Coalbed methane enrichment model of low-rank coals in multi-coals superimposed regions: a case study in the middle section of southern Junggar Basin

Abstract

The Middle Jurassic Xishanyao Formation in the central section of the southern Junggar Basin has substantial amounts of low-ranked coalbed methane (CBM) recourses and is typically characterized by multi superimposed coal seams. To establish the CBM enrichment model, a series of experimental and testing methods were adopted, including coal maceral observation, pro-ximate analysis, low temperature nitrogen adsorption (LTNA), methane carbon isotope determination, porosity/permeability simulation caused by overburden, and gas content testing. The controlling effect of sedimentary environment, geological tectonic, and hydrogeological condition on gas content was analyzed in detail. The results demonstrate that the areas with higher gas content (an average of 8.57 m³/t) are mainly located in the Urumqi River-Santun River (eastern study area), whereas gas content (an average of 3.92 m³/t) in the Manasi River-Taxi River (western study area) is relatively low. Because of the combined effects of strata temperature and pressure, the gas content in coal seam first increases and then decreases with increasing buried depth, and the critical depth of the inflection point ranges from 600 m to 850 m. Affected by the changes in topography and water head height, the direction of groundwater migration is predicted from south to north and from west to east. Based on the gas content variation, the lower and middle parts of the Xishanyao Formation can be divided into three independent coal-bearing gas systems. Within a single gas-bearing system, there is a positive correlation between gas content and strata pressure, and the key mudstone layers separating each gas-bearing system are usually developed at the end of each highstand system tract. The new CBM accumulation model of the multi-coals mixed genetic gas shows that both biological and thermal origins are found in a buried depth interval between 600 m and 850 m, suggesting that the coals with those depths are the CBM enrichment horizons and favorable exploration regions in the middle section of the southern Junggar Basin. An in-depth discussion of the low-rank CBM enrichment model with multi-coal seams in the study region can provide a basis for the optimization of CBM well locations and favorable exploration horizons.

Graphical abstract

Keywords

Xishanyao Formation / multi-coal seams superimposed region / low rank coal / main controlling factors / enrichment model

References

[1] Ayers W B J (2002). Coalbed gas systems, resources, and production and a review of contrasting cases from the San Juan and Powder River basins. AAPG Bull, 86(11): 1853–1890

[2] Chen B T, Yu X H, Wang T Q, Pan S X, Yang L S, Tan C P, Li S L (2014). Characteristics of sequence stratigraphy and coal enrichment controlling factors of lower-middle Jurassic coal-bearing series, south margin of Junggar Basin, NW China. Acta Sedimentol Sin, 32(1): 61–67 (in Chinese)

[3] Chen Y, Ma D M, Fang S Y, Guo C, Yang F, Hou D Z (2019). Enrichment and high-yield models of coalbed methane influenced by geologic structures and hydrologic conditions. J Xi’an Univ Sci Tech, 39(4): 644–655 (in Chinese)

[4] Chen Y, Tang D Z, Xu H, Li Y, Meng Y J (2015). Structural controls on coalbed methane accumulation and high production models in the eastern margin of Ordos Basin, China. J Nat Gas Sci Eng, 23: 524–537

[5] Cienfuegos P, Loredo J (2010). Coalbed methane resources assessment in Asturias (Spain). Int J Coal Geol, 83(4): 366–376

[6] Fu H J, Tang D Z, Pan Z J, Yan D T, Yang S G, Zhuang X G, Li G Q, Chen X, Wang G (2019). A study of hydrogeology and its effect on coalbed methane enrichment in the southern Junggar Basin, China. AAPG Bull, 103(1): 189–213

[7] Fu H J, Tang D Z, Xu H, Xu T, Chen B L, Hu P, Yin Z Y, Wu P, He G J (2016). Geological characteristics and CBM exploration potential evaluation: a case study in the middle of the southern Junggar Basin, NW China. J Nat Gas Sci Eng, 30: 557–570

[8] Fu H J, Tang D Z, Xu T, Xu H, Tao S, Zhao J L, Chen B L, Yin Z Y (2017). Preliminary research on CBM enrichment models of low-rank coal and its geological controls: a case study in the middle of the southern Junggar Basin, NW China. Mar Pet Geol, 83: 97–110

[9] Fu H J, Yan D T, Yang S G, Wang X M, Zhuang Z, Sun M D (2020). Characteristics of in situ stress and its influence on coalbed methane development: a case study in the eastern part of the southern Junggar Basin, NW China. Energy Sci Eng, 8(2): 515–529

[10] Hamilton S K, Esterle J S, Golding S D (2012). Geological interpretation of gas content trends, Walloon Subgroup, eastern Surat Basin, Queensland, Australia. Int J Coal Geol, 101: 21–35

[11] Hou H H, Shao L Y, Guo S Q, Li Z, Zhang Z J, Yao M L, Zhao S, Yan C Z (2017). Evaluation and genetic analysis of coal structures in deep Jiaozuo Coalfield, northern China: investigation by geophysical logging data. Fuel, 209: 552–566

[12] Hou H H, Shao L Y, Tang Y, Li Y N, Liang G D, Xin Y L, Zhang J Q (2021). Coal seam correlation in terrestrial basins by sequence stratigraphy and its implications for palaeoclimate and palaeoenvironment evolution. J Earth Sci

[13] Hou H H, Shao L Y, Tang Y, Zhao S, Yuan Y, Li Y N, Mu G Y, Zhou Y, Liang G D, Zhang J Q (2020). Quantitative characterization of low-rank coal reservoirs in the southern Junggar Basin, NW China: Implications for pore structure evolution around the first coalification jump. Mar Pet Geol, 113: 104165

[14] Hou H H, Shao L Y, Wang S, Xiao Z H, Wang X T, Li Z, Mu G Y (2019). Influence of depositional environment on coalbed methane accumulation in the Carboniferous-Permian coal of the Qinshui Basin, northern China. Front Earth Sci, 13(3): 535–550

[15] Li G H (2016). Coal reservoir characteristics and their controlling factors in the eastern Ordos Basin in China. Int J Min Sci Technol, 26(6): 1051–1058

[16] Li G H, Zhang H (2013). The origin mechanism of coalbed methane in the eastern edge of Ordos Basin. Sci China Earth Sci, 56(10): 1701–1706

[17] Li M H, Li Z D, Liao J D (2005). Analysis of ground stress in the southern part of the Junggar Basin and discussion of the related issues. Xinjiang Geol, 23(4): 343–346 (in Chinese)

[18] Li M, Jiang B, Lin S F, Lan F J, Wang J L (2013). Structural controls on coalbed methane reservoirs in Faer coal mine, southwest China. J Earth Sci, 24(3): 437–448

[19] Li W, Wang X K, Zhang B J, Chen Z X, Pei S Q, Yu Z C (2020). Large-scale gas accumulation mechanisms and reservoir-forming geological effects in sandstones of central and western China. Pet Explor Dev, 47(4): 714–725

[20] Li X, Fu X H, Yang X S, Ge Y Y, Quan F K (2018a). Coalbed methane accumulation and dissipation patterns: a case study of the Junggar Basin, NW China. J Asian Earth Sci, 160: 13–26

[21] Li Y J, Shao L Y, Eriksson K A, Tong X, Gao C X, Chen Z S (2014a). Linked sequence stratigraphy and tectonics in the Sichuan continental foreland basin, Upper Triassic Xujiahe Formation, southwest China. J Asian Earth Sci, 88: 116–136

[22] Li Y N, Shao L Y, Hou H H, Tang Y, Yuan Y, Zhang J Q, Shang X X, Lu J (2018b). Sequence stratigraphy, palaeogeography, and coal accumulation of the fluvio-lacustrine Middle Jurassic Xishanyao Formation in central segment of southern Junggar Basin, NW China. Int J Coal Geol, 192: 14–38

[23] Li Y, Tang D Z, Fang Y, Xu H, Meng Y J (2014b). Distribution of stable carbon isotope in coalbed methane from the east margin of Ordos Basin. Sci China Earth Sci, 57(8): 1741–1748

[24] Li Y, Yang J H, Pan Z J, Meng S Z, Wang K, Niu X L (2019). 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 Geolo Sin-Engl, 93(1): 111–129

[25] Liu D M, Wang Y J, Cai Y D (2018). Main controlling geological factors and accumulation model analysis of low-rank CBM enrichment. Coal Sci Tech, 46(6): 1–8 (in Chinese)

[26] Lv Y M, Tang D Z, Xu H, Luo H H (2012). Production characteristics and the key factors in high-rank coalbed methane fields: a case study on the Fanzhuang Block, Southern Qinshui Basin, China. Int J Coal Geol, 96–97: 93–108

[27] Moore T A (2012). Coalbed methane: a review. Int J Coal Geol, 101: 36–81

[28] Ouyang Y L, Sun B, Wang B, Tian W G, Zhao Y, Cao H X (2017). CBM sealing system and its relationship with CBM enrichment. Nat Gas Ind B, 4(1): 39–47

[29] Pan J N, Zhao Y Q, Hou Q L, Jin Y (2015). Nanoscale pores in coal related to coal rank and deformation structures. Transp Porous Media, 107(2): 543–554

[30] Pashin J C, Groshong R H Jr (1998). Structural control of coalbed methane production in Alabama. Int J Coal Geol, 38(1–2): 89–113

[31] Pashin J C, Mcintyre-Redden M R, Mann S D, Kopaska-Merkel D C, Varonka M, Orem W (2014). Relationships between water and gas chemistry in mature coalbed methane reservoirs of the Black Warrior Basin. Int J Coal Geol, 126(2): 92–105

[32] Qin Y, Moore T A, Shen J, Yang Z B, Shen Y L, Wang G (2018). Resources and geology of coalbed methane in China: a review. Int Geol Rev, 60(5–6): 777–812

[33] Scheltens M, Zhang L F, Xiao W J, Zhang J J (2015). Northward subduction-related orogenesis of the southern Altaids: constraints from structural and metamorphic analysis of the HP/UHP accretionary complex in Chinese southwestern Tianshan, NW China. Geoscience Frontiers, 6(2): 191–209

[34] Shao L Y, Hou H H, Tang Y, Lu J, Qiu H J, Wang X T, Zhang J Q (2015). Selection of strategic replacement areas for CBM exploration and development in China. Nat Gas Ind B, 2(2–3): 211–221

[35] Shen Y L, Qin Y, Wang G G X, Guo Y H, Shen J, Gu J Y, Xiao Q, Zhang T, Zhang C L, Tong G C (2017). Sedimentary control on the formation of a multi-superimposed gas system in the development of key layers in the sequence framework. Mar Pet Geol, 88: 268–281

[36] Song G (2015). Simulation research on biogenic and thermogenic gas from brown coal in Dananhu depression of Tuha Basin. Dissertation for Master’s Degree. Xuzhou: China University of Mining and Technology (in Chinese)

[37] Song Y, Li Z, Jiang L, Hong F (2015). The concept and the accumulation characteristics of unconventional hydrocarbon resources. Petrol Sci, 12(4): 563–572

[38] Song Y, Liu H L, Hong F, Qin S F, Liu S B, Li G Z, Zhao M J (2012). Syncline reservoir pooling as a general model for coalbed methane (CBM) accumulations: mechanisms and case studies. J Petrol Sci Eng, 88–89: 5–12

[39] Song Y, Liu S B, Ma B Z, Li J W, Ju Y W, Li G Z, Yang Z Y (2016). Research on formation model and geological evaluation method of the middle to high rank coalbed methane enrichment and high production area. Earth Sci Front, 23(3): 1–9 (in Chinese)

[40] Sun D, Liu X Z, Yang H J, Cao N, Zhang Z P, Chen Y S, Li D M (2019). Analysis of hydrogeological characteristics and water environmental impact pathway of typical shale gas exploration and development zones in Sichuan Basin, China. J Groundw Sci Eng, 7(3): 195–213

[41] Sun Z M, Shen J (2014). Bogda nappe structure and its relations to hydrocarbon in Xinjiang. Petrol Geol & Exp, 36(4): 429–434 (in Chinese)

[42] Tang Y (2020). Research on layer selection method for fracturing of multi-layer superimposed CBM system in the southern Junggar Basin. Dissertation for Doctor’s Degree. Beijing: China University of Geosciences (Beijing) (in Chinese)

[43] Wang K X (2019). Research on main geological controls and enrichment model of coalbed methane distribution in China. Earth Env Sci, 300: 022071

[44] Wood D A, Hazra B (2017). Characterization of organic-rich shales for petroleum exploration & exploitation: a review. Part 3: applied geomechanics, petrophysics and reservoir modeling. J Earth Sci, 28(5): 779–803

[45] Xiao X M, Wei Q, Gai H F, Li T F, Wang M L, Pan L, Chen J, Tian H (2015). Main controlling factors and enrichment area evaluation of shale gas of the Lower Paleozoic marine strata in south China. Petrol Sci, 12(4): 573–586

[46] Yang Z B, Qin Y, Wang G X, An H (2015). Investigation on coal seam gas formation of multi-coalbed reservoir in Bide-Santang Basin, Southwest China. Arab J Geosci, 8(8): 5439–5448

[47] Yao Y B, Liu D M, Yan T (2014). Geological and hydrogeological controls on the accumulation of coalbed methane in the Weibei field, southeastern Ordos Basin. Int J Coal Geol, 121: 148–159

[48] Yuan Y, Shan Y S, Tang Y, Cao D Y (2020). Coalbed methane enrichment regularity and major control factors in the Xishanyao Formation in the western part of the southern Junggar Basin. Acta Geolo Sin-Engl, 94(2): 485–500

[49] Yuan Y, Tang Y, Shan Y S, Zhang J Q, Cao D Y, Wang A M (2018). Coalbed methane reservoir evaluation in the Manas Mining area, Southern Junggar Basin. Energ Explor Exploit, 36(1): 114–131

[50] Zhang Z, Qin Y, Fu X H, Yang Z B, Guo C (2015). Multi-layer superposed coalbed methane system in southern Qinshui Basin, Shanxi Province, China. J Earth Sci, 26(3): 391–398

[51] Zou C N, Yang Z, Zhu R K, Zhang G S, Hou L H, Wu S T, Tao S Z, Yuan X J, Dong D Z, Wang Y M, Wang L, Huang J L, Wang S F (2015). Progress in China’s unconventional oil & gas exploration and development and theoretical technologies. Acta Geolo Sin-Engl, 89(3): 938–971

Acknowledgments

This research paper was supported by the China Geological Survey Project (DD20160204-3), the Discipline Innovation Team of Liaoning Technical University (LNTU20TD-05; LNTU20TD-14; LNTU20TD-30), the Guiding Program of Liaoning Natural Science Founds (2019-ZD-0046), and the Scientific Research Funding Project of Liaoning Education Department (LJ2019JL004).

RIGHTS & PERMISSIONS

2021 Higher Education Press