Evolution of pore structure in organic shale with type III kerogen and high kaolinite content in Ningwu Basin

Abstract

Special deposition environment makes organic-rich shales in Ningwu Basin have type III kerogen and high kaolinite content, which are also famous as the kaolinite ore. The specific composition of shale in Ningwu Basin can change the pore structure and thus, influence the shale gas storage and transport. This study focuses on the pore structure and its evolution in shales with type III kerogen and high kaolinite content. In this study, 14 Upper Paleozoic shale samples, whose total organic matter contents (TOC) range from 0.39% to 5.91% and maturities (represented by vitrinite reflectance) range from 1.22% to 2.06%, were collected. Scanning electron microscopy (SEM), high-pressure mercury injection, and low-temperature N₂ adsorption experiments were used to analyze pore structure of these shale samples. Results show that when the TOC content is smaller than 1.4%, the kaolinite content decreases linearly and quartz content increases linearly with increasing the TOC content. In contrast, when TOC content is>1.4%, the clay content tends to increase with increasing TOC. Based on the SEM images, organic pores and clay pores were identified in shale samples with type III kerogen and high kaolinite content. During the maturation process, the kaolinite content decreases and illite content increases with increasing the vitrinite reflectance. At the same time, the pore volume and pore surface area both increase with increasing the vitrinite reflectance, and it may be because more organic pores and clay pores in the illite were generated during the maturation process. This study can provide further understandings of shale gas accumulation in shale with type III kerogen and high kaolinite content.

Graphical abstract

Keywords

pore structure / type III kerogen / kaolinite / low-temperature N₂ adsorption / high-pressure mercury porosimetry / influencing factors

References

[1] Avnir D, Jaroniec M (1989). An isotherm equation for adsorption on fractal surfaces of heterogeneous porous materials. Langmuir, 5(6): 1431–1433

[2] Bahadur J, Ruppert L F, Pipich V, Sakurovs R, Melnichenko Y B (2018). Porosity of the Marcellus Shale: a contrast matching small-angle neutron scattering study. Int J Coal Geol, 188: 156–164

[3] Bernard S, Horsfield B, Schulz H M, Wirth R, Schreiber A, Sherwood N (2012). Geochemical evolution of organic-rich shales with increasing maturity: a STXM and TEM study of the Posidonia Shale (Lower Toarcian, northern Germany). Marine Petrol Geo, 31(1): 70–89

[4] Brunauer S, Deming L S, Deming W E, Teller E (1940). On the theory of Van der Waal’s adsorption of gases. J Am Chem Soc, 62(7): 1723–1732

[5] Chen Y, Xu J, Wang P (2020). Shale gas potential in China: a production forecast of the Wufeng-Longmaxi Formation and implications for future development. Energ Polic, 147: 111868

[6] Clarkson C R, Solano N R, Bustin R M, Bustin A M M, Chalmers G R L, He L, Melnichenko Y B, Radliński A P, Blach T P (2013). Pore structure characterization of North American shale gas reservoirs using USANS/SANS, gas adsorption, and mercury intrusion. Fuel, 103: 606–616

[7] Curtis J B (2002). Fractured shale-gas systems. AAPG Bull, 86(11): 1921–1938

[8] Curtis M E, Cardott B J, Sondergeld C H, Rai C S (2012). Development of organic porosity in the woodford shale with increasing thermal maturity. Int J Coal Geol, 103: 26–31

[9] Feng Z, Dong D, Tian J, Qiu Z, Wu W, Zhang C (2018). Geochemical characteristics of Longmaxi Formation shale gas in the Weiyuan area, Sichuan Basin, China. J Petrol Sci Eng, 167: 538–548

[10] Fu H, Wang X, Zhang L, Gao R, Li Z, Xu T, Zhu X, Xu W, Li Q (2015). Investigation of the factors that control the development of pore structure in lacustrine shale: a case study of block X in the Ordos Basin, China. J Nat Gas Sci Eng, 26: 1422–1432

[11] Guo X (2019). Major factors controlling the shale gas accumulations in Wufeng-Longmaxi Formation of the Pingqiao Shale Gas Field in Fuling Area, Sichuan Basin, China. J Nat Gas Geosci, 4(3): 129–138

[12] Hazra B, Wood D A, Kumar S, Saha S, Dutta S, Kumari P, Singh A K (2018). Fractal disposition, porosity characterization and relationships to thermal maturity for the Lower Permian Raniganj Basin shales, India. J Nat Gas Sci Eng, 59: 452–465

[13] Jarvie D M, Hill R J, Ruble T E, Pollastro R M (2007). Unconventional shale-gas systems: the Mississippian Barnett Shale of north-central Texas as one model for thermogenic shale-gas assessment. AAPG Bull, 91(4): 475–499

[14] Jiang F, Chen D, Wang Z, Xu Z, Chen J, Liu L, Huyan Y, Liu Y (2016). Pore characteristic analysis of a lacustrine shale: a case study in the Ordos Basin, NW China. Mar Pet Geol, 73: 554–571

[15] Jiang P, Xu J (1989). Formation and evolution of the Ningwu Basin as a Mesozoic pull-apart basin. Chinese J Geo, 24(4): 314–322

[16] Kanniah V, Wu P, Mandzy N, Grulke E A (2012). Fractal analysisasa complimentary technique for characterizing nanoparticle size distributions. Powder Technol, 226: 189–198

[17] Katz B J, Arango I (2018). Organic porosity: a geochemist’s view of the current state of understanding. Org Geochem, 123: 1–16

[18] Kuang L, Dong D, He W, Wen S, Sun S, Li S, Qiu Z, Liao X, Li Y, Wu J, Zhang L, Shi Z, Guo W, Zhang S (2020). Geological characteristics and development potential of transitional shale gas in the east margin of the Ordos Basin, NW China. Petrol Explor Devel, 47(3): 471–482

[19] Li J, Zhou S, Li Y, Ma Y, Yang Y, Li C (2016c). Effect of organic matter on pore structure of mature lacustrine organic-rich shale: a case study of the Triassic Yanchang shale, Ordos Basin, China. Fuel, 185: 421–431

[20] Li Y, Tang D, Wu P, Niu X, Wang K, Qiao P, Wang Z (2016a). Continuous unconventional natural gas accumulations of Carboniferous-Permian coal-bearing strata in the Linxing area, northeastern Ordos Basin, China. J Nat Gas Sci Eng, 36: 314–327

[21] Li Y, Wang Z, Gan Q, Niu X, Xu W (2019a). Paleoenvironmental conditions and organic matter accumulation in Upper Paleozoic organic-rich rocks in the east margin of the Ordos Basin, China. Fuel, 252: 172–187

[22] Li Y, Yang J, Pan Z, Meng S, Wang K, Niu X (2019b). Unconventional natural gas accumulations in stacked deposits: a discussion of Upper Paleozoic coal-bearing strata in the east margin of the Ordos Basin, China. Acta Geol Sin (English Ed) , 93(1): 111–129

[23] Li Y, Yang J, Pan Z, Tong W (2020). Nanoscale pore structure and mechanical property analysis of coal: an insight combining AFM and SEM images. Fuel, 260: 116352

[24] Li Y, Zhang C, Tang D, Gan Q, Niu X, Wang K, Shen R (2017). Coal pore size distributions controlled by the coalification process: an experimental study of coals from the Junggar, Ordos, and Qinshui basins in China. Fuel, 206: 352–363

[25] Li Z, Oyediran I A, Huang R, Hu F, Du T, Hu R, Li X (2016b). Study on pore structure characteristics of marine and continental shale in China. J Nat Gas Sci Eng, 33: 143–152

[26] Li Z, Shen X, Qi Z, Hu R (2018). Study on the pore structure and fractal characteristics of marine and continental shale based on mercury porosimetry, N₂ adsorption and NMR methods. J Nat Gas Sci Eng, 53: 12–21

[27] Liu G, Huang Z, Chen F, Jiang Z, Gao X, Li T, Chen L, Xia L, Han W (2016). Reservoir characterization of Chang 7 member shale: a case study of lacustrine shale in the Yanchang Formation, Ordos Basin, China. J Nat Gas Sci Eng, 34: 458–471

[28] Liu K, Ostadhassan M, Sun L, Zou J, Yuan Y, Gentzis T, Zhang Y, Carvajal-Ortiz H, RezaeeR(2019). A comprehensive pore structure study of the Bakken Shale with SANS, N₂ adsorption and mercury intrusion. Fuel, 245: 274–285

[29] Liu W, Wu J, Jiang H, Zhou Z, Luo C, Wu W, Li X, Liu S, Deng B (2021). Cenozoic exhumation and shale-gas enrichment of the Wufeng-Longmaxi formation in the southern Sichuan Basin, western China. Mar Pet Geol, 125: 104865

[30] Liu X, Xiong J, Liang L (2015). Investigation of pore structure and fractal characteristics of organic-rich Yanchang formation shale in central China by nitrogen adsorption/desorption analysis. J Nat Gas Sci Eng, 22(7): 62–72

[31] Loucks R G, Reed R M, Ruppel S C, Hammes U (2012). Spectrum of pore types and networks in mudrocks and a descriptive classification for matrix-related mudrock pores. AAPG Bull, 96(6): 1071–1098

[32] Nie H, Li D, Liu G, Lu Z, Hu W, Wang R, Zhang G (2020). An overview of the geology and production of the Fuling shale gas field, Sichuan Basin, China. Energy Geoscience, 1(3–4): 147–164

[33] Pan Y, Hui D, Luo P, Zhang Y, Zhang L, Sun L (2018). Influences of subcritical and supercritical CO₂ treatment on the pore structure characteristics of marine and terrestrial shales. J CO₂ Utilization, 28: 152–67

[34] Qin L, Li S, Zhai C, Lin H, Zhao P, Shi Y, Bai Y (2020). Changes in the pore structure of lignite after repeated cycles of liquid nitrogen freezing as determined by nitrogen adsorption and mercury intrusion. Fuel, 267: 117214

[35] Sanyal D, Ramachandrarao P, Gupta O P A (2006). Fractal description of transport phenomena in dendritic porous network. Chem Eng Sci, 61(2): 307–315

[36] Shi M, Yu B, Xue Z, Wu J, Yuan Y (2015). Pore characteristics of organic-rich shaleswith high thermal maturity: a case study of the Longmaxi gas shale reservoirs from well Yuye-1 in southeastern Chongqing, China. J Nat Gas Sci Eng, 26: 948–959

[37] Slatt R M, O’Brien N R (2011). Pore types in the Barnett and Woodford gas shales: contribution to understanding gas storage and migration pathways in fine-grained rocks. AAPG Bull, 95(12): 2017–2030

[38] Sun C, Tang S, Zhang S, Wei J, Hou Y, Zhang T (2017). Nanopore characteristics of Late Paleozoic transitional facies coal-bearing shale in Ningwu Basin, China investigated by nuclear magnetic resonance and low-pressure nitrogen adsorption. J Nanosci Nanotechnol, 17(9): 6433–6444

[39] Wang Q, Chen X, Jha A N, Rogers H (2014a). Natural gas from shale formation- the evolution, evidences and challenges of shale gas revolution in United States. Renew Sustain Energy Rev, 30(2): 1–28

[40] Wang X, Gao S, Gao C (2014b). Geological features of Mesozoic lacustrine shale gas in south of Ordos Basin, NW China. Pet Explor Dev, 41(3): 326–337

[41] Wang X, Zhu Y, Song Y, Jonathan P (2020). Structure and partial ordering of terrestrial kerogen: insight from high-resolution transmission electron microscopy. Fuel, 281: 118759

[42] Wang Y, Wang L, Wang J, Jiang Z, Jin C, Wang Y (2018). Characterization of organic matter pores in typical marine and terrestrial shales, China. J Nat Gas Sci Eng, 49: 56–65

[43] Wang Y, Wang L, Wang J, Jiang Z, Wang C, Fu Y, Song F, Wang Y, Liu D, Jin C (2019). Multiscale characterization of three-dimensional pore structures in a shale gas reservoir: a case study of the Longmaxi shale in Sichuan Basin, China. J Nat Gas Sci Eng, 66: 207–216

[44] Xiong F, Jiang Z, Li P, Wang X, Bi H, Li Y, Wang Z, Amooie M A, Soltanian M R, Moortgat J(2017). Pore structure of transitional shales in the Ordos Basin, NW China: effects of composition on gas storage capacity. Fuel, 206: 504–515

[45] Xu Q, Liu B, Ma Y, Song X, Wang Y, Chen Z (2017). Geological and geochemical characterization of lacustrine shale: a case study of the Jurassic Da’anzhai member shale in the central Sichuan Basin, southwest China. J Nat Gas Sci Eng, 47: 124–139

[46] Xu Q, Xu F, Jiang B, Zhao Y, Zhao X, Ding R, Wang J (2018). Geology and transitional shale gas resource potentials in the Ningwu Basin, China. Energy Explor & Exploit, 36(6): 1482–1497

[47] Yang F, Ning Z, Liu H (2014). Fractal characteristics of shales from a shale gas reservoir in the Sichuan Basin, China. Fuel, 115: 378–384

[48] Yang F, Ning Z, Wang Q, Zhang R, Krooss B M (2016a). Pore structure characteristics of lower Silurian shales in the southern Sichuan Basin, China: insights to pore development and gas storage mechanism. Int J Coal Geol, 156: 12–24

[49] Yang Y, Zhang W, Gao Y, Wan Y, Su Y, An S, Sun H, Zhang L, Zhao J, Liu L (2016b). Influence of stress sensitivity on microscopic pore structure and fluid flow in porous media. J Nat Gas Sci Eng, 36 (Part A): 20–31

[50] Yang R, He S, Yi J, Hu Q (2016c). 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. Mar Pet Geol, 70: 27–45

[51] Yuan Y, Rezaee R (2019). Fractal analysis of the pore structure for clay bound water and potential gas storage in shales based on NMR and N₂ gas adsorption. J Petrol Sci Eng, 177: 756–765

[52] Zhang B X, Fu X H, Shen Y L, Zhang Q H, Deng Z (2021). Mineral composition and its control on nanopores of marine-continental transitional shale from the Ningwu Basin, North China. J Nanosci Nanotechnol, 21(1): 168–180

[53] Zhang J, Li X, Xie Z, Li J, Zhang X, Sun K, Wang F (2018). Characterization of microscopic pore types and structures in marine shale: examples from the Upper Permian Dalong Formation, Northern Sichuan Basin, South China. J Nat Gas Sci Eng, 59: 326–342

[54] Zhang M, Fu X, Zhang Q, Cheng W (2019). Research on the organic geochemical and mineral composition properties and its influence on pore structure of coal-measure shales in Yushe-Wuxiang Block, South Central Qinshui Basin, China. J Petrol Sci Eng, 173: 1065–1079

[55] Zhou J, Yang K, Tian S, Zhou L, Xian X, Jiang Y, Liu M, Cai J (2020). CO₂-water-shale interaction induced shale microstructural alteration. Fuel, 263: 116642

[56] Zhou L, Kang Z (2016). Fractal characterization of pores in shales using NMR: a case study from the Lower Cambrian Niutitang Formation in the Middle Yangtze Platform, Southwest China. J Nat Gas Sci Eng, 35: 860–872

RIGHTS & PERMISSIONS

Higher Education Press