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Both sensitivity and nonlinearity are important for the efficiency of an estimation algorithm. Knowledge of a general nature on sensitivity and/or nonlinearity for some class of models can perhaps be utilized to improve the estimation efficiency for this class.For an ODE model, a correlation between high nonlinearity, low sensitivity, and small-scale perturbations, has been reported. Also, it was found that representing the unknown function by a multi-scale basis lead to faster estimation convergence than use of a single-scale local basis. This was explained referring to the above-mentioned correlation. Recently, the existence of such a correlation for a large class of nonlinear models, including the above-mentioned ODE model, was found.Here, we further investigate into utilization of the correlation Address all correspondence to this author. † Now with Nansen Environmental and Remote Sensing Center, Edvard Griegsvei 3a, N-5037 Solheimsviken, Norway, E-mail: karib@nrsc.no ‡ Now with RF-Rogaland Research, Thormøhlensgt. 55, Norway, between nonlinearity, scale, and sensitivity within parameter estimation. Results from numerical experiments with alternative optimizers on ODE and PDE models describing flow in porous media, are presented.

While most works on CCS in connection with CO 2 EOR credit all the benefit of the additional oil production to the CCS entity, this work investigate the impact of alternative EOR methods on the valuation on CO 2 EOR storage. Based on a generic model suitable for CO 2 EOR in Norwegian oil fields, EOR production with CO 2 injection is compared to the EOR production with chemical EOR for different scenarios.The comparison shows that depending on the scenario combination considered the added value of using the CO 2 EOR method instead of the chemical EOR method varies from -4 to 33 €/bbl produced equivalent to -4 to 56 €/tCO 2,avoided . In most of the cases considered, the CO 2 EOR method would therefore be preferred with however more or less value creation depending on the case. The evaluation shows that for an oil price minus the normal production costs equal to 50 €/bbl, the oil value which shall be considered for CO 2 EOR application varies between 8 and 41 €/bbl, which can therefore be significantly lower than the 50 €/bbl which shall be considered if chemical EOR is not an alternative. The value one would be willing to pay to have CO 2 delivered at a field varies between -4 and 56 €/t CO2 depending on the scenario combinations considered and can therefore also be significantly lower than in cases in which chemical EOR is not an alternative. For example, in the medium CO 2 EOR scenario, the CO 2 value is between 27 and 60% lower if chemical EOR is considered as an alternative option for EOR. As a consequence, a CCS chain including CO 2 EOR would overestimate its benefits if it does not considered chemical EOR as an alternative to CO 2 EOR for Oil & Gas companies. Finally, the sensitivity analyses identify the factors having the largest influence on the value one would be willing to pay to have CO 2 delivered at its field.

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