Influência da adição de cinza do bagaço de cana calcinada em sistemas de pastas para cimentação de poços petrolíferos

Cementing operation is one of the most important stages in the oil well drilling processes and has main function to form hydraulic seal between the various permeable zones traversed by the well. However, several problems may occur with the cement sheath, either during primary cementing or during the well production period. Cements low resistance can cause fissures in the cement sheath and compromise the mechanical integrity of the annular, resulting in contamination of groundwater and producing zones. Several researches show that biomass ash, in particular, those generated by the sugarcane industry have pozzolanic activity and can be added in the composition of the cementing slurries in diverse applications, providing improvements in mechanical properties, revenue and cement durability. Due to the importance of a low cost additive that increases the mechanical properties in a well cementing operations, this study aimed to potentiate the use of sugarcane bagasse ash as pozzolanic material, evaluate the mechanisms of action of this one on cement pastes properties and apply this material in systems slurries aimed to cementing a well with 800 m depth and geothermal gradient of 1.7 °F/100 ft, as much primary cementing operations as squeeze. To do this, the ash beneficiation methods were realized through the processes of grinding, sifting and reburning (calcination) and then characterization by X-ray fluorescence, XRD, TG / DTG, specific surface area, particle size distribution by laser diffraction and mass specific. Moreover, the ash pozzolanic activity added to the cement at concentrations of 0%, 20% and 40% BWOC was evaluated by pozzolanic activity index with lime and with Portland cement. The evaluation of the pozzolanic activity by XRD, TG / DTG and compressive strength confirmed the ash reactivity and indicated that the addition of 20% in the composition of cement slurries produces improvement 34% in the mechanical properties of the slurry cured. Cement slurries properties evaluated by rheological measurements, fluid loss, free fluid, slurry sedimentation, thickening time and sonic strength (UCA) were satisfactory and showed the viability of using the sugarcane ash in cement slurries composition for well cementing

Mapeamento da isoterma de Curie na Bacia do Parnaíba estimada através da profundidade da base das fontes magnéticas

Located on the western edge of the Brazilian northeast, the Parnaíba Basin is an intra cratonic basin with oil production. This study aims at understanding its genesis and evolution, using aeromagnetic and gravity data. We used the spectral analysis of aeromagnetic data to map the depth to the bottom of the magnetic sources in order to assimilate this depth with the depth of the Curie isotherm, and infer the geothermal gradient. Using the spectral analysis technique, we succeeded in mapping the surface of the depth to the bottom of magnetic sources (SBFM), which marks the depth that occur magnetization. In the Parnaíba Basin the SBFM presented depths around -20,5 and -28,5 , which was consistent with an inversion of the same dataset using the technique of Magnetization Vector Inversion (MVI). Furthermore, SBFM topography correlates well with Moho depth, which was estimated from satellite gravimetric data from the GOCE mission (Gravity Field and Steady-State Ocean Circulation Explorer). Assuming that SBFM coincides with the Curie isotherm of magnetite (ICM), defined as the surface at which magnetite ( ) looses its ferromagnetic properties, it was possible to estimate the geothermal gradient. The geothermal gradient in the basin showed values between 19.2 and 26.5 , allowing to estimate the heat flow for the Parnaíba basin after assuming a conductivity of 2.69 . The resulting heat flow values ranged between 51.6 and 71.3 , which is consistent with values found in other works throughout the South American continent. Lithospheric thickness using an empirical relationship, finding values between -65.8 and -89.2 . We propose that thermal structure of Parnaíba basin is influenced by a deep thermal anomaly. This anomaly has heated the lithosphere beneath the basin and has resulted in relatively thin values for the lithospheric thickness and relatively high surface heat flow values. The origin of the anomaly is not clear, but the correlation between Curie depth and Moho topography, suggests that tectonic extension processes could have played a role.

Influência da adição de cinza do bagaço de cana calcinada em sistemas de pastas para cimentação de poços petrolíferos

Cementing operation is one of the most important stages in the oil well drilling processes and has main function to form hydraulic seal between the various permeable zones traversed by the well. However, several problems may occur with the cement sheath, either during primary cementing or during the well production period. Cements low resistance can cause fissures in the cement sheath and compromise the mechanical integrity of the annular, resulting in contamination of groundwater and producing zones. Several researches show that biomass ash, in particular, those generated by the sugarcane industry have pozzolanic activity and can be added in the composition of the cementing slurries in diverse applications, providing improvements in mechanical properties, revenue and cement durability. Due to the importance of a low cost additive that increases the mechanical properties in a well cementing operations, this study aimed to potentiate the use of sugarcane bagasse ash as pozzolanic material, evaluate the mechanisms of action of this one on cement pastes properties and apply this material in systems slurries aimed to cementing a well with 800 m depth and geothermal gradient of 1.7 °F/100 ft, as much primary cementing operations as squeeze. To do this, the ash beneficiation methods were realized through the processes of grinding, sifting and reburning (calcination) and then characterization by X-ray fluorescence, XRD, TG / DTG, specific surface area, particle size distribution by laser diffraction and mass specific. Moreover, the ash pozzolanic activity added to the cement at concentrations of 0%, 20% and 40% BWOC was evaluated by pozzolanic activity index with lime and with Portland cement. The evaluation of the pozzolanic activity by XRD, TG / DTG and compressive strength confirmed the ash reactivity and indicated that the addition of 20% in the composition of cement slurries produces improvement 34% in the mechanical properties of the slurry cured. Cement slurries properties evaluated by rheological measurements, fluid loss, free fluid, slurry sedimentation, thickening time and sonic strength (UCA) were satisfactory and showed the viability of using the sugarcane ash in cement slurries composition for well cementing

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

Novo método para estimativa do gradiente de fratura para poços de petróleo

The development of oil wells drilling requires additional cares mainly if the drilling is in offshore ultra deep water with low overburden pressure gradients which cause low fracture gradients and, consequently, difficult the well drilling by the reduction of the operational window. To minimize, in the well planning phases, the difficulties faced by the drilling in those sceneries, indirect models are used to estimate fracture gradient that foresees approximate values for leakoff tests. These models generate curves of geopressures that allow detailed analysis of the pressure behavior for the whole well. Most of these models are based on the Terzaghi equation, just differentiating in the determination of the values of rock tension coefficient. This work proposes an alternative method for prediction of fracture pressure gradient based on a geometric correlation that relates the pressure gradients proportionally for a given depth and extrapolates it for the whole well depth, meaning that theses parameters vary in a fixed proportion. The model is based on the application of analytical proportion segments corresponding to the differential pressure related to the rock tension. The study shows that the proposed analytical proportion segments reaches values of fracture gradient with good agreement with those available for leakoff tests in the field area. The obtained results were compared with twelve different indirect models for fracture pressure gradient prediction based on the compacting effect. For this, a software was developed using Matlab language. The comparison was also made varying the water depth from zero (onshore wellbores) to 1500 meters. The leakoff tests are also used to compare the different methods including the one proposed in this work. The presented work gives good results for error analysis compared to other methods and, due to its simplicity, justify its possible application

Estudos analíticos dos grafoelementos do eletroencefalograma em sono: fusos do sono, ondas agudas do vértex e o gradiente de freqüência e amplitude, como indicadores de comprometimento neurológico na criança

Innumerable studies have focused been reported on the sleep spindles (SS), Sharp Vertex Waves (SVW) and REM, NREM Sleep as indicators interpreting EEG patterns in children. However, Frequency and Amplitud Gradient (FAG) is rarely cited sleep parameter in children,that occurs during NREM Sleep. It was first described by Slater and Torres, in 1979, but has not been routinely evaluated in EEG reports. The aim of this study was to assess the absence of SS, SVW and FAG, as an indication of neurological compromise in children. The sample consisted of 1014 EEGs of children referred to the Clinical Neurophysiology Laboratory, Hospital Universitário de Brasília (HUB), from January 1997 to March 2003, with ages ranging from 3 months to 12 years old, obtained in spontaneous sleep or induced by choral hydrate. The study was transversal and analytical, in which, visual analysis of EEG traces was perfumed individually and independently by two electroencephalographers without prior knowledge of the EEG study or neurological findings. After EEG selection, the investigators analyzed the medical reports in order to define and correlate neurological pattern was classified according to the presence or absence of neurological compromise, as Normal Neurological Pattern (NNP), and Altered Neurological Pattern (ANP) respectively. From the visual analysis of the EEG(s), it was possible to characterize 6 parameters: 1- FAG present (64,1%); 2- FAG absent (35,9%); 3 - normal SS (87,9%); 4 - altered SS s (12,1%); 5 - normal SVW s (95,7%); 6 - altered SVW s (4,3%). The prevalence of well-formed FAG is found in the 3 months to 5 years age group in the children with NNF. FAG was totally absent from the age of 10 years. When comparing the three sleep graphielements, it was observed that SVW and SS were predominant in children with NNF. However, FAG absent was more prevalent in the ANF than in altered SS an SVW. The statistical analysis showed that there is a strong association of FAG absent, with isolated alteration, in ANF patients, in that the prevalence ratio was 6,60. The association becomes stronger when FAG absent + altered SS(s) is considered (RP= 6,68). Chi-square test, corrected by Yates technique, showed a highly significant relation for FAG ρ= 0,00000001, for error X of 5%, or else the 95% confidence interval (ρ<0,05). Thus, the FAG absent were more expressive in ANF patient than altered SS(s) and SVW(s). The association becomes stronger in order to establish a prognostic relation, when the FAG is combined with the SS. The results os this study allow us to affirm that the FAG, when absent at ages ranging from 3 months to 5 years , is an indication of neurological compromise. FAG is an age-dependent EEG parameter and incorporated systematically, in the interpretation criteria of the EEG of children s sleep, not only in the maturational point of view, but also neurological disturbances with encephalic compromise

Efeitos da tilápia do Nilo, Oreochromis niloticus, sobre a biomassa planctônica e a transparência da água ao longo de um gradiente de enriquecimento por nutrientes

The omnivorous filter-feeding fish, Nile tilapia (Oreochromis niloticus), can have negative effects on water quality enhancing the eutrophication process. These effects depend on the nutrient enrichment level in the water. We carried out a mesocosm experiment for five weeks in a tropical man-made lake in Brazil to test ifthe effects of tilapias depend on of the level of nutrient enrichment. The experiment lasted for 5 weeks and a factorial 2x5 experimental design was used where the presence and absence of tilapias were manipulated in combination to 5 different levels of nutrient load in a total of 10 treatments. A two way repeated measure ANOVA was performed to evaluate the effects of time (t), tilapia (F), nutrients (NP) and the interactions among these factors on: chlorophyll a, water transparency, total phosphorous, total nitrogen, N:P ratio, zooplankton biomass and phytoplankton biovolume. The tilapia effect was evident, but nutrient enrichment didn t have any effect on the variables analyzed. Tilapia decreased the water transparency, total zooplankton biomass, calanoid copepod biomass, nauplii copepod biomass and cladocerans biomass. On the other hand, tilapia had no effect on phytoplankton biovolume. This lack of effect on phytoplankton is probably due to tilapia grazing that may counteract the positive effect of tilapia on phytoplankton via trophic cascades and nutrient recycling. Hence, a reduction in tilapia stock would not be an effective way to reduce phytoplankton biomass and improve water quality

Desenvolvimento de sistemas de pastas leves para aplicação em cimentação de poços petrolíferos com baixo gradiente de fratura

All around the world, naturally occurring hydrocarbon deposits, consisting of oil and gas contained within rocks called reservoir rocks , generally sandstone or carbonate exists. These deposits are in varying conditions of pressure and depth from a few hundred to several thousand meters. In general, shallow reservoirs have greater tendency to fracture, since they have low fracture gradient, ie fractures are formed even with relatively low hydrostatic columns of fluid. These low fracture gradient areas are particularly common in onshore areas, like the Rio Grande do Norte basin. During a well drilling, one of the most favorable phases for the occurrence of fractures is during cementing, since the cement slurry used can have greater densities than the maximum allowed by the rock structure. Furthermore, in areas which are already naturally fractured, the use of regular cement slurries causes fluid loss into the formation, which may give rise to failures cementations and formation damages. Commercially, there are alternatives to the development of lightweight cement slurries, but these fail either because of their enormous cost, or because the cement properties were not good enough for most general applications, being restricted to each transaction for which the cement paste was made, or both reasons. In this work a statistical design was made to determine the influence of three variables, defined as the calcium chloride concentration, vermiculite concentration and nanosilica concentration in the various properties of the cement. The use of vermiculite, a low density ore present in large amounts in northeastern Brazil, as extensor for cementing slurries, enabled the production of stable cements, with high water/cement ratio, excellent rheological properties and low densities, which were set at 12.5 lb / gal, despite the fact that lower densities could be achieved. It is also seen that the calcium chloride is very useful as gelling and thickening agent, and their use in combination with nanosilica has a great effect on gel strength of the cement. Hydrothermal Stability studies showed that the pastes were stable in these conditions, and mechanical resistance tests showed values of the order of up to 10 MPa

Produção de estrutura com gradiente de porosidade a partir da sinterização por plasma da mistura de pós Ti-Nb-Sn

Porous structures are being widely investigated for use in biomedical implants, aiming to mechanically integrate and functionally the implant inside the bone tissue. Moreover, this structure is also important for drugs that can be stored and can induce and accelerate the process of osseointegration. With the purpose to investigate this effect, Ti, Nb and Sn metal powders, were sintered by plasma using a hollow cathode discharge. Sintering was performed in argon plasma set at 4 mbar pressure and temperatures of 500 ° C, 600 ° C and 700 ° C. Samples were also sintered in the electrical resistance furnace at 1200 ° C in order to compare plasma sintering with the conventional method. It was observed that plasma samples sintered with the hollow cathode configuration showed a gradient in porosity, while the samples sintered in the resistive furnace did not. Furthermore, differences in the microstructure of the samples were found, were a surface with higher porosity and ales porous core were obtained at different temperatures. The percolation profile of distilled water and the chemical compositions of the porous layers of the plasma treated samples were the main results obtained. Based on these results, we can conclude that this structure is particularly important for application in the biomedical field such as scaffolds for drug delivery and implants

Distribuição e uso de habitat por peixes recifais em um gradiente ambiental: estudo de caso em recifes areníticos

There are several abiotic factors reported in the literature as regulators of the distribution of fish species in marine environments. Among them stand out structural complexity of habitat, benthic composition, depth and distance from the coast are usually reported as positive influencers in the diversity of difentes species, including reef fish. These are dominant elements in reef systems and considered high ecological and socioeconomic importance. Understanding how the above factors influence the distribution and habitat use of reef fish communities are important for their management and conservation. Thus, this study aims to evaluate the influence of these variables on the community of reef fishes along an environmental gradient of depth and distance from shore base in sandstone reefs in the coast of state of Rio Grande do Norte, Brazil. These variables are also used for creating a simple predictive model reef fish biomass for the environment studied. Data collection was performed through visual surveys in situ, and recorded environmental data (structural complexity of habitat, type of coverage of the substrate, benthic invertebrates) and ecological (wealth, abundance and reef fish size classes). As a complement, information on the diet were raised through literature and the biomass was estimated from the length-weight relationship of each species. Overall, the reefs showed a low coverage by corals and the Shallow reefs, Intermediate I and II dominated by algae and the Funds by algae and sponges. The complexity has increased along the gradient and positively influenced the species richness and abundance. Both attributes influenced in the structure of the reef fish community, increasing the richness, abundance and biomass of fish as well as differentiating the trophic structure of the community along the depth gradient and distance from the coast. Distribution and use of habitat by recifas fish was associated with food availability. The predictor model identified depth, roughness and coverage for foliose algae, calcareous algae and soft corals as the most significant variables influencing in the biomass of reef fish. In short, the description and understanding of these patterns are important steps to elucidate the ecological processes. In this sense, our approach provides a new understanding of the structure of the reef fish community of Rio Grande do Norte, allowing understand a part of a whole and assist future monitoring actions, evaluation, management and conservation of these and other reefs of Brazil.

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

Novo método para estimativa do gradiente de fratura para poços de petróleo

The development of oil wells drilling requires additional cares mainly if the drilling is in offshore ultra deep water with low overburden pressure gradients which cause low fracture gradients and, consequently, difficult the well drilling by the reduction of the operational window. To minimize, in the well planning phases, the difficulties faced by the drilling in those sceneries, indirect models are used to estimate fracture gradient that foresees approximate values for leakoff tests. These models generate curves of geopressures that allow detailed analysis of the pressure behavior for the whole well. Most of these models are based on the Terzaghi equation, just differentiating in the determination of the values of rock tension coefficient. This work proposes an alternative method for prediction of fracture pressure gradient based on a geometric correlation that relates the pressure gradients proportionally for a given depth and extrapolates it for the whole well depth, meaning that theses parameters vary in a fixed proportion. The model is based on the application of analytical proportion segments corresponding to the differential pressure related to the rock tension. The study shows that the proposed analytical proportion segments reaches values of fracture gradient with good agreement with those available for leakoff tests in the field area. The obtained results were compared with twelve different indirect models for fracture pressure gradient prediction based on the compacting effect. For this, a software was developed using Matlab language. The comparison was also made varying the water depth from zero (onshore wellbores) to 1500 meters. The leakoff tests are also used to compare the different methods including the one proposed in this work. The presented work gives good results for error analysis compared to other methods and, due to its simplicity, justify its possible application

Ventilação e prescrições urbanísticas: uma aplicação simulada para a Orla da Praia do Meio em Natal/RN

This work analyses a study on natural ventilation and its relation to the urban legislation versus the building types in an urban fraction of coastal area of Praia do Meio in the city of Natal/RN, approaching the type or types of land use most appropriate to this limited urban fraction. The objective of this study is to analyse the effects of the present legislation as well as the types of buildings in this area on the natural ventilation. This urban fraction was selected because it is one of the sites from where the wind flows into the city of Natal. This research is based on the hypothesis stating that the reduction on the porosity of the urban soil (decrease in the set back/boundary clearance), and an increase in the form (height of the buildings) rise the level of the ventilation gradient, consequently causing a reduction on the wind speed at the lowest part of the buildings. Three-dimensional computational models were used to produce the modes of occupation allowed in the urban fraction within the area under study. A Computational Fluid Dynamics (CFD) software was also used to analyse the modes of land occupation. Following simulation, a statistical assessment was carried out for validation of the hypothesis. It was concluded that the reduction in the soil porosity as a consequence of the rates that defined the minimum boundary clearance between the building and the boundary of the plot (and consequently the set back), as well as the increase in the building form (height of the buildings) caused a reduction in the wind speed, thus creating heat islands

Ventilação e prescrições urbanísticas: uma aplicação simulada no bairro de Petrópolis em Natal/RN

The present work studies the natural ventilation and its relationship with the urban standards, which establishes the form of occupation and use of the land in our cities. The method simulates the application of the urban standards of the City Master Plan over the last three years. The simulation takes place in the District of Petrópolis, in the city of Natal , Brazil and analyses the effects of the standards of natural ventilation. The formulated hypothesis states that the reductions in the urban spaces between buildings rises up the vertical profile of ventilation, reducing, therefore, the velocity of the wind at the lower levels of the buildings. To develop the study, occupation models were built, using computerized, three-dimensional models. These occupation models were analyzed using the CFD (Computational Fluid Dynamics) code. The conclusion is that the more we reduce the urban space between buildings, the more we reduce the wind speed in constructed areas, increasing, therefore, the possibility to generate heat islands

Avaliação espaço-temporal do zooplâncton da laguna estuarina de Guaraíras (RN, Brasil)

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