Roy, Nilanjan. M.S., Department of Earth and Environmental Sciences, Wright State University, 2008. Analysis and Interpretation of 2D Seismic Data Over the Ancona Gas Storage Facility, Illinois, Using PETREL Visualization Software.
Intriguing features of the North American mid-continent are the widespread and prominent subhorizontal seismic reflectors that are thought to be associated with thick sequences of layered rocks beneath the Phanerozoic cover of the Illinois Basin. The present investigation was an effort to identify and interpret new structural features of the pre-Paleozoic crust at the Ancona Gas Storage field in north-central Illinois. A grid of existing seismic data was reprocessed using the technique of extended correlation.
The reprocessed data was then analyzed using Schlumberger’s Petrel visualization software for seismic interpretation and reconstruction of the 2D and 3D crustal geometry. The reprocessing unveiled strong, intermittent, subhorizontal reflectors underlying the Paleozoic basinal sediments. Existence of analogous subhorizontal reflectors in Arizona, southern United States, and the Siljan ring impact area in Sweden indicate that these features might be mafic intrusions in the Proterozoic crust. Alternatively, as revealed by the Kola Superdeep Borehole study in Kola, Russia, presence of fluid-filled fractures in the deeper crustal rocks could produce such strong subhorizontal reflectivity.
Basement faults possibly produced by pre-Paleozoic crustal reactivation appear to project beneath the steeper part of the Ancona anticline. These faults are interpreted from a combination of isolated dipping reflections, diffractions, and truncations of reflectors in the seismic data.
Future research in this region would require longer seismic lines with longer range of offsets than the original 2D channel data, along with velocity information from bore holes, to develop a better structural model. However, an important conclusion of this work is that extended correlation of existing vibroseis datasets allowed the detection of structures deeper than what would have been possible through conventional processing.