Abstract: In order to clarify the hydrothermal dolomite gas reservoir enrichment pattern of Maokou Formation, the basement fault properties, formation and evolution and their significance for the hydrocarbon accumulation in the Maokou Formation and establish a hydrocarbon accumulation mode. Research indicates that there are three tectonic styles in the basement fault cross section, including "Y" and reverse "Y" style, "flower style" and upright style. Three basement faults were identified laterally, including No.15, No.15-1 and No.16 basement faults, which all show a northwest to southeast distribution. The basement fault indicates stratified properties in the longitudinal direction and segmentation along the fault strike. The middle and upper tectonic layer activity of the basement fault No.15 and No.15-1 is higher than that of the basement fault No.16, and the west section activity is higher than that of the east section in the basement fault No.15. The basement fault controls the formation and distribution of Maokou Formation hydrocarbon reservoirs. The dolomite reservoirs show a zonal distribution along the two sides of basement fault. The underlying Silurian sourcerock contribution increases with the decrease of distance to the basement fault. The well test production increases with the increase of gas content. An "on-source accumulation, dual-source hydrocarbon supply" hydrocarbon accumulation mode was established by comprehensively considering the basement fault, sourcerock and reservoir development pattern. This research could provide certain guidance for further understanding the Maokou Formation hydrothermal dolomite in Fuling, and it can also offer certain reference for the hydrocarbon accumulation characterization in other basement fault development areas.

Key words: basement fault, fault feature, hydrocarbon accumulation, Maokou Formation, southeastern Sichuan