New mathematical models and a hybrid Grouping Evolution Strategy algorithm for optimal helicopter routing and crew pickup and delivery

- Two mathematical models are proposed and analyzed for Helicopter Routing Problem.
- An effective hybrid Grouping Evolution Strategy is presented for the problem.
- The proposed hybrid algorithm proves to be efficient for operational purposes.
- The paper is motivated by the real problem in the South Pars Gas Field.

Most jacket installations located in offshore regions require daily transportation of crew with helicopter, which imposes huge operational costs on oil and gas companies. In order to save on crew exchange costs, the daily flight schedule must be planned in a way that all constraints related to origin-destination itinerary, sortieing, flight length, capacity and crew member's arrival time to the onshore base be met and the finish time of the final sortie be minimized. For this helicopter routing and crew exchange problem, two different mathematical models are developed which differ in the way the nodes and arcs are defined, and accordingly, the way the decision variables are defined. These models were solved to optimality for test problems up to 11 jackets and 28 crew members, and for the real case of South Pars Gas Field, the world's largest gas field, up to 11 jackets and 46 passengers. Considering the future extensions of the South Pars Gas Field and for problems of larger sizes, given the nature of the problem which is a grouping problem, a new algorithm, namely the hybrid Grouping Evolution Strategy (HGES), is proposed which works based on the composition of the flight sorties rather than working with each nodes in isolation. Several heuristics and a local search algorithm are incorporated in the body of GES to enhance its performance. Extensive computational experiments demonstrate that HGES can produce good solutions in an acceptable amount of time which is fit for operational use, as compared with particle swarm optimization (PSO) and pure Grouping Evolution Strategy algorithm. A GUI has also been designed to eliminate the complexity and inefficiency of the current method which is on “by-eye” basis.