it's adding up, page-53

I am not sure if the potential production from each zone can simply be added up. Ideally, a well in primary production produces from one homogenous zone. Perforating the casing across different formations and comingling this in the well would expose low pressure zones to deeper higher pressure zones. Packers can be set between formations to isolate them but there may be a practical limit to how many of the formations can be produced from simultaneously.