东海盆地西湖凹陷古近系煤的生烃动力学

通过高温高压封闭体系条件下的热模拟实验和生烃动力学模拟分析，获得了西湖凹陷古近系平湖组和花港组煤生成气态烃的产率及其动力学参数。结合古地温演化史和热演化史恢复了西湖凹陷西部斜坡带、西次凹及中央构造带的古近系平湖组和花港组煤的生烃演化历史，并基于预测的镜质体反射率（R_o）建立了研究区煤的生气演化模式。研究结果表明，西湖凹陷煤所生成的天然气以甲烷（C₁）为主，重烃气（C₂—C₅）较少，C₁和总气态烃（C₁—C₅）的产率增长速率在煤的高成熟阶段（1.10%≤R_o<2.20%）最大，在成熟阶段（0.50%≤R_o<1.10%）次之，在过成熟阶段（R_o≥2.20%）最小，且含碳原子个数不同的重烃气（C₂、C₃、C₄和C₅）的主裂解期不同。在西湖凹陷煤的生烃演化过程中，西部斜坡带平湖组和花港组中的煤所生成的气态烃最少，生烃条件最差；而西次凹、中央构造带平湖组和花港组中煤所生成的气态烃较多，是比较有利的生烃区。花港组中煤生成气态烃的产率远小于平湖组，且至今尚未达到生烃高峰。

Hydrocarbon generation kinetics of Paleogene coal in Xihu sag,East China Sea Basin

Through thermal simulation experiments and simulation analysis of hydrocarbon generation kinetics under the closed system with high temperature and high pressure, this paper obtains the yields and kinetic parameters of gaseous hydrocarbons generated by coal from the Paleogene Pinghu Formation and Huagang Formation in Xihu sag. Further in combination with the evolution history of paleo-temperature and thermal evolution, the paper restores the hydrocarbon generation and evolution history of coal from the Paleogene Pinghu Formation and Huagang Formation in the western slope belt, the western sub-sag and the central structural belt of Xihu sag, and establishes the gas generation and evolution model of coal in the study area based on the predicted vitrinite reflectance value (R_o). The research results show that gas produced by coal in Xihu sag is domininated by methane (C₁), with less heavy hydrocarbon gas (C₂-C₅). The rate of rise in the yield of C₁ and the total yield of gaseous hydrocarbons (C₁-C₅) is the largest in the high mature stage of coal (1.10% ≤ R_o<2.20%), followed by the mature stage (0.50% ≤ R_o<1.10%), and the smallest in the over-mature stage (R_o ≥ 2.20%). Moreover, the heavy hydrocarbon gas with different numbers of carbon atom (C₂, C₃, C₄ and C₅) have different main cracking periods. During the hydrocarbon generation and evolution of coal in Xihu sag, coal in Pinghu Formation and Huagang Formation in the western slope belt produced the least gaseous hydrocarbons and had the worst hydrocarbon generation conditions; while Pinghu Formation and Huagang Formation in the western sub-sag and central structural belt produces more gaseous hydrocarbons and are favorable source areas. The yield of gaseous hydrocarbon from coal in Huagang Formation is much lower than that in Pinghu Formation, and it has not yet reached the hydrocarbon generation peak.