scholarly journals Multiple Controls on the Accumulation of Organic-Rich Sediments in the Besa River Formation of Liard Basin, British Columbia, Canada

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-18
Author(s):  
Jiyoung Choi ◽  
Hyun Suk Lee ◽  
Yuri Kim ◽  
Omid H. Ardakani ◽  
Sung Kyung Hong
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
High Resolution ◽  
Organic Carbon ◽  
Sea Level ◽  
Shale Gas ◽  
Biogenic Silica ◽  
Gas Production ◽  
Geochemical Data ◽  
Geographic Variations

The Late Devonian Besa River Formation is an organic-rich shale sequence in Liard Basin, northeastern British Columbia, Canada, with significant natural gas reserves. High-resolution elemental geochemistry of three long continuous cored intervals of the Besa River Formation was used to better understand the paleodepositional environment of organic-rich intervals in this thick marine shale. The studied core intervals were divided into five chemostratigraphic units based on organic and inorganic geochemical proxies. The highest total organic carbon (TOC) content (up to 13 wt.%) was identified in the upper part of the Patry member (Unit III) within the Liard Basin. During the deposition of Unit III, low clastic influx and euxinic bottom conditions mostly contributed to the high accumulation of organic carbon. Moreover, a high productivity and organic influx may have increased organic-rich basinal sediments, which further depleted the seawater column oxygen content in the presence of a large amount of organic matter. This took place within the oxygen-deficient bottom water from the Patry–Exshaw stratigraphic units. This high TOC interval was most likely deposited through abundant biogenic silica production by radiolarians, thereby utilizing the supply of nutrients from the upwelling. Sea level change was also an important factor that controlled organic matter accumulation in the Besa River Formation. The transgression in sea level changed the residence time of the organic matter in oxic zones within the water column, which limited its supply in deeper water; this decreased the TOC content in Unit IV. Before the deposition, silica production collapsed and was replaced by terrestrial sedimentation of clay minerals in the upper part of the Exshaw member, which caused organic matter dilutions in Unit V (under 5 wt.%). These results provide new insights into the effects of relative sea level changes on redox conditions, productivity, and detrital flux, which are related to organic matter enrichment patterns and their geographic variations. Unit III is characterized by an organic-rich interval as well as an abundance of biogenic silica that is closely related to fracturing. Thus, Unit III is expected to have the highest shale gas potential in the Devonian Besa River Formation. The high-resolution geochemical data integrated with well log and/or seismic data can be used to determine the distribution of the perspective interval for shale gas production in the Liard Basin.

scholarly journals A global hotspot for dissolved organic carbon in hypermaritime watersheds of coastal British Columbia

2017 ◽  
Vol 14 (15) ◽  
pp. 3743-3762 ◽  
Author(s):  
Allison A. Oliver ◽  
Suzanne E. Tank ◽  
Ian Giesbrecht ◽  
Maartje C. Korver ◽  
William C. Floyd ◽  
...  
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
Organic Carbon ◽  
Stream Water ◽  
Coastal Ocean ◽  
Stream Discharge ◽  
Coastal Margin ◽  
Doc Concentration ◽  
Small Catchments ◽  
Dom Composition

Abstract. The perhumid region of the coastal temperate rainforest (CTR) of Pacific North America is one of the wettest places on Earth and contains numerous small catchments that discharge freshwater and high concentrations of dissolved organic carbon (DOC) directly to the coastal ocean. However, empirical data on the flux and composition of DOC exported from these watersheds are scarce. We established monitoring stations at the outlets of seven catchments on Calvert and Hecate islands, British Columbia, which represent the rain-dominated hypermaritime region of the perhumid CTR. Over several years, we measured stream discharge, stream water DOC concentration, and stream water dissolved organic-matter (DOM) composition. Discharge and DOC concentrations were used to calculate DOC fluxes and yields, and DOM composition was characterized using absorbance and fluorescence spectroscopy with parallel factor analysis (PARAFAC). The areal estimate of annual DOC yield in water year 2015 was 33.3 Mg C km−2 yr−1, with individual watersheds ranging from an average of 24.1 to 37.7 Mg C km−2 yr−1. This represents some of the highest DOC yields to be measured at the coastal margin. We observed seasonality in the quantity and composition of exports, with the majority of DOC export occurring during the extended wet period (September–April). Stream flow from catchments reacted quickly to rain inputs, resulting in rapid export of relatively fresh, highly terrestrial-like DOM. DOC concentration and measures of DOM composition were related to stream discharge and stream temperature and correlated with watershed attributes, including the extent of lakes and wetlands, and the thickness of organic and mineral soil horizons. Our discovery of high DOC yields from these small catchments in the CTR is especially compelling as they deliver relatively fresh, highly terrestrial organic matter directly to the coastal ocean. Hypermaritime landscapes are common on the British Columbia coast, suggesting that this coastal margin may play an important role in the regional processing of carbon and in linking terrestrial carbon to marine ecosystems.

scholarly journals Elemental Geochemical Characterization of Sedimentary Conditions and Organic Matter Enrichment for Lower Cambrian Shale Formations in Northern Guizhou, South China

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 793
Author(s):  
Shuangbiao Han ◽  
Yuanlong Zhang ◽  
Jie Huang ◽  
Yurun Rui ◽  
Zhiyuan Tang
Keyword(s):  
Organic Matter ◽  
Deposition Rate ◽  
Black Shale ◽  
South China ◽  
Shale Gas ◽  
Geochemical Data ◽  
Shale Formations ◽  
Average Value ◽  
Geochemical Elements ◽  
Niutitang Formation

The black shale deposited in the Niutitang Formation and its adjacent strata is considered to be a favorable source rock in northern Guizhou of south China and has become a target horizon for shale gas exploration in recent years. Based on SQ-1 and CY-1 core samples, the organic matter properties and geochemical elements were obtained through experimental analysis. Provenance, paleoredox, paleoclimate, paleoproductivity and deposition conditions were analyzed, and the sedimentary effects on organic matter enrichment were discussed. The results show that total organic carbon (TOC) is between 0.22–10.10 wt.% in SQ-1, with an average of 2.60 wt.%, and TOC is between 0.23–7.7 wt.% in CY-1, with an average of 1.45 wt.%. The geochemical data of the samples indicate that the black shale of the Niutitang Formation and adjacent strata are deposited in the tectonic background of the passive continental margin. The provenance shows moderate weathering, with hot and humid paleoenvironmental characteristics and fast deposition rate. Using multiple ancient redox indicators, it is concluded that the formation has undergone changes in the oxidizing environment and anaerobic environment during deposition. According to the (La/Yb)N value (the average value of SQ-1 is 1.23 and the average value of CY-1 is 1.26), it shows a faster deposition rate of the two wells and shortens the residence time of organic matter in the microbial degradation zone. The Babio indicates that the bottom has a high paleoproductivity when deposited. Considering the influencing factors, the paleoproductivity mainly controls the organic matter enrichment, followed by ancient redox conditions and the deposition rate. The research results provide a reference for deepening sedimentary understanding and shale gas exploration in the study area.

scholarly journals Water-Gas Two-Phase Flow Behavior of Multi-Fractured Horizontal Wells in Shale Gas Reservoirs

Processes ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 664 ◽  
Author(s):  
Lei Li ◽  
Guanglong Sheng ◽  
Yuliang Su
Keyword(s):  
Organic Matter ◽  
Shale Gas ◽  
Flow Behavior ◽  
Horizontal Wells ◽  
Gas Production ◽  
Phase Flow ◽  
Gas Reservoirs ◽  
Two Phase ◽  
Fractured Horizontal Wells ◽  
Water Gas

Hydraulic fracturing is a necessary method to develop shale gas reservoirs effectively and economically. However, the flow behavior in multi-porosity fractured reservoirs is difficult to characterize by conventional methods. In this paper, combined with apparent porosity/permeability model of organic matter, inorganic matter and induced fractures, considering the water film in unstimulated reservoir volume (USRV) region water and bulk water in effectively stimulated reservoir volume (ESRV) region, a multi-media water-gas two-phase flow model was established. The finite difference is used to solve the model and the water-gas two-phase flow behavior of multi-fractured horizontal wells is obtained. Mass transfer between different-scale media, the effects of pore pressure on reservoirs and fluid properties at different production stages were considered in this model. The influence of the dynamic reservoir physical parameters on flow behavior and gas production in multi-fractured horizontal wells is studied. The results show that the properties of the total organic content (TOC) and the inherent porosity of the organic matter affect gas production after 40 days. With the gradual increase of production time, the gas production rate decreases rapidly compared with the water production rate, and the gas saturation in the inorganic matter of the ESRV region gradually decreases. The ignorance of stress sensitivity would cause the gas production increase, and the ignorance of organic matter shrinkage decrease the gas production gradually. The water film mainly affects gas production after 100 days, while the bulk water has a greater impact on gas production throughout the whole period. The research provides a new method to accurately describe the two-phase fluid flow behavior in different scale media of fractured shale gas reservoirs.

scholarly journals Development of Upwelling during the Sedimentary Period of the Organic-Rich Shales in the Wufeng and Longmaxi Formations of the Upper Yangtze Region and Its Impact on Organic Matter Enrichment

2019 ◽  
Vol 7 (4) ◽  
pp. 99 ◽  
Author(s):  
Shao-Ze Zhao ◽  
Yong Li ◽  
Hua-Jun Min ◽  
Tong Wang ◽  
Zhou Nie ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Biogenic Silica ◽  
Vertical Direction ◽  
Burial Depth ◽  
Mineral Component ◽  
Longmaxi Formation ◽  
Component Content ◽  
Upwelling Intensity

This study uses logging data, mineral component content, total organic carbon (TOC) content, and microscopic characteristics of the organic-rich shales in the Wufeng and Longmaxi Formations, as well as data reported by other researchers, to demonstrate that upwelling has played an important role in the organic matter enrichment. The results show that (1) the organic-rich shales of Well N211 in the Upper Yangtze region are located in the Wufeng Formation and the lower Longmaxi Formation, with a burial depth between 2308–2357 m. (2) The organic-rich shales are enriched in biogenic silica. (3) Based on paleogeographic location and characteristics of organisms, this study determines that upwelling occurred during the deposition of the organic-rich shales in the Wufeng and Longmaxi Formations, promoting the enrichment of organic matter in the shales. (4) The upwelling intensity gradually increased from the sedimentary period of the organic-rich shales in the mid-lower Wufeng Formation to the sedimentary period of the Guanyinqiao Member, and then decreased gradually from the sedimentary period of the Guanyinqiao Member to the sedimentary period of the organic-rich shales in the Longmaxi Formation, and leads to the different enrichment of organic matter in the vertical direction. The different developments of upwelling led to the coexistence of both high and low TOC contents in the Guanyinqiao Member along the vertical direction.

scholarly journals Sedimentary Evolution Characteristics of Fine-Grained Lithofacies under the High-Resolution Isochronous Shelf System: Insights from the Wufeng-Longmaxi Shales in the Sichuan Basin

Lithosphere ◽  
2021 ◽  
Vol 2021 (Special 1) ◽  
Author(s):  
Guanping Wang ◽  
Zhijun Jin ◽  
Zongquan Hu ◽  
Guangxiang Liu ◽  
Tong Zhu ◽  
...  
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Shale Gas ◽  
Transgressive System Tract ◽  
Fine Grained ◽  
Sedimentary Sequences ◽  
Evolution Characteristics ◽  
Sedimentary System ◽  
Siliceous Shale ◽  
System Tract

Abstract The deposition and evolution of fine-grained sediments is a hot topic in fine-grained sedimentary rock studies and is important for accurately evaluating shale gas sweet spots. In this paper, the fine-grained deposition and evolution characteristics of the Wufeng-Longmaxi shales, major targets for Chinese shale gas exploration, were studied by using core observations, thin section analyses, scanning electron microscopy, geochemical analysis, and fossil identification. This work accurately identified six typical lithofacies; among them, the organic matter-rich siliceous shale facies (OMRSSF), the high-organic matter siliceous argillaceous shale facies (HOMSASF), and the medium-high organic matter low calcareous siliceous shale facies (M-HOMLCSASF) are favorable facies for shale gas exploration. The high-resolution isochronous unit in the shelf fine-grained sedimentary system was established, and the differential evolution of lithofacies in the system tract was discussed. The lithofacies deposition and differentiation in the transgressive system tract were controlled by the transgressive scale and tectonics under increasingly shallow water conditions. The lithofacies deposition and differentiation in the regressive system tract were controlled by tectonics and the preexisting lithofacies. The lithofacies in the regressive system tract had more frequent facies transitions and greater differentiation than those in the transgressive system tract, and they exhibited significant spatiotemporal inheritance. Sequential differential sedimentary sequences and symmetric differential sedimentary sequences were distinguished in the continental shelf sedimentary system. The lithofacies depocenters and subsidence centers were consistent in the transgressive system tract, while the tectonically active paleocontinent was important in the regression system tract. This study is of great significance for further high-resolution exploration of marine shale and improvement of the theory of shelf fine-grained sedimentary systems.

scholarly journals Geochemistry and shale gas potential of the lower Permian marine-continental transitional shales in the Eastern Ordos Basin

2020 ◽  
pp. 014459872097924
Author(s):  
Jingyi Wei ◽  
Yongli Wang ◽  
Gen Wang ◽  
Zhifu Wei ◽  
Wei He
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Higher Plants ◽  
Ordos Basin ◽  
Organic Matter Content ◽  
Lower Permian ◽  
Gas Desorption ◽  
Geochemical Parameters

Marine–continental transitional strata were widely developed in the Ordos Basin in Upper Carboniferous - Lower Permian. The Taiyuan - Shanxi Formation possesses promising shale gas exploration layers. Shale samples from two drilling wells of Shanxi-Taiyuan Formation in Shilou and Xixian, Ordos Basin, were investigated to study their carbon–sulfur contents and distribution characteristics of organic components using carbon/sulfur analyzer and gas chromatography–mass spectroscopy. Using results of total organic carbon analyses, Rock-Eval pyrolysis, X-ray diffraction analysis, shale gas desorption experiments, and other relevant experimental data, the shale samples were comprehensively analyzed. The exploitability of the shale in the study area was evaluated. The Shanxi-Taiyuan Shale in the Shilou and Xixian areas was characterized by high total organic carbon contents of 7.1% and 2.1% and high Tmax values of 499 and 505 °C, respectively. The organic matter of the shale is types II2 and III. Moreover, biomarker parameters including n-alkanes, Paq, Pwax, average carbon chain length, and the ternary diagram of C27-C28-C29 steranes show the organic matter constituted terrestrial higher plants and aquatic low biological algae. Multiple n-alkane parameters show the organic matter input in the Shilou area is mainly derived from terrestrial higher plants. The Pr/Ph value and trace element indicators show the deposition environment is dominated by weak oxidation–reduction conditions. A shale gas desorption experiment shows the average desorbed gas contents of the shale samples in the Shilou and Xixian areas were 1.79 and 0.37 m3/t, respectively. The organic matter content determined the differences in shale gas properties between the two areas in Ordos Basin. The composition and content of inorganic minerals affect the reservoir physical properties. According to the analyses, the shale in the Shilou area has good shale gas reservoir characteristics in terms of desorbed gas content and the above-mentioned geochemical parameters. Furthermore, the Shanxi shale has good potential for shale gas industrial exploitation.

scholarly journals Shale favorable area optimization in coal-bearing series: A case study from the Shanxi Formation in Northern Ordos Basin, China

2017 ◽  
Vol 36 (5) ◽  
pp. 1295-1309 ◽  
Author(s):  
Wei Guo ◽  
Weijun Shen ◽  
Shangwen Zhou ◽  
Huaqing Xue ◽  
Dexun Liu ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Shale Gas ◽  
Ordos Basin ◽  
Sedimentary Facies ◽  
Gas Content ◽  
Burial Depth ◽  
Organic Carbon Content ◽  
River Channels

Shales in the Well district of Yu 106 of the Shanxi Formation in the Eastern Ordos Basin is deposited in the swamp between delta plains, distributary river channels, natural levee, the far end of crevasse splay, and depression environments. According to organic geochemistry, reservoir physical property, gas bearing capacity, lithology experimental analysis, combined with the data of drilling, logging, testing and sedimentary facies, the reservoir conditions of shale gas and the distribution of an advantageous area in Shanxi Formation have been conducted. The results show that the total organic carbon content of the Shanxi Formation is relatively high, with an average content value of 5.28% in the segment 2 and 3.02% in segment 1, and the organic matter is mainly kerogen type II2 and III. The maturity of organic matter is high with 1.89% as the average value of Ro which indicates the superior condition for gas generation of this reservoir. The porosity of shales is 1.7% on average, and the average permeability is 0.0415 × 10−3 µm2. The cumulative thickness is relatively large, with an average of 75 m. Brittle mineral and clay content in shales are 49.9% and 50.1%, respectively, but the burial depth of shale is less than 3000 m. The testing gas content is relatively high (0.64 × 104 m3/d), which shows a great potential in commercial development. The total organic carbon of the segment 2 is higher than that of the segment 1, and it is also better than segment 1 in terms of gas content. Based on the thickness of shale and the distribution of sedimentary facies, it is predicted that the advantageous area of shale gas in the segment 2 is distributed in a striped zone along the northeast and the northsouth direction, which is controlled by the swamp microfacies between distributary river channels.

Geochemistry and depositional history of the Union Springs Member, Marcellus Formation in central Pennsylvania

2015 ◽  
Vol 3 (3) ◽  
pp. SV17-SV33 ◽  
Author(s):  
Anna K. Wendt ◽  
Mike A. Arthur ◽  
Rudy Slingerland ◽  
Daniel Kohl ◽  
Reed Bracht ◽  
...  
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Water Column ◽  
Appalachian Basin ◽  
Depositional Environments ◽  
Source Rocks ◽  
Geochemical Data ◽  
Inorganic Elements ◽  
Central Pennsylvania ◽  
Marcellus Formation

Debate continues over paleoenvironmental conditions that prevail during deposition of organic-carbon (C)-rich marine source rocks in foreland basins and epicontinental seas. The focus of disagreement centers largely on paleowater depth and the prevalence of anoxia/euxinia. The issues of paleodepth and water column conditions are important for prediction of lateral variations in source quality within a basin because the viability of a hydrocarbon play depends on a thorough understanding of the distribution of source rock quality and depositional environments. We used inorganic geochemical data from the Middle Devonian Marcellus Shale in the Appalachian Basin to illustrate interpretive strategies that provided constraints on conditions during deposition. Source evaluation typically relies on the analysis and interpretation of organic geochemical indicators, potentially also providing evidence of the degree of thermal maturity and conditions of the preservation of the organic matter. The Marcellus Formation is thermally mature, making the evaluation of the organic-carbon fraction for geologic interpretation inadequate. Because most labile organic matter has largely been destroyed in the Marcellus Formation, analysis of inorganic elements may be used as an alternative interpretative technique. Several inorganic elements have been correlated to varying depositional settings, allowing for their use as proxies for understanding the paleodepositional environments of formations. A high-resolution geochemical data set has been constructed for the Union Springs Member along a transect of cores from proximal to distal in the Appalachian Basin in central Pennsylvania using major, minor, and trace elemental data. Our results suggested that during deposition, the sediment-water interface, and a portion of the water column, was anoxic to euxinic. As deposition continued, euxinia was periodically interrupted by dysoxia and even oxic conditions, and a greater influx of clastic material occurred. Such variations were likely related to fluctuations in water depth and progradation of deltaic complexes from the eastern margin of the Appalachian Basin.

scholarly journals Shelf erosion and submarine river canyons: implications for deep-sea oxygenation and ocean productivity during glaciation

2010 ◽  
Vol 7 (6) ◽  
pp. 1973-1982 ◽  
Author(s):  
I. Tsandev ◽  
C. Rabouille ◽  
C. P. Slomp ◽  
P. Van Cappellen
Keyword(s):  
Organic Matter ◽  
Organic Carbon ◽  
Sea Level ◽  
Deep Sea ◽  
Oxygen Demand ◽  
Coupled Model ◽  
Submarine Canyon ◽  
Open Ocean ◽  
Oxygen Levels ◽  
Organic Carbon Burial

Abstract. The areal exposure of continental shelves during glacial sea level lowering enhanced the transfer of erodible reactive organic matter to the open ocean. Sea level fall also activated submarine canyons thereby allowing large rivers to deposit their particulate load, via gravity flows, directly in the deep-sea. Here, we analyze the effects of shelf erosion and particulate matter re-routing to the open ocean during interglacial to glacial transitions, using a coupled model of the marine phosphorus, organic carbon and oxygen cycles. The results indicate that shelf erosion and submarine canyon formation may significantly lower deep-sea oxygen levels, by up to 25%, during sea level low stands, mainly due to the supply of new material from the shelves, and to a lesser extent due to particulate organic matter bypassing the coastal zone. Our simulations imply that deep-sea oxygen levels can drop significantly if eroded shelf material is deposited to the seafloor. Thus the glacial ocean's oxygen content could have been significantly lower than during interglacial stages. Primary production, organic carbon burial and dissolved phosphorus inventories are all affected by the erosion and rerouting mechanisms. However, re-routing of the continental and eroded shelf material to the deep-sea has the effect of decoupling deep-sea oxygen demand from primary productivity in the open ocean. P burial is also not affected showing a disconnection between the biogeochemical cycles in the water column and the P burial record.

scholarly journals Hummocks in alpine tundra, northern British Columbia, Canada: distribution, morphology and organic carbon composition

2019 ◽  
Vol 5 (3) ◽  
pp. 127-147
Author(s):  
Marjolaine Verret ◽  
Yifeng Wang ◽  
Jean Bjornson ◽  
Denis Lacelle
Keyword(s):  
British Columbia ◽  
Organic Matter ◽  
Organic Carbon ◽  
Late Holocene ◽  
Organic Content ◽  
Alpine Tundra ◽  
Carbon Density ◽  
Freezing And Thawing ◽  
Fine Grained ◽  
Alkyl Groups

Hummocks develop by cryoturbation in fine-grained frost-susceptible soils and their stage of maturity may affect the translocation of organics in Cryosols. This study examines the distribution and morphology of hummocks in the Chuck Creek Trail Valley (northern British Columbia) and determines the quantity, distribution, and composition of organic matter in their soils. Hummocks occupy about 5%–20% of the valley and their morphology is largely affected by their silt content. Cryoturbated intrusions, radiocarbon dated to 2814 and 1648 cal year B.P., suggest that hummock development was initiated during the cooler late Holocene. Hummocks have an average soil organic carbon density of 16.3 kg m−2 in the uppermost 1 m, with 62% stored in the top 25 cm. Organics are mainly present as particulate organic matter in the O-horizon (25%–80%), characterized by degradable alkyl C and O/N-alkyl groups, but occur as mineral-associated organic matter (96%–98%) composed of recalcitrant aromatic and aliphatic C groups in the underlying B and C horizons. Minor differences in organic content and composition occur between hummock tops and troughs, and between hummocks showing different stages of maturity. In the absence of an observed frost table, contemporary hummock activity is attributed to seasonal freezing and thawing.

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