Modelling stress distribution around boreholes

Abstract

The stress distribution around boreholes plays an important role for wellbore problems. This study aims to model the stress distribution around boreholes of offshore petroleum wells. The stress model around boreholes, which is associated with the in-situ stresses, rock properties as well as the wellbore pressure and configuration, is developed. The new approach uses transformation formula of a full stress tensor including its orientations and magnitudes. A calculating program for the stress analysis of wellbores (SAoWB), which is written in Matlab language, has described and calculated all components of the stress tensor at the wellbore wall as well as around boreholes. In this study, case studies are considered using the program SAoWB based on the new approach. The field case studies are applied for boreholes of the studied wells at Cuu Long basin, offshore Vietnam. The obtaining results from our program SAoWB are in good agreement with the failure observations from high solution image logs of the studied wellbore as well as coring data. They are the bases to study its implications which benefit for offshore petroleum industry activities such as wellbore stability, optimum drilling wellbore trajectories for well planning, drilling mud selection, sanding prediction and control, hydraulic fracturing, etc. Modelling the stress distribution around boreholes from the program SAoWB not only enhances knowledge of in-situ stress tensors but also impacts on well problems, especially for offshore petroleum wells.