基于地震沉积学方法的湖相浊积砂体识别——以东营凹陷牛20区块沙三中亚段为例

    dentification of Lacustrine Turbidite Sand Bodies Based on Seismic Sedimentology: A Case from the Niu 20 Block of Dongying Depression

    • 摘要: 湖相浊积岩体积小、粒度细、单层厚度薄、相变快,受上覆三角洲前缘厚层砂体的屏蔽作用、沉积规律以及现有地震资料分辨率的影响,湖相浊积砂体的地震预测技术一直难有突破。以东营凹陷牛20区块为例,利用地震沉积学方法和技术,将沉积模式与地震反射特征、时频分析技术相结合,以井点为约束,通过识别前积界面,建立了等时层序地层格架;提高地震资料的分辨率和实现地震相位具有岩性地层意义是识别和预测湖相浊积砂体的关键。在等时界面控制下,通过正演模拟方法,认为混合相位子波拓频技术和分频技术相结合可以有效提高地震资料的主频与分辨率,采用90°相位转换可以将反射波瓣提到地层的中心,实现地震相位的岩性地层意义,最终将地层切片与地震属性相结合实现了浊积砂体的有效识别和预测。

       

      Abstract: It is difficult to predict lacustrine turbidite sand bodies with seismic data due to their small volume, fine grain size, small thickness of single layer and drastic facies change, and the shielding effect of the overlying thick deltaic sand body, in addition to the low resolution of existing seismic data. Taking the Niu 20 block of the Dongying Depression as an example, this paper adopts the principles and methods of seismic sedimentology to make interpretation of seismic data. Sedimentary models are combined together with seismic reflection characteristics and time-frequency analysis under the constraint of well points, and thus the isochronal sequence stratigraphic framework was established by identification of the front boundaries of sedimentary facies.The resolution of seismic data is enhanced. The seismic phases with lithological and stratigraphic significance are the keys to identify and predict lacustrine turbidite sand bodies. Under the control of isochronal interface, using forward modeling method as a tool, it is considered that the combination of mixed phase wavelet frequency extension technology and frequency division technology can effectively improve the main frequency and resolution of seismic data. The reflection lobe can be brought to the center of the stratum by 90 degree phase conversion, which realize the lithological and stratigraphic significance of seismic phase.Finally, the combination of strata slice and seismic attributes can effectively identify and predict turbidite sand bodies.

       

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