A method may include obtaining a selection of various user-defined coarsening parameters. The user-defined coarsening parameters may include a predetermined fine-grid region in a geological region of interest and a predetermined cell distance. The method may further include determining an area of interest (AOI) mask for the geological region of interest based on the predetermined fine-grid region. The method may further include determining a geological property mask based on the user-defined coarsening parameters. The geological property mask may correspond to a predetermined geological feature within the predetermined cell distance from the AOI mask. The method may further include generating a coarsened grid model using grid model data and well data for the geological region of interest. The method may further include performing a reservoir simulation of the geological region of interest using the coarsened grid model.