Objective The Lower Triassic Feixianguan Formation in the Sichuan Basin contains thick oolitic beach reservoirs, which is the key layer of present oil and gas exploration. As the reserve strategic replacement field of the Sichuan Basin, the sedimentary system, reservoir properties and favorable zones in the Tieshanpo and Qilibei areas of the Feixianguan Formation are not clear, which restricts the potential deployment of oil and gas exploration in this area. Methods This study adopted comprehensive analysis of core, thin section, logging and seismic data to determine sedimentary facies types and the evolution of favorable reservoir zones in the region. Results In the study area, the Feixianguan Formation is a rimmed platform structure comprising five sedimentary facies: restricted platform, open platform, platform margin, slope and basin facies. The platform margin largely consists of oolitic beach development with obvious aggradational⁃lateral accretionary characteristics. These are mainly superimposed in the ssq2 to ssq4 periods vertically, with the largest in ssq2. Horizontally, the beach body was unstable and tended to migrate into the basin. The reservoir rock types are mainly (residual) oolitic limestone, (residual) oolitic dolomite and powder-fine crystalline dolomite. Conclusions The platform margin oolitic beach microfacies favors reservoir development in the Feixianguan Formation, and the porosity and permeability conditions are promising. well Po 5-well Poxi 1-well Po 2-well Po 1 in the Tieshanpo area and well Qilibei 1-well Qibei 102 in the Qilibei area are potentially favorable reservoir development zones. The spatial and temporal distribution and migration behavior of the beach bodies in the fourth-order sequence framework and the predicted favorable reservoir zones provide a basis for deepening the exploration and development of oolitic beach reservoirs in this region.
| 科 Family | 属数 Number of genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) | 属 Genus | 种数 Number of species | 占总种数比例 Percentage of total species (%) |
|---|---|---|---|---|---|---|
| 鹅膏菌科Amanitaceae | 2 | 11 | 5.26 | 鹅膏菌属 Amanita | 10 | 4.78 |
| 小菇科 Mycenaceae | 2 | 12 | 5.74 | 丝盖伞属 Inocybe | 5 | 2.39 |
| 多孔菌科 Polyporaceae | 8 | 14 | 6.70 | 蜡蘑属 Laccaria | 5 | 2.39 |
| 红菇科 Russulaceae | 3 | 23 | 11.00 | 小皮伞属 Marasmius | 6 | 2.87 |
| 小菇属 Mycena | 11 | 5.26 | ||||
| 光柄菇属 Pluteus | 5 | 2.39 | ||||
| 红菇属 Russula | 17 | 8.13 | ||||
| 栓菌属 Trametes | 5 | 2.39 |