东海平湖油气田平湖组P12段沉积模式新认识

A New Understanding on the Sedimentary Model for the P12 of Pinghu Formation in Pinghu Oil and Gas Field, East China Sea

张兵

ZHANG Bing

上海石油天然气有限公司, 上海 200041

Shanghai Petroleum Corporation Ltd., Shanghai 200041, China

平湖组深部P12段沉积类型一直颇有争议，至今没有形成统一认识。通过微量元素硼恢复了P12段的盐度信息，发现其处在咸化较严重的水体环境中，受强烈海侵影响；岩心观察结果表明平湖组深部受到潮汐、河流等多重作用影响，形成了丰富的韵律层理、生物扰动、双流向河道等沉积现象；D井的含砾石英中砂岩所对应的UFR砂坪也证明了平湖组P12段发育的是潮控河口湾相沉积；另外地震振幅图上清晰表现出了潮控河口湾相下部低水位期下切河谷河流沉积，中部海侵河口湾潮汐砂坝沉积，上部高水位期潮坪沉积三套特征岩相配置关系，据此建立了平湖组深部P12段潮控河口湾沉积演化模式。

The sedimentary type of the lower Pinghu Formation (P12) has been a controversial issue and not formed a unifed understanding yet. The restore of paleo-salinity by trace element B shows that the sedimentation of P12 was strongly affected by the transgression and taken place in a strongly salinized water environment. The core observation indicates the sedimentation of lower Pinghu Formation was influenced bymultiple hydrodynamic forces such as tide, river etc. as demonstrated by the presence of abundant rhythmic beddings, bioturbations, and two-way flow channel sediments in the interval. P12 of Pinghu Formation belongs to tide-dominated estuarine in origin and can be proved by the conglomerate-bearing quartz sandstones of UFR sand flat in Well D. In addition, the seismic amplitude maps also reveal the sedimentary characteristics in the different part of tide-dominated estuary facies sequence i.e. incised valley fluvial deposits of the lowstand period at the lower part, tidal sand bar sedimentsof transgression period at the middle part and tidal flat deposits of highstand period at the upper part. Accordingly, a sedimentary evolution model of the tide-dominated estuary sedimentation recorded in the lower Pinghu Formation (P12) is summarized.

https://doi.org/10.3969/j.issn.1008-2336.2016.04.001