Full
LIU Meng,born in 1998,is a master degree candidate. She is mainly engaged in research related to sedimentology,reservoir geology and related fields. E-mail: liumeng2356@163.com.
Outline
Lacustrine deep-water gravity flow sedimentary sand bodies are the crucial targets for oil and gas development. Investigating the depositional characteristics of gravity flow sand bodies at the development scale can complement gravity flow depositional models and provide a basis for efficient exploitation of gravity flow reservoir. Based on cores,well logging and other data,this study examines the depositional characteristics,microfacies classification,and distribution of the Chang 71 gravity flow in Heshuinan area of the Ordos Basin at the development scale. We compare the reservoir characteristics between the different microfacies and summarizes the gravity flow depositional model. The results show the presence of six lithofacies types and six lithofacies combinations of the Chang 71,including Massive-bedded fine sandstone(Sm),Massive-bedded fine sandstone with mud pebbles and mudstone rip-up clasts(Smm),Normally graded-bedding fine sandstone(Sn),Parallel-bedded muddy siltstone(MSp),Lenticular-bedded silty mudstone(MSl),Massive-like mudstone(Mm). This study subdivides the unconfined channel area into four sedimentary microfacies: main channel,channel margin,overflow bank,mud faice of semi-deep to deep lake mud. The main channel is predominantly formed by sandy debris flow deposits,exhibiting good reservoir properties,mainly consisting of Sm-Mm(MSl)-Sm and Sm-Smm lithofacies combinations. The channel margin is mostly formed by the hybrid flow deposits,exhibiting moderate reservoir properties,primarily developing MSp-Sm and Sn-Sm(Smm)lithofacies combinations. The overflow bank is mainly formed by the turbidity current deposits,with the poorest reservoir properties,dominated by Sn-MSp and Sn-Mm(MSl)lithofacies combinations. The Chang 71 gravity flow in the Heshuinan area underwent three evolutionary stages: sandy debris flow,hybrid flow,turbidity current. The gentle topography and complex fluid evolution result in significant lateral facies variations perpendicular to the sediment source direction. During the same period,three main sedimentary facies developed: main channel,channel margin,and overflow bank. Gravity flow depositional characteristics,and sedimentary patterns are investigated in small-scale in this study,providing the theoretical guidance for effective exploitation of gravity flow hydrocarbon reservoir.
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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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