摘要
长岭断陷下白垩统营城组和登娄库组获得高产工业性气流或良好的气显示,生储盖组合配置比较有利,勘探前景十分广阔。在对长岭断陷部分探井天然气样品的化学组分和碳同位素组成特征剖析的基础上,综合多种天然气成因判别标准以及典型图版,探讨了天然气的成因类型,并结合研究区地质背景和烃源岩发育特征,与徐家围子断陷天然气成因加以对比,对其气源进行初步判识。研究结果表明,长岭断陷天然气烃类气体主要为甲烷,重烃含量低,干燥系数大于0.95,处于高成熟—过成熟阶段,烃类气体碳同位素值偏高,并存在同位素倒转现象,非烃气体包括CO2和N2,不同构造带天然气成分差别大。烃类气体属于腐殖型裂解气,CO2以无机成因为主。气源分析表明,研究区烃类气主要来源于沙河子组腐殖型烃源岩的裂解气,其次为营城组,火石岭组或更深层源岩的贡献较小。
The industriai gas flow with high production or gas show in the lower Crataceous Yingcheng Formation and Denglouku Formation of Changling fault depression was gotten, with favorable combination of source-reservoir-cap, suggesting good exploration prospect. Based on chemical and carbon isotopic compositions of natural gas from Changling fault depression, the genetic types of natural gas was discussed, in combination with standard of gas classification and empirical pattern. Based on geologic background and geochemistry of source rock, the gas source correction was also discussed, in comparison with origin of natural gas from Xujiaweizi fault depression. In natural gas from Changling fault depression, CH4 is dominant gas, with low content of heavy alkane gas and dryness coefficient more than 0.95, suggesting high-over mature stage of thermal maturity. Hydrocarbon gas is enriched in ^13C, with reversal trend of stable carbon isotope of alkane gases with carbon number. Non-hydrocarbon gas is CO2 and N2, but chemical composition of natural gas is distinct at different structural belts. Alkane gas is of thermally decomposed gas origin source from humic kerogen, but CO2 was sourced from inorganic gas. Alkane gas was mainly sourced from Shahezi formation humic source rock, then from Yingcheng Formation, a little contribution of gas from Huoshiling Formation or underneath would exist.
出处
《天然气地球科学》
EI
CAS
CSCD
北大核心
2010年第2期331-337,共7页
Natural Gas Geoscience
关键词
长岭断陷
天然气
组分
碳同位素
成因类型
气源分析
Changling Fault Depression
Natural gas
Chemical composition
Carbon isotope
Genesis
Gas source correlation.
