渤海湾中部南堡35-2地区新第三系河流沉积及油气勘探意义

FLUVIAL SEDIMENTS AND THEIR OIL-GAS EXPLORATION SIGNIFICANCE OF THE NEOGENE IN THE NANPU 35-2 AREA OF CENTRAL BOHAI GULF

渤海湾中部南堡 35 - 2地区新三系河流沉积十分发育 ,可分为曲流河沉积和辫状河沉积两种类型。曲流河沉积以发育点砂坝、决口扇、天然堤和泛滥平原等微相单元为特征。辫状河沉积主要发育河道和心滩微相 ,泛滥平原微相不太发育。本文重点研究了河流沉积各类微相的沉积特点 ,并将河流沉积的垂向层序归纳为 6种类型。本文还探讨了各类砂体的储集物性特征 ,认为点砂坝和心滩砂体是形成大油气田的优质储层 ,而油气藏的形成除与砂体的储集物性有关外 ,主要与区域构造条件密切相关。

The fluvial sediments of the Neogene in the Nanpu 35-2 area of Central Bohai Gulf are well-developed and can be divided into two types as meandering river sediments and braided river sediments. The depositional sequences of meandering river are typical of the development of point bars, crevasse-splays, natural levees and flood plains. The depositional sequences of braided rivers mainly consist of braided channel lag deposits and mid-channel bar sandstones. Based on sedimentary structures, grain-size probability curves, C-M charts, sedimentary sequences and logging curves, etc., this paper has discussed the sedimentary characteristics of each microfacies for fluvial sediments and concludes 6 types of vertical sequences which reflect different sedimentation and features separately. This paper also probes into reservoir properties of the sand-bodies and suggests that point bar and mid-channel bar sandbodies can be considered the high quality reservoirs for great oil-gas field, and the formation of oil-gas pool not only be related to reservoir quality of sandbodies, but also to regional tectonic conditions.