Fractal characteristics of micropore structure of Taiyuan Formation bauxite reservoir in Longdong area of Ordos Basin

Abstract

As an unconventional gas reservoir, bauxite gas reservoirs have often been studied as weathered crust cover layers rather than reservoirs in the past. The Taiyuan Formation bauxite in the Longdong area of the Ordos Basin has achieved breakthroughs, and some wells have obtained industrial airflow. Therefore, it is necessary to conduct basic geological research on the bauxite reservoir. The application of casting thin sections, scanning electron microscopy (SEM), X-ray diffraction (XRD), high-pressure mercury injection (HPMI), and low-temperature nitrogen adsorption (L-TNA) techniques provides a comprehensive framework for studying reservoir characteristics as well as the micropore fractal structure. The results indicate that (1) the bauxite reservoir has logging characteristics of high natural gamma (500API) and low acoustic wave time difference (60–90 us/m), with natural gamma being the most critical parameter in identifying the bauxite reservoir in the logging curve. (2) The bauxite rocks in the Longdong region belong to sedimentary formation, and three types of micro ancient landforms (buried pits, terraces, and grooves) have different lithological combinations. Among them, the combination of the bauxite rocks in the buried pits and carbonaceous mudstones has been subjected to freshwater leaching for a long time, and the thickness of the bauxite rocks is the largest. (3) The pores of bauxite reservoir are mainly dissolution pores within particles, intergranular dissolution pores, intergranular pores, and microcracks. The average porosity of the reservoir is 8.49%, and the average permeability is 0.261 × 10⁻³ μm², with a low permeability standard greater than 0.4 accounting for 17.19%. (4) The fractal dimension D2 of micropore D1 and nanopore D2 were calculated by high-pressure mercury injection and nitrogen adsorption experiments, respectively. Through correlation analysis, we found that the fractal dimension D2 (calculated from nitrogen adsorption data) more effectively characterizes the comprehensive quality of nanopores within the bauxite reservoir compared to the fractal dimension D1 obtained from high-pressure mercury injection (HPMI). We have established classification evaluation standards: Type I D1 is 2.2∼2.6, Type II D1 is 2.6∼2.8, and Type III D1 is 2.8∼3. Among them, Class I bauxite reservoir is a high-quality reservoir and can be the preferred target for exploration in the study area.

Keywords

bauxite Taiyuan Formation micropores fractal characteristics reservoirs Ordos Basin

Get full access to this article

View all access options for this article.

References

Iqbal

Bibi

Wagreich

. Geochemistry of the Triassic-Jurassic lateritic bauxites of the salt range: implications for eastward extension of the Tethyan bauxite deposits into Pakistan. Int J Earth Sci 2023; 112(5): 1527–1552.

Radusinovic

Papadopoulos

. The potential for REE and associated critical metals in karstic bauxites and bauxite residue of Montenegro. Minerals 2021; 11(9): 975.

Long

Yang

, et al. Exploration and sources of bauxite deposit in the Boloven plateau, Southern Laos. J Earth Sci 2019; 30(1): 121–130.

Gao

Wang

Xiong

, et al. Minerogenetic characteristics and resource potential analysis of bauxite in China. Chin Geol 2015; 42(4): 853–863.

Komolossy

. Review on global bauxites: resources, origin and types. In: The 18th international academic conference on bauxite, alumina and aluminum industry, Zhengzhou, 2010.

Gong

, et al. Characteristics of the critical metal enrichment and the resource potential for bauxite-bearing rocks in the Xinmin bauxite deposit in Daozhen County, Guizhou Province, China. Acta Mineral Sin 2021; 41(4/5): 400–412.

Zhang

Zhong

, et al. REE geochemical characteristics and geological significance of bauxite from Xing County, Shanxi Province. Journal of the Chinese Society of Rare Earths 2018; 36(3): 338–349.

Liu

Yang

, et al. Mineralogical and geochemical investigations on the early Permian Yuxi karstic bauxite deposit, central Yunnan, China. Ore Geol Rev 2023; 153: 105296.

Wang

Bian

Guo

, et al. New discovery and geologic feature of karst accumulated bauxite deposit in Henan. Light Met 2013; 41(12): 1–3, 52.

10.

Zhang

, et al. Breakthrough in the exploration of bauxite gas reservoir in Longdong area of the Ordos Basin and its petroleum geological implications. Nat Gas Ind 2021; 41(11): 1–11.

11.

Shen

Guo

, et al. Sequence stratigraphy of Benxi -Taiyuan Formation in eastern Ordos Basin. Acta Geosci Sin 2009; 30(2): 187–193.

12.

Wang

Men

, et al. Sedimentary facies of lower permian in southeast of Ordos Basin. Geoscience 2013; 27(5): 1051–1057.

13.

Wang

Chen

. Depositonal models of Taiyuan Formation in daniudi gas field, Ordos Basin. Nat Gas Ind 2007; 27(12): 49–51.

14.

Barrett

. The geomorphology of the tidal flats of Strangford Lough, Co. Down, Northern Ireland, 2004.

15.

Yin

Shi

, et al. Micro-morphology and contemporary sedimentation rate of tidal flat in Rudong, Jiangsu Province. J Palaeogeogr 2011; 13(2): 150–160.

16.

Luo

Jiang

Dong

, et al. Characteristics and evolution of tidal flat profile. Sci Technol Rev 2018; 36(14): 35–41.

17.

Liu

Zhang

Yang

, et al. Well logging evaluation of bauxite reservoirs in Ordos Basin. Xinjiang Pet Geol 2022; 43(3): 261–270.

18.

Luo

Xin

, et al. Provenance difference analysis of the eastern and western Taiyuan Formation in the northern Margin of the Ordos Basin and its tectonic significance. Minerals 2023; 13(2): 155.

19.

Shi

Nan

. Characteristics of clastic reservoir of the upper Paleozoic Taiyuan and Xiashihezi formations in northeastern Ordos Basin. J Palaeogeogr 2010; 12(5): 609–617.

20.

Najwa

Haryati

Ramadhansyah

, et al. A comparative study of Kuantan bauxite mineralogy as potential material in civil engineering. In: 2nd National Colloquium on Wind and Earthquake Engineering (NCWE), 2019.

21.

Guha

Kumar

. Comparative analysis on utilisation of linear spectral unmixing and band ratio methods for processing ASTER data to delineate bauxite over a part of Chotonagpur plateau, Jharkhand, India. Geocarto Int 2016; 31(4): 367–384.

22.

Zhao

. The features and ore proportioning scheme of high iron bauxite in Luoyang. Light Met 2015; 9: 6–11.

23.

Zhang

Wang

Liu

, et al. Provenance and ore-forming process of Permian lithium-rich bauxite in central Yunnan, SW China. Ore Geol Rev 2022; 145: 104862.

24.

Tao

Peng

Xiao

, et al. Numerical simulation and microscopic stress mechanism for the microscopic pore deformation during soil compression. Adv Civ Eng 2019; 2019(1). https://onlinelibrary.wiley.com/doi/full/10.1155/2019/1542797

25.

Wang

Shen

Zhang

, et al. Microscopic pore structure characteristics after ASP flooding based on CT scanning technique of the full-diameter core. Pet Geol Oilfield Dev Daqing 2019; 38(2): 81–86.

26.

Zhao

Xue

, et al. Effect of SEM parameters on quantitative evaluation of shale micropores. Oil Gas Geol 2019; 40(5): 1141–1154.

27.

Zhang

. Characterization of microscopic pore structure of tight sandstone reservoirs through nitrogen adsorption experiment:Case study of Shahezi Formation in Xujiaweizi Fault Depression,Songliao Basin,China. Nat Gas Geosci 2017; 28(6): 898–908.

28.

Wang

Liu

Zhi

. et al. Micro-nanopore throat structure and occurrence characteristics of tight sandstone gas: a case study in the Ordos Basin, China. Int J Oil Gas Coal Technol 2020; 25(3): 237–257.

29.

Lai

Wang

. Fractal analysis of tight gas sandstones using high-pressure mercury intrusion techniques. J Nat Gas Sci Eng 2015; 24: 185–196.

30.

Ueoka

Ogata

Matsushita

, et al. Numerical analysis of microscopic coke strength factors using a homogenization method. Tetsu to Hagane-Journal of the Iron and Steel Institute of Japan 2007; 93(12): 728–735.

31.

Liu

Lin

. Using rock SEM image to create pore-scale finite element calculation mesh. In: 2011 international conference on physics science and technology (ICPST), 2011, G Lee, G Lee Editors. p. 227–232.

32.

Yang

, et al. Study on the quantitative characterization and heterogeneity of pore structure in deep ultra-high pressure tight glutenite reservoirs. Minerals 2023; 13(5): 601.

33.

Lai

Wang

Cao

, et al. Investigation of pore structure and petrophysical property in tight sandstones. Mar Petrol Geol 2018; 91: 179–189.

34.

Sheng

Sun

Zhao

, et al. Quantitative evaluation of microscopic pore structure parameters of tight sandstone gas reservoir: a case the Southeast Area of Sulige Gas Field. Journal of Northwest University. Natural Science Edition 2015; 45(6): 913–924.