The Steam-Assisted Gravity Drainage (SAGD) Process involves the injection of steam through a horizontal well and the production of heavy oil through a lower horizontal well. Several authors have tried to model this process using analytical, semi-analytical and fully numerical means. In this dissertation, we improve the predictive ability of previous models by accounting for the effect of anisotropy, the effect of heat transfer on capillarity and the effect of water-in-oil (W/O) emulsion formation and transport which serves to enhance heat transfer during SAGD. We account for the effect of anisotropy during SAGD by performing elliptical transformation of the resultant gravity head and resultant oil drainage vectors on to a space described by the vertical and horizontal permeabilities. Our results, show that unlike for the isotropic case, the effect of anisotropy is time dependent and there exists a given time beyond which it ceases to have any effect on SAGD rates. This result will impact well spacing design and optimization during SAGD. Butler et al. (1981) derived their classical SAGD model by solving a 1-D heat conservation equation for single phase flow. This model has excellent predictive capability at experimental scales but performs poorly at field scales. By assuming a linear saturation -- temperature relationship, Sharma and Gates (2010b) developed a model that accounts for multiphase flow ahead of the steam chamber interface. In this work, by decomposing capillary pressure into its saturation and temperature components, we coupled the mass and energy conservation equations and showed that the multi-scale, multiphase flow phenomenon occurring during SAGD is the classical Marangoni (or thermo-capillary) effect which can be characterized by the Marangoni number. At low Marangoni numbers (typical of experimental scales) we get the Butler solution while at high Marangoni numbers (typical of field scales), we approximate the Sharma and Gates solution. The Marangoni flow concept was extended to the Expanding Solvent SAGD (ES-SAGD) process and our results show that there exists a given Marangoni number threshold below which the ES-SAGD process will not fare better than the SAGD process. Experimental results presented in Sasaki et al. (2002) demonstrate the existence of water-in-oil emulsions adjacent to the steam chamber wall during SAGD. In this work we show that these emulsions enhanced heat transfer at the chamber wall and hence oil recovery. We postulate that these W/O emulsions are principally hot water droplets that carry convective heat energy. We perform calculations to show that their presence can practically double the effective heat transfer coefficient across the steam chamber interface which overcomes the effect of reduced oil rates due to the increased emulsified phase viscosity. Our results also compared well with published experimental data. The SAGD (and ES-SAGD) process is a short length-scaled process and hence, short length-scaled phenomena (typically ignored in other EOR or conventional processes) such as thermo-capillarity and in-situ emulsification should not be ignored in predicting SAGD recoveries. This work will find unique application in predictive models used as fast proxies for predicting SAGD recovery and for history matching purposes. / text

The Marcellus Shale is an important resource play prevalent in several states in the eastern United States. The productive zone of the Marcellus Shale has variations in rock properties such as clay content, kerogen content and pore aspect ratio, and these variations may strongly effect elastic anisotropy. The objective of this study is to characterize surface seismic sensitivity for variations in anisotropic parameters relating to kerogen content and aspect ratio of kerogen saturated pores. The recognized sensitivity may aid to characterize these reservoir from surface seismic observations for exploration and production of hydrocarbon. In this study, I performed VTI anisotropic modeling based on geophysical wireline log data from Harrison County, WV. The wireline log data includes spectral gamma, density, resistivity, neutron porosity, monopole and dipole sonic logs. Borehole log data were analyzed to characterize the Marcellus Shale interval, and quantify petrophysical properties such as clay content, kerogen content and porosity. A rock physics model was employed to build link between petrophysical properties and elastic constants. The rock physics model utilized differential effective medium (DEM) theory, bounds and mixing laws and fluid substitution equations in a model scheme to compute elastic constants for known variations in matrix composition, kerogen content and pore shape distribution. The seismic simulations were conducted applying a vertical impulse source and three component receivers. The anisotropic effect to angular amplitude variations for PP, PS and SS reflections were found to be dominantly controlled by the Thomsen Ɛ parameter, characterizing seismic velocity variations with propagation direction. These anisotropic effect to PP data can be seen at large offset (>15o incidence angle). The most sensitive portion of PS reflections was observed at mid offset (15o-30o). I also analyzed seismic sensitivity for variations in kerogen content and aspect ratio of structural kerogen. Elastic constants were computed for 5%, 10%, 20% and 30% kerogen content from rock physics model and provided to the seismic model. For both kerogen content and aspect ratio model, PP amplitudes varies significantly at zero to near offset while PS amplitude varied at mid offsets (12 to 30 degree angle of incidences). / text

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The Woodford Shale is an important unconventional oil and gas resource. It can act as a source rock, seal and reservoir, and may have significant elastic anisotropy, which would greatly affect seismic response. Understanding how anisotropy may affect the seismic response of the Woodford Shale is important in processing and interpreting surface reflection seismic data. The objective of this study is to identify the differences between isotropic and anisotropic seismic responses in the Woodford Shale, and to understand how these anisotropy parameters and physical properties influence the resultant synthetic seismograms. I divide the Woodford Shale into three different units based on the data from the Pioneer Reliance Triple Crown #1 (RTC #1) borehole, which includes density, gamma ray, resistivity, sonic, dipole sonic logs, part of imaging (FMI) logs, elemental capture spectroscopy (ECS) and X-ray diffraction (XRD) data from core samples. Different elastic parameters based on the well log data are used as input models to generate synthetic seismograms. I use a vertical impulsive source, which generates P-P, P-SV and SV-SV waves, and three component receivers for synthetic modeling. Sensitivity study is performed by assuming different anisotropic scenarios in the Woodford Shale, including vertical transverse isotropy (VTI), horizontal transverse isotropy (HTI) and orthorhombic anisotropy. Through the simulation, I demonstrate that there are notable differences in the seismic response between isotropic and anisotropic models. Three different types of elastic waves, i.e., P-P, P-SV and SV-SV waves respond differently to anisotropy parameter changes. Results suggest that multicomponent data might be useful in analyzing the anisotropy for the surface seismic data. Results also indicate the sensitivity offset range might be helpful in determining the location for prestack seismic amplitude analysis. All these findings demonstrate the potentially useful sensitivity parameters to the seismic data. The paucity of data resources limits the evaluation of the anisotropy in the Woodford. However, the seismic modeling with different type of anisotropy assumptions leads to understand what type of anisotropy and how this anisotropy affects the change of seismic data. / text

Τα τελευταία χρόνια υπάρχει εκτεταμένη πειραματική και θεωρητική μελέτη στην περιοχή των νανοσωματιδίων διότι βρίσκουν εφαρμογές σαν μέσα μαγνητικής εγγραφής και αποθήκευσης πληροφοριών και πιο πρόσφατα στην ιατρική. Στόχος των ερευνών είναι να κατασκευαστούν όσο το δυνατό μικρότερα σε μέγεθος νανοσωματίδια, στα οποία όμως οι μαγνητικές ιδιότητες να είναι σταθερές σε θερμοκρασία δωματίου, δηλαδή με μεγάλη ανισοτροπία. Τα σύνθετα νανοσωματίδια με μορφολογία σιδηρομαγνητικού πυρήνα/αντισιδηρομαγνητικού φλοιού εμφανίζουν μία επιπλέον ανισοτροπία την ανισοτροπία ανταλλαγής η οποία τα καθιστά θερμικά σταθερά σε μικρό μέγεθος. Στην παρούσα εργασία χρησιμοποιήθηκε η τεχνική Μetropolis Monte Carlo για την μελέτη της μαγνητικής συμπεριφοράς νανοσωματιδίων με μορφολογία πυρήνα/φλοιού τα οποία εμφανίζουν την ανισοτροπία ανταλλαγής. Η τεχνική αυτή έχει το πλεονέκτημα ότι μπορεί να περιλάβει στους υπολογισμούς τις λεπτομέρειες της μικροδομής του συστήματος και την θερμοκρασία. Στόχος της εργασίας μας ήταν με την ανάπτυξη κατάλληλου θεωρητικού μοντέλου να μελετηθεί ο μηχανισμός που προκαλεί την εμφάνιση της ανισοτροπίας ανταλλαγής και οι παράγοντες που επηρεάζουν τόσο την εμφάνιση της όσο και την ισχύ της. Βρήκαμε ότι η ανισοτροπία ανταλλαγής η οποία επάγεται από την αλληλεπίδραση ανταλλαγής κατά μήκος της σιδηρομαγνητική/αντισιδηρομαγνητική διεπιφάνειας οφείλεται στην ύπαρξη μη αντισταθμισμένων μαγνητικών ροπών στην διεπιφάνεια μεταξύ σιδηρομαγνητικού πυρήνα του νανοσωματιδίου και αντισιδηρομαγνητικού φλοιού και οι παράγοντες που επηρεάζουν το μέγεθος της είναι α)το πάχος του φλοιού, έχουμε εμφάνιση της μετά το δεύτερο στρώμα αντισιδηρομαγνητικού φλοιού β)το μέγεθος της σταθεράς ανταλλαγής στην διεπιφάνεια και λιγότερο στον φλοιό που ενισχύουν το φαινόμενο, γ)το και το είδος της ανισοτροπίας στον φλοιό, είναι πιο έντονη για ανισοτροπία z-άξονα στο φλοιό και δ)από το μέγεθος της ανισοτροπίας της διεπιφάνειας. Ένα άλλο φαινόμενο που συνδέεται με την εμφάνιση της ανισοτροπίας ανταλλαγής είναι η κάθετη μετατόπιση. Δηλαδή η ασσυμετρία του βρόχου υστέρησης των σύνθετων νανοσωματιδίων με μορφολογία πυρήνα φλοιού στον κάθετο άξονα της μαγνήτισης. Οι υπολογισμοί μας έδειξαν ότι σε αντίθεση με την ανισοτροπία ανταλλαγής η κάθετη μετατόπιση οφείλεται στην ύπαρξη του συνολικού αριθμού των μη αντισταθμισμένων μαγνητικών ροπών του φλοιού και όχι μόνο της διεπιφάνειας. Οι υπολογισμοί μας συγκρίθηκαν με πρόσφατα πειραματικά αποτελέσματα, και βρέθηκαν σε πολύ καλή συμφωνία. Επιβεβαιώνοντας ότι οι ανταγωνιστικές αλληλεπιδράσεις που οφείλονται στην ύπαρξη ανταγωνιστικών αλληλεπιδράσεων ανταλλαγής σε σύνθετα νανοσωματίδια με μορφολογία σιδηρομαγνητικού πυρήνα/αντισιδηρομαγνητικού φλοιού είναι υπεύθυνες για τη μεταβολή των μαγνητικών τους ιδιοτήτων σε σχέση με αυτές των σιδηρομαγνητικών νανοσωματιδίων. / The magnetic properties of nanoparticles have been subject of continuously growing interest, driven by fundamental research and technological interest especially in the magnetic recording industry and more recently in medicine. The small size of the nanoparticles and the reduced symmetry at their surface result in high coercivity. More recently, the requirement for stable magnetic behavior of the nanoparticles at room temperature led to the development of complex spin nanostructures with core/shell morphology that results to enhanced magnetic anisotropy. Composite nanoparticles with ferromagnetic core/ antiferromagnetic shell morphology have an extra anisotropy, the exchange anisotropy which makes them thermally stable in room temperature even in the case of very small size. In the current work we use the Metropolis Monte Carlo method to study the magnetic behaviour of nanoparticles with core/shell morphology which exhibit exchange anisotropy. The advantages of this method is that the microstructure of the nanoparticles is explicitly included and the temperature. The main goal of this thesis was to develop an appropriate theoretical model for the study of the origin of the exchange anisotropy and the parameters which affect its appearance and its magnitude. We find that the exchange anisotropy which is induced by the exchange interaction between ferromagnetic core and antiferromagnetic shell in the interface can is due to the existence of uncompensated bonds along the interface. The size of the exchange anisotropy depends on a) the shell thickness, at least two antiferromagnetic shell layers are necessary for the appearance of the effect, b) the magnitude of exchange interaction at the interface and at the shell influence the strength of the exchange anisotropy also c) the type of anisotropy in the antiferromagnetic shell, it is bigger for z-axis shell anisotropy and d) the magnitude of anisotropy at the interface. Another phenomenon which is related with exchange anisotropy is the vertical shift i.e. the asymmetry of the hysterisis loop on the vertical axis. Our calculations show that this shift depends on the total number of the uncompensated spins in the antiferromagnetic shell and not only from the interface. Our calculations are in good agreement with recent experimental results. This confirms that exchange interaction between ferromagnetic core and antiferromagnetic shell is responsible for the exchange anisotropy effect in these composite nanoparticles with ferromagnetic core/antiferromagnetic shell morphology that results to magnetic behaviour different from that of pure ferromagnetic nanoparticles.

Nonspherical large cages in structure I (sI) clathrates impose non-uniform motion of nonspherical guest molecules and anisotropic lineshapes in NMR spectra of the guest. In this work, we calculate the lineshape anisotropy of the linear CO2 molecule in large sI clathrate cages based on molecular dynamics simulations of this inclusion compound. The methodology is general and does not depend on the temperature and type of inclusion compound or guest species studied. The nonspherical shape of the sI clathrate hydrate large cages leads to preferential alignment of linear CO2 molecules in directions parallel to the two hexagonal faces of the cages. The angular distribution of the CO2 guests in terms of a polar angle θ and azimuth angle  and small amplitude vibrational motions in the large cage are characterized by molecular dynamics simulations at different temperatures in the stability range of the CO2 sI clathrate. These distributions are used to calculate the NMR powder spectrum of CO2 at different temperatures. The experimental 13C NMR lineshapes of CO2 guests in the large cages show a reversal of the skew between the low temperature (77 K) and the high temperature (238 K) limits of the stability of the clathrate. Good agreement between experimental lineshapes and calculated lineshapes is obtained. No assumptions regarding the nature of the guest motions in the cages are required.

Aquest treball presenta l’estudi teòric de l’anisotropia magnètica en complexos de metalls de transició, combinant esquemes de càlcul multiconfiguracionals relativistes amb derivacions analítiques basades en la teoria del camp del lligand, el que permet racionalitzar a través de conceptes senzills els resultats quantitatius obtinguts i interpretar les propietats estudiades. Es desenvolupa primer una metodologia per extreure els paràmetres d’anisotropia en complexos mononuclears de metalls de transició. El mètode es basa en assignar els resultats d’un càlcul ab initio d’alt nivell a un Hamiltonià model mitjançant la teoria d’Hamiltonians efectius. Aquesta metodologia s’aplica a complexos de Ni(II), Co(II) i Mn(III) i es comprova que és aplicable de forma general a complexos mononuclears. S’estén després la metodologia a complexos binuclears, pels quals l’Hamiltonià model usualment utilitzat té una base menys rigorosa. L’Hamiltonià efectiu obtingut per un complex binuclear de Ni(II) introdueix una nova parametrització amb termes addicionals de les interaccions anisotròpiques en sistemes polinuclears. Es tracta d’un procediment universal que proporciona valors precisos i a més és capaç de contrastar la consistència interna dels Hamiltonians models existents. Per racionalitzar les correlacions magnetoestructurals dels paràmetres d’anisotropia en complexos de Ni(II) i Mn(III), es descriuen els mecanismes electrònics bàsics en base a consideracions de la teoria del camp del lligand. Aquest procediment proporciona regles senzilles per augmentar l’anisotropia, que poden ser aplicades en el disseny de nous materials. Finalment, s’estudien les interaccions anisotròpiques simètriques i antisimètriques en compostos binuclears de Cu(II), interaccions de gran importància per explicar les propietats d’alguns materials d’interès tecnològic. Les interaccions antisimètriques s’extreuen a partir de càlculs ab initio d’estructura electrònica per primer cop en aquest treball. Es concentra l’atenció d’aquesta part en dos sistemes: el conegut complex binuclear de Cu(II) amb quatre ponts acetat, i l’òxid de coure en el que recentment s’ha evidenciat una fase ferroelèctrica.

The class of high Tc superconductors share one common structural aspect, the existence of planes of copper and oxygen ions. These planes are thought to be the source of the superconducting behaviour. They can be represented as a two-dimensional lattice of ions, which facilitates their study using numerical models. One such model is the t − J model. In most studies utilising numerical models, the planes have been considered isotropic. However, recent analysis of cuprate structure has illustrated that this may not be representative of the copper oxide planes. A number of cuprate structures exhibit different phases in which the planes are not isotropic, such as the low temperature orthorhombic and low temperature tetragonal phases. This work will examine the effects of introducing anisotropy into the t − J model in order to understand how these phases affect the results gained from numerical studies. / x, 89 leaves : ill. ; 29 cm.

Considerable efforts are being devoted to designing enhanced molecular magnetic materials, in particular single molecule magnets (SMMs) that can meet the requirements for future technologies such as quantum computing and spintronics. A current trend in the field is enhancing the global anisotropy in metal complexes using single-ion anisotropy. The work in this dissertation is devoted to the synthesis and characterization of new building blocks of the highly anisotropic early transition metal ion V(III) with the aim of incorporating them into heterometallic molecular materials. The results underscore the importance of tuning the local coordination environments of metal ions in order to ensure enhanced single ion anisotropy. A family of mononuclear axially distorted vanadium (III) compounds, A[L_(3)VX_(3)] (3-9) (X = F, Cl or Br, A^(+) = Et_(4)N^(+), nBu_(4)N^(+) or PPN^(+) , L_(3) = Tp or Tp* (Tp = tris(-1-pyrazolyl)borohydride), Tp* = tris(3,5-dimethyl-1-pyrazolyl)borohydride)), and [Tp*V(DMF)_(3)](PF_(6))_(2) were studied. Replacement of the Tp ligand in 3 with the stronger π-donor Tp* results in a near doubling of the magnitude of the axial zero-field splitting parameter D_(z) (D_(z) = -16.0 cm^(-1) in 3, and -30.0 cm^(-1) in 4) as determined by magnetic measurements. Such findings support the idea that controlling the axial crystal field distortion is an excellent way to enhance single-ion anisotropy. High Field-High Frequency EPR measurements on 4 revealed an even higher D value, -40.0 cm^(-1). Interestingly, compound 4 exhibits evidence for an out-of-phase ac signal under dc field. In another effort, a new series of vanadium cyanide building blocks, PPN[V(acac)_(2)(CN)_(2)]∙PPNCl (13) (acac = acetylacetonate), A[V(L)(CN)_(2)] (A^(+) = Et_(4)N^(+), L = N,N'-Ethylenebis(salicylimine) (14), A = PPN^(+), L = N,N'-Ethylenebis(salicylimine) (15), L = N,N'-Phenylenebis(salicylimine) (16), and L = N,N'-Ethylenebis(2-methoxysalicylimine) (17)) were synthesized. Magnetic studies revealed moderate Dz values (-10.0, 5.89, 3.7, 4.05 and 4.36 cm^(-1) for 13-17 respectively). The first family of cyanide-bridged lanthanide containing molecules with a trigonal bipyramidal (TBP) geometry, (Et_(4)N)_(2)[(Re(triphos)(CN)_(3))_(2)(Ln(NO_(3))_(3))_(3)]-∙4CH_(3)CN (19-27 with Ln = La, Ce, Pr, Nd, Sm, Gd, Tb, Dy and Ho) were prepared using the [(triphos)Re(CN)_(3)]^(-) building block, results that add valuable information to our database of compounds with a TBP geometry. Magnetic studies revealed diverse magnetic responses including slow relaxation of the magnetization at zero field for 25 and 26 , an indication of SMM behavior.