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Bui H Hoang - One of the best experts on this subject based on the ideXlab platform.
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hinterland setting and composition of an oligocene deep rift lake sequence gulf of tonkin vietnam implications for petroleum Source Rock Deposition
Marine and Petroleum Geology, 2020Co-Authors: Malgorzata Rizzi, Michael B W Fyhn, Niels H Schovsbo, Christoph Korte, Jussi Hovikoski, Mette Olivarius, Tonny B Thomsen, Nynke Keulen, N T T Thuy, Bui H HoangAbstract:Abstract Most SE Asian oil accumulations are Sourced from Paleogene lacustrine mudstones. Even so, the mechanisms controlling formation of these Source Rocks are not fully understood. Bach Long Vi Island, located in the northwestern South China Sea, offers a unique opportunity to study these mechanisms. A continuous, 800 m thick, organic rich and highly oil-prone, lacustrine section was investigated in outcrop and in a continuously cored section. The Oligocene deep-lake succession formed in the Bach Long Vi Graben that connects the Beibuwan Basin with the Yinggehai-Song Hong Basin. Petrography, detrital zircon U-Th-Pb geochronology and heavy mineral assemblages of sandstone intervals document a locally derived sediment Source isolated from the Red River. Orientations of ripple cross lamination in gravity flow sands indicate axial sediment transport along the graben. Combined with the local structural configuration, this suggests that sediments were derived from the Qixi High through a relay ramp located about 10 km south of the island. Rare earth and major elements, detrital zircon ages, sandstone petrography and garnet composition, suggest a dominantly Ordovician – Silurian aged felsic and metasedimentary hinterland. The limited sediment supply from the small hinterland allowed tectonic subsidence to keep pace with graben infill. This promoted the establishment of a long-lived, deep lake favorable for Source Rock generation. In addition, heavy mineral and geochemical data document an unusually high content of detrital phosphate minerals in the investigated section indicative of a phosphate-rich hinterland. Tropical leaching resulted in an extraordinary high phosphorus input into the lake that catalyzed a high organic productivity and promoted the generation of highly prolific, oil-prone Source Rocks. The study documents that hinterland size and composition play a primary role in lacustrine Source Rock Deposition. Comparable petroleum Source Rocks are likely to exist in other ancient rift basins surrounded by small, phosphate-rich hinterlands sheltered from significant sediment input.
Yuanyuan Yang - One of the best experts on this subject based on the ideXlab platform.
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lacustrine Source Rock Deposition in response to co evolution of environments and organisms controlled by tectonic subsidence and climate bohai bay basin china
Organic Geochemistry, 2011Co-Authors: Xinhuai Zhou, Yuanyuan YangAbstract: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.
Wenquan Xie - One of the best experts on this subject based on the ideXlab platform.
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lacustrine environmental evolution and implications on Source Rock Deposition in the upper cretaceous paleocene of the south yellow sea basin offshore eastern china
Marine and Petroleum Geology, 2020Co-Authors: Yu Song, Chuanbo Shen, Wenquan XieAbstract:Abstract Lacustrine Source Rocks are well developed within the Upper Cretaceous-Paleocene in the South Yellow Sea Basin (SYSB) in offshore eastern China. Understanding the Deposition of these Source Rocks could provide critical information for hydrocarbon exploration in the SYSB, as well as reveal the paleoenvironment across the Cretaceous/Paleogene boundary in eastern China. This study investigates the lacustrine environmental evolution during the Upper Cretaceous Taizhou Formation (K2t) to Paleocene Funing Formation (E1f) within the SYSB and its implications on Source Rock Deposition based on core observation combined with organic geochemical indicators. Multiple maturity parameters (vitrinite reflectance, Tmax and biomarker isomerization ratios) reveal that the organic matter (OM) has reached early oil window maturity. The OM of Source Rocks is dominated by kerogen Type II-III (liptinite and vitrinite). Anoxic, saline-brackish deep to semi-deep lacustrine environments prevailed during the Deposition of K2t2 (second member of the K2t), E1f2 (second member of the E1f) and E1f4L (lower unit of fourth member of the E1f). The Deposition of three intervals was influenced by marine incursion, as evidenced by geochemical and paleontological results. Low to moderate TOC contents (avg. 0.78 wt% to 1.91 wt%), which corresponds to low to moderate terrestrial OM input, are observed through three intervals. Abundant freshwater, together with high terrestrial OM flowed into the lacustrine environments during the Deposition of E1f4U (upper unit of fourth member of the E1f), leading to dysoxic-oxic and freshwater conditions. High terrestrial OM input is probably the major controlling factor for relatively high TOC contents (avg. 2.49%) in the E1f4U. An evolution from balanced-fill to overfilled lake-type is observed in the Upper Cretaceous-Paleocene of SYSB, consistent with an evolution from semi-arid to humid paleoclimate conditions. The E1f4U and E1f2 Source Rocks exhibit fair to good potential, whereas poor to fair potential is present in the E1f4L and K2t2 Source Rocks. Compared with the Paleogene Source Rocks in onshore eastern China, the Upper Cretaceous-Paleocene Source Rocks in the SYSB probably hold good potential for generating commercial quantity of oil, although further study on hydrocarbon generation kinetics of Source Rocks and overall basin history are needed.
Zhenfeng Wang - One of the best experts on this subject based on the ideXlab platform.
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Source Rock Deposition controlled by tectonic subsidence and climate in the western pearl river mouth basin china evidence from organic and inorganic geochemistry
Marine and Petroleum Geology, 2017Co-Authors: Yongbin Quan, Fang Hao, Jianzhang Liu, Dijiang Zhao, Jinqiang Tian, Zhenfeng WangAbstract:Abstract Interest in factors controlling lacustrine Source Rock Deposition has increased over the last few decades because this type of deposits contain significant petroleum reSources. Generally, tectonic subsidence and climate are the two root causes as they control the accommodation potential, water column properties and Sources of organic matter. In this study, coupling organic geochemical and elemental geochemical data, two potential Source Rocks, i.e., the Eocene Wenchang Formation (E 2 w) and Oligocene Enping Formation (E 3 e) were investigated. Two models were finally raised to explain Deposition of the two set of Source Rocks according to their paleoclimatic and tectonic properties. The Source Rock potential shows a strong heterogeneity. The second member of the Eocene Wenchang Formation (E 2 w 2 ) is characterized by high organic matter content and oil-prone kerogen type. In contrast, the first member of the Eocene Wenchang Formation (E 2 w 1 ) and the Oligocene Enping formation (E 3 e) are characterized by low organic matter content and gas-prone kerogen type. The primary productivity and Depositional environment exhibit notable differences between the two potential Source Rocks horizons and show an obvious variation from the depocenter to the slope and can be best explained by the coevolution of tectonic subsidence and climate. During the E 2 w Depositional stage, low sediment supply led to mudstone deposited in deep lacustrine environment and resulted in underfilled lake basin. The low water inflow provided little terrigenous organic matter (low bicadinane, perylene and floranthene contents) and oxygen. Besides, the low area/depth ratio impeded the water circulation, thus resulted in shallow thermocline and anoxic-suboxic bottom environment (abundant dibenzothiophene and high C 35 /C 31 22S hopane ratios). Therefore abundant algae, which contributed to the high amorphous organic matter (AOM) content, can be preserved. The warm and wet climate (high Mn/Mg ratios) gave birth to autochthonous organism, such as dinoflagellates and Pavlova gyrans (abundant 4-methyl sterane). During the E 3 e Depositional stage, the sufficient sedimentary supply resulted in expanding, shallow lacustrine and swamp environment. The higher area/depth ratio and high sediment supply made environment unstable and can be strongly influenced by external environment (broader range of Mn/Mg ratios). Enough terrigenous organic matter (TOM) was transported to the slope but little to the depocenter. The slightly hot and dry climate (low Mn/Mg ratios) led to decreasing autochthonous organism and evaporation environment. The shallow water depth and relative dry climate resulted in saline, suboxic-dysoxic acid bottom environment. The co-variation of organic and inorganic indexes indicates the combination is a valid method in reconstructing Source Rock Depositional models.
Jinqiang Tian - One of the best experts on this subject based on the ideXlab platform.
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Source Rock Deposition controlled by tectonic subsidence and climate in the western pearl river mouth basin china evidence from organic and inorganic geochemistry
Marine and Petroleum Geology, 2017Co-Authors: Yongbin Quan, Fang Hao, Jianzhang Liu, Dijiang Zhao, Jinqiang Tian, Zhenfeng WangAbstract:Abstract Interest in factors controlling lacustrine Source Rock Deposition has increased over the last few decades because this type of deposits contain significant petroleum reSources. Generally, tectonic subsidence and climate are the two root causes as they control the accommodation potential, water column properties and Sources of organic matter. In this study, coupling organic geochemical and elemental geochemical data, two potential Source Rocks, i.e., the Eocene Wenchang Formation (E 2 w) and Oligocene Enping Formation (E 3 e) were investigated. Two models were finally raised to explain Deposition of the two set of Source Rocks according to their paleoclimatic and tectonic properties. The Source Rock potential shows a strong heterogeneity. The second member of the Eocene Wenchang Formation (E 2 w 2 ) is characterized by high organic matter content and oil-prone kerogen type. In contrast, the first member of the Eocene Wenchang Formation (E 2 w 1 ) and the Oligocene Enping formation (E 3 e) are characterized by low organic matter content and gas-prone kerogen type. The primary productivity and Depositional environment exhibit notable differences between the two potential Source Rocks horizons and show an obvious variation from the depocenter to the slope and can be best explained by the coevolution of tectonic subsidence and climate. During the E 2 w Depositional stage, low sediment supply led to mudstone deposited in deep lacustrine environment and resulted in underfilled lake basin. The low water inflow provided little terrigenous organic matter (low bicadinane, perylene and floranthene contents) and oxygen. Besides, the low area/depth ratio impeded the water circulation, thus resulted in shallow thermocline and anoxic-suboxic bottom environment (abundant dibenzothiophene and high C 35 /C 31 22S hopane ratios). Therefore abundant algae, which contributed to the high amorphous organic matter (AOM) content, can be preserved. The warm and wet climate (high Mn/Mg ratios) gave birth to autochthonous organism, such as dinoflagellates and Pavlova gyrans (abundant 4-methyl sterane). During the E 3 e Depositional stage, the sufficient sedimentary supply resulted in expanding, shallow lacustrine and swamp environment. The higher area/depth ratio and high sediment supply made environment unstable and can be strongly influenced by external environment (broader range of Mn/Mg ratios). Enough terrigenous organic matter (TOM) was transported to the slope but little to the depocenter. The slightly hot and dry climate (low Mn/Mg ratios) led to decreasing autochthonous organism and evaporation environment. The shallow water depth and relative dry climate resulted in saline, suboxic-dysoxic acid bottom environment. The co-variation of organic and inorganic indexes indicates the combination is a valid method in reconstructing Source Rock Depositional models.