--> Reservoir Oriented Non-Linear Full Waveform Inversion of Seismic Data
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Reservoir Oriented Non-Linear Previous HitFullNext Hit Previous HitWaveformNext Hit Previous HitInversionNext Hit of Seismic Data

Abstract

We present target-oriented Previous HitfullNext Hit Previous HitwaveformNext Hit non-linear Previous HitinversionNext Hit of seismic data for the purpose of obtaining seismic driven quantitative input for reservoir modelling. The method solves directly for the rock compressibility modulus and the shear modulus on a fine grid (down to 3 m) over an approx. 500 m long depth interval containing reservoir units and top and bottom seals. Solving directly for the elastic parameters allows the detection and mapping of DHIs that would not show up from conventional Previous HitinversionNext Hit approaches aiming at impedances. In addition, the non-linear character of the relationship between seismic data and the rock-properties make it peremptory that 4D effects are analysed with the help of a Previous HitfullNext Hit Previous HitwaveformNext Hit non-linear approach. The new Previous HitfullNext Hit Previous HitwaveformNext Hit Previous HitinversionNext Hit approach consists of two alternating steps. First, we solve the wave-equation for the total wavefield in the target domain. Then, we invert the measured data for the rock-properties over the same domain, driven by our best current knowledge of the total wavefield. This iterative approach solves the full non-linear problem, with considerably reduced risk of getting trapped in local minima. The keys to the success of the scheme are the regularisation of the inversions and the stabilisation of the iterative solution of the wave-equation based on still inaccurate properties. The results presented in this paper are both synthetic examples and real data cases. The synthetic examples give insight in the method and illustrate the benefits of non-linear Previous HitfullNext Hit Previous HitwaveformNext Hit Previous HitinversionNext Hit. Particularly illustrative are the results from a very elaborate synthetic reservoir model based on real outcrop data. Also the importance of the new technology for 4D is demonstrated with the help of a controlled synthetic experiment. Several real data examples will be presented covering various geological settings, ranging from on-shore tertiary deltaic to deep North Sea Carboniferous. Common features of all real data cases are that the non-linear Previous HitfullNext Hit Previous HitwaveformNext Hit Previous HitinversionTop is very robust against poor quality input data and that it generally produces a higher spatial bandwidth for the property images than could have been expected on the basis of the temporal bandwidth of the input data. This is due to the non-linear relationship between data and properties. In the deep North Sea example a gas related amplitude effect was revealed that had not been identified on the seismic data.