Managing the Risk of Wellbore Instability Using Geomechanical Modeling and Wellbore Stability Analysis for Muzhil Shale Formation in Gulf of Suez, Egypt

Abstract

Wellbore instability constitutes potential risks during wellbore drilling operation; these risks may cause complicated states, and in some cases, can lead to costly operational issues. In this study we present the best solution by predicting and quantifying wellbore instability in Muzhil field, Gulf of Suez, using a 1-DMechanical Earth Model (1DMEM) built with well logs, pressure measurements, and drilling events reports. Firstly we created 1DMEM by calculating the pore pressure, vertical stress, rock strength, rock elastic parameters, and horizontal stresses. Mohr Coulomb, Modified Lade and Mogi Coulomb failure criteria determined the well deformation possibility. Lastly 1-DMEM can be used to conduct a comprehensive geo-mechanical wellbore stability analysis for the trouble zones of Muzhil Formation. 1-DMEM results showed that the best azimuth for Vertical and slightly inclined Wells will be (40º–60º) clockwise from the North, i.e. parallel to SHmin (NE40SW). The wellbore stability analysis showed that the vertical and low deviated wellbore (less than 40º) is safe and more stable than the horizontal and high deviated wellbore and unsuitable Mud Weight (MW) is a major cause of the wellbore instability. The optimal solution to wellbore instability is to follow the optimum wellbore path and use safe MW. The optimum MW in shale formation ranges from (13.5-15) ppg. The results contribute in development plan of the wellbores nearby the studied area and reducing nonproductive time and cost.

Keywords

• rock failure criteria
• wellbore instability
• geomechanical earth model
• well trajectory
• in situ stresses in rocks