济阳坳陷民丰地区天然气成因

Origin of natural gas in Mingfeng area,the Jiyang Depression

济阳坳陷民丰地区天然气存在源岩热解和原油裂解成因的争议,利用古近系沙四段烃源岩、原油样品的热模拟实验与地质分析相结合的方法,提出了源岩热解气和原油裂解气的鉴别标志。源岩热解气以甲烷的快速生成为特征,成熟阶段,源岩热解气的环烷烃和苯含量低,高成熟阶段,源岩热解气和原油裂解气均以环烷烃和苯含量高为特征。民丰沙四段凝析油和天然气的ln(C1/C2)比ln(C2/C3)变化大,且环烷烃、异构烷烃和芳烃含量较高,具有高成熟阶段源岩热解气的特征,研究认为民丰地区天然气为源岩热解成因。

It is controversial about the origin of the natural gas in Minfeng area. A set of indexes for differentia- ting kerogen-pyrolysis gas and oil-cracked gas is presented based on geologic analysis and thermal simulation ex- periments on source rocks and crude oil samples from the Es4. In mature phase, the kerogen-pyrolysis gas fea- tures in rapid generation of methane and low contents of cyclane and benzene. While in high mature phase,both kerogen-pyrogenic gas and oil-cracked gas are characterized by high contents of cyclane and benzene. The con- densate oil and natural gas in Mingfeng area show a larger scope of ln（ C1/C2 ） ranging from 2 to 6 than that of ln（ C2/C3 ） varing from 1 to 1.5 and have relatively high contents of cyclane,isoalkane and aromatic hydrocarbon, revealing the characteristics of kerogen-pyrolysis gas natural gas in Minfeng area is of kerogen-pyrolysis gas.