Sensitivity analysis of thermal phenomena in APB (Annular Pressure Buildup) in oil wells

Resumo

This paper presents a sensitivity analysis aimed at understanding how certain parameters of the thermal problem affect the increase in Annular Pressure Buildup (APB) in oil wells. The structure of an oil well experiences high-temperature gradients throughout its lifespan, directly affecting its components such as casings, cement, and rock formation. Among the undesirable effects caused by temperature variation, APB stands out, related to the expansion of fluids confined between casings, being a severe phenomenon that can lead to well collapse. This justifies studies aimed at better understanding temperature distributions and, consequently, the increase in pressure in the annular spaces of oil wells. On the other hand, changes in fluid and component temperatures during well operation depend on many factors, such as operating flow rate, inlet pressure and temperature, operating time, formation type, and properties of the produced/injected fluid. Some of these parameters are chosen for inclusion in the parametric analysis proposed in this work. To achieve the proposed objective, the methodology adopted in this work is based on four steps: a) selection of a reference well used for the analyses; b) definition of the variables to be studied and their assumed values; c) generation and simulation of scenarios formed by the combination of chosen variables; and d) selection and description of the sensitivity analysis method to be employed. The main contribution of this work is to present a sensitivity analysis of certain well parameters in annular pressure buildup, allowing inference about the importance of some isolated properties in the thermomechanical response. Additionally, the methodology presented can be applied to other parameters and thus improve understanding of how each property influences well APB.