Deposition of Yanchang Formation Deep-Water Sandstone under the Control of Tectonic Events, Ordos Basin
详细信息
- 责任者：Yang Hua (Changqing Oilfield Company ; PetroChina ; Xi’an 710018 ; China) ; Deng Xiuqin
- 刊名：Petroleum Exploration and Development
- 出版年：2013
- 卷期：40(5)
- 关键词：砂岩储集层 ; sandstone reservoirs ; 构造热事件 ; tectonic thermal event ; 鄂尔多斯盆地 ; Ordos Basin
- 页码：p.513-520
- 图表：7 illus., 1 table, 30 refs.
- 分类号：1003
- issnNo：ISSN1000-0747
- isbnNo：CN11-2360/TE
摘要
A large area of deep-water sandstone was formed under the combined action of delta and gravity flow in the central Ordos Basin during the depositional period of the Ch6 and Ch7 oil-bearing formations of the Upper Triassic Yanchang Formation. According to U-Pb dating of zircons by the method of LA-ICP-MS, the ages of the tuff layers at the bottom and upper parts of Ch7 oil-bearing formation are 228.2± 2.0 Ma and 221.8±2.0 Ma, respectively. Based on the ages of the tuff layers, it is suggested that the gravity flow complexes at middle-upper Ch7 and lower-middle Ch6 oil-bearing formations were formed during 215-224 Ma. The depositional time of tuff and gravity flow is roughly the same as the time when tectonics are most active in the Qinling area, i.e. middle Indosinian period. The steadily widespread tuff at the bottom of the Ch7 oil-bearing formation and the extensive gravity flow sediments formed at early lake regression period are the direct outcomes of the tectonic event. Tuff layers are widely deposited at the bottom of Ch7 oil-bearing formation under the influence of the middle Indosinian tectonic events. Divided by the tuff layers, there is obvious difference in clastic composition between the lower and upper strata. The events control formation of large-area deep-water depressions, change of depositional system, migration of depositional center, and occurrence of gravity flow.