辽东湾地区辽中凹陷东营组烃源岩评价

Assessment of the source rocks from the Dongying Formation in the Liaozhong depression, Liaodong Bay

关键词:  烃源岩  有机质丰度  有机质类型  成熟度

Key words:  source rock  organic matter abundance  organic matter type  maturity

摘要:

依据烃源岩地球化学实验手段和油气地化理论,对辽东湾地区辽中凹陷东营组东二下段(Ed^2-1)和东三段(Ed³)地层进行了有机地化分析。在实验获取总有机碳(TOC)、生烃潜量(S₁+S₂)、氢指数(I_H)、氢碳比(H/C)、氧碳比(O/C)、最大热解峰温(T_max)、镜质体反射率(Ro)等有机地化参数的基础上,对有机质丰度、类型、成熟度等进行了系统分析,同时对东营组烃源岩进行了综合评价。研究表明,东二下段S₁+S₂集中在0~3 mg/g,TOC集中在0%~1.5%;东三段S₁+S₂集中分布在4~9 mg/g之间,TOC集中分布在1%~1.25%。东二下段有机质类型主要是III型,东三段有机质类型为II₁、II₂型。东二下段Ro < 0.5,东三段Ro > 0.5,并且随着深度的增加东三段烃源岩Ro相应的增加。T_max随着深度的增加呈现出先增加后减少的异常现象,该种异常现象出现的原因与烃源岩有机质类型和有机质丰度之间存在很大关联。

Abstract:

The present paper deals with the organic geochemical analysis and assessment of the source rocks from the lower submember of the 2nd member of the Dongying Formation (Ed^2-1) and the 3rd member of the Dongying Formation (Ed³) in the Liaozhong depression, Liaodong Bay, with the emphasis on organic matter abundance, type and maturity based on the organic geochemical parameters such as total organic carbon (TOC), hydrocarbon potential (S₁ + S₂), hydrogen index (I_H), hydrogen/carbon ratios (H/C), oxygen/carbon ratios (O/C), maximum temperatures of thermolysis (T_max) and vitrinite reflectance (Ro). The analytical results indicate that the source rocks from the lower submember of the 2nd member of the Dongying Formation (Ed^2-1) display 0 to 3 mg/g for S₁ + S₂, 0% to 1.5% for TOC, Ro < 0.5% and III to II₂ types of organic matter, indicating immature or poor source rocks. The source rocks from the 3rd member of the Dongying Formation (Ed³) display 4 to 9 mg/g for S₁ + S₂, 1% to 1.25% for TOC, Ro < 0.5 and II₁ to II₂ types of organic matter, indicating mature or better source rocks.