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Objective This study aimed to define the high-quality reservoir development model of the Xu3 member in the source rock stratum， that is， the tight sandstone gas exploration in the Xu3 member of the Xujiahe Formation， Western Sichuan Depression， and provide theoretical guidance. Methods The core， thin section， scanning electron microscope， fluid inclusion， situ stable carbon and oxygen isotopes， porosity， and permeability data were integrated. Based on the basic characteristics of Xu3 member tight sandstone reservoirs in the Western Sichuan Depression and the types of diagenesis， the heterogeneity of the reservoirs and the development model of high-quality reservoirs were analyzed systematically. Results The results show that lithic quartz sandstone and lithic sandstone were the main rock type of the Xu3 member， and the reservoir space was primarily composed of intragranular dissolution pores and fractures， with porosity less than 7% and permeability less than 1×10-3μm2. Therefore， the sandstone reservoirs could be divided into intragranular dissolution pore and fracture- intragranular dissolution pore types. The diagenesis of the Xu3 member sandstones included compaction， cementation， and dissolution and experienced early humic acid， middle organic acid， and late hydrothermal fluids during the evolution process. In addition， two types of vertical sedimentary cycles， sandstone with sandstone and sandstone with mudstone， were identified in the Xu3 member. Conclusions The results indicated that the tight sandstone was altered by the early humic acid and middle organic acid continuously via the intergranular pore throat and fracture and in favour of reservoir formation. However， the late hydrothermal fluid acted solely in the late large scale fracture and had an insignificant effect on reservoir quality. In addition， the high-quality reservoir of the sandstone with the sandstone vertical sedimentary cycle mainly developed in the lower part of the cycle which characterized by relatively coarse-grain， but the high-quality reservoir of the sandstone with mudstone vertical sedimentary cycle mainly developed in the lower part of the cycle with relatively coarse-grain； the upper part of the cycle is adjacent to the mudstone.
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| 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 |
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