Formation damage is a common problem in petroleum reservoirs and happens in different stages of reservoir development from drilling to production. The causes of formation damage include particle invasion, formation fines migration, chemical precipitation, and pore deformation or collapse. Formation damage adversely affects productivity of wells by reducing the permeability of near wellbore region. Furthermore, formation damage also affects well logging results. Therefore, understanding the mechanism of formation damage is vital to predict the extent and severity of formation damage and to control it. This thesis is focused on the study of formation damage caused by external particle invasion. A simplified numerical method based on a commercial code PFC (Particle Flow Code) is proposed to simulate the particle invasion process. The fluid-particle interaction is simplified as hydrodynamic drag forces acted on particles by fluids; the particle-grain interaction is modeled as two rigid balls on contact. Furthermore, an pore network flow model is developed in this study to estimate permeability of damaged formations, which contain two well-separated particle sizes. The effects of the particle size and the initial formation porosity on formation damage are studied in detail. Our study shows that big particles tend to occupy the formation face, while small particles invade deep into the formation. Moreover, particles which are smaller than pore throats (entrances) impair permeability more than those bigger than pore throats. Our study also indicates that a higher initial formation porosity results in more particle invasion and permeability impairment. It is suggested that, in order to reduce formation damage, mud particle size distributions should be carefully selected according to given formation properties. Although our model has some limitations, it may serve as a tool to predict formation damage according to given parameters, and to understand the mechanism of formation damage from a micro-scopic point of view. / text

Αντικείμενο της παρούσας Μεταπτυχιακής Διπλωματικής Εργασίας είναι η διερεύνηση της τιμής του συντελεστή διαπερατότητας άμμων διαφορετικής κοκκομετρικής σύνθεσης, η αξιολόγηση των αποτελεσμάτων και η σύγκριση τους με τιμές που προκύπτουν εφαρμόζοντας γνωστές εξισώσεις πρόβλεψης της τιμής του συντελεστή διαπερατότητας και, τέλος, η ειδική εφαρμογή των αποτελεσμάτων σε μια προσπάθεια διαμόρφωσης μοντέλου πρόβλεψης της ενεσιμότητας αιωρημάτων τσιμέντου σε άμμους. / Purpose of the Thesis is to investigate the value of the coefficient of sands permeability, the evaluation of results and their comparison with values obtained by applying known predictive formulas of coefficient of permeability and finally, the implementation of the results in creating a predicting model of the groutability of cement suspensions in sands.

Cellular energy transduction processes are often driven by transmembrane ion gradients, and a number of artificial membrane systems have been developed that allow for chemically or light-induced transport of ions across lipid bilayers. These liposomal architectures, however, are not readily interfaced to a solid-state transducer. A significant step toward this goal is described here by assessing the possibility of coupling a lipid bilayer directly to a transducer to form a stable uniform film using hybrid bilayer membranes (HBMs).Although the surface attachment of self-assembled monolayer increases the robustness of the lipid assembly, HBMs cannot maintain film uniformity under harsher conditions due to the absence of strong lipid-lipid interactions. Therefore, HBMs were prepared and characterized using a cross-linking polymerizable lipid, bis-SorbPC. Several parameters relating to lipid deposition and film stabilization through polymerization were examined. Film characterization strongly suggests that polymerization of bis-SorbPC stabilizes the HBM such that its structure is largely preserved even after the dehydration process. This work suggests that network formation in the upper monolayer is not enough to prevent oligomer desorption, intermonolayer covalent linking is also a prerequisite in making uniform, defect-free planar supported lipid assemblies.Some of the challenges associated with the application of lipids involve the creation of supported bilayers that are stable to chemical and physical disruptions, yet retain their ion barrier properties, and allow transmembrane ion transport by lipid-soluble shuttles. Polymerized lipid films provide the stability required for these structures, but permeability properties of cations across poly(lipid) membranes are not known. Therefore, convenient liposome-based proton and calcium permeability assays were developed. These assays were applied to various poly(lipid) compositions.In addition, three novel sorbyl-substituted head group polymerizable lipids, which have been synthesized based on a strategy that head group polymerization would minimally perturb the characteristic ion impermeability of the membrane, were evaluated for their lipid characteristics and ability to form polymers. None of these compounds forms vesicles by itself. Therefore, attempts were made to form mixed vesicles with other fluid lipids. The miscibility of the mixed monolayers was assessed using Langmuir isotherms.

国立情報学研究所で電子化したコンテンツを使用している。

Thesis--University of California, Berkeley. / "UCRL-9012." "Contract no. W-7405-eng-48." Includes bibliographical references (p. 91-101).

Thesis (doctoral)--University of Uppsala, 1981. / Includes bibliographical references (p. 21-15).

This dissertation presents contributions to the understanding of the dynamic nature of permeability of Indonesian coal. It is the first-of-its-kind study, first presenting a comparison of experimental results with those obtained using existing analytical permeability models, and then modifying the existing anisotropic model for application to the unique physical structure of Indonesian coal. The first problem addressed in this dissertation was establishing the pressure-dependentpermeability of coal in a laboratory environment replicating in situ conditions for two coal types from the Sanga Sanga basin of Kalimantan, Indonesia. The change in permeability with depletion and the corresponding volumetric strain of coal were measured in the laboratory under uniaxial strain condition (zero lateral strain). Two gases, helium and methane, were used as the flowing fluids during experimental work. The results showed that, decreasing pore pressure resulted in significant decrease in horizontal stress and increased permeability. The permeability increase at low reservoir pressure was significant, a positive finding for Indonesian coals. Using the measured volumetric changes with variations in pressure, the cleat compressibility for the two coal types was estimated. In a separate effort, volumetric strain as a result of desorption of gases was measured using sister samples under unconstrained condition, in absence of the stress effect. Sorptioninduced strain processes were modeled using the Langmuir-type model to acquire the two important shrinkage parameters. All parameters calculated using the experimental data were used for the modeling exercise. The second component of this dissertation is the permeability variation modeling to enable projecting long-term gas production in the Sanga Sanga basin. For this, two commonly used isotropic permeability models were selected. These models, developed primarily for the San Juan coal, were unable to match the measured permeability data. This was believed to be due to the inappropriate geometry used to represent Indonesian coal, where butt cleats are believed to be absent. This was followed by application of the most recent model, incorporating partial anisotropy in coal. This consideration improved the modeling results although there clearly was room for improvement. The final challenge addressed in this dissertation was to consider the coal geometry appropriate for Indonesian coal, stack of sheets as opposed to a bundle of matchsticks. In order to incorporate the structural anisotropy for the stack of sheets geometry, two input parameters were modified, based on geo-mechanical anisotropy. After applying these to the modified model, the permeability modeling results were compared with the experimental data. The matches improved significantly. Finally, the effect of maximum horizontal stress on permeability of coal was estimated by using high and low maximum horizontal stress values and constant vertical and minimum horizontal stresses. The effect of maximum horizontal stress on permeability was found to be significant under uniaxial strain condition for both coals.

Drosophila are used extensively for genetic, developmental and now molecular biology research. At present, germline transformation of these organisms can only be achieved by microinjection of P-element vectors into the pole cells of young embryos. The technique of microinjection however, requires a delicate touch and is quite laborious. Therefore, the development of a rapid and simple technique was investigated. Electroporation, like microinjection, is a physical means of introducing DNA into a cell and is therefore potentially applicable to all cell types. Electroporation involves the use of an electrical current to create pores in the membrane of a cell. Macromolecules, such as DNA may enter a cell via these pores. Electroporation is a quick, reproducible, and efficient method for transforming cells. Through studies of the survival and permeability of Drosophila melanogaster embryos exposed to electrical currents, it was discovered that although the survival of the embryos decreased steadily as field strength increased, the embryos did not become permeable to a water soluble dye unless a pulse of 10 kV/cm was applied. Few embryos survived this extreme voltage required for dye uptake. Attempts to introduce DNA into dechorionated Drosophila embryos utilizing this technique however, produced no transformants. These results suggested that the remaining protective coatings of the dechorionated embryo were obstructing efficient pore formation, thus preventing DNA penetration. In view of these results, methods to eliminate the wax layer, present between the chorion and vitelline membrane of laid eggs, were examined. Wax removal by detergent solubilization, solvent extraction and melting by heating were investigated, yet did not produce a satisfactory procedure. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

Cumulative clinical and experimental evidence indicates that volatile sulphur compounds (VSC) the principal components of oral malodour, may play an important role in the pathogenesis of periodontal disease. As their (H₂S and CH₃SH) concentrations in gingival sulci increase with the severity of periodontal involvement, the objective of this investigation is to ascertain if they exert an effect on the permeability of oral mucosa. Permeability determinations were performed on excised porcine sublingual mucosal specimens which consisted of non-keratinized epithelium, basal membrane and connective tissue layers mounted in a two compartment perfusion apparatus. Using radioactive and fluorescent-labelled penetrants, it was found that exposure of the epithelial surface to an atmosphere containing physiological concentrations of both thiols (15 ng H₂S or CH₃SH / ml of 95% air - 5% C0₂) increased the permeability of the mucosa to (³⁵S)-S0₄⁻², (³H)-prostaglandin E₂ (PGE₂) and fluorescein isothiocyanate labelled E. coli lipopolysaccharide (F-LPS). A three hour exposure of the mucosa to H₂S and CH₃SH resulted in a 75% and 103% increase respectively in permeability to (³⁵S)-labelled sulphate ion. Similarly, the mercaptan induced up to a 70% increase in permeability of the mucosa to (³H)-prostaglandin E₂. The magnitude of changes in the permeability were found to depend on duration of exposure to the thiols and to their concentration. Studies using (³⁵S)-H₂S suggest that the observed changes in the tissue permeability are related to the reaction of the thiols with tissue components. In addition, the (³⁵S)-H₂S is capable of perfusing through all three layers of the mucosa at 12.3 ng / cm². In contrast to H₂S , the CH₃SH effect was irreversible in control air / C0₂ environment. This infers that CH₃SH is potentially a more deleterious agent to the tissue barrier. However, its effect can also be reversed by treatment of tissues with 0.22% ZnCl₂ either prior to or after exposure to mercaptan. This suggests that Zn⁺² ion may be useful in preventing the potentially harmful effects of VSC. Fluorescent studies with F-LPS indicate that thiols can also potentiate the penetration of endotoxin. Whereas the fluorescence of the F-LPS in control systems was confined to the superficial epithelial layer in contact with the endotoxin, the CH₃SH- exposed mucosa exhibited fluorescence throughout the epithelial and connective tissue layers. Fluorescent staining of the mucosal specimens with fluorescein diacetate followed by counter staining with ethidium bromide provides evidence of membrane impairment to some cells by CH₃SH. Collectively these observations provide strong experimental evidence that the VSC, products of putrefaction produced in the gingival sulcus by oral microflora, may adversely affect the integrity of the crevicular barrier to deleterious agents and thus contribute to the etiology of periodontal disease. / Dentistry, Faculty of / Graduate

Content: Soluble soybean polysaccharide (SSPS) is good in emulsification, and stable emulsion may be formed with the addition of SSPS in fatliquoring agents. In this paper, with wet blues as raw materials, after being retanned and neutralized, fatliquoring and filling up with SSPS were carried out at the same time, with different amounts of SSPS, i.e., 1%, 3%, 5%,7% in weight. The leather samples were dried at room temperature. The effects of SSPS amounts on the thickness, air permeability and water vapor permeability of the crust leather were studied. The tensile properties of the leathers filled by SSPS were analyzed. The results indicated that with increasing the amounts of SSPS, the thickness and the water vapor permeability of the leathers increase, while the air permeability decreases slightly. The maximum stress-strain capacity of leathers decreases with increasing the SSPS amount. At the SSPS amount of 3%, the leather is good in softness, as well as in physical and mechanical properties. Take-Away: 1.SSPS from soybean dregs is an acidic polysaccharide, which is rich in raw materials and low in cost. 2.Leathers filled with SSPS have good performance.