Desafios tecnológicos na exploração de petróleo em águas profundas: o sistema PETROBRAS de inovação

Pós-graduação em Economia - FCLAR

Morfoestruturas quilométricas em forma de crescente nas águas profundas do Golfo de Cádis

O levantamento batimétrico MATESPRO, realizado no NW do Golfo de Cádis, revelou a existência de intrigantes objectos morfológicos jacentes entre os 4300 e os 4700 metros de profundidade. Estes objectos, de dimensões quilométricas, são constituídos por uma depressão interna limitada parcialmente por uma escarpa em forma em crescente que pode atingir mais de 100 m de altura, com declives que variam entre os 6 e os 27° e cuja parte interna é constituída por uma depressão preenchida por unidades progradantes, que se desenvolvem no sentido da escarpa. Estes objectos são interpretados como o resultado da acção conjunta de processos tectónicos e sedimentares e da sua interacção com correntes de fundo. A actividade tectónica gera rupturas de declive no fundo do mar. As correntes de fundo e turbidíticas interagem com estas irregularidades morfológicas, amplificando-as através da sua acção erosiva, permitindo assim a criação das escarpas abruptas dos crescentes e a formação de corpos sedimentares progradantes. ABSTRACT; Multi-beam swath bathymetry carried out in NW Gulf of Cadiz revealed several intriguing features, lying at depths between -4300 and- 4700 m. These features display kilometric crescent escarpments up to 100 m high with slopes between 6 and 27 degrees, in an area characterized by very shallow general slope gradients (0,5 °). The internal part of a Crescent consists of a depression filled up with upslope prograding drift developing towards the scarp. These features are interpreted as the coupled result of sedimentary and tectonic processes. It is proposed that the Crescents formed when a local morphologic irregularity, corresponding to the bathymetric expression of movement on an underlying thrust, is enhanced by the erosional activity of turbidity and bottom currents. The drift results from the re-deposition of the eroded material in the same location.

Caracterização térmica de tubos de explorações petrolíferas em águas profundas

Este trabalho foi realizado devido aos novos desafios existentes na área petrolífera, pois tem-se verificado novas necessidades na transferência de calor em tubagens em águas profundas. Com estes novos cenários de produção em águas profundas, existe a preocupação de garantir o escoamento do produto evitando cenários de obstrução nas tubagens. Os principais problemas aquando da exploração petrolífera prendem-se com a ocorrência de parafinas nas paredes dos tubos bem como a formação de hidratos. É descrito neste trabalho as soluções existentes para a transferência do produto e comparação das mesmas. Numa segunda fase é realizado um modelo matemático para análise térmica das tubagens comparando os materiais isolantes propostos, afim de garantir a temperatura mínima do fluido circulante. De salientar que houve a preocupação de ter em conta uma paragem na exploração do petróleo, por motivos de manutenção por exemplo, e garantir dessa maneira a temperatura mínima do mesmo. Este trabalho propõe soluções de isolamento térmico e discute todos os desafios e problemas existentes.

Caracterização térmica de tubos de explorações petrolíferas em águas profundas

Este trabalho foi realizado devido aos novos desafios existentes na área petrolífera, pois tem-se verificado novas necessidades na transferência de calor em tubagens em águas profundas. Com estes novos cenários de produção em águas profundas, existe a preocupação de garantir o escoamento do produto evitando cenários de obstrução nas tubagens. Os principais problemas aquando da exploração petrolífera prendem-se com a ocorrência de parafinas nas paredes dos tubos bem como a formação de hidratos. É descrito neste trabalho as soluções existentes para a transferência do produto e comparação das mesmas. Numa segunda fase é realizado um modelo matemático para análise térmica das tubagens comparando os materiais isolantes propostos, afim de garantir a temperatura mínima do fluido circulante. De salientar que houve a preocupação de ter em conta uma paragem na exploração do petróleo, por motivos de manutenção por exemplo, e garantir dessa maneira a temperatura mínima do mesmo. Este trabalho propõe soluções de isolamento térmico e discute todos os desafios e problemas existentes.

Amarração de plataformas offshore flutuantes com cabos de poliéster

Trabalho Final de Mestrado para obtenção do grau de Mestre em Engenharia Civil na Área de Especialização de Estruturas

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

Caracterização tectono-estratigráfica da sequência transicional na sub-bacia de Sergipe

This thesis deals with the tectonic-stratigraphic evolution of the Transitional Sequence in the Sergipe Sub-basin (the southern segment of the Sergipe-Alagoas Basin, Northeast Brazil), deposited in the time interval of the upper Alagoas/Aptian stage. Sequence boundaries and higher order internal sequences were identified, as well as the structures that affect or control its deposition. This integrated approach aimed to characterize the geodynamic setting and processes active during deposition of the Transitional Sequence, and its relations with the evolutionary tectonic stages recognized in the East Brazilian Margin basins. This subject addresses more general questions discussed in the literature, regarding the evolution from the Rift to the Drift stages, the expression and significance of the breakup unconformity, the relationships between sedimentation and tectonics at extensional settings, as well as the control on subsidence processes during this time interval. The tectonic-stratigraphic analysis of the Transitional Sequence was based on seismic sections and well logs, distributed along the Sergipe Sub-basin (SBSE). Geoseismic sections and seismic facies analysis, stratigraphic profiles and sections, were compiled through the main structural blocks of this sub-basin. These products support the depositional and tectonic-stratigraphic evolutionary models built for this sequence. The structural analysis highlighted similarities in deformation styles and kinematics during deposition of the Rift and Transitional sequences, pointing to continuing lithospheric extensional processes along a NW trend (X strain axis) until the end of deposition of the latter sequence was finished by the end of late Aptian. The late stage of extension/rifting was marked by (i) continuous (or as pulses) fault activity along the basin, controling subsidence and creation of depositional space, thereby characterizing upper crustal thinning and (ii) sagstyle deposition of the Transitional Sequence at a larger scale, reflecting the ductile stretching and thinnning of lower and sub crustal layers combined with an increasing importance of the thermal subsidence regime. Besides the late increments of rift tectonics, the Transitional Sequence is also affected by reactivation of the border faults of SBSE, during and after deposition of the Riachuelo Formation (lower section of the Transgressive Marine Sequence, of Albian age). It is possible that this reactivation reflects (through stress propagation along the newlycreated continental margin) the rifting processes still active further north, between the Alagoas Sub-basin and the Pernambuco-Paraíba Basin. The evaporitic beds of the Transitional Sequence contributed to the development of post-rift structures related to halokinesis and the continental margin collapse, affecting strata of the overlying marine sequences during the Middle Albian to the Maastrichtian, or even the Paleogene time interval. The stratigraphic analysis evidenced 5 depositional sequences of higher order, whose vertical succession indicates an upward increase of the base level, marked by deposition of continental siliciclastic systems overlain by lagunar-evaporitic and restricted marine systems, indicating that the Transitional Sequence was deposited during relative increase of the eustatic sea level. At a 2nd order cycle, the Transitional Sequence may represent the initial deposition of a Transgressive Systems Tract, whose passage to a Marine Transgressive Sequence would also be marked by the drowning of the depositional systems. At a 3rd order cycle, the sequence boundary corresponds to a local unconformity that laterally grades to a widespread correlative conformity. This boundary surface corresponds to a breakup unconformity , being equivalent to the Pre-Albian Unconformity at the SBSE and contrasting with the outstanding Pre-upper Alagoas Unconformity at the base of the Transitional Sequence; the latter is alternatively referred, in the literature, as the breakup unconformity. This Thesis supports the Pre-Albian Unconformity as marker of a major change in the (Rift-Drift) depositional and tectonic setting at SBSE, with equivalent but also diachronous boundary surfaces in other basins of the Atlantic margin. The Pre-upper Alagoas Unconformity developed due to astenosphere uplift (heating under high lithospheric extension rates) and post-dates the last major fault pulse and subsequent extensive block erosion. Later on, the number and net slip of active faults significantly decrease. At deep to ultra deep water basin segments, seaward-dipping reflectors (SDRs) are unconformably overlain by the seismic horizons correlated to the Transitional Sequence. The SDRs volcanic rocks overly (at least in part) continental crust and are tentatively ascribed to melting by adiabatic decompression of the rising astenospheric mantle. Even though being a major feature of SBSE (and possibly of other basins), the Pre-upper Alagoas Unconformity do not correspond to the end of lithospheric extension processes and beginning of seafloor spreading, as shown by the crustal-scale extensional structures that post-date the Transitional Sequence. Based on this whole context, deposition of the Transitional Sequence is better placed at a late interval of the Rift Stage, with the advance of an epicontinental sea over a crustal segment still undergoing extension. Along this segment, sedimentation was controled by a combination of thermal and mechanical subsidence. In continuation, the creation of oceanic lithosphere led to a decline in the mechanical subsidence component, extension was transferred to the mesoceanic ridge and the newly-formed continental margin (and the corresponding Marine Sequence) began to be controlled exclusively by the thermal subsidence component. Classical concepts, multidisciplinary data and new architectural and evolutionary crustal models can be reconciled and better understood under these lines

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

O enigma da "reação espermatofórica": breve síntese do conhecimento sobre a estrutura e o funcionamento dos espermatóforos dos cefalópodes (Mollusca: Cephalopoda)

Cefalópodes coleóides (lulas, sépias e polvos) produzem espermatóforos muito complexos que são transferidos à fêmea durante a cópula por meio do hectocótilo, um apêndice modificado nos machos. Durante a transferência à fêmea, ocorre a chamada "reação espermatofórica", complexo processo de evaginação do aparato ejaculatório do espermatóforo, que conduz à exteriorização da massa espermática e corpo cimentante. A presente revisão sintetiza o conhecimento acerca da morfologia e funcionamento desta estrutura exclusiva dos coleóides, identificando lacunas e definindo estratégias que possibilitem avanços na área. Poucos trabalhos abordam com detalhes a morfologia e anatomia funcional dos espermatóforos dos cefalópodes, grande parte do conhecimento acerca da estrutura do espermatóforo tendo sido gerada por trabalhos clássicos do século XIX e início do século XX. Investigações acerca do funcionamento dos espermatóforos são consideravelmente mais raras, estando o conhecimento básico sobre a reação espermatofórica restrito a apenas 19 espécies de coleóides. A revisão da literatura especializada permite sugerir que existem dois tipos básicos de fixação de espermatóforos em Decapodiformes (lulas e sepióides): fixação superficial e implante profundo (ou intra-dérmico). Na fixação superficial, comum em diversas espécies (e.g., Loliginidae, Sepiidae, Ommastrephidae), a base dos espermatângios é aderida ao tecido-alvo aparentemente por meio do corpo cimentante, a partir de substâncias adesivas e, em alguns casos, estruturas de fixação. No implante profundo, comum em alguns grupos de lulas oceânicas e de águas profundas (e.g., Architeuthidae, Cranchiidae, Octopoteuthidae, Sepiolidae), os espermatóforos implantam-se inteiramente no corpo da fêmea, de forma autônoma. Permanece desconhecido o mecanismo responsável pelo implante profundo. Em Octopodiformes (polvos), o espermatóforo é inserido no gonoduto feminino, alcançando a glândula oviducal, onde estão localizadas as espermatecas, ou a cavidade do ovário. Como o funcionamento extracorpóreo dos espermatóforos depende exclusivamente da intrincada estrutura e organização de seus componentes (e.g., membranas e túnicas), somente investigações detalhadas dessas estruturas proverão as bases para a compreensão do funcionamento e da exata função do complexo espermatóforo dos coleóides. Recomenda-se o desenvolvimento de um protocolo simples e eficiente para coloração e preparação total de espermatóforos, de forma que seja possível expandir as descrições morfológicas do espermatóforo em estudos taxonômicos e anatômicos, permitindo, portanto, ampliação do conhecimento acerca desta enigmática estrutura.