At the start of this work in 1988, apart from bulk relaxation experiments four authors had reported discrimination of oil from water in core samples under static conditions by MRI, and only one, Baldwin (1986) had reported visualisation of flowing oil and water using doping agents Mn++. The aim of this research was to develop the application of MRI to petroleum engineering and in particular to develop Enhanced Oil Recovery (EOR) techniques. A synergistic approach was adopted involving collaboration with AGIP Oil, Italy and the Petroleum Engineering Department of Imperial College. A systematic study of properties of the fluids and their interaction with rock types was mounted, to investigate suitable contrast mechanisms. This was followed by static and dynamic imaging experiments. The chemical shift imaging technique has been used to measure oil and water saturations during flooding experiments with Portland Limestone. For the first time MRI has been used to generate relative permeability, and fractional flow curves for a core plug. The capillary pressure gradient was also determined from the data. The new method was compared to the results of traditional core analysis. Miscible displacements in Lochaline Sandstone were then studied using D2O, glycerol and polymer solutions. The spin echo imaging technique was used to determine the angle of the interface between the fluids. This angle is determined by the ratio of viscous to capillary forces. From this information the core permeability (liquid) and polymer viscosity were measured. These measurements compared well with conventional methods and the results break new ground for MRI. The polymer viscosity measurements are of particular interest since the fluid is non-Newtonian. In separate experiments tertiary chemicals were identified directly during displacement experiments by MRI for the first time. Finally a new model system was developed for image calibration.

Made available in DSpace on 2014-06-11T19:32:09Z (GMT). No. of bitstreams: 0 Previous issue date: 2013-03-08Bitstream added on 2014-06-13T18:43:08Z : No. of bitstreams: 1 sampaio_jc_dr_guara.pdf: 3963543 bytes, checksum: b4f779a20e975ebe02712d88a9373d1e (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / O crescente número de objetos orbitando a Terra justifica a grande atenção e interesse no espaço entre o Planeta e a Lua nos últimos anos. Estes estudos envolvem diferentes perturbações e ressonâncias nos movimentos orbitais destes objetos distribuídos por diferentes altitudes. Neste trabalho, o problema da ressonância no movimento de satélites artificiais é estudado. O desenvolvimento do geopotencial inclui os harmônicos zonais J20 e J40 e os harmônicos tesserais J22 e J42. Através de um procedimento de média e sucessivas transformações de Mathieu, a ordem do sistema dinâmico é reduzida e o sistema final é resolvido por integração numérica. No modelo dinâmico simplificado, três ângulos críticos são estudados. A semi-largura da separatriz é calculada através de um modelo linearizado, o qual descreve o comportamento do sistema dinâmico na vizinhança de cada ângulo crítico. Através do critério de sobreposição das ressonâncias, os possíveis movimentos regulares e irregulares são investigados pelo comportamento no tempo do semi-eixo maior, argumento do pericentro e excentricidade. O maior expoente de Lyapunov é usado como ferramenta para verificar o movimento caótico. Nos estudos sobre os objetos ressonantes, os TLE (Two-Line Elements) do NORAD (North American Defense) são estudados observando o período ressonante dos objetos orbitando a Terra e a ressonância principal na região LEO (Low Earth Orbits). O comportamento no tempo do semi-eixo maior, excentricidade e inclinação de alguns satélites artificiais e detritos espaciais são estudados. Possíveis movimentos irregulares são observados pela presença de diferentes ângulos ressonantes descrevendo a dinâmica orbital destes objetos / The increasing number of objects orbiting the Earth justifies the great attention and interest in the space between the Planet and the Moon in the last years. These studies involve different disturbances and resonances in the orbital motions of these objects distributed by the distinct altitudes. In this work, the resonance problem in the artificial satellites motion is studied. The development of the geopotential includes the zonal harmonics J20 and J40 and the tesseral harmonics J22 and J42. Through an averaging procedure and successive Mathieu transformations, the order of dynamical system is reduced and the final system is solved by numerical integration. In the simplified dynamical model, three critical angles are studied. The half-width of the separatrix is calculated through a linearized model which describes the behavior of the dynamical system in a neighborhood of each critical angle. Through the resonance overlap criterion the possible regular and irregular motions are investigated by the time behavior of the semimajor axis, argument of perigee and eccentricity. The largest Lyapunov exponent is used as tool to verify the chaotic motion. In the studies about the resonant objects the TLE (Two-Line Elements) of the NORAD are studied observing the resonant period of the objects orbiting the Earth and the main resonance in the LEO region. The time behavior of the semi-major axis, eccentricity and inclination of some artificial satellites and space debris are studied. Possible irregular motions are observed by the presence of different resonant angles describing the orbital dynamics of these objects

Exposure of a range of dilute solutions of halogenobenzenes in fluoro-trichloromethane to 60Co y-rays at 77 K gave the corresponding cations characterised by their ESR spectra. The approximate spin-densities on the halogens were greater than predicted by comparison with neutral x-bromo radicals and increased from ca, 8% for PhF+ to 23% for PhCl+, 30% for PhBr+ and 46% for PhI+ In accord with the fall in the ionization potential for this series of halogen. For PhBr+, replacement of para hydrogen by Br, OH and SH gave a steady fall in spin-density on Br reflecting increasing n delocallsation onto the para substituent. Evidence for dimer cation formation in concentrated solutions is presented. The major species obtained from benzyl chloride suggested a preferred conformation with the chlorine close to, but not in, the plane of the benzene ring, with a significant barrier for the in-plane site, in contrast with benzyl bromide with strong hyperfine coupling to bromine [Chapters 3, 4 and 9]. Exposure of dilute solutions of Me2C(Br)C(Br)Me2 In CD3OD and MeTHF to 60Co y-rays at 77 K gave the radical Me2CC(Br)Me2. From changes in the e.s.r. spectrum of this radical, it is deduced that the stable structure is asymmetric, but that the rate of migration of bromine between the two equivalent sites becomes fast on the e.s.r. time-scale at ca. 100-1 [Chapter 6]. Evidence is given for the 1,2-intramolecular proton shift in the interconversion of isobutyl to tert-butyl radicals. The parent material was dissolved in a variety of matrices and exposed to 60Co y-rays at 77 K. The reaction was observed using an in-cavity Proportional, Integral and Differential (PID) temperature control system [Chapter 5]. A single crystal of ethyl iodide was grown and irradiated at 77 K with a a 60Co y-ray source. The spectra were orientation dependent but it was not possible to determine the principal g-values and the elements of the hyperfine tensor [Chapter 7]. 1-Bromo adamantane was dissolved in a variety of deuterated matrices and exposed to 60Co y-rays at 77 K. No firm conclusions can be drawn regarding the single proton coupling of ca. 65 G to the bromine. Exposure of dilute solutions of m-dinitrobenzene or s-trinitrobenzene in methyltetrahydrofuran to 60Co y-rays at 77 K gave two species at 77 K. One, favoured at low doses, had features characteristic of mono-anions with the unpaired electron localized on one nitro-group. At high 7-ray doses a second species with triplet state characteristics grew at the expense of the first. The average separation between the two unpaired electrons was estimated to be 5-6 A.

This thesis forms part of a continuing programme of research to investigate the application of NMR to fluid saturated rock. The work falls into four sections; (i) The development of a novel broad line NMR imaging technique for the study of short T2 fluid components in reservoir rock The technique is a repetitive pulse variant of an established gradient echo method which employs oscillating magnetic field gradients. The variant uses low flip angle r.f. pulses to reduce image rounding artefacts and provide naturally T1 weighted data. (ii) The selective imaging of fluids within preserved reservoir rock and the first broad line NMR imaging study of immiscible fluid flow. The selective imaging of reservoir fluids within preserved rock core samples has been achieved using T1 weighted MRI methods. To account for the natural heterogeneity of the rock and the observed mixed wettability, T1 suppression has been enhanced by lowering the temperature of the rock cores, thus exploiting the difference in dominant relaxation mechanisms of the two core fluids. A model has been developed to explain this temperature dependence in terms of pore surface relaxation theory. Fluid flow processes within reservoir rock have been investigated using chemical substitution and T1 weighted imaging. Due to the short transverse relaxation times expected at irreducible saturation, short T2 imaging protocols have been adopted and represent the first such study. This has provided quantitative data from which the individual phase saturations can be directly obtained. (iii) The first broad line NMR imaging study of liquid and vapour phase diffusion processes in partially saturated rock. Excellent agreement is found between the NMR diffusion profiles of partially saturated rock and a model based on a combination of vapour and liquid phase transport. Estimates of the surface water diffusion coefficient and vapour percolation threshold have thus been obtained. (iv) A detailed study of proton relaxation times of water-saturated rock as a function of saturation. The saturation levels range from 0.06%, equivalent to monolayer water coverage, to 100%. The results have been used to test fast diffusion relaxation theory in rock over the full saturation range for the first time. The relaxation measurements at monolayer coverage have led to the first unambiguous estimates of rock plug pore surface relaxivity. Evidence has been obtained for the effect of pore throats on the relaxation times and pore throat size estimates have been made.

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No description available.

The keto-enol tautomeric systems of cyclic 1,3 diones have been studied by the proton magnetic resonance method. The presence of both keto and enol forms were confirmed in chloroform and acetonitrile solutions . From the concentration dependence of OH proton chemical shift, the equilibrium among the three forms has been suggested: (formula omitted). A linear relationship was found between the OH proton chemical shift and l/√c. The chemical shift of the hydrogen bonded OH proton was found to be -740 cps from T.M.S. at 60 M.c. by extrapolation to infinite concentration. That of the non-hydrogen bonded OH proton was found to be -440 cps, which gave the most reasonable equilibrium constant, K₁ , for all concentrations. The equilibrium constants were obtained from the observed OH chemical shift and from the ratio of the areas under the specific peaks for each species. Measurements were also made in the temperature range 302°K to 357°K for cyclohexane 1,3 dione in chloroform. The overall heat of conversion from the dimer enol form to the monomer keto form was found to be 2.05 Kcal/mole. The proton magnetic resonance spectra of methyl pyridines have been investigated both in carbontetrachloride and trifluoroacetic acid. The broad triplets which were observed at the pyridine concentration of 6~8 mole %, in trifluorocacetic acid confirmed the presence of the pyridine cations . Almost, all the signals, shifted to low field on protonation. The factors which affect the chemical shift were split into several terms on the basis of Pople's theory.¹²⁵ The chemical shifts of the pyridine and pyridinium systems were compared with the benzene system. Dominating factors were found to be; the inductive and anisotropic effects of the nitrogen atom or the protonated nitrogen atom, the mesomerlc effect of the above, and the inductive and anisotropic effects of the methyl groups. Using these values, which were obtained from the simple compounds, the chemical shifts were calculated and compared with the observed values. They agreed in most of the cases within ± 5 cps at 60 M.c. The ortho coupling constants between the 2 and 3 ring protons in the puridine system are much smaller than those in the benzene system. The slight increases in coupling constants on protonation were only understandable considering the pyridinium cations as odd sequences from the benzene and pyridine systems. It was observed that the C¹³-H¹ coupling constants increased on protonation as a result of the increase in the electronegativity of the nitrogen atom. That is the s character in the carbon atomic orbital increased on protonation. / Science, Faculty of / Chemistry, Department of / Graduate

The magnetic resonance signal of a spin system quantized in the rotating reference frame was observed. The experiment consisted of subjecting the electron spins in solid 2,2 Diphenyl-l-Picrylhydrazyl (DPPH) to a strong r.f. field in the 8 mm. microwave range and observing the Larmor frequency corresponding to the effective field of the rotating frame. Signals from 7 to 52 Mc/s were observed. The results are compared with the theory developed by Redfield for this case, utilizing the concept of a spin temperature. Also observed were the Overhauser and Solid effects, which are two possible ways in which a net polarization of one spin species (in this case the protons in DPPH) may be achieved from the spin-spin coupling to another spin species (the electrons in DPPH). The enhancements obtained (60 and 100 respectively) are higher than those so far reported, although experimental errors make detailed comparisons questionable. The Solid effect is compared with a simplified theory of enhancement utilizing the spin temperature concept, and put forward by I. Solomon. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

High resolution nuclear magnetic resonance is used to investigate proton exchange in two hydrogen bonded systems. The change of the chemical shift of the acid proton with concentration in mixtures of trifluoroacetic acid and quinoline have been used to indicate the formation of a strongly hydrogen bonded ion pair in the pure acid-base system and in acetonitrile as solvent. Spectra at -18°C show resolved peaks for the ≽NH⁺ and -COOH protons confirming the nature of the exchange process. The kinetic processes involved in the exchange are discussed but the experimental difficulty in carrying out a low temperature (0 to -60°C) study of an equimolar mixture of the two components prevents any detailed investigation of the rate processes. The chemical shifts measured for the acid and hetero-ring protons are averages for the various environments so that charge density changes on protonation of a basic species are not proportional to the observed chemical shift changes. Intermolecular hydrogen bonding and proton transfer rates between methanol and orthochlorophenol have been experimentally investigated in the slow exchange approximation for the modified Bloch Equations (0°C to -41.1°C). Interpolations of the results to the fast exchange limit are consistent with experimental line widths in this region. The activation energy obtained for the first order kinetics is 4.58 Kcal mole⁻¹. It is considered that the intramolecular hydrogen bond in orthochlorophenol does not impede the proton exchange process in the two component system. Variations in the line width of the exchange averaged -OH resonance signal are used to indicate the effect of small quantities of water added to the methanol-orthochlorophenol mixtures. / Science, Faculty of / Chemistry, Department of / Graduate

The chemical shift of protons in intramolecular hydrogen bonds has been measured in 41 ortho substituted phenol type compounds. The change in chemical shift " ΔσOH " on formation of these hydrogen bonds is taken as the difference between the infinite dilution chemical shift of the parent phenol compound in CCl₄ solution and the chemical shift measured for the proton in the intramolecular hydrogen bond. This change in chemical shift is correlated with the corresponding frequency shift " ΔνOH " in the -OH stretching region of the infra-red spectrum. The dilution chemical shift for the -OH proton in the o-halophenols has been investigated over a concentration range 1-5 mole % in CS₂ and a temperature region -53 to 107°C Using the infinite dilution shift values, the equilibrium constants of the cis-trans conversion were obtained. Values for δCIS, the chemical shift of the completely hydrogen bonded form; δ TRANS, the chemical shift of the unbonded form, and ΔH , the enthalpy of formation of the hydrogen bond, were also calculated. From these results a value for ΔH, the enthalpy of formation for the dimer was calculated, assuming that the major dimer species in solution was formed from the combination of a cis and trans bonded form. Temperature studies of the change in chemical shift of the -OH proton for 2,1,6-trihalosubstituted phenols is also reported. The temperature range in this case was 0°C to 111°0. / Science, Faculty of / Chemistry, Department of / Graduate