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1

Petrophysical and geomechanical analysis to delineating reservoirs in the miocene Niger delta region of Nigeria

Ojo Odunayo Tope, Adeoye James Adejimi, Okoli Emeka Austin, Emegha Joseph Onyeka

Geoinformatica Polonica

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2023

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T. 22

105--121

EN

The application of various petrophysical and elastic metrics has advanced reservoir characterization and provided critical geological formation information. Porosity declines with depth, according to sonic, neutron, and density logs. Lithology, pressure, and hydrocarbons all contribute to this. Formation resistivity and fluid saturation are used to identify hydrocarbon-bearing zones. Because oil and gas are non-conductive, hydrocarbon-containing rocks are more resistant than water. In lithological categorization, gamma logs and the Vp/Vs ratio have helped classify reservoirs as Agbada Formation sand-shale reservoirs. Reservoir elastic characteristics, specifically sandstones, have been studied at various depths. These discoveries have an impact on their brittleness, strength, and failure risk in a variety of scenarios. Hydrocarbon accumulation has been influenced by diagenetic compaction equilibrium in pressure-exposed shale source beds. The research advances our understanding of the geological formations of the Niger Delta and gives practical insights for exploration and production. Decisions on oil and gas are based on hydrocarbon reservoir assessments at various depths, including porosity, fluid saturation, and lithology. Well logs from Wells B001, B002, and B003 revealed the diverse properties of several Niger Delta reservoirs. These discoveries have benefited hydrocarbon exploration and production decision-making significantly.

PL

Charakterystykę zbiorników wodnych poszerzono dzięki różnym pomiarom petrofizycznym i pomiarom elastyczności, dostarczając wartościowych informacji o formacjach geologicznych. Określenia porowatości przy użyciu zapisów dźwięku, badania neutronów oraz gęstości wykazały wyraźną tendencję do zmniejszania się porowatości wraz z głębokością. Przyczynia się do tego litologia, ciśnienie i obecność węglowodorów. Strefy węglowodoronośne są identyfikowane przez korelację pomiędzy tworzeniem się oporności a nasyceniem skał węglowodorami. Wyższa oporność skał nasyconych węglowodorami wynika ze złego przewodnictwa ropy naftowej i gazu, w porównaniu z wodą. Klasyfikacja litologiczna na podstawie zapisu gamma i ilorazu Vp/Vs doprowadziła do głębszego zrozumienia składu złóż, klasyfikując je jako złoża piaskowo-łupkowe formacji Agbada. Elastyczne właściwości złóż, szczególnie piaskowców, wykazały ważne korelacje związane z głębokością, która ma wpływ na kruchość złóż, ich odporność oraz podatność na zniszczenie w różnych warunkach. Obserwowana w złożach łupkowych pod ciśnieniem równowaga ścisłości diagenetycznej odegrała znaczącą rolę w akumulacji węglowodorów. Wyniki badań nie tylko przyczyniają się do zrozumienia formacji geologicznych w rejonie delty rzeki Niger, ale również dostarczają podstaw do przedsięwzięć związanych z poszukiwaniem i eksploatacją złóż. Charakterystyka złóż węglowodorowych na różnych głębokościach i ich cechy, takie jak porowatość, nasycenie płynem i litologia, przyczynią się do podejmowania decyzji w przemyśle naftowo-gazowym. Analiza danych z odwiertów B001, B002 oraz B003 pozwoliła na znalezienie cech charakterystycznych dla wielu złóż w rejonie delty Nigru, dostarczając wartościowych informacji dla podejmowania decyzji dotyczących poszukiwań i wydobycia węglowodorów.

2

Właściwości sprężyste ciekłych kryształów

Raszewski Zbigniew, Kłosowicz Stanisław, Zieliński Jerzy, Mazur Rafał

Biuletyn Wojskowej Akademii Technicznej

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2023

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Vol. 72, nr 3

15--42

PL

W artykule omówiono właściwości sprężyste ciekłych kryształów, koncentrując się na fazie nematycznej. Przedstawiono zarys rozwoju teorii opisujących te właściwości. sformułowano model ciekłego kryształu jako ośrodka ciągłego. szczegółowo omówiono krzywiznową teorię sprężystości nematycznych ciekłych kryształów opartą na podejściu Zochera - Oseena - Franka. w tym ujęciu opisano podstawowe deformacje sprężyste nematyków oraz charakteryzujące je parametry materiałowe.

EN

The paper presents elastic properties of liquid crystals, especially their nematic phase. An outline of a development of theories describing these properties is given. The model describing liquid crystal as continuous medium is formulated. The curvature theory of elasticity of nematic liquid crystals based on Zocher - Oseen - Frank’s approach is discussed in details. in this way, essential elastic properties of nematics as well their relative material parameters are described.

3

Estimating the 3-D spatial distribution of mechanical properties of rock by seismic data and well logs

Darjani Mohsen, Bakhtiyari Ehsan, Sen Souvik, Abioui Mohamed

Acta Geophysica

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2023

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Vol. 71, no. 5

2089--2106

EN

The rock mechanical properties influence the selection of drilling parameters, optimized drilling trajectory, and appropriate hydraulic fracturing intervals. Estimating the 3-D spatial distribution of these geomechanical properties at the reservoir scale is a challenging task, especially in the case of limited data only at the well locations. Advanced geostatistical techniques can be utilized to represent a reservoir’s inherent spatial variation more realistically. In this study, we investigate the spatial variability of rock mechanical properties, including Young’s modulus, shear modulus, bulk modulus, and Poisson’s ratio, as major constituents of the reservoir geomechanical model. The data are extracted from a hydrocarbon field located southwest of Iran and consist of forty wells. We first build a 1-D model of rock elastic moduli at each well by integrating petrophysical and core-based laboratory measurements and then develop a corresponding 3-D model using geostatistical simulation techniques. Thereafter, 3-D seismic data are employed to optimize the geomechanical model. Results show that the integration of well logs with seismic data increases the accuracy of field-wise 3-D elastic moduli models. Furthermore, we used various co-simulation techniques to demonstrate the improving effect of complementary data in constructing a more realistic reservoir geomechanical model.

4

Wielowariantowa predykcja prędkości fali S w ocenie parametrów sprężystych formacji łupkowych

Kaczmarczyk Weronika, Słota-Valim Małgorzata

Nafta-Gaz

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2020

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R. 76, nr 7

441--448

PL

Rozpoznanie i udostępnianie złóż niekonwencjonalnych stanowi ogromne wyzwanie. Złoża te ze względu na swoją nietypowość, objawiającą się ograniczonymi właściwościami filtracyjnymi, wymagają indywidualnego podejścia i wykorzystania specyficznych rozwiązań. Obejmują one między innymi wyznaczanie stref o wyższym potencjale węglowodorowym, tzw. sweet spotów, dowiercanie się do złoża przy wykorzystaniu technologii wiercenia poziomego czy planowanie, jak też przeprowadzanie zabiegów stymulacji skał na drodze szczelinowania hydraulicznego. Analiza odpowiedniej kombinacji parametrów w tym przypadku może okazać się kluczowa i dostarczać niezwykle istotnych informacji o złożu. Parametry sprężyste, jako jedne z istotniejszych parametrów pozwalających scharakteryzować złoże, np. pod kątem podatności skał na szczelinowanie, wymagają między innymi dostępności informacji o przebiegu fali poprzecznej Vs, która w przeciwieństwie do danych dotyczących prędkości fali podłużnej Vp, jest rzadko mierzona w standardzie krajowym. W związku z tym w niniejszym artykule omówiono wielowariantową predykcję prędkości fali poprzecznej przy wykorzystaniu znanych zźliteratury i zmodyfikowanych modeli teoretycznych, w tym modelu Castagny oraz Greenberga i Castagny. Wykorzystując otrzymane wyniki, obliczono parametry sprężyste, na których podstawie w kolejnym etapie możliwa była interdyscyplinarna charakterystyka formacji złożowej, np. w aspekcie oceny podatności formacji złożowej na szczelinowanie hydrauliczne i powstanie tym samym szczelin technologicznych stanowiących ścieżkę migracji dla płynów złożowych. Bazując na różnych rozwiązaniach, opracowano w skali otworów wiertniczych 5 wariantów prędkości fali poprzecznej, której wyniki następnie posłużyły do obliczenia modułów sprężystych: modułu Younga iźwspółczynnika Poissona. Ponieważ analizowany obszar badań charakteryzował się dostępnością danych o prędkości fali poprzecznej we wszystkich 4 analizowanych otworach, możliwa była weryfikacja wyników estymowanych parametrów. W dalszej kolejności do przestrzennej charakterystyki złoża zastosowano warianty obliczeń modułu Younga, wykorzystując w procesie integracji dane sejsmiczne. Analizę prowadzono w ordowicko-sylurskich formacjach łupkowych zdeponowanych w basenie bałtyckim, w interwałach wzbogaconych w materię organiczną.

EN

: Exploration and development of the hydrocarbons reservoir in unconventional rock formation is a huge challenge. Due to their specific nature, which is manifested by limited filtration properties, they require an appropriate approach and the use of specific solutions. They include, among others, the determination of zones with higher hydrocarbon potential – so called sweet spots, application of horizontal drilling technology, or designing as well as performing rock stimulation treatments of rocks usually with low or almost zero permeability with the use of hydraulic fracturing. The analysis of the right combination of parameters in this case can be essential and provide extremely important information about the reservoir in an unconventional rock formation. As one of the most important parameters allowing, among others, to characterize the reservoir in terms of rock susceptibility to hydraulic fracturing, elastic properties require the availability of shear wave Vs, which in contrast to compressional wave Vp in the Polish standard is measured rarely. Therefore, in this paper, a multivariate prediction of shear wave velocity was developed with the use of theoretical models known from the literature and modified, based on which we estimate the elastic parameters. Using the obtained results, the elastic parameters were calculated on the basis of which, in the next stage, interdisciplinary characterization of reservoir formation is possible, e.g. in the aspect of assessing the reservoir formation susceptibility to hydraulic fracturing and thus creating technological fractures constituting the migration path for reservoir fluids. Based on different solutions, 5 variants of shear wave velocity were developed in the borehole scale, the results of which were then used to calculate the elastic modules: the Young modulus and the Poisson ratio. Because of the availability of the measured shear wave in each analyzed wellbores, it was possible to verify the results of the estimated variants. Subsequently, for the purpose of spatial characterization of the reservoir, calculated variants of the Young modulus were integrated with the seismic data. The analysis was conducted in Ordovician – Silurian shale formations in the Baltic Basin, at intervals enriched with organic matter.

5

X-ray diffraction study of the elastic properties of jagged spherical CdS nanocrystals

Dey Pijush Ch., Sarkar Sumit, Das Ratan

Materials Science Poland

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2020

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Vol. 38, No. 2

271--278

EN

In this work, jagged spherical CdS nanocrystals have been synthesized by chemical method to study their elastic properties. The synthesized CdS nanocrystal has been characterized by transmission electron microscopy (TEM) and X-ray diffraction (XRD). The transmission electron microscope images show that the average size of the nanocrystal is 100 nm approximately. X-ray diffraction (XRD) study confirms that the CdS nanocrystals are in cubic zinc blende structure. The size calculated from the XRD is consistent with the average size obtained from the TEM analysis. The XRD data have been analyzed to study the elastic properties of the jagged spherical CdS nanocrystals, such as intrinsic strain, stress and energy density, using Williamson-Hall plot method. Williamson-Hall method and size-strain plot (SSP) have been used to study the individual effect of crystalline size and lattice strain on the peak broadening of the jagged spherical CdS nanocrystals. Size-strain plot (SSP) and root mean square (RMS) strain further confirm the results obtained from W-H plots.

6

Surface characterization of the raw and cooked bovine cortical metatarsal bone

Petrovic Bojan B., Kojic Sanja, Peric Tamara O., Šipovac Milica, Lazarevic Jovana, Stefanovic Sofija, Stojanovic Goran

Acta of Bioengineering and Biomechanics

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2019

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Vol. 21, no. 1

13--21

EN

The purpose of this study was to quantify the elastic properties and evaluate microscopical features of raw and boiled metatarsal bovine bone. Methods: The elastic modulus, hardness and microscopic surface of raw and cooked bovine metatarsal bone have been investigated using nanoindentation, SEM/EDX and Panasis microscope. Results: Regarding raw bovine bone, the average elastic modulus was 30.515 ± 6,769 GPa, while the average hardness was 0.5683 ± 0.211 GPa. When it comes to boiled bone corresponding values were 22.298 ± 7.0303 GPa and 0.408 ± 0.199 GPa, respectively. The values for investigated parameters were significantly higher ( p < 0.05) in raw bone specimens. Elastic modulus significantly correlated with hardness ( p < 0.05). EDX analysis revealed significant decrease in wt% of oxygen in boiled samples ( p < 0.05) No significant differences could be observed in SEM images particularly when analysing in smaller magnifications. Using higher magnification, additional branching of the existing voids as well as discrete reorganization and smoother edges of nutrient canals could be observed. The surface of boiled specimens was without the presence of crusts and layering, and no microscopical evidence of structural damage could be observed. Conclusions: This study provides detailed analysis of hardness, elastic modulus of raw and cooked bovine bone and their relation and changes during exposure to temperature. These results of elastic moduli and hardness could be comparable to similar studies of bovine and human bone tissue, but the careful analysis of experimental design, type of the bone as well as limitations of the employed techniques must be carried out before interpolation of the results to other theoretical, clinical, biomaterial and archeological studies.

7

Rock physics modelling for determination of effective elastic properties of the lower Paleozoic shale formation, North Poland

Wawrzyniak-Guz Kamila

Acta Geophysica

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2019

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Vol. 67, no. 6

1967--1989

EN

This paper presents an application of rock physics templates constructed with the use of the granular effective medium theory and the shale model to estimate the elastic properties of the Silurian and Ordovician shale formations from the Baltic Basic, Poland. The author uses available logging data from three nearby wells and their petrophysical interpretation to distinguish various lithologies and to determine average matrix mineral composition of each lithology group, essential in further rock physics modelling. Anisotropy estimation and investigation of the relation between various petrophysical parameters precede the rock physics modelling. The logging data cross-plotted in Vp/Vs/ ratio–acoustic impedance domain reveals distinct compaction trend for shales, which is not followed by shales with increased organic matter and calcareous deposits. These two lithology groups present own trends, which are related to increasing kerogen and carbonate minerals contents, respectively. The trends are the subject of rock physics modelling. Granular effective medium rock physics templates are constructed for each lithology group. The rock physics analyses reveal that the elastic properties of strongly compacted shales, including shales with organic matter, might be successfully described by the lower modified Hashin–Shtrikman bound, which is useful in compaction trend modelling. Marly deposits can be modelled in a similar way to shales. The upper modified Hashin– Shtrikman bound provides a better template for carbonates as it models the cementation process. The shale model provides independent rock physics template for shales. Comparison of these two approaches shows that the granular effective medium method better describes the elastic properties of the analysed formations. The paper includes also the proposition of the final rock physics template constructed for the Silurian and the Ordovician formation from the Baltic Basin that can contribute to a better understanding of the elastic properties of the lower Paleozoic shale plays in Poland.

8

Określanie mechanicznych właściwości skał na podstawie właściwości fizycznych przy użyciu sztucznych sieci neuronowych

Słota-Valim M.

Nafta-Gaz

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2018

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R. 74, nr 5

343--355

PL

W niniejszej pracy opracowano szereg związków między poszukiwaną cechą geomechaniczną, w tym parametrami sprężystymi – modułem Younga (E) i współczynnikiem Poissona (ʋ) oraz parametrami wytrzymałościowymi – wytrzymałością na ściskanie jednoosiowe (UCS) oraz stałą Biota (α), a cechami ośrodka, które najczęściej są standardowo mierzone lub szacowane dla większości obiektów złożowych. Cel pracy realizowano na obiekcie o potencjale węglowodorowym, w którym przedmiotem zainteresowania był interwał osadów dolnego paleozoiku, zdeponowanych w północnej części basenu bałtyckiego na obszarze koncesji Wejherowo. Do opracowania związków między poszukiwaną właściwością geomechaniczną ośrodka skalnego a innymi, standardowo mierzonymi lub interpretowanymi cechami fizycznymi skały zastosowano sztuczne sieci neuronowe z użyciem algorytmu wstecznej propagacji błędów (ang. back propagation). Algorytm wstecznej propagacji był wykorzystywany w środowisku oprogramowania Petrel (Schlumberger).

EN

In this work, a number of relationships were found between the geomechanical properties, including elastic moduli – Young’s modulus (E) and Poisson’s ratio (ʋ) and strength properties – uniaxial compression strength (UCS) and Biot’s coefficient (α), and commonly measured and interpreted properties, fitting in a standard exploration of the reservoir rock. For this purpose, the shale formation of lower Paleozoic age deposited in the northern part of the Baltic Basin were investigated. An artificial neural network using back propagation algorithm, was used to develop the relationship between the geomechanical properties and other, more commonly measured or interpreted physical properties of rocks.

9

Elastic properties of a unidirectional composite reinforced with hexagonal array of fibers

Czaplinski T., Drygaś P., Gluzman S., Mityushev V., Nawalaniec W., Zietek G.

Archives of Mechanics

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2018

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Vol. 70, nr 3

207--239

EN

It is difficult to measure the transverse shear modulus of the fibrous composites. Thus, theoretical investigations by means of analytical and numerical techniques are paramount. In particular, they are important for the regime with high-concentration of fibers. We apply general techniques to study the mechanical properties of unidirectional fibers with a circular section embedded into the matrix and organized into the hexagonal array. Our theoretical considerations are designed to include two regimes, of low and high concentrations of inclusions. The former regime is controlled by Hashin–Shtrikman lower bounds, while the latter is controlled by square-root singularity. We derived the analytical formulae for the effective shear, Young and bulk moduli in the form of the rational expressions valid up to O(f7) by the method of functional equations. The obtained formulae contains elastic constants of components in a symbolic form as well as the concentration f. The general scheme based on the asymptotically equivalent transformations is developed to extend the obtained analytical formulae to the critical concentration of touching fibers. A comparison with the numerical FEM is performed for all concentrations of inclusions. Good agreement is achieved for all available concentrations.

10

Geomechanical modeling as a basic step in secondary reservoir stimulation treatment design

Słota-Valim M., Jędrzejowska-Tyczkowska H.

Nafta-Gaz

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2017

|

R. 73, nr 1

3--13

EN

Unconventional reservoirs require a new approach at every level of the operation on the object, starting from exploration of reservoir formation, through well and drilling design and ending with well completion including reservoir development. Due to the specific nature of unconventional reservoir properties, the hydrocarbons bearing formation requires stimulation treatments like hydraulic fracturing, aiming to improve the pores connectivity and enabling the free flow of the gas into the well bore, which in the end brings production rates to economic levels. In the paper a geomechanical model of the synthetic object, allowing the analysis of many processes accompanying real hydrocarbons exploitation was presented. Special attention was paid to the demonstration of changes in the state of stress in the geological formation, due to the exploitation of hydrocarbons and the influence of the initial horizontal stresses relationship (σH/σh), on the effectiveness of stimulation treatments in unconventional formations.

PL

Formacje złożowe o charakterze niekonwencjonalnym do poprawy właściwości transportowych i uzyskania eksploatacji na poziomie uzasadnionym ekonomicznie wymagają stymulacji poprzez szczelinowanie hydrauliczne, którego efektywność uzależniona jest od panujących warunków mechanicznych, m.in. właściwości sprężystych szczelinowanego ośrodka i oddziałującego pola naprężeń. W pracy przedstawiono i omówiono wyniki modelowania geomechanicznego obiektu syntetycznego, pozwalającego na analizę wielu procesów towarzyszących wydobyciu węglowodorów. Specjalną uwagę poświęcono zmianom w rozkładzie naprężeń w górotworze będących skutkiem eksploatacji oraz wpływowi początkowego układu naprężeń poziomych na efektywność zabiegów udostępnienia niekonwencjonalnej formacji złożowej.

11

Elastic properties and structural observations of Distaloy SA powder sintered with boron and carbon

Perek-Nowak M., Karwan-Baczewska J.

Metallurgy and Foundry Engineering

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2017

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Vol. 43, no. 2

107--115

EN

One of the methods aimed at increasing the density in PM parts is the process of activated sintering performed by adding boron as elementary boron powder, for example. Under this researchwork novel, PM materials were obtained based on prealloyed and diffusion bonded powder (type: Distaloy SA) with the following chemical composition: Fe-1.75%Ni-1.5%Cu-0.5%Mo, with the addition of 0.55 wt.% carbon and boron (0.2, 0.4 and 0.6 wt.%). Distaloy SA samples alloyed with carbon and boron were manufactured by mixing the powders in a Turbula mixer, then compacting the mixture in a hydraulic press under a pressure of 600 MPa and sintered in a tube furnace at 1473 K for 60 minutes in a hydrogen atmosphere. The densification process of Distaloy SA parts with boron and carbon depends on the sintering mechanism. In order to evaluate the sintering mechanism of the PM samples, structural investigations using SEM/EDS were performed. During sintering of these materials at 1473 K, a liquid phase is generated as a result of the reaction occurring between the alloy matrix and the complex of carbo-borides, which leads to a considerable degree of consolidation. The elastic properties of the sintered samples (such as Young’s modulus and the damping coefficient) were measured in a tensile test with a Förster elastometer.

PL

Jedną z metod mających na celu zwiększenie gęstości części PM jest proces aktywnego spiekania, zachodzący np. w wyniku dodania boru w formie elementarnego proszku boru. W badaniach omawianych w niniejszym artykule nowoczesne materiały PM zostały uzyskane ze stopowanych i dyfuzyjnie związanych proszków Distaloy SA o składzie Fe-1,75%Ni-1,5%Cu-0,5%Mo z dodatkiem 0,55% wag. węgla i boru (0,2, 0,4 i 0,6% wag.). Próbki Distaloy SA stopowane węglem i borem otrzymano w wyniku mieszania proszków w mieszalniku Turbula, a następnie zagęszczenia na prasie hydraulicznej pod ciśnieniem 600 MPa i spiekania w piecu rurowym w temperaturze 1473 K w atmosferze wodoru przez 60 min. Zagęszczanie części ze stopu Distaloy SA z borem i węglem zależy od mechanizmu spiekania. W celu określenia mechanizmu spiekania próbek PM dokonano obserwacji strukturalnych za pomocą SEM z przystawką EDS. Podczas spiekania omawianych materiałów w temperaturze 1473 K w wyniku reakcji pomiędzy osnową a złożonymi węglano-borkami tworzy się ciekła faza, która prowadzi do znacznej konsolidacji. Własności mechaniczne spiekanych próbek takie jak moduł Younga czy współczynnik tłumienia zostały zmierzone w próbie rozciągania i na elastometrze Förstera.

12

Influence of the variability of the elastics properties on plastic zone and fatigue crack growth

Kebir T., Benguediab M., Imad A.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 4

919--934

EN

Several theoretical models have been proposed to predict the fatigue crack growth range (FCGR) process using solid mechanics, based theoretical tools and basic or fundamental mechanical properties. Moreover crack growth is linked to the existence of a plastic zone at the crack tip when the formation and intensification are accompanied by dissipation of energy. The overall objective of the present research is to develop, verify, and extend the computational efficiency of the model for fatigue crack growth range (FCGR) function by elastic properties, cyclic hardening and celebrated Paris law. The influence of the variability to elastic properties (Young’s modulus E, tensile strength e and cyclic hardening exponent n’) is a necessary analysis in this work. The predictions of the proposed model were compared with experimental data obtained by [1].

13

Buckling of rectangular plates with different central holes

Benguediab S., Kettaf F. Z., Benguediab M.

Mechanics and Mechanical Engineering

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2017

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Vol. 21, nr 4

885--895

EN

The behavior of thin rectangular perforated plates under the action of uniform compressive deformation is studied using finite element analysis. The central holes are either circular holes or square holes. The effects of plate-support conditions, plate aspect ratio, hole geometry, and hole size on the buckling strengths of the perforated plates was studied. The results show that for the same plate weight density, the buckling strengths of the plates with square holes generally surpass those of the plates with circular holes over the range of hole sizes.

14

Geomechanical modelling of Paleozoic Shale Gas Formation: a case study from the Baltic Basin, northern Poland

Słota-Valim M., Sowiżdżał K., Jędrzejowska-Tyczkowska H.

Geology, Geophysics and Environment

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2017

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Vol. 43, no. 3

249--269

EN

The article presents the importance and position of geomechanical modelling workflow in reservoir characterization studies dedicated to unconventional shale reservoirs. We show the results of 3D geomechanical modelling carried out in an onshore area within the Baltic Basin, northern Poland, where the Silurian and Ordovician shale formations are the exploration targets. The fundamental elements of the methodology, processes, and available datasets used in the modelling are discussed. The petrophysical, elastic, and mechanic properties of the rock were applied in the modelling process, along with the principal stresses and pore pressure in the geological formation. Moreover, the main calculation methods and data requirements for the Mechanical Earth Model construction are discussed. A comprehensive 3D geomechanical model was constructed, providing important information to engineers and decision makers which allows them to optimize well placement, the direction of the horizontal section of the borehole and the parameters of hydraulic fracturing treatment. The model can identify zones of higher potential within the area of interest in terms of efficient stimulation treatment design.

15

A Model for Fatigue Crack Growth in the Paris Regime under the Variability of Cyclic Hardening and Elastic Properties

Kebir T., Benguediab M., Imad A.

Fatigue of Aircraft Structures

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2017

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Iss. 9

117--135

EN

Over the last 60 years, several models have been developed governing different zones of fatigue crack growth from the threshold zone to final failure. The best known model is the Paris law and a number of its based on mechanical, metallurgical and loading parameters governing the propagation of cracks. This paper presents an analytical model developed to predict the fatigue crack propagation rate in the Paris regime, for different material properties, yield strength (σy), Young’s modulus (E) and cyclic hardening parameters (K’, n’) and their influence by variability. The cyclic plastic deformation at a crack tip or any other cyclic hardening rule may be used to reach this objective, for to investigate this influence, these properties of the model are calibrated using available experimental data in the literature. This FCGR model was validated on Al-alloys specimens under constant amplitude load and shows good agreement with the experimental results.

16

Mechanical properties variation and constitutive modelling of biomedical polymers after sterilization

Zanelli L., Todros S., Carniel E. L., Pavan P. G., Natali A. N.

Acta of Bioengineering and Biomechanics

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2017

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Vol. 19, no. 3

3--9

EN

Purpose: In this work, the mechanical behavior of two block copolymers for biomedical applications is studied with particular regard to the effects induced by a steam sterilization treatment that biomedical devices usually undergo in healthcare facilities. This investigation is aimed at describing the elasto-plastic behavior of the stress-strain response, determining a functional dependence between material constitutive parameters, to obtain an optimal constitutive model. Methods: The mechanical properties of these polymers are analyzed through uniaxial tensile tests, before and after the sterilization process. The effect of sterilization on the mechanical behavior is evaluated. The Ramberg-Osgood model is used to describe the elasto-plastic behavior of the stress-strain response. Results: Data from uniaxial tensile tests are discussed in the light of previous data on the same polymeric materials, in order to highlight the correlation between physicochemical and mechanical properties variation. The material constitutive parameters are determined and the functional dependence between them is found, thus enabling an optimal constitutive model to be obtained. Conclusions: The effect of sterilization on the material constitutive parameters is studied, to evaluate the suitability of the model in describing the mechanical response of biomedical polymer before and after sterilization treatment. The same approach can be applied to other biomaterials, under various tensile tests, and for several processes that induce variation in mechanical properties.

17

First principle calculation of structural, electronic and elastic properties of rare earth nitride

Bhardwaj P., Singh S.

Materials Science Poland

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2016

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Vol. 34, No. 4

715--720

EN

First principle calculation of the electronic and elastic properties of CeN nitride, which crystallizes in the rock-salt structure, is reported in the present paper. The ground state properties, such as lattice constant (a0), bulk modulus (B) and its pressure derivative (B′) are reported. These results show good agreement with the experimental and other theoretical results. Besides, we have studied the Murnaghan’s equation of state, and used it to fit the theoretical electronic ground state energy and obtain thermodynamic quantities such as the bulk modulus. Furthermore the electronic band structure, total density of states and partial density of states of CeN are also discussed.

18

Anisotropic elastic properties of FexB (x = 1, 2, 3) under pressure. First-principles study

Gueddouh A., Bentria B., Bourourou Y., Maabed S.

Materials Science Poland

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2016

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Vol. 34, No. 3

503--516

EN

Spin-polarization (SP) and pressure effects have been used to better clarify and understand anisotropic elastic properties of Fe-B intermetallic compounds using the first-principles calculation with generalized gradient approximation (GGA) within the plane-wave pseudopotential density functional theory. Elastic properties, including bulk, shear and Young’s moduli as well as Poisson ratio were obtained by Voigt-Reuss-Hill approximation. All studied Fe-B compounds were mechanically stable. The brittle and ductile properties were discussed using bulk to shear moduli ratio (B/G) of the studied structures in the pressure range of 0 GPa to 90 GPa in order to predict the critical pressure of phase transition from ferromagnetic (FM) to nonmagnetic (NM) state. Mechanical anisotropy in both cases was discussed by calculating different anisotropic indexes and factors. We have plotted three-dimensional (3D) surfaces and planar contours of the bulk and Young’s moduli of Fex B (x = 1, 2, 3) compounds for some crystallographic planes, (1 0 0), (0 1 0) and (0 0 1), to reveal their elastic anisotropy. On the basis of anisotropic elastic properties the easy and hard axes of magnetization for the three studied compounds were predicted.

19

Static and dynamic elastic properties, the cause of the difference and conversion methods – case study

Słota-Valim M.

Nafta-Gaz

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2015

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R. 71, nr 11

816--826

EN

In this study the characteristics of elastic parameters of the lower Paleozoic shale formation is presented. Dynamic elastic properties are calculated based on available seismic data calibrated with elastic properties obtained from well logging. Comparison between dynamic and static elastic properties is conducted and the cause of observed difference is discussed. Finally, methods for conversion of dynamic to static elastic properties is presented. Detailed characterization of the shale formation helps highlight which zones are more susceptible to hydraulic fracturing while conversion of dynamic to static elastic properties is performed for further geomechanical modeling purposes and allow more advanced mechanical analysis of unconventional reservoir object.

PL

Dokładne rozpoznanie cech obiektu złożowego to podstawowy warunek, którego spełnienie owocuje trafnym wyznaczeniem lokalizacji wiercenia, projektem otworu wiertniczego i jego uzbrojeniem, a także planem efektywnych zabiegów udostępniania złoża węglowodorów. Z punktu widzenia eksploracji złóż typu niekonwencjonalnego, które od paru lat stały się tematem intensywnych badań również i w Polsce, spośród wymienionych wyżej etapów rozpoznania obiektu szczególnie istotny jest projekt otworu, a zwłaszcza jego poziomy odcinek oraz plan zabiegów udostępniania złoża. Niejednorodność formacji gazonośnej na horyzontalnym odcinku otworu, wzdłuż którego planowane są zabiegi szczelinowania hydraulicznego, nakazuje dokładne rozpoznanie ośrodka skalnego. Jego brak pociąga za sobą konsekwencje, gdyż niewłaściwe rozmieszczenie poszczególnych sektorów poddawanych kolejno zabiegom szczelinowania może przyczynić się do nachodzenia na siebie stref zczerpania gazu, co z kolei skutkuje niską lub zerową produkcją. W artykule przedstawiono charakterystykę parametrów elastycznych formacji łupkowej dolnego Paleozoiku, która pozwoliła na wytypowanie stref bardziej podatnych na zabieg szczelinowania hydraulicznego.

20

Investigations of structural, elastic, electronic and thermodynamic properties of lutetium filled skutterudite LuFe4P12 under pressure effect: FP-LMTO method

Boudia K., Ameri M., Al-Douri Y., Ameri I., Bouafia H.

Materials Science Poland

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2015

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Vol. 33, No. 4

867--878

EN

Structural, elastic, electronic and thermodynamic properties of ternary cubic filled skutterudite compound were calculated. We have computed the elastic modulus and its pressure dependence. From the elastic parameter behavior, it is inferred that this compound is elastically stable and ductile in nature. Through the quasi-harmonic Debye model, in which phononic effects are considered, the effect of pressure P (0 to 50 GPa) and temperature T (0 to 3000 degrees C) on the lattice constant, elastic parameters, bulk modulus B, heat capacity, thermal expansion coefficient alpha, internal energy U, entropy S, Debye temperature theta(D), Helmholtz free energy A, and Gibbs free energy G are investigated.