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Yong Wang - One of the best experts on this subject based on the ideXlab platform.

  • hydrocarbon generation capability of sinian lower cambrian shale mudstone and carbonate rocks in the sichuan basin southwestern china implications for contributions to the giant sinian dengying Natural Gas accumulation
    AAPG Bulletin, 2018
    Co-Authors: Chunhua Shi, Jian Cao, Xiucheng Tan, Bing Luo, Wei Zeng, Haitao Hong, Xin Huang, Yong Wang
    Abstract:

    The giant Natural Gas accumulation recently discovered within the (Neoproterozoic) Dengying Formation in the Sichuan Basin of southwestern China represents a new and important supplement to the ancient Neoproterozoic–Cambrian petroleum systems worldwide. However, the source of this Gas is controversial because there are five possibilities based on geology, from bottom to top including the Lower Sinian Doushantuo mudstone, the Upper Sinian Dengying algal dolomite, the mudstone of the third member of the Dengying Formation, the Lower Cambrian Maidiping argillaceous dolomite, and the Lower Cambrian Qiongzhusi shale. To improve the understanding of this issue, 33 samples from the five possible source rock units in the study area were investigated for their character and maturity via petrology, total organic carbon (TOC), pyrobitumen reflectance, kerogen carbon isotope, and biomarker analyses. Based on the results, we address their hydrocarbon generation capabilities and contributions to the giant Gas accumulation. Results show that present-day TOC values of the samples range from 0.03% to 2.36% and vary both regionally and stratigraphically, with the Qiongzhusi shales in the central basin and the Weiyuan–Ziyang area ranking the highest. In contrast, the organic matter source and maturity within these rocks are relatively homogenous with slight variation throughout the study area. The organic matter is predominantly derived from algae and bacteria with different compositions deposited in marine reducing environments. The rocks range in thermal maturity from postmature to overmature. These results imply that the generation capability of source rock had been high in the past, and the Gas in the study area is most likely originated from oil cracking and the late generation directly from the kerogen of source rocks, with the Qiongzhusi shales being the dominant source rock. Thus, the hydrocarbon migration pattern in the study area is a lateral migration from deep-seated and younger Cambrian source rocks in sags to shallow-seated and older Sinian dolomite reservoirs in uplifts. The migration process occurred in the oil phase with the oil being later cracked. The differences in Natural Gas geochemistry may be controlled by complex factors, e.g., thermal maturity, the migration–accumulation process, and differing contributions from source rocks besides the dominant Qiongzhusi. Regionally, the central basin and the Weiyuan–Ziyang area have had high hydrocarbon generation capability and thus should be considered as favorable targets for Natural Gas Exploration in the future. This study of China provides an additional example of Neoproterozoic–Cambrian petroleum systems worldwide and thus can help to synthesize the systematics of such systems and understand the sedimentary transition across the Precambrian–Cambrian boundary.

Deyu Gong - One of the best experts on this subject based on the ideXlab platform.

  • genetic types origins and accumulation process of Natural Gas from the southwestern junggar basin new implications for Natural Gas Exploration potential
    Marine and Petroleum Geology, 2021
    Co-Authors: Dongming Zhi, Yong Song, Menglin Zheng, Zhijun Qin, Deyu Gong
    Abstract:

    Abstract Although the Junggar Basin is one of the four largest petroliferous basins in China, the proved reserves of Natural Gas is primarily concentrated in the eastern and southern parts of the basin and only account for 9.0% of the total resources. In this study, four types of Natural Gas are identified in the southwestern Junggar Basin based on their molecular composition, stable carbon isotopes, and low molecular weight hydrocarbons. Type I Gas is coal-type Gas generated from highly mature–overmature humic source rocks of the deeply buried Carboniferous (C)–Lower Permian Jiamuhe Formation (P1j) in the Shawan Sag. Type II Gas is derived from lacustrine source rocks of the Lower Permian Fengcheng Formation (P1f), which can be further divided into the two subtypes IIA and IIB. The former is highly mature oil-type Gas from the Shawan Sag, while the latter is low-mature oil-type Gas from the Mahu Sag. Type III Gas is a mixture of Types I and II Gases. Type IV Gas is secondary microbial Gas formed by the biodegradation of oils. The ethane and propane are systematically affected by biodegradation, and the selective biodegradation of propane is most notable. Based on the results of reservoir fluid inclusions and the reconstructed burial and thermal histories, two stages of oil and Gas charging events and one stage of oil and Gas adjustment are identified in the study area. The first stage of oil and Gas charging event occurred from the Late Triassic to the Early Jurassic in terms of the homogenization temperatures of ~70–100 °C of hydrocarbon inclusions. During this stage, hydrocarbons generated from P1j/C and P1f source rocks in the Shawan Sag migrated along faults and unconformities to structural highs and accumulated in reservoirs. In the Late Jurassic, a large-scale uplifting event occurred, and the early Natural Gas was extensively lost and the oils suffered severe biodegradation, leading to the formation of a large amount of secondary microbial methane. The second charging event occurred during the Early Cretaceous based on the homogenization temperature of hydrocarbon inclusions (~100–125 °C). At this stage, the study area began to subside again and large amounts of highly mature coal-type and oil-type Gases were generated from the P1f and P1j/C source rocks, which migrated to structural highs to form new Gas pools. These results confirm that there are two sets of effective Gas source rocks i.e., C/P1j and P1f, in the southwestern Junggar Basin, revealing a new field for Natural Gas Exploration. The results of this study represent a case study regarding the Gas–source correlation and restoration of the accumulation process under complex geological conditions and improve the understanding of the Natural Gas Exploration potential in the Junggar Basin.

Chunhua Shi - One of the best experts on this subject based on the ideXlab platform.

  • hydrocarbon generation capability of sinian lower cambrian shale mudstone and carbonate rocks in the sichuan basin southwestern china implications for contributions to the giant sinian dengying Natural Gas accumulation
    AAPG Bulletin, 2018
    Co-Authors: Chunhua Shi, Jian Cao, Xiucheng Tan, Bing Luo, Wei Zeng, Haitao Hong, Xin Huang, Yong Wang
    Abstract:

    The giant Natural Gas accumulation recently discovered within the (Neoproterozoic) Dengying Formation in the Sichuan Basin of southwestern China represents a new and important supplement to the ancient Neoproterozoic–Cambrian petroleum systems worldwide. However, the source of this Gas is controversial because there are five possibilities based on geology, from bottom to top including the Lower Sinian Doushantuo mudstone, the Upper Sinian Dengying algal dolomite, the mudstone of the third member of the Dengying Formation, the Lower Cambrian Maidiping argillaceous dolomite, and the Lower Cambrian Qiongzhusi shale. To improve the understanding of this issue, 33 samples from the five possible source rock units in the study area were investigated for their character and maturity via petrology, total organic carbon (TOC), pyrobitumen reflectance, kerogen carbon isotope, and biomarker analyses. Based on the results, we address their hydrocarbon generation capabilities and contributions to the giant Gas accumulation. Results show that present-day TOC values of the samples range from 0.03% to 2.36% and vary both regionally and stratigraphically, with the Qiongzhusi shales in the central basin and the Weiyuan–Ziyang area ranking the highest. In contrast, the organic matter source and maturity within these rocks are relatively homogenous with slight variation throughout the study area. The organic matter is predominantly derived from algae and bacteria with different compositions deposited in marine reducing environments. The rocks range in thermal maturity from postmature to overmature. These results imply that the generation capability of source rock had been high in the past, and the Gas in the study area is most likely originated from oil cracking and the late generation directly from the kerogen of source rocks, with the Qiongzhusi shales being the dominant source rock. Thus, the hydrocarbon migration pattern in the study area is a lateral migration from deep-seated and younger Cambrian source rocks in sags to shallow-seated and older Sinian dolomite reservoirs in uplifts. The migration process occurred in the oil phase with the oil being later cracked. The differences in Natural Gas geochemistry may be controlled by complex factors, e.g., thermal maturity, the migration–accumulation process, and differing contributions from source rocks besides the dominant Qiongzhusi. Regionally, the central basin and the Weiyuan–Ziyang area have had high hydrocarbon generation capability and thus should be considered as favorable targets for Natural Gas Exploration in the future. This study of China provides an additional example of Neoproterozoic–Cambrian petroleum systems worldwide and thus can help to synthesize the systematics of such systems and understand the sedimentary transition across the Precambrian–Cambrian boundary.

Cnpc Key - One of the best experts on this subject based on the ideXlab platform.

  • significant advancement in Natural Gas Exploration and development in china during the past sixty years
    Oil and Gas Geology, 2010
    Co-Authors: Cnpc Key
    Abstract:

    Based on analyzing the reserve and production growth of Natural Gas in China from 1949 to 2009,we summarize theoretical and practical significances of the coal-derived Gas theory and sum up the achievements in Exploration and development of giant Gas fields and their significances.Over the past sixty years,significant advancement has been made in Gas Exploration and production in China.First,China has become one of the world’s top players in Natural Gas reserves.In 1949,China’s proved geological reserves was only 0.385BCM,but in 2009,this number exceeded 7 000BCM.Second,with a annual production of 85.2BCM in 2009,China is the world’s 7th biggest Gas producer now,while it only produced 11.17MCM of Gas in 1949.Third,the theory on coal-derived Gas has promoted the rapid advancement of Gas Exploration and production.In 1979,the theory on coal-derived Gas emerged as a new theory to lead the Exploration and production of Natural Gas.Fourth,it is an important way to rapidly development China’s Natural Gas industry by exploring and developing giant Gas fields.By 2009,44 large and giant Gas fields have been discovered in China.They account for 80.5% of the total reserves and 66.4% of total Gas production in China.Significant progress has been made in Natural Gas Exploration and development in China during the past sixty years.

Zhang Shulin - One of the best experts on this subject based on the ideXlab platform.