饶阳凹陷沙河街组沙三下亚段沉积特征及意义

Sedimentary characteristics and significance of the lower submember of the third member of Shahejie formation in Raoyang sag

为了揭示饶阳凹陷沙河街组沙三下亚段层序地层特征及沉积演化规律,在区域沉积背景分析基础上,利用岩心、测井及地震资料,建立沙三下亚段层序地层格架,并对沉积演化规律进行了研究.认为沙三下亚段为一个完整的三级层序,可划分为低位、湖侵和高位3个体系域,主要发育辫状河三角洲、扇三角洲和湖泊等3种沉积相类型,辫状河三角洲发育于断陷西部缓坡带,扇三角洲发育于断陷东部陡坡带,湖泊发育于断陷中部.低位域、高位域时期辫状河三角洲、扇三角洲规模较大,储集体发育,湖侵域时期湖盆扩张,烃源岩发育.结果表明:高位域时期的水下分流河道储层物性最好,为Ⅰ类有利区;低位域时期的水下分流河道、席状砂储层物性次之,为Ⅱ类有利区,此类砂体与湖侵域烃源岩形成有利的生储盖组合,是下步勘探的有利方向.

In order to reveal the sequence stratigraphic characteristics and sedimentary evolution rule of the lower submember of the third member of Shahejie formation in Raoyang sag, based on the analysis of regional sedimentary background and the core, well-logging and seismic da- ta, the sequence stratigraphic framework was established and the sedimentary evolution rule was studied. The results show that the lower submember of the third member of Shahejie for- mation is a third-order sequence and can be divided into the low stand system tract （LST）, the lacustrine transgressive system tract （TST） and the high stand system tract （HST）. The low- er submember of the third member of Shahejie formation develops braided river delta deposi- tion, fan delta deposition and lacustrine facies deposition. Braided river delta deposition devel- ops in the west gentle slope zone in fault depression. Fan delta deposition develops in the east steep slope zone in fault depression. During the LST and HST, the large-scale braided river delta deposition and fan delta deposition develop and the reservoirs develop. During the TST, the lake basin expands and hydrocarbon source rock develops. The subaqueous distributary channel sand bodies during the HST have the best reservoir properties, which are the class I fa- vorable exploration area. The sand bodies of sheet bar and subaqueous distributary channel during the LST are the class II favorable exploration area, which can form the valuable source- reservoir-cap combination combined with hydrocarbon source rock of the TST and will be the favorable exploration direction in the future.