Análise em regime transiente da transferência de calor em poços de petróleo

Abstract

The objective of this study is to perform a transient analysis of heat transfer in vertical oil wells, through the development of a mathematical model designed to predict the transient temperature field within these structures. Traditionally, the most commonly adopted strategy for modeling thermal phenomena in wells is the pseudo-steady-state approach, which assumes steady-state heat transfer conditions. However, this simplification can lead to significant errors, particularly under operational conditions such as the start-up or shut-down of well operations. In such cases, accounting for the transient regime can improve the accuracy of predictions. Accordingly, this work proposes a mathematical model for transient heat transfer in vertical wells, incorporating mechanisms that are often overlooked, such as radiation in the annular spaces and convective heat transfer at the wellhead surface. To achieve this objective, the adopted methodology comprises four main stages: a) a literature review on thermal modeling in oil wells; b) the development of a mathematical model for predicting the temperature field in vertical wells, based on the conservation equations of mass, momentum, and energy; c) the presentation of a numerical strategy to solve the proposed mathematical model; and d) the application of the model to determine temperature distributions in oil wells, with comparisons drawn against field data and other models from the literature, along with the performance of parametric studies. The results showed that the model demonstrated good agreement with sensor data from an offshore well and with other models reported in the literature, generally presenting errors below 5%. Furthermore, the parametric studies highlighted that radiation has a significant impact in gas-filled annuli, where as surface convection is critical for predicting wellbore cooling during shut-in operations. Thus, this study advances the understanding of thermal effects in oil wells by emphasizing the influence of mechanisms such as annular radiation and surface convection. Its application may contribute to structural integrity analyses, optimization of artificial lift methods, diagnosis of production issues, prevention of hydrate formation, evaluation of casing corrosion, and the planning of natural gas storage operations