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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Simulation Study to Investigate the Effect of Natural Fractures on the Performance of Surfactant-Polymer Flood in Carbonate Reservoirs

Sayedakram, Nawaf Ibrahim A 2010 August 1900 (has links)
This thesis presents a comprehensive simulation study on the impact of natural fractures on the performance of surfactant polymer flood in a field scale surfactantpolymer flood. The simulation model utilized for the study is a dual porosity dual permeability model representing 1/8 of a 20-acre 5-spot pattern. The model parameters studied include wettability alteration, IFT changes and mobility reduction effect. The results of this study clearly indicate the importance of reservoir description and fracture modeling for a successful surfactant-polymer flood. Naturally fractured carbonate reservoirs are usually characterized by mixed wettablility and low matrix permeability which leads to low oil recovery and high remaining oil saturation. Enhanced oil recovery methods such as surfactant-polymer flood (SPF) enhance the recovery by increasing the spontaneous imbibitions either by lowering the interfacial tension or altering the wettability. However, one of the main reasons for failed surfactant-polymer floods is under-estimating the importance of the reservoir especially the description of natural fractures and their effect on recovery. Sensitivity runs were made to compare oil recovery capillary force, buoyancy force and viscous force. The simulation study indicates that critical water saturation should be reached before the start of surfactant-polymer flood to maximize oil recovery and utilize the capillary force. Also, when a surfactant alters the rock wettability, an optimum IFT should be identified for faster and higher imbibitions. The study shows that a contrast in permeability between that of the fracture and that of the matrix will result in a slightly lower oil recovery. Having the fracture perpendicular to the injector producer will result in a higher areal sweep and lower residual oil. A sensitivity study on the effect of the size of surfactant polymer slug was not conclusive. Maximum adsorption capacity was reached which was one of the causes of low imbibitions rate. Following the surfactant-polymer with water flood was able to reverse the adsorption and restore some of the movable oil. The results show that if the enhanced fluid that alter the wettability, imbibed in the matrix, injecting high IFT brine will increase the rate of imbibition. The study calls for further investigation of this phenomenon through research using a scaled laboratory model to verify the simulation results.
42

Studies on the Anisotropic Wet Wtching Characteristic of Silicon Wafer

Chen, Po-Ying 01 July 2003 (has links)
Abstract Anisotropic wet etching is one of the key technologies for the microstructure fabrication in Micro Electro Mechanical Systems (MEMS). Agitation technique is one of the key parameters to affect significantly the quality of silicon anisotropic wet etching, which includes the etch rate and surface roughness. In general, magnetic stirring is used during silicon anisotropic wet etching operation. The ultrasonic agitation and add surfactant have been to replaced and to proceed a series of experiment for KOH solution and TMAH solution in this study. The results show that the ultrasonic agitation can reduce the surface roughness and achieve the high-quality etching surface, its roughness even is only about Ra 47.5Å. Besides, the etch rate is also increased slightly. But it is easily to cause the damage of the microstructure. The addition of anionic surfactant to the KOH solution without any agitation condition can achieve the same at the etching performance of the ultrasonic agitation. The addition of anionic surfactant and nonionic surfactant to the TMAH solution without any agitation condition can achieve the same at the etching performance of the ultrasonic agitation. TMAH solution adds nonionic surfactant not only improves the surface roughness, but also retards the phenomenon of the undercut. Keyword¡Ganisotropic wet etching, magnetic stirring, ultrasonic, surfactant
43

A study of offshore viscous oil production by polymer flooding

Wang, Like, active 2013 05 December 2013 (has links)
Due to capillary pressure, reservoir heterogeneity, oil mobility, and lack of reservoir energy, typically more than 50 % of the original oil in place is left in the reservoir after primary and secondary recovery oil production. With relatively easy-to-get conventional oil resources diminishing and the price of oil hovering around triple digits, enhanced oil recovery methods, such as polymer flooding, have become very attractive ways to recover oil effectively from existing reservoirs. Enhanced oil recovery methods can be categorized into three categories: water or chemical based, gas based, and thermal based. This thesis will focus on the chemical injection of surfactants, alkali, and polymer of the water based methods. Surfactants are used to alter the interfacial tension of the aqueous and oleic phases in order to facility oil production. Alkali chemicals are used to create surfactants by reacting with acidic oil. And polymer is used to reduce injection water mobility to effectively displace the contacted oil in heterogeneous reservoirs by improving the volumetric and displacement sweep efficiencies. This research presents several laboratory results of polymer and alkali/surfactant/polymer core floods performed in the Center for Petroleum and Geosystems Engineering laboratories. Properties of polymer and surfactant phase behavior were measured and modeled and each coreflood was history matched with UTCHEM, a three-dimensional chemical flooding simulator. The coreflood results and the history matched model parameters were then upscaled to a pilot case for viscous oil in offshore environment with four wells in a line drive pattern. The potential of polymer flooding was investigated and several sensitivity cases were performed to evaluate the effect of various physical property parameters on oil recovery. Water salinity and hardness (i.e. amount of calcium and magnesium) has detrimental effects on polymer viscosity and its stability. The potential benefits of low salinity water injection by desalinization of seawater for polymer flood projects have been discussed in recent publications. The effect of low salinity polymer flood was also investigated. A series of sensitivity studies on well pattern and well spacing is carried out to investigate the impact on recovery factor and recovery time. / text
44

Pluronic-Based Nanoparticles for Gene Therapy Applications

Madkhali, Osama January 2013 (has links)
Non-viral delivery vectors have potential advantages over the viral systems that currently are used extensively for delivering therapeutic genes of interest. However, non-viral gene therapy has low efficiencies in vivo, in part due to the aggregation of the particles in the delivery system associated with serum proteins and other components of the blood. An effective technique for overcoming this problem to use PluronicTM block copolymers to cover the surfaces of the particles in the delivery system with polyethylene oxide, which decreases their charge density and reduces their interactions with the serum proteins. The objectives of this project were to characterize a Pluronic-gemini surfactant system to be used as non-viral vectors for gene therapy. Five Pluronics (L44, F68, F87, F108, and F127) were evaluated by studying their physiochemical properties, including particle size and zeta potential. Also, these systems were evaluated in OVCAR-3 cell culture for gene expression and cell viability. The in vitro systems showed small particle sizes (approximately 200 nm) for all Pluronics. The particle sizes in the systems were increased dramatically (up to 2000 nm) by adding dioleylphosphatidylethanolamine (DOPE) to the systems. The zeta potential of these systems shifted the negative zeta potential of DNA (-43 mV) to a positive value (+35 mV). The addition of DOPE had very little effect on zeta potential. The in vitro transfection efficiency in OVCAR-3 showed that all of the Pluronics were able to transfect OVCAR-3 at various DNA/gemini surfactant ratios. The highest transfection efficiency was obtained with Pluronics L44, F87 and F108. PluronicF127 demonstrated the lowest transfection efficiency among the five Pluronics. Adding DOPE did not improve the transfection efficiency in any of the pluronic-gemini surfactant systems. The viabilities of the cells in these systems were high, and there were greater than the positive control (Lipofectamine 2000). The greatest cell viability (about 60%) was observed when the DNA to gemini surfactant ratio was 1:2. After adding DOPE, the cell viability decreased in all of the Pluronics except for Pluronic F68. The results of this investigation indicated that Pluronic block copolymers can transfect OVCAR-3 cell cultures in vitro and that they had a low level of cytotoxicity.
45

Control of pulmonary surfactant secretion : an evolutionary perspective /

Wood, Philip January 1999 (has links) (PDF)
Thesis (Ph.D.) -- University of Adelaide, Dept. of Physiology, 1999. / Bibliography: leaves 209-254.
46

Development of the pulmonary surfactant system in non-mammalian amniotes /

Johnston, Sonya D. January 2001 (has links) (PDF)
Thesis (Ph.D.) -- University of Adelaide, Dept. of Physiology, 2001. / "March 2001". Bibliography: leaves 193-238.
47

Association and interactions of pulmonary surfactant lipids and proteins in model membranes at the air-water interface /

Nag, Kaushik, January 1996 (has links)
Thesis (Ph.D.)--Memorial University of Newfoundland, 1997. / Bibliography: leaves 304-374.
48

The kinetics of surfactant adsorption

Dalton, James Spencer January 1999 (has links)
No description available.
49

The degradation of refractory mineral oil residues using bioreactors

Osman, Suhana Hanum January 1998 (has links)
This thesis is concerned with the biodegradation of oily sludges typically found at refinery sites as waste residues from the refining of mineral oil. Currently these type of wastes represent significant environmental risk. Current technology that addresses containment during treatment to regulate the release of volatile organic carbons and reduction of the polynuclear aromatic hydrocarbons in the sludge, is incineration. Incineration is a costly option and this research has shown that the same treatment standards as incineration is achievable through bioreactor treatment with the correct process and reactor design.
50

Sum-frequency spectroscopy of molecules at interfaces

Ward, Robert Neil January 1993 (has links)
No description available.

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