97 2. Surface geophysical methods a pre-processing step. The initial velocity is derived from travel time tomography and is mainly a 1D model (not represented here). Specific attention is paid to the preservation of energy in the dataset between 1.5 to 2 Hz: this is a crucial step in the FWI construction of the velocity model. Acoustic FWI largely outperforms standard travel time tomography. More work is needed in future to consider higher frequencies and more complex physics. The obtention of accurate velocity models is a key point for seismic imaging and for estimating mechanical and petrophysical properties of geological formations. Velocity models can be obtained by tomography, full waveform inversion or simultaneous joint inversion of seismic and non-seismic measurements (De Stefano et al., 2021). Simultaneous joint inversion of two sets of geophysical data (seismic and ERT) can lead to obtaining two consistent geophysical models (seismic velocity and resistivity) to characterize geological heterogeneities (Gallardo and Meju, 2004). Ceci et al. (2024a,b) shows an example of application of an integrated Multiphysics modelling workflow, including 3D MT, 2D seismic and 3D gravity data where the combined use of the data allows the reduction of the intrinsic uncertainty of each method and the obtention of a consistent seismic velocity field controlled by MT and gravity measurements. Geothermal reservoirs can be explored and characterized using reflection seismic methods. The use of seismic methods remains a challenge for geothermal exploration due to a lack of reliable well and seismic data stemming from limited budgets and access restrictions when operating in urbanized areas. Through the last few years, porosity and permeability in the Dogger and in the Triassic reservoirs of Paris basin have been a big challenge depending on their location, particularly under tertiary deposits. Nowadays, predicting the reservoir quality from seismic is one of current challenge to derisk the geothermal topics, west of Paris Basin, near to the “Sillon marneux” area. For decades, this subject has been a real challenge, as a dedicated 3D seismic survey was shot in the Villeperdue area in 90’s to study the capacity of seismic to highlight reservoir quality variations. The approach needs to strongly correlate well and seismic data. Because of the distance between wells with interesting information, the use of seismic needs to integrate several seismic lines. CDP Consulting developed through these past years several programs of regional lines combining old vintage lines to recognize an overall basin. In this way, an innovative sequence must be developed to highlight the favourable reservoir areas, for many topics, particularly for geothermal derisking. This integrates an accurate 2D seismic sequence, possibility to provide seismic inversion on true amplitude PSTM. To perform accurate reservoir study from seismic line, it is very important to avoid some key points: • avoid seismic artefact, particularly due to stack optimization (problem of statics and signal to noise ratio), • avoid effects linked to the change of seismic parameters between lines from different seismic campaigns and introducing several difficulties in many steps of processing.
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