Aditivos químicos e biológicos na ensilagem de cana-de-açúcar: 1. composição química das silagens, ingestão, digestibilidade e comportamento ingestivo

Avaliou-se o efeito da inclusão de aditivos na ensilagem de cana-de-açúcar (Saccharum officinarum L.) sobre a composição químico-bromatológica das silagens, o comportamento ingestivo, o consumo voluntário e a digestibilidade em bovinos de corte. Utilizaram-se cinco novilhos da raça Nelore providos de cânula ruminal, alocados em delineamento quadrado latino 5 ´ 5 e alimentados com dietas com 65% de volumoso na MS. Foram avaliadas cinco silagens (base úmida): controle - cana-de-açúcar sem aditivos; uréia - cana-de-açúcar + 0,5% uréia; benzoato - cana-de-açúcar + 0,1% de benzoato de sódio; LP - cana-de-açúcar inoculada com Lactobacillus plantarum (1 ´ 10(6) ufc/g MV); LB - cana-de-açúcar inoculada com L. buchneri (3,6 ´ 10(5) ufc/g forragem). A forragem foi armazenada em silos do tipo poço por 90 dias antes do fornecimento aos animais. A composição químico-bromatológica da cana-de-açúcar foi alterada após a ensilagem, em relação à cana-de-açúcar original, com redução no teor de carboidratos solúveis e na digestibilidade in vitro e elevação relativa nos teores de FDN e FDA. Os teores de etanol (0,30% da MS) e ácidos orgânicos (0,99% de ácido lático e 2,31% de acético) foram baixos e semelhantes entre as silagens. Os aditivos aplicados na ensilagem não promoveram alterações no consumo e na digestibilidade aparente da MS (7,2 kg/dia e 63,6%, respectivamente). O comportamento ingestivo dos animais também não foi alterado, com tempos médios de 230,6; 519,6 e 672,8 minutos/dia despendidos com ingestão de ração, ruminação e ócio, respectivamente. Os aditivos acrescidos à cana-de-açúcar promoveram pequenas alterações na maioria das variáveis avaliadas.

Aditivos químicos ou biológicos na ensilagem de cana-de-açúcar: 2. parâmetros ruminais e degradabilidade da matéria seca e das frações fibrosas

Objetivou-se avaliar o efeito da inclusão de aditivos na ensilagem de cana-de-açúcar (Saccharum officinarum L.) sobre a degradação de MS e de componentes da parede celular e sobre os parâmetros de fermentação ruminal em bovinos alimentados com dietas contendo essas silagens. Utilizaram-se cinco novilhos da raça Nelore providos de cânula ruminal, alocados em delineamento quadrado latino 5 ´ 5 e alimentados com dietas com 65% de volumoso (%) MS. Foram avaliadas cinco silagens (base úmida): controle - cana-de-açúcar, sem aditivos; uréia - cana-de-açúcar + 0,5% ureia; benzoato - cana-de-açúcar + 0,1% de benzoato de sódio; LP - cana-de-açúcar inoculada com Lactobacillus plantarum (1 ´ 10(6) ufc/g MV); LB - cana-de-açúcar inoculada com L. buchneri (3,6 ´ 10(5) ufc/g forragem). A forragem foi armazenada em silos do tipo poço por 90 dias antes do fornecimento aos animais. Os parâmetros ruminais foram afetados de forma moderada pelas silagens e tiveram forte efeito do horário de coleta de amostras. As concentrações molares médias dos ácidos acético, propiônico e butírico foram de 60,9; 19,3 e 10,2 mM, respectivamente. O ambiente ruminal proporcionado por dietas formuladas com silagens de cana-de-açúcar foi satisfatório e similar ao tradicionalmente observado em dietas contendo cana. O uso de aditivos na ensilagem influenciou, de forma não-significativa, a degradabilidade ruminal da MS e da MO, mas não alterou a degradabilidade ruminal da fração fibrosa. Os aditivos aplicados à cana-de-açúcar resultaram em pequenas alterações na maior parte das variáveis avaliadas. Apesar de a degradabilidade ruminal das silagens ter sido pouco afetada pelo uso de aditivos, os valores observados foram próximos aos observados para a cana-de-açúcar in natura.

Análise hidromecânica do problema de fraturamento hidráulico

Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Civil e Ambiental, 2016.

Adição de superplastificante e anti-segregante à base de CMC em pastas de cimento para Poços de Petróleo

Oil well cementing materials consist of slurries of Special class Portland cement dispersed in water. Admixtures can be used to provide the necessary fluidity, so the material can be efficiently pumped down as well as penetrate porous rocks with controlled filter loss. Construction admixtures can be used to modify the properties of oil well cements provided they can withstand and hold their properties at the higher than ambient temperatures usually encountered in oil fields. In civil construction, superplasticizer play the role of dispersants that reduce the facto r of water cement improve mechanical properties and fluidity of the cement, whereas anti-segregation agents improve the workability of the slurry. In the present study, oil well cement slurries were produced adding both a dispersant and an anti-segregation agent conventionally used in Portland CPII-Z-32 RS cement aiming at materials for primary cementing and squeeze operations. Three basic aspects were evaluated: fluidity, filter loss and the synergetic effect of the admixtures at two temperatures, i.e., 27°C and 56°C, following API RP 10B practical recommendations. The slurries were prepared using admixture concentrations varying from 2.60 Kgf/m3 (0.02 gallft3) to 5.82 Kgf/m3 (0.045 galJft3) BWOC. The density of the slurries was set to 1.89 g/cm3 (15.8 Ib/gal). 0.30 to 0.60% BWOC of a CMC-based anti-segregation agent was added to the cement to control the filter loss. The results showed that the addition of anti-segregation at concentrations above 0.55% by weight of cement resulted in the increased viscosity of the folders in temperatures evaluated. The increasing the temperature of the tests led to a reduction in the performance of anti-segregation. At concentrations of 5.20 kgf/m3 (0,040 gallft3) and 5.82 Kgf/m3 (0,045 gal/ft 3) observed a better performance of the properties evaluated in the proposed system. At low temperature was observed instability in the readings of rheology for all concentrations of anti-segregation. Contents that increasing the concentration of anti¬-segregation is limited concentrations greater than 0.55 % BWOC of the CMC in temperature analyzed. The use of the system with CMC promoted a good performance against the properties evaluated. The principal function of anti¬-segregation was optimized with increasing concentration of superplasticizer, at temperatures above the 2rC. The study of the behaviour of systemic additives, resulting in slurries of cement, which can be optimized face studies of other intrinsic properties in oil fields

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

Avaliação da influência do nacl em pastas de cimento portland para cimentação de poços de petróleo em zonas evaporíticas

One of the major current challenges for oilwell companies is the extraction of oil from evaporitic zones, also known as pre-salt basins. Deep reservoirs are found under thick salt layers formed from the evaporation of sea water. Salt layers seal the flow of oil from underneath rock formations, which store hydrocarbons and increase the probability of success in oil and gas exploration. Oilwells are cemented using Portland-based slurries to promote mechanical stability and zonal isolation. For pre-salt oilwells, NaCl must be added to saturate the cement slurries, however, the presence of salt in the composition of slurries affects their overall behavior. Therefore, the objective of the present study was to evaluate the effect of the addition of 5 to 25% NaCl on selected properties of Portland-based slurries. A series of tests were carried out to assess the rheological behavior, thickening time, free water and ultrassonic compressive strength. In addition, the slurries were also characterized by thermal analysis, X ray diffraction and scanning electron microscopy. The results showed that the addition of NaCl affected the thickening time of the slurries. NaCl contents up to 10% shortened the thickening time of the slurries. On the other hand, concentrations in excess of 20% not only extended the thickening time, but also reduced the strength of hardened slurries. The addition of NaCl resulted in the formation of a different crystalline phase called Friedel´s salt, where free chlorine is bonded to tricalcium aluminate

Desenvolvimento de pastas de cimento flexíveis para poços de petróleo submetidos à injeção de vapor utilizando látex do tipo SBR

Novel cementing materials formulations containing flexible polymeric admixtures have been studied aiming at improving the mechanical behavior of oil well cement slurries submitted to steam injection. However, research activities in this sector are still under development. The steam injected directly into the well causes casing dilation, which after a reduction in temperature, tends to return to its original dimensions, resulting in crack formation and hydraulic isolation loss of the well, which will result in shortening of well life. In this scenario, the objective of the present study was to evaluate the mechanical behavior of Portland-based slurries containing SBR latex, applied in oil well cementing of wells submitted to steam injection. Were formulated slurries with densities of 1.797 g/cm3 (15.0 lb/Gal) and 1.869 g/cm3 (15.6 lb/Gal), containing admixtures with a latex concentration of 0; 66.88; 133.76; 200.64 and 267.52 L/m3 (0, 0.5, 1.0, 1.5 and 2.0 gpc). Tests including rheology, fluid loss control, thickening time, API compressive strength and splitting tensile strength, beyond steam injection simulation. Microstrutural characteristics of the slurries were also performed (XRD, TG, FTIR and SEM). The results showed that increasing the polymer concentration increased in the rheological properties and fluid loss, and a decrease in the elasticity modulus of the cement slurries. The results obtained showed that the slurries can be applied in cementing operations of oil wells submitted to steam injection.

Otimização e análise mecânica de pastas geopoliméricas para uso em poços sujeitos à injeção cíclica de vapor

Oil wells subjected to cyclic steam injection present important challenges for the development of well cementing systems, mainly due to tensile stresses caused by thermal gradients during its useful life. Cement sheath failures in wells using conventional high compressive strength systems lead to the use of cement systems that are more flexible and/or ductile, with emphasis on Portland cement systems with latex addition. Recent research efforts have presented geopolymeric systems as alternatives. These cementing systems are based on alkaline activation of amorphous aluminosilicates such as metakaolin or fly ash and display advantageous properties such as high compressive strength, fast setting and thermal stability. Basic geopolymeric formulations can be found in the literature, which meet basic oil industry specifications such as rheology, compressive strength and thickening time. In this work, new geopolymeric formulations were developed, based on metakaolin, potassium silicate, potassium hydroxide, silica fume and mineral fiber, using the state of the art in chemical composition, mixture modeling and additivation to optimize the most relevant properties for oil well cementing. Starting from molar ratios considered ideal in the literature (SiO2/Al2O3 = 3.8 e K2O/Al2O3 = 1.0), a study of dry mixtures was performed,based on the compressive packing model, resulting in an optimal volume of 6% for the added solid material. This material (silica fume and mineral fiber) works both as an additional silica source (in the case of silica fume) and as mechanical reinforcement, especially in the case of mineral fiber, which incremented the tensile strength. The first triaxial mechanical study of this class of materials was performed. For comparison, a mechanical study of conventional latex-based cementing systems was also carried out. Regardless of differences in the failure mode (brittle for geopolymers, ductile for latex-based systems), the superior uniaxial compressive strength (37 MPa for the geopolymeric slurry P5 versus 18 MPa for the conventional slurry P2), similar triaxial behavior (friction angle 21° for P5 and P2) and lower stifness (in the elastic region 5.1 GPa for P5 versus 6.8 GPa for P2) of the geopolymeric systems allowed them to withstand a similar amount of mechanical energy (155 kJ/m3 for P5 versus 208 kJ/m3 for P2), noting that geopolymers work in the elastic regime, without the microcracking present in the case of latex-based systems. Therefore, the geopolymers studied on this work must be designed for application in the elastic region to avoid brittle failure. Finally, the tensile strength of geopolymers is originally poor (1.3 MPa for the geopolymeric slurry P3) due to its brittle structure. However, after additivation with mineral fiber, the tensile strength became equivalent to that of latex-based systems (2.3 MPa for P5 and 2.1 MPa for P2). The technical viability of conventional and proposed formulations was evaluated for the whole well life, including stresses due to cyclic steam injection. This analysis was performed using finite element-based simulation software. It was verified that conventional slurries are viable up to 204ºF (400ºC) and geopolymeric slurries are viable above 500ºF (260ºC)

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

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

Perceção da evasão e fraude fiscal em Portugal: um estudo sociológico

A presente dissertação versa sobre a análise da perceção da evasão e fraude fiscais em Portugal. A literatura internacional sublinha a existência de diversos fatores ou determinantes que influenciam a decisão do contribuinte cumprir ou não cumprir com as suas obrigações fiscais. Entre eles salientamos os fatores demográficos, económicos, culturais, sociológicos, psicológicos e técnicos (Torgler, 2006; Tsakumis, 2007; McGee, 2009). A nossa investigação pretende dar uma pequena contribuição para o estudo da relação entre os fatores sociológicos e os diversos comportamentos dos contribuintes em relação ao cumprimento ou não cumprimento fiscal. Para atingir estes objectivos, recorremos, para o efeito, a uma amostra heterogénea da população de contribuintes individuais portugueses, no sentido de aferir acerca do comportamento dos contribuintes em relação à atitude de cumprir ou não cumprir com o sistema tributário, bem como em relação aos fatores que influenciam essas mesmas atitudes. Da nossa análise podemos, em síntese, concluir que a evasão e fraude fiscais se encontram associadas a fatores como o género, a idade, o nível de escolaridade ou a profissão e actividade exercida, os quais refletem a realidade social do país. Verificou-se, ainda, que cerca um terço dos contribuintes inquiridos admitiu que a evasão fiscal é justificável em determinadas circunstâncias. Os principais argumentos justificativos da evasão fiscal estão associados à injustiça do sistema fiscal, à elevada carga tributária, ao desperdício ou má utilização do dinheiro dos impostos e à corrupção entre a classe política. Ao invés, um dos argumentos menos forte encontra-se relacionado com o facto de os contribuintes poderem vir a ser descobertos pelas autoridades fiscais, verificando-se, então, que este não é um elemento dissuasor da prática da evasão e fraude fiscais em Portugal.

Utilização de nanosílica como aditivo estendedor para pastas cimentantes de baixa densidade destinadas à cimentação de poços petrolíferos

Cementing operations are conducted at different times of the well s life and they have high importance, because the functions are fundamental to keep good properties during a long life of the well, such as, maintain the mechanical stability of the well, to promote the isolation hydraulic and support the tubing. In some situations, the rocky zones have low fractures pressures and require the use of lightweight slurries to prevent the hydrostatic pressure in the formation is greater than the pressure of fracture. There are three ways to reduce the density of cement slurries: exterders water additives, microspheres and foamed slurries. The most used extender water additive is sodium bentonite, which is a clay with a good capacity of water absorption and expansion of its volume, the main disadvantage of this additive is the reduction of the strength. Currently, the use of nanoscale particles has received special attention, mainly because they get new functionalities. Following this trend, this paper aims to use a colloidal solution of nano-silica as an exterders water additives for use in oil wells. Slurries were designed with fixed 13lb/gal density and concentration of nano silica 0.1 gpc; 0.4 gpc; 0.7 and 1gpc, the influence of nano-silica was studied at these levels in isolation and combined varying concentrations of CaCl2,. Tests including rheology, stability, strength, thickening time, porosity and permeability. Besides the API tests, microstructural characterizations were performed after 28 days of the slurries, X-ray diffraction (XRD) and scanning electron microscopy (SEM)

O efeito do envelhecimento nas forças de adesão à dentina

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

Desenvolvimento de um sistema misto de pasta à base de geopolímero e cimento portland para correção de perda de circulação

The materials engineering includes processes and products involving several areas of engineering, allowing them to prepare materials that fulfill the needs of various new products. In this case, this work aims to study a system composed of cement paste and geopolymers, which can contribute to solving an engineering problem that directly involves the exploitation of oil wells subject to loss of circulation. To correct it, has been already proposed the use of granular materials, fibers, reducing the drilling fluid or cement paste density and even surface and downhole mixed systems. In this work, we proposed the development of a slurry mixed system, the first was a cement-based slurry and the second a geopolymer-based slurry. The cement-based slurry was formulated with low density and extenders, 12.0 ppg (1.438 g/cm ³), showing great thixotropic characteristics. It was added nano silica at concentrations of 0.5, 1.0 and 1.5 gps (66.88, 133.76 and 200.64 L/m3) and CaCl2 at concentrations of 0.5, 1, 0 and 1.5%. The second system is a geopolymer-based paste formulated from molar ratios of 3.5 (nSiO2/nAl2O3), 0.27 (nK2O/nSiO2), 1.07 (nK2O/nAl2O3) and 13.99 (nH2O/nK2O). Finally, we performed a mixture of these two systems, for their application for correction of circulation lost. To characterize the raw materials, XRD, XRF, FTIR analysis and titration were performed. The both systems were characterized in tests based on API RP10B. Compressive strength tests were conducted after curing for 24 hours, 7 and 28 days at 58 °C on the cement-based system and the geopolymer-based system. From the mixtures have been performed mixability tests and micro structural characterizations (XRD, SEM and TG). The results showed that the nano silica, when combined with CaCl2 modified the rheological properties of the cement slurry and from the concentration of 1.5 gpc (200.64 L / m³) it was possible to obtain stable systems. The system mixture caused a change in the microstructure of the material by favoring the rate of geopolymer formation to hinder the C3S phase hydration, thus, the production of CSH phases and Portlandite were harmed. Through the mixability tests it can be concluded that the system, due to reduced setting time of the mixture, can be applied to plug lost circulation zones when mixed downhole