Abstract

Wellbore stability analysis plays an important role in the oil and gas drilling. Instability problems during the drilling phase are often the results of a combination of both mechanical and chemical effects. This study aims to assess the mechanical wellbore stability based on the stress model around boreholes. The development of the stress model around boreholes, which is associated with the in-situ stresses, rock properties as well as the wellbore pressure and configuration, are presented. It could visualize the stress distribution around an arbitratily orientated wellbore. Next, lower hemisphere diagrams are presented to demonstrate the wellbore pressure required to initiate borehole tensile and compressive failures. A program for the risk analysis of wellbore (RAoWB) is designed and developed by the Matlab programming language to describe and analyse the risk diagrams of the drilling induced tensile fractures (DITFs) and breakouts (BOs). They help to choice the optimum wellbore trajectories for well planning, as well as to predict the wellbore instabilities caused by inappropriate wellbore pressures.