WELLBORE STABILITY PREDICTION IN A HYDROCARBON RESERVOIR

Abstract

This thesis presents a geomechanical stability modelling of a well situated at Jharia Coal field mines, Jharkhand (India). Analysis required calculating the mechanical parameters of rock and the in-situ stress state conditions for which well and image logs were used along with the core samples data. Instability might be a result of both mechanical and chemical effects but this study focuses on the mechanical aspects only. Model calibration was done using the core data available at different depths. The methodology assesses the stability risk for vertical wells drilled in coal seams. Use of RokDoc software to investigate factors such as the minimum mud weight required to prevent instability was attempted. Tensile fractures occur when the mud penetrates the formation due to mud weight being greater than what is predicted. On the other hand, shear failure or borehole breakouts can take place in case the mud weight is lower. The region lies in the normal faulting regime which was used to determine the stress parameters. The mud weight window is finally then computed at different depths and analyzed for safe drilling operations.