The aim of this study is to explain the mechanics of tubular expansion in irregularly shaped boreholes such as those frequently observed in the upper Natih reservoirs. Statistical analysis of borehole data does not indicate a strong correlation between the non-circularity and expanded tubular's in such boreholes. A two-dimensional (2-D) finite element model was developed using commercial software to determine the non-circularity of an expanded tubular and those data were compared with the measured values. A parametric study was also conducted and spider plots were generated to determine the amount of irregularity in the expanded tubulars so that optimum operational parameters could be identified to limit cross-section irregularities during the expansion process.