Abstract
The Chang 8 formation of the Yanchang Group, located in Yuancheng area of the Ordos Basin, is a typical tight oil reservoir in China. This reservoir is characterized by low porosity, low permeability, strong non-homogeneity, and significant difficulty in evaluating the reservoir parameters. To examine and investigate the microscopic pore structure characteristics of the Chang 8 formation, cast thin section and scanning electron microscopy techniques were utilized in this study, Moreover, tests on the core physical properties were conducted and the data from these tests were integrated into the analysis of basic characteristics of the reservoir rock mineralogy, pore permeability, and other fundamental characteristics. The shapes of piezomercury curves were systematically examined to study the characteristics and features of pore structures for the 17 samples. In accordance with the fractal dimension of the NMR T2 spectrum, the reservoir was classified into four categories, and a conversion model delineating the correlation between the NMR T2 spectrum and the capillary pressure curve was formulated through the application of the segmented power function method. This model was then implemented in the interpretation of NMR logging, facilitating the acquisition of a seamless pseudo-capillary pressure curve spanning the entire well section. Three essential parameters reflecting the microscopic pore structure, namely the expulsion pressure, median pressure, and sorting coefficient of the core samples, were extracted. The association between reservoir parameters and reservoir categorization was then determined through the application of a generalized regression neural network. The pseudo-capillary pressure curve reservoir parameters of the whole well section were processed to derive the classification profile of the reservoir, and the classification results demonstrated a strong alignment with those of the mercury injection experiments. This study highlights that the proposed method can provide crucial foundation for the investigations on pore structures in tight oil reservoirs and the evaluation of reservoir classification.
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References
Baoquan M, Shumin C, Weilin Y, Chengyan L, Hong Z, Zhifeng S et al (2021) Pore structure evaluation of low permeability clastic reservoirs based on sedimentation diagenesis: a case study of the Chang 8 reservoirs in the Zhenbei region, Ordos Basin. J Petrol Sci Eng 18:28. https://doi.org/10.1016/j.petrol.2020.107841
Dong J, Huang Z, Chen J, Li T, Qu T, Yang Y (2023a) An evaluation method of gas-bearing properties based on Gaussian bimodal function pore structure characterization: a case study of tight Sandstone in the East China Sea Basin. Processes. https://doi.org/10.3390/pr11113169
Dong J, Huang ZL, Chen JL, Li TJ, Zhao J, Pan YS, Qu T (2023b) Pore structure and fractal characteristics of tight sandstone: a case study for Huagang Formation in the Xihu Sag, East China Sea Basin China. Energies. https://doi.org/10.3390/en16042013
Feng C, Yang ZQ, Feng ZY, Zhong YT, Ling KG (2020) A novel method to estimate resistivity index of tight sandstone reservoirs using nuclear magnetic resonance logs. J Nat Gas Sci Eng. https://doi.org/10.1016/j.jngse.2020.103358
Glen WL (1947) Santiago Pool, Kern County, California: GEOLOGICAL NOTES. AAPG Bulletin, 31. https://doi.org/10.1306/3d933a91-16b1-11d7-8645000102c1865d
Gong YJ, Liu KY (2020) Pore throat size distribution and oiliness of tight sands-A case study of the Southern Songliao Basin, China. J Pet Sci Eng 184:106508. https://doi.org/10.1016/j.petrol.2019.106508
Hao LW, Tang J, Wang Q, Tao HF, Ma XF, Ma DX, Ji HJ (2017) Fractal characteristics of tight sandstone reservoirs: a case from the Upper Triassic Yanchang Formation, Ordos Basin, China. J Petrol Sci Eng 158:243–252. https://doi.org/10.1016/j.petrol.2017.08.060
Hou J, Zhao L, Zeng X, Zhao WQ, Chen YF, Li JX et al (2022) Characterization and evaluation of carbonate reservoir pore structure based on machine learning. Energies 15(19):7126. https://doi.org/10.3390/en15197126
Hu T, Pan T, Chen L, Li J, Liu Y (2023) Pore structure characterization and deliverability prediction of fractured tight glutenite reservoir based on geophysical well logging. Acta Geophys. https://doi.org/10.1007/s11600-023-01110-8
Huang HX, Chen L, Sun W, Xiong FY, Ji W, Jia JK et al (2018) Pore-throat structure and fractal characteristics of Shihezi formation tight gas sandstone in the Ordos Basin, China. Fractals-Complex Geom Patterns Scaling Nat Soc 26(2):1840005. https://doi.org/10.1142/S0218348x18400054
Jiang FJ, Huo LN, Chen D, Cao L, Zhao RJ, Li Y, Guo TW (2023a) The controlling factors and prediction model of pore structure in global shale sediments based on random forest machine learning. Earth-Sci Rev. https://doi.org/10.1016/j.earscirev.2023.104442
Jiang Z, Li G, Zhao P, Zhou Y, Mao Z, Liu Z (2023b) Study on spontaneous imbibition and displacement characteristics of mixed-wet tight sandstone reservoir based on high-precision balance and NMR method. Fuel 345:128247. https://doi.org/10.1016/j.fuel.2023.128247
Jiang ZH, Mao ZQ, Shi YJ, Wang DX (2018) Multifractal characteristics and classification of tight sandstone reservoirs: a case study from the Triassic Yanchang formation, Ordos Basin, China. Energies 11(9):2242. https://doi.org/10.3390/en11092242
Lai J, Wang GW (2015) Fractal analysis of tight gas sandstones using high-pressure mercury intrusion techniques. J Nat Gas Sci Eng 24:185–196. https://doi.org/10.1016/j.jngse.2015.03.027
Lai J, Wang GW, Wang ZY, Chen J, Pang XJ, Wang SC et al (2018) A review on pore structure characterization in tight sandstones. Earth Sci Rev 177:436–457. https://doi.org/10.1016/j.earscirev.2017.12.003
Lian PQ, Duan TZ, Xu R, Li LL, Li M (2018) Pressure behavior of shale-gas flow in dual porous medium based on fractal theory. Interpret J Subsurface Charact 6(4):1–10. https://doi.org/10.1190/Int-2018-0002.1
Liu K, Wang R, Shi WZ, Trave A, Martin-Martin JD, Baques V et al (2022) Diagenetic controls on reservoir quality and heterogeneity of the Triassic Chang 8 tight sandstones in the Binchang area (Ordos Basin, China). Mar Pet Geol 146:105974. https://doi.org/10.1016/j.marpetgeo.2022.105974
Liu M, Xie R, Li C, Li X, Jin G, Guo J (2018) Determining the segmentation point for calculating the fractal dimension from mercury injection capillary pressure curves in tight sandstone. J Geophys Eng 15(4):1350–1362. https://doi.org/10.1088/1742-2140/aab1d8
Lu H, Xia D, Li Q, Yue D, Wu S, Wang W, Zhang X (2021) Quantitative characterization and differences of the pore structure in lacustrine siliceous shale and argillaceous shale: a case study of the upper triassic yanchang formation shales in the Southern Ordos basin. China Energy Fuels 35(19):15525–15544. https://doi.org/10.1021/acs.energyfuels.1c01823
Luan BB, Zhang B, Wang DD, Deng C, Wang F (2022) Quantitative evaluation of tight oil reservoirs in the Chang 8 Member of the Yanchang formation in southern Ordos Basin. Front Earth Sci 10:963316. https://doi.org/10.3389/feart.2022.963316
Mandelbrot BB (2006) On the geometry of homogeneous turbulence, with stress on the fractal dimension of the ISO-surfaces of scalars. J Fluid Mech. https://doi.org/10.1017/s0022112075003047
Maugeri L (2013) The shale oil boom: A U.S. Phenomenon. Environment & Natural Resources
Qiu XL, Ding L, Liu JK, Yan ZD, Bao YX, Tan CQ (2023) Quantitative evaluation of reservoir quality of tight oil sandstones in chang 7 member of Ordos Basin. Front Earth Sci 10:1046489. https://doi.org/10.3389/feart.2022.1046489
Shao XH, Pang XQ, Jiang FJ, Li LL, Huyan YY, Zhene DY (2017) Reservoir characterization of tight sandstones using nuclear magnetic resonance and incremental pressure mercury injection experiments: implication for tight sand gas reservoir quality. Energy Fuels 31(10):10420–10431. https://doi.org/10.1021/acs.energyfuels.7b01184
Shi BB, Chang XC, Yin W, Li Y, Mao LX (2019) Quantitative evaluation model for tight sandstone reservoirs based on statistical methods—a case study of the Triassic Chang 8 tight sandstones, Zhenjing area, Ordos Basin, China. J Petrol Sci Eng 173:601–616. https://doi.org/10.1016/j.petrol.2018.10.035
Teng Y, Er C, Zhao J, Guo Q, Shen C, Tan S (2023) Pore structure characterization based on NMR experiment: a case from the Shanxi Formation tight sandstones in the Daning-Jixian area, eastern Ordos Basin. Energy Geosci 4(3):100192. https://doi.org/10.1016/j.engeos.2023.100192
Vo Thanh H, Sheini Dashtgoli D, Zhang H, Min B (2023) Machine-learning-based prediction of oil recovery factor for experimental CO2-Foam chemical EOR: Implications for carbon utilization projects. Energy 278:127860. https://doi.org/10.1016/j.energy.2023.127860
Wang F, Zeng F (2020) Novel insights into the movable fluid distribution in tight sandstones using nuclear magnetic resonance and rate-controlled porosimetry. Nat Resour Res 29(5):3351–3361. https://doi.org/10.1007/s11053-020-09635-1
Wang GW, Chang XC, Yin W, Li Y, Song TT (2017) Impact of diagenesis on reservoir quality and heterogeneity of the Upper Triassic Chang 8 tight oil sandstones in the Zhenjing area, Ordos Basin, China. Mar Pet Geol 83:84–96. https://doi.org/10.1016/j.marpetgeo.2017.03.008
Wang WR, Yue DL, Eriksson KA, Qu XF, Li W, Lv M et al (2020) Quantification and prediction of pore structures in tight oil reservoirs based on multifractal dimensions from integrated pressure- and rate-controlled porosimetry for the upper Triassic Yanchang formation, Ordos Basin. China Energy Fuels 34(4):4366–4383. https://doi.org/10.1021/acs.energyfuels.0c00178
Wei H, Xie R, Guo J, Liu J, Xu C, Wang Y (2022) Classification of tight sandstone reservoirs based on the nuclear magnetic resonance T2 distribution: a case study on the shaximiao formation in Central Sichuan. China Energy Fuels 36(18):10803–10812. https://doi.org/10.1021/acs.energyfuels.2c01612
Wu B, Xie R, Wang X, Wang T, Yue W (2020) Characterization of pore structure of tight sandstone reservoirs based on fractal analysis of NMR echo data. J Nat Gas Sci Eng 81:103483. https://doi.org/10.1016/j.jngse.2020.103483
Xie WB, Yin QL, Zeng JB, Wang GW, Feng C, Zhang P (2023) Fractal-based approaches to pore structure investigation and water saturation prediction from NMR measurements: a case study of the gas-bearing tight sandstone reservoir in Nanpu Sag. Fractal Fract 7(3):273. https://doi.org/10.3390/fractalfract7030273
Xu Z, Liu L, Liu B, Wang T, Zhang Z, Wu K et al (2019) Geochemical characteristics of the Triassic Chang 7 lacustrine source rocks, Ordos Basin, China: Implications for paleoenvironment, petroleum potential and tight oil occurrence. J Asian Earth Sci 178:112–138. https://doi.org/10.1016/j.jseaes.2018.03.005
Zhang HT, Li GR, Guo HP, Zhang WJ, Wang YM, Li WB et al (2020) Applications of nuclear magnetic resonance (NMR) logging in tight sandstone reservoir pore structure characterization. Arab J Geosci 13(13):1–8. https://doi.org/10.1007/s12517-020-05590-6
Zhang Q, Jiao T, Huang H, Qi Z, Jiang T, Chen G et al (2021) Pore structure and fractal characteristics of ultralow-permeability sandstone reservoirs in the upper triassic yanchang formation. Ordos Basin Interpret 9(3):T747–T765. https://doi.org/10.1190/int-2020-0185.1
Zhou L, Kang ZH (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. https://doi.org/10.1016/j.jngse.2016.09.030
Zhu F, Hu WX, Cao J, Sun FN, Liu YF, Sun ZM (2018) Micro/nanoscale pore structure and fractal characteristics of tight gas sandstone: a case study from the Yuanba area, northeast Sichuan Basin, China. Mar Pet Geol 98:116–132. https://doi.org/10.1016/j.marpetgeo.2018.08.013
Acknowledgements
We express our sincere gratitude to the Research Institute of Exploration and Development, PetroChina Qinghai Oilfield Company, for generously providing the samples. Additionally, we appreciate the experimental facilities made available to us by Xi’an University of Science and Technology.
Funding
This study was supported by the National Natural Science Foundation of China Fund Project (42304143) and Natural Science Foundation of Shaanxi Provincial Department of Education Upper Level Fund Project (2022JM-147).
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SL analyzed experimental data and contributed to the writing of the articles. HB offered guidance on research ideas. DZ conducted experimental tests and processed experimental data. YL verified the article’s data and reviewed the manuscript. GL conducted experimental tests. FW contributed ideas, managed, and coordinated the planning and execution of research activities.
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Edited by Prof. Dr. Liang Xiao (ASSOCIATE EDITOR) / Prof. Gabriela Fernández Viejo (CO-EDITOR-IN-CHIEF).
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Li, S., Bian, H., Zhang, D. et al. Research on pore structure and classification evaluation of tight oil reservoirs based on fractal theory. Acta Geophys. (2024). https://doi.org/10.1007/s11600-024-01299-2
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DOI: https://doi.org/10.1007/s11600-024-01299-2