Distribution pattern and origin of the columnar pull-down anomalies in Gaoshiti Block of Central Sichuan Basin, SW China

The targets of this study are located in the Gaoshiti block, Central Sichuan Basin. Reprocessing the seismic data with reverse time migration (RTM) and using high-precision coherence analysis, this paper analyzed the distribution pattern and origin of the pull-down anomalies on the seismic sections. The study found that these anomalies are widely developed in Gaoshiti block, and believed that they are hydrothermal channels formed on the basis of tiny-grabens caused by the pull-apart function of strike-slip faults, and they had endured long-period, multistage hydrothermal reformation. Taking the reservoir of Dengying Formation as the example, integrated analysis of seismic and geology proved that the hydrothermal activities had constructively reformed the carbonate reservoirs mainly by dissolution during long period. Therefore, it was proposed that the hydrothermal channels and fracture zones are the favorable area for good reservoirs. The discovery of hydrothermal channels is very meaningful for locating high-production well sites and extending exploration fields.