富油煤作为煤基油气资源在我国西部地区拥有丰富的资源量，对其规模化提取油气不仅有利于提高国内能源供给能力，同时有利于改善煤炭的高碳属性。富油煤原位热解技术在提取煤中油气资源的过程中，具有绿色、低碳、地质结构损害小的优势，但其油气产出可能面临流体迁移约束与滞留问题。利用低场核磁共振实验和热重分析实验充分证实了富油煤热解残样中存在油气滞留特征，基于傅里叶红外光谱数据探讨了煤基质结构演化对热解流体迁移的束缚和滞留机制。研究结果表明，低场核磁共振T1-T2谱显示富油煤500 ℃热解后存在较强烈的油性小分子信号，利用热重分析技术对500 ℃热解后的半焦再次进行热解实验，发现其初始热解温度仅为461.5 ℃，低于前期500 ℃预处理温度。对比该热解样品与未热解的富油煤原始样品，在371～462 ℃热解温度段活化能前者却远低于后者。上述现象充分说明500 ℃富油煤热解阶段存在油的束缚情况。随着热解温度的升高，煤中含氧官能团和脂肪结构不断减少，导致煤-油相互作用增强、煤-水相互作用减弱，这一方面使煤基质对热解焦油的迁移约束性增强，另一方面使煤中可动水含量逐渐增多。此外，煤的芳香结构不断增多，使得煤基质塑性减弱、表面张力增强，也不利于热解产物形成的气泡突破基质壳体，从而产生滞留。然而，700 ℃热解样品几乎没有束缚油特征，这主要是由于该温度段热解产物发生了强烈的二次热解反应，滞留物质多以气态小分子形式存在。上述研究有助于深化富油煤原位热解流体迁移与产出认识。

Tar⁃rich coal is regarded as a coal⁃based oil and gas resource. There are abundant resource of tar⁃rich coalin the western China. The large⁃scale extraction of oil and gas from tar⁃rich coal is conducive to improving the abilityof energy supply,and optimizing the high⁃carbon properties of coal. For the extraction of oil and gas,the undergroundin⁃situ pyrolysis of tar⁃rich coal has the advantages of green, low⁃carbon, and less damage to the geologicalstructure. However,the volatiles such as oil and gas may be blocked and even trapped in the coal matrix during pyrolysis. In this study, low⁃field nuclear magnetic resonance measurement and thermogravimetric analysis wereconducted to confirm the existence of trapped oil and gas in the oil⁃rich coal after pyrolysis. Then the effect of coal mo⁃lecular structure on the migration of pyrolytic volatiles and the tap mechanism were discussed based on Fourier infraredspectroscopy. The results show that the low⁃field nuclear magnetic resonance T1 -T2 spectrum displays a strong signalof oily small molecule in the tar⁃rich coal after the pyrolysis at 500 ℃. Moreover,the thermogravimetric analysiswas conducted on the tar⁃rich coal preheated at 500 ℃. Its initial pyrolysis temperature is only 461.5 ℃,which is low⁃er than the preheated temperature. Comparing this pyrolyzed sample with the raw coal about the activation energy ran⁃ging from 371 ℃ to 462 ℃,the former is also much lower than the latter. All the characteristics above confirm the ex⁃istence of oil trapped in the tar⁃rich coal during pyrolysis at 500 ℃. With the increase of pyrolysis temperature,the ox⁃ygen⁃containing functional groups and aliphatic structure of coal decrease,which result in the improvement of coal⁃oilinteraction and the coal⁃water interaction weakened. These changes enhance the difficulty of volatiles migration,andimprove the content of free water. In addition,the increase of coal aromatic structure weakens the thermal plasticityof the coal that leads the⁃urface tension increase. It is not conducive to the volatile bubbles to break through the matrixshell. However,the tar⁃rich coal pyrolysis at 700 ℃ has almost no trapped oil signal. The reason is that the strong sec⁃ondary pyrolysis reaction occurs with the trapped volatiles at this temperature,which exist mostly in the form of gaseoussmall molecules. This research is helpful to have a deep understanding on the volatile migration and extraction in tar⁃rich coal during underground in⁃situ pyrolysis.