Prediction and Modeling the Mud Weight Window Using Well-Logging Data at One of the Iranian South Gas Field

Pore pressure and Fracture gradients are the key inputs for geomechanical applications. Knowledge of these pressures is essential for cost-effective drilling, safe well planning and efficient reservoir modeling. The main objective of this study is to determine the safe mud weight windowusing well log data at one of the gas fields in south of Iran. To obtain this goal, the formation pore pressure and fracture gradient are estimated. The formation pore pressure is estimated from well logging data by applying Eaton’s prediction method with some modifications. In order to determine the fracture pressure, the estimated pore pressure is used along with calculating Poisson’s ratio from compressional and shears velocities. The estimated fracture and pore pressures are used as the top and bottom limits of the safe mud weight window. Finally, in order to generate the 3D model, well-log-based estimated fracture and pore pressures are upscaled and distributed along the 3D structural grid with a geostatistical approach in Petrel software. The obtained model is validated using a mud weight data which was not used in the modeling. The result shows that the estimated model is appropriate for the purpose of drilling plan.