Hybrid Structural Petrophysical Joint Inversion as a Novel Inversion Technique for CO₂ Monitoring

We present a novel hybrid structural-petrophysical joint inversion approach for monitoring of geological storage of CO₂ both onshore and offshore. It integrates multiple geophysical datasets to produce consistent geophysical models that can serve a key input for a reliable quantification of reservoir parameters, e.g., saturation or pressure. The structural encourages structural similarity of the different geophysical models, while in the petrophysical joint inversion, models are linked using quasi-linear petrophysical models that can be defined from well logs. As the petrophysical joint inversion will only produce meaningful results where the petrophysical models are valid, part of the joint inversion workflow consists of exploring their validity in the model space. An important part of the efficient application of the method is a suitable workflow, which we demonstrat using seismic and electrical data from 2012 repeat surveys at the Ketzin CO₂ storage pilot in Germany.

The hybrid structural-petrophysical joint inversion results show clear improvements over independent inversions and structural and petrophysical joint inversions. Hybrid joint inversion combines the benefits of both approaches, suggesting hybrid joint inversion as a tool that can support quantitative interpretation of reservoir parameters and the amount of injected CO₂.