Rock reliability indicator for projects and monitoring of oil and gas wells drilling

Orientador: José Ricardo Pelaquim MendesDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia MecânicaResumo: O principal risco durante a construção de poços de petróleo é a possibilidade de ocorrência de fluxos descontrolados de hidrocarbonetos do poço para o meio ambiente, mais comumente chamado de blowout. Após o acidente de Macondo, no Golfo do México, em 2010, houve um aumento significativo nos últimos anos nas pesquisas relacionadas tanto à integridade quanto à segurança operacional de poços de petróleo. Uma possível abordagem é buscar ferramentas capazes de prever cenários desastrosos e dar suporte ao processo de tomada de decisão. Neste contexto, este trabalho propõe um indicador para avaliar a confiabilidade da rocha mais frágil da seção de poço aberto, assumindo que esta esteja imediatamente abaixo da sapata do último revestimento assentado. A confiabilidade, nesse caso, se refere à probabilidade de que a rocha não frature durante um possível kick ou durante a circulação do fluido de perfuração sem kick. Houve uma preocupação em tratar as incertezas inerentes ao problema, as quais podem acarretar na falha da barreira de segurança "rocha". A modelagem foi feita atribuindo distribuições probabilísticas aos parâmetros incertos e propondo dois tipos de soluções. Para os casos em que as distribuições geradas são todas normais, é possível calcular a confiabilidade pela solução analítica; já para os casos em que há mais de um tipo de distribuição nas variáveis de entrada e a solução analítica não mais se aplica, foram utilizadas simulações de Monte Carlo para obter o resultado numericamente. A solução numérica não requer valores de médias e desvios padrões das variáveis de saída, e se torna particularmente útil quando essas características são desconhecidas. Seguindo essa metodologia, é possível incorporar as incertezas aos cálculos, não só para garantir a segurança operacional, como também para manter a integridade do poço. O indicador pode ser utilizado tanto para avaliar e comparar o grau de segurança de diferentes projetos de poços, do ponto de vista da integridade da rocha, como também auxiliar no acompanhamento em tempo real da perfuração. Os resultados da execução da metodologia proposta são os gráficos dos parâmetros de entrada e os valores de confiabilidade ao longo da fase perfurada, calculados a partir de dados geomecânicos de um poço real da bacia de Campos em dois cenários diferentes: com e sem kickAbstract: The main risk during the construction of oil wells is the possibility of uncontrolled hydrocarbon flows occurring from the well to the environment, commonly known as blowout. After the Macondo accident, in Gulf of Mexico, in 2010, there has been in recent years a significant increase in researches related to both oil wells integrity and operational safety. A possible approach is to seek tools that can predict disastrous scenarios and support the decision making process. In this context, this work proposes an indicator to evaluate the reliability of the weaker rock in the open hole section, assuming it is immediately below the last seated casing shoe. Reliability, in this case, refers to the likelihood that the rock does not fracture during a possible kick or during drilling fluid circulation without kick. There was a concern to address the uncertainties inherent to the problem, which may lead to the failure of the "rock" safety barrier. The modelling was done by assigning probabilistic distributions to the uncertain parameters and by proposing two types of solutions. For cases in which the generated distributions are all normal, it is possible to calculate the reliability using the analytical solution; and for cases in which there are more than one type of distribution in the input variables and the analytical solution no longer applies, Monte Carlo simulations were used to obtain the result numerically. The numerical solution does not require mean values and standard deviations of the output variables, and becomes particularly useful when these characteristics are unknown. Thus, following this methodology, it is possible to incorporate uncertainties in the calculations in order not only to ensure operational safety but also to maintain well integrity. The indicator can be used to both evaluate and compare the safety of different well designs, from a rock integrity standpoint, as well as to assist in real time drilling monitoring. The results of the execution of the proposed methodology are the graphs of the input parameters and the reliability values along the drilled phase, calculated from geomechanical data of a real well from Campos basin in two different scenarios: with and without kickMestradoExplotaçãoMestre em Ciências e Engenharia de Petróleo5282Funcam

Mathematical Modeling of the Differential Sticking Coefficient of Clay Drilling Fluids

The main objective of this work is to propose a mathematical model for the differential sticking coefficient of clayey drilling fluids with a lubricant as an additive and evaluate the influence of differential pressure and lubricant content on filter cake thickness and permeability. Tests were carried out on fluids composed of water and 4.86% of active bentonite clay prepared in Hamilton Beach agitators at a high rotation speed (17000 rpm) for 20 minutes. After a 24-hour time-out in a closed container, lubricants were added to the fluids at different levels. To obtain the differential sticking coefficient (DSC), and the filter cake, a differential sticking tester by Fann with a spherical torque plate was used, and the filter cake thickness was determined in an extensometer. The setting time, differential pressure, and lubricant content were defined as the input variables (independent variables) to the DSC mathematical model. The differential pressure and lubricant rate were the independent variables to the mathematical model of filter cake thickness (FCT) and permeability (K), which varied according to a factorial planning, was known as a second order model. The experimental data regression was performed utilizing Statistic software, version 7.0. The results clearly showed that it was possible to obtain a statistically meaningful and predictive mathematical model for DSC. It was also observed that the increase in the lubricant content was responsible for a DSC value reduction due to the fact that the lubricant was a dispersing agent reducing the filtrate volume and the filter cake thickness, and thereby decreasing the sticking risk due to differential pressure. Finally, from the analysis of point values and response surfaces for FCT and K, it was possible to observe tendencies that made clear that the differential pressure and lubricant content influenced filter cake properties