Numerical modeling of casing failure prediction in Offshore Gas Field

In this study, we conducted a numerical analysis of the casing failure issue in an Iranian offshore gas field. The initial hypothesis suggested that abnormal formation pressure or fault shear failure might be the causes of the casing collapse. Compaction from depletion was not considered because no gas production had occurred in recent years. A geomechanical model was constructed using well logs, laboratory tests, and drilling data. Mechanical properties and stresses were derived from measurements and the geomechanical model. We developed a finite element (FE) model to simulate the casing conditions at depth and to identify potential collapse scenarios. The FE modeling results indicated a high stress concentration around the ۷″-diameter casing. These stress concentrations were evaluated using the Von Mises yield criterion, showing that they exceeded the casing's ultimate capacity as per API standards. Alongside numerical modeling, analytical solutions with new equations were employed to examine the collapse issue. Ultimately, it was recommended to implement a new casing with higher strength values to prevent such failures in future wells

Keywords:

Casing failure , Geomechanical model , Abnormal pressure , Shear failure