A coupled model of wellbore-formation thermal phenomena and salt creep in offshore wells

Abstract

The present work proposes a mathematical framework for calculating heat transport and annular pressure buildup (APB) in petroleum wells, taking into account salt creep in uncemented annular segments. To achieve this, we propose a Laplace Transform-based semi-analytic method to calculate transient heat flow in the wellbore. To estimate wellbore closure due to creep, we developed a Finite Element Method (FEM) formulation to handle the three deformation components that affect salt displacement. In addition to the time-dependent creep deformation of the rock, the model initially considers the elastic deformation of the rock due to geomechanical loads and pressure changes in the exposed annulus. The model was compared against field data from a well that contained an 800-m long uncemented second annulus exposed to halite. Regarding APB, considering creep in the salt layer resulted in a 2.55-MPa increase (approximately 15%) in annulus pressure. The thermal expansion of the salt rock did not significantly affect APB but significantly increased the computational cost of the simulations.