In the past, the oil and gas industry has typically used the single gradient system to drill wells offshore. With this system the bottom hole pressure was controlled by a mud column extending from the drilling rig to the bottom of the wellbore. This mud column was used to achieve the required bottom hole pressure. But, as the demand for oil and gas increased, the industry started exploring for oil and gas in deep waters. Because of the narrow margin between the pore and fracture pressures it is somewhat difficult to reach total depth with the single gradient system. This led to the invention of the dual gradient system. In the dual gradient method, heavy density fluid runs from the bottom hole to the mudline and a low density fluid from the mudline to the rig floor so as to maintain the bottom hole pressure. Several methods have been developed to achieve the dual gradient drilling principle. For this research project, we paid more attention to the liquid lift, dual gradient drilling (riser dilution method). This method of achieving dual gradient drilling was somewhat different from the others, because it does not utilize elaborate equipment and no major changes are made on the existing drilling rigs. In this thesis the technical feasibility of using the liquid lift method over the other methods of achieving dual gradient drilling was determined. A computer program was developed to simulate the wellbore hydraulics under static and dynamic conditions, injection rate and base fluid density required to dilute the riser fluid and finally, u-tubing phenomena. In this thesis we also identified some problems associated with the liquid lift method and recommendations were made on how these problems can be eliminated or reduced. Emphases were placed on the effect of u-tubing, injection rate of base fluid at the bottom of the riser and well control issues facing this system.

Field-proven solutions already exist to reduce the loss of gas production when liquid loading begins to occur. However, the choice of remedial technique, its feasibility, and its cost, vary considerably depending on a field's location, size export route, and the individual operator's experience. The selection of the best remedial technique and the timeframe within which the remedial action is undertaken are critical to a project's profitability. Although there are literature reviews available regarding solutions to liquid loading problems in gas wells, a tool capable of helping an operator select the best remedial option for a specific field case still does not exist. This thesis proposes a newly developed decision matrix to screen the possible remedial options available to the operator. The matrix can not only provide a critical evaluation of potential solutions to the problem of liquid loading in gas wells vis-à-vis the existing technical and economic constraints, but can also serve as a reference to operators for investment decisions and as a quick screening tool for the selection of production optimisation strategies. Under its current status of development, this new tool consists of a decision algorithm built around a decision tree. Unlike other data mining techniques, decision trees quickly allow for subdividing large initial datasets into successively smaller sets by a series of decision rules. The rules are based on information available in the public domain. The effectiveness of the matrix is now ready to be tested against real field datasets.

In the present study we investigate the use of polymer liquid crystal for holographic recording. Holographic patterns were produced by means of two-beam interference using an Ar+ laser. The polymer liquid crystal thin layers were prepared by injecting RM257 into cells through capillary action at 140¢XC where the RM257 mesogen was in isotropic state. By exposing the mesogenic layer to the laser interference patterns, we have successfully imprint holographic patterns into RM257 thin layers. In order to reach the best alignment, the intensity of laser beam, sample temperature, the spacial period and exposure time must be properly set.

RM257 consists of photoactive mesogenic end groups. By in situ polymerization of the mesogen, the optical information can be recorded into RM257 thin film. In this study, the RM257 thin films were exposed to a holography irradiation created using an Ar+ laser. The holography patterns have been found to be imprinted into the polymer thin films. The refractive efficiency can be increased when the sample temperature is properly controlled during holography irradiation. The work was started from the use of two beam interferometry, and further to use three beam interference. The molecular arrangement in the resultant polymer film and their function in optical modulation have been studied.

Discotic liquid crystal (LC) molecules have a structure that is comprised of a rigid aromatic core with side-chain molecules. Intermolecular £k-£k interactions force the tube to orient and form one-dimensional columnar structures which can act as molecular wires. In recent years, discotic LC molecules have been deposited on surfaces from solution to create the solid-state electronic elements used widely in solar cells, organic light-emitting diodes (OLED), organic photovoltaic, field-effect transistors (FET), and molecular wires. Different stacking morphologies can change the behavior of the material and thus will have potential for different applications. Hence, effective control over the stacking of the LC molecules on surfaces is important for optimizing the performance and effectiveness of LC-based electronic components and devices. This study has focused on LC molecules with acid and ester containing functional groups, and how these groups influence the stacking behavior on surfaces. Here, the self-aggregation behavior of the discotic LC ester in solution was investigated quantitatively by determining the concentration dependence of the 1H NMR chemical shifts. Our results showed that discotic LC ester has different self-aggregation behavior in CH2Cl2, THF and Benzene organic solvents. THF solvent showed the highest degree of aggregation, followed by CH2Cl2, and then benzene. We also studied the effects of (i) different solvents (THF, CH2Cl2, and Benzene), (ii) different surface functional groups (OH, CH3, NH2, SH, and diphenyl), and (iii) temperature, on the stacking phenomenon of discotic LCs on silicon surfaces. In part (i) our results showed that discotic LC ester had different morphologies on silicon surfaces due to differences in solvent polarity and evaporation rate. In part (ii), we observed that different surface functional groups did not affect the intermolecular interaction between either the ester- or acid-type LC molecules. For the acid-type LC, strong hydrogen bonding interactions with the surface caused the crystals to form rod-like fiber structures. However, the ester-type LC molecules formed ribbon-like stacks on the surfaces. For functional groups containing CH3 (more hydrophobic surfaces), we observed no LC molecules on the surface, which was likely due to the poor wettability of the solvents on OTS. In part (iii), we observed that both acid and ester discotic LCs formed large aggregates on the surfaces due to a ¡§ripening effect¡¨. With increased temperature, the molecules were able to overcome the wetting interaction with the surface and self-aggregate into three-dimensional clusters.

Includes bibliographical references (p. 103-109).

Thesis (Ph. D.)--Lehigh University, 2004. / Includes bibliographical references and vita.

Thesis (Ph. D.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 308-330). Also available in electronic version. Access restricted to campus users.

Title from PDF of title page (University of Missouri--Columbia, viewed on Feb 17, 2010). The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Dissertation advisor: Wouter Montfrooij. Vita. Includes bibliographical references.

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