Abstract
The transportation of crude oil from production fields to refineries is a very important operation in the oil industry. In this paper, an inventory routing problem for crude oil transportation is studied, where the crude oil is transported from a central depot to a set of customers with dynamic demand using multiple transportation modes. Oil can be transported through marine routes, pipelines or a combination of the two modes. The marine transportation of crude oil is performed by a heterogeneous fleet of tankers with limited capacity owned by an oil distributor itself and/or the tankers of different types rented from a third party. Each transportation operation has a lead time and the storage capacity of oil at each customer is limited. The problem is to determine over a given planning horizon an optimal oil transportation plan that minimizes the total transportation and inventory costs subject to various constraints. The plan defines the number of tankers of each type to rent and the number of tankers of each type to dispatch on each route in each period. A mixed-integer programming model is established for the problem. Because of the high complexity and large size of the problem, the model is too complicated to be solved exactly. A metaheuristic method, the Greedy Randomized Adaptive Search Procedure (GRASP) enhanced by an intensification strategy based on Path Relinking is developed to find its near-optimal solutions. Numerical test results of the method demonstrate the effectiveness of the method.