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Shu Jiang - One of the best experts on this subject based on the ideXlab platform.
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difference analysis of Organic Matter enrichment mechanisms in upper ordovician lower silurian shale from the yangtze region of southern china and its geological significance in shale gas exploration
Geofluids, 2019Co-Authors: Zhenxue Jiang, Kun Zhang, Yan Song, Shu Jiang, Yizhou Huang, Chuanxun ZhouAbstract:The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The Organic Matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of Organic Matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total Organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying Sedimentary Organic Matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The Sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of Sedimentary Organic Matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich Sedimentary Organic Matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.
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mechanism analysis of Organic Matter enrichment in different Sedimentary backgrounds a case study of the lower cambrian and the upper ordovician lower silurian in yangtze region
Marine and Petroleum Geology, 2019Co-Authors: Kun Zhang, Weiwei Liu, Ming Wen, Zhenxue Jiang, Yan Song, Shu Jiang, Yizhou Huang, Chengzao Jia, Xuelian XieAbstract:Abstract In order to meet the demand of shale oil and gas exploration, it is more and more important to study the controlling effect of Sedimentary environment on the enrichment of Organic Matter. In this paper, the Lower Cambrian and Upper Ordovician-Lower Silurian shales in the Yangtze region are studied. Firstly, according to the content of Mo and TOC, the water closure property of the shale depositional period is judged. Then this study selected typical wells, and calculated quantitatively whether there was excess siliceous minerals in shale and the content of it. The origin of excess siliceous minerals is determined by Al, Fe and Mn element. The results show that the Lower Cambrian shale is deposited in a weak to moderate restricted water environment, and the Upper Ordovician and Lower Silurian shales are deposited in a strong restricted water environment in the Yangtze region. Excess siliceous minerals in the Lower Cambrian shale is of hydrothermal origin. On the one hand, hydrothermal activity can enhance the reductivity of the water bottom. On the other hand, it can improve the biological productivity, so that the Sedimentary Organic Matter can be enriched. Excess siliceous minerals in Upper Ordovician and Lower Silurian shale is biogenic. The strong restriction of the water leads to stratification. The oxygen content in the upper layer makes the biological productivity higher and the lower layer more reductive, which is beneficial to the preservation of Sedimentary Organic Matter.
Kun Zhang - One of the best experts on this subject based on the ideXlab platform.
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the role of deep geofluids in the enrichment of Sedimentary Organic Matter a case study of the late ordovician early silurian in the upper yangtze region and early cambrian in the lower yangtze region south china
Geofluids, 2020Co-Authors: Kun Zhang, Jun Peng, Weiwei Liu, Qingsong Xia, Sihong Cheng, Yiming Yang, Yao Zeng, Ming Wen, Dongmei LiuAbstract:Organic Matter is the material basis for shales to generate hydrocarbon, as well as the main reservoir space and seepage channel for shale gas. When the thermal evolution degree is consistent, the Organic carbon content in present shales is subject to the abundance of primitive Sedimentary Organic Matter. Deep geofluids significantly influence the Sedimentary Organic Matter’s enrichment, but the mechanism remains unclear. This paper is aimed at determining how hydrothermal and volcanic activities affected the enrichment of Sedimentary Organic Matter by studying lower Cambrian shales in the lower Yangtze region and upper Ordovician-lower Silurian shales. Oxidation-reduction and biological productivity are used as indicators in the study. The result shows that hydrothermal or volcanic activities affected the enrichment of Sedimentary Organic Matter by influencing climate changes and the nutrients’ sources on the waterbody’s surface and reducing water at the bottom. In the lower Cambrian shales of the Wangyinpu Formation in the lower Yangtze region, hydrothermal origin caused excess silicon. During the Sedimentary period of the lower and middle-upper Wangyinpu Formation, vigorous hydrothermal activities increased the biological productivity on the waterbody’s surface and intensified the reducibility at the bottom of the waterbody, which enabled the rich Sedimentary Organic Matter to be well preserved. During the Sedimentary period of the lower upper Ordovician Wufeng Formation and the lower Silurian Longmaxi Formation in the upper Yangtze region, frequent volcanic activities caused high biological productivity on the waterbody surface and strong reducibility at the bottom of the waterbody. As a result, the abundant Organic Matter deposited from the water surface can be well preserved. During the Sedimentary period of the upper Longmaxi Formation, volcanic activities died down gradually then disappeared, causing the biological productivity on the water surface to decrease. Besides, the small amount of Organic Matter deposited from the water surface was destroyed due to oxidation.
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difference analysis of Organic Matter enrichment mechanisms in upper ordovician lower silurian shale from the yangtze region of southern china and its geological significance in shale gas exploration
Geofluids, 2019Co-Authors: Zhenxue Jiang, Kun Zhang, Yan Song, Shu Jiang, Yizhou Huang, Chuanxun ZhouAbstract:The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The Organic Matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of Organic Matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total Organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying Sedimentary Organic Matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The Sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of Sedimentary Organic Matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich Sedimentary Organic Matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.
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mechanism analysis of Organic Matter enrichment in different Sedimentary backgrounds a case study of the lower cambrian and the upper ordovician lower silurian in yangtze region
Marine and Petroleum Geology, 2019Co-Authors: Kun Zhang, Weiwei Liu, Ming Wen, Zhenxue Jiang, Yan Song, Shu Jiang, Yizhou Huang, Chengzao Jia, Xuelian XieAbstract:Abstract In order to meet the demand of shale oil and gas exploration, it is more and more important to study the controlling effect of Sedimentary environment on the enrichment of Organic Matter. In this paper, the Lower Cambrian and Upper Ordovician-Lower Silurian shales in the Yangtze region are studied. Firstly, according to the content of Mo and TOC, the water closure property of the shale depositional period is judged. Then this study selected typical wells, and calculated quantitatively whether there was excess siliceous minerals in shale and the content of it. The origin of excess siliceous minerals is determined by Al, Fe and Mn element. The results show that the Lower Cambrian shale is deposited in a weak to moderate restricted water environment, and the Upper Ordovician and Lower Silurian shales are deposited in a strong restricted water environment in the Yangtze region. Excess siliceous minerals in the Lower Cambrian shale is of hydrothermal origin. On the one hand, hydrothermal activity can enhance the reductivity of the water bottom. On the other hand, it can improve the biological productivity, so that the Sedimentary Organic Matter can be enriched. Excess siliceous minerals in Upper Ordovician and Lower Silurian shale is biogenic. The strong restriction of the water leads to stratification. The oxygen content in the upper layer makes the biological productivity higher and the lower layer more reductive, which is beneficial to the preservation of Sedimentary Organic Matter.
Zhenxue Jiang - One of the best experts on this subject based on the ideXlab platform.
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difference analysis of Organic Matter enrichment mechanisms in upper ordovician lower silurian shale from the yangtze region of southern china and its geological significance in shale gas exploration
Geofluids, 2019Co-Authors: Zhenxue Jiang, Kun Zhang, Yan Song, Shu Jiang, Yizhou Huang, Chuanxun ZhouAbstract:The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The Organic Matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of Organic Matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total Organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying Sedimentary Organic Matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The Sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of Sedimentary Organic Matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich Sedimentary Organic Matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.
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mechanism analysis of Organic Matter enrichment in different Sedimentary backgrounds a case study of the lower cambrian and the upper ordovician lower silurian in yangtze region
Marine and Petroleum Geology, 2019Co-Authors: Kun Zhang, Weiwei Liu, Ming Wen, Zhenxue Jiang, Yan Song, Shu Jiang, Yizhou Huang, Chengzao Jia, Xuelian XieAbstract:Abstract In order to meet the demand of shale oil and gas exploration, it is more and more important to study the controlling effect of Sedimentary environment on the enrichment of Organic Matter. In this paper, the Lower Cambrian and Upper Ordovician-Lower Silurian shales in the Yangtze region are studied. Firstly, according to the content of Mo and TOC, the water closure property of the shale depositional period is judged. Then this study selected typical wells, and calculated quantitatively whether there was excess siliceous minerals in shale and the content of it. The origin of excess siliceous minerals is determined by Al, Fe and Mn element. The results show that the Lower Cambrian shale is deposited in a weak to moderate restricted water environment, and the Upper Ordovician and Lower Silurian shales are deposited in a strong restricted water environment in the Yangtze region. Excess siliceous minerals in the Lower Cambrian shale is of hydrothermal origin. On the one hand, hydrothermal activity can enhance the reductivity of the water bottom. On the other hand, it can improve the biological productivity, so that the Sedimentary Organic Matter can be enriched. Excess siliceous minerals in Upper Ordovician and Lower Silurian shale is biogenic. The strong restriction of the water leads to stratification. The oxygen content in the upper layer makes the biological productivity higher and the lower layer more reductive, which is beneficial to the preservation of Sedimentary Organic Matter.
Richard G Keil - One of the best experts on this subject based on the ideXlab platform.
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Sedimentary Organic Matter geochemistry of clayoquot sound vancouver island british columbia
Limnology and Oceanography, 2005Co-Authors: Jonathan M Nuwer, Richard G KeilAbstract:Surface sediment samples from three interconnected fjords of Clayoquot Sound, British Columbia, were density fractionated (1.6 g cm -3 ) to isolate discrete Organic debris (OD) from mineral-associated Organic Matter (MOM). Total Organic carbon (OC) values varied greatly, ranging from <0.1% to 8.8% by weight, with a general decreasing trend from fjord head to the continental shelf. Within the sediment, terrestrial OM was present either as vascular plant debris or soil MOM. Down-fjord, the woody vascular plant material in the OD fraction acquires nitrogen, which is hypothesized to be due to the bacterial incorporation of nitrogen from the water. Terrestrial OC in the MOM is incompletely replaced by marine OC within the fjords, resulting in a 65% net loss of MOM. Sediments deposited under oxic and intermittently anoxic water column conditions have Organic carbon to surface area ratios (OC:SA) ranging from 0.4 to 1.2 mg C m -2 , similar to that of typical continental margin sediments. Given that temperate fjords contain an estimated 12% of the continental margin sediment deposited during the last 100,000 yr, and that they bury at least a margin-equivalent amount of OC (either weight or surface area normalized), we hypothesize that temperate fjords may contain 12% or more of the Sedimentary OC buried during this time.
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Sedimentary Organic Matter preservation a test for selective degradation under oxic conditions
American Journal of Science, 1999Co-Authors: John I Hedges, Allan H Devol, Hilairy E Hartnett, Elizabeth Tsamakis, Richard G KeilAbstract:The authors report here a test of the hypothesis that the extent of Organic Matter preservation in continental margin sediments is controlled by the average period accumulating particles reside in oxic porewater immediately beneath the water/sediment interface. Oxygen penetration depths, Organic element compositions, and mineral surface areas were determined for 16 sediment cores collected along an offshore transect across the Washington continental shelf, slope, and adjacent Cascadia Basin. Individual amino acid, sugar, and pollen distributions were analyzed for a 11 to 12 cm horizon from each core, and {sup 14}C-based sediment accumulation rates and stable carbon isotope compositions were determined from depth profiles within a subset of six cores from representative sites. Sediment accumulation rates decreased, and dissolved O{sub 2} penetration depths increased offshore along the sampling transect. As a result, oxygen exposure times (OET) increased seaward from decades (mid-shelf and upper slope) to more than a thousand years (outer Cascadia Basin). Organic contents and compositions were essentially constant within individual sediment cores but varied consistently with location. In particular, Organic carbon/surface area ratios decreased progressively offshore and with increasing OET. Three independent compositional parameters demonstrated that the remnant Organic Matter in farther offshore sediments is more degraded. Both concentrationmore » and compositional patterns indicated that Sedimentary Organic Matter exhibits a distinct and reproducible oxic effect. OET helps integrate and explain Organic Matter preservation in accumulating continental margin sediments and hence provides a useful tool for assessing transfer of Organic Matter from the biosphere to the geosphere.« less
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Sedimentary Organic Matter preservation an assessment and speculative synthesis
Marine Chemistry, 1995Co-Authors: John I Hedges, Richard G KeilAbstract:Throughout Earth history, almost all preserved Organic Matter has been incorporated in marine sediments deposited under oxygenated waters along continental margins. Given modern oceanic productivity and sediment burial rates of 50 × 1015 and 0.16 × 1015 gC yr−1, respectively, Organic preservation in the marine environment is < 0.5% efficient. Although correlative information is often used to suggest that productivity, sediment accumulation rate, bottom water oxicity, and Organic Matter source are key variables, the mechanisms governing Sedimentary Organic Matter preservation have remained unclear. The factors which directly determine preservation vary with depositional regime, but have in common a critical interaction between Organic and inOrganic materials over locally variable time scales. More than 90% of total Sedimentary Organic Matter from a wide variety of marine depositional environments cannot be physically separated from its mineral matrix. This strongly associated Organic component varies directly in concentration with sediment surface area and thus appears to be sorbed to mineral grains. Sediments accumulating outside deltas along continental shelves and upper slopes characteristically exhibit mineral surface area loadings approximately equivalent to a single molecular covering. These monolayer-equivalent coatings include a fraction of reversibly bound Organic molecules that are intrinsically labile, but resist appreciable mineralization as they pass rapidly through oxygenated surface sediments and are preserved within underlying anoxic deposits. The delivery of mineral surface area is the primary control on Organic Matter preservation within these expansive coastal margin regions where roughly 45% of all Organic carbon accumulates. Deltaic sediments account for roughly another 45% of global carbon burial, but often exhibit much less than monolayer-equivalent Organic coatings. This pattern is seen in periodically oxygenated sediments off the mouth of the Amazon River, even though the component clastic minerals are discharged by the river with monolayer coatings. Comparably extensive losses of Organic Matter, including distinct particles such as pollen grains, occur in the surfaces of deep-sea turbidites in which long term reaction with O2 is clearly the causative factor. Sub-monolayer Organic coatings also are observed in continental rise and abyssal plain sediments where slower accumulation rates and deeper O2 penetration depths result in increased oxygen exposure times and little (~ 5% of the global total) Organic Matter preservation. A transition zone between monolayer and sub-monolayer Organic coatings apparently occurs on lower continental slopes, and is marked along the Washington coast by parallel offshore decreases in total Organic Matter and pollen between 2000–3000 m water depth. Sediments underlying highly productive, low-oxygen coastal waters such as off Peru and western Mexico are characteristically rich in Organic Matter, but account for only ~ 5% of total Organic carbon burial. These sediments show a direct relationship between Organic Matter content and mineral surface area, but at Organic loadings 2–5 times a monolayer equivalent. Organic materials sorbed in excess of a monolayer thus also may be partially protected. Such high Sedimentary Organic contents may result from equilibration with DOM-rich porewaters, or very brief O2 exposure times which allow preservation of extremely oxygen-sensitive Organic materials such as pigments and unsaturated lipids. Thus Organic Matter preservation throughout much of the ocean may be controlled largely by competition between sorption at different protective thresholds and oxic degradation. Future research strategies should be specifically directed at delineating the mechanisms for Organic Matter preservation in marine sediments. In particular, special effort is needed to determine the amounts and types of sorbed Organic materials and the nature of their bonding to mineral surfaces. The extent and dynamics with which Organic molecules are partitioned between porewaters and solid phases also should be determined, as well as the effects of these phase associations on their reactivities toward chemical and biological agents. In addition, processes for slow oxic (and suboxic) degradation of Organic materials bear investigation in deep-sea sediments, as well as in other extreme environments such as oxidizing turbidites, weathering shales, and soils. Such studies should include characterizations of hydrolysis-resistant Organic materials and emphasize the complementary use of biochemical compositions with readily separable particles such as pollen to calibrate and typify the mechanisms and stages of Sedimentary Organic degradation.
Chuanxun Zhou - One of the best experts on this subject based on the ideXlab platform.
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difference analysis of Organic Matter enrichment mechanisms in upper ordovician lower silurian shale from the yangtze region of southern china and its geological significance in shale gas exploration
Geofluids, 2019Co-Authors: Zhenxue Jiang, Kun Zhang, Yan Song, Shu Jiang, Yizhou Huang, Chuanxun ZhouAbstract:The upper Ordovician-lower Silurian shale has always been the main target of marine shale gas exploration in southern China. However, the shale gas content varies greatly across different regions. The Organic Matter content is one of the most important factors in determining gas content; therefore, determining the enrichment mechanisms of Organic Matter is an important problem that needs to be solved urgently. In this paper, upper Ordovician-lower Silurian shale samples from the X-1 and Y-1 wells that are located in the southern Sichuan area of the upper Yangtze region and the northwestern Jiangxi area of the lower Yangtze region, respectively, are selected for analysis. Based on the core sample description, well logging data analysis, mineral and elemental composition analysis, silicon isotope analysis, and TOC (total Organic carbon) content analysis, the upper Ordovician-lower Silurian shale is studied to quantitatively calculate its content of excess silicon. Subsequently, the results of elemental analysis and silicon isotope analysis are used to determine the origin of excess silicon. Finally, we used U/Th to determine the characteristics of the redox environment and the relationship between excess barium and TOC content to judge paleoproductivity and further studied the mechanism underlying Sedimentary Organic Matter enrichment in the study area. The results show that the excess silicon from the upper Ordovician-lower Silurian shale in the upper Yangtze area is derived from biogenesis. The Sedimentary water body is divided into an oxygen-rich upper water layer that has higher paleoproductivity and a strongly reducing lower water that is conducive to the preservation of Sedimentary Organic Matter. Thus, for the upper Ordovician-lower Silurian shale in the upper Yangtze region, exploration should be conducted in the center of the blocks with high TOC contents and strongly reducing water body. However, the excess silicon in the upper Ordovician-lower Silurian shale of the lower Yangtze area originates from hydrothermal activity that can enhance the reducibility of the bottom water and carry nutrients from the crust to improve paleoproductivity and enrich Sedimentary Organic Matter. Therefore, for the upper Ordovician-lower Silurian shale in the lower Yangtze region, exploration should be conducted in the blocks near the junction of the two plates where hydrothermal activity was active.
