源内残留沥青原位裂解生气对有机质生烃的影响

Effect of gas generation from in-situ cracking of residual bitumen in source on hydrocarbon generation from organic matter

利用金管模拟装置进行了一系列全岩升温热解实验,探讨了源内残留沥青的原位裂解生气行为及其对源岩生烃的影响。矿山梁地区泥岩和抽提样品升温热解结果表明,残留沥青对源岩生油和生气具有重要贡献,其裂解生气量可达源岩总生气量的32.3%。动力学计算表明,源内残留沥青原位裂解生气平均活化能为234.1kJ/mol,要明显低于油藏中正常原油的裂解。矿山梁地区泥岩生成烃类气体的最大产率为28.5 mg/g,要明显高于抽提样品,且前者的活化能相对较高。基于实验结果和地质推演可发现,源内残留沥青原位裂解的门限温度仅为140℃,比排出(源外)原油的裂解低30℃左右。此外,麻柳桥地区泥岩及抽提样品的全岩热解表明,残留沥青是高成熟源岩的主要气源。

The gas generation behavior of residual bitumen in source rocks （in-source） by in-situ cracking and its effect on hydrocarbon generation from source rocks are examined through non-isothermal pyrolysis of whole rocks in a gold-tube simulation device. Results of the analysis using mudstone and sample extract from Kuangshanliang area show that residual bitumen in-source makes a significant contribution to oil and gas generation, and the yield of bitumen-cracked gas accounts for up to 32.3% of total gas yield from source rocks. The kinetics calculations indicate that the average activation energy for in situ cracking of residual bitumen in source is 234. ] kJ/mol, apparently lower than that for normal oil cracking in reservoirs. The maximum yield of hydrocarbon gases from Kuangshan- liang mudstone is approximately 28.5 rag/g, substantially higher than that of the sample extract. Likewise, the activation energy for gas generation from Kuangsbanliang mudstone is slightly higher than for the sample extract. Through a combination of experimental analysis, kinetics calculation and geological extrapolation, the threshold temperature for in-situ cracking of residual bitumen in-source is 140℃ only, approximately 30℃lower than that for cracking the oil expelled （out-source）. Additionally, results of whole rock py- rolysis with mudstone and sample extract from Maliuqiao area demonstrate that residual bitumen is the primary source of gas genera- tion from source rocks of high maturity.