石油与天然气地质 ›› 2012, Vol. 33 ›› Issue (3): 329-334,345.doi: 10.11743/ogg20120301

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湖相烃源岩生排烃机制及生排烃效率差异性——以渤海湾盆地东营凹陷为例

蔡希源   

  1. 中国石油化工股份有限公司, 北京 100728
  • 收稿日期:2012-01-10 修回日期:2012-04-30 出版日期:2012-06-28 发布日期:2012-07-10
  • 第一作者简介:蔡希源(1953-),男,教授级高级工程师、博士生导师,矿产普查与勘探。

Hydrocarbon generation-expulsion mechanisms and efficiencies of lacustrine source rocks:a case study from the Dongying sag, Bohai Bay Basin

Cai Xiyuan   

  1. China Petroleum & Chemical Corporation, Beijing 100728, China
  • Received:2012-01-10 Revised:2012-04-30 Online:2012-06-28 Published:2012-07-10

摘要:

湖相断陷盆地所形成的烃源岩具有强烈的非均一性,而东营凹陷作为该类盆地的典型代表,其主力烃源岩是古近系沙河街组四段上亚段(Es4(上))、沙河街组三段下亚段(Es3(下))和沙河街组三段中亚段(Es3(中)),它们来自于咸水和淡水两种沉积环境。在沉积相与有机质特征研究的基础上,对比了3套地层中普通烃源岩[有机碳含量(TOC)<2%]和优质烃源岩(TOC>2%)残留液态烃产率、生烃潜力指数的演化特征,分析了排烃机制和排烃效率的差异性。由于沉积环境和埋深的不同,3套烃源岩的生排烃潜力、效率均有明显不同,相比较而言,各自的优质烃源岩是供烃成藏的主要贡献者,体现在该类烃源岩不但能形成更充足的物质基础,而且其多层理的结构也利于排烃。此外,针对不同的沉积环境总结了排烃模式。咸水环境烃源岩存在低熟和成熟两个生烃阶段,其排烃周期长、排烃效率高;而淡水环境烃源岩只存在成熟生烃阶段,其排烃周期短、排烃效率较低。沙河街组四段上亚段对资源量的贡献最大,沙河街组三段下亚段次之,而沙河街组三段中亚段最小。

关键词: 优质烃源岩, 生排烃机制, 生排烃效率, 断陷盆地, 东营凹陷, 渤海湾盆地

Abstract:

Source rocks formed in lacustrine fault basins are strongly heterogenous.The Dongying sag is one typical representative of the continental fault basins with the major source rocks including the Upper Es4,Lower Es3 and Middle Es3 members of the Paleogene Shahejie Formation deposited in saline water and fresh water environments.Based on the analysis of sedimentary facies and organic features,a comparative study of the residual hydrocarbon yields and hydrocarbon generation potential indices between the ordinary source rocks (TOC<2%) and high quality source rocks (TOC>2%) for the three members of Shahejie Formation was performed to understand their differences in hydrocarbon expulsion mechanisms and efficiencies.As they are different in depositional environments and buried depths,their hydrocarbon generation-expulsion potentials and efficiencies are significantly differe-nt.In comparison with the ordinary source rocks,the high quality source rocks are the main contributor to hydrocarbon accumulation.They not only can generate abundant hydrocarbons,but also can expulse hydrocarbons efficiently thanks to their microstratifications.In addition,hydrocarbon expulsion models were built for source rocks deposited in different environments.The source rocks that were deposited in saline water environment generate hydrocarbons in two stages,i.e.immature and mature stages and expulse hydrocarbons in longer period and higher efficiencies.In contrast,the source rocks that were deposited in fresh water environment only generate hydrocarbons in mature stage and feature in shorter hydrocarbon expulsion period and lower expulsion efficiencies.The Upper Es4 Member has the greatest contribution to hydrocarbon pooling,followed by the lower and middle Es3 members.

Key words: quality source rock, hydrocarbon generation-expulsion mechanism, hydrocarbon generation-expulsion efficiency, fault basin, Dongying sag, Bohai Bay Basin

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