惠州凹陷新近系K系列海平面变化定量分析及大数据应用展望

Eustatic fluctuations of the Neogene K successions of Huizhou Sag: High resolution quantitative analysis and application of Bayes-Laplace principle with big data

本文以珠江口盆地惠州凹陷南部为例,对地质历史时期的相对海平面变化进行了定量分析和估算,得到了研究区的相对海平面变化曲线。通过对比分析,INPEFA方法得出的曲线更能代表相对海平面变化。研究区K系列沉积时期,海平面总体是上升的,但上升的速率在不同的位置不尽相同。总体而言,四级层序海侵体系域(TST)的上升速率要稍高于与其相邻的同级别高位体系域(HST)的速率。海平面主要以交替的快速上升(海侵)和缓慢上升(海退)为特点。Fischer方法得出的曲线在本地区不直接反映相对海平面(可容纳空间)变化,但可以指示富砂层段的位置。本文进一步分析认为,可以利用地层的层序结构、分形特性以及离散的地层年龄等数据,依据贝叶斯-拉普拉斯(Bayes-Laplace)原理构建数据驱动的迭代模型,进而从粗略到精细,实现相对海平面在时间域的高精度刻画,为小尺度古环境研究和精细油藏描述提供支撑。

Taking K successions of the Zhujiang Formation in the southern part of Huizhou Sag as an example, this paper studied the changes of the relative sea levels. On the basis of sequence division, by Fischer plots and maximum entropy spectral analysis methods （INPEFA curve method）, the relative sea level changes during the formation of the K successions have been quantitatively estimated and a relative sea level changing curve was acquired. By comparison, it is concluded that the curve based on the INPEFA method is more reliable than that based on the Fischer plot in revealing the relative sea level changes. During the formation of the K successions, the relative sea level kept rising in an overall view, while the rate of rising varied from time to time. In general, the rising rates of Transgressive Systems Tracts （TSTs） are higher than those of Highstand Systems Tracts （HSTs）. The relative sea level is characterized by alternatively fast rising （transgression） and slow rising （regression）. The curve based on the Fischer plot, in contrast, does not reveal the relative sea level （accommodation） change, while it can indicate the advantageous positions of sand-rich zones. On the basis of the relative sea level curve in depth domain, this paper furtherly proposed a Bayes-Laplace based approach to acquire the relative sea level in geological time domain. This paper aims at proposing an approach for analyzing relative sea level in a high resolution scale, which is supposed to support the small scaled paleoenvironment study and fine reservoir characterization.