scholarly journals Petroleum geomechanics modelling in the Eastern Mediterranean basin: analysis and application of fault stress mechanics

2018 ◽  
Vol 73 ◽  
pp. 57 ◽  
Author(s):  
Nikolaos Markou ◽  
Panos Papanastasiou
Keyword(s):  
Stress Analysis ◽  
Pore Pressure ◽  
Shear Failure ◽  
Eastern Mediterranean ◽  
Prediction Method ◽  
Earth Model ◽  
Gas Field ◽  
Wide Range ◽  
The Stability

A fault stress analysis of a typical gas field in the Eastern Mediterranean is presented. The objective of this study is to provide estimates of thein situstresses and pore pressure for populating a regional Mechanical Earth Model and to characterize the stability of faults under current and changing reservoir conditions. The fault stability analysis is based on the Mohr-Coulomb frictional faulting theory. The verticalin situstress is estimated using seismic and density data and the bounds of the horizontal stresses were determined for different fault regimes. The pore pressure for determining the effectivein situstresses is estimated using the Bowers pore pressure prediction method. Fault stress analysis is performed in a series of calculations and the results are plotted on Mohr diagrams for shear failure. The fault stress analysis is performed on a wide range of alternative azimuth orientations forSHmaxin order to capture the uncertainty on the actual orientation. Sensitivity with respect to reservoir pore pressure change suggests that pressure reduction in the reservoir improves the fault stress stability, ignoring in the current analysis any stress arching effects. Pore pressure increase decreases the normal stress on the fault leading to increasing risk of shear failure of the critically stressed faults. The case study examines eight faults on the Aphrodite gas field with the objective to characterize if the faults are active or remain dormant under current stress conditions and how the stability may change in reservoir injection or depletion conditions.

scholarly journals Machine Learning: A Useful Tool in Geomechanical Studies, a Case Study from an Offshore Gas Field

Energies ◽  
2020 ◽  
Vol 13 (14) ◽  
pp. 3528 ◽  
Author(s):  
Seyedalireza Khatibi ◽  
Azadeh Aghajanpour
Keyword(s):  
Machine Learning ◽  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Linear Method ◽  
Earth Model ◽  
Learning Approaches ◽  
Gas Field ◽  
In Situ Stresses

For a safe drilling operation with the of minimum borehole instability challenges, building a mechanical earth model (MEM) has proven to be extremely valuable. However, the natural complexity of reservoirs along with the lack of reliable information leads to a poor prediction of geomechanical parameters. Shear wave velocity has many applications, such as in petrophysical and geophysical as well as geomechanical studies. However, occasionally, wells lack shear wave velocity (especially in old wells), and estimating this parameter using other well logs is the optimum solution. Generally, available empirical relationships are being used, while they can only describe similar formations and their validation needs calibration. In this study, machine learning approaches for shear sonic log prediction were used. The results were then compared with each other and the empirical Greenberg–Castagna method. Results showed that the artificial neural network has the highest accuracy of the predictions over the single and multiple linear regression models. This improvement is more highlighted in hydrocarbon-bearing intervals, which is considered as a limitation of the empirical or any linear method. In the next step, rock elastic properties and in-situ stresses were calculated. Afterwards, in-situ stresses were predicted and coupled with a failure criterion to yield safe mud weight windows for wells in the field. Predicted drilling events matched quite well with the observed drilling reports.

scholarly journals Application of Pickering emulsion in oil drilling and production

2021 ◽  
Vol 11 (1) ◽  
pp. 26-39
Author(s):  
Lipei Fu ◽  
Qianli Ma ◽  
Kaili Liao ◽  
Junnan An ◽  
Jinmei Bai ◽  
...  
Keyword(s):  
Oil And Gas ◽  
Petroleum Industry ◽  
Pickering Emulsion ◽  
Pickering Emulsions ◽  
Gas Field ◽  
Oil Drilling ◽  
Wide Range ◽  
Reservoir Conditions ◽  
Oil And Gas Field ◽  
The Stability

Abstract When surfactant is used as emulsifier, the stability of emulsion is often greatly reduced with the influence of reservoir conditions (temperature, pressure, salinity, etc.), which shortens the validity period of emulsion. Pickering emulsion has a wide range of applications in the oil and gas field due to its advantages of good stability and easy regulation. In this article, the formation, stabilization mechanism, and influencing factors of Pickering emulsions were introduced, and the application status and prospects of Pickering emulsions in oil and gas field were summarized. It was pointed out that Pickering emulsion has many advantages and important research value when applied in deep strata and complicated reservoirs. It is expected that this article can effectively reflect the application value of Pickering emulsion in oil and gas field and promote the application of Pickering emulsion in petroleum industry.

Effect of initial pore pressure on undrained shear behaviour of fine-grained gassy soil

2017 ◽  
Vol 54 (11) ◽  
pp. 1592-1600 ◽  
Author(s):  
Y. Hong ◽  
L.Z. Wang ◽  
Charles W.W. Ng ◽  
B. Yang
Keyword(s):  
Pore Pressure ◽  
Fossil Fuels ◽  
Oil And Gas ◽  
Shear Behaviour ◽  
Excess Pore Pressure ◽  
Triaxial Tests ◽  
Fine Grained ◽  
Wide Range ◽  
The Stability ◽  
Undrained Shear

Many of the world reserves of fossil fuels are located at various water depths in fine-grained sediment under the seabed. The fine-grained sediment contains relatively large biogas bubbles, which has been posing challenges to the stability of offshore foundations supporting oil and gas platforms. Although fine-grained gassy soil was found to exhibit different undrained shear strengths (cu) by altering the initial pore pressure, ui (relevant to water depth), systematic studies concerning the effect of ui on undrained shear behaviours of the soil are still lacking. This study reports a series of undrained triaxial tests aiming to compare and investigate the responses of reconstituted fine-grained gassy soil with the same consolidation pressure ([Formula: see text]), but at a wide range of varying ui (0–1000 kPa). The shearing-induced excess pore pressure (Δu) in the gassy specimens highly depends on ui. It can be either smaller than that of the saturated specimen with the same [Formula: see text] (due to partial dissipation of Δu into relatively large bubbles at low ui) or larger than that of the saturated specimen (related to collapse of relatively small bubbles at high ui). Consequently, the presence of bubbles had beneficially increased cu at relatively low ui (ui/[Formula: see text] < 0.6), and vice versa. The critical stress ratio of the reconstituted fine-grained gassy soil, however, did not appear to be altered by ui.

scholarly journals <i>Blastodinium</i> spp. infect copepods in the ultra-oligotrophic marine waters of the Mediterranean Sea

2011 ◽  
Vol 8 (8) ◽  
pp. 2125-2136 ◽  
Author(s):  
C. Alves-de-Souza ◽  
C. Cornet ◽  
A. Nowaczyk ◽  
S. Gasparini ◽  
A. Skovgaard ◽  
...  
Keyword(s):  
Mediterranean Sea ◽  
Gene Sequence ◽  
Eastern Mediterranean ◽  
Gut Contents ◽  
Wide Range ◽  
The Mediterranean ◽  
Successive Generations ◽  
Oligotrophic Ecosystems ◽  
Distinct Distribution

Abstract. Blastodinium are chloroplast-containing dinoflagellates which infect a wide range of copepods. They develop inside the gut of their host, where they produce successive generations of sporocytes that are eventually expelled through the anus of the copepod. Here, we report on copepod infections in the oligotrophic to ultra-oligotrophic waters of the Mediterranean Sea sampled during the BOUM cruise. Based on a DNA-stain screening of gut contents, 16 % of copepods were possibly infected in samples from the Eastern Mediterranean infected, with up to 51 % of Corycaeidae, 33 % of Calanoida, but less than 2 % of Oithonidae and Oncaeidae. Parasites were classified into distinct morphotypes, with some tentatively assigned to species B. mangini, B. contortum, and B. cf. spinulosum. Based upon the SSU rDNA gene sequence analyses of 15 individuals, the genus Blastodinium was found to be polyphyletic, containing at least three independent clusters. The first cluster grouped all sequences retrieved from parasites of Corycaeidae and Oncaeidae during this study, and included sequences of Blastodinium mangini (the "mangini" cluster). Sequences from cells infecting Calanoida belonged to two different clusters, one including B. contortum (the "contortum" cluster), and the other uniting all B. spinulosum-like morphotypes (the "spinulosum" cluster). Cluster-specific oligonucleotidic probes were designed and tested by fluorescence in situ hybridization (FISH) in order to assess the distribution of dinospores, the Blastodinium dispersal and infecting stage. Probe-positive cells were all small thecate dinoflagellates, with lengths ranging from 7 to 18 μm. Maximal abundances of Blastodinium dinospores were detected at the Deep Chlorophyll Maximum (DCM) or slightly below. This was in contrast to distributions of autotrophic pico- and nanoplankton, microplanktonic dinoflagellates, and nauplii which showed maximal concentrations above the DCM. The distinct distribution of dinospores and nauplii argues against infection during the naupliar stage. Dinospores, described as autotrophic in the literature, may escape the severe nutrient limitation of ultra-oligotrophic ecosystems by living inside copepods.

In-situ electrical-resistivity measurements in the high-voltage electron microscope

1978 ◽  
Vol 36 (1) ◽  
pp. 68-69
Author(s):  
W. E. King
Keyword(s):  
Electrical Resistivity ◽  
Electron Microscope ◽  
High Voltage ◽  
Resistivity Measurements ◽  
Voltage Electron ◽  
High Voltage Electron Microscope ◽  
High Voltage Electron ◽  
Wide Range ◽  
Helium Gas

A side-entry type, helium-temperature specimen stage that has the capability of in-situ electrical-resistivity measurements has been designed and developed for use in the AEI-EM7 1200-kV electron microscope at Argonne National Laboratory. The electrical-resistivity measurements complement the high-voltage electron microscope (HVEM) to yield a unique opportunity to investigate defect production in metals by electron irradiation over a wide range of defect concentrations.A flow cryostat that uses helium gas as a coolant is employed to attain and maintain any specified temperature between 10 and 300 K. The helium gas coolant eliminates the vibrations that arise from boiling liquid helium and the temperature instabilities due to alternating heat-transfer mechanisms in the two-phase temperature regime (4.215 K). Figure 1 shows a schematic view of the liquid/gaseous helium transfer system. A liquid-gas mixture can be used for fast cooldown. The cold tip of the transfer tube is inserted coincident with the tilt axis of the specimen stage, and the end of the coolant flow tube is positioned without contact within the heat exchanger of the copper specimen block (Fig. 2).

Influence of ion-milling on the T2 phase in Al-2.5%Li-2.5%Cu alloy

1989 ◽  
Vol 47 ◽  
pp. 288-289
Author(s):  
J. R. Reed ◽  
D. J. Michel ◽  
P. R. Howell
Keyword(s):  
Thin Foil ◽  
Icosahedral Symmetry ◽  
Ion Milling ◽  
Cu Alloy ◽  
Thin Foils ◽  
Heat Treated ◽  
Aluminum Solid Solution ◽  
In Situ Heating ◽  
The Stability

The Al6Li3Cu (T2) phase, which exhibits five-fold or icosahedral symmetry, forms through solid state precipitation in dilute Al-Li-Cu alloys. Recent studies have reported that the T2 phase transforms either during TEM examination of thin foils or following ion-milling of thin foil specimens. Related studies have shown that T2 phase transforms to a microcrystalline array of the TB phase and a dilute aluminum solid solution during in-situ heating in the TEM. The purpose of this paper is to report results from an investigation of the influence of ion-milling on the stability of the T2 phase in dilute Al-Li-Cu alloy.The 3-mm diameter TEM disc specimens were prepared from a specially melted Al-2.5%Li-2.5%Cu alloy produced by conventional procedures. The TEM specimens were solution heat treated 1 h at 550°C and aged 1000 h at 190°C in air to develop the microstructure. The disc specimens were electropolished to achieve electron transparency using a 20:80 (vol. percent) nitric acid: methanol solution at -60°C.

Performance of Electronic Structure Methods for the Description of Hückel-Möbius Interconversions in Extended π-Systems

2019 ◽  
Author(s):  
Tatiana Woller ◽  
Ambar Banerjee ◽  
Nitai Sylvetsky ◽  
Xavier Deraet ◽  
Frank De Proft ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Basis Set ◽  
Dft Methods ◽  
Molecular Switching ◽  
Wide Range ◽  
Electronic Structure Methods ◽  
Explicitly Correlated ◽  
Relative Errors ◽  
The Stability ◽  
Basis Set Expansion

<p>Expanded porphyrins provide a versatile route to molecular switching devices due to their ability to shift between several π-conjugation topologies encoding distinct properties. Taking into account its size and huge conformational flexibility, DFT remains the workhorse for modeling such extended macrocycles. Nevertheless, the stability of Hückel and Möbius conformers depends on a complex interplay of different factors, such as hydrogen bonding, p···p stacking, steric effects, ring strain and electron delocalization. As a consequence, the selection of an exchange-correlation functional for describing the energy profile of topological switches is very difficult. For these reasons, we have examined the performance of a variety of wavefunction methods and density functionals for describing the thermochemistry and kinetics of topology interconversions across a wide range of macrocycles. Especially for hexa- and heptaphyrins, the Möbius structures have a pronouncedly stronger degree of static correlation than the Hückel and figure-eight structures, and as a result the relative energies of singly-twisted structures are a challenging test for electronic structure methods. Comparison of limited orbital space full CI calculations with CCSD(T) calculations within the same active spaces shows that post-CCSD(T) correlation contributions to relative energies are very minor. At the same time, relative energies are weakly sensitive to further basis set expansion, as proven by the minor energy differences between MP2/cc-pVDZ and explicitly correlated MP2-F12/cc-pVDZ-F12 calculations. Hence, our CCSD(T) reference values are reasonably well-converged in both 1-particle and n-particle spaces. While conventional MP2 and MP3 yield very poor results, SCS-MP2 and particularly SOS-MP2 and SCS-MP3 agree to better than 1 kcal mol<sup>-1</sup> with the CCSD(T) relative energies. Regarding DFT methods, only M06-2X provides relative errors close to chemical accuracy with a RMSD of 1.2 kcal mol<sup>-1</sup>. While the original DSD-PBEP86 double hybrid performs fairly poorly for these extended p-systems, the errors drop down to 2 kcal mol<sup>-1</sup> for the revised revDSD-PBEP86-NL, again showing that same-spin MP2-like correlation has a detrimental impact on performance like the SOS-MP2 results. </p>

Site specific agricultural soil management with the use of new technologies

2013 ◽  
Vol 16 (1) ◽  
pp. 59-67
Keyword(s):  
New Technologies ◽  
Digital Interface ◽  
Appropriate Treatment ◽  
Wide Range ◽  
Soil Variation ◽  
Soil Information ◽  
Remote Sensing Techniques ◽  
Agricultural Areas

<p>The Soil Science Institute of Thessaloniki produces new digitized Soil Maps that provide a useful electronic database for the spatial representation of the soil variation within a region, based on in situ soil sampling, laboratory analyses, GIS techniques and plant nutrition mathematical models, coupled with the local land cadastre. The novelty of these studies is that local agronomists have immediate access to a wide range of soil information by clicking on a field parcel shown in this digital interface and, therefore, can suggest an appropriate treatment (e.g. liming, manure incorporation, desalination, application of proper type and quantity of fertilizer) depending on the field conditions and cultivated crops. A specific case study is presented in the current work with regards to the construction of the digitized Soil Map of the regional unit of Kastoria. The potential of this map can easily be realized by the fact that the mapping of the physicochemical properties of the soils in this region provided delineation zones for differential fertilization management. An experiment was also conducted using remote sensing techniques for the enhancement of the fertilization advisory software database, which is a component of the digitized map, and the optimization of nitrogen management in agricultural areas.</p>

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