A Method for Quantitative Characterization of Gravel Orientation and Its Application
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摘要: 砾石定向性可用于辅助判断粗粒沉积物沉积环境的介质动力性质与强度。在岩芯图像分析与测量的基础上,运用砾石长轴视倾角玫瑰花图中任意相邻三个小扇形的半径之和的最大值(参数a)和小扇形半径大小偏离程度(参数σ)对玛湖地区百口泉组砂砾岩中砾石定向性进行等级划分和定量表征。通过该方法的应用,建立了该区不同级别砾石定向性的定量划分方案:有明显定向性(a大于35%且σ大于4)、有一定定向性(a大于35%且σ小于4)、有模糊定向性(a小于35%且σ大于4)、定向性杂乱(a小于35%且σ小于4)。并对研究区典型季节性辫状河道和暂时性辫状河道的定向性进行了实测,结果表明季节性辫状河道中σ为4.8~8.13,a为40%~62%,而暂时性辫状河道中σ小于4,a小于35%。该方法能够有效表征砾石定向性,并为沉积环境判断提供依据。Abstract: Gravel orientation can be used to judge the environment of coarse grain deposits. On the basis of the analysis and measurement of the gravel image from the core image, using the parameters a and parameters σ to determine the grading orientation and quantitative characterization of gravel orientation in the Baokuquan Formation sandstone in the Mahu sag. The parameter a is the maximum value of the sum of the radii of the gravitational axis of any adjacent three small fans, parameter σ is the degree of deviation of the small fan radius. It is found that the larger the a and σ is, the better the orientation of the gravel is. The method is applied to the Mahu area, and the quantitative division scheme of different levels of gravel orientation has been established:clear orientation (a is greater than 35% and σ is greater than 4), a certain orientation (a is greater than 35% and σ is less than 4), a fuzzy orientation (a is less than 35% and σ is greater than 4), no orientation(a is less than 35% and σ is less than 4). And the directivity of typical seasonal braided channel and temporary braided channel in the study area were studied, the results show that the value of σ in the seasonal braided channel is 4.8~8.13, the value of a is 40%~62%, and the value of σ in the braided channel is less than 4, the parameter a is less than 35%. It can be seen that the method can effectively characterize the orientation of gravel and provide the auxiliary basis for the judgment of sedimentary environment.
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Key words:
- Mahu sag /
- Baikouquan Formation /
- gravel orientation /
- quantitative characterization /
- orientation degree /
- single well
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