地震资料中柱状流体运移通道形态参数及其地质意义

Morphological parameters and geological significance of the columnar fluid migration pathways in seismic profiles

  • 摘要: 深部流体在向上运移的过程中,能够形成垂直—近似垂直的柱状通道,如气烟囱构造、流体逸散管道等。利用高分辨率地震资料,能够直观地对这些柱状地球物理异常进行精细的描述与刻画,从而统计其形态参数。综合不同海域的研究成果,本次研究系统总结归纳了柱状流体运移通道的8个重要参数,分别是发育层位、终止层位、平面形状、直径、高度和宽高比、反射偏移、椭圆率、拟合椭圆方位角。形态参数分别与通道群在平面上的展布方位、特殊的海底异常地貌(如海底麻坑、丘状体等)、深部构造发育与分布(如底辟、断层等)等进行耦合关联,能够进一步揭示柱状流体运移通道的地质含义。可将形态参数分为:(1)从形态学上对柱状通道进行直接分类的参数;(2)指示柱状通道形成诱发因素或形成过程的参数;(3)划分柱状通道幕式流体活动及期次的参数;(4)定义柱状通道中流体活动时间区间的参数;(5)间接反映柱状通道中流体通量相对大小的参数。实际研究过程中,单一形态参数难以准确反映出复杂地质背景下柱状通道的真实地质含义,多参数组合、相互对比验证,能够更好地对柱状流体通道的地质含义做出综合分析。

     

    Abstract: Some columnar seismic anomalies with chimney structures and seepage pipes could be observed in seismic profiles. They are usually interpreted as the vertical migrating pathways of gas-bearing fluids. On the basis of comprehensive description from high-resolution seismic data, some morphological parameters of these columnar fluid migration pathways are calculated in this study. About eight important morphological parameters were systematically summarized, including the root zone level, termination level, plane shape, diameter, length/width ratio, vertical reflection offset, ellipticity, and fitting ellipse azimuth. Combined the spatial distribution pattern of morphological parameters with some special seafloor geomorphologies, such as pockmarks and mounds, and deeper structures, such as diapirs and faults, morphological parameters could be further used to reveal the geology of columnar migrating pathways for gas-bearing fluids. We divided all the parameters into five types, as (ⅰ) parameters for morphological classification of the columnar fluid flow structures; (ⅱ) parameters for reveal the genetic factors and forming mechanisms; (ⅲ) parameters for dating the episodic fluid activities; (ⅳ) parameters for defining the initial and terminal times; and (ⅴ) parameters for indirectly reflecting the relative fluid fluxes. Therefore, integrated analysis based on multi-parameters and comparisons between parameters are important for interpreting these columnar fluid migration pathways formed upon different geological background.

     

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