presents the author’s considerations on the significance of the investment package diversifying natural gas supplies as part of the Northern Gate in ensuring Poland’s energy security. Data found in literature concerning the possibilities of importing the raw material by sea (terminals, gas pipelines) includes investments at various stages of concept development and construction. However, these documents lack cohesive information about a full investment package being implemented. The author has thus attempted at creating variants concerning the diversification capacities of the Republic of Poland in reference to several key offshore and onshore projects. A problem has therefore been formulated: To what extend will the Northern Gate investment package increase Poland’s energy security as a result of increased supply of natural gas from the sea? To answer this questions, researchers were forced to verify their working hypothesis which assumed that Northern Gate investments including a comprehensive package of projects had the potential of significantly improving the level of energy security in Poland by extending the possibility of importing natural gas. To solve the problem and verify the hypothesis, the researchers applied systemic analysis, deduction and variant analysis, which were used to estimate the possible import capacities of the raw material by sea. As a result of the works, the researchers created four variants including various investment projects assuming the import of 7.75 m3 to 30,95 B m3 of natural gas a year by sea. The variant which was adopted as the most probable indicates the possibility of importing 17.75 through 22.75 B m3 of gas a year, which is 111% of the average annual demand in Poland.
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Abstract

The natural gas supply is used from Russia Federation as a political instrument in the geopolitical and territorial conflict with Ukraine. The effectiveness of Russian strategy towards Ukraine is due to the fact that power in Kiev is also exercised by the pro-Russian politicians and supported on the part of Ukrainian oligarchs. The two countries are interdependent in terms of energy by means of the existing gas infrastructure and long-term contracts, because Ukraine guarantees the Russian Federation the transit of natural gas to Europe through its system of transmission gas pipelines, and Russia pays for the transit and used to supply the agreed amount of gas to Ukraine. For the first time – in 2016 – Ukraine didn’t import natural gas directly from the Russia Federation. This article attempts to obtain an answer to the research question, whether Ukraine actually strives to diversify its natural gas supply. What part of this policy is the Ukrainian political instrument in terms of Russia, and what part is the real political objective? Especially in the context of the gas contract between both States, ending in 2019. What role will be played the underground gas storage in the geopolitical struggle? Despite Nord Stream II the Russian Federation still needs the Ukrainian pipelines to fulfill contractual obligations in gas supplies to Europe. What are the strategic goals of the energy policy of Ukraine and Russia? The geopolitical as well as geo-economic theories will be applied. Moreover, a factor analysis as well as a decision-making analysis will be used. The political analysis method and the forecasting technique are applied to obtain, not only theoretical, but also practical input.
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Abstract

Increasing the share of energy production from renewable sources (RES) plays a key role in the sustainable and more competitive development of the energy sector. Among the renewable energy sources, the greatest increase can be observed in the case of solar and wind power generation. It should be noted that RES are an increasingly important elements of the power systems and that their share in energy production will continue to rise. On the other hand the development of variable generation sources (wind and solar energy) poses a serious challenge for power systems as operators of unconventional power plants are unable to provide information about the forecasted production level and the energy generated in a given period is sometimes higher than the demand for energy in all of the power systems. Therefore, with the development of RES, a considerable amount of the generated energy is wasted. The solution is energy storage, which makes it possible to improve the management of power systems. The objective of this article is to present the concept of electricity storage in the form of the chemical energy of hydrogen (Power to Gas) in order to improve the functioning of the power system in Poland. The expected growth in the installed capacity of wind power plants will result in more periods in which excess energy will be produced. In order to avoid wasting large amounts of energy, the introduction of storage systems is necessary. An analysis of the development of wind power plants demonstrates that the Power to Gas concept can be developed in Poland, as indicated by the estimated installed capacity and the potential amount of energy to be generated. In view of the above, the excess electricity will be available for storage in the form of chemical energy of hydrogen, which
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Abstract

The determination of the content of ecotoxic elements directly in flue gas is important for determining its actual emission from coal combustion. Moreover, in the BAT for large combustion plants conclusions adopted in 2017, apart from tightening of pollutants emission standards, i.e. SO 2, NO x and dusts, and setting emission limits, among others, for mercury, the monitoring of the actual emission of toxic elements has been established with the use of specific analytical methods. The review and comparison of available methods of analyzing the content of elements in flue gases in accordance with American and European standards has been presented in the article. Moreover, the factors influencing the quality of the obtained measurement results were identified.
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Abstract

In the over 150 years of hydrocarbon history, the year 2017 will be one of the many similar. However, it will be a breakthrough year for liquefied natural gas. In Asia, China grew to become the leader of import growth, becoming the second world importer, overtaking even South Korea and chasing Japan. The Panama Canal for LNG trade and the “Northern Passage” was opened, so that Russian LNG supplies appeared in Europe. The year 2017 was marked by a dramatic shortening of the length of long-term concluded contracts, their shorter tenure and reduction of volumes – that is, it was another period of market commoditization of this energy resource. The article describes the current state of LNG production and trade till 2018. It focuses on natural gas production in the United States, Qatar, Australia, Russia as countries that can produce and supply LNG to the European Union. The issue of prices and the contracts terms in 2017 was analyzed in detail. The authors stress that the market is currently characterized by an oversupply and will last at least until mid–2020. Novatek, Total – Yamal-LNG project leaders have put the condensing facility at 5.5 million tons into operation. The Christophe de Margerie oil tanker was the first commercial unit to cross the route to Norway and then further to the UK without icebreakers and set a new record on the North Sea Road. In 2017, the Russian company increased its share in the European gas market from 33.1 to 34.7%. In 2017, Russia and Norway exported record volumes of „tubular” – classic natural gas to Europe (and Turkey), 194 and 122 billion m3 respectively, which is 15 and 9 billion m3 more natural gas than in 2016. The thesis was put forward that Russia would not easily give up its sphere of influence and would do everything and use various mechanisms, not only on the market, that it would simply be more expensive and economically unprofitable than natural gas. It was also emphasized that the pressure of the technically possible and economically viable redirection to European terminals of methane carriers landed in the American LNG, results in Gazprom not having a choice but to adjust its prices. The Americans, but also any other supplier (Australia?) can simply do the same and this awareness alone is enough for Russian gas to be present in Europe at a good price.
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Abstract

Recently, the search for new effective energy production solutions has been focused on the production of electricity using renewable and environmentally friendly carriers. This resulted in an increased interest in PV cells and cogeneration systems. The article looks at the main factors affecting their operational parameters against the background of the development history of subsequent generations of PV cells. Average daily solar radiation and wind velocity in Lodz were characterized. The research was done on a static and tracking system with a total peak power of 15 kWp and a 30 kW microturbine. PV panels are installed on the building of the Institute of Electrical Power Engineering of the Lodz University of Technology and they work as part of DERLab. A microturbine is inside the building. Energy measurements were carried out in 2016 giving grounds for the analysis of energy efficiency and financial analysis of the energy supply in buildings. Energy yields in the static and tracking system as well as percentage coverage of electricity from PV cells and microturbines were assessed. The distribution of monthly savings, annual savings of energy costs and the payback time of the investment costs of the systems subject to the test were determined. The research we have done allows us to say that the energy produced by follow-up modules is about 3 times greater than that generated in stationary modules. On the other hand, the annual savings of energy costs using gas micro-turbines are about 10 times higher than those of lagging panels. The analysis shows that it is possible to determine the profitability of the microturbine and photovoltaic panels use despite large financial outlays. The payback period of investment outlays is about 12 years when using the installation throughout the year.
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Abstract

In the last decade, Poland has become one of the most active markets for unconventional hydrocarbon deposits exploration. At present, there are twenty concessions for the exploration and/or discovery of reserves, including shale gas. The area covered by exploration concessions constitutes ca. 7.5% of the country’s area. Four main stages can be distinguished In the shale gas development and exploitation project: the selection and preparation of the place of development of the wells, hydraulic drilling and fracturing, exploitation (production) and marketing, exploitation suppression and land reclamation. In the paper, the concept of cost analysis of an investment project related to the exploration and development of a shale gas field/area was presented. The first two stages related to the preparatory work, carried out on the selected site, as well as drilling and hydraulic fracturing were analyzed. For economic reasons, the only rational way to make shale gas reserves available is to use horizontal drilling, either singly or in groups. The number of drilling pads covering the concession area is a fundamental determinant of the development cost of the deposit. In the paper, the results of the cost analysis of various types of reaming method with an area of 25,000,000 m2 were presented. Cost estimates were prepared for two variants: group drilling for three types of drilling pads: with three, five and seven wells and for single wells. The results show that, as the number of horizontal wells increases, the total cost of the development of the deposit is reduced. For tree-wells pad, these costs are 7% lower than in the second variant, for five-well pads they are 11% lower, and for seven-well pads they are 11.5% smaller than in the second variant. Authors, using applied methodology, indicate the direction of further research that will enable the optimization of shale gas drilling operations.
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Abstract

This work presents the methodology for analyzing the impact of ground vibrations induced during the drilling of gas/oil exploration wells on the surrounding constructions, as well as on humans and the natural environment. In the primary stage, this methodology is based on measurements of ground vibrations induced by a specific type of drilling system in the so-called reference site. In the next stage, ground vibrations are estimated in similar conditions to another design site, these conditions are assumed for a given drilling system, treated as a vibration source. In both sites, special seismic and geotechnical data are collected to construct numerical models for dynamic analyses. Finally, if it is required, a protection system is proposed with respect to the drilling technology and local conditions. The methodology presented has been tested on the terrain of an active natural gas mine used as the design site, and located in the southeastern part of Poland. The reference site was placed in the terrain of a working drilling system in similar conditions in the central part of Poland. Based on the results of numerical simulations, one may verify the different locations of the drilling rig in the design site with respect to the existing industrial structure. Due to the hazard from destructive ground vibrations, a certain vibroisolation system was proposed at the design site. Based on the results of numerical simulations one could rearrange the components of the drilling system in order to provide maximum security for the surrounding structures.
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Abstract

Natural gas plays a significant role in the energy structure of many world economies. Many of them are highly dependent on domestic resources exploitation, other on its deliveries from non-domestic directions. In Poland its importance was relatively low, but in recent years we can observe an increase of interest in this raw material. The aim of the paper is to present the role of natural gas as a primary energy carrier and to determine its impact on the sustainable development and energy security of Poland. The role of gas in the European Union restrictions and development of the domestic economy is also a point. Theoretical deliberations are focused on the most important features of the Polish natural gas market. The article presents the most important national regulations concerning the development of the gas sector in Poland. The amount of natural gas resources are shown as well as indigenous production of the fuel and imports, including the directions from which natural gas is imported. Both political and geographical aspects of the directions of natural gas acquisition are discussed. The level and potential abilities of the diversification of the natural gas supply are discussed. The importance of gas storages in underground gas repositories is underlined. The authors point to the increase in the diversification of raw materials in the structure of electricity, heat production and the transition to pro-ecological fuels.
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Abstract

This article presents the effects of the application of the passive method of flue gas purification from mercury compounds emitted during combustion. The research was carried out on a fluidized bed installation using coal. The dry method of acid gas pollutants reduction was applied during the combustion with the use of 9 modified sodium sorbents. They were fed into a gas jet of 573 K in two molar ratios (sodium contained in the sorbent to the sulphur contained in the fuel). The mercury emission level into the atmosphere was determined based on the mercury content in the solid substrates of the combustion process (in the fuel and the sorbent) and the solid products (fly ash and bottom waste). The combustion process was accompanied by mercury emission 14.7 μgHg/m3. During the removal of acid pollutants from fumes, a decrease in mercury concentration was achieved. The degree of the mercury reduction depended on the type the sorbent used, the manner of modification and the molar ratio in which they were fed into the installation (2 Na/S = 0.5; 2.1). Each time, the more the sorbent was fed into the installation, the bigger the reduction of the mercury emission level. Among the unmodified sorbents, the lowest emission level was achieved for the raw bicarbonate – 3.7 μgHg/m3. For baking soda it was 9.7 μgHg/m3. The application of mechanically modified compounds based on baking soda resulted in the reduction of the Hg emission in fumes up to 2.5–2.6 μgHg/m3. The determined mercury concentration levels in the gases during the purification of the fumes were compared with the accepted Hg emissions contained in the BAT conclusions for large combustion plants. As for all of the existing and newly built plants with a heat capacity below 300 MW, satisfactory effects would be achieved by the use of mechanically modified sorbents in the molar concentration of 2 Na/S = 2.1.
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Abstract

The role and importance of energy security increases with the development of civilization, whose inherent element has become the demand for energy and its carriers. The article discusses the issue of cooperation in the field of energy security in Central Europe at the moment of finishing work on the North-South Corridor, which changes the existing gas architecture in the region. In order to better understand the situation in the region, the energy systems of the Visegrad Group countries, identical to the Central European region, have been analysed, according to the definition of the World Bank and OECD. Considering the historical and geopolitical connections of the Visegrad Group’s fate, it is important to create a common gas market. The physical interconnection of gas systems greatly increases energy security in this region. Moreover, thanks to the construction of LNG terminals in Poland and Croatia, it will be possible to diversify not only the routes, but also the sources of supply of this important raw material.
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Abstract

A ccording to the Polish Geological and Mining Law the granting of a concession for the exploration of a hydrocarbon deposit and the production of hydrocarbons from a deposit, or a concession for the production of hydrocarbons from a deposit in Poland is proceeded according to a tender procedure or open door procedure (upon a request of an entity). O n June 28, 2018 the Polish Minister of the Environment announced 5 tender areas. These areas (promising for discoveries of conventional and unconventional oil and gas deposits) were selected by the geologists of the Polish Geological Institute-NRI and Department of Geology and Geological Concessions of the Ministry of the Environment based on the geological data resources stored in the National Geological Archive. These are: Bestwina-Czechowice, Królówka, Pyrzyce, Złoczew i Żabowo. The main exploration target on the areas located in central and north-western Poland (Pyrzyce, Żabowo and Złoczew) is related to Permian Rotliegend sandstones and carbonates of the Zechstein/Main Dolomite. The Bestwina-Czechowice and Królówka areas (southern Poland) are prospective for conventional and hybrid-type accumulations of gas in the Miocene of the Carpathian Foredeep below the Carpathian Overthrust and in the Paleozoic-Mesozoic basement. The beginning of the 4th bidding round for hydrocarbon concessions is planned in Q4 2019. The entity can also choose the area and apply for a license submitting an application to the Ministry of the Environment. The area indicated by the entity cannot be the subject of a tender or any other concession, and the maximum acreage is 1,200 km2.
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Abstract

The paper presents a study of the performance of some selected UV detectors. Unlike many similar works, the obtained data refer to commercial photodiodes (not only to detector materials). The main task of the research was to determine the influence of the operating temperature and annealing on the detector spectral responsiveness. A comparison of the results obtained for the photodiodes made of GaN and SiC was also performed. Although both kinds of detectors can work at high temperatures for a long time, some modification of their properties was observed. However, for GaN and SiC photodiodes, this modification has a substantially different nature. It is very important for some applications, e.g. fire alarms and a military equipment.
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Abstract

We investigated the germination requirements of Androsace villosa L. (Hairy Androsace), which spreads on limestone or granite screes or ledges of rocky or turfy slopes and hilltops of the alpine zone. With seeds collected from Uludag Mt. (Bursa, Turkey, 2200-2300 m a.s.l.), germination was studied in fresh seeds, seeds subjected to short-time moist chilling (15 d, +4°C), to GA3 (100, 150 and 250 ppm), and to chilling plus GA3. The hormone and moist chilling treatments were carried out in continuous darkness (20°C) and under a 12 h photoperiod at 20/10°C. Seeds maintained in darkness gave higher germination percentages than seeds maintained under a photoperiod. Germination rates rose to 90-97% with 100-250 ppm GA3 and short-time moist chilling in continuous darkness (20°C). Seeds germinated rapidly under a combination of GA3 and short-time moist chilling in continuous darkness, generally giving the lowest mean germination times (4.4-5.0 d) among the treatments.
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Abstract

In this paper, dynamic response improvement of the grid connected hybrid system comprising of the wind power generation system (WPGS) and the photovoltaic (PV) are investigated under some critical circumstances. In order to maximize the output of solar arrays, a maximum power point tracking (MPPT) technique is presented. In this paper, an intelligent control technique using the artificial neural network (ANN) and the genetic algorithm (GA) are proposed to control the MPPT for a PV system under varying irradiation and temperature conditions. The ANN-GA control method is compared with the perturb and observe (P&O), the incremental conductance (IC) and the fuzzy logic methods. In other words, the data is optimized by GA and then, these optimum values are used in ANN. The results are indicated the ANN-GA is better and more reliable method in comparison with the conventional algorithms. The allocation of a pitch angle strategy based on the fuzzy logic controller (FLC) and comparison with conventional PI controller in high rated wind speed areas are carried out. Moreover, the pitch angle based on FLC with the wind speed and active power as the inputs can have faster response that lead to smoother power curves, improving the dynamic performance of the wind turbine and prevent the mechanical fatigues of the generator.
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Abstract

This paper presents an improved approach for locating and identifying faults for UHV overhead Transmission line by using GA-ANFIS. The proposed method uses one end data to identify the fault location. The ANFIS can be viewed either as a Fuzzy system, neural network or fuzzy neural network FNN. The integration with neural technology enhances fuzzy logic system on learning capabilities are proposed to analyze the UHV system under different fault conditions. The performance variation of two controllers in finding fault location is analyzed. This paper analyses various faults under different conditions in an UHV using Matlab/simulink. The proposed method is evaluated under different fault conditions such as fault inception angle, fault resistance and fault distance. Simulation results confirm that the proposed method can be used as an efficient for accurate fault location on the transmission line.
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Abstract

The paper presents the experimental study of a novel unsteady-statemembrane gas separation approach for recovery of a slow-permeant component in the membrane module with periodical retentate withdrawals. The case study consisted in the separation of binary test mixtures based on the fast-permeant main component (N2O, C2H2) and the slow-permeant impurity (1%vol. of N2) using a radial countercurrent membrane module. The novel semi-batch withdrawal technique was shown to intensify the separation process and provide up to 40% increase in separation efficiency compared to a steady-state operation of the same productivity.
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Abstract

The article compares the management of energy resources in Poland and Ukraine over the period 2000–2017. The analysis took changes in the volume of coal, oil and natural gas resources into consideration. The indicators of supplies of these fuels for Poland and Ukraine have additionally been compared with selected EU countries. In order to assess energy security of Poland and Ukraine, the changes in the primary energy consumption have been analyzed in general in first order, then the possibilities of meeting the demand for natural gas, coal and oil have been determined based on the domestic extraction of individual energy resources. Such a comparison indicates the dominant role of coal in Poland while the extraction of oil and natural gas meets the domestic demand to a greater extent in Ukraine. Over the period 2000-2017, trends in primary energy consumption were different; a 17% increase was noted in Poland, while a nearly 40% decline was noted in Ukraine. The main factors responsible for radical changes in fuel and energy management in Ukraine have been identified: military operations in the east of the country and the annexation of Crimea, demographic changes. These events had a negative impact especially on the volume of hard coal mining in Ukraine; the significant increase in imports from 5.36 to 19.14 million tons in 2011-2017 was necessary for balancing. The balance of foreign exchange for electricity was also compared. Over the past years, this comparison has been favorable for Ukraine, where the dominance of electricity exports over imports is noticeable, which generated revenues of over USD 200 million in 2017.
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Abstract

The events that took place on April 10,2010 on the Gulf of Mexico began an international debate on minimizing and materializing the risk of dangerous occurrences and accidents during the exploitation of offshore energy resources. In the aftermath of this event to ensure safe operation in European maritime areas, the European Union decided to introduce regulations throughout the entire EU. On June 12, 2013, Directive 2013/30/EU of the European Parliament and of the Council on safety of offshore oil and gas operations and amending Directive 2004/35/EC was issued. The main aim of the Directive is to reduce the occurrence of major accidents relating to offshore oil and gas operations and limits their consequences. The article is a review of provision of Directive 2013/30/UE with particular regard to requirements at the national level. What is more, the paper indicates solutions which must be introduced by July 19, 2018 in offshore companies. The incorporated solutions must include the protection of the marine environment against pollutions (especially oil spills), establish minimum conditions for safe offshore exploration and the production of oil and gas and improve the response mechanism in the eventof an accident. The paper also presents accidents which take place in oil and gas fields which are a background of necessary improvements of safety during offshore operations.
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Abstract

The Silurian Pelplin Formation is a part of a thick, mud-prone distal fill of the Caledonian foredeep, which stretches along the western margin of the East European Craton. The Pelplin Formation consists of organic carbon- rich mudstones that have recently been the target of intensive investigations, as they represent a potential source of shale gas. The Pelplin mudstones host numerous calcite concretions containing authigenic pyrite and barite. Mineralogical and petrographic examination (XRD, optical microscopy, cathodoluminoscopy, SEM-EDS) and stable isotope analyses (δ13Corg, δ13C and δ18O of carbonates, δ34S and δ18O of barite) were carried out in order to understand the diagenetic conditions that led to precipitation of this carbonate-sulfide-sulfate paragenesis and to see if the concretions can enhance the understanding of sedimentary settings in the Baltic and Lublin basins during the Silurian. Barite formed during early diagenesis before and during the concretionary growth due to a deceleration of sedimentation during increased primary productivity. The main stages of concretionary growth took place in yet uncompacted sediments shortly after their deposition in the sulfate reduction zone. This precompactional cementation led to preferential preservation of original sedimentary structures, faunal assemblages and early- diagenetic barite, which have been mostly lost in the surrounding mudstones during burial. These components allowed for the reconstruction of important paleoenvironmental conditions in the Baltic and Lublin basins, such as depth, proximity to the detrital orogenic source and marine primary productivity. Investigation of the concretions also enabled estimation of the magnitude of mechanical compaction of the mudstones and calculation of original sedimentation rates. Moreover, it showed that biogenic methane was produced at an early-diagenetic stage, whereas thermogenic hydrocarbons migrated through the Pelplin Formation during deep burial.
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Abstract

The paper presents the method and results of low-frequency noise measurements of modern mid-wavelength infrared photodetectors. A type-II InAs/GaSb superlattice based detector with nBn barrier architecture is compared with a high operating temperature (HOT) heterojunction HgCdTe detector. All experiments were made in the range 1 Hz - 10 kHz at various temperatures by using a transimpedance detection system, which is examined in detail. The power spectral density of the nBn’s dark current noise includes Lorentzians with different time constants while the HgCdTe photodiode has more uniform 1/f - shaped spectra. For small bias, the low-frequency noise power spectra of both devices were found to scale linearly with bias voltage squared and were connected with the fluctuations of the leakage resistance. Leakage resistance noise defines the lower noise limit of a photodetector. Other dark current components give raise to the increase of low-frequency noise above this limit. For the same voltage biasing devices, the absolute noise power densities at 1 Hz in nBn are 1 to 2 orders of magnitude lower than in a MCT HgCdTe detector. In spite of this, low-frequency performance of the HgCdTe detector at ~ 230K is still better than that of InAs/GaSb superlattice nBn detector.
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