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.

Elisión y clandestinidad en la escritura de Erri de Luca: estrategias de la ocultación, una traducción al español de Tre Cavalli

El objetivo de este trabajo es proponer una nueva traducción al español de la novela Tre Cavalli, del escritor italiano Erri De Luca (Nápoles, 1950). Para llevar a cabo la traducción de esta novela italiana, en primer lugar se delineará la figura del escritor Erri De Luca, con unas noticias sobre su biografía y las obras publicadas en italiano, luego se centrará la atención en Tre Cavalli. Será fundamental, en relación a este extremo, conocer el argumento de la novela y la estructura general del texto, dos elementos funcionales al proceso de traducción. El trasfondo histórico en el que se enmarca Tre Cavalli es la dictadura militar argentina del Proceso de Reorganización Nacional (1976-1983). Por la especial estructura narrativa de la novela, que nunca revela claramente el período histórico al que se refiere, será necesario proporcionar informaciones sobre las causas y las consecuencias de los acontecimientos que caracterizaron esa época argentina y así explicitar el contexto de la novela. En este trabajo se quiere también analizar el caso editorial de Tres caballos, traducción española de la novela italiana publicada en 2002 por la editorial Akal y descatalogada por la editorial misma en poco tiempo. Por lo tanto, se presentará una investigación sobre la recepción de Erri De Luca en España como autor de novelas y un análisis del caso de descatalogación de Tres caballos, avanzando hipótesis basadas en la teoría de la estética de la recepción de Robert Hans Jauss (1921-1977). Después de haber recogido las informaciones necesarias sobre los elementos extra – textuales de la novela, para la nueva traducción al español será necesario también identificar las peculiaridades del texto que pueden representar ‘problemas’ de traducción a la hora de la creación del texto de llegada, analizando los rasgos textuales más especiales, con un enfoque profundizado en la técnica narrativa de la elisión. Se tratará de una propuesta de traducción que se fija como objetivo principal prestar el mayor respeto a la identidad del texto, a sus peculiaridades a las de su autor y, al mismo tiempo, anular las barreras de las diferencias idiomáticas y culturales para alcanzar la difícil síntesis entre la materia original el contenido de la obra y su mejor recreación en la lengua de llegada.

Evaluación de metodologías de formulación de mezclas para el control de pérdidas de circulación durante la perforación de pozos geotérmicos

El trabajo de graduación describe una metodología para mitigar un problema bastante común durante la perforación de pozos geotérmicos, dicho problema se conoce como pérdida de circulación y ocurre cuando el fluido de perforación en vez de ascender por el espacio anular se pierde en las formaciones ya perforadas. La solución que se plantea para esta problemática, es el uso de materiales de pérdida de circulación (LCM´s), para ello se propone diez píldoras obturantes con diferentes combinaciones de LCM´s. En primera instancia las píldoras son sometidas a un análisis técnico-operativo, compuesto de pruebas fisicoquímicas a nivel de laboratorio tales como: Prueba de pH, alcalinidad, densidad, filtrado, análisis reológico, etc. Posteriormente se procede con un análisis económico y ambiental para que de esa forma se escojan aquellos lodos o píldoras que puedan tener un mejor desempeño durante las pérdidas de circulación. Es importante mencionar que no se realizaron pruebas in-situ en ningún campo geotérmico y que el análisis planteado es a nivel de laboratorio como una primera aproximación

Influência da vermiculita expandida na resistência à compressão e reologia de pastas cimentantes de poços de petróleo

Several problems related to the loss of hydraulic seal in oilwells, causing gas migration and/or contamination of the production zone by water, have been reported. The loss of the hydraulic seal is a consequence of cracks which can be occasioned either by the invasion of gas during the wait on cement or by the expansion of the casing causing the fracture of the cement sheath. In case of the pressure of the formation is higher than the pressure in the annulus, gas can migrate into the slurry and form microannulus, which are channels where gas migrates after the cement is set. Cracks can be also occasioned by the fracture of the cement sheath when it does not withstand the thermal and dynamic loads. In reservoirs where the oil is heavy, steam water injection operation is required in order to get the oil flowing. This operation increases the temperature of the casing, and then it expands and causes the fracture of the cement sheath in the annulus. When the failures on the cement are detected, remedial cementing is required, which raise costs caused by the interventions. Once the use of cement in the construction civil sector is older than its use in the petroleum sector, it is common to bring technologies and solutions from the civil construction and apply them on the petroleum area. In this context, vermiculite, a mineral-clay widely encountered in Brazil, has been used, on its exfoliated form, in the civil construction, especially on the manufacture of lights and fireproof concretes with excellent thermal and acoustical properties. It has already been reported in scientific journals, studies of the addition of exfoliated vermiculite in Portland cements revealing good properties related to oilwell cementing operations. Thus, this study aimed to study the rheological behavior, thickening time, stability and compressive strength of the slurries made of Portland cement and exfoliated vermiculite in 5 different compositions, at room temperature and heated. The results showed that the compressive strength decreased with the addition of exfoliated vermiculite, however the values are still allowed for oiwell cementing operations. The thickening time of the slurry with no exfoliated vermiculite was 120 min and the thickening time of the slurry with 12 % of exfoliated vermiculite was 98 min. The stability and the rheological behavior of the slurries revealed that the exfoliated vermiculite absorbed water and therefore increased the viscosity of the slurries, even though increasing the factor cement-water. The stability experiment carried out at 133 ºF showed that, there was neither sedimentation nor reduction of the volume of the cement for the slurry with 12 % of exfoliated vermiculite. Thus, the addition of exfoliated vermiculite accelerates the set time of the cement and gives it a small shrinkage during the wait on cement, which are important to prevent gas migration

Adição de vermiculita expandida mícron em pastas de baixa densidade para cimentação de poços de petróleo

The northeastern region of Brazil has a large number of wells producing oil using a method of secondary recovery steam injection, since the oil produced in this region is essentially viscous. This recovery method puts the cement / coating on thermal cycling, due to the difference in coefficient of thermal expansion between cement and metal coating causes the appearance of cracks at this interface, allowing the passage of the annular fluid, which is associated with serious risk socioeconomic and environmental. In view of these cracks, a correction operation is required, resulting in more costs and temporary halt of production of the well. Alternatively, the oil industry has developed technology for adding new materials in cement pastes, oil well, providing high ductility and low density in order to withstand the thermo-mechanical loads generated by the injection of water vapor. In this context, vermiculite, a clay mineral found in abundance in Brazil has been applied in its expanded form in the construction industry for the manufacture of lightweight concrete with excellent insulation and noise due to its high melting point and the presence of air in their layers lamellar. Therefore, the vermiculite is used for the purpose of providing low-density cement paste and withstand high temperatures caused by steam injection. Thus, the present study compared the default folder containing cement and water with the folders with 6%, 8% and 10% vermiculite micron conducting tests of free water, rheology and compressive strength where it obtained the concentration of 8 % with the best results. Subsequently, the selected concentration, was compared with the results recommended by the API standard tests of filtered and stability. And finally, analyzed the results from tests of specific gravity and time of thickening. Before the study we were able to make a folder with a low density that can be used in cementing oil well in order to withstand the thermo-mechanical loads generated by steam injection

Constitución y democracia: la cuadratura del círculo

Sin lugar a dudas, uno de los debates teóricos y empíricos determinantes de la filosofía política del siglo XXI es el de la democracia. Se encuentran diferentes concepciones de la democracia dependiendo de la filosofía pública subyacente en la teoría que respalda el sistema político. Una es la conservadora, de tinte elitista, que desconfía de la intervención ciudadana en los asuntos públicos, debido a los rasgos de irracionalidad y las tendencias plebiscitarias que caracterizan el accionar de las mayorías; otra visión opuesta es la populista, que tiene como punto de partida una actitud de confianza en las capacidades cívicas de las mayorías que actúan colectivamente y de su tendencia a actuar siempre de manera racional y, encontramos, además, la concepción deliberativa de la democracia que parte también de una actitud de confianza en torno a las capacidades de la ciudadanía, pero sin la necesidad de presuponer una conexión ontológica, necesaria, entre la voluntad mayoritaria y la razón. A su vez, la teoría nos ofrece dos grandes corrientes de pensamientos en lo que al control judicial de las leyes se refiere. De un lado, están los teóricos que aceptan la revisión judicial de las leyes y, con ello, que frente a los aspectos fundamentales que regulan la vida colectiva los jueces tengan la “última palabra”, pese a su carácter contramayoritario; de otro lado, están los teóricos críticos del control judicial de las leyes y del hecho de que los jueces tengan la última palabra en los aspectos fundamentales de la organización de la vida social. Esta última corriente de pensamiento, apela al carácter contramayoritorio del poder judicial para cuestionar el hecho de que en una democracia los jueces tengan la posibilidad de declarar la inconstitucionalidad de una norma jurídica derivada de los órganos políticos que eligen las mayorías y, por tanto, anular sus efectos. Estas temáticas, cuya actualidad es indiscutible, reclaman de la academia un análisis desde el punto de vista jurídico y político del papel del poder judicial en los sistemas democráticos contemporáneos. En este quehacer se abre paso el VI Seminario Internacional de Teoría General del Derecho y el libro que el lector hoy tiene en sus manos, que parte de las experiencias investigativas de sus autores, convirtiéndose en una obra que aporta al debate contemporáneo en torno a la cuadratura del círculo: Constitución y democracia. Son, pues, doce trabajos de autores nacionales e internacionales que se dejan en manos del lector y de su juicio.

Adição do resíduo de biomassa da cana-de-açúcar em pastas para cimentação de poços petrolíferos produtores de óleos pesados

The Potiguar basin has large fields of viscous oil where the used method for recovering is based on vapor injection; this operation is carried out by injecting vapor in the oilwell directly, without the protection of a revetment through thermal insulation, what causes its dilation and, consequently, cracks in the cement placed on the annular, and lost of hydraulic insulation; this crack is occasioned by the phenomenon of retrogression of the compressive resistance due to the conversion of the hydrated calcium silicate in phases calcium-rich, caused by the high temperatures in the wells, subjected to thermal recuperation. This work has evaluated the application of composite pastes with addition of residue of biomass of ground sugar-cane bagasse as anti-retrogression mineral admixture for cementation of oil-wells subjected to thermal recuperation. The addition of the mineral residue was carried out considering a relative amount of 10, 20, 30, 40 and 59% in relation to cement mass, trying to improve the microstructure of the paste, still being developed a reference paste only with cement and a paste with addition of 40% of silica flour - renowned material in the oil industry as anti-retrogression additive. Pozzolanic activity of the ash was evaluated through XRD, TG/DTG, as the resistance to compression, and it was also determined the physical and mechanical behavior of the pastes when submitted to cure at low temperatures (22 and 38º C); besides it was evaluated the behavior of the pastes when submitted to two cycles of cure at high temperature (280ºC) and pressure (7 MPa). It was verified that the ash of the sugar-cane biomass presents pozzolanic reaction and has great efficiency in decrease the permeability of the paste by filler effect, as well as that addition of ash in a relative amount of 10, 20 e 30% increases cured compressive resistance at low temperatures. It was also showed that the ash in a relative amount of 40% and 59% has very significant efficiency as anti-retrogression additive, since it prevents the decrease of compressive resistance and forms hydrated calcium silicate type xenotlita and tobermorita which have more resistance and stability in high temperatures

Gestation and breastfeeding in schistosomotic mothers differently modulate the immune response of adult offspring to postnatal Schistosoma mansoni infection

Schistosoma mansoni antigens in the early life alter homologous and heterologous immunity during postnatal infections. We evaluate the immunity to parasite antigens and ovalbumin (OA) in adult mice born/suckled by schistosomotic mothers. Newborns were divided into: born (BIM), suckled (SIM) or born/suckled (BSIM) in schistosomotic mothers, and animals from noninfected mothers (control). When adults, the mice were infected and compared the hepatic granuloma size and cellularity. Some animals were OA + adjuvant immunised. We evaluated hypersensitivity reactions (HR), antibodies levels (IgG1/IgG2a) anti-soluble egg antigen and anti-soluble worm antigen preparation, and anti-OA, cytokine production, and CD4+FoxP3+T-cells by splenocytes. Compared to control group, BIM mice showed a greater quantity of granulomas and collagen deposition, whereas SIM and BSIM presented smaller granulomas. BSIM group exhibited the lowest levels of anti-parasite antibodies. For anti-OA immunity, immediate HR was suppressed in all groups, with greater intensity in SIM mice accompanied of the remarkable level of basal CD4+FoxP3+T-cells. BIM and SIM groups produced less interleukin (IL)-4 and interferon (IFN)-g. In BSIM, there was higher production of IL-10 and IFN-γ, but lower levels of IL-4 and CD4+FoxP3+T-cells. Thus, pregnancy in schistosomotic mothers intensified hepatic fibrosis, whereas breastfeeding diminished granulomas in descendants. Separately, pregnancy and breastfeeding could suppress heterologous immunity; however, when combined, the responses could be partially restored in infected descendants.

Formulação de pastas cimentícias com adição de suspensões de quitosana para cimentação de poços de petróleo

Primary cementing is one of the main operations in well drilling responsible for the mechanical stability and zonal isolation during the production of oil. However, the cement sheath is constantly under mechanical stresses and temperature variations caused by the recovery of heavy oil. In order to minimize fracture and wear of the cement sheath, new admixtures are developed to improve the properties of Portland cement slurries and avoid environmental contamination caused by leaking gas and oil. Polymers with the ability to form polymeric films are candidates to improve the properties of hardened cement slurries, especially their fracture energy. The present study aimed at evaluating the effect of the addition of a chitosan suspension on cement slurries in order to improve the properties of the cement and increase its performance on heavy oil recovery. Chitosan was dissolved in acetic ac id (0.25 M and 2 M) and added to the formulation of the slurries in different concentrations. SEM analyses confirmed the formation of polymeric films in the cementitious matrix. Strength tests showed higher fracture energy compared to slurries without the addition of chitosan. The formation of the polymeric films also reduced the permeability of the slurry. Therefore, chitosan suspensions can be potentially used as cementing admixtures for heavy oil well applications

Prostaglandinas e o movimento dentário

Dissertação para obtenção do grau de Mestre no Instituto Superior de Ciências da Saúde Egas Moniz

Avaliação da adição de Nanosílica e silicato de sódio em pastas de cimento para poços de petróleo com baixo gradiente de fratura

The oil wells cementing is a critical step during the phase of well drilling, because problems during the operation of slurry pumping and an incomplete filling of the annular space between the metal casing and the formation can cause the slurry loss. Therefore, the slurry adopted in primary cementing an oil well must be properly dosed so that these problems are avoided during its pumping. When you drill a well in a weak rock formation requires even more careful, because should be a limit of hydrostatic pressure exerted during cementation, that does not occur rock collapse. With the objective of performing the cementing of a well whose formation is weak or unconsolidated are employed lighter slurries. Thus, this study used slurries with sodium silicate and nano silica in concentrations of 0,1; 0,4; 0,7 e 1,0 gpc, in which the slurries with nano silica showed the rheological parameters higher concentrations of up to 0.7 gpc and for concentration of 1.0 the slurry with sodium silicate obtained the highest values, remaining above the limits for application in fields, mainly wells with low fracture gradient, because a significant increase in viscosity may result in an increase in pressure pumping in operations of secondary cementations. Furthermore, there was no decrease in strength with increasing concentration of additive. Then, it is possible use of these additives to formulate Lighter slurry

Avaliação do comportamento reológico de pastas de cimento para poços de petróleo com adição de plastificantes

The isolation of adjacent zones encountered during oilwell drilling is carried out by Portland-based cement slurries. The slurries are pumped into the annular positions between the well and the casing. Their rheological behavior is a very important component for the cementing process. Nowadays, several alternative materials are used in oilwell cementing, with goal the modification and the improvement of their properties, mainly the increase of the fluidity. And this can be reached by using plasticizers additives able to account for different oilwell conditions, yielding compatible cement slurries and allowing enough time for the complete cementing operation. If the rheological properties of the slurry are properly characterized, the load loss and flow regime can be correctly predicted. However, this experimental characterization is difficult. Rheological models capable of describing the cement slurry behavior must be capable of predicting the slurry cement deformation within reasonable accuracy. The aim of this study was to characterize rheologically the slurries prepared with a especial class of Portland cement, water and plasticizers based on lignosulfonate, melamine and polycarboxylate at temperatures varying from 27°C to 72°C. The tests were carried out according to the practical recommendations of the API RP 10B guidelines. The results revealed a great efficiency and the dispersive power of the polycarboxylate, for all temperatures tested. This additive promoted high fluidity of the slurries, with no sedimentation. High lignosulfonate and melamine concentrations did not reduce the rheological parameters (plastic viscosity and yield stress) of the slurries. It was verified that these additives were not compatible with the type of cement used. The evaluated rheological models were capable of describing the behavior of the slurries only within concentration and temperature ranges specific for each type of additive

Influência da vermiculita expandida na formulação de pastas leves para evitar a migração de gás em cimentação de poços petrolíferos

The gas migration during the cementing of wells is one of the main problems of oil wells engineering. Its occurrence can cause severe problems since shortly to loss of control of the well after cementation. Recently, 20/04/2010 In an accident of major proportions in the Gulf of Mexico, among other factors, faulty cementing operation provided the gas migration, causing the accident, in which 11 people died and 17 were injured occurred. Besides the serious consequences that can be caused by gas migration, remediation of the problem, which is made by injecting cement in damaged areas, usually involves additional costs and is not always effective. Therefore, preventing gas migration to be preferred. Some methods are used to prevent the migration of the pressurized gas as the annular space, application of pressure pulses, reducing the height of the cement column compressible cement pastes of low permeability, pastes and to control free filtered water, and binders of thixotropic cement expandable and flexible. Thus, the cement pastes used to prevent gas migration must meet the maximum these methods. Thus, this study aimed to formulate a cement paste to prevent gas migration, using the expanded vermiculite, and evaluate the behavior of the folder trials necessary for use in oil wells. Free water content, rheological properties, compressive strength, loss of liquid phase sedimentation of solids, specific weight, thickening time and gas migration: The following tests were performed. The results show that meets the specifications paste formulated for use in oil wells and the use of expanded vermiculite contribute to the absorption of free water, thixotropy and low density. The absorption of free water is proven to result in zero percentage test free water content, thixotropy is observed with the high value of the initial gel strength (Gi) in testing rheological properties and low density is proven in test weight specific

Cytomegalovirus and Langerhans Cell Histiocytosis: Is There a Link?

Background: Langerhans cell histiocytosis is a rare proliferative histiocytic disease of unknown etiology. Histologically, it is characterized by granuloma-like proliferation of Langerhans-type dendritic cells derived from bone marrow. Many investigators have suggested the possible role of viruses such as Epstein-Barr virus, human herpesvirus-6 (HHV-6), herpes simplex virus (HSV) types 1 and 2, and Cytomegalovirus in the pathogenesis of Langerhans cell histiocytosis. Objectives: In this study, we have investigated the presence of Cytomegalovirus in Langerhans cell histiocytosis in Iranian children. Patients and Methods: In this retrospective study, we have investigated the presence of Cytomegalovirus DNA expression, using paraffin-embedded tissue samples of 30 patients with Langerhans cell histiocytosis and 30 age and site-matched controls by qualitative Polymerase Chain Reaction (PCR) method. Results: No significant difference in prevalence of Cytomegalovirus presence between patients and controls was found. Cytomegalovirus was found by qualitative PCR in only 2 (6.66%) out of 30 patients and in 1 (3.3%) of 30 control samples with a P value of 1 (1.00 > 0.05) using chi-square test with OR: 2.07; 95% CI of OR: 0.18 - 24.15. Conclusions: Our findings do not support the hypothesis of a possible role for Cytomegalovirus in the pathogenesis of Langerhans cell histiocytosis.

Escola : família :matemática : que relações?

X Encontro da Seção de Matemática da Sociedade das Ciências da Educação, realizado na Consolação, Peniche em 2001