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Towards Developing a Robust Q-Extraction Method From Full-Waveform Acoustic Logs
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, 79th EAGE Conference and Exhibition 2017, Jun 2017, Volume 2017, p.1 - 5
Abstract
There is the potential that the relation between wave attenuation and fluid saturation can be exploited in sonic logging by extracting intrinsic wave attenuation from full-waveform acoustic logs and interpreting it as a fluid saturation indicator. This, however, requires the development of accurate and robust sonic attenuation extraction methods. The median frequency shift (MFS) method is considered to be effective and robust compared to the more conventional spectral ratio method. However, attenuation (Q) extraction from full-waveform sonic data with the MFS method is still a challenge and can yield to unreliable predictions if complicating factors such as geometrical spreading and transmission losses are not properly accounted for. Finite-difference simulations provide a versatile and accurate means to generate synthetic records and thereby allow us to thoroughly test the Q extraction procedure. We extract the Q-profile for models with different complexities with the MFS method and demonstrate the significance of the geometrical spreading effect. Using a combination of elastic and viscoelastic finite-difference simulations we devise a method that accurately compensates the geometrical spreading effect.