Rational selection of a field development solution is a complex process, and it will significantly affect the overall project economics, schedule, and risk. Analytic Hierarchy Process (AHP) is a multi-criteria methodology which improves the qualitative and quantitative aspects of the decision-making process. However, AHP is based on pairwise comparison between different alternatives, which is a cumbersome process when the number of alternatives is large. Moreover, AHP views alternatives as monolithic, i.e. unchangeable ideas either to be eliminated or selected. This paper presents an improved screening process which combines AHP with an Even Swaps Analysis (ESA) method. The screening starts with developing potential alternatives based on different combinations of building blocks. Unfeasible or obviously inferior alternatives are eliminated and this yields a longlist of options. Instead of applying AHP to all alternatives directly, we apply AHP to the selection criteria to derive weighting factors for the criteria. These criteria are subsequently used to narrow the longlist down to a shortlist of options by consistent comparisons. Finally, the ESA method, which focuses on changes needed to improve alternatives instead of unilaterally eliminating them, is used to reach a final selection decision.
A generic case study is used to illustrate the application of the proposed screening process to select an offshore floating facility in a harsh environment. Hundreds of options are generated based on combinations of three building blocks. Elimination of unfeasible combinations results in a longlist of about twenty options. The AHP method is thereafter applied to generate criteria weights. A shortlist of five options emerges after initial screening. The ESA method is then used to balance pros and cons by changing the alternatives and studying the impact of the changes on various criteria. Eventually, by establishing a consequences table, the final concept is selected.
A robust concept screening methodology is critical for offshore development in deeper water and with complex reservoirs, which bring in increased technical, financial and execution risks. This paper provides one such methodology for concept selection in offshore field developments. The proposed method has also great potentials for complicated decision making problems in other areas.