鄂尔多斯长7段油页岩不同阶段热解反应特征

Pyrolysis Reaction Characterization at Different Stages in Oil Shale from the Ordos Chang 7 Section

蒋海岩 胡清萍 王 姣 刘 帅 袁士宝 申志兵

JIANG Haiyan HU Qingping WANG Jiao LIU Shuai YUAN Shibao SHEN Zhibing

针对原位热采开发油页岩矿藏中热解反应变化复杂、控温困难等问题，通过热重分析实验对鄂尔多斯盆地长7油页岩热解过程进行阶段划分；通过X射线衍射测试、气相色谱-质谱联用等实验重点检测有机质裂解放热阶段的产物成分，分析不同阶段演化的主要化学反应，进一步验证阶段划分。结果表明，油页岩在氮气氛围下的热解可以划分为 3 个阶段：脱水阶段（＜300 ℃）、有机质裂解放热阶段（300～720 ℃）、矿物吸热分解阶段（＞720 ℃）。在有机质裂解放热阶段，油页岩的失重约为总失重的74%，无机矿物未发生热裂解。有机质裂解放热阶段可进一步划分为3个阶段：300 ℃≤T＜450 ℃的低温初始段、450 ℃≤T＜600 ℃的中温热解段、600 ℃≤T≤ 720 ℃的高温热解完成段。有机质的热解主要发生在中温热解段。随温度升高，烷烃脱氢反应、酯化反应变为以酯类化合物热裂解反应、烷烃断链生成小分子烃类反应为主；温度升至 600～720 ℃时，会促使化合物发生聚合向油页岩半焦转化；当温度控制在中温热解段时，油页岩油成分最好，含 27.70%酯类、29.89%脂肪烃、14.49%醇类、12.66%芳香烃等。研究结果为油页岩热解机理分析、油页岩数值模拟模型的建立和提高现场采收率提供理论指导，并对控制有机质的反应温度范围提供依据，保证较高的转化率。

To address the complex changes in pyrolysis reactions and the difficulty of temperature control in in-situ thermal recovery of oil shale deposits，thermogravimetric analysis experiments were conducted to segment the pyrolysis process of the Chang 7 oil shale in Ordos Basin. X-ray diffraction（XRD）and gas chromatography-mass spectrometry（GC-MS）were utilized to examine the composition of products during the organic matter pyrolysis and exothermic stage. The main chemical reactions evolving at different stages were analyzed to further validate the segmentation. The results showed that the pyrolysis of oil shale under a nitrogen atmosphere could be divided into three stages：dehydration（＜300 ℃），organic matter pyrolysis and exothermic stage（300—720 ℃），and mineral endothermic decomposition（＞720 ℃）. During the organic matter pyrolysis and exothermic stage，the mass loss of oil shale accounted for approximately 74% of the total mass loss，with no thermal decomposition of inorganic minerals. This stage could be further subdivided into three phases：low-temperature initial phase （300 ℃≤T＜450 ℃），mid-temperature pyrolysis phase（450 ℃≤T＜600 ℃），and high-temperature pyrolysis completion phase（600 ℃≤T≤720 ℃）. The primary pyrolysis of organic matter occurred in the mid-temperature phase. As the temperature increased，dehydrogenation reactions of alkanes and esterification reactions transitioned to the thermal cracking of esters and the chain scission of alkanes producing small molecular hydrocarbons. When the temperature rose to 600—720 ℃，compounds tended to polymerize into semi-coke. At the mid-temperature pyrolysis phase， the composition of shale oil was optimal， including 27.70% esters， 29.89% aliphatic hydrocarbons，14.49% alcohols and 12.66% aromatic hydrocarbons. These findings provided theoretical guidance for analyzing the pyrolysis mechanism of oil shale，establishing numerical simulation models for oil shale，and improving on-site recovery rates. They also offered a basis for controlling the reaction temperature range of organic matter to ensure a high conversion rate.

10.19346/j.cnki.1000-4092.2024.03.010