Modeling and Analysis of Thermal Effects on A Fractured Wellbore During Lost Circulation and Wellbore Strengthening Processes
Abstract
To successfully prevent fracture propagation and combat lost circulation, a thorough understanding of the stress state in the near-wellbore region with fractures is imperative. One important factor that is not yet fully understood is how temperature variation during lost circulation affects pre-existing or newly initiated fractures. To address this problem, a 3D finite element analysis was conducted in this study to simulate the transport processes and state of stresses in the near-wellbore region during mud invasion into fractures. To take the thermal effects into account, a thermo-poro-elasticity model was coupled with flow and heat transfer processes. This study included a series of sensitivity analyses based on different formation properties and mud loss conditions to delineate the relative importance of different parameters on induced thermal stresses. The results demonstrate how the stresses redistribute as non-isothermal mud invasion takes place in fractures. They shows that a temperature difference between the formation rock and the circulating muds can facilitate fracture propagation during mud invasion. The thermal effect can also diminish the enhanced hoop stress, which is the tangential stress acts to close the fracture, provided by Wellbore Strengthening and other lost circulation prevention methods. Such information is important to successful management of lost circulation by taking into account thermal effects from different lost circulation prevention approaches. The conclusions of this study are particularly relevant when a large temperature difference exists between circulating fluids and surrounding rock as commonly seen in high pressure high temperature (HPHT) and deepwater wells.