Risk Based Fuzzy Modeling of Cost Estimating Relationships for Floating Structures

The increasing cost of offshore developments involving floating structures has resulted in the need to ensure accurate cost estimates are developed very early in the project lifecycle. A number of conceptual costs estimating approaches exist in the industry however, there are concerns about their accuracy and applicability in the early stages of the project. Cost Estimating Relationships (CERs) that can be applied at the concept development phase of floating structures have therefore been developed. They are derived from the reported cost and weight of existing Floating Production, Storage and Off take (FPSOs) vessels and have been applied to ship based offshore development concepts. These CERs are risk based, to produce varying results on a cost (weight) and schedule basis, such that overestimates/ underestimates are offset by risk ranking, to yield a relatively small error in the cost estimates. The uncertainties identified in the risk ranking of components of the development concepts (and resulting cost estimates) are accounted for by applying fuzzy logic to the CERs. This paper presents some of the results of ongoing research that is expected to contribute significantly to the development of floating offshore structures while improving confidence levels in conceptual cost estimates, thus facilitating a comprehensive front-end evaluation of offshore developments.