Análise e modelagem do escoamento transitório de fluidos de perfuração

Drilling fluids present a thixotropic behavior and they usually gel when at rest. The sol-gel transition is fundamental to prevent the deposit of rock fragments, generated by drilling the well, over the drill bit during eventual stops. Under those conditions, high pressures are then required in order to break-up the gel when circulation is resumed. Moreover, very high pressures can damage the rock formation at the bottom of the well. Thus, a better understanding of thixotropy and the behavior of thixotropic materials becomes increasingly important for process control. The mechanisms that control thixotropy are not yet well defined and modeling is still a challenge. The objective of this work is to develop a mathematical model to study the pressure transmission in drilling fluids. This work presents a review of thixotropy and of different mathematical models found in the literature that are used to predict such characteristic. It also shows a review of transient flows of compressible fluids. The problem is modeled as the flow between the drillpipe and the annular region (space between the wall and the external part of the drillpipe). The equations that describe the problem (mass conservation, momentum balance, constitutive and state) are then discretized and numerically solved by using a computational algorithm in Fortran. The model is validated with experimental and numerical data obtained from the literature. Comparisons between experimental data obtained from Petrobras and calculated by three viscoplastic and one pseudoplastic models are conducted. The viscoplastic fluids, due to the yield stress, do not fully transmit the pressure to the outlet of the annular space. Sensibility analyses are then conducted in order to evaluate the thixotropic effect in pressure transmission.

A racionalização das condições de trabalho nos hospitais: uma análise crítica baseada em relatos de ginecologistas obstetras e pediatras atuantes na urgência e emergência

Hospitals are a big part of the service sector. Thus, such institutions are highly influenced by the logic of the capitalist accumulation, technology and forms of labor organization, especially by private organizations. Starting with the restructuring process motion and incorporation of technologies, many changes in the working process occur, therefore, the activities of medical professionals as well. During the preparation of this research items regarding the banalization of evil were identified. This banalization and resignation of the professionals face to violence are caused by the adoption of collective defense strategies. Therefore, this research aims to analyze how the rationalization of working conditions by gynecologists obstetricians and pediatricians working in the emergency rooms of public and private hospitals in Curitiba and metropolitan region occurs. An approach of mixed methods was used as methodological procedures. The naturalization of violence, the suffering which professionals are submitted to, are combined with the political and ideological control, bureaucratic control, the imaginary built about hospitals and collective defense strategies. It is therefore possible to understand that labor conditions of gynecologists obstetricians and pediatricians in emergency rooms are rationalized. When social injustice is naturalized, political strategies for changes are not possible. For this reason, the first step is to gather awareness, there is a need to unveil the reality, to understand the phenomena at its core and discard superficialities. It is also necessary that the actions and expressions of indignation to come hand in hand with political actions in order to change to happen.