地震属性在天然气水合物预测中的应用

THE APPLICATION OF SEISMIC ATTRIBUTES TO THE PREDICTION OF GAS HYDRATES

  • 摘要: 地震属性是地震资料中可描述的、可定量化的特征,它代表了原始地震资料中所包含的总信息的子集。地震属性分析就是将地震数据分解成各种属性。当地层中沉积物的孔隙内充填天然气水合物之后,沉积物的许多物理性质会发生相应的变化,这种变化导致了地震波的运动学和动力学特征发生改变,从而引起其地震属性的变化。针对南海北部陆坡天然气水合物研究区的地震数据提取各类地震属性,包括瞬时振幅、瞬时相位、瞬时频率、相对极性、能量半衰时、AVO1、AVO9和波阻抗属性。通过分析各种地震属性的响应特征及其与天然气水合物沉积层的关系,建立含天然气水合物地层的地震属性响应识别特征,利用统计学和聚类分析方法,结合地震正演结果对天然气水合物矿层目标进行预测,研究其平面分布规律,从而为天然气水合物钻探井位的确定提供可靠依据。

     

    Abstract: The seismic attributes, either describable or quantifiable, are regarded as the useful information derived from the original seismic data. The goal of seismic attribute analysis is to extract various characteristics from the seismic data for further study. The interstitial pores filled with gas hydrates may cause the change in physical attributes, making them completely different from those without gas hydrate fillings. Those changes would influence the condition of the seismic wave kinematics and dynamics, and further give rise to the variation in seismic attributes. In this article, we make use of the seismic data from the Northern Slope of South China Sea to extract the various seismic attributes for gas hydrate study, which include instantaneous amplitude, instantaneous phase, instantaneous frequency, relative polarity, energy half period, AVO1, AVO9 and wave impedance. Through establishing the relationship between the seismic responses and gas hydrate bearing sediments, we set up a model for recognizing the seismic attributes of gas hydrate-bearing sediments. In addition, by applying the means of statistics and cluster analysis with the results of seismic deduction, we try to carry out gas hydrate reservoirs forecasting, to reveal the planar distribution pattern of gas hydrate, and at last to provide reliable guidelines for appropriate borehole positioning.

     

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