Experimental investigation of drilling fluid formulations and processing methods for a riser dilution approach to dual density drilling

Oil and natural gas resources in the deepwater Gulf of Mexico are important for the U.S. economy, but development is limited by high costs. Dual density drilling concepts that result in wellbore pressure gradients similar to the natural subsurface gradients can simplify well designs and reduce costs. Riser dilution may be an economical means of achieving such a system. This system would use a low density fluid to dilute the weighted wellbore fluid and give an intermediate density fluid in the riser. Two key concerns addressed in this study are whether a drilling fluid can be formulated that will suspend solids and transport cuttings after dilution and whether the fluid returning from the riser can be separated into wellbore and dilution fluids for a continuous process. The first concern was addressed by laboratory testing of synthetic-base drilling fluids. The wellbore, riser, and dilution fluids were formulated with the same synthetic fluid to water ratio and liquid phase product concentrations with only the barite concentration, and therefore density, being different. Formulations with good emulsion stability over the maximum density range needed for real deepwater applications were developed. However, appropriate rheologies for the extreme case of 17.0 ppg wellbore fluid and 9.5 ppg riser fluid were not achieved with laboratory muds. Separation testing was conducted to address the second concern using a laboratory centrifuge and hydrocyclones. The laboratory centrifuge demonstrated that practically all barite could be removed from the dilution stream and retained in a wellbore stream, but also that the wellbore stream rheologies were excessively high. Hydrocyclone results implied the need for two stages of separation. The most successful two stage trial gave less contrast in densities than the laboratory centrifuge, but gave better rheologies and emulsion stabilities than either the laboratory fluid or the laboratory centrifuge tests. Also, the rheologies from hydrocyclone testing were only slightly less than the rheology values considered necessary for a working riser dilution system. Both the density contrast and the rheologies were also close to the best centrifuge results published by others working on similar systems

CONSTRUCTING COLDSTREAM: SUSTAINABILITY AND THE POLITICS OF LOCAL ECONOMIC DEVELOPMENT

This thesis explores the evolution of the Coldstream Research Campus, a high-tech research park operated by the University of Kentucky. Conceived of in the late 1980s and built in 1992, Coldstream was expected to become the „economic engine‟ of central Kentucky through the commercialization of applied scientific and technological research coming out of the university. Twenty years later, with Coldstream having failed to live up to expectations, the university initiated the process of updating the Coldstream Master Plan to incorporate a decided emphasis on the concept of sustainability. Through a mix of archival research and semi-structured interviews, this thesis argues that the newfound emphasis on sustainability is important insofar as it opens up the possibility for perpetuating the existence of the Coldstream Research Campus as a real estate development, even in spite of its failures in other arenas

Doctor of Philosophy

dissertationLow back pain (LBP) is a common and costly problem. Among the top primary care research priorities are identifying prognostic subgroups of patients with LBP and identifying specific management strategies based on relevant subgroups. The Start Back Screening Tool (SBST) is a primary care decision tool that stratifies patients into prognostic subgroups based on the patient's risk for prolonged disability. Other subgrouping strategies screen for patients who fit a prediction rule (CPR) that may identify them as likely to respond to spinal manipulation (SM). It is unclear whether patients who are stratified by the SBST (high- and medium-risk) and who meet a CPR respond differentially to SM with exercise based on their risk stratification. In a secondary analysis of a randomized controlled trial, we found no 2-way interactions between risk stratification and treatment group at 4-week, 3-month or 1-year time points for disability or pain, indicating that the effects of treatment were no different between the medium- and high-risk groups. When we examined the effects of treatment separately within each risk subgroup, SM with exercise was superior to usual care at 3 months for disability and pain in those categorized as high-risk (mean difference = 3.95, 95% CI: 0.02, 7.87). After controlling for covariates, the SBST accounted for 2.4% (β = 4.25, p = 0.035) of the variance in the 4-week disability. In the same group of patients, we explored the relationship between the SBST and treatment expectations. Expectations of benefit from ten commonly used interventions for LBP were represented by four principal components: Exercise, Passive, Rest/Medication and Surgery). There were no associations between the components and the SBST (high versus medium- and low-risk). Finally, we retrospectively examined the influence of a mental health (MH) comorbidity on LBP-related healthcare costs in new consulters to primary care for LBP. Interaction terms between mental health comorbidity and patient factors were explored as contributors to predicting total costs. Individuals with a comorbid MH condition had higher LBP-related costs than those without. Males with a MH comorbidity experienced greater LBP-related healthcare costs than females (mean difference = $1077.26 USD, 95% CI = 428.10 - 1776.43)

The Urban Geographical Imagination in the Age of Big Data

This paper explores the variety of ways that emerging sources of (big) data are being used to re-conceptualize the city, and how these understandings of what the urban is shapes the design of interventions into it. Drawing on work on the performativity of economics, this paper uses two vignettes of the ‘new urban science’ and municipal vacant property mapping in order to argue that the mobilization of Big Data in the urban context doesn’t necessarily produce a single, greater understanding of the city as it actually is, but rather a highly variegated series of essentialized understandings of the city that render it knowable, governable and intervene-able. Through the construction of new, data-driven urban geographical imaginaries, these projects have opened up the space for urban interventions that work to depoliticize urban injustices and valorize new kinds of technical expertise as the means of going about solving these problems, opening up new possibilities for a remaking of urban space in the image of these sociotechnical paradigms. Ultimately, this paper argues that despite the importance of Big Data, as both a discourse and practice, to emerging forms of urban research and management, there is no singular or universal understanding of the urban that is promoted or developed through the application of these new sources of data, which in turn opens up meaningful possibilities for developing alternative uses of Big Data for understanding and intervening in the city in more emancipatory ways

What influences the Changes in REIT CEO Compensation?: Evidence from Panel Data

This study examines what influences the changes in REIT CEO compensation using the following performance measures: average three-year total returns to shareholders, market value added, Tobin's q, and change in funds from operations. In addition, we examine the impact of managerial power on the change in compensation. Unbalanced panel data is employed to capture both the time-series and cross-sectional effects. The empirical evidence indicates that firm performance and size do not influence the change in CEO salary, while risk, tenure, title, ownership, and age have significant impacts. Contrary to previous findings and a priori expectations, bonuses are not influenced by risk, size, or CEO power; however, they are influenced by performance. Option awards are affected by performance and CEO power.

The role of anaerobic digestion in the sustainable treatment of yeast related food industry waste

The worldwide yeast extract business is large and may increase with the interest in natural products and nutrients. The wastes from the yeast extract industry have traditionally been used as animal food or soil injection for agricultural benefit. This process is now being challenged and is experiencing increasing costs therefore alternative options for disposal routes are being considered. The poor biodegradability of activated sludge cell walls is well known and it has been suggested that the rigid, double layered yeast cells will be even more recalcitrant. Previous work reviewed in the thesis, had indicated yeast cell walls are some of the most refractory natural microbes in comparison, for example with activated sludge. The thesis revisits the issue of solids hydrolysis and in particular with a waste containing yeast cell walls as model solids. The literature review discusses previous work on the treatment of yeast containing wastes, including reactor designs and potential pre-treatments. It covers the work done on the fundamental characteristics of solids which might affect biodegradation rates, e.g. particle size, cross linking, rigidity and viscosity. Laboratory experiments were conducted and the results analysed from batch biodegradability testing and continuous simulation trials comparing anaerobic reactors. These were CSTR, Filters and UASB the latter noted for its vulnerability to solids. Laboratory work is also reported on the potential for ultrasonic, thermal and acclimatization to improve degradation rates. Utilisation of ultrasonic pre-treatment at 20,000 KHz, increased soluble organic carbon from between 14 to 120% dependant upon power and exposure time period. The results also showed that continuous recycle at low power produced the best results with increased gas yield and organic conversion from a lower solids retention. Results are also reported from onsite pilot trials using a 25m3 UAF digester and an analysis of previously unreported full scale yeast processing plants in the UK. These results confirmed that solids (cell) degradation rates were low. In conclusion the thesis suggests the degradability of the yeast cells are linked to their unique cell walls. Anaerobic digestion does give organic conversion albeit with long HRT's. The use of ultrasonics as a pre-treatment process enhances this conversion and improves gas yield