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Geir Evensen

Research Professor

+47 51 87 56 15
+47 930 90 947
Nygårdsgaten 112, 5008 Bergen, Norway

Evensen has extensive experience with data assimilation in ocean and weather models, as well as ensemble-based history matching within petroleum-reservoir models. He has initiated and led several international research projects from an initial idea to operational implementation in various disciplines.

Since 2016, he has worked as a Chief scientist at the International Research Institute of Stavanger (IRIS), which from 2018, merged into NORCE.

He started as a researcher at the Nansen Environmental and Remote Sensing Center (NERSC) in 1989. There he completed a PhD and a Postdoc in applied mathematics, focussing on data-assimilation methods. At the Nansen Center, he developed new ensemble-based data-assimilation methods, e.g., the Ensemble Kalman Filter (EnKF), which is now operational in all major international weather services.

He also developed the Ensemble Smoother (ES), which has become the dominant method for history matching oil-reservoir models in the petroleum industry.

From 2003 to 2016, he worked at Norsk Hydro and Statoil, where he managed the development and implementation of the Fast-Model-Update technology. Fast Model Update is an ensemble-based tool for multidisciplinary and multi-realization reservoir modelling and management and is the preferred modelling technology used at Equinor.

Evensen also holds a secondary position as Research Director at the Nansen Centre.

Geir Evensen


Energy & Technology

Research themes

Data assimilation
Decision support systems
Reservoir Modelling

Research Groups

Data Assimilation and Optimization

More information about Geir

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A Stochastic Covariance Shrinkage Approach in Ensemble Transform Kalman Filtering – Tellus A: Dynamic Meteorology and Oceanography 2023
Learning from weather and climate science to prepare for a future pandemic – Proceedings of the National Academy of Sciences of the United States of America 2023
An ensemble-based decision workflow for reservoir management – Journal of Petroleum Science and Engineering 2022
Data Assimilation Fundamentals: A Unified Formulation of the State and Parameter Estimation Problem – Springer 2022
Subspace Ensemble Randomized Maximum Likelihood with Local Analysis for Time-Lapse-Seismic-Data Assimilation – SPE Journal 2021
A study of disproportionately affected populations by race/ethnicity during the SARS-CoV-2 pandemic using multi-population SEIR modeling and ensemble data assimilation – Foundations of Data Science (FoDS) 2021
p-Kernel Stein Variational Gradient Descent for Data Assimilation and History Matching – Mathematical Geosciences 2021
Formulating the history matching problem with consistent error statistics – Computational Geosciences 2021
Handling Big Models and Big Data Sets in History-Matching Problems through an Adaptive Local Analysis Scheme – SPE Journal 2020
An international initiative of predicting the SARS-CoV-2 pandemic using ensemble data assimilation – Foundations of Data Science (FoDS) 2020
4D seismic history matching: Assessing the use of a dictionary learning based sparse representation method – Journal of Petroleum Science and Engineering 2020
Efficient Implementation of an Iterative Ensemble Smoother for Data Assimilation and Reservoir History Matching – Frontiers in Applied Mathematics and Statistics 2019
Revising the stochastic iterative ensemble smoother – Nonlinear processes in geophysics 2019
Sparse Representation of 4D Seismic Signal Based on Dictionary Learning – 2019
Accounting for model errors in iterative ensemble smoothers – Computational Geosciences 2019
Introducing Stochastic Model Errors In Ensemble-Based History Matching – 2018
Correlation-Based Adaptive Localization for Ensemble-Based History Matching: Applied To the Norne Field Case Study – SPE Reservoir Evaluation and Engineering 2018
Data assimilation in the geosciences: An overview of methods, issues, and perspectives – Wiley Interdisciplinary Reviews: Climate Change (WIRESs) 2018
History Matching Using an Iterative Ensemble Smoother with Correlation-Based Adaptive Localization - A Real Field Case Study – 2018
Conditioning reservoir models on rate data using ensemble smoothers – Computational Geosciences 2018
Correlation-Based Adaptive Localization for Ensemble-Based History Matching: Applied to the Norne Field Case Study – 2018
Analysis of iterative ensemble smoothers for solving inverse problems – Computational Geosciences 2018
Forecasting non-linear systems with the Ensemble Kalman Filter and related data assimilation methods (eVITA-EnKF) – Nansen Senter for Miljø og Fjernmåling 2011
Asynchronous data assimilation with the EnKF – Tellus A: Dynamic Meteorology and Oceanography 2010
Structural Surface Uncertainty Modeling and Updating Using the Ensemble Kalman Filter – SPE Journal 2010
The Ensemble Kalman Filter for Combined State and Parameter Estimation MONTE CARLO TECHNIQUES FOR DATA ASSIMILATION IN LARGE SYSTEMS – Control Systems Magazine 2009
Forecasting non-linear systems with the Ensemble Kalman Filter and related data assimilation methods (eVITA-EnKF) – Nansen Environmental and Remote Sensing Center (NERSC) 2009
History Matching Using the Ensemble Kalman Filter on a North Sea Field Case – SPE Journal 2008
Incorporating 4D seismic data in reservoir simulation models using ensemble Kalman filter – SPE Journal 2007
Coastal Physical and Biochemical Processes – 2006
The impact of ensemble filter definition on the assimilation of temperature profiles in the tropical Pacific – Quarterly Journal of the Royal Meteorological Society 2005
Monitoring the Norwegian Coastal Zone Environment (MONCOZE) – 2003
Developing a Marine Information System by Integrating Existing Ocean Models Using Object-Oriented Technology – Marine Geodesy 2003
Indian Ocean: Validation of the Miami Isopycnic Coordinate Ocean Model and ENSO events during 1958-1998 – Journal of Geophysical Research (JGR) 2002
Mesoscale modelling study of the oceanographic conditions off the southwest coast of India – Indian Academy of Science(Earth and Planetary Science) 2002
A singular evolutive extended Kalman filter to assimilate ocean colour data in a coupled physical-biogeochemical model for the North Atlantic – Ocean Modelling 2001
Satellite earth observation in operational oceanography – Coastal Engineering 2000
Coordinate Transformation on a Sphere Using Conformal Mapping – Monthly Weather Review 1999
A review of the possible applications of earth observations data within EuroGOOS. Review book proceedings from "The First International Conference on EuroGOOS" – Elsevier Sciences Ltd 1997
Monitoring and modeling of the marine coastal environment – Photogrammetric Engineering and Remote Sensing 1993
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