Sequence Stratigraphy and Subtle Hydrocarbon Reservoir of Paleogene in Chezhen Sag, Bohai Bay Basin
WANG Jiao(1),JIANG Zai-xing(1,2),CHEN Shi-yue(1) (1. Faculty of Geo-Resource and Information,University of Petroleum,China, Dongying 257061, China;2. Faculty of Earth Sciences and Resources,China University of Geosciences, Beijing100083, China)
Based on comprehensive study of outcrops, drilling data, ancient life, well logging and seismic data, the Paleogene Es_3-Ed strata of the studied area were divided into two secondary sequences(Es_3-EsL_2, EsU_2-Ed), and six third class sequences(EsL_3, EsM_3, EsU_3-EsL_2, EsU_2-Es_1, Ed_3, Ed_(1-2)). The deep-faulted third class sequence was mainly controlled by the episodic fault depression and are ideal for subtle hydrocarbon reservoirs for their strong rifting activity undergone, abundant sediment supply, rich and excellent source rocks, as well as for their lower-stand fan facies, sequence style and favorable tract making-up models. The upper part of Es_3 to the lower part of Es_2 is a typical deep-faulted third class sequence that can be further divided into LST, TST and HST system tracts. In this sequence, rifting activity was strongest, sediment supply was abundant, depositional features of continuous steep slope was typical. The control of the sequences on sedimentation, the characteristics of the sedimentary system and the spatiotemporal distribution of favorable sandstone bodies are discussed. Favorable districts for subtle hydrocarbon reservoirs are predicted and ten favorable districts of four different types are outlined.