Qualitative–quantitative multiscale pore characteristics of black shale from the Upper Ordovician and Lower Silurian black shale in the Southern Sichuan Basin, China

Qualitative–quantitative multiscale pore characteristics of black shale from the Upper Ordovician and Lower Silurian black shale in the Southern Sichuan Basin, China Chao Han Yuetong Zhang Guorui Wang Hua Li Zhihui Zhang Qiang Li

Accurate investigation of shale pores is critical to the assessment of shale-gas reservoir properties. Qualitative and quantitative methods have been commonly conducted in shale pore studies. In this study, we take the black shale from the Upper Ordovician and Lower Silurian black shale in the Southern Sichuan Basin as an example. Both qualitative and quantitative methods were used to study the pores at multiple scales, and we discuss the effectiveness of shale pore detection by multiple methods. The following results were obtained: 1) The black shale is composed of quartz, feldsaper, calcite, dolomite and clay minerals in the study area, and its average TOC and porosity are 2.19 and 2.12%, respectively. 2) The CT results show that the pore size of macropores (pore size >0.5 μm) mainly ranges from 2 to 16 μm. Nitrogen adsorption analysis shows that organic-rich shale has abundant organic matter pores with narrow necks and wide bodies. The pores of organic-poor shale are mainly composed of mineral-associated pores with narrow slit shapes. The NMR results show that with increasing TOC, the left peak T 2 relaxation times move leftwards, meaning that organic matter pores have a larger pore size than matrix pores at the mesopore scale. 3) CT data identify lamellation fractures and bed-cutting fractures, and their development is controlled by mineral type and content, TOC and laminae density. 4) The determination of segmentation thresholds in CT and transverse surface relaxivity in NMR seriously affects the accuracy of the results.
9 13 2022 981127 10.3389/feart.2022.981127 1 10.3389/crossmark-policy frontiersin.org true National Natural Science Foundation of China http://dx.doi.org/10.13039/501100001809 41702131 41972108 https://creativecommons.org/licenses/by/4.0/ 10.3389/feart.2022.981127 https://www.frontiersin.org/articles/10.3389/feart.2022.981127/full https://www.frontiersin.org/articles/10.3389/feart.2022.981127/full Fuel Bai 105 645 2013 Rock characterization of Fayetteville shale gas plays 10.1016/j.fuel.2012.09.043 Trans. AIME Brown 207 262 1956 Measurements of fractional wettability of oil fields' rocks by the nuclear magnetic relaxation method 10.2118/743-G J. Pet. Sci. Eng. Cai 195 107798 2020 The effect of shale bedding on supercritical CO2 jet fracturing: A experimental study 10.1016/j.petrol.2020.107798 J. Min. Strata Control Eng. Chen 3 023522 2021 Mechanical properties and failure mechanism of combined bodies with different coal-rock ratios and combinations 10.13532/j.jmsce.cn10-1638/td.20210108.001 NMR logging principles and applications Coates 1999 Curtis 2010 10.2118/137693-MS Structural characterization of gas shales on the micro-and nano-scales The structure and propertied of porous materials De Boer 1958 Earth Sc Front. Ding 19 212 2012 Dominant factor of fracture development in shale and its relationship to gas accumulation Bulletin Gale 101 2165 2017 Natural fractures in shale: A review and new observations 10.1306/08121413151 J. Pet. Sci. Eng. Gu 192 107277 2020 Developmental characteristics and dominant factors of natural fractures in lower silurian marine organic-rich shale reservoirs: A case study of the Longmaxi Formation in the fenggang block, southern China 10.1016/j.petrol.2020.107277 Geol. J. Han 54 438 2019 Source analysis of quartz from the Upper Ordovician and Lower Silurian black shale and its effects on shale gas reservoir in the southern Sichuan Basin and its periphery, China 10.1002/gj.3192 Mar. Pet. Geol. Han 75 181 2016 The lithofacies and reservoir characteristics of the upper ordovician and lower silurian black shale in the southern Sichuan Basin and its periphery, China 10.1016/j.marpetgeo.2016.04.014 Lithosphere Han 2022 9662175 2022 Characteristics and dominant factors for natural fractures in deep shale gas reservoirs: A case study of the wufeng-longmaxi formations in luzhou block, southern China 10.2113/2022/9662175 Energy Explor. Exploitation Han 36 665 2018 Mineral compositional controls on the porosity of black shales from the Wufeng and Longmaxi Formations (Southern Sichuan Basin and its surroundings) and insights into shale diagenesis 10.1177/0144598718763890 Energy fuels. He 35 10551 2021 Influence of mineral compositions on shale pore development of longmaxi formation in the dingshan area, southeastern sichuan basin, china 10.1021/acs.energyfuels.1c01026 Arab. J. Geosci. Huang 13 94 2020 Comparative study of porosity test methods for shale 10.1007/s12517-020-5086-5 Am. Assoc. Pet. Geol. Bull. Jarvie 91 475 2007 Unconventional shale-gas systems: The Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment 10.1306/12190606068 Int. J. Coal Geol. Ji 174 31 2017 Pore characterization of isolated organic matter from high matured gas shale reservoir 10.1016/j.coal.2017.03.005 J. Min. Strata Control Eng. Lan 3 033024 2021 Experimental study on acoustic emission characteristics of fault slip process based on damage factor 10.13532/j.jmsce.cn10-1638/td.20210510.002 Energy Rep. Li 8 4344 2022 Research progress on evaluation methods and factors influencing shale brittleness: A review 10.1016/j.egyr.2022.03.120 Mar. Pet. Geol. Li 127 104992 2021 Pore characteristics and pore structure deformation evolution of ductile deformed shales in the Wufeng-Longmaxi Formation, southern China 10.1016/j.marpetgeo.2021.104992 Pet. Sci. Li 15 498 2018 Study of the relationship between fractures and highly productive shale gas zones, Longmaxi Formation, Jiaoshiba area in eastern Sichuan 10.1007/s12182-018-0249-7 Energy Geosci. Li 1 55 2020 Development of unconventional gas and technologies adopted in China 10.1016/j.engeos.2020.04.004 J. Pet. Sci. Eng. Liang 147 154 2016 A new methodology of constructing pseudo capillary pressure (Pc) curves from nuclear magnetic resonance (NMR) logs 10.1016/j.petrol.2016.05.015 Int. J. COAL Geol. Liu 2020 103261 2020 Application of nuclear magnetic resonance (NMR) in coalbed methane and shale reservoirs: A review 10.1016/j.coal.2019.103261 Am. Assoc. Pet. Geol. Bull. Loucks 96 1071 2012 Spectrum of pore types and networks in mudrocks and a descriptive classification for matrix-related mudrock pores 10.1306/08171111061 Mar. Pet. Geol. Lv 112 104041 2020 The complex transgression and regression history of the northern margin of the Palaeogene Tarim Sea (NW China), and implications for potential hydrocarbon occurrences 10.1016/j.marpetgeo.2019.104041 Acta Geol. Sin. Mou 85 526 2011 Early Paleozoic sedimentary environment of hydrocarbon source rocks in the Middle-Upper Yangtze region and petroleum and gas exploration 10.1007/s12583-011-0163-z ACS Omega Qian 7 8724 2022 Study on the pore structure and fractal characteristics of different lithofacies of Wufeng–Longmaxi Formation shale in southern Sichuan Basin, China 10.1021/acsomega.1c06913 Pure Appl. Chem. Sing 57 603 1985 Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity (Recommendations 1984) 10.1351/pac198557040603 Sondergeld 2010 10.2118/131771-MS Micro-structural studies of gas shales Sci. China Earth Sci. Wang 57 313 2013 Quantitative characterization of reservoir space in the lower silurian longmaxi shale, southern sichuan, China 10.1007/s11430-013-4645-y J. Nat. Gas. Sci. Eng. Wang 66 207 2019 Multiscale characterization of three-dimensional pore structures in a shale gas reservoir: A case study of the longmaxi shale in Sichuan basin, China 10.1016/j.jngse.2019.04.009 J. Nat. Gas. Sci. Eng. WangLiu 81 103419 2020 Comparison of the pore structures of lower silurian Longmaxi Formation shales with different lithofacies in the southern Sichuan Basin, China 10.1016/j.jngse.2020.103419 J. Pet. Sci. Eng. Xiang 209 109877 2022 Structural deformation and its pore-fracture system response of the Wufeng-Longmaxi shale in the Northeast Chongqing area, using FE-SEM, gas adsorption, and SAXS 10.1016/j.petrol.2021.109877 J. Asian Earth Sci. Xu 193 104271 2020 Pore structures of different types of shales and shale gas exploration of the Ordovician Wufeng and Silurian Longmaxi successions in the eastern Sichuan Basin, South China 10.1016/j.jseaes.2020.104271 J. Petroleum Sci. Eng. Xu 207 109091 2021 Controlling factors of lamellation fractures in marine shales: A case study of the fuling area in eastern Sichuan Basin, China 10.1016/j.petrol.2021.109091 Mar. Pet. Geol. Yang 70 27 2016 Nano-scale pore structure and fractal dimension of organic-rich Wufeng-Longmaxi shale from Jiaoshiba area, Sichuan Basin: Investigations using FE-SEM, gas adsorption and helium pycnometry 10.1016/j.marpetgeo.2015.11.019 Fuel Yao 89 1371 2010 Petrophysical characterization of coals by low-field nuclear magnetic resonance (NMR) 10.1016/j.fuel.2009.11.005 Mar. Pet. Geol. Yin 100 1 2020 Geomechanical simulation of low-order fracture of tight sandstone 10.1016/j.marpetgeo.2020.104359 J. ASIAN EARTH Sci. Zeng 75 251 2013 Fracture development in Paleozoic shale of Chongqing area (South China). Part one: Fracture characteristics and comparative analysis of main controlling factors 10.1016/j.jseaes.2013.07.014 Energy fuels. Zhang 31 6951 2017 Shale pore characterization using NMR Cryoporometry with octamethylcyclotetrasiloxane as the probe liquid 10.1021/acs.energyfuels.7b00880 J. Nat. Gas. Sci. Eng. Zhang 27 321 2015 The characterization of a marine shale gas reservoir in the lower Silurian Longmaxi Formation of the northeastern Yunnan Province, China 10.1016/j.jngse.2015.08.070 J. Min. Strata Control Eng. Zhao 3 023520 2021 Investigation of the characteristics of hydraulic fracture initiation by using maximum tangential stress criterion 10.13532/j.jmsce.cn10-1638/td.20201217.001 Mar. Pet. Geol. Zhao 140 105648 2022 Multi-scale pore structure characterization of lacustrine shale and its coupling relationship with material composition: An integrated study of multiple experiments 10.1016/j.marpetgeo.2022.105648 Energy Geosci. Zheng 1 36 2020 Geology and geomechanics of hydraulic fracturing in the Marcellus shale gas play and their potential applications to the Fuling shale gas development 10.1016/j.engeos.2020.05.002