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About the first author LI Qirui,born in 1995,is a masteral candidate at Southwest Petroleum University. He is mainly engaged in researches on seismic sedimentology and reservoir geology. E-mail: li186159@163.com.
Outline
During the Ordovician-Silurian transition,the southern Sichuan Basin experienced the superposition of global and regional geological events,resulting in the complexity of its underwater topography. This complexity led to the variation of the environment during the deposition period of the Longmaxi Formation shale in this area,which in turn controlled the development of shale lithofacies. This study takes the Longmaxi Formation shale in Changning area of southern Sichuan Basin as the research object. Based on drilling wells,seismic data and various analytical test data,the underwater topography and lithofacies development characteristics during the depositional period of the Longmaxi Formation in this area were studied. The results show that: (1)The underwater topography during the depositional period of the Longmaxi Formation in Changning area has a pattern of alternating high land and depression,which can be further divided into underwater high land,slope area and depression;(2)The lithofacies types of the Longmaxi Formation shale in Changning area are diverse and the reservoir differences are obvious. The shale lithofacies have obvious “storage and gas content control” characteristics. Among them,the mixed siliceous shale lithofacies(S-2)and the calcareous siliceous shale lithofacies(S-3)are the dominant lithofacies of the Longmaxi Formation shale in Changning area,which have the “three highs”(high TOC,high porosity and high total gas content)characteristics;(3)The underwater topography pattern has an obvious differential control effect on the development of shale lithofacies. The underwater high land is mainly occupied by mixed shale lithofacies association(M)and siliceous shale lithofacies association(S),the slope area is dominated by siliceous shale lithofacies association(S),and the depression is mainly composed of mixed shale lithofacies association(M)and siliceous shale lithofacies association(S). The mixed siliceous shale lithofacies(S-2),the best lithofacies with high TOC,high gas content and high porosity,is mainly distributed in the slope area and the area close to the underwater high land. This study is of great significance for revealing the distribution law of shale lithofacies and predicting the planar distribution of favorable shale lithofacies.
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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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