不同期次浊积扇体地震沉积学研究——以车西洼陷缓坡带车40-44块沙三上亚段为例

以车西洼陷缓坡带车40-44块沙三上亚段为例,针对研究区浊积扇体"单期厚度难辨、纵向多期叠置,单个形态难识、横向顺势延展"的特点,在井震标定和分频解释共同确定的等时层序地层界限之内,以沉积相模式为指导,采用地震相分析与地层属性切片相结合的方法,对浊积扇体的横向展布形态和纵向演化规律进行描述和刻画,由此达到对不同期次浊积扇体进行精确识别和精细描述的目的。在研究过程中,主要形成以下几点认识:①Es₃1和Es₃4期次顶、底界限由井震结合标定,其等时性可利用分频解释技术确定;②根据地震相的分布位置及特点,发现浊积扇体均分布于同沉积断层下降盘,且"纵向叠置、横向迁移";③通过地层切片与均方根振幅属性相结合分析,刻画出不同期次浊积扇体横向上受地势影响、呈裙带状分布的规律,和纵向上自下而上扇体数量增多且连续性增强的变化规律。

Seismic Sedimentology Research on Turbidite Fan Body of Different Stages:In case of the Gentle Slope Belt of Chexi Depression's Che40-44 Area of Upper Submember of Es3

Taking the gentle slope belt of Chexi depression’s Che40 44 area of Upper Submember of Es 3 as an example,the authors study a set of methods for identifying and describing different stages of turbidite fans based on seismic sedimentology.The turbidite fan body of the studied area has such characteristics as “single stage is difficult to identify for its thickness,as it is overlapped vertically with many others;single fan body is difficult to identify for its shape,as it extends horizontally with many others together”.In the limit of chorostratigraphy which is determined by well and seismic combined calibration and frequency-division interpretation,and under the guidance of sedimentary facies model,a method combined with seismic facies analysis and horizontal attribute slices is used to describe the shape of turbidite fan body,and to summarize the longitudinal evolutionary pattern of fans,so that the turbidite fan of different stages are precisely identified and described.Following conclusions can be drawn from this research:1)the top and bottom boundaries of Es 3 1 and Es 3 4 can be calibrated by well and seismic data in combination,and its isochroneity can be determined by the spectral decomposition interpretation technique;2)according to the distribution and characteristics of seismic facies,it can be found that all turbidite fan bodies locate in the descending stage of the contemporaneous fault,and they are usually overlapped in vertical and shifted in horizon;3)by analyzing the strata slices and mean root of seismic waveform amplitude,evolutionary law of turbidite fans of different stages can be drawn that they are prone to be affected by terrains and spread like ribbons in horizon,and number of fans increases and continuity enhances from top to bottom in vertical.