This document discusses modeling a tilted oil-water contact (OWC) in a reservoir simulation by rotating the simulation grid. It notes that it is not possible to directly define a tilted OWC, but one can be modeled by closing the model along the aquifer plane or rotating the grid to the desired position. Rotating the grid allows preserving grid properties and well locations while defining a horizontal OWC at the desired depths, and tilted OWC can be visualized by populating results from the rotated grid into an unrotated grid.