高分辨率层序构型及对储层构型的控制——以东营凹陷梁11断块沙二段第7、第8砂层组为例

High-resolution sequence architecture and its control over reservoir architecture:taking Es^(2-7,8) sand group of Liang 11 fault block of Dongying depression as example

砂体内部结构及其控制因素对于预测剩余油分布有重要作用。作者综合利用岩心、测井曲线形态、砂体的几何形态等资料,研究了基准面变化及其与三角洲前缘砂体内部结构的关系。结果表明,研究层段发育2个中期基准面旋回、7个短期基准面旋回和20个超短期旋回,早期中期旋回由3个向上变浅的非对称型短期基准面旋回组成,晚期中期旋回由4个向上变深的非对称型短期旋回组成,20个超短期旋回均属于非对称型;基准面的升降及物源供应共同控制了砂体发育的规模、岩石类型及内部结构。基准面下降、沉积物供给充足时,河口坝砂体规模增大,岩性以细砂岩、中砂岩等为主,夹层在不同位置发育程度不同,其中坝主体以钙质夹层、过渡性夹层为主,厚度较小且不甚稳定。基准面上升、沉积物供给充足时,水下分流河道宽,砂体厚度大,砂体内除了发育钙质夹层之外,泥质侧积层也较为发育;基准面较高、物源供应较少时,河道较窄,砂体厚度较小,平面上呈窄带状镶嵌于泥岩中产出,粒度偏细,且砂体内主要发育为数不多的钙质夹层,鲜见泥质侧积层;对于基准面较高背景下发育的远砂坝或前缘席状砂,粒度较细,主要发育泥质夹层且横向不稳定。

The internal architecture of sand is the main controlling factor of the remaining oil distribution.To find out the internal architecture of sand body and the macro controlling factors are important to predict the distribution of the remaining oil.Synthetically using the core analyzing results of Well L11-6,log curve and sand body geometry etc.,the authors study the relationship between the base level changes and the internal architecture of the delta front sand bodies.The studies suggest that there are two middle-term base level cycles,7 short-term base level cycles and 20 ultrashort-term cycles.There are three shallowing upward asymmetric short-term base level cycles in the early middle-term base level cycle.The late middle-cycle consists of 4 deepening upward asymmetric short-term base level cycles.20 ultra-short-term cycles are asymmetric.The results show that the change of the base level and the material supply control the size,rock type and internal structure of the sand body.When the base level lowers and the sediment supply is sufficient,the size of the mouth bar sand body is larger,and the rock type is mainly fine sandstone and medium sandstone,etc.The development degree of the sandwich is different in different locations of the estuary dam.There are calcareous interbeds and transitional interlayers in the subject positions of the estuary dam,which have small thickness,less stable and poor barrier.When the base level rises and the sediment supply is sufficient,the underwater distributary channels are wider and the sands are thick.In addition to the development of calcareous interbeds,the muddy lateral accretion layers are also well developed.When the base level is higher and the sediment supply is less,the channels are narrow.The sandstone body thickness is thin and its debris size is fine.And the channel sands are striped and insert into mudstones.There is a few calcareous sandstone sandwiches in the channel sands,it is difficult to see the muddy lateral accretion layer.At the same time,there is mainly mud sandwich in the distal bar and sheeted sand,which is unstable in lateral distribution.