湖相页岩的解吸特征及其对气体运移的指示——以鄂尔多斯盆地中部延长组长7段页岩为例
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戴欣洋(1999—),男,山西大同人,在读硕士研究生,从事石油天然气与地质学方面的研究工作。E-mail:2188654161@qq.com

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Desorption characteristics of lacustrine shale and its indication for gas migration:A case study of Chang 7 shale in central Ordos Basin
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    广泛开展的针对页岩的解吸实验,推动了页岩气气体组分以及碳同位素领域的研究,但利用气体组分识别气体运移的研究还相对薄弱。为此,以鄂尔多斯盆地中部三叠系延长组长7段页岩为研究对象,通过系统采集不同构造部位的页岩样品,开展可对比性的解吸实验,对页岩气气体组分及碳同位素的差异进行刻画,并结合区域地质背景深入分析气体运移的控制因素,厘清页岩气的运移规律,为气体的运移研究提供参考。研究结果表明,研究区长7段页岩的有机质丰度高,生烃能力强,其总有机碳含量、游离烃含量、热解烃含量的平均值分别为4.10%、3.29 mg/g和6.43 mg/g。但页岩的解吸气含量偏低,平均解吸气含量为1.39 m3/t。通过系统分析解吸气体组分特征,发现长7段页岩气为油型气,属于干酪根热解成因气。基于运移作用的强弱,可将研究区长7段页岩气划分为原位生成气、原位残留气和运移聚集气3种类型。原位生成气主要赋存于生烃中心带未经历明显运移的页岩储层中,具有解吸气含量高、N2含量低、CO2含量高、碳同位素偏重的特征。运移聚集气则富集于构造高部位或断裂带附近,表现为解吸气含量低、N2含量高、CO2含量低、碳同位素偏轻等特征。原位残留气则介于原位生成气与运移聚集气之间,主要分布于生烃中心外围过渡区域。

    Abstract:

    The extensive desorption experiments conducted on shale have promoted research in the fields of shale gas components and carbon isotopes,but the research on identifying gas migration through gas components is still relatively weak. This study focused on the shale in the seventh member of the Triassic Yanchang Formation(Chang 7 shale)in the central Ordos Basin and conducted comparative desorption experiments to explore the gas components and carbon isotopes in the shale by systematically collecting shale samples from different structural areas. In combination with the regional geological background,a detailed analysis of the controlling factors of gas migration was conducted,and the migration patterns of shale gas were clarified,providing a reference for the research on gas migration. The research results show that the organic matter abundance of the Chang 7 shale in the study area is high,and the hydrocarbon generation capacity is strong. The average values of total organic carbon content,free hydrocarbon content,and pyrolysis hydrocarbon content are 4.10%,3.29 mg/g,and 6.43 mg/g,respectively. The volume of desorbed gas is relatively low,with an average value of 1.39 m3/t. Through systematic analysis of the characteristics of the desorbed gas components,it is found that Chang 7 shale gas is oil-type gas,and it is pyrolysis gas originating from kerogen. Based on the strength of the migration process,the Chang 7 shale gas can be divided into three types:in-situ generated gas,in-situ residual gas,and migrated and accumulated gas. In-situ generated gas is mainly stored in the shale reservoirs within the hydrocarbon generation center zone that have not undergone significant migration. It has the characteristics of high desorption gas content,low N2 content,high CO2 content,and heavy carbon isotopes. The migrated and accumulated gas is concentrated in the high parts of the structure or near the fault zones,presenting characteristics such as low desorbed gas content,high N2 content,low CO2 content,and light carbon isotopes. In-situ residual gas lies between in-situ generated gas and migrated accumulated gas and is mainly distributed in the transitional area around the hydrocarbon generation center.

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戴欣洋,师 良,范柏江.湖相页岩的解吸特征及其对气体运移的指示——以鄂尔多斯盆地中部延长组长7段页岩为例[J].油气地质与采收率,2025,32(5):35~45

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  • 收稿日期:2024-08-01
  • 最后修改日期:2025-05-15
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  • 在线发布日期: 2025-09-26
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