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Optimization of Workflow for Structural Uncertainty Assessment in Caspian Offshore FieldNormal access

Authors: D. Ovsyannikov and D. Machukaev
Event name: Saint Petersburg 2018
Session: Risk and Uncertainty Analysis & Economic Geology
Publication date: 09 April 2018
DOI: 10.3997/2214-4609.201800269
Organisations: EAGE
Language: Russian
Info: Extended abstract, PDF ( 1.06Mb )
Price: € 20

Considering as much as possible uncertainty sources in risk assessment seems to be a good idea unless it leads to excessive calculations and time cost. For this reason optimization of calculation algorithm is a crucial task for experts operating in the area of uncertainty estimation. The research is based on multi-realization geomodeling of gas-bearing pre-Fasila formation. The overlying Fasila formation has been penetrated by more than 150 wells. To reduce the uncertainty of pre-Fasila structural model the technique of horizons constructing by adding isochores to a reference surface is applied. The algorithm of error assessment is adapted to the applied technique. As a result the structural uncertainty for pre-Fasila formation is decreased by 65-70% in comparison with the modeling approach which ignores overlying strata. Furthermore, depth uncertainty becomes negligible in comparison with gross thickness uncertainty, meaning that multi-realization calculations can be significantly simplified by reducing structural uncertainty to gross thickness variation. This effect is presumably produced due to both the applied modeling technique and the simulated object geometric features. The retrospective analysis of multi-realization modeling outputs allows conclusion that structural modeling algorithm can be simplified without accuracy loss by selection of optimal modeling methods     

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