Decommissioning Optimization in a Multioperator Landscape
Authors: Carpenter Chris 
Published: December 2017

This article, written by JPT Technology Editor Chris Carpenter, contains highlights of paper SPE 186147, “Decommissioning Optimization in a Multioperator Landscape,” by T.D. Huijskes, R.E. Stoeller, E. Kreft, E.T. van Ewijk, C.T.J. van Langen, and B.C. Scheffers, Energie Beheer Nederland, and G.W. de Mare, H.C.M. Bossers, M.H. de Wolff, and G.G. de Vries, Ortec, prepared for the 2017 SPE Offshore Europe Conference and Exhibition, Aberdeen, 5–8 September. The paper has not been peer reviewed.
Total offshore decommissioning expenditures (ABEX) for the Netherlands are significant, currently estimated at more than EUR 5 billion. This equals one-third of the total future offshore revenues. Energie Beheer Nederland (EBN), the state participant in all offshore gas assets, is responsible for approximately 40% of decommissioning costs. EBN is investigating opportunities to reduce these costs without compromising safety or environmental standards. The optimization model presented in the complete paper is the first multioperator offshore network-optimization model that considers decommissioning in the Netherlands.
Introduction
A network-optimization model including platforms, wells, and technical production forecasts was built to investigate value optimization on a portfolio basis, considering gas revenues, operating expenses (OPEX), and ABEX. Future offshore decommissioning projects are shared across the coming 3 decades by 11 operators. The resulting complexities can be overcome in several ways, but these, in turn, result in organizational challenges. The complete paper thus discusses five options for decommissioning planning with different collaboration strategies, which are defined as scenarios:
Reference scenario—no collaboration. Stop production at zero economic margin.
Operator optimization—no collaboration. Optimize within operator portfolios.
Cross-operator optimization—all operators collaborate to full efficiency.
Pairs—create a pair of operators that cooperate bilaterally.
Decommissioning company—a separate company executes all decommissioning activities.
Note that the reference scenario does not include any cost reduction or ABEX-optimization strategies. It calculates the timing and amount of realized ABEX, which is effectively the amount of estimated ABEX per individual project.
Model Overview
The model used for this study combines net-present-value (NPV) -optimization strategies while describing a real network of wells, platforms, and pipelines. The technical production forecasts of gas fields are coupled by wells to platforms. Existing infrastructure connects platforms and the onshore delivery points. OPEX has to be carried by the revenues. Current OPEX and tariffs are used and assumed to be constant over time. This might cause platforms to have a cessation-of-production date that is slightly earlier than in reality, because it is usually assumed that OPEX decreases in late life because of OPEX-reduction measures. The ABEX input used is generic; an average value is used for well-decommissioning and platform-decommissioning costs. A distinction is made between small and large platforms.