Reservoir simulation models are becoming increasingly sophisticated in tandem with the rapid development of geological modeling methods. Widely used commercial simulators usually model flow through heavily faulted and structurally complex geometries with the flexibility provided by corner-point geometry. However, the nonorthogonality component present within these frameworks may compromise the solution accuracy of the model and the subsequent operational decisions involved. We propose a systematic methodology to evaluate the impact of complex gridding introducing a new streamline formulation for corner-point geometry. Based on a new time-like variable, the new formulation provides a significantly simpler and more robust development to handle the complexity in structurally demanding and faulted systems. It retains the simplicity and speed of streamline-based flow models and provides an efficient way to visualize nonorthogonal effects. Applied to various geometries showing challenging features of geology and flow, the displacement fronts obtained from streamline-derived analytic calculation identified the discrepancies characteristic between known solutions and results from two widely used commercial simulators.