Cascading Knapsack Inequalities: reformulation of a crude oil distribution problem

In this paper we consider the problem in which crude oil is shipped from platforms to terminals using oil tankers at minimum transportation cost. This subproblem, which arises in petroleum supply chain models, can be surprisingly expensive to solve with a straightforward formulation involving inventory balances. We present a reformulation that has a special structure defined in this paper as Cascading Knapsack Inequalities. This is used as the basis for deriving tight reformulations for special cases with a limited number of classes of tankers. Numerical results are presented to demonstrate that significant computational savings can be accomplished with the proposed reformulations.