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Pingan Peng - One of the best experts on this subject based on the ideXlab platform.
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climate driven variations in the Depositional Environment and organic matter accumulation of lacustrine mudstones evidence from organic and inorganic geochemistry in the biyang depression nanxiang basin china
Energy & Fuels, 2019Co-Authors: Shuangfang Lu, Wenhao Li, Yuying Zhang, Taohua He, Pingan PengAbstract:The influence of the paleoclimate on the organic matter (OM) accumulation and Depositional process in the third member of the Hetaoyuan Formation shales is unclear in the Paleogene lacustrine systems in the Biyang Depression, Nanxiang Basin, Eastern China. Here, inorganic and organic geochemical analyses were performed on samples from a 25 m profile to examine the effects of paleoclimate change on the Depositional Environment and OM accumulation within this interval. Based on mineralogical and geochemical data from the B1 Well, two major lithofacies assemblages, calcareous mudstone-dominated (LA1) and clay-rich mudstone-dominated (LA2), were identified. Although generally anoxic bottom water was present during sedimentation, subtle differences in Depositional Environment and OM enrichment were found for the two lithofacies. The mineral composition and multiple geochemical proxies, including detritus index (sum of quartz, clay minerals, and feldspar contents), C-value [∑(Fe + Mn + Cr + Ni + V + Co)/∑(Ca + ...
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Depositional Environment of the late santonian lacustrine source rocks in the songliao basin ne china implications from organic geochemical analyses
Organic Geochemistry, 2018Co-Authors: Xiaoning Tong, Jianfang Hu, Dangpeng Xi, Jianzhong Song, Pingan PengAbstract:Abstract The Songliao Basin (SLB) located in northeastern China is one of the largest Cretaceous continental sedimentary basins in the world. The SLB is filled with sediments deposited in the Upper Jurassic, the Lower Cretaceous and the Upper Cretaceous epochs. The Nenjiang Formation (K2n) is subdivided into five members, where Member 2 (K2n2) was deposited in the late Santonian in the lower part of the Nenjiang Formation. This member is characterized by a thick succession of organic-rich source rocks. However, the complexity of the Depositional Environment raises questions about the specific factors that drove this accumulation of organic material. Here, we present data on the total organic carbon (TOC) contents and their stable carbon isotope values (δ13Corg), as well as biomarker data from 50 outcrop samples collected from the Yuewangcheng (YWC) section, in the southeastern SLB. According to the variations of the bulk organic parameters (TOC and δ13Corg) and biomarker indices, the profile could be divided into three stages (stages I–III). The distribution of biomarkers (n-alkanes, steranes and hopanes) and δ13Corg values indicate that the organic matter (OM) in the Lower K2n2 is derived largely from algae and macrophytes, with a minor input from bacteria and land plants. The water column was stratified, as indicated by the presence of gammacerane. Variations in the pristane/phytane (Pr/Ph) and aryl isoprenoids relative to phenanthrene ratio (A-i/P) suggest that bottom waters were anoxic during Stage I (31.5–26.0 m) and Stage II (26.0–16.3 m), with the anoxic layer impinging on the euphotic zone and a relative oxic Environment at Stage III (16.3–0 m). This brackish Environment persisted in the water over the interval represented by the section, as reflected by methytrimethyltridecyl chromans (MTTCs) Index (MTTCI) and α-MTTC/γ-MTTC ratios. Marine transgressions, with subsequent seawater incursions, can be detected with the presence of 24-n-propyl-cholestanes and 24-isopropyl-cholestanes in the Lower K2n2 sediments, especially during Stage I. These seawater incursions are closely correlated with anoxic conditions and the deposition of organic-rich source rocks.
Doris Gross - One of the best experts on this subject based on the ideXlab platform.
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Depositional Environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china
International Journal of Coal Geology, 2017Co-Authors: Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Xuan ChenAbstract:Abstract The non-marine Santanghu Basin in northwest China hosts one of the richest and thickest Permian lacustrine source rock intervals in the world. Conventional oil in Jurassic sandstone reservoirs and tight oil in the tuffaceous Permian Tiaohu Formation were sourced from mudrocks in the underlying second member of Lucaogou Formation, which also have tight oil potential proved by recent commercial discoveries. Based on inorganic and organic geochemistry, organic petrography, and stable isotope geochemistry, the Depositional Environment and the tight oil potential of the second member of Permian Lucaogou Formation were investigated. The data imply a gradual evolution of the Depositional Environment from a stratified, saline to a freshwater lake. The succession can be subdivided into a lower, middle, and an upper unit, each characterized by decreasing water salinity. High bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria. Water column stratification accelerated the activity of methanothrophs, as indicated by low δ13C values of hopanes. Biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of Prasinophytae compared to other algae with decreasing salinity. Enhanced terrigenous organic matter input appeared during periods of high freshwater inflow. Low total organic carbon (TOC) contents in the lower unit are most likely caused by rapid sedimentation rate. High bioproductivity and excellent preservation conditions resulted in high TOC contents in the middle unit. Terrigenous organic matter input increased together with fresh water inflow in the upper unit, resulting in high TOC values during periods of possibly low sedimentation rates in a deep water column. The samples of the second member exhibit a good to very good potential to generate conventional oil. High TOC and extractable organic matter yields, together with the thickness of the fine-grained sediments, show that the middle and upper units of the second member of Lucaogou Formation hold significant tight oil potential. Mineralogical composition of this dolomite-rich shale with respect to abundance of brittle minerals (including quartz and carbonates) and rare clay testifies a good tight oil potential.
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organic geochemistry of mississippian shales bowland shale formation in central britain implications for Depositional Environment source rock and gas shale potential
Marine and Petroleum Geology, 2015Co-Authors: Doris Gross, Achim Bechtel, R F Sachsenhofer, L Pytlak, Bernhard Rupprecht, Eva WegererAbstract:Abstract Marine Carboniferous shales are proven hydrocarbon source rocks in central Britain. In this contribution the Depositional Environment and shale gas/liquid potential of the lower Namurian part of the Bowland Shale Formation is studied using 77 thermally immature samples from the Duffield borehole. The Bowland Shale Formation comprises mudstone and turibidite lithofacies reflecting a pronounced sea level controlled cyclicity. The total organic carbon (TOC) content of the mudstones lithofacies (including marine bands) and of fine-grained rocks within the turibidite lithofacies varies between 1.3 and 9.1%. Hydrogen index (HI) values imply the presence of kerogen type III-II. According to biomarker ratios and bulk geochemical parameters, marine bands (maximum flooding surfaces, mfs) were deposited in deep water with slightly enhanced, normal, or slightly reduced salinity. Mudstones of the highstand systems tract (HST) were deposited in Environments with normal to reduced salinity, whereas photic zone anoxia favoured the preservation of marine organic matter during deposition of the mfs and the HST. The supply of landplant debris increased during the HST. Turbidites and their non-calcareous mudstone equivalents represent lowstand systems tracts deposited in low salinity Environments. Terrestrial organic matter dominates in turbiditic sediments, marine organisms prevail in time-equivalent mudstones. Mudstone beneath marine bands represents transgressive systems tracts when normal marine conditions and photic zone anoxia were re-established. The mudstone lithofacies exhibits a very good to excellent potential to generate conventional mixed oil and gas. TOC content of fine-grained rocks in the turbidite lithofacies depends on the amount of detrital minerals supplied from the south. Moreover, their organic matter is gas-prone. High TOC contents and large thicknesses of the mudstone lithofacies show that the Bowland Shale Formation holds a significant shale gas/liquid potential in areas with appropriate maturity. A relatively low average HI and high clay contents may have negative effects on the shale gas potential.
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Depositional Environment of oil shale within the eocene jijuntun formation in the fushun basin ne china
Marine and Petroleum Geology, 2014Co-Authors: Susanne A I Strobl, Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Syed Nadeem Hussain Bokhari, Qingtao MengAbstract:Abstract The non-marine Fushun Basin in NE China is a fault-controlled basin filled with Eocene sediments. It hosts the largest opencast coal and oil shale mine in Asia. A single thick oil shale layer overlying sub-bituminous coal occurs within the Middle Eocene Jijuntun Formation. Based on mineralogy, inorganic and organic geochemistry, organic petrography, stable isotope geochemistry, and vitrinite reflectance measurements, the Depositional Environment and the oil shale potential of the oil shale-bearing succession were investigated. The Jijuntun Formation is subdivided into a lower and an upper unit characterized by a low and high quality oil shale, respectively. The thick oil shale layer of the Jijuntun Formation developed under long-lasting stable conditions in a deep freshwater lake, after drowning of a swamp. The organic matter in the lower unit is characterized by landplant-derived macerals. The sediments containing a type II kerogen (HI: ∼400 mgHC/gTOC) were deposited during warm and humid conditions. Lacustrine organisms predominant in the upper unit are forming kerogen type I (HI: ∼700 mgHC/gTOC). High bioproductivity and excellent preservation conditions resulted in high TOC contents up to 23.6 wt.% in the upper unit. The organic matter preservation was controlled by photic zone anoxia originating in a temperature stratified water column in the deep lake, without significant changes in bottom water salinity. Mid-Eocene cooling during deposition of the upper unit of the Jijuntun Formation is reflected by clay mineral composition. A hot and arid climate favoring brackish conditions in a shallow lake prevailed during accumulation of the overlying carbonate-rich Xilutian Formation. Individual geochemical parameters in the Fushun Basin have to be used with caution, e.g. the maturity proxy Tmax is affected by kerogen type, the redox proxy Pr/Ph ratio is probably biased by different sources of isoprenoids. This demonstrates the importance of multi-proxy studies.
Achim Bechtel - One of the best experts on this subject based on the ideXlab platform.
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Depositional Environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china
International Journal of Coal Geology, 2017Co-Authors: Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Xuan ChenAbstract:Abstract The non-marine Santanghu Basin in northwest China hosts one of the richest and thickest Permian lacustrine source rock intervals in the world. Conventional oil in Jurassic sandstone reservoirs and tight oil in the tuffaceous Permian Tiaohu Formation were sourced from mudrocks in the underlying second member of Lucaogou Formation, which also have tight oil potential proved by recent commercial discoveries. Based on inorganic and organic geochemistry, organic petrography, and stable isotope geochemistry, the Depositional Environment and the tight oil potential of the second member of Permian Lucaogou Formation were investigated. The data imply a gradual evolution of the Depositional Environment from a stratified, saline to a freshwater lake. The succession can be subdivided into a lower, middle, and an upper unit, each characterized by decreasing water salinity. High bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria. Water column stratification accelerated the activity of methanothrophs, as indicated by low δ13C values of hopanes. Biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of Prasinophytae compared to other algae with decreasing salinity. Enhanced terrigenous organic matter input appeared during periods of high freshwater inflow. Low total organic carbon (TOC) contents in the lower unit are most likely caused by rapid sedimentation rate. High bioproductivity and excellent preservation conditions resulted in high TOC contents in the middle unit. Terrigenous organic matter input increased together with fresh water inflow in the upper unit, resulting in high TOC values during periods of possibly low sedimentation rates in a deep water column. The samples of the second member exhibit a good to very good potential to generate conventional oil. High TOC and extractable organic matter yields, together with the thickness of the fine-grained sediments, show that the middle and upper units of the second member of Lucaogou Formation hold significant tight oil potential. Mineralogical composition of this dolomite-rich shale with respect to abundance of brittle minerals (including quartz and carbonates) and rare clay testifies a good tight oil potential.
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organic geochemistry of mississippian shales bowland shale formation in central britain implications for Depositional Environment source rock and gas shale potential
Marine and Petroleum Geology, 2015Co-Authors: Doris Gross, Achim Bechtel, R F Sachsenhofer, L Pytlak, Bernhard Rupprecht, Eva WegererAbstract:Abstract Marine Carboniferous shales are proven hydrocarbon source rocks in central Britain. In this contribution the Depositional Environment and shale gas/liquid potential of the lower Namurian part of the Bowland Shale Formation is studied using 77 thermally immature samples from the Duffield borehole. The Bowland Shale Formation comprises mudstone and turibidite lithofacies reflecting a pronounced sea level controlled cyclicity. The total organic carbon (TOC) content of the mudstones lithofacies (including marine bands) and of fine-grained rocks within the turibidite lithofacies varies between 1.3 and 9.1%. Hydrogen index (HI) values imply the presence of kerogen type III-II. According to biomarker ratios and bulk geochemical parameters, marine bands (maximum flooding surfaces, mfs) were deposited in deep water with slightly enhanced, normal, or slightly reduced salinity. Mudstones of the highstand systems tract (HST) were deposited in Environments with normal to reduced salinity, whereas photic zone anoxia favoured the preservation of marine organic matter during deposition of the mfs and the HST. The supply of landplant debris increased during the HST. Turbidites and their non-calcareous mudstone equivalents represent lowstand systems tracts deposited in low salinity Environments. Terrestrial organic matter dominates in turbiditic sediments, marine organisms prevail in time-equivalent mudstones. Mudstone beneath marine bands represents transgressive systems tracts when normal marine conditions and photic zone anoxia were re-established. The mudstone lithofacies exhibits a very good to excellent potential to generate conventional mixed oil and gas. TOC content of fine-grained rocks in the turbidite lithofacies depends on the amount of detrital minerals supplied from the south. Moreover, their organic matter is gas-prone. High TOC contents and large thicknesses of the mudstone lithofacies show that the Bowland Shale Formation holds a significant shale gas/liquid potential in areas with appropriate maturity. A relatively low average HI and high clay contents may have negative effects on the shale gas potential.
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Depositional Environment of oil shale within the eocene jijuntun formation in the fushun basin ne china
Marine and Petroleum Geology, 2014Co-Authors: Susanne A I Strobl, Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Syed Nadeem Hussain Bokhari, Qingtao MengAbstract:Abstract The non-marine Fushun Basin in NE China is a fault-controlled basin filled with Eocene sediments. It hosts the largest opencast coal and oil shale mine in Asia. A single thick oil shale layer overlying sub-bituminous coal occurs within the Middle Eocene Jijuntun Formation. Based on mineralogy, inorganic and organic geochemistry, organic petrography, stable isotope geochemistry, and vitrinite reflectance measurements, the Depositional Environment and the oil shale potential of the oil shale-bearing succession were investigated. The Jijuntun Formation is subdivided into a lower and an upper unit characterized by a low and high quality oil shale, respectively. The thick oil shale layer of the Jijuntun Formation developed under long-lasting stable conditions in a deep freshwater lake, after drowning of a swamp. The organic matter in the lower unit is characterized by landplant-derived macerals. The sediments containing a type II kerogen (HI: ∼400 mgHC/gTOC) were deposited during warm and humid conditions. Lacustrine organisms predominant in the upper unit are forming kerogen type I (HI: ∼700 mgHC/gTOC). High bioproductivity and excellent preservation conditions resulted in high TOC contents up to 23.6 wt.% in the upper unit. The organic matter preservation was controlled by photic zone anoxia originating in a temperature stratified water column in the deep lake, without significant changes in bottom water salinity. Mid-Eocene cooling during deposition of the upper unit of the Jijuntun Formation is reflected by clay mineral composition. A hot and arid climate favoring brackish conditions in a shallow lake prevailed during accumulation of the overlying carbonate-rich Xilutian Formation. Individual geochemical parameters in the Fushun Basin have to be used with caution, e.g. the maturity proxy Tmax is affected by kerogen type, the redox proxy Pr/Ph ratio is probably biased by different sources of isoprenoids. This demonstrates the importance of multi-proxy studies.
R F Sachsenhofer - One of the best experts on this subject based on the ideXlab platform.
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Depositional Environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china
International Journal of Coal Geology, 2017Co-Authors: Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Xuan ChenAbstract:Abstract The non-marine Santanghu Basin in northwest China hosts one of the richest and thickest Permian lacustrine source rock intervals in the world. Conventional oil in Jurassic sandstone reservoirs and tight oil in the tuffaceous Permian Tiaohu Formation were sourced from mudrocks in the underlying second member of Lucaogou Formation, which also have tight oil potential proved by recent commercial discoveries. Based on inorganic and organic geochemistry, organic petrography, and stable isotope geochemistry, the Depositional Environment and the tight oil potential of the second member of Permian Lucaogou Formation were investigated. The data imply a gradual evolution of the Depositional Environment from a stratified, saline to a freshwater lake. The succession can be subdivided into a lower, middle, and an upper unit, each characterized by decreasing water salinity. High bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria. Water column stratification accelerated the activity of methanothrophs, as indicated by low δ13C values of hopanes. Biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of Prasinophytae compared to other algae with decreasing salinity. Enhanced terrigenous organic matter input appeared during periods of high freshwater inflow. Low total organic carbon (TOC) contents in the lower unit are most likely caused by rapid sedimentation rate. High bioproductivity and excellent preservation conditions resulted in high TOC contents in the middle unit. Terrigenous organic matter input increased together with fresh water inflow in the upper unit, resulting in high TOC values during periods of possibly low sedimentation rates in a deep water column. The samples of the second member exhibit a good to very good potential to generate conventional oil. High TOC and extractable organic matter yields, together with the thickness of the fine-grained sediments, show that the middle and upper units of the second member of Lucaogou Formation hold significant tight oil potential. Mineralogical composition of this dolomite-rich shale with respect to abundance of brittle minerals (including quartz and carbonates) and rare clay testifies a good tight oil potential.
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organic geochemistry of mississippian shales bowland shale formation in central britain implications for Depositional Environment source rock and gas shale potential
Marine and Petroleum Geology, 2015Co-Authors: Doris Gross, Achim Bechtel, R F Sachsenhofer, L Pytlak, Bernhard Rupprecht, Eva WegererAbstract:Abstract Marine Carboniferous shales are proven hydrocarbon source rocks in central Britain. In this contribution the Depositional Environment and shale gas/liquid potential of the lower Namurian part of the Bowland Shale Formation is studied using 77 thermally immature samples from the Duffield borehole. The Bowland Shale Formation comprises mudstone and turibidite lithofacies reflecting a pronounced sea level controlled cyclicity. The total organic carbon (TOC) content of the mudstones lithofacies (including marine bands) and of fine-grained rocks within the turibidite lithofacies varies between 1.3 and 9.1%. Hydrogen index (HI) values imply the presence of kerogen type III-II. According to biomarker ratios and bulk geochemical parameters, marine bands (maximum flooding surfaces, mfs) were deposited in deep water with slightly enhanced, normal, or slightly reduced salinity. Mudstones of the highstand systems tract (HST) were deposited in Environments with normal to reduced salinity, whereas photic zone anoxia favoured the preservation of marine organic matter during deposition of the mfs and the HST. The supply of landplant debris increased during the HST. Turbidites and their non-calcareous mudstone equivalents represent lowstand systems tracts deposited in low salinity Environments. Terrestrial organic matter dominates in turbiditic sediments, marine organisms prevail in time-equivalent mudstones. Mudstone beneath marine bands represents transgressive systems tracts when normal marine conditions and photic zone anoxia were re-established. The mudstone lithofacies exhibits a very good to excellent potential to generate conventional mixed oil and gas. TOC content of fine-grained rocks in the turbidite lithofacies depends on the amount of detrital minerals supplied from the south. Moreover, their organic matter is gas-prone. High TOC contents and large thicknesses of the mudstone lithofacies show that the Bowland Shale Formation holds a significant shale gas/liquid potential in areas with appropriate maturity. A relatively low average HI and high clay contents may have negative effects on the shale gas potential.
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Depositional Environment of oil shale within the eocene jijuntun formation in the fushun basin ne china
Marine and Petroleum Geology, 2014Co-Authors: Susanne A I Strobl, Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Syed Nadeem Hussain Bokhari, Qingtao MengAbstract:Abstract The non-marine Fushun Basin in NE China is a fault-controlled basin filled with Eocene sediments. It hosts the largest opencast coal and oil shale mine in Asia. A single thick oil shale layer overlying sub-bituminous coal occurs within the Middle Eocene Jijuntun Formation. Based on mineralogy, inorganic and organic geochemistry, organic petrography, stable isotope geochemistry, and vitrinite reflectance measurements, the Depositional Environment and the oil shale potential of the oil shale-bearing succession were investigated. The Jijuntun Formation is subdivided into a lower and an upper unit characterized by a low and high quality oil shale, respectively. The thick oil shale layer of the Jijuntun Formation developed under long-lasting stable conditions in a deep freshwater lake, after drowning of a swamp. The organic matter in the lower unit is characterized by landplant-derived macerals. The sediments containing a type II kerogen (HI: ∼400 mgHC/gTOC) were deposited during warm and humid conditions. Lacustrine organisms predominant in the upper unit are forming kerogen type I (HI: ∼700 mgHC/gTOC). High bioproductivity and excellent preservation conditions resulted in high TOC contents up to 23.6 wt.% in the upper unit. The organic matter preservation was controlled by photic zone anoxia originating in a temperature stratified water column in the deep lake, without significant changes in bottom water salinity. Mid-Eocene cooling during deposition of the upper unit of the Jijuntun Formation is reflected by clay mineral composition. A hot and arid climate favoring brackish conditions in a shallow lake prevailed during accumulation of the overlying carbonate-rich Xilutian Formation. Individual geochemical parameters in the Fushun Basin have to be used with caution, e.g. the maturity proxy Tmax is affected by kerogen type, the redox proxy Pr/Ph ratio is probably biased by different sources of isoprenoids. This demonstrates the importance of multi-proxy studies.
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Depositional Environment and hydrocarbon source potential of the oligocene ruslar formation kamchia depression western black sea
Marine and Petroleum Geology, 2009Co-Authors: R F Sachsenhofer, Reinhard Gratzer, A Bechtel, Barbara Stummer, Georgi Georgiev, Rudolf Dellmour, Stepan CoricAbstract:Abstract The Oligocene Ruslar Formation is a hydrocarbon source rock in the Kamchia Depression, located in the Western Black Sea area. Depositional Environment and source potential of the predominantly pelitic rocks were investigated using core and cuttings samples from four offshore wells. In these wells the Ruslar Formation is up to 500 m thick. Based on lithology and well logs, the Ruslar Formation is subdivided from base to top into units I–VI. Dysoxic to anoxic conditions and mesohaline to euhaline salinities prevailed during deposition of the Ruslar Formation. Relatively high oxygen contents occurred during early Solenovian times (lower part of unit II), when brackish surface water favoured nannoplankton blooms and the deposition of bright marls (“Solenovian event”). Anoxic conditions with photic zone anoxia were established during late Oligocene times (units III and IV) and, probably, reflect a basin-wide anoxic event in the Eastern Paratethys during Kalmykian times. Organic carbon content in the Ruslar Formation is up to 3%. Autochthonous aquatic and allochthonous terrigenous biomass contribute to the organic matter. Relatively high amounts of aquatic organic matter occur in the lower part of the Ruslar Formation (units I and II) and in its upper part (unit VI). Diatoms are especially abundant in the lower part of unit VI. The kerogen is of type III and II with HI values ranging from 50 to 400 mgHC/gTOC. Units I and II (Pshekian, lower Solenovian) are characterized by a fair (to good) potential to produce gas and oil, but potential sources for gas and oil also occur in the Upper Oligocene units IV–VI.
Reinhard Gratzer - One of the best experts on this subject based on the ideXlab platform.
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Depositional Environment of oil shale within the second member of permian lucaogou formation in the santanghu basin northwest china
International Journal of Coal Geology, 2017Co-Authors: Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Xuan ChenAbstract:Abstract The non-marine Santanghu Basin in northwest China hosts one of the richest and thickest Permian lacustrine source rock intervals in the world. Conventional oil in Jurassic sandstone reservoirs and tight oil in the tuffaceous Permian Tiaohu Formation were sourced from mudrocks in the underlying second member of Lucaogou Formation, which also have tight oil potential proved by recent commercial discoveries. Based on inorganic and organic geochemistry, organic petrography, and stable isotope geochemistry, the Depositional Environment and the tight oil potential of the second member of Permian Lucaogou Formation were investigated. The data imply a gradual evolution of the Depositional Environment from a stratified, saline to a freshwater lake. The succession can be subdivided into a lower, middle, and an upper unit, each characterized by decreasing water salinity. High bioproductivity has been caused by the bloom of algae and photosynthetic cyanobacteria. Water column stratification accelerated the activity of methanothrophs, as indicated by low δ13C values of hopanes. Biomarker composition provides evidence for decreasing contributions of cyanobacteria to the biomass and increasing abundance of Prasinophytae compared to other algae with decreasing salinity. Enhanced terrigenous organic matter input appeared during periods of high freshwater inflow. Low total organic carbon (TOC) contents in the lower unit are most likely caused by rapid sedimentation rate. High bioproductivity and excellent preservation conditions resulted in high TOC contents in the middle unit. Terrigenous organic matter input increased together with fresh water inflow in the upper unit, resulting in high TOC values during periods of possibly low sedimentation rates in a deep water column. The samples of the second member exhibit a good to very good potential to generate conventional oil. High TOC and extractable organic matter yields, together with the thickness of the fine-grained sediments, show that the middle and upper units of the second member of Lucaogou Formation hold significant tight oil potential. Mineralogical composition of this dolomite-rich shale with respect to abundance of brittle minerals (including quartz and carbonates) and rare clay testifies a good tight oil potential.
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Depositional Environment of oil shale within the eocene jijuntun formation in the fushun basin ne china
Marine and Petroleum Geology, 2014Co-Authors: Susanne A I Strobl, Achim Bechtel, R F Sachsenhofer, Doris Gross, Reinhard Gratzer, Syed Nadeem Hussain Bokhari, Qingtao MengAbstract:Abstract The non-marine Fushun Basin in NE China is a fault-controlled basin filled with Eocene sediments. It hosts the largest opencast coal and oil shale mine in Asia. A single thick oil shale layer overlying sub-bituminous coal occurs within the Middle Eocene Jijuntun Formation. Based on mineralogy, inorganic and organic geochemistry, organic petrography, stable isotope geochemistry, and vitrinite reflectance measurements, the Depositional Environment and the oil shale potential of the oil shale-bearing succession were investigated. The Jijuntun Formation is subdivided into a lower and an upper unit characterized by a low and high quality oil shale, respectively. The thick oil shale layer of the Jijuntun Formation developed under long-lasting stable conditions in a deep freshwater lake, after drowning of a swamp. The organic matter in the lower unit is characterized by landplant-derived macerals. The sediments containing a type II kerogen (HI: ∼400 mgHC/gTOC) were deposited during warm and humid conditions. Lacustrine organisms predominant in the upper unit are forming kerogen type I (HI: ∼700 mgHC/gTOC). High bioproductivity and excellent preservation conditions resulted in high TOC contents up to 23.6 wt.% in the upper unit. The organic matter preservation was controlled by photic zone anoxia originating in a temperature stratified water column in the deep lake, without significant changes in bottom water salinity. Mid-Eocene cooling during deposition of the upper unit of the Jijuntun Formation is reflected by clay mineral composition. A hot and arid climate favoring brackish conditions in a shallow lake prevailed during accumulation of the overlying carbonate-rich Xilutian Formation. Individual geochemical parameters in the Fushun Basin have to be used with caution, e.g. the maturity proxy Tmax is affected by kerogen type, the redox proxy Pr/Ph ratio is probably biased by different sources of isoprenoids. This demonstrates the importance of multi-proxy studies.
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Depositional Environment and hydrocarbon source potential of the oligocene ruslar formation kamchia depression western black sea
Marine and Petroleum Geology, 2009Co-Authors: R F Sachsenhofer, Reinhard Gratzer, A Bechtel, Barbara Stummer, Georgi Georgiev, Rudolf Dellmour, Stepan CoricAbstract:Abstract The Oligocene Ruslar Formation is a hydrocarbon source rock in the Kamchia Depression, located in the Western Black Sea area. Depositional Environment and source potential of the predominantly pelitic rocks were investigated using core and cuttings samples from four offshore wells. In these wells the Ruslar Formation is up to 500 m thick. Based on lithology and well logs, the Ruslar Formation is subdivided from base to top into units I–VI. Dysoxic to anoxic conditions and mesohaline to euhaline salinities prevailed during deposition of the Ruslar Formation. Relatively high oxygen contents occurred during early Solenovian times (lower part of unit II), when brackish surface water favoured nannoplankton blooms and the deposition of bright marls (“Solenovian event”). Anoxic conditions with photic zone anoxia were established during late Oligocene times (units III and IV) and, probably, reflect a basin-wide anoxic event in the Eastern Paratethys during Kalmykian times. Organic carbon content in the Ruslar Formation is up to 3%. Autochthonous aquatic and allochthonous terrigenous biomass contribute to the organic matter. Relatively high amounts of aquatic organic matter occur in the lower part of the Ruslar Formation (units I and II) and in its upper part (unit VI). Diatoms are especially abundant in the lower part of unit VI. The kerogen is of type III and II with HI values ranging from 50 to 400 mgHC/gTOC. Units I and II (Pshekian, lower Solenovian) are characterized by a fair (to good) potential to produce gas and oil, but potential sources for gas and oil also occur in the Upper Oligocene units IV–VI.
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molecular indicators of palaeosalinity and Depositional Environment of small scale basins within carbonate platforms the late triassic hauptdolomite wiestalstausee section near hallein northern calcareous alps austria
Organic Geochemistry, 2007Co-Authors: A Bechtel, Reinhard Gratzer, Hansjurgen Gawlick, M Tomaselli, Wilhelm PuttmannAbstract:Abstract Microfacies and biomarker analyses are used to determine the Environmental conditions during deposition of marly dolomicrites from the Hauptdolomite Wiestalstausee section near Hallein (Salzburg, Austria), part of the Late Triassic Hauptdolomite/Dachstein carbonate platform of the Northern Calcareous Alps. Phytoplankton and photosynthetic bacteria are considered to be the major primary producers of the organic matter in these immature (∼0.5% equivalent vitrinite reflectance), carbonate-rich rocks. Contributions from vascular plants are suggested from the n -alkane distribution pattern and high content of C 29 steranes. Enhanced microbial activity in the Depositional Environment is proposed on the basis of the hopanoid content. The occurrence of aryl isoprenoids, probably derived from carotenoids of the photosynthetic green sulfur bacteria ( Chlorobiaceae ) indicates the presence of free H 2 S in the bottom water. Mesohaline conditions in the upper part of the water column are deduced from the presence of dimethylated and trimethylated 2-methyl-2-(tridecylchromans) (MTTCs). Co-variation in the distribution of MTTCs and pristane/phytane ratio and the concentration of a C 16 aryl isoprenoid argue for photic zone anoxia due to salinity stratification. The biomarker composition points to a high productivity marine Environment with limited water exchange and a stratified water column confirmed by microfacies analysis. A small scale basin formed within the restricted inner lagoonal area of the Hauptdolomite/Dachstein carbonate platform through erosion by currents, followed by a sea level rise is considered the most appropriate Depositional Environment of the dolomicrites of the Wiestalstausee section.