Gas portfolio and transport optimization

The transport of natural gas has received significant attention in the last months with the large price spikes in the UK facing sudden cold weather and the flow stop from Russia to Ukraine. Transport is a necessity in a world where gas sources are far removed from the gas demand, and in which a gas portfolio easily spans several countries. Meanwhile, the range of options within a gas portfolio is growing with an increasing number of instruments and increasing international gas trading. This has led to a situation where decisions have become non-trivial. The objective of this article is to describe the construction of an integrated approach for gas portfolio and transport optimization. In general an energy company with a gas portfolio is faced with gas deliveries at various locations, gas consumers at other locations and a grid of pipelines connecting them. While the supplies and demands change over time, the energy company must balance the flows at all times. In practice, the energy company has many instruments available in order to make the flows balance and should decide which ones to choose and how to utilize them. In this article we put an emphasis on costs and consider the central question of how to balance the gas network such that the operational costs are kept as low as possible. In the next section we first identify the different instruments constituting a gas portfolio and transport system. Then we describe the costs associated with the utilization of these instruments, and consider a basic optimization model. Next we give an example of how the model works, and address the complexity of the model. Finally we discuss how the model can be used in practice by traders and other professionals, and conclude with some directions for future research

Optimal threshold policies in a workload model with a variable number of service phases per job

We consider a basic model for two essential on-Iine decisions that have to be taken in workload models. The first is the decision to either continue or abort the service of a job. The second concerns the decision to either accept or reject new jobs. We show that under certain regularity conditions, there exist optimal threshold policies for these two types of decisions