Sequence stratigraphy and importance of syndepositional structural slope-break for architecture of Paleogene syn-rift lacustrine strata,Bohai Bay Basin,E. China |
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| Institution: | 1. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China;2. Energy & Geoscience Institute, University of Utah, Salt Lake City 84108, Utah, USA;3. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;4. School of Ocean Sciences, China University of Geosciences, Beijing 100083, China;5. Key Laboratory of Tectonics and Petroleum Resources of Ministry of Education, China University of Geosciences, Wuhan 430074, China;1. School of Energy Resource, China University of Geosciences, Beijing 100083, China;2. Tarim Basin Branch, RIPED of Petro China, Beijing 100083, China;3. College of Earth & Space Science, Peking University, Beijing 100871, China;1. Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Wuhan 430074, Hubei, China;2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;3. Tianjin Branch of China National Offshore Oil Corporation Ltd., Tianjin 300452, China;4. Research Institute of Petroleum Exploration and Development, PetroChina, Beijing 100083, China;5. CSIRO Earth Science and Resource Engineering, P.O. Box 1130, Bentley, W.A. 6102, Australia;1. Key Laboratory of Tectonics and Petroleum Resources, China University of Geosciences, Ministry of Education, Wuhan 430074, China;2. Faculty of Earth Resources, China University of Geosciences, Wuhan 430074, China;3. Shenzhen Branch of China National Offshore Oil Corporation Ltd., Shenzhen 510240, China;1. Research Institute of Petroleum Exploration and Development, Petrochina, Beijing 100083, China;2. Energy & Geoscience Institute, University of Utah, Salt Lake City 84108, UT, USA |
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| Abstract: | Sequence stratigraphy and syndepositional structural slope-break zones define the architecture of the Paleogene syn-rift, lacustrine succession in eastern China's Bohai Bay Basin. Jiyang, Huanghua and Liaohe subbasins are of particular interest and were our primary research objectives. Interpretation of 3D seismic data, well logs and cores reveals: One first-order sequence, 4 second-order sequences, and ten to thirteen third-order sequences were identified on the basis of the tectonic evolution, lithologic assemblage and unconformities in the subbasins of Bohai Bay Basin. Three types of syndepositional paleo-structure styles are recognized in this basin. They are identified as fault controlled, slope-break zone; flexure controlled, slope-break zone; and gentle slope.The three active structural styles affect the sequence stratigraphy. Distinct third-order sequences, within second-order sequences, have variable systems tract architecture due to structuring effects during tectonic episodes. Second-order sequences 1 and 2 were formed during rifting episodes 1 and 2. The development of the third-order sequences within these 2 second-order sequences was controlled by the active NW and NE oriented fault controlled, slope-break zones. Second-order sequence 3 formed during rifting episode 3, the most intense extensional faulting of the basin. Two types of distinctive lacustrine depositional sequence were formed during rifting episode 3: one was developed in an active fault controlled, slope-break zone, the other in an active flexure controlled, slope-break zone. Second-order sequence 4 was formed during the fourth episode of rifting. Syndepositional, fault- and flexure-controlled slope-break zones developed in the subsidence center (shore to offshore areas) of the basin and controlled the architecture of third-order sequences in a way similar to that in second-order sequence 3. Sequences in the gentle slope and syndepositional, flexure controlled slope-break zones were developed in subaerial region.Distribution of lowstand sandbodies was controlled primarily by active structuring on the slope-break zones, and these sandbodies were deposited downdip of the slope-break zones. Sand bodies within lowstand systems tracts have good reservoir quality, and are usually sealed by the shale sediments of the subsequent transgressive systems tract. They are favorable plays for stratigraphic trap exploration. |
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| Keywords: | Lacustrine basin Episodic rifting Sequence stratigraphy Syndepositional fault slope-break zone Syndepositional flexural slope-break zone Stratigraphic reservoir Paleogene Bohai Bay Basin |
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