塔里木盆地库车坳陷烃源岩生成甲烷的动力学参数及其应用

Kinetic Parameters of Methane Generated from Source Rocks and Its Application in the Kuqa Depression of the Tarim Basin

根据压力下黄金管封闭体系热模拟实验结果 ,应用 Kinetics和 GOR- Isotope Kinetics专用软件 ,获得了塔里木盆地库车坳陷三叠系—侏罗系烃源岩的生烃动力学参数及碳同位素动力学参数。库车坳陷侏罗系煤、煤系泥岩及三叠系泥岩热解生成甲烷具有各自的活化能分布范围 ,分别是 197～ 2 6 8k J/ mol、180～ 2 6 0 k J/ mol、2 14～2 89k J/ m ol,频率因子各为 5 .2 6 5× 10 1 3s- 1、9.76 1× 10 1 1 s- 1、2 .2 70× 10 1 4s- 1 ,反映它们的生烃行为有所差异 ;其相应的碳同位素动力学参数也有差别 ,平均活化能分别是 2 2 8k J/ mol、2 0 5 k J/ mol、2 31k J/ mol。在此基础上 ,应用这些动力学参数 ,并结合地质背景 ,进一步探讨了依南 2气藏天然气的成因和运聚成藏模式。研究表明 ,依南 2气藏天然气主要来源于库车坳陷阳霞凹陷中心侏罗系煤系烃源岩 ,主要聚气时间为 5～ 0 Ma,对应 Ro 为 1.2 5 %～ 1.95 % ,天然气散失率为 2 5 %～ 30 %。该研究对塔里木盆地 ,乃至我国其他地区天然气藏的成因评价与成藏过程研究具有参考和借鉴意义。

In a thermal simulation experiment of closed-system gold tube-high pressure vessels under a given pressure (50 MPa) and calculation with the specific Kinetics and GOR-Isotope Kinetics software's, kinetic parameters of gas generation and methane carbon isotope from Triassic—Jurassic source rocks in the Kuqa depression of the Tarim Basin are obtained. The ranges of activation energies of methane paralyzed from Jurassic coal, Jurassic mudstone and Triassic mudstone in the Kuqa Depression are 197～268 kJ/mol, 180～260 kJ/mol, and 214～289 kJ/mol, respectively. The frequency ratios are 5.265×10 13/s, 9.761×10 11/s, and 2.270×10 14/s. This suggests that there are different activation energies and frequency ratios for methanes generated from Jurassic coal, coal-associated mudstone and Triassic mudstone in the Kuqa Depression, and reflect their differences of hydrocarbon generation behaviors. The kinetic parameters of methane carbon isotope are also different in Jurassic coal, Jurassic mudstone and Triassic mudstone. Their average activation energies were 228 kJ/mol, 205 kJ/mol, and 231 kJ/mol, respectively. On the basis of the above research, combined with the geological background, the origin of natural gas in the Yinan 2 gas pool was further discussed using these kinetic parameters, and its gas accumulation model is thus established. The natural gas of the Yinan 2 gas pool was primarily derived from Jurassic coal-bearing source rocks at the center of the Yangxia Sag and generally belong to the staged accumulative gas. The Yinan 2 gas was mainly gathered at 5～0 Ma with a R o range of 1.25%～1.95% and lost about 25%～30%.