Methods and systems for modeling complex well completions include identifying a well that is a candidate for receiving a complex well completion and generating initial configuration data representing completion devices for the well. The well is modeled as a set of wellbore segments defining a well network based on the initial configuration data. The well network is integrated into a reservoir simulation grid by locating the wellbore segments within the simulated reservoir at particular locations within the reservoir simulation grid. A portion of the well network within a first area of the reservoir is selected comprising at least one wellbore segment. The reservoir simulation grid is refined within the first area and coarsened outside the first area. A simulation of the reservoir simulator is executed generating production data representing the production from the well. A simulated production profile of the well is rendered for display.