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Impact of initial ensembles on posterior distribution of ensemble-based assimilation methods

Jahanbakhshi, S ; Sharif University of Technology | 2018

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  1. Type of Document: Article
  2. DOI: 10.1016/j.petrol.2018.07.022
  3. Publisher: Elsevier B.V , 2018
  4. Abstract:
  5. In this study, impact of initial ensembles on posterior distribution of ensemble-based assimilation methods is statistically analyzed. Along with, sampling performance as well as uncertainty quantification of these methods are compared in terms of their ability to accurately and consistently evaluate unknown reservoir model parameters and reservoir future performance. For this purpose, a synthetic test problem, which is a small but highly nonlinear reservoir model under two-phase flow, is utilized. Subsequently, different initial ensemble sets are considered and are updated through the assimilation process performed on the test problem using ensemble-based assimilation methods. Afterwards, consistency of the updated ensemble sets of permeability field as well as consistency of the predicted ensemble sets of cumulative water production have been assessed to reveal dependence of assimilation methods to the initial ensembles. Results of multi-sample hypothesis tests clearly disclose the inconsistencies between different updated ensemble sets of permeability field, and also between different predicted ensemble sets of cumulative water production. This is probably due to spurious correlations among the updated ensemble members within each set. Furthermore, the effects of ensemble size and type of the observation data on the associated inconsistency are investigated. © 2018 Elsevier B.V
  6. Keywords:
  7. Bayes’ rule ; Ensemble-based assimilation ; Future performance ; Hypothesis test ; Spurious correlation ; Statistical inconsistency ; Petroleum reservoirs ; Reservoirs (water) ; Ensemble-based assimilation ; Future performance ; Hypothesis tests ; Permeability fields ; Posterior distributions ; Reservoir modeling ; Statistical inconsistencies ; Uncertainty quantifications ; Two phase flow ; Correlation ; Ensemble forecasting ; Hydrocarbon reservoir ; Parameterization ; Permeability ; Statistical analysis ; Two phase flow
  8. Source: Journal of Petroleum Science and Engineering ; Volume 171 , 2018 , Pages 82-98 ; 09204105 (ISSN)
  9. URL: https://www.sciencedirect.com/science/article/abs/pii/S0920410518305977