Regional tectonic state and poro-thermo-elasticity analysis of near wellbore zone in field development plan: Utilization of an uncoupled approach

Abstract

The main aim of this work is to investigate the effects of temperature and pore pressure on stability of wellbore wall, considering the wellbore spatial orientation and regional tectonic state of the field in which the well is drilled. An uncoupled approach was proposed in this research study. Although the combination of fluid and temperature diffusion can be intensely alter the pore pressure and temperature of the near wellbore zone, the uncoupled approach can be considered as a primary, fast and simple method for optimization purposes at the earliest stages of field development when the technical data/information to conduct a coupled simulation is limited. The data used for this study were collected from real, literature and simulation cases. The real data are from geological and geophysical studies of gas reservoirs in Siberia, Russia. The results show that the problem of wellbore breakout (shear failure) happens in the final stages of field development however, the hydraulic fracturing and fluid loss (tensile failure) are the most common problems at the early stages of field development. Increasing wellbore temperature increases the shear failure risk for any wellbore orientation and regional tectonic state however it decreases the risk of tensile failure by increasing the tensile strength of rock. Effect of zenith angle on shear and tensile failure of wellbore depends on the regional fault regime. At the regions with normal fault regime, vertical wellbores are more stable than horizontal and vice-versa for strike-slip cases. For reverse fault regime, there is an optimum wellbore zenith angle where the shear failure is minimum and tensile failure is maximum. The results are further considered not only from drilling point of view but also for hydraulic fracturing job and hot fluid injection in field production life. Real well data from gas condensate reservoir in normal fault regime was provided for comparison and model validation purposes, showing a good agreement.