optimal fleet composition and mix periodic location-routing problem with time windows in an offshore oil and gas industry: a case study of national iranian oil company

This paper presents a new mixed-integer non-linear programming (minlp) model for a supply vessel planning (svp) problem. the traditional svp, which is a maritime transportation problem, is developed to a maritime fleet sizing mix periodic location-routing problem with time windows (mfsmplrptw) by considering suppliers, location of onshore-base(s) and some real life aspects. the objective of this model is to decide the composition of fleets, optimal voyages, schedules and also the optimal location(s) for onshore-base(s) in such a way that the total cost is minimized and the needs of operation regions are fulfilled. the mfsmplprtw model is solved by an exact two-phase solution approach for both small and medium cases. also, two   meta-heuristic algorithms are used to solve the large-sized instances. in order to justify and show how the model and solution can lead to significant economic improvements for real life instances, a case study by the iooc is considered, which is the only offshore oil and gas producer in iran that has lots of installations and operation regions in the persian gulf and the sea of oman.