Effect of lithofacies on differential movable fluid behaviors of saline lacustrine fine-grained mixed sedimentary sequences in the Jimusar sag, Junggar Basin, NW China: Forcing mechanisms and multi-scale models

Yang, Wei; Wang, Yaohua; Xie, Ming; Li, Yingyan; Gao, Yang; Deng, Yuan; Xu, Changfu; Qin, Jianhua; Peng, Shouchang; Yang, Leilei; Yao, Linjie; Hou, Haodong

doi:10.1016/j.marpetgeo.2023.106150

Cited by 4 publications

(2 citation statements)

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“…These methods are limited by the principle of testing and differ from the pore range and reservoir structure parameters of experimental testing [22,23]. In addition to these test methods, fractal theory is currently widely used for quantitatively describing the heterogeneity of pore structures [24]. At present, in many quantitative experimental methods, the quantitative characterization of all pore sizes is difficult to complete through a single technical means [21][22][23]25].…”

Section: Introductionmentioning

confidence: 99%

“…The best fluid mobility is typically found in fine-grained, cross-bedded sandstones (Sc), while the worst fluid mobility is typically found in siltstone to silt-grained sandstones (Ss) [14]. For Chang 7 interlayer shale oil reservoirs, different types of lithofacies have undergone different sedimentary diageneses, corresponding to different pore throat distribution relations, resulting in differences in the occurrence characteristics of mobile fluids [21,[24][25][26][27][28]. However, previous studies have simply divided the rock types and ignored the influence of lithofacies on movable fluid [9,10].…”

Section: Introductionmentioning

confidence: 99%

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Pore Structure Characteristics of Shale Oil Reservoirs with Different Lithofacies and Their Effects on Mobility of Movable Fluids: A Case Study of the Chang 7 Member in the Ordos Basin, China

Xiao,

Ye,

Wang

et al. 2024

Energies

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The Chang 7 member of the Triassic Yanchang Formation in the Ordos Basin is a significant continent shale oil reservoir in China. Therefore, conducting an in-depth investigation into the pore structure and fluid mobility characteristics of the Chang 7 shale oil reservoir holds immense importance for advancing shale oil exploration. This study conducts a detailed analysis of the pore structures and their impact on fluid mobility of the Chang 7 shale oil reservoir using multiple methodologies, i.e., a cast thin section, scanning electron microscopy (SEM), X-ray diffraction (XRD), high-pressure mercury injection (HPMI), low-temperature nitrogen adsorption (LTNA), and nuclear magnetic resonance (NMR). The results show that the sandstone in the Yanwumao area of the Chang 7 shale oil reservoir consists mainly of lithic arkose and feldspathic litharenite, which can be classified into three lithofacies (massive fine-grained sandstone (Sfm), silt-fine sandstone with graded bedding (Sfgb), and silt-fine sandstone with parallel bedding (Sfp)). Moreover, three pore structures (Type I, II, and III), and four pore spaces (nanopores, micropores, mesopores, and macropores) can be characterized. Pore structure Type I, characterized by large pores, exhibits bimodal pore diameter curves, resulting in the highest levels of movable fluid saturation (MFS) and movable fluid porosity (MFP). Pore structure Type II demonstrates unimodal pore structures, indicating robust connectivity, and higher MFS and MFP. Pore structure Type III primarily consists of dissolved and intercrystalline pores with smaller pore radii, a weaker pore configuration relationship, and the least fluid mobility. Furthermore, a correlation analysis suggests that the pore structure significantly impacts the fluid flowability in the reservoir. Favorable petrophysical properties and large pores enhance fluid flowability. Micropores and mesopores with high fractal dimensions have a greater impact on reservoir fluid mobility compared to macropores and nanopores. Mesopores mainly control MFS and MFP, while micropores govern the shift from bound fluid to movable fluid states. Among the lithofacies types, the Sfm lithofacies exhibit the highest fluid mobility due to their significant proportion of macropores and mesopores, whereas the Sfgb lithofacies have lower values because they contain an abundance of micropores. The Sfp lithofacies also dominate macropores and mesopores, resulting in medium fluid mobility levels. This study combines lithofacies types, micro-reservoir pore structure characteristics, and mobile fluid occurrence characteristics to better understand the dominant reservoir distribution characteristics of the Chang 7 shale oil reservoirs in the Ordos Basin and provide theoretical information for further optimization of production strategies.

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Section: Introductionmentioning

confidence: 99%