应用岩性统计方法判别沉积相——以珠江口盆地三角洲沉积为例

摘要

传统的沉积相分析方法人为影响因素较大,对于相同的沉积构造、曲线形态及地震反射特征,不同人可能会有不同的认识,而岩性相对比较容易识别,并且能通过精密的仪器准确获得,因此,利用岩性数据进行沉积相判别,可以避免沉积相分析过程中人为认识相标志不同造成的差异.作者以珠江口盆地三角洲沉积的岩性数据为基础,通过对能够反映沉积速率、沉积物供给量及沉积水动力条件的不同岩性地层的厚度和层数的统计,选取单层厚度、地层厚度比、出现频率及层数比等统计参数,以交汇图、岩性百分含量三角图及箱线图为依托,最终建立各沉积亚相的定量判别标准.通过检验,其准确率在75%左右,可见该方法基本可行,为沉积相定量化研究提供了一种可供借鉴的方法.%The traditional research approaches for sedimentary facies are affected by artificial subjective factors. For the same sedimentary structure, curve shape and seismic reflection characteristics, different people have different views. But lithologic characteristics are doubtless, and these data are easy to obtain by instrumental measurement. Therefore, the use of lithologic data to distinguish sedimentary facies, can avoid differences which are caused by artificial subjective factors in identifying sedimentary facies indicators. The well logging lithological interpretation results from the Neogene deltaic deposits of Pearl River Mouth Basin have been used to measure the thickness and layer number of these different lithology. Statistic shows that there are close relations among the single layer thickness, formation thickness rate and other characters of these strata, the variation of these characters are close related to subfacies of the deltaic deposits. The subfacies can be distinguished quantitatively by the use of these relations, such as crossplot, triangular diagram and boxplot. The critical parameters and diagrams for different subfacies have been used to recognize the facies of other wells which are not to be used to calculate the criterion. The result shows the correctness is above 75％, and the method is basically feasible that using lithological statistics to recognize deltaic subfacies. These results may provide an available approach to the quantitative study of sedimentary facies.