Effects of Lost Circulation Material on Cement Properties

Master's thesis in Petroleum engineeringThis study aims to find the effect lost circulation materials has on cement slurries through testing in viscometer, pressurised consistometer and static gel strength analyser at selected concentrations. A worksheet containing a basic cement slurry recipe was used as basis for comparison against the slurries containing lost circulation material. SafeCarb 250, OptiSeal II, OptiSeal IV and G-Seal were the materials used to obtain the results for this thesis. The chosen concentrations for lost circulation material were, by recommendation, 100 kg/m$^3$, 150 kg/m$^3$ and 200 kg/m$^3$. For the thickening time and compressive strength tests, only the highest and lowest concentrations were chosen. All three concentrations were used when conducting tests on the viscometer. The rheology of the slurries were tested in the viscometers subjected to surface and downhole conditions. It was found that OptiSeal II, containing both graphite and calcium carbonate, had 73,5\% higher viscosity and 15,24\% higher yield stress at surface conditions compared to the base slurry. G-Seal, containing coarse-sized graphite, had 100\% higher viscosity and 56,4\% higher yield stress at downhole conditions. OptiSeal IV, a calcium carbonate, showed the overall lowest values compared to the base slurry with 28,1\% lower yield stress at surface conditions, 32\% lower yield stress and 8,36\% lower viscosity at downhole conditions. Thickening times were tested in a pressurised consistometer. Tests showed that the addition of SafeCarb 250, a calcium carbonate, decreased thickening time with 18\% as concentrations of SafeCarb increased. Compressive strengths were tested in a static gel strength analyser. All materials containing calcium carbonate achieved a higher compressive strength than the base slurry. OptiSeal II was 47,5\% higher than base slurry on the highest concentration. G-Seal had a 34\% lower compressive strength on the lowest concentration but exceeded the base slurry again at the highest concentration

Demand for Micro Life Insurance in Sri Lanka: Impact of Social Capital and Religion

Micro-life insurance provides protection against small premiums to low-income people in developing countries. Demand, however, is very moderate. The aim of this empirical work is to explain, how social capital and religion affect life insurance demand in developing countries using the example of Sri Lanka. Social networks allow for access to information, money, or innovation in an environment where infrastructure is not well functioning or less developed. Thus, social networks shape both, the consumption and the risk management behavior of individuals. In addition, cross-country studies show that the religion of Islam has a negative impact on life insurance consumption. This research follows a mixed-method research approach to study the role of social capital and religion on micro life insurance demand. The qualitative focus group discussions and the quantitative household surveys were conducted in the Eastern province of Sri Lanka in 2013. This work identifies three mechanisms through which social capital influences the demand for micro-life insurance: imitation, information exchange, informal risk sharing. People buy a micro-life insurance if they know an insured person. Informal risk management practices crowd-out formal micro-life insurance and the exchange between friends, family members or neighbors can reduce consumption if prior negative experiences weaken the confidence in the insurance promise. Regarding religion, the qualitative study shows that Muslims are reluctant to buy conventional insurance as they perceived it as a financial product contradicting with their religion. This study confirms that the financial situation contributes significantly to the purchase decision. It further found, that people are motivated to sign-up for micro life insurance by the perception to support other people in need with their purchase

Sovereignty and Armed Intervention in Libya 2011

This thesis will examine the implications the United Nations Security Council Resolution 1973 (2011) poses to sovereignty and its current understanding in relation to military intervention for the protection of civilians in an internal armed conflict. Resolution 1973 provides an opportunity to examine: the development of sovereignty from its earliest inception to its position within the modern international system of states; the challenge humanitarian intervention posed to accepted principles of sovereignty, non-interference and the use of force; the recent addition of the concept of the Responsibility to Protect which re-conceptualised sovereignty as responsibility; and the Security Council's established practice in relation to authorising armed intervention, which is integral to this thesis. Supporting this body of work is the Charter of the United Nations (1945) which articulates the body of rules that states are guided by in matters of international peace and security, and the protection of human rights, and which also determines the parameters of Security Council action. This thesis aims to establish that Resolution 1973 is a substantial contribution to the incremental development of sovereignty and how it is currently understood within international law

Methodical selection of thermal conductivity models for porous silica-based media with variation of gas type and pressure

If the effective thermal conductivity of a silica powder in any gas atmosphere is to be calculated analytically, one is faced with a whole series of decisions. There are a lot of different models for the gas thermal conductivity in the pores, the thermal accommodation coefficient or the effective thermal conductivity itself in the literature. Furthermore, it has to be decided which input parameters should be used. This paper gives an overview and recommendations as to which calculation methods are best suited for the material classes of precipitated silica, fumed silica, silica gel and glass spheres. All combinations of the described methods result in a total of 2800 calculation models which are compared with pressure-dependent thermal conductivity measurements of 15 powdery materials with 7 different gases using Matlab computations. The results show that with a model based on a spherical unit cell, which considers local Knudsen numbers, the measuring points of all powder-gas combinations can be determined best with an average variance of about 18.5%. If the material class is known beforehand, the result can be predicted with an average accuracy of about 10% with the correspondingly determined methods

Frauenarbeit im unterentwickelten Kapitalismus

Der Subsistenzsektor in Ländern des peripheren Kapitalismus ist weder durch die Modernisierungstheorien, deren Bankrott schon häufig erklärt, deren Anwendung aber doch praktiziert wird, noch durch den Theorieansatz der strukturellen Heterogenität oder des ungleichen Tausches in zureichendem Maß erfaßt worden. Die Ambivalenz der Teilauflösung des Subsistenzsektors einerseits, seiner Aufrechterhaltung andererseits und das Wissen von der kapitalistischen als der dominanten Produktionsweise, sagt wenig über die vorherrschenden Beziehungen und die Produzenten innerhalb dieses Sektors aus. Hinlänglich unbekannt war bis vor kurzem, daß die Frau in vielen Regionen der Dritten Welt die Hauptarbeitskraft im Subsistenzsektor der Landwirtschaft ist.Frauen tragen die Hauptlast der Unterentwicklung in Ländern des peripheren Kapitalismus; sie werden zum Verharren im traditionellen, stagnanten Subsistenzsektor gezwungen, während die Männer eher migrieren und zumindest tendenziell in den kapitalistischen Sektor Eingang finden. Diese von un~ aufgestellten Thesen sollen im Folgenden auf zwei einander ergänzenden Ebenen ausgeführt und belegt werden

Passive room conditioning using phase change materials—Demonstration of a long-term real size experiment

The thermal properties of lightweight buildings can be efficiently improved by using phase change materials (PCMs). The heat storage capacity of the building can be extended exactly at the desired temperature level, which leads to an enormous increase in residential comfort. This is shown in the present paper using the example of a prefabricated wooden house. The house was divided into two identical rooms. One of them was equipped with almost one ton of phase change material based on salt hydrates with a melting temperature of approx. 21°C. The material was encapsulated in 1-l Polyethylene containers and installed in two back-ventilated layers inside of the walls. The house was monitored for a period of 87 days in terms of temperatures, solar radiation and air velocity inside the PCM wall system. A considerable temperature buffering could be observed in the PCM room compared to the reference room. An overall reduction of the temperature fluctuations of 57% and a reduction of the day/night fluctuations of 62% compared to the reference room could be obtained. In addition, a prediction regarding the energy demand of such buildings is discussed on the basis of a simulation program. Thus, the annual cooling capacity can be reduced by 36.5% compared to the regular timber construction technique by introducing PCM. Furthermore, the good correlation of the simulation results with the experimental ones allows using the simulation as a tool to design a house with additional thermal storages

Comparison of Two Different Designs of a Scraped Surface Crystallizer for Desalination Effect and Hydraulic and Thermodynamic Numbers

The design of a desalination plant is most important if the desired product purity has to be as high as possible. This is also true for freeze crystallization plants. A correct solid-to-liquid ratio has to be ensured when pressing is used as a post-treatment. Thus, the dependence of the overall plant design on the achieved ice quality but also on different hydraulic and thermodynamic numbers is important. In this research, a scraped screw crystallizer plant is presented and examined for two different screw designs. Experiments with a low initial concentration, as for the usage to desalinate groundwater to gain it as process water, were conducted. Furthermore, solutions with high initial concentrations simulating seawater to produce potable water were used as another set of test solutions. The findings showed that neither of the screw designs is more favorable than the other, but it is important to have a plant design fitting the existing parameters on site

Empirical investigation to explore potential gains from the amalgamation of Phase Changing Materials (PCMs) and wood shavings

The reduction of gained heat, heat peak shifting and the mitigation of air temperature fluctuations are some desirable properties that are sought after in any thermal insulation system. It cannot be overstated that these factors, in addition to others, govern the performance of such systems thus their effect on indoor ambient conditions. The effect of such systems extends also to Heating, Ventilation and Air-conditioning (HVAC) systems that are set up to operate optimally in certain conditions. Where literature shows that PCMs and natural materials such as wood-shavings can provide efficient passive insulation for buildings, it is evident that such approaches utilise methods that are of a degree of intricacy which requires specialist knowledge and complex techniques, such as micro-encapsulation for instance. With technical and economic aspects in mind, an amalgam of PCM and wood-shavings has been created for the purpose of being utilised as a feasible thermal insulation. The amalgamation was performed in the simplest of methods, through submerging the wood shavings in PCM. An experimental procedure was devised to test the thermal performance of the amalgam and compare this to the performance of the same un-amalgamated materials. Comparative analysis revealed that no significant thermal gains would be expected from such amalgamation. However, significant reduction in the total weight of the insulation system would be achieved that, in this case, shown to be up to 20.94%. Thus, further reducing possible strains on structural elements due to the application of insulation on buildings. This can be especially beneficial in vernacular architectural approaches where considerably large amounts and thicknesses of insulations are used. In addition, cost reduction could be attained as wood shavings are significantly cheaper compared to the cost of PCMs