丽水凹陷古新统沉积相研究新认识

New understanding on the study of Paleocene sedimentary facies in Lishui sag

丽水凹陷古新统沉积相类型缺乏较为统一的认识,制约了丽水凹陷的勘探选区。通过物源、岩石学特征、沉积环境、岩石相、测井相、地震反射特征、生物遗迹种属和沉积序列等各类相标志的分析,认为丽水凹陷古新统发育西北物源的浪控三角洲(Ⅵ型)和西南物源、东部物源的河控三角洲(Ⅰ型)沉积体系。其中浪控三角洲以前缘改造后的砂坝-席状砂沉积为主,各层段均有发育,东、西次凹河控三角洲以前缘和前三角洲沉积为主,西次凹主要分布于西南物源方向,月桂峰组和灵峰组最为发育,东次凹月桂峰组和明月峰组最为发育。不同沉积体系的有利相带分布为丽水凹陷古新统岩性-地层油气藏的形成提供了良好的储集砂体,是有利区带筛选的基础。

The lack of a unified understanding of Paleocene sedimentary facies types in Lishui sag restricts the exploration target selection in Lishui sag. Based on the analysis of provenance, petrological characteristics, sedimentary environment, lithofacies, logging facies, seismic reflection characteristics, trace fossils, sedimentary sequence and various facies marks, it is considered that there are two depositional systems in Paleocene of Lishui sag: wave-controlled delta of northwest provenance(type VI) and fluvial-controlled delta of southwest and east provenance(type I). Among them, wave-controlled delta is dominated by sand bar-sheet deposits after front transformation in all sequences, while fluvial-controlled delta of East and West subsags is dominated by front and prodelta deposits. For the West subsag, the deposits are mainly distributed in the southwest provenance direction, and the Yueguifeng and Lingfeng formations are the most developed;while for the East subsag, the Yueguifeng and Mingyuefeng formations are the most developed. The distribution of favorable facies belts in different depositional systems provides a good reservoir sand body for the formation of Paleocene litho-stratigraphic oil-gas reservoir in Lishui sag, which is the basis for the selection of favorable zones.