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[pt] Existem muitas formações no mundo hoje que armazenam uma quantidade significante de petróleo, sendo um grande valor para a indústria petroleira. As bacias de Pré-sal da costa do Brasil atualmente estão em grande foco devido aos descobrimentos recentes de petróleo e os desafios que eles criam na perfuração. Ao contrário de muitas formações, a rocha salina exibe fluência, uma vez que, a perfuração seja realizada a rocha começa se realiviar das tensões geostáticas por fechamento com o tempo. A profundidade e os altos níveis de tensões induzidas pelo sal no revestimento requerem a cimentação para fornecer estabilidade adicional. Mesmo assim, um defeito no cimento complica a análise para os engenheiros a modelar e predizer seu comportamento. Um revestimento bem cimentado não é sempre alcançado em águas profundas. A geometria e o tamanho têm uma grande influência nas tensões no defeito do cimento. A ovalização do revestimento pode reduzir as tensões máximas de compressão induzidas pelo sal dependendo da geometria do defeito. Excentricidade reduz os efeitos da ovalização enquanto muda o estado de tensões do cimento. Portanto, é importante que o cimento e o sal sejam entendidos inteiramente a fim de realizar decisões racionais em engenharia. O foco desta pesquisa é atingir um conhecimento mais profundo de poços de offshore mal cimentados sujeitos ao carregamento não uniforme. Um modelo de elementos finitos foi gerado pelo software Abaqus para implementar simulações e análise de vários cenários de falhas no cimento. / [en] There exist several salt rock formations in the world today which store a substantial amount of oil, being a great asset to the petroleum industry. The pre-salt basins off the coast of Brazil have been a primary focus due to the challenges they provide in oil drilling. Unlike most formations, salt rock exhibits creep behavior where, once the drilling has been performed, the rock begins to relieve itself from the applied stress by closing gradually with time. This may lead to cases of well collapse and well abandonment, creating an economical issue to oil drillers. Well cementing is always seeked to be performed with excellence, caution and thoroughness. Nevertheless, an unevenly distributed cement job complicates the analysis for engineers to model and predict its behavior. A well-cemented casing is not always achieved in deepwater wells. Geometry and size greatly influence the stresses on the defected area. Hence, it is important that the cement and salt formation be fully understood in order to make rational engineering decisions. The focus of this research study is to attain a deeper understanding of poorly-cemented offshore wells subjected to non-uniform salt loading. A finite element model was generated by the commercial software program Abaqus to implement simulations and analyses of various failure scenarios.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.

Experiments were conducted to investigate the shear behaviour of large deep beams subjected to uniform load. Six tests were performed on specimens with identical cross sections and reinforcing, but under different loading configurations. Variables included: span, degree of cracking prior to loading, proximity to a disturbed region near a reaction, and type of flexural stress on the loaded face. The findings indicate a specific set of variables resulting in unconservative predictions made using a strut-and-tie model for simply-supported beams subjected to uniform load, confirming and validating recent results by other researchers. A fanning strut model is proposed and is shown to provide more conservative results. The emerging trend of high capacity in continuous uniformly-loaded specimens is supported by the experimental results, as is the high capacity of specimens uniformly-loaded on their flexural tension face. Further, the high strength of specimens with suboptimal crack orientations supports recent experimental work.