Improved seismic image by Q-compensated reverse time migration: Application to crosswell field data, west Texas

To test the effectiveness of the Q-compensated reverse time migration (Q-RTM) method, we applied it to crosswell seismic data from western Texas. This crosswell field survey was aimed at determining the boundaries and even the internal features of the reservoir. In this area, the reservoir geologic body exhibits strong attenuation that reduces high frequencies more rapidly. Thus, conventional acoustic RTM produces a dimmed image (reduced amplitude and low resolution) of the reservoir area and structures underneath. In contrast, Q-RTM is able to compensate for the attenuation effects during imaging. The V_P and Q_P profiles needed for Q-RTM were produced by joint traveltime and frequency shift tomography. Preprocessing of the data was carried out to reduce noise, remove tube waves, and to separate up- and downgoing wavefields. Along with recovered high wavenumbers, the final Q-RTM image provided many details about geologic layers and structures. The lateral and vertical extent and internal structures within the reservoir unit were clearly determined. These geologic features were also correlated to the velocity profile and sonic logs. We concluded that Q-RTM imaging practically improved the image resolution in attenuating geologic media.