Investigation of convolutional variational autoencoders for facies calibration within ensemble-smoother multiple data assimilation
摘要
In history matching workflows, facies parameters cannot be straightforwardly calibrated by ensemble-based methods, because they are characterized by a categorical nature. In this work, we treat 3D synthetic reservoir images with channelized facies adopting a Convolutional Variational AutoEncoder (CVAE), which is then coupled with an Ensemble Smoother with Multiple Data Assimilation (ESMDA) workflow. The goal is to parameterize the ensemble of reservoir models into a latent space and to calibrate it. An extensive hyperparamters tuning is conducted: the identification of optimal parameters allows to find a compromise between the reconstruction accuracy and the generative ability of the network. Thanks to this study, the results of the history match are significantly improved. A sensitivity analysis to assess the possibility of reducing the training set size without deteriorating the ESMDA accuracy is also carried out.