Mechanical Earth Modeling for a vertical well drilled in a naturally fractured tight carbonate gas reservoir in the Persian Gulf
Abstract In this study, a comprehensive integrated geomechanical analysis has been performed for the construction of a one dimensional Mechanical Earth Model (MEM) for a vertical well drilled in a naturally fractured tight carbonate gas reservoir of Oxfordian age in the Persian Gulf. The critical points touched upon in this manuscript are wellbore stability based on regional stress trends, rock deformation and mechanical stratigraphy and fracture study based on core samples and image logs for different lithologies. In addition to distribution of properties such as porosity and density, the model also incorporates pore pressures, state of stress, and rock mechanical properties associated with different faulting regimes. The MEM constructed for this particular well drilled in a tectonically complex HPHT region utilizes the dynamic data available in the form of logs, and using correlations, converts it to mechanical properties. The static data obtained from the core samples (for mainly tight limestone, organic rich argillaceous limestone and shale) are correlated to the properties obtained from the log analysis. With these correlations continuous profiles for the rock strength parameters are constructed to formulate equations which are used for the entire depth of the well. Based on these formation properties, regional stress trends and inferences drawn from wellbore breakouts, a comprehensive analysis for wellbore stability is carried out. Integrating the information about breakouts and natural fractures obtained from image logs, the stress concentration around the wellbore is studied to devise a safe mud weight window for the stability of the well.