Characteristics of Pore Structure and Gas Content of the Lower Paleozoic Shale from the Upper Yangtze Plate, South China

This study is predominantly about the differences in shale pore structure and the controlling factors of shale gas content between Lower Silurian and Lower Cambrian from the upper Yangtze plate, which are of great significance to the occurrence mechanism of shale gas. The field emission scanning electron microscopy combined with Particles (Pores) and Cracks Analysis System software, CO2/N2 adsorption and the high-pressure mercury injection porosimetry, and methane adsorption were used to investigate characteristics of overall shale pore structure and organic matter pore, heterogeneity and gas content of the Lower Paleozoic in southern Sichuan Basin and northern Guizhou province from the upper Yangtze plate. Results show that porosity and the development of organic matter pores of the Lower Silurian are better than that of the Lower Cambrian, and there are four main types of pore, including interparticle pore, intraparticle pore, organic matter pore and micro-fracture. The micropores of the Lower Cambrian shale provide major pore volume and specific surface areas. In the Lower Silurian shale, there are mesopores besides micropores. Fractal dimensions representing pore structure complexity and heterogeneity gradually increase with the increase in pore volume and specific surface areas. There is a significant positive linear relationship between total organic carbon content and micropores volume and specific surface areas of the Lower Paleozoic shale, and the correlation of the Lower Silurian is more obvious than that of the Lower Cambrian. The plane porosity of organic matter increases with the increase in total organic carbon when it is less than 5%. The plane porosity of organic matter pores is positively correlated with clay minerals content and negatively correlated with brittle minerals content. The adsorption gas content of Lower Silurian and Lower Cambrian shale are 1.51–3.86 m3/t (average, 2.31 m3/t) and 0.35–2.38 m3/t (average, 1.36 m3/t). Total organic carbon, clay minerals and porosity are the main controlling factors for the differences in shale gas content between Lower Cambrian and Lower Silurian from the upper Yangtze plate. Probability entropy and organic matter plane porosity of the Lower Silurian are higher than those of Lower Cambrian shale, but form factor and roundness is smaller.

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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 ◽

10.1155/2019/9524507 ◽

2019 ◽

Vol 2019 ◽

pp. 1-14 ◽

Cited By ~ 1

Author(s):

Ming Wen ◽

Zhenxue Jiang ◽

Kun Zhang ◽

Yan Song ◽

Shu Jiang ◽

...

Keyword(s):

Organic Matter ◽

Shale Gas ◽

Southern China ◽

Sedimentary Organic Matter ◽

Gas Content ◽

Silicon Isotope ◽

Upper Ordovician ◽

Lower Silurian ◽

Excess Silicon ◽

Lower Yangtze

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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RETRACTED ARTICLE: Characterization of the microscopic pore structure of the lower paleozoic shale gas reservoir in the Southern Sichuan Basin and its influence on gas content

Petroleum Science and Technology ◽

10.1080/10916466.2017.1390682 ◽

2017 ◽

Vol 35 (23) ◽

pp. 2165-2171 ◽

Cited By ~ 2

Author(s):

Zhe Wang

Keyword(s):

Pore Structure ◽

Shale Gas ◽

Sichuan Basin ◽

Gas Content ◽

Gas Reservoir ◽

Lower Paleozoic ◽

Shale Gas Reservoir ◽

Retracted Article

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Effect of the hydrothermal activity in the Lower Yangtze region on marine shale gas enrichment: A case study of Lower Cambrian and Upper Ordovician-Lower Silurian shales in Jiangye-1 well

Open Geosciences ◽

10.1515/geo-2018-0046 ◽

2018 ◽

Vol 10 (1) ◽

pp. 582-592 ◽

Cited By ~ 1

Author(s):

Weiwei Liu ◽

Kun Zhang ◽

Zhenxue Jiang ◽

Shu Jiang ◽

Yan Song ◽

...

Keyword(s):

Organic Matter ◽

Shale Gas ◽

Lower Cambrian ◽

Hydrothermal Activity ◽

Sedimentary Organic Matter ◽

Upper Ordovician ◽

Lower Silurian ◽

Excess Silicon ◽

Lower Yangtze Region ◽

Lower Yangtze

Abstract Finding favorable sites for the exploration of shale gas, is still one of the important areas of research that needs immediate attention. The content of organic matter in shale plays a crucial role in the hydrocarbon generation potential, reservoir space and gas-bearing capacity of shales. Therefore, studying the sedimentary environment of organic shale can provide a scientific basis for locating favorable exploration areas for shale gas. The article takes the Lower Cambrian and the Upper Ordovician-Lower Silurian shales in the Yangtze region as the research object and selects representative wells to quantitatively calculate the existence of excess silicon in shale siliceous minerals and the content of excess silicon. Then, the origin of excess silicon can be clarified by the Al, Fe and Mn elemental analysis. Finally, the sedimentary organic matter enrichment mechanism is analyzed from water oxidation-reduction environments and biological productivity. The results of the study show that the excess silicon in the Lower Cambrian and Upper Ordovician-Lower Silurian shales in the Lower Yangtze region is of hydrothermal origin. The hydrothermal activity improves biological fertility on the one hand; whereas on the other hand, it can enhance the reducing capacity of the bottom water conducive for the preservation of organic matter thereby enriching the sedimentary organic matter. The place near the junction of Yangtze plate and Cathaysian plate, where hydrothermal activities were more intense, provided favorable loci for shale gas exploration in the Lower Yangtze region. It was observed that, since the hydrothermal activity was stronger in the Early Cambrian than in the Late Ordovician-Early Silurian times, the total organic carbon (TOC) content of the Lower Cambrian shale was higher than that of the Upper Ordovician-Lower Silurian shales.

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Pore structure and sorption capacity investigations of Ediacaran and Lower Silurian gas shales from the Upper Yangtze platform, China

Geomechanics and Geophysics for Geo-Energy and Geo-Resources ◽

10.1007/s40948-021-00262-5 ◽

2021 ◽

Vol 7 (3) ◽

Author(s):

Zhazha Hu ◽

Garri Gaus ◽

Timo Seemann ◽

Qian Zhang ◽

Ralf Littke ◽

...

Keyword(s):

Organic Matter ◽

Pore Structure ◽

Clay Minerals ◽

Sorption Capacity ◽

Shale Gas ◽

Gas Storage ◽

Micropore Volume ◽

Thermal Maturity ◽

Yangtze Platform ◽

Lower Silurian

Abstract The shale gas potential of Ediacaran and Lower Silurian shales from the Upper Yangtze platform is assessed in this study with a focus on the contributions of clay minerals and organic matter to sorption capacity. For this purpose, a multidisciplinary assessment was carried out using petrophysical, mineralogical, petrographic and geochemical methods. In terms of TOC contents (4.2%), brittle mineral contents (68.6%) and maximum gas storage capacities (0.054–0.251 mmol/g) Ediacaran shales from this study show comparable properties to other producing shale gas systems although the thermal maturity is extremely high (VRr = 3.6%). When compared to lower Silurian shales from the same region, it is evident that (1) deeper maximum burial and (2) a lack of silica-associated preservation of the pores resulted in a relatively lower mesopore volume, higher micropore volume fraction and lower overall porosity (Ediacaran shales: 1.4–4.6%; Silurian shales: 6.2–7.4%). Gas production is therefore retarded by poor interconnectivity of the pore system, which was qualitatively demonstrated by comparing experimental gas uptake kinetics. TOC content exhibits a prominent control on sorption capacity and micropore volume for both shales. However, different contributions of clay minerals to sorption capacity were identified. This can partly be attributed to different clay types but is likely also related to burial-induced recrystallisation and different origins of illite. Additionally, it was shown that variations in sorption capacity due to incorrect estimates of clay mineral contribution are in the same range as variations due to differences in thermal maturity. Article highlights Pore structure and gas storage characteristics are evaluated for the first time for Ediacaran Shales from the Upper Yangtze platform Due to a lower free gas storage capacity and diffusivity, the Ediacaran shale can be regarded as a less favorable shale gas prospect when compared to the Silurian shale Clay mineral contribution to sorption capacity is evaluated taking clay mineralogy into consideration Maturity-related changes of organic matter sorption capacity have been discussed on the basis of a compiled data set

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Geochemistry and Mineralogy of Lower Paleozoic Heituao Shale from Tadong Low Uplift of Tarim Basin, China: Implication for Shale Gas Development

Minerals ◽

10.3390/min11060635 ◽

2021 ◽

Vol 11 (6) ◽

pp. 635

Author(s):

Shihu Zhao ◽

Yanbin Wang ◽

Yong Li ◽

Honghui Li ◽

Zhaohui Xu ◽

...

Keyword(s):

Organic Matter ◽

Tarim Basin ◽

Shale Gas ◽

Organic Matter Content ◽

Matter Content ◽

Mature Stage ◽

Lower Paleozoic ◽

Development Potential ◽

Middle Ordovician ◽

Average Value

Tarim Basin is the largest Petroliferous basin in China, while its shale gas development potential has not been fully revealed. The organic-rich black shale in middle Ordovician Heituao Formation from Tadong low uplift of Tarim Basin has been considered as an important source rock and has the characteristic of large thickness, high organic matter content and high thermal maturity degree. To obtain its development potential, geochemical, mineralogical and mechanics research is conducted based on Rock-Eval pyrolysis, total organic carbon (TOC), X-ray diffraction (XRD) and uniaxial compression experiments. The results show that: (1) the TOC content ranges between 0.63 and 2.51 wt% with an average value of 1.22 wt%, the Tmax values are 382–523 °C (average = 468.9 °C), and the S2 value is relatively low which ranges from 0.08 to 1.37 mg HC/g rock (averaging of 0.42 mg HC/g rock); (2) the organic matter of Heituao shale in Tadong low uplift show poor abundance as indicated by low S2 value, gas-prone property, and post mature stage (stage of dry gas). (3) Quartz is the main mineral component in Heituao shale samples, accounting for 26–94 wt% with an average of 72 wt%. Additionally, its Young’s modulus ranges from 20.0 to 23.1 GPa with an average of 21.2 GPa, Poisson’s ratio ranges between 0.11 and 0.21 (average = 0.15); (4) the fracability parameter of brittleness index (BI) ranges between 0.28 and 0.99 (averaging of 0.85), indicating good fracability potential of Heituao shale of Tadong low uplift and has the potential for shale gas development. This study reveals the shale gas accumulation potential in middle Ordovician of the Tarim Basin, and beneficial for future exploration and production practice.

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Effect of Hydrothermal Activity on Organic Matter Enrichment of Shale: A Case Study of the Upper Ordovician and the Lower Silurian in the Lower Yangtze, South China

Minerals ◽

10.3390/min8110495 ◽

2018 ◽

Vol 8 (11) ◽

pp. 495 ◽

Cited By ~ 2

Author(s):

Yizhou Huang ◽

Zhenxue Jiang ◽

Kun Zhang ◽

Yan Song ◽

Shu Jiang ◽

...

Keyword(s):

Organic Matter ◽

Oxygen Isotope ◽

Shale Gas ◽

Organic Matter Content ◽

Hydrothermal Activity ◽

Late Ordovician ◽

Sedimentary Organic Matter ◽

Upper Ordovician ◽

Lower Silurian ◽

Activity Intensity

The effect of organic matter on hydrocarbon potential, storage space, and gas content of shale is well-known. Additionally, present-day content of sedimentary organic matter in shale is controlled by depositional and preservation processes. Therefore, a study of the enrichment mechanisms of sedimentary organic matter provides a scientific basis for the determination of favorable areas of shale gas. In this study the Upper Ordovician Xinkailing Fm. and the first member of the Lower Silurian Lishuwo Fm. were examined. Stratigraphic sequences were identified through conventional logs and elemental capture spectrum data. Oxygen isotope analysis was applied to recover paleotemperature of seawater in the study area. The excess silicon content was calculated and the origin of the silica was determined by the Fe-Al-Mn ternary plot. The enrichment mechanism of organic matter was analyzed by two aspects: redox conditions and paleoproductivity. As a result, the stratigraphic interval was divided into two 3rd-order sequences. Through oxygen isotope, the paleotemperature of seawater was 62.7–79.2 °C, providing evidence of the development of hydrothermal activity. Analysis of excess siliceous minerals identified two siliceous mineral origins: terrigenous and hydrothermal. It also revealed an upwards decreasing tendency in hydrothermal activity intensity. Strong hydrothermal activity during the Late Ordovician, recognized as TST1, formed a weak-oxidizing to poor-oxygen environment with high paleoproductivity, which promoted organic matter enrichment. During the Late Ordovician to the Early Silurian, identified as RST1, TST2, and RST2, weakening hydrothermal activity caused the decline of paleoproductivity and increased oxidation of bottom waters, leading to a relative decrease of organic matter content in the shale. Therefore, favorable areas of shale gas accumulation in the Upper Ordovician and Lower Silurian are determined stratigraphically as the TST1, with a high total organic carbonate content. Geographically, the hydrothermally-active area near the plate connection of the Yangtze and the Cathaysian is most favorable.

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Pore Structure of TiO2- Modified ZrO2 Particles Prepared by the Glycothermal Method

Advanced Engineering Forum ◽

10.4028/www.scientific.net/aef.38.17 ◽

2020 ◽

Vol 38 ◽

pp. 17-22

Author(s):

Fuya Sugiyama ◽

Shunsuke Hayashi ◽

Shinji Iwamoto

Keyword(s):

Thermal Stability ◽

Thermal Treatment ◽

Pore Structure ◽

High Performance ◽

Spherical Particles ◽

Size Distributions ◽

Catalytic Materials ◽

Surface Areas ◽

Pore Size Distributions ◽

Specific Surface Areas

Titania-modified zirconias with different Ti/Zr ratios were synthesized via thermal treatment of zirconium (IV) tetra-n-propoxide and titanium (IV) tetra-iso-propoxide in 1,4-butanediol at 300 °C. The obtained products were spherical particles composed of nanocrystals with the tetragonal ZrO2 structure. The products had large specific surface areas, large pore volumes, and relatively narrow pore size distributions in the mesopore region. After calcination at high temperatures, the obtained TiO2-modified ZrO2 samples preserved large surface areas and pore structure. Having these superior thermal stability and pore structure, the obtained TiO2-modified ZrO2 particles are expected to show high performance as catalytic materials.

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The effects of shale composition and pore structure on gas adsorption potential in highly mature marine shales, Lower Paleozoic, central Yangtze, China

Canadian Journal of Earth Sciences ◽

10.1139/cjes-2016-0015 ◽

2017 ◽

Vol 54 (10) ◽

pp. 1033-1048 ◽

Cited By ~ 12

Author(s):

Yuguang Hou ◽

Sheng He ◽

Nicholas B. Harris ◽

Jizheng Yi ◽

Yi Wang ◽

...

Keyword(s):

Organic Matter ◽

Pore Structure ◽

Surface Area ◽

Sorption Capacity ◽

Gas Adsorption ◽

Bet Surface Area ◽

Lower Paleozoic ◽

Longmaxi Formation ◽

Methane Sorption ◽

Shale Composition

The Ordovician Wufeng Formation and Silurian Longmaxi Formation are two of the most organic-rich and gas-prospective shale formations in the central Yangtze area, China. In this study, we investigate the controls exerted by shale composition and pore structure on methane sorption of these highly matured marine shales (Ro ranges from 2.0% to 4.0%). Samples were analyzed by SEM pore imaging of Ar-ion milled samples, high pressure methane adsorption, and low temperature nitrogen adsorption. In the high TOC Wufeng and lower Longmaxi formations, numerous organic matter pores are present. A positive correlation exists between TOC, BET surface area, and CH4 sorption capacity, indicating that porosity associated with organic matter is the key factor controlling methane sorption capacity of shale samples. In the organic-lean upper Longmaxi Formation, pores within clay particles and carbonate minerals are the major pore types. Organic-lean shale samples from the upper Longmaxi Formation have higher clay content, lower BET surface area, and lower adsorption capacity than organic-rich shales. Within several low TOC samples, a relatively strong correlation exists between illite content and methane sorption capacity, which is interpreted to result from clay mineral-hosted porosity.

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