砂岩透镜体成藏的动力学机制

doi:10.11743/ogg20070212

摘要/Abstract

摘要：

砂岩透镜体的成藏动力学机制是一个还没有完全解决的问题.四周为生烃泥岩所包围的砂体是一个封闭或半封闭的水力系统,烃类如何充注进去而孔隙水又如何被排替出来,就成为问题的关键和难点.在对比岩性和构造圈闭成藏特征的基础上,对泥岩中初次运移的动力和砂体中二次运移相态的转换以及浮力的作用进行了综合研究和动态分析.认为充注的动力主要是异常高压力、毛细管压差、分子扩散和渗透压力;在砂体中油气聚集和排水的动力主要是浮力及其产生的附加压力.这些成藏动力随生烃泥岩热演化阶段的不同,也有所侧重和不同.在低熟阶段主要是压实和渗透水流的充注;在成熟阶段主要是以烃-水两相渗流、毛细管压差和分子扩散等方式进行充注,同时在浮力作用下油气在砂体中开始聚集;在高成熟阶段除继承上述充注方式外,同时又不断有天然气从砂体顶部扩散出来,最终导致砂体中以油相聚集为主.影响砂岩透镜体成藏的地质要素是生烃泥岩的质量、厚度以及砂体的物性和产状.总之,砂岩透镜体成藏要比构造圈闭成藏困难得多.

关键词: 砂岩透镜体, 成藏动力学, 油气充注, 异常高压, 毛细管压差, 分子扩散

Abstract:

The dynamic mechanism of petroleum accumulation in sand lens remains poorly understood.Therefore,an explanation is still needed to address the key issue concerning how hydrocarbons charged into and expulsed from the closed or semi-closed hydraulic system made of sandstones encircled by source mudstones.By comparing the characteristics of lithology and the reservoiring features of structural traps,a comprehensive study and dynamic analysis was carried out on the driving forces of the primary hydrocarbon migration and the phase transformation and buoyancy effect during the secondary migration in mudstone.The results show that the predominant charging forces include abnormally high reservoir pressure,capillary pressure difference,molecular diffusion,and osmotic pressure,and that the buoyancy and relevant additional pressure contribute greatly to hydrocarbon accumulation and water displacement in sandbodies.These dynamics vary with different evolution stages of source mudstones.The compaction and seepage water dominated the charging during low maturity stage;while in mature stage,two phase flow(hydrocarbon and water seepage),capillary pressure difference,and molecular diffusion,controlled the charging process,and hydrocarbons entered into the lens by the action of buoyancy.In the highly matured stage,the charging process continued and was further accompanied by natural gas diffusion from the top of sandbodies,resulting in a final oil accumulation in the lens.Factors that affect the sand lens reservoirs include the quality and thickness of source mudstone,and the physical properties and occurrence of the sandbodies.In summary,hydrocarbon accumulation in sand lens is much more difficult than that in structural traps.

Key words: sand lens, reservoiring dynamics, oil-gas charging, abnormally high reservoir pressure,capillary pressure difference, molecular diffusion

中图分类号:

TE112.3

李明诚,单秀琴,马成华,等. 砂岩透镜体成藏的动力学机制[J]. 石油与天然气地质, 2007, 28(2): 209-215. doi: 10.11743/ogg20070212 Li Mingcheng,Shan Xiuqin,Ma Chenghua,et al. Dynamics of sand lens reservoir[J]. Oil & Gas Geology, 2007, 28(2): 209-215. doi: 10.11743/ogg20070212

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