Cost optimization of shuttle tanker offloading operations

Abstract

This paper proposes an optimization model accounting for voyage costs, charter costs, and the cost of lost production for scheduling the operation of shuttle tankers that are used to transport the oil from the oil production units in deep water, to onshore terminals. This model introduces the effect of the costs from lost production, which can vastly surpass both voyage and charter costs, improving on previous research on the scheduling of such operations, which has focused solely on the optimization of voyage and charter costs, with the cost of lost production in case of failure of the logistics system being ignored. A simulation-optimization method is proposed, allowing for uncertainty in weather condition and oil production. Given the highly structured nature of the policies governing the underlying inventory routing problem, the problem can be recast as a routing problem, to great computational advantage. A novel efficient voyage-based optimization formulation is proposed, and optimality is achieved for instances with a size much larger than those of previous research. The application of the method is illustrated for Brazil, where problem instance sizes faced in practice are considerably large. Sensitivity analysis shows the considerable impact of costs from lost production on the obtained schedules.