Eventos Anais de eventos
COBEM 2023
27th International Congress of Mechanical Engineering
Modeling Flow Restart Effects on Annular Pressure Build-up
Submission Author:
Ricardo Knesebeck , PR
Co-Authors:
Ricardo Knesebeck, Nezia de Rosso, Cezar Otaviano Ribeiro Negrao
Presenter: Ricardo Knesebeck
doi://10.26678/ABCM.COBEM2023.COB2023-1231
Abstract
During oil well drilling, metal casings are attached to the wellbore to ensure its structural stability and prevent fluid leaks into the rock formation. Consequently, fluid ends up confined in the annular spaces between the casings and is subject to an increase in pressure known as annular pressure build-up (APB) due to temperature increase. APB is mainly caused by the temperature variations that the well undergoes throughout its life cycle, due to geothermal gradients and fluid flow. Several studies have focused on predicting and mitigating its causes and effects, usually calculating the well temperature and relating it to the confined fluid’s density and volume variations. However, most studies consider a constant operating condition to obtain the steady state condition of pressure and temperature, while transient analysis are relatively recent. The present work proposes a one-dimensional transient mathematical model to predict annular pressure changes due to temperature changes in a well’s cross section, caused by flow restart after a well shut-in. A transient heat transfer model is coupled to linear elasticity model and solved by using the finite-differences method. Results show the pressure variations in the annuli following a flow restart, where the innermost annulus experiences the most pronounced pressure variation. The abrupt pressure difference causes a stress peak on the innermost casing, presenting concern for casing integrity. Observed effects emphasize the transient nature of APB and the need for modeling of varying operational conditions. In conclusion, the one-dimensional approach provides valuable insight in transient APB while being computationally fast and easy to implement. The main factors that affect APB can be categorized in: well’s geometry, material properties and operating conditions. Well design and operational procedures must be based on each well’s unique circumstances.
Keywords
annular pressure buildup, transient, Oil well, casing stress
