Full
LUO Bing,born in 1982,senior engineer,is engaged in researches on oil and gas geology and exploration development. E-mail: lb2001@petroChina.com.cn.
Outline
Following the discovery of the Anyue extra-large gas field in central Sichuan,significant exploration breakthroughs have been achieved in Member 2 of Dengying Formation in the Penglai area of northern Sichuan Basin in recent years. However,the exploration and development of this region remain constrained due to the complex microfacies types,considerable burial depth and strong heterogeneity of microbial mounds and shoals within the Dengying Formation. Based on core data from Well Wang-1C—a fully cored scientific exploration well located in northern Sichuan Basin—this study systematically investigates the microfacies types,sedimentary evolution,and reservoir characteristics of microbial mounds-bank complex in the Member 2 of Dengying Formation. The main findings are as follows: (1)Four primary dolomite lithofacies are identified in the Member 2 of Dengying Formation at Well Wang-1C: microbial dolomite,granular dolomite,crystalline dolomite,and dolomite breccia. Among these,laminated stromatolite dolomite,thrombolite dolomite,botryoidal dolomite,and mud-crystalline dolomite are the most developed. (2)Member 2 is predominantly composed of restricted platform deposits,with key microfacies including basal mound,core mound,mound crest,grain bank,and subtidal flat. (3)Three distinct microfacies assemblages can be recognized within the microbial mound-bank system: (Ⅰ)subtidal flat-basal mound-core mound,(Ⅱ)subtidal flat-grain dolomite bank,and(Ⅲ)subtidal flat-basal mound-core mound-grain dolomite bank. Each assemblage exhibits a substantial thickness,typically ranging from 25 to 50 m. (4)Reservoir spaces in the microbial mound-bank complex include primary pores and secondary dissolution pores. Reservoir development is primarily controlled by microfacies distribution,high-frequency sea-level fluctuations,and diagenetic processes. Notably,the microbial mound-core and mound-crest facies exhibit the most favorable reservoir properties,followed by granular shoal facies,whereas the subtidal flat facies displays the poorest physical characteristics. The above results can provide geological theoretical basis for the prediction of the distribution of ultra-deep microbial mound and flat reservoirs,and the exploration and development of natural gas in the northern Sichuan Basin.
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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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