Planning of an Offshore Well Plugging Campaign: A Vehicle Routing Approach
Steffen Bakker  1@  
1 : Norwegian University of Science and Technology - NTNU (NORWAY)  (NTNU)  -  Website
Alfred Getz' vei 3, 7034 Trondheim -  Norway

When a petroleum well no longer serves its purpose, the operator is required to perform plug and abandonment (P\&A) operations on the well to avoid contamination of reservoir fluids. An increasing number of offshore wells need to be P\&A'd in the near future, and the costs of these operations are substantial. Research on planning methods in order to allocate the required resources to perform these operations in a cost-efficient manner is therefore essential. We take a tactical planning level perspective and consider a set of wells that have to be P&A'd, making use of different vessels. The plugging of each well consists of the execution of a set of operations that has to be performed in a strict sequence. We use an optimisation approach and propose a mixed integer linear programming model formulation based on an extension of the uncapacitated vehicle routing problem with time windows with a heterogeneous fleet of vessels, precedence and non-concurrence constraints. The problem minimises permanent P&A costs by scheduling P&A operations and assigning routes to vessels. We refer to such a problem as a P&A campaign. We are currently able to solve instances with approximately 20 wells to optimality. Making use of a realistic case study, based on real-life data, we show that our approach may lead to significant cost savings compared to traditional planning methods.

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