Using a combination of micromechanical force and flowloop measurements, hydrate deposition on a pipe wall surface was investigated for ‘dry’ hydrates formed in the bulk phase and for hydrates growing on the pipe surface. Cyclopentane ‘dry’ hydrates (without a free water phase) were used to predict whether hydrates, formed in a bulk condensate phase, would adhere to a pipe wall. Adhesion forces between cyclopentane hydrates and steel were measured using a micro-mechanical force apparatus. The average force of adhesion was measured to be very small, less than 0.01 N/m. This force was used in a particle force balance, predicting that hydrates formed in the bulk phase would not deposit on the pipe wall. It was hypothesized than in the presence of a water saturated hydrocarbon, hydrates would grow on the pipe wall as the fluid cooled below its equilibrium temperature. This hypothesis was confirmed using a single pass condensate flowloop. Water was continuously dissolved into the flowloop inlet stream as water deposited in the flowloop test section, resulting in both a pressure drop and fluid temperature increase. This work illustrates the need for a hydrate wall growth model.

CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / CNPq - Conselho Nacional de Desenvolvimento Científico e Tecnológico / A extração de petróleo em águas profundas impõe diversos desafios às empresas de óleo e gás e, dentre eles, destaca-se o desgaste sofrido na parte interna dos dutos de transporte devido à ação da água produzida (elevado teor salino), gases e particulados, principalmente a areia produzida. O objetivo deste trabalho foi estudar a erosão-corrosão de um aço com baixo teor de carbono (VMEC 134AP) em um flowloop sob condições dinâmicas: fluido em escoamento com 3,5 % de NaCl, areia em concentração de 40 g cm-3 e adição de substância inibidora de corrosão, com foco principal em observar a possível interação entre o agente erosivo e o inibidor. Para isso, realizaram-se ensaios de erosão-corrosão em um circuito fechado de tubulações com quatro polegadas de diâmetro interno (101,2 mm) e foram aplicadas as técnicas de medição da taxa de desgaste: cupons de perda de massa, resistência à polarização linear e espectroscopia de impedância eletroquímica. Foram monitoradas também a concentração de inibidor no fluido e as modificações na superfície dos corpos de prova por microscopia eletrônica de varredura. Ao fim deste trabalho, concluiu-se que o aço apresenta uma taxa de corrosão de 3,5 mm ano-1 sem a adição de inibidor e 0,4 mm ano-1 com a adição de inibidor. Não foi observada interação direta entre a areia e o inibidor de corrosão que pudesse comprometer a eficiência do mesmo. A técnica de espectroscopia eletroquímica foi empregada com sucesso em condições dinâmicas por meio de uma célula projetado especificamente para tubulações. Os resultados mostraram que a célula e a técnica foram capazes de identificar o efeito sinergético da erosão-corrosão na parte inferior da tubulação e também a atuação do inibidor de corrosão. / Deep water oil production imposes several challenges for oil and gas companies, and among them, the wear suffered in the interior of the transportation pipelines due to the action of produced water (high salt content), gases and particulates, especially produced sand. The objective of this work was to study the erosion-corrosion of a low carbon steel in a flowloop under dynamic conditions: fluid with 3.5% NaCl, sand at a concentration of 40 g cm-3 and addition of a corrosion inhibitory substance, with a main focus on observing the possible interaction between the erosive agent and the inhibitor. For this purpose, we performed erosion-corrosion tests in a closed circuit of pipes of four inches of internal diameter and we applied the corrosion rate measurement techniques of mass loss coupons, linear polarization resistance and electrochemical impedance spectroscopy. We also monitored the concentration of inhibitor in the fluid and the modifications on the surface of the specimens by scanning electron microscopy. At the end of this work, we concluded that the steel presents a corrosion rate of 3.5 mm year-1 without the addition of inhibitor and 0.4 mm year-1 with the addition of inhibitor. We did not observe any direct interaction between the sand and corrosion inhibitor that could compromise the efficiency of the substance. We also concluded that electrochemical techniques can be successfully employed in dynamic conditions by means of a cell specifically designed for pipelines. The results showed that the cell and the technique were able to identify the synergistic effect of erosion-corrosion in the bottom of the pipe and also the action of the corrosion inhibitor. / Tese (Doutorado)