The oil well will only produce if the refinery it is delivery to has a demand of goods from towns. You will need to provide this service also. Try connecting the refinery to 2 or 3 towns and watch the production of both industries skyrocket. Don’t forget the 20 minute rule, all cargo has to reach its destination from source in this time, that includes the trip from the industry to the station, waiting time, transport time and final trip from the destination station to the specific destination point. You also need to consider that if it is quicker for a unit of cargo to travel on its own then it wont use your line
Hope that helps