Improving thin-bed resolution: Application of a sparse-layer inversion on 3D seismic observations from the In Salah carbon dioxide storage project

摘要

The In Salah carbon dioxide storage project in Algeria has injected more than 3 million tons of carbon dioxide into a thin water-filled tight-sand formation. Interferometric synthetic aperture radar range change data revealed a double-lobe pattern of surface uplift, which has been interpreted as the existence of a subvertical fracture, or damage, zone. The reflection seismic data found a subtle linear push-down feature located along the depression between the two lobes thought to be due to the injection of carbon dioxide. Understanding of the C0_2 distribution within the injection interval and migration within the fracture zone requires a precise subsurface layer model from the injection interval to above the top of the fracture zone. To improve the resolution of the existing seismic model, we applied a sparse-layer seismic inversion, with basis pursuit decomposition on the 3D seismic data between 1.0 and 1.5 s. The inversion results, including reflection coefficients and band-limited impedance cubes, provided improved subsurface imaging for two key layers (seismic horizons) above the injection interval. These horizons could be used as part of a more detailed earth model to study the C0_2 storage at In Salah.