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| 1 | Effect of Organic Matter Type and Maturity on Organic Matter Pore Formation of Transitional Facies Shales: A Case Study on Upper Permian Longtan and Dalong Shales in Middle Yangtze Region, China显示文摘Organic matter(OM)nanopores developed in transitional facies shales,i.e.,the Upper Permian Longtan and Dalong Formations in the Yangtze Platform,China,were investigated to determine the corre-sponding influence of thermal maturity and OM types within the geological conditions.A suite of 16 core samples were taken from Type-Ⅲ Longtan shales and Type-Ⅱ Dalong shales from two wells covering a ma-turity(Ro,vitrinite reflectance)ranging from 1.22%to 1.43%and 2.62%to 2.97%,respectively.Integrated analysis of the shale samples was carried out,including field-emission scanning electron microscopy(FESEM),low-pressure N2 and CO2 adsorption,high-pressure CH4 adsorption,and mercury intrusion capillary pressure(MICP)analysis.The fluid inclusions of liquid and gas hydrocarbons trapped in calcite vein samples in Dalong shales of two wells were studied using laser Raman and fluorescence spectroscopy.FE-SEM images indicated that OM pores in different formations varied substantially in terms of shape,size,and distribution density.OM pores in Type-Ⅱ Dalong shales of Well XY1 were mainly micropore,sparsely distributed in the gas-prone kerogen with a spot-like and irregular shape,while bitumen rarely developed observable pores.In contrast,the morphology of OM pores in Type-Ⅲ Longtan shales were significantly different,which was due to differences in the OM type.The primary OM pores in some terrestrial woody debris in Longtan shales had a relatively larger pore diameter,ranging from hundreds of nanometers to a few micrometers and were al-most all rounded in shape,which might be one of the factors contributing to larger pore volume and gas adsorption capacity than Dalong shales of Well XY1.Comparing Dalong shales of Well XY1 with relatively lower thermal maturity,there were abundant spongy-like pores,densely developed in the pyrobitumen in Type-Ⅱ Dalong shales of Well EY1,with an irregular shape and diameter ranging from several to hundreds of nanometers.Many blue fluorescent oil inclusions and a small number of CH4 inclusions mixed with C2H6 could be observed within calcite veins in Dalong shales of Well XY1,whereas only CH4 inclusions could be identified within calcite veins in Dalong shales of Well EJ1.Therefore,thermal maturity not only controlled the type of hydrocarbons generated,but also makes a significant contribution to the formation of OM pores,resulting in larger pore volumes and adsorption capacity of Type-Ⅱ shale samples in the dry gas window. | Zhongrui Wu Sheng He Yuanjia Han Gangyi Zhai Xipeng He Zhi Zhou | 2020 | Journal of Earth Science2020,31,2: | 12 |
| 2 | Geological Characteristics of Shale Gas in Different Strata of Marine Facies in South China显示文摘In the Middle and Upper Yangtze region of South China,there are well developed sets of marine shale strata.Currently only Wufeng Longmaxi shale gas has been developed in scale,while the Sinian and Cambrian shale gas are still under exploration.The various shale strata show different characteristics in lithological features,such as lithofacies types and reservoir physical properties,which are due to the influence of tectonic pattern,sedimentary environment,and diagenesis caused by tectonic subsidence.This will affect the later fracturing technology and fracturing effect.The shale reservoirs of Sinian doushantuo,Cambrian Niutitang,Upper Ordovician Wufeng,and the Lower Silurian Longmaxi Formation shale were evaluated and compared with each other with respect to their sedimentary environments,lithofacies,minerals compositions,and micro pore characteristics.The reservoir characteristics of the shale and the main control factors of shale gas enrichment were summarized in this study. | Yufang Wang Gangyi Zhai Guoheng Liu Wanzhong Shi Yongchao Lu Juan Li Yunxiao Zhang | 2021 | Journal of Earth Science2021,32,4: | 1 |
| 3 | Latest Progress and Trend Forecast of China’s Shale Gas Exploration and Development显示文摘1 Introduction With almost five years of efforts,we have made major breakthrough and important advances in shale gas in many areas,such as the marine and continental shale in Sichuan Basin,the continental shale in Erdos Basin and the transitional shale in North China.China has begun shale gas productivity constructions in many shale | WANG Yufang ZHAI Gangyi BAO Shujing REN Shoumai GE Mingna ZHOU Zhi | 2015 | Acta Geologica Sinica(English Edition)2015,89,A01: | 1 |
| 4 | Maturity Assessment of the Lower Cambrian and Sinian Shales Using Multiple Technical Approaches显示文摘The Lower Cambrian Niutitang and Sinian Doushantuo shales are the most important and widespread source rocks and target layers in South China. Reliable data of the thermal maturity of organic matter(OM) is widely used to assess hydrocarbon generation and is a key property used in determining the viability and hydrocarbon potential of these new shales. Nevertheless, traditional thermal maturity indicators are no longer suited to the vitrinite-lack marine shales. This study aims to combine high throughput Raman and infrared spectroscopy analysis to confirm and validate the thermal maturity in comparison with the bitumen reflectance(R_(b)). Raman parameters such as the differences between the positions of the two bands(V_(G)–V_(D)) are strong parameters for calculating the thermal maturity in a large vitrinite reflectance(R_(o)) ranging from 1.60% to 3.80%. The infrared spectroscopy analysis indicates that the aromatic C=C bands and CH_(2)/CH_(3) aliphatic groups both are closely correlated with thermal maturity. The calculated R_(o) results from Raman and infrared spectroscopy are in strong coincidence with the R_(b). The relationships between R_(b) and pore volumes/surface areas(calculated from N_(2) adsorption) indicate that the sample with R_(b) of 3.40% has the lowest pore volumes and surface areas. Focused ion beam scanning electron microscopy(FIB-SEM) observations of OM pores indicate that R_(o) of approximately 3.60% may be an upper limit for OM porosity development. Obviously, kerogen Raman and infrared spectroscopy can indicate methods for reducing the risk in assessing maturity with practical, low-cost accurate results. Exploration of shale gas in the high maturity(>3.40%–3.60%) region carries huge risks. | Wei Yang Sheng He Gangyi Zhai Ze Tao Xiaoqing Yuan Sile Wei | 2021 | Journal of Earth Science2021,32,5: | 0 |
| 5 | Characteristics and controlling factors of shale gas reservoir in the Fuling area,Sichuan Basin显示文摘Statistical analysis of massive laboratory analytical data shows that for intervals in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Fuling area,Sichuan Basin,the total organic carbon content is 0.55%-5.89%with an average of 2.54%,presenting a gradual increase trend from top to bottom.Based on whole-rock X-ray diffraction data,the content of clay minerals of the shale is 16.6%-62.8%with an average of 40.9%,gradually decreasing from top to bottom.The content of brittle minerals gradually increases from top to bottom,ranging from 37.2%to 83.4%with an average of 59.1%.Porosity is 1.17%-7.98%with an average of 4.61%through the helium injection method.The horizontal permeability is 0.002-335.209 mD with an average of 23.785 mD by the steady-state method.Massive analytical data from the high-pressure mercury injection method show the micropores are well developed in the shale,and mainly provide the primary specific surface area of pores,while the micropores,transitional pores and mesopores primarily contribute to permeability.The pore types were observed using SEM in combination with argon ion polishing technology.From top to bottom of the shale interval,the organic pores increase and the inorganic pores decrease.Gas desorption data show that the total gas content is 0.44-5.19 m^(3)/t with an average of 1.97 m^(3)/t,and gradually increase from top to bottom of the shale interval.The development of marine shale gas reservoir in Well A is controlled by mineral compositions,the development characteristics of organic matter.TOC is not only a major intrinsic factor controlling the lower reservoir interval,but also an important material to provide the reservoir space for the shale gas.In the late diagenetic stage,the clay mineral assemblages changed from montmorillonite to illite,forming new micropores and leading to an increase of the porosity and great influences on the upper reservoir interval.The content of brittle minerals is more than 50%,facilitating formation of fractures,and the permeability performance can be enhanced significantly.In general,the Wufeng Formation and the bottom interval of the Longmaxi Formation are both high-quality reservoirs and primary pay intervals. | Xiaoming Zhang Wanzhong Shi Gangyi Zhai Qinghai Xu Ren Wang Zhuang Xu Jian Wang Chao Wang Qi Yuan | 2017 | Petroleum Research2017,2,1: | 0 |
| 6 | Quartz crystallinity index:New quantitative evidence for biogenic silica of the Late Ordovician to Early Silurian organic-rich shale in the Sichuan Basin and adjacent areas,China显示文摘Quartz crystallinity index(QCI)was used to reflect the crystallisation of silica in the Late Ordovician Wufeng(WF)and Early Silurian Longmaxi(LM)Formation shale,as well as the airborne volcanic ash-derived silica in the Lucaogou Formation tuffaceous shale,to distinguish the two types of silica.The silica in different graptolite biozones exhibited different crystallisation.The WF2–3,LM1–4 graptolite biozones showed obviously lower QCI values than the LM5–9 graptolite biozones and the Lucaogou Formation samples.The graptolite organisms played the role of adsorption,fixation,and precipitation in silicon accumulation and enrichment in stratum.The biogenic origin caused the poorest quartz crystallisation in WF2–3 and LM1–4 graptolite biozones samples.The airborne volcanic ash-derived silica in the Lucaogou Formation tuffaceous shale exhibited relatively poor quartz crystallisation because of weaker diagenesis intensity.Generally,although the WF2–3 and LM1–4 graptolite biozones underwent strong diagenesis and contained a small amount of detrital quartz,the silica still exhibited lower QCI values than the airborne volcanic ash-derived silica in the Lucaogou Formation tuffaceous shale.The biogenic silica crystallisation was much poorer than that of the airborne volcanic ash-derived silica.QCI is an effective quantitative index to demonstrate the biogenic silica in the organic-rich and silica-rich shale. | Guoheng LIU Gangyi ZHAI Rui YANG Tingpeng HE Bin WEI | 2021 | Science China Earth Sciences2021,64,5: | 0 |