The pore structure and fractal characteristics of shales with low thermal maturity from the Yuqia Coalfield, northern Qaidam Basin, northwestern China

Haihai HOU, Longyi SHAO, Yonghong LI, Zhen LI, Wenlong ZHANG, Huaijun WEN

PDF(912 KB)
PDF(912 KB)
Front. Earth Sci. ›› 2018, Vol. 12 ›› Issue (1) : 148-159. DOI: 10.1007/s11707-016-0617-y
RESEARCH ARTICLE
RESEARCH ARTICLE

The pore structure and fractal characteristics of shales with low thermal maturity from the Yuqia Coalfield, northern Qaidam Basin, northwestern China

Author information +
History +

Abstract

The continental shales from the Middle Jurassic Shimengou Formation of the northern Qaidam Basin, northwestern China, have been investigated in recent years because of their shale gas potential. In this study, a total of twenty-two shale samples were collected from the YQ-1 borehole in the Yuqia Coalfield, northern Qaidam Basin. The total organic carbon (TOC) contents, pore structure parameters, and fractal characteristics of the samples were investigated using TOC analysis, low-temperature nitrogen adsorption experiments, and fractal analysis. The results show that the average pore size of the Shimengou shales varied from 8.149 nm to 20.635 nm with a mean value of 10.74 nm, which is considered mesopore-sized. The pores of the shales are mainly inkbottle- and slit-shaped. The sedimentary environment plays an essential role in controlling the TOC contents of the low maturity shales, with the TOC values of shales from deep to semi-deep lake facies (mean: 5.23%) being notably higher than those of the shore-shallow lake facies (mean: 0.65%). The fractal dimensions range from 2.4639 to 2.6857 with a mean of 2.6122, higher than those of marine shales, which indicates that the pore surface was rougher and the pore structure more complex in these continental shales. The fractal dimensions increase with increasing total pore volume and total specific surface area, and with decreasing average pore size. With increasing TOC contents in shales, the fractal dimensions increase first and then decrease, with the highest value occurring at 2% of TOC content, which is in accordance with the trends between the TOC and both total specific surface area and total pore volume. The pore structure complexity and pore surface roughness of these low-maturity shales would be controlled by the combined effects of both sedimentary environments and the TOC contents.

Keywords

shale gas / pore structure / fractal dimension / Yuqia Coalfield / Jurassic / northern Qaidam Basin

Cite this article

Download citation ▾
Haihai HOU, Longyi SHAO, Yonghong LI, Zhen LI, Wenlong ZHANG, Huaijun WEN. The pore structure and fractal characteristics of shales with low thermal maturity from the Yuqia Coalfield, northern Qaidam Basin, northwestern China. Front. Earth Sci., 2018, 12(1): 148‒159 https://doi.org/10.1007/s11707-016-0617-y

References

[1]
Barrett E P, Joyner  L G, Halenda  P P (1951). The determination of pore volume and area distribution in porous substances. I. Computations from nitrogen isotherms. J Am Chem Soc, 73(1): 373–380
CrossRef Google scholar
[31]
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). Mar Pet Geol, 31(1): 70–89
CrossRef Google scholar
[2]
Bowker K A (2007). Barnett shale gas production, Fort Worth Basin: issues and discussion. AAPG Bull, 91(4): 523–533
CrossRef Google scholar
[3]
Brunauer S, Emmett  P H, Teller  E (1938). Adsorption of gases in multimolecular layers. J Am Chem Soc, 60(2): 309–319
CrossRef Google scholar
[4]
Cao T T, Song  Z G, Luo  H Y, Liu  G X (2015). The differences of microscopic pore structure characteristics of coal, oil shale and shales and their storage mechanisms. Natural Gas Geoscience, 26(11): 2208–2218 (in Chinese)
[5]
Chalmers G R, Bustin  R M (2008). Lower Cretaceous gas shales in northeastern British Columbia, Part I: geological controls on methane sorption capacity. Bull Can Pet Geol, 56(1): 1–21
CrossRef Google scholar
[6]
Chalmers G R, Bustin  R M, Power  I M (2012). Characterization of gas shale pore systems by porosimetry, pycnometry, surface area, and field emission scanning electron microscopy/transmission electron microscopy image analyses: examples from the Barnett, Woodford, Haynesville, Marcellus, and Doig units. AAPG Bull, 96(6): 1099–1119
CrossRef Google scholar
[7]
Donaldson E C,  Kendall R F,  Baker B A,  Manning F S (1975). Surface-area measurement of geological matereials. Soc Pet Eng J, 15(02): 111–116
CrossRef Google scholar
[8]
Dow W G (1977). Kerogen studies and geological interpretations. J Geochem Explor, 7(2): 79–99
CrossRef Google scholar
[9]
Fildani A, Hanson  A D, Chen  Z Z, Moldowan  J D, Graham  S A, Arriola  P R (2005). Geochemical characteristics of oil and source rocks and implication for petroleum system, Talara basin, northwest Peru. AAPG Bull, 89(11): 1519–1545
CrossRef Google scholar
[10]
Gauden P A, Terzyk  A P, Rychlicki  G (2001). The new correlation between microporosity of strictly microporous activated carbons and fractal dimension on the basis of the Polanyi-Dubinin theory of adsorption. Carbon, 39(2): 267–278
CrossRef Google scholar
[11]
Gregg S J, Sing  K S W (1982). Adsorption, Surface Area and Porosity (2nd ed). London: Academic Press, 42–55
[12]
Li A, Ding  W L, He  J H, Dai  P, Yin S,  Xie F (2016). Investigation of pore structure and fractal characteristics of organic-rich shale reservoirs: a case study of Lower Cambrian Qiongzhusi Formation in Malong block of eastern Yunnan Province, South China. Mar Pet Geol, 70: 46–57
CrossRef Google scholar
[13]
Li M, Shao  L Y, Lu  J, Spiro B,  Wen H J,  Li Y H (2014). Sequence stratigraphy and paleogeography of the Middle Jurassic coal measures in the Yuqia Coalfield, northern Qaidam Basin, northwestern China. AAPG Bull, 98(12): 2531–2550
CrossRef Google scholar
[14]
Li Y J, Li  X J, Wang  Y L, Yu  Q C (2015). Effects of composition and pore structure on the reservoir gas capacity of Carboniferous shale from Qaidam Basin, China. Mar Pet Geol, 62: 44–57
CrossRef Google scholar
[15]
Liang L X, Xiong  J, Liu X J (2015). An investigation of the fractal characteristics of the Upper Ordovician Wufeng Formation shale using nitrogen adsorption analysis. J Nat Gas Sci Eng, 27(10): 402–409
CrossRef Google scholar
[16]
Liu S X, Zhong  J H, Ma  Y S, Yin  C M, Liu  C L, Li  Z X, Liu  X, Li Y,  Liu X G (2015a). Study of microscopic pore structure and adsorption isothermal of carboniferous shale, Eastern Qaidam Basin. Journal of China University of Petroleum, 39(1): 33–42 (in Chinese)
[17]
Liu X J, Xiong  J, Liang L X (2015b). 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: 62–72
CrossRef Google scholar
[18]
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
CrossRef Google scholar
[19]
Luo C, Liu  S G, Sun  W, Ran B,  Wang S Y,  Yang D, Bai  Z Q, Ye  Y C, Zhang  X, Deng B (2014). Pore structure characterization of black shale in the Lower Cambrian Niutitang Formation in western Hubei and eastern Chongqing area. Journal of Northeast Petroleum University, 38(2): 8–17 (in Chinese)
[20]
Micromeritics Instrument Corporation (2012). TriStarII 3020 Operator’s Manual. Georgia: C15–C20
[21]
Milliken K L, Rudnicki  M, Awwiller D N,  Zhang T (2013). Organic matter-hosted pore system, Marcellus Formation (Devonian), Pennsylvains. AAPG Bull, 97(2): 177–200
CrossRef Google scholar
[22]
Montgomery S L,  Jarvie D M,  Bowker K A,  Pollastro R M (2005). Mississippian Barnett shale, Fort Worth Basin, North-Central Texas: gas-shale play with multi-trillion cubic foot potential. AAPG Bull, 89(2): 155–175
CrossRef Google scholar
[23]
Nakagawa T, Komaki  I, Sakawa M,  Nishikawa K (2000). Small angle X-ray scattering sudy on change of fractal property of Witbank coal with heat treatment. Fuel, 79(11): 1341–1346
CrossRef Google scholar
[24]
Pfeifer P, Avnir  D (1983). Chemistry in noninteger dimensions between two and three. I. Fractal theory of heterogeneous surfaces. J Chem Phys, 79(7): 3558–3565
CrossRef Google scholar
[25]
Pyun S I, Rhee  C K (2004). An investigation of fractal characteristics of mesoporous carbon electrodes with various pore structures. Electrochim Acta, 49(24): 4171–4180
CrossRef Google scholar
[26]
Qi H, Ma  J, Wong P Z (2002). Adsorption isotherms of fractal surfaces. Colloid Surface A, 206(1‒3): 401–407 
CrossRef Google scholar
[27]
Rigby S P (2005). Predicting surface diffusivities of molecules from equilibrium adsorption isotherms. Colloid Surface A, 262(1‒3): 139–149
CrossRef Google scholar
[28]
Shao L Y, Li  M, Li Y H,  Zhang Y P,  Lu J, Zhang  W L, Tian  Z, Wen H J (2014). Geological characteristics and controlling factors of shale gas in the Jurassic of the northern Qaidam Basin. Earth Sci Front, 21(4): 311–322 (in Chinese)
[29]
Shao L Y, Liu  L, Wen H J,  Li Y H,  Zhang W L,  Li M (2016). Characteristics and influencing factors of nanopores in the Midddle Jurassic Shimengou shale in Well YQ-1 of the northern Qaidam Basin. Earth Sci Front, 23(1): 164–173 (in Chinese)
[30]
Sing K S W (1982). Reporting physisorption data for gas/solid systems with special reference to the determination of surface area and porosity. Pure Appl Chem, 54(11): 2201–2218
CrossRef Google scholar
[32]
Tang X L, Jiang  Z X, Li  Z, Gao Z Y,  Bai Y Q,  Zhao S, Feng  J (2015). The effect of the variation in material composition on the heterogeneous pore structure of high-maturity shale of the Silurian Longmaxi formation in the southeastern Sichuan Basin, China. J Nat Gas Sci Eng, 23: 464–473
CrossRef Google scholar
[33]
Wang M, Xue  H T, Tian  S S, Wilkins  R W T, Wang  Z W (2015). Fractal characteristics of Upper Cretaceous lacustrine shale from the Songliao Basin, NE China. Mar Pet Geol, 67: 144–153
CrossRef Google scholar
[34]
Wang X Z, Gao  S L, Gao  C (2014). Geological features of Mesozoic lacustrine shale gas in south of Ordos Basin, NW China. Petrol Explor Develop, 41(3): 326–337
CrossRef Google scholar
[35]
Wu J G, Liu  D M, Yao  Y B (2014). Characteristics and controlling factors of nanopores in shales in Weibei, Ordos Basin. Oil & Gas Geology, 35(4): 542–550 (in Chinese)
[36]
Xiao Z H, Wang  C H, Yang  F R, Feng  T, Wang Q R,  Huang Y R,  Chen X Y,  Deng Y (2013). Reservoir conditions of shale gas in Lower Cambrian Niutitang Formation, northwestern Hunan. Acta Geol Sin, 87(10): 1612–1623 (in Chinese)
[37]
Xie H P (1996). A Study for Fractal and Rock Mechanics. Beijing: Science Publishing House, 93–95 (in Chinese)
[38]
Yang F, Ning  Z F, Liu  H Q (2014). Fractal characteristics of shales from a shale gas reservoir in the Sichuan Basin, China. Fuel, 115(1): 378–384
CrossRef Google scholar
[39]
Yao Y B, Liu  D M, Tang  D Z, Tang  S H, Huang  W H (2008). Fractal characterization of adsorption-pores of coals from North China: an investigation on CH4 adsorption capacity of coals. Int J Coal Geol, 73(1): 27–42
CrossRef Google scholar
[40]
Zhang D W, Li  Y X, Zhang  J C, Qiao  D W, Jiang  W L, Zhang  J F (2012). The Evaluation of Shale Gas Resources and Potential Investigation in China. Beijing: Geology Publishing House, 70–78 (in Chinese)
[41]
Zhang J C, Jin  Z J, Yuan  M S (2004). Reservoir mechanism of shale gas and its distribution. Natural Gas Industry, 24(7): 15–18 (in Chinese)
[42]
Zhu X M (2008). Sedimentary Petrology (4th ed). Beijing: Petroleum Industry Press, 208–286 (in Chinese)

Acknowledgments

This research was supported by the National Science and Technology Major Project (2016ZX05041004-003) and the China Geological Survey Scientific Research Project (12120114019501 and 1212011220794). The authors are grateful for the valuable comments from two anonymous reviewers.

RIGHTS & PERMISSIONS

2016 Higher Education Press and Springer-Verlag Berlin Heidelberg
AI Summary AI Mindmap
PDF(912 KB)

Accesses

Citations

Detail

Sections
Recommended

/