华南五峰组和龙马溪组页岩储层有机孔隙非均质性及其对储层吸收能力的影响

IF 3.6
Yuying Zhang , Zhiliang He , Shuangfang Lu , Dianshi Xiao , Yifei Li , Yang Liu
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引用次数: 0

摘要

本研究旨在确定华南地区上奥陶统五峰组和下志留统龙马溪组(又称WF-LMX组)储层页岩气吸附能力的变化及控制因素。利用扫描氦离子显微镜(he)和氮气(N2)、甲烷(CH4)吸附实验数据,分析了A井WF-LMX组页岩有机孔隙非均质性及其对页岩气吸附的影响。利用Frenkel-Halsey-Hill (FHH)模型,将氮气吸附实验数据转化为分形维数,可以反映有机孔隙的复杂性和非均质性,同时也为定量评价孔隙结构复杂性提供了新的指标。结果表明:A井WF-LMX组页岩可划分为(Ⅰ)五峰组和龙马溪组下段(深度约2871.0 ~ 2898.6 m)和(Ⅱ)龙马溪组上段(深度:<;2871.0米)。Ⅰ剖面的有机孔隙内部结构复杂、表面粗糙、相互连接,而Ⅱ剖面的有机孔隙则简单、光滑、孤立。此外,前者比后者具有更大的比表面积(SSAs)。分形分析表明,页岩层序有机质孔隙可分为微孔(2 nm)、中孔(2 ~ 10 nm)和大孔(10 nm)。分形维数计算结果表明,Ⅰ剖面有机孔隙,尤其是大孔隙的非均质性优于Ⅱ剖面。有机质大孔是控制WF-LMX组页岩储层有机质孔ssa的主要孔隙。Ⅰ剖面有机孔隙对页岩气的吸附能力优于Ⅱ剖面。有机孔隙的非均质性可能影响页岩在地层中的吸附能力。总体而言,页岩层序Ⅰ段有机大孔隙结构更复杂,ssa更大,导致Ⅰ段页岩储层的吸附能力比Ⅱ段更强。
本文章由计算机程序翻译,如有差异,请以英文原文为准。

Organic pore heterogeneity and its impact on absorption capacity in shale reservoirs in the Wufeng and Longmaxi formations, South China

Organic pore heterogeneity and its impact on absorption capacity in shale reservoirs in the Wufeng and Longmaxi formations, South China
This study aims to determine the variation and controlling factors of shale gas adsorption capacity in reservoirs in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation (also referred to as the WF-LMX formations), South China. Based on data obtained using scanning helium ion microscopy (HIM) and nitrogen (N2) and methane (CH4) adsorption experiments, this study analyzed the organic pore heterogeneity of shales in the WF-LMX formations in well A and its effect on shale gas adsorption. Using the Frenkel-Halsey-Hill (FHH) model, data from N2 adsorption experiments were converted into fractal dimensions, which can reflect the complexity and heterogeneity of organic pores while also serving as a novel indicator for quantitatively assessing the pore structure complexity. The results indicate that shales in the WF-LMX formations in well A can be divided into two sections: (Ⅰ) the Wufeng Formation and the lower Longmaxi Formation (depths: ca. 2871.0–2898.6 m), and (Ⅱ) the upper Longmaxi Formation (depths: < 2871.0 m). Organic pores in Section Ⅰ typically exhibit complex internal structures, coarse surfaces, and interconnectivity, whereas those in Section Ⅱ are simple, smooth, and isolated. Moreover, the former possesses larger specific surface areas (SSAs) than the latter. A fractal analysis reveals that organic pores in the shale sequence can be classified into micropores (<2 nm), mesopores (2–10 nm), and macropores (>10 nm). The calculated fractal dimensions show greater heterogeneity of organic pores, especially macropores, in Section Ⅰ compared to Section Ⅱ. The results also reveal that organic macropores are the primary pores controlling the SSAs of organic pores in shale reservoirs in the WF-LMX formations. Organic pores in Section Ⅰ manifest a superior shale gas adsorption capacity compared to Section Ⅱ. The heterogeneity of organic pores might affect the adsorption capacity of shales in the formations. Generally, organic macropores in Section Ⅰ of the shale sequence exhibit more complex structures and larger SSAs, leading to a stronger absorption capacity of shale reservoirs in Section Ⅰ compared to Section Ⅱ.
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