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Hao F.,China University of Petroleum - Beijing | Hao F.,Wuhan University | Zhou X.,Zhejiang University | Zhu Y.,Tianjin Branch of China National Offshore Oil Co. | Yang Y.,China University of Petroleum - Beijing
Organic Geochemistry | Year: 2011

Three Paleogene syn-rift intervals from the Bohai Bay Basin, the most petroliferous basin in China, were analyzed with sedimentological and geochemical techniques to characterize the lateral source rock heterogeneities, to reveal the environmental and ecological changes through geologic time and to construct depositional models for lacustrine source rocks under different tectonic and climatic conditions. The third (Es3) and first (Es1) members of the Eocene Shahejie Formation and the Oligocene Dongying Formation (Ed) display widely variable total organic carbon contents, hydrogen indices and visual kerogen compositions, suggesting changes in organic facies from deep to marginal sediments. Carefully selected deep-lake facies samples from any interval, however, display fairly uniform biomarker composition. These three intervals have distinctly different biomarker assemblages, which indicate weakly alkaline, freshwater lakes with a moderately deep thermocline during Es3 deposition, alkaline-saline lakes with shallow chemocline during Es1 deposition and acidic, freshwater lakes with deep, unstable thermocline during the deposition of the Dongying Formation. Such environmental changes corresponded to changes in subsidence rate and paleoclimate, from rapid subsidence and wet climate during Es3 deposition, through slow subsidence and arid climate during Es1 deposition to rapid subsidence and wet climate during Ed deposition and resulted in synchronous changes in terrigenous organic matter input, phytoplankton community and primary productivity. The co-evolution of environments and organisms controlled by tectonic subsidence and climate accounted for the deposition and distribution of high quality lacustrine source rocks with distinctly different geochemical characteristics. Most rift basins experienced changes in subsidence rates and possibly changes in climates during their syn-rift evolutions. The models constructed in this paper may have important implications for source rock prediction in other lacustrine rift basins. © 2011 Elsevier Ltd. Source

Hao F.,Wuhan University | Hao F.,China University of Petroleum - Beijing | Zhou X.,Tianjin Branch of China National Offshore Oil Co. | Zou H.,China University of Petroleum - Beijing | And 2 more authors.
Journal of Earth Science | Year: 2012

This paper discusses origin and charging histories of the Bozhong (Chines source) 25-1 field (BZ25-1) in the Bozhong sub-basin, Bohai (Chines source) Bay basin. Petroleum is contained in both Paleogene and Neogene reservoirs in the BZ25-1 field. The origin of the field was studied using biomarker distributions for 61 source rock samples and 34 oil samples. Oil in the Paleogene reservoirs was derived from the third member (Es 3, 43. 0-38. 0 Ma in age) of the Eocene Shahejie (Chines source) Formation, whereas oil in the Neogene reservoirs was a mixtures of oil generated from the third member and the first member (Es 1, 35. 8-32. 8 Ma) of the Eocene Shahejie Formation. Charging of the shallow Neogene reservoirs was dynamic, probably ongoing, which was a combined result of the existence of active source rocks, the development of overpressure and the fault reactivation since about 5. 1 Ma. On the contrary, the deep Paleogene reservoirs experienced intensive oil leakage as indicated by the high GOI (grains-containing-oil-inclusions) values (up to 30%) for samples below the present-day oil-water contact. Part of the oil that leaked from the Paleogene reservoirs re-accumulated in the shallow Neogene reservoirs. The variation of oil origins within the BZ25-1 field, and the dynamic petroleum charging into the shallow Neogene reservoirs and leakage from the deep Paleogene reservoirs have important implications for petroleum exploration. © 2012 China University of Geosciences and Springer-Verlag Berlin Heidelberg. Source

Teng C.,Wuhan University | Hao F.,Wuhan University | Zou H.,China University of Petroleum - Beijing | Zhou X.,Tianjin Branch of China National Offshore Oil Co. | Xu C.,Tianjin Branch of China National Offshore Oil Co.
AAPG Bulletin | Year: 2016

The Tan-Lu fault system in the central Liaodong Bay subbasin, Bohai Bay Basin, has complex structural characteristics, and its tectonism during the Cenozoic is an important factor in oil accumulation. Three-dimensional seismic data were used to document the structural features and evolution of the system. Variations in source rock occurrence, oil catchment area, and faulting intensity were comprehensively evaluated to discuss the heterogeneity of oil occurrence along the system. Detailed analysis of the seismic data indicates a right-lateral slip for the Tan-Lu fault system. Transpression and transtension occur on two branches of the Tan-Lu fault with different orientations, indicating a likely slip azimuth that is between the two orientations, i.e., 30°-35°. The strike-slip began at the middle stage of deposition of the Shahejie Formation and reached its climax during deposition of the first and second members of the Dongying Formation. To date, the slip is still continuing. In the transpressional system, the lower strata on opposite sides of the strike-slip fault were shortened and folded, whereby the upper strata were stretched and normal faulted. As a result, a negative flower structure developed immediately above a positive flower structure. Strain distribution in this system is similar to that in a classic fold. Moderate tectonic deformation could enlarge the oil catchment area, benefiting oil accumulation. Weak or intense deformation is unfavorable for commercial oil accumulation because of a small oil catchment area and poor oil preservation, respectively. © Copyright 2016. The American Association of Petroleum Geologists. All rights reserved. Source

Xu S.,China University of Petroleum - Beijing | Hao F.,China University of Petroleum - Beijing | Hao F.,Wuhan University | Xu C.,Tianjin Branch of China National Offshore Oil Co. | And 2 more authors.
AAPG Bulletin | Year: 2014

Tracing petroleum migration pathways is essential for predicting petroleum occurrence and reducing exploration risks associated with hydrocarbon charge, but a difficult task because of rapid lateral and vertical facies changes in lacustrine basins. An integration of geological, geophysical, and geochemical analysis is employed to investigate the origin of crude oil, the carrier-bed architecture, and migration pathways from source to trap in the JX1-1 oil field, Liaodong Bay subbasin, Bohai Bay Basin. Detailed geochemical studies suggest that three potential source-rock intervals (E2S3, E2S1 and E3d3) exist in the Liaodong Bay subbasin, and crude oil in the JX1-1 field was derived from the E2S3 and E2S1 source rocks. The carrier beds from E2S3 and E2S1 source rocks to the trap were characterized using geophysical data. The fan-delta sandstone in the E2S3 Member has an immediate contact with E2S3 source rock and served as dominant conduit for the expulsion and migration of oil generated from E2S3 source rock. The E3d3 braided-delta sandstones overlying the E2S1 source rock served as dominant conduit for E2s1-sourced oil. The focusing of petroleum migration pathways and the merge of migration pathways in E2S3 and E3d3 sandstones account for the accumulation of the JX1-1 field and the mixing of E2S3- and E2s1-sourced oil in the field. This study suggests that the distribution of permeable sandstones and their stratigraphic contact with the source rocks are key for petroleum migration and occurrence, and integration of geophysical, geological, and geochemical studies provide an effective way to trace petroleum migration pathways. Copyright © 2014. The American Association of Petroleum Geologists. All rights reserved. Source

Jin S.,Wuhan University | Wang H.,Wuhan University | Chen S.,Wuhan University | Gan H.,Wuhan University | And 2 more authors.
Journal of Earth Science | Year: 2013

Yinger sag is the main petroleum generative sag in eastern Jiuquan Basin, and only the Changshaling oil resource has been found after 60 years prospecting. Changshaling anticline crest zone was formed above the regional uplift, and was slightly affected by over thrust during Tertiary Period. The anticline crest was identified as a structural transposition zone. Based on analysis of seismic facies, logging facies and seismic inversion technique, it has been demonstrated that anticline crest zone conducts drainage entering basin and dominates sedimentary detritus further dispersing, and the anticline crest zone controls the distribution of sand bodies and the development of sedimentary system consequently. The sequence stratigraphic patterns of multi-step fault belt in Member 3 of Xiagou Formation in Lower Cretaceous in the anticline crest zone is composed of the development of sedimentary facies in plan and distribution of multi-step fault belt sand bodies in spatial. This research investigates the sand-control models and sequence patterns, and finally a model of reservoirs in anticline crest zone is identified. © 2013 China University of Geosciences and Springer-Verlag Berlin Heidelberg. Source

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