Experimental study on the Klinkenberg effect for gas permeability in carboniferous shales, Eastern Qaidam Basin, China

IF 1.9 4区 工程技术 Q4 ENERGY & FUELS
Jun Gao, Zongxing Li, Meihua Wei, Changsheng Zhang
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Abstract

It is crucial to understand the conditions and influencing mechanisms of shale gas slip effect for predicting the productivity of shale gas reservoirs. This study focuses on the Carboniferous Hurleg Formation shales in the eastern Qaidam Basin and conducts gas permeability tests using different gases (He/N2), as well as geochemical and pore-structure tests. The slip behavior of different gases in micro- and nanopores as well as the anisotropy of gas permeability were analyzed and discussed. The results show that helium permeability is 1.81–3.56 times higher than nitrogen permeability, with a greater difference at lower pore pressures. These permeability differences are attributed to variations in gas molecule size and slip effects. Specifically, the slip effect of helium gas has a greater contribution to permeability at lower pore pressures, with a helium slip factor averaging 2.79 times that of nitrogen. The effective pore size of shale, calculated based on the helium slip factor, is 0.74 to 1.51 times larger than when nitrogen is used, with an average of 1.67 times. Helium molecules have smaller diameters and longer average molecular free paths, resulting in a more pronounced slip effect compared to nitrogen. While helium does not adsorb, nitrogen exhibits some adsorption, causing radial expansion during gas penetration. Furthermore, when testing with different gases, the horizontal permeability (S043∥; S052∥) is higher than the vertical permeability (S043⊥; S052⊥). The anisotropy of permeability is controlled by the pore system formed by the arrangement and combination of minerals. Calcium-rich samples (S052) tend to exhibit higher anisotropy compared to calcite-rich samples (S043). The effective pore size in the vertical sample is larger than that in the parallel sample, and the gas slip effect is significantly greater in the vertical sample. These findings provide valuable data for future studies on shale gas slip effects and productivity prediction.
中国东柴达木盆地石炭系页岩天然气渗透性的克林肯贝格效应实验研究
了解页岩气滑移效应的条件和影响机制对于预测页岩气储层的产能至关重要。本研究以柴达木盆地东部石炭纪 Hurleg Formation 页岩为研究对象,使用不同气体(He/N2)进行了气体渗透性测试,并进行了地球化学和孔隙结构测试。对不同气体在微孔和纳米孔中的滑移行为以及气体渗透率的各向异性进行了分析和讨论。结果表明,氦气渗透率是氮气渗透率的 1.81-3.56 倍,在较低的孔隙压力下差异更大。这些渗透率差异归因于气体分子大小的变化和滑移效应。具体来说,氦气的滑移效应在较低的孔隙压力下对渗透率的影响更大,氦气的滑移系数平均是氮气的 2.79 倍。根据氦气滑移系数计算出的页岩有效孔径比使用氮气时大 0.74 到 1.51 倍,平均为 1.67 倍。氦气分子直径较小,平均分子自由路径较长,因此滑移效应比氮气更明显。氦气没有吸附作用,而氮气则有一定的吸附作用,导致气体渗透时径向膨胀。此外,在使用不同气体进行测试时,水平渗透率(S043∥;S052∥)高于垂直渗透率(S043⊥;S052⊥)。渗透率的各向异性受矿物排列组合形成的孔隙系统控制。与富含方解石的样品(S043)相比,富钙样品(S052)往往表现出更高的各向异性。垂直样品的有效孔隙尺寸大于平行样品,气体滑移效应在垂直样品中明显更大。这些发现为今后研究页岩气滑移效应和产能预测提供了宝贵的数据。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Energy Exploration & Exploitation
Energy Exploration & Exploitation 工程技术-能源与燃料
CiteScore
5.40
自引率
3.70%
发文量
78
审稿时长
3.9 months
期刊介绍: Energy Exploration & Exploitation is a peer-reviewed, open access journal that provides up-to-date, informative reviews and original articles on important issues in the exploration, exploitation, use and economics of the world’s energy resources.
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