Carbon isotope fractionation characteristics during shale gas release
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摘要: 钻井现场开展页岩岩心解吸气同位素监测,由于损失气样品缺失,而不能得到岩心气体释放全过程同位素的变化规律。通过加工岩心甲烷高压饱和-解吸装置,并接入色谱-同位素质谱联机系统,满足在线实时监测解吸气甲烷碳同位素变化的要求。在此基础上,开展页岩岩心释气的正演模拟实验,发现了解吸气甲烷碳同位素先期稳定、后期变轻后逐渐变重的变化规律,揭示了岩心中游离气和吸附气的相态转化、二者混合比例的动态演化与同位素变化趋势的相关性,表明同位素在页岩气开发状态的示踪方面具有应用潜力。Abstract: The isotope monitoring of desorption gas from shale cores was carried out at the drill site. Gas is lost during core recovery and thus the isotope variation for the whole process of gas release from shale cores cannot be obtained. A high pressure methane saturation-desorption device was developed and connected to the chromatographic-isotope mass spectrometry system to monitor the carbon isotope change of released CH4 on-line. The isotopic curves of releaed methane were initially stable, and then tended to become lighter and finally heavier, which was related to the phase transformation and the mixing ratio of free gas and adsorbed gas. Isotopes have potential applications in monitoring shale gas development.
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Key words:
- carbon isotope /
- isotopic fractionation /
- methane /
- shale gas
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表 1 在线连续流甲烷碳同位素重复性检测
Table 1. On-line continuous flow methane isotope repeatability measurement
序号 信号强度44 mV 信号强度45 mV δ13CCH4/‰ 序号 信号强度44 mV 信号强度45 mV δ13CCH4/‰ 1 20 042 22 619 -42.00 7 19 940 22 497 -41.92 2 20 056 22 633 -41.92 8 19 916 22 470 -41.92 3 19 994 22 563 -41.94 9 19 951 22 510 -41.92 4 19 775 22 313 -42.01 10 20 002 22 565 -41.95 5 19 733 22 264 -41.96 11 19 757 22 285 -41.94 6 19 882 22 435 -41.96 12 20 005 22 567 -41.94 -
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