Development of an algorithm for wellbore stability calculation with arbitrary deviations

As the world’s demand for oil and gas increases, oil exploration companies require drilling through more complex pressure profiles. In such complex pressure environments, drilling companies often encounter severe geomechanical challenges such as small drilling margins from overpressure. This problem is routinely observed in offshore environments, including sections of the Gulf of Mexico. The complex pressure profile in this field is a result of sediment loading of low-permeability strata. This situation creates formation overpressure, which causes difficulties in drilling into target formations. To avoid these challenges, we create wellbore stability models before drilling. This study uses a 3D well trajectory, which is used to reflect the required mud weight, wellbore breakout angle, and likelihood of tensile failure. This plot visually highlights hazardous drilling intervals. To verify the optimum mud density, the developed algorithm calculates pore pressure, overburden pressure, minimum and maximum horizontal stress from actual well logs. To indicate wellbore breakout angle, this model applies the rock failure criteria such as Mohr-Coulomb, Drucker-Prager, and Modified Lade. This algorithm also provides the depths at which tensile failure might happen. 3D visualization enables the presentation of well trajectory and optimum mud weight, wellbore breakout angle, and the depth of tensile failure simultaneously. This research applied this model to an actual offshore well, in Eugene Island 330. The purpose of developing this model is not only to analyze the wellbore stability for the desired field but also to serve as an educational tool to show the fundamental concepts of borehole stability. As a next step, future studies should use calibrated geomechanical parameters from laboratory experiments and apply this model to other wells to confirm the model accuracy.