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

A forma do privilégio: renda, acessibilidade e densidade em Natal-RN

The aim of this work is to understand the morphological expression of ground occupation by the higher income population, by focusing on population distribution in accordance with income layers and demographical density, as well as topological accessibility (HILLIER and HANSON, 1984) resulting from the urban grid structure. It endeavors to identify a functional organizing principle regarding the intra-urban space of Natal capital city of the state of Rio Grande do Norte, the research focus. In order to achieve this, census data as well as syntactic data were utilized for mapping and spatial analysis of income patterns, topological accessibility and demographical density using Geographical Information System GIS. The organizing principle was named as the Form of Privilege, a pattern that concentrates or tends to concentrate wealth, topological accessibility and low demographical density. Attempting to assess its extent, beyond Natal, this principle was applied to other Brazilian northeastern capitals such as: Fortaleza, CE; Teresina, PI; Aracaju, SE; Recife, PE; and João Pessoa, PB. Findings point out that although the urban structures of these cities are not immune to the Form of Privilege, Natal is emblematic of this phenomenon, a fact that demonstrates the perverse character of its spatial process, which historically creates privileged areas within the city, by means of the appropriation of accessibility as well as of the many urban benesses that are related to it by higher income groups at the expense of the major part of the population, which though being the people mostly in need of the benefits originating from the urban form are excluded from them

Parâmetros urbanísticos na regulação do uso e ocupação do solo: estudo da densidade e do coeficiente de aproveitamento nos planos diretores de Natal de 1994 e 2007

A Constituição Federal de 1988 e o Estatuto da Cidade estabelecem o Plano Diretor como instrumento básico da política de ordenamento territorial, tendo como princípio fundamental o cumprimento da função social da propriedade e do direito à cidade. Na perspectiva de adequação às diretrizes e objetivos da política urbana estabelecidos em 1988, o município de Natal elaborou os Planos Diretores de 1994 e 2007, definindo instrumentos e parâmetros de regulação do uso e ocupação do solo possíveis de assegurar o cumprimento da função social da propriedade urbana e de gerar subsídios ao planejamento e à gestão da cidade. Apesar de Natal ter sido um dos municípios brasileiros pioneiros na adoção desses princ pios, antecipando e incorporando os instrumentos que em 2001 viriam a ser definidos no Estatuto da Cidade, identifica-se que alguns desses instrumentos e parâmetros direcionados à regulação do uso e ocupação do solo não tiveram sua aplicação plena, a exemplo do mecanismo de acompanhamento e controle dado pelo Estoque de Área Edificável e da Densidade, que foi substituída pelo Coeficiente de Aproveitamento no Plano Diretor de 2007. Questionando esse procedimento, busca-se na presente pesquisa investigar de que maneira essa substituição do parâmetro densidade pelo coeficiente de aproveitamento influenciou na capacidade da gestão pública de regular os processos de uso e ocupação do solo, de forma a adequar a sua intensificação ao suporte da infraestrutura instalada. Foram tomadas como referência teórico-conceitual as contribuições sobre a prática de planejamento urbano no Brasil, nos marcos do ideário da reforma urbana, com destaque para as reflexõe s de Flávio Villaça, Orlando Alves Santos Junior e Daniel Todtmann Montandon, Luiz César de Q. Ribeiro, Raquel Rolnik, Ermínia Maricato, Laura Machado de Bueno e Renato Cymbalista, José Roberto Bassul e Carlos F. Lago Burnett, e, com relação aos parâmetros de controle urbanístico, o estudo identifica as diferentes abordagens sobre a densidade urbana e o coeficiente de aproveitamento com base nas reflexões de Claudio Acioly Jr., Forbes Davidson, Juan Luis Mascaró, Ricardo Ojima, Marcelo de Souza, José Rámon Navarro Vera e Armando Ortuño Padilla, Nestor Goulart Reis, Marta Dora Grostein e Susana Ricardo Alves. Como conclusão, discute-se a hipótese formulada, inicialmente, de que a mudança de parâmetros verificada colocou limites para o município realizar uma gestão adequada do solo urbano e, portanto, de fazer cumprir a função social da propriedade, considerando a necessidade de adequação entre a intensificação do uso e ocupação do solo e a infraestrutura instalada

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

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

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

Desenvolvimento de tubulação em compósito polimérico revestida externamente com poliuretano de alta densidade

Pipelines for the transport of crude oil from the production wells to the collecting stations are named production lines . These pipes are subjected to chemical and electrochemical corrosion according to the environment and the type of petroleum transported. Some of these lines, depending upon the composition of the fluid produced, may leak within less than one year of operation due to internal corrosion. This work aims at the development of composite pipes with an external protecting layer of high density polyurethane for use in production lines of onshore oil wells, meeting operational requirements. The pipes were manufactured using glass fibers, epoxy resin, polyester resin, quartz sand and high density polyurethane. The pipes were produced by filament winding with the deposition of high density polyurethane on the external surface and threaded ends (API 15 HR/PM-VII). Three types of pipes were manufactured: glass/epoxy, glass/epoxy with an external polyurethane layer and glass/epoxy with an intermediate layer of glass fiber, polyester, sand and with an external polyurethane layer. The three samples were characterized by Scanning Electronic Microscopy (SEM) and for the determination of constituent content. In addition, the following tests were conducted: hydrostatic test, instant rupture, shorttime failure pressure, Gardner impact, transverse stiffness and axial tension. Field tests were conducted in Mossoró RN (BRAZIL), where 1,677 meters of piping were used. The tests results of the three types of pipes were compared in two events: after two months from manufacturing of the samples and after nine months of field application. The results indicate that the glass/epoxy pipes with an intermediate layer of fiber glass composite, polyester e sand and with an external layer of high density polyurethane showed superior properties as compared to the other two and met the requirements of pressure class, axial tensile strength, transverse stiffness, impact and environmental conditions, for onshore applications as production lines

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)

Efeito da incorporação de diatomita na estabilidade e permeabilidade de compósitos cimentíceos espumados aplicados a poços de petróleo

Lightweight oilwell cement slurries have been recently studied as a mean to improve zonal isolation and sheath-porous formation adherence. Foamed slurries consisting of Portland cement and air-entraining admixtures have become an interesting option for this application. The loss in hydrostatic pressure as a consequence of cement hydration results in the expansion of the air bubbles entrapped in the cement matrix, thus improving the sheath-porous formation contact. Consequently, slurries are able to better retain their water to complete the hydration process. The main objective of the present study was to evaluate the effect of the addition of an air-entraining admixture on the density, stability and permeability of composite slurries containing Portland cement and diatomite as light mineral load. Successful formulations are potential cementing materials for low fracture gradient oilwells. The experimental procedures used for slurry preparation and characterization were based on the American Petroleum Institute and ABNT guidelines Slurries containing a pre-established concentration of the air-entraining admixture and different contents of diatomite were prepared aiming at final densities of 13 to 15 lb/gal. The results revealed that the reduction of 15 to 25% of the density of the slurries did not significantly affect their strength. The addition of both diatomite and the air-entraining admixture increased the viscosity of the slurry providing better air-bubble retention in the volume of the slurry. Stable slurries depicted bottom to top density variation of less than 1.0 lb/gal and length reduction of the stability sample of 5.86 mm. Finally, permeability coefficient values between 0.617 and 0.406 mD were obtained. Therefore, lightweight oilwell cement slurries depicting a satisfactory set of physicochemical and mechanical properties can be formulated using a combination of diatomite and air-entraining admixtures for low fracture gradient oilwells

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

Análise de DFA e de agrupamento do perfil de densidade de poços de petróleo

In recent years, the DFA introduced by Peng, was established as an important tool capable of detecting long-range autocorrelation in time series with non-stationary. This technique has been successfully applied to various areas such as: Econophysics, Biophysics, Medicine, Physics and Climatology. In this study, we used the DFA technique to obtain the Hurst exponent (H) of the profile of electric density profile (RHOB) of 53 wells resulting from the Field School of Namorados. In this work we want to know if we can or not use H to spatially characterize the spatial data field. Two cases arise: In the first a set of H reflects the local geology, with wells that are geographically closer showing similar H, and then one can use H in geostatistical procedures. In the second case each well has its proper H and the information of the well are uncorrelated, the profiles show only random fluctuations in H that do not show any spatial structure. Cluster analysis is a method widely used in carrying out statistical analysis. In this work we use the non-hierarchy method of k-means. In order to verify whether a set of data generated by the k-means method shows spatial patterns, we create the parameter Ω (index of neighborhood). High Ω shows more aggregated data, low Ω indicates dispersed or data without spatial correlation. With help of this index and the method of Monte Carlo. Using Ω index we verify that random cluster data shows a distribution of Ω that is lower than actual cluster Ω. Thus we conclude that the data of H obtained in 53 wells are grouped and can be used to characterize space patterns. The analysis of curves level confirmed the results of the k-means

Formulação e caracterização de pastas espumadas por incorporação de ar e estabilizantes minerais

Cementing operations may occur at various stages of the life cycle of an oil well since its construction until its definitive abandonment. There are some situations in which the interest zones are depleted or have low fracture pressure. In such cases, the adoption of lowdensity cement slurries is an efficient solution. To this end, there are basically three ways to reduce the density of cement slurries: using microspheres, water extending additives or foamed cement. The objective of this study is to formulate, to study and to characterize lowdensity foamed cement, using an air entrainment surfactant with vermiculite or diatomite as water extenders and stabilizers. The methodology consists on preparation and evaluation of the slurries under the American Petroleum Institute (API) and the Brazilian Association of Technical Standards (ABNT) guidelines. Based on calculated densities between 13 and 15 ppg (1.559 and 1.799 g/cm3), the slurries were prepared with fixed surfactant concentration, varying the concentrations of vermiculite and diatomite and were compared with the base slurries. The results of plastic viscosity, yield point and gel strength and the compressive strength for 24 h showed that the slurries presented suitable rheology and mechanical strength for cementing operations in oil wells, and had their densities reduced between 8.40 and 11.89 ppg (1.007 and 1.426 g/cm3). The conclusion is that is possible, under atmospheric conditions, to obtain light weighted foamed cement slurries with satisfactory rheological and mechanical properties by means of air entrainment and mineral additions with extenders and stabilizers effects. The slurries have great potential for cementing operations; applicability in deep wells, in low fracture gradient formations and in depleted zones and bring cost savings by reducing the cementing consumption

Desenvolvimento de pastas leves utilizando incorporadores de ar para aplicação em poços de petróleo

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior

Efeito da adição de microfibras de lã de vidro na tenacidade à ruptura de pastas de cimento para poços de petróleo

Although there are a wide variety of additives that act in fresh state, to adjust the properties of cement, there is also a search by additions that improve the tenacity of the cement in the hardened state. This, in turn, can often be increased by inserting fibers, which act on the deflection of microcracks. This study aimed to use a microfiber glass wool (silica-based) as an additive reinforcing the cement matrix, improving the rupture tenacity, in order to prevent the propagation of microcracks in the cement sheath commonly found in oil wells submitted to high temperatures. The fibers were added at different concentrations, 2 to 5% (BWOC) and varied average sizes, grinding for 90 s, 180 s, 300 s, 600 s. The cement slurries were made with a density of 1,90 g/ cm3 (15,6 lb/gal), using Portland cement CPP- Special Class as the hydraulic binder and 40% silica flour. The characterization of the fiber was made by scanning electron microscopy (SEM), particle size by sieving, X-ray fluorescence (XRF), X-ray diffraction (XRD) and thermogravimetry (TG / DTG). Were performed technological tests set by the API (American Petroleum Institute) by rheology, stability, free water, compressive strength, as well as testing rupture energy, elastic modulus and permeability. The characterization results showed good thermal stability of the microfiber glass wool for application in oil wells submitted to steam injection and, also, that from the particle size data, it was possible to suggest that microfibers milled up to 300 s, are ideal to act as reinforcement to the cement slurries. The rheological parameters, there was committal of plastic viscosity when larger lengths were inserted of microfiber (F90). The values obtained by free water and stability were presented according to API. The mechanical properties, the incorporation of microfiber to the cement slurries gave better rupture tenacity, as compared to reference cement slurries. The values of compressive strength, elastic modulus and permeability have been maintained with respect to the reference cement slurries. Thus, cement slurries reinforced with microfiber glass wool can ensure good application for cementing oil wells submitted to steam injection, which requires control of microcracks, due to the thermal gradients

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

Efeito da salinidade, densidade de estocagem e da infecção hipodermal e necrose hematopoiética (IHHN) na imunidade do camarão Litopenaeus vannamei cultivados em fazendas do Rio Grande do Norte

The main problem faced by the shrimp industry are the infectious diseases. The hypodermal and hematopoietic necrosis infection (IHHN) is one of the major cause of disease in the cultured shrimp, Litopenaeus vannamei. Environmental changes involving water quality, oxygen concentration, salinity, temperature, stocking density, presence of pathogens, among others, triggering a stressing condition for the cultured shrimp, weakening them and allowing the outbreak of diseases. The stress on the animal leads to a change in the molecules immune response components, which can be used as indicators of shrimp health. Thus, the objective of the present study was to evaluate the effect of salinity, stocking density and IHHNV infection on the L. vannamei shrimp. The immune parameters used to check the shrimp health were the total hemocytes counts (THC), the agglutinating activity (AA) and the clotting time (CT) of the serum of shrimp. These parameters were analyzed in healthy and IHHNV-infected shrimp, grown in low (0-0.5 ), medium (19-24 ) and high (> 38 ) salinity, and extensive (7-12 cam.m-2), semi-intensive (15-25 cam.m-2) and intensive (33-45 cam.m -2) stocking density. The IHHNV infection rate was significantly higher in low salinity (P<0.005) and intensive density (P<0.005), both stressful conditions for L. vannamei. Low salinity significantly increased THC (P<0.05) and decreased and CT (P<0.05) in healthy and infected shrimp, but AA (P<0.05) significantly decreased in healthy shrimp at medium salinity. Culture intensification did not affect the THC, AA and CT of healthy and infected shrimp (P>0.05). The IHHNV infection did not affect any immune parameters of shrimp cultured at different salinities and stocking densities. It is necessary to emphasize that this study was conducted in shrimp grown in ponds, where several environmental factors are acting simultaneously. Thus, further studies are needed about the influence of other environmental factors on the immune parameters of shrimp cultured in pond